traefik

2023-12-18 · traefik, reverse-proxy

This post is a response to a comment from one of my subscribers, who suggested the topic for the next post:

… how to set up Docker so the LB routes straight into the right containers

How do I see the task?

Development is done in containers;
Several projects, possibly related, may be running at the same time;
In front of the projects we need to deploy an LB that automatically picks up the running services and routes traffic to them.

I’ll describe a fairly simple approach using traefik¹. It’s not the only correct approach, but it’s straightforward and easy to reproduce in a local environment. Whether to apply it in your own projects is up to you.

Let’s assume you’ve already got dnsmasq² set up, or that you’ve added the hostnames to /etc/hosts the old-fashioned way.

To start, let’s spin up a traefik container:

services:
  reverse-proxy:
    image: traefik:v2.10
    command: --api.insecure=true --providers.docker
    ports:
      - "80:80"
      - "8080:8080"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock

Port 80 is our entry point; 8080 hosts the nice traefik admin UI. The socket volume is mounted so that traefik can react to events when other containers are created.

Hostname info will live in the containers’ labels. For clarity, let’s create two more docker-compose files describing two services — each file emulates a local deployment of an independent project:

---
services:
  svc1:
    image: hashicorp/http-echo
    command: -text="svc1"
    labels:
      - "traefik.http.routers.svc1.rule=Host(`svc1.dmz`)"
---
services:
  svc2:
    image: hashicorp/http-echo
    command: -text="svc2"
    labels:
      - "traefik.http.routers.svc2.rule=Host(`svc2.dmz`)"

On startup, traefik will automatically pick up the configured addresses and proxy traffic to them.

traefik

Let’s call out a huge advantage of this approach — there’s no need to publish ports through which the services would be reached from the host. That takes the headache of picking and remembering free ports for new projects off the table.