Hacker News new | ask | show | jobs
by Laremere 1699 days ago
The context derived from WithContext is scoped to the lifetime of errgroup (after they all return, or any return with an error). This way the function passed to Group.Go can spawn other go routines that will get properly cleaned up.

Why those other go routines would spawn processes that they don't clean up otherwise? They probably shouldn't, but canceling the context should always be safe, and is more likely to safely handle what otherwise would be a bug, than it is to cause a bug.
1 comments
scottlamb 1699 days ago
> canceling the context should always be safe, and is more likely to safely handle what otherwise would be a bug, than it is to cause a bug.

They gave an example of a bug it caused, and I haven't seen any examples of bugs it would have prevented, so I'm not sure I agree.

link
reltuk 1699 days ago
I think the contract in the context package is that WithCancel may leak resources if cancel is not called and the parent context is cancelable but never canceled. At least, that seems to be the behavior I see in the implementation here:

https://github.com/golang/go/blob/master/src/context/context...

So in this case, errgroup probably doesn't have a choice and needs to call cancel() at some point.

link
scottlamb 1699 days ago
Ahh. Yeah, that's unfortunate but explains this choice.

btw, I realized I'm not being entirely fair in saying it caused a bug. There would have been one anyway. If conflictsBuilder.Wait() failed, it wouldn't cancel the other two operations. It'd wait them out even though the overall operation was doomed. Maybe not a very noticeable bug under normal conditions but still not right.

link