k8s基本概念-配置调度策略之(Taints-and-Tolerations)
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k8s基本概念-配置调度策略之(Taints-and-Tolerations)2018/4/12
通过定义 Taints and Tolerations 来达到 node 排斥 pod 的目的
- 通过一个典型实例来描述 taint 和 toleration 之间的关联
- 测试前的集群状态
- 部署app
whoami-t1
- 测试 taint 的用法
- 测试结果
- 测试使用
toleration
- 测试结果
- 如何移除指定的 taint 呢?
- 聊一聊 Taints and Tolerations 的细节
- 概念
通过一个典型实例来描述 taint 和 toleration 之间的关联
测试前的集群状态
部署集群的时候,你极可能有留意到,集群中设置为 master 角色的节点,是不会有任务调度到这里来执行的,这是为何呢?
[[email protected] whoami]# kubectl get nodes
NAME STATUS ROLES AGE VERSION
tvm-01 Ready master 8d v1.9.0
tvm-02 Ready master 8d v1.9.0
tvm-03 Ready master 8d v1.9.0
tvm-04 Ready <none> 8d v1.9.0
[[email protected] whoami]# kubectl describe nodes tvm-01 |grep -E ‘(Roles|Taints)‘
Roles: master
Taints: node-role.kubernetes.io/master:NoSchedule
[[email protected] whoami]# kubectl describe nodes tvm-02 |grep -E ‘(Roles|Taints)‘
Roles: master
Taints: node-role.kubernetes.io/master:NoSchedule
[[email protected] whoami]# kubectl describe nodes tvm-03 |grep -E ‘(Roles|Taints)‘
Roles: master
Taints: node-role.kubernetes.io/master:NoSchedule
部署app whoami-t1
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
name: whoami-t1
labels:
app: whoami
spec:
replicas: 3
selector:
matchLabels:
app: whoami
template:
metadata:
labels:
app: whoami
spec:
containers:
- name: whoami
image: opera443399/whoami:0.9
ports:
- containerPort: 80
部署后可以发现,所有任务都被调度到 worker 节点上
[[email protected] whoami]# kubectl apply -f app-t1.yaml deployment "whoami-t1" created [[email protected] whoami]# kubectl get ds,deploy,svc,pods --all-namespaces -o wide -l app=whoami NAMESPACE NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR default deploy/whoami-t1 3 3 3 3 46s whoami opera443399/whoami:0.9 app=whoami
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
default po/whoami-t1-6cf9cd6bf4-62bhc 1/1 Running 0 46s 172.30.105.1 tvm-04
default po/whoami-t1-6cf9cd6bf4-dss72 1/1 Running 0 46s 172.30.105.2 tvm-04
default po/whoami-t1-6cf9cd6bf4-zvpsk 1/1 Running 0 46s 172.30.105.0 tvm-04
##### 测试 taint 的用法
给 tvm-04 配置一个 taint 来调整调度策略
```bash
[[email protected] whoami]# kubectl taint nodes tvm-04 node-role.kubernetes.io/master=:NoSchedule
node "tvm-04" tainted
##### 符合预期
[[email protected] whoami]# kubectl describe nodes tvm-04 |grep -E ‘(Roles|Taints)‘
Roles: <none>
Taints: node-role.kubernetes.io/master:NoSchedule
上述 taint 的指令含义是:
给节点tvm-04
配置一个 taint (可以理解为:污点)
其中,这个 taint 的
key 是node-role.kubernetes.io/master
value 是` (值为空)<br/>taint effect 是
NoSchedule<br/>这意味着,没有任何 pod 可以调度到这个节点上面,除非在这个 pod 的描述文件中有一个对应的
toleration` (可以理解为:设置 pod 容忍了这个污点)
测试结果
我们发现,之前部署的 deploy/whoami-t1
并未被驱逐
[[email protected] whoami]# kubectl get ds,deploy,svc,pods --all-namespaces -o wide -l app=whoami
NAMESPACE NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
default deploy/whoami-t1 3 3 3 3 17m whoami opera443399/whoami:0.9 app=whoami
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
default po/whoami-t1-6cf9cd6bf4-62bhc 1/1 Running 0 17m 172.30.105.1 tvm-04
default po/whoami-t1-6cf9cd6bf4-dss72 1/1 Running 0 17m 172.30.105.2 tvm-04
default po/whoami-t1-6cf9cd6bf4-zvpsk 1/1 Running 0 17m 172.30.105.0 tvm-04
接着我们尝试着再部署一个app whoami-t2
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
name: whoami-t2
labels:
app: whoami
spec:
replicas: 3
selector:
matchLabels:
app: whoami
template:
metadata:
labels:
app: whoami
spec:
containers:
- name: whoami
image: opera443399/whoami:0.9
ports:
- containerPort: 80
tolerations:
- key: "node-role.kubernetes.io/master"
operator: "Equal"
value: ""
effect: "NoSched
下述操作表明:策略已经生效,只是旧的 deploy 默认不会受到影响(被强制驱逐)
##### 部署
[[email protected] whoami]# kubectl apply -f app-t2.yaml
deployment "whoami-t2" created
[[email protected] whoami]# kubectl get ds,deploy,svc,pods --all-namespaces -o wide -l app=whoami
NAMESPACE NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
default deploy/whoami-t1 3 3 3 3 20m whoami opera443399/whoami:0.9 app=whoami
default deploy/whoami-t2 3 3 3 0 38s whoami opera443399/whoami:0.9 app=whoami
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
default po/whoami-t1-6cf9cd6bf4-62bhc 1/1 Running 0 20m 172.30.105.1 tvm-04
default po/whoami-t1-6cf9cd6bf4-dss72 1/1 Running 0 20m 172.30.105.2 tvm-04
default po/whoami-t1-6cf9cd6bf4-zvpsk 1/1 Running 0 20m 172.30.105.0 tvm-04
default po/whoami-t2-6cf9cd6bf4-5f9wl 0/1 Pending 0 38s <none> <none>
default po/whoami-t2-6cf9cd6bf4-8l59z 0/1 Pending 0 38s <none> <none>
default po/whoami-t2-6cf9cd6bf4-lqpzp 0/1 Pending 0 38s <none> <none>
[[email protected] whoami]# kubectl describe deploy/whoami-t2
Name: whoami-t2
(omited)
Annotations: deployment.kubernetes.io/revision=1
Replicas: 3 desired | 3 updated | 3 total | 0 available | 3 unavailable
(omited)
Conditions:
Type Status Reason
---- ------ ------
Available False MinimumReplicasUnavailable
Progressing True ReplicaSetUpdated
(omited)
[[email protected] whoami]# kubectl describe po/whoami-t2-6cf9cd6bf4-5f9wl
Name: whoami-t2-6cf9cd6bf4-5f9wl
(omited)
Status: Pending
IP:
Controlled By: ReplicaSet/whoami-t2-6cf9cd6bf4
(omited)
Conditions:
Type Status
PodScheduled False
(omited)
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning FailedScheduling 27s (x14 over 3m) default-scheduler 0/4 nodes are available: 4 PodToleratesNodeTaints.
测试使用 toleration
增加 toleration
相关的配置来调度 whoami-t2
到 master
节点上
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
name: whoami-t2
labels:
app: whoami
spec:
replicas: 3
selector:
matchLabels:
app: whoami
template:
metadata:
labels:
app: whoami
spec:
containers:
- name: whoami
image: opera443399/whoami:0.9
ports:
- containerPort: 80
tolerations:
- key: "node-role.kubernetes.io/master"
operator: "Equal"
value: ""
effect: "NoSchedule"
测试结果
下述操作表明:之前不可用的节点,调整后,节点处于可用状态, pod 部署成功
##### 更新
[[email protected] whoami]# kubectl apply -f app-t2.yaml
deployment "whoami-t2" configured
##### 连续 2 次查看状态
[[email protected] whoami]# kubectl describe deploy/whoami-t2
Name: whoami-t2
(omitted)
Annotations: deployment.kubernetes.io/revision=2
Replicas: 3 desired | 3 updated | 4 total | 2 available | 2 unavailable
Conditions:
Type Status Reason
---- ------ ------
Available False MinimumReplicasUnavailable
Progressing True ReplicaSetUpdated
OldReplicaSets: whoami-t2-6cf9cd6bf4 (1/1 replicas created)
NewReplicaSet: whoami-t2-647c9cb7c5 (3/3 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 39m deployment-controller Scaled up replica set whoami-t2-6cf9cd6bf4 to 3
Normal ScalingReplicaSet 14s deployment-controller Scaled up replica set whoami-t2-647c9cb7c5 to 1
Normal ScalingReplicaSet 12s deployment-controller Scaled down replica set whoami-t2-6cf9cd6bf4 to 2
Normal ScalingReplicaSet 12s deployment-controller Scaled up replica set whoami-t2-647c9cb7c5 to 2
Normal ScalingReplicaSet 6s deployment-controller Scaled down replica set whoami-t2-6cf9cd6bf4 to 1
Normal ScalingReplicaSet 6s deployment-controller Scaled up replica set whoami-t2-647c9cb7c5 to 3
[[email protected] whoami]# kubectl describe deploy/whoami-t2
Name: whoami-t2
(omitted)
Annotations: deployment.kubernetes.io/revision=2
Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable
(omitted)
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: whoami-t2-647c9cb7c5 (3/3 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 39m deployment-controller Scaled up replica set whoami-t2-6cf9cd6bf4 to 3
Normal ScalingReplicaSet 28s deployment-controller Scaled up replica set whoami-t2-647c9cb7c5 to 1
Normal ScalingReplicaSet 26s deployment-controller Scaled down replica set whoami-t2-6cf9cd6bf4 to 2
Normal ScalingReplicaSet 26s deployment-controller Scaled up replica set whoami-t2-647c9cb7c5 to 2
Normal ScalingReplicaSet 20s deployment-controller Scaled down replica set whoami-t2-6cf9cd6bf4 to 1
Normal ScalingReplicaSet 20s deployment-controller Scaled up replica set whoami-t2-647c9cb7c5 to 3
Normal ScalingReplicaSet 12s deployment-controller Scaled down replica set whoami-t2-6cf9cd6bf4 to 0
[[email protected] whoami]# kubectl get ds,deploy,svc,pods --all-namespaces -o wide -l app=whoami
NAMESPACE NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
default deploy/whoami-t1 3 3 3 3 1h whoami opera443399/whoami:0.9 app=whoami
default deploy/whoami-t2 3 3 3 3 45m whoami opera443399/whoami:0.9 app=whoami
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
default po/whoami-t1-6cf9cd6bf4-62bhc 1/1 Running 0 1h 172.30.105.1 tvm-04
default po/whoami-t1-6cf9cd6bf4-dss72 1/1 Running 0 1h 172.30.105.2 tvm-04
default po/whoami-t1-6cf9cd6bf4-zvpsk 1/1 Running 0 1h 172.30.105.0 tvm-04
default po/whoami-t2-647c9cb7c5-9b5b6 1/1 Running 0 6m 172.30.105.3 tvm-04
default po/whoami-t2-647c9cb7c5-kmj6k 1/1 Running 0 6m 172.30.235.129 tvm-01
default po/whoami-t2-647c9cb7c5-p5gwm 1/1 Running 0 5m 172.30.60.193 tvm-03
如何移除指定的 taint 呢?
[[email protected] whoami]# kubectl taint nodes tvm-04 node-role.kubernetes.io/master:NoSchedule-
node "tvm-04" untainted
##### 符合预期
[[email protected] whoami]# kubectl describe nodes tvm-04 |grep -E ‘(Roles|Taints)‘
Roles: <none>
Taints: <none>
聊一聊 Taints and Tolerations 的细节
Taints
和Node affinity
是对立的概念,用来允许一个 node 拒绝某一类 podsTaints
和tolerations
配合起来可以保证 pods 不会被调度到不合适的 nodes 上干活
一个 node 上可以有多个taints
将tolerations
应用到 pods 来允许被调度到合适的 nodes 上干活
概念
示范增加一个 taint 到 node 上的操作:
kubectl taint nodes tvm-04 demo.test.com/app=whoami:NoSchedule
在节点 tvm-04
上配置了一个 taint
,其中:key
是 demo.test.com/app
value
是 whoami
taint effect
是 NoSchedule
如果要移除 taint
则:
kubectl taint nodes tvm-04 demo.test.com/app:NoSchedule-
然后在 PodSpec
中定义 toleration
使得该 pod 可以被调度到 tvm-04
上,有下述 2 种方式:
tolerations:
- key: "demo.test.com/app"
operator: "Equal"
value: "whoami"
effect: "NoSchedule"
tolerations:
- key: "demo.test.com/app"
operator: "Exists"
effect: "NoSchedule"
taint
和 toleration
要匹配上,需要满足两者的 keys
和 effects
是一致的,且:
- 当
operator
是Exists
(意味着不用指定value
的内容)时,或者 - 当
operator
是Equal
时values
也相同
注1: operator
默认值是 Equal
如果不指定的话
注2: 留意下面 2 个使用 Exists
的特例
- key 为空且
operator
是Exists
时,将匹配所有的keys
,values
和effects
,这表明可以tolerate
所有的taint
tolerations:
-
operator: "Exists"
effect
为空将匹配demo.test.com/app
这个key
对应的所有的effects
tolerations:
- key: "demo.test.com/app"
operator: "Exists"
上述 effect
使用的是 NoSchedule
,其实还可以使用其他的调度策略,例如:
- PreferNoSchedule : 这意味着不是一个强制必须的调度策略(尽量不去满足不合要求的 pod 调度到 node 上来)
- NoExecute : 后续解释
可以在同一个 node 上使用多个 taints
,也可以在同一个 pod 上使用多个 tolerations
,而 k8s 在处理 taints and tolerations
时类似一个过滤器:
- 对比一个 node 上所有的
taints
- 忽略掉和 pod 中
toleration
匹配的taints
- 遗留下来未被忽略掉的所有
taints
将对 pod 产生effect
尤其是:
- 至少有 1 个未被忽略的
taint
且effect
是NoSchedule
时,则 k8s 不会将该 pod 调度到这个 node 上 - 不满足上述场景,但至少有 1 个未被忽略的
taint
且effect
是PreferNoSchedule
时,则 k8s 将尝试不把该 pod 调度到这个 node 上 - 至少有 1 个未被忽略的
taint
且effect
是NoExecute
时,则 k8s 会立即将该 pod 从该 node 上驱逐(如果已经在该 node 上运行),或着不会将该 pod 调度到这个 node 上(如果还没在这个 node 上运行)
实例,有下述 node 和 pod 的定义:
kubectl taint nodes tvm-04 key1=value1:NoSchedule
kubectl taint nodes tvm-04 key1=value1:NoExecute
kubectl taint nodes tvm-04 key2=value2:NoSchedule
tolerations:
- key: "key1"
operator: "Equal"
value: "value1"
effect: "NoSchedule"
- key: "key1"
operator: "Equal"
value: "value1"
effect: "NoExecute"
上述场景中,
- 该 pod 不会调度到 node 上,因为第 3 个 taint 不满足
- 如果该 pod 已经在该 node 上运行,则不会被驱逐
通常而言,不能 tolerate
一个 effect
是 NoExecute
的 pod 将被立即驱逐,但是,通过指定可选的字段 tolerationSeconds
则可以规定该 pod 延迟到一个时间段后再被驱逐,例如:
tolerations:
- key: "key1"
operator: "Equal"
value: "value1"
effect: "NoExecute"
tolerationSeconds: 3600
也就是说,在 3600 秒后将被驱逐。但是,如果在这个时间点前移除了相关的 taint
则也不会被驱逐
注3:关于被驱逐,如果该 pod 没有其他地方可以被调度,也不会被驱逐出去(个人实验结果,请自行验证)
ZYXW、参考
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