Tracking Metadata

The broker uses Pub/Sub message attributes to track metadata for provenance and performance benchmarking.

Each morning, night conductor processes the Pub/Sub “counter” subscriptions, collects the metadata, and stores it in the metadata BigQuery table. See the script at broker/night_conductor/end_night/

Currently, the collected metadata includes the publish timestamp of each message, and information about the Avro file storage and the survey’s originating Kafka stream.

To track additional metadata:

  1. Add desired information to a custom attribute(s) on the appropriate Pub/Sub message. Note, the message’s publish timestamp is automatically attached; it does not need to be added manually.

  2. Add the corresponding column(s) to the schema template(s) for the metadata table(s) in broker/setup_broker/templates/. The format for a column name must be: the name of the attribute plus the name stub of the publishing topic, separated by a double underscore. If this is a new Pub/Sub stream, remember to add a column for the publish timestamp.

  3. If this is a new Pub/Sub stream:

    • Attach a “counter” subscription to the new topic. The subscription name stub should have the form <topic_name_stub>-counter.

    • Add the topic name stub to the resource names at the top of the processing script at broker/night_conductor/end_night/ The script will automatically process the subscription and collect all attributes for which there is a corresponding column in the BigQuery table.