在《研发工程师玩转Kubernetes——启动、存活和就绪探针》中，我们讲了就绪探针和服务之间的特殊关系。就绪探针检测失败并不代表整个程序处于“非存活”状态，可能只是短暂临时的不可以提供服务，比如CPU阶段性占满，导致就绪探针检测超时而导致失败。这个时候就绪探针并不会向存活探针那样尝试重启容器，而只是简单的把它从何它关联的Service中摘除。
带Readiness Probe的Nginx
代码语言：javascript复制apiVersion: apps/v1
kind: Deployment
metadata:
name: readiness-nginx-deployment
spec:
selector:
matchLabels:
app: readiness-nginx
replicas: 2
template:
metadata:
labels:
app: readiness-nginx
spec:
containers:
- name: readiness-nginx-container
image: nginx
ports:
- containerPort: 80
command: ["/bin/sh", "-c", "sleep 3; touch /tempdir/readiness-nginx; while true; do sleep 5; done"]
volumeMounts:
- name: probe-volume
mountPath: /tempdir
readinessProbe:
exec:
command:
- cat
- /tempdir/readiness-nginx
initialDelaySeconds: 2
failureThreshold: 6
periodSeconds: 1
successThreshold: 1
volumes:
- name: probe-volume
emptyDir:
medium: Memory
sizeLimit: 1GiNginx关联的Service
代码语言：javascript复制kind: Service
apiVersion: v1
metadata:
name: readiness-nginx-service
spec:
selector:
app: readiness-nginx
ports:
- protocol: TCP
port: 80
targetPort: 80实验
创建上述组件，可以看到启动了下面的Pod
代码语言：javascript复制kubectl get pod -o wideNAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
readiness-nginx-deployment-57b7fd5644-7x7wc 1/1 Running 0 25s 10.1.43.223 ubuntuc <none> <none>
readiness-nginx-deployment-57b7fd5644-lhszp 1/1 Running 0 25s 10.1.209.155 ubuntub <none> <none>Service也绑定了这些IP。
代码语言：javascript复制kubectl describe endpoints readiness-nginx-service Name: readiness-nginx-service
Namespace: default
Labels: <none>
Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2023-08-14T14:35:33Z
Subsets:
Addresses: 10.1.209.155,10.1.43.223
NotReadyAddresses: <none>
Ports:
Name Port Protocol
---- ---- --------
<unset> 80 TCP
Events: <none>现在我们挑选一个容器（readiness-nginx-deployment-57b7fd5644-7x7wc，10.1.43.223），观察该容器的Event状态：
代码语言：javascript复制kubectl describe pod readiness-nginx-deployment-57b7fd5644-7x7wcName: readiness-nginx-deployment-57b7fd5644-7x7wc
Namespace: default
Priority: 0
Service Account: default
Node: ubuntuc/172.22.247.176
Start Time: Mon, 14 Aug 2023 14:35:27 0000
Labels: app=readiness-nginx
pod-template-hash=57b7fd5644
Annotations: cni.projectcalico.org/containerID: c475d3e82ff0d5adbd35252ab990608ad75955f8d0862bb8b0c54ee60a0878eb
cni.projectcalico.org/podIP: 10.1.43.223/32
cni.projectcalico.org/podIPs: 10.1.43.223/32
Status: Running
IP: 10.1.43.223
IPs:
IP: 10.1.43.223
Controlled By: ReplicaSet/readiness-nginx-deployment-57b7fd5644
Containers:
readiness-nginx-container:
Container ID: containerd://5d82d8467bc6e0c8151e40ee3258d54bffec8659bcdad4a441848ea8f77a3223
Image: nginx
Image ID: docker.io/library/nginx@sha256:67f9a4f10d147a6e04629340e6493c9703300ca23a2f7f3aa56fe615d75d31ca
Port: 80/TCP
Host Port: 0/TCP
Command:
/bin/sh
-c
sleep 3; touch /tempdir/readiness-nginx; while true; do sleep 5; done
State: Running
Started: Mon, 14 Aug 2023 14:35:30 0000
Ready: True
Restart Count: 0
Readiness: exec [cat /tempdir/readiness-nginx] delay=2s timeout=1s period=1s #success=1 #failure=6
Environment: <none>
Mounts:
/tempdir from probe-volume (rw)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-c4tcl (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
probe-volume:
Type: EmptyDir (a temporary directory that shares a pod's lifetime)
Medium: Memory
SizeLimit: 1Gi
kube-api-access-c4tcl:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 3m53s default-scheduler Successfully assigned default/readiness-nginx-deployment-57b7fd5644-7x7wc to ubuntuc
Normal Pulling 3m53s kubelet Pulling image "nginx"
Normal Pulled 3m50s kubelet Successfully pulled image "nginx" in 2.489885583s (2.489893984s including waiting)
Normal Created 3m50s kubelet Created container readiness-nginx-container
Normal Started 3m50s kubelet Started container readiness-nginx-container
Warning Unhealthy 3m48s (x2 over 3m48s) kubelet Readiness probe failed: cat: /tempdir/readiness-nginx: No such file or directory可以看到就绪探针在第3次检测时就存在了，这个时候Pod的Ready和ContainersReady都是True的状态。
就绪->非就绪
现在我们删除就绪标志文件
代码语言：javascript复制kubectl exec pods/readiness-nginx-deployment-57b7fd5644-7x7wc --container readiness-nginx-container -- rm /tempdir/readiness-nginx再观察其状态，可以发现
代码语言：javascript复制Name: readiness-nginx-deployment-57b7fd5644-7x7wc
Namespace: default
Priority: 0
Service Account: default
Node: ubuntuc/172.22.247.176
Start Time: Mon, 14 Aug 2023 14:35:27 0000
Labels: app=readiness-nginx
pod-template-hash=57b7fd5644
Annotations: cni.projectcalico.org/containerID: c475d3e82ff0d5adbd35252ab990608ad75955f8d0862bb8b0c54ee60a0878eb
cni.projectcalico.org/podIP: 10.1.43.223/32
cni.projectcalico.org/podIPs: 10.1.43.223/32
Status: Running
IP: 10.1.43.223
IPs:
IP: 10.1.43.223
Controlled By: ReplicaSet/readiness-nginx-deployment-57b7fd5644
Containers:
readiness-nginx-container:
Container ID: containerd://5d82d8467bc6e0c8151e40ee3258d54bffec8659bcdad4a441848ea8f77a3223
Image: nginx
Image ID: docker.io/library/nginx@sha256:67f9a4f10d147a6e04629340e6493c9703300ca23a2f7f3aa56fe615d75d31ca
Port: 80/TCP
Host Port: 0/TCP
Command:
/bin/sh
-c
sleep 3; touch /tempdir/readiness-nginx; while true; do sleep 5; done
State: Running
Started: Mon, 14 Aug 2023 14:35:30 0000
Ready: False
Restart Count: 0
Readiness: exec [cat /tempdir/readiness-nginx] delay=2s timeout=1s period=1s #success=1 #failure=6
Environment: <none>
Mounts:
/tempdir from probe-volume (rw)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-c4tcl (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
probe-volume:
Type: EmptyDir (a temporary directory that shares a pod's lifetime)
Medium: Memory
SizeLimit: 1Gi
kube-api-access-c4tcl:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning Unhealthy 7s (x22 over 6m6s) kubelet Readiness probe failed: cat: /tempdir/readiness-nginx: No such file or directory可以看到Ready和ContainersReady都变成了False状态。 我们再观察Service
代码语言：javascript复制kubectl describe endpoints readiness-nginx-service Name: readiness-nginx-service
Namespace: default
Labels: <none>
Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2023-08-14T14:41:18Z
Subsets:
Addresses: 10.1.209.155
NotReadyAddresses: 10.1.43.223
Ports:
Name Port Protocol
---- ---- --------
<unset> 80 TCP
Events: <none>可以看到被删除了就绪探针检测文件的Pod被从Service中摘掉了。
非就绪->就绪
我们再将检测文件还原
代码语言：javascript复制kubectl exec pods/readiness-nginx-deployment-57b7fd5644-7x7wc --container readiness-nginx-container -- touch /tempdir/readiness-nginx观察对应Pod的状态，其Ready和ContainersReady又变成了True状态。
代码语言：javascript复制Name: readiness-nginx-deployment-57b7fd5644-7x7wc
Namespace: default
Priority: 0
Service Account: default
Node: ubuntuc/172.22.247.176
Start Time: Mon, 14 Aug 2023 14:35:27 0000
Labels: app=readiness-nginx
pod-template-hash=57b7fd5644
Annotations: cni.projectcalico.org/containerID: c475d3e82ff0d5adbd35252ab990608ad75955f8d0862bb8b0c54ee60a0878eb
cni.projectcalico.org/podIP: 10.1.43.223/32
cni.projectcalico.org/podIPs: 10.1.43.223/32
Status: Running
IP: 10.1.43.223
IPs:
IP: 10.1.43.223
Controlled By: ReplicaSet/readiness-nginx-deployment-57b7fd5644
Containers:
readiness-nginx-container:
Container ID: containerd://5d82d8467bc6e0c8151e40ee3258d54bffec8659bcdad4a441848ea8f77a3223
Image: nginx
Image ID: docker.io/library/nginx@sha256:67f9a4f10d147a6e04629340e6493c9703300ca23a2f7f3aa56fe615d75d31ca
Port: 80/TCP
Host Port: 0/TCP
Command:
/bin/sh
-c
sleep 3; touch /tempdir/readiness-nginx; while true; do sleep 5; done
State: Running
Started: Mon, 14 Aug 2023 14:35:30 0000
Ready: True
Restart Count: 0
Readiness: exec [cat /tempdir/readiness-nginx] delay=2s timeout=1s period=1s #success=1 #failure=6
Environment: <none>
Mounts:
/tempdir from probe-volume (rw)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-c4tcl (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
probe-volume:
Type: EmptyDir (a temporary directory that shares a pod's lifetime)
Medium: Memory
SizeLimit: 1Gi
kube-api-access-c4tcl:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning Unhealthy 3m5s (x262 over 13m) kubelet Readiness probe failed: cat: /tempdir/readiness-nginx: No such file or directoryService也重新将其加回来了。
代码语言：javascript复制Name: readiness-nginx-service
Namespace: default
Labels: <none>
Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2023-08-14T14:48:23Z
Subsets:
Addresses: 10.1.209.155,10.1.43.223
NotReadyAddresses: <none>
Ports:
Name Port Protocol
---- ---- --------
<unset> 80 TCP
Events: <none>
