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Current state: Under Discussion

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]

JIRA: KAFKA-10469

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Log4j (and log4j2, see KIP-653) use a hierarchical model for configuring loggers within an application. A logger is an entity which can generate logging.
Loggers have names which are usually based on the fully-qualified class name of the class where the logger is used. Thus dots separate the components of a logger name.
One logger is an ancestor of another if the components in its name are a (strict) prefix of the components of the other's name. Such ancestor loggers are not typically used to emit logging messages, but exist to configure descendent loggers in a hierarchical way. There is a root logger (which in log4j has an empty name, "", but in Kafka is identified by the name "root"), which is the ancestor of all other loggers. If follows that loggers which are not explicitly configured, and with no intermediate ancestor which _is_ configured, will inherit their configuration from the root logger.

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The current behaviour for DescribeConfigs is explicitly defined in at least KIP-412 (search for "Returns the root logger's log level if this logger is not set explicitly yet").

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