feat(openmetrics): add 9 missing host RRD metrics

[mpiton]

Description

Add 9 missing host RRD metrics to the OpenMetrics plugin and synchronize them in xapi-stats (legacy).

New host metrics exposed:

Metric	Type	Description
xcp_host_load	gauge	Normalized host load
xcp_host_memory_reclaimed_bytes	gauge	Reclaimed host memory
xcp_host_memory_reclaimed_max_bytes	gauge	Maximum reclaimable host memory
xcp_host_running_vcpus	gauge	Total number of running vCPUs
xcp_host_network_aggregated_receive_bytes	gauge	Aggregated PIF received bytes/s
xcp_host_network_aggregated_transmit_bytes	gauge	Aggregated PIF transmitted bytes/s
xcp_host_disk_iops_total	gauge	Total IOPS (read + write) per SR
xcp_host_disk_throughput_total_bytes	gauge	Total I/O throughput per SR
xcp_host_disk_latency_seconds	gauge	Combined I/O latency per SR

Unit conversions:

• OpenMetrics: µs → seconds (Prometheus convention)
• xapi-stats: µs → ms (xo-web formatTime convention)
• KiB → bytes, MiB/s → bytes/s (both systems)

Tested against live XOA endpoint : all 9 metrics return valid data on a 3-host pool.

Fixes XO-2227

Checklist

• Commit
  • Title follows commit conventions
  • Reference the relevant issue (Fixes XO-2227)
  • If bug fix, add Introduced by — N/A (new feature)
• Changelog
  • If visible by XOA users, add changelog entry
  • Update "Packages to release" in CHANGELOG.unreleased.md
• PR
  • If UI changes, add screenshots
  • If not finished or not tested, open as Draft

Changes

File	Change
packages/xo-server-openmetrics/src/openmetric-formatter.mts	+9 MetricDefinition entries in HOST_METRICS
packages/xo-server-openmetrics/src/openmetric-formatter.test.mts	+11 unit tests (match, transform, labels, non-collision)
packages/xo-server/src/xapi-stats.mjs	+9 host metrics in STATS.host, clarified latency comments
docs/docs/advanced.md	Updated host metrics table (18 → 27 metrics), simplified PromQL example
CHANGELOG.unreleased.md	Added enhancement entry + xo-server minor + xo-server-openmetrics minor

Review process

If you are an external contributor, you can skip this part. Simply create the pull request, and we'll get back to you as soon as possible.

This 2-passes review process aims to:

• develop skills of junior reviewers
• limit the workload for senior reviewers
• limit the number of unnecessary changes by the author

1. The author creates a PR.
2. Review process:
   1. The author assigns the junior reviewer.
   2. The junior reviewer conducts their review:
      • Resolves their comments if they are addressed.
      • Adds comments if necessary or approves the PR.
   3. The junior reviewer assigns the senior reviewer.
   4. The senior reviewer conducts their review:
      • If there are no unresolved comments on the PR → merge.
      • Otherwise, we continue with 3.
3. The author responds to comments and/or makes corrections, and we go back to 2.

Notes:

1. The author can request a review at any time, even if the PR is still a Draft.
2. In theory, there should not be more than one reviewer at a time.
3. The author should not make any changes:
   • When a reviewer is assigned.
   • Between the junior and senior reviews.

[plane-sync-vates]

Linked to Plane Work Item(s)

• [XO-2227] [XO][Plugins][RRD] add missing metrics

This comment was auto-generated by Plane