sync.WaitGroup doesnt waits
-2
May be I can not see obvious thing, what am I doing wrong:
func printSize (listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
If I remove wg and go, I receive the size of each url body correctly. If I do it as in above, it prints zeroes almost instantly. The getUrlBody() takes time to execute sometimes minutes.
Answering comment: I also tried it this way, to be sure, and it demonstrate same behaviour.
I found the error was in getUrlBody and main() function...
func printSize(listOfUrls string) {
var wg sync.WaitGroup
wg.Add(len(listOfUrls))
for _, myurl := range listOfUrls {
go f(myurl, &wg)
}
wg.Wait()
}
func f(myurl string, wg *sync.WaitGroup) {
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}
concurrency go
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
|
show 2 more comments
-2
May be I can not see obvious thing, what am I doing wrong:
func printSize (listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
If I remove wg and go, I receive the size of each url body correctly. If I do it as in above, it prints zeroes almost instantly. The getUrlBody() takes time to execute sometimes minutes.
Answering comment: I also tried it this way, to be sure, and it demonstrate same behaviour.
I found the error was in getUrlBody and main() function...
func printSize(listOfUrls string) {
var wg sync.WaitGroup
wg.Add(len(listOfUrls))
for _, myurl := range listOfUrls {
go f(myurl, &wg)
}
wg.Wait()
}
func f(myurl string, wg *sync.WaitGroup) {
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}
concurrency go
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
2
You have a racecondition in your code onmyurl. You should copy it by passing it to the closure. Otherwise, it will probably mostly refer to the last element in your range in all of your goroutines.
– inf
Jun 1 '15 at 17:43
Yes, I added 2nd version which I guess correct, but does not works too.
– MikeKlemin
Jun 1 '15 at 17:57
What happens when you run the second version?
– ThunderCat
Jun 1 '15 at 17:59
If listOfUrls has say 4 urls, It prints ("Getting url:") from getBodyUrls four times, and then it prints zeroes for length also four times... In theory it should print "Done url: " from getBodyUrls, and print correct size...
– MikeKlemin
Jun 1 '15 at 18:02
It's not possible to comment on what's going on because none of the print statements mentioned in your comment are in the code that you have shown.
– ThunderCat
Jun 1 '15 at 18:08
|
show 2 more comments
-2
-2
-2
May be I can not see obvious thing, what am I doing wrong:
func printSize (listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
If I remove wg and go, I receive the size of each url body correctly. If I do it as in above, it prints zeroes almost instantly. The getUrlBody() takes time to execute sometimes minutes.
Answering comment: I also tried it this way, to be sure, and it demonstrate same behaviour.
I found the error was in getUrlBody and main() function...
func printSize(listOfUrls string) {
var wg sync.WaitGroup
wg.Add(len(listOfUrls))
for _, myurl := range listOfUrls {
go f(myurl, &wg)
}
wg.Wait()
}
func f(myurl string, wg *sync.WaitGroup) {
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}
concurrency go
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
May be I can not see obvious thing, what am I doing wrong:
func printSize (listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
If I remove wg and go, I receive the size of each url body correctly. If I do it as in above, it prints zeroes almost instantly. The getUrlBody() takes time to execute sometimes minutes.
Answering comment: I also tried it this way, to be sure, and it demonstrate same behaviour.
I found the error was in getUrlBody and main() function...
func printSize(listOfUrls string) {
var wg sync.WaitGroup
wg.Add(len(listOfUrls))
for _, myurl := range listOfUrls {
go f(myurl, &wg)
}
wg.Wait()
}
func f(myurl string, wg *sync.WaitGroup) {
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}
concurrency go
concurrency go
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
edited Jun 1 '15 at 18:49
MikeKlemin
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
asked Jun 1 '15 at 17:39
MikeKleminMikeKlemin
372416
372416
2
You have a racecondition in your code onmyurl. You should copy it by passing it to the closure. Otherwise, it will probably mostly refer to the last element in your range in all of your goroutines.
– inf
Jun 1 '15 at 17:43
Yes, I added 2nd version which I guess correct, but does not works too.
– MikeKlemin
Jun 1 '15 at 17:57
What happens when you run the second version?
– ThunderCat
Jun 1 '15 at 17:59
If listOfUrls has say 4 urls, It prints ("Getting url:") from getBodyUrls four times, and then it prints zeroes for length also four times... In theory it should print "Done url: " from getBodyUrls, and print correct size...
– MikeKlemin
Jun 1 '15 at 18:02
It's not possible to comment on what's going on because none of the print statements mentioned in your comment are in the code that you have shown.
– ThunderCat
Jun 1 '15 at 18:08
|
show 2 more comments
2
You have a racecondition in your code onmyurl. You should copy it by passing it to the closure. Otherwise, it will probably mostly refer to the last element in your range in all of your goroutines.
– inf
Jun 1 '15 at 17:43
Yes, I added 2nd version which I guess correct, but does not works too.
– MikeKlemin
Jun 1 '15 at 17:57
What happens when you run the second version?
– ThunderCat
Jun 1 '15 at 17:59
If listOfUrls has say 4 urls, It prints ("Getting url:") from getBodyUrls four times, and then it prints zeroes for length also four times... In theory it should print "Done url: " from getBodyUrls, and print correct size...
– MikeKlemin
Jun 1 '15 at 18:02
It's not possible to comment on what's going on because none of the print statements mentioned in your comment are in the code that you have shown.
– ThunderCat
Jun 1 '15 at 18:08
2
2
You have a racecondition in your code on
myurl. You should copy it by passing it to the closure. Otherwise, it will probably mostly refer to the last element in your range in all of your goroutines.– inf
Jun 1 '15 at 17:43
You have a racecondition in your code on
myurl. You should copy it by passing it to the closure. Otherwise, it will probably mostly refer to the last element in your range in all of your goroutines.– inf
Jun 1 '15 at 17:43
Yes, I added 2nd version which I guess correct, but does not works too.
– MikeKlemin
Jun 1 '15 at 17:57
Yes, I added 2nd version which I guess correct, but does not works too.
– MikeKlemin
Jun 1 '15 at 17:57
What happens when you run the second version?
– ThunderCat
Jun 1 '15 at 17:59
What happens when you run the second version?
– ThunderCat
Jun 1 '15 at 17:59
If listOfUrls has say 4 urls, It prints ("Getting url:") from getBodyUrls four times, and then it prints zeroes for length also four times... In theory it should print "Done url: " from getBodyUrls, and print correct size...
– MikeKlemin
Jun 1 '15 at 18:02
If listOfUrls has say 4 urls, It prints ("Getting url:") from getBodyUrls four times, and then it prints zeroes for length also four times... In theory it should print "Done url: " from getBodyUrls, and print correct size...
– MikeKlemin
Jun 1 '15 at 18:02
It's not possible to comment on what's going on because none of the print statements mentioned in your comment are in the code that you have shown.
– ThunderCat
Jun 1 '15 at 18:08
It's not possible to comment on what's going on because none of the print statements mentioned in your comment are in the code that you have shown.
– ThunderCat
Jun 1 '15 at 18:08
|
show 2 more comments
1 Answer
1
active
oldest
votes
2
All of the goroutines are sharing the single myurl variable. See https://golang.org/doc/faq#closures_and_goroutines for more information.
Change the code to:
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(myurl string){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}(myurl)
}
wg.Wait()
}
or
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
myurl := myurl
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
Thank you. Please, if my edit with addition to start topic, makes sense?
– MikeKlemin
Jun 1 '15 at 17:54
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
2
All of the goroutines are sharing the single myurl variable. See https://golang.org/doc/faq#closures_and_goroutines for more information.
Change the code to:
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(myurl string){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}(myurl)
}
wg.Wait()
}
or
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
myurl := myurl
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
Thank you. Please, if my edit with addition to start topic, makes sense?
– MikeKlemin
Jun 1 '15 at 17:54
add a comment |
2
All of the goroutines are sharing the single myurl variable. See https://golang.org/doc/faq#closures_and_goroutines for more information.
Change the code to:
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(myurl string){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}(myurl)
}
wg.Wait()
}
or
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
myurl := myurl
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
Thank you. Please, if my edit with addition to start topic, makes sense?
– MikeKlemin
Jun 1 '15 at 17:54
add a comment |
2
2
2
All of the goroutines are sharing the single myurl variable. See https://golang.org/doc/faq#closures_and_goroutines for more information.
Change the code to:
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(myurl string){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}(myurl)
}
wg.Wait()
}
or
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
myurl := myurl
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
All of the goroutines are sharing the single myurl variable. See https://golang.org/doc/faq#closures_and_goroutines for more information.
Change the code to:
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
go func(myurl string){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}(myurl)
}
wg.Wait()
}
or
func f(listOfUrls string){
var wg sync.WaitGroup
wg.Add(len(listOfUrl))
for _, myurl := range(listOfUrls){
myurl := myurl
go func(){
body := getUrlBody(myurl)
fmt.Println(len(body))
wg.Done()
}()
}
wg.Wait()
}
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
edited Jun 1 '15 at 17:50
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
answered Jun 1 '15 at 17:45
ThunderCatThunderCat
53k56686
53k56686
Thank you. Please, if my edit with addition to start topic, makes sense?
– MikeKlemin
Jun 1 '15 at 17:54
add a comment |
Thank you. Please, if my edit with addition to start topic, makes sense?
– MikeKlemin
Jun 1 '15 at 17:54
Thank you. Please, if my edit with addition to start topic, makes sense?
– MikeKlemin
Jun 1 '15 at 17:54
Thank you. Please, if my edit with addition to start topic, makes sense?
– MikeKlemin
Jun 1 '15 at 17:54
add a comment |
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2
You have a racecondition in your code on
myurl. You should copy it by passing it to the closure. Otherwise, it will probably mostly refer to the last element in your range in all of your goroutines.– inf
Jun 1 '15 at 17:43
Yes, I added 2nd version which I guess correct, but does not works too.
– MikeKlemin
Jun 1 '15 at 17:57
What happens when you run the second version?
– ThunderCat
Jun 1 '15 at 17:59
If listOfUrls has say 4 urls, It prints ("Getting url:") from getBodyUrls four times, and then it prints zeroes for length also four times... In theory it should print "Done url: " from getBodyUrls, and print correct size...
– MikeKlemin
Jun 1 '15 at 18:02
It's not possible to comment on what's going on because none of the print statements mentioned in your comment are in the code that you have shown.
– ThunderCat
Jun 1 '15 at 18:08