Honor max segment size during only_expunge_deletes

[msfroh]

Description

There are latency-sensitive users for whom the default 20% allowable accumulation of deletes is too high, so they force merge with "only_expunge_deletes".

Unfortunately, this has ignored the max segment size, so despite the word "only" in there, they get the terrible side-effect of producing segments larger than the max segment size. These oversized segments are unlikely to participate in future merges, until they have so many deletes that they could drop back below the max segment size, likely making the whole "too many deletes" problem even worse.

This commit fixes that so that "only_expunge_deletes" ONLY EXPUNGES DELETES without creating oversized segments.

Related Issues

Resolves #7644

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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 (Jenkins) Run Completed with:

• RESULT: null ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/25538/
• CommitID: 46e1134
  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]

Compatibility status:

Checks if related components are compatible with change 7d265b4

Incompatible components

Skipped components

Compatible components

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

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/25537/
• CommitID: df3ee13

[codecov]

Codecov Report

Merging #10036 (df7f441) into main (70a582f) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main   #10036      +/-   ##
============================================
+ Coverage     71.06%   71.18%   +0.12%     
- Complexity    58103    58171      +68     
============================================
  Files          4825     4825              
  Lines        274024   274024              
  Branches      39926    39926              
============================================
+ Hits         194730   195075     +345     
+ Misses        62978    62604     -374     
- Partials      16316    16345      +29     

Files Changed	Coverage Δ
.../opensearch/index/OpenSearchTieredMergePolicy.java	100.00% <100.00%> (+3.33%)	⬆️

... and 497 files with indirect coverage changes

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/25730/
• CommitID: 7d265b4
  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 (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/25731/
• CommitID: df7f441
  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 (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/25733/
• CommitID: df7f441

[andrross]

I'm convinced by your reasoning, @msfroh. We should document this behavior change, but it appears we don't have documentation for the force_merge API at all. I created an issue here to track that: opensearch-project/documentation-website#5057

[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-10036-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 1dde018a1aa9cb606c274a4119348de285b80a65
# Push it to GitHub
git push --set-upstream origin backport/backport-10036-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-10036-to-2.x.