Optimize checksum creation for remote cluster state

[himshikha]

Description

This change parallelizes checksum creation for cluster state components, with the aim to reduce remote state publication latency.

Related Issues

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

Check List

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

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 1b5edaa: 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?

[Bukhtawar]

Thanks @himshikha would you be able to share the perf numbers with this change

[github-actions]

❌ Gradle check result for 542d709: 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?

[github-actions]

❌ Gradle check result for 93f9a43: 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?

[himshikha]

❌ Gradle check result for 93f9a43: 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?

Flaky test #14324

[github-actions]

❌ Gradle check result for f14898c: 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?

[himshikha]

❌ Gradle check result for f14898c: 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?

Flaky test #15944, #15812

[github-actions]

❕ Gradle check result for 989e4fe: UNSTABLE

• TEST FAILURES:

      3 org.opensearch.index.shard.RemoteIndexShardTests.classMethod
      1 org.opensearch.search.SearchTimeoutIT.testSimpleTimeout {p0={"search.concurrent_segment_search.enabled":"true"}}
      1 org.opensearch.index.shard.RemoteIndexShardTests.testSegmentReplication_With_EngineClosedConcurrently

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

[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-16046-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 a767e92f3eeaf57c066deb9ad075d40ed00f4a58
# Push it to GitHub
git push --set-upstream origin backport/backport-16046-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-16046-to-2.x.

[himshikha]

Backport PR #16150