In the main function, ensure you have the following code to get the port from the os environment

if __name__ == '__main__':
    port = int(os.environ.get("PORT", 6000))
    app.run(host="0.0.0.0", port=port, debug=True)

Dockerfile

# syntax=docker/dockerfile:1

FROM python:3.9-slim-buster

WORKDIR /python-docker

COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt

COPY . .

CMD [ "python", "app.py"]

The requirements.txt are the list of dependencies packages required by our app to function properly. In this case my requirements.txt look something like this

google-ai-generativelanguage==0.6.2
google-api-core==2.19.0
google-api-python-client==2.129.0
google-auth==2.29.0
google-auth-httplib2==0.2.0
google-generativeai==0.5.2
googleapis-common-protos==1.63.0
Flask==3.0.3
python-dotenv==1.0.0

To automatically write all package dependencies to requirements.txt, run the following command:

pip3 freeze > requirements.txt

Deployment

1. Build the project

docker build --platform linux/amd64 -t <TAG_NAME> .

2. Make sure the image is there

docker image ls

3. Tag the image with the heroku registry app

docker tag <TAG_NAME>registry.heroku.com/<APP_NAME>/web

4. Push the image to heroku

docker pushregistry.heroku.com/<APP_NAME>/web

If for some reason upon docker push, you are getting unauthorized: authentication required error, please run the following command

heroku container:login

5. Release

heroku container:release web -a <APP_NAME>

In this post, I'll explain how to dockerize a .Net core app. This post specifically talks about dockerizing in Apple Silicon M1 chip (arm64 architecture) as there are some difficulties with building the solution in docker with this architecture.

This post won't be going over what is Docker. If you are interested in learning docker please visit this official website from docker.

Let's dive in!

Step by Step to Dockerize and Deploy .NET to Heroku

Here are the steps to create and deploy app to Heroku:

1. Create .NET app

2. Create Heroku project

3. Containerize our app and deploy to Heroku

Create your .NET App

source: https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-web-api?view=aspnetcore-8.0&tabs=visual-studio-code

1. In your root project, open the terminal and start the project

dotnet new webapi --use-controllers -o <YourAppName>

1. A new project folder will be created

1. Run dotnet run in terminal and check if your app is running successfully. In this example I'm using Microsoft's weather forecast example.

Heroku Setup

1. Login to your Heroku account and create an app. Let's say the project name is PalladiumFloorsBE

Containerize

1. In your VSCode project's root folder terminal type in the following:

    heroku login
   

   A window will pop up in your browser prompting you to login to your heroku account

2. Next open your Docker Desktop app

3. Run the following command in your terminal

    heroku container:login
   

4. Make a release file of your solution by running the following command:

    dotnet publish -c Release -o out
   

   This should create a folder with name out

5. In that out folder, create a Dockerfile file and paste the following:

    FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS runtime
    WORKDIR /App
    COPY . .
    CMD ASPNETCORE_URLS=http://*:$PORT dotnet <YourProjectName>.dll
   

   • Replace the runtime image on the first line according to your project's needs. To find which version is your using, you can go to the .csproj file at the root of the project and find the following line:

           <TargetFramework>net8.0</TargetFramework>
     

   • In this case my project is using .NET8

   • On the last line, replace the <YourProjectName> with the proper project name. Your project name should be the same one that you typed in step 1 of Create Your .NET App section of this post

6. Build your project

    docker build --platform linux/amd64 -t palladiumfloorsbe ./out
   

   • the --platform is to specify which architecture to run on. By default if you are using the M1 Apple Silicon chip, it will configure the platform to be arm64, which is not available by Heroku container registry

7. Tag and push your image

    docker tag palladiumfloorsbe registry.heroku.com/<YourAppNameInHeroku>/web
    docker push registry.heroku.com/<YourAppNameInHeroku>/web
   

8. Release and deploy

     heroku container:release web -a <YourAppNameInHeroku>
   

9. Congrats!! You have deployed your project. Happy coding

Troubleshooting

• If you app is deployed but there are errors, you can monitor them by running the following command:

    heroku logs --tail
  

• Whenever you change your code and would like to release. You need to refollow step 6 to 8