K8S中DaemonSet

DaemonSet

DaemonSet sure to run a copy of the Pod on all (or some) Node. When Node joins the cluster, they will add one for
a Pod. When a Node is removed from the cluster, the Pod will be recovered. Delete DaemonSet will delete all Pod that it creates
some typical Usage DaemonSet of:

• Running clustered storage daemon, such as running glusterd on each Node, ceph
• Collecting log daemon running on each Node, e.g. fluentd, logstash
• On each Node operation monitoring daemon, e.g. Prometheus Node Exporter, collectd, Datadog agents, New Relic agent, or Ganglia gmond

[root@k8s-master mnt]# cat daemonset.yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: deamonset-example
  labels:
    app: daemonset
spec:
  selector:
    matchLabels:
      name: deamonset-example
  template:
    metadata:
      labels:
        name: deamonset-example
    spec:
      containers:
      - name: daemonset-example
        image: wangyanglinux/myapp:v3
[root@k8s-master mnt]#

 

[root@k8s-master mnt]# vim daemonset.yaml
[root@k8s-master mnt]# kubectl create -f daemonset.yaml
daemonset.apps/deamonset-example created
[root@k8s-master mnt]# kubectl get pod -o wide
NAME                      READY   STATUS    RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES
deamonset-example-tpdf8   1/1     Running   0          8s    10.244.2.21   k8s-node01   <none>           <none>
deamonset-example-xxt2z   1/1     Running   0          8s    10.244.1.23   k8s-node02   <none>           <none>
[root@k8s-master mnt]# curl 10.244.2.21
Hello MyApp | Version: v3 | <a href="hostname.html">Pod Name</a>
[root@k8s-master mnt]# kubectl delete deamonset-example-tpdf8
error: resource(s) were provided, but no name, label selector, or --all flag specified
[root@k8s-master mnt]# kubectl delete pod deamonset-example-tpdf8
pod "deamonset-example-tpdf8" deleted
[root@k8s-master mnt]# kubectl get pod -o wide
NAME                      READY   STATUS    RESTARTS   AGE    IP            NODE         NOMINATED NODE   READINESS GATES
deamonset-example-vdzjp   1/1     Running   0          3s     10.244.2.22   k8s-node01   <none>           <none>
deamonset-example-xxt2z   1/1     Running   0          107s   10.244.1.23   k8s-node02   <none>           <none>

After deleting, re-create one.

 Designated Node node

DaemonSet ignored unschedulable state Node There are two ways to specify Pod run only on the specified Node node:

• nodeSelector: Only scheduled on the label matches the specified Node
• nodeAffinity: more feature-rich Node selector, such as support for set operations
• Node scheduling the Pod meeting the conditions where: podAffinity

nodeSelector example

First to tag the Node

kubectl label nodes node-01 disktype=ssd

 

And then specify the nodeSelector daemonset is disktype = ssd:

spec:
  nodeSelector:
    disktype: ssd

 

nodeAffinity example

nodeAffinity currently supports two: requiredDuringSchedulingIgnoredDuringExecution and preferredDuringSchedulingIgnoredDuringExecution, representing the conditions and preferred conditions must be met. Representative examples such as the following schedule to include a label and kubernetes.io/e2e-az-name value or the Node e2e-az1 e2e-az2, and preferably also with the tag another-node-label-key = another-node- label-value of Node.

apiVersion: v1
kind: Pod
metadata:
  name: with-node-affinity
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: kubernetes.io/e2e-az-name
            operator: In
            values:
            - e2e-az1
            - e2e-az2
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 1
        preference:
          matchExpressions:
          - key: another-node-label-key
            operator: In
            values:
            - another-node-label-value
  containers:
  - name: with-node-affinity
    image: gcr.io/google_containers/pause:2.0

 

podAffinity example

Pod podAffinity based label selected Node, the Node scheduling only to satisfy the condition where the Pod, and support podAffinity podAntiAffinity. This function is relatively around, as an example in the following examples:

• If a "Node is located in Zone comprises at least one security = S1 and the operation of the tag with a Pod", it can be scheduled to the Node
• Not scheduled "comprising at least one label and with security = S2 Pod operation" on the Node

apiVersion: v1
kind: Pod
metadata:
  name: with-pod-affinity
spec:
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: security
            operator: In
            values:
            - S1
        topologyKey: failure-domain.beta.kubernetes.io/zone
    podAntiAffinity:
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 100
        podAffinityTerm:
          labelSelector:
            matchExpressions:
            - key: security
              operator: In
              values:
              - S2
          topologyKey: kubernetes.io/hostname
  containers:
  - name: with-pod-affinity
    image: gcr.io/google_containers/pause:2.0

Static Pod

In addition to DaemonSet, you can also use static Pod to run on each machine specified in the Pod, which requires kubelet manifest specified directory at startup:

kubelet --pod-Manifest-path = / etc / kubernetes / Manifests

Then the required Pod definition file into the directory specified in the manifest.

Note: Static Pod API Server can not be deleted, but can be automatically deleted by deleting the corresponding Pod manifest file.