fix(go): complete TCP client teardown when conn.Close fails (#3670)

Golang SDK TCP client returns the error directly when `c.conn.Close()`
returns an error. This stops it from finishing the disconnect and shutdown process.

Author: chengxilo

foreign/go/client/tcp/tcp_core.go

@@ -433,12 +433,20 @@ func (c *IggyTcpClient) sendLocked(wirePayload []byte) ([]byte, error) {
 
 // invalidateConnLocked closes the connection and marks it as disconnected
 func (c *IggyTcpClient) invalidateConnLocked() {
-	if c.conn != nil {
-		_ = c.conn.Close()
-	}
+	_ = c.closeConnLocked()
 	c.state = iggcon.StateDisconnected
 }
 
+// closeConnLocked closes and drops the current connection.
+func (c *IggyTcpClient) closeConnLocked() error {
+	if c.conn == nil {
+		return nil
+	}
+	err := c.conn.Close()
+	c.conn = nil
+	return err
+}
+
 func (c *IggyTcpClient) GetConnectionInfo() *iggcon.ConnectionInfo {
 	c.mtx.Lock()
 	defer c.mtx.Unlock()
@@ -610,22 +618,17 @@ func (c *IggyTcpClient) disconnect() error {
 	c.mtx.Lock()
 	defer c.mtx.Unlock()
 
-	if c.state == iggcon.StateDisconnected {
+	if c.state == iggcon.StateDisconnected || c.state == iggcon.StateShutdown {
 		return nil
 	}
 
 	c.logger.Info("Iggy client is disconnecting from server...", slog.String("client_address", c.clientAddress))
 	c.state = iggcon.StateDisconnected
-
-	if c.conn != nil {
-		if err := c.conn.Close(); err != nil {
-			return err
-		}
-	}
+	err := c.closeConnLocked()
 
 	c.logger.Info("Iggy client has disconnected from server.", slog.String("client_address", c.clientAddress))
 	// TODO event pushing logic
-	return nil
+	return err
 }
 
 func (c *IggyTcpClient) shutdown() error {
@@ -638,16 +641,12 @@ func (c *IggyTcpClient) shutdown() error {
 
 	c.logger.Info("Shutting down the Iggy TCP client...", slog.String("client_address", c.clientAddress))
 
-	if c.conn != nil {
-		if err := c.conn.Close(); err != nil {
-			return err
-		}
-	}
-
+	err := c.closeConnLocked()
 	c.state = iggcon.StateShutdown
+
 	c.logger.Info("Iggy TCP client has been shutdown.", slog.String("client_address", c.clientAddress))
 	// TODO push shutdown event
-	return nil
+	return err
 }
 
 func (c *IggyTcpClient) Close() error {

foreign/go/client/tcp/tcp_core_test.go

@@ -272,3 +272,60 @@ func TestNewIggyTcpClient_StoresProvidedLogger(t *testing.T) {
 		t.Errorf("expected logger output to contain 'source=tcp', got: %q", output)
 	}
 }
+
+var errCloseFailed = errors.New("close failed")
+
+// failingCloseConn is a connection whose Close always fails, standing in for a
+// socket whose teardown reports an error the client cannot act on.
+type failingCloseConn struct {
+	net.Conn
+	closes int
+}
+
+func (f *failingCloseConn) Close() error {
+	f.closes++
+	return errCloseFailed
+}
+
+func TestShutdown_FailedCloseStillCompletesTeardown(t *testing.T) {
+	c, _ := newTestClient(t)
+	conn := &failingCloseConn{Conn: c.conn}
+	c.conn = conn
+
+	if err := c.shutdown(); !errors.Is(err, errCloseFailed) {
+		t.Fatalf("got %v, want %v", err, errCloseFailed)
+	}
+	if c.state != iggcon.StateShutdown {
+		t.Errorf("expected state %v, got %v", iggcon.StateShutdown, c.state)
+	}
+	if c.conn != nil {
+		t.Error("expected the closed connection to be dropped")
+	}
+
+	if err := c.shutdown(); err != nil {
+		t.Errorf("expected the second shutdown to be a no-op, got %v", err)
+	}
+	if conn.closes != 1 {
+		t.Errorf("expected the connection to be closed once, got %d", conn.closes)
+	}
+}
+
+func TestDisconnect_ShutdownClientIsNotResurrected(t *testing.T) {
+	c, _ := newTestClient(t)
+
+	if err := c.shutdown(); err != nil {
+		t.Fatalf("unexpected shutdown error: %v", err)
+	}
+	if err := c.disconnect(); err != nil {
+		t.Fatalf("unexpected disconnect error: %v", err)
+	}
+
+	if c.state != iggcon.StateShutdown {
+		t.Errorf("expected state to stay %v, got %v", iggcon.StateShutdown, c.state)
+	}
+
+	_, err := c.sendWireAndFetchResponse(context.Background(), emptyWireReq)
+	if !errors.Is(err, ierror.ErrClientShutdown) {
+		t.Errorf("got %v, want %v", err, ierror.ErrClientShutdown)
+	}
+}