Chen Qin created FLINK-4266:
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Summary: Cassandra Statebackend
Key: FLINK-4266
URL: https://issues.apache.org/jira/browse/FLINK-4266
Project: Flink
Issue Type: New Feature
Components: State Backends, Checkpointing
Affects Versions: 1.0.3, 1.2.0
Reporter: Chen Qin
Priority: Minor
Current FileSystem statebackend limits whole state size to disk space.
For long running task that hold window content for long period of time, it
needs to split out states to durable remote storage and replicated across data
centers.
We look into implementation from leverage checkpoint timestamp as versioning
and do range query to get current state; we also want to reduce "hot states"
hitting remote db per every update between adjacent checkpoints by tracking
update logs and merge them, do batch updates only when checkpoint; lastly, we
are looking for eviction policy that can identify "hot keys" in k/v state and
lazy load those "cold keys" from Cassandra.
For now, we don't have good story regarding to data retirement. We might have
to keep forever until manually run command and clean per job related state
data. Some of features might related to incremental checkpointing feature, we
hope to align with effort there also.
Welcome comments, I will try to put a draft design doc after gathering some
feedback.
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