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: [email protected]



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 <[email protected]> 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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