sdks/python/apache_beam/yaml/examples/transforms/io/kafka.yaml

# coding=utf-8
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# A pipeline that both writes to and reads from the same Kafka topic.

pipeline:
  transforms:
    - type: ReadFromText
      name: ReadFromGCS
      config:
        path: gs://dataflow-samples/shakespeare/kinglear.txt

    - type: MapToFields
      name: BuildKafkaRecords
      input: ReadFromGCS
      config:
        language: python
        fields:
          value:
            callable: |
              def func(row):
                return row.line.encode('utf-8')
            output_type: bytes

    - type: WriteToKafka
      name: SendRecordsToKafka
      input: BuildKafkaRecords
      config:
        format: "RAW"
        topic: "{{ TOPIC }}"
        bootstrap_servers: "{{ BOOTSTRAP_SERVERS }}"
        producer_config_updates:
          sasl.jaas.config: "org.apache.kafka.common.security.plain.PlainLoginModule required \
            username={{ USERNAME }} \
            password={{ PASSWORD }};"
          security.protocol: "SASL_PLAINTEXT"
          sasl.mechanism: "PLAIN"

    - type: ReadFromKafka
      name: ReadFromMyTopic
      config:
        format: "RAW"
        topic: "{{ TOPIC }}"
        bootstrap_servers: "{{ BOOTSTRAP_SERVERS }}"
        auto_offset_reset_config: earliest
        consumer_config:
          sasl.jaas.config: "org.apache.kafka.common.security.plain.PlainLoginModule required \
            username={{ USERNAME }} \
            password={{ PASSWORD }};"
          security.protocol: "SASL_PLAINTEXT"
          sasl.mechanism: "PLAIN"

    - type: MapToFields
      name: ParseKafkaRecords
      input: ReadFromMyTopic
      config:
        language: python
        fields:
          text:
            callable: |
              def func(row):
                # Kafka RAW format reads messages as bytes 
                # in the 'payload' field of a Row
                return row.payload.decode('utf-8')

    - type: LogForTesting
      input: ParseKafkaRecords

# Since the pipeline both writes to and reads from a Kafka topic, we expect
#   the first pipeline component to write the rows containing the `value`
#   field as bytes to Kafka, and the second pipeline component to read the byte
#   messages from Kafka before parsing them as string in the new `text` field.
# Expected:
#  Row(value=b'Fool\tThou shouldst not have been old till thou hadst')
#  Row(value=b'\tbeen wise.')
#  Row(value=b'KING LEAR\tNothing will come of nothing: speak again.')
#  Row(value=b'\tNever, never, never, never, never!')
#  Row(text='Fool\tThou shouldst not have been old till thou hadst')
#  Row(text='\tbeen wise.')
#  Row(text='KING LEAR\tNothing will come of nothing: speak again.')
#  Row(text='\tNever, never, never, never, never!')