2.0.0 Migration Guide

The 2.0 release of the google-cloud-pubsub client is a significant upgrade based on a next-gen code generator, and includes substantial interface changes. Existing code written for earlier versions of this library will likely require updates to use this version. This document describes the changes that have been made, and what you need to do to update your usage.

If you experience issues or have questions, please file an issue.

Supported Python Versions

WARNING: Breaking change

The 2.0.0 release requires Python 3.6+.

Method Calls

WARNING: Breaking change

Almost all methods that send requests to the backend expect request objects. We provide a script that will convert most common use cases.

  • Install the library
python3 -m pip install google-cloud-pubsub
  • The script fixup_pubsub_v1_keywords.py is shipped with the library. It expects an input directory (with the code to convert) and an empty destination directory. Optionally, the --use-keywords switch can be added to generate flattened keyword parameters instead of a request dictionary (see the following section for an explanation).
$ scripts/fixup_pubsub_v1_keywords.py --input-directory .samples/ --output-directory samples/

Before:

from google.cloud import pubsub

publisher = pubsub.PublisherClient()

project_path = "projects/{}".format(PROJECT_ID)
topics = publisher.list_topics(project_path)

After:

from google.cloud import pubsub

publisher = pubsub.PublisherClient()

project_path = f"projects/{PROJECT_ID}"
topics = publisher.list_topics(request={"project": project_path})

More Details

In google-cloud-pubsub<2.0.0, parameters required by the API were positional parameters and optional parameters were keyword parameters.

Before:

    def list_topics(
        self,
        project,
        page_size=None,
        retry=google.api_core.gapic_v1.method.DEFAULT,
        timeout=google.api_core.gapic_v1.method.DEFAULT,
        metadata=None,
    ):

In the 2.0.0 release, almost all methods that interact with the backend have a single positional parameter request. Method docstrings indicate whether a parameter is required or optional.

NOTE: The exception are hand written methods such as publisher.publish() and subscriber.subscribe() that implement additional logic (e.g. request batching) and sit on top of the API methods from the generated parts of the library. The signatures of these methods have in large part been preserved.

Some methods have additional keyword only parameters. The available parameters depend on the google.api.method_signature annotation specified by the API producer.

After:

    def list_topics(
        self,
        request: pubsub.ListTopicsRequest = None,
        *,
        project: str = None,
        retry: retries.Retry = gapic_v1.method.DEFAULT,
        timeout: float = None,
        metadata: Sequence[Tuple[str, str]] = (),
    ) -> pagers.ListTopicsPager:

NOTE: The request parameter and flattened keyword parameters for the API are mutually exclusive. Passing both will result in an error.

Both of these calls are valid:

response = client.list_topics(
    request={
        "project": project_path,
        "metadata": [("foo", "bar"), ("baz", "quux")],
    }
)

response = client.list_topics(
    project=project_path,
    metadata=[("foo", "bar"), ("baz", "quux")],
)

This call is invalid because it mixes request with a keyword argument metadata. Executing this code will result in an error:

response = client.synthesize_speech(
    request={"project": project_path},
    metadata=[("foo", "bar"), ("baz", "quux")],
)

NOTE: The request parameter of some methods can also contain a more rich set of options that are otherwise not available as explicit keyword only parameters, thus these must be passed through request.

Removed Utility Methods

WARNING: Breaking change

Some utility methods such as publisher client’s subscription_path() have been removed and now only exist in the relevant client, e.g. subscriber.subscription_path().

The project_path() method has been removed from both the publisher and subscriber client, this path must now be constructed manually:

project_path = f"project/{PROJECT_ID}"

Removed client_config Parameter

The publisher and subscriber clients cannot be constructed with client_config argument anymore. If you want to customize retry and timeout settings for a particular method, you need to do it upon method invocation by passing the custom timeout and retry arguments, respectively.