What are Prometheus Federation and Long-term Storage?

Question

Accepted Answer

**Federation** — aggregation of metrics from multiple Prometheus. **Long-term Storage** — storing historical data.

**Federation:**
```yaml
scrape_configs:
  - job_name: "federation"
    honor_labels: true
    metrics_path: "/federate"
    params:
      "match[]":
        - "{job=~".*"}"
    static_configs:
      - targets:
          - "prometheus-us:9090"
          - "prometheus-eu:9090"
```

**Thanos (long-term):**
- **Sidecar** — sends data to S3.
- **Query** — aggregates from Object Storage.
- **Store Gateway** — reads from S3.
- **Compactor** — aggregates old data.

**Prometheus → Thanos Sidecar → S3 → Thanos Query → Grafana**

**Alternatives:** Cortex, Mimir.

DevOps: What are Prometheus Federation and Long-term Storage?