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Customizing generated Dockerfile and behavior of built-in transformer

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In this example, we look at how to make Move2Kube add custom Dockerfile and a custom file.

  1. Let us start by creating an empty workspace directory say workspace and make it the current working directory. We will assume all commands are executed within this directory.
      $ mkdir workspace && cd workspace
    
  2. Lets use the enterprise-app as input for this flow.
      $ curl https://move2kube.konveyor.io/scripts/download.sh | bash -s -- -d samples/enterprise-app/src -r move2kube-demos
      $ ls src
      README.md		config-utils		customers	docs			frontend		gateway			orders
    
  3. Let’s first run Move2Kube without any customization.
    • If we notice the Dockerfile generated for the frontend app, it uses registry.access.redhat.com/ubi8/nodejs-12 as base image
    • There are no scripts named start-nodejs.sh in the frontend service directory
    • The Kubernetes yamls are generated in myproject/deploy/yamls directory
     $ move2kube transform -s src/ --qa-skip && ls myproject/source/frontend && cat myproject/source/frontend/Dockerfile && ls myproject/deploy && rm -rf myproject
     Dockerfile		README.md		dr-surge.js		manifest.yml		package-lock.json	server.js		stories			test-setup.js		webpack.common.js	webpack.prod.js LICENSE		__mocks__		jest.config.js		nodemon.json		package.json		src			stylePaths.js		tsconfig.json		webpack.dev.js
    
     FROM registry.access.redhat.com/ubi8/nodejs-12
     COPY . .
     RUN npm install
     RUN npm run build
     EXPOSE 8080
     CMD npm run start
    
     cicd			compose			knative			knative-parameterized	yamls			yamls-parameterized
    

Let’s say, we want to change

  • The base image of the Dockerfile generated for nodejs from registry.access.redhat.com/ubi8/nodejs-12 to quay.io/konveyor/nodejs-12
  • Add a new script named start-nodejs.sh in the nodejs app directories along with the Dockerfile, in our case frontend directory
  • Change the location of Kubernetes yamls from myproject/deploy/yamls to myproject/yamls-elsewhere
  1. We will use a custom configured version of the nodejs built-in transformer and kubernetes built-in transformer to achieve this. We copy it into the customizations sub-directory.
      $ curl https://move2kube.konveyor.io/scripts/download.sh | bash -s -- -d custom-dockerfile-change-built-in-behavior -r move2kube-transformers -o customizations
    
  2. Now lets transform with this customization. Specify the customization using the -c flag.
      $ move2kube transform -s src/ -c customizations/ --qa-skip
    

Once the output is generated, we can observe

  • The Dockerfile generated for the frontend app contains the custom base image
  • A new file named start-nodejs.sh is generated in the frontend directory
  • The kubernetes yamls are now generated in myproject/yamls-elsewhere directory, and hence the parameterized yamls are also in myproject/yamls-elsewhere-parameterized directory.
    $ ls myproject/source/frontend
    Dockerfile		README.md		dr-surge.js		manifest.yml		package-lock.json	server.js		start-nodejs.sh		stylePaths.js		tsconfig.json		webpack.dev.js LICENSE		__mocks__		jest.config.js		nodemon.json		package.json		src			stories			test-setup.js		webpack.common.js	webpack.prod.js
    $ cat myproject/source/frontend/Dockerfile
    FROM quay.io/konveyor/nodejs-12
    COPY . .
    RUN npm install
    RUN npm run build
    EXPOSE 8080
    CMD sh start-nodejs.sh
    $ ls myproject
    Readme.md			deploy				scripts				source				yamls-elsewhere			yamls-elsewhere-parameterized
    

Anatomy of transformers in custom-dockerfile-change-built-in-behavior

The two customized transformers in the directory are nodejs and kubernetes. The contents of custom-dockerfile-custom-files are as shown below:

  $ tree customizations
  customizations
  └── custom-dockerfile-change-built-in-behavior
      ├── kubernetes
      │   └── kubernetes.yaml
      └── nodejs
          ├── nodejs.yaml
          └── templates
              ├── Dockerfile
              └── start-nodejs.sh

To custom configure an built-in transformer, you can copy the built-in transformer’s configuration directory from move2kube source, change the configurations and use it as a customization. You can make it override the built-in transformer using the override config in the yaml.

In this case, we change the Dockerfile template, add a script and change the transformer configuration yaml.

  1. To change the template, we have added our custom template in customizations/custom-dockerfile-change-built-in-behavior/nodejs/templates/Dockerfile. The template is the same as the one used in the built-in transformer, except that we are using a custom base image and a custom CMD here.
      $ cat customizations/custom-dockerfile-change-built-in-behavior/nodejs/templates/Dockerfile
      FROM quay.io/konveyor/nodejs-12
      COPY . .
      RUN npm install
      {{- if .Build }}
      RUN npm run build
      {{- end}}
      EXPOSE {{ .Port }}
      CMD sh start-nodejs.sh
    
  2. Add customizations/custom-dockerfile-change-built-in-behavior/nodejs/templates/start-nodejs.sh.
      $ ls customizations/custom-dockerfile-change-built-in-behavior/nodejs/templates/
      Dockerfile	start-nodejs.sh
    
  3. The transformer.yaml is the transformer configuration. We have two changes here compared to the built-in transformer:
    • The name of our custom transformer is Nodejs-CustomFiles (see name field in the metadata section).
    • We are also specifying an override section which is asking Move2Kube to disable the transformer named Nodejs-Dockerfile if this transformer is present.
        $ cat customizations/custom-dockerfile-change-built-in-behavior/nodejs/nodejs.yaml
      
        apiVersion: move2kube.konveyor.io/v1alpha1
        kind: Transformer
        metadata:
       name: Nodejs-CustomFiles
       labels:
         move2kube.konveyor.io/task: containerization
         move2kube.konveyor.io/built-in: true
        spec:
       class: "NodejsDockerfileGenerator"
       directoryDetect:
         levels: -1
       consumes:
         Service: 
       merge: false
       produces:
         Dockerfile:
       disabled: false
         DockerfileForService:
       disabled: false
       override:
         matchLabels: 
       move2kube.konveyor.io/name: Nodejs-Dockerfile
       config:
         defaultNodejsVersion: "12"
      
  4. In the kubernetes transformer, we change the name and override config too. But in addition, we change the default behavior of the transformer, which is to put the Kubernetes yamls in deploy/yamls directory by changing the spec.config.outputPath to yamls-elsewhere.
      $ cat customizations/custom-dockerfile-change-built-in-behavior/kubernetes/kubernetes.yaml
    
      apiVersion: move2kube.konveyor.io/v1alpha1
      kind: Transformer
      metadata:
     name: KubernetesWithCustomOutputDirectory
     labels:
       move2kube.konveyor.io/built-in: true
      spec:
     class: "Kubernetes"
     directoryDetect:
       levels: 0
     consumes:
       IR:
         merge: true
     produces:
       KubernetesYamls:
         disabled: false
     override:
       matchLabels:
         move2kube.konveyor.io/name: Kubernetes
     dependency:
       matchLabels:
         move2kube.konveyor.io/kubernetesclusterselector: "true"
     config:
       outputPath: "yamls-elsewhere"
       ingressName: "{{ .ProjectName }}"
    

Next step Adding custom annotations to Kubernetes YAMLs