[DOC] Tiered caching in OpenSearch

[sgup432]

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.
We are adding a tiered caching feature where we will extend the existing RequestCache within OpenSearch to include disk cache as well. This is the first milestone.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.
opensearch-project/OpenSearch#10024
Milestone1 - opensearch-project/OpenSearch#10870

[hdhalter]

@sgup432 - Please let me know if this isn't going to make it in 2.12. Thanks!

[bbarani]

@sgup432 @kkhatua Can you please confirm if this feature will make it to 2.12.0 release?

[kkhatua]

Unfortunately no. I've updated the labels. @sgup432 will do for the others as well so as to reflect the revised feature release correctly.

[kkhatua]

Reopened since there is documentation around the Stats API that is missing.

[hdhalter]

Thanks, @kkhatua. @sgup432 - what is the ETA for producing the doc PR? To meet entrance criteria, the PR must be open and in review by 4/30. Thanks!

[sgup432]

@hdhalter I will open it by tomorrow. There are few more changes which needs to be merged in 2.14, so waiting on that before I open up a doc PR.

[kiranprakash154]

@sgup432 can you also add docs to these settings ?

IndicesRequestCache.INDICES_REQUEST_CACHE_CLEANUP_INTERVAL_SETTING,
IndicesRequestCache.INDICES_REQUEST_CACHE_STALENESS_THRESHOLD_SETTING,

introduced in opensearch-project/OpenSearch#12625 and registered in opensearch-project/OpenSearch#12941 ?

[sgup432]

Adding this for reminder.
Need to add doc for below setting. If this is disabled, we expect the user to clear the disk cache manually. See opensearch-project/OpenSearch#13373 (comment)

TIERED_SPILLOVER_DISK_CACHE_SETTING

[hdhalter]

Doc PR in progress.

[sgup432]

@kiranprakash154 Can you pick up the task to add below settings? Or open up a new task for this.

IndicesRequestCache.INDICES_REQUEST_CACHE_CLEANUP_INTERVAL_SETTING,
IndicesRequestCache.INDICES_REQUEST_CACHE_STALENESS_THRESHOLD_SETTING,

We need to see where we can add this. Might require a new sub section.