[PIP 86][Function] add funtion api to support preload and release external resources

[wangjialing218]

Motivation

This patch is based on #11112, I have talked with @wuchenxi123 and I will continue the work for this feature.

Modifications

Introduce RichFunction interface extends Function, which provide setup and tearDown API.
setup is called only once when function instance started. tearDown is called when function instance closed.
User could use these interface to initialize and release their external resources such as RedisClient.

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• The public API: ( yes)

Documentation

Check the box below and label this PR (if you have committer privilege).

Need to update docs?

• doc-required
  I think we need to add chapter to tell user how to use the API in functions-develop.md

[wangjialing218]

@nlu90 @eolivelli could you please have a check

[nlu90]

@wangjialing218 Did you call a vote for the PIP-86 in the dev@pulsar mailing list? Also you may want to update the PIP-86 content to reflect the newest idea.

It's good if we can get feedback from the community. And then start the review work.

[eolivelli]

Overall is good.
Please add unit tests and integration tests.

There is a duplicate PR for this PIP, please close the old one

[nlu90]

The PIP Vote has been passed.

And some updates in the PIP-86 needed to reflect the actual changes we added here.

[wangjialing218]

/pulsarbot run-failure-checks

[wangjialing218]

/pulsarbot run-failure-checks

[wangjialing218]

@nlu90 @eolivelli please have a check again

[nlu90]

LGTM

[eolivelli]

The change looks good.
But in your test your are not testing that the new methods are executed.
I suggest to add some static variables in the function in order to be able to check that the function runs

[wangjialing218]

The change looks good. But in your test your are not testing that the new methods are executed. I suggest to add some static variables in the function in order to be able to check that the function runs

@eolivelli I tried to add static variables in function but failed to get correct value in test code, may be caused by different class loader, could you give some suggestion?
Anyway, in the test function, process() will throw exception if initialize() did not run, and test code could check whether all messages received.

[nlu90]

@eolivelli Could you help take a look again when you are available?

[eolivelli]

+1