Hi again.
Ø There's no way to test that a WaitGroup is done without waiting for it, and
even if there was it would be racy because between the Close() and WaitGroup
wait call tasks could complete.
If you don’t mind being blocked, then Wait is just what you want. Since it’s
occurring in the same function (main) that the Add is taking place earlier,
there is no race.
John
John Souvestre - New Orleans LA
From: [email protected] [mailto:[email protected]] On
Behalf Of Evan Digby
Sent: 2016 September 13, Tue 14:19
To: golang-nuts
Subject: Re: [go-nuts] Having difficulty testing this "cleanly"
Hi John,
Thanks for the reply. I've tried many incarnations that include WaitGroups;
however, none seem to achieve the desired result.
If I add a WaitGroup with a defer done in the handler, and then wait after the
Close() then the test itself implements the requirement and won't protect from
future refactors. There's no way to test that a WaitGroup is done without
waiting for it, and even if there was it would be racy because between the
Close() and WaitGroup wait call tasks could complete. If I wrapped the wait and
the done in goroutines to see which one happened first, also racy.
If you have something else in mind can you elaborate on how it would help in
this case?
Thanks again!
Evan
On Tuesday, 13 September 2016 12:01:29 UTC-7, John Souvestre wrote:
Have you considered using a sync.WaitGroup?
John
John Souvestre - New Orleans LA
From: [email protected] <javascript:>
[mailto:[email protected] <javascript:> ] On Behalf Of Evan Digby
Sent: 2016 September 13, Tue 13:56
To: golang-nuts
Subject: [go-nuts] Having difficulty testing this "cleanly"
Has anyone come across a good way, non-racy way to ensure that N tasks are
guaranteed to be completed after a function is called? Essentially I have a
“Close” function that must be guaranteed to block until all tasks are finished.
Achieving this was pretty simple: wrap each task in an RLock, and then a Lock
on close.
Example: https://play.golang.org/p/7lhBPUhkUE
Now I want to write a solid test to guarantee Close will meet that requirement
of all tasks must finish first for posterity. In that example, try commenting
out the RLock/RUnlock on lines 25/26. You'll see that it no longer outputs
many, if any, lines. I'm trying to prevent that from happening in the future by
some cowboy refactor!
All of the ways I can come up with involve Sleeping or launching more tasks
than I _think_ can be finished in time--obviously not good!
I feel like I must be missing some obvious way to test this and I'll end up
feeling silly once someone replies with the solution. I'm okay with that!
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