View Source brod_group_member behaviour (brod v4.4.0)
Implement brod_group_member behaviour callbacks to allow a process to act as a group member without having to deal with Kafka group protocol details. A typical workflow:
1. Spawn a group coordinator by calling brod_group_coordinator:start_link/6.
2. Subscribe to partitions received in the assignments from assignments_received/4 callback.
3. Receive messages from the assigned partitions (delivered by the partition workers (the pollers) implemented in brod_consumer).
4. Unsubscribe from all previously subscribed partitions when assignments_revoked/1 is called.
For group members that commit offsets to Kafka, do:
1. Call brod_group_coordinator:ack/5. to acknowledge successful consumption of the messages. Group coordinator will commit the acknowledged offsets at configured interval.
2. Call brod_group_coordinator:commit_offsets/2 to force an immediate offset commit if necessary.
For group members that manage offsets locally, do:
1. Implement the get_committed_offsets/2 callback. This callback is evaluated every time when new assignments are received.
Summary
Callbacks
-callback assign_partitions(pid(), [brod:group_member()], [{brod:topic(), brod:partition()}]) -> [{brod:group_member_id(), [brod:partition_assignment()]}].
-callback assignments_received(pid(), brod:group_member_id(), brod:group_generation_id(), brod:received_assignments()) -> ok.
-callback assignments_revoked(pid()) -> ok.
-callback get_committed_offsets(pid(), [{brod:topic(), brod:partition()}]) -> {ok, [{{brod:topic(), brod:partition()}, brod:offset()}]}.