Enable concurrent_segment_search auto mode by default

[Vikasht34]

Description

1. Auto Mode for Concurrent Segment Search :- With this change by default behaviour for concurrent search will be changed to auto mode from disabled.
2. Default Slicing :- Math.min(vCPU / 2, 4).

Related Issues

Resolves #17981

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 8633e9f: 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?

[rishabh6788]

{"run-benchmark-test": "id_4"}

[github-actions]

The Jenkins job url is https://build.ci.opensearch.org/job/benchmark-pull-request/2882/ . Final results will be published once the job is completed.

[github-actions]

✅ Gradle check result for af1ca8e: SUCCESS

[rishabh6788]

{"run-benchmark-test": "id_6"}

[github-actions]

The Jenkins job url is https://build.ci.opensearch.org/job/benchmark-pull-request/2959/ . Final results will be published once the job is completed.

[opensearch-ci-bot]

Benchmark Results

Benchmark Results for Job: https://build.ci.opensearch.org/job/benchmark-pull-request/2959/

Metric	Task	Value	Unit
Cumulative indexing time of primary shards		142.234	min
Min cumulative indexing time across primary shards		142.234	min
Median cumulative indexing time across primary shards		142.234	min
Max cumulative indexing time across primary shards		142.234	min
Cumulative indexing throttle time of primary shards		0	min
Min cumulative indexing throttle time across primary shards		0	min
Median cumulative indexing throttle time across primary shards		0	min
Max cumulative indexing throttle time across primary shards		0	min
Cumulative merge time of primary shards		101.934	min
Cumulative merge count of primary shards		85
Min cumulative merge time across primary shards		101.934	min
Median cumulative merge time across primary shards		101.934	min
Max cumulative merge time across primary shards		101.934	min
Cumulative merge throttle time of primary shards		15.3141	min
Min cumulative merge throttle time across primary shards		15.3141	min
Median cumulative merge throttle time across primary shards		15.3141	min
Max cumulative merge throttle time across primary shards		15.3141	min
Cumulative refresh time of primary shards		3.49752	min
Cumulative refresh count of primary shards		111
Min cumulative refresh time across primary shards		3.49752	min
Median cumulative refresh time across primary shards		3.49752	min
Max cumulative refresh time across primary shards		3.49752	min
Cumulative flush time of primary shards		12.8786	min
Cumulative flush count of primary shards		95
Min cumulative flush time across primary shards		12.8786	min
Median cumulative flush time across primary shards		12.8786	min
Max cumulative flush time across primary shards		12.8786	min
Total Young Gen GC time		3.676	s
Total Young Gen GC count		110
Total Old Gen GC time		0	s
Total Old Gen GC count		0
Store size		35.9748	GB
Translog size		5.12227e-08	GB
Heap used for segments		0	MB
Heap used for doc values		0	MB
Heap used for terms		0	MB
Heap used for norms		0	MB
Heap used for points		0	MB
Heap used for stored fields		0	MB
Segment count		15
Min Throughput	index-append	15671.7	docs/s
Mean Throughput	index-append	16290.2	docs/s
Median Throughput	index-append	16177.2	docs/s
Max Throughput	index-append	17793.2	docs/s
50th percentile latency	index-append	2030.2	ms
90th percentile latency	index-append	3427.34	ms
99th percentile latency	index-append	8606.41	ms
99.9th percentile latency	index-append	11201.4	ms
100th percentile latency	index-append	13358.5	ms
50th percentile service time	index-append	2030.6	ms
90th percentile service time	index-append	3427.11	ms
99th percentile service time	index-append	8605.59	ms
99.9th percentile service time	index-append	11201.4	ms
100th percentile service time	index-append	13358.5	ms
error rate	index-append	0	%
Min Throughput	wait-until-merges-finish	0	ops/s
Mean Throughput	wait-until-merges-finish	0	ops/s
Median Throughput	wait-until-merges-finish	0	ops/s
Max Throughput	wait-until-merges-finish	0	ops/s
100th percentile latency	wait-until-merges-finish	680433	ms
100th percentile service time	wait-until-merges-finish	680433	ms
error rate	wait-until-merges-finish	0	%

[github-actions]

❌ Gradle check result for 932fa0f: 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?

[bowenlan-amzn]

@github-actions commented on Apr 23, 2025, 2:49 PM PDT:

❌ Gradle check result for 932fa0f: 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?

Originally posted by @github-actions[bot] in #17978 (comment)

Flaky test #16576

[github-actions]

✅ Gradle check result for 932fa0f: SUCCESS

[github-actions]

❌ Gradle check result for 1925434: 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 1925434: SUCCESS

[opensearch-trigger-bot]

The backport to 3.0 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-3.0 3.0
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-3.0
# Create a new branch
git switch --create backport/backport-17978-to-3.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 e7ed33f60d275c3482ee7b82007ff8bdb00dbe90
# Push it to GitHub
git push --set-upstream origin backport/backport-17978-to-3.0
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-3.0

Then, create a pull request where the base branch is 3.0 and the compare/head branch is backport/backport-17978-to-3.0.