Service Routing

Service Routing with Traefik

Traefik serves as the API gateway and load balancer in this architecture. This page explains how to configure routing for your services using Traefik Docker labels.

Basic Routing Configuration

Traefik uses Docker labels to create routing rules. Here are the basic labels you need to add to your service:

services:
  my-service:
    # ... other configuration
    labels:
      - "traefik.enable=true"  # Enable Traefik for this container
      - "traefik.http.routers.my-service.rule=PathPrefix(`/my-service`)"  # Route based on path
      - "traefik.http.services.my-service.loadbalancer.server.port=8080"  # Container port
      - "traefik.docker.network=microservices_template_traefik-net"  # Docker network

Path Prefixes and Stripping

Often, you want to strip the prefix before forwarding the request to your service:

labels:
  - "traefik.http.middlewares.strip-my-service-prefix.stripprefix.prefixes=/my-service"
  - "traefik.http.routers.my-service.middlewares=strip-my-service-prefix"

With this configuration:

• A request to /my-service/api/users will be forwarded to your service as /api/users
• Your service doesn't need to know about the /my-service prefix

Applying Middlewares

Middlewares modify requests before they reach your service or responses before they're sent back to the client.

Using Pre-configured Middlewares from Consul

labels:
  - "traefik.http.routers.my-service.middlewares=rate-limit@consul,secure-headers@consul"

The template pre-configures several middlewares in Consul:

• rate-limit@consul: Limits the number of requests per time period
• secure-headers@consul: Adds security headers to responses
• compress@consul: Compresses responses

Creating Your Own Middlewares

You can define custom middlewares directly in your Docker labels:

labels:
  # Basic Authentication
  - "traefik.http.middlewares.my-auth.basicauth.users=admin:$$apr1$$H6uskkkW$$IgXLP6ewTrSuBkTrqE8wj/"
  
  # Redirect HTTP to HTTPS
  - "traefik.http.middlewares.https-redirect.redirectscheme.scheme=https"
  - "traefik.http.middlewares.https-redirect.redirectscheme.permanent=true"
  
  # Apply the middlewares
  - "traefik.http.routers.my-service.middlewares=my-auth,https-redirect"

HTTPS Configuration

To enable HTTPS for your service:

labels:
  - "traefik.http.routers.my-service.tls=true"
  - "traefik.http.routers.my-service.tls.certresolver=letsencrypt"

The template is pre-configured to use Let's Encrypt for automatic certificate issuance.

Advanced Routing Rules

Traefik supports complex routing rules:

Multiple Path Prefixes

labels:
  - "traefik.http.routers.my-service.rule=PathPrefix(`/api`) || PathPrefix(`/docs`)"

Host-Based Routing

labels:
  - "traefik.http.routers.my-service.rule=Host(`api.example.com`)"

Combining Path and Host Rules

labels:
  - "traefik.http.routers.my-service.rule=Host(`example.com`) && PathPrefix(`/api`)"

Header-Based Routing

labels:
  - "traefik.http.routers.my-service.rule=Headers(`X-Custom-Header`, `value`)"

Query Parameter Routing

labels:
  - "traefik.http.routers.my-service.rule=Query(`version`, `v1`)"

Load Balancing

Traefik automatically load balances between multiple instances of the same service:

services:
  my-service:
    # ... other configuration
    deploy:
      replicas: 3

Circuit Breaking

Prevent cascading failures with circuit breakers:

# Define circuit breaker in Consul
curl -X PUT -d '{
  "circuitBreaker": {
    "expression": "NetworkErrorRatio() > 0.5"
  }
}' http://consul-server:8500/v1/kv/traefik/http/middlewares/my-circuit-breaker/

# Reference in your service
labels:
  - "traefik.http.routers.my-service.middlewares=my-circuit-breaker@consul"

Traffic Mirroring

Test new service versions without affecting users:

# Mirror traffic to a canary service
labels:
  - "traefik.http.middlewares.mirror-to-canary.mirror.service=my-service-canary"
  - "traefik.http.middlewares.mirror-to-canary.mirror.maxBodySize=5M"
  - "traefik.http.routers.my-service.middlewares=mirror-to-canary"

Middleware Chains

Create complex request processing pipelines:

# Define a chain of middlewares
labels:
  - "traefik.http.middlewares.auth-chain.chain.middlewares=rate-limit@consul,secure-headers@consul,my-auth"
  - "traefik.http.routers.my-service.middlewares=auth-chain"

Verifying Routing Configuration

To verify your routing configuration, check the Traefik dashboard at http://localhost:8080. It shows:

• Configured routers
• Middleware chains
• Service endpoints
• Health status

Best Practices

1. Use namespaced router names: Include your service name in router names to avoid conflicts
2. Keep middleware chains short: Long chains can impact performance
3. Test routing rules thoroughly: Ensure rules match the expected paths
4. Use circuit breakers for critical services: Prevent cascading failures
5. Monitor Traefik metrics: Watch for unusual patterns or errors