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From "Keith Turner (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-869) Determine best default classloader hierarchy
Date Fri, 14 Dec 2012 18:00:15 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13532500#comment-13532500
] 

Keith Turner commented on ACCUMULO-869:
---------------------------------------

bq. I would say no as I believe it also references $HADOOP_HOME and $ZK_HOME

I think the parent classloader for the current code will have ACCUMULO_HOME/lib/*, ACCUMULO_HOME/lib/ext/*,
hadoop jars and conf, zookeeper, and accumulo_start.  I am thinking if we make the parent
classloader.getSystemClassLoader() that this classloader will only have accumulo_start on
it.   Therefore you get a much cleaner parent.

bq. We could do that, but it would likely increase complexity a lot. It would be one more
thing to track and manage. I'm not against it.

I was just trying to think how users might use this advanced option.  It seems like they wanted
to use it, using on a single table instead of all tables may be desirable.
                
> Determine best default classloader hierarchy 
> ---------------------------------------------
>
>                 Key: ACCUMULO-869
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-869
>             Project: Accumulo
>          Issue Type: Sub-task
>          Components: start
>            Reporter: Keith Turner
>            Assignee: Dave Marion
>             Fix For: 1.5.0
>
>         Attachments: ACCUMULO-869-1.patch
>
>
> A user created context classloader in the current patch does not have the system context
as it parent.  If the system context contained Accumulo jars, then the user context would
have to add its own Accumulo jars.  The drawback of this is that the user context may use
a different version of accumulo jars than the system context leading to unexpected behavior.
  The advantage of this is that user context could load newer jars.  For example, if Accumulo
depended on an old json library the user context could load a newer version with no problems.

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