[Writable Warm] Composite Directory implementation and integrating it with FileCache

[rayshrey]

Description

Implements and design Composite Directory (and integrates it with FileCache) which can fall back to the on-demand fetch when requested data is not present locally.

Opening this PR to get initial review comments on the design and implementation of Composite Directory in this issue - #12781, hence haven't added any tests apart from one IT test for testing the basic functionality. Will include tests in the following revisions to this PR.

Related Issues

Resolves #[12781]

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

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]

Compatibility status:

Checks if related components are compatible with change f442533

Incompatible components

Skipped components

Compatible components

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

[github-actions]

❌ Gradle check result for d507327: 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?

[rayshrey]

Flaky tests causing build to fail intermittently over the past week

#9464
#14319
#14304
#14288
#14291

[github-actions]

❕ Gradle check result for 901849b: 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.

[sohami]

❕ Gradle check result for 901849b: 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.

#14291

[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-12782-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 b8c78196438897132f6819460ebb7d4222b39297
# Push it to GitHub
git push --set-upstream origin backport/backport-12782-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-12782-to-2.x.

[sohami]

@rayshrey Can you please create a manual backport PR for 2.x as above failed