On Tue, Apr 11, 2017 at 6:09 PM, Alex Flint <alex.fl...@gmail.com> wrote: > > Suppose I have a long-running computation that I wish to be cancelable via a > context. By this I mean something that's just churning away on some > computation, not blocking on a syscall or I/O operation or anything like > that. Should I just poll ctx.Err() periodically in the inner loop of my > computation?
Technically you should poll ctx.Done, as ctx.Err is not defined until the channel returned by ctx.Done is closed. But see https://golang.org/issue/19856 . Anyhow, that aside, yes, poll periodically. > Also, can anyone give any insight into approximately how costly > context.Err() is for the contexts constructed in the context package -- I > don't want my computation to be dominated by checking for cancellation! Calling Done (or Err) for a cancellable context will acquire and release a sync.Mutex. Other than that they are very cheap. Note that I wouldn't necessarily poll in the inner loop. How often to poll depends on what your program is doing. For example, if it's a background computation, then it doesn't matter much if it runs too long, and polling in the next-to-inner loop would typically be acceptable. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
