You are viewing a plain text version of this content. The canonical link for it is here.
Posted to common-user@hadoop.apache.org by Inifok Song <ha...@gmail.com> on 2009/08/28 05:36:13 UTC
Difference between copyOutput() and fetchOutputs()
Hello all,
In class ReduceTask, there are a lot of methods to deal with fetching
intermediate output. And I think copyOutput() and fetchOutputs() are the
most important. However, they are invoked by different methods. I wonder
know whether they deal with the same thing? What's the difference between
them?
Thank you.
Inifok
Re: Difference between copyOutput() and fetchOutputs()
Posted by Inifok Song <ha...@gmail.com>.
Oops! I'm so careless that haven't noticed it. This is really a rookie
question. Thanks for your answer.
2009/8/28 Jothi Padmanabhan <jo...@yahoo-inc.com>
> Reduce Task creates a ReduceCopier object and invokes fetchOutput method on
> this object to start the fetch process.
>
> fetchOutputs internally launches several MapOutputCopier threads to do the
> fetching and each of these thread do the copyOutput.
>
> Jothi
>
>
> On 8/28/09 9:06 AM, "Inifok Song" <ha...@gmail.com> wrote:
>
> > Hello all,
> >
> > In class ReduceTask, there are a lot of methods to deal with fetching
> > intermediate output. And I think copyOutput() and fetchOutputs() are the
> > most important. However, they are invoked by different methods. I wonder
> > know whether they deal with the same thing? What's the difference between
> > them?
> >
> > Thank you.
> >
> > Inifok
>
>
Re: Difference between copyOutput() and fetchOutputs()
Posted by Jothi Padmanabhan <jo...@yahoo-inc.com>.
Reduce Task creates a ReduceCopier object and invokes fetchOutput method on
this object to start the fetch process.
fetchOutputs internally launches several MapOutputCopier threads to do the
fetching and each of these thread do the copyOutput.
Jothi
On 8/28/09 9:06 AM, "Inifok Song" <ha...@gmail.com> wrote:
> Hello all,
>
> In class ReduceTask, there are a lot of methods to deal with fetching
> intermediate output. And I think copyOutput() and fetchOutputs() are the
> most important. However, they are invoked by different methods. I wonder
> know whether they deal with the same thing? What's the difference between
> them?
>
> Thank you.
>
> Inifok