dockercook

Build and manage multiple docker image layers to speed up deployment. For a tutorial see below or the example directory.

Install

Requirements: GHC7.8 and cabal or stack

• From Hackage: cabal install dockercook
• From Source: git clone https://github.com/factisresearch/dockercook.git && cd dockercook && cabal install
• From Source (stack): git clone https://github.com/factisresearch/dockercook.git && cd dockercook && stack setup && stack install

Commands

Usage: dockercook [-v|--verbosity INT] COMMAND
  Speed up docker image building

Available options:
  -h,--help                Show this help text
  -v,--verbosity INT       log levels for 0 - 3

Available commands:
  cook                     Cook docker images
  check                    Validate a Dockercook file
  sync                     Sync local state with remote docker server
  version                  Show programs version
  timing                   Looking build times for image
  init                     Enable dockercook for current project / directory

Cookfile Directives

BASE COOK [cookfile]

Define the current cookfiles parent cookfile. You can only use this directive once at the top and you can't use it in combination with BASE DOCKER [dockerimage].

BASE DOCKER [dockerimage]

The cook-image will depend on an existing docker image. You can only use this directive once at the top and you can't use it in combination with BASE DOCKER [dockerimage].

INCLUDE [filepattern]

Include and depend on a file. You can use this anywhere in your cook file, but it will be moved to the top before UNPACK [target_dir].

UNPACK [target_dir]

All included files will be unpacked to this directory. It will also ensure that the directory exists. Requires a tar binary inside your docker-container. You can only use this directive once.

BEGIN

Begin a transaction. You can only put SCRIPT [script] and RUN [bash_cmd] commands inside a transaction. All commands inside the transaction will result in a single layer.

COMMIT

Commit a transaction. This is only possible if you began a transaction ;-)

SCRIPT [script]

Run a bash script and put it's result at the current position in the dockerfile.

DOWNLOAD [url] [filepath]

Download a file from [url] to [filepath] in your docker container. The server must set one of the following headers and support HEAD requests: Last-Modified, ETag, Content-MD5

PREPARE [shell-command]

This shell command is executed in an empty directory and is useful to copy additional files into the build context. Any file that you copy in the working directory of the shell-command will be available in your cook file from the /_cookpreps directory. All PREPARE commands in one file will be executed in the same preparation directory. For more information check the example.

COOKCOPY [cookfile] [image-dir] [target-dir]

Copy a file or directory from an image described by [cookfile] to /_cookpreps/[target-dir] in your current context. This can be very useful for binary-only containers. Behind the scenes this starts the image (entrypoint is set to ""), uses docker cp to extract files and then kills the container.

COOKVAR [var-name] [default-value]

This allows compile time environment variables. They can be set using --set-var (multiple times) with the dockercook cook command. The default value is optional. A COOKVAR directive is translated to dockers ENV command and populated with the correct value. If a COOKVAR does not have a default value and is not supplied via --set-var the build will fail.

All Docker-Commands

Most other docker-commands are allowed in Cookfiles. ADD and COPY commands are not recommended, as the dependencies aren't tracked. The FROM command is not allowed.

Emacs support

There's a basic cookfile-mode.el in the repository :-)

Motivation / Tutorial

Consider the following Dockerfile for a sample nodejs project:

Dockerfile

FROM ubuntu:14.04
RUN apt-get update
RUN apt-get install -y nodejs npm
RUN ln -s /usr/bin/nodejs /usr/bin/node
RUN mkdir /app
ADD package.json /app/package.json
WORKDIR /app
RUN npm install
ADD . /app
CMD node ./app.js 

We have two branches for this nodejs project with the following package.json:

Branch A: package.json

{
    "name": "sample-app",
    "version": "0.1.0",
    "dependencies" : {
        "bloomfilter"   :  "0.0.12",
        "express" :  "2.1.x",
        "mongoose" :  "2.2.x",
        "moment": "2.5.x"
    }
}

Branch B: package.json

{
    "name": "sample-app",
    "version": "0.1.1",
    "dependencies" : {
        "bloomfilter"   :  "0.0.12",
        "express" :  "3.4.x",
        "mongoose" :  "3.6.x",
        "moment": "2.5.x",
        "request": "2.34.x"
    }
}

Building these two branches alternately on the same machine using docker and the Dockerfile above you'll notice the following behaviour:

• docker build branch A (from scratch)
• docker build branch B (starts at “ADD package.json /app”)
• docker build branch B (from cache)
• docker build branch A (starts at “ADD package.json /app”)
• docker build branch A (from cache)
• docker build branch B (starts at “ADD package.json /app”)

Lot's of time is wasted reinstalling the packages over and over again. (See: Build caching: what invalids cache and not?)

You can solve this by building more efficient Dockerfiles, but then you'd need two "package images" and two "app images" for your two branches and manage, delete and update these manually.

dockercook solves this issue by slicing the repository and managing those "intermediate" images for you. Back to our sample node js app, you would create three cook Files:

system.cook

BASE DOCKER ubuntu:14.04
BEGIN
RUN apt-get update
RUN apt-get install -y nodejs npm
RUN apt-get clean
RUN ln -s /usr/bin/nodejs /usr/bin/node
COMMIT

node-pkg.cook

BASE COOK system.cook
INCLUDE package.json
UNPACK /app
WORKDIR /app
RUN npm install

app.cook

BASE COOK node-pkg.cook
INCLUDE *.js
UNPACK /app
CMD node ./app.js

Now you'd build your repository branches using dockercook cook:

$ cd $HOME/my-repo
$ dockercook init # only the first time
$ git checkout branchA
...
$ dockercook cook cookfiles/app.cook
...
$ cd $HOME/my-repo && git checkout branchB
...
$ dockercook cook cookfiles/app.cook

You'll notice the following behaviour:

• build branch A (builds: system + node-pkg + app)
• build branch B (builds: node-pkg’ + app’)
• build branch B (builds: app’)
• build branch A (builds: app)
• build branch A (builds: -)
• build branch B (builds: -)

Lot's of time is saved because you don't need to reinstall all your packages dependencies everytime you switch branches.

Related work

• docker-buildcache