[fedora-java] Hadoop + log4j2 = fullstop

[Aleksandar Kurtakov]

Alexander Kurtakov
Red Hat Eclipse team

----- Original Message -----
> From: "Robert Rati" <rrati at redhat.com>
> To: "Fedora Big Data SIG" <bigdata at lists.fedoraproject.org>, "Development discussions related to Fedora"
> <devel at lists.fedoraproject.org>, "Fedora Java Development List" <java-devel at lists.fedoraproject.org>
> Sent: Wednesday, May 21, 2014 7:03:42 PM
> Subject: Hadoop + log4j2 = fullstop
> 
> I've been working on updating the hadoop package to the latest 2.4.0
> release and at this point I've resolved all the issues but I'm now
> blocked by the log4j2 update.  log4j2 breaks the hadoop build pretty
> severely, and it doesn't seem the log4j2 team has spent much time
> thinking about how to provide backwards compatibility to existing
> log4j1.2 users.  From my investigation of log4j2:
> 
> log4j.properties file is no longer read at all
> configuration file is now in XML or JSON
> configuration file name is log4j2.[xml|json|jsn]
> V2 isn't backwards compatible with V1.  There's a shim for v1 api but it
> will only work for a limited set of cases, and for some cases it does
> work for it turns some operations into noop calls.
> 
> This is a pretty major change and even the compatibility layer, if it
> will work for a project, does not seem to guarantee like functionality
> and minimally will require a re-do of all log4j configuration files a
> project ships.  I'm not sure many sizable upstream projects would
> undertake/accept such a drastic change very quickly.
> 
> The list of projects currently blocked by this update are:
> hadoop
> hbase
> oozie
> hive
> apache-log4j-extras
> amplab-tachyon
> 
> I would be surprised if there aren't a lot more.  I understand Fedora is
> always pushing for the latest versions, but for some fundamental
> packages can there be compatibility packages introduced at the same time
> as an incompatible update? 

Nothing stops compatibility packages from appearing. But it's the people that need it that have to drive it. Everyone is time constrained so whoever needs something must do it. 
It's really is as simple as that.

Alexander Kurtakov
Red Hat Eclipse team

> Package maintainers of dependent packages
> will still need to touch their packages and determine if the new version
> will work for them.  Providing a compat package will also allow packages
> to update to their newer versions while not held up on trying to
> integrate changes from a compatibility breaking dependency update.
> 
> Rob
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