[ESQL] Add informative timestamps to ESQL async

[AlexGPlay]

Closes #137672

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[kertal]

@nik9000 @alex-spies if you have some time, could you give this a quick look to figure out if this draft would look good to you? @AlexGPlay of @elastic/kibana-data-discovery in a exploration phase created this draft, that would help us with our background search effort 🙏

[luigidellaquila]

Thanks @AlexGPlay
It looks good in general, but it needs some BWC checks, see my comments below.

[luigidellaquila]

This needs a TransportVersion check, for bwc.
You'll need to define a new TransportVersion constant (see this) and then you'll have to add a check like

if(in.getTransportVersion().supports(YOUR_NEW_CONSTANT_NAME_HERE)) {
// ... read the values 
} else {
//  ... some defaults...?

[luigidellaquila]

see also https://github.com/elastic/elasticsearch/blob/main/docs/internal/Versioning.md

[AlexGPlay]

thank you! I'll update with this

[luigidellaquila]

Same here, this needs a TransportVersion check

[AlexGPlay]

@luigidellaquila i've added the TransportVersion and moved all the fields behind a check for the response in case they are not populated, happy to update if that's not the expected pattern 494a55f

[luigidellaquila]

Thanks @AlexGPlay, the implementation looks good.
You still have quite a few BWC test failures, due to the fact that now you have new fields, that the old nodes don't recognize.
To fix them, you'll need to declare a new EsqlCapability and use it to run the test conditionally, eg. see https://github.com/elastic/elasticsearch/blob/main/x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/FieldExtractorTestCase.java#L1366

[luigidellaquila]

LGTM, thanks @AlexGPlay!

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)