Openshift中Pod的SpringBoot2健康檢查

Openshift中Pod的SpringBoot2應用程序健康檢查

1. 準備測試的SpringBoot工程, 須要Java 8 JDK or greater and Maven 3.3.x or greater.

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

假設您已經掌握基本JAVA應用程序開發，Openshift容器平臺已經部署成功。咱們的測試工程依賴庫Spring Boot Actuator2, 有如新特性

• 支持 Jersey RESTful Web 服務
• 支持基於反應式理念的 WebFlux Web App
• 新的端點映射
• 簡化用戶自定義端點的建立
• 加強端點的安全性

Actuator提供了13個接口，以下:

在Spring Boot 2.x中爲了安全起見，Actuator只開放了兩個端點/actuator/health和/actuator/info，能夠在配置文件中設置開關。

部署編譯jar文件到Openshift容器平臺

Openshift的部署過程簡述以下(這裏採用是二進制部署方式)：

--> 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

以上過程最近暴露Router, 方便咱們演示

演示過程：

第一回合

修改剛部署的deploymentConfig的yaml，增長readiness配置，以下：

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

對於以幾個參數，咱們說明下，你們須要理解

• initialDelaySeconds：容器啓動後第一次執行探測是須要等待多少秒。
• periodSeconds：執行探測的頻率。默認是10秒，最小1秒。
• timeoutSeconds：探測超時時間。默認1秒，最小1秒。
• successThreshold：探測失敗後，最少連續探測成功多少次才被認定爲成功。默認是 1。對於 liveness 必須是 1。最小值是 1。
• failureThreshold：探測成功後，最少連續探測失敗多少次才被認定爲失敗。默認是 3。最小值是 1。

或是採用openshift cli命令行來配置readiness:

oc set probe dc/app-cli \

--readiness \

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

--initial-delay-seconds=5

$ oc get pod -w

#剛纔修改 deploymentConfig，pod從新部署了

NAME READY                 STATUS   RESTARTS  AGE

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

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

執行HTTP API 來STOP中止Tomcat，curl http://${value-name-app}-MY_PROJECT_NAME.LOCAL_OPENSHIFT_HOSTNAME/api/stop,   注意此處URL相部署的DNS環境有關係

程序中日誌以下:

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'

#跟蹤pod的動態

$ 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

#咱們查閱pod的詳細描述

$ 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，咱們發現POD沒有被重啓，由於咱們只配置了readiness

第二回合

對以前部署後應用，增長health check， /actuator/health 是SpringBoot2.0的示例工程默認的健康檢查的端點

修改deploymentConfig，增長readiness與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

也能夠經過Web 控制檯來修改，示例截圖以下：

咱們看到 WEB UI的配置與yaml中參數是同樣的。

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

移動 probe

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

執行stop後，此時請求ROUTER已顯示，POD還在運行，瀏覽器返回

Application is not available

經過URL執行後，STOP tomcat，pod中程序部分日誌以下：

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'

過一下子，咱們監控pod動態

$ 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

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

後瀏覽器顯示：

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

此時POD已經被重啓，應用程序的日誌以下：

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

Annotations: kubernetes.io/created-by={"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"ReplicationController","namespace":"hshreport-stage","name":"health-demo-3","uid":"23ad2f21-347f-11ea-856c...

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

第二次咱們執行 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 請求返回結果:

{"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

Annotations: kubernetes.io/created-by={"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"ReplicationController","namespace":"hshreport-stage","name":"health-demo-3","uid":"23ad2f21-347f-11ea-856c...

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

發現，POD的名稱health-demo-3-02v11沒有變，演示到這兒結束

小結

Liveness probes可作三種檢查

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的區別

     readiness 就是意思是否能夠訪問，liveness就是是否存活。若是一個readiness 爲fail 的後果是把這個pod 的全部service 的endpoint裏面的改pod ip 刪掉，意思就這個pod對應的全部service都不會把請求轉到這pod來了。可是若是liveness 檢查結果是fail就會直接kill container，固然若是你的restart policy 是always 會重啓pod。

Readiness探針和Liveness探針都是用來檢測容器進程狀態的。區別在於前者關注的是是否把進程的服務地址加入Service的負載均衡列表；然後者則決定是否去重啓這個進程來排除故障。它們在進程的整個生命週期中都存在並且同時工做，職責分離。

Kubelet 能夠選擇是否執行在容器上運行的兩種探針執行和作出反應：

• livenessProbe：指示容器是否正在運行。若是存活探測失敗，則 kubelet 會殺死容器，而且容器將受到其 重啓策略 的影響。若是容器不提供存活探針，則默認狀態爲 Success。
• readinessProbe：指示容器是否準備好服務請求。若是就緒探測失敗，端點控制器將從與 Pod 匹配的全部 Service 的端點中刪除該 Pod 的 IP 地址。初始延遲以前的就緒狀態默認爲 Failure。若是容器不提供就緒探針，則默認狀態爲 Success。

最佳實踐

      通常來說，Readiness的執行間隔要比Liveness設置的較長一點比較好。由於當後端進程負載高的時候，咱們能夠暫時從轉發列表裏面摘除，可是Liveness決定的是進程是否重啓，其實這個時候進程不必定須要重啓。因此Liveness的檢測週期能夠稍微長一點，另外失敗的容忍數量也能夠多一點。具體根據實際狀況判斷吧。

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做者：Petter Liu
出處：http://www.cnblogs.com/wintersun/ 本文版權歸做者和博客園共有，歡迎轉載，但未經做者贊成必須保留此段聲明，且在文章頁面明顯位置給出原文鏈接，不然保留追究法律責任的權利。 該文章也同時發佈在個人獨立博客中-Petter Liu Blog。