What is Kubernetes Watch and Bookmark?

Question

Accepted Answer

**Watch** — get real-time notifications of resource changes. **Bookmark** — optimization for long watches.

```bash
# Watch resources
kubectl get pods -w  # Watch for changes
kubectl get events -w --sort-by=.lastTimestamp
kubectl get deployments -w -n production

# Watch specific fields
kubectl get pods -w -o json | jq -c '.' | while read line; do
  echo "$line" | jq -r 'select(.object.status.phase != "Running") | .metadata.name'
done

# Watch with label selector
kubectl get pods -l app=myapp -w

# Watch for specific events
kubectl get events -w --field-selector reason=FailedScheduling
kubectl get events -w --field-selector reason=Killing

# Watch endpoint changes
kubectl get endpoints myapp -w

# API server watch (raw)
kubectl get --raw "/api/v1/pods?watch=true" | jq -c '.'
kubectl get --raw "/apis/apps/v1/deployments?watch=true&resourceVersion=0" | jq -c '.'

# Bookmark optimization
kubectl get pods --watch-bookmark -w  # Get bookmark events
```

```typescript
// Kubernetes JS client watch example
import { CoreV1Api, Watch } from '@kubernetes/client-node';

const kc = new KubeConfig();
kc.loadFromDefault();
const k8sApi = kc.makeApiClient(CoreV1Api);
const watch = new Watch(kc);

watch.watch('/api/v1/pods', {}, (phase, apiObj) => {
  console.log(`Pod ${phase}: ${apiObj.metadata.name}`);
}, (err) => {
  console.error(`Watch error: ${err}`);
});
```

**Event Types:**
- ADDED: resource created.
- MODIFIED: resource updated.
- DELETED: resource removed.
- BOOKMARK: resourceVersion bookmark.

**Use cases:**
- Controllers.
- Real-time dashboards.
- Event-driven automation.

DevOps: What is Kubernetes Watch and Bookmark?