[Twisted-Python] Example of a long-polling asynchronous web servic?
Hey guys I'm trying to implement some web-services over JSON-RPC, and one of the methods needs to use server-push. I will try and explain my problem as well as I can. I have a client, which is an iPhone, natively running a JSON-RPC( or XML-RPC ) client implementation. I need to do something like this from the iPhone service = ServerProxy("http://mydomain.com/webservice") init_data = service.subscribe_to_updates() ... ... ... some_result = service.some_regular_function(params) How can I implement this in Twisted? -- Stephen Mattison
On Tue, Oct 6, 2009 at 11:30 PM, Stephen Mattison <stephenmattison@gmail.com
wrote:
How can I implement this in Twisted?
You can use DeferredResource: http://twistedmatrix.com/documents/8.2.0/api/twisted.web.util.DeferredResour... or you can return NOT_DONE_YET from Resource.render(), and hold on to the request: http://twistedmatrix.com/documents/8.2.0/api/twisted.web.resource.Resource.h... to leave the connection open until something happens. For a more elaborate example of a long-polling server component, you could see Nevow's Athena: http://www.divmod.org/trac/wiki/DivmodNevow/Athena This does not implement JSON-RPC or XML-RPC, but it has lots of code for managing the outstanding connection, which may give you some ideas. -Glyph
Hey Glyph thanks for responding so promptly! First if I understand correctly on the server-side we have some code like: def get_data_updates(): if (!has_updates): return NO_DATA return json.encode(the_updates) and on the client side def poll_for_updates(): while True: response = service.get_data_updates() if response != NO_DATA: break sleep(1) do_something_with_response(response) poll_for_updates() As far as I can tell doing this has NO guarantee that all messages are delivered unless every server->client connection maintains a stack of "new" messages, whereas in a message-brokered setting the server just keeps sending "global" updates as they occur, and the broker guarantees that clients will receive every one. Where as in this situation, since the client is asking the server for updates, unless the server strictly maintains all of the updates for a specific client, some of them might be thrown on the ground. Am I correct here? On Tue, Oct 6, 2009 at 8:46 PM, Glyph Lefkowitz <glyph@twistedmatrix.com>wrote:
On Tue, Oct 6, 2009 at 11:30 PM, Stephen Mattison < stephenmattison@gmail.com> wrote:
How can I implement this in Twisted?
You can use DeferredResource:
http://twistedmatrix.com/documents/8.2.0/api/twisted.web.util.DeferredResour...
or you can return NOT_DONE_YET from Resource.render(), and hold on to the request:
http://twistedmatrix.com/documents/8.2.0/api/twisted.web.resource.Resource.h...
to leave the connection open until something happens.
For a more elaborate example of a long-polling server component, you could see Nevow's Athena:
http://www.divmod.org/trac/wiki/DivmodNevow/Athena
This does not implement JSON-RPC or XML-RPC, but it has lots of code for managing the outstanding connection, which may give you some ideas.
-Glyph
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-- Stephen Mattison
participants (2)
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Glyph Lefkowitz -
Stephen Mattison