...

Currently the ERROR state in KStreams means that there are no threads running. However, in KIP-663 streamThreads can be added dynamically so this definition no longer is useful. In that kip, the automatic transition to ERROR state upon the death of all threads is removed. Also Error , ERROR state should be terminal. This KIP should clarify the use of ERROR state as well as bring it into alignment with the other states

...

The following transitions will be added:

• RUNNING → PENDING_ERROR
• REBALENCING REBALANCING → PENDING_ERROR
• PENDING_ERROR → ERROR

...

The SHUTDOWN_CLIENT should leave the client state in ERROR not ERROR instead of NOT_RUNNING

Proposed Changes

ERROR will be redefined to mean that the streams client is in an unrecoverable state and should not be restarted until the problem has been investigated. Streams will only reach ERROR state in the event of an exceptional failure in which the `StreamsUncaughtExceptionHandler` chose to either shutdown the application or the client. It is not recommended to automatically restart form from ERROR state.

As ERROR will now be a terminal state, PENDING_ERROR will be added. This will mirror PENDING_SHUTDOWN and mean that resources are closing before the client transitions to ERROR. Currently, the client goes to ERROR before it closes the resources and does not signal when done.

In order to be consistent SHUTDOWNconsistent, SHUTDOWN_CLIENT will leave the client state in ERROR not instead of NOT_RUNNING. ERROR should be the state that exceptional failures leave the application in, not NOT_RUNNING.

Compatibility, Deprecation, and Migration Plan

...