Go + Docker + DigitalOcean Example

A minimal example demonstrating how to create a dockerized Go app that can easily be deployed as a DigitalOcean droplet.

Structure

/src/...
/docker-compose.yml
/Dockerfile

App

The app source is placed under /src

Dockerfile

• The dockerfile is based off of the official golang based image, which contains the desired go environment.
• Different variants are example. For example, for a specific version of go, use golang:1.6 instead of golang:latest.
• For more information see the golang docker image.

docker-compose

The docker-compose configuration sets up the app service and a simple nginx-proxy service for routing.

The nginx-proxy service automatically links up any other services that have a VIRTUAL_HOST environment variable, and forwards any requests that match the routes.

Both services use restart: always to automatically restart in case the machine restarts.

Log history is capped at 100m to prevent running out of disk space 😅 (I learned that the hard way once).

Testing

To run the services locally

docker-compose build && docker-compose up

To run the services locally (detached)

docker-compose build && docker-compose up -d

To see the status:

docker-compose ps

To test the app:

curl -H 'Host: foobar.example.com' localhost

Note that we have to supply an explicit host header since we're testing locally. We could also add another VIRTUAL_HOST to the service for localhost to receive requests from http://localhost/.

Deploying

Deploying to DigitalOcean is pretty straightforward.

1) Create a new droplet

• Create > Droplet
• One-click apps
• Docker 17.05.0-ce on 16.04 (or newer)
• Choose desired size
• Choose desired region
• Select Monitoring
• Choose desired hostname

2a) Deploy using User Data

When creating the droplet, enable User Data and enter your script:

#!/bin/bash
git clone https://<token>@<repo> ~/app
cd ~/app && docker-compose build && docker-compose up -d

Note: Logs for User Data cloud init scripts can be found here: /var/log/cloud-init-output.log.

2b) (Re-)Deploy using SSH

1. SSH into the droplet

• ssh root@<ip>

2. Clone the source repo:

• git clone <repo>

3. Deploy

• cd app && docker-compose build && docker-compose up -d

4. Optionally, create monitoring alerts in DigitalOcean

5. To re-deploy, repeat steps 2-4