Increase index_searcher thread count to 2x processor

[jed326]

Description

With the Lucene 9.9 changes the search threadpool will now offload all the tasks to the index_searcher threadpool. Since the number of threads for the index_searcher threadpool today is allocatedProcessors, this will significantly reduce the throughput of concurrent segment search.

Previously, there are 1.5x processors for the search threadpool and 1x processors for the index_searcher threadpool, giving 2.5x processor threads available for search. With the Lucene 9.9 change there will only be 1x processors available for the index_searcher threadpool to use. Even for the single slice case this is a significant throughput decrease as previously the single slice case would be executed on the search threadpool which has 1.5x processor threads.

This PR bumps the index_searcher thread count to 2x to move the search throughput back towards the original level.

Related Issues

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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[jed326]

@reta @sohami @peternied

Apologies for the last minute change but would really like to get this into 2.12 if possible.

[sohami]

Thanks Jay for making this change. It makes sense to me to start with 2x the processor count given the change in lucene 9.9, as you explained it is between 1.5x and 2.5x thread count. With 2x, it will multiplex 2 threads on each vCPU atleast to provide benefit for cases when there is some disk IO happening on search thread.

[github-actions]

Compatibility status:

Checks if related components are compatible with change 4e986b1

Incompatible components

Skipped components

Compatible components

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

[github-actions]

❌ Gradle check result for 74a5af0: 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 74a5af0: FAILURE

• [BUG] org.opensearch.repositories.azure.AzureBlobContainerRetriesTests.testWriteBlobWithRetries is faky #7934

There are also a lot of failing bwc tests. They shouldn't be related to this change, more likely failed due to the Jenkins issues.

Not able to open https://build.ci.opensearch.org/job/gradle-check/33396/ link anymore actually

[github-actions]

❌ Gradle check result for 74a5af0:

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]

I think the "todo" here needs to be done: f67ed17#diff-afe8d7298c117ffe707f8755d7e981f9f1103dbd0b040b40642efb555428aeec

[github-actions]

❌ Gradle check result for 74a5af0: 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]

BWC failures are due to this: #12111 (comment)
It's also happening in other PRs: #12194 (comment)

[kotwanikunal]

BWC failures are due to this: #12111 (comment) It's also happening in other PRs: #12194 (comment)

Raised a PR here: #12201

[jed326]

BWC failures are due to this: #12111 (comment) It's also happening in other PRs: #12194 (comment)

Raised a PR here: #12201

@kotwanikunal I just pushed a commit doing the same to this PR too. I'm fine with undoing my changes in favor of your PR or vice versa, no strong preference here.

[kotwanikunal]

BWC failures are due to this: #12111 (comment) It's also happening in other PRs: #12194 (comment)

Raised a PR here: #12201

@kotwanikunal I just pushed a commit doing the same to this PR too. I'm fine with undoing my changes in favor of your PR or vice versa, no strong preference here.

Thanks @jed326!
A bunch of PRs are blocked on that change. Let's pull it in independently.

[kotwanikunal]

Added backport 2.12 since the branch is already cut.

[github-actions]

❕ Gradle check result for ba3a847: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.remotestore.RemoteIndexPrimaryRelocationIT.testPrimaryRelocationWhileIndexing
      1 org.opensearch.cluster.routing.allocation.decider.DiskThresholdDeciderIT.testIndexCreateBlockIsRemovedWhenAnyNodesNotExceedHighWatermarkWithAutoReleaseEnabled

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

Attention: 138 lines in your changes are missing coverage. Please review.

Comparison is base (3cbf54e) 71.40% compared to head (4e986b1) 71.34%.
Report is 5 commits behind head on main.

Files	Patch %	Lines
...rch/search/fetch/subphase/MatchedQueriesPhase.java	0.00%	37 Missing ⚠️
...src/main/java/org/opensearch/search/SearchHit.java	58.73%	17 Missing and 9 partials ⚠️
...ansport/top_queries/TransportTopQueriesAction.java	24.00%	18 Missing and 1 partial ⚠️
.../insights/core/listener/QueryInsightsListener.java	73.58%	10 Missing and 4 partials ⚠️
...opensearch/search/builder/SearchSourceBuilder.java	42.85%	4 Missing and 4 partials ⚠️
.../resthandler/top_queries/RestTopQueriesAction.java	61.11%	7 Missing ⚠️
.../insights/rules/action/top_queries/TopQueries.java	66.66%	5 Missing ⚠️
...search/ingest/common/RemoveByPatternProcessor.java	95.77%	1 Missing and 2 partials ⚠️
...s/rules/action/top_queries/TopQueriesResponse.java	93.18%	3 Missing ⚠️
...g/opensearch/search/internal/SubSearchContext.java	0.00%	3 Missing ⚠️
... and 8 more

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #12196      +/-   ##
============================================
- Coverage     71.40%   71.34%   -0.07%     
- Complexity    59636    59675      +39     
============================================
  Files          4944     4952       +8     
  Lines        280322   280638     +316     
  Branches      40728    40773      +45     
============================================
+ Hits         200175   200223      +48     
- Misses        63501    63863     +362     
+ Partials      16646    16552      -94     

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

[github-actions]

❌ Gradle check result for 57fe433: 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 4e986b1: SUCCESS

[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-12196-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 237cee38a03aa5cc45ccea9ff1017a2744bcfbe4
# Push it to GitHub
git push --set-upstream origin backport/backport-12196-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-12196-to-2.x.

[opensearch-trigger-bot]

The backport to 2.12 failed:

The process '/usr/bin/git' failed with exit code 1

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-2.12 2.12
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.12
# Create a new branch
git switch --create backport/backport-12196-to-2.12
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 237cee38a03aa5cc45ccea9ff1017a2744bcfbe4
# Push it to GitHub
git push --set-upstream origin backport/backport-12196-to-2.12
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.12

Then, create a pull request where the base branch is 2.12 and the compare/head branch is backport/backport-12196-to-2.12.