[Canvas] Migrate expression runner from bfetch to an HTTP route

[lukasolson]

Summary

Resolves #190267.

Moves the Canvas expression runner off of bfetch and onto the core http router.

Checklist

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• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• Flaky Test Runner was used on any tests changed
• Any UI touched in this PR is usable by keyboard only (learn more about keyboard accessibility)
• Any UI touched in this PR does not create any new axe failures (run axe in browser: FF, Chrome)
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This renders correctly on smaller devices using a responsive layout. (You can test this in your browser)
• This was checked for cross-browser compatibility

Risk Matrix

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Before closing this PR, invite QA, stakeholders, and other developers to identify risks that should be tested prior to the change/feature release.

When forming the risk matrix, consider some of the following examples and how they may potentially impact the change:

Risk	Probability	Severity	Mitigation/Notes
Multiple Spaces—unexpected behavior in non-default Kibana Space.	Low	High	Integration tests will verify that all features are still supported in non-default Kibana Space and when user switches between spaces.
Multiple nodes—Elasticsearch polling might have race conditions when multiple Kibana nodes are polling for the same tasks.	High	Low	Tasks are idempotent, so executing them multiple times will not result in logical error, but will degrade performance. To test for this case we add plenty of unit tests around this logic and document manual testing procedure.
Code should gracefully handle cases when feature X or plugin Y are disabled.	Medium	High	Unit tests will verify that any feature flag or plugin combination still results in our service operational.
See more potential risk examples

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[lukasolson]

/ci

[lukasolson]

/ci

[lukasolson]

/ci

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[nreese]

Not sure if I am testing correctly, but I am still seeing bfetch requests in canvas. I would expect not to see bsearch request.

[lukasolson]

Not sure if I am testing correctly, but I am still seeing bfetch requests in canvas. I would expect not to see bsearch request.

Any bsearch requests are separate from the route that was migrated as part of this PR. Those are expected if you're using data from either "Elasticsearch SQL" or "Elasticsearch documents" as part of a Canvas data source. The route that has changed in this PR is POST /internal/canvas/fns.

Before this PR, it uses bfetch to batch multiple calls:

before.mov

After this PR, each request goes out individually:

after.mov

[nreese]

Any bsearch requests are separate from the route that was migrated as part of this PR. Those are expected if you're using data from either "Elasticsearch SQL" or "Elasticsearch documents" as part of a Canvas data source. The route that has changed in this PR is POST /internal/canvas/fns.

Thanks for clarifying. Could you provide an example element expression that uses a function?

[nreese]

kibana-presentation changes LGTM. Thanks for removing bfetch from canvas.
code review and tested in chrome

[TinaHeiligers]

kibana.jsonc changes LGTM

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 2a817f9

Failed CI Steps

• FTR Configs #65

Test Failures

• [job] [logs] FTR Configs #65 / Cloud Security Posture Test adding Cloud Security Posture Integrations CSPM AWS CIS_AWS Organization Manual Shared Access CIS_AWS Organization Manual Shared Access Workflow

Metrics [docs]

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
canvas	13.9KB	13.9KB	+9.0B

History

• 💛 Build #229947 was flaky be838b7
• 💛 Build #229889 was flaky be838b7
• 💔 Build #229596 failed 48449d2
• 💔 Build #229553 failed 48449d2

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @lukasolson