Custom build images

Sometimes you may need to use a custom build image for your build tasks and the use of the base SDK image is not enough. In this case Welder allows you to create a custom build image on-the-fly instead of wasting time and effort to manage additional build image.

Custom image

With the customImage property you can specify a custom build image in any build task:

schemaVersion: 1.8.0
tasks:
  build:
    customImage:
      dockerFile: ${project:root}/Dockerfile
    script:
      - go build ...

Where ${project:root}/Dockerfile is a path to a Dockerfile that will be used to build the image before running your script tasks.

Build parameters

Like any other Docker image built by Welder you can pass build arguments to the Dockerfile:

schemaVersion: 1.8.0
tasks:
  build:
    customImage:
      dockerFile: ${project:root}/Dockerfile
      build:
        contextPath: ${project:root}/modules/server
        args:
          - name: version
            value: ${project:version}

Inline Dockerfile

Welder also allows to use inline Dockerfiles right within welder.yaml descriptor to avoid additional Dockerfiles:

schemaVersion: 1.8.0
tasks:
  build:
    customImage:
      # adding docker CLI to golang image so we can use it in tests
      inlineDockerFile: |-
        FROM golang:1.18
        ENV DOCKERVERSION=20.10.12
        RUN curl -fsSLO https://download.docker.com/linux/static/stable/x86_64/docker-${DOCKERVERSION}.tgz \
          && tar xzvf docker-${DOCKERVERSION}.tgz --strip 1 \
                         -C /usr/local/bin docker/docker \
          && rm docker-${DOCKERVERSION}.tgz
    script:
      - go build ...

In the above example we use golang:1.18 image as a base and then install Docker CLI inside to allow docker commands to be used in tests.

Note

You can use any of the supported expressions within inline dockerfile to parameterize it.