Enable HTTP/2 again

config/http_config.go

@@ -141,8 +141,8 @@ func newClient(rt http.RoundTripper) *http.Client {
 
 // NewClientFromConfig returns a new HTTP client configured for the
 // given config.HTTPClientConfig. The name is used as go-conntrack metric label.
-func NewClientFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives, enableHTTP2 bool) (*http.Client, error) {
-	rt, err := NewRoundTripperFromConfig(cfg, name, disableKeepAlives, enableHTTP2)
+func NewClientFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives bool) (*http.Client, error) {
+	rt, err := NewRoundTripperFromConfig(cfg, name, disableKeepAlives)
 	if err != nil {
 		return nil, err
 	}
@@ -151,7 +151,7 @@ func NewClientFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives, e
 
 // NewRoundTripperFromConfig returns a new HTTP RoundTripper configured for the
 // given config.HTTPClientConfig. The name is used as go-conntrack metric label.
-func NewRoundTripperFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives, enableHTTP2 bool) (http.RoundTripper, error) {
+func NewRoundTripperFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives bool) (http.RoundTripper, error) {
 	newRT := func(tlsConfig *tls.Config) (http.RoundTripper, error) {
 		// The only timeout we care about is the configured scrape timeout.
 		// It is applied on request. So we leave out any timings here.
@@ -172,19 +172,18 @@ func NewRoundTripperFromConfig(cfg HTTPClientConfig, name string, disableKeepAli
 				conntrack.DialWithName(name),
 			),
 		}
-		if enableHTTP2 {
-			// HTTP/2 support is golang has many problematic cornercases where
-			// dead connections would be kept and used in connection pools.
-			// https://github.com/golang/go/issues/32388
-			// https://github.com/golang/go/issues/39337
-			// https://github.com/golang/go/issues/39750
-			// TODO: Re-Enable HTTP/2 once upstream issue is fixed.
-			// TODO: use ForceAttemptHTTP2 when we move to Go 1.13+.
-			err := http2.ConfigureTransport(rt.(*http.Transport))
-			if err != nil {
-				return nil, err
-			}
+		// TODO: use ForceAttemptHTTP2 when we move to Go 1.13+.
+		rt2, err := http2.ConfigureTransports(rt.(*http.Transport))
+		if err != nil {
+			return nil, err
 		}
+		// ReadIdleTimeout is the timeout after which a health check using ping
+		// frame will be carried out if no frame is received on the
+		// connection. 5 minutes is above maximum sane scrape interval,
+		// we should not have this small overhead on the scrape connections.
+		// For other cases, this is used to validate that the connection can
+		// still be used.
+		rt2.ReadIdleTimeout = 5 * time.Minute
 
 		// If a bearer token is provided, create a round tripper that will set the
 		// Authorization header correctly on each request.

config/http_config_test.go

@@ -205,7 +205,7 @@ func TestNewClientFromConfig(t *testing.T) {
 		}
 		defer testServer.Close()
 
-		client, err := NewClientFromConfig(validConfig.clientConfig, "test", false, true)
+		client, err := NewClientFromConfig(validConfig.clientConfig, "test", false)
 		if err != nil {
 			t.Errorf("Can't create a client from this config: %+v", validConfig.clientConfig)
 			continue
@@ -255,7 +255,7 @@ func TestNewClientFromInvalidConfig(t *testing.T) {
 	}
 
 	for _, invalidConfig := range newClientInvalidConfig {
-		client, err := NewClientFromConfig(invalidConfig.clientConfig, "test", false, true)
+		client, err := NewClientFromConfig(invalidConfig.clientConfig, "test", false)
 		if client != nil {
 			t.Errorf("A client instance was returned instead of nil using this config: %+v", invalidConfig.clientConfig)
 		}
@@ -294,7 +294,7 @@ func TestMissingBearerAuthFile(t *testing.T) {
 	}
 	defer testServer.Close()
 
-	client, err := NewClientFromConfig(cfg, "test", false, true)
+	client, err := NewClientFromConfig(cfg, "test", false)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -483,7 +483,7 @@ func TestBasicAuthNoPassword(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Error loading HTTP client config: %v", err)
 	}
-	client, err := NewClientFromConfig(*cfg, "test", false, true)
+	client, err := NewClientFromConfig(*cfg, "test", false)
 	if err != nil {
 		t.Fatalf("Error creating HTTP Client: %v", err)
 	}
@@ -509,7 +509,7 @@ func TestBasicAuthNoUsername(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Error loading HTTP client config: %v", err)
 	}
-	client, err := NewClientFromConfig(*cfg, "test", false, true)
+	client, err := NewClientFromConfig(*cfg, "test", false)
 	if err != nil {
 		t.Fatalf("Error creating HTTP Client: %v", err)
 	}
@@ -535,7 +535,7 @@ func TestBasicAuthPasswordFile(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Error loading HTTP client config: %v", err)
 	}
-	client, err := NewClientFromConfig(*cfg, "test", false, true)
+	client, err := NewClientFromConfig(*cfg, "test", false)
 	if err != nil {
 		t.Fatalf("Error creating HTTP Client: %v", err)
 	}
@@ -686,7 +686,7 @@ func TestTLSRoundTripper(t *testing.T) {
 			writeCertificate(bs, tc.cert, cert)
 			writeCertificate(bs, tc.key, key)
 			if c == nil {
-				c, err = NewClientFromConfig(cfg, "test", false, true)
+				c, err = NewClientFromConfig(cfg, "test", false)
 				if err != nil {
 					t.Fatalf("Error creating HTTP Client: %v", err)
 				}
@@ -758,7 +758,7 @@ func TestTLSRoundTripperRaces(t *testing.T) {
 	writeCertificate(bs, TLSCAChainPath, ca)
 	writeCertificate(bs, ClientCertificatePath, cert)
 	writeCertificate(bs, ClientKeyNoPassPath, key)
-	c, err = NewClientFromConfig(cfg, "test", false, true)
+	c, err = NewClientFromConfig(cfg, "test", false)
 	if err != nil {
 		t.Fatalf("Error creating HTTP Client: %v", err)
 	}

go.mod

@@ -12,8 +12,8 @@ require (
 	github.com/prometheus/client_golang v1.7.1
 	github.com/prometheus/client_model v0.2.0
 	github.com/sirupsen/logrus v1.6.0
-	golang.org/x/net v0.0.0-20200625001655-4c5254603344
-	golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae
+	golang.org/x/net v0.0.0-20201024042810-be3efd7ff127
+	golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f
 	gopkg.in/alecthomas/kingpin.v2 v2.2.6
 	gopkg.in/yaml.v2 v2.3.0
 )