The platforms we plan to run on our cloud are generally web-based, and each listening on their own unique TCP port. When a container in a swarm exposes a port, then connecting to any swarm member on that port will result in your request being forwarded to the appropriate host running the container. (Docker calls this the swarm "routing mesh")
So we get a rudimentary load balancer built into swarm. We could stop there, just exposing a series of ports on our hosts, and making them HA using keepalived.
There are some gaps to this approach though:
- No consideration is given to HTTPS. Implementation would have to be done manually, per-container.
- No mechanism is provided for authentication outside of that which the container providers. We may not want to expose every interface on every container to the world, especially if we are playing with tools or containers whose quality and origin are unknown.
To deal with these gaps, we need a front-end load-balancer, and in this design, that role is provided by Traefik.
In 2021, this recipe was updated for Traefik v2. There's really no reason to be using Traefikv1 anymore ;)
- Docker swarm cluster with persistent shared storage
- DNS entry for the hostname you intend to use (or a wildcard), pointed to your keepalived IP
New: * [ ] Traefik configured per design * [ ] Access to update your DNS records for manual/automated LetsEncrypt DNS-01 validation, or ingress HTTP/HTTPS for HTTP-01 validation
While it's possible to configure traefik via docker command arguments, I prefer to create a config file (
traefik.toml). This allows me to change traefik's behaviour by simply changing the file, and keeps my docker config simple.
/var/data/config/traefikv2/traefik.toml as per the following example:
[global] checkNewVersion = true # Enable the Dashboard [api] dashboard = true # Write out Traefik logs [log] level = "INFO" filePath = "/traefik.log" [entryPoints.http] address = ":80" # Redirect to HTTPS (why wouldn't you?) [entryPoints.http.http.redirections.entryPoint] to = "https" scheme = "https" [entryPoints.https] address = ":443" [entryPoints.https.http.tls] certResolver = "main" # Let's Encrypt [certificatesResolvers.main.acme] email = "email@example.com" storage = "acme.json" # uncomment to use staging CA for testing # caServer = "https://acme-staging-v02.api.letsencrypt.org/directory" [certificatesResolvers.main.acme.dnsChallenge] provider = "route53" # Uncomment to use HTTP validation, like a caveman! # [certificatesResolvers.main.acme.httpChallenge] # entryPoint = "http" # Docker Traefik provider [providers.docker] endpoint = "unix:///var/run/docker.sock" swarmMode = true watch = true
Prepare the docker service config
"We'll want an overlay network, independent of our traefik stack, so that we can attach/detach all our other stacks (including traefik) to the overlay network. This way, we can undeploy/redepoly the traefik stack without having to bring down every other stack first!" - voice of hard-won experience
/var/data/config/traefik/traefik.yml as per the following example:
version: "3.2" # What is this? # # This stack exists solely to deploy the traefik_public overlay network, so that # other stacks (including traefik-app) can attach to it services: scratch: image: scratch deploy: replicas: 0 networks: - public networks: public: driver: overlay attachable: true ipam: config: - subnet: 172.16.200.0/24
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/var/data/config/traefikv2/traefikv2.env with the environment variables required by the provider you chose in the LetsEncrypt DNS Challenge section of
traefik.toml. Full configuration options can be found in the Traefik documentation. Route53 and CloudFlare examples are below.
# Route53 example AWS_ACCESS_KEY_ID=<your-aws-key> AWS_SECRET_ACCESS_KEY=<your-aws-secret> # CloudFlare example # CLOUDFLARE_EMAIL=<your-cloudflare-email> # CLOUDFLARE_API_KEY=<your-cloudflare-api-key>
/var/data/config/traefikv2/traefikv2.yml as per the following example:
version: "3.2" services: app: image: traefik:v2.4 env_file: /var/data/config/traefikv2/traefikv2.env # Note below that we use host mode to avoid source nat being applied to our ingress HTTP/HTTPS sessions # Without host mode, all inbound sessions would have the source IP of the swarm nodes, rather than the # original source IP, which would impact logging. If you don't care about this, you can expose ports the # "minimal" way instead ports: - target: 80 published: 80 protocol: tcp mode: host - target: 443 published: 443 protocol: tcp mode: host - target: 8080 published: 8080 protocol: tcp volumes: - /var/run/docker.sock:/var/run/docker.sock:ro - /var/data/config/traefikv2:/etc/traefik - /var/data/traefikv2/traefik.log:/traefik.log - /var/data/traefikv2/acme.json:/acme.json networks: - traefik_public # Global mode makes an instance of traefik listen on _every_ node, so that regardless of which # node the request arrives on, it'll be forwarded to the correct backend service. deploy: mode: global labels: - "traefik.docker.network=traefik_public" - "traefik.http.routers.api.rule=Host(`traefik.example.com`)" - "traefik.http.routers.api.entrypoints=https" - "traefik.http.routers.api.tls.domains.main=example.com" - "traefik.http.routers.api.tls.domains.sans=*.example.com" - "traefik.http.routers.api.tls=true" - "traefik.http.routers.api.tls.certresolver=main" - "traefik.http.routers.api.service=api@internal" - "traefik.http.services.dummy.loadbalancer.server.port=9999" # uncomment this to enable forward authentication on the traefik api/dashboard #- "traefik.http.routers.api.middlewares=forward-auth" placement: constraints: [node.role == manager] networks: traefik_public: external: true
Docker won't start a service with a bind-mount to a non-existent file, so prepare an empty acme.json and traefik.log (with the appropriate permissions) by running:
touch /var/data/traefikv2/acme.json touch /var/data/traefikv2/traefik.log chmod 600 /var/data/traefikv2/acme.json chmod 600 /var/data/traefikv2/traefik.log
Pay attention above. You must set
acme.json's permissions to owner-readable-only, else the container will fail to start with an ID-10T error!
Traefik will populate acme.json itself when it runs, but it needs to exist before the container will start (Chicken, meet egg.)
Likewise with the log file.
First, launch the traefik stack, which will do nothing other than create an overlay network by running
docker stack deploy traefik -c /var/data/config/traefik/traefik.yml
[root@kvm ~]# docker stack deploy traefik -c /var/data/config/traefik/traefik.yml Creating network traefik_public Creating service traefik_scratch [root@kvm ~]#
Now deploy the traefik application itself (which will attach to the overlay network) by running
docker stack deploy traefikv2 -c /var/data/config/traefikv2/traefikv2.yml
[root@kvm ~]# docker stack deploy traefikv2 -c /var/data/config/traefikv2/traefikv2.yml Creating service traefikv2_traefikv2 [root@kvm ~]#
Confirm traefik is running with
docker stack ps traefikv2:
root@raphael:~# docker stack ps traefikv2 ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS lmvqcfhap08o traefikv2_app.dz178s1aahv16bapzqcnzc03p traefik:v2.4 donatello Running Running 2 minutes ago *:443->443/tcp,*:80->80/tcp root@raphael:~#
Check Traefik Dashboard
You should now be able to access1 your traefik instance on
https://traefik.<your domain\> (if your LetsEncrypt certificate is working), or
http://<node IP\>:8080 (if it's not)- It'll look a little lonely currently (below), but we'll populate it as we add recipes
- An overlay network to permit traefik to access all future stacks we deploy
- Frontend proxy which will dynamically configure itself for new backend containers
- Automatic SSL support for all proxied resources
Chef's notes 📓
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