desaikomal opened a new pull request, #2530:
URL: https://github.com/apache/helix/pull/2530

   ### Issues
   - [ ] My PR addresses the following Helix issues and references them in the 
PR description:
   
   ### Description
   - [x] Here are some details about my PR, including screenshots of any UI 
changes:
   
   WAGED is constraint based algorithm and in ideal-state calculation it always 
satisfies all the hard constraint. But while trying to converge toward the 
ideal state, in intermediate state transitions, this constraint is not 
satisfied.
   This test is explicitly written to show n - n+1 scenario.
   
   Here is the scenario: 6 node with instance capacity of 100 each. Create 3 
resource, 10 partition, 3 replicas - each with default weight of 6. 
   Cluster is super tight.
   Add an instance, so capacity become 700
   Change the default weight for one resource to 10, this will cause partition 
movements where n - n+1 contraint in intermediate state is not satisfied.
   
   Here is the sample output of current state:
   "instanceCurrent.txt" - show the currentState just after new instance has 
been added.
   "partitioonCurrent.txt" - shows the currentState after weight for 
Test-WagedDB-0 changes which causes resources to move from one instance to 
another and that's when n/n+1 constraint will not hold true.
   
   
   diff instanceCurrent.txt partitionCurrent.txt 
   2c2
   <    [Test-WagedDB-0_0, Test-WagedDB-0_2, Test-WagedDB-0_3, Test-WagedDB-0_4]
   ---
   >    [Test-WagedDB-0_0, Test-WagedDB-0_1, Test-WagedDB-0_2, Test-WagedDB-0_3]
   32c32
   <    [Test-WagedDB-0_0, Test-WagedDB-0_1, Test-WagedDB-0_2, 
Test-WagedDB-0_3, Test-WagedDB-0_4]
   ---
   >    [Test-WagedDB-0_0, Test-WagedDB-0_2, Test-WagedDB-0_3, Test-WagedDB-0_4]
   38c38
   <    [Test-WagedDB-0_1, Test-WagedDB-0_8]
   ---
   >    [Test-WagedDB-0_1, Test-WagedDB-0_4, Test-WagedDB-0_8]
   ### Tests
   
   - [x] The following tests are written for this issue:
   testIncreaseResourcePartitionWeight()
   
   (List the names of added unit/integration tests)
   
   - The following is the result of the "mvn test" command on the appropriate 
module:
   - mvn test is in-progress.
   
   (If CI test fails due to known issue, please specify the issue and test PR 
locally. Then copy & paste the result of "mvn test" to here.)
   
   ### 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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