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Posted to user@flink.apache.org by mahesh dhabade <ma...@gmail.com> on 2017/12/16 07:53:07 UTC

Flink CEP state store

Hello,

Can anyone shed some light on the intermittent state store mechanism used
by Flink CEP ?
Based on the kind of pattern, the state-store may be overwhelmed with
intermittent states. How does Flink CEP manage this ? Does it use a
persistent store, or just an in-memory store with a cap on the number
states etc ?

Thanks,
Mahesh

Re: Flink CEP state store

Posted by Dawid Wysakowicz <wy...@gmail.com>.

Hi Mahesh,

You are right that it based on the Pattern you write there might be a big amount of intermittent states created. Flink CEP library keeps all its State in  State Backend. So if you use e.g. RocksDBStateBackend it will be backed by disc. Nevertheless it is vital to allow clearing the state by using either within (that will timeout states) or do not use nondeterministic continuity (e.g. followedByAny or looping patterns without until).

Hope it helps.

Regards
Dawid
> On 16 Dec 2017, at 08:53, mahesh dhabade <ma...@gmail.com> wrote:
> 
> Hello,
> 
> Can anyone shed some light on the intermittent state store mechanism used by Flink CEP ?
> Based on the kind of pattern, the state-store may be overwhelmed with intermittent states. How does Flink CEP manage this ? Does it use a persistent store, or just an in-memory store with a cap on the number states etc ?
> 
> Thanks,
> Mahesh