Matthias J. Sax created KAFKA-10555:
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Summary: Improve client state machine
Key: KAFKA-10555
URL: https://issues.apache.org/jira/browse/KAFKA-10555
Project: Kafka
Issue Type: Improvement
Components: streams
Reporter: Matthias J. Sax
The KafkaStreams client exposes its state to the user for monitoring purpose
(ie, RUNNING, REBALANCING etc). The state of the client depends on the state(s)
of the internal StreamThreads that have their own states.
Furthermore, the client state has impact on what the user can do with the
client. For example, active task can only be queried in RUNNING state and
similar.
With KIP-671 and KIP-663 we improved error handling capabilities and allow to
add/remove stream thread dynamically. We allow adding/removing threads only in
RUNNING and REBALANCING state. This puts us in a "weird" position, because if
we enter ERROR state (ie, if the last thread dies), we cannot add new threads
and longer. However, if we have multiple threads and one dies, we don't enter
ERROR state and do allow to recover the thread.
Before the KIPs the definition of ERROR state was clear, however, with both
KIPs it seem that we should revisit its semantics.
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