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From "Lars George (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13907) Document how to deploy a coprocessor
Date Wed, 12 Aug 2015 14:20:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14693552#comment-14693552
] 

Lars George commented on HBASE-13907:
-------------------------------------

[~misty] So the open question #3 is, what if a CP was loaded using the site file, using custom
config values for it, and then an admin tries to override them in the CLI? How would that
be possible, the CP is already loaded, no? I tried once and did issue the same CP load command
on the CLI, which added the same CP twice, just with a higher ID. So, if you have loaded a
system CP using the site XML file, you can load another on the CLI, same class, but it will
have lower priority.

> Document how to deploy a coprocessor
> ------------------------------------
>
>                 Key: HBASE-13907
>                 URL: https://issues.apache.org/jira/browse/HBASE-13907
>             Project: HBase
>          Issue Type: Bug
>          Components: documentation
>            Reporter: Misty Stanley-Jones
>            Assignee: Misty Stanley-Jones
>         Attachments: HBASE-13907-1.patch, HBASE-13907-2.patch, HBASE-13907-v3.patch,
HBASE-13907.patch
>
>
> Capture this information:
> > Where are the dependencies located for these classes? Is there a path on HDFS or
local disk that dependencies need to be placed so that each RegionServer has access to them?
> It is suggested to bundle them as a single jar so that RS can load the whole jar and
resolve dependencies. If you are not able to do that, you need place the dependencies in regionservers
class path so that they are loaded during RS startup. Do either of these options work for
you? Btw, you can load the coprocessors/filters into path specified by hbase.dynamic.jars.dir
[1], so that they are loaded dynamically by regionservers when the class is accessed (or you
can place them in the RS class path too, so that they are loaded during RS JVM startup).
> > How would one deploy these using an automated system? (puppet/chef/ansible/etc)
> You can probably use these tools to automate shipping the jars to above locations?
> > Tests our developers have done suggest that simply disabling a coprocessor, replacing
the jar with a different version, and enabling the coprocessor again does not load the newest
version. With that in mind how does one know which version is currently deployed and enabled
without resorting to parsing `hbase shell` output or restarting hbase?
> Actually this is a design issue with current classloader. You can't reload a class in
a JVM unless you delete all the current references to it. Since the current JVM (classloader)
has reference to it, you can't overwrite it unless you kill the JVM, which is equivalent to
restarting it. So you still have the older class loaded in place. For this to work, classloader
design should be changed. If it works for you, you can rename the coprocessor class name and
the new version of jar and RS loads it properly.
> > Where does logging go, and how does one access it? Does logging need to be configured
in a certain way?
> Can you please specify which logging you are referring to?
> > Where is a good location to place configuration files?
> Same as above, are these hbase configs or something else? If hbase configs, are these
gateway configs/server side? 



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