2026-02-07 — Prometheus + Grafana (LXC node_exporter) status

What works right now

Each LXC template has node_exporter installed.
Prometheus is scraping container exporters via HTTP service discovery from the API.
Grafana can display metrics using a standard Node Exporter dashboard (and a custom "ZLH LXC Overview" dashboard).

Prometheus config (current)

On zlh-monitor:

/etc/prometheus/prometheus.yml includes a dynamic job:

  - job_name: 'zlh_lxc'
    scrape_interval: 15s
    http_sd_configs:
      - url: http://10.60.0.245:4000/sd/exporters
        refresh_interval: 30s
        authorization:
          type: Bearer
          credentials: '<TOKEN>'

This is why containers show up even though there are no hardcoded container IPs.

The earlier failure mode

Prometheus log showed:

dial tcp 10.60.0.245:80: connect: connection refused

That happened when the SD URL was missing the port (or using the wrong path). Correct is :4000/... (or whatever the API listens on).

Grafana dashboard import gotcha

When importing JSON dashboards:

If the JSON references a datasource UID that does not exist (example error: "Datasource PROM was not found"), you must either:
- select the real datasource during import, or
- edit the dashboard JSON datasource UID to match your Grafana datasource UID.

Once the datasource was mapped, the "ZeroLagHub - LXC Overview" dashboard started drawing data.

CPU mismatch vs `top` (note)

You observed CPU% in Grafana not matching what top was showing.

This can be normal depending on:

how CPU is computed (rate window, per-core vs normalized, cgroup accounting in containers, etc.)
dashboard query math (e.g. averaging across cores)

We decided not to block on perfect parity right now — the dashboard is good enough for:

"is it pegged?"
"is it trending up/down?"
"is this instance dead?"

If we need tighter parity later:

validate the container is exporting the right counters
compare node_cpu_seconds_total raw series
consider container-aware exporters/cAdvisor (optional)

Next step (portal)

Goal:

show "CPU / RAM / Disk / Net" indicators on the portal server cards.

Two practical routes:

Query Prometheus from API (recommended)
- API calls Prometheus HTTP API (server-side)
- portal calls API
- avoids exposing Prometheus or Grafana to end users
Embed Grafana panels (works, but needs careful auth + iframe settings)
- useful for internal admin views
- more risk for multi-tenant UI unless you add strict access control

Short-term plan:

build API endpoints like:
- GET /api/metrics/servers/:vmid/summary
- returns a small payload suitable for server cards:
  - cpu_percent
  - mem_percent
  - disk_percent
  - net_in/out (rate)

Quick PromQL building blocks (reference)

CPU (percent used, 5m window):

100 - (avg by (instance) (rate(node_cpu_seconds_total{mode="idle"}[5m])) * 100)

Memory (percent used):

100 * (1 - (node_memory_MemAvailable_bytes / node_memory_MemTotal_bytes))

Disk (percent used, excluding tmpfs/overlay):

100 * (1 - (node_filesystem_avail_bytes{fstype!~"tmpfs|overlay"} / node_filesystem_size_bytes{fstype!~"tmpfs|overlay"}))

Network in/out:

sum by (instance) (rate(node_network_receive_bytes_total{device!~"lo"}[5m]))
sum by (instance) (rate(node_network_transmit_bytes_total{device!~"lo"}[5m]))

If your SD labels include vmid, prefer grouping by vmid.

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