k8s-workshop

Presentation

The presentation used in the workshop is available here

Demo Application

Basic Todo application with ASP.NET Core 2.1 Razor Pages as Front end & ASP.NET Core 2.1 WEB API as backend.

This slimmed down version has its inspiration from the full blown application : https://github.com/paolosalvatori/service-fabric-acs-kubernetes-multi-container-app

Built using Visual Studio for Mac and Visual Studio Code. Container images are created using Docker for Mac. Application was tested against minikube running within a Mac machine. All the below mentioned steps should work everywhere irrespective of Windows/Linux/Mac.

Prerequisites

• Visual Studio 2017 or Visual Studio for Mac or Visual Studio Code
• .NET Core SDK 2.1
• Docker for Windows/Docker for Mac
• minikube
• kubectl

Step 1 : Running aspnet core 2.1 application

• Clone the repository
• Run the k8s-todo-api app first by running the command dotnet run from k8s-todo-api folder
• Browse the swagger ui for the api using http://localhost:5000/swagger/index.html
• Run the k8s-todo-web app by running the command dotnet run from k8s-todo-web folder
• Browse the application using http://localhost:3000

Step 2 : Dockerizing the aspnet core 2.1 application

Dockerizing the API application

• Navigate to the k8s-todo-api folder and create a Dockerfile and paste the below contents

  
    FROM microsoft/dotnet:2.1-aspnetcore-runtime AS base
    WORKDIR /app
    ENV ASPNETCORE_URLS http://*:5000
    EXPOSE 5000
     
    FROM microsoft/dotnet:2.1-sdk AS build
    WORKDIR /src
    COPY k8s-todo-api.csproj k8s-todo-api/
    RUN dotnet restore k8s-todo-api/k8s-todo-api.csproj
    WORKDIR /src/k8s-todo-api
    COPY . .
    RUN dotnet build k8s-todo-api.csproj -c Release -o /app
  
    FROM build AS publish
    RUN dotnet publish k8s-todo-api.csproj -c Release -o /app
  
    FROM base AS final
    WORKDIR /app
    COPY --from=publish /app .
    ENTRYPOINT ["dotnet", "k8s-todo-api.dll"]
    

• Create the docker image

  Run the below command to build the docker image

   docker build -t k8s-todo-api:latest . 

• Run the API app in a container

  Run the below command to run the image in a container

   docker run -p 5000:5000 k8s-todo-api:latest 

Dockerizing the Web Application

• Navigate to the k8s-todo-web folder and create a new Dockerfile

    
    FROM microsoft/dotnet:2.1-aspnetcore-runtime AS base
    WORKDIR /app
    ENV ASPNETCORE_URLS http://*:3000
    EXPOSE 3000

    FROM microsoft/dotnet:2.1-sdk AS build
    WORKDIR /src
    COPY k8s-todo-web.csproj k8s-todo-web/
    RUN dotnet restore k8s-todo-web/k8s-todo-web.csproj
    WORKDIR /src/k8s-todo-web
    COPY . .
    RUN dotnet build k8s-todo-web.csproj -c Release -o /app

    FROM build AS publish
    RUN dotnet publish k8s-todo-web.csproj -c Release -o /app

    FROM base AS final
    WORKDIR /app
    COPY --from=publish /app .
    ENTRYPOINT ["dotnet", "k8s-todo-web.dll"]
    
   

• Make the below code changes before building the docker image

1. Remove the Endpoint value from the appSettings.json file. appSettings.json should look like below:

  {
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "TodoApiService": {
    "EndpointUri": ""
  },
  "AllowedHosts": "*"
}

2. Remove the UseUrls from the WebHostBuilder configuration in Program.cs file. The CreateWebHostBuilder method should look like below

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup();
    }

• Build the image for k8s-todo-web application

docker build -t k8s-todo-web:latest . 

At this point if you run the web application it might not work properly, as it needs to invoke the API application correctly to load the todo information

Orchestrating WEB & API app execution in containers

• Navigate to the root folder of the repo and create a Docker-Compose.yml file

version: '3'

services:
  todoapi:
    image: todoapi
    ports: 
      - "5000:5000"
    build:
      context: ./k8s-todo-api
      dockerfile: Dockerfile

  todoweb:
    image: todoweb
    ports: 
      - "3000:3000"
    build:
      context: ./k8s-todo-web
      dockerfile: Dockerfile

• Create another file called docker-compose-override.yml with the below contents. This file is required to inject the appSettings value dynamically

version: '3'

services:
  todoapi:
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
    ports:
      - "5000"

  todoweb:
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - TodoApiService__EndpointUri=todoapi:5000
    ports:
      - "3000"

• Running both containers

Run the below command to bring up both the containers in order (api container will be up before creating the web container)

 docker-compose up 

Pushing docker images to docker hub

• Connect your local docker host with the docker hub by logging in to your account docker login

• Push the api app image

  docker push <your-repo-name>/k8s-todo-api:latest

• Push the web app image

  docker push <your-repo-name>/k8s-todo-web:latest

Step : 3 Deploying to Kubernetes

• Ensure you have the below tools installed in your machine to work with kubernetes(k8s) locally

1. minikube
2. kubectl

TO understand the various basic/important commandlets in kubectl refer : k8s-getting-started.md

• Navigate to the root folder and Create a new configmap file called k8s-todo-configmap.yml to store the runtime configuration values to be supplied to aspnetcore's appSettings.json

apiVersion: v1
kind: ConfigMap
metadata:
  name: k8s-todo-configmap
  namespace: default
data:
  aspNetCoreEnvironment: Development
  todoApiServiceEndpointUri: todoapi:5000
  

• Apply the config map to the minikube

kubectl create --filename k8s-todo-configmap --record

• Navigate to the root folder of the repo and Create a new file k8s-todo-deployment.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: todoapi
  labels:
    app: todoapi
spec:
  replicas: 3
  selector:
    matchLabels:
      app: todoapi
  strategy:
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  minReadySeconds: 5
  template:
    metadata:
      labels:
        app: todoapi
    spec:
      containers:
      - name: todoapi
        image: /k8s-todo-api:latest
        ports:
        - containerPort: 5000
        env:
        - name: ASPNETCORE_ENVIRONMENT
          valueFrom:
            configMapKeyRef:
              name: k8s-todo-configmap
              key: aspNetCoreEnvironment

• Deploy the API app to minikube

  Run the below command to create a deployment using the yml file created above

  kubectl create --filename k8s-todo-deployment.yml --record

• Expose the API app as k8s service

  Run the below command to expose the deployment as service

  kubectl expose deployment/todoapi --type=NodePort --port 5000

• List all the services and find out the port to connect to the API

  kubectl get services

• Browse the API by combining the output of minikube ip command and the NodePort assigned to the service. for e.g., in my local the services were exposed at http://192.168.99.100:32335/swagger/index.html