apache_beam.io.gcp.pubsub module¶

Google Cloud PubSub sources and sinks.

Cloud Pub/Sub sources and sinks are currently supported only in streaming pipelines, during remote execution.

This API is currently under development and is subject to change.

Updates to the I/O connector code

For any significant updates to this I/O connector, please consider involving corresponding code reviewers mentioned in https://github.com/apache/beam/blob/master/sdks/python/OWNERS

class apache_beam.io.gcp.pubsub.PubsubMessage(data, attributes, message_id=None, publish_time=None, ordering_key='')[source]¶

Bases: object

Represents a Cloud Pub/Sub message.

Message payload includes the data and attributes fields. For the payload to be valid, at least one of its fields must be non-empty.

data¶: (bytes) Message data. May be None.

attributes¶: (dict) Key-value map of str to str, containing both user-defined and service generated attributes (such as id_label and timestamp_attribute). May be None.

message_id¶: (str) ID of the message, assigned by the pubsub service when the message is published. Guaranteed to be unique within the topic. Will be reset to None if the message is being written to pubsub.

publish_time¶: (datetime) Time at which the message was published. Will be reset to None if the Message is being written to pubsub.

ordering_key¶: (str) If non-empty, identifies related messages for which publish order is respected by the PubSub subscription.

class apache_beam.io.gcp.pubsub.ReadFromPubSub(topic=None, subscription=None, id_label=None, with_attributes=False, timestamp_attribute=None)[source]¶

Bases: apache_beam.transforms.ptransform.PTransform

A PTransform for reading from Cloud Pub/Sub.

Initializes ReadFromPubSub.

Parameters:

topic – Cloud Pub/Sub topic in the form “projects/<project>/topics/<topic>”. If provided, subscription must be None.
subscription – Existing Cloud Pub/Sub subscription to use in the form “projects/<project>/subscriptions/<subscription>”. If not specified, a temporary subscription will be created from the specified topic. If provided, topic must be None.
id_label – The attribute on incoming Pub/Sub messages to use as a unique record identifier. When specified, the value of this attribute (which can be any string that uniquely identifies the record) will be used for deduplication of messages. If not provided, we cannot guarantee that no duplicate data will be delivered on the Pub/Sub stream. In this case, deduplication of the stream will be strictly best effort.
with_attributes – True - output elements will be PubsubMessage objects. False - output elements will be of type bytes (message data only).
timestamp_attribute –
Message value to use as element timestamp. If None, uses message publishing time as the timestamp.

Timestamp values should be in one of two formats:
- A numerical value representing the number of milliseconds since the Unix epoch.
- A string in RFC 3339 format, UTC timezone. Example: 2015-10-29T23:41:41.123Z. The sub-second component of the timestamp is optional, and digits beyond the first three (i.e., time units smaller than milliseconds) may be ignored.

expand(pvalue)[source]¶

to_runner_api_parameter(context)[source]¶

apache_beam.io.gcp.pubsub.ReadStringsFromPubSub(topic=None, subscription=None, id_label=None)[source]¶

apache_beam.io.gcp.pubsub.WriteStringsToPubSub(topic)[source]¶

class apache_beam.io.gcp.pubsub.WriteToPubSub(topic, with_attributes=False, id_label=None, timestamp_attribute=None)[source]¶

Bases: apache_beam.transforms.ptransform.PTransform

A PTransform for writing messages to Cloud Pub/Sub.

Initializes WriteToPubSub.

Parameters:

topic – Cloud Pub/Sub topic in the form “projects/<project>/topics/<topic>”.
with_attributes – True - input elements will be PubsubMessage objects. False - input elements will be of type bytes (message data only).
id_label – If set, will set an attribute for each Cloud Pub/Sub message with the given name and a unique value. This attribute can then be used in a ReadFromPubSub PTransform to deduplicate messages.
timestamp_attribute – If set, will set an attribute for each Cloud Pub/Sub message with the given name and the message’s publish time as the value.

static message_to_proto_str(element)[source]¶

static bytes_to_proto_str(element)[source]¶

expand(pcoll)[source]¶

to_runner_api_parameter(context)[source]¶

display_data()[source]¶

class apache_beam.io.gcp.pubsub.PubSubSourceDescriptor[source]¶

Bases: tuple

A PubSub source descriptor for MultipleReadFromPubSub`

source¶: Existing Cloud Pub/Sub topic or subscription to use in the form “projects/<project>/topics/<topic>” or “projects/<project>/subscriptions/<subscription>”

id_label¶: The attribute on incoming Pub/Sub messages to use as a unique record identifier. When specified, the value of this attribute (which can be any string that uniquely identifies the record) will be used for deduplication of messages. If not provided, we cannot guarantee that no duplicate data will be delivered on the Pub/Sub stream. In this case, deduplication of the stream will be strictly best effort.

timestamp_attribute¶

Message value to use as element timestamp. If None, uses message publishing time as the timestamp.

Timestamp values should be in one of two formats:

A numerical value representing the number of milliseconds since the Unix epoch.
A string in RFC 3339 format, UTC timezone. Example: 2015-10-29T23:41:41.123Z. The sub-second component of the timestamp is optional, and digits beyond the first three (i.e., time units smaller than milliseconds) may be ignored.

Create new instance of PubSubSourceDescriptor(source, id_label, timestamp_attribute)

source: Alias for field number 0

id_label: Alias for field number 1

timestamp_attribute: Alias for field number 2

class apache_beam.io.gcp.pubsub.MultipleReadFromPubSub(pubsub_source_descriptors, with_attributes=False)[source]¶

Bases: apache_beam.transforms.ptransform.PTransform

A PTransform that expands ReadFromPubSub to read from multiple PubSubSourceDescriptor.

The MultipleReadFromPubSub transform allows you to read multiple topics and/or subscriptions using just one transform. It is the recommended transform to read multiple Pub/Sub sources when the output PCollection are going to be flattened. The transform takes a list of PubSubSourceDescriptor and organize them by type (topic / subscription) and project::

topic_1 = PubSubSourceDescriptor('projects/myproject/topics/a_topic')
topic_2 = PubSubSourceDescriptor(
            'projects/myproject2/topics/b_topic',
            'my_label',
            'my_timestamp_attribute')
subscription_1 = PubSubSourceDescriptor(
            'projects/myproject/subscriptions/a_subscription')

results = pipeline | MultipleReadFromPubSub(
            [topic_1, topic_2, subscription_1])

Initializes PubSubMultipleReader.

Parameters:	pubsub_source_descriptors – List of Cloud Pub/Sub topics or subscriptions of type ~PubSubSourceDescriptor. with_attributes – True - input elements will be `PubsubMessage` objects. False - input elements will be of type `bytes` (message data only).

expand(pcol)[source]¶