The inclusive offset range on one source partition that holds the payloads
of a timeline page. A range is a hint for bounded polls, not a promise that
every offset in it belongs to the session.
The body of one process heartbeat on agent.heartbeats: the sessions in
one stream that the process holds leases on. A process with sessions in
several streams writes one heartbeat per stream.
How far the session index has folded one source partition. Offsets are
never compared across topics. topic_generation is the topic creation time
in microseconds, so a recreated topic with a reused id is a different source.