In this demo, you will see how you can use Zrb to:

• Create a modular-monolith CRUD application.
• Add some entities/fields.
• Run the application as monolith/microservices.

No coding skill is required.

Before starting the demo, you need to make sure you have the following software installed:

• Python (3.10 or higher)
• Pip
• Venv
• Zrb

Once everything is set, you can run the following script on your terminal:

./init.sh

The commands will give you:

• A folder named my-project.
• A Python application under the project (my-project/src/myapp).
• A library module under the application (myproject/src/myapp/src/module/library)
• A book entity under the library module.
• A field named title under the book entity.

It will also run the application on your local computer.

You can visit http://localhost:3000 to see how the application works.

The default username and password will be root and toor.

Try to add some books.

You can override the system username and password by setting some environment variables:

# press ctrl + c to stop the application
export MYAPP_APP_AUTH_ADMIN_USERNAME=gofrendi
export MYAPP_APP_AUTH_ADMIN_PASSWORD=aVeryStrongPassword73
zrb project myapp monolith start 

Currently, myapp is running as a single process on your local computer.

Let's confirm this by opening a new terminal and invoking the following command:

pgrep fastapi -a

You should see a single process like this:

46252 ... fastapi dev main.py --port 3000

Now let's go back to your first terminal; so that you can kill my-app process by pressing ctrl + c.

Stay in your first terminal, and try to invoke the following command:

zrb project myapp microservices start

Once started, you will be able to access http://localhost:3000 as you have done previously.

Now let's invoke the following command on your second terminal:

pgrep fastapi -a

46252 ... fastapi dev main.py --port 3001
46254 ... fastapi dev main.py --port 3002
46256 ... fastapi dev main.py --port 3003

You can see that now you have multiple processes.

Each process handles different aspect of the application:

• myapp-gateway (port: 3001)
  • Handle HTTP requests from user
  • Send HTTP requests to other services
• myapp-auth-service (port: 3002)
  • Handle and reply HTTP requests from gateway
• myapp-library-service (port: 3003)
  • Handle and reply HTTP requests from gateway

You can see that you can run myapp as either microservices or as a Monolith.