[Request]: Document SLO Transforms and troubleshooting steps

[lucabelluccini]

Description

SLO hugely rely on transforms

• What are the built-in transforms and what they do
• Overall architecture to explain at high level the SLO<>Transforms relationship
• What are the additional transforms created, their naming and what they do
• How to understand if a transform is associated to SLO and if it is not healthy (as Transforms are not handled by o11y teams, we can link the platform docs)

Resources

We have an internal document (reach me out privately) with diagrams and troubleshooting steps.
I think a part of this would be useful for users.

Which documentation set does this change impact?

Stateful and Serverless

Feature differences

None afaik

What release is this request related to?

N/A

Collaboration model

Other (please describe below)

Point of contact.

Request by @lucabelluccini

We need engineering to provide material and an overview.

[lucabelluccini]

Note elastic/kibana#181351 is a good self-diagnostic step for the final user. It has been delivered in 8.15.0.
The feature introduced to call out the health of the underlying Transform is great.

[eedugon]

Based on a conversation with @lucabelluccini , ideally we should create a new troubleshooting doc for SLOs to cover:

• explain a SLO rely on Transforms (at least on stateful).
• Help users to to make use of the warning page introduced in 8.15 about unhealthy transforms, and point to the transform troubleshooting docs (https://www.elastic.co/guide/en/elasticsearch/reference/current/transform-troubleshooting.html). We shouldn't focus much on transforms troubleshooting as it's not our domain.
• explain a SLO rely on Transforms and the cluster requires at least 1 node with the transform role
• explain a SLO rely on Ingest pipelines and the cluster requires at least 1 node with the ingest role
• explain SLO relies on some built-in transforms slo-summary* and those have not be deleted or stopped - and eventually document if they're auto-recreated (or how to do it)

Probably some of the items could be added to the main SLO landing page as Notes or Tips, like the requirement of having at least 1 transform and 1 ingest node in the cluster.