Question

I have a pull queue being serviced by a backend and when the queue is empty I need to trigger another script.

At the moment I am using a very crude detection in the method that leases the tasks from the queue, so that if the task list returned is empty we presume that there are no more to lease and trigger the next step. However, while this works most of the time, occasionally a lease request seems to return an empty list even though there are tasks available.

Anyway, the better way to do it I think is to use the fetch_statistics method of the Queue. That way the script can monitor whats going on in the pull queue and know that there are no more items left in the queue. Now this is obviously available via the REST api for queues, but it seems rather backward to use this when I am using these internally.

So I am making the Queue.fetch_statistics() call, but it throws an error. I’ve tried putting the stated error into Google, but it returns nothing. Same here on stackoverflow.

It always throws:

AttributeError: type object 'QueueStatistics' has no attribute '_QueueStatistics__TranslateError'

My code is:

    q = taskqueue.Queue('reporting-pull')
    try:
        logging.debug(q.fetch_statistics())
    except Exception, e:
        logging.exception(e)

Can anyone shed any light on this? I am I doing something really stupid here?

Answer 1

The Task Queue Statistics API is now documented and publicly available. The error no longer occurs.