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79 lines
2.5 KiB
79 lines
2.5 KiB
3 years ago
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"""
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Application Dispatcher
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======================
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This middleware creates a single WSGI application that dispatches to
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multiple other WSGI applications mounted at different URL paths.
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A common example is writing a Single Page Application, where you have a
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backend API and a frontend written in JavaScript that does the routing
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in the browser rather than requesting different pages from the server.
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The frontend is a single HTML and JS file that should be served for any
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path besides "/api".
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This example dispatches to an API app under "/api", an admin app
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under "/admin", and an app that serves frontend files for all other
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requests::
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app = DispatcherMiddleware(serve_frontend, {
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'/api': api_app,
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'/admin': admin_app,
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})
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In production, you might instead handle this at the HTTP server level,
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serving files or proxying to application servers based on location. The
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API and admin apps would each be deployed with a separate WSGI server,
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and the static files would be served directly by the HTTP server.
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.. autoclass:: DispatcherMiddleware
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:copyright: 2007 Pallets
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:license: BSD-3-Clause
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"""
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import typing as t
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if t.TYPE_CHECKING:
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from _typeshed.wsgi import StartResponse
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from _typeshed.wsgi import WSGIApplication
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from _typeshed.wsgi import WSGIEnvironment
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class DispatcherMiddleware:
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"""Combine multiple applications as a single WSGI application.
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Requests are dispatched to an application based on the path it is
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mounted under.
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:param app: The WSGI application to dispatch to if the request
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doesn't match a mounted path.
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:param mounts: Maps path prefixes to applications for dispatching.
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"""
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def __init__(
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self,
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app: "WSGIApplication",
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mounts: t.Optional[t.Dict[str, "WSGIApplication"]] = None,
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) -> None:
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self.app = app
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self.mounts = mounts or {}
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def __call__(
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self, environ: "WSGIEnvironment", start_response: "StartResponse"
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) -> t.Iterable[bytes]:
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script = environ.get("PATH_INFO", "")
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path_info = ""
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while "/" in script:
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if script in self.mounts:
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app = self.mounts[script]
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break
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script, last_item = script.rsplit("/", 1)
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path_info = f"/{last_item}{path_info}"
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else:
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app = self.mounts.get(script, self.app)
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original_script_name = environ.get("SCRIPT_NAME", "")
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environ["SCRIPT_NAME"] = original_script_name + script
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environ["PATH_INFO"] = path_info
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return app(environ, start_response)
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