ringhash: fix bug where ring hash can be stuck in transient failure d…

…espite having available endpoints (#7364)

internal/testutils/blocking_context_dialer.go

@@ -127,3 +127,13 @@ func (h *Hold) Fail(err error) {
  h.blockCh <- err
  close(h.blockCh)
 }
+
+// IsStarted returns true if this hold has received a connection attempt.
+func (h *Hold) IsStarted() bool {
+ select {
+ case <-h.waitCh:
+ return true
+ default:
+ return false
+ }
+}

internal/testutils/blocking_context_dialer_test.go

@@ -59,6 +59,10 @@ func (s) TestBlockingDialer_HoldWaitResume(t *testing.T) {
  d := NewBlockingDialer()
  h := d.Hold(lis.Addr().String())
 
+ if h.IsStarted() {
+ t.Fatalf("hold.IsStarted() = true, want false")
+ }
+
  done := make(chan struct{})
  ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
  defer cancel()
@@ -69,13 +73,22 @@ func (s) TestBlockingDialer_HoldWaitResume(t *testing.T) {
  t.Errorf("BlockingDialer.DialContext() got error: %v, want success", err)
  return
  }
+
+ if !h.IsStarted() {
+ t.Errorf("hold.IsStarted() = false, want true")
+ }
  conn.Close()
  }()
 
  // This should block until the goroutine above is scheduled.
  if !h.Wait(ctx) {
  t.Fatalf("Timeout while waiting for a connection attempt to %q", h.addr)
  }
+
+ if !h.IsStarted() {
+ t.Errorf("hold.IsStarted() = false, want true")
+ }
+
  select {
  case <-done:
  t.Fatalf("Expected dialer to be blocked.")