Topics#

Define API Topics.

class google.cloud.pubsub.topic.Topic(name, client, timestamp_messages=False)[source]#

Bases: object

Topics are targets to which messages can be published.

Subscribers then receive those messages.

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics

Parameters:	name (string) – the name of the topic client (`google.cloud.pubsub.client.Client`) – A client which holds credentials and project configuration for the topic (which requires a project). timestamp_messages (boolean) – If true, the topic will add a `timestamp` key to the attributes of each published message: the value will be an RFC 3339 timestamp.

subscription(name, ack_deadline=None, push_endpoint=None)[source]#

Creates a subscription bound to the current topic.

Example: pull-mode subcription, default paramter values

    sub_defaults = topic.subscription(SUB_DEFAULTS)

Example: pull-mode subcription, override ack_deadline default

    sub_ack90 = topic.subscription(SUB_ACK90, ack_deadline=90)

Example: push-mode subcription

    subscription = topic.subscription(SUB_PUSH, push_endpoint=PUSH_URL)
    subscription.create()               # API request

Parameters:	name (string) – the name of the subscription ack_deadline (int) – the deadline (in seconds) by which messages pulled from the back-end must be acknowledged. push_endpoint (string) – URL to which messages will be pushed by the back-end. If not set, the application must pull messages.
Return type:	`Subscription`
Returns:	The subscription created with the passed in arguments.

classmethod from_api_repr(resource, client)[source]#

Factory: construct a topic given its API representation

Parameters:	resource (dict) – topic resource representation returned from the API client (`google.cloud.pubsub.client.Client`) – Client which holds credentials and project configuration for the topic.
Return type:	`google.cloud.pubsub.topic.Topic`
Returns:	Topic parsed from `resource`.
Raises:	`ValueError` if `client` is not `None` and the project from the resource does not agree with the project from the client.

project#: Project bound to the topic.

full_name#: Fully-qualified name used in topic / subscription APIs

create(client=None)[source]#

API call: create the topic via a PUT request

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/create

Example:

    topic = client.topic(TOPIC_NAME)
    topic.create()              # API request

Parameters:	client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current topic.

exists(client=None)[source]#

API call: test for the existence of the topic via a GET request

See https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/get

Example:

    assert not topic.exists()   # API request
    topic.create()              # API request
    assert topic.exists()       # API request

Parameters:	client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current topic.
Return type:	bool
Returns:	Boolean indicating existence of the topic.

delete(client=None)[source]#

API call: delete the topic via a DELETE request

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/delete

Example:

    assert topic.exists()       # API request
    topic.delete()
    assert not topic.exists()   # API request

Parameters:	client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current topic.

publish(message, client=None, **attrs)[source]#

API call: publish a message to a topic via a POST request

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/publish

Example without message attributes:

    topic.publish(b'This is the message payload')               # API request

With message attributes:

    topic.publish(b'Another message payload', extra='EXTRA')    # API request

Parameters:	message (bytes) – the message payload client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current topic. attrs (dict (string -> string)) – key-value pairs to send as message attributes
Return type:	str
Returns:	message ID assigned by the server to the published message

batch(client=None)[source]#

Return a batch to use as a context manager.

Example:

    with topic.batch() as batch:
        batch.publish(PAYLOAD1)
        batch.publish(PAYLOAD2, extra=EXTRA)

Note

The only API request happens during the __exit__() of the topic used as a context manager, and only if the block exits without raising an exception.

Parameters:	client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current topic.
Return type:	`Batch`
Returns:	A batch to use as a context manager.

list_subscriptions(page_size=None, page_token=None, client=None)[source]#

List subscriptions for the project associated with this client.

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics.subscriptions/list

Example:

    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

Parameters:	page_size (int) – maximum number of topics to return, If not passed, defaults to a value set by the API. page_token (string) – opaque marker for the next “page” of topics. If not passed, the API will return the first page of topics. client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current topic.
Return type:	tuple, (list, str)
Returns:	list of `Subscription`, plus a “next page token” string: if not None, indicates that more topics can be retrieved with another call (pass that value as `page_token`).

get_iam_policy(client=None)[source]#

Fetch the IAM policy for the topic.

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/getIamPolicy

Example:

    policy = topic.get_iam_policy()             # API request

Parameters:	client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current batch.
Return type:	`google.cloud.pubsub.iam.Policy`
Returns:	policy created from the resource returned by the `getIamPolicy` API request.

set_iam_policy(policy, client=None)[source]#

Update the IAM policy for the topic.

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/setIamPolicy

Example:

    ALL_USERS = policy.all_users()
    policy.viewers.add(ALL_USERS)
    LOGS_GROUP = policy.group('cloud-logs@google.com')
    policy.editors.add(LOGS_GROUP)
    new_policy = topic.set_iam_policy(policy)   # API request

Parameters:	policy (`google.cloud.pubsub.iam.Policy`) – the new policy, typically fetched via `get_iam_policy()` and updated in place. client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current batch.
Return type:	`google.cloud.pubsub.iam.Policy`
Returns:	updated policy created from the resource returned by the `setIamPolicy` API request.

check_iam_permissions(permissions, client=None)[source]#

Verify permissions allowed for the current user.

See: https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/testIamPermissions

Example:

    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)

Parameters:	permissions (list of string) – list of permissions to be tested client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current batch.
Return type:	sequence of string
Returns:	subset of `permissions` allowed by current IAM policy.

class google.cloud.pubsub.topic.Batch(topic, client)[source]#

Bases: object

Context manager: collect messages to publish via a single API call.

Helper returned by :meth:Topic.batch

Parameters:	topic (`google.cloud.pubsub.topic.Topic`) – the topic being published client (`google.cloud.pubsub.client.Client`) – The client to use.

publish(message, **attrs)[source]#

Emulate publishing a message, but save it.

Parameters:	message (bytes) – the message payload attrs (dict (string -> string)) – key-value pairs to send as message attributes

commit(client=None)[source]#

Send saved messages as a single API call.

Parameters:	client (`Client` or `NoneType`) – the client to use. If not passed, falls back to the `client` stored on the current batch.