> Is there maybe something blocking involved in http.Get()? Yes of course - first establishing a TCP connection across the network, then sending data over it and waiting for the response.
Each of these is a point where the goroutine gets descheduled because it has nothing more to do; it's waiting for an external event which may not come for several milliseconds (an aeon in computer time). On Wednesday, 6 April 2022 at 14:43:15 UTC+1 golf_mike wrote: > Hi, > > As a fun way of getting into Go I decided to create a "random" number > generator by timing a number of requests to a specific URL, and reducing > the results to one number. For practice pusposes I made a "naive" version > with just a for loop and a version that uses goroutines. > As I am interested in the timings for each individual request, there was > an interesting result. Implemented in the for loop, each request was timed > as expected. For the goroutines however the timings incremented for each > individual timing, where the last timing was equal or a microsecond or so > below the total timing for all requests. > Upon further inspection, it seems that the time.Now() for the startTime is > called almost immediately for all, but the time.Now() for the stopSub is > called much later. > How is it possible that all goroutines start execution at the same time, > but finish not at the same time? Is there maybe something blocking involved > in http.Get()? > I posted all code for this on Stackoverflow a couple of days ago but no > answers there yet (go - Unexpected behaviour of time.Now() in goroutine - > Stack Overflow > <https://stackoverflow.com/questions/71737286/unexpected-behaviour-of-time-now-in-goroutine>). > > See below for the goroutine and how it is called. > > Execution of goroutines: > *start := time.Now()* > * ch := make(chan int64, 100)* > * url := "https://www.nu.nl <https://www.nu.nl>"* > * for i := 0; i < len(timings_parallel); i++ {* > * wg.Add(1)* > * go func() {* > * defer wg.Done()* > * doGet(url, ch)* > * }()* > * }* > * wg.Wait()* > * close(ch)* > * // feed the results from the channel into the result array* > * count := 0* > * for ret := range ch {* > * timings_parallel[count] = ret* > * count++* > * }* > * // get total running time for this part* > * time_parallel := time.Since(start).Milliseconds()* > Goroutine: > *func doGet(address string, channel chan int64) {* > * startTime := time.Now()* > * startSub := startTime.UnixMilli()* > > * _, err := http.Get(address)* > * if err != nil {* > * log.Fatalln(err)* > * }* > * stopSub := time.Now().UnixMilli()* > * delta := stopSub - startSub* > > * channel <- delta* > *}* > > > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/e9a22dae-054a-45e5-b09a-093f56073c1bn%40googlegroups.com.
