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https://issues.apache.org/jira/browse/HADOOP-4757?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12676930#action_12676930
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Alex Loddengaard commented on HADOOP-4757:
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After some digging, and with some help from Aaron Kimball, I've realized that
Hadoop's current implementation depends on a few global log4j variables to be
set in order for Java code to dynamically overwrite the variable values.
Namely, org.apache.hadoop.mapred.TaskRunner sets the "hadoop.tasklog.taskid"
variable, which allows org.apache.hadoop.mapred.TaskLogAppender to output logs
with the task ID in the log filename.
According to the DTD, Log4j XML files do not allow for top-level "param"
elements, making it seem as though global variables are impossible in the XML
file. With that said, Hadoop's current task log implementation is incompatible
with Log4j XML files.
Though having XML files would be nice for purposes of unlocking Log4j features
(AsyncAppenders, for example), I don't have enough Log4j fu to propose a new
implementation of the current TaskLogAppender/TaskRunner/Log4j setup. Thoughts?
> Replace log4j.properties with log4j.xml
> ---------------------------------------
>
> Key: HADOOP-4757
> URL: https://issues.apache.org/jira/browse/HADOOP-4757
> Project: Hadoop Core
> Issue Type: Improvement
> Reporter: Alex Loddengaard
> Assignee: Alex Loddengaard
> Priority: Minor
> Attachments: log4j_xml_config.patch, log4j_xml_config_v2.patch
>
>
> Certain log4j features are not configurable via the log4j.properties file,
> not to mention the log4j.properties file is messy. For this reason, we
> should transition to a XML file to configure log4j. The .properties vs. .xml
> argument has only come up in HADOOP-211, where the XML configuration was
> vetoed for Tomcat integration issues.
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