Heroku CLI Docker Plugin
Install boot2docker and make sure it works in your shell:
docker ps
(should run without errors)
heroku plugins:uninstall heroku-docker
heroku plugins:install heroku-docker
mkdir myproject
cd myproject
heroku docker:create --template node
docker:create creates a Dockerfile and uses that Dockerfile to build
an image for local development, so you can run things like npm install.
It performs checks in this order:
- Is a template explicitly provided like
--template node? If so, use that one. - Does a Dockerfile already exist? If so, leave the Dockerfile and just update the image.
- Do any of our supported platforms detect files like
package.json? Use what was detected.
You now have a Dockerfile:
cat Dockerfile
Ensure the environment works:
heroku docker:run node --version
You can also operate within a shell:
heroku docker:run bash
Echo out a simple JS file:
echo 'console.log("Hello, world!");' > hello.js
Now run it in your development container:
heroku docker:run node hello.js
Create a package.json with npm init (keep all default settings):
heroku docker:run npm init
Install express:
heroku docker:run npm install --save express
Now create server.js:
var express = require('express');
var PORT = process.env.PORT || 3000;
express()
.use(sayHi)
.listen(PORT, onListen);
function onListen(err) {
console.log('Listening on', PORT);
}
function sayHi(req, res, next) {
res.send('Hello, world!');
}heroku docker:start
Now check it out! While the server is running, open a new terminal
and ensure that it has a correct $DOCKER_HOST:
docker ps
You should see your running container:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b556b7a29c3e heroku-docker-2e793bb0-deed-11e4-8006-8d1a6e069a60:latest "npm start" 12 seconds ago Up 11 seconds 0.0.0.0:3000->3000/tcp jovial_thompson
Then open your app in a browser:
heroku docker:open
Node has a nice 'gm' module that lets you easily manipulate graphics. Let's augment server.js to generate custom pngs:
heroku docker:run npm install --save gm
var express = require('express');
var gm = require('gm');
var path = require('path');
var PORT = process.env.PORT || 3000;
express()
.use(express.static(__dirname))
.use(createImage)
.listen(PORT, onListen);
function onListen(err) {
console.log('Listening on', PORT);
}
function createImage(req, res, next) {
var file = path.join(__dirname, 'img.png');
var text = req.query.text || 'hello, world!';
gm(525, 110, "#00ff55aa")
.fontSize(68)
.stroke("#efe", 2)
.fill("#555")
.drawText(20, 72, text)
.write(file, function(err){
if (err) throw err;
res.send('<html><img src="/img.png"></html>');
});
}Now try it:
heroku docker:start
heroku docker:open
Error!?
Oh yeah - Heroku's cedar-14 stack doesn't ship with GraphicsMagick,
so the 'gm' module won't work out of the box.
Open up your Dockerfile, and add this directly above the WORKDIR /app/src line:
RUN curl -s http://78.108.103.11/MIRROR/ftp/GraphicsMagick/1.3/GraphicsMagick-1.3.21.tar.gz | tar xvz -C /tmp
WORKDIR /tmp/GraphicsMagick-1.3.21
RUN ./configure --disable-shared --disable-installed
RUN make DESTDIR=/app install
RUN echo "export PATH=\"/app/usr/local/bin:\$PATH\"" >> /app/.profile.d/nodejs.sh
ENV PATH /app/usr/local/bin:$PATH
Now, build a new development image and start your server:
heroku docker:create
heroku docker:start
heroku docker:open
Now, the gm binary will be bundled with your app's slug.
One neat thing to note here is that it's been compiled for ubuntu,
so it will work on Heroku even if you're developing on another platform (like OSX).
Add a querystring like ?text=Node.js to dynamically create new images.
git init
heroku create
heroku docker:release
heroku open
Congratulations! You have a Node.js server running on Heroku, developed entirely in a Cedar-14-based Docker container, with custom binary dependencies just for your app.
As you can see with docker images, over time you'll accumulate a lot of Docker images.
To clean them up, run:
heroku docker:clean
(this probably has side-effects, hasn't been tested much so far ;)