Develop .NET docker images - Part 1.2

Posted on October 25, 2020 in Develop
Updated: December 20, 2020

This blog is part of a serie:

Intro

This blog is an example of a development cycle developing in C# on Windows using VSCode editor - also for debugging docker containers - and deploying to k8s.

This blog is inspired by content from an eBook and some tutorials.
You find its code in this git repo: rasor/eBook-UsingNETCoreDockerKubernetes.

Main Sources are:

Free eBook (2019): Syncfusion Free Ebooks | Using .NET Core, Docker, and Kubernetes Succinctly
- By @apomic80
  - Github: apomic80
Guide: Inner-loop development workflow for Docker apps
- from free eBook (2020): Containerized Docker Application Lifecycle with Microsoft Platform and Tools from Microsoft

PreRequisites

Windows 10
.NET Core 3.1 SDK
Git Bash
Visual Studio Code
- C# for VSCode
Docker Desktop for Windows user manual
k8s (I am using kind for creating cluster)
Optional: choco
Optional: jq
Optional: helm
- choco install kubernetes-helm or arkade get helm
Optional: draft

Chapters from eBook Using .NET Core, Docker, and Kubernetes

Chapter 1 ASP.NET and Docker Together

Chapter 1.1 Execute .NET Core application with Docker

See Part 1.1: Run docker containers

Chapter 2 Create Your Application with Docker

Chapter 2.1 Develop your ASP.NET Core application using Docker

Dotnet core commands:

dotnet new: Creates a new project from the specified template. If you want to create an MVC application, you can use dotnet new mvc.
dotnet restore: Restores all the NuGet dependencies of our application.
dotnet build: Builds our project.
dotnet run: Executes our project.
dotnet watch run: Runs our project and watches for file changes to rebuild and re-run it.
dotnet publish: Creates a deployable build (the .dll) of our project.

Install VSCode plugin Docker

# Terminal 1:
# Create a C# gitignore file in the root
dotnet new gitignore

# create a folder for MVC frontend
mkdir -p cpt2/frontend
cd cpt2/frontend
# Create mvc web
dotnet new mvc

# Build an run a webserver
dotnet build
dotnet run

# Terminal 2:
# open a browser
start https://localhost:5001/

Stop the webserver in Teminal 1 with ctrl-c.

Now create .vscode files launch.json and tasks.json:

Ctrl-shft-p # to open cmd palette
.NET: Generate Assets for Build and Debug
- Choose ASPNET Core, linux container and ports 5000, 5001

You can now goto RUN pane with ctrl-shft-d, select the .NET Core Launch (web) config and press run.
In the Debug console you will see

# Debug console
# Using launch settings from 'C:\Users\zzz\eBook-UsingNETCoreDockerKubernetes/cpt2/frontend\Properties\launchSettings.json' [Profile 'frontend']...
# Loaded 'C:\Users\zzz\eBook-UsingNETCoreDockerKubernetes\cpt2\frontend\bin\Debug\netcoreapp3.1\frontend.dll'. Symbols loaded.
# .....

You can hit breakpoints.

Now create a Dockerfile, .dockerignore and docker-compose.yml:

In explorer put cursor on cpt2\frontend
Ctrl-shft-p # to open cmd palette
Docker: Add Docker files to workspace
- Choose ASPNET Core, linux container and ports 5000, 5001, yes to create compose file
  (Img from Microsoft) Add Dockerfile in VSCode

# Generated Dockerfile
# 1. Target img to deploy to
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
WORKDIR /app
EXPOSE 5000
EXPOSE 5001

# 5. Source img to build on
FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
WORKDIR /src
# 7. Copy project file from local pc into Source img
COPY ["cpt2/frontend/frontend.csproj", "cpt2/frontend/"]
RUN dotnet restore "cpt2/frontend/frontend.csproj"
COPY . .
WORKDIR "/src/cpt2/frontend"
# 11. Build .dll
RUN dotnet build "frontend.csproj" -c Release -o /app/build

FROM build AS publish
# 13. Create a deployable package
RUN dotnet publish "frontend.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
# 16. Copy from Source img to Target img
COPY --from=publish /app/publish .
# 17. Define start command
ENTRYPOINT ["dotnet", "frontend.dll"]

Change cmd 7 to 10, so you'll be able to docker build from inside folder cpt2/frontend

# 7. Copy project file from local pc into Source img
COPY ./frontend.csproj .
RUN dotnet restore frontend.csproj
COPY . .
WORKDIR /src

Dockerfile reference

Let's build our docker img

# verify docker is running
docker images
# goto folder with Dockerfile
cd cpt2/frontend
docker build --help
# build img and tag it frontend2
docker build -t frontend2 .

# System.InvalidOperationException: Unable to configure HTTPS endpoint. No server certificate was specified, and the default developer certificate could not be found or is out of date.


# Sending build context to Docker daemon  6.432MB
# Step 1/17 : FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
# 3.1: Pulling from dotnet/core/aspnet
# bb79b6b2107f: Pull complete
# fd6f53cfcb35: Pull complete
# 29b35ed07a14: Pull complete
# fd068c4127c7: Pull complete
# dc51486f316e: Pull complete
# Digest: sha256:4030ec40f9b5c1e8cac5d550639b7b05d1d6af0c89b4b47d66bad7f93379c9eb
# Status: Downloaded newer image for mcr.microsoft.com/dotnet/core/aspnet:3.1
#  ---> e3559b2d50bb
# Step 2/17 : WORKDIR /app
#  ---> Running in 14fd02991c3d
# Removing intermediate container 14fd02991c3d
#  ---> df46b5f3b46a
# Step 3/17 : EXPOSE 5000
#  ---> Running in 5adf5a71198d
# Removing intermediate container 5adf5a71198d
#  ---> 817df2c51839
# Step 4/17 : EXPOSE 5001
#  ---> Running in 1815541a6c6a
# Removing intermediate container 1815541a6c6a
#  ---> 02891abd8059
# Step 5/17 : FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
# 3.1: Pulling from dotnet/core/sdk
# e4c3d3e4f7b0: Pull complete
# 101c41d0463b: Pull complete
# 8275efcd805f: Pull complete
# 751620502a7a: Pull complete
# 8e306865fd07: Pull complete
# 9d2f53e752c2: Pull complete
# 143a93e01eba: Pull complete
# Digest: sha256:d09eefeaad2129f0a0ac047095792afc6792e7aae4b8bb1c1fa5b6650caae240
# Status: Downloaded newer image for mcr.microsoft.com/dotnet/core/sdk:3.1
#  ---> 5fe503d51830
# Step 6/17 : WORKDIR /src
#  ---> Running in 143a136929b6
# Removing intermediate container 143a136929b6
#  ---> 0e5a8185b7a2
# Step 7/17 : COPY ./frontend.csproj .
#  ---> 203c96e3d357
# Step 8/17 : RUN dotnet restore frontend.csproj
#  ---> Running in cd917bface5b
#   Determining projects to restore...
#   Restored /src/frontend.csproj (in 170 ms).
# Removing intermediate container cd917bface5b
#  ---> 866543516985
# Step 9/17 : COPY . .
#  ---> 6ac6636b092c
# Step 10/17 : WORKDIR /src
#  ---> Running in 40c27a3098f1
# Removing intermediate container 40c27a3098f1
#  ---> d3f07b018611
# Step 11/17 : RUN dotnet build "frontend.csproj" -c Release -o /app/build
#  ---> Running in 56cc1964bf83
# Microsoft (R) Build Engine version 16.7.0+7fb82e5b2 for .NET
# Copyright (C) Microsoft Corporation. All rights reserved.
#   Determining projects to restore...
#   Restored /src/frontend.csproj (in 185 ms).
#   frontend -> /app/build/frontend.dll
#   frontend -> /app/build/frontend.Views.dll
# Build succeeded.
#     0 Warning(s)
#     0 Error(s)
# Time Elapsed 00:00:05.03
# Removing intermediate container 56cc1964bf83
#  ---> 7ccf08805a5b
# Step 12/17 : FROM build AS publish
#  ---> 7ccf08805a5b
# Step 13/17 : RUN dotnet publish "frontend.csproj" -c Release -o /app/publish
#  ---> Running in 27507652111d
# Microsoft (R) Build Engine version 16.7.0+7fb82e5b2 for .NET
# Copyright (C) Microsoft Corporation. All rights reserved.
#   Determining projects to restore...
#   All projects are up-to-date for restore.
#   frontend -> /src/bin/Release/netcoreapp3.1/frontend.dll
#   frontend -> /src/bin/Release/netcoreapp3.1/frontend.Views.dll
#   frontend -> /app/publish/
# Removing intermediate container 27507652111d
#  ---> c08c7122d789
# Step 14/17 : FROM base AS final
#  ---> 02891abd8059
# Step 15/17 : WORKDIR /app
#  ---> Running in b52e89be9e92
# Removing intermediate container b52e89be9e92
#  ---> 97d3ac799145
# Step 16/17 : COPY --from=publish /app/publish .
#  ---> 2ac048ea1f90
# Step 17/17 : ENTRYPOINT ["dotnet", "frontend.dll"]
#  ---> Running in 7359a524012b
# Removing intermediate container 7359a524012b
#  ---> f7828ef4f47e
# Successfully built f7828ef4f47e
# Successfully tagged frontend2:latest
# SECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host. All files and directories added to build context will have 
# '-rwxr-xr-x' permissions. It is recommended to double check and reset permissions for sensitive files and directories.

# Print image
docker images
# REPOSITORY                             TAG                 IMAGE ID            CREATED             SIZE  
# frontend2                              latest              f7828ef4f47e        5 minutes ago       212MB 
# mcr.microsoft.com/dotnet/core/aspnet   3.1                 e3559b2d50bb        7 days ago          207MB 
# mcr.microsoft.com/dotnet/core/sdk      3.1                 5fe503d51830        7 days ago          708MB 

# Test run the img
docker run -p 5000:5000 --name nfrontend2 -t frontend2 -e "ASPNETCORE_URLS=http://+:5000"
#docker run -p 5000:5000 -p 5001:5001 --name nfrontend2 -t frontend2
#docker create -p 5000:5000 -p 5001:5001 --name nfrontend2 -t frontend2 --entrypoint 'dotnet dev-certs https && # warn: Microsoft.AspNetCore.DataProtection.Repositories.FileSystemXmlRepository[60]
#       Storing keys in a directory '/root/.aspnet/DataProtection-Keys' that may not be persisted outside of the container. Protected data will be unavailable 
# when container is destroyed.
#       No XML encryptor configured. Key {22010cbd-95fa-4543-9ae3-63ee61afff7f} may be persisted to storage in unencrypted form.
#       Now listening on: http://[::]:80
#       Application started. Press Ctrl+C to shut down.
#       Hosting environment: Production
#       Content root path: /app

# Terminal 2:
docker start nfrontend2
# Which containers are running?
docker ps
# CONTAINER ID        IMAGE               COMMAND                 CREATED             STATUS              PORTS                              NAMES
# 6fc16e63dbd5        frontend2           "dotnet frontend.dll"   18 seconds ago      Up 17 seconds       0.0.0.0:5000-5001->5000-5001/tcp   nfrontend2   

# Print entry point
docker ps -a --format "table {{.Image}}:\t {{.Command}}" --no-trunc
# IMAGE:                   COMMAND
# frontend2:               "dotnet frontend.dll…"

# Print as json
docker ps -a --format " {{json .}}" | jq '{ID, Image, Command}'

# Open browser
start http://localhost:5000

# Cleanup
docker stop nfrontend2
docker rm nfrontend2
# Cleanup done?
docker ps -a

Chapter 2.1B (not in eBook) Debug your docker container

To be able to debug on port 5000 you need to do a change in the launcsetting:

Before:

// .vscode/tasks.json
                        "label": "docker-run: debug",
                        "dependsOn": [
                                "docker-build: debug"
                        ],
                        "dockerRun": {},

After:

// .vscode/tasks.json
                        "label": "docker-run: debug",
                        "dependsOn": [
                                "docker-build: debug"
                        ],
                        "dockerRun": {
                                "env": {
                                        "ASPNETCORE_URLS": "https://+:5001;http://+:5000"
                                },
                                "ports": [
                                        { "hostPort": 5000, "containerPort": 5000 },
                                        { "hostPort": 5001, "containerPort": 5001 }
                                ]
                        },

If you goto RUN pane and choose Docker .NET Core Launch in the dropdown and then press the "Play" button then you can place breakpoints in your code and remote debug into your container. VSCode will show this:

#> Executing task: docker-build: debug <

docker build --rm --pull -f "C:\Users\zzz\eBook-UsingNETCoreDockerKubernetes/cpt2/frontend/Dockerfile" --label "com.microsoft.created-by=visual-studio-code" -t "ebookusingnetcoredockerkubernetes:dev" --target "base" "C:\Users\zzz\eBook-UsingNETCoreDockerKubernetes"

# Where
# -f, --file string         Name of the Dockerfile (Default is 'PATH/Dockerfile')
# --label list              Set metadata for an image
# --pull                    Always attempt to pull a newer version of the image
# --rm                      Remove intermediate containers after a successful build (default true)
# -t, --tag list            Name and optionally a tag in the 'name:tag' format
# --target string           Set the target build stage to build.

#> Executing task: docker-run: debug <

docker run -dt -P --name "ebookusingnetcoredockerkubernetes-dev" -e "DOTNET_USE_POLLING_FILE_WATCHER=1" -e "ASPNETCORE_ENVIRONMENT=Development" -e "ASPNETCORE_URLS=https://+:5001;http://+:5000" --label "com.microsoft.created-by=visual-studio-code" -v "C:\Users\zzz\eBook-UsingNETCoreDockerKubernetes/cpt2/frontend:/app:rw" -v "c:\Users\zzz\eBook-UsingNETCoreDockerKubernetes:/src:rw" -v "C:\Users\zzz\.vsdbg:/remote_debugger:ro" -v "C:\Users\zzz\.nuget\packages:/root/.nuget/packages:ro" -v "C:\Program Files\dotnet\sdk\NuGetFallbackFolder:/root/.nuget/fallbackpackages:ro" -v "C:\Users\zzz\AppData\Roaming\Microsoft\UserSecrets:/root/.microsoft/usersecrets:ro" -v "C:\Users\zzz\AppData\Roaming\ASP.NET\Https:/root/.aspnet/https:ro" -p "5000:5000" -p "5001:5001" "ebookusingnetcoredockerkubernetes:dev"

# Where
# -d, --detach                         Run container in background and print container ID
# -t, --tty                            Allocate a pseudo-TTY
# -l, --label list                     Set meta data on a container
# -P, --publish-all                    Publish all exposed ports to random ports
# -v, --volume list                    Bind mount a volume
# Some from tasks.json:
# -e, --env list                       Set environment variables
# -p, --publish list                   Publish a container's port(s) to the host

Isn't that nice?

Ref: Debug an app running in a Docker container

Chapter 2.2 Add containers to your project

To Be Added

Chapter 2.3 Run your container with Docker Compose

When you used Command Palette command Docker: Add Docker files to workspace then you said yes to create compose files:

# Generated docker-compose.debug.yml
# Please refer https://aka.ms/HTTPSinContainer on how to setup an https developer certificate for your ASP .NET Core service.

version: '3.4'

services:
    frontend:
        image: frontend
        build:
            context: .
            dockerfile: cpt2/frontend/Dockerfile
        ports:
            - 5000
            - 5001
        environment:
            - ASPNETCORE_ENVIRONMENT=Development
            - ASPNETCORE_URLS=http://+:5000
        volumes:
            - ~/.vsdbg:/remote_debugger:rw

Change frontend in both the .debug.yml and then non-debug yml to:

    frontend:
        image: frontend2
        # Add this
        container_name: frontend2 # then you can attach to this name
        build:
            context: ./cpt2/frontend
            dockerfile: Dockerfile
        environment:
        # Add this to the non-debug
            - ASPNETCORE_URLS=https://+:5001;http://+:5000

So now we can start several containers at once (if more containeres were present in the compose file).
Compose will also create a docker network for the containers to communicate through.

# ensure you find the root folder
cd cpt2/frontend
# go back to root, where docker-compose.yml exists
cd ../..

docker-compose up

start http://localhost:5000

# ctrl-c to stop the servers
# or
docker-compose stop
# or
docker-compose down # will also remove (docker-compose rm)

# check which containers exists
docker ps -a

# then restart # if not removed
docker-compose start

Refs:
- Overview of docker-compose CLI

Can we debug code running in a container by attiching our local code to it?

Goto the RUN pane
In the Run-dropdown - do Àdd Confuguration
Choose Docker .NET Core Attach (Preview)

This will create most of this

//.vscode/launch.json
        {
                "name": "Docker .NET Core Attach (Preview)",
                "type": "docker",
                "request": "attach",
                "containerName": "frontend2",
                "platform": "netCore",
                "sourceFileMap": {
                        "/src": "${workspaceFolder}"
                },
        },

Optionally add containerName in or to auto attach to a specific running container.

Now spin up the container

# use debug compose file
docker-compose -f docker-compose.debug.yml up

That will show in a docker terminal:

# Docker terminal
# > Executing task: docker-compose -f "docker-compose.debug.yml" up -d --build <

# Creating network "ebook-usingnetcoredockerkubernetes_default" with the default driver
# Building frontend
# Step 1/17 : FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
#  ---> e3559b2d50bb
# ......
# Step 17/17 : ENTRYPOINT ["dotnet", "frontend.dll"]
#  ---> Using cache
#  ---> 6572076fad45

# Successfully built 6572076fad45
# Successfully tagged frontend2:latest
# Creating frontend2 ... done

Now in the RUN pane select the Docker .NET Core Attach (Preview) config and press run.
In the Debug console you will see

# Debug console
# Starting: "docker" exec -i frontend2 /remote_debugger/vsdbg --interpreter=vscode
# .....
# Loaded '/app/frontend.dll'. Symbols loaded.
# .....

You should be able to set breakpoints in your code and break.
But something is not quite right, yet. It does not work on my PC.

Refs:
- Use Docker Compose to work with multiple containers
  - Debug NetCore: NetCore
- Attach to a running container using Visual Studio Code Remote Development

Chapter 2.4 Create the final image for publication

Publish image to docker hub

Create a docker hub repo. I'll publish to
https://hub.docker.com/repository/docker/rasor/usingnetcoredockerkubernetes

# goto folder with Dockerfile
cd cpt2/frontend
docker build --help
# build img and tag it
docker build -t frontend2:v1 .
# Successfully built 6572076fad45
# Successfully tagged frontend2:v1

docker images | grep frontend2
# frontend2                              latest              6572076fad45        3 days ago          212MB
# frontend2                              v1                  6572076fad45        3 days ago          212MB

# tag the image, so you can upload it to docker hub
# docker tag local-image:tagname new-repo:tagname
docker tag frontend2:v1 rasor/usingnetcoredockerkubernetes:frontend2-v1

docker images | grep frontend2
# REPOSITORY                             TAG                 IMAGE ID            CREATED             SIZE
# rasor/usingnetcoredockerkubernetes     frontend2-v1        6572076fad45        3 days ago          212MB
# frontend2                              latest              6572076fad45        3 days ago          212MB
# frontend2                              v1                  6572076fad45        3 days ago          212MB

# upload docker img to https://hub.docker.com/repository/docker/rasor/usingnetcoredockerkubernetes
# docker push new-repo:tagname
docker push rasor/usingnetcoredockerkubernetes:frontend2-v1
# The push refers to repository [docker.io/rasor/usingnetcoredockerkubernetes]
# ...
# frontend2-v1: digest: sha256:e413934f1dba2e85b66f69125f6b4ac9944122c8f1c3d8f0f97355abb6ad8ec9 size: 1793

# When you want to download it do:
# docker pull rasor/usingnetcoredockerkubernetes:frontend2-v1

Chapter 3 Deploy Your Application on Kubernetes

Chapter 3.2 Deploy your images in Kubernetes

See Part 1.3

The End