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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: Why does the Hive CLI start a subprocess?
Date Thu, 10 Dec 2009 20:52:33 GMT
On Thu, Dec 10, 2009 at 3:08 PM, Philip Zeyliger <philip@cloudera.com> wrote:
>> >
>> > So definitely the subprocess has different libjars. But those libjars
>> > are not needed by the CLI. Does that make sense?
>>
>
> Sure.  In theory, though, you could do stuff like
> "Thread.currentThread().setContextClassLoader(...)".  Hadoop does this on
> occasion already.
>
> I'm curious if anyone's tried that approach and failed. :)
>
> -- Philip
>

Phillip,

> "Thread.currentThread().setContextClassLoader(...)".

Really there is no need to add jars to the Cli. The UDF never needs to
be in the classpath of the CLI.

If you look at the comment..
/**
 * Alternate implementation (to ExecDriver) of spawning a mapreduce
task that runs it from
 * a separate jvm. The primary issue with this is the inability to
control logging from
 * a separate jvm in a consistent manner
 **/

So this must have done this specifically. I am guessing that some
Hadoop/hive singletons might involved and spanning a separate task
gives you total isolation.

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