Google Cloud Pub/Sub API client library
Project description
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.
Quick Start
In order to use this library, you first need to go through the following steps:
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.
Supported Python Versions
Python >= 3.6
Deprecated Python Versions
Python == 2.7.
The last version of this library compatible with Python 2.7 is google-cloud-pubsub==1.7.0.
Mac/Linux
pip install virtualenv
virtualenv <your-env>
source <your-env>/bin/activate
<your-env>/bin/pip install google-cloud-pubsubWindows
pip install virtualenv
virtualenv <your-env>
<your-env>\Scripts\activate
<your-env>\Scripts\pip.exe install google-cloud-pubsubExample 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
Google Cloud Platform Python developers hang out in Slack in the #python channel, click here to get an invitation.
License
Apache 2.0 - See the LICENSE for more information.
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