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https://issues.apache.org/jira/browse/FLINK-5982?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15939521#comment-15939521
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Wei-Che Wei commented on FLINK-5982:
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Hi [~till.rohrmann]
Thanks for your replying. For the first question, I sill feel a little confused
and I would like to getting your suggestion. Thank you.
# It's a good choice to check passed environment in {{AbstractInvokable}} and
pass a {{DummyEnvironment}} instead of {{null}}. I am not sure if it is good to
state instances as well, since sometimes the state instances will be {{null}}
in {{Task}}. If checking state instances are not {{null}}, it might need to add
one more constructor or pass an empty state object in {{Task}}. What do you
think?
# The exception is {{IllegalStateException("Found operator state for a
non-stateful task invokable")}}. Now, I only put it in {{BatchTask}} not it the
testing classes. I think it would not change their behavior. I will check it
once again before I finish this task.
# What I want to do is leave it empty and let those classes who need to support
the state methods to override them, but I think your way is better. I will
implement like that and let the state methods in {{AbstractInvokable}} be
abstract methods.
> Refactor AbstractInvokable and StatefulTask
> -------------------------------------------
>
> Key: FLINK-5982
> URL: https://issues.apache.org/jira/browse/FLINK-5982
> Project: Flink
> Issue Type: Improvement
> Components: Distributed Coordination, State Backends, Checkpointing
> Affects Versions: 1.2.0
> Reporter: Wei-Che Wei
> Assignee: Wei-Che Wei
>
> Currently, running a invokable in {{Task}} needs to call
> {{setEnvironment(env)}} and {{invoke()}}. If the invokable is also a
> {{StatefulTask}}, it need to call {{setInitialState(state)}}. That makes the
> difficulty in doing the eager initialization on invokable during
> {{DEPLOYING}} state. One solution discussed in FLINK-4714 is to separate
> {{invoke()}} into {{open()}} and {{invoke()}}, but that makes the complexity
> for running it in {{Task}}.
> This task wants to refactor {{AbstractInvokable}} and {{StatefulTask}} to
> make it easier to construct and run an invokable.
> # Refactor abstract class to have one default constructor.
> #* Drop {{StatefulTask}} and assume all subclasses of {{AbstractInvokable}}
> are stateful.
> #* Remove {{setEnvironment(env)}} and {{setInitialState(state)}}. Make
> {{AbstractInvokable}} have a two argument constructor with {{Environment}}
> and {{TaskStateHandles}}.
> # Update all subclass
> #* Make all subclass of {{AbstractInvokable}} have a two argument constructor
> and call the constructor in {{AbstractInvokable}}.
> #* Throw an error in {{BatchTask}} if the initial state is not null. (This
> will be removed after {{BatchTask}} have been stateful.)
> # Change the creation of the invokable to call that constructor, update all
> the tests.
> Then, we can simplify the logic to run an invokable by using constructor and
> {{invoke()}}. The eager initialization can easily be placed in the
> constructor to fulfill the requirement such as FLINK-4714.
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