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？
[root@tvm-02 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
[root@tvm-02 whoami]# kubectl describe nodes tvm-01 |grep -E '(Roles|Taints)'
Roles: master
Taints: node-role.kubernetes.io/master:NoSchedule
[root@tvm-02 whoami]# kubectl describe nodes tvm-02 |grep -E '(Roles|Taints)'
Roles: master
Taints: node-role.kubernetes.io/master:NoSchedule
[root@tvm-02 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
[root@tvm-02 whoami]# kubectl apply -f app-t1.yaml deployment "whoami-t1" created [root@tvm-02 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
[root@tvm-02 whoami]# kubectl taint nodes tvm-04 node-role.kubernetes.io/master=:NoSchedule
node "tvm-04" tainted
##### 符合预期
[root@tvm-02 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
[root@tvm-02 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
[root@tvm-02 whoami]# kubectl apply -f app-t2.yaml
deployment "whoami-t2" created
[root@tvm-02 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>
[root@tvm-02 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)
[root@tvm-02 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
[root@tvm-02 whoami]# kubectl apply -f app-t2.yaml
deployment "whoami-t2" configured
##### 连续 2 次查看状态
[root@tvm-02 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
[root@tvm-02 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
[root@tvm-02 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？
[root@tvm-02 whoami]# kubectl taint nodes tvm-04 node-role.kubernetes.io/master:NoSchedule-
node "tvm-04" untainted
##### 符合预期
[root@tvm-02 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/appvalue 是 whoamitaint 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tainttolerations: -
operator: "Exists"
effect为空将匹配demo.test.com/app这个key对应的所有的effectstolerations:- 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:NoScheduletolerations:
- 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）