Publish "Making docker-compose easier with wdocker"
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#+TITLE: Making docker-compose easier with wdocker
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#+DATE: 2016-02-21
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#+COLESLAW_TAGS: wdocker docker docker-compose
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#+OPTION: num:nil
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* Introduction
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237
wdocker_compose.post
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237
wdocker_compose.post
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;;;;;
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title: Making docker-compose easier with wdocker
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date: 2016-02-21
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tags: wdocker docker docker-compose
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format: html
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;;;;;
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<div id="outline-container-orgheadline1" class="outline-2">
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<h2 id="orgheadline1"><span class="section-number-2">1</span> Introduction</h2>
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<div class="outline-text-2" id="text-1">
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<p>
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<a href="https://github.com/babab/wdocker">wdocker</a> is a little utility written by a <a href="https://benjamin.althu.es">friend</a> and former colleague
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of mine. It allows you to define commands for it in a
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<code>Dockerfile</code>. He wrote it because he used a lot of composite
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commands when writing docker images like:
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</p>
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<div class="org-src-container">
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<pre class="src src-sh">docker stop CONTAINER && docker rm CONTAINER && docker rmi IMAGE && <span class="org-sh-escaped-newline">\</span>
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docker build -t IMAGE && docker run --name CONTAINER IMAGE
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</pre>
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</div>
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<p>
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By using wdocker to define a command he can greatly simplify his own
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workflow. Let's call it rebuild:
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</p>
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<div class="org-src-container">
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<pre class="src src-dockerfile"><span class="org-comment-delimiter">#</span><span class="org-comment">wd# container = CONTAINER</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# image = IMAGE</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# stop = docker stop {container}</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# rm = docker rm {container}</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# rmi = docker rmi {container}</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# build = docker build -t {image}</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# run = docker run --name {container} {image}</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# rebuild: {stop} && {rm} && {rmi} && {build} && {run}</span>
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<span class="org-keyword">FROM</span> ubuntu
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<span class="org-comment-delimiter"># </span><span class="org-comment">...</span>
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</pre>
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</div>
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<p>
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Now he can use the following command instead of the list presented
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before:
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</p>
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<pre class="example">
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wdocker rebuild
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</pre>
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</div>
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</div>
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<div id="outline-container-orgheadline2" class="outline-2">
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<h2 id="orgheadline2"><span class="section-number-2">2</span> Syntax</h2>
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<div class="outline-text-2" id="text-2">
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<p>
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wdocker has very simple syntax. You can define variables and
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commands:
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</p>
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<pre class="example">
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#wd# variable = value
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#wd# command: program
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</pre>
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<p>
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Variables can be used by putting them in braces, including in other
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variables, as you've seen in the first example.
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</p>
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<pre class="example">
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#wd# variable = -l
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#wd# list: ls {variable}
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</pre>
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<p>
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This would run <code>ls -l</code> when the command <code>wdocker list</code> is called.
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</p>
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<p>
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As you can see you're not limited to using docker in your wdocker
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commands. This property is what allows me to use wdocker in my
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workflow.
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</p>
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</div>
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</div>
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<div id="outline-container-orgheadline3" class="outline-2">
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<h2 id="orgheadline3"><span class="section-number-2">3</span> Combining with docker-compose</h2>
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<div class="outline-text-2" id="text-3">
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<p>
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I started using docker not too long ago at work to develop our
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projects in. This is nice because it allows me to completely isolate
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my development environments. Since we have a few processes running
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together a single docker image isn't a great option, so I use
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docker-compose to define and combine the containers I need.
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</p>
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<p>
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As a side-effect this requires me to write long commands to do
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something like run rspec tests:
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</p>
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<pre class="example">
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docker-compose run --rm -e RACK_ENV=test -e RAILS_ENV=test \
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container bundle exec rspec
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</pre>
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<p>
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The alternative is defining a specialized test container with a
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bogus entry command (such as <code>true</code>) and use that, which would still
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make the command:
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</p>
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<pre class="example">
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docker-compose run --rm test-container bundle exec rspec
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</pre>
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<p>
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Instead I can define a wdocker command in the <code>Dockerfile</code> used to
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build the containers used:
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</p>
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<div class="org-src-container">
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<pre class="src src-dockerfile"><span class="org-comment-delimiter">#</span><span class="org-comment">wd# rspec: docker-compose run --rm -e RACK_ENV=test -e RAILS_ENV=test container bundle exec rspec</span>
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<span class="org-keyword">FROM</span> ruby
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<span class="org-comment-delimiter">#</span><span class="org-comment">...</span>
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</pre>
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</div>
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<p>
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Now I can run the following, much shorter, command to run the rspec
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tests:
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</p>
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<pre class="example">
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wdocker rspec
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</pre>
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<p>
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We also use cucumber for some other tests, which is even longer to
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type in, adding the <code>cucumber</code> command is easy:
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</p>
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<div class="org-src-container">
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<pre class="src src-dockerfile"><span class="org-comment-delimiter">#</span><span class="org-comment">wd# rspec: docker-compose run --rm -e RACK_ENV=test -e RAILS_ENV=test container bundle exec rspec</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# cucumber: docker-compose run --rm -e RACK_ENV=test -e RAILS_ENV=test container bundle exec cucumber</span>
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<span class="org-keyword">FROM</span> ruby
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<span class="org-comment-delimiter"># </span><span class="org-comment">...</span>
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</pre>
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</div>
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<p>
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Now I can run <code>wdocker cucumber</code> as well.
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</p>
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<p>
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The latest git version of wdocker passes any arguments after the
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command name directly to the command to be executed. So if I need to
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run tests in a single spec file I can just do:
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</p>
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<pre class="example">
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wdocker rspec spec/models/mymodel_spec.rb
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</pre>
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<p>
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We have two commands defined now that are 90% the same. I always use
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the <code>--rm</code> switch to remove the started container after it's done, I
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don't want a lot of containers piling up. I also always have to use
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<code>bundle exec</code> to run commands, since the containers don't use rvm or
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add the script directories to <code>$PATH</code>. We can extract them to some
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variables:
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</p>
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<div class="org-src-container">
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<pre class="src src-dockerfile"><span class="org-comment-delimiter">#</span><span class="org-comment">wd# run = docker-compose run --rm</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# exec = bundle exec</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# test = -e RACK_ENV=test -e RAILS_ENV=test</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# rspec: {run} {test} container {exec} rspec</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# cucumber: {run} {test} container {exec} cucumber</span>
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<span class="org-keyword">FROM</span> ruby
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<span class="org-comment-delimiter"># </span><span class="org-comment">...</span>
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</pre>
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</div>
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<p>
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Right now these commands always use the <code>container</code> service defined
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in <code>docker-compose.yml</code>. I could add it to the <code>run</code> command, but I
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might need to run some commands on another container, but I can
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define another variable:
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</p>
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<div class="org-src-container">
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<pre class="src src-dockerfile"><span class="org-comment-delimiter">#</span><span class="org-comment">wd# run = docker-compose run --rm</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# test = -e RACK_ENV=test -e RAILS_ENV=test</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# run-test-container = {run} {test} container</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# exec = bundle exec</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# rspec: {run-test-container} {exec} rspec</span>
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<span class="org-comment-delimiter">#</span><span class="org-comment">wd# cucumber: {run-test-container} {exec} cucumber</span>
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<span class="org-keyword">FROM</span> ruby
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<span class="org-comment-delimiter"># </span><span class="org-comment">...</span>
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</pre>
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</div>
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<p>
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Now you also see that variables can be nested in other variables.
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</p>
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<p>
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If you ever forget what you defined or if the mix of commands and
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variables becomes too much for you, you can call the wdocker command
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without arguments to see the commands you defined and the shell
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commands they'll run.
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</p>
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</div>
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</div>
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