TaskQueue behavior for duplicate tasks in a list during Queue.add()

[soundofjw]

I have some questions about the behavior of taskqueue.Queue().add(task_list) when 1 of the tasks is duplicate, but the others are not.

I am not aware of any documentation around the taskqueue API that explains this behavior - as such it seems undefined.

My concern is that adding a list of multiple tasks, where 1 may already have been tombstoned/created, may cause the other legitimate tasks to fail.

This affects the pipeline library in the following codeblock:

try:
  taskqueue.Queue(self.queue_name).add(task_list)
except (taskqueue.TombstonedTaskError, taskqueue.TaskAlreadyExistsError):
  pass

appengine-pipelines/python/src/pipeline/pipeline.py

Lines 1659 to 1663 in bd9fa1e

	if task_list:
	try:
	taskqueue.Queue(self.queue_name).add(task_list)
	except (taskqueue.TombstonedTaskError, taskqueue.TaskAlreadyExistsError):
	pass

Any clues? This may be a good question for @tkaitchuck.
This was brought up in issue #54.

[tkaitchuck]

As far as I can tell this is ok. If it turns out not to be, it should be treated as a bug in taskqueue, as a TaskAlreadyExistsError should be raised at a lower priority than a failure for other reasons.

[soundofjw]

@tkaitchuck It's definitely a task-queue related question, but it's unclear as to what happens to all 10 tasks when 1 out of 10 tasks is a duplicate. Any ideas?

[tkaitchuck]

I know that is the case for Java's task queue that all 10 will be attempted and only if there is no more serious error will that be raised. So I assume it is for the python client as well.