k8s控制器:Daemonset
一、DaemonSet概述
1.1、DaemonSet概述
DaemonSet控制器能够确保k8s集群所有的节点都运行一个相同的pod副本,当向k8s集群中增加node节点时,这个node节点也会自动创建一个pod副本,当node节点从集群移除,这些pod也会自动删除;删除Daemonset也会删除它们创建的pod
1.2、DaemonSet工作原理
daemonset的控制器会监听kuberntes的daemonset对象、pod对象、node对象,这些被监听的对象之变动,就会触发syncLoop
循环让kubernetes集群朝着daemonset对象描述的状态进行演进。
1.3、Daemonset典型的应用场景
1)在集群的每个节点上运行存储,比如:glusterd 或 ceph。
2)在每个节点上运行日志收集组件,比如:flunentd 、 logstash、filebeat等。
3)在每个节点上运行监控组件,比如:Prometheus、 Node Exporter 、collectd等
1.4、DaemonSet 与 Deployment 的区别
Deployment 部署的副本 Pod 会分布在各个 Node 上,每个 Node 都可能运行好几个副本。
DaemonSet 的不同之处在于:每个 Node 上最多只能运行一个副本。
二、DaemonSet使用案例:部署日志收集组件fluentd
# 编写一个DaemonSet资源清单
[root@k8s-master1 ~]# cat daemonset.yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: fluentd-elasticsearch
namespace: kube-system
labels:
k8s-app: fluentd-logging
spec:
selector:
matchLabels:
name: fluentd-elasticsearch
template:
metadata:
labels:
name: fluentd-elasticsearch
spec:
tolerations:
- key: node-role.kubernetes.io/master
effect: NoSchedule
containers:
- name: fluentd-elasticsearch
image: xianchao/fluentd:v2.5.1
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
[root@k8s-master1 ~]# kubectl apply -f daemonset.yaml
daemonset.apps/fluentd-elasticsearch created
[root@k8s-master1 ~]# kubectl get ds -n kube-system
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE
calico-node 3 3 3 3 3 kubernetes.io/os=linux 2d12h
fluentd-elasticsearch 3 3 3 3 3 <none> 8s
kube-proxy 3 3 3 3 3 kubernetes.io/os=linux 2d13h
[root@k8s-master1 ~]# kubectl get pods -n kube-system -o wide -l name=fluentd-elasticsearch
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
fluentd-elasticsearch-9hjqc 1/1 Running 0 83s 10.244.159.134 k8s-master1 <none> <none>
fluentd-elasticsearch-bdfs6 1/1 Running 0 83s 10.244.36.124 k8s-node1 <none> <none>
fluentd-elasticsearch-wh44b 1/1 Running 0 83s 10.244.169.152 k8s-node2 <none> <none>
# 镜像更新
# kubectl set image daemonsets fluentd-elasticsearch fluentd-elasticsearch=image_name -n kube-system