Chapter 12. Event filter plugins

Events sometimes have extra data that is unnecessary and might overwhelm the rule engine. Use event filters to remove that extra data so you can focus on what matters to your rules. Event filters might also change the format of the data so that the rule conditions can better match the data.

Events are defined as python code and distributed as collections. The default eda collection has the following filters:

You can chain event filters one after the other, and the updated data is sent from one filter to the next. Event filters are defined in the rulebook after a source is defined. When the rulebook starts the source plugin it associates the correct filters and transforms the data before putting it into the queue.

sources:
  - name: azure_service_bus
    ansible.eda.azure_service_bus:
      conn_str: "{{connection_str}}"
      queue_name: "{{queue_name}}"
    filters:
      - json_filter:
          include_keys: ['clone_url']
          exclude_keys: ['*_url', '_links', 'base', 'sender', 'owner', 'user']
      - dashes_to_underscores:

In this example the data is first passed through the json_filter and then through the dashes_to_underscores filter. In the event payload, keys can only contain letters, numbers, and underscores. The period (.) is used to access nested keys.

Since every event should record the origin of the event the filter eda.builtin.insert_meta_info is added automatically by ansible-rulebook to add the source name, type, and received_at. The received_at stores a date time in UTC ISO8601 format and includes the microseconds. The uuid stores the unique id for the event. The meta key is used to store metadata about the event and its needed to correctly report about the events in the aap-server.

   # my_namespace.my_collection/extensions/eda/plugins/event_filter/my_filter.py
    def main(event: dict, arg1, arg2):
        # Process event data here
        return event

  sources:
    - name: azure_service_bus
      ansible.eda.azure_service_bus:
        conn_str: "{{connection_str}}"
        queue_name: "{{queue_name}}"
      filters:
        - my_namespace.my_collection.my_filter:
            arg1: hello
            arg2: world