You cannot share markers across sources and topics. If two sources produce events to the same topic, each of the topics would have their own start and stop events with their identifier.

The source ID is part of the marker event. If the source controller fails at any point, there is the possibility that you might have duplicate events for the same source. When the system comes up, and the event processor starts processing events again, if there is an existing marker event, it drops the duplicate start and stop markers from the same source based on the ID.