Method HandleCancel

pgconn/pgconn.go:2978–3006

(context.Context)

}

func (h *CancelRequestContextWatcherHandler) HandleCancel(context.Context) {
	h.cancelFinishedChan = make(chan struct{})
	var handleUnwatchedAfterCancelCalledCtx context.Context
	handleUnwatchedAfterCancelCalledCtx, h.handleUnwatchAfterCancelCalled = context.WithCancel(context.Background())

	deadline := time.Now().Add(h.DeadlineDelay)
	h.Conn.conn.SetDeadline(deadline)

	go func() {
		defer close(h.cancelFinishedChan)

		select {
		case <-handleUnwatchedAfterCancelCalledCtx.Done():
			return
		case <-time.After(h.CancelRequestDelay):
		}

		cancelRequestCtx, cancel := context.WithDeadline(handleUnwatchedAfterCancelCalledCtx, deadline)
		defer cancel()
		h.Conn.CancelRequest(cancelRequestCtx)

		// CancelRequest is inherently racy. Even though the cancel request has been received by the server at this point,
		// it hasn't necessarily been delivered to the other connection. If we immediately return and the connection is
		// immediately used then it is possible the CancelRequest will actually cancel our next query. The
		// TestCancelRequestContextWatcherHandler Stress test can produce this error without the sleep below. The sleep time
		// is arbitrary, but should be sufficient to prevent this error case.
		time.Sleep(100 * time.Millisecond)
	}()
}

func (h *CancelRequestContextWatcherHandler) HandleUnwatchAfterCancel() {
	h.handleUnwatchAfterCancelCalled()