Services

Updated Feb 05, 2023 ·

Overview

Services in Traefik let you connect your app to the outside world. When you deploy a service, Traefik automatically gives it a way to handle traffic.

• Each service gets a load balancer by default
• If app has more than one instance, traffic is split between them
• Load balancer uses round-robin for multiple app instances
• A service can have health checks to monitor if it's working
• A service can connect to more than one router

This helps spread traffic evenly across your app’s running instances.

Health Checks on Services

Load balancers can check if your service is still healthy.

• You can define custom health check paths like /health or /ping
• You can also check health by port like 8080

If the service is unhealthy, it’s removed from Traefik routing until it's healthy again.

How Requests Travel

Here’s how a request moves through the system.

• Request hits a port like 8443 (entry point)
• Then it goes to a router that checks the rules
• If it matches, it sends traffic to the right service
• Load balancer in the service splits traffic between app instances

This whole flow lets your service handle many requests at once smoothly.

Common Service Configurations

Here are the most common settings used in real projects.

- `traefik.http.services.myservice.loadbalancer.server.port`

- `traefik.http.services.myservice.loadbalancer.passhostheader=true`

- `traefik.http.services.myservice.loadbalancer.healthcheck.path=/health`

- `traefik.http.services.myservice.loadbalancer.healthcheck.port=42`

These define the app's port, whether to pass headers, and where to run health checks.

These basic settings are enough to start routing traffic properly.

Docker-specific Options

When you use Docker, you need to tell Traefik which containers to watch.

• Add this to enable service:

  traefik.enable=true 

• Use this to pick the right network:

  traefik.docker.network

• If using Docker Swarm:

  traefik.docker.swarmMode=true

• Use Swarm's built-in loadbalancer instead of Traefik:

  traefik.docker.lbswarm=true

Here’s a sample Docker Compose:

services:
  myapp:
    image: myapp:latest
    labels:
      - "traefik.enable=true"
      - "traefik.http.services.myapp.loadbalancer.server.port=8080"
      - "traefik.http.services.myapp.loadbalancer.healthcheck.path=/health"

Traefik starts watching this container and can now route traffic to it.

TCP and UDP Services

You can deploy TCP or UDP services just like HTTP.

• Use same settings, just change entry point to TCP or UDP
• Fewer options to configure compared to HTTP
• Services are configured just for the connection between

For example, to create a TCP service:

labels:
  - "traefik.tcp.routers.myapp.entrypoints=tcp"
  - "traefik.tcp.services.myapp.loadbalancer.server.port=9000"

The setup is the same idea, just simpler.

Clone the Repository

To try out the examples, clone the project repository from GitHub.

• Github repo: joseeden/labs-traefik

Clone and move into the project directory:

git clone https://github.com/joseeden/labs-traefik.git 
cd labs-traefik/03-routers-and-services

Project structure:

03-routers-and-services
.
├── docker-compose.yml
└── traefik.yml 

Lab: Cat App Router

This lab lets you test how Traefik handles services and routing in a real setup.

• Deploy Traefik
• Add a service
• Add labels step-by-step
• Troubleshoot issues

Inside the lab directory, we have the docker-compose.yml file.

version: "3"

services:
  traefik:
    image: traefik:v2.3
    ports:
      - "80:80" # web requests
      - "8080:8080" # Traefik dashboard
      - "443:443" # HTTPS requests
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - ./traefik.yml:/etc/traefik/traefik.yml

  catapp:
    image: mikesir87/cats:1.0
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.catapp.rule=Host(`catapp.localhost`)"
      - "traefik.http.routers.catapp.entrypoints=web"
      - "traefik.http.routers.catapp.service=catapp"
      - "traefik.http.services.catapp.loadbalancer.server.port=5000"

This configuration tells Traefik:

• Only handle requests for catapp.localhost
• Use the web entry point (port 80)
• Forward traffic to the app service
• Use port 5000 inside the container

Apply the files:

docker stack deploy -c docker-compose.yml traefik  

Output:

Creating network traefik_default
Creating service traefik_traefik
Creating service traefik_catapp

After deploying, you can access the app at:

http://catapp.localhost

You can also check your setup in the Traefik dashboard.

http://localhost:8080

It will show:

• The router name (catapp)
• The matched host rule
• The assigned service and entry point

This helps confirm everything is working as expected.

Make everything Dynamic

Next, comment out the Service and Load Balancer Labels to see how Traefik will dynamically create the service and Load Balancer.

Edit the docker-compose.yml:

version: "3"

services:
  traefik:
    image: traefik:v2.3
    ports:
      - "80:80" # web requests
      - "8080:8080" # Traefik dashboard
      - "443:443" # HTTPS requests
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - ./traefik.yml:/etc/traefik/traefik.yml

  catapp:
    image: mikesir87/cats:1.0
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.catapp.rule=Host(`catapp.localhost`)"
      - "traefik.http.routers.catapp.entrypoints=web"
      # - "traefik.http.routers.catapp.service=catapp"
      # - "traefik.http.services.catapp.loadbalancer.server.port=5000"

Re-deploy:

docker stack deploy -c docker-compose.yml traefik  

Output:

Updating service traefik_traefik (id: 0q9tjql7txwqnypxsk6k007aw)
Updating service traefik_catapp (id: 7gebiqdo292oowjk31lepkzyh)

Go back to the Traefik dashboard > Routers > Explore.

As we can see here, Traefik dynamically resolves everything by creating the loadbalancer and assigning random hash to the service.

Click the Host(catapp.localhost) to see more details:

Checking the app again, we see that it still works:

http://catapp.localhost

Cleanup

To remove the resources:

docker compose -f <CONFIG_FILE_PATH> down

To check all stacks in your Swarm:

docker stack ls

To remove the specific stack:

docker stack rm <STACK_NAME>

To remove all stacks currently deployed in your Swarm:

docker stack ls --format '{{.Name}}' | xargs -r docker stack rm