fsk119 opened a new pull request #15520:
URL: https://github.com/apache/flink/pull/15520
…ts before exits
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## What is the purpose of the change
*The failed test is mainly to test the view thread has the ability to exit
gracefully when users(main thread) interrupt the view thread.*
*We have 3 threads in the test: main thread, view thread and refresh thread.*
*The main thread has the resource Terminal and uses the the resource to
create the view thread. When the view thread starts, it set the interrupt flag
on the view thread and close the Terminal until view thread exits*
- *When view thread start, it start the refresh thread and monitors the user
input. In the test, it only monitors interrput signal.*
- *When get the signal, it mark the flag isRunning of the refresh thread
false and notify the refresh thread.*
- *The refresh thread is used to fetch the data from the remote periodically
and display the results on Terminal. When exits, the refresh thread will invoke
the `Executor.cancelQuery` and count down the cancellation.*
*The reason why we can NPE is because when view thread exits, it only
notifies the refresh thread instead of waiting for the refresh thread exits.
It's possible*
1. *the view thread notifies the refresh thread*
2. *the refresh thread wakes up and prepares to display the result on the
terminal*
3. *the view thread exits*
4. *the main thread finds the view thread exit and closes the resource*
5. *the refresh thread gets NPE*
6. *the main thread find the cancellation is not as same as the expected*
*Therefore, we should request the view thread wait for the refresh thread
exit.*
*To reproduce the bug, we can request the refresh thread sleep 1 seconds
before display.*
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes / **no**)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes / **no**)
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- The S3 file system connector: (yes / **no** / don't know)
## Documentation
- Does this pull request introduce a new feature? (yes / **no**)
- If yes, how is the feature documented? (**not applicable** / docs /
JavaDocs / not documented)
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