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From Aljoscha Krettek <aljos...@apache.org>
Subject Re: Window state with rocksdb backend
Date Thu, 09 Aug 2018 11:54:00 GMT

the objects you get in the WindowFunction are not supposed to be mutated. Any changes to them
are not guaranteed to be synced back to the state backend.

Why are you modifying in the objects? Maybe there's another way of achieving what you want
to do.


> On 9. Aug 2018, at 10:36, 祁明良 <mqi@xiaohongshu.com> wrote:
> Hi all,
> This is mingliang, I got a problem with rocksdb backend.
> I'm currently using a 15min SessionWindow which also fires every 10s, there's no pre-aggregation,
so the input of WindowFunction would be the whole Iterator of input object.
> For window operator, I assume this collection is also a state that maintained by Flink.
> Then, in each 10s fire, the window function will take the objects out from iterator and
do some update, and in next fire, I assume I would get the updated value of that object.
> With File system backend it was successful but eats a lot of memory and finally I got
GC overhead limit, then I switch to rocksdb backend and the problem is the object in the next
fire round is not updated by the previous fire round.
> Do I have to do some additional staff with rocksdb backend in this case?
> Thanks in advance
> Mingliang
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