In case someone arrives here with the same question I'm going to post a
simple example that does what Tamás suggested a few days ago. Use context
to block on .Done() and pass the responseWriter as a context Value. Please
comment if passing the responseWriter as a context value is not considered
a good practice.
package main
import (
"context"
"net/http"
"time"
)
var reqChan chan context.Context
func ConcPrinter(reqChan chan context.Context) {
for c := range reqChan {
w := c.Value("reqW").(http.ResponseWriter)
f := c.Value("cancel").(context.CancelFunc)
// Expensive operation
time.Sleep(time.Second)
w.Write([]byte("Done!"))
f()
}
}
func rootHandler(w http.ResponseWriter, r *http.Request) {
cont, f := context.WithCancel(context.WithValue(r.Context(), "reqW", w))
contC := context.WithValue(cont, "cancel", f)
reqChan <- contC
<-contC.Done()
}
func main() {
http.HandleFunc("/", rootHandler)
reqChan = make(chan context.Context)
go ConcPrinter(reqChan)
http.ListenAndServe(":8080", nil)
}
Cheers,
Pablo
On Wednesday, December 7, 2016 at 4:01:18 PM UTC-8, Pablo Rozas-Larraondo
wrote:
>
> Hi gophers,
>
> I'm designing a service exposed through a http server which uses a pool of
> workers to process requests. At the moment my handlerFunc look similar to
> this:
>
> func aHandler(w http.ResponseWriter, r *http.Request) {
> var wg sync.WaitGroup
> wg.Add(1)
> reqQueue <- &RequestParams{&wg, r, w}
> wg.Wait()
> }
>
> When a worker is done, it writes on the w and calls wg.Done(). This
> approach works fine but I'm not sure if passing the WaitGroup around is the
> best approach. Has anyone encountered a similar situation or can suggest
> alternative approaches? Could the new context package and its Done()
> channel be of any help in this case?
>
> Thank you very much for your help,
> Pablo
>
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