Before the fix, coordinator stream was read redundantly 5 times by the metadata store as illustrated by the following logs:
xiliu-mn4:logs xiliu$ cat job-activity-aggregation-runner.out |grep "CoordinatorStreamStore" |grep "Registering system stream partition"
2019-03-31 08:55:09.655 [main] CoordinatorStreamStore [INFO] Registering system stream partition: SystemStreamPartition [samzametadatasystem, __samza_coordinator_job-activity-aggregation_i001, 0] with offset: 0.
2019-03-31 08:55:18.733 [main] CoordinatorStreamStore [INFO] Registering system stream partition: SystemStreamPartition [samzametadatasystem, __samza_coordinator_job-activity-aggregation_i001, 0] with offset: 0.
2019-03-31 08:55:26.661 [main] CoordinatorStreamStore [INFO] Registering system stream partition: SystemStreamPartition [samzametadatasystem, __samza_coordinator_job-activity-aggregation_i001, 0] with offset: 0.