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Why Discord is switching from Go to Rust

blog.discordapp.com

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Re: Why Discord is switching from Go to Rust

#101

Post by nemo1618 »

_ph_ wrote: post #87
flafla2 wrote: post #16

> After digging through the Go source code, we learned that Go will force a garbage collection run every 2 minutes at minimum. In other words, if garbage collection has not run for 2 minutes, regardless of heap growth, go will still force a garbage collection. > We figured we could tune the garbage collector to happen more often in order to prevent large spikes, so we implemented an endpoint on the service to change…

With recent Go releases, GC pauses have become neglible for most applications. So this should not get into your way. However, it can easily tweaked, if needed. There is runtime.ForceGCPeriod, which is a pointer to the forcegcperiod variable. A Go program, which really needs to change this, can do it, but most programs shouldn't require this. Also, it is almost trivial to edit the Go sources (they are included in the…

runtime.ForceGCPeriod is only exported in testing, so you wouldn't be able to use it in production. But as you said, the distribution could easily be modified to fit their needs.

Re: Why Discord is switching from Go to Rust

#102

Post by dragonwriter »

giancarlostoro wrote: post #94
nickserv wrote: post #76

Earlier quoted context omitted.

It's just an example of something that the Go team took a decision on, and won't allow you to change. I mean, even Python lets you choose. I don't really have a problem with it however, even if I do prefer spaces.

Python chose spaces a la PEP8 by the way.

PEP8 isn't a language requirement, but a style guide. There are tools to enforce style on Python, but the language itself does not.

Re: Why Discord is switching from Go to Rust

#103

Post by marrs »

ptrincr wrote: post #24
flafla2 wrote: post #16

> After digging through the Go source code, we learned that Go will force a garbage collection run every 2 minutes at minimum. In other words, if garbage collection has not run for 2 minutes, regardless of heap growth, go will still force a garbage collection. > We figured we could tune the garbage collector to happen more often in order to prevent large spikes, so we implemented an endpoint on the service to change…

You are able to disable GC with: GOGC=off As someone mentions below. More details here: https://golang.org/pkg/runtime/

How does Go allow you to manage memory manually? Malloc/free or something more sophisticated?

Re: Why Discord is switching from Go to Rust

#104

Post by _ph_ »

abraxas wrote: post #65
flafla2 wrote: post #16

> After digging through the Go source code, we learned that Go will force a garbage collection run every 2 minutes at minimum. In other words, if garbage collection has not run for 2 minutes, regardless of heap growth, go will still force a garbage collection. > We figured we could tune the garbage collector to happen more often in order to prevent large spikes, so we implemented an endpoint on the service to change…

Seems like Go is more suitable for the “spin up, spin down, never let the GC run” kind of scenario that is being pushed by products like AWS Lambda and other function as a service frameworks.

Why do you think it is? Go has a really great gc which mostly runs in parallel to your program with gc stops only in the doman of less than milliseconds. Discord ran into a corner case where they did not create enough garbage to trigger gc cycles, but had a performance impact due to scheduled gc cycles for returning memory to the OS (which they wouldn't need to do either).

Re: Why Discord is switching from Go to Rust

#105

Post by dilyevsky »

kardianos wrote: post #23

I'm glad they found a good solution (rust) to solve their problem! Also note this was with Go1.9. I know GC work was ongoing during that time, I wonder if this time of situation would still happen?

LOL that should’ve been at the top. The improvement in gc between 1.9 and 1.12 is absolutely massive. They could’ve just upgraded go toolchain.

Re: Why Discord is switching from Go to Rust

#106

Post by tasty_freeze »

andai wrote: post #66
nickserv wrote: post #57

Earlier quoted context omitted.

This is in line with Go's philosophy, they try to keep the language as simple as possible. Sometimes it means an easy thing in most other languages is difficult or tiresome to do in Go. Sometimes it means hard-coded values/decisions you can't change (only tabs anyone?). But overall this makes for a language that's very easy to learn, where code from project to project and team to team is very similar and quick to und…

Offtopic but what are you missing when you have to use tabs instead of spaces? I can understand different indentation preferences but I can change the indentation width per tab in my editor. And then everyone can read the code with the indentation they prefer, while the file stays the same.

> everyone can read the code with the indentation they prefer, while the file stays the same.

Have you ever worked in a code base with many contributors that changed over the course of years? In my experience it always ends up a jumble where indentation is screwed up and no particular tab setting makes things right. I've worked on files where different lines in the same file might assume tab spacing of 2, 3, 4, or 8.

For example, say there is a function with a lot of parameters, so the argument list gets split across lines. The first line has, say, two tabs before the start of the function call. The continuation line ideally should be two tabs then a bunch of spaces to make the arguments line up with the arguments from the first line. But in practice people end up putting three or four tabs to make the 2nd line line up with the arguments of the first line. It looks great with whatever tab setting the person used at that moment, but then change tab spacing and it no longer is aligned.

Re: Why Discord is switching from Go to Rust

#107

Post by heinrich5991 »

reificator wrote: post #59
JBReefer wrote: post #21

Earlier quoted context omitted.

Go always feels like an amateur language to me, I’ve given up on it. This feels right in line - similar to the hardcode GitHub magic.

I could be wrong, but I don't believe there is "hardcoded[d] GitHub magic". IIRC I have used GitLab and Bitbucket and self-hosted Gitea instances the same exact way, and I'm fairly sure there was an hg repo in one of those. Don't recall doing anything out of the ordinary compared to how I would use a github URL.

There are a couple of hosting services hardcoded in Go. I believe it was about splitting the URL into the actual URL and the branch name.

Re: Why Discord is switching from Go to Rust

#109

Post by onebot »

jhgg wrote: post #27
mperham wrote: post #20

Better title: "One Discord microservice with extremely high traffic is moving to Rust"

This is one of multiple, we did not blog about this one, but switching a Python http service for analytics ingest that was purely CPU bound to rust resulted in a 90% reduction in compute required to power it. However, that's not too interesting because it's known that Python is slow haha. We have 2 golang services left, one of them has a rewrite in rust in PR as of last week (as a fun side project an engineer wanted…

Think replacing elixir with Rust would ever be a consideration? Rust isn't there yet, but if you are NIF'ing a bunch of stuff, seems like it could make sense at some point?

Re: Why Discord is switching from Go to Rust

#110

Post by marsokod »

giancarlostoro wrote: post #94
nickserv wrote: post #76

Earlier quoted context omitted.

It's just an example of something that the Go team took a decision on, and won't allow you to change. I mean, even Python lets you choose. I don't really have a problem with it however, even if I do prefer spaces.

Python chose spaces a la PEP8 by the way.

You can use tabs to indent your python code. Ok, you might be lynched if you share your code but as long as you don't mix tabs and spaces, it is fine.
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