google-cloud-pubsub 2.36.0

Google Cloud Pub/Sub API client library

‘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.

• Client Library Documentation

• Product Documentation

Quick Start

In order to use this library, you first need to go through the following steps:

1. Select or create a Cloud Platform project.

2. Enable billing for your project.

3. Enable the Google Cloud Pub/Sub.

4. Set up Authentication.

Installation

Install this library in a virtual environment using venv. venv is a tool that creates isolated Python environments. These isolated environments can have separate versions of Python packages, which allows you to isolate one project’s dependencies from the dependencies of other projects.

With venv, it’s possible to install this library without needing system install permissions, and without clashing with the installed system dependencies.

Code samples and snippets

Code samples and snippets live in the samples/ folder.

Supported Python Versions

Python >= 3.9

Deprecated Python Versions

Python < 3.9

The last version of this library compatible with Python 3.7 and 3.8 is google-cloud-pubsub==2.34.0.

The last version of this library compatible with Python 2.7 is google-cloud-pubsub==1.7.0.

Mac/Linux

python3 -m venv <your-env>
source <your-env>/bin/activate
pip install google-cloud-pubsub

Windows

py -m venv <your-env>
.\<your-env>\Scripts\activate
pip 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

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.

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.

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:

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.

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:

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)

Versioning

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.

Contributing

Contributions to this library are always welcome and highly encouraged.

See the CONTRIBUTING doc for more information on how to get started.

Community

The best place to ask questions is via Stackoverflow: https://stackoverflow.com/questions/tagged/google-cloud-pubsub

License

Apache 2.0 - See the LICENSE for more information.

Next Steps

• Read the Client Library Documentation for Google Cloud Pub/Sub to see other available methods on the client.

• Read the Google Cloud Pub/Sub Product documentation to learn more about the product and see How-to Guides.

• View this README to see the full list of Cloud APIs that we cover.

Logging

This library uses the standard Python logging functionality to log some RPC events that could be of interest for debugging and monitoring purposes. Note the following:

1. Logs may contain sensitive information. Take care to restrict access to the logs if they are saved, whether it be on local storage or on Google Cloud Logging.

2. Google may refine the occurrence, level, and content of various log messages in this library without flagging such changes as breaking. Do not depend on immutability of the logging events.

3. By default, the logging events from this library are not handled. You must explicitly configure log handling using one of the mechanisms below.

Simple, environment-based configuration

To enable logging for this library without any changes in your code, set the GOOGLE_SDK_PYTHON_LOGGING_SCOPE environment variable to a valid Google logging scope. This configures handling of logging events (at level logging.DEBUG or higher) from this library in a default manner, emitting the logged messages in a structured format. It does not currently allow customizing the logging levels captured nor the handlers, formatters, etc. used for any logging event.

A logging scope is a period-separated namespace that begins with google, identifying the Python module or package to log.

• Valid logging scopes: google, google.cloud.asset.v1, google.api, google.auth, etc.

• Invalid logging scopes: foo, 123, etc.

NOTE: If the logging scope is invalid, the library does not set up any logging handlers.

Environment-Based Examples

• Enabling the default handler for all Google-based loggers

export GOOGLE_SDK_PYTHON_LOGGING_SCOPE=google

• Enabling the default handler for a specific Google module (for a client library called library_v1):

export GOOGLE_SDK_PYTHON_LOGGING_SCOPE=google.cloud.library_v1

Advanced, code-based configuration

You can also configure a valid logging scope using Python’s standard logging mechanism.

Code-Based Examples

• Configuring a handler for all Google-based loggers

import logging

from google.cloud import library_v1

base_logger = logging.getLogger("google")
base_logger.addHandler(logging.StreamHandler())
base_logger.setLevel(logging.DEBUG)

• Configuring a handler for a specific Google module (for a client library called library_v1):

import logging

from google.cloud import library_v1

base_logger = logging.getLogger("google.cloud.library_v1")
base_logger.addHandler(logging.StreamHandler())
base_logger.setLevel(logging.DEBUG)

Logging details

1. Regardless of which of the mechanisms above you use to configure logging for this library, by default logging events are not propagated up to the root logger from the google-level logger. If you need the events to be propagated to the root logger, you must explicitly set logging.getLogger("google").propagate = True in your code.

2. You can mix the different logging configurations above for different Google modules. For example, you may want use a code-based logging configuration for one library, but decide you need to also set up environment-based logging configuration for another library.

   1. If you attempt to use both code-based and environment-based configuration for the same module, the environment-based configuration will be ineffectual if the code -based configuration gets applied first.

3. The Google-specific logging configurations (default handlers for environment-based configuration; not propagating logging events to the root logger) get executed the first time any client library is instantiated in your application, and only if the affected loggers have not been previously configured. (This is the reason for 2.i. above.)