Update readme with example of pod and json

README.md

@@ -34,3 +34,61 @@ When running locally, this assumes you have a Kubernetes context already configu
     ```bash
     ./openmeter-pod-runtime-watcher
     ```
+
+## How it works
+
+This application will query for pods in a namespace with the `k8s.openmeter.cloud/monitor` label set.
+For each pod found, it will look up each label that starts with `k8s.openmeter.cloud/data-` and use the suffix as the key to send to OpenMeter.
+Here's a full example of a pod and the data it will send to OpenMeter:
+
+```yaml
+# source: examples/k8s-manifests/pod.yaml
+kind: Pod
+apiVersion: v1
+metadata:
+  name: openmeter-pod-runtime-watcher-example
+  labels:
+    k8s.openmeter.cloud/monitor: kernel_runtime
+    k8s.openmeter.cloud/subject: eli-test
+    k8s.openmeter.cloud/data-file_id: 00703462-bb3e-4d99-966e-518fa207fcf8
+    k8s.openmeter.cloud/data-kernel_session_id: 934f5a4b-8f59-44bd-a69c-2d39bda56aad
+    k8s.openmeter.cloud/data-project_id: 6f0dff14-67d4-4cdf-bca4-b60019211e1a
+    k8s.openmeter.cloud/data-space_id: 285698d3-23cc-4816-b891-d554351611d0
+    k8s.openmeter.cloud/data-hardware_kind: cpu
+    k8s.openmeter.cloud/data-hardware_size: small
+spec:
+  containers:
+    - name: busybox
+      image: busybox
+      command: ['sh', '-c', 'echo The app is running! && sleep 3600']
+```
+
+This will map to the following cloudevents JSON request to OpenMeter:
+
+```json
+{
+    "specversion": "1.0",
+    "type": "kernel_runtime",
+    "source": "kubernetes-api",
+    "id": "9c6d076d-3c8f-456a-9df1-85e247e34151",
+    "time": "2023-10-03T20:00:00Z",
+    "datacontenttype": "application/json",
+    "data": {
+       "file_id": "00703462-bb3e-4d99-966e-518fa207fcf8",
+        "kernel_session_id": "934f5a4b-8f59-44bd-a69c-2d39bda56aad",
+        "project_id": "6f0dff14-67d4-4cdf-bca4-b60019211e1a",
+        "space_id": "285698d3-23cc-4816-b891-d554351611d0",
+        "hardware_kind": "cpu",
+        "hardware_size": "small",
+        "subject": "eli-test",
+        "duration": "5"
+    }
+}
+```
+
+The rate at which events are sent for pods is configurable using the `MONITOR_RATE_SECONDS` environment variable.
+Or, the `settings.monitor_rate_seconds` helm chart value.
+
+The source can also be configured using the `SOURCE` environment variable or the `settings.source` helm chart value.
+
+By default, we send events to the https://openmeter.cloud API, but if you self-host, this can be configured using the `OPENMETER_URL` environment variable or the `settings.openmeter_url` helm chart value.