kubernetes守护进程

DaemonSet 简介

服务守护进程，它的主要作用是在Kubernetes集群的所有节点中运行我们部署的守护进程，相当于在集群节点上分别部署Pod副本，如果有新节点加入集群，DaemonSet会自动的在该节点上运行我们需要部署的Pod副本，相反如果有节点退出集群，DaemonSet也会移除掉部署在旧节点的Pod副本。

DaemonSet示例

DaemonSet一般运行在集群的所有节点上，是一些常驻服务，通常可以用来收集日志，作为存储节点，运行监控进程等。

下面是一个日志收集的DaemonSet的定义：

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd-elasticsearch
  namespace: kube-system
  labels:
    k8s-app: fluentd-logging
spec:
  selector:
    matchLabels:
      name: fluentd-elasticsearch
  updateStrategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
      maxSurge: "100%"
  template:
    metadata:
      labels:
        name: fluentd-elasticsearch
    spec:
      # nodeSelector:
      #   node-role.kubernetes.io/worker: "true"
      tolerations:
      - key: node-role.kubernetes.io/master
        operator: Exists
        effect: NoSchedule
      containers:
      - name: fluentd-elasticsearch
        image: quay.io/fluentd_elasticsearch/fluentd:v2.5.2
        resources:
          limits:
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 200Mi
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
      terminationGracePeriodSeconds: 30
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /var/lib/docker/containers