Routes

Module

A network policy is a specification of how groups of pods are allowed to communicate with each other and other network endpoints. NetworkPolicy resources use labels to select pods and define rules which specify what traffic is allowed to the selected pods.

Overview

At the end of this module, you will :

  • Learn to manage the external access of internal resources

  • Learn to manage ingress controller

  • Learn to secure the cluster access

Prerequisites

Create the directory data/routes in your home folder to manage the YAML file needed in this module.

mkdir ~/data/routes

This module needs an Ingress controller to be deployed on the cluster. The default Ingress controller used in this module is Nginx. Ensure this module is up and running before continuing.

Create

Ingress exposes HTTP and HTTPS routes from outside the cluster to Services within the cluster. Traffic routing is controlled by rules defined on the ingress resource.

An ingress can be configured to give services externally-reachable URLs, load balance traffic, terminate SSL, and offer name based virtual hosting. An ingress controller is responsible for fulfilling the ingress, usually with a loadbalancer, though it may also configure your edge router or additional frontends to help handle the traffic.

In order for the ingress resource to work, the cluster must have an ingress controller running :

The create command can create a Ingress object based on a yaml file definition.

Exercise n°1

On Minikube, ensure that the ingress addons is enable before continuing :

minikube addons enable ingress

First, deploy two static website in two different deployments. Then, expose each one on the port 80.

~/data/routes/01_deployments.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: webserver1
spec:
  replicas: 2
  selector:
    matchLabels:
      app: webserver1
  template:
    metadata:
      labels:
        app: webserver1
    spec:
      containers:
      - name: static
        image: dockersamples/static-site
        env:
        - name: AUTHOR
          value: wikitops1
        ports:
        - containerPort: 80
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: webserver2
spec:
  replicas: 2
  selector:
    matchLabels:
      app: webserver2
  template:
    metadata:
      labels:
        app: webserver2
    spec:
      containers:
      - name: static
        image: dockersamples/static-site
        env:
        - name: AUTHOR
          value: wikitops2
        ports:
        - containerPort: 80

Expose each on of the Deployment on port 80.

~/data/routes/02_services.yaml
apiVersion: v1
kind: Service
metadata:
  name: webserver1
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: webserver1
---
apiVersion: v1
kind: Service
metadata:
  name: webserver2
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: webserver2

Create an Ingress resource to expose an Nginx pod Service's on port 80.

~/data/routes/03_ingress.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
  name: myfirstingress
spec:
  rules:
  - host: training.wikitops.io
    http:
      paths:
      - backend:
          serviceName: webserver1
          servicePort: 80
        path: /path1
      - backend:
          serviceName: webserver2
          servicePort: 80
        path: /path2

Create each resources based on the previous yaml files definition.

kubectl create -f ~/data/routes/

On Minikube, the last step is to configure the /etc/hosts file to resolve the training.wikitops.io domain name with the minikube ip :

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

Once the Pods are up and running, you should be able to connect to this two urls :

Get

The get command list the object asked. It could be a single object or a list of multiple objects comma separated. This command is useful to get the status of each object. The output can be formatted to only display some information based on some json search or external tools like tr, sort, uniq.

The default output display some useful information about each services :

  • Name : the name of the newly created resource

  • Hosts : the host to apply the newly created resource

  • Address : the address exposed by the newly created resource

  • Ports : the ports exposed by the resource

  • Age : the age since his creation

Exercise n°1

List the current Ingress resources created.

kubectl get ingress

Describe

Once an object is running, it is inevitably a need to debug problems or check the configuration deployed.

The describe command display a lot of configuration information about the Ingress (labels, annotations, events, backend associated, IP address associated, etc.) and the rules available for each ingress (hosts, path, backend associated).

This command is really useful to introspect and debug an object deployed in a cluster.

Exercise n°1

Describe one of the existing Ingress in the default namespace.

kubectl describe ingress myfirstingress

Explain

Kubernetes come with a lot of documentation about his objects and the available options in each one. Those information can be fin easily in command line or in the official Kubernetes documentation.

The explain command allows to directly ask the API resource via the command line tools to display information about each Kubernetes objects and their architecture.

Exercise n°1

Get the documentation of a specific field of a resource.

kubectl explain ingresses.spec

Add the --recursive flag to display all of the fields at once without descriptions.

Delete

The delete command delete resources by filenames, stdin, resources and names, or by resources and label selector.

Be careful on the deletion of a Ingress object. This will interupt existing communication based on this resource.

Note that the delete command does NOT do resource version checks, so if someone submits an update to a resource right when you submit a delete, their update will be lost along with the rest of the resource.

Exercise n°1

Delete the previous ingress in command line.

# Delete Ingress
kubectl delete ingress myfirstingress

# Delete Deployments
kubectl delete deployment webserver1 webserver2

# Delete Services
kubectl delete service webserver1 webserver2

Module exercise

The purpose of this section is to manage each steps of the lifecycle of an application to better understand each concepts of the Kubernetes course.

The main objective in this module is to understand how to manage and secure the external access of Kubernetes resources.

For more information about the application used all along the course, please refer to the Exercise App > Voting App link in the left panel.

Based on the principles explain in this module, try by your own to handle this steps. The development of a yaml file is recommended.

The file developed has to be stored in this directory : ~/data/votingapp/12_routes

  1. Expose the vote Services as an Ingress controller.

  2. Expose the result Services as an Ingress controller.

  3. Ensure that you accessed both services externally.

External documentation

Those documentations can help you to go further in this topic :

PreviousNetworksNextHigh Availability

Last updated