Check if cc.conns == nil before reading cc.conns

Author: menghanl

call_test.go

@@ -276,3 +276,18 @@ func TestInvokeCancel(t *testing.T) {
 	cc.Close()
 	server.stop()
 }
+
+// TestInvokeCancelClosedNonFail checks that a canceled non-failfast RPC
+// on a closed client will terminate.
+func TestInvokeCancelClosedNonFailFast(t *testing.T) {
+	server, cc := setUp(t, 0, math.MaxUint32)
+	var reply string
+	cc.Close()
+	req := "hello"
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if err := Invoke(ctx, "/foo/bar", &req, &reply, cc, FailFast(false)); err == nil {
+		t.Fatalf("canceled invoke on closed connection should fail")
+	}
+	server.stop()
+}

clientconn.go

@@ -479,6 +479,10 @@ func (cc *ClientConn) getTransport(ctx context.Context, opts BalancerGetOptions)
 	if cc.dopts.balancer == nil {
 		// If balancer is nil, there should be only one addrConn available.
 		cc.mu.RLock()
+		if cc.conns == nil {
+			cc.mu.RUnlock()
+			return nil, nil, toRPCErr(ErrClientConnClosing)
+		}
 		for _, ac = range cc.conns {
 			// Break after the first iteration to get the first addrConn.
 			ok = true