| DaemonSet
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应用。典型的应用包括：
日志收集，比如fluentd，logstash等
系统监控，比如Prometheus Node Exporter，collectd，New Relic
agent，Ganglia gmond等
系统程序，比如kube-proxy, kube-dns, glusterd, ceph等
使用Fluentd收集日志的例子：
apiVersion:
extensions/v1beta1
kind: DaemonSet
metadata:
name: fluentd
spec:
template:
metadata:
labels:
app: logging
id: fluentd
name: fluentd
spec:
containers:
- name: fluentd-es
image: gcr.io/google_containers/fluentd-elasticsearch:1.3
env:
- name: FLUENTD_ARGS
value: -qq
volumeMounts:
- name: containers
mountPath: /var/lib/docker/containers
- name: varlog
mountPath: /varlog
volumes:
- hostPath:
path: /var/lib/docker/containers
name: containers
- hostPath:
path: /var/log
name: varlog |
指定Node节点
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：
nodeSelector：只调度到匹配指定label的Node上
nodeAffinity：功能更丰富的Node选择器，比如支持集合操作
podAffinity：调度到满足条件的Pod所在的Node上
nodeSelector示例
首先给Node打上标签
| kubectl
label nodes node-01 disktype=ssd |
然后在daemonset中指定nodeSelector为disktype=ssd：
spec:
nodeSelector:
disktype: ssd |
nodeAffinity示例
nodeAffinity目前支持两种：requiredDuringSchedulingIgnoredDuringExecution和preferredDuringSchedulingIgnoredDuringExecution，分别代表必须满足条件和优选条件。比如下面的例子代表调度到包含标签kubernetes.io/e2e-az-name并且值为e2e-az1或e2e-az2的Node上，并且优选还带有标签another-node-label-key=another-node-label-value的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示例
podAffinity基于Pod的标签来选择Node，仅调度到满足条件Pod所在的Node上，支持podAffinity和podAntiAffinity。这个功能比较绕，以下面的例子为例：
如果一个“Node所在Zone中包含至少一个带有security=S1标签且运行中的Pod”，那么可以调度到该Node
不调度到“包含至少一个带有security=S2标签且运行中Pod”的Node上
apiVersion:
v1
kind: Pod
metadata:
name: with-pod-affinity
spec:
affinity:
podAffinity:
requiredDuring SchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: security
operator: In
values:
- S1
topologyKey: failure -domain.beta.kubernetes.io/zone
podAntiAffinity:
preferredDuringScheduling IgnoredDuringExecution:
- 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 |
静态Pod
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：
| kubelet
--pod-manifest-path =/etc/kubernetes/manifests |
然后将所需要的Pod定义文件放到指定的manifest目录中。
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。 |
