[jira] [Created] (FLINK-1762) Make Statefulness of a Streaming Function explicit

["Stephan Ewen (JIRA)" <ji...@apache.org>]

Stephan Ewen created FLINK-1762:
-----------------------------------

             Summary: Make Statefulness of a Streaming Function explicit
                 Key: FLINK-1762
                 URL: https://issues.apache.org/jira/browse/FLINK-1762
             Project: Flink
          Issue Type: Improvement
          Components: Streaming
    Affects Versions: 0.9
            Reporter: Stephan Ewen


Currently, the state of streaming functions stored in the {{StreamingRuntimeContext}}.

That is rather inexplicit, a function may or may not make use of the state. This also hides from the system whether a function is stateful or not.

How about we make this explicit by letting stateful functions extend a special interface (see below). That would allow the stream graph to already know which functions are stateful. Certain vertices would not participate in the checkpointing, if they only contain stateless vertices. We can set up the ExecutionGraph to expect confirmations only from the participating vertices, saving messages.

{code}
public interface Statehandle {

 get, put, ...
}

public interface Stateful {

    void setStateHandle(Statehandle handle);
}
{code}



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