⛴️ Micro Applications

What is a Micro App?

A Micro App is a small, independent application that runs on its own server (HTTP or HTTPS) and port. It can be part of a larger Duck-powered project but operates separately, handling its own requests and responses.

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Key Features

• Independent Servers: Each micro app runs on its own server, meaning it does not affect other parts of the application.

• Custom Ports: You can assign a specific port for your micro app, so it won’t interfere with other services.

• Custom Views: Micro apps handle their own requests through a view method or async_view for asynchronous support, allowing you to define custom behavior.

• Redirect HTTP to HTTPS: Duck includes a built-in HttpsRedirectMicroApp, which automatically redirects HTTP traffic to HTTPS for better security.

Note

Middlewares are not applied automatically — you must manually attach them to either the request or the response.
This design allows for clearer separation between your main application and micro applications, especially in cases where certain middlewares are not applicable to micro apps.

To simplify default middleware or error handling, you can use the built-in processors:

• Use the default RequestProcessor or AsyncRequestProcessor—both can be passed to a micro app’s view or async_view methods.
  These processors provide convenient methods like:

  • check_middlewares()

  • check_base_errors()

  • check_errors()

• Alternatively, use the ASGI/WSGI integration via
  duck.settings.loaded.SettingsLoaded.

For example, you can use:

• apply_middlewares_to_response() from the ASGI or WSGI settings to automatically apply response middlewares.

Here is an example of HTTPS redirect microapp:

from duck.http.core.processor import (
    AsyncRequestProcessor,
    RequestProcessor,
)
from duck.http.request import HttpRequest
from duck.http.response import (
    HttpRedirectResponse,
    HttpResponse,
)
from duck.utils.urlcrack import URL


class HttpsRedirectMicroApp(MicroApp):
    """
    HttpsRedirectMicroApp class capable of redirecting http traffic to https.
    """

    def __init__(self, location_root_url: str, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.location_root_url = URL(location_root_url)
        
    def view(self, request: HttpRequest, request_processor: RequestProcessor) -> HttpResponse:
        """
        Returns an http redirect response.
        """
        query = request.META.get("QUERY_STRING", "")
        dest_url = self.location_root_url.join(request.path)
        dest_url.query = query
        dest_url = dest_url.to_str()
        redirect = HttpRedirectResponse(location=dest_url, permanent=False)
        
        # Return response
        return redirect

    async def async_view(self, request: HttpRequest, request_processor: AsyncRequestProcessor) -> HttpResponse:
        """
        Returns an http redirect response.
        """
        query = request.META.get("QUERY_STRING", "")
        dest_url = self.location_root_url.join(request.path)
        dest_url.query = query
        dest_url = dest_url.to_str()
        redirect = HttpRedirectResponse(location=dest_url, permanent=False)
        
        # Return response
        return redirect

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How to Use Micro Apps

1. Creating a Micro App: To create a micro app, simply instantiate the MicroApp class and configure its address and port.

from duck.app import MicroApp

# Create a simple micro app running on port 8081
app = MicroApp(port=8080)

if __name__ == "__main__":
    app.run()

2. Defining a View: Define a view method within your micro app to handle incoming requests and generate responses.

class MyMicroApp(MicroApp):
    def view(self, request, processor):
        return HttpResponse("Hello from My Micro App!")

3. Handling HTTP to HTTPS Redirects: Duck provides a built-in HttpsRedirectMicroApp, which automatically redirects HTTP traffic to HTTPS. This can be controlled via the configuration in Duck’s settings, so you don’t need to manually implement it.

To enable HTTPS redirection, simply configure Duck to use the HttpsRedirectMicroApp in your settings:

FORCE_HTTPS = True
ENABLE_HTTPS = True

4. Running the Micro App: Once your micro app is configured, you can run it independently, and it will handle requests on its own port.