Prompt: What does this code do?

pipeline_options = PipelineOptions(pipeline_args)

with beam.Pipeline(options=options) as p:
    (p | "Read" >> ReadFromPubSub(subscription=input_subscription)
       | "Process" >> ParDo(ProcessMessage())
       | "Write" >> WriteToPubSub(topic=output_topic))

Response: This code reads messages from the Pub/Sub subscription input_subscription using the ReadFromPubSub function and processes them. The code then writes the resulting collection to the Pub/Sub topic output_topic using the WriteToPubSub transform.

Pub/Sub is only supported in streaming pipelines.

Reading messages directly from a topic is also supported. In this case, a temporary subscription is created automatically.

ReadFromPubSub produces a PCollection of PubsubMessage objects or a PCollection of byte sequences. The behavior is controlled by the with_attributes parameter, with byte sequences being the default. For more information about the PCollection object, see the Beam Programming Guide.

The ProcessMessage class processes the messages. This class is a subclass of the DoFn class. Its implementation might look like the following example:

class ProcessMessage(beam.DoFn):
    def process(self, element):
        yield element

For more information about the DoFn class, see the Beam Programming Guide.

For more details, see the Pub/Sub I/O transform documentation.

For a common pattern for configuring pipeline options, see the Pipeline option patterns section.