"I'm not entirely convinced about websocket solutions in Python yet, but I've been told flask-websockets is awesome. Nevertheless this doesn't solve the problem for you. Cause the request is just keeping an open line and waiting for a response....blocking is bad."
Tornado only blocks if you do something silly. It's event based, and can keep hundreds of connections open and waiting for it's async response event before actioning/responding the open connection.
"The most simplest advise I would have is to have the ajax request trigger a background task and return immediately. The background task will then have some kind of side effect (ie. write some result to a database somewhere) which the ajax request can the look for with some kind of polling mechanism (on some other endpoint)."
Wow, overkill much? Polling is bad, and is exactly the kind of bad solution that a lot of these libraries are in place to prevent developers from needing to do.
Websockets were made to solve the long-polling and poll-spamming that was prevalent. Now all you have to do is keep a light, open web-socket connection to the server. And the server, being async/evented, will respond when the task is good and ready. Nice and clean.
"Tornado only blocks if you do something silly. It's event based, and can keep hundreds of connections open and waiting for it's async response event before actioning/responding the open connection." - Yes pure tornado based apps are probably fine if you know what you are doing.
"Wow, overkill much? Polling is bad, and is exactly the kind of bad solution that a lot of these libraries are in place to prevent developers from needing to do." - Polling is not bad if you have a good use case. You just cannot do non-blocking stuff with Django for instance, or it's very very hard and tricky. Websockets also limit you with the number of connections you can have open at once.
"The most simplest advise I would have is to have the ajax request trigger a background task and return immediately. The background task will then have some kind of side effect (ie. write some result to a database somewhere) which the ajax request can the look for with some kind of polling mechanism (on some other endpoint)." Wow, overkill much? Polling is bad, and is exactly the kind of bad solution that a lot of these libraries are in place to prevent developers from needing to do.
Websockets were made to solve the long-polling and poll-spamming that was prevalent. Now all you have to do is keep a light, open web-socket connection to the server. And the server, being async/evented, will respond when the task is good and ready. Nice and clean.