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From "Josh Wills (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CRUNCH-536) crunch jobs fail to use hbase api of secured hbase
Date Mon, 06 Jul 2015 18:08:04 GMT

    [ https://issues.apache.org/jira/browse/CRUNCH-536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14615415#comment-14615415
] 

Josh Wills commented on CRUNCH-536:
-----------------------------------

[~janvanbesien] sorry for the lag, 4th of July weekend over here. A couple of thoughts:

1. I think we can safely modify the Hook interface to be something that accepts the MRJob
class as an argument, ala "void run(MRJob job)". I generally don't like to modify the public
interfaces to the API, but as I read through the code, there's really no way to use the Hooks
outside of the context of CrunchControlledJob, so I think it's okay to do and avoids the overhead
of having two "hook" interfaces.

2. I think for clarity, I prefer "MRPipeline addPrepareHook(Hook hook)" and "MRPipeline addCompletionHook(Hook
hook)" to adding constructor arguments.

3. We'll need some sort of "CompositeHook" class to make that work w/the existing Prepare
and CompletionHook in CrunchJobHooks. We can make the guarantee that the hooks will be executed
in the order that they are added, with the condititon that Crunch's built-in Hooks will always
run first.

What do you think?

> crunch jobs fail to use hbase api of secured hbase
> --------------------------------------------------
>
>                 Key: CRUNCH-536
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-536
>             Project: Crunch
>          Issue Type: Bug
>            Reporter: Jan Van Besien
>         Attachments: CRUNCH-536.patch
>
>
> When accessing a secured hbase from within a mapreduce job, it is required that the hbase
credentials are initialized on the job before it was submitted. This can be done with TableMapReduceUtil.initCredentials(job).
> In case the job is the consequence of using HBaseSourceTarget, crunch-hbase can take
care of it, see CRUNCH-535.
> However, it is also possible to write DoFn's that use the HBase api directly, without
using hbase input/output format. As an example use case, consider a job that bulk writes data
to hbase by writing HFiles on HDFS which are later to be loaded into HBase. Such a job doesn't
read or write from/to hbase using an input/output format directly, but it might still require
access to other tables in HBase, for example auxiliary tables with metadata specific to the
application. 
> We can of course not expect crunch-core to call initCredentials (which is HBase specific)
on all jobs, just in case, but it would be nice to be able to register a callback on the MRPipeline
which is applied to every job before it is submitted, to cover this use case.
> I will provide a patch which will help to explain what I am suggesting here.



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