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Source to Image: Publish an App without a Dockerfile

Source-to-Image (S2I) is a toolkit and workflow for building reproducible container images from source code. S2I produces ready-to-run images by injecting source code into a container image and letting the container prepare that source code for execution. KubeSphere integrates S2I to automatically build images and publish them to Kubernetes without any Dockerfile.

This tutorial demonstrates how to use S2I to import source code of a Java sample project into KubeSphere by creating a Service. Based on the source code, the KubeSphere Image Builder will create a Docker image, push it to a target repository and publish it to Kubernetes.

build-process

Prerequisites

  • You need to enable the KubeSphere DevOps System as S2I is integrated into it.
  • You need to create a GitHub account and a Docker Hub account. GitLab and Harbor are also supported. This tutorial uses a GitHub repository to provide the source code for building and pushes an image to Docker Hub.
  • You need to create a workspace, a project and an account (project-regular). The account must be invited to the project with the role of operator. For more information, see Create Workspaces, Projects, Accounts and Roles.
  • Set a CI dedicated node for building images. This is not mandatory but recommended for the development and production environment as it caches dependencies and reduces build time. For more information, see Set a CI Node for Dependency Caching.

Use Source-to-Image (S2I)

Step 1: Fork the example repository

Log in to GitHub and fork the GitHub repository devops-java-sample to your personal GitHub account.

fork-repository

Step 2: Create Secrets

Log in to KubeSphere as project-regular. Go to your project and create a Secret for Docker Hub and GitHub respectively. For more information, see Create the Most Common Secrets.

Note

You do not need to create the GitHub Secret if your forked repository is open to the public.

Step 3: Create a Service

  1. In the same project, navigate to Services under Application Workloads and click Create.

    create-service

  2. Choose Java under Build a New Service from Source Code Repository, name it s2i-demo and click Next.

    select-lang-type

    Note

    KubeSphere has integrated common S2I templates such as Java, Node.js and Python. If you want to use other languages or customize your S2I templates, see Customize S2I Templates.
  3. On the Build Settings page, provide the following information accordingly and click Next.

    build-settings

    Service Type: Select Stateless Service for this example. For more information about different Services, see Service Type.

    Build Environment: Select kubesphere/java-8-centos7:v2.1.0.

    Code URL: The source code repository address (currently support Git). You can specify the code branch and the relative path in the source code terminal. The URL supports HTTP and HTTPS. Paste the forked repository URL (your own repository address) into this field.

    copy-repo-code

    Branch: The branch that is used for image building. Enter master for this tutorial. You can enter dependency for a cache test.

    Secret: You do not need to provide any Secret for a public repository. Select the GitHub Secret if you want to use a private repository.

    imageName: Customize an image name. As this tutorial will push an image to Docker Hub, enter dockerhub_username/s2i-sample. dockerhub_username is your Docker ID and make sure it has the permission to push and pull images.

    tag: The image tag. Enter latest.

    Target image repository: Select the Docker Hub Secret as the image is pushed to Docker Hub.

    Advanced Settings: You can define the code relative path. Use the default / for this field.

  4. On the Container Settings page, scroll down to Service Settings to set the access policy for the container. Select HTTP for Protocol, customize the name (for example, http-1), and enter 8080 for both Container Port and Service Port.

    service-settings

  5. Scroll down to Health Checker and check it. Set a readiness probe by filling out the following parameters. Click when you finish setting the probe and then click Next to continue.

    health-checker

    HTTP Request: Select HTTP as the protocol, enter / as the path (root path in this tutorial), and enter 8080 as the port exposed.

    Initial Delays: The number of seconds after the container has started before the liveness probe is initiated. Enter 30 for this field.

    Timeouts: The number of seconds after which the probe times out. Enter 10 for this field.

    For other fields, use the default value directly. For more information about how to configure probes and set other parameters on the Container Settings page, see Container Image Settings.

  6. On the Mount Volumes page, you can add a volume for the container. For more information, see Volumes. Click Next to continue.

  7. On the Advanced Settings page, check Internet Access and select NodePort as the access method. Click Create to finish the whole process.

    create-finish

  8. Click Image Builder from the navigation bar and you can see that the example image is being built.

    building

Step 4: Check results

  1. Wait for a while and you can see the status of the image has reached Successful.

    success-result

  2. Click this image to go to its detail page. Under Job Records, click the arrow icon on the right of a record to see building logs. You can see Build completed successfully at the end of the log if everything runs normally.

    build-log

  3. Go back to the previous page, and you can see the corresponding Job, Deployment and Service of the image have been all created successfully.

    Service

    service

    Deployment

    deployment

    Job

    job

  4. In your Docker Hub repository, you can see that KubeSphere has pushed the image to the repository with the expected tag.

    docker-image

Step 5: Access the S2I Service

  1. On the Services page, click the S2I Service to go to its detail page.

    service-detail

  2. To access the Service, you can either use the endpoint with the curl command or visit Node IP:Port Number. For example:

    $ curl 10.10.131.44:8080
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    Note

    If you want to access the Service outside the cluster, you may need to open the port in your security groups and configure port forwarding rules depending on your deployment environment.