presto-main/src/main/java/io/prestosql/operator/HttpPageBufferClient.java/HttpPageBufferClient/handleFailure
class HttpPageBufferClient:    private void handleFailure(Throwable t, HttpResponseFuture<?> expectedFuture)
    {
        // Can not delegate to other callback while holding a lock on this
        checkNotHoldsLock(this);

        requestsFailed.incrementAndGet();
        requestsCompleted.incrementAndGet();

        if (t instanceof PrestoException) {
            clientCallback.clientFailed(HttpPageBufferClient.this, t);
        }

        synchronized (HttpPageBufferClient.this) {
            if (future == expectedFuture) {
                future = null;
            }
            lastUpdate = DateTime.now();
        }
        clientCallback.requestComplete(HttpPageBufferClient.this);
    }