message send by upstream tasks
startTime that can be used to decide from when a source producer task should replay the data source, or from when a processor task should recover its checkpoint data in to in-memory state.
This can be used to cleanup resource when the application finished.
This can be used to cleanup resource when the application finished.
handler for unmanaged message
For managed message(type of Message), the sender mean nothing, you should not use this directory
For managed message(type of Message), the sender mean nothing, you should not use this directory
For unmanaged message, the sender represent the sender actor
This represent the min-clock of state None means there is no in-memory state, Or the in-memory state doesn't requires recovery.
This represent the min-clock of state None means there is no in-memory state, Or the in-memory state doesn't requires recovery.