Ruby on Rails and the importance of being stupid

I read the moderation policy where it's suggested that reviews of the post are not valued. However I feel an obligation to point out the factual errors in this post. There are dozens of nonsensical assertions and could potentially be very misleading to anyone who doesn't understand Rails or web development in general.

My first general critique is that there is no real comparison going on here. It says the business guy called up Microsoft and they recommended buying a bunch of hardware, but there's no discussion of who developed the site or how they got up and running. There's no discussion of the price of the hardware, which clearly looks to be well into the 5-figures, or the price of the fiber connection at home, system administration, backups, etc. To get into some specifics:

The programmer, being way smarter than the swaptree idiot, decided to use Ruby on Rails, the latest and greatest Web development tool. As only a fool would use obsolete systems such as SQL Server or Oracle, our brilliant programmer chose MySQL.

This is a caricature of an "MIT Genius" that doesn't jive with reality. Anyone who was actually that smart would know better than to dismiss Oracle in favor of MySQL. They may prefer using Ruby on Rails and be more productive than if they used .NET, but they wouldn't go around calling people idiot's for such superficial reasons. Therefore you're not describing an actual genius, just someone who thinks they are a genius, but is actually a fool. Using such a person as the basis for an argument of why Microsoft's recommendations are better than Rails is intellectually dishonest.

How do you get scale and reliability? Start by virtualizing everything. The database server should be a virtual “slice” of a physical machine, without direct access to memory or disk, the two resources that dumb old database administrators thought that a database management system needed.

The reason that virtualization is done in the web deployment world is so that you can get access to fast and reliable hardware if you need less than the cost of the full resources. A degenerate example would be that if your capacity requirements could be met by a 250mhz processor, you would get better throughput by using 1/8th of a 2Ghz server. The reasoning for this is that the vast majority of sites don't need dedicated hardware, which you seem to imply as being cheaper, but clearly it is not if you are leasing server capacity.

Ruby and Rails should run in some virtual “slices” too, restricted maybe to 500 MB or 800 MB of RAM. More users? Add some more slices!

I'm going to assume you are talking about EngineYard here, since that is the managed Rails hosting provider I am most familiar with and is somewhat inline with your pricing figures below. First, the 500 or 800 MB is just a base amount of RAM that is good for most small Rails apps. When that starts to run out, the solution is NOT to add more slices, you simply commission more RAM. EY can do this without even restarting your slice. Incidentally you can also commission more CPU if you need it. The reason they start with two production slices is for redundancy. One of your slices goes down for some reason? That's okay because there's a backup.

The cost for all of this hosting wizardry at an expert Ruby on Rails shop? $1100 per month.

What you described above is a very poor description of what you are paying for at a managed hosting provider like EngineYard. I will describe managed hosting in a minute. But to compare to your unmanaged Microsoft example, I currently pay $8/month for a 256MB of unmanaged hosting that is plenty to server significant traffic on a well optimized app. This is an order of magnitude less than the Verizon FiOS line alone, and provides much better network connectivity (ie. multiple tier-1 connections, lower latency to more endpoints).

With managed hosting at EngineYard, you are not just paying for the server. You are basically paying for a fulltime system administrator. They have people all over the world ready to help you at a moment's notice any time of day or night. They proactively monitor your server and contact you if they notice any abnormalities. They provide a large suite of finely tuned recipes and standard software installations that they can install on a moment's notice, and will tie into their monit-based server monitoring setup. The individual machines in the cluster are optimized for their specific tasks. The network hardware and topography is optimized for real world usage scenarios. They continuously tune the machines for throughput and move clients around to avoid bottlenecks. They will even take significant steps towards helping the client tune their own application, above and beyond their contractual obligations for server adminstration. In short, you've completely ignored 95% of what they do, and painted it as extremely expensive without even providing a comparison against the overhead costs of buying and managing your own servers.

For the last six months, my friend and his programmer have been trying to figure out why their site is so slow. It could take literally 5 minutes to load a user page. Updates to the database were proceeding at one every several seconds. Was the site heavily loaded? About one user every 10 minutes.

If a request on an unloaded server takes 5 minutes to load, and the programmer can not figure it out in 6 months, then that programmer is incompetent plain and simple. Laying this at the feet of Rails is just plain ridiculous.

I began emailing the sysadmins of the slices. How big was the MySQL database? How big were the thumbnail images? It turned out that the database was about 2.5 GB and the thumbnails and other stuff on disk worked out to 10 GB. The servers were thrashing constantly and every database request went to disk. I asked “How could this ever have worked?” The database “slice” had only 5 GB of RAM. It was shared with a bunch of other sites, all of which were more popular than mitgenius.com.

Are you implying that you need enough RAM to keep the entire database in physical memory? That is patently false. In a worst case scenario, yes it could take performance down quite a bit, but disc access is not nearly as slow as implied above. I've served tons of sites on pure shared hosting (not even virtualized) with much higher load and orders of magnitude better performance than you are describing here.

How could a “slice” with 800 MB of RAM run out of memory and start swapping when all it was trying to do was run an HTTP server and a scripting language interpreter? Only a dinosaur would use SQL as a query language. Much better to pull entire tables into Ruby, the most beautiful computer language ever designed, and filter down to the desired rows using Ruby and its “ActiveRecord” facility.

This is nonsense Philip. Please don't take this as an ad-hominem, because there's no other way to put this. What you described here is 100% pure nonsense. ActiveRecord, like any ORM component, abstracts away some SQL in order to simplify common database interactions. The lion's share of ActiveRecord code is all about constructing efficient SQL. When you are developing with Rails it shows you all the SQL running the development log, and you can quickly spot n+1 errors. If you need something more efficient, it offers plenty of levels of access right down to pure SQL.

In reviewing email traffic, I noticed much discussion of “mongrels” being restarted. I never did figure out what those were for ... What am I missing? To my inexperienced untrained-in-the-ways-of-Ruby mind, it would seem that enough RAM to hold the required data is more important than a “mongrel”. Can it be that simple?

I'm shocked that a programmer would speculate so wildly as to say something like this. A mongrel is an application server. I don't understand what you seem to think it is, but it's simply the process serving up Rails requests to the web server and passed through to the client. Typically you run more than one so you can serve multiple requests concurrently, but for a well-optimized app usually no more than 3 or 4 are necessary. Rails uses a non-threaded share-nothing architecture which means you can scale horizontally across unlimited servers. Note that I am not talking about virtualized servers. I'm talking about when you have more traffic than the biggest server in the world can handle, Rails will let you scale out painlessly at the web server level until your database can not be served by a single box. At that point you need to look at database sharding, or alternative data stores using Map-Reduce or some other scalable database solution.

None of this is to say Rails doesn't have its warts. Ruby is memory hungry, leaky, and relatively slow. Deployment has traditionally been very complicated compared to something like PHP (although it's much improved with Phusion Passenger aka. mod_rails for Apache/Nginx). There are many reasons why you would be well-advised not to use Rails, however this article doesn't touch on any of them. Rails, just like Oracle, .NET, Java or many other technologies is a proven platform with pros and cons. In this article you pit an apparently competent programmer developing swaptree.com against what can be described as nothing less than a complete bumbling idiot using Rails. You insist the cost of Rails is high without any justification or direct comparison against the costs of swaptree.com.

I've read your blog in the past and found it to be pretty interesting, which is why I've taken the time to write this response, and suggest politely that you retract this article.

Seems to me the main problem is that his "MIT trained" friend had no experience building a scalable web service. He would've botched it up in PHP, Python, Java, whatever. There's nothing about his main mistakes- running your database on a shared server, naive (ab)use of SQL- that is unique to Rails.

And this bit: "pull entire tables into Ruby, the most beautiful computer language ever designed, and filter down to the desired rows using Ruby and its “ActiveRecord” facility" is completely incorrect and makes it obvious Philip Greenspun knows less than nothing about what he's ranting about.

This is hardly a new idea. The fact that a bad programmer used Ruby on Rails, or Django, or PHP, or C++ to write bad code and implement it on a shoddy system is no reflection on anything. This is essentially a story of someone who took good advice for a hosting environment, and someone who took bad advice for a hosting environment.

Learn your tool, don't buy into the hype. Make sure you are aware of the reason behind everything that you do (because they I read it on a blog is not a reason). Don't be a bad programmer.

That will do EXACTLY the opposite of what he wants. Give it a swap file and unneeded parts of memory will be swapped out to disk, freeing memory for use as a file system cache.

There is _never_ a reason to configure a system without a swap file - except if it's a laptop and you don't want the disk to spin up.

Don't want the system to use swap space? Don't allocate more memory than you have (or buy more memory), but disabling the swapfile never helps. In some cases disabling it doesn't hurt anything, but it never helps.

Now, I disagree about keeping it in your basement, at least once you have users on it. co-locating a 2 cpu box is going to cost you around $100/month, and you get much better connectivity than DSL at that price. DSL isn't much cheaper, if you get a reasonable uplink speed (at least around here) and I don't know about you, but the power in my house (I live in California) isn't exactly /enterprise grade/.

But yeah, I see a largely untapped market for renting high-ram otherwise-cheap servers; I've rented out one 32GiB server with a bunch of drives (and some slow CPUs) to a guy for $1200 setup and $175/month... once my next load of servers is up and built, I'm thinking about chasing that business model again, if I can build the servers faster than I get new vps signups, anyhow.

"Not helping matters was the fact that the sysadmins found some public pages that went into MySQL 1500 times with 1500 separate queries (instead of one query returning 1500 rows)."

Looks like someone forgot to use :include on some finders. Let's say you have 1000 users with an address each. This will produce 1000 SQL queries:

  User.all.each do |user|
    p user.address.street_name
  end

  User.all(:include =>:address).each do |user|
    p user.address.street_name
  end

It seems to me they didn't really know what setup they were running if they are wondering what a 'mongrel' is.

I hope they weren't trying to serve the site on only a couple of mongrels.

My first thoughts,

Benchmark a bit, use a tool like fiveruns to find out what's really happening. I wonder what the real bottleneck is.

Of course they shouldn't use a shared database server, but I'm wondering if they are they using caching? What I'm reading about that site I think they could cache the hell out of it. I've only used the builtin Rails cache methods but a tool like memcached should help out on all the database requests.

I'd expect similarly disastrous results had he used the same 100% ignorant approach to any other language or platform.

I guess some things don't change (much)

Greenspun's Tenth Rule of Programming: "Any sufficiently complicated C or Fortran program contains an ad-hoc, informally-specified bug-ridden slow implementation of half of Common Lisp."

right now i use a LIMIT of 100 to minimize sql queries, and memory. i might try going to 1000 rows or about 10k in data, but in my experience when the DB has to return that much data you are not really gaining that much.

what do you think? any other optimizations i should look to?

The altrernative approach is about using mix of technologies and tools to complete actual tasks. Today's linux distributions, which are actually mix (if not mess) of applications and tools written on every possible scripting language is a good example.

In the area of web-development the same approach works the same way - you can build different [sub]services and [sub]systems with different tools which are more appropriate for some particular task. REST-JSON-Key-Value-Storage here, classic SQL back-end there and so on.