[KAFKA-9174] Improve documentation for State Restore lifecycle

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Component/s: documentation, streams
• Labels: user-experience
• Environment: N/A
• Assignee: Unassigned
• Reporter: Javier Holguera
• Created: 12/Nov/19 17:18
• Updated: 13/Nov/19 02:12

Description

This is triggered by a question in the Kafka Users mailing list:
https://lists.apache.org/thread.html/cc9b2faec61795dba3806c54f8fbace80cdcd2ef65853fe4098934c3@%3Cusers.kafka.apache.org%3E

The question was what happened with the State Restore listener when a new partition was assigned, long after the application has started. It wasn't clear if the state restore listener would be invoked and what state the KafkaStreams would go into while the restoration for the state of the newly assigned partition happened.

This ticket is a placeholder to improve the documentation and clarify those two points:

• What state will the KafkaStreams be in while restoring the state for the newly assigned partitions
• Will the State Restore listener be called as it would when the state is restored when the application starts