Dropping subscription with UserInitiated in ExecuteActionAsync

alexey.zimarev · September 14, 2018, 2:47pm

I am wondering what is the reason to use UserInitiated reason when the subscription is dropped in ExecuteActionAsync due to the action queue overflow? Clearly, the user has not initiated anything. The reason is technical but we cannot react to it, because to the client it looks like we have asked to stop the subscription. Hint: we did not.

github.com

EventStore/EventStore/blob/7e98bd4206d5b0aec0cbc24d12002dfe195643fe/src/EventStore.ClientAPI/ClientOperations/SubscriptionOperation.cs#L260


        _log.Debug("Subscription {0:B} to {1}: event appeared ({2}, {3}, {4} @ {5}).",
                  _correlationId, _streamId == string.Empty ? "<all>" : _streamId,
                  e.OriginalStreamId, e.OriginalEventNumber, e.OriginalEvent.EventType, e.OriginalPosition);

    ExecuteActionAsync(() => _eventAppeared(_subscription, e));
}

private void ExecuteActionAsync(Func<Task> action)
{
    _actionQueue.Enqueue(action);
    if (_actionQueue.Count > _maxQueueSize) DropSubscription(SubscriptionDropReason.UserInitiated, new Exception("client buffer too big"));
    if (Interlocked.CompareExchange(ref _actionExecuting, 1, 0) == 0)
        ThreadPool.QueueUserWorkItem(ExecuteActions);
}

private async void ExecuteActions(object state)
{
    do
    {
        Func<Task> action;
        while (_actionQueue.TryDequeue(out action))

alexey.zimarev · September 14, 2018, 4:25pm

Greg_Young1 · September 14, 2018, 4:35pm

Could be reasonable to add a “QueueBlewUp” reason.

alexey.zimarev · September 14, 2018, 4:46pm

There is already ProcessingQueueOverflow, maybe this one should be ActionQueueOverflow?

Greg_Young1 · September 14, 2018, 6:24pm

That seems legit. I will accept the PR just make sure that the docs get updated as well to state the reason

alexey.zimarev · September 16, 2018, 12:57pm

Don’t you think the the SubscriptionOperation._maxQueueSize, which is not a constant (2000) needs to be set to the same value as EventStoreCatchUpSubscription.MaxPushQueueSize?

alexey.zimarev · September 16, 2018, 12:57pm

which is now a constant (2000)