[DOC] Concurrent Segment Search support in OpenSearch

[sohami]

What do you want to do?

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Tell us about your request. Provide a summary of the request and all versions that are affected.
Add documentation about the concurrent segment search functionality and the knobs it exposes for the users to consume. For now adding as a placeholder issue and details will be added later.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.
opensearch-project/OpenSearch#2587

** Additional Issues **
#4281

[Naarcha-AWS]

@sohami: Which version is concurrent segment search going into?

[jed326]

Taking a note to mention the settings from opensearch-project/OpenSearch#7956. Specifically, the index setting for concurrent search will override the cluster setting, which I believe is a new behavior for settings in general.

[sohami]

@sohami: Which version is concurrent segment search going into?

@Naarcha-AWS For now we are targeting for 2.10

[jed326]

As a part of opensearch-project/OpenSearch#8371 we are updating the definition of terminate_after search parameter to be per leaf slice instead of per shard. In the non-concurrent search case there is no behavior change.

[jed326]

As a part of opensearch-project/OpenSearch#9469 there is a new supportsConcurrentSegmentSearch method in the AggregatorFactory class that needs to be overridden for any new aggregators that intend to support concurrent segment search.

[kolchfa-aws]

When this feature is GA, we should incorporate the additional introduced/modified fields in their respective tables in the API pages. See #4990 for the changed APIs.

[kolchfa-aws]

@sohami Is there any documentation needed for the 2.11 version for this issue?

[kolchfa-aws]

Per offline sync with @sohami, there's no work to be done for 2.11 for this issue

[sohami]

Yes we created separate doc issue for 2.11 where specific updates are needed. Thanks for moving this to 2.12 for now.

• [DOC] New threadpool metric thread_pool.total_wait_time #5007
• [DOC] Concurrent Segment Search is disabled in terminate_after workflow #5142

[kolchfa-aws]

@sohami Is there any documentation needed for the 2.12 version for this issue? Or is all the work done in #4281? Thanks!

[jed326]

Taking note to document "slice_size" change from opensearch-project/OpenSearch#11585

[jed326]

Taking note to document descending sort considerations wrt concurrent segment search

References:

• Enable point based sort optimization for all custom comparators OpenSearch#8167
• [Performance] sort query improvement for sequential ordered data [e.g. timestamp field sort in log data] apache/lucene#12448
• Improve search performance for numeric sort queries OpenSearch#10867 (comment)

[jed326]

@kolchfa-aws Compiling a list of all the docs related updates we will need for concurrent segment search GA:

• Profile API changes - [DOC] Update search profile API documentation with concurrency related changes #4281
• Remove feature flag & experimental from docs, default Concurrent segment search cluster & Index settings to false - [DOC] Concurrent Segment Search support in OpenSearch #3662 (comment) [@kolchfa-aws]
• Add new concurrent search stats to main stats page - Add concurrent segment search documentation #4990 (comment) [@kolchfa-aws]
• Add slice_size change to terms aggregation documentation - [DOC] Concurrent Segment Search support in OpenSearch #3662 (comment) [@jed326]
• Add descending sort considerations wrt concurrent segment search - [DOC] Concurrent Segment Search support in OpenSearch #3662 (comment) [@jed326]

@sohami @ticheng-aws @yigithub @neetikasinghal please let me know if you think of anything else!

[ticheng-aws]

@kolchfa-aws Compiling a list of all the docs related updates we will need for concurrent segment search GA:

• Profile API changes - [DOC] Update search profile API documentation with concurrency related changes #4281
• Concurrent segment search cluster & Index settings - [DOC] Concurrent Segment Search support in OpenSearch #3662 (comment)
• Add new concurrent search stats to main stats page - Add concurrent segment search documentation #4990 (comment)
• Add slice_size change to terms aggregation documentation - [DOC] Concurrent Segment Search support in OpenSearch #3662 (comment)
• Add descending sort considerations wrt concurrent segment search - [DOC] Concurrent Segment Search support in OpenSearch #3662 (comment)

@sohami @ticheng-aws @yigithub @neetikasinghal please let me know if you think of anything else!

We also need a PR to remove the "experimental" keyword altogether.

[jed326]

Added terms aggregation concurrent search docs and improvements here: #6355

[jed326]

Summarizing the concurrent search related PRs we have floating around:

• Concurrent segment search GA and API changes #6356
• Improve terms aggregation documentation and add concurrent segment search caveats #6355
• Add things to know for concurrent segment search #6362