Docker-in-Docker Drone plugin

This is a plugin for Drone that is aimed mainly at enabling Testcontainers to be used during CI build/test steps. Due to Drone's architecture, Docker-in-Docker is often the most practical way to run builds that require a Docker daemon.

This plugin:

• Is based upon an Docker-in-Docker image
• Includes a startup script that:
  • Starts a nested docker daemon
  • Optionally starts a pull of required images (in parallel with your build, so as to reduce overall time spent waiting for images to be pulled)
  • Starts a specified build container inside the Docker-in-Docker context, containing your source code and with a docker socket available to it

Prerequisites

Either:

• (Drone >= 0.8): To enable on a per-repository basis, enable the Trusted setting for the repository. Or
• (Drone >= 0.8): To enable this plugin globally in your Drone instance, add the image name to the DRONE_ESCALATE environment variable that the Drone process runs under.

Usage/Migration

Modify steps of the pipeline to resemble:

steps:
  - name: build
    image: timbze/dind-drone-plugin
    environment:
      CI_WORKSPACE: "/drone/src"
      # Optional
      EXTRA_DOCKERD_OPTIONS: --dns 8.8.8.8 208.67.222.222
    settings:
      # This specifies the command that should be executed to perform build, test and
      #  integration tests. Not to be confused with Drone's `command`:
      cmd: sleep 5 && ./gradlew clean check --info
      # This image will run the cmd with your build steps
      build_image: adoptopenjdk:14-openj9
      # Not mandatory; enables pre-fetching of images in parallel with the build, so may save 
      #  time:
      prefetch_images:
        - "redis:4.0.6"
      # Not mandatory; sets up image name 'aliases' by pulling from one registry and tagging
      #  as a different name. Intended as a simplistic mechanism for using a private registry 
      #  rather than Docker Hub for a known set of images. Accepts a dictionary of
      #  private registry image name to the Docker Hub image that it is a substitute for.
      #  Note that all images are pulled synchronously before the build starts, so this is
      #  inefficient if any unnecessary images are listed.
      image_aliases:
        someregistry.com/redis:4.0.6: redis:4.0.6
    volumes:
      - name: dockersock
        path: /var/run

# Specify docker:dind as a service
services:
- name: docker
  image: docker:dind
  privileged: true
  volumes:
  - name: dockersock
    path: /var/run

volumes:
- name: dockersock
  temp: {}

When migrating to use this plugin from an ordinary build step, note that:

• commands should be changed to cmd. Note that commas are not supported within cmd lines due to the way these are passed in between Drone and this plugin.
• image should be changed to build_image
• prefetch_images is optional, but recommended. This specifies a list of images that should be pulled in parallel with your build process, thus saving some time.

Drone 0.8 or older

Modify the build step of the pipeline to resemble:

pipeline:
  ...
  build:
    image: timbze/dind-drone-plugin
    build_image: openjdk:8-jdk-alpine
    # This specifies the command that should be executed to perform build, test and 
    #  integration tests. Not to be confused with Drone's `command`:
    cmd: ./gradlew clean check --info
    # Not mandatory; enables pre-fetching of images in parallel with the build, so may save 
    #  time:
    prefetch_images:
      - "redis:4.0.6"
    # Not mandatory; sets up image name 'aliases' by pulling from one registry and tagging
    #  as a different name. Intended as a simplistic mechanism for using a private registry 
    #  rather than Docker Hub for a known set of images. Accepts a dictionary of
    #  private registry image name to the Docker Hub image that it is a substitute for.
    #  Note that all images are pulled synchronously before the build starts, so this is
    #  inefficient if any unnecessary images are listed.
    image_aliases:
      someregistry.com/redis:4.0.6: redis:4.0.6

Extending

Users with custom requirements can build a new image using this as a base image.

This image uses hook scripts, if present, to perform custom actions. Such scripts may be placed as executable files in any of /dind-drone-plugin/hooks/{pre_daemon_start,post_daemon_start,pre_run,post_run}, depending on which phase they are required to run in.

Some initial hook scripts already exist, which should be overwritten or removed if needed.

Copyright

This repository contains code which was mainly developed at Skyscanner, and is licenced under the Apache 2.0 Licence.

(c) 2017-2020 Skyscanner Ltd.