Allow changing number of replicas of searchable snapshot index

[bugmakerrrrrr]

Description

#5907 uses a whitelist to control which settings of searchable snapshot can be changed, but index.number_of_shards is not on the list. I think it is necessary to allow user to change the number of replicas based on their cost or performance needs.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)
• Public documentation issue/PR created

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For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[bugmakerrrrrr]

@andrross what do you think about this idea?

[github-actions]

Compatibility status:

Checks if related components are compatible with change c28c3bc

Incompatible components

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/performance-analyzer.git]

[github-actions]

✅ Gradle check result for e13e1b7: SUCCESS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ed1c8b7) 71.34% compared to head (c28c3bc) 71.29%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #11317      +/-   ##
============================================
- Coverage     71.34%   71.29%   -0.05%     
- Complexity    58964    58983      +19     
============================================
  Files          4890     4890              
  Lines        277477   277477              
  Branches      40308    40308              
============================================
- Hits         197961   197838     -123     
- Misses        62976    63230     +254     
+ Partials      16540    16409     -131     

☔ View full report in Codecov by Sentry.
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[andrross]

Thanks @bugmakerrrrrr! This is definitely a gap as configuring replicas is something that should be allowed.

[andrross]

Thanks @bugmakerrrrrr. This change looks good. Can you please add an entry to the changelog under [Unreleased 2.x]?

[bugmakerrrrrr]

@andrross Done. Btw, I find that allow changing allocation filter settings (index.routing.allocation.include/exclude/require.*) of searchable snapshot may also be necessary. Can I add support for it in this PR? or should I open a new PR?

[github-actions]

❕ Gradle check result for b4fd24b: UNSTABLE

• TEST FAILURES:

      2 org.opensearch.smoketest.SmokeTestMultiNodeClientYamlTestSuiteIT.test {yaml=pit/10_basic/Delete all}

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

[github-actions]

❕ Gradle check result for c28c3bc: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.smoketest.SmokeTestMultiNodeClientYamlTestSuiteIT.test {yaml=pit/10_basic/Delete all}

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

[andrross]

@andrross Done. Btw, I find that allow changing allocation filter settings (index.routing.allocation.include/exclude/require.*) of searchable snapshot may also be necessary. Can I add support for it in this PR? or should I open a new PR?

Let's do that in a separate PR. Feel free to open an issue to track it as well.

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-11317-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c4e703f9e7c31e991a57f3719910fdc086120e93
# Push it to GitHub
git push --set-upstream origin backport/backport-11317-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-11317-to-2.x.