Why Discord is switching from Go to Rust

Non programmer here, but would it make sense to add a keyword (or flag) to Go to manually allocate a piece of memory (ie not use GC). That way, for some use cases, you could use avoid GC for the critical path. Then when GC happened, it could be very fast as there would be far less to pause-and-scan (in this use case example). Obviously this would have to be optional and discouraged...but there seems to be no way to write an intensive real-time app with a GC based language. (again non-programmer that is writing this to learn more ;-)

Tokio author here (mentioned in blog post). It is really great to see these success stories.

I also think it is great that Discord is using the right tool for the job. It isn't often that you need the performance gains that Rust & Tokio so pick what works best to get the job done and iterate.

There are two things you'd have to do at the same time that make this complicated:

- You'd have to ensure that your large data structure gets allocated entirely within the special region. That's simple enough if all you have is a big array, but it gets more complicated if you've got something like a map of strings. Each map cell and each string would need to get allocated in the special region, and all of the types involved would need new APIs to make that happen.

- You'd have to ensure that data structures in your special region never hold references to anything outside. Since the whole point of the region is that the GC doesn't scan it, nothing in the region will be able to keep anything outside the region alive. Any external references could easily become dangling pointers to freed memory, which is the sort of security vulnerability that GC itself was designed to prevent.

All of this is doable in theory, but it's sufficiently difficult, and it comes with sufficiently many downsides, that it makes more sense for a project with these performance needs to just use C or Rust or something.

"We want to make sure Discord feels super snappy all the time" is hilarious coming from a program that is infamous for making you read 'quirky' loading lines while a basic chat application takes several seconds to start up.

Don't really know about Go versus Rust for this purpose, but don't really care because read states (like nearly everything that makes Discord less like IRC) is an anti-feature in any remotely busy server. Anything important enough that it shouldn't be missed can be pinned, and it encourages people to derail conversations by replying out of context to things posted hours or days ago.

I don't see why that's hilarious. Lots of programs take a second or two to load and it only happens once on boot for me. "Read states" is just discord telling you which channels and servers you have unread messages in