[jira] [Created] (FLINK-21171) Introduce TypedValue to the StateFun request-reply protocol

["Tzu-Li (Gordon) Tai (Jira)" <ji...@apache.org>]

Tzu-Li (Gordon) Tai created FLINK-21171:
-------------------------------------------

             Summary: Introduce TypedValue to the StateFun request-reply protocol
                 Key: FLINK-21171
                 URL: https://issues.apache.org/jira/browse/FLINK-21171
             Project: Flink
          Issue Type: New Feature
          Components: Stateful Functions
            Reporter: Tzu-Li (Gordon) Tai
            Assignee: Tzu-Li (Gordon) Tai
             Fix For: statefun-3.0.0


Currently, all values being passed around via the request-reply protocol, are of the Protobuf {{Any}} type. This includes payloads of outgoing messages to other functions, and also state values.

This has a few shortcomings:
* All user records are strictly required to be modeled and wrapped as a Protobuf message - even for simple primitive type. This makes it awkward to work with for many common types of messages, for example JSON.
* For data persisted as state, with each state value being a Protobuf {{Any}}, each value would also redundantly store the type urls associated with each Protobuf message.

Instead, we'd like to introduced a {{TypedValue}} construct that replaces {{Any}} everywhere in the protocol, for both messages and state values:
{code}
message TypedValue {
    string typename = 1;
    bytes value = 2;
}
{code}

The {{typename}} here directly maps to the type concept introduced in FLINK-21061.
For state, we directly write the value bytes of a {{TypedValue}} into state, and the {{typename}} is the meta information snapshotted by the state serializer (see FLINK-21061).



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