I know, this is "Monday morning quarterbacking", but that's what you get for an outage this big that had me tied up for half a day.
I know, this is "Monday morning quarterbacking", but that's what you get for an outage this big that had me tied up for half a day.
1. Their bot management system is designed to push a configuration out to their entire network rapidly. This is necessary so they can rapidly respond to attacks, but it creates risk as compared to systems that roll out changes gradually.
2. Despite the elevated risk of system wide rapid config propagation, it took them 2 hours to identify the config as the proximate cause, and another hour to roll it back.
SOP for stuff breaking is you roll back to a known good state. If you roll out gradually and your canaries break, you have a clear signal to roll back. Here was a special case where they needed their system to rapidly propagate changes everywhere, which is a huge risk, but didn’t quite have the visibility and rapid rollback capability in place to match that risk.
While it’s certainly useful to examine the root cause in the code, you’re never going to have defect free code. Reliability isn’t just about avoiding bugs. It’s about understanding how to give yourself clear visibility into the relationship between changes and behavior and the rollback capability to quickly revert to a known good state.
Cloudflare has done an amazing job with availability for many years and their Rust code now powers 20% of internet traffic. Truly a great team.
Once every 5m is not "rapidly". It isn't uncommon for configuration systems to do it every few seconds [0].
> While it’s certainly useful to examine the root cause in the code.
Believe the issue is as much an output from a periodic run (clickhouse query) caused by (on the surface, an unrelated change) causing this failure. That is, the system that validated the configuration (FL2) was different to the one that generated it (ML Bot Management DB).
Ideally, it is the system that vends a complex configuration that also vends & tests the library to consume it, or the system that consumes it, does so as if it was "tasting" the configuration first before devouring it unconditionally [1].
Of course, as with all distributed system failures, this is all easier said and done in hindsight.
[0] Avoiding overload in distributed systems by putting the smaller service in control (pg 4), https://d1.awsstatic.com/builderslibrary/pdfs/Avoiding%20ove...
[1] Lessons from CloudFront (2016), https://youtube.com/watch?v=n8qQGLJeUYA&t=1050
Isn't rapidly more of how long it takes to get from A to Z rather than how often it is performed? You can push out a configuration update every fortnight but if it goes through all of your global servers in three seconds, I'd call it quite rapid.
In a productive way, this view also shifts the focus to improving the system (visibility etc), empowering the team, rather than focusing on the code which broke (probably strikes fear in the individuals, to do anything!)
I don’t really buy this requirement. At least make it configurable with a more reasonable default for “routine” changes. E.g. ramping to 100% over 1 hour.
As long as that ramp rate is configurable, you can retain the ability to respond fast to attacks by setting the ramp time to a few seconds if you truly think it’s needed in that moment.
Of course, this is all so easy to say after the fact..
> In the internal incident chat room, we were concerned that this might be the continuation of the recent spate of high volume Aisuru DDoS attacks:
https://developers.cloudflare.com/bots/get-started/bot-manag...
> Unrelated to this incident, we were and are currently migrating our customer traffic to a new version of our proxy service, internally known as FL2. Both versions were affected by the issue, although the impact observed was different.
> Customers deployed on the new FL2 proxy engine, observed HTTP 5xx errors. Customers on our old proxy engine, known as FL, did not see errors, but bot scores were not generated correctly, resulting in all traffic receiving a bot score of zero. Customers that had rules deployed to block bots would have seen large numbers of false positives. Customers who were not using our bot score in their rules did not see any impact.
If every time there's a new bot someone needs to write code that can blow up their whole service, maybe they need to iterate a bit on this design?
In fact, the root bug (faulty assumption?) was in one or more SQL catalog queries that were presumably written some time ago.
(Interestingly the analysis doesn’t go into how these erroneous queries made it into production OR whether the assumption was “to spec” and it’s the security principal change work that was faulty. Seems more likely to be the former.)
Generally I would say we as an industry are more nonchalant about config changes vs binary changes. Where an org might have great processes and systems in place for binary rollouts, the whole fleet could be reading config from a database in a much more lax fashion. Those systems are quite risky actually.
Even only in CF’s “critical path” there must be dozens of interconnected services and systems. How do you close the loop between an observed panic at the edge and a database configuration change N systems upstream?
And yes, there is a lint you can use against slicing ('indexing_slicing') and it's absolutely wild that it's not on by default in clippy.
[lints.clippy]
dbg_macro = "deny"
unwrap_used = "deny"
expect_used = "deny"This is sobering.
My new fear is some dependency unwrap()ing or expect()ing something where they didn't prove the correctness.
Unwrap() and expect() are an anti-pattern and have no place in idiomatic Rust code. The language should move to deprecate them.
Perhaps it needs a scarier name, like "assume_ok".
This lets me do logging at minimum. Sometimes I can gracefully degrade. I try to be elegant in failure as possible, but not to the point where I wouldn't be able to detect errors or would enter a bad state.
That said, I am totally fine with your use case in your application. You're probably making sane choices for your problem. It should be on each organization to decide what the appropriate level of granularity is for each solution.
My worry is that this runtime panic behavior has unwittingly seeped into library code that is beyond our ability and scope to observe. Or that an organization sets a policy, but that the tools don't allow for rigid enforcement.
The handler could log the error and then panic. Much better than chasing bad hunches about a DDoS.
If you're using Result<T,E>, there's no automatic language feature for statically typing a nested E that mirrors how it was called.
So out of brevity, they unwrap.
Expect to see this sort of error crop up a lot as people use LLMs to vibe with the borrow checker.
As the user, I can't tell the difference, but it might have sped up their recovery a bit.
I imagine it would also require less time debugging a panic. That kind of breadcrumb trail in your logs is a gift to the future engineer and also customers who see a shorter period of downtime.
I'm sure that there are misapplied guidelines to do that instead of being nice to incoming bot management configuration files, and someone might have been scolded (or worse) for proposing or attempting to handle them more safely.
Both are important, and I am pretty sure, that someone is gonna fix that line of code pretty soon.
How can you write the proxy without handling the config containing more than the maximum features limit you set yourself?
How can the database export query not have a limit set if there is a hard limit on number of features?
Why do they do non-critical changes in production before testing in a stage environment?
Why did they think this was a cyberattack and only after two hours realize it was the config file?
Why are they that afraid of a botnet? Does not leave me confident that they will handle the next Aisuru attack.
I'm migrating my customers off Cloudflare. I don't think they can swallow the next botnet attacks and everyone on Cloudflare go down with the ship, so it will be safer to not be behind Cloudflare when it hits.
But the case for Cloudflare here is complicated. Every engineer is very free to make a better system though.
Cloudflare builds a global scale system, not an iphone app. Please act like it.
There will always be bugs in code, even simple code, and sometimes those things don't get caught before they cause significant trouble.
The failing here was not having a quick rollback option, or having it and not hitting the button soon enough (even if they thought the problem was probably something else, I think my paranoia about my own code quality is such that I would have been rolling back much sooner just in case I was wrong about the “something else”).
It goes over my head why Cloudflare is HN's darling while others like Google, Microsoft and AWS don't usually enjoy the same treatment.
Do the others you mentioned provide such detailed outage reports, within 24 hours of an incident? I’ve never seen others share the actual code that related to the incident.
Or the CEO or CTO replying to comments here?
>Press Release
This is not press release, they always did these outage posts from the start of the company.
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
Azure (albeit pretty old): https://devblogs.microsoft.com/devopsservice/?p=17665
AWS: https://aws.amazon.com/message/101925/
GCP: https://status.cloud.google.com/incidents/ow5i3PPK96RduMcb1S...
The code sample might as well be COBOL for people not familiar with Rust and its error handling semantics.
> Or the CEO or CTO replying to comments here?
I've looked around the thread and I haven't seen the CTO here nor the CEO, probably I'm not familiar with their usernames and that's on me.
> This is not press release, they always did these outage posts from the start of the company.
My mistake calling them press releases. Newspapers and online publications also skim this outage report to inform their news stories.
I wasn't clear enough on my previous comment. I'd like all major players in the internet and web infrastructure to be held to higher standards. As it stands when it comes to them or the tech department of a retail store the retail store must answer to more laws when surface area of combined activities is took into account.
Yes, Cloudflare excels where others don't or barely bother and I too enjoyed the pretty graphs, diagrams and I've learned some nifty Rust tricks.
EDIT: I've removed some unwarranted snark from my comment which I apologize for.
Every system has a non-reducible risk and no data rollback is trivial, especially for a CDN.
I guess the noncritical change here was the change to the database? My experience has been a lot of teams do a poor job having a faithful replica of databases in stage environments to expose this type of issue.
Permissions stuff might be caught without a completely faithful replica, but there are always going to be attributes of the system that only exist in prod.
Is that an overreaction?
Name me global, redundant systems that have not (yet) failed.
And if you used cloudflare to protect against botnet and now go off cloudflare... you are vulnerable and may experience more downtime if you cannot swallow the traffic.
I mean no service have 100% uptime - just that some have more nines than others.
Whatever you do, unless you have their bandwidth capacity, at some point those "self-hosted" will get flooded with traffic.
The fact that cloudflare can literally ready every bit of communication (as it sits between the client and your server) is already plenty bad. And yet, we accept this more easily, then a bit of downtime. We shall not ask about the prices for that service ;)
To me its nothing more then the whole "everybody on the cloud" issue, when most do not need the resource that cloud companies like AWS provide (and the bill), and yet, get totally tied down to this one service.
I am getting old lol ...
What is the cost of many-9s uptime from Cloudflare? For DDoS protection it is $0/month on their free tier:
Its free as long as you really are small, not worth milking. The moment you can afford to run your own mini dc at your office, you start to enter the "well, hello there" for CF.
As someone who has (and is) runs (running) a DC with all the electrical/UPS, cooling, piping, HVAC+D stuff to deal with: it can be a lot of just time/overhead.
Especially if you don't have a number of folks in-house to deal with all that 'non-IT' equipment (I'm a bit strange in that I have an interest in both IT and HVAC-y stuff).
The bandwidth costs of a ddos alone would close down a small shop.
Cloudflare provide an incredibly good service with a great track record, and sometimes shit happens.
What would some good examples of those be? I think something like Anubis is mostly against bot scraping, not sure how you'd mitigate a DDoS attack well with self-hosted infra if you don't have a lot of resources?
On that note, what would be a good self-hosted WAF? I recall using mod_security with Apache and the OWASP ruleset, apparently the Nginx version worked a bit slower (e.g. https://www.litespeedtech.com/benchmarks/modsecurity-apache-... ), there was also the Coraza project but I haven't heard much about it https://coraza.io/ or maybe the people who say that running a WAF isn't strictly necessary also have a point (depending on the particular attack surface).
Genuine questions.
There is haproxy-protection, which I believe is the basis of Kiwiflare. Clients making new connections have to solve a proof-of-work challenge that take about 3 seconds of compute time.
Enterprise: https://www.haproxy.com/solutions/ddos-protection-and-rate-l...
How they magically manage DDOS larger than their bandwidth?
If the plan is to have larger bandwidth than any DDOS it is going to be expensive, quickly.
If you're just renting servers instead, you have a few options that are effectively closer to a 1% commit, but better have a plan B for when your upstreams drop you if the incoming attack traffic starts disrupting other customers - see Neoprotect having to shut down their service last month.
But at the same time, what value do they add if they:
* Took down the the customers sites due to their bug.
* Never protected against an attack that our infra could not have handled by itself.
* Don't think that they will be able to handle the "next big ddos" attack.
It's just an extra layer of complexity for us. I'm sure there are attacks that could help our customers with, that's why we're using them in the first place. But until the customers are hit with multiple ddos attacks that we can not handle ourself then it's just not worth it.
That is always a risk with using a 3rd party service, or even adding extra locally managed moving parts. We use them in DayJob, and despite this huge issue and the number of much smaller ones we've experienced over the last few years their reliability has been pretty darn good (at least as good as the Azure infrastructure we have their services sat in front of).
> • Never protected against an attack that our infra could not have handled by itself.
But what about the next one… Obviously this is a question sensitive to many factors in our risk profiles and attitudes to that risk, there is no one right answer to the “but is it worth it?” question here.
On a slightly facetious point: if something malicious does happen to your infrastructure, that it does not cope well with, you won't have the “everyone else is down too” shield :) [only slightly facetious because while some of our clients are asking for a full report including justification for continued use of CF and any other 3rd parties, which is their right both morally and as written in our contracts, most, especially those who had locally managed services affected, have taken the “yeah, half our other stuff was affected to, what can you do?” viewpoint].
> • Don't think that they will be able to handle the "next big ddos" attack.
It is a war of attrition. At some point a new technique, or just a new botnet significantly larger than those seen before, will come along that they might not be able to deflect quickly. I'd be concerned if they were conceited enough not to be concerned about that possibility. Any new player is likely to practise on smaller targets first before directly attacking CF (in fact I assume that it is rather rare that CF is attacked directly) or a large enough segment of their clients to cause them specific issues. Could your infrastructure do any better if you happen to be chosen as one of those earlier targets?
Again, I don't know your risk profile so can say which is the right answer, if there even is an easy one other than “not thinking about it at all” being a truly wrong answer. Also DDoS protection is not the only service many use CF for, so those need to be considered too if you aren't using them for that one thing.
I do like the flat cost of Cloudflare and feature set better but they have quite a few outages compared to other large vendors--especially with Access (their zero trust product)
I'd lump them into GitHub levels of reliability
We had a comparable but slightly higher quote from an Akamai VAR.
They explain that at some length in TFA.
That's often the case with human error as especially aviation safety experts know: https://en.wikipedia.org/wiki/Swiss_cheese_model
Any big and noticeable incident is one of the "we failed on so many levels here" kind, by definition.
Isn’t getting cyberattacked their core business?
Yet you omit to acknowledge that the remaining 99.99999% logic written that powers Cloudflare works flawlessly.
Also, hindsight is 20/20
A system that is 99.99999% flawless, can still be unusable.
optimism bias: 100/100
Having an unprivileged application querying system.columns to infer the table layout is just bad; Not having a proper, well-defined table structure indicates sloppiness in the overall schema design, specially if it changes quickly. Considering specifically clickhouse, and even if this approach would be a good idea, the unprivileged way of doing it would be "DESCRIBE TABLE <name>", NOT iterating system.columns. The gist of it - sloppy design not even well implemented.
Having a critical application issuing ad-hoc commands to system.* tablespace instead of using a well-tested library is just amateurism, and again - bad engineering; IMO it is good practice to consider all system.* privileged applications and ensure their querying is completely separate from your application logic; Sometimes some system tables change, and fields are added and/or removed - not planning for this will basically make future compatibility a nightmare.
Not only the problematic query itself, but the whole context of this screams "lack of proper application design" and devs not knowing how to use the product and/or read the documentation. Granted, this is a bit "close to home" for me, because I use ClickHouse extensively (at a scale - I'm assuming - several orders of magnitude smaller than CloudFlare) and I have spent a lot of time designing specifically to avoid at least some of these kind of mistakes. But, if I can do it at my scale, why aren't they doing it?
The database issue screamed at me: lack of expertise. I don't use CH, but seeing someone to mess with a production system and they being surprised "Oh, it does that?", is really bad. And this is obviously not knowledge that is hard to achieve, buried deep in a manual or an edge case only discoverable by source code, it's bread and butter knowledge you should know.
What is confusing, that they didn't add this to their follow-up steps. With some benefit of doubt I'd assume they didn't want to put something very basic as a reason out there, just to protect the people behind it from widespread blame. But if that's not the case, then it's a general problem. Sadly it's not uncommon that components like databases are dealt with, on an low effort basis. Just a thing we plug in and works. But it's obviously not.
It's not that many things had to fail, it's that many things that are obvious haven't been done. It would be a valid excuse if many "exotic" scenarios would have to align, not when it's obvious error cases that weren't handled and changes have not been tested.
While having wrong first assumptions is just how things work when you try to analyze the issue[1], not testing changes before production is just stupidity and nothing else.
The story would be different if eg. multiple unlikely, hard to track things happened at once without anyone making a clearly linkable event, something that would also happen in staging. Most of the things mentioned could essentially statically checked. This is the prime example of what you want as any tech person, because it's not hard to prevent compared to a lot of scenarios where you deal with balancing likelihoods of scenarios, timings, etc.
You don't think someone is a great plumber, because they forgot their tools and missed that big hole in the pipe and also rang at the wrong door, because all these things failed. You think someone is a good plumber if they said they would have to go back to fetch a bulky specialized tool, because this is the rare case in which they need it, but they could also do this other thing in this spcific case. They are great plumbers if they tell you how this happened in first place and how to fix it. They are great plumbers if they manage to fix something outside of their usual scope.
Here pretty much all of the things that you pay them for failed. At a large scale.
I am sure this has there are reasons which we don't now about, and I hope that CloudFlare can fix them. Be it management focusing on the wrong things, be it developers not being in the wrong position or annoyed enough to care or something else entirely. However, not doing these things is (likely) a sign that currently they are not in the state of creating reliable systems - at least none reliable enough for what they are doing. It would be perfectly fine if they ran a web shop or something, but if as experienced many other companies rely on you being up or their stuff fails, then maybe you should not run a company with products like "Always Online".
[1] And should make you adapt the process of analyzing issues. Eg. making sure config changes are "very loud" in monitoring. It's one of the most easily tracked thing that can go wrong, and can relatively easily be mapped to a point in time compared to many other things.
Let those who have never written a bug before cast the first stone.
Reminds me of House of Dynamite, the movie about nuclear apocalypse that really revolves around these very human factors. This outage is a perfect example of why relying on anything humans have built is risky, which includes the entire nuclear apparatus. “I don’t understand why X wasn’t built in such a way that wouldn’t mean we live in an underground bunker now” is the sentence that comes to mind.
I guess you are right, likely a social issue, but certainly not a single exhausted parent.
The new config file was not (AIUI) invalid (syntax-wise) but rather too big:
> […] That feature file, in turn, doubled in size. The larger-than-expected feature file was then propagated to all the machines that make up our network.
> The software running on these machines to route traffic across our network reads this feature file to keep our Bot Management system up to date with ever changing threats. The software had a limit on the size of the feature file that was below its doubled size. That caused the software to fail.
"To make error is human. To propagate error to all server in automatic way is #devops"
This saying dates back to 1969: To err is human but to really foul things up requires a computer.
* https://quoteinvestigator.com/2010/12/07/foul-computer/
Also: I know there’s a proverb which says ‘To err is human,’ but a human error is nothing to what a computer can do if it tries.
If this was a routine config change, I could see how it could take 2 hours to start the mediation plan. However they should have dashboards that correlate config setting changes with 500 errors (or equivalent). It gets difficult when you have many of of these going out at the same time and they are slowly rolled out.
The root cause document is mostly for high level and the public. The details on this specific outage will be in a internal document with many action items, some of them maybe quarter long projects including fixing this specific bug and maybe some linter/monitor to prevent it from happening again.
That and why the hell wasn't their alerting showing up colossal amount of panics in their bot manager thing?
This is also a pretty good example why having stack traces by default is great. That error could have been immediately understood just from a stack trace and a basic exception message.
This is the danger of automated control systems. If they get hacked or somehow push out bad things (CloudStrike), they will have complete control and be very efficient.
It's not necessarily invalid to use unwrap in production code if you would just call panic anyway. But just like every unsafe block needs a SAFETY comment, every unwrap in production code needs an INFALLIBILITY comment. clippy::unwrap_used can enforce this.
How about indexing into a slice/map/vec? Should every `foo[i]` have an infallibility comment? Because they're essentially `get(i).unwrap()`.
For the 5% of cases that are too complex for standard iterators? I never bother justifying why my indexes are correct, but I don't see why not.
You very rarely need SAFETY comments in Rust because almost all the code you write is safe in the first place. The language also gives you the tool to avoid manual iteration (not just for safety, but because it lets the compiler eliminate bounds checks), so it would actually be quite viable to write these comments, since you only need them when you're doing something unusual.
So: first, identify code that cannot be allowed to panic. Within that code, yes, in the rare case that you use [i], you need to at least try to justify why you think it'll be in bounds. But it would be better not to.
There are a couple of attempts at getting the compiler to prove that code can't panic (e.g., the no-panic crate).
I want to ban crates that panic from my dependency chain.
The language could really use an extra set of static guarantees around this. I would opt in.
Something that allows me to tag annotate a function (or my whole crate) as "no panic", and get a compile error if the function or anything it calls has a reachable panic.
This will allow it to work with many unmodified crates, as long as constant propagation can prove that any panics are unreachable. This approach will also allow crates to provide panicking and non panicking versions of their API (which many already do).
On the subject of this, I want more ability to filter out crates in our Cargo.toml. Such as a max dependency depth. Or a frozen set of dependencies that is guaranteed not to change so audits are easier. (Obviously we could vendor the code in and be in charge of our own destiny, but this feels like something we can let crate authors police.)
Which means banning anything that allocates memory and thousands of stdlib functions/methods.
I'm fine with allocation failures. I don't want stupid unwrap()s, improper slice access, or other stupid and totally preventable behavior.
There are things inside the engineer's control. I want that to not panic.
I don't want dependencies deciding to unwrap() or expect() some bullshit and that causing my entire program to crash because I didn't anticipate or handle the panic.
Code should be written, to the largest extent possible, to mitigate errors using Result<>. This is just laziness.
I want checks in the language to safeguard against lazy Rust developers. I don't want their code in my dependency tree, and I want static guarantees against this.
edit: I just searched unwrap() usage on Github, and I'm now kind of worried/angry:
https://github.com/search?q=unwrap%28%29+language%3ARust&typ...
A lot of this is just pure laziness.
Look at how many lazy cases of this there are in Rust code [1].
Some of these are no doubt tested (albeit impossible to statically guarantee), but a lot of it looks like sloppiness or not leaning on the language's strong error handling features.
It's disappointing to see. We've had so much of this creep into the language that eventually it caused a major stop-the-world outage. This is unlikely to be the last time we see it.
[1] https://github.com/search?q=unwrap%28%29+language%3ARust&typ...
A language DX feature I quite like is when dangerous things are labelled as such. IIRC, some examples of this are `accursedUnutterablePerformIO` in Haskell, and `DO_NOT_USE_OR_YOU_WILL_BE_FIRED_EXPERIMENTAL_CREATE_ROOT_CONTAINERS` in React.js.
I still think we should remove them outright or make production code fail to compile without a flag allowing them. And we also need tools to start cleaning up our dependency tree of this mess.
Unless the language addresses no-panic in its governing design or allows try-catch, not sure how you go about this.
https://github.com/search?q=unwrap%28%29+language%3ARust&typ...
This is ridiculous. We're probably going to start seeing more of these. This was just the first, big highly visible instance.
We should have a name for this similar to "my code just NPE'd". I suggest "unwrapped", as in, "My Rust app just unwrapped a present."
I think we should start advocating for the deprecation and eventual removal of the unwrap/expect family of methods. There's no reason engineers shouldn't be handling Options and Results gracefully, either passing the state to the caller or turning to a success or fail path. Not doing this is just laziness.
Could you share some more details, maybe one fully concrete scenario? There are lots of techniques, but there's no one-size-fits-all solution.
The developer was lazy.
A lot of Rust developers are: https://github.com/search?q=unwrap%28%29+language%3ARust&typ...
The details depend a lot on what you're doing and how you're doing it. Does the graph grow? Shrink? Do you have more than one? Do you care about programmer error types other than panic/UB?
Suppose, e.g., that your graph doesn't change sizes, you only have one, and you only care about panics/UB. Then you can get away with:
1. A dedicated index type, unique to that graph (shadow / strong-typedef / wrap / whatever), corresponding to whichever index type you're natively using to index nodes.
2. Some mechanism for generating such indices. E.g., during graph population phase you have a method which returns the next custom index or None if none exist. You generated the IR with those custom indexes, so you know (assuming that one critical function is correct) that they're able to appropriately index anywhere in your graph.
3. You have some unsafe code somewhere which blindly trusts those indices when you start actually indexing into your array(s) of node information. However, since the very existence of such an index is proof that you're allowed to access the data, that access is safe.
Techniques vary from language to language and depending on your exact goals. GhostCell [0] in Rust is one way of relegating literally all of the unsafe code to a well-vetted library, and it uses tagged types (via lifetimes), so you can also do away with the "only one graph" limitation. It's been awhile since I've looked at it, but resizes might also be safe pretty trivially (or might not be).
The general principle though is to structure your problem in such a way that a very small amount of code (so that you can more easily prove it correct) can provide promises that are enforceable purely via the type system (so that if the critical code is correct then so is everything else).
That's trivial by itself (e.g., just rely on option-returning .get operators), so the rest of the trick is to find a cheap place in your code which can provide stronger guarantees. For many problems, initialization is the perfect place (e.g., you can bounds-check on init and then not worry about it again) (e.g., if even bounds-checking on initialization is too slow then you can still use the opportunity at initialization to write out a proof of why some invariant holds and then blindly/unsafely assert it to be true, but you then immediately pack that hard-won information into a dedicated type so that the only place you ever have to think about it is on initialization).
* Graph/tree traversal functions that take a visitor function as a parameter
* Binary search on sorted arrays
* Binary heap operations
* Probing buckets in open-addressed hash tables
The smoltcp crate typically uses runtime checks to ensure slice accesses made by the library do not cause a panic. It's not exactly equivalent to GP's assertion, since it doesn't cover "every single slice access", but it at least covers slice accesses triggered by the library's public API. (i.e. none of the public API functions should cause a panic, assuming that the runtime validation after the most recent mutation succeeds).
Example: https://docs.rs/smoltcp/latest/src/smoltcp/wire/ipv4.rs.html...
I think adoption would have played out very different if there had only been some more syntactic-sugar. For example, an easy syntax for saying: "In this method, any (checked) DeepException e that bubbles up should immediately be replaced by a new (checked) MylayerException(e) that contains the original one as a cause.
We might still get lazy programmers making systems where every damn thing goes into a generic MylayerException, but that mess would still be way easier to fix later than a hundred scattered RuntimeExceptions.
I think it comes down to a psychological or use-case issue: People hate thinking about errors and handling them, because it's that hard stuff that always consumes more time than we'd like to think. Not just digitally, but in physical machines too. It's also easier to put off "for later."
1. in most cases they don't want to handle `InterruptedException` or `IOException` and yet need to bubble them up. In that case the code is very verbose.
2. it makes lambdas and functions incompatible. So eg: if you're passing a function to forEach, you're forced to wrap it in runtime exception.
3. Due to (1) and (2), most people become lazy and do `throws Exception` which negates most advantages of having exceptions in the first place.
In line-of-business apps (where Java is used the most), an uncaught exception is not a big deal. It will bubble up and gets handled somewhere far up the stack (eg: the server logger) without disrupting other parts of the application. This reduces the utility of having every function throw InterruptedException / IOException when those hardly ever happen.
This is true, but the hate predated lambdas in Java.
In my experience, it actually is a big deal, leaving a wake of indeterminant state behind after stack unrolling. The app then fails with heisenbugs later, raising more exceptions that get ignored, compounding the problem.
People just shrug off that unreliability as an unavoidable cost of doing business.
The problem is that any non-trivial software is composition, and encapsulation means most errors aren't recoverable.
We just need easy ways to propagate exceptions out to the appropriate reliability boundary, ie. the transaction/ request/ config loading, and fail it sensibly, with an easily diagnosable message and without crashing the whole process.
C# or unchecked Java exceptions are actually fairly close to ideal for this.
The correct paradigm is "prefer throw to catch" -- requiring devs to check every ret-val just created thousands of opportunities for mistakes to be made.
By contrast, a reliable C# or Java version might have just 3 catch clauses and handle errors arising below sensibly without any developer effort.
https://literatejava.com/exceptions/ten-practices-for-perfec...
Exceptions force a panic on all errors, which is why they're supposed to be used in "exceptional" situations. To avoid exceptions when an error is expected, (eof, broken socket, file not found,) you either have to use an unnatural return type or accept the performance penalty of the panic that happens when you "throw."
In Rust, the stack trace happens at panic (unwrap), which is when the error isn't handled. IE, it's not when the file isn't found, it's when the error isn't handled.
Can't Hotspot not generate the stack trace when it knows the exception will be caught and the stack trace ignored?
Actually it can also just turn off the collection of stack traces entirely for throw sites that are being hit all the time. But most Java code doesn't need this because code only throws exceptions for exceptional situations.
What do you mean?
Exceptions do not force panic at all. In most practical situations, an exception unhandled close to where it was thrown will eventually get logged. It's kind of a "local" panic, if you will, that will terminate the specific function, but the rest of the program will remain unaffected. For example, a web server might throw an exception while processing a specific HTTP request, but other HTTP requests are unaffected.
Throwing an exception does not necessarily mean that your program is suddenly in an unsupported state, and therefore does not require terminating the entire program.
When everyone uses runtime exceptions and doesn’t count for exception handling in every possible code path, that’s exactly what it means.
When you work with exceptions, the key is to assume that every line can throw unless proven otherwise, which in practice means almost all lines of code can throw. Once you adopt that mental model, things get easier.
It also makes errors part of the API contract, which is where they belong, because they are.
The point about being explicitly part of the API stands, though.
That's not what a panic means. Take a read through Go's panic / resume mechanism; it's similar to exceptions, but the semantics (with multiple return values) make it clear that panic is for exceptional situations. (IE, panic isn't for "file not found," but instead it's for when code isn't written to handle "file not found.")
Even Rust has mechanisms to panic without aborting the process, although I will readily admit that I haven't used them and don't understand them: https://doc.rust-lang.org/std/panic/fn.resume_unwind.html
In theory, theory and practice are the same. In practice...
You can't throw a checked exception in a stream, this fact actually underlines the key difference between an exception and a Result: Result is in return position and exceptions are a sort of side effect that has its own control flow. Because of that, once your method throws an Exception or you are writing code in a try block that catches an exception, you become blind to further exceptions of that type, even if you might be able to or required to fix those errors. Results are required to be handled individually and you get syntactic sugar to easily back propagate.
It is trivial to include a stack trace, but stack traces are really only useful for identifying where something occurred, and generally what is superior is attaching context as you back propagate which trivially occurs with judicious use of custom error types with From impls. Doing this means that the error message uniquely defines the origin and paths it passed through without intermediate unimportant stack noise. With exceptions you would always need to catch each exception and rethrow a new exception containing the old to add contextual information, then to avoid catching to much you need variables that will be initialized inside the try block defined outside of the try block. So stack traces are basically only useful when you are doing Pokemon exception handling.
The same is required for any principled error handling.
It's not a checked exception without a stack trace.
Rust doesn't have Java's checked or unchecked exception semantics at the moment. Panics are more like Java's Errors (e.g. OOM error). Results are just error codes on steroids.
A few ideas:
- It should not compile in production Rust code
- It should only be usable within unsafe blocks
- It should require explicit "safe" annotation from the engineer. Though this is subject to drift and become erroneous.
- It should be possible to ban the use of unsafe in dependencies and transitive dependencies within Cargo.
unwrap() should effectively work as a Result<> where the user must manually invoke a panic in the failure branch. Make special syntax if a match and panic is too much boilerplate.
This is like an implicit null pointer exception that cannot be statically guarded against.
I want a way to statically block any crates doing this from my dependency chain.
How was I informed as a user? It's not in the type signature.
Sounds like I get to indeterminately crash at runtime and have a fun time debugging.
Absent that there are hacks like no_panic[2]
[0] https://blog.yoshuawuyts.com/extending-rusts-effect-system/ [1] https://koka-lang.github.io/koka/doc/book.html#why-effects [2] https://crates.io/crates/no-panic
I don’t think you can ever completely eliminate panics, because there are always going to be some assumptions in code that will be surprisingly violated, because bugs exist. What if the heap allocator discovers the heap is corrupted? What if you reference memory that’s paged out and the disk is offline? (That one’s probably not turned into a panic, but it’s the same principle.)
Software engineers tend to get stuck in software problems and thinking that everything should be fixed in code. In reality there are many things outside of the code that you can do to operate unreliable components safely.
There's also an assumption here that if the unwrap wasn't there, the caller would have handled the error properly. But if this isn't part of some common library at CF, then chances are the caller is the same person who wrote the panicking function in the first place. So if a new error variant they introduced was returned they'd probably still abort the thread either by panicking at that point or breaking out of the thread's processing loop.
if (userOpt.isPresent()) {
var user = userOpt.get();
var accountOpt = accountRepository.selectAccountOpt(user.getId());
var account = accountOpt.orElseThrow();
}
Idea checks it by default and highlights if I've used `get()` without previous check. It's not forced at compiler level, but it's good enough for me.Not unlike people having a blind spot for Rust in general, no?
An unwrap should never make it to production IMHO. It's fine while prototyping, but once the project gets closer to production it's necessary to just grep `uncheck` in your code and replace those that can happen with a proper error management and replace those that cannot happen with `expect`, with a clear justification of why they cannot happen unless there's a bug somewhere else.
unwrap isn't like that.
The message isn't really here to be displayed during a crash (since the crash should never happen in the first place), it's here to communicate the invariant in the code, to the developer reading and modifying it later on.
We are now discussing what can be done to improve code correctness beyond memory and thread safety. I am excited for what is to come.
I am not sure that watching the trendy forefront successfully reach the 1990s and discuss how unwrapping Option is potentially dangerous really warm my heart. I can’t wait for the complete meltdown when they discover effect systems in 2040.
To be more serious, this kind of incident is yet another reminder that software development remains miles away from proper engineering and even key providers like Cloudfare utterly fail at proper risk management.
Celebrating because there is now one popular language using static analysis for memory safety feels to me like being happy we now teach people to swim before a transatlantic boat crossing while we refuse to actually install life boats.
To me the situation has barely changed. The industry has been refusing to put in place strong reliability practices for decades, keeps significantly under investing in tools mitigating errors outside of a few fields where safety was already taken seriously before software was a thing and keeps hiding behind the excuse that we need to move fast and safety is too complex and costly while regulation remains extremely lenient.
I mean this Cloudfare outage probably cost millions of dollars of damage in aggregate between lost revenue and lost productivity. How much of that will they actually have to pay?
> I mean this Cloudfare outage probably cost millions of dollars of damage in aggregate between lost revenue and lost productivity. How much of that will they actually have to pay?
Probably nothing, because most paying customers of cloudflare are probably signing away their rights to sue Cloudflare for damages by being down for a while when they purchase Cloudflare's services (maybe some customers have SLAs with monetary values attached, I dunno). I honestly have a hard time suggesting that those customers are individually wrong to do so - Cloudflare isn't down that often, and whatever amount it cost any individual customer by being down today might be more than offset by the DDOS protection they're buying.
Anyway if you want Cloudflare regulated to prevent this, name the specific regulations you want to see. Should it be illegal under US law to use `unwrap` in Rust code? Should it be illegal for any single internet services company to have more than X number of customers? A lot of the internet also breaks when AWS goes down because many people like to use AWS, so maybe they should be included in this regulatory framework too.
We have collectively agreed to a world where software service providers have no incentive to be reliable as they are shielded from the consequences of their mistakes and somehow we see it as acceptable that software have a ton of issues and defects. The side effect is that research on actually lowering the cost of safety has little return on investment. It doesn't have be so.
> Anyway if you want Cloudflare regulated to prevent this, name the specific regulations you want to see.
I want software provider to be liable for the damage they cause and minimum quality regulation on par with an actual engineering discipline. I have always been astounded that nearly all software licences start with extremely broad limitation of liability provisions and people somehow feel fine with it. Try to extend that to any other product you regularly use in your life and see how that makes you fell.
How to do proper testing, formal methods and resilient design have been known for decades. I would personnaly be more than okay with let's move less fast and stop breaking things.
So do you want to make it illegal to punish GNU GPL licensed software because that license has a warranty disclaimer? Do you want to make it illegal for a company like Cloudflare to use open source licensed software with similar warranty disclaimers, or for the SLA agreements and penalties for violating them that they make with their own paying customers to be legally unenforceable? What if I just have a personal website and I break the javascript on it because I was careless, how should that be legally treated?
I'm not against research into more reliable software or using better engineering techniques that result in more reliable software. What I'm concerned about is the regulatory regime - in other words, what software it is or is not legal to write or sell for money - and how to properly incentivize software service providers to use techniques that result in more reliable software without causing a bunch of bad second order effects.
You can't go out in the middle of your city, build a shoddy bridge, say you wave all responsibilities and then wash your hands with the consequences when it predictably breaks. Why can you do that with pieces of software?
Limiting the scope of liability waivers is not the same things as censoring what software can be produced. It's just ensuring that everyone actually take responsibility for the things they distribute.
As I said previously, the current situation doesn't make sense to me. People have been brainwashed in believing that the way software is released currently, half finished and crippled with bugs, is somehow normal and acceptable. It absolutely doesn't have to be this way.
It'a beyond shameful that the average developers today is blissfully unaware of anything related to producing actually secure pieces of software. I am pretty sure I can walk into more than 90% of development shops today and no one there will know what formal methods are. With some luck, they might have some static analysers running, probably from a random provider and be happy with the crappy percentages that it outputs.
It's not about research. It's about a field which entirely refuses to become mature despite being pivotal to the modern economy. And why would it? Software products somehow get a free pass for the shit they push on everyone.
We are in the classical "market for lemons" trap where negative externalities are not priced in and investing in security will just get you to lose against companies that don't care. Every major incidents remind us we need out. The market has already showed it won't self correct. It's a classical case where regulatory intervention is necessary and legitimate.
The shift is already happening by the way. The EU product liability directive was adopted in 2024 and the transition period ends in December 2026. The US "National Cybersecurity Strategy" signals intend to review the status quo. It's coming faster that people realise.
That we’re even having this discussion is a major step forward. That we’re still having this discussion is a depressing testament to how slow slowly the mainstream has adopted better ideas.
Zig is undergoing this meltdown. Shame it's not memory safe. You can only get so far in developing programming wisdom before Eternal September kicks in and we're back to re-learning all the lessons of history as punishment for the youthful hubris that plagues this profession.
But yes, I wish I had learned more, and somehow stumbled upon all the good stuff, or be taught at university about at least what Rust achieves today.
I think it has to be noted Rust still allows performance with the safety it provides. So that's something maybe.
The most useful thing exceptions give you is not static compile time checking, it's the stack trace, error message, causal chain and ability to catch errors at the right level of abstraction. Rust's panics give you none of that.
Look at the error message Cloudflare's engineers were faced with:
thread fl2_worker_thread panicked: called Result::unwrap() on an Err value
That's useless, barely better than "segmentation fault". No wonder it took so long to track down what was happening.A proxy stack written in a managed language with exceptions would have given an error message like this:
com.cloudflare.proxy.botfeatures.TooManyFeaturesException: 200 > 60
at com.cloudflare.proxy.botfeatures.FeatureLoader(FeatureLoader.java:123)
at ...
and so on. It'd have been immediately apparent what went wrong. The bad configs could have been rolled back in minutes instead of hours.In the past I've been able to diagnose production problems based on stack traces so many times I was been expecting an outage like this ever since the trend away from providing exceptions in new languages in the 2010s. A decade ago I wrote a defense of the feature and I hope we can now have a proper discussion about adding exceptions back to languages that need them (primarily Go and Rust):
https://blog.plan99.net/what-s-wrong-with-exceptions-nothing...
tldr: Capturing a backtrace can be a quite expensive runtime operation, so the environment variables allow either forcibly disabling this runtime performance hit or allow selectively enabling it in some programs.
By default it is disabled in release mode.
Similarly, capturing a stack trace in a error type (within a Result for example) is perfectly possible. But this is a choice left to the programmer, because capturing a trace is not cheap.
I used to be an SRE at Google. Back then we also had big outages caused by bad data files pushed to prod. It's a common enough issue so I really sympathize with Cloudflare, it's not nice to be on call for issues like that. But Google's prod environments always generated stack traces for every kind of failure, including CHECK failures (panics) in C++. You could also reflect the stack traces of every thread via HTTP. I used to diagnose bugs in production under time pressure quite regularly using just these tools. You always need detailed diagnostics.
Languages shouldn't have panics, tbh, it's a primitive concept. It so rarely makes sense to handle errors that way. I know there's a whole body of Rust/Go lore claiming panics are fine, but it's not a good move and is one of the reasons I've stayed away from Go over the years and wouldn't use Rust for anything higher than low level embedded components or operating system code that has to export a C ABI. You always want diagnostics and recoverable errors; this kind of micro-optimization doesn't make sense outside of extremely constrained embedded environments that very few of us work in.
https://doc.rust-lang.org/std/panic/index.html
An uncaught exception in C++ or an uncaught panic in Rust terminates the program. The unwinding is the same mechanism. I think the implementation is what comes with LLVM, but I haven't checked.
I was also a Google SRE, and I liked the stacktrace facilities so much that I got permission to open source a library inspired from it: https://github.com/bombela/backward-cpp (I know I am not doing a great job maintaining it)
At Uber I implemented a similar stackrace introspection for RPC tasks via HTTP for Go services.
You can also catch a Go panic. Which we did in our RPC library at Uber.
It would be great for all of that to somehow come ready made though. A sort of flag "this program is a service, turn on all the good diagnostics, here is my main loop".
IMO making unwrap a clippy lint (or perhaps a warning) would be a decent start. Or maybe renaming unwrap.
A tenet of systems code is that every possible error must be handled explicitly and exhaustively close to the point of occurrence. It doesn’t matter if it is Rust, C, etc. Knowing how to write systems code is unrelated to knowing a systems language. Rust is a systems language but most people coming into Rust have no systems code experience and are “holding it wrong”. It has been a recurring theme I’ve seen with Rust development in a systems context.
C is pretty broken as a language but one of the things going for it is that it has a strong systems code culture surrounding it that remembers e.g. why we do all of this extra error handling work. Rust really needs systems code practice to be more strongly visible in the culture around the language.
A tenet of systems code is that every possible error must be handled
explicitly and exhaustively close to the point of occurrence.
All the more reason it doesn't really belong in examples for third party libraries.Change your API boundary, surface the discrepancy between your requirements and the potential failing case at the edges where it can be handled.
If you need the value, you need to handle the case that it’s not available explicitly. You need to define your error path(s)
Anything else leads to, well, this.
This is a failure caused by lazy Rust programming and not relying on the language's design features.
It's a shame this code can even be written. It is surprising and escapes the expected safety of the language.
I'm terrified of some dependency using unwrap() or expect() and crashing for something entirely outside of my control.
We should have an opt-in strict Cargo.toml declaration that forbids compilation of any crate that uses entirely preventable panics. The only panics I'll accept are those relating to memory allocation.
This is one of the sharpest edges in the language, and it needs to be smoothed away.
The problem starts with Rust stdlib. It panics on allocation failure. You expect Rust programmers to look at stdlib and not imitate it?
Sure, you can try to taboo unwrap(), but 1) it won't work, and 2) it'll contort program design in places where failure really is a logic bug, not a runtime failure, and for which unwrap() is actually appropriate.
The real solution is to go back in time, bonk the Rust designers over the head with a cluebat, and have them ship a language that makes error propagation the default and syntactically marks infallible cleanup paths --- like C++ with noexcept.
Of course it will. I've built enormous systems, including an entire compiler, without once relying on the local language equivalent of `.unwrap()`.
> 2) it'll contort program design in places where failure really is a logic bug, not a runtime failure, and for which unwrap() is actually appropriate.
That's a failure to model invariants in your API correctly.
> ... have them ship a language that makes error propagation the default and syntactically marks infallible cleanup paths --- like C++ with noexcept.
Unchecked exceptions aren't a solution. They're a way to avoid taking the thought, time, and effort to model failure paths, and instead leave that inherent unaddressed complexity until a runtime failure surprises users. Like just happened to Cloudflare.
Your argument also implies that things like `slice[i]` are never okay.
The blog post doesn’t address the issue, it simply pretends it’s not a real problem.
Also from the post: “If we were to steelman advocates in favor of this style of coding, then I think the argument is probably best limited to certain high reliability domains. I personally don’t have a ton of experience in said domains …”
Enough said.
> The blog post doesn’t address the issue, it simply pretends it’s not a real problem.
It very explicitly addresses it! It even gives real examples.
> Also from the post: “If we were to steelman advocates in favor of this style of coding, then I think the argument is probably best limited to certain high reliability domains. I personally don’t have a ton of experience in said domains …” > > Enough said.
Ad hominem... I don't have experience working on, e.g., medical devices upon which someone's life depends. So the point of that sentence is to say, "yes, I acknowledge this advice may not apply there." You also cherry picked that quote and left off the context, which is relevant here.
And note that you said:
> I have to disagree that unwrap is ever OK.
That's an extreme position. It isn't caveated to only apply to certain contexts.
It's not orthogonal. `Result` isn't a local invariant, and yes, `.unwrap()` does require lying. If your code depends on an API that can fail, and you cannot handle that failure locally (`.unwrap()` is not handling it), then your type signature needs to express that you can fail -- and you need to raise an error on that failure.
> That's an extreme position. It isn't caveated to only apply to certain contexts.
No, it's a principled position. Correct code doesn't `.unwrap()`, but code that hides failure cases -- or foists invariant enforcement onto programmers remembering not to screw up -- does.
I've built and worked on ridiculously complex code bases without a single instance of `.unwrap()` or the local language equivalent; it's just not necessary. This is just liked the unchecked exception debate in Java -- complex explanations for a very simple goal of avoiding the thought, time, and effort to accurately model a system's invariants.
I don't think you understand what an internal runtime invariant is. Either way, I don't know of any widespread libraries (in any language) that follow this "principled" position. That makes it de facto extreme.
> I've built and worked on ridiculously complex code bases without a single instance of `.unwrap()` or the local language equivalent; it's just not necessary.
Show me. If you're using `slice[i]`, then you're using `unwrap()`. It introduces a panicking branch.
> If your code depends on an API that can fail, and you cannot handle that failure locally (`.unwrap()` is not handling it), then your type signature needs to express that you can fail -- and you need to raise an error on that failure.
You use `unwrap()` when you know the failure cannot happen.
I note you haven't engaged with any of the examples I provided in the blog.
That’s an invariant meant to be expressed by your type system — and it is.
You’ve failed to model your invariants in your API — and thus the type system — if you ever reach a point where an engineer has to manually assess and assert whether “cannot” applies.
You will get it wrong. That is bad code.
That gives you the same behavior as unwrap with a less useful error message though. In theory you can write useful messages, but in practice (and your example) expect is rarely better than unwrap in modern rust
This is Rust's Null Pointer Exception.
unwrap(), expect(), bad math, etc. - this is all caused by lazy Rust developers or Rust developers not utilizing the language's design features.
The language should grow the ability to mark this code as dangerous, and we should have static tools to exclude this code from our dependency tree.
I don't want some library I use to `unwrap()` and cause my application to crash because I didn't anticipate their stupid panic.
Rust developers have clearly leaned on this crutch far too often:
https://github.com/search?q=unwrap%28%29+language%3ARust&typ...
The Rust team needs to plug this leak.
My blog on this topic was linked above, you should read it: https://burntsushi.net/unwrap/
> The language should grow the ability to mark this code as dangerous, and we should have static tools to exclude this code from our dependency tree.
Might be useful to point out that this static tool exists (clippy::unwrap_used).
> unwrap(), expect(), bad math, etc. - this is all caused by lazy Rust developers or Rust developers not utilizing the language's design features.
That's factually incorrect. (And insulting.)
Note that they're not criticizing the language. I read "Rust developers" in this context as developers using Rust, not those who develop the language and ecosystem. (In particular they were not criticizing you.)
I think it's reasonable to question the use of unwrap() in this context. Taking a cue from your blog post^ under runtime invariant violations, I don't think this use matches any of your cases. They assumed the size of a config file is small, it wasn't, so the internet crashed.
> We shouldn't be using unwrap() or expect() at all.
So the context of their comment is not some specific nuanced example. They made a blanket statement.
> Note that they're not criticizing the language. I read "Rust developers" in this context as developers using Rust, not those who develop the language and ecosystem.
I have the same interpretation.
> I think it's reasonable to question the use of unwrap() in this context. Taking a cue from your blog post^ under runtime invariant violations, I don't think this use matches any of your cases. They assumed the size of a config file is small, it wasn't, so the internet crashed.
Yes? I didn't say it wasn't reasonable to question the use of unwrap() here. I don't think we really have enough information to know whether it was inappropriate or not.
unwrap() is all about nuance. I hope my blog post conveyed that. Because unwrap() is a manifestation of an assertion on a runtime invariant. A runtime invariant can be arbitrarily complicated. So saying things like, "we shouldn't be using unwrap() or expect() at all" is an extreme position to carve out that is also way too generalized.
I stand by what I said. They are factually mistaken in their characterization of the use of unwrap()/expect() in general.
That is their opinion, I disagree with it, but I don't think it's an insulting or invalid opinion to have. There are codebases that ban nulls in other languages too.
> They are factually mistaken in their characterization of the use of unwrap()/expect() in general.
It's an opinion about a stylistic choice. I don't see what fact there is here that could be mistaken.
> unwrap(), expect(), bad math, etc. - this is all caused by lazy Rust developers or Rust developers not utilizing the language's design features.
The factually incorrect part of this is the statement that use of `unwrap()`, `expect()` and so on is caused by X or Y, where X is "lazy Rust developers" and Y is "Rust developers not utilizing the language's design features." But there are, factually, other causes than X or Y for use of `unwrap()`, `expect()` and so on. So stating that it is all caused by X or Y is factually incorrect. Moreover, X is 100% insulting when applied to any one specific individual. Y can be insulting when applied to any one specific individual.
Now this:
> We shouldn't be using unwrap() or expect() at all.
That's an opinion. It isn't factually incorrect. And it isn't insulting.
> unwrap(), expect(), bad math, etc. - this is all caused by lazy Rust developers or Rust developers not utilizing the language's design features
I just read that line as shorthand for large outages caused by misuse of unwrap(), expect(), bad math etc. - all caused by...
That's also an opinion, by my reading.
I assumed we were talking specifically about misuses, not all uses of unwrap(), or all bad bugs. Anyway, I think we're ultimately saying the same thing. It's ironic in its own way.
I fully agree with burntsushi that echelon is taking an extreme and arguably wrong stance. His sentiment becomes more and more correct as Rust continues to evolve ways to avoid unwrap as an ergonomic shortcut, but I don't think we are quite there yet for general use. There absolutely is code that should never panic, but that involves tradeoffs and design choices that aren't true for every project (or even the majority of them)
And because it gets picked up by LLMs. It would be interesting to know if this particular .unwrap() was written by a human.
In theory, experienced human code reviewers can course correct newer LLM-guided devs work before it blows up. In practice, reviewers are already stretched thin and submitters absolute to now rapidly generate more and more code to review makes that exhaustion effect way worse. It becomes less likely they spot something small but obvious amongst the haystack of LLM generated code bailing there way.
Yes, and: I've found this to be mostly true, if you make sure you take the time to deeply understand what the code is doing. When I asked an LLM to do something for me in Javascript, then I said, "What if X happens, wouldn't that cause Y? Would it be better to restructure it like so and so to make it more robust?" The LLM immediately improves it.
Any experienced programmer who was taking the time to review this code, on learning that unwrap() has a "panic" inside, would certainly change it. But as you say, reviewers are already stretched thin.
It's not about whether you should ban unwrap() in production. You shouldn't. Some errors are logic bugs beyond which a program can't reasonably continue. The problem is that the language makes it too easy for junior developers (and AI!) to ignore non-logic-bug problems with unwrap().
Programmers early in their careers will do practically anything to avoid having to think about errors and they get angry when you tell them about it.
You might start with a basic timeline of what happened, then you'd start exploring: why did this change affect so many customers (this would be a line of questioning to find a potential root cause), why did it take so long to discover or recover (this might be multiple lines of questioning), etc.
That's too semantic IMHO. The failure mode was "enforced invariant stopped being true". If they'd written explicit code to fail the request when that happened, the end result would have been exactly the same.
> That's too semantic IMHO. The failure mode was "enforced invariant stopped being true". If they'd written explicit code to fail the request when that happened, the end result would have been exactly the same.
Problem is, the enclosing function (`fetch_features`) returns a `Result`, so the `unwrap` on line #82 only serves as a shortcut a developer took due to assuming `features.append_with_names` would never fail. Instead, the routine likely should have worked within `Result`.
But it's a fatal error. It doesn't matter whether it's implicit or explicit, the result is the same.
Maybe you're saying "it's better to be explicit", as a broad generalization I don't disagree with that.
But that has nothing to do with the actual bug here, which was that the invariant failed. How they choose to implement checking and failing the invariant in the semantics of the chosen language is irrelevant.
Maybe the new config has a new update. Who knows? Do we want to keep operating on the old config? Maybe maybe not.
But operating on old config when you don't want to is definitely worse.
Crashing on a config update is usually only done if it could cause data corruption if the configs aren't in sync. That's obviously not the case here since the updates (although distributed in real time) are not coupled between hosts. Such systems usually are replicated state machines where config is totally ordered relative to other commands. Example: database schema and write operations (even here the way many databases are operated they don't strongly couple the two).
Crashing is generally better than behaving incorrectly due to stale configs. Because the problem would get fixed faster.
> But it's a fatal error. It doesn't matter whether it's implicit or explicit, the result is the same.
I agree it is an error, but disagree that it should be a fatal error at that location. The reason being is the method defining the offending `unwrap` construct produces a `Result`, which is fully capable of representing any error `features.append_with_names` could produce.
> But that has nothing to do with the actual bug here, which was that the invariant failed.
The bug is by invoking `unwrap` the process crashed. To the degree that Cloudfare had a massive outage.
Had the logic been such that a `Result` representing this error condition activated an alternate workflow to handle the error (perhaps by logging it, emitting a notification event alerting SRE's, transitioning into a failure mode, or all of these options), then a global outage might have been averted.
Which makes:
> How they choose to implement checking and failing the invariant in the semantics of the chosen language is irrelevant.
Very relevant indeed.
If the `.unwrap()` was replaced with `.expect("Feature config is too large!")` it would certainly make the outage shorter.
It wouldn't, not meaningfully. The outage was caused by change in how they processed the queries. They had no way to observe the changes, nor canaries to see that change is killing them. Plus, they would still need to manually feed and restart services that ingested bad configs.
`expect` would shave a few minutes; you would still spend hours figuring out and fixing it.
Granted, using expect is better, but it's not a silver bullet.
Or the good old:
let x = match res {
Ok(x) => x,
Err(_) => unreachable!(),
}1:
?
2: map_err, or, or_else, etc.
3: match ... {
Ok(..) => {},
Err(..) => {},
}
4: if let ... {
}
Then it would have been idiomatic Rust code and wouldn't have failed at all.The function signature returned a `Result<(), (ErrorFlags, i32)>`
Seems like it should have returned an Err((ErrorFlags, i32)) here. Case 2 or 3 above would have done nicely.
Removing unwrap() from Rust would have forced the proper handling of the function call and would have prevented this.
Unwrap() is Rust's original sin.
The root cause here was that a file was mildly corrupt (with duplicate entries, I guess). And there was a validation check elsewhere that said "THIS FILE IS TOO BIG".
But if that's a validation failure, well, failing is correct? What wasn't correct was that the failure reached production. What should have happened is that the validation should have been a unified thing and whatever generated the file should have flagged it before it entered production.
And that's not an issue with function return value API management. The software that should have bailed was somewhere else entirely, and even there an unwrap explosion (in a smoke test or pre-release pass or whatever) would have been fine.
Ideally every validation should have a well-defined failure path. In the case of a config file rotation, validation failure of the new config could mean keeping the old config and logging a high-priority error message. In the case of malformed user-provided data, it might mean dropping the request and maybe logging it for security analysis reasons. In the case of "pi suddenly equals 4" checks the most logical approach might be to intentionally crash, as there's obviously something seriously wrong and application state has corrupted in such a way that any attempt to continue is only going to make things worse.
But in all cases there's a reason behind the post-validation-failure behavior. At a certain point leaving it up to "whatever happens on .unwrap() failure" isn't good enough anymore.
The real issue is further up the chain where the malformed feature file got created and deployed without better checks.
I do not think that if the bot detection model inside your big web proxy has a configuration error it should panic and kill the entire proxy and take 20% of the internet with it. This is a system that should fail gracefully and it didn't.
> The real issue
Are there single "real issues" with systems this large? There are issues being created constantly (say, unwraps where there shouldn't be, assumptions about the consumers of the database schema) that only become apparent when they line up.
The thing I dislike most about Nginx is that if you are using it as a reverse proxy for like 20 containers and one of them is up, the whole web server will refuse to start up:
nginx: [emerg] host not found in upstream "my-app"
Obviously making 19 sites also unavailable just because one of them is caught in a crash loop isn't ideal. There is a workaround involving specifying variables, like so (non-Kubernetes example, regular Nginx web server running in a container, talking to other containers over an internal network, like Docker Compose or Docker Swarm): location / {
resolver 127.0.0.11 valid=30s; # Docker DNS
set $proxy_server my-app;
proxy_pass http://$proxy_server:8080/;
proxy_redirect default;
}
Sadly, if you try to use that approach, then you just get: nginx: [emerg] "proxy_redirect default" cannot be used with "proxy_pass" directive with variables
Sadly, switching the redirect configuration away from the default makes some apps go into a redirect loop and fail to load: mostly legacy ones, where Firefox shows something along the lines of "The page isn't redirecting properly". It sucks especially badly if you can't change the software that you just need to run and suddenly your whole Nginx setup is brittle. Apache2 and Caddy don't have such an issue.That's to say that all software out there has some really annoying failure modes, even is Nginx is pretty cool otherwise.
I'm really confused how so many people are finding it acceptable to bring down your entire reverse-proxy because the length of feature sets for the ML model in one of your components was longer than expected.
But more generally you could catch the panic at the FL2 layer to make that decision intentional - missing logic at that layer IMHO.
But the bigger change is to make sure that config changes roll out gradually instead of all at once. That’s the source of 99% of all widespread outages
Another option is to make sure that config changes that fail to parse continue using the old config instead of resulting in an unusable service.
But ultimately it’s not the panic that’s the problem but a failure to specify how panics within FL2 layers should be handled; each layer is at least one team and FL2’s job is providing a safe playground for everyone to safely coexist regardless of the misbehavior of any single component
But as always such failures are emblematic of multiple things going wrong at once. You probably want to end up using both catch_unwind for the typical case and the supervisor for the case where there’s a segfault in some unsafe code you call or native library you invoke.
I also mention the fundamental tension of do you want to fail open or closed. Most layers should probably fail open. Some layers (eg auth) it’s safer to fail closed.
OR even, the bot code crashing should itself be generating alerts.
Canary deployment would be automatically rolled back until P0 incident resolved.
All of this could probably have happened and contained at their scale in less than a minute as they would likely generate enough "omg the proxy cannot handle its config" alerts off of a deployment of 0.001% near immediately.
Maybe the validation code should've handled the larger size, but also the db query produced something invalid. That shouldn't have ever happened in the first place.
Agreed, that's also my takeaway.
I don't see the problem being "lazy programmers shouldn't have called .unwrap()". That's reductive. This is a complex system and complex system failures aren't monocausal.
The function in question could have returned a smarter error rather than panicking, but what then? An invariant was violated, and maybe this system, at this layer, isn't equipped to take any reasonable action in response to that invariant violation and dying _is_ the correct thing to do.
But maybe it could take smarter action. Maybe it could be restarted into a known good state. Maybe this service could be supervised by another system that would have propagated its failure back to the source of the problem, alerting operators that a file was being generated in such a way that violated consumer invariants. Basically, I'm describing a more Erlang model of failure.
Regardless, a system like this should be able to tolerate (or at least correctly propagate) a panic in response to an invariant violation.
The point of option is the crash path is more verbose and explicit than the crash-free path. It takes more code to check for NULL in C or nil in Go; it takes more code in Rust to not check for Err.
2. You’re getting confused by technology again. This isn’t about technology.
> This wasn't an attack, but a classic chain reaction triggered by “hidden assumptions + configuration chains” — permission changes exposed underlying tables, doubling the number of lines in the generated feature file. This exceeded FL2's memory preset, ultimately pushing the core proxy into panic.
> Rust mitigates certain errors, but the complexity in boundary layers, data flows, and configuration pipelines remains beyond the language's scope. The real challenge lies in designing robust system contracts, isolation layers, and fail-safe mechanisms.
> Hats off to Cloudflare's engineers—those on the front lines putting out fires bear the brunt of such incidents.
> Technical details: Even handling the unwrap correctly, an OOM would still occur. The primary issue was the lack of contract validation in feature ingest. The configuration system requires “bad → reject, keep last-known-good” logic.
> Why did it persist so long? The global kill switch was inadequate, preventing rapid circuit-breaking. Early suspicion of an attack also caused delays.
> Why not roll back software versions or restart?
> Rollback isn't feasible because this isn't a code issue—it's a continuously propagating bad configuration. Without version control or a kill switch, restarting would only cause all nodes to load the bad config faster and accelerate crashes.
> Why not roll back the configuration?
> Configuration lacks versioning and functions more like a continuously updated feed. As long as the ClickHouse pipeline remains active, manually rolling back would result in new corrupted files being regenerated within minutes, overwriting any fixes.
* For clarity, I am aware that the original tweets are written in Chinese, and they still have the stench of LLM writing all over them; it's not just the translation provided in the above comment.
> classic chain reaction triggered by “hidden assumptions + configuration chains”
"Classic/typical "x + y"", particularly when diagnosing an issue. This one is a really easy tell because humans, on aggregate, do not use quotation marks like this. There is absolutely no reason to quote these words here, and yet LLMs will do a combined quoted "x + y" where a human would simply write something natural like "hidden assumptions and configuration chains" without extraneous quotes.
> The configuration system requires “bad → reject, keep last-known-good” logic.
Another pattern with overeager usage of quotes is this ""x → y, z"" construct with very terse wording.
> This wasn't an attack, but a classic chain reaction
LLMs aggressively use "Not X, but Y". This is also a construct commonly used by humans, of course, but aside from often being paired with an em-dash, another tell is whether it actually contributes anything to the sentence. "Not X, but Y" is strongly contrasting and can add a dramatic flair to the thing being constrasted, but LLMs overuse it on things that really really don't need to be dramatised or contrasted.
> Rust mitigates certain errors, but the complexity in boundary layers, data flows, and configuration pipelines remains beyond the language's scope. The real challenge lies in designing robust system contracts, isolation layers, and fail-safe mechanisms.
Two lists of three concepts back-to-back. LLMs enjoy, love, and adore this construct.
> Hats off to Cloudflare's engineers—those on the front lines putting out fires bear the brunt of such incidents.
This kind of completely vapid, feel-good word soup utilising a heroic analogy for something relatively mundane is another tell.
And more broadly speaking, there's a sort of verbosity and emptiness of actual meaning that permeates through most LLM writing. This reads absolutely nothing like what an engineer breaking down an outage looks like. Like, the aforementioned line of... "Rust mitigates certain errors, but the complexity in boundary layers, data flows, and configuration pipelines remains beyond the language's scope. The real challenge lies in designing robust system contracts, isolation layers, and fail-safe mechanisms.". What is that actually communicating to you? It piles on technical lingo and high-level concepts in a way that is grammatically correct but contains no useful information for the reader.
Bad writing exists, of course. There's plenty of bad writing out there on the internet, and some of it will suffer from flaws like these even when written by a human, and some humans do like their em-dashes. But it's generally pretty obvious when the writing is taken on aggregate and you see recognisable pattern after pattern combined with em-dashes combined with shallowness of meaning combined with unnecessary overdramatisations.
Like GP I'm not very good at spotting these patterns yet, so explicit real-world examples go a long way.
I don't like to use implicit unwrap. Even things that are guaranteed to be there, I treat as explicit (For example, (self.view?.isEnabled ?? false), in a view controller, instead of self.view.isEnabled).
I always redefine @IBOutlets from:
@IBOutlet weak var someView!
to: @IBOutlet weak var someView?
I'm kind of a "belt & suspenders" type of guy.In this particular case, I would rather crash. It’s easier to spot in a crash report and you get a nice stack trace.
Silent failure is ultimately terrible for users.
Note: for the things I control I try to very explicitly model state in such a way as I never need to force unwrap at all. But for things beyond my control like this situation, I would rather end the program than continue with a state of the world I don’t understand.
See my above/below comment.
A good tool for catching stuff during development, is the humble assert()[0]. We can use precondition()[1], to do the same thing, in ship code.
The main thing is, is to remain in control, as much as possible. Rather than let the PC leave the stack frame, throw the error immediately when it happens.
[0] https://docs.swift.org/swift-book/documentation/the-swift-pr...
[1] https://docs.swift.org/swift-book/documentation/the-swift-pr...
Agreed.
Unfortunately, crashes in iOS are “silent failures,” and are a loss of control.
What this practice does, is give me the option to handle the failure “noisily,” and in a controlled manner; even if just emitting a log entry, before calling a system failure. That can be quite helpful, in threading. Also, it gives me the option to have a valid value applied, if there’s a structural failure.
But the main reason that I do that with @IBOutlets, is that it forces me to acknowledge, throughout the rest of the code, that it’s an optional. I could always treat implicit optionals as if they were explicit, anyway. This just forces me to.
I have a bunch of practices that folks can laugh at, but my stuff works pretty effectively, and I sleep well.
Also, I have found App Store crash reports to be next to useless. TestFlight ones are a bit better.
But if I spend a lot of time, doing it right, the first time, we can avoid all kinds of heartbreak.
What have you found useless about the crash reports from the App Store? It would be really nice for it to have something like a breadcrumb capability, but typically the stack trace of the crash is sufficient to see what went wrong.
Crash early, crash often. Find the bugs and bad assumptions.
No it's not. Read my other comments.
ToMAYto, ToMAHto.
I have learned that it's a bad idea to trash other folks' methodologies without taking the time to understand why they do things, the way they do.
I have found dogma to be an impediment, in my own work. As I've gotten older, the sharp edges have been sanded off.
Have a great day!
Oh I am aware. They do it because
A) they don’t have a mental model of correct execution. Events just happen to them with a feeling of powerlessness. So rather than trying to form one they just litter the code with cases things that might happen
> As I've gotten older, the sharp edges have been sanded off.
B) they have grown in bad organizations with bad incentives that penalize the appearance of making mistakes. So they learn to hide them.
For example there might be an initiative that rewards removing crashes in favor of silent error.
How so? “Parse, don’t validate” implies converting input into typed values that prevent representation of invalid state. But the parsing still needs to be done correctly. An unchecked unwrap really has nothing to do with this.
> Bad data was only generated if the query ran on a part of the cluster which had been updated. As a result, every five minutes there was a chance of either a good or a bad set of configuration files being generated and rapidly propagated across the network.
The file should be versioned and rollout of new versions should be staged.
(There is definitely a trade-off; often times in the security critical path, you want to go as fast as possible because changes may be blocking a malicious actor. But if you move too fast, you break things. Here, they had a potential poison input in the pathway for synchronizing this state and Murphy's Law suggests it was going to break eventually, so the question becomes "How much damage can we tolerate when it does?")
That feature file is generated every 5 minutes at all times; the change to permissions was rolled out gradually over the clickhouse cluster, and whether a bad version of that file was generated depended on whether the part of the cluster that had the bad permissions generated the file.
While there are certainly many things to admire about Rust, this is why I prefer Golang's "noisy" error handling. In golang that would be either:
feature_values, err := features.append_with_names(...)
And the compiler would have complained that this value of `err` was unused; or you'd write: feature_values, _ := features.append_with_names(...)
And it would be far more obvious that an error message is being ignored.(Renaming `unwrap` to `unwrapOrPanic` would probably help too.)
fvs, err := features.AppendWithNames(..)
if err != nil {
// this will NEVER break
panic(err)
}
Ultimately I don't think language design can be the sole line of defence against system failures; it can only guide developers to think about error casesPeople's biggest complaints about golang's errors:
1. You have to _TYPE_OUT_ what to do on EVERY.SINGLE.ERROR. SOO BOORING!
2. They clutter up the code and make it look ugly.
Rust is so much cleaner and more convenient (they say)! Just add ?, or .unwrap()!
Well, with ".unwrap()", you can type it fast enough that you're on to the next problem before it occurs to your brain to think about what to do if there is an error. Whereas, in golang, by the time you type in, "if err != nil {", you've broken the flow enough that now you're much more likely to be thinking, "Hmm, could this ever fail? What should we do if it does?" That break in flow is annoying, but necessary.
And ".unwrap()" looks so unassuming, it's easy to overlook on review; that "panic()" looks a lot more dangerous, and again, would be more likely to trigger a reviewer into thinking, "Wait, is it OK if this thing panics? Is this really so unlikely to happen?"
Renaming it `.unwrap_or_panic()` would probably help with both.
1. Culturally, using `unwrap` is an omerta to Rust developers in the same way `panic` is an omerta to Go devs;
2. In the Rust projects I've seen there is usually a linter rule forbidding `unwrap` so you can't use it in production
Unfortunately none of the meanings Wikipedia knows [1] seems to fit this usage. Did you perhaps mean "taboo"?
I disagree that "unwrap()" seems as scary as "panic()", but I will certainly agree to sibling commenters have a point when they say that "bar, _ := foo()" is a lot less scary than "unwrap()".
- it's literally written out that you're assuming it to be Ok
- there are no indications that the `_` is an error: it could very well be some other return value from the function. in your example, it could be the number of appended features, etc
That's why Go's error handling is indeed noisy: it's noise and you reduce noise by not handling errors. Rust's is terse yet verbose: if you add stuff it's because you're doing something wrong. You explicitly spelled out the error is being ignored.
Haven't used Go so maybe I'm missing some consideration, but I don't see how ", _" is more obvious than ".unwrap()". If anything it seems less clear, since you need to check/know the function's signature to see that it's an error being ignored (wouldn't be the case for a function like https://pkg.go.dev/math#Modf).
I have been saying for years that Rust botched error handling in unfixable ways. I will go to the grave believing Rust fumbled.
The design of the Rust language encourages people to use unwrap() to turn foreseeable runtime problems into fatal errors. It's the path of least resistance, so people will take it.
Rust encourages developers to consider only the happy path. No wonder it's popular among people who've never had to deal with failure.
All of the concomitant complexity--- Result, ?, the test thing, anyhow, the inability for stdlib to report allocation failure --- is downstream of a fashion statement against exceptions Rust cargo-culted from Go.
The funniest part is that Rust does have exceptions. It just calls them panics. So Rust code has to deal with the ergonomic footgun of Result but pays anyway for the possibility of exceptions. (Sure, you can compile with panic=abort. You can't count on it.)
I could not be more certain that Rust should have been a language with exceptions, not Result, and that error objects are a gross antipattern we'll regret for decades.
(You usually want to make a function infallible if you're using your noexcept function as part of a cleanup path or part of a container interface that allows for more optimizations of it knows certain container operations are infallible.)
Rust makes infallibility the syntactic default and makes you write Result to indicate fallibility. People often don't want to color their functions this way. Guess what happens when a programmer is six levels deep in infallible-colored function calls and does something that can fail.
.unwrap()
Guess what, in Rust, is fallible?
Mutex acquire.
Guess what you need to do often on infallible cleanup paths?
Mutex acquire.
Them calling unwrap on a limit check is the real issue imo. Everything that takes in external input should assume it is bad input and should be fuzz tested imo.
In the end, what is the point of having a limit check if you are just unwrapping on it
Using the question mark operator [1] and even adding in some anyhow::context goes a long way to being able to fail fast and return an Err rather then panicking.
Sure you need to handle Results all the way up the stack but it forces you to think about how those nested parts of your app will fail as you travel back up the stack.
[1]: https://doc.rust-lang.org/rust-by-example/std/result/questio...
The way they wrote the code means that having more than 200 features is a hard non-transient error - even if they recovered from it, it meant they'd have had the same error when the code got to the same place.
I'm sure when the process crashed, k8s restarted the pod or something - then it reran the same piece of code and crashed in the same place.
While I don't necessarily agree with crashing as business strategy, I don't think that doing anything other than either dropping the extra rules or allocating more memory - neither of which the original code was built to do (probably by design).
The code made the local hard assumption that there won't ever be more than 200 rules and its okay to crash if that count is exceeded.
If you design your code around an invariant never being violated (which is fine), you have to make it clear on a higher level that they did.
This isn't a Rust problem (though Rust does make it easy to do the wrong thing here imo)
That's not always foolproof, e.g. a freshly (re)started process doesn't have any prior state it can fall back to, so it just hard crashes. But restarts are going to be rate limited anyways, so even then there is time to mitigate the issue before it becomes a large scale outage
It may be that forcing handling at every call tends to makes code verbose, and devs insensitized to bad practice. And the diagnostic Rust provided seems pretty garbage.
There is bad practice here too -- config failure manifesting as request failure, lack of failing to safe, unsafe rollout, lack of observability.
Back to language design & error handling. My informed view is that robustness is best when only major reliability boundaries need to be coded.
This the "throw, don't catch" principle with the addition of catches on key reliability boundaries -- typically high-level interactions where you can meaningfully answer a failure.
For example, this system could have a total of three catch clauses "Error Loading Config" which fails to safe, "Error Handling Request" which answers 5xx, and "Socket Error" which closes the HTTP connection.
Rust has a lot of helpers to make it less verbose, even that error they demonstrate could've been written in some form `...code()?` with `?` helper that would have propagated the error forwards.
However I do acknowledge that writing Error types is boring sometimes so people don't bother to change their error types and just unwrap. But even my dinghy little apps for my personal use I do simple serach `unwrap` and make sure I have as few as possible.
The end result would've been the exact same if they "handled" the error: a bunch of 500s. The language being used doesn't matter if an invariant in your system is broken.
As usual: people problem, not a tech problem. In the last years a lot of strides have been made. But people will be people.
at some point machine would be better in coding because well machine code is machine instruction task
same like chess, engine is better than human grandmaster because its solvable math field
coding is no different
Might be worth noting that your description of chess is slightly incorrect. Chess technically isn't solved in the sense that the optimal move is known for any arbitrary position is known; it's just that chess engines are using what amounts to a fancy brute force for most of the game and the combination of hardware and search algorithm produces a better result than the human brain does. As such, chess engines are still capable of making mistakes, even if actually exploiting them is a challenge.
"chess engines are still capable of making mistakes", I'm sorry no
inaccurate yes but not mistake
The thing is that there is no known general objective criteria for "best" and "bad" moves. The best we have so far is based on engine evaluations, but as I said before that is because chess engines are better at searching the board's state space than humans, not because chess engines have solved chess in the mathematical sense. Engines are quite capable of misevaluating positions, as demonstrated quite well by the Top Chess Engine Championship [0] where one engine thinks it made a good move while the other thinks that move is bad, and this is especially the case when resources are limited.
The closest we are to solving chess are via tablebases, which are far from covering the entire state space and are basically as much of an exemplar of pure brute force as you can get.
> "chess engines are still capable of making mistakes", I'm sorry no
If you think chess engines are infalliable, then why does the Top Chess Engine Championship exist? Surely if chess engines could not make mistakes they would always agree on a position's evaluation and what move should be made, and therefore such an exercise would be pointless?
> inaccurate yes but not mistake
From the perspective to attaining perfect play an inaccuracy is a mistake.
[0]: https://en.wikipedia.org/wiki/Top_Chess_Engine_Championship
are you playing chess or not?????? if you playing chess then its oblivious how to differentiate bad move and best move
Yes it is objective, these thing called best move not without reason
"If you think chess engines are infalliable, then why does the Top Chess Engine Championship exist?"
to create better chess engine like what do even talking about here????, are you saying just because there are older bad engine that mean this thing is pointless ????
if you playing chess up to a decent level 1700+ (like me), you know that these argument its wrong and I assure you to learn chess to a decent level
up until that point that you know high level chess is brute force games and therefore solvable math
The key words in what I said are "general" and "objective". Yes, it's possible to determine "good" or "bad" moves in specific positions. There's no known method to determine "good" or "bad" moves in arbitrary positions, as would be required for chess to be considered strongly solved.
Furthermore, if it's "obvious" how to differentiate good and bad moves then we should never see engines blundering, right?
So (for example) how do you explain this game between Stockfish and Leela where Stockfish blunders a seemingly winning position [0]? After 37... Rdd8 both Stockfish and Leela think white is clearly winning (Stockfish's evaluation is +4.00, while Leela's evaluation is +3.81), but after 38. Nxb5 Leela's evaluation plummets to +0.34 while Stockfish's evaluation remains at +4.00. In the end, it turns out Leela was correct after 40... Rxc6 Stockfish's evaluation also drops from +4.28 to 0.00 as it realizes that Leela has a forced stalemate.
Or this game also between Stockfish and Leela where Leela blunders into a forced mating sequence and doesn't even realize it for a few moves [1]?
Engines will presumably always play what they think is the "best" move, but clearly sometimes this "best" move is wrong. Evidently, this means differentiating "good" and "bad" moves is not always obvious.
> Yes it is objective, these thing called best move not without reason
If it's objective, then why is it possible for engines to disagree on whether a move is good or bad, as they do in the above example and others?
> to create better chess engine like what do even talking about here????
The ability to create better chess engines necessarily implies that chess engines can and do make mistakes, contrary to what you asserted.
> are you saying just because there are older bad engine that mean this thing is pointless ????
No. What I'm saying is that your explanation for why chess engines are better than humans is wrong. Chess engines are not better than humans because they have solved chess in the mathematical sense; chess engines are better than humans because they search the state space faster and more efficiently than humans (at least until you reach 7 pieces on the board).
> up until that point that you know high level chess is brute force games and therefore solvable math
"Solvable" and "solved" are two very different things. Chess is solvable, in theory. Chess is very far from being solved.
[0]: https://www.chess.com/computer-chess-championship#event=309&...
[1]: https://www.chess.com/computer-chess-championship#event=309&...
In a fascinating coincidence, there is a tonyhart7 on both chess.com and lichess, and they have been banned for cheating on both websites.
But now after we are past that and it has a lot of mind share, I'd say it's time to start tightening the bolts.
Rust's unwrap isn't the same as std::expected::value. The former panics - i.e. either aborts the program or unwinds depending on context and is generally not meant to be handled. The latter just throws an exception that is generally expected to be handled. Panics and exceptions use similar machinery (at least they can depending on compiler options) but they are not equivalent - for example nested panics in destructors always abort the program.
In code that isn't meant to crash `unwind` should be treated as a sign saying that "I'm promising that this will never happen", but just like in C++ where you promise that pointers you deference are valid and signed integers you add don't overflow making promises like that is a necessary part of productive programming.
Panics aren't exceptions, any "panic" in Rust can be thought of as an abort of the process (Rust binaries have the explicit option to implement panics as aborts). Companies like Dropbox do exactly this in their similar Rust-based systems, so it wouldn't surprise me if Cloudflare does the same.
"Banning exceptions" wouldn't have done anything here, what you're looking for is "banning partial functions" (in the Haskell sense).
If anything, the "crash early" mentality may even be nefarious: instead of handling the error and keeping the old config, you would spin on trying to load a broken config on startup.
_In theory_ they could have used the old config, but maybe there are reasons that’s not possible in Cloudflare’s setup. Whether or not that’s an invariant violation or just an error that can be handled and recovered from is a matter of opinion in system design.
And crashing on an invariant violation is exactly the right thing to do rather than proceed in an undefined state.
At a previous job (cloud provider), we've had exactly this kind of issue, with exactly the same root cause. The entrypoint for the whole network had a set of rules (think a NAT gateway) that were reloaded periodically from the database. Someone rewrote that bit of plumbing from Python to Go. Someone else performed a database migration. Suddenly, the plumbing could not find the data, and pushed an empty file to prod. The rewrite lacked "if empty, do nothing and raise an alert", that the previous one had. I'll let you imagine what happened next :)
This .unwrap() sounds too easy for what it does, certainly much easier than having an entire try..catch block with an explicit panic. Full disclosure: I don't actually know Rust.
Any project has to reason about what sort of errors can be tolerated gracefully and which cannot. Unwrap is reasonable in scenarios you expect to never be reached, because otherwise your code will be full of all sorts of possible permutations and paths that are harder to reason about and may cascade into extremely nuanced or subtle errors.
Rust also has a version of unwrap called "expect" where you provide a string that logs why the unwrap occurred. It's similar, but for pieces of code that are crucial it could be a good idea to require all 'unwraps' to instead be 'expects' so that people at least are forced to write down a reason why they believe the unwrap can never be reached.
The config bug reaching prod without this being caught and pinpointed immediately is the strange part.
And, it took like over an hour between the problem started til my sites went down. That is just crazy.
Also wonder with a sharded system why are they not slow rolling out changes and monitoring?
Average Go code has much less panics than Rust has unwraps, which are functionally equivalent.
I'd prefer a loud crash over that.
In the original PHP code, all worked, only it didn't properly check for bots.
The new Rust code did a loud crash and took off half of the internet.
It's not in the type system, but it's idiomatic
it'd be kinda hard to amend the clippy lints to ignore coroutine unwraps but still pipe up on system ones. i guess.
edit: i think they'd have to be "solely-task-color-flavored" so definitely probably not trivial to infer
First multi-million dollar .unwrap() story.
Except maybe Haskell.
How many times can you truly prove that an `unwrap()` is correct and that you also need that performance edge?
Ignoring the performance aspect that often comes from a hat-trick, to prove such a thing you need to be wary of the inner workings of a call giving you a `Return`. That knowledge is only valid at the time of writing your `unwrap()`, but won't necessarily hold later.
Also, aren't you implicitly forcing whoever changes the function to check for every smartass dev that decided to `unwrap` at their callsite? That's bonkers.
If I were Cloudflare I would immediately audit the codebase for all uses of unwrap (or similar rust panic idioms like expect), ensure that they are either removed or clearly documented as to why it's worth crashing the program there, and then add a linter to their CI system that will fire if anyone tries to check in a new commit with unwrap in it.
So the point of unwrap() is not to prove anything. Like an assertion it indicates a precondition of the function that the implementer cannot uphold. That's not to say unwrap() can't be used incorrectly. Just that it's a valid thing to do in your code.
Note that none of this is about performance.
A function or a keyword would interrupt that and make it less tempting
Returning a Result by definition means the method can fail.
No more than returning an int by definition means the method can return -2.
Some call points to a function that returns an int will never return -2.
Sometimes you know things the type system does not know.
What? Returning an int does in fact mean that the method can return -2. I have no idea what your argument is with this, because you seem to be disagreeing with the person while actually agreeing with them.
What? No it doesn't.
fn square(n: i32) -> i32 {
n * n
}
This method cannot return -2.Though in this case it's more like knowing that the specific way you call the function in foo.rs will never get back a -2.
fn bar(n: i32, allow_negative: bool) -> i32 {
let new = n * 2;
if allow_negative || new >= 0 { new } else { 0 }
}
bar(x, false)If unwrap() were named UNWRAP_OR_PANIC(), it would be used much less glibly. Even more, I wish there existed a super strict mode when all places that can panic are treated as compile-time errors, except those specifically wrapped in some may_panic_intentionally!() or similar.
It's way less book-keeping with exceptions, since you, intentionally, don't have to write code for that exceptional behavior, except where it makes sense to. The return by value method, necessarily, implements the same behavior, where handling is bubbled up to the conceptually appropriate place, through returns, but with much more typing involved. Care is required for either, since not properly bubbling up an exception can happen in either case (no re-raise for exceptions, no return after handling for return).
That is the main reason why zig doesn’t have exceptions.
With return values, you can trivially ignore an exception.
let _ = fs::remove_file("file_doesn't_exist");
or
value, error = some_function()
// carry on without doing anything with error
In the wild, I've seen far more ignoring return errors, because of the mechanical burden of having type handling at every function call.This is backed by decades of writing libraries. I've tried to implement libraries without exceptions, and was my admittedly cargo-cult preference long ago, but ignoring errors was so prevalent among the users of all the libraries that I now always include a "raise" type boolean that defaults to True for any exception that returns an error value, to force exceptions, and their handling, as default behavior.
> In big projects you can basically never know when or how something can fail.
How is this fundamentally different than return value? Looking at a high level function, you can't know how it will fail, you just know it did fail, from the error being bubbled up through the returns. The only difference is the mechanism for bubbling up the error.
Maybe some water is required for this flame war. ;)
The great Raymond Chen wrote an excellent blog post on how this isn't really true, and how exceptions can lure programmers into mistakenly thinking they can just forget about failure cases.
Cleaner, more elegant, and harder to recognize https://devblogs.microsoft.com/oldnewthing/20050114-00/?p=36...
(ctrl-f for taskbar to skip to heart of his point.)
What he seems to be saying is that "obviously in C I would be checking the icon handle for being non-null so clearly error value handling is superior" but this is only obvious to someone knowing the API and checking values for validity has to be done in exception based code too. It's just that exception based code doesn't pretend that it cannot panic somewhere where you don't know. The default, better assumption for programming is that you don't know what this code is doing but it should just work. Unchecked exception handling is the best way to fit that paradigm, you should not have to care about every single line and what it does and constantly sort of almost obsessively check error values of all the APIs you ever use to have this false hope that it cannot panic because you did your duty. No, it can still panic and all this error checking is not helping you program better or more clearly or faster. It swamps the code with so many extra lines that it's practically double the size. All this makes it less clear and that is also what his post shows.
In practice, programmers don't find it easy to keep in mind that certain functions might throw. This is a real problem with unchecked exceptions and with C-style error codes that sloppy programmers might ignore entirely.
> [...] on which properties to set first can happen in any language
A carefully designed library using a statically typed functional language, especially a pure functional language, might sometimes be able to eliminate such hidden ordering bugs.
Rust used to have a feature to help the compiler detect invalid ordering of imperative operations, called typestates. This feature has since been mostly removed, though, as it saw little use. [0]
> isn't related at all to whether you use try-catch handling or error values as return codes
I guess Chen is assuming a reasonably diligent programmer who makes a habit of never discarding status/error values returned by functions. C++'s [[nodiscard]] can help ensure this.
(Of course, outside of C++, those aren't the only options. Idiomatic Haskell and Zig code forces the programmer to explicitly handle the possibility of an error. Same goes for Java's checked exceptions.)
> What he seems to be saying is that "obviously in C I would be checking the icon handle for being non-null so clearly error value handling is superior"
I don't think he's exactly arguing for the C-style approach, he's more just criticizing exceptions, especially unchecked exceptions. I agree the C-style approach has considerable problems.
> It's just that exception based code doesn't pretend that it cannot panic somewhere where you don't know.
With checked exceptions, you know precisely which operations can throw.
> Unchecked exception handling is the best way to fit that paradigm, you should not have to care about every single line and what it does and constantly sort of almost obsessively check error values of all the APIs you ever use to have this false hope that it cannot panic because you did your duty
You do need to care about every line, or your plausible-looking code is likely to misbehave when an exception occurs, as Chen's post demonstrates. Unchecked exceptions deprive the compiler of the ability to ensure good exception-handling coverage. There is no error-handling model that allows to programmer to write good code by pretending errors won't arise.
(I presume that by panic you mean throw an unchecked exception.)
try {
data = some_sketchy_function();
} catch (e) {
handle the error;
}
vs result = some_sketchy_function();
if let Err(e) = result {
handle the error;
}
Or better yet, compare the problematic cases where the error isn't handled: data = some_sketchy_function();
vs data = some_sketchy_function().UNWRAP_OR_PANIC();
In the former (the try-catch version that doesn't try or catch), the lack of handling is silent. It might be fine! You might just depend on your caller using `try`. In the latter, the compiler forces you to use UNWRAP_OR_PANIC (or, in reality, just unwrap) or `data` won't be the expected type and you will quickly get a compile failure.What I suspect you mean, because it's a better argument, is:
try {
sketchy_function1();
sketchy_function2();
sketchy_function3();
sketchy_function4();
} catch (e) {
...
}
which is fair, although how often is it really the right thing to let all the errors from 4 independent sources flow together and then get picked apart after the fact by inspecting `e`? It's an easier life, but it's also one where subtle problems constantly creep in without the compiler having any visibility into them at all.There is already a try/catch around that code, which produces the Result type, which you can presumptuously .unwrap() without checking if it contains an error.
Instead, one should use the question mark operator, that immediately returns the error from the current function if a Result is an error. This is exactly similar to rethrowing an exception, but only requires typing one character, the "?".
React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED comes to mind. I did have to reach to this before, but it certainly works for keeping this out of example code and other things like reading other implementations without the danger being very apparent.
At some point it was renamed to __CLIENT_INTERNALS_DO_NOT_USE_OR_WARN_USERS_THEY_CANNOT_UPGRADE which is much less fun.
Not for this guy:
Also, exception handling is hard and lame. We don't need exceptions, just add a "match" block after every line in your program.
I'm also not sure what you're getting at with the comment about exception handling being lame. I think the ML/Haskell inspired model that Rust uses of having a parameterized Result type for fallible operations is generally better than exceptions for a variety of reasons (although maybe better Exception semantics could help with some of this), but what does this have to do with match blocks?
Undoubtedly yes.
> ...but what does this have to do with match blocks?
You tell me. You're the one advocating for placing one after every single function call.
Rust compiler is a god of sorts, or at least a law of nature haha
Way to comment and go instantly off topic