Kostas Kloudas created FLINK-7043:
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Summary: Optimize state handling in NFA
Key: FLINK-7043
URL: https://issues.apache.org/jira/browse/FLINK-7043
Project: Flink
Issue Type: Improvement
Components: CEP
Affects Versions: 1.3.1
Reporter: Kostas Kloudas
Assignee: Dawid Wysakowicz
Fix For: 1.4.0
The checkpointed state of the NFA is consisted of:
1) The States/ windowTime/ handleTimeout flag (also contains the
IterativeConditions)
2) The sharedBuffer
3) The computationStates
>From these 3:
1) is static, as it is the description of the NFA which is static throughout
the lifetime of the NFA, and
2) and 3) that are dynamic, as at any point they depend on the already consumed
input.
This issue proposes to leverage the fact the 1 is static and store it on a
separate keyed valueState than the NFA. This way, in the
{{AbstractKeyedCEPPatternOperator.getNFA()}} which is called at each watermark
and for each active key, we will just serialize/deserialize the dynamic state,
while the static one we will serialize it only upon checkpointing, and
deserialize it upon restoring.
We need to checkpoint also the static state because we want in the future to be
able to add Patterns at runtime to the same operator, e.g. through a coStream.
So given that now we must have a way to match the dynamic with the static state
of the NFA, we will have to introduce a name (or id) for a given Pattern/NFA.
This will be stored with both the
static and the dynamic state, and upon restoring we will be able to match the
two based on that name. This name will be user-defined and can be specified
through a `name()` method in the Pattern class (like the begin()).
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