May 10, 2016 Nicolas Girault 6 min read

Docker shakes up the way we use to put into production. In this article, I'll present the main obstacles I encountered to set up the production workflow of a simple Node.js API called cinelocal.

Erratum: I am now using docker-machine instead of Ansible. You can read in the comments why

Step 1: set up a development environment

Docker-compose is a tool for defining and running multi-container Docker applications. Cinelocal-api requires 3 services running in 3 containers:

node

postgres

data

Here is the corresponding docker-compose.yml defining the 3 services and their relations:

# docker-compose.yml data: image: busybox volumes: - /data db: image: postgres:9.4 volumes_from: - data ports: - "5432:5432" api: image: node:wheezy working_dir: /app volumes: - .:/app links: - db ports: - "8000:8000" command: npm run watch

Notice the .:/app line in the API container that mounts the current folder as a container's volume so when you edit a source file it will be detected inside the container.

The npm command of the API container is defined in the package.json file. It runs database migrations (if any) and starts nodemon which is a utility that monitors for any change in your source and automatically restarts your server.

package.json:

{ "scripts" : { "watch" : "db-migrate up --config migrations/database.json && node ./node_modules/nodemon/bin/nodemon.js src/server.coffee" } }

Now the API can be started using the command docker-compose up api (it might crash the first time because the node container does not wait for the postgres container to be ready. It will work the second time. This is a known compose issue).

Unfortunately using Docker adds a layer of complexity to the usual commands such as installing a new Node.js package or creating a new migration because it must be run in the container. So:

All your commands should be prefixed by docker-compose run --rm api

The edited files ( package.json with npm install or migration files with db-migrate) will be owned by the docker user.

To bypass this complexity, you can use a Makefile that provides a set of commands.

# Makefile whoami := $(shell whoami) migration-create: docker-compose run --rm api \ ./node_modules/db-migrate/bin/db-migrate create --config migrations/database.json $(name)\ && sudo chown -R ${whoami}:${whoami} migrations migration-up: docker-compose run --rm api ./node_modules/db-migrate/bin/db-migrate up --config migrations/database.json migration-down: docker-compose run --rm api ./node_modules/db-migrate/bin/db-migrate down --config migrations/database.json install: docker-compose run --rm api npm install npm-install: docker-compose run --rm api \ npm install --save $(package)\ && sudo chown ${whoami}:${whoami} package.json

Now to install a package you can run: make npm-install package=lodash or to create a new migration: make migration-create name=add-movie-table .

Step 2: Provisioning a server

With Docker, whatever your stack is, the provisioning will be the same. You'll have to install docker and optionally docker-compose, that's it.

Ansible is a great tool to provision a server. You can compose a playbook with roles found on ansible galaxy.

To install docker and docker-compose on a server:

# devops/provisioning.yml - name: cinelocal-api provisioning hosts: all sudo: true pre_tasks: - locale_gen: name=en_US.UTF-8 state=present roles: - angstwad.docker_ubuntu - franklinkim.docker-compose vars: docker_group_members: - ubuntu update_docker_package: true

Before running the playbook you need to install the roles:

ansible-galaxy install -r devops/requirements.yml -p devops/roles

with:

# devops/requirements.yml - src: angstwad.docker_ubuntu - src: franklinkim.docker-compose

I tested this provisioning with Ansible 2.0.2 on Ubuntu Server 14.04.

# Makefile install: ansible-galaxy install -r devops/requirements.yml -p devops/roles provisioning: ansible-playbook devops/provisioning.yml -i devops/hosts/production

Step 3: Package your app and deploy

Each time I deploy the API, I build a new Docker image that I push on Docker Hub (the GitHub of Docker images).

The construction of the API image is described in a Dockerfile :

FROM node:wheezy # Create app directory RUN mkdir -p /app WORKDIR /app # Install app dependencies COPY package.json /app/ RUN npm install # Bundle app source COPY . /app EXPOSE 8000 CMD [ "npm", "start" ]

To build and push the image on Docker Hub, I added these two tasks in the Makefile:

# Makefile build: docker build -t nicgirault/cinelocal-api . push: build docker push nicgirault/cinelocal-api

Now make push builds the image and pushes it on Docker Hub (after authentication).

In a development environment, I want to mount my code as a volume whereas it should not be the case in production. Using multiple Compose files enables you to customize a Compose application for different environments. In our case, we want to split the description of the api service in a common configuration and an environment specific configuration.

# docker-compose.yml (common configuration) api: working_dir: /app links: - db ports: - "8000:8000" environment: DB_DATABASE: postgres DB_USERNAME: postgres

# docker-compose.dev.yml (development specific configuration) api: image: node:wheezy volumes: - .:/app command: npm run watch

# docker-compose.prod.yml (production specific configuration) api: image: nicgirault/cinelocal-api

To merge the specific configuration into the common configuration:

docker-compose -f docker-compose.yml -f docker-compose.dev.yml up api

By default, Compose checks the presence of docker-compose.override.yml so I renamed docker-compose.dev.yml to docker-compose.override.yml.

Now I can deploy the API using 3 commands described in a simple Ansible playbook:

# devops/deploy.yml - name: Cinelocal-api deployment hosts: all sudo: true vars: repository: https://github.com/nicgirault/cinelocal-api.git path: /home/ubuntu/www image: nicgirault/cinelocal-api tasks: - name: Pull github code git: repo={{ repository }} dest={{ path }} - name: Pull API container shell: docker pull {{ image }} - name: Start API container shell: docker-compose -f docker-compose.yml -f docker-compose.prod.yml up -d api args: chdir: {{ path }}

In the Makefile:

deploy: push ansible-playbook -i devops/hosts/production devops/deploy.yml

make deploy builds the image, pushes it and runs the playbook.

Note: Ansible embeds docker commands that avoid installing docker-compose on the server but forced to duplicate the docker architecture description. Although I didn't use it for this project you might consider using it.

Bonus: continuous integration

This section explains how to automatically deploy on production when merging on the master branch if the build passes.

This is quite simple with circleCI and Docker Hub:

Here is a circle.yml file that runs the tests and deploys if the build passes provided the destination branch is master:

machine: services: - docker python: version: 2.7.8 post: # circle instance already run postgresql - sudo service postgresql stop dependencies: pre: - pip install ansible - pip install --upgrade setuptools override: - docker info - docker build -t nicgirault/cinelocal-api . test: override: - docker-compose run api npm test deployment: prod: branch: master commands: - docker login -e $DOCKER_EMAIL -u $DOCKER_USER -p $DOCKER_PASS - docker push nicgirault/cinelocal-api - echo "openstack ansible_host=$PROD_HOST ansible_ssh_user=$PROD_USER" > devops/hosts/production - ansible-playbook -i devops/hosts/production devops/deploy.yml

In addition, you'll have to:

define the environment variables used in this file in the circleCI project settings page

authorize circleCI to deploy on your server: generate a ssh key pair (use the command ssh-keygen) add the private key on the project settings on circleCI interface add the public key on the ~/.ssh/autorized_keys on the server



From now deploying on production will be as simple as merging a branch to master.