feat(transport): configure HTTP/2 ReadIdleTimeout (#882)

Setting this config causes the HTTP/2 transport to send a ping on idle connections every 15s and prune ones that have been severed. This should give increased reliability during network issues between the client and CFE.

go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/googleapis/gax-go/v2 v2.0.5
 	go.opencensus.io v0.23.0
 	golang.org/x/lint v0.0.0-20201208152925-83fdc39ff7b5
+	golang.org/x/net v0.0.0-20210316092652-d523dce5a7f4
 	golang.org/x/oauth2 v0.0.0-20210413134643-5e61552d6c78
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
 	golang.org/x/sys v0.0.0-20210412220455-f1c623a9e750

transport/http/configure_http2_go116.go

@@ -0,0 +1,25 @@
+// Copyright 2021 Google LLC.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.16
+
+package http
+
+import (
+	"net/http"
+	"time"
+
+	"golang.org/x/net/http2"
+)
+
+// configureHTTP2 configures the ReadIdleTimeout HTTP/2 option for the
+// transport. This allows broken idle connections to be pruned more quickly,
+// preventing the client from attempting to re-use connections that will no
+// longer work.
+func configureHTTP2(trans *http.Transport) {
+	http2Trans, err := http2.ConfigureTransports(trans)
+	if err == nil {
+		http2Trans.ReadIdleTimeout = time.Second * 15
+	}
+}

transport/http/configure_http2_not_go116.go

@@ -0,0 +1,16 @@
+// Copyright 2021 Google LLC.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !go1.16
+
+package http
+
+import (
+	"net/http"
+)
+
+// configureHTTP2 configures the ReadIdleTimeout HTTP/2 option for the
+// transport. The interface to do this is only available in Go 1.16 and up, so
+// this performs a no-op.
+func configureHTTP2(trans *http.Transport) {}

transport/http/dial.go

@@ -175,6 +175,10 @@ func defaultBaseTransport(ctx context.Context, clientCertSource cert.Source) htt
 		}
 	}
 
+	// If possible, configure http2 transport in order to use ReadIdleTimeout
+	// setting. This can only be done in Go 1.16 and up.
+	configureHTTP2(trans)
+
 	return trans
 }