Traefik & CRD & Let's Encrypt

Traefik with an IngressRoute Custom Resource Definition for Kubernetes, and TLS Through Let's Encrypt.

This document is intended to be a fully working example demonstrating how to set up Traefik in Kubernetes,with the dynamic configuration coming from the IngressRoute Custom Resource,and TLS setup with Let's Encrypt.However, for the sake of simplicity, we're using k3s docker image for the Kubernetes cluster setup.

Please note that for this setup, given that we're going to use ACME's TLS-ALPN-01 challenge, the host you'll be running it on must be able to receive connections from the outside on port 443.And of course its internet facing IP address must match the domain name you intend to use.

In the following, the Kubernetes resources defined in YAML configuration files can be applied to the setup in two different ways:

  • the first, and usual way, is simply with the kubectl apply command.
  • the second, which can be used for this tutorial, is to directly place the files in the directory used by the k3s docker image for such inputs (/var/lib/rancher/k3s/server/manifests).

Kubectl Version

With the rancher/k3s version used in this guide (0.8.0), the kubectl version needs to be >= 1.11.

k3s Docker-compose Configuration

Our starting point is the docker-compose configuration file, to start the k3s cluster.You can start it with:

  1. docker-compose -f k3s.yml up
  1. server:
  2.   image: rancher/k3s:v0.8.0
  3.   command: server --disable-agent --no-deploy traefik
  4.   environment:
  5.     - K3S_CLUSTER_SECRET=somethingtotallyrandom
  6.     - K3S_KUBECONFIG_OUTPUT=/output/kubeconfig.yaml
  7.     - K3S_KUBECONFIG_MODE=666
  8.   volumes:
  9.     # k3s will generate a kubeconfig.yaml in this directory. This volume is mounted
  10.     # on your host, so you can then 'export KUBECONFIG=/somewhere/on/your/host/out/kubeconfig.yaml',
  11.     # in order for your kubectl commands to work.
  12.     - /somewhere/on/your/host/out:/output
  13.     # This directory is where you put all the (yaml) configuration files of
  14.     # the Kubernetes resources.
  15.     - /somewhere/on/your/host/in:/var/lib/rancher/k3s/server/manifests
  16.   ports:
  17.     - 6443:6443
  19. node:
  20.   image: rancher/k3s:v0.8.0
  21.   privileged: true
  22.   links:
  23.     - server
  24.   environment:
  25.     - K3S_URL=https://server:6443
  26.     - K3S_CLUSTER_SECRET=somethingtotallyrandom
  27.   volumes:
  28.     # this is where you would place a alternative traefik image (saved as a .tar file with
  29.     # 'docker save'), if you want to use it, instead of the traefik:v2.0 image.
  30.     - /sowewhere/on/your/host/custom-image:/var/lib/rancher/k3s/agent/images

Cluster Resources

Let's now have a look (in the order they should be applied, if using kubectl apply) at all the required resources for the full setup.

IngressRoute Definition

First, the definition of the IngressRoute and the Middleware kinds.Also note the RBAC authorization resources; they'll be referenced through the serviceAccountName of the deployment, later on.

  1. apiVersion: apiextensions.k8s.io/v1beta1
  2. kind: CustomResourceDefinition
  3. metadata:
  4.   name: ingressroutes.traefik.containo.us
  6. spec:
  7.   group: traefik.containo.us
  8.   version: v1alpha1
  9.   names:
  10.     kind: IngressRoute
  11.     plural: ingressroutes
  12.     singular: ingressroute
  13.   scope: Namespaced
  15. ---
  16. apiVersion: apiextensions.k8s.io/v1beta1
  17. kind: CustomResourceDefinition
  18. metadata:
  19.   name: ingressroutetcps.traefik.containo.us
  21. spec:
  22.   group: traefik.containo.us
  23.   version: v1alpha1
  24.   names:
  25.     kind: IngressRouteTCP
  26.     plural: ingressroutetcps
  27.     singular: ingressroutetcp
  28.   scope: Namespaced
  30. ---
  31. apiVersion: apiextensions.k8s.io/v1beta1
  32. kind: CustomResourceDefinition
  33. metadata:
  34.   name: middlewares.traefik.containo.us
  36. spec:
  37.   group: traefik.containo.us
  38.   version: v1alpha1
  39.   names:
  40.     kind: Middleware
  41.     plural: middlewares
  42.     singular: middleware
  43.   scope: Namespaced
  45. ---
  46. apiVersion: apiextensions.k8s.io/v1beta1
  47. kind: CustomResourceDefinition
  48. metadata:
  49.   name: tlsoptions.traefik.containo.us
  51. spec:
  52.   group: traefik.containo.us
  53.   version: v1alpha1
  54.   names:
  55.     kind: TLSOption
  56.     plural: tlsoptions
  57.     singular: tlsoption
  58.   scope: Namespaced
  60. ---
  61. apiVersion: apiextensions.k8s.io/v1beta1
  62. kind: CustomResourceDefinition
  63. metadata:
  64.   name: traefikservices.traefik.containo.us
  66. spec:
  67.   group: traefik.containo.us
  68.   version: v1alpha1
  69.   names:
  70.     kind: TraefikService
  71.     plural: traefikservices
  72.     singular: traefikservice
  73.   scope: Namespaced
  75. ---
  76. kind: ClusterRole
  77. apiVersion: rbac.authorization.k8s.io/v1beta1
  78. metadata:
  79.   name: traefik-ingress-controller
  81. rules:
  82.   - apiGroups:
  83.       - ""
  84.     resources:
  85.       - services
  86.       - endpoints
  87.       - secrets
  88.     verbs:
  89.       - get
  90.       - list
  91.       - watch
  92.   - apiGroups:
  93.       - extensions
  94.     resources:
  95.       - ingresses
  96.     verbs:
  97.       - get
  98.       - list
  99.       - watch
  100.   - apiGroups:
  101.       - extensions
  102.     resources:
  103.       - ingresses/status
  104.     verbs:
  105.       - update
  106.   - apiGroups:
  107.       - traefik.containo.us
  108.     resources:
  109.       - middlewares
  110.     verbs:
  111.       - get
  112.       - list
  113.       - watch
  114.   - apiGroups:
  115.       - traefik.containo.us
  116.     resources:
  117.       - ingressroutes
  118.     verbs:
  119.       - get
  120.       - list
  121.       - watch
  122.   - apiGroups:
  123.       - traefik.containo.us
  124.     resources:
  125.       - ingressroutetcps
  126.     verbs:
  127.       - get
  128.       - list
  129.       - watch
  130.   - apiGroups:
  131.       - traefik.containo.us
  132.     resources:
  133.       - tlsoptions
  134.     verbs:
  135.       - get
  136.       - list
  137.       - watch
  138.   - apiGroups:
  139.       - traefik.containo.us
  140.     resources:
  141.       - traefikservices
  142.     verbs:
  143.       - get
  144.       - list
  145.       - watch
  147. ---
  148. kind: ClusterRoleBinding
  149. apiVersion: rbac.authorization.k8s.io/v1beta1
  150. metadata:
  151.   name: traefik-ingress-controller
  153. roleRef:
  154.   apiGroup: rbac.authorization.k8s.io
  155.   kind: ClusterRole
  156.   name: traefik-ingress-controller
  157. subjects:
  158.   - kind: ServiceAccount
  159.     name: traefik-ingress-controller
  160.     namespace: default

Services

Then, the services. One for Traefik itself, and one for the app it routes for, i.e. in this case our demo HTTP server: whoami.

  1. apiVersion: v1
  2. kind: Service
  3. metadata:
  4.   name: traefik
  6. spec:
  7.   ports:
  8.     - protocol: TCP
  9.       name: web
  10.       port: 8000
  11.     - protocol: TCP
  12.       name: admin
  13.       port: 8080
  14.     - protocol: TCP
  15.       name: websecure
  16.       port: 4443
  17.   selector:
  18.     app: traefik
  20. ---
  21. apiVersion: v1
  22. kind: Service
  23. metadata:
  24.   name: whoami
  26. spec:
  27.   ports:
  28.     - protocol: TCP
  29.       name: web
  30.       port: 80
  31.   selector:
  32.     app: whoami

Deployments

Next, the deployments, i.e. the actual pods behind the services.Again, one pod for Traefik, and one for the whoami app.

  1. apiVersion: v1
  2. kind: ServiceAccount
  3. metadata:
  4.   namespace: default
  5.   name: traefik-ingress-controller
  7. ---
  8. kind: Deployment
  9. apiVersion: apps/v1
  10. metadata:
  11.   namespace: default
  12.   name: traefik
  13.   labels:
  14.     app: traefik
  16. spec:
  17.   replicas: 1
  18.   selector:
  19.     matchLabels:
  20.       app: traefik
  21.   template:
  22.     metadata:
  23.       labels:
  24.         app: traefik
  25.     spec:
  26.       serviceAccountName: traefik-ingress-controller
  27.       containers:
  28.         - name: traefik
  29.           image: traefik:v2.0
  30.           args:
  31.             - --api.insecure
  32.             - --accesslog
  33.             - --entrypoints.web.Address=:8000
  34.             - --entrypoints.websecure.Address=:4443
  35.             - --providers.kubernetescrd
  36.             - --certificatesresolvers.default.acme.tlschallenge
  37.             - [email protected]
  38.             - --certificatesresolvers.default.acme.storage=acme.json
  39.             # Please note that this is the staging Let's Encrypt server.
  40.             # Once you get things working, you should remove that whole line altogether.
  41.             - --certificatesresolvers.default.acme.caserver=https://acme-staging-v02.api.letsencrypt.org/directory
  42.           ports:
  43.             - name: web
  44.               containerPort: 8000
  45.             - name: websecure
  46.               containerPort: 4443
  47.             - name: admin
  48.               containerPort: 8080
  50. ---
  51. kind: Deployment
  52. apiVersion: apps/v1
  53. metadata:
  54.   namespace: default
  55.   name: whoami
  56.   labels:
  57.     app: whoami
  59. spec:
  60.   replicas: 2
  61.   selector:
  62.     matchLabels:
  63.       app: whoami
  64.   template:
  65.     metadata:
  66.       labels:
  67.         app: whoami
  68.     spec:
  69.       containers:
  70.         - name: whoami
  71.           image: containous/whoami
  72.           ports:
  73.             - name: web
  74.               containerPort: 80

Port Forwarding

Now, as an exception to what we said above, please note that you should not let the ingressRoute resources below be applied automatically to your cluster.The reason is, as soon as the ACME provider of Traefik detects we have TLS routers, it will try to generate the certificates for the corresponding domains.And this will not work, because as it is, our Traefik pod is not reachable from the outside, which will make the ACME TLS challenge fail.Therefore, for the whole thing to work, we must delay applying the ingressRoute resources until we have port-forwarding set up properly, which is the next step.

  1. kubectl port-forward --address 0.0.0.0 service/traefik 8000:8000 8080:8080 443:4443 -n default

Also, and this is out of the scope if this guide, please note that because of the privileged ports limitation on Linux, the above command might fail to listen on port 443.In which case you can use tricks such as elevating caps of kubectl with setcaps, or using authbind, or setting up a NAT between your host and the WAN.Look it up.

Traefik Routers

We can now finally apply the actual ingressRoutes, with:

  1. kubectl apply -f 04-ingressroutes.yml
  1. apiVersion: traefik.containo.us/v1alpha1
  2. kind: IngressRoute
  3. metadata:
  4.   name: simpleingressroute
  5.   namespace: default
  6. spec:
  7.   entryPoints:
  8.     - web
  9.   routes:
  10.   - match: Host(`your.domain.com`) && PathPrefix(`/notls`)
  11.     kind: Rule
  12.     services:
  13.     - name: whoami
  14.       port: 80
  16. ---
  17. apiVersion: traefik.containo.us/v1alpha1
  18. kind: IngressRoute
  19. metadata:
  20.   name: ingressroutetls
  21.   namespace: default
  22. spec:
  23.   entryPoints:
  24.     - websecure
  25.   routes:
  26.   - match: Host(`your.domain.com`) && PathPrefix(`/tls`)
  27.     kind: Rule
  28.     services:
  29.     - name: whoami
  30.       port: 80
  31.   tls:
  32.     certResolver: default

Give it a few seconds for the ACME TLS challenge to complete, and you should then be able to access your whoami pod (routed through Traefik), from the outside.Both with or (just for fun, do not do that in production) without TLS:

  1. curl [-k] https://your.domain.com/tls
  1. curl [-k] http://your.domain.com:8000/notls

Note that you'll have to use -k as long as you're using the staging server of Let's Encrypt, since it is not an authorized certificate authority on systems where it hasn't been manually added.