You need to pass the context to the expensive work a periodically check if it
has been cancelled.
> On Jan 7, 2021, at 8:55 PM, Amit Saha <amitsaha...@gmail.com> wrote:
>
> Hi all, I want to confirm whether my understanding related to handling
> HTTP client disconnections is correct or not.
>
> Consider this:
>
> func longRunningProcessing(ctx context.Context, w http.ResponseWriter) {
> done := make(chan bool)
> go func() {
> expensiveWork() # This is a blocking expensive processing call
> done <- true
> }()
> select {
> case <-ctx.Done():
> log.Printf("Client disconnected. Cancelling expensive operation.")
> return
> case <- done:
> fmt.Fprintf(w, "Done!")
> }
> }
>
> func apiHandler(w http.ResponseWriter, r *http.Request) {
> ctx := r.Context()
> longRunningProcessing(ctx)
> }
>
> When a client connection close is detected, the Done() call in select
> unblocks and the call goes out of the longRunningProcessing()
> function.
> However, the goroutine with the expensiveWork() is actually still running?
>
> It seems like there is *no* way there is *not* going to be a goroutine
> leak (and resources associated with it) in a pattern like the above
> unless
> I have control over expensiveWork() and can instrument it with a child
> context. I am also thinking if there is a way to obtain the behavior
> similar to exec.CommandContext() command
> which does a hard kill of the external process when the context is cancelled.
>
> Thanks for any insights and clarifications.
>
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