Ted Yu created KAFKA-7174:
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Summary: Improve version probing of subscription info
Key: KAFKA-7174
URL: https://issues.apache.org/jira/browse/KAFKA-7174
Project: Kafka
Issue Type: Improvement
Reporter: Ted Yu
During code review for KAFKA-5037, [~guozhang] made the following suggestion:
Currently the version probing works as the following:
when leader receives the subscription info encoded with a higher version that
it can understand (e.g. the leader is on version 3, while one of the
subscription received is encode with version 4), it will send back an empty
assignment with the assignment encoded with version 3, and also
latestSupportedVersion set to 3.
when the member receives the assignment, it checks if latestSupportedVersion is
smaller than the version it used for encoding the sent subscription (i.e. the
above logic). If it is smaller, then it means that leader cannot understand, in
this case, version 4. It will then set the flag and then re-subscribe but with
a down-graded encoding format of version 3.
NOW with PR #5322, we can let leader to clearly communicate this error via the
error code, and upon receiving the assignment, if the error code is
VERSION_PROBING, then the member can immediately know what happens, and hence
can simplify the above logic.
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