Monitoring

Cetacean works without Prometheus, but you’ll miss out on CPU/memory charts, resource gauges, capacity bars, per-task sparklines, and stack-level drill-downs.

Setup

Deploy the bundled monitoring stack alongside Cetacean and point Cetacean at it:

docker stack deploy -c compose.monitoring.yaml monitoring

environment:
  CETACEAN_PROMETHEUS_URL: http://prometheus:9090

Both stacks need to share an overlay network (monitoring) so they can reach each other by service name. The compose file deploys Prometheus on a manager node, with node-exporter and cAdvisor as global services (one per node).

If you already run Prometheus, just set the URL and make sure it scrapes node-exporter and cAdvisor targets. Cetacean expects the standard metric names — custom relabeling is not supported.

Cetacean auto-detects your monitoring setup and shows a status banner on the cluster overview when components are missing or unreachable.

Prometheus Proxy

Cetacean proxies read-only Prometheus queries through its own API, so the browser never talks to Prometheus directly. This means no CORS configuration on Prometheus and no need to expose it outside the swarm network. See the API reference for the proxy endpoints.

Self-Metrics

Cetacean exposes Prometheus metrics about its own operation at /-/metrics (HTTP requests, SSE connections, cache state, proxy latency, recommendation runs). Scrape it as a standard Prometheus target:

scrape_configs:
  - job_name: cetacean
    static_configs:
      - targets: ["cetacean:9000"]
    metrics_path: /-/metrics

Disable with server.self_metrics = false.