The precise ordering of things is a bit non-deterministic at the fringe. If
precise ordering really matters (maybe for cancelling a stream like this, it
doesn’t, sometimes it does), a default case in the select statement is really
useful, and it also matters what DoSomething does.
________________________________
From: golang-nuts@googlegroups.com <golang-nuts@googlegroups.com> on behalf of
Torsten Bronger <bron...@physik.rwth-aachen.de>
Sent: Monday, December 19, 2022 1:52:36 AM
To: golang-nuts@googlegroups.com <golang-nuts@googlegroups.com>
Subject: [go-nuts] Context cancellation: Is it sufficient to make long-running
things interruptible?
Hallöchen!
The context documentation gives this example:
// Stream generates values with DoSomething and sends them to out
// until DoSomething returns an error or ctx.Done is closed.
func Stream(ctx context.Context, out chan<- Value) error {
for {
v, err := DoSomething(ctx)
if err != nil {
return err
}
select {
case <-ctx.Done():
return ctx.Err()
case out <- v:
}
}
}
What if the channel “out” is drained very efficiently? Then, an
arbitrary number of loop iterations could happen before a
cancellation is detected, couldn’t it?
I would additionally check for ctx.Err() != nil somewhere in the
loop. Or is there a reason why this is not necessary?
Regards,
Torsten.
--
Torsten Bronger
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