Lately we've noticed that when adding some cluster-level stats (#68603 and #64935), those collectors are not registered as Usage or Stats collector in Kibana, because they are not supposed to be reported as part of the stack_stats.kibana.plugins payload.

This results in missing some information when monitoring is enabled. As far as I could understand from taking a look at the code in x-pack/plugins/monitoring, the information reported to the Monitoring cluster is collected via the code in x-pack/plugins/monitoring/server/kibana_monitoring. More specifically, in the bulk_uploader.js file.

I'm creating this issue to review the logic in BulkUploader to:

• Do not start collecting until Self-Monitoring is enabled and fully started.
• Provide a way to report Kibana-collected cluster-stats to be used later on when sending telemetry from the Monitoring cluster.
• When Kibana belongs to a monitoring cluster, but that same cluster is not self-monitoring itself (only has monitoring info from other clusters), it won't report any telemetry about itself.
• Are there any differences when Metricbeat is used vs. the legacy collector mechanism? Has this API

  kibana/src/legacy/server/status/routes/api/register_stats.js

  Line 67 in 3d0552e

  path: '/api/stats',

  anything to do with it?