#
# Licensed to the Apache Software Foundation (ASF) under one or more
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# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
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# http://www.apache.org/licenses/LICENSE-2.0
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# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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#
"""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.
Description of common arguments used in this module:
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.
"""
from __future__ import absolute_import
import re
from builtins import object
from past.builtins import basestring
from apache_beam import coders
from apache_beam.io.iobase import Read
from apache_beam.io.iobase import Write
from apache_beam.runners.dataflow.native_io import iobase as dataflow_io
from apache_beam.transforms import Map
from apache_beam.transforms import PTransform
from apache_beam.transforms.display import DisplayDataItem
try:
from google.cloud.proto.pubsub.v1 import pubsub_pb2
except ImportError:
pubsub_pb2 = None
__all__ = ['PubsubMessage', 'ReadFromPubSub', 'ReadStringsFromPubSub',
'WriteStringsToPubSub']
[docs]class PubsubMessage(object):
"""Represents a message from Cloud Pub/Sub.
This interface is experimental. No backwards compatibility guarantees.
Attributes:
payload: (str) Message payload, as a byte string.
attributes: (dict) Map of string to string.
"""
def __init__(self, payload, attributes):
"""Constructs a message.
Beam users should not directly construct ``PubsubMessages``.
"""
self.payload = payload
self.attributes = attributes
def __eq__(self, other):
return isinstance(other, PubsubMessage) and (
self.payload == other.payload and
self.attributes == other.attributes)
def __repr__(self):
return 'PubsubMessage(%s, %s)' % (self.payload, self.attributes)
@staticmethod
def _from_proto(proto_msg):
"""Construct from serialized form of ``PubsubMessage``.
https://cloud.google.com/pubsub/docs/reference/rpc/google.pubsub.v1#google.pubsub.v1.PubsubMessage
"""
msg = pubsub_pb2.PubsubMessage()
msg.ParseFromString(proto_msg)
# Convert ScalarMapContainer to dict.
attributes = dict((key, msg.attributes[key]) for key in msg.attributes)
return PubsubMessage(msg.data, attributes)
@staticmethod
def _from_message(msg):
"""Construct from ``google.cloud.pubsub.message.Message``.
https://google-cloud-python.readthedocs.io/en/latest/pubsub/subscriber/api/message.html
"""
# Convert ScalarMapContainer to dict.
attributes = dict((key, msg.attributes[key]) for key in msg.attributes)
return PubsubMessage(msg.data, attributes)
[docs]class ReadFromPubSub(PTransform):
"""A ``PTransform`` for reading from Cloud Pub/Sub."""
# Implementation note: This ``PTransform`` is overridden by Directrunner.
def __init__(self, topic=None, subscription=None, id_label=None,
timestamp_attribute=None):
"""Initializes ``ReadFromPubSub``.
Args:
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.
"""
super(ReadFromPubSub, self).__init__()
# TODO(BEAM-4536): Add with_attributes to kwargs once fixed.
self.with_attributes = False
self._source = _PubSubSource(
topic=topic,
subscription=subscription,
id_label=id_label,
with_attributes=self.with_attributes,
timestamp_attribute=timestamp_attribute)
[docs] def expand(self, pvalue):
pcoll = pvalue.pipeline | Read(self._source)
if self.with_attributes:
pcoll = pcoll | Map(PubsubMessage._from_proto)
pcoll.element_type = PubsubMessage
else:
pcoll.element_type = bytes
return pcoll
[docs] def to_runner_api_parameter(self, context):
# Required as this is identified by type in PTransformOverrides.
# TODO(BEAM-3812): Use an actual URN here.
return self.to_runner_api_pickled(context)
[docs]class ReadStringsFromPubSub(PTransform):
"""A ``PTransform`` for reading utf-8 string payloads from Cloud Pub/Sub.
Outputs elements of type ``unicode``, decoded from UTF-8.
This class is deprecated.
"""
def __init__(self, topic=None, subscription=None, id_label=None):
super(ReadStringsFromPubSub, self).__init__()
self.topic = topic
self.subscription = subscription
self.id_label = id_label
[docs] def expand(self, pvalue):
p = (pvalue.pipeline
| ReadFromPubSub(self.topic, self.subscription, self.id_label)
| 'DecodeString' >> Map(lambda b: b.decode('utf-8')))
p.element_type = basestring
return p
[docs]class WriteStringsToPubSub(PTransform):
"""A ``PTransform`` for writing utf-8 string payloads to Cloud Pub/Sub."""
def __init__(self, topic):
"""Initializes ``WriteStringsToPubSub``.
Attributes:
topic: Cloud Pub/Sub topic in the form "/topics/<project>/<topic>".
"""
super(WriteStringsToPubSub, self).__init__()
self._sink = _PubSubPayloadSink(topic)
[docs] def expand(self, pcoll):
pcoll = pcoll | 'EncodeString' >> Map(lambda s: s.encode('utf-8'))
pcoll.element_type = bytes
return pcoll | Write(self._sink)
[docs] def to_runner_api_parameter(self, context):
# Required as this is identified by type in PTransformOverrides.
# TODO(BEAM-3812): Use an actual URN here.
return self.to_runner_api_pickled(context)
PROJECT_ID_REGEXP = '[a-z][-a-z0-9:.]{4,61}[a-z0-9]'
SUBSCRIPTION_REGEXP = 'projects/([^/]+)/subscriptions/(.+)'
TOPIC_REGEXP = 'projects/([^/]+)/topics/(.+)'
def parse_topic(full_topic):
match = re.match(TOPIC_REGEXP, full_topic)
if not match:
raise ValueError(
'PubSub topic must be in the form "projects/<project>/topics'
'/<topic>" (got %r).' % full_topic)
project, topic_name = match.group(1), match.group(2)
if not re.match(PROJECT_ID_REGEXP, project):
raise ValueError('Invalid PubSub project name: %r.' % project)
return project, topic_name
def parse_subscription(full_subscription):
match = re.match(SUBSCRIPTION_REGEXP, full_subscription)
if not match:
raise ValueError(
'PubSub subscription must be in the form "projects/<project>'
'/subscriptions/<subscription>" (got %r).' % full_subscription)
project, subscription_name = match.group(1), match.group(2)
if not re.match(PROJECT_ID_REGEXP, project):
raise ValueError('Invalid PubSub project name: %r.' % project)
return project, subscription_name
class _PubSubSource(dataflow_io.NativeSource):
"""Source for the payload of a message as bytes from a Cloud Pub/Sub topic.
This ``NativeSource`` is overridden by a native Pubsub implementation.
Attributes:
with_attributes: If False, will fetch just message payload. Otherwise,
fetches ``PubsubMessage`` protobufs.
"""
def __init__(self, topic=None, subscription=None, id_label=None,
with_attributes=False, timestamp_attribute=None):
# We are using this coder explicitly for portability reasons of PubsubIO
# across implementations in languages.
self.coder = coders.BytesCoder()
self.full_topic = topic
self.full_subscription = subscription
self.topic_name = None
self.subscription_name = None
self.id_label = id_label
self.with_attributes = with_attributes
self.timestamp_attribute = timestamp_attribute
# Perform some validation on the topic and subscription.
if not (topic or subscription):
raise ValueError('Either a topic or subscription must be provided.')
if topic and subscription:
raise ValueError('Only one of topic or subscription should be provided.')
if topic:
self.project, self.topic_name = parse_topic(topic)
if subscription:
self.project, self.subscription_name = parse_subscription(subscription)
@property
def format(self):
"""Source format name required for remote execution."""
return 'pubsub'
def display_data(self):
return {'id_label':
DisplayDataItem(self.id_label,
label='ID Label Attribute').drop_if_none(),
'topic':
DisplayDataItem(self.full_topic,
label='Pubsub Topic').drop_if_none(),
'subscription':
DisplayDataItem(self.full_subscription,
label='Pubsub Subscription').drop_if_none()}
def reader(self):
raise NotImplementedError
def is_bounded(self):
return False
class _PubSubPayloadSink(dataflow_io.NativeSink):
"""Sink for the payload of a message as bytes to a Cloud Pub/Sub topic."""
def __init__(self, topic):
# we are using this coder explicitly for portability reasons of PubsubIO
# across implementations in languages.
self.coder = coders.BytesCoder()
self.full_topic = topic
self.project, self.topic_name = parse_topic(topic)
@property
def format(self):
"""Sink format name required for remote execution."""
return 'pubsub'
def display_data(self):
return {'topic': DisplayDataItem(self.full_topic, label='Pubsub Topic')}
def writer(self):
raise NotImplementedError(
'PubSubPayloadSink is not supported in local execution.')