Removing String format in RemoteStoreMigrationAllocationDecider

[RS146BIJAY]

Description

String.format is a relatively expensive operation for concatenating strings. Inside RemoteStoreMigrationAllocationDecider, the function calls to String.format stands out as the most resource-intensive operation in terms of latency.

This PR improves the latency of RemoteStoreMigrationAllocationDecider by replacing calls to String.format with more efficient StringBuilder for string concatenation.

Latency improvements

For initialising 225K shards on 500 nodes, we are observing an improvement of 31 seconds with above change.

Before the change

391,940.31 ms

After the change

360,279.58 ms

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for 790919f: FAILURE

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❌ Gradle check result for 4232c37: FAILURE

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❌ Gradle check result for a41da6a: FAILURE

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[github-actions]

❌ Gradle check result for f74b597: FAILURE

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❌ Gradle check result for 01cc8cd: FAILURE

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[github-actions]

❕ Gradle check result for 3e4fd1e: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.cluster.MinimumClusterManagerNodesIT.testThreeNodesNoClusterManagerBlock

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Attention: Patch coverage is 93.75000% with 1 line in your changes missing coverage. Please review.

Project coverage is 71.78%. Comparing base (6267e94) to head (3e4fd1e).
Report is 2 commits behind head on main.

Files	Patch %	Lines
...decider/RemoteStoreMigrationAllocationDecider.java	93.75%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #14612      +/-   ##
============================================
+ Coverage     71.65%   71.78%   +0.12%     
- Complexity    62272    62323      +51     
============================================
  Files          5140     5140              
  Lines        293020   293028       +8     
  Branches      42347    42347              
============================================
+ Hits         209977   210354     +377     
+ Misses        65766    65327     -439     
- Partials      17277    17347      +70     

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[Bukhtawar]

Thanks, can you please point me to a test that validates the messages

[RS146BIJAY]

Thanks, can you please point me to a test that validates the messages

@Bukhtawar This is the unit test which validates this message:

OpenSearch/server/src/internalClusterTest/java/org/opensearch/remotemigration/RemoteMigrationAllocationDeciderIT.java

Line 158 in f9512db

"[remote_store migration_direction]: primary shard copy can not be allocated to a non-remote node",