himanshukandwal opened a new pull request, #2600:
URL: https://github.com/apache/helix/pull/2600

   ### Issues
   
   - [X] My PR addresses the following Helix issues and references them in the 
PR description:
   #2596
   
   ### Description
   
   - [X] Here are some details about my PR, including screenshots of any UI 
changes:
   In WAGED: Emergency Pipeline, when checking for an active node down we are 
seeing internal ForkJoinPool threads getting stuck in blocking state, and FJP 
ending up creating a lot of worker threads. This happens when the cluster has a 
lot of resources with many partitions, and with parallel stream we try to 
evaluate the node activeness check for all the nodes without batching or 
back-pressure. 
   
   In the solution we are doing the evaluation linearly and using 
[allMatch](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#allMatch-java.util.function.Predicate-)
 we short-circuit if an inactive node is found.
   
   Stacktrace:
   ```console
   java.util.concurrent.RejectedExecutionException: 
java.util.concurrent.RejectedExecutionException: Thread limit exceeded 
replacing blocked worker
           at 
jdk.internal.reflect.GeneratedConstructorAccessor191.newInstance(Unknown 
Source) ~[?:?]
           at 
jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
 ~[?:?]
           at java.lang.reflect.Constructor.newInstance(Constructor.java:490) 
~[?:?]
           at 
java.util.concurrent.ForkJoinTask.getThrowableException(ForkJoinTask.java:600) 
~[?:?]
           at 
java.util.concurrent.ForkJoinTask.reportException(ForkJoinTask.java:678) ~[?:?]
           at java.util.concurrent.ForkJoinTask.invoke(ForkJoinTask.java:737) 
~[?:?]
           at 
java.util.stream.ForEachOps$ForEachOp.evaluateParallel(ForEachOps.java:159) 
~[?:?]
           at 
java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateParallel(ForEachOps.java:173)
 ~[?:?]
           at 
java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:233) ~[?:?]
           at 
java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:497) ~[?:?]
           at 
java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:661) 
~[?:?]
           at 
org.apache.helix.controller.rebalancer.waged.WagedRebalancer.emergencyRebalance(WagedRebalancer.java:655)
 ~
   ```
   
   ### Tests
   
   - [X] The following tests are written for this issue:
   Validated the solution with the existing test cases: 
   * TestWagedRebalancer.testAlgorithmException
   * TestWagedRebalancer.testEmergencyRebalance
   * TestWagedRebalancer.testInvalidClusterStatus
   
   - The following is the result of the "mvn test" command on the appropriate 
module:
   
   ```console
   [INFO] Tests run: 15, Failures: 0, Errors: 0, Skipped: 0
   [INFO] 
   [INFO] 
   [INFO] --- jacoco:0.8.6:report (generate-code-coverage-report) @ helix-core 
---
   [INFO] Loading execution data file 
/Users/hkandwal/Documents/workspaces/projects/helix_os_hk/helix-core/target/jacoco.exec
   [INFO] Analyzed bundle 'Apache Helix :: Core' with 799 classes
   [WARNING] Classes in bundle 'Apache Helix :: Core' do not match with 
execution data. For report generation the same class files must be used as at 
runtime.
   [WARNING] Execution data for class 
org/apache/helix/tools/ClusterVerifiers/BestPossibleExternalViewVerifier does 
not match.
   [INFO] 
------------------------------------------------------------------------
   [INFO] BUILD SUCCESS
   [INFO] 
------------------------------------------------------------------------
   [INFO] Total time:  6.104 s
   [INFO] Finished at: 2023-08-16T10:54:02-07:00
   [INFO] 
------------------------------------------------------------------------
   ```
   
   ### Changes that Break Backward Compatibility (Optional)
   
   - My PR contains changes that break backward compatibility or previous 
assumptions for certain methods or API. They include:
   
   (Consider including all behavior changes for public methods or API. Also 
include these changes in merge description so that other developers are aware 
of these changes. This allows them to make relevant code changes in feature 
branches accounting for the new method/API behavior.)
   
   ### Documentation (Optional)
   
   - In case of new functionality, my PR adds documentation in the following 
wiki page:
   
   (Link the GitHub wiki you added)
   
   ### Commits
   
   - My commits all reference appropriate Apache Helix GitHub issues in their 
subject lines. In addition, my commits follow the guidelines from "[How to 
write a good git commit message](http://chris.beams.io/posts/git-commit/)":
     1. Subject is separated from body by a blank line
     1. Subject is limited to 50 characters (not including Jira issue reference)
     1. Subject does not end with a period
     1. Subject uses the imperative mood ("add", not "adding")
     1. Body wraps at 72 characters
     1. Body explains "what" and "why", not "how"
   
   ### Code Quality
   
   - My diff has been formatted using helix-style.xml 
   (helix-style-intellij.xml if IntelliJ IDE is used)
   


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