The WaitGroup is better than the lock approach, since the lock approach could block an outstanding task. The key to using waitgroups is to call Add() outside of goroutines that might call done:
https://play.golang.org/p/QVWoy8fCmI On Tuesday, September 13, 2016 at 12:19:16 PM UTC-7, Evan Digby wrote: > > 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:* golan...@googlegroups.com [mailto:golan...@googlegroups.com] *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! >> >> -- >> 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...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. >> > -- 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.
