baalajimaestro/traefik

Fork 0

nogoegst be0dbd62c1 Drop capabilities in Kubernetes DaemonSet example

2018-03-22 16:44:05 +01:00

25 KiB

Raw Blame History

Kubernetes Ingress Controller

This guide explains how to use Træfik as an Ingress controller for a Kubernetes cluster.

If you are not familiar with Ingresses in Kubernetes you might want to read the Kubernetes user guide

The config files used in this guide can be found in the examples directory

Prerequisites

A working Kubernetes cluster. If you want to follow along with this guide, you should setup minikube on your machine, as it is the quickest way to get a local Kubernetes cluster setup for experimentation and development.

!!! note The guide is likely not fully adequate for a production-ready setup.

The kubectl binary should be installed on your workstation.

Role Based Access Control configuration (Kubernetes 1.6+ only)

Kubernetes introduces Role Based Access Control (RBAC) in 1.6+ to allow fine-grained control of Kubernetes resources and API.

If your cluster is configured with RBAC, you will need to authorize Træfik to use the Kubernetes API. There are two ways to set up the proper permission: Via namespace-specific RoleBindings or a single, global ClusterRoleBinding.

RoleBindings per namespace enable to restrict granted permissions to the very namespaces only that Træfik is watching over, thereby following the least-privileges principle. This is the preferred approach if Træfik is not supposed to watch all namespaces, and the set of namespaces does not change dynamically. Otherwise, a single ClusterRoleBinding must be employed.

!!! note RoleBindings per namespace are available in Træfik 1.5 and later. Please use ClusterRoleBindings for older versions.

For the sake of simplicity, this guide will use a ClusterRoleBinding:

---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: traefik-ingress-controller
rules:
  - apiGroups:
      - ""
    resources:
      - services
      - endpoints
      - secrets
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - extensions
    resources:
      - ingresses
    verbs:
      - get
      - list
      - watch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: traefik-ingress-controller
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: traefik-ingress-controller
subjects:
- kind: ServiceAccount
  name: traefik-ingress-controller
  namespace: kube-system

examples/k8s/traefik-rbac.yaml

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/traefik-rbac.yaml

For namespaced restrictions, one RoleBinding is required per watched namespace along with a corresponding configuration of Træfik's kubernetes.namespaces parameter.

Deploy Træfik using a Deployment or DaemonSet

It is possible to use Træfik with a Deployment or a DaemonSet object, whereas both options have their own pros and cons:

The scalability is much better when using a Deployment, because you will have a Single-Pod-per-Node model when using the DaemonSet.
It is possible to exclusively run a Service on a dedicated set of machines using taints and tolerations with a DaemonSet.
On the other hand the DaemonSet allows you to access any Node directly on Port 80 and 443, where you have to setup a Service object with a Deployment.

The Deployment objects looks like this:

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
  labels:
    k8s-app: traefik-ingress-lb
spec:
  replicas: 1
  selector:
    matchLabels:
      k8s-app: traefik-ingress-lb
  template:
    metadata:
      labels:
        k8s-app: traefik-ingress-lb
        name: traefik-ingress-lb
    spec:
      serviceAccountName: traefik-ingress-controller
      terminationGracePeriodSeconds: 60
      containers:
      - image: traefik
        name: traefik-ingress-lb
        args:
        - --api
        - --kubernetes
        - --logLevel=INFO
---
kind: Service
apiVersion: v1
metadata:
  name: traefik-ingress-service
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress-lb
  ports:
    - protocol: TCP
      port: 80
      name: web
    - protocol: TCP
      port: 8080
      name: admin
  type: NodePort

examples/k8s/traefik-deployment.yaml

!!! note The Service will expose two NodePorts which allow access to the ingress and the web interface.

The DaemonSet objects looks not much different:

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
---
kind: DaemonSet
apiVersion: extensions/v1beta1
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
  labels:
    k8s-app: traefik-ingress-lb
spec:
  template:
    metadata:
      labels:
        k8s-app: traefik-ingress-lb
        name: traefik-ingress-lb
    spec:
      serviceAccountName: traefik-ingress-controller
      terminationGracePeriodSeconds: 60
      hostNetwork: true
      containers:
      - image: traefik
        name: traefik-ingress-lb
        ports:
        - name: http
          containerPort: 80
          hostPort: 80
        - name: admin
          containerPort: 8080
        securityContext:
          capabilities:
            drop:
            - ALL
            add:
            - NET_BIND_SERVICE
        args:
        - --api
        - --kubernetes
        - --logLevel=INFO
---
kind: Service
apiVersion: v1
metadata:
  name: traefik-ingress-service
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress-lb
  ports:
    - protocol: TCP
      port: 80
      name: web
    - protocol: TCP
      port: 8080
      name: admin
  type: NodePort

examples/k8s/traefik-ds.yaml

To deploy Træfik to your cluster start by submitting one of the YAML files to the cluster with kubectl:

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/traefik-deployment.yaml

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/traefik-ds.yaml

There are some significant differences between using Deployments and DaemonSets:

The Deployment has easier up and down scaling possibilities. It can implement full pod lifecycle and supports rolling updates from Kubernetes 1.2. At least one Pod is needed to run the Deployment.
The DaemonSet automatically scales to all nodes that meets a specific selector and guarantees to fill nodes one at a time. Rolling updates are fully supported from Kubernetes 1.7 for DaemonSets as well.

Check the Pods

Now lets check if our command was successful.

Start by listing the pods in the kube-system namespace:

kubectl --namespace=kube-system get pods

NAME                                         READY     STATUS    RESTARTS   AGE
kube-addon-manager-minikubevm                1/1       Running   0          4h
kubernetes-dashboard-s8krj                   1/1       Running   0          4h
traefik-ingress-controller-678226159-eqseo   1/1       Running   0          7m

You should see that after submitting the Deployment or DaemonSet to Kubernetes it has launched a Pod, and it is now running. It might take a few moments for Kubernetes to pull the Træfik image and start the container.

!!! note You could also check the deployment with the Kubernetes dashboard, run minikube dashboard to open it in your browser, then choose the kube-system namespace from the menu at the top right of the screen.

You should now be able to access Træfik on port 80 of your Minikube instance when using the DaemonSet:

curl $(minikube ip)

404 page not found

If you decided to use the deployment, then you need to target the correct NodePort, which can be seen when you execute kubectl get services --namespace=kube-system.

curl $(minikube ip):<NODEPORT>

404 page not found

!!! note We expect to see a 404 response here as we haven't yet given Træfik any configuration.

All further examples below assume a DaemonSet installation. Deployment users will need to append the NodePort when constructing requests.

Deploy Træfik using Helm Chart

!!! note The Helm Chart is maintained by the community, not the Træfik project maintainers.

Instead of installing Træfik via Kubernetes object directly, you can also use the Træfik Helm chart.

Install the Træfik chart by:

helm install stable/traefik

For more information, check out the documentation.

Submitting an Ingress to the Cluster

Lets start by creating a Service and an Ingress that will expose the Træfik Web UI.

apiVersion: v1
kind: Service
metadata:
  name: traefik-web-ui
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress-lb
  ports:
  - port: 80
    targetPort: 8080
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-web-ui
  namespace: kube-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: traefik-ui.minikube
    http:
      paths:
      - backend:
          serviceName: traefik-web-ui
          servicePort: 80

examples/k8s/ui.yaml

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/ui.yaml

Now lets setup an entry in our /etc/hosts file to route traefik-ui.minikube to our cluster.

In production you would want to set up real DNS entries. You can get the IP address of your minikube instance by running minikube ip:

echo "$(minikube ip) traefik-ui.minikube" | sudo tee -a /etc/hosts

We should now be able to visit traefik-ui.minikube in the browser and view the Træfik web UI.

Add a TLS Certificate to the Ingress

!!! note For this example to work you need a TLS entrypoint. You don't have to provide a TLS certificate at this point. For more details see here.

To setup an HTTPS-protected ingress, you can leverage the TLS feature of the ingress resource.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-web-ui
  namespace: kube-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: traefik-ui.minikube
    http:
      paths:
      - backend:
          serviceName: traefik-web-ui
          servicePort: 80
  tls:
    secretName: traefik-ui-tls-cert

In addition to the modified ingress you need to provide the TLS certificate via a Kubernetes secret in the same namespace as the ingress. The following two commands will generate a new certificate and create a secret containing the key and cert files.

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout tls.key -out tls.crt -subj "/CN=traefik-ui.minikube"
kubectl -n kube-system create secret tls traefik-ui-tls-cert --key=tls.key --cert=tls.crt

If there are any errors while loading the TLS section of an ingress, the whole ingress will be skipped.

!!! note The secret must have two entries named tls.keyand tls.crt. See the Kubernetes documentation for more details.

!!! note The TLS certificates will be added to all entrypoints defined by the ingress annotation traefik.frontend.entryPoints. If no such annotation is provided, the TLS certificates will be added to all TLS-enabled defaultEntryPoints.

!!! note The field hosts in the TLS configuration is ignored. Instead, the domains provided by the certificate are used for this purpose. It is recommended to not use wildcard certificates as they will match globally.

Basic Authentication

It's possible to protect access to Træfik through basic authentication. (See the Kubernetes Ingress configuration page for syntactical details and restrictions.)

Creating the Secret

A. Use htpasswd to create a file containing the username and the base64-encoded password:

htpasswd -c ./auth myusername

You will be prompted for a password which you will have to enter twice. htpasswd will create a file with the following:

cat auth

myusername:$apr1$78Jyn/1K$ERHKVRPPlzAX8eBtLuvRZ0

B. Now use kubectl to create a secret in the monitoring namespace using the file created by htpasswd.

kubectl create secret generic mysecret --from-file auth --namespace=monitoring

!!! note Secret must be in same namespace as the Ingress object.

C. Attach the following annotations to the Ingress object:

ingress.kubernetes.io/auth-type: "basic"
ingress.kubernetes.io/auth-secret: "mysecret"

They specify basic authentication and reference the Secret mysecret containing the credentials.

Following is a full Ingress example based on Prometheus:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
 name: prometheus-dashboard
 namespace: monitoring
 annotations:
   kubernetes.io/ingress.class: traefik
   ingress.kubernetes.io/auth-type: "basic"
   ingress.kubernetes.io/auth-secret: "mysecret"
spec:
 rules:
 - host: dashboard.prometheus.example.com
   http:
     paths:
     - backend:
         serviceName: prometheus
         servicePort: 9090

You can apply the example as following:

kubectl create -f prometheus-ingress.yaml -n monitoring

Name-based Routing

In this example we are going to setup websites for three of the United Kingdoms best loved cheeses: Cheddar, Stilton, and Wensleydale.

First lets start by launching the pods for the cheese websites.

---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: stilton
  labels:
    app: cheese
    cheese: stilton
spec:
  replicas: 2
  selector:
    matchLabels:
      app: cheese
      task: stilton
  template:
    metadata:
      labels:
        app: cheese
        task: stilton
        version: v0.0.1
    spec:
      containers:
      - name: cheese
        image: errm/cheese:stilton
        ports:
        - containerPort: 80
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: cheddar
  labels:
    app: cheese
    cheese: cheddar
spec:
  replicas: 2
  selector:
    matchLabels:
      app: cheese
      task: cheddar
  template:
    metadata:
      labels:
        app: cheese
        task: cheddar
        version: v0.0.1
    spec:
      containers:
      - name: cheese
        image: errm/cheese:cheddar
        ports:
        - containerPort: 80
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: wensleydale
  labels:
    app: cheese
    cheese: wensleydale
spec:
  replicas: 2
  selector:
    matchLabels:
      app: cheese
      task: wensleydale
  template:
    metadata:
      labels:
        app: cheese
        task: wensleydale
        version: v0.0.1
    spec:
      containers:
      - name: cheese
        image: errm/cheese:wensleydale
        ports:
        - containerPort: 80

examples/k8s/cheese-deployments.yaml

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/cheese-deployments.yaml

Next we need to setup a Service for each of the cheese pods.

---
apiVersion: v1
kind: Service
metadata:
  name: stilton
spec:
  ports:
  - name: http
    targetPort: 80
    port: 80
  selector:
    app: cheese
    task: stilton
---
apiVersion: v1
kind: Service
metadata:
  name: cheddar
spec:
  ports:
  - name: http
    targetPort: 80
    port: 80
  selector:
    app: cheese
    task: cheddar
---
apiVersion: v1
kind: Service
metadata:
  name: wensleydale
  annotations:
    traefik.backend.circuitbreaker: "NetworkErrorRatio() > 0.5"
spec:
  ports:
  - name: http
    targetPort: 80
    port: 80
  selector:
    app: cheese
    task: wensleydale

!!! note We also set a circuit breaker expression for one of the backends by setting the traefik.backend.circuitbreaker annotation on the service.

examples/k8s/cheese-services.yaml

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/cheese-services.yaml

Now we can submit an ingress for the cheese websites.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: cheese
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: stilton.minikube
    http:
      paths:
      - path: /
        backend:
          serviceName: stilton
          servicePort: http
  - host: cheddar.minikube
    http:
      paths:
      - path: /
        backend:
          serviceName: cheddar
          servicePort: http
  - host: wensleydale.minikube
    http:
      paths:
      - path: /
        backend:
          serviceName: wensleydale
          servicePort: http

examples/k8s/cheese-ingress.yaml

!!! note we list each hostname, and add a backend service.

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/cheese-ingress.yaml

Now visit the Træfik dashboard and you should see a frontend for each host. Along with a backend listing for each service with a server set up for each pod.

If you edit your /etc/hosts again you should be able to access the cheese websites in your browser.

echo "$(minikube ip) stilton.minikube cheddar.minikube wensleydale.minikube" | sudo tee -a /etc/hosts

Path-based Routing

Now lets suppose that our fictional client has decided that while they are super happy about our cheesy web design, when they asked for 3 websites they had not really bargained on having to buy 3 domain names.

No problem, we say, why don't we reconfigure the sites to host all 3 under one domain.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: cheeses
  annotations:
    kubernetes.io/ingress.class: traefik
    traefik.frontend.rule.type: PathPrefixStrip
spec:
  rules:
  - host: cheeses.minikube
    http:
      paths:
      - path: /stilton
        backend:
          serviceName: stilton
          servicePort: http
      - path: /cheddar
        backend:
          serviceName: cheddar
          servicePort: http
      - path: /wensleydale
        backend:
          serviceName: wensleydale
          servicePort: http

examples/k8s/cheeses-ingress.yaml

!!! note We are configuring Træfik to strip the prefix from the url path with the traefik.frontend.rule.type annotation so that we can use the containers from the previous example without modification.

kubectl apply -f https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/cheeses-ingress.yaml

echo "$(minikube ip) cheeses.minikube" | sudo tee -a /etc/hosts

You should now be able to visit the websites in your browser.

Specifying Routing Priorities

Sometimes you need to specify priority for ingress routes, especially when handling wildcard routes. This can be done by adding the traefik.frontend.priority annotation, i.e.:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: wildcard-cheeses
  annotations:
    traefik.frontend.priority: "1"
spec:
  rules:
  - host: *.minikube
    http:
      paths:
      - path: /
        backend:
          serviceName: stilton
          servicePort: http

kind: Ingress
metadata:
  name: specific-cheeses
  annotations:
    traefik.frontend.priority: "2"
spec:
  rules:
  - host: specific.minikube
    http:
      paths:
      - path: /
        backend:
          serviceName: stilton
          servicePort: http

Note that priority values must be quoted to avoid numeric interpretation (which are illegal for annotations).

Forwarding to ExternalNames

When specifying an ExternalName, Træfik will forward requests to the given host accordingly and use HTTPS when the Service port matches 443. This still requires setting up a proper port mapping on the Service from the Ingress port to the (external) Service port.

Disable passing the Host Header

By default Træfik will pass the incoming Host header to the upstream resource.

However, there are times when you may not want this to be the case. For example, if your service is of the ExternalName type.

Disable globally

Add the following to your TOML configuration file:

disablePassHostHeaders = true

Disable per Ingress

To disable passing the Host header per ingress resource set the traefik.frontend.passHostHeader annotation on your ingress to "false".

Here is an example definition:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: example
  annotations:
    kubernetes.io/ingress.class: traefik
    traefik.frontend.passHostHeader: "false"
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /static
        backend:
          serviceName: static
          servicePort: https

And an example service definition:

apiVersion: v1
kind: Service
metadata:
  name: static
spec:
  ports:
  - name: https
    port: 443
  type: ExternalName
  externalName: static.otherdomain.com

If you were to visit example.com/static the request would then be passed on to static.otherdomain.com/static, and static.otherdomain.com would receive the request with the Host header being static.otherdomain.com.

!!! note The per-ingress annotation overrides whatever the global value is set to. So you could set disablePassHostHeaders to true in your TOML configuration file and then enable passing the host header per ingress if you wanted.

Partitioning the Ingress object space

By default, Træfik processes every Ingress objects it observes. At times, however, it may be desirable to ignore certain objects. The following sub-sections describe common use cases and how they can be handled with Træfik.

Between Træfik and other Ingress controller implementations

Sometimes Træfik runs along other Ingress controller implementations. One such example is when both Træfik and a cloud provider Ingress controller are active.

The kubernetes.io/ingress.class annotation can be attached to any Ingress object in order to control whether Træfik should handle it.

If the annotation is missing, contains an empty value, or the value traefik, then the Træfik controller will take responsibility and process the associated Ingress object. If the annotation contains any other value (usually the name of a different Ingress controller), Træfik will ignore the object.

Between multiple Træfik Deployments

Sometimes multiple Træfik Deployments are supposed to run concurrently. For instance, it is conceivable to have one Deployment deal with internal and another one with external traffic.

For such cases, it is advisable to classify Ingress objects through a label and configure the labelSelector option per each Træfik Deployment accordingly. To stick with the internal/external example above, all Ingress objects meant for internal traffic could receive a traffic-type: internal label while objects designated for external traffic receive a traffic-type: external label. The label selectors on the Træfik Deployments would then be traffic-type=internal and traffic-type=external, respectively.

Production advice

Resource limitations

The examples shown deliberately do not specify any resource limitations as there is no one size fits all.

In a production environment, however, it is important to set proper bounds, especially with regards to CPU:

too strict and Træfik will be throttled while serving requests (as Kubernetes imposes hard quotas)
too loose and Træfik may waste resources not available for other containers

When in doubt, you should measure your resource needs, and adjust requests and limits accordingly.

25 KiB Raw Blame History