Remove non-functional variable definition in log4j.properties

[rocketraman]

In log4j.properties, a property kafka.logs.dir was defined. However, modifying this property has no effect because log4j.properties does not support variable substitution in this manner. Rather ${kafka.logs.dir} is looked up as a System property, which is set in bin/kafka-run-class.sh, and must currently be changed there if the log4j logging location is to be modified.

[junrao]

It seems kafka.logs.dir is just local variable for local reference.

[rocketraman]

It seems kafka.logs.dir is just local variable for local reference.

It isn't though. Try changing its value. You will see that nothing actually changes i.e. the value of the kafka.logs.dir system property is used instead. So having it there is highly misleading (I was bitten by this).

[rocketraman]

A little bit more information: according to http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/PropertyConfigurator.html the property is first searched in the system properties, and then only if the system property does not exist, then in the local file (which is weird, I would have implemented it in the reverse search order, to allow a system default with a local override).

Since kafka.logs.dir is always created as a system property by the start script, the local property in log4j.properties is never used.

[junrao]

Thanks for the explanation. Could you create a Kafka jira and attach a patch there? This will take care of the Apache licensing stuff.

[rocketraman]

Done: https://issues.apache.org/jira/browse/KAFKA-1801

[ijuma]

Can you please close this pull request since the issue has been solved (we can't do it ourselves without asking Apache Infra via a ticket).

[rocketraman]

Done!