[Good first issue] Exception while processing response

[superhx]

Error Log

2025-02-14 09:14:38.114 +0000 ERROR [kafka.network.Processor]  Exception while processing response for 10.132.46.173:9092-10.221.143.9:40948-238589
java.lang.IllegalStateException: Attempt to retrieve channel for which there is no connection. Connection id 10.132.46.173:9092-10.221.143.9:40948-238589 existing connections [...]
	at org.apache.kafka.common.network.Selector.openOrClosingChannelOrFail(Selector.java:1005)
	at org.apache.kafka.common.network.Selector.unmute(Selector.java:771)
	at kafka.network.Processor.processNewResponses(SocketServer.scala:1090)
	at kafka.network.Processor.run(SocketServer.scala:1016)

Expect

• Check whether the log action is reasonable.
• If it's reasonable, then degrade it to WARN level.

[decadezzz]

could you please assign this task to me?

[renoyuan]

/assign

[fjhdream]

Description

There is a proposal to downgrade the error level in Selector.openOrClosingChannelOrFail method from throwing an IllegalStateException to a WARN level log. After careful analysis, I believe this change would be inappropriate for the following reasons:

Analysis

1. Based on the error call stack, this issue occurs when processing an EndThrottlingResponse in the processNewResponses() method.
2. This error can only be triggered if a StartThrottlingResponse has been previously processed for the same channel.
3. This suggests an abnormal situation where the KafkaChannel has been prematurely removed from the channels map, which indicates a potential bug or race condition in the code.

Reasoning

Downgrading this error to a WARN level would hide a legitimate issue that should be addressed. The IllegalStateException correctly indicates that the system has reached an inconsistent state:
A channel was throttled (via StartThrottlingResponse)
Later, when trying to unthrottle it (via EndThrottlingResponse), the channel no longer exists
This sequence should not happen in normal operation.

[cdxiaodong]

/assign

[K-onsuki]

/assign

[mxllAs]

/assign

[Zhang-BC-05]

/assign