Comment by mikem170 | Hacker News Reader

Comment by mikem170 | Hacker News Reader

Parent Full thread

>I don't think that understanding your dependencies is a reasonable criterion

I agree, I've never gone as far as reviewing/understanding source code for all the libraries I use. Might be nice to have the time ;-)

>it is _good_ to black box things

I trust that you are talking about using other people's black boxes, as opposed to reinventing your own?

I would say that there is some element of risk in trusting a library that someone else made, particularly over time as systems need to be upgraded. Will there be problems during or after an upgrade? Is the whole dependency chain upgradable? Will the upgrades work on all operating systems in use? Are there relevant corporate policies and/or whitelists that might interfere with or slow down upgrades?

Personally I pay close attention to the dependencies I'm using in a project, especially long-lived projects. I find it super aggravating when something I've tested and deployed breaks a couple years later after routine upgrades due to some kind of drift problem to do with a dependency.

How much benefit am I getting by using the library? Best is using base library that comes with the language. Next best would be a well maintained third-party library with a good reputation in the community, one that doesn't have too many dependencies itself. Am I happy with the api of the library, and its documentation? Is is reasonably easy to approach given its functionality? Is the library available as a package in the operating systems I'm working with? How long has it existed? How stable has it been over time? Is the library a good fit for what I am doing, or do I have to bend my code to use it as intended? Do I have multiple libraries to choose from? Can I use the library in such a way that I can change my mind later?

I think there is value in trying to minimize the use of external libraries, up to a point.

"Might be nice to have the time ;-)"

It's not about having the time, but -making- the time. For the most part we simply do not prioritize looking into the source code of the libraries we use, to any meaningful degree. (I'm guilty of this for sure). Hence things like leftpad and the many other instances of dependency controversies.

In an ideal world we [and our employers] would put emphasis on inspecting the huge amounts of code we pull in and allocate time for it.

How would you ever have time to write new code?

if you don't write new code, you also don't pull in new dependencies, and have time start new code ;) And cost to dependencies makes you optimize what you pull in.

(Cost to dependencies doesn't have to be just review time. E.g. in my embedded software projects, the calculus for "will we need to update this" looks very differently than it would for your typical web app. And extracting interesting bits from libraries and including only that into the main project is maybe more common, reducing the surface of a dependency - which would be a bad idea if you expect frequent changes, but these projects typically don't)

I have plenty of time to write new code. I write code (often lots of code) every single day.

I don't mind dependencies, but I won't use them for anything mission-critical, unless I spend a great deal of time vetting the dependency. That might mean auditing the code, but more often, it is auditing the coder.

The main thing is, is that we need to really think about anything we add to our precious project, from outside. In my experience, people seem to be alarmingly casual about this.

Good results can be building very big systems, in a very short period of time, using very few resources, and everything works great.

Bad results can be building very big systems, in a very short period of time, using very few resources, and everything works great.

Until it doesn't.

For example, an upgrade introduces things like renamed CSS hooks, or introduces thread safety issues. A PR isn't vetted properly, and license-problematic code, or malicious code is introduced into the system. Maybe the author has a car accident, and can't manage the library anymore. Maybe a dependency down the chain gets taken over by someone that uses...let's say "solarwinds123" as the password for their CI server, and they get pwn3d, but, since they are buried three levels down, no one in the main dependency realizes what happened, and so on. Maybe you get to a point where you outgrow your backend, and need to change to a more robust or secure backend, but the SDK you are using has you addicted to the initial backend that you selected, when the project was still in the crib, etc.

It should not be a casual decision.

In my original post, I talk about having to yank a dependency.

It was a phone-number parser. If you know anything about phone numbers, parsing them is non-trivial. Apple has a built-in utility (a scanner for URLs, phone numbers, addresses, etc.), but that is not as effective as the parser I imported, which had a fairly good pedigree. I looked at the code, and checked out the author, and it looked good.

The issue that I encountered was most likely (can't be sure) a thread-safety issue. I ran parses in non-main threads, and noticed memory leaks, and random crashes.

I do not suffer memory leaks or crashes of any kind, in my apps, so it had to go.

Phone number parsing wasn't a dealbreaker. Because it was a dependency, its application was fairly encapsulated (I always encapsulate external dependencies -just plain old horse sense), so I can go back and maybe reinstate it (if I can fix the issue, or use it only in main threads), or add a different one in the future. In the meantime, the Apple tool is fine for my development.

The backend for the project, on the other hand, is mission critical, so I wrote it myself. I am not a backend expert, but there are some things that I needed assurance on, that no backend engine can give me. It's highly encapsulated and layered, so future efforts can replace it. I can tell you that whatever it gets replaced with, will need to meet my exacting criteria.

My current project has one external dependency (it has quite a few, that I wrote): A keychain abstraction. It's very simple, and is actively maintained. I've used it in other projects for years.

The dependencies that I wrote are pretty intense; even the small ones. The testing code dwarfs the implementation code in all of them. One of them is an SDK for a pretty vast system, where I was the original architect, but has since passed on to a new team that has my complete confidence; so I guess you could also call that an "external" dependency, but one that I know very, very well.

Reply on news.ycombinator.com