> ## Documentation Index > Fetch the complete documentation index at: https://docs.use.observer/llms.txt > Use this file to discover all available pages before exploring further. # Define your first metric (HTTP probe) > Install the agent, define a metric backed by an HTTP probe, and report status to Observer Cloud. This page walks through installing the Observer Agent, defining a metric that probes an HTTP endpoint directly, and confirming that the cloud receives status pushes. Use this path when no Prometheus server is in place, or when the signal you want to measure is the endpoint's reachability and response time itself. ## Prerequisites * An HTTP endpoint reachable from the host or cluster that will run the agent. * A container runtime (Docker or Kubernetes) or a Linux host with systemd. * An Observer Cloud account. Sign up at [use.observer](https://use.observer). > [!NOTE] > > **HTTP vs Prometheus** > > HTTP probes report `response_time_ms` for successful requests > and `no_data` with a reason code on failure. Prometheus probes > evaluate a PromQL query that already reflects the system's own > observation of itself. Pick HTTP when the question is "is this > endpoint reachable and fast"; pick Prometheus when the question > is "is this metric within bounds". The > [Prometheus quickstart](https://docs.use.observer/docs/quickstart/first-metric.md) covers > the latter. ## Steps **1. Create an organisation** Sign in at [use.observer](https://use.observer/console/auth) and create an organisation. The organisation slug becomes the URL path under `/console/` and defines the tenant boundary for every resource below. **2. Create an agent and copy its key** In the console, open **Agents**, then **Add agent**. Pick where it will run, give it a name (typically the hostname), and select **Create agent and key**. The install command then carries the agent key, shown once. Copy it before navigating away. **3. Run the agent** HTTP probes do not require Prometheus. Omit `PROMETHEUS_SERVER_URL` from the agent's environment when no Prometheus probes are defined. > [tab] Docker > > ```bash title="docker run" theme={null} > docker run -d \ > --name observer-agent \ > -p 10101:10101 \ > -e AGENT_KEY=obs_live_... \ > -e CLOUD_SERVER_URL=https://use.observer \ > ghcr.io/useobserver/agent:1.7.2 > ``` > [tab] Kubernetes > > ```yaml title="agent.yaml" theme={null} > apiVersion: apps/v1 > kind: Deployment > metadata: > name: observer-agent > spec: > replicas: 1 > selector: { matchLabels: { app: observer-agent } } > template: > metadata: { labels: { app: observer-agent } } > spec: > containers: > - name: agent > image: ghcr.io/useobserver/agent:1.7.2 > ports: [{ containerPort: 10101 }] > env: > - name: AGENT_KEY > valueFrom: { secretKeyRef: { name: observer, key: agent-key } } > - name: CLOUD_SERVER_URL > value: https://use.observer > ``` Verify the connection. With Docker, browse `http://:10101`. In Kubernetes, port-forward the deployment with `kubectl port-forward deploy/observer-agent 10101:10101` and open `http://localhost:10101`. The dashboard's *Cloud link* card shows a recent **Last heartbeat**. The Agents page in the console marks the agent as **running** within roughly 90 seconds. **4. Define an HTTP metric** In the console, open **Metrics**, then **New metric**. Select the agent created above and set the source type to **HTTP**. Configure the probe: * **URL**: the full URL the agent should hit, for example `https://api.example.com/healthz`. * **Method**: `GET`. * **Expected status**: `200` (the probe reports `no_data` with `unexpected_status:` for any other code). * **Timeout (ms)**: `5000`. The probe reports `ETIMEDOUT` if the request takes longer. Set thresholds against `response_time_ms`: * Healthy: `under 500` (response under 500ms). * Unhealthy: `over 2000` (response over 2 seconds). Values that match neither boundary resolve to `degraded`. > [!NOTE] > > **Body match (optional)** > > For endpoints that return 200 even when the underlying service > is degraded, set **Body match** to a marker string that only > appears in the healthy response (for example, `"status":"ok"`). > The probe reports `body_mismatch` if the response body is > missing that string. Only the first 4KB of the response is > read. Set **Polling interval** to `1` minute and save. The probe runs every minute. The agent pushes `response_time_ms` plus the resolved status to the cloud whenever the status changes, and at least once per **Report at least every** interval (15 minutes by default). **5. Confirm reporting** Within one push interval the metric appears in the Metrics list with its current status. Open the metric to see the latest value, last push timestamp, and rolling history. To verify the round trip, lower the unhealthy threshold below the current response time. The metric flips to `unhealthy` once the new status has held for the confirmation time (180 seconds by default). Restore the original threshold and the metric returns to `healthy` after the recovery confirmation time (300 seconds by default). ## Probe behaviour The agent computes status client-side. The cloud receives only the verdict: ```text theme={null} { metric_id, value: , status: , timestamp, reason } ``` The full HTTP request runs from the agent's vantage point. The cloud has no path to the endpoint. Request bodies, response bodies, and headers stay in your network. The full reason-code list and field reference are in [Configure HTTP probes](https://docs.use.observer/agent/guides/http-probes.md). ## Next * [Define your first SLO](https://docs.use.observer/docs/quickstart/first-slo.md) * [Publish your first status page](https://docs.use.observer/docs/quickstart/first-status-page.md) * [Configure HTTP probes](https://docs.use.observer/agent/guides/http-probes.md) covers the full per-field reference: redirects, custom headers, TLS verification, and body matching. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.