DO188 - ch08s05

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Lab: Container Orchestration with Kubernetes and OpenShift

Debug and deploy a multi-container application to the Red Hat OpenShift Container Platform (RHOCP).

Outcomes

You should be able to:

Verify and correct the configuration of the Service and Deployment RHOCP objects.
Deploy RHOCP objects.

In this exercise, your task is to deploy the quotes application to RHOCP.

The quotes application uses the quotes-api and quotes-ui containerized microservices.

Your colleague managed to deploy the first tier of the application, the quotes-ui container, to RHOCP. However, the pod crashes and does not respond to requests. Additionally, the colleague faces difficulties when trying to deploy the quotes-api container to RHOCP. You, the RHOCP expert in the company, are tasked with helping your colleague.

As the student user on the workstation machine, use the lab command to:

Create the ocp-lab project.
Deploy the quotes-ui microservice.

[student@workstation ~]$ lab start openshift-lab

The lab script continuously evaluates the objectives of this lab. Keep the script running in a terminal window and complete the objectives of this lab from a new terminal window.

Instructions

[student@workstation ~]$ oc login -u developer -p developer \
https://api.ocp4.example.com:6443
Login successful.

...output omitted...

Ensure that you use the ocp-lab project.

[student@workstation ~]$ oc project ocp-lab
Already on project "ocp-lab" on server "https://api.ocp4.example.com:6443".

Change into the ~/DO188/labs/openshift-lab/ directory.
This directory contains the quotes-api YAML files that your colleague created. Be aware that the YAML files might contain mistakes.
```
[student@workstation ~]$ cd ~/DO188/labs/openshift-lab/
```

Use the deployment.yaml file to deploy the quotes-api container in the ocp-lab RHOCP project.

Try to create the deployment by using the deployment.yaml file.

[student@workstation openshift-lab]$ oc create -f deployment.yaml
The Deployment "quotes-api" is invalid: spec.template.metadata.labels: Invalid value: map[string]string{"app":"quotes-api"}: `selector` does not match template `labels`

The deployment defines an application pod with the app=quotes-api label. However, the spec.selector.matchLabels field uses a different label.

Open the deployment.yaml file in a text editor, such as gedit, and modify the spec.selector.matchLabels field to use the same label as the spec.template.metadata.labels field.

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: quotes-api
  name: quotes-api
spec:
  replicas: 1
  selector:
    matchLabels:
      app: quotes-api
  template:
    metadata:
      labels:
        app: quotes-api
    spec:
      containers:
      - image: registry.ocp4.example.com:8443/redhattraining/podman-quotes-api:openshift
        name: podman-quotes-api

Create the deployment by using the deployment.yaml file.
```
[student@workstation openshift-lab]$ oc create -f deployment.yaml
Warning: would violate PodSecurity ...output omitted...
deployment.apps/quotes-api created
```
Note
You can ignore pod security warnings for exercises in this course. Red Hat OpenShift uses the Security Context Constraints controller to provide safe defaults for pod security.

Verify that the quotes-api application pod is in the RUNNING state.

[student@workstation openshift-lab]$ oc get po
NAME                          READY   STATUS             RESTARTS        AGE
quotes-api-6c9f758574-nk8kd   1/1     Running            0               5s
quotes-ui-d7d457674-mljrb     0/1     CrashLoopBackOff   15 (3m9s ago)   55m

If the application pod is in the ContainerCreating state, then execute the previous command again after a few seconds.

Use the service.yaml file to configure the quotes-ui container networking in the ocp-lab project.

Configure the service.yaml file to conform to the following requirements:

The quotes-ui container must reach the quotes-api container at the http://quotes-api:8080 URL.
The quotes-api container listens on port 8080 by default.
Deploy the quotes-ui container after the quotes-api container becomes available on the quotes-api host. The application architect advised you to restart the quotes-ui application if it is deployed in the incorrect order.

Note

If you make a mistake, delete and recreate the Service object.

For example, you can use the oc delete -f service.yaml command to delete the Service object.

Open the service.yaml file in a text editor, such as gedit. Then, configure the service to serve on port 8080.

...file omitted...
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 3000
  selector:
    app: quotes

Configure the service to send requests to port 8080.

...file omitted...
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
  selector:
    app: quotes

Configure the service to send requests to pods with the quotes-api label.

...file omitted...
spec:
  ports:
  - port: 8080
    protocol: TCP
    targetPort: 8080
  selector:
    app: quotes-api

Configure the service to be available on the quotes-api hostname.

apiVersion: v1
kind: Service
metadata:
  labels:
    app: quotes
  name: quotes-api
...file omitted...

Create the service by using the service.yaml file.

[student@workstation openshift-lab]$ oc create -f service.yaml
service/quotes-api created

Verify the service configuration.

The endpoint IP address might differ in your output.

[student@workstation openshift-lab]$ oc describe service quotes-api
Name:              quotes-api
Namespace:         ocp-lab
Labels:            app=quotes
Annotations:       <none>
Selector:          app=quotes-api
...output omitted...
Port:              <unset>  8080/TCP
TargetPort:        8080/TCP
Endpoints:         10.8.0.102:8080
...output omitted...

If your output differs from the highlighted output of the previous command, return to the previous steps and ensure you configured your service correctly.

Verify that the quotes-ui container is still failing.

[student@workstation openshift-lab]$ oc get po
NAME                          READY   STATUS             RESTARTS        AGE
quotes-api-6c9f758574-nk8kd   1/1     Running            0               20m
quotes-ui-d7d457674-mljrb     0/1     CrashLoopBackOff   15 (3m9s ago)   55m

Restart the quotes-ui container.

You can delete containers that contain the app=quotes-ui label, and let the quotes-ui deployment recreate the container.

[student@workstation openshift-lab]$ oc delete pod -l app=quotes-ui
pod "quotes-ui-d7d457674-9cw7l" deleted

Then, verify that the quotes-ui deployment created a new container.

[student@workstation openshift-lab]$ oc get po
NAME                          READY   STATUS    RESTARTS   AGE
quotes-api-6c9f758574-nk8kd   1/1     Running   0          39m
quotes-ui-d7d457674-rbkl7     1/1     Running   0          67s

In a web browser, navigate to http://quotes-ui-ocp-lab.apps.ocp4.example.com and verify that the application works.

Finish

As the student user on the workstation machine, use the lab command to complete this exercise. This is important to ensure that resources from previous exercises do not impact upcoming exercises.

[student@workstation ~]$ lab finish openshift-lab

Discuss Red Hat OpenShift Development I: Introduction to Containers with Podman

Go to community

Red Hat OpenShift Development I: Introduction to Containers with Podman (DO188)

Haley_Ruccio

26 lip 2023

A developer introduction to building and managing containers with Podman for deploying applications on Red Hat OpenShift Container Platform.Red Hat OpenShift Development I: Introduction to Containers with Podman (DO188) introduces students to building, running, and managing containers with Podman and Red Hat OpenShift. This course helps students build the core skills for developing containerized applications through hands-on experience. These skills can be applied using all versions of OpenShift, including Red Hat OpenShift on AWS (ROSA), Azure Red Hat OpenShift, and OpenShift Container Platform.This course is based on Red Hat® Enterprise Linux® 8, Podman 4.2 and Red Hat OpenShift® 4.12.Course content summaryIntroduction to containersRun containers with Podman CLI and Podman DesktopBuild custom container imagesManage container imagesRemote debugging with containersBasic container networkingPersist data with containersRun multi-container applicationsTroubleshoot Container DeploymentsOrchestrate containers with OpenShift and KubernetesAudience for this courseDevelopers and Site Reliability Engineers that are new to container technology.System administrators and platform operators who are interested in managing OpenShift clusters and containerized applications should enroll in Red Hat OpenShift Administration I: Containers & Kubernetes (DO180).Prerequisites for this courseTake our free assessment to gauge whether this offering is the best fit for your skills.Some experience with web application architectures and their corresponding technologies.Experience in the use of a Linux terminal session, issuing operating system commands, and familiarity with shell scripting is recommended.Technology considerationsRequires internet connection.

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Welcome to the Red Hat OpenShift Development: Intro to containers with Podman (DO188) group!

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We are excited to launch a space dedicated to the Red Hat Training courseRed Hat OpenShift Development I: Introduction to Containers with Podman! To gain the most value from this group - click the "Join Group" button in the upper right hand corner.We encourage group members to collaborate in this group to discuss topics, ask questions, share best practices and tips, provide course feedback, and share their accomplishments as it relates to DO188.Read more about Red Hat OpenShift Development: Intro to containers with Podman here.

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Revision: do188-4.14-8c43a16