http2: log pings and RoundTrip retries when http2debug=1

Change-Id: I3a7358db65ebc474712817a776d8468d0b09f0ab
Reviewed-on: https://go-review.googlesource.com/c/net/+/359914
Trust: Damien Neil <[email protected]>
Run-TryBot: Damien Neil <[email protected]>
Trust: Brad Fitzpatrick <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

http2/transport.go

@@ -501,12 +501,14 @@ func (t *Transport) RoundTripOpt(req *http.Request, opt RoundTripOpt) (*http.Res
 			if req, err = shouldRetryRequest(req, err); err == nil {
 				// After the first retry, do exponential backoff with 10% jitter.
 				if retry == 0 {
+					t.vlogf("RoundTrip retrying after failure: %v", err)
 					continue
 				}
 				backoff := float64(uint(1) << (uint(retry) - 1))
 				backoff += backoff * (0.1 * mathrand.Float64())
 				select {
 				case <-time.After(time.Second * time.Duration(backoff)):
+					t.vlogf("RoundTrip retrying after failure: %v", err)
 					continue
 				case <-req.Context().Done():
 					err = req.Context().Err()
@@ -732,10 +734,13 @@ func (cc *ClientConn) healthCheck() {
 	// trigger the healthCheck again if there is no frame received.
 	ctx, cancel := context.WithTimeout(context.Background(), pingTimeout)
 	defer cancel()
+	cc.vlogf("http2: Transport sending health check")
 	err := cc.Ping(ctx)
 	if err != nil {
+		cc.vlogf("http2: Transport health check failure: %v", err)
 		cc.closeForLostPing()
-		return
+	} else {
+		cc.vlogf("http2: Transport health check success")
 	}
 }