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Re: Run a job async
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Cheolsoo,

Can you make a JIRA for this? I can imagine a slightly heavier test suite,
but I like where you started. If it's not far off, then I think it'll be a
win to make it thread safe. But we need to make sure to test the most
advanced features...UDF's (esp the same name but different udf in different
invocations), scripting UDFs (same thing), and so on.
2013/1/25 Cheolsoo Park <[EMAIL PROTECTED]>

> >> if you have multiple threads that run a query via PigServer, there is a
> great chance of the internals clashing because of the use of static
> variable within Pig.
>
> Recently, I spent some time on this, and what I found is that the Pig
> front-end is quite thread-safe. Here is how I tested it:
>
> 1) Wrote a PigUnit test that runs in MR mode.
> 2) Executed test cases concurrently in 4 threads using a JUnit extension
> called temps-fugit:
> http://tempusfugitlibrary.org/documentation/junit/parallel/
>
> After fixing PIG-3096, I was able to successfully run Pig queries in
> parallel. It's important to note that only the front-end needs to be
> thread-safe since that's what is executed in parallel.
>
> I arbitrarily selected queries from e2e test cases, so they are probably
> not complex enough to mimic real-world examples. Nevertheless, my test
> program ran without a problem for few days. I couldn't continue my
> experiment because I was pulled out into something else. However, I think
> that making the front-end thread-safe is an achievable goal.
>
> Thanks,
> Cheolsoo
>
>
>
> On Thu, Jan 24, 2013 at 11:18 PM, Ramakrishna Nalam
> <[EMAIL PROTECTED]>wrote:
>
> > That clarifies it for me, thanks a lot.
> >
> > Regards,
> > Rama.
> >
> >
> > On Fri, Jan 25, 2013 at 10:09 AM, Jonathan Coveney <[EMAIL PROTECTED]
> > >wrote:
> >
> > > Well, when I say that Pig is not multi-threaded, what I mean is that if
> > you
> > > have multiple threads that run a query via PigServer, there is a great
> > > chance of the internals clashing because of the use of static variables
> > > within Pig. Pig itself, when running a single query, is multi-threaded.
> > > It's just not "multi-threaded" in the sense that multiple instances can
> > > safely be run in the same JVM.
> > >
> > >
> > > 2013/1/24 Ramakrishna Nalam <[EMAIL PROTECTED]>
> > >
> > > > Hi Jonathan,
> > > >
> > > > Pardon if it's a naive question, but Interesting that you say Pig is
> > not
> > > > multithreaded.
> > > > We're using Pig 0.10.0, and looking at the code, it seems to do the
> > right
> > > > things to handle multi threaded requests (ThreadLocal for ScriptState
> > for
> > > > eg).
> > > >
> > > > Would be great if you can point out to the kind of issues there could
> > be.
> > > >
> > > >
> > > > Regards,
> > > > Rama.
> > > >
> > > >
> > > >
> > > > On Thu, Jan 24, 2013 at 8:32 PM, Praveen M <[EMAIL PROTECTED]>
> > > > wrote:
> > > >
> > > > > Are there any plans on making the pigserver multi-threaded?
> > > > >
> > > > > since there is "PigProcessNotificationListener" to subscribe for
> > async
> > > > > callbacks when the pig job completes, is there any real need to
> keep
> > > the
> > > > > pig job submitting thread waiting until the job completes?
> > > > >
> > > > > Is this just a shortcoming today or are there more concrete reasons
> > > > against
> > > > > providing with a pigserver which can submit to the cluster in
> > mapreduce
> > > > > mode async?
> > > > >
> > > > > Thanks,
> > > > > Praveen
> > > > >
> > > > >
> > > > >
> > > > > On Wed, Jan 23, 2013 at 10:56 PM, Jonathan Coveney <
> > [EMAIL PROTECTED]
> > > > > >wrote:
> > > > >
> > > > > > I think whatever way you slice it, handling thousands of pig jobs
> > > > > > asynchronously is going to be a bear. I mean, this is essentially
> > > what
> > > > > the
> > > > > > job tracker does, albeit with a lot less information.
> > > > > >
> > > > > > Either way, Pig is not multi-threaded so having more than one
> > > instance
> > > > of
> > > > > > Pig in the same JVM is going to start causing problems (which is