google-cloud-python/0.19.0/pubsub-usage.html at gh-pages · kenyanerd/google-cloud-python

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<!DOCTYPE html>

<html class="no-js" lang="en" >

<head>

<title>Using the API — google-cloud 0.19.0 documentation</title>

</head>

<a href="index.html" class="icon icon-home"> google-cloud

</a>

</form>

</div>

google-cloud

<ul>

<li class="toctree-l1"><a class="reference internal" href="google-cloud-api.html">Shared Core Modules</a></li>

<li class="toctree-l1"><a class="reference internal" href="google-cloud-config.html">Configuration</a></li>

<li class="toctree-l1"><a class="reference internal" href="google-cloud-auth.html">Authentication</a></li>

<li class="toctree-l1"><a class="reference internal" href="operation-api.html">Long-Running Operations</a></li>

</ul>

Datastore

<ul>

<li class="toctree-l1"><a class="reference internal" href="datastore-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="datastore-entities.html">Entities</a></li>

<li class="toctree-l1"><a class="reference internal" href="datastore-queries.html">Queries</a></li>

<li class="toctree-l1"><a class="reference internal" href="datastore-transactions.html">Transactions</a></li>

<li class="toctree-l1"><a class="reference internal" href="datastore-batches.html">Batches</a></li>

<li class="toctree-l1"><a class="reference internal" href="datastore-helpers.html">Helpers</a></li>

</ul>

Storage

<ul>

<li class="toctree-l1"><a class="reference internal" href="storage-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="storage-blobs.html">Blobs / Objects</a></li>

<li class="toctree-l1"><a class="reference internal" href="storage-buckets.html">Buckets</a></li>

<li class="toctree-l1"><a class="reference internal" href="storage-batch.html">Batches</a></li>

</ul>

Pub/Sub

<li class="toctree-l1 current"><a class="current reference internal" href="#">Using the API</a><ul>

<li class="toctree-l2"><a class="reference internal" href="#authentication-configuration">Authentication / Configuration</a></li>

<li class="toctree-l2"><a class="reference internal" href="#manage-topics-for-a-project">Manage topics for a project</a></li>

<li class="toctree-l2"><a class="reference internal" href="#publish-messages-to-a-topic">Publish messages to a topic</a></li>

<li class="toctree-l2"><a class="reference internal" href="#manage-subscriptions-to-topics">Manage subscriptions to topics</a></li>

<li class="toctree-l2"><a class="reference internal" href="#pull-messages-from-a-subscription">Pull messages from a subscription</a></li>

</ul>

</li>

<li class="toctree-l1"><a class="reference internal" href="pubsub-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="pubsub-topic.html">Topics</a></li>

<li class="toctree-l1"><a class="reference internal" href="pubsub-subscription.html">Subscriptions</a></li>

<li class="toctree-l1"><a class="reference internal" href="pubsub-message.html">Message</a></li>

<li class="toctree-l1"><a class="reference internal" href="pubsub-iam.html">IAM Policy</a></li>

</ul>

BigQuery

<ul>

<li class="toctree-l1"><a class="reference internal" href="bigquery-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigquery-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigquery-dataset.html">Datasets</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigquery-table.html">Tables</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigquery-query.html">Query</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigquery-schema.html">Schemas</a></li>

</ul>

Cloud Bigtable

<ul>

<li class="toctree-l1"><a class="reference internal" href="bigtable-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-client-intro.html">Base for Everything</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-instance-api.html">Instance Admin API</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-table-api.html">Table Admin API</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-instance.html">Instance</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-cluster.html">Cluster</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-table.html">Table</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-column-family.html">Column Families</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-row.html">Bigtable Row</a></li>

<li class="toctree-l1"><a class="reference internal" href="bigtable-row-filters.html">Bigtable Row Filters</a></li>

</ul>

Resource Manager

<ul>

<li class="toctree-l1"><a class="reference internal" href="resource-manager-api.html">Overview</a></li>

<li class="toctree-l1"><a class="reference internal" href="resource-manager-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="resource-manager-project.html">Projects</a></li>

</ul>

DNS

<ul>

<li class="toctree-l1"><a class="reference internal" href="dns-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="dns-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="dns-zone.html">Managed Zones</a></li>

<li class="toctree-l1"><a class="reference internal" href="dns-resource-record-set.html">Resource Record Sets</a></li>

<li class="toctree-l1"><a class="reference internal" href="dns-changes.html">Change Sets</a></li>

</ul>

Stackdriver Logging

<ul>

<li class="toctree-l1"><a class="reference internal" href="logging-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-usage.html#python-logging-handler-transports">Python logging handler transports</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-logger.html">Logger</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-entries.html">Entries</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-metric.html">Metrics</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-sink.html">Sinks</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-handlers.html">Python Logging Module Handler</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-transports-sync.html">Python Logging Handler Sync Transport</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-transports-thread.html">Python Logging Handler Threaded Transport</a></li>

<li class="toctree-l1"><a class="reference internal" href="logging-transports-base.html">Python Logging Handler Sync Transport</a></li>

</ul>

Stackdriver Error Reporting

<ul>

<li class="toctree-l1"><a class="reference internal" href="error-reporting-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="error-reporting-client.html">Client</a></li>

</ul>

Stackdriver Monitoring

<ul>

<li class="toctree-l1"><a class="reference internal" href="monitoring-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="monitoring-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="monitoring-metric.html">Metric Descriptors</a></li>

<li class="toctree-l1"><a class="reference internal" href="monitoring-resource.html">Monitored Resource Descriptors</a></li>

<li class="toctree-l1"><a class="reference internal" href="monitoring-group.html">Groups</a></li>

<li class="toctree-l1"><a class="reference internal" href="monitoring-query.html">Time Series Query</a></li>

<li class="toctree-l1"><a class="reference internal" href="monitoring-timeseries.html">Time Series</a></li>

<li class="toctree-l1"><a class="reference internal" href="monitoring-label.html">Label Descriptors</a></li>

</ul>

Translate

<ul>

<li class="toctree-l1"><a class="reference internal" href="translate-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="translate-client.html">Client</a></li>

</ul>

Vision

<ul>

<li class="toctree-l1"><a class="reference internal" href="vision-usage.html">Using the Vision API</a></li>

<li class="toctree-l1"><a class="reference internal" href="vision-client.html">Vision Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="vision-color.html">Vision Image Properties</a></li>

<li class="toctree-l1"><a class="reference internal" href="vision-entity.html">Vision Entity</a></li>

<li class="toctree-l1"><a class="reference internal" href="vision-feature.html">Vision Feature</a></li>

<li class="toctree-l1"><a class="reference internal" href="vision-face.html">Vision Face</a></li>

<li class="toctree-l1"><a class="reference internal" href="vision-image.html">Vision Image</a></li>

<li class="toctree-l1"><a class="reference internal" href="vision-safe-search.html">Vision Safe Search</a></li>

</ul>

Natural Language

<ul>

<li class="toctree-l1"><a class="reference internal" href="language-usage.html">Using the API</a></li>

<li class="toctree-l1"><a class="reference internal" href="language-client.html">Client</a></li>

<li class="toctree-l1"><a class="reference internal" href="language-document.html">Document</a></li>

<li class="toctree-l1"><a class="reference internal" href="language-responses.html">Natural Language Response Classes</a></li>

</ul>

External Links

<ul>

<li class="toctree-l1"><a class="reference external" href="https://github.com/GoogleCloudPlatform/google-cloud-python/">GitHub</a></li>

<li class="toctree-l1"><a class="reference external" href="https://github.com/GoogleCloudPlatform/google-cloud-python/issues">Issues</a></li>

<li class="toctree-l1"><a class="reference external" href="http://stackoverflow.com/questions/tagged/google-cloud-python">Stack Overflow</a></li>

</ul>

</div>

</nav>

<a href="index.html">google-cloud</a>

</nav>

<li>Using the API</li>

<a href="_sources/pubsub-usage.txt" rel="nofollow"> View page source</a>

</li>

</ul>

<hr/>

</div>

<h1>Using the API<a class="headerlink" href="#using-the-api" title="Permalink to this headline">#</a></h1>

<h2>Authentication / Configuration<a class="headerlink" href="#authentication-configuration" title="Permalink to this headline">#</a></h2>

<ul>

<li>Use <a class="reference internal" href="pubsub-client.html#google.cloud.pubsub.client.Client" title="google.cloud.pubsub.client.Client"><code class="xref py py-class docutils literal">Client</code></a> objects to configure

your applications.

</li>

<li>In addition to any authentication configuration, you should also set the

<code class="xref std std-envvar docutils literal">GOOGLE_CLOUD_PROJECT</code> environment variable for the project you’d like

to interact with. If you are Google App Engine or Google Compute Engine

this will be detected automatically.

</li>

<li>The library now enables the <code class="docutils literal">gRPC</code> transport for the pubsub API by

default, assuming that the required dependencies are installed and

importable. To disable this transport, set the

<code class="xref std std-envvar docutils literal">GOOGLE_CLOUD_DISABLE_GRPC</code> environment variable to a

non-empty string, e.g.: <code class="docutils literal">$ export GOOGLE_CLOUD_DISABLE_GRPC=true</code>.

</li>

<li><a class="reference internal" href="pubsub-client.html#google.cloud.pubsub.client.Client" title="google.cloud.pubsub.client.Client"><code class="xref py py-class docutils literal">Client</code></a> objects hold both a <code class="docutils literal">project</code>

and an authenticated connection to the PubSub service.

</li>

<li>The authentication credentials can be implicitly determined from the

environment or directly via

<code class="xref py py-meth docutils literal">from_service_account_json</code>

and

<code class="xref py py-meth docutils literal">from_service_account_p12</code>.

</li>

<li>After setting <code class="docutils literal">GOOGLE_APPLICATION_CREDENTIALS</code> and <code class="docutils literal">GOOGLE_CLOUD_PROJECT</code>

environment variables, create a <a class="reference internal" href="pubsub-client.html#google.cloud.pubsub.client.Client" title="google.cloud.pubsub.client.Client"><code class="xref py py-class docutils literal">Client</code></a>

<div class="highlight-default"><div class="highlight"><pre>>>> from google.cloud import pubsub

>>> client = pubsub.Client()

</pre></div>

</div>

</li>

</ul>

</div>

<h2>Manage topics for a project<a class="headerlink" href="#manage-topics-for-a-project" title="Permalink to this headline">#</a></h2>

List topics for the default project:

<div class="highlight-default"><div class="highlight"><pre> topics, token = client.list_topics() # API request

while True:

for topic in topics:

do_something_with(topic)

if token is None:

break

topics, token = client.list_topics(page_token=token) # API request

</pre></div>

</div>

Create a new topic for the default project:

<div class="highlight-default"><div class="highlight"><pre> topic = client.topic(TOPIC_NAME)

topic.create() # API request

</pre></div>

</div>

Check for the existence of a topic:

<div class="highlight-default"><div class="highlight"><pre> assert not topic.exists() # API request

topic.create() # API request

assert topic.exists() # API request

</pre></div>

</div>

Delete a topic:

<div class="highlight-default"><div class="highlight"><pre> assert topic.exists() # API request

topic.delete()

assert not topic.exists() # API request

</pre></div>

</div>

Fetch the IAM policy for a topic:

<div class="highlight-default"><div class="highlight"><pre> policy = topic.get_iam_policy() # API request

</pre></div>

</div>

Update the IAM policy for a topic:

<div class="highlight-default"><div class="highlight"><pre> ALL_USERS = policy.all_users()

policy.viewers.add(ALL_USERS)

LOGS_GROUP = policy.group('[email protected]')

policy.editors.add(LOGS_GROUP)

new_policy = topic.set_iam_policy(policy) # API request

</pre></div>

</div>

Test permissions allowed by the current IAM policy on a topic:

<div class="highlight-default"><div class="highlight"><pre> from google.cloud.pubsub.iam import OWNER_ROLE, EDITOR_ROLE, VIEWER_ROLE

TO_CHECK = [OWNER_ROLE, EDITOR_ROLE, VIEWER_ROLE]

ALLOWED = topic.check_iam_permissions(TO_CHECK)

assert set(ALLOWED) == set(TO_CHECK)

</pre></div>

</div>

<h2>Publish messages to a topic<a class="headerlink" href="#publish-messages-to-a-topic" title="Permalink to this headline">#</a></h2>

Publish a single message to a topic, without attributes:

<div class="highlight-default"><div class="highlight"><pre> topic.publish(b'This is the message payload') # API request

</pre></div>

</div>

Publish a single message to a topic, with attributes:

<div class="highlight-default"><div class="highlight"><pre> topic.publish(b'Another message payload', extra='EXTRA') # API request

</pre></div>

</div>

Publish a set of messages to a topic (as a single request):

<div class="highlight-default"><div class="highlight"><pre> with topic.batch() as batch:

batch.publish(PAYLOAD1)

batch.publish(PAYLOAD2, extra=EXTRA)

</pre></div>

</div>

Note

The only API request happens during the <code class="docutils literal">__exit__()</code> of the topic

used as a context manager, and only if the block exits without raising

an exception.

</div>

<h2>Manage subscriptions to topics<a class="headerlink" href="#manage-subscriptions-to-topics" title="Permalink to this headline">#</a></h2>

List all subscriptions for the default project:

<div class="highlight-default"><div class="highlight"><pre> subscriptions, token = client.list_subscriptions() # API request

while True:

for subscription in subscriptions:

do_something_with(subscription)

if token is None:

break

subscriptions, token = client.list_subscriptions(

page_token=token) # API request

</pre></div>

</div>

List subscriptions for a topic:

<div class="highlight-default"><div class="highlight"><pre> subscriptions, token = topic.list_subscriptions() # API request

while True:

for subscription in subscriptions:

do_something_with(subscription)

if token is None:

break

subscriptions, token = topic.list_subscriptions(

page_token=token) # API request

</pre></div>

</div>

Create a new pull subscription for a topic, with defaults:

<div class="highlight-default"><div class="highlight"><pre> sub_defaults = topic.subscription(SUB_DEFAULTS)

</pre></div>

</div>

Create a new pull subscription for a topic with a non-default ACK deadline:

<div class="highlight-default"><div class="highlight"><pre> sub_ack90 = topic.subscription(SUB_ACK90, ack_deadline=90)

</pre></div>

</div>

Create a new push subscription for a topic:

<div class="highlight-default"><div class="highlight"><pre> subscription = topic.subscription(SUB_PUSH, push_endpoint=PUSH_URL)

subscription.create() # API request

</pre></div>

</div>

Check for the existence of a subscription:

<div class="highlight-default"><div class="highlight"><pre> assert subscription.exists() # API request

</pre></div>

</div>

Convert a pull subscription to push:

push_endpoint=PUSH_URL) # API request

</pre></div>

</div>

Convert a push subscription to pull:

<div class="highlight-default"><div class="highlight"><pre> subscription.modify_push_configuration(push_endpoint=None) # API request

</pre></div>

</div>

Re-synchronize a subscription with the back-end:

<div class="highlight-default"><div class="highlight"><pre> subscription.reload() # API request

</pre></div>

</div>

Fetch the IAM policy for a subscription

<div class="highlight-default"><div class="highlight"><pre> policy = subscription.get_iam_policy() # API request

</pre></div>

</div>

Update the IAM policy for a subscription:

new_policy = subscription.set_iam_policy(policy) # API request

</pre></div>

</div>

Test permissions allowed by the current IAM policy on a subscription:

ALLOWED = subscription.check_iam_permissions(TO_CHECK)

</pre></div>

</div>

Delete a subscription:

<div class="highlight-default"><div class="highlight"><pre> subscription.delete() # API request

</pre></div>

</div>

<h2>Pull messages from a subscription<a class="headerlink" href="#pull-messages-from-a-subscription" title="Permalink to this headline">#</a></h2>

Fetch pending messages for a pull subscription:

<div class="highlight-default"><div class="highlight"><pre> pulled = subscription.pull(max_messages=2)

</pre></div>

</div>

Note that received messages must be acknowledged, or else the back-end

will re-send them later:

<div class="highlight-default"><div class="highlight"><pre> for ack_id, message in pulled:

try:

do_something_with(message)

except ApplicationException as e:

log_exception(e)

else:

subscription.acknowledge([ack_id])

</pre></div>

</div>

Fetch messages for a pull subscription without blocking (none pending):

<div class="highlight-default"><div class="highlight"><pre> pulled = subscription.pull(return_immediately=True)

</pre></div>

</div>

Update the acknowlegement deadline for pulled messages:

<div class="highlight-default"><div class="highlight"><pre> for ack_id, _ in pulled:

subscription.modify_ack_deadline(ack_id, 90) # API request

</pre></div>

</div>

Fetch pending messages, acknowledging those whose processing doesn’t raise an

error:

<div class="highlight-default"><div class="highlight"><pre> from google.cloud.pubsub.subscription import AutoAck

with AutoAck(subscription, max_messages=10) as ack:

for ack_id, message in list(ack.items()):

try:

do_something_with(message)

except Exception: # pylint: disable=broad-except

del ack[ack_id]

</pre></div>

</div>

Note

The <code class="docutils literal">pull</code> API request occurs at entry to the <code class="docutils literal">with</code> block, and the

<code class="docutils literal">acknowlege</code> API request occurs at the end, passing only the <code class="docutils literal">ack_ids</code>

which haven’t been deleted from <code class="docutils literal">ack</code>

</div>

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