Add support for index level slice count setting

[Gankris96]

Description

Adds support for index level slice count setting. This slice count value will take precedence over the cluster level slice count value if set.

Related Issues

Resolves #15268

Check List

• [x ] Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable. Created the issue here : [DOC] Document support for index level max_slice_count setting and search.concurrent_segment_search.mode setting documentation-website#8068

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

❌ Gradle check result for e671e35: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[neetikasinghal]

@Gankris96 looks like the gradle precommit is failing - u will have to run ./gradlew :server:spotlessApply to fix it.
Also, add a change log entry for this change.

[Gankris96]

Tested out locally by setting the setting as follows:

Index setting before update:

curl --location 'localhost:9200/movies/_settings?include_defaults=null' \
--data ''

{
    "movies": {
        "settings": {
            "index": {
                "replication": {
                    "type": "DOCUMENT"
                },
                "number_of_shards": "1",
                "provided_name": "movies",
                "creation_date": "1724263596286",
                "number_of_replicas": "1",
                "uuid": "AdlJhZC3ShqP1ZL9BRwqYg",
                "version": {
                    "created": "137217827"
                }
            }
        }
    }
}

curl --location --request PUT 'localhost:9200/movies/_settings' \
--header 'Content-Type: application/json' \
--data '{
    "index": {
    "search.concurrent.max_slice_count": 2
  }
}'

{
    "acknowledged": true
}

After update the index setting would look like:

curl --location 'localhost:9200/movies/_settings' \
--data ''

{
    "movies": {
        "settings": {
            "index": {
                "replication": {
                    "type": "DOCUMENT"
                },
                "search": {
                    "concurrent": {
                        "max_slice_count": "2"
                    }
                },
                "number_of_shards": "1",
                "provided_name": "movies",
                "creation_date": "1724263095594",
                "number_of_replicas": "1",
                "uuid": "Y6IkbrSkQbu2B6Orc6gnzQ",
                "version": {
                    "created": "137217827"
                }
            }
        }
    }
}

[jed326]

Can you add a changelog entry as well?

[github-actions]

❌ Gradle check result for 6532815: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[Gankris96]

@jed326 Opened a docs issue here opensearch-project/documentation-website#8068

[github-actions]

❌ Gradle check result for c2f2401:

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for 84071f2: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[jed326]

❌ Gradle check result for 84071f2: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

@Gankris96 can you try to rebase from main to see if that fixes these?

[harishbhakuni]

Changes LGTM.

[github-actions]

❕ Gradle check result for 1b6be03: UNSTABLE

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

All modified and coverable lines are covered by tests ✅

Project coverage is 71.93%. Comparing base (abb1041) to head (1b6be03).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main   #15336   +/-   ##
=========================================
  Coverage     71.93%   71.93%           
+ Complexity    63223    63221    -2     
=========================================
  Files          5214     5214           
  Lines        295938   295943    +5     
  Branches      42754    42754           
=========================================
+ Hits         212876   212887   +11     
+ Misses        65601    65514   -87     
- Partials      17461    17542   +81     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[neetikasinghal]

Other changes look good to me, please ensure to check my comment #15336 (comment) as a follow-up!

[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-15336-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 b6b04039ab9b05de4da50863503b68f6be74e424
# Push it to GitHub
git push --set-upstream origin backport/backport-15336-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-15336-to-2.x.

[jed326]

@Gankris96 can you manually backport?

[Gankris96]

@jed326 backport to 2.x pr #15371