Ufuk Celebi created FLINK-3779:
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Summary: Add support for queryable state
Key: FLINK-3779
URL: https://issues.apache.org/jira/browse/FLINK-3779
Project: Flink
Issue Type: Improvement
Components: Distributed Runtime
Reporter: Ufuk Celebi
Assignee: Ufuk Celebi
Flink offers state abstractions for user functions in order to guarantee
fault-tolerant processing of streams. Users can work with both non-partitioned
(Checkpointed interface) and partitioned state
(getRuntimeContext().getState(ValueStateDescriptor) and other variants).
The partitioned state interface provides access to different types of state
that are all scoped to the key of the current input element. This type of state
can only be used on a KeyedStream, which is created via stream.keyBy().
Currently, all of this state is internal to Flink and used in order to provide
processing guarantees in failure cases (e.g. exactly-once processing).
The goal of Queryable State is to expose this state outside of Flink by
supporting queries against the partitioned key value state.
This will help to eliminate the need for distributed operations/transactions
with external systems such as key-value stores which are often the bottleneck
in practice. Exposing the local state to the outside moves a good part of the
database work into the stream processor, allowing both high throughput queries
and immediate access to the computed state.
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