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78 lines
2.7 KiB
78 lines
2.7 KiB
.. _app-dispatch: |
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Application Dispatching |
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======================= |
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Sometimes you might want to use multiple instances of the same application |
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with different configurations. Assuming the application is created inside |
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a function and you can call that function to instanciate it, that is |
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really easy to implement. In order to develop your application to support |
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creating new instances in functions have a look at the |
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:ref:`app-factories` pattern. |
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Dispatch by Subdomain |
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--------------------- |
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A very common example would be creating applications per subdomain. For |
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instance you configure your webserver to dispatch all requests for all |
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subdomains to your application and you then use the subdomain information |
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to create user-specific instances. |
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Once you have your server set up to listen on all subdomains you can use a |
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very simple WSGI application to do the dynamic application creation. |
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The code for the dispatching looks roughly like this: |
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.. sourcecode:: python |
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from threading import Lock |
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class SubdomainDispatcher(object): |
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def __init__(self, domain, create_app): |
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self.domain = domain |
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self.create_app = create_app |
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self.lock = Lock() |
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self.instances = {} |
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def get_application(self, host): |
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host = host.split(':')[0] |
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assert host.endswith(self.domain), 'Configuration error' |
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subdomain = host[:-len(self.domain)].rstrip('.') |
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with self.lock: |
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app = self.instances.get(subdomain) |
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if app is None: |
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app = self.make_app(subdomain) |
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self.instances[subdomain] = app |
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return app |
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def make_app(self, subdomain): |
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return self.create_app(subdomain) |
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def __call__(self, environ, start_response): |
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app = self.get_application(environ['HTTP_HOST']) |
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return app(environ, start_response) |
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If you want to use it, you can do something like this: |
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.. sourcecode:: python |
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from myapplication import create_app, get_user_for_subdomain |
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from werkzeug.exceptions import NotFound |
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def make_app(subdomain): |
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user = get_user_for_subdomain(subdomain) |
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if user is None: |
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# if there is no user for that subdomain we still have |
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# to return a WSGI application that handles that request. |
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# We can then just return the NotFound() exception as |
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# application which will render a default 404 page. |
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# You might also redirect the user to the main page then |
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return NotFound() |
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# otherwise create the application for the specific user |
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return create_app(user) |
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application = SubdomainDispatcher('example.com', make_app)
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