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https://issues.apache.org/jira/browse/ZOOKEEPER-2342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15195905#comment-15195905
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Chris Nauroth commented on ZOOKEEPER-2342:
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At this point, I am +1 for reverting ZOOKEEPER-1371. From my incomplete work
on this patch so far, it looks like it's going to be a huge effort to migrate
to Log4J 2 if we hope to maintain some basic level of compatibility/usability
that administrators are used to. I don't want that to hold up further 3.5
releases.
bq. I don't see where we've done much thought on b/w compatibility. It's barely
mentioned on these two jiras.
Backward compatibility absolutely was one of my goals for the scope of this
JIRA. The attached v001 patch doesn't achieve it, so it is not yet committed.
ZOOKEEPER-1371 was a backwards-incompatible change committed for 3.5.2-alpha,
hence my motivation for marking this one a 3.5.2-alpha blocker. I was hoping
to restore backwards-compatibility in the scope of this patch, but I'm no
longer comfortable with the risk.
bq. Have we considered what other Hadoop ecosystem components are doing?
At least for Hadoop itself, I know Log4J 2 migration is not on the schedule
yet. It has been mentioned casually, but there is no real plan yet.
bq. What's the impact on systems that need to manage ZK? e.g. do they need to
change the way they generate/edit/manage the log4j.conf file?
>From my work so far, I can tell that there is no way to achieve complete
>backwards-compatibility for administrators editing (and by extension systems
>that auto-generate) the Log4J configuration file. I've been trying to find a
>good way to at least maintain our behavior of allowing appender/level
>overrides by passing the {{zookeeper.root.logger}} property on JVM startup.
>Even if we can at least maintain that, the actual content of the Log4J
>configuration file is completely different in version 2.
> ZooKeeper cannot write logs, because there is no SLF4J binding available on
> the runtime classpath.
> --------------------------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-2342
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2342
> Project: ZooKeeper
> Issue Type: Bug
> Reporter: Chris Nauroth
> Assignee: Chris Nauroth
> Priority: Blocker
> Fix For: 3.5.2, 3.6.0
>
> Attachments: ZOOKEEPER-2342.001.patch
>
>
> ZOOKEEPER-1371 removed our source code dependency on Log4J. It appears that
> this also removed the Log4J SLF4J binding jar from the runtime classpath.
> Without any SLF4J binding jar available on the runtime classpath, the it is
> impossible to write logs.
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