[Request]: Document what products/integrations are able to populate the hosts/infra applications (e.g. also when embedded in APM)

[lucabelluccini]

Description

It's not clear how some O11y tabs under APM can be populated.

E.g.

• Why my infrastructure tab under APM application is empty?
• Why mi infrastructure tab under APM application is populated? E.g. https://demo.elastic.co/app/apm/services/productCatalogService/infrastructure?comparisonEnabled=true&environment=ENVIRONMENT_ALL&kuery=&latencyAggregationType=avg&offset=1d&rangeFrom=now-15m&rangeTo=now&serviceGroup=&transactionType=request
• What should the user do in order to populate those? Should they install/use:
  • Elastic APM Agents collecting metrics?
  • Metricbeat System module? Docker module? K8s module? Prometheus module?
  • EA with System integration? Docker integration? K8s integration? Prometheus integration?
  • OTel processors & OTel Collector? Which processors? On which version?
  • ...
• Are there additional information/metadata to add to the documents in order to benefit from correlation of APM & Metrics?

Resources

We have some pointers at https://discuss.elastic.co/t/infrastructure-tab-in-the-apm-ui-app/323577/2

It would be nice to give hints to users on how to "populate" that parts or self-diagnose why they're empty.

Current doc is limited https://www.elastic.co/guide/en/observability/current/apm-infrastructure.html

Should we enrich and point to https://www.elastic.co/guide/en/observability/current/view-infrastructure-metrics.html ?

Which documentation set does this change impact?

Stateful and Serverless

Feature differences

None

What release is this request related to?

8.15

Collaboration model

Other (please describe below)

Point of contact.

Main contact: @roshan-elastic + @smith ?

Stakeholders: