Openshift中Pod的SpringBoot2应用程序健康检查

1. 准备测试的SpringBoot工程, 需要Java 8 JDK or greater and Maven 3.3.x or greater.

git clone https://github.com/megadotnet/Openshift-healthcheck-demo.git

假设您已经掌握基本JAVA应用程序开发，Openshift容器平台已经部署成功。我们的测试工程依赖库Spring Boot Actuator2, 有如新特性

支持 Jersey RESTful Web 服务
支持基于反应式理念的 WebFlux Web App
新的端点映射
简化用户自定义端点的创建
增强端点的安全性

Actuator提供了13个接口，如下:

在Spring Boot 2.x中为了安全起见，Actuator只开放了两个端点/actuator/health和/actuator/info，可以在配置文件中设置开关。

部署编译jar文件到Openshift容器平台

Openshift的部署过程简述如下(这里采用是二进制部署方式)：

--> Found image dc046fe (16 months old) in image stream "openshift/s2i-java" under tag "latest" for "s2i-java:latest"

Java S2I builder 1.0

--------------------

Platform for building Java (fatjar) applications with maven or gradle

Tags: builder, maven-3, gradle-2.6, java, microservices, fatjar

* A source build using binary input will be created

* The resulting image will be pushed to image stream "health-demo:latest"

* A binary build was created, use 'start-build --from-dir' to trigger a new build

--> Creating resources with label app=health-demo ...

imagestream "health-demo" created

buildconfig "health-demo" created

--> Success

Uploading directory "oc-build" as binary input for the build ...

build "health-demo-1" started

--> Found image fb46616 (5 minutes old) in image stream "hshreport-stage/health-demo" under tag "latest" for "health-demo:latest"

Java S2I builder 1.0

--------------------

Platform for building Java (fatjar) applications with maven or gradle

Tags: builder, maven-3, gradle-2.6, java, microservices, fatjar

* This image will be deployed in deployment config "health-demo"

* Ports 7575/tcp, 8080/tcp will be load balanced by service "health-demo"

* Other containers can access this service through the hostname "health-demo"

--> Creating resources with label app=health-demo ...

deploymentconfig "health-demo" created

service "health-demo" created

--> Success

Run 'oc status' to view your app.

route "health-demo" exposed

以上过程最近暴露Router, 方便我们演示

演示过程：

第一回合

修改刚部署的deploymentConfig的yaml，增加readiness配置，如下：

---
readinessProbe:
   failureThreshold: 3
   httpGet:
     path: /actuator/health
     port: 8080
     scheme: HTTP
   initialDelaySeconds: 10
   periodSeconds: 10
   successThreshold: 1
   timeoutSeconds: 1

对于以几个参数，我们说明下，大家需要理解

initialDelaySeconds：容器启动后第一次执行探测是需要等待多少秒。
periodSeconds：执行探测的频率。默认是10秒，最小1秒。
timeoutSeconds：探测超时时间。默认1秒，最小1秒。
successThreshold：探测失败后，最少连续探测成功多少次才被认定为成功。默认是 1。对于 liveness 必须是 1。最小值是 1。
failureThreshold：探测成功后，最少连续探测失败多少次才被认定为失败。默认是 3。最小值是 1。

或是采用openshift cli命令行来配置readiness:

oc set probe dc/app-cli \

--readiness \

--get-url=http://:8080/notreal \

--initial-delay-seconds=5

$ oc get pod -w

#刚才修改 deploymentConfig，pod重新部署了

NAME READY STATUS RESTARTS AGE

health-demo-1-build 0/1 Completed 0 16m

health-demo-2-sqh4z 1/1 Running 0 11m

执行HTTP API 来STOP停止Tomcat，curl http://${value-name-app}-MY_PROJECT_NAME.LOCAL_OPENSHIFT_HOSTNAME/api/stop, 注意此处URL相部署的DNS环境有关系

程序中日志如下:

Stopping Tomcat context.

2020-01-11 22:17:21.004 INFO 1 --- [nio-8080-exec-9] o.apache.catalina.core.StandardWrapper : Waiting for [1] instance(s) to be deallocated for Servlet [dispatcherServlet]

2020-01-11 22:17:22.008 INFO 1 --- [nio-8080-exec-9] o.apache.catalina.core.StandardWrapper : Waiting for [1] instance(s) to be deallocated for Servlet [dispatcherServlet]

2020-01-11 22:17:23.012 INFO 1 --- [nio-8080-exec-9] o.apache.catalina.core.StandardWrapper : Waiting for [1] instance(s) to be deallocated for Servlet [dispatcherServlet]

2020-01-11 22:17:23.114 INFO 1 --- [nio-8080-exec-9] o.a.c.c.C.[Tomcat].[localhost].[/] : Destroying Spring FrameworkServlet 'dispatcherServlet'

#跟踪pod的动态

$ oc get pod –w

NAME READY STATUS RESTARTS AGE

health-demo-1-build 0/1 Completed 0 16m

health-demo-2-sqh4z 1/1 Running 0 11m

health-demo-2-sqh4z 0/1 Running 0 13m

#我们查阅pod的详细描述

$ oc describe pod/health-demo-2-sqh4z

Name: health-demo-2-sqh4z

Namespace: hshreport-stage

Security Policy: restricted

Node: openshift-lb-02.hsh.io/10.108.78.145

Start Time: Sat, 11 Jan 2020 22:08:59 +0800

Labels: app=health-demo

deployment=health-demo-2

deploymentconfig=health-demo

Annotations: kubernetes.io/created-by={"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"ReplicationController","namespace":"hshreport-stage","name":"health-demo-2","uid":"e6436263-347b-11ea-856c...

openshift.io/deployment-config.latest-version=2

openshift.io/deployment-config.name=health-demo

openshift.io/deployment.name=health-demo-2

openshift.io/generated-by=OpenShiftNewApp

openshift.io/scc=restricted

Status: Running

IP: 10.131.5.124

Controllers: ReplicationController/health-demo-2

Containers:

health-demo:

Container ID: docker://25cdf63f55d839610287b4e2a3cc67182377bfe5010990357f83329286c7e64f

Image: docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6

Image ID: docker-pullable://docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6

Ports: 7575/TCP, 8080/TCP

State: Running

Started: Sat, 11 Jan 2020 22:09:09 +0800

Ready: False

Restart Count: 0

Readiness: http-get http://:8080/actuator/health delay=10s timeout=1s period=10s #success=1 #failure=3

Environment:

APP_OPTIONS: -Xmx512m -Xss512k -Djava.net.preferIPv4Stack=true -Dfile.encoding=utf-8

DEPLOYER: liu.xxxxx (Administrator) (cicd-1.1.24)

REVISION:

SPRING_PROFILES_ACTIVE: stage

TZ: Asia/Shanghai

Mounts:

/var/run/secrets/kubernetes.io/serviceaccount from default-token-n4klp (ro)

Conditions:

Type Status

Initialized True

Ready False

PodScheduled True

Volumes:

default-token-n4klp:

Type: Secret (a volume populated by a Secret)

SecretName: default-token-n4klp

Optional: false

QoS Class: BestEffort

Node-Selectors: region=primary

Tolerations: <none>

Events:

FirstSeen LastSeen Count From SubObjectPath Type Reason Message

--------- -------- ----- ---- ------------- -------- ------ -------

16m 16m 1 default-scheduler Normal Scheduled Successfully assigned health-demo-2-sqh4z to openshift-lb-02.hsh.io

16m 16m 1 kubelet, openshift-lb-02.hsh.io spec.containers{health-demo} Normal Pulling pulling image "docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6"

16m 16m 1 kubelet, openshift-lb-02.hsh.io spec.containers{health-demo} Normal Pulled Successfully pulled image "docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6"

15m 15m 1 kubelet, openshift-lb-02.hsh.io spec.containers{health-demo} Normal Created Created container

15m 15m 1 kubelet, openshift-lb-02.hsh.io spec.containers{health-demo} Normal Started Started container

15m 15m 1 kubelet, openshift-lb-02.hsh.io spec.containers{health-demo} Warning Unhealthy Readiness probe failed: Get http://10.131.5.124:8080/actuator/health: dial tcp 10.131.5.124:8080: getsockopt: connection refused

7m 5m 16 kubelet, openshift-lb-02.hsh.io spec.containers{health-demo} Warning Unhealthy Readiness probe failed: HTTP probe failed with statuscode: 404

注意上面的WARN事件，我们发现POD没有被重启，因为我们只配置了readiness

第二回合

对之前部署后应用，增加health check， /actuator/health 是SpringBoot2.0的示例工程默认的健康检查的端点

修改deploymentConfig，增加readiness与liveness

---
livenessProbe:
   failureThreshold: 3
   httpGet:
     path: /actuator/health
     port: 8080
     scheme: HTTP
   initialDelaySeconds: 60
   periodSeconds: 10
   successThreshold: 1
   timeoutSeconds: 1
name: health-demo
ports:
   -
     containerPort: 7575
     protocol: TCP
   -
     containerPort: 8080
     protocol: TCP
readinessProbe:
   failureThreshold: 3
   httpGet:
     path: /actuator/health
     port: 8080
     scheme: HTTP
   initialDelaySeconds: 10
   periodSeconds: 10
   successThreshold: 1
   timeoutSeconds: 1

也可以通过Web 控制台来修改，示例截图如下：

我们看到 WEB UI的配置与yaml中参数是一样的。

oc cli命令行方法 #Configure Liveness/Readiness probes on DCs

oc set probe dc cotd1 --liveness -- echo ok

oc set probe dc/cotd1 --readiness --get-url=http://:8080/index.php --initial-delay-seconds=2

TCP的示例

oc set probe dc/blog --readiness --liveness --open-tcp 8080

移动 probe

$ oc set probe dc/blog --readiness --liveness –remove

执行stop后，此时请求ROUTER已显示，POD还在运行，浏览器返回

Application is not available

通过URL执行后，STOP tomcat，pod中程序部分日志如下：

Stopping Tomcat context.

2020-01-11 22:17:21.004 INFO 1 --- [nio-8080-exec-9] o.apache.catalina.core.StandardWrapper : Waiting for [1] instance(s) to be deallocated for Servlet [dispatcherServlet]

2020-01-11 22:17:22.008 INFO 1 --- [nio-8080-exec-9] o.apache.catalina.core.StandardWrapper : Waiting for [1] instance(s) to be deallocated for Servlet [dispatcherServlet]

2020-01-11 22:17:23.012 INFO 1 --- [nio-8080-exec-9] o.apache.catalina.core.StandardWrapper : Waiting for [1] instance(s) to be deallocated for Servlet [dispatcherServlet]

2020-01-11 22:17:23.114 INFO 1 --- [nio-8080-exec-9] o.a.c.c.C.[Tomcat].[localhost].[/] : Destroying Spring FrameworkServlet 'dispatcherServlet'

过一会儿，我们监控pod动态

$ oc get pod -w

NAME READY STATUS RESTARTS AGE

health-demo-1-build 0/1 Completed 0 33m

health-demo-3-02v11 1/1 Running 0 5m

health-demo-3-02v11 0/1 Running 0 7m

health-demo-3-02v11 0/1 Running 1 7m

$ oc get pod

NAME READY STATUS RESTARTS AGE

health-demo-1-build 0/1 Completed 0 36m

health-demo-3-02v11 1/1 Running 1 8m

请求 curl http://${value-name-app}-MY_PROJECT_NAME.LOCAL_OPENSHIFT_HOSTNAME/api/greeting?name=s2i

后浏览器显示：

{"content":"Hello, s2i!"} (the recovery took 41.783 seconds)

此时POD已经被重启，应用程序的日志如下：

2020-01-11 22:35:13.597 INFO 1 --- [ main] s.b.a.e.w.s.WebMvcEndpointHandlerMapping : Mapped "{[/actuator],methods=[GET],produces=[application/vnd.spring-boot.actuator.v2+json || application/json]}" onto protected java.util.Map<java.lang.String, java.util.Map<java.lang.String, org.springframework.boot.actuate.endpoint.web.Link>> org.springframework.boot.actuate.endpoint.web.servlet.WebMvcEndpointHandlerMapping.links(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)

2020-01-11 22:35:13.750 INFO 1 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup

2020-01-11 22:35:13.873 INFO 1 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''

2020-01-11 22:35:13.882 INFO 1 --- [ main] dev.snowdrop.example.ExampleApplication : Started ExampleApplication in 8.061 seconds (JVM running for 9.682)

2020-01-11 22:35:22.445 INFO 1 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring FrameworkServlet 'dispatcherServlet'

2020-01-11 22:35:22.445 INFO 1 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization started

2020-01-11 22:35:22.485 INFO 1 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization completed in 39 ms

$ oc describe pod/health-demo-3-02v11

Name: health-demo-3-02v11

Namespace: hshreport-stage

Security Policy: restricted

Node: openshift-node-04.hsh.io/10.108.78.139

Start Time: Sat, 11 Jan 2020 22:32:12 +0800

Labels: app=health-demo

deployment=health-demo-3

deploymentconfig=health-demo

openshift.io/deployment-config.latest-version=3

openshift.io/deployment-config.name=health-demo

openshift.io/deployment.name=health-demo-3

openshift.io/generated-by=OpenShiftNewApp

openshift.io/scc=restricted

Status: Running

IP: 10.129.5.178

Controllers: ReplicationController/health-demo-3

Containers:

health-demo:

Container ID: docker://3e5a6b081022c914d8e118dce829294570e54f441b84394a2b13f6eebb4f5c74

Image: docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6

Image ID: docker-pullable://docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6

Ports: 7575/TCP, 8080/TCP

State: Running

Started: Sat, 11 Jan 2020 22:35:04 +0800

Last State: Terminated

Reason: Error

Exit Code: 143

Started: Sat, 11 Jan 2020 22:32:15 +0800

Finished: Sat, 11 Jan 2020 22:35:03 +0800

Ready: True

Restart Count: 1

Liveness: http-get http://:8080/actuator/health delay=60s timeout=1s period=10s #success=1 #failure=3

Readiness: http-get http://:8080/actuator/health delay=10s timeout=1s period=10s #success=1 #failure=3

Environment:

APP_OPTIONS: -Xmx512m -Xss512k -Djava.net.preferIPv4Stack=true -Dfile.encoding=utf-8

DEPLOYER: liu.xxxxxx(Administrator) (cicd-1.1.24)

REVISION:

SPRING_PROFILES_ACTIVE: stage

TZ: Asia/Shanghai

Mounts:

/var/run/secrets/kubernetes.io/serviceaccount from default-token-n4klp (ro)

Conditions:

Type Status

Initialized True

Ready True

PodScheduled True

Volumes:

default-token-n4klp:

Type: Secret (a volume populated by a Secret)

SecretName: default-token-n4klp

Optional: false

QoS Class: BestEffort

Node-Selectors: region=primary

Tolerations: <none>

Events:

FirstSeen LastSeen Count From SubObjectPath Type Reason Message

--------- -------- ----- ---- ------------- -------- ------ -------

17m 17m 1 default-scheduler Normal Scheduled Successfully assigned health-demo-3-02v11 to openshift-node-04.hsh.io

15m 14m 3 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Warning Unhealthy Liveness probe failed: HTTP probe failed with statuscode: 404

15m 14m 3 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Warning Unhealthy Readiness probe failed: HTTP probe failed with statuscode: 404

17m 14m 2 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Pulling pulling image "docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6"

17m 14m 2 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Pulled Successfully pulled image "docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6"

17m 14m 2 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Created Created container

14m 14m 1 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Killing Killing container with id docker://health-demo:pod "health-demo-3-02v11_hshreport-stage(27e5a1da-347f-11ea-856c-0050568d3d78)" container "health-demo" is unhealthy, it will be killed and re-created.

17m 14m 2 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Started Started container

第二次我们执行 STOP的HTTP API

$ oc get pod –w

NAME READY STATUS RESTARTS AGE

health-demo-1-build 0/1 Completed 0 47m

health-demo-3-02v11 1/1 Running 1 19m

health-demo-3-02v11 0/1 Running 1 19m

health-demo-3-02v11 0/1 Running 2 20m

health-demo-3-02v11 1/1 Running 2 20m

$ oc get pod

NAME READY STATUS RESTARTS AGE

health-demo-1-build 0/1 Completed 0 49m

health-demo-3-02v11 1/1 Running 2 21

HTTP 请求返回结果:

{"content":"Hello, s2i!"} (the recovery took 51.984 seconds)

$ oc describe pod/health-demo-3-02v11

Name: health-demo-3-02v11

Namespace: hshreport-stage

Security Policy: restricted

Node: openshift-node-04.hsh.io/10.108.78.139

Start Time: Sat, 11 Jan 2020 22:32:12 +0800

Labels: app=health-demo

deployment=health-demo-3

deploymentconfig=health-demo

openshift.io/deployment-config.latest-version=3

openshift.io/deployment-config.name=health-demo

openshift.io/deployment.name=health-demo-3

openshift.io/generated-by=OpenShiftNewApp

openshift.io/scc=restricted

Status: Running

IP: 10.129.5.178

Controllers: ReplicationController/health-demo-3

Containers:

health-demo:

Container ID: docker://e12d1975aa26b07643ae1666ae6bce7ceab4f25fb4c6c947427ba526ad6fdf7b

Image: docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6

Image ID: docker-pullable://docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6

Ports: 7575/TCP, 8080/TCP

State: Running

Started: Sat, 11 Jan 2020 22:47:14 +0800

Last State: Terminated

Reason: Error

Exit Code: 143

Started: Sat, 11 Jan 2020 22:35:04 +0800

Finished: Sat, 11 Jan 2020 22:47:02 +0800

Ready: True

Restart Count: 2

Liveness: http-get http://:8080/actuator/health delay=60s timeout=1s period=10s #success=1 #failure=3

Readiness: http-get http://:8080/actuator/health delay=10s timeout=1s period=10s #success=1 #failure=3

Environment:

APP_OPTIONS: -Xmx512m -Xss512k -Djava.net.preferIPv4Stack=true -Dfile.encoding=utf-8

DEPLOYER: liu.xxxxx (Administrator) (cicd-1.1.24)

REVISION:

SPRING_PROFILES_ACTIVE: stage

TZ: Asia/Shanghai

Mounts:

/var/run/secrets/kubernetes.io/serviceaccount from default-token-n4klp (ro)

Conditions:

Type Status

Initialized True

Ready True

PodScheduled True

Volumes:

default-token-n4klp:

Type: Secret (a volume populated by a Secret)

SecretName: default-token-n4klp

Optional: false

QoS Class: BestEffort

Node-Selectors: region=primary

Tolerations: <none>

Events:

FirstSeen LastSeen Count From SubObjectPath Type Reason Message

--------- -------- ----- ---- ------------- -------- ------ -------

21m 21m 1 default-scheduler Normal Scheduled Successfully assigned health-demo-3-02v11 to openshift-node-04.hsh.io

21m 6m 3 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Pulling pulling image "docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6"

19m 6m 6 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Warning Unhealthy Liveness probe failed: HTTP probe failed with statuscode: 404

19m 6m 6 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Warning Unhealthy Readiness probe failed: HTTP probe failed with statuscode: 404

18m 6m 2 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Killing Killing container with id docker://health-demo:pod "health-demo-3-02v11_hshreport-stage(27e5a1da-347f-11ea-856c-0050568d3d78)" container "health-demo" is unhealthy, it will be killed and re-created.

21m 6m 3 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Pulled Successfully pulled image "docker-registry.default.svc:5000/hshreport-stage/health-demo@sha256:292f09b7d9ca9bc12560febe3f4ba73e50b3c1a5701cbd55689186e844157fb6"

21m 6m 3 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Created Created container

21m 6m 3 kubelet, openshift-node-04.hsh.io spec.containers{health-demo} Normal Started Started container

#看下事件

$ oc get ev

LASTSEEN FIRSTSEEN COUNT NAME KIND SUBOBJECT TYPE REASON SOURCE MESSAGE

29m 41m 6 health-demo-3-02v11 Pod spec.containers{health-demo} Warning Unhealthy kubelet, openshift-node-04.hsh.io Liveness probe failed: HTTP probe failed with statuscode: 404

29m 41m 6 health-demo-3-02v11 Pod spec.containers{health-demo} Warning Unhealthy kubelet, openshift-node-04.hsh.io Readiness probe failed: HTTP probe failed with statuscode: 404

29m 41m 2 health-demo-3-02v11 Pod spec.containers{health-demo} Normal Killing kubelet, openshift-node-04.hsh.io Killing container with id docker://health-demo:pod "health-demo-3-02v11_hshreport-stage(27e5a1da-347f-11ea-856c-0050568d3d78)" container "health-demo" is unhealthy, it will be killed and re-created.

19m 19m 1 health-demo-3-02v11 Pod spec.containers{health-demo} Normal Killing kubelet, openshift-node-04.hsh.io Killing container with id docker://health-demo:Need to kill Pod

44m 44m 1 health-demo-3-deploy Pod Normal Scheduled default-scheduler Successfully assigned health-demo-3-deploy to openshift-lb-02.hsh.io

44m 44m 1 health-demo-3-deploy Pod spec.containers{deployment} Normal Pulled kubelet, openshift-lb-02.hsh.io Container image "openshift/origin-deployer:v3.6.1" already present on machine

44m 44m 1 health-demo-3-deploy Pod spec.containers{deployment} Normal Created kubelet, openshift-lb-02.hsh.io Created container

44m 44m 1 health-demo-3-deploy Pod spec.containers{deployment} Normal Started kubelet, openshift-lb-02.hsh.io Started container

44m 44m 1 health-demo-3 ReplicationController Normal SuccessfulCreate replication-controller Created pod: health-demo-3-02v11

19m 19m 1 health-demo-3 ReplicationController Normal SuccessfulDelete

发现，POD的名称health-demo-3-02v11没有变，演示到这儿结束

小结

Liveness probes可做三种检查

HTTP(S) checks—Checks a given URL endpoint served by the container, and evaluates the HTTP response code.

Container execution check—A command, typically a script, that’s run at intervals to verify that the container is behaving as expected. A non-zero exit code from the command results in a liveness check failure.

TCP socket checks—Checks that a TCP connection can be established on a specific TCP port in the application pod.

Readiness和liveness的区别

readiness 就是意思是否可以访问，liveness就是是否存活。如果一个readiness 为fail 的后果是把这个pod 的所有service 的endpoint里面的改pod ip 删掉，意思就这个pod对应的所有service都不会把请求转到这pod来了。但是如果liveness 检查结果是fail就会直接kill container，当然如果你的restart policy 是always 会重启pod。

Readiness探针和Liveness探针都是用来检测容器进程状态的。区别在于前者关注的是是否把进程的服务地址加入Service的负载均衡列表；而后者则决定是否去重启这个进程来排除故障。它们在进程的整个生命周期中都存在而且同时工作，职责分离。

Kubelet 可以选择是否执行在容器上运行的两种探针执行和做出反应：

livenessProbe：指示容器是否正在运行。如果存活探测失败，则 kubelet 会杀死容器，并且容器将受到其重启策略的影响。如果容器不提供存活探针，则默认状态为 Success。
readinessProbe：指示容器是否准备好服务请求。如果就绪探测失败，端点控制器将从与 Pod 匹配的所有 Service 的端点中删除该 Pod 的 IP 地址。初始延迟之前的就绪状态默认为 Failure。如果容器不提供就绪探针，则默认状态为 Success。

最佳实践

一般来讲，Readiness的执行间隔要比Liveness设置的较长一点比较好。因为当后端进程负载高的时候，我们可以暂时从转发列表里面摘除，但是Liveness决定的是进程是否重启，其实这个时候进程不一定需要重启。所以Liveness的检测周期可以稍微长一点，另外失败的容忍数量也可以多一点。具体根据实际情况判断吧。

今天先到这儿，希望对云原生，技术领导力，企业管理，系统架构设计与评估，团队管理, 项目管理, 产品管管，团队建设有参考作用 , 您可能感兴趣的文章:
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作者：Petter Liu
出处：http://www.cnblogs.com/wintersun/
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。该文章也同时发布在我的独立博客中-Petter Liu Blog。

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Openshift中Pod的SpringBoot2健康检查

Openshift中Pod的SpringBoot2应用程序健康检查

演示过程：

第一回合

第二回合

小结

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