Configure http2 with higher maxconcurrent streams (#7363)

This value is needed for Minio's internode communication,
read the meaning of this value as per the HTTP 2.0 spec

https://http2.github.io/http2-spec/#rfc.section.5.1.2

cmd/http/server.go

@@ -25,6 +25,8 @@ import (
 	"time"
 
 	humanize "github.com/dustin/go-humanize"
+	"golang.org/x/net/http2"
+
 	"github.com/minio/minio-go/pkg/set"
 	"github.com/minio/minio/pkg/certs"
 )
@@ -46,6 +48,9 @@ const (
 
 	// DefaultMaxHeaderBytes - default maximum HTTP header size in bytes.
 	DefaultMaxHeaderBytes = 1 * humanize.MiByte
+
+	// DefaultHTTP2MaxConcurrentStreams - default value for HTTP 2.0 maximum concurrent streams allowed.
+	DefaultHTTP2MaxConcurrentStreams = 1024
 )
 
 // Server - extended http.Server supports multiple addresses to serve and enhanced connection handling.
@@ -56,7 +61,7 @@ type Server struct {
 	TCPKeepAliveTimeout    time.Duration // timeout used for underneath TCP connection.
 	UpdateBytesReadFunc    func(int)     // function to be called to update bytes read in bufConn.
 	UpdateBytesWrittenFunc func(int)     // function to be called to update bytes written in bufConn.
-	listenerMutex          *sync.Mutex   // to guard 'listener' field.
+	listenerMutex          sync.Mutex    // to guard 'listener' field.
 	listener               *httpListener // HTTP listener for all 'Addrs' field.
 	inShutdown             uint32        // indicates whether the server is in shutdown or not
 	requestCount           int32         // counter holds no. of request in progress.
@@ -120,6 +125,11 @@ func (srv *Server) Start() (err error) {
 
 	// Start servicing with listener.
 	if tlsConfig != nil {
+		if err = http2.ConfigureServer(&srv.Server, &http2.Server{
+			MaxConcurrentStreams: DefaultHTTP2MaxConcurrentStreams,
+		}); err != nil {
+			return err
+		}
 		return srv.Server.Serve(tls.NewListener(listener, tlsConfig))
 	}
 	return srv.Server.Serve(listener)
@@ -202,7 +212,6 @@ func NewServer(addrs []string, handler http.Handler, getCert certs.GetCertificat
 		Addrs:               addrs,
 		ShutdownTimeout:     DefaultShutdownTimeout,
 		TCPKeepAliveTimeout: DefaultTCPKeepAliveTimeout,
-		listenerMutex:       &sync.Mutex{},
 	}
 	httpServer.Handler = handler
 	httpServer.TLSConfig = tlsConfig

cmd/http/server_test.go

@@ -77,10 +77,6 @@ func TestNewServer(t *testing.T) {
 			t.Fatalf("Case %v: server.TCPKeepAliveTimeout: expected: %v, got: %v", (i + 1), DefaultTCPKeepAliveTimeout, server.TCPKeepAliveTimeout)
 		}
 
-		if server.listenerMutex == nil {
-			t.Fatalf("Case %v: server.listenerMutex: expected: <non-nil>, got: <nil>", (i + 1))
-		}
-
 		if server.ReadTimeout != DefaultReadTimeout {
 			t.Fatalf("Case %v: server.ReadTimeout: expected: %v, got: %v", (i + 1), DefaultReadTimeout, server.ReadTimeout)
 		}