[Internal]: Add "FAQ" section to Service Map in APM docs

[miloszmarcinkowski]

Description

The original feature introduced the popover in the Service Map, which allows users to troubleshoot requests between nodes. Later, we found that there are specific scenarios in which it isn't possible to obtain metrics for edges. For those, we implemented an informational message letting users understand why they can't see metrics. We would like to point users to the docs where they can clearly understand what is happening.

We'd like to add a FAQ section (or similar) covering two scenarios:

1. Messaging consumer edges (message queues)

When services communicate through a message queue (e.g., Kafka, RabbitMQ), the Service Map shows three nodes: the producing service, the messaging dependency, and the consuming service. The edge from the producing service to the messaging dependency works normally and displays metrics (latency, throughput, error rate).

However, the edge from the messaging dependency to the consuming service is inferred. No APM agent directly observes this connection - it is derived by matching the span.destination.service.resource identifier across services. Since no agent recorded span metrics for this direction, there are no metrics to display. Users will see a message indicating that no metrics are available.

2. Grouped dependency nodes

When multiple external dependencies share the same span.type and span.subtype (e.g., several HTTP backends), the Service Map groups them into a single node to reduce visual clutter. Clicking the edge to a grouped node does not show metrics because the edge represents an aggregation of multiple distinct dependencies, and there is no single meaningful set of span metrics to display for the group as a whole.

Resources

This features was implemented in kibana#255823

This feature was scoped and researched in kibana#255821

Context for this feature is described in: kibana#248646

Which documentation set does this change impact?

Elastic On-Prem and Cloud (all)

Feature differences

No difference between deployments.

What release is this request related to?

9.4

Serverless release

The week of Mar 16, 2026

Collaboration model

The documentation team

Point of contact.

Main contact: @miloszmarcinkowski

Stakeholders: @roshan-elastic

[roshan-elastic]

Thanks @miloszmarcinkowski

For Docs team
Could you let us know when these docs are live?

We have a short-link in the UI which currently points to https://ela.st/docs-service-map-no-metrics-available (which points to the generic service maps docs) but once this change has been made - we'll update to point to the specific section which you're making here (so it's important we can link directly to it, e.g. https://docs.com/page#heading).

Thanks!