Not Tested sofar by myself but https://github.com/dc0d/goroutines seems to hide all the complexity in a nice streamlined API.
Am Montag, 19. März 2018 08:46:07 UTC+1 schrieb Sathish VJ: > > Looks like this last one works but also quite complicated. > > One question ... what is the effect of having "default" on line 24 as > empty? > > > On 18 March 2018 at 14:21, 'Reinhard Luediger' via golang-nuts < > golan...@googlegroups.com <javascript:>> wrote: > >> I came to the following solution for my long running tasks, using >> go-routines & the context package, >> >> https://play.golang.org/p/2V_29lHt4Wn >> >> package main >> >> import ( >> "context" >> "fmt" >> "time" >> ) >> >> //LongRunningTask >> func LongRunningTask(ctx context.Context, index int) (err error) { >> // we'll signal on that channel when we finished >> var finished chan struct{} >> fmt.Printf("Starting task %d at: %s\n", index, time.Now()) >> var cancelWork = make(chan struct{},0) >> go func() { >> workloop: >> for i:= 0 ;i < 10 ;i++{ >> // sleeping for a long time >> time.Sleep(time.Second * 2) >> select { >> case <-cancelWork: >> fmt.Printf("Canceling work for Index: %d\n",index) >> break workloop >> default: >> } >> } >> finished <- struct{}{} >> }() >> >> select { >> // when the task finished normal we'll get a notification on the finished >> channel >> case <-finished: >> fmt.Printf("Task %d finished at:%s\n", index, time.Now()) >> return nil >> >> // If the context gets canceled we receive a signal on that channel >> case <-ctx.Done(): >> err := ctx.Err() >> _=err >> //the context.Err() method gives us the reason why it was canceled >> fmt.Printf("task %d aborted reason:%s at: %s\n", index, ctx.Err(), >> time.Now()) >> cancelWork <- struct{}{} >> return ctx.Err() >> } >> >> } >> >> func main() { >> var ctx context.Context >> >> // get a new Context and the corresponding cancel function >> ctx, cancel := context.WithCancel(context.Background()) >> >> // create a new context with a timeout value of 4 Seconds derived from >> the context above >> ctx, _ = context.WithTimeout(ctx, time.Second*4) >> >> // Sleeping for one Second to clarify that the timeout is running from >> the point where it is created >> time.Sleep(time.Second * 1) >> >> fmt.Printf("Starting background tasks time %s", time.Now()) >> for i := 0; i < 7; i++ { >> go LongRunningTask(ctx, i) >> >> } >> >> // if we sllep longer than the timeout we'll see that the tasks will be >> canceled after timeout >> time.Sleep(time.Second * 8) >> >> // The call of the cancel function has only effect when we slept shorter >> then the defined timeout >> // if so the single call of the cancel function will send a cancellation >> information to all child context >> cancel() >> >> // Sleep a while to see the cancellation messages >> time.Sleep(time.Second * 4) >> >> } >> >> >> Am Freitag, 16. März 2018 15:45:00 UTC+1 schrieb Sathish VJ: >>> >>> All the examples I've seen use some kind of ticker to run various cases >>> of a select statement. But how does one run a long running task that is >>> still cancelable? >>> >>> >>> In the example below the quit part is never reached. >>> >>> https://play.golang.org/p/PLGwrUvKaqn (it does not run properly on >>> play.golang.org). >>> >>> package main >>> >>> >>> import ( >>> "fmt" >>> "os" >>> "time" >>> ) >>> >>> >>> func f(quit chan bool) { >>> for { >>> select { >>> case <-time.After(0 * time.Second): >>> // start long running task immediately. >>> for { >>> time.Sleep(500 * time.Millisecond) >>> fmt.Printf(". ") >>> } >>> case <-quit: >>> fmt.Println("quit called") >>> //deallocate resources in other long running task and then return >>> from function. >>> os.Exit(0) // or return >>> } >>> } >>> } >>> >>> >>> func main() { >>> var quit chan bool >>> go f(quit) >>> >>> >>> println("quit sending ... ") >>> quit <- true >>> println("after quit sent") >>> >>> >>> var i chan int >>> <-i >>> } >>> >>> >>> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "golang-nuts" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/golang-nuts/l2A0PS91T0A/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> golang-nuts...@googlegroups.com <javascript:>. >> 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.
