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How Discord Scaled Elixir to 5M Concurrent Users

blog.discordapp.com

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Re: How Discord Scaled Elixir to 5M Concurrent Users

#71

Post by quaunaut »

jhgg wrote: post #64
jmcgough wrote: post #47

Earlier quoted context omitted.

It became open source in the 90s. It's been used by several high-traffic sites/apps to support chat clients (Riot Games, WhatsApp, and I think Fetlife), but outside of that has seen very little adoption. I think it's a lot harder to sell people on a language that looks syntactically unintelligible to a lot of web developers. Most people I know working with Elixir now are/were Rubyists, so it's easy for them to make t…

Elixir/Erlang is great, but in addition to knowing the language, there is a huge library of tools within OTP/ERTS that you need to understand to effectively use it and skills learned from other languages don't map too well to Erlang/Elixir as they would to other languages (like going from Python to Go for example). In addition to learning OTP, you also have to learn how a functional language works if you're not famil…

I mean, personally I'm using Elixir more for the language itself than OTP. I have a basic knowledge of OTP now after using the language for 2 years, but FP was my main reason for coming and staying, which for me has been the real fun of it.

Then again, FP for me was not difficult at all, and actually made several of the issues I had with my Ruby code not being expressive/obvious enough, or difficulty in composition, disappear overnight.

Re: How Discord Scaled Elixir to 5M Concurrent Users

#72

Post by _asummers »

jaequery wrote: post #18

Anyone know if Phoenix/Elixir have something similar to Ruby's bettererror gem? I see Phoenix has a built-in error stack trace page which looks like a clone of bettererror but it doesn't have the real-time console inside of it. Also, I wish they had a ORM like Sequel. These two are really what is holding me back from going full in on Elixir. Anyone can care to comment on this?

Ecto is hands down the best "ORM" I've used. At no point has it ever gotten in the way of us dynamically creating queries on the fly, just following the Ecto internals (not recommended, but totally doable) and has an extremely expressive syntax. The team behind it has been rolling out new features and are extremely responsive to requests on the mailing list. I encourage you to give it a chance.

The mental shift is that "schemas" are not objects in an ORM sense, but instead are just data, or views over data. The functions come from taking in data or a Changeset and manipulating those, versus calling a function on a class.

As far as errors, Elixir 1.4.5 has much better error messages, specifically printing the args to crashes and such, and OTP 20/ Elixir 1.5 should drastically improve Dialyzer error messages. I am not a Ruby guy, so perhaps you can say what you feel is missing from Elixir's messages and how the Ruby gem improves it. Also you can literally inspect running state on the fly with the BEAM tooling, so the need for things like debuggers goes down.

Re: How Discord Scaled Elixir to 5M Concurrent Users

#73

Post by quaunaut »

danso wrote: post #10

According to Wikipedia, Discord's initial release was March 2015. Elixir hit 1.0 in September 2014 [0]. That's impressively early for adoption of a language for prototyping and for production. [0] https://github.com/elixir-lang/elixir/releases/tag/v1.0.0

If I remember right, they were using Erlang at the beginning, and moved slowly to Elixir as they got more comfortable, and the ecosystem built up around them.

Re: How Discord Scaled Elixir to 5M Concurrent Users

#74

Post by _asummers »

geogriffin wrote: post #66
janekm wrote: post #46

Earlier quoted context omitted.

I read it a little differently. The whole article is about how Erlang/Elixir fails at its core reason for existence (fast message passing between distributed processes) and all the complicated work-arounds they had to implement to avoid actually using this core feature of Erlang.

I'm an erlang fan but I wouldn't claim message passing is "fast" in the sense that you might be thinking of (though copying data does have some GC and CPU cache performance benefits that are harder to reason about.) There's no magic in Erlang; copying data is copying data. The benefits of Erlang lie elsewhere, and I've heard Joe Armstrong, when asked about BEAM performance, say something along the lines of "why do yo…

With OTP20, copying data isn't always necessary anymore :)

Re: How Discord Scaled Elixir to 5M Concurrent Users

#75

Post by lojack »

janekm wrote: post #46
iagooar wrote: post #19

This writeup make me even more convinced of Elixir becoming one of the large players when it comes to hugely scaling applications. If there is one thing I truly love about Elixir, it is the easiness of getting started, while standing on the shoulders of a giant that is the Erlang VM. You can start by building a simple, not very demanding application with it, yet once you hit a large scale, there is plenty of battle-p…

I read it a little differently. The whole article is about how Erlang/Elixir fails at its core reason for existence (fast message passing between distributed processes) and all the complicated work-arounds they had to implement to avoid actually using this core feature of Erlang.

I read it as "Elixir was a good choice, but it isn't a silver bullet." The fact that they spend most of the article talking about the gotcha's makes their statement about going with Elixir given the opportunity to repeat more favorable in my mind.

Re: How Discord Scaled Elixir to 5M Concurrent Users

#77

Post by _asummers »

rubyn00bie wrote: post #58
toolz wrote: post #37

Earlier quoted context omitted.

I think the next big push in elixir is tooling around metrics. Once there are hard numbers to market to non-techies I think we'll see a large shift towards elixir.

Just look for Erlang tools, there are loads available. The only problem with Elixir right now is sometimes people forget to look at Erlang for already solved problems/tooling/etc. Erlang/BEAM has been alive and well in some very serious mission critical applications for 20 years. Just look at how telecoms used it (its origin).

We use Elixir at work, and Erlang tools have a bit of a discovery problem. You can peek at download counts on Hex, if the author uses it, but that doesn't take account CI systems and such that inflate DL counts, or GitHub only repos that are not on Hex (see things like e.g. shell history prior to OTP20).

That said, when there is no Elixir tool to do what I want, the very next thing I do is look for an Erlang tool, and there is often one that gets me most of the way to where I need to go. Wrapper libs are nice sugar, but they're almost always unnecessary when you can just call Erlang directly (String v charlist conversions notwithstanding!).

Re: How Discord Scaled Elixir to 5M Concurrent Users

#78

Post by pmarreck »

rdtsc wrote: post #5

Good stuff. Erlang VM FTW! > mochiglobal, a module that exploits a feature of the VM: if Erlang sees a function that always returns the same constant data, it puts that data into a read-only shared heap that processes can access without copying the data There is a nice new OTP 20.0 optimization - now the value doesn't get copied even on message sends on the local node. Jesper L. Andersen (jlouis) talked about it in h…

I would like to subscribe to your newsletter

Seriously, though, I might need your services in the future, if you're available.

Also, I'm pretty sure the security of your career is pretty guaranteed at this point lol (looking at Indeed data, interest in Elixir has risen 20fold in the past 3 years and the slope of that line is far steeper than all other languages in that space)

Re: How Discord Scaled Elixir to 5M Concurrent Users

#79

Post by pmarreck »

nichochar wrote: post #54
ConanRus wrote: post #35

I do not see there any Elixir specific, it is all basically Erlang/Erlang VM/OTP stuff. When you using Erlang, you think in terms of actors/processes and message passing, and this is (IMHO) a natural way of thinking about distributed systems. So this article is a perfect example how simple solutions can solve scalability issues if you're using right platform for that.

You're right. Elixir doesn't pretend to do anything except make using the wonderful erlang VM/OTP stuff easier. The VM is an absolute marvel of engineering, and it's insane to me that it doesn't have more adoption yet in big tech companies. My best theory is that engineers in top engineering companies are actually not the best engineers but simply career engineers that learn one skill (python/java/C++) and then expla…

> and it's insane to me that it doesn't have more adoption yet in big tech companies.

elixir (and winter) is coming

> My best theory is that engineers in top engineering companies are actually not the best engineers but simply career engineers that learn one skill (python/java/C++) and then explain to every employer that this technology is the best for the problem they have, over and over again.

you conflated "top" with "large".

Re: How Discord Scaled Elixir to 5M Concurrent Users

#80

Post by pmarreck »

ShaneWilton wrote: post #9

Thanks for putting this writeup together! I use Elixir and Erlang every day at work, and the Discord blog has been incredibly useful in terms of pointing me towards the right tooling when I run into a weird performance bottleneck. FastGlobal in particular looks like it nicely solves a problem I've manually had to work around in the past. I'll probably be pulling that into our codebase soon.

Note that Erlang 20 may have solved the problem that FastGlobal tries to fix (that of not copying large amounts of data unnecessarily)
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