[jira] [Created] (KAFKA-18831) Document the behavior changes of adjusting logger level after migrating to log4j2

["Chia-Ping Tsai (Jira)" <ji...@apache.org>]

Chia-Ping Tsai created KAFKA-18831:
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             Summary: Document the behavior changes of adjusting logger level after migrating to log4j2
                 Key: KAFKA-18831
                 URL: https://issues.apache.org/jira/browse/KAFKA-18831
             Project: Kafka
          Issue Type: Improvement
            Reporter: Chia-Ping Tsai
            Assignee: Chia-Ping Tsai
             Fix For: 4.0.0


There are two behavior changes introduced by log4j 2

1)
in log4j 1, users can't change the logger by parent if the logger is declared by properties explicitly. For example, `org.apache.kafka.controller` has level explicitly in the properties. Hence, we can't use "org.apache.kafka=INFO" to change the level of `org.apache.kafka.controller` to INFO. By contrast, log4j2 allows us to change all child loggers by the parent logger.

2) in log4j2, we can change the level of root to impact all loggers' level. By contrast, log4j 1 can't. 



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