Souquières Adam created KAFKA-20829:
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Summary: StreamThread floods logs with "Request joining group due
to: Shutdown requested" during ▎ SHUTDOWN_APPLICATION under the
classic protocol
Key: KAFKA-20829
URL: https://issues.apache.org/jira/browse/KAFKA-20829
Project: Kafka
Issue Type: Bug
Components: streams
Affects Versions: 4.3.1, 4.2.1
Reporter: Souquières Adam
Assignee: Souquières Adam
When a Streams application triggers an app-wide shutdown (e.g., a
{{StreamsUncaughtExceptionHandler}} returning {{{}SHUTDOWN_APPLICATION{}}}),
every {{StreamThread}} running the classic rebalance protocol spams the logs
with {{Request joining group due to: Shutdown requested}} — once per run-loop
iteration, at CPU speed.
*Root cause:* {{StreamThread.maybeSendShutdown()}} executes on every loop pass.
KAFKA-19054 throttled the {{log.warn(...)}} call to once per 10s, but left the
{{mainConsumer.enforceRebalance("Shutdown requested")}} call unthrottled. That
call reaches the unguarded {{{}AbstractCoordinator.requestRejoin{}}}, which
unconditionally logs at info level ({{{}Request joining group due to: {}{}}}).
Since the shutdown rebalance's {{pollPhase()}} polls non-blocking
({{{}Duration.ZERO{}}}), the loop free-spins and re-triggers the log line on
every pass.
*Scope:* Classic protocol only. KIP-1071, which signals shutdown via the
heartbeat, is unaffected.
*Fix:* Apply the same 10s throttle guarding the warn to the
{{enforceRebalance}} call as well. The first occurrence still fires
immediately, so shutdown latency is unaffected, and the periodic re-assertion
remains in place as a retry safety net.
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