[Meta][Search] Cancel search requests

[Dosant]

Search service provides API for canceling search requests.

Search service, SearchSource, and expressions consumers should explicitly search in the following scenarios:

Client-side usage:

1. When the user navigates away before the search completes
2. When a new search is requested before the prior one completes

Server-side usage:

1. When KibnaRequest aborts

   kibana/src/core/server/http/router/request.ts

   Line 67 in 7f2dbe5

   aborted$: Observable<void>;

Why this is important:

Dashboard use-case (bsearch cancelation)

Assume there are 2 visualizations on a dashboard that use search service, one can cancel requests and another can't.
Search services batch their requests into a single network request. Our batch search has a limitation that the underlying network request is canceled only when all included search requests are canceled. In this dashboard scenario, there is no performance benefit until all visualization that search through search plugin can properly cancel request

Server side search requests

Some visualization (e.g. Timelion and TSVB) use search service on the server.
Consider the following:

1. Tsvb vis calls tsvb route api/metrics/vis/data
2. Server-side tsvb route uses search service: data.search()
3. User closes browser without waiting for result
4. api/metrics/vis/data is aborted, but server-side data.search() keeps running server-side

In the scope of this issue:

• Review client-side/ server-side search code, check if cancelation is properly configured, create related issues, and notify teams
• Adjust documentation and example plugin to properly cancel requests [Search] Add cancelation logic to search example #118176
• TSVB: [TSVB] Cancel discarded searches #46353 (both client side and server side) @elastic/kibana-vis-editors
• Timelion: [Timelion] Cancel discarded searches #46354 (both client side and server side) @elastic/kibana-vis-editors
• TODO? other? ML embeddable?

[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)

[vadimkibana]

Closing as it seems all tasks on the list are completed.