144 lines
3.7 KiB
Markdown
144 lines
3.7 KiB
Markdown
# DaemonSet
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DaemonSet保证在每个Node上都运行一个容器副本，常用来部署一些集群的日志、监控或者其他系统管理程序。典型的应用常见包括：
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* 日志收集，比如fluentd，logstash等
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* 系统监控，比如Prometheus Node Exporter，collectd，New Relic agent，Ganglia gmond等
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* 系统程序，比如kube-proxy, kube-dns, glusterd, ceph等
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使用Fluentd收集日志的例子：
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```yaml
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apiVersion: extensions/v1beta1
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kind: DaemonSet
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metadata:
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name: fluentd
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spec:
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template:
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metadata:
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labels:
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app: logging
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id: fluentd
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name: fluentd
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spec:
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containers:
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- name: fluentd-es
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image: gcr.io/google_containers/fluentd-elasticsearch:1.3
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env:
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- name: FLUENTD_ARGS
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value: -qq
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volumeMounts:
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- name: containers
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mountPath: /var/lib/docker/containers
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- name: varlog
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mountPath: /varlog
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volumes:
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- hostPath:
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path: /var/lib/docker/containers
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name: containers
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- hostPath:
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path: /var/log
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name: varlog
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```
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## 指定Node节点
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DaemonSet会忽略Node的unschedulable状态，有两种方式来指定Pod只运行在指定的Node节点上：
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- nodeSelector：只调度到匹配指定label的Node上
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- nodeAffinity：功能更丰富的Node选择器，比如支持集合操作
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- podAffinity：调度到满足条件的Pod所在的Node上
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nodeSelector示例：
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```yaml
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spec:
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nodeSelector:
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disktype: ssd
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```
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nodeAffinity示例：
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```yaml
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metadata:
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name: with-node-affinity
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annotations:
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scheduler.alpha.kubernetes.io/affinity: >
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{
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"nodeAffinity": {
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"requiredDuringSchedulingIgnoredDuringExecution": {
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"nodeSelectorTerms": [
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{
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"matchExpressions": [
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{
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"key": "kubernetes.io/e2e-az-name",
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"operator": "In",
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"values": ["e2e-az1", "e2e-az2"]
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}
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]
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}
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]
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}
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}
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}
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another-annotation-key: another-annotation-value
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```
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podAffinity示例：
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```yaml
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metadata:
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name: with-pod-affinity
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annotations:
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scheduler.alpha.kubernetes.io/affinity: >
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{
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"podAffinity": {
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"requiredDuringSchedulingIgnoredDuringExecution": [
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{
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"labelSelector": {
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"matchExpressions": [
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{
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"key": "security",
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"operator": "In",
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"values": ["S1"]
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}
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]
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},
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"topologyKey": "failure-domain.beta.kubernetes.io/zone"
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}
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]
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},
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"podAntiAffinity": {
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"requiredDuringSchedulingIgnoredDuringExecution": [
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{
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"labelSelector": {
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"matchExpressions": [
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{
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"key": "security",
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"operator": "In",
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"values": ["S2"]
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}
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]
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},
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"topologyKey": "kubernetes.io/hostname"
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}
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]
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}
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}
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spec:
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...
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```
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## 静态Pod
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除了DaemonSet，还可以使用静态Pod来在每台机器上运行指定的Pod，这需要kubelet在启动的时候指定manifest目录：
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```bash
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kubelet --pod-manifest-path=<the directory>
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```
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然后将所需要的Pod定义文件放到指定的manifest目录中即可。
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注意：静态Pod不能通过API Server来删除，但可以通过删除manifest文件来自动删除对应的Pod。
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