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"""Unbounded source and sink transforms for
`Kafka <href="http://kafka.apache.org/>`_.
These transforms are currently supported by Beam portable runners (for
example, portable Flink and Spark) as well as Dataflow runner.
**Setup**
Transforms provided in this module are cross-language transforms
implemented in the Beam Java SDK. During the pipeline construction, Python SDK
will connect to a Java expansion service to expand these transforms.
To facilitate this, a small amount of setup is needed before using these
transforms in a Beam Python pipeline.
There are several ways to setup cross-language Kafka transforms.
* Option 1: use the default expansion service
* Option 2: specify a custom expansion service
See below for details regarding each of these options.
*Option 1: Use the default expansion service*
This is the recommended and easiest setup option for using Python Kafka
transforms. This option is only available for Beam 2.22.0 and later.
This option requires following pre-requisites before running the Beam
pipeline.
* Install Java runtime in the computer from where the pipeline is constructed
and make sure that 'java' command is available.
In this option, Python SDK will either download (for released Beam version) or
build (when running from a Beam Git clone) a expansion service jar and use
that to expand transforms. Currently Kafka transforms use the
'beam-sdks-java-io-expansion-service' jar for this purpose.
*Option 2: specify a custom expansion service*
In this option, you startup your own expansion service and provide that as
a parameter when using the transforms provided in this module.
This option requires following pre-requisites before running the Beam
pipeline.
* Startup your own expansion service.
* Update your pipeline to provide the expansion service address when
initiating Kafka transforms provided in this module.
Flink Users can use the built-in Expansion Service of the Flink Runner's
Job Server. If you start Flink's Job Server, the expansion service will be
started on port 8097. For a different address, please set the
expansion_service parameter.
**More information**
For more information regarding cross-language transforms see:
- https://beam.apache.org/roadmap/portability/
For more information specific to Flink runner see:
- https://beam.apache.org/documentation/runners/flink/
"""
# pytype: skip-file
from __future__ import absolute_import
import typing
from past.builtins import unicode
from apache_beam.transforms.external import BeamJarExpansionService
from apache_beam.transforms.external import ExternalTransform
from apache_beam.transforms.external import NamedTupleBasedPayloadBuilder
ReadFromKafkaSchema = typing.NamedTuple(
'ReadFromKafkaSchema',
[
('consumer_config', typing.List[typing.Tuple[unicode, unicode]]),
('topics', typing.List[unicode]),
('key_deserializer', unicode),
('value_deserializer', unicode),
])
[docs]def default_io_expansion_service():
return BeamJarExpansionService('sdks:java:io:expansion-service:shadowJar')
[docs]class ReadFromKafka(ExternalTransform):
"""
An external PTransform which reads from Kafka and returns a KV pair for
each item in the specified Kafka topics. If no Kafka Deserializer for
key/value is provided, then the data will be returned as a raw byte array.
Experimental; no backwards compatibility guarantees.
"""
# Returns the key/value data as raw byte arrays
byte_array_deserializer = (
'org.apache.kafka.common.serialization.ByteArrayDeserializer')
URN = 'beam:external:java:kafka:read:v1'
def __init__(
self,
consumer_config,
topics,
key_deserializer=byte_array_deserializer,
value_deserializer=byte_array_deserializer,
expansion_service=None):
"""
Initializes a read operation from Kafka.
:param consumer_config: A dictionary containing the consumer configuration.
:param topics: A list of topic strings.
:param key_deserializer: A fully-qualified Java class name of a Kafka
Deserializer for the topic's key, e.g.
'org.apache.kafka.common.
serialization.LongDeserializer'.
Default: 'org.apache.kafka.common.
serialization.ByteArrayDeserializer'.
:param value_deserializer: A fully-qualified Java class name of a Kafka
Deserializer for the topic's value, e.g.
'org.apache.kafka.common.
serialization.LongDeserializer'.
Default: 'org.apache.kafka.common.
serialization.ByteArrayDeserializer'.
:param expansion_service: The address (host:port) of the ExpansionService.
"""
super(ReadFromKafka, self).__init__(
self.URN,
NamedTupleBasedPayloadBuilder(
ReadFromKafkaSchema(
consumer_config=list(consumer_config.items()),
topics=topics,
key_deserializer=key_deserializer,
value_deserializer=value_deserializer,
)),
expansion_service or default_io_expansion_service())
WriteToKafkaSchema = typing.NamedTuple(
'WriteToKafkaSchema',
[
('producer_config', typing.List[typing.Tuple[unicode, unicode]]),
('topic', unicode),
('key_serializer', unicode),
('value_serializer', unicode),
])
[docs]class WriteToKafka(ExternalTransform):
"""
An external PTransform which writes KV data to a specified Kafka topic.
If no Kafka Serializer for key/value is provided, then key/value are
assumed to be byte arrays.
Experimental; no backwards compatibility guarantees.
"""
# Default serializer which passes raw bytes to Kafka
byte_array_serializer = (
'org.apache.kafka.common.serialization.ByteArraySerializer')
URN = 'beam:external:java:kafka:write:v1'
def __init__(
self,
producer_config,
topic,
key_serializer=byte_array_serializer,
value_serializer=byte_array_serializer,
expansion_service=None):
"""
Initializes a write operation to Kafka.
:param producer_config: A dictionary containing the producer configuration.
:param topic: A Kafka topic name.
:param key_deserializer: A fully-qualified Java class name of a Kafka
Serializer for the topic's key, e.g.
'org.apache.kafka.common.
serialization.LongSerializer'.
Default: 'org.apache.kafka.common.
serialization.ByteArraySerializer'.
:param value_deserializer: A fully-qualified Java class name of a Kafka
Serializer for the topic's value, e.g.
'org.apache.kafka.common.
serialization.LongSerializer'.
Default: 'org.apache.kafka.common.
serialization.ByteArraySerializer'.
:param expansion_service: The address (host:port) of the ExpansionService.
"""
super(WriteToKafka, self).__init__(
self.URN,
NamedTupleBasedPayloadBuilder(
WriteToKafkaSchema(
producer_config=list(producer_config.items()),
topic=topic,
key_serializer=key_serializer,
value_serializer=value_serializer,
)),
expansion_service or default_io_expansion_service())