rpc: set pong read deadline (#23556)

This PR adds a 30s timeout for the remote part to answer a ping message, thus detecting (silent) disconnnects
blocknative · dmarzzz · Dec 9, 2021 · Aug 30, 2021 · Aug 31, 2021 · Aug 31, 2021
commit 51ececb64e9cacaaa9b736b5bc2455225d061edb
diff --git a/rpc/websocket.go b/rpc/websocket.go
@@ -37,6 +37,7 @@ const (
 	wsWriteBuffer      = 1024
 	wsPingInterval     = 60 * time.Second
 	wsPingWriteTimeout = 5 * time.Second
+	wsPongTimeout      = 30 * time.Second
 	wsMessageSizeLimit = 15 * 1024 * 1024
 )
 
@@ -241,6 +242,10 @@ type websocketCodec struct {
 
 func newWebsocketCodec(conn *websocket.Conn) ServerCodec {
 	conn.SetReadLimit(wsMessageSizeLimit)
+	conn.SetPongHandler(func(appData string) error {
+		conn.SetReadDeadline(time.Time{})
+		return nil
+	})
 	wc := &websocketCodec{
 		jsonCodec: NewFuncCodec(conn, conn.WriteJSON, conn.ReadJSON).(*jsonCodec),
 		conn:      conn,
@@ -287,6 +292,7 @@ func (wc *websocketCodec) pingLoop() {
 			wc.jsonCodec.encMu.Lock()
 			wc.conn.SetWriteDeadline(time.Now().Add(wsPingWriteTimeout))
 			wc.conn.WriteMessage(websocket.PingMessage, nil)
+			wc.conn.SetReadDeadline(time.Now().Add(wsPongTimeout))
 			wc.jsonCodec.encMu.Unlock()
 			timer.Reset(wsPingInterval)
 		}

diff --git a/rpc/websocket_test.go b/rpc/websocket_test.go
@@ -18,11 +18,15 @@ package rpc
 
 import (
 	"context"
+	"io"
 	"net"
 	"net/http"
 	"net/http/httptest"
+	"net/http/httputil"
+	"net/url"
 	"reflect"
 	"strings"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -188,6 +192,63 @@ func TestClientWebsocketLargeMessage(t *testing.T) {
 	}
 }
 
+func TestClientWebsocketSevered(t *testing.T) {
+	t.Parallel()
+
+	var (
+		server = wsPingTestServer(t, nil)
+		ctx    = context.Background()
+	)
+	defer server.Shutdown(ctx)
+
+	u, err := url.Parse("http://" + server.Addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rproxy := httputil.NewSingleHostReverseProxy(u)
+	var severable *severableReadWriteCloser
+	rproxy.ModifyResponse = func(response *http.Response) error {
+		severable = &severableReadWriteCloser{ReadWriteCloser: response.Body.(io.ReadWriteCloser)}
+		response.Body = severable
+		return nil
+	}
+	frontendProxy := httptest.NewServer(rproxy)
+	defer frontendProxy.Close()
+
+	wsURL := "ws:" + strings.TrimPrefix(frontendProxy.URL, "http:")
+	client, err := DialWebsocket(ctx, wsURL, "")
+	if err != nil {
+		t.Fatalf("client dial error: %v", err)
+	}
+	defer client.Close()
+
+	resultChan := make(chan int)
+	sub, err := client.EthSubscribe(ctx, resultChan, "foo")
+	if err != nil {
+		t.Fatalf("client subscribe error: %v", err)
+	}
+
+	// sever the connection
+	severable.Sever()
+
+	// Wait for subscription error.
+	timeout := time.NewTimer(3 * wsPingInterval)
+	defer timeout.Stop()
+	for {
+		select {
+		case err := <-sub.Err():
+			t.Log("client subscription error:", err)
+			return
+		case result := <-resultChan:
+			t.Error("unexpected result:", result)
+			return
+		case <-timeout.C:
+			t.Error("didn't get any error within the test timeout")
+			return
+		}
+	}
+}
+
 // wsPingTestServer runs a WebSocket server which accepts a single subscription request.
 // When a value arrives on sendPing, the server sends a ping frame, waits for a matching
 // pong and finally delivers a single subscription result.
@@ -290,3 +351,31 @@ func wsPingTestHandler(t *testing.T, conn *websocket.Conn, shutdown, sendPing <-
 		}
 	}
 }
+
+// severableReadWriteCloser wraps an io.ReadWriteCloser and provides a Sever() method to drop writes and read empty.
+type severableReadWriteCloser struct {
+	io.ReadWriteCloser
+	severed int32 // atomic
+}
+
+func (s *severableReadWriteCloser) Sever() {
+	atomic.StoreInt32(&s.severed, 1)
+}
+
+func (s *severableReadWriteCloser) Read(p []byte) (n int, err error) {
+	if atomic.LoadInt32(&s.severed) > 0 {
+		return 0, nil
+	}
+	return s.ReadWriteCloser.Read(p)
+}
+
+func (s *severableReadWriteCloser) Write(p []byte) (n int, err error) {
+	if atomic.LoadInt32(&s.severed) > 0 {
+		return len(p), nil
+	}
+	return s.ReadWriteCloser.Write(p)
+}
+
+func (s *severableReadWriteCloser) Close() error {
+	return s.ReadWriteCloser.Close()
+}