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From Gyula Fóra <gyf...@apache.org>
Subject Re: [DISCUSS] Refactor StateBackend into Partitioned State and Non-Partitioned State Backends
Date Thu, 07 Jan 2016 10:17:28 GMT


I think it would be a good idea to separate the 2 state backends. I think
you are right in most cases the new partitioned state implementations will
benefit from this as it removes a lot of additional overhead (although
sometimes it's nice to have the 2 together, for instance if they both use
the filesystem) :)


Aljoscha Krettek <aljoscha@apache.org> ezt írta (időpont: 2016. jan. 7.,
Cs, 11:02):

> Hi,
> I’m currently examining ways to 1) change the window operators to use the
> partitioned state abstraction for window state and 2) implement state
> backends for managed memory/out-of-core state.
> I think it would be helpful to pull the state backend apart. Right now,
> for example, the DbStateBackend has a custom way of specifying another
> state backend that should be used for non-partitioned state since a data
> base really only makes sense for partitioned state. I was thinking about
> adding a state backend based on RocksDB, which would also only make sense
> for partitioned state. Pulling the two ways of state apart would allow the
> implementation to focus on the important parts and give the user
> flexibility without requiring every state backend to implement this.
> What do you think about pulling the back ends apart?
> —
> Aljoscha
> P.S. I have a prototype WindowOperator on partitioned state that does not
> regress in performance compared to the current WindowOperator. Also, I have
> a prototype RocksDB state backend. Here, the performance is about 1/10th
> compared to using the in-memory state backend (with 100.000 keys) but it
> scales way better (with the in-memory state backend performance goes down
> when increasing the number of keys while it stays constant with RocksDB).
> This is quite nice since it allows to use the same windowing code while
> exchanging the state backend based on the job requirements.

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