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From Aljoscha Krettek <aljos...@apache.org>
Subject Re: Parallel execution on AllWindows
Date Wed, 03 Aug 2016 16:11:16 GMT
Hi,
"rebalance" simply specifies the strategy to use when sending elements
downstream to the next operator(s). There is no interaction or competition
between the parallel window operator instances. Each will do windowing
locally based on the elements that it receives from upstream.

Cheers,
Aljoscha

On Wed, 3 Aug 2016 at 08:26 <andrew.ge-wu@eniro.com> wrote:

> Hi Aljoscha
>
> Thanks for the explanation.
> One other thing, when you say there is no coordination is that means
> rebalance() will not be honored, and each window operator instance will
> compete for the next available window?
>
> Thanks
>
> Andrew
> From mobile
>
> From: Aljoscha Krettek
> Sent: Wednesday, August 3, 17:11
> Subject: Re: Parallel execution on AllWindows
> To: user@flink.apache.org
>
> Hi,
>
> if you manually force a parallelism different from 1 after a *windowAll()
> then you will get parallel execution of your window. For example, if you do
> this:
>
> input.countWindowAll(100).setParallelism(5)
>
> then you will get five parallel instances of the window operator that each
> wait for 100 elements before they fire the window. There is no global
> coordination between the parallel instances that would allow it to fire
> once 100 elements are received across the parallel instances.
>
> Cheers,
>
> Aljoscha
>
> On Wed, 3 Aug 2016 at 05:10 Andrew Ge Wu <andrew.ge-wu@eniro.com> wrote:
>
> Hi,
>
> I have such task that I want to count window on a stream and execute them
> batch by batch.
>
> Execute a count window may take some time, so I want it to be executed in
> *parallel*.
>
> I read this part in the documentation when I found it automatically
> reduced parallelization to 1
>
> * Note: This operation can be inherently non-parallel since all elements
> have to pass through
> * the same operator instance. (Only for special cases, such as aligned
> time windows is
> * it possible to perform this operation in parallel).
>
> (It looks like the java doc is copied from timeWindowAll)
>
> If I force all window function to run in parallel, what will happen?
>
> Will a time/count window broadcast to all instances of the function? or
> will it be send to one of the instance so I can parallelize my work?
>
> Thanks!
>
>
> Andrew
>
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