[jira] [Commented] (ACCUMULO-867) Support common use cases for loading classes from context (e.g. HDFS)

["Keith Turner (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ACCUMULO-867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531877#comment-13531877 ] 

Keith Turner commented on ACCUMULO-867:
---------------------------------------

For table classpaths I was concerned about how an Accumulo adminstrator could control what code was introduced into the system.   Was discussing this with Dave Marion and he suggested having per table classpaths reference context.  Do this instead of directly specifying URIs as shown in the issue description.  Context would be defined through system properties and therefore not just anyone with ALTER_TABLE could modify them.   Inorder to make this convenient, would need to modify how the current code works so that context config can be stored in zookeeper.  The current code only reads context config from accumulo-site.xml.  

So inorder to setup a per table classpath, a user would set a system property like the following.

{noformat}
  classloader.vfs.context.classpath.cx1=hdfs://nn:8092/myApp
{noformat}

and then set a per table property

{noformat}
  table.classpath.context=cx1
{noformat}

                
> Support common use cases for loading classes from context (e.g. HDFS)
> ---------------------------------------------------------------------
>
>                 Key: ACCUMULO-867
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-867
>             Project: Accumulo
>          Issue Type: Sub-task
>          Components: start
>            Reporter: Keith Turner
>             Fix For: 1.5.0
>
>
> We need to decide how want to make this new classloader functionality available to users.   
> One use case is making per-table class loaders availiable.   This would allow the user to set a per table property like the following.
> {noformat}
>    table.classpath=hdfs://nn:8092/myApp
> {noformat}
> Setting this would allow iterators specific to the table to be loaded from a given location.   Currently when a user iterator is placed in lib/ext all tables see the iterator.
> Another possible use case is per-scan classpath. 

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