[DOC] Add async search state explanations

[Caaaas]

What do you want to do?

• [ ] Request a change to existing documentation
• [x] 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.

The possible states for async searches are listed in the documentation, with the possible values being RUNNING, SUCCEEDED, FAILED, PERSISTING, PERSIST_SUCCEEDED, PERSIST_FAILED, CLOSED and STORE_RESIDENT. However, the information about what the states actually mean are not documented. Only information I'm able to find is that STORE_RESIDENT means the response is successfully persisted, but that is listed under the title "Get partial results", so it's unclear whether we get back partial or full results.

What is the difference between SUCCEEDED and PERSIST_SUCCEEDED? What is the difference between FAILED and PERSIST_FAILED? What does CLOSED mean? And so on.

Which states mean that I can expect to get back partial results? Which states mean that I can expect to get fully completed results?

It would be great to get an explanation of all possible states and what they mean.

All versions (including the latest) seems to be affected. Older versions are missing some of the states, but that seems to be updated and more correct in the later versions.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

Only documentation I'm able to find about the async states are from the current documentation.

Some hints on what the different states does are available from the opensearch-project/asynchronous-search project

[hdhalter]

@kolchfa-aws - do you know who might be able to help us out with these descriptions? Thanks.

[kolchfa-aws]

Not sure. Paging @opensearch-project/asynchronous-search

[hdhalter]

Looks like @eisrep is the developer for this.