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上一篇文章中kubernetes系列教程（七）深入玩轉pod調度介紹了kubernetes中Pod的調度機制，通過實戰演練介紹Pod調度到node的幾種方法：1. 通過nodeName固定選擇調度，2. 通過nodeSelector定向選擇調度，3. 通過node Affinity親和力調度，接下來介紹kubernetes系列教程pod的健康檢查機制。
應用在運行過程中難免會出現錯誤，如程序異常，軟件異常，硬件故障，網絡故障等，kubernetes提供Health Check健康檢查機制，當發現應用異常時會自動重啟容器，將應用從service服務中剔除，保障應用的高可用性。k8s定義了三種探針Probe：
每種探測機制支持三種健康檢查方法，分別是命令行exec，httpGet和tcpSocket，其中exec通用性最強，適用與大部分場景，tcpSocket適用于TCP業務，httpGet適用于web業務。
每種探測方法能支持幾個相同的檢查參數，用于設置控制檢查時間：
許多應用程序運行過程中無法檢測到內部故障，如死鎖，出現故障時通過重啟業務可以恢復，kubernetes提供liveness在線健康檢查機制，我們以exec為例，創建一個容器啟動過程中創建一個文件/tmp/liveness-probe.log，10s后將其刪除，定義liveness健康檢查機制在容器中執行命令ls -l /tmp/liveness-probe.log，通過文件的返回碼判斷健康狀態，如果返回碼非0，暫停20s后kubelet會自動將該容器重啟。
[root@node-1 demo]# cat centos-exec-liveness-probe.yaml
apiVersion: v1
kind: Pod
metadata:
name: exec-liveness-probe
annotations:
kubernetes.io/description: "exec-liveness-probe"
spec:
containers:
- name: exec-liveness-probe
image: centos:latest
imagePullPolicy: IfNotPresent
args: #容器啟動命令，生命周期為30s
- /bin/sh
- -c
- touch /tmp/liveness-probe.log && sleep 10 && rm -f /tmp/liveness-probe.log && sleep 20
livenessProbe:
exec: #健康檢查機制，通過ls -l /tmp/liveness-probe.log返回碼判斷容器的健康狀態
command:
- ls
- l
- /tmp/liveness-probe.log
initialDelaySeconds: 1
periodSeconds: 5
timeoutSeconds: 1[root@node-1 demo]# kubectl apply -f centos-exec-liveness-probe.yaml
pod/exec-liveness-probe created[root@node-1 demo]# kubectl describe pods exec-liveness-probe | tail
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 28s default-scheduler Successfully assigned default/exec-liveness-probe to node-3
Normal Pulled 27s kubelet, node-3 Container image "centos:latest" already present on machine
Normal Created 27s kubelet, node-3 Created container exec-liveness-probe
Normal Started 27s kubelet, node-3 Started container exec-liveness-probe
#容器已啟動
Warning Unhealthy 20s (x2 over 25s) kubelet, node-3 Liveness probe failed: /tmp/liveness-probe.log
ls: cannot access l: No such file or directory #執行健康檢查，檢查異常
Warning Unhealthy 15s kubelet, node-3 Liveness probe failed: ls: cannot access l: No such file or directory
ls: cannot access /tmp/liveness-probe.log: No such file or directory
Normal Killing 15s kubelet, node-3 Container exec-liveness-probe failed liveness probe, will be restarted
#重啟容器[root@node-1 demo]# kubectl get pods exec-liveness-probe
NAME READY STATUS RESTARTS AGE
exec-liveness-probe 1/1 Running 6 5m19s[root@node-1 demo]# cat nginx-httpGet-liveness-readiness.yaml
apiVersion: v1
kind: Pod
metadata:
name: nginx-httpget-livess-readiness-probe
annotations:
kubernetes.io/description: "nginx-httpGet-livess-readiness-probe"
spec:
containers:
- name: nginx-httpget-livess-readiness-probe
image: nginx:latest
ports:
- name: http-80-port
protocol: TCP
containerPort: 80
livenessProbe: #健康檢查機制，通過httpGet實現實現檢查
httpGet:
port: 80
scheme: HTTP
path: /index.html
initialDelaySeconds: 3
periodSeconds: 10
timeoutSeconds: 3[root@node-1 demo]# kubectl apply -f nginx-httpGet-liveness-readiness.yaml
pod/nginx-httpget-livess-readiness-probe created
[root@node-1 demo]# kubectl get pods nginx-httpget-livess-readiness-probe
NAME READY STATUS RESTARTS AGE
nginx-httpget-livess-readiness-probe 1/1 Running 0 6s
查詢pod所屬的節點
[root@node-1 demo]# kubectl get pods nginx-httpget-livess-readiness-probe -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-httpget-livess-readiness-probe 1/1 Running 1 3m9s 10.244.2.19 node-3 <none> <none>
登錄到pod中將文件刪除
[root@node-1 demo]# kubectl exec -it nginx-httpget-livess-readiness-probe /bin/bash
root@nginx-httpget-livess-readiness-probe:/# ls -l /usr/share/nginx/html/index.html
-rw-r--r-- 1 root root 612 Sep 24 14:49 /usr/share/nginx/html/index.html
root@nginx-httpget-livess-readiness-probe:/# rm -f /usr/share/nginx/html/index.html [root@node-1 demo]# kubectl get pods nginx-httpget-livess-readiness-probe
NAME READY STATUS RESTARTS AGE
nginx-httpget-livess-readiness-probe 1/1 Running 1 4m22s
[root@node-1 demo]# kubectl describe pods nginx-httpget-livess-readiness-probe | tail
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 5m45s default-scheduler Successfully assigned default/nginx-httpget-livess-readiness-probe to node-3
Normal Pulling 3m29s (x2 over 5m45s) kubelet, node-3 Pulling image "nginx:latest"
Warning Unhealthy 3m29s (x3 over 3m49s) kubelet, node-3 Liveness probe failed: HTTP probe failed with statuscode: 404
Normal Killing 3m29s kubelet, node-3 Container nginx-httpget-livess-readiness-probe failed liveness probe, will be restarted
Normal Pulled 3m25s (x2 over 5m41s) kubelet, node-3 Successfully pulled image "nginx:latest"
Normal Created 3m25s (x2 over 5m40s) kubelet, node-3 Created container nginx-httpget-livess-readiness-probe
Normal Started 3m25s (x2 over 5m40s) kubelet, node-3 Started container nginx-httpget-livess-readiness-probe[root@node-1 demo]# cat nginx-tcp-liveness.yaml
apiVersion: v1
kind: Pod
metadata:
name: nginx-tcp-liveness-probe
annotations:
kubernetes.io/description: "nginx-tcp-liveness-probe"
spec:
containers:
- name: nginx-tcp-liveness-probe
image: nginx:latest
ports:
- name: http-80-port
protocol: TCP
containerPort: 80
livenessProbe: #健康檢查為tcpSocket，探測TCP 80端口
tcpSocket:
port: 80
initialDelaySeconds: 3
periodSeconds: 10
timeoutSeconds: 3[root@node-1 demo]# kubectl apply -f nginx-tcp-liveness.yaml
pod/nginx-tcp-liveness-probe created
[root@node-1 demo]# kubectl get pods nginx-tcp-liveness-probe
NAME READY STATUS RESTARTS AGE
nginx-tcp-liveness-probe 1/1 Running 0 6s
獲取pod所在node
[root@node-1 demo]# kubectl get pods nginx-tcp-liveness-probe -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-tcp-liveness-probe 1/1 Running 0 99s 10.244.2.20 node-3 <none> <none>
登錄到pod中
[root@node-1 demo]# kubectl exec -it nginx-httpget-livess-readiness-probe /bin/bash
#執行apt-get update更新和apt-get install htop安裝工具
root@nginx-httpget-livess-readiness-probe:/# apt-get update
Get:1 http://cdn-fastly.deb.debian.org/debian buster InRelease [122 kB]
Get:2 http://security-cdn.debian.org/debian-security buster/updates InRelease [39.1 kB]
Get:3 http://cdn-fastly.deb.debian.org/debian buster-updates InRelease [49.3 kB]
Get:4 http://security-cdn.debian.org/debian-security buster/updates/main amd64 Packages [95.7 kB]
Get:5 http://cdn-fastly.deb.debian.org/debian buster/main amd64 Packages [7899 kB]
Get:6 http://cdn-fastly.deb.debian.org/debian buster-updates/main amd64 Packages [5792 B]
Fetched 8210 kB in 3s (3094 kB/s)
Reading package lists... Done
root@nginx-httpget-livess-readiness-probe:/# apt-get install htop
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
lsof strace
The following NEW packages will be installed:
htop
0 upgraded, 1 newly installed, 0 to remove and 5 not upgraded.
Need to get 92.8 kB of archives.
After this operation, 230 kB of additional disk space will be used.
Get:1 http://cdn-fastly.deb.debian.org/debian buster/main amd64 htop amd64 2.2.0-1+b1 [92.8 kB]
Fetched 92.8 kB in 0s (221 kB/s)
debconf: delaying package configuration, since apt-utils is not installed
Selecting previously unselected package htop.
(Reading database ... 7203 files and directories currently installed.)
Preparing to unpack .../htop_2.2.0-1+b1_amd64.deb ...
Unpacking htop (2.2.0-1+b1) ...
Setting up htop (2.2.0-1+b1) ...
root@nginx-httpget-livess-readiness-probe:/# kill 1
root@nginx-httpget-livess-readiness-probe:/# command terminated with exit code 137
查看pod情況
[root@node-1 demo]# kubectl get pods nginx-tcp-liveness-probe
NAME READY STATUS RESTARTS AGE
nginx-tcp-liveness-probe 1/1 Running 1 13m[root@node-1 demo]# kubectl describe pods nginx-tcp-liveness-probe | tail
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 14m default-scheduler Successfully assigned default/nginx-tcp-liveness-probe to node-3
Normal Pulling 44s (x2 over 14m) kubelet, node-3 Pulling image "nginx:latest"
Normal Pulled 40s (x2 over 14m) kubelet, node-3 Successfully pulled image "nginx:latest"
Normal Created 40s (x2 over 14m) kubelet, node-3 Created container nginx-tcp-liveness-probe
Normal Started 40s (x2 over 14m) kubelet, node-3 Started container nginx-tcp-liveness-probe就緒檢查用于應用接入到service的場景，用于判斷應用是否已經就緒完畢，即是否可以接受外部轉發的流量，健康檢查正常則將pod加入到service的endpoints中，健康檢查異常則從service的endpoints中刪除，避免影響業務的訪問。
[root@node-1 demo]# cat httpget-liveness-readiness-probe.yaml
apiVersion: v1
kind: Pod
metadata:
name: nginx-tcp-liveness-probe
annotations:
kubernetes.io/description: "nginx-tcp-liveness-probe"
labels: #需要定義labels，后面定義的service需要調用
app: nginx
spec:
containers:
- name: nginx-tcp-liveness-probe
image: nginx:latest
ports:
- name: http-80-port
protocol: TCP
containerPort: 80
livenessProbe: #存活檢查探針
httpGet:
port: 80
path: /index.html
scheme: HTTP
initialDelaySeconds: 3
periodSeconds: 10
timeoutSeconds: 3
readinessProbe: #就緒檢查探針
httpGet:
port: 80
path: /test.html
scheme: HTTP
initialDelaySeconds: 3
periodSeconds: 10
timeoutSeconds: 3[root@node-1 demo]# cat nginx-service.yaml
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: nginx-service
spec:
ports:
- name: http
port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
type: ClusterIP[root@node-1 demo]# kubectl apply -f httpget-liveness-readiness-probe.yaml
pod/nginx-tcp-liveness-probe created
[root@node-1 demo]# kubectl apply -f nginx-service.yaml
service/nginx-service created[root@node-1 ~]# kubectl get pods nginx-httpget-livess-readiness-probe
NAME READY STATUS RESTARTS AGE
nginx-httpget-livess-readiness-probe 1/1 Running 2 153m
#readiness健康檢查異常，404報錯（最后一行）
[root@node-1 demo]# kubectl describe pods nginx-tcp-liveness-probe | tail
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 2m6s default-scheduler Successfully assigned default/nginx-tcp-liveness-probe to node-3
Normal Pulling 2m5s kubelet, node-3 Pulling image "nginx:latest"
Normal Pulled 2m1s kubelet, node-3 Successfully pulled image "nginx:latest"
Normal Created 2m1s kubelet, node-3 Created container nginx-tcp-liveness-probe
Normal Started 2m1s kubelet, node-3 Started container nginx-tcp-liveness-probe
Warning Unhealthy 2s (x12 over 112s) kubelet, node-3 Readiness probe failed: HTTP probe failed with statuscode: 404[root@node-1 ~]# kubectl describe services nginx-service
Name: nginx-service
Namespace: default
Labels: app=nginx
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"app":"nginx"},"name":"nginx-service","namespace":"default"},"s...
Selector: app=nginx
Type: ClusterIP
IP: 10.110.54.40
Port: http 80/TCP
TargetPort: 80/TCP
Endpoints: <none> #Endpoints對象為空
Session Affinity: None
Events: <none>
#endpoints狀態
[root@node-1 demo]# kubectl describe endpoints nginx-service
Name: nginx-service
Namespace: default
Labels: app=nginx
Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2019-09-30T14:27:37Z
Subsets:
Addresses: <none>
NotReadyAddresses: 10.244.2.22 #pod處于NotReady狀態
Ports:
Name Port Protocol
---- ---- --------
http 80 TCP
Events: <none>[root@node-1 ~]# kubectl exec -it nginx-httpget-livess-readiness-probe /bin/bash
root@nginx-httpget-livess-readiness-probe:/# echo "readiness probe demo" >/usr/share/nginx/html/test.html健康檢查正常
[root@node-1 demo]# curl http://10.244.2.22/test.html
查看endpoints情況
readines[root@node-1 demo]# kubectl describe endpoints nginx-service
Name: nginx-service
Namespace: default
Labels: app=nginx
Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2019-09-30T14:33:01Z
Subsets:
Addresses: 10.244.2.22 #就緒地址，已從NotReady中提出，加入到正常的Address列表中
NotReadyAddresses: <none>
Ports:
Name Port Protocol
---- ---- --------
http 80 TCP
查看service狀態
[root@node-1 demo]# kubectl describe services nginx-service
Name: nginx-service
Namespace: default
Labels: app=nginx
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"app":"nginx"},"name":"nginx-service","namespace":"default"},"s...
Selector: app=nginx
Type: ClusterIP
IP: 10.110.54.40
Port: http 80/TCP
TargetPort: 80/TCP
Endpoints: 10.244.2.22:80 #已和endpoints關聯
Session Affinity: None
Events: <none>刪除站點信息，使健康檢查異常
[root@node-1 demo]# kubectl exec -it nginx-tcp-liveness-probe /bin/bash
root@nginx-tcp-liveness-probe:/# rm -f /usr/share/nginx/html/test.html
查看pod健康檢查event日志
[root@node-1 demo]# kubectl get pods nginx-tcp-liveness-probe
NAME READY STATUS RESTARTS AGE
nginx-tcp-liveness-probe 0/1 Running 0 11m
[root@node-1 demo]# kubectl describe pods nginx-tcp-liveness-probe | tail
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 12m default-scheduler Successfully assigned default/nginx-tcp-liveness-probe to node-3
Normal Pulling 12m kubelet, node-3 Pulling image "nginx:latest"
Normal Pulled 11m kubelet, node-3 Successfully pulled image "nginx:latest"
Normal Created 11m kubelet, node-3 Created container nginx-tcp-liveness-probe
Normal Started 11m kubelet, node-3 Started container nginx-tcp-liveness-probe
Warning Unhealthy 119s (x32 over 11m) kubelet, node-3 Readiness probe failed: HTTP probe failed with statuscode: 404
查看endpoints
[root@node-1 demo]# kubectl describe endpoints nginx-service
Name: nginx-service
Namespace: default
Labels: app=nginx
Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2019-09-30T14:38:01Z
Subsets:
Addresses: <none>
NotReadyAddresses: 10.244.2.22 #健康檢查異常，此時加入到NotReady狀態
Ports:
Name Port Protocol
---- ---- --------
http 80 TCP
Events: <none>
查看service狀態，此時endpoints為空
[root@node-1 demo]# kubectl describe services nginx-service
Name: nginx-service
Namespace: default
Labels: app=nginx
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"app":"nginx"},"name":"nginx-service","namespace":"default"},"s...
Selector: app=nginx
Type: ClusterIP
IP: 10.110.54.40
Port: http 80/TCP
TargetPort: 80/TCP
Endpoints: #為空
Session Affinity: None
Events: <none>TKE中可以設定應用的健康檢查機制，健康檢查機制包含在不同的Workload中，可以通過模板生成健康監測機制，定義過程中可以選擇高級選項，默認健康檢查機制是關閉狀態，包含前面介紹的兩種探針：存活探針livenessProbe和就緒探針readinessProbe，根據需要分別開啟
開啟探針之后進入設置健康檢查，支持上述介紹的三種方法：執行命令檢查、TCP端口檢查，HTTP請求檢查
選擇不同的檢查方法填寫不同的參數即可，如啟動間隔，檢查間隔，響應超時，等參數，以HTTP請求檢查方法為例：
設置完成后創建workload時候會自動生成yaml文件，以剛創建的deployment為例，生成健康檢查yaml文件內容如下：
apiVersion: apps/v1beta2
kind: Deployment
metadata:
annotations:
deployment.kubernetes.io/revision: "1"
description: tke-health-check-demo
creationTimestamp: "2019-09-30T12:28:42Z"
generation: 1
labels:
k8s-app: tke-health-check-demo
qcloud-app: tke-health-check-demo
name: tke-health-check-demo
namespace: default
resourceVersion: "2060365354"
selfLink: /apis/apps/v1beta2/namespaces/default/deployments/tke-health-check-demo
uid: d6cf1f25-e37d-11e9-87fd-567eb17a3218
spec:
minReadySeconds: 10
progressDeadlineSeconds: 600
replicas: 1
revisionHistoryLimit: 10
selector:
matchLabels:
k8s-app: tke-health-check-demo
qcloud-app: tke-health-check-demo
strategy:
rollingUpdate:
maxSurge: 1
maxUnavailable: 0
type: RollingUpdate
template:
metadata:
creationTimestamp: null
labels:
k8s-app: tke-health-check-demo
qcloud-app: tke-health-check-demo
spec:
containers:
- image: nginx:latest
imagePullPolicy: Always
livenessProbe: #通過模板生成的健康檢查機制
failureThreshold: 1
httpGet:
path: /
port: 80
scheme: HTTP
periodSeconds: 3
successThreshold: 1
timeoutSeconds: 2
name: tke-health-check-demo
resources:
limits:
cpu: 500m
memory: 1Gi
requests:
cpu: 250m
memory: 256Mi
securityContext:
privileged: false
procMount: Default
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
dnsPolicy: ClusterFirst
imagePullSecrets:
- name: qcloudregistrykey
- name: tencenthubkey
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30本章介紹kubernetes中健康檢查兩種Probe：livenessProbe和readinessProbe，livenessProbe主要用于存活檢查，檢查容器內部運行狀態，readiness主要用于就緒檢查，是否可以接受流量，通常需要和service的endpoints結合，當就緒準備妥當時加入到endpoints中，當就緒異常時從endpoints中刪除，從而實現了services的健康檢查和服務探測機制。對于Probe機制提供了三種檢測的方法，分別適用于不同的場景：1. exec命令行，通過命令或shell實現健康檢查，2. tcpSocket通過TCP協議探測端口，建立tcp連接，3. httpGet通過建立http請求探測，讀者可多實操掌握其用法。
健康檢查：https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/
TKE健康檢查設置方法：https://cloud.tencent.com/document/product/457/32815
當你的才華撐不起你的野心時，你就應該靜下心來學習
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