What is Kubernetes DaemonSet for observability?

Question

Accepted Answer

**DaemonSet** — one Pod per node. Ideal for observability agents.

**Fluent Bit (logs):**
```yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluent-bit
  namespace: observability
spec:
  selector:
    matchLabels:
      name: fluent-bit
  template:
    metadata:
      labels:
        name: fluent-bit
    spec:
      serviceAccountName: fluent-bit
      tolerations:
        - key: node-role.kubernetes.io/control-plane
          effect: NoSchedule
      containers:
        - name: fluent-bit
          image: fluent/fluent-bit:latest
          volumeMounts:
            - name: varlog
              mountPath: /var/log
              readOnly: true
            - name: containers
              mountPath: /var/lib/docker/containers
              readOnly: true
            - name: config
              mountPath: /fluent-bit/etc/
      volumes:
        - name: varlog
          hostPath:
            path: /var/log
        - name: containers
          hostPath:
            path: /var/lib/docker/containers
        - name: config
          configMap:
            name: fluent-bit-config
```

**Node Exporter (node metrics):**
```yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: node-exporter
spec:
  template:
    spec:
      hostNetwork: true
      hostPID: true
      containers:
        - name: node-exporter
          image: prom/node-exporter:latest
          args:
            - --path.procfs=/host/proc
            - --path.sysfs=/host/sys
            - --path.rootfs=/host/root
          volumeMounts:
            - name: proc
              mountPath: /host/proc
              readOnly: true
            - name: sys
              mountPath: /host/sys
              readOnly: true
      tolerations:
        - operator: Exists
```

**Cilium (CNI + observability):** DaemonSet with eBPF for network flows.

**Problem with DaemonSet + spot instances:** Use tolerations + priorityClass for guaranteed scheduling.

DevOps: What is Kubernetes DaemonSet for observability?