[PR] fix: stop flink job error by using flink cancel command before process kill [dolphinscheduler]

["shenshichao163-oss (via GitHub)" <gi...@apache.org>]

shenshichao163-oss opened a new pull request, #18554:
URL: https://github.com/apache/dolphinscheduler/pull/18554

   ## What this PR does
   
   Fixes the issue where stopping Flink tasks from the DolphinScheduler page fails to send proper kill signals, causing errors in worker node logs.
   
   ### Root Cause
   
   When a user clicks "Stop" on a Flink task, DolphinScheduler uses the generic `AbstractCommandExecutor.cancelApplication()` method, which sends OS-level kill signals (SIGINT → SIGTERM → SIGKILL) to the process tree. This approach does not properly stop the Flink job — it kills the shell process but fails to gracefully cancel the Flink application, leading to:
   - Error logs in worker nodes
   - Flink jobs not being properly terminated
   - Resource leaks in the YARN/Kubernetes cluster
   
   ### Fix
   
   Override `cancelApplication()` in `FlinkTask` to:
   
   1. **First attempt graceful cancellation** using the `flink cancel <appId>` command (via `FlinkArgsUtils.buildCancelCommandLine()`). This method already existed in the codebase but was never called.
   2. **Fall back to process-level kill** (the parent class implementation) if the Flink cancel command fails, times out (30s), or no appIds are available.
   
   ### Changes
   
   - **`FlinkTask.java`**: Added `cancelApplication()` override that tries `flink cancel` first, then falls back to `super.cancelApplication()`
   - Added imports: `TaskException`, `TaskCallBack`
   
   ### Issue Link
   
   Fixes #16789
   
   ### Before
   
   Stopping a Flink task from the page → `AbstractCommandExecutor.cancelApplication()` → `ProcessUtils.kill()` (SIGINT/SIGTERM/SIGKILL) → Flink job not properly cancelled, worker logs show errors
   
   ### After
   
   Stopping a Flink task from the page → `FlinkTask.cancelApplication()` → `flink cancel <appId>` (graceful) → if fails → `super.cancelApplication()` (process kill as fallback)
   
   ### Checklist
   
   - [x] I have searched the [issues](https://github.com/apache/dolphinscheduler/issues) of this repository and believe that this is not a duplicate.
   - [x] I have checked that this modification does not cause CI to fail.
   - [x] I will sign the Apache CLA if required.
   - [x] The code follows the projects coding style.


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Re: [PR] fix: stop flink job error by using flink cancel command before process kill [dolphinscheduler]

["SbloodyS (via GitHub)" <gi...@apache.org>]

SbloodyS closed pull request #18554: fix: stop flink job error by using flink cancel command before process kill
URL: https://github.com/apache/dolphinscheduler/pull/18554


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Re: [PR] fix: stop flink job error by using flink cancel command before process kill [dolphinscheduler]

["boring-cyborg[bot] (via GitHub)" <gi...@apache.org>]

boring-cyborg[bot] commented on PR #18554:
URL: https://github.com/apache/dolphinscheduler/pull/18554#issuecomment-5301521177

   Thanks for opening this pull request! Please check out our contributing guidelines. (https://github.com/apache/dolphinscheduler/blob/dev/docs/docs/en/contribute/join/pull-request.md)
   


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