使用DaemonSet部署集群守护进程集

使用DaemonSet部署集群守护进程集

一、使用DaemonSet部署日志收集守护进程集

Fluentd是用于统一日志层的开源数据收集器。Kubernetes开发了Elasticsearch组件来实现集群的日志管理。Elasticsearch是一个搜索引擎，负责存储日志并提供查询接口；Fluentd负责从Kubernetes搜集日志并发送给Elasticsearch。

（1）创建YAML格式的DaemonSet文件

[root@master ~]# vim fluentd-daemonset.yaml
[root@master ~]# cat fluentd-daemonset.yaml 
apiVersion: apps/v1
kind: DaemonSet                                # 资源类型为DaemonSet
metadata:
  name: fluentd-elasticsearch
  namespace: kube-system                      # 名称空间采用内置的kube-system
  labels:
    k8s-app: fluentd-logging                 # DaemonSet资源的标签
spec:
  selector:
    matchLabels:                   # 必须指定与spec.template的标签匹配的Pod选择运算符
      name: fluentd-elasticsearch
  template:                                         # 创建Pod副本所依据的模板
    metadata:
      labels:                                         # Pod模板必须指定标签
        name: fluentd-elasticsearch
    spec:
      tolerations:        # 容忍度设置，此处设置让该守护进程集在控制平面节点或主节点上运行
      - key: node-role.kubernetes.io/control-plane
        operator: Exists
        effect: NoSchedule
      - key: node-role.kubernetes.io/master
        operator: Exists
        effect: NoSchedule
      containers:
      - name: fluentd-elasticsearch
        image: quay.io/fluentd_elasticsearch/fluentd:v2.5.2    # 镜像
        resources:                                                    # 容器资源限制
          limits:
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 200Mi
        volumeMounts:                                                # Pod的卷挂载点
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
      terminationGracePeriodSeconds: 30
      volumes:                                         # 声明卷（本例定义了两个卷）
      - name: varlog
        hostPath:                                     # 卷类型为HostPath（主机路径）
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /var/lib/docker/containers

（2）基于上述YAML配置文件创建DaemonSet

[root@master ~]# kubectl apply -f fluentd-daemonset.yaml 
daemonset.apps/fluentd-elasticsearch created

（3）查看该DaemonSet的Pod部署（操作该DaemonSet必须指定名称空间）

[root@master ~]# kubectl get pods --namespace=kube-system -l name=fluentd-elasticsearch -o wide
NAME                          READY   STATUS             RESTARTS   AGE    IP               NODE     NOMINATED NODE   READINESS GATES
fluentd-elasticsearch-4zwp8   0/1     ImagePullBackOff   0          7m1s   10.244.104.25    node2    <none>           <none>
fluentd-elasticsearch-gc5nd   0/1     ImagePullBackOff   0          7m1s   10.244.166.169   node1    <none>           <none>
fluentd-elasticsearch-w9b8q   0/1     ImagePullBackOff   0          7m1s   10.244.219.95    master   <none>           <none>

可以发现3个节点各自运行了Pod，DaemonSet会先遍历节点列表，检查是否带有此标签的Pod在运行，若没有，则创建。

（4）查看详细信息

[root@master ~]# kubectl describe daemonset fluentd-elasticsearch --namespace=kube-system
Name:           fluentd-elasticsearch
Selector:       name=fluentd-elasticsearch
Node-Selector:  <none>
Labels:         k8s-app=fluentd-logging
Annotations:    deprecated.daemonset.template.generation: 1
Desired Number of Nodes Scheduled: 3
Current Number of Nodes Scheduled: 3
Number of Nodes Scheduled with Up-to-date Pods: 3
Number of Nodes Scheduled with Available Pods: 0
Number of Nodes Misscheduled: 0
Pods Status:  0 Running / 3 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  name=fluentd-elasticsearch
  Containers:
   fluentd-elasticsearch:
    Image:      quay.io/fluentd_elasticsearch/fluentd:v2.4
    Port:       <none>
    Host Port:  <none>
    Limits:
      memory:  200Mi
    Requests:
      cpu:        100m
      memory:     200Mi
    Environment:  <none>
    Mounts:
      /var/lib/docker/containers from varlibdockercontainers (ro)
      /var/log from varlog (rw)
  Volumes:
   varlog:
    Type:          HostPath (bare host directory volume)
    Path:          /var/log
    HostPathType:  
   varlibdockercontainers:
    Type:          HostPath (bare host directory volume)
    Path:          /var/lib/docker/containers
    HostPathType:  
Events:
  Type    Reason            Age   From                  Message
  ----    ------            ----  ----                  -------
  Normal  SuccessfulCreate  10m   daemonset-controller  Created pod: fluentd-elasticsearch-w9b8q
  Normal  SuccessfulCreate  10m   daemonset-controller  Created pod: fluentd-elasticsearch-4zwp8
  Normal  SuccessfulCreate  10m   daemonset-controller  Created pod: fluentd-elasticsearch-gc5nd
[root@master ~]# 

---

二、管理DaemonSet部署的集群守护进程集

由于每个节点只能运行一个Pod副本，DaemonSet不支持扩缩容操作。对DaemonSet的管理主要是更新和回滚。

1.对DaemonSet执行滚动更新操作

• OnDelete：在更新DaemonSet模板后，只有用户手动删除旧的Pod之后，新的Pod才会被自动创建。
• RollingUpdate：这是默认的更新策略，即滚动更新。在更新DaemonSet模板后，旧的Pod将被自动终止，并且将以受控方式自动创建新的Pod。期间，每个节点上最多只能有一个DaemonSet部署的Pod运行。

（1）检查DaemonSet的更新策略

[root@master ~]# kubectl get ds/fluentd-elasticsearch -o go-template='{{.spec.updateStrategy.type}}{{"\n"}}' -n kube-system
RollingUpdate

（2）更新DaemonSet模板中的容器镜像

[root@master ~]# kubectl set image ds/fluentd-elasticsearch fluentd-elasticsearch=quay.io/fluentd_elasticsearch/fluentd:v2.6.0 -n kube-system
daemonset.apps/fluentd-elasticsearch image updated

（3）监视DaemonSet的滚动更新状态和进度

[root@master ~]# kubectl rollout status ds/fluentd-elasticsearch -n kube-system
Waiting for daemon set "fluentd-elasticsearch" rollout to finish: 0 of 3 updated pods are available...

2.对DaemonSet执行回滚操作

（1）查看该DaemonSet的修订版本历史

[root@master ~]# kubectl rollout history ds/fluentd-elasticsearch -n kube-system
daemonset.apps/fluentd-elasticsearch 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>

（2）直接回滚到该DaemonSet的上一版本

[root@master ~]# kubectl rollout undo ds/fluentd-elasticsearch -n kube-system
daemonset.apps/fluentd-elasticsearch rolled back

（3）监视该DaemonSet的回滚进度

[root@master ~]# kubectl rollout status ds/fluentd-elasticsearch -n kube-system
Waiting for daemon set "fluentd-elasticsearch" rollout to finish: 0 of 3 updated pods are available...

3.删除DaemonSet

（1）从名称空间中删除

[root@master ~]# kubectl delete ds fluentd-elasticsearch -n kube-system
daemonset.apps "fluentd-elasticsearch" deleted

（2）进一步验证

[root@master ~]# kubectl get pods -n kube-system -l name=fluentd-elasticsearch -o wide
No resources found in kube-system namespace.