jackc/pgx · error

write to connection for cancellation

Error message

write to connection for cancellation: %w

What it means

The cancel request payload could not be written to the cancellation connection — the write syscall failed, likely because the connection closed or was interrupted. The cancel signal was not delivered.

Solutions

1. Check if the server closed the connection (wrapped error detail)
2. Retry the cancel request via Context cancellation instead
3. Verify network stability between client and server
4. Treat as best-effort; the query may complete normally

When it happens

Trigger: Thrown at pgconn/pgconn.go:1159 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of jackc/pgx@ec1a0befd2 (2026-08-04). Data as JSON: /api/errors/b791abf6ad7a75fb. Report an issue: GitHub.

Appendix: source

Thrown at pgconn/pgconn.go:1159

			tlsCancelConn = tls.Client(cancelConn, pgConn.tlsConfig)
		} else {
			tlsCancelConn, err = startTLS(cancelConn, pgConn.tlsConfig)
			if err != nil {
				return fmt.Errorf("tls error on cancel connection: %w", err)
			}
		}
		cancelConn = tlsCancelConn
		defer cancelConn.Close()
	}

	buf := make([]byte, 12+len(pgConn.secretKey))
	binary.BigEndian.PutUint32(buf[0:4], uint32(len(buf)))
	binary.BigEndian.PutUint32(buf[4:8], 80877102)
	binary.BigEndian.PutUint32(buf[8:12], pgConn.pid)
	copy(buf[12:], pgConn.secretKey)

	if _, err := cancelConn.Write(buf); err != nil {
		return fmt.Errorf("write to connection for cancellation: %w", err)
	}

	// Wait for the cancel request to be acknowledged by the server.
	// It copies the behavior of the libpq: https://github.com/postgres/postgres/blob/REL_16_0/src/interfaces/libpq/fe-connect.c#L4946-L4960
	_, _ = cancelConn.Read(buf)

	return nil
}

// WaitForNotification waits for a LISTEN/NOTIFY message to be received. It returns an error if a notification was not
// received.
func (pgConn *PgConn) WaitForNotification(ctx context.Context) error {
	if err := pgConn.lock(); err != nil {
		return err
	}
	defer pgConn.unlock()

	if ctx != context.Background() {

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