SystemConsumers that want to be notified about checkpoints for their SSPs and potentially modify them may implement this interface.
CheckpointManagers read and write
A checkpoint is a mapping of all the streams a job is consuming and the most recent current offset for each.
Checkpointed changelog offset has the format: [checkpointId, offset], separated by a colon.
Checkpoint ID has the format: [currentTimeMillis, last 6 digits of nanotime], separated by a dash.