[GitHub] [iotdb] alany9552 opened a new pull request #4380: Fixed a flaky test

[GitBox <gi...@apache.org>]

alany9552 opened a new pull request #4380:
URL: https://github.com/apache/iotdb/pull/4380


   ## Description
   Fixed a flaky test causes by non-deterministic concurrent map
   
   ### Reason of change
   Original file has a flaky test when running:
   `mvn -pl cluster edu.illinois:nondex-maven-plugin:1.1.2:nondex 
   -Dtest=org.apache.iotdb.cluster.log.snapshot.MetaSimpleSnapshotTest#testSerialize
   `
   The test is flaky because in `serialize()` method, it uses a concurrent map to store `nodeSlot` which returns
   non deterministic results for each run. To fix this, I changed the concurrent map to `synchronizedMap()` to ensure the orders
   and the threads' safety.
   
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   <hr>
   
   This PR has:
   - [X] been self-reviewed.
       - [X] concurrent read
       - [X] concurrent write
       - [X] concurrent read and write 
   - [ ] added documentation for new or modified features or behaviors.
   - [ ] added Javadocs for most classes and all non-trivial methods. 
   - [ ] added or updated version, __license__, or notice information
   - [ ] added comments explaining the "why" and the intent of the code wherever would not be obvious 
     for an unfamiliar reader.
   - [ ] added unit tests or modified existing tests to cover new code paths, ensuring the threshold 
     for code coverage.
   - [ ] added integration tests.
   - [ ] been tested in a test IoTDB cluster.
   
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   <hr>
   
   ##### Key changed/added classes (or packages if there are too many classes) in this PR
   


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[GitHub] [iotdb] alany9552 commented on pull request #4380: Fixed flaky tests

[GitBox <gi...@apache.org>]

alany9552 commented on pull request #4380:
URL: https://github.com/apache/iotdb/pull/4380#issuecomment-979751024


   > Thanks for your job. However, I can not get your point, are you going to keep the order of map elements? if we use `Collections.synchronizedMap` relpace the `ConcurrentHashMap`, which may occur `ConcurrentModificationException`.
   
   Originally I was thinking about using just `LinkedHashMap` but it not thread safe, so that's why I choose to use `Collections.synchronizedMap`. 


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[GitHub] [iotdb] alany9552 commented on pull request #4380: Fixed flaky tests

[GitBox <gi...@apache.org>]

alany9552 commented on pull request #4380:
URL: https://github.com/apache/iotdb/pull/4380#issuecomment-979750021


   
   
   
   
   > Thanks for your job. However, I can not get your point, are you going to keep the order of map elements? if we use `Collections.synchronizedMap` relpace the `ConcurrentHashMap`, which may occur `ConcurrentModificationException`.
   
   Yeah I understand your concerns. The order of the map elements keeps the same and pass for the regular runs, but the order can't be guaranteed when running `NonDex` tests because `ConcurrentHashMap`. If using `ConcurrentHashMap` is the best in this situation as you mentioned the exception, it would be better to change the test code in that doesn't require orders, otherwise the tests will be keep flaky when running. 


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