Customizing generated Dockerfile and behavior of built-in transformer

Big picture

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

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
```

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

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-14 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      __mocks__       jest.config.js    package-lock.json    src               test-setup.js         webpack.dev.js
 LICENSE         dist            manifest.yml      package.json         stories           tsconfig.json         webpack.prod.js
 README.md       dr-surge.js     nodemon.json      server.js            stylePaths.js     webpack.common.js

 FROM registry.access.redhat.com/ubi8/nodejs-14
 COPY . .
 RUN npm install
 RUN npm run build
 USER root
 RUN chown -R 1001:0 /opt/app-root/src/.npm
 RUN chmod -R 775 /opt/app-root/src/.npm
 USER 1001
 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-14 to registry.access.redhat.com/ubi8/nodejs-14-minimal
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

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

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        __mocks__         jest.config.js    package-lock.json src               stylePaths.js     webpack.common.js
LICENSE           dist              manifest.yml      package.json      start-nodejs.sh   test-setup.js     webpack.dev.js
README.md         dr-surge.js       nodemon.json      server.js         stories           tsconfig.json     webpack.prod.js
$ cat myproject/source/frontend/Dockerfile
FROM registry.access.redhat.com/ubi8/nodejs-14-minimal
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
      │   └── transformer.yaml
      └── nodejs
          ├── mappings
          │   └── nodeversions.yaml
          ├── templates
          │   ├── Dockerfile
          │   └── start-nodejs.sh
          └── transformer.yaml

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.

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 registry.access.redhat.com/ubi8/nodejs-14-minimal
  COPY . .
  RUN npm install
  {{- if .Build }}
  RUN npm run build
  {{- end}}
  EXPOSE {{ .Port }}
  CMD sh start-nodejs.sh
```

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

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/transformer.yaml

  apiVersion: move2kube.konveyor.io/v1alpha1
  kind: Transformer
  metadata:
 name: Nodejs-CustomFiles
 labels:
   move2kube.konveyor.io/task: containerization
   move2kube.konveyor.io/built-in: false
  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

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/transformer.yaml

  apiVersion: move2kube.konveyor.io/v1alpha1
  kind: Transformer
  metadata:
 name: KubernetesWithCustomOutputDirectory
 labels:
   move2kube.konveyor.io/built-in: false
  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

Customizing generated Dockerfile and behavior of built-in transformer

Big picture

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

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