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Middlewares in Panther#

Middlewares allow you to process requests and responses globally or for all or specific APIs. They are useful for tasks such as logging, timing, and other cross-cutting concerns.

Global Middlewares#

To apply middlewares globally, define a MIDDLEWARES list in your configs. Each item can be either a string (dotted path to the middleware class) or the class itself (useful for single-file applications):

class Middleware(HTTPMiddleware):
    pass

MIDDLEWARES = [
    'core.middlewares.MyMiddleware',  # Import by dotted path
    Middleware,                       # Or directly by class
]

Per-API Middlewares#

You can assign middlewares to specific APIs, either class-based or function-based:

apis.py
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from panther.app import API, GenericAPI
from panther.middlewares import HTTPMiddleware

class Middleware(HTTPMiddleware):
    pass

# Class-Based API
class MyAPI(GenericAPI):
    middlewares = [Middleware]

# Function-Based API
@API(middlewares=[Middleware])
def my_api():
    pass

Middleware Execution Order#

Middlewares are executed in the following order:

  1. Global middlewares: __call__() (enter)
  2. Per-API middlewares: __call__() (enter)
  3. Per-API middlewares: dispatch (return)
  4. Global middlewares: dispatch (return)

Creating Custom Middlewares#

Types of Middlewares#

Panther provides two types of middleware base classes:

  • HTTPMiddleware: For HTTP requests only
  • WebsocketMiddleware: For WebSocket connections only

Make sure to inherit from the correct base class:

# For HTTP requests
from panther.middlewares import HTTPMiddleware

# For WebSocket connections
from panther.middlewares import WebsocketMiddleware

Implementing a Middleware#

  • Create a class inheriting from HTTPMiddleware or WebsocketMiddleware.
  • Implement an asynchronous __call__ method.
  • Always return either await self.dispatch(...) or a Response/GenericWebsocket instance at the end of __call__().

Example: HTTP Middleware#

middlewares.py
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from datetime import datetime
from panther.middlewares.base import HTTPMiddleware
from panther.request import Request
from panther.response import Response

class CustomMiddleware(HTTPMiddleware):
    async def __call__(self, request: Request) -> Response:
        start_time = datetime.now()
        response = await self.dispatch(request=request)
        duration = datetime.now() - start_time
        print(f'Request took {duration.total_seconds()} seconds')
        return response

Example: WebSocket Middleware#

middlewares.py
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from datetime import datetime
from panther.middlewares.base import WebsocketMiddleware
from panther.websocket import GenericWebsocket, Websocket

class TimerMiddleware(WebsocketMiddleware):
    async def __call__(self, connection: Websocket) -> GenericWebsocket:
        start_time = datetime.now()
        response = await self.dispatch(connection=connection)
        duration = datetime.now() - start_time
        print(f'Connection lasted {duration.total_seconds()} seconds')
        return response

Built-in Middlewares#

Panther provides several built-in middlewares to help with common tasks. Below are the available options and how to use them:

CORS Middleware#

  • Purpose: Enables Cross-Origin Resource Sharing (CORS) for your APIs.
  • Usage: Add panther.middlewares.CORSMiddleware to your global MIDDLEWARES list.
  • Configuration: Requires specific global settings. See the CORS Middleware documentation for configuration details.

Monitoring Middleware#

  • Purpose: Logs request and connection data for monitoring and analytics.
  • Usage: Add panther.middlewares.MonitoringMiddleware to your global MIDDLEWARES list.
  • Note: This middleware or WebsocketMonitoringMiddleware is required if you want to use the panther monitor command.

WebSocket Monitoring Middleware#

  • Purpose: Similar to MonitoringMiddleware, but specifically logs data for WebSocket connections.
  • Usage: Add panther.middlewares.WebsocketMonitoringMiddleware to your global MIDDLEWARES list if you want to monitor WebSocket traffic.
  • Note: This middleware or MonitoringMiddleware is required if you want to use the panther monitor command.

Tips#

  • Use global middlewares for logic that should apply to all requests.
  • Use per-API middlewares for logic specific to certain endpoints.
  • Always ensure your __call__ method is asynchronous and returns the appropriate value.