[Infra] Consider only docs from system and APM in the hosts view

[crespocarlos]

Summary

Infra has only one setting to define the index pattern. The index pattern can be as generic as metric-* which also includes APM indices and any other integration that sends host.name field.

In the hosts view we need to consider only docs generated by the system module and APM.

For that we can apply a filter by event.module: 'system' or metricset.module: 'system' to the queries. To continue supporting filter by service.name (or any other APM fields), we'll build a service in APM data access to return host names,

This is what the API needs to do:

sequenceDiagram
    participant HostsView as Hosts View
    participant InfraPlugin as Infra Plugin
    participant APMDataAccess as APM Data Access

    HostsView->>InfraPlugin: Request hosts
    InfraPlugin->>InfraPlugin: Retrieve system module filtered host names
    InfraPlugin->>APMDataAccess: Request filtered host names
    APMDataAccess-->>InfraPlugin: Return filtered host names
    InfraPlugin->>InfraPlugin: Collect metrics for the hosts names
    InfraPlugin->>InfraPlugin: Identify which hosts are monitored with the system module
    InfraPlugin-->>HostsView: Return hosts with metrics

Loading

Extra

Change the metrics/infra endpoint to accept the type as path parameter -> metrics/infra/{assetType}

Acceptance Criteria

• Only hosts collected by system module and APM are returned by the API
• Only hosts collected by system module and APM are considered in the hosts count.
• Filter by service.name works
  • NOTE: it is expected that not all APM services will have a matching host name in system module docs. In order for the filter to work, it's required that the user configure their environment correctly (see https://github.com/elastic/observability-dev/issues/3321#issuecomment-2238890762)
  • In the oblt cluster, the following services should work: adservice, packetbeat, frontend, cartservice, recommendationservice, frauddetectionservice, accountingservice, cartservice, productcatalogservice

[elasticmachine]

Pinging @elastic/obs-ux-infra_services-team (Team:obs-ux-infra_services)

[crespocarlos]

The new filter will affect the otel onboarding. I created a proposal to address it: https://github.com/elastic/opentelemetry-dev/issues/338

[crespocarlos]

The scope of the ticket was changed due to the impossibility of successfully filter out APM docs without compromising the current feature too much.