Google Cloud Pub/Sub API client library
|GA| |pypi| |versions|
Google Cloud Pub / Sub
_ is a fully-managed real-time messaging service that
allows you to send and receive messages between independent applications. You
can leverage Cloud Pub/Sub’s flexibility to decouple systems and components
hosted on Google Cloud Platform or elsewhere on the Internet. By building on
the same technology Google uses, Cloud Pub / Sub is designed to provide “at
least once” delivery at low latency with on-demand scalability to 1 million
messages per second (and beyond).
Publisher applications can send messages to a topic
and other applications
can subscribe to that topic to receive the messages. By decoupling senders and
receivers, Google Cloud Pub/Sub allows developers to communicate between
independently written applications.
Product Documentation
_Client Library Documentation
_.. |GA| image:: https://img.shields.io/badge/support-GA-gold.svg :target: https://github.com/googleapis/google-cloud-python/blob/main/README.rst#general-availability .. |pypi| image:: https://img.shields.io/pypi/v/google-cloud-pubsub.svg :target: https://pypi.org/project/google-cloud-pubsub/ .. |versions| image:: https://img.shields.io/pypi/pyversions/google-cloud-pubsub.svg :target: https://pypi.org/project/google-cloud-pubsub/ .. _Google Cloud Pub / Sub: https://cloud.google.com/pubsub/ .. _Product Documentation: https://cloud.google.com/pubsub/docs .. _Client Library Documentation: https://cloud.google.com/python/docs/reference/pubsub/latest
In order to use this library, you first need to go through the following steps:
Select or create a Cloud Platform project.
_Enable billing for your project.
_Enable the Google Cloud Pub / Sub API.
_Setup Authentication.
_.. _Select or create a Cloud Platform project.: https://console.cloud.google.com/project .. _Enable billing for your project.: https://cloud.google.com/billing/docs/how-to/modify-project#enable_billing_for_a_project .. _Enable the Google Cloud Pub / Sub API.: https://cloud.google.com/pubsub .. _Setup Authentication.: https://googleapis.dev/python/google-api-core/latest/auth.html
Installation
Install this library in a `virtualenv`_ using pip. `virtualenv`_ is a tool to
create isolated Python environments. The basic problem it addresses is one of
dependencies and versions, and indirectly permissions.
With `virtualenv`_, it's possible to install this library without needing system
install permissions, and without clashing with the installed system
dependencies.
.. _`virtualenv`: https://virtualenv.pypa.io/en/latest/
Supported Python Versions
^^^^^^^^^^^^^^^^^^^^^^^^^
Python >= 3.7
Deprecated Python Versions
^^^^^^^^^^^^^^^^^^^^^^^^^^
Python <= 3.6.
The last version of this library compatible with Python 2.7 is google-cloud-pubsub==1.7.0.
Mac/Linux
^^^^^^^^^
.. code-block:: console
pip install virtualenv
virtualenv <your-env>
source <your-env>/bin/activate
<your-env>/bin/pip install google-cloud-pubsub
Windows
^^^^^^^
.. code-block:: console
pip install virtualenv
virtualenv <your-env>
<your-env>\Scripts\activate
<your-env>\Scripts\pip.exe install google-cloud-pubsub
Example Usage
Publishing ^^^^^^^^^^
To publish data to Cloud Pub/Sub you must create a topic, and then publish messages to it
.. code-block:: python
import os
from google.cloud import pubsub_v1
publisher = pubsub_v1.PublisherClient()
topic_name = 'projects/{project_id}/topics/{topic}'.format(
project_id=os.getenv('GOOGLE_CLOUD_PROJECT'),
topic='MY_TOPIC_NAME', # Set this to something appropriate.
)
publisher.create_topic(name=topic_name)
future = publisher.publish(topic_name, b'My first message!', spam='eggs')
future.result()
To learn more, consult the publishing documentation
_.
.. _publishing documentation: https://cloud.google.com/python/docs/reference/pubsub/latest
Subscribing ^^^^^^^^^^^
To subscribe to data in Cloud Pub/Sub, you create a subscription based on the topic, and subscribe to that, passing a callback function.
.. code-block:: python
import os
from google.cloud import pubsub_v1
topic_name = 'projects/{project_id}/topics/{topic}'.format(
project_id=os.getenv('GOOGLE_CLOUD_PROJECT'),
topic='MY_TOPIC_NAME', # Set this to something appropriate.
)
subscription_name = 'projects/{project_id}/subscriptions/{sub}'.format(
project_id=os.getenv('GOOGLE_CLOUD_PROJECT'),
sub='MY_SUBSCRIPTION_NAME', # Set this to something appropriate.
)
def callback(message):
print(message.data)
message.ack()
with pubsub_v1.SubscriberClient() as subscriber:
subscriber.create_subscription(
name=subscription_name, topic=topic_name)
future = subscriber.subscribe(subscription_name, callback)
The future returned by the call to subscriber.subscribe
can be used to
block the current thread until a given condition obtains:
.. code-block:: python
try:
future.result()
except KeyboardInterrupt:
future.cancel()
It is also possible to pull messages in a synchronous (blocking) fashion. To
learn more about subscribing, consult the subscriber documentation
_.
.. _subscriber documentation: https://cloud.google.com/python/docs/reference/pubsub/latest
Authentication ^^^^^^^^^^^^^^
It is possible to specify the authentication method to use with the Pub/Sub
clients. This can be done by providing an explicit Credentials
_ instance. Support
for various authentication methods is available from the google-auth
_ library.
For example, to use JSON Web Tokens, provide a google.auth.jwt.Credentials
_ instance:
.. code-block:: python
import json
from google.auth import jwt
service_account_info = json.load(open("service-account-info.json"))
audience = "https://pubsub.googleapis.com/google.pubsub.v1.Subscriber"
credentials = jwt.Credentials.from_service_account_info(
service_account_info, audience=audience
)
subscriber = pubsub_v1.SubscriberClient(credentials=credentials)
# The same for the publisher, except that the "audience" claim needs to be adjusted
publisher_audience = "https://pubsub.googleapis.com/google.pubsub.v1.Publisher"
credentials_pub = credentials.with_claims(audience=publisher_audience)
publisher = pubsub_v1.PublisherClient(credentials=credentials_pub)
.. _Credentials: https://google-auth.readthedocs.io/en/latest/reference/google.auth.credentials.html#google.auth.credentials.Credentials .. _google-auth: https://google-auth.readthedocs.io/en/latest/index.html .. _google.auth.jwt.Credentials: https://google-auth.readthedocs.io/en/latest/reference/google.auth.jwt.html#google.auth.jwt.Credentials
This library follows Semantic Versioning
_.
It is currently in major version one (1.y.z), which means that the public API should be considered stable.
.. _Semantic Versioning: http://semver.org/
Contributions to this library are always welcome and highly encouraged.
See the CONTRIBUTING doc
_ for more information on how to get started.
.. _CONTRIBUTING doc: https://github.com/googleapis/google-cloud-python/blob/main/CONTRIBUTING.rst
The best place to ask questions is via Stackoverflow: https://stackoverflow.com/questions/tagged/google-cloud-pubsub
Apache 2.0 - See the LICENSE
_ for more information.
.. _the LICENSE: https://github.com/googleapis/google-cloud-python/blob/main/LICENSE