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This article introduces how to conduct readinessProbe in kubernetes. The content is very detailed. Interested friends can use it for reference. I hope it will be helpful to you.

Just because the docker container starts successfully does not mean that the services in the container can handle external requests. For example, it takes a while for the java web project to start.

Kubernetes provides readiness probe to detect whether containers in pod can accept external traffic.

You can provide an interface in the java project to which kubernetes sends requests, and when this interface returns data, the service is ready to accept external requests.

Let's look at a simple example and prepare a spring boot project that provides an external interface. The port number for the following services is 10012

@ GetMapping ("/ test02/version")

Public String version () {

Return "app02/version/v1"

}

On the node node, write the Docker configuration file and mirror it

Dockerfile

FROM openjdk:8

ADD * .jar / app/app.jar

ADD entrypoint.sh / app/

# PORT= "10012" is the project port number

ENV PORT= "10012" TIME= "Asia/Shanghai" JAVA_OPS= "- Xmx256m-Xms256m-XX:+UseConcMarkSweepGC"

RUN set-e\

& & chmod + x / app/entrypoint.sh\

& & ln-snf / usr/share/zoneinfo/$TIME / etc/localtime\

& & echo $TIME > / etc/timezone

ENTRYPOINT ["/ app/entrypoint.sh"]

EXPOSE $PORT

STOPSIGNAL SIGTERM

Entrypoint.sh

#! / bin/sh

Exec java ${JAVA_OPS}-jar / app/app.jar

Make a mirror codingsoldier/app02:v1.

Docker build-t codingsoldier/app02:v1.

Write the deployment file on the master node

K8s-service.yaml

ApiVersion: v1

Kind: Service

Metadata:

Name: service-app02

Spec:

Selector:

App: app02

Ports:

-name: http

Port: 10012

TargetPort: 10012

K8s-app02.yaml

ApiVersion: apps/v1

Kind: Deployment

Metadata:

Name: deployment-app02

Spec:

Replicas: 2

Selector:

MatchLabels:

App: app02

Template:

Metadata:

Labels:

App: app02

Spec:

Containers:

-name: app02

Image: codingsoldier/app02:v1

Ports:

-name: http

ContainerPort: 10012

Deployment servic

Kubectl apply-f k8s-service

Kubectl apply-f k8s-app02

Get the ip of k8s-service

Kubectl get svc

Reopen a terminal, call the interface in a loop, do not turn off the terminal, keep it open.

While true;\

Curl http://10.101.75.203:10012/test02/version;\

Echo "";\

Do sleep 1;\

Done

Let's upgrade the version now.

1. Change the return value of / test02/version API to v2

@ GetMapping ("/ test02/version")

Public String version () {

Return "app02/version/v2"

}

2. Package it into jar and upload it to all node nodes.

3. Generate docker image

Docker build-t codingsoldier/app02:v2.

4. Modify the k8s-app02.yaml image to v2

Image: codingsoldier/app02:v2

5. Reopen a terminal and execute kubectl get pod-w to dynamically check the pod status.

6. Redeploy k8s-app02.yaml

Kubectl apply-f k8s-app02.yaml

In the monitoring of the circular invocation, you can see that the service is unable to provide the service for a short time.

The reason is: if the docker container starts successfully, K8s thinks the container can provide services. But in fact, when the docker container starts successfully, the java service has not been started, and the service cannot be provided to the outside world for the time being.

As a workaround, use readiness probe to detect whether containers in pod can accept external traffic.

1. Add a service-ready API to java project.

/ / Service ready API, which is provided to k8s for detection

@ GetMapping ("/ readiness")

Public String readiness () {

Return "yes"

}

2. K8s-app02.yaml plus ready probe

ReadinessProbe:

HttpGet:

Port: http

Path: / readiness

InitialDelaySeconds: 20

PeriodSeconds: 10

Detailed configuration of readinessProbe:

InitialDelaySeconds: how many seconds does it take to perform the probe for the first time after the container is started.

PeriodSeconds: the frequency at which probes are performed. The default is 10 seconds, with a minimum of 1 second.

TimeoutSeconds: probe timeout. Default 1 second, minimum 1 second.

SuccessThreshold: after a probe fails, at least how many consecutive probes are successful before they are considered successful. The default is 1. Must be 1 for liveness. The minimum value is 1.

FailureThreshold: after a successful probe, at least how many consecutive probe failures can be considered as failures. The default is 3. The minimum value is 1.

HttpGet configuration items:

Host: the hostname of the connection, which is connected to the IP of pod by default. You may want to set "Host" in http header instead of using IP.

Scheme: the schema used for the connection. The default is HTTP.

Path: the path of the HTTP server visited.

HttpHeaders: header of the custom request. HTTP runs a duplicate header.

Port: the port name or port number of the container being accessed. The port number must be between 1 and 65525.

3. Change the return value app02/version/v3 of / test02/version

4. Modify the version image: codingsoldier/app02:v3 of the image in k8s-app02.yaml

5. Type it into jar and upload it.

6. make a mirror image

Docker build-t codingsoldier/app02:v3.

7. Redeploy the service

Kubectl apply-f k8s-app02.yaml

Check the terminal of the circular call interface. The service is always available.

View terminals running kubectl get pod-w

1. The new pod is in the Running state, but the READY is 0 Universe 1. Pod is already running but not ready to receive external requests at this time

After 2 and 25 seconds, the new pod is in the Running state and the READY is 1 to 1. Pod can receive external requests

3. After the new pod is able to receive external requests, an old pod begins to terminate

4. Since the number of pod services is set to 2, another new pod is created at this time. The process is the same as above. After the new pod receives the request, the old pod is terminated.

So much for sharing about kubernetes readinessProbe. I hope the above content can be of some help to you and learn more knowledge. If you think the article is good, you can share it for more people to see.

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