Goroutine leak in timeout

[peter-crist]

In timeout.go, context cancellation isn't check for when running the command goroutine. This causes the errc <- next.Run(ctx, f) call to block indefinitely if the command times out.

ctx, _ = context.WithTimeout(ctx, cfg.Timeout)

// Run the command
errc := make(chan error)
go func() {
	errc <- next.Run(ctx, f) //This blocks indefinitely if the context is cancelled due to a timeout.
}()

// Wait until the deadline has been reached or we have a result.
select {
// Finished correctly.
case err := <-errc:
	return err
// Timeout.
case <-ctx.Done():
	metricsRecorder.IncTimeout()
	return errors.ErrTimeout
}

The simple fix is to select:

go func() {
	select {
	case <-ctx.Done():
	case errc <- next.Run(ctx, f):
	}
}()

[eugennicoara]

Maybe this fix would have helped me avoid this OOM:

goroutine profile: total 238162
236204 @ 0x43d2d6 0x4079ee 0x40759d 0x981c70 0x471041
#       0x981c6f        github.com/slok/goresilience/timeout.NewMiddleware.func1.1.1+0x4f       /root/go/pkg/mod/github.com/slok/[email protected]/timeout/timeout.go:61

711 @ 0x43d2d6 0x44d91e 0x75e0ab 0x471041
#       0x75e0aa        net/http.setRequestCancel.func4+0x8a    /usr/local/go/src/net/http/client.go:398