PubSub Client: list_subscriptions returns all subscriptions, not just for that topic

[anorth2]

2. OS type and version
   Any and all

3. Python version and virtual environment information python --version
   Python 3.6.3

4. google-cloud-python version pip show google-cloud, pip show google-<service> or pip freeze
   google==1.9.3
   google-api-core==0.1.1
   google-auth==1.2.1
   google-cloud-core==0.28.0
   google-cloud-pubsub==0.29.0
   google-gax==0.15.16
   googleapis-common-protos==1.5.3
   grpc-google-iam-v1==0.11.4

5. Stacktrace if available

6. Steps to reproduce
   Run example code for listing subscriptions for a topic from here:
   https://cloud.google.com/pubsub/docs/admin

7. Code example

def list_subscriptions_in_topic(project, topic_name):
    """Lists all subscriptions for a given topic."""
    subscriber = pubsub_v1.SubscriberClient()
    topic_path = subscriber.topic_path(project, topic_name)

    for subscription in subscriber.list_subscriptions(topic_path):
        print(subscription.name)

topic path being used as shown by topic_path = subscriber.topic_path(project, topic_name):
projects/my-team-dev/topics/testing-topic

Using GitHub flavored markdown can help make your request clearer.
See: https://guides.github.com/features/mastering-markdown/

[gylu]

+1
I'm seeing this also, on google-cloud-pubsub:0.29.0, google-cloud:0.30.0
If the topic_path doesn't adhere to the form projects/project/topics/topic, then an exception is caught, but if it's projects/project/topics/some-topic-name-that-doesnt-exist, then all subscriptions for all topics are listed.

[dhermes]

So this is an issue, but not really as reported. The problem is that subscriber.list_subscriptions() is meant to be for the entire project:

In [1]: import google.auth

In [2]: from google.cloud import pubsub_v1

In [3]: _, project = google.auth.default()

In [4]: publisher = pubsub_v1.PublisherClient()
E1215 14:50:02.433979430   11896 ev_epollex_linux.cc:1482]   Skipping epollex becuase GRPC_LINUX_EPOLL is not defined.
E1215 14:50:02.434013514   11896 ev_epoll1_linux.cc:1261]    Skipping epoll1 becuase GRPC_LINUX_EPOLL is not defined.
E1215 14:50:02.434020956   11896 ev_epollsig_linux.cc:1761]  Skipping epollsig becuase GRPC_LINUX_EPOLL is not defined.

In [5]: subscriber = pubsub_v1.SubscriberClient()

In [6]: subscriber.list_subscriptions?
Signature: subscriber.list_subscriptions(project, ...)
Docstring:
Lists matching subscriptions.

...

Args:
    project (str): The name of the cloud project that subscriptions belong to.
        Format is ``projects/{project}``.
...

In [7]: project_path = subscriber.project_path(project)

In [8]: LS = list(subscriber.list_subscriptions(project_path))

In [9]: len(LS)
Out[9]: 6

The method you want is publisher.list_topic_subscriptions:

In [10]: topic_path = publisher.topic_path(project, 'abcdef2')

In [11]: LTS = list(publisher.list_topic_subscriptions(topic_path))

In [12]: len(LTS)
Out[12]: 3

In [13]: publisher.list_topic_subscriptions?
Signature: publisher.list_topic_subscriptions(topic, ...)
Docstring:
Lists the name of the subscriptions for this topic.

...

Args:
    topic (str): The name of the topic that subscriptions are attached to.
        Format is ``projects/{project}/topics/{topic}``.

The actual issue is that subscriber.list_subscriptions doesn't reject requests with the topic path (likely because the topic path starts with the project path):

In [14]: topic_path.startswith(project_path)
Out[14]: True

In [15]: LS_ALSO = list(subscriber.list_subscriptions(topic_path))

In [16]: LS_ALSO == LS
Out[16]: True

I think an issue could be filed with the backend to reject those requests with the topic_path where a project_path should be.

/cc @kir-titievsky

[dhermes]

I filed https://issuetracker.google.com/issues/70727179 with the backend team.

[anorth2]

@dhermes If this is indeed the issue, then this needs to be updated: https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/pubsub/cloud-client/subscriber.py#L30

The docs state that my method was the way to retrieve by topic.
https://cloud.google.com/pubsub/docs/admin#pubsub-list-subscriptions-python

[dhermes]

Thanks for finding that @anorth2 (I'm only loosely aware of what's in python-docs-samples). I filed GoogleCloudPlatform/python-docs-samples#1305 against that repo.