[WIP][mysql] Add ExternalSystemListener to notify user about the status of connector.

[lvyanquan]

this closes https://github.com/ververica/flink-cdc-connectors/issues/2520

Try to support notification about the status of connector, since it may be a common demand from community. However, I met some problem when add a preliminary implementation, want to get some advice from yours.

1. When I try to define an enum of ExternalSystemEvent, I found that it's similar to AssignerStatus, can we reuse it?
2. Should we send information about finished splits to listener? then it would be very similar to checkpoint.
3. Should we add a default implement like KafkaListener?

[lvyanquan]

Hi, @ruanhang1993 Not sure if my design and confusion are reasonable, Looking forward to your advice. 😊

[SML0127]

@lvyanquan Wow.. First of all, Thank you for implementing this function I was hoping for.

I've been so busy at work and was just about to implement it, but you've already implemented it! 🤣🤣🤣

Can I run this pr with our company in-house notification tools and give you some comment??🙇🏻‍♂️🙇🏻‍♂️

[SML0127]

@lvyanquan Wow.. First of all, Thank you for implementing this function I was hoping for.

I've been so busy at work and was just about to implement it, but you've already implemented it! 🤣🤣🤣

Can I run this pr with our company in-house notification tools and give you some comment??🙇🏻‍♂️🙇🏻‍♂️

I added some information (e.g. startupMode, gtids) for notification message and created PR.

As our team implemented and used this notification feature, we realized that the startupMode and gtids information was really useful. So I added it.

I hope you give it a try, and thanks for any comments!! 😄🙇🏻‍♂️

[lvyanquan]

It makes sense to me, and I create an abstract class AbstractListenerMessage since there are other datasources like oracle、postgreSQL.

[SML0127]

It makes sense to me, and I create an abstract class AbstractListenerMessage since there are other datasources like oracle、postgreSQL.

LGTM! I learn a lot from your implementation😃

[yuxiqian]

Is there any progress on this PR? cc @lvyanquan

[github-actions[bot]]

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