[jira] [Commented] (KAFKA-20289) Broker configs with group config names masquerading as static broker config

["majialong (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-20289?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18065436#comment-18065436 ] 

majialong commented on KAFKA-20289:
-----------------------------------

Hi [~schofielaj] 

I've found the root cause and am working on a fix. One thing I'd like to confirm before proceeding:

Should the describeConfigs output for group configs show the broker-level static config as a STATIC_BROKER_CONFIG synonym? I'm inclined to support this, similar to how topic configs show their broker-level synonyms — it would give better visibility into the config resolution chain.

For example, with 
{code:java}
group.share.heartbeat.interval.ms=5001{code}
 in server.properties and 
{code:java}
share.heartbeat.interval.ms=5003{code}
 set at the group level, the expected output would be:
{code:java}
share.heartbeat.interval.ms=5003 sensitive=false synonyms={
    DYNAMIC_GROUP_CONFIG:share.heartbeat.interval.ms=5003,
    STATIC_BROKER_CONFIG:group.share.heartbeat.interval.ms=5001,
    DEFAULT_CONFIG:share.heartbeat.interval.ms=5000
}{code}
Please let me know your thoughts on this. Thanks !

> Broker configs with group config names masquerading as static broker config
> ---------------------------------------------------------------------------
>
>                 Key: KAFKA-20289
>                 URL: https://issues.apache.org/jira/browse/KAFKA-20289
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions: 4.2.0
>            Reporter: Andrew Schofield
>            Assignee: majialong
>            Priority: Major
>
> While testing [https://github.com/apache/kafka/pull/21633], I noticed that there is a strange interaction between broker and group configurations which seems only to manifest itself in surprising output from `bin/kafka-configs.sh --describe` and as a result `Admin.describeConfigs`.
> If I define a broker config whose name matches a group config (and it's not a valid broker config), the presence of the broker config and its value appears in the output of bin/kafka-configs.sh. I have defined the group config `share.heartbeat.interval.ms` but also added the bogus `share.heartbeat.interval.ms` to my `config/server.properties` and restarted the broker.
>  * Here the command output:
> % bin/kafka-configs.sh --bootstrap-server localhost:9092 --entity-type groups --describe
> Dynamic configs for group G1 are:
> share.heartbeat.interval.ms=5003 sensitive=false synonyms= \{DYNAMIC_GROUP_CONFIG:share.heartbeat.interval.ms=5003, STATIC_BROKER_CONFIG:share.heartbeat.interval.ms=5001}
> The static broker config is not supposed to be there, so it looks like some code is checking for group config names in the broker config and leaping to the wrong conclusion.



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