Is it possible to send intermediate content to a browser with pylons? the use-case is if I have a long process I would like to send some content to the browser, run my long process and then send the rest of the content in real-time. Currently an action waits for the must return the Response, meaning that all the content is sent all at once rather then incremental. Thanks for any and all help
> Is it possible to send intermediate content to a browser with pylons? > the use-case is if I have a long process I would like to send some > content to the browser, run my long process and then send the rest of > the content in real-time. Currently an action waits for the must > return the Response, meaning that all the content is sent all at once > rather then incremental. > Thanks for any and all help
You'll want to return a generator as your response like so:
Note that you need to bring special vars like request, c, g, and session into scope for the generator closure so that they'll be available when the generator is used for the response.
Right now in the controller, it is called with the full WSGI interface. The WSGIController then calls your action, and returns the output in a Response object. To do intermediate content, you need to put the content returning stuff into an iterator. This way it will start sending as it has the information.
Here's how you can send an iterator in an action that's sending data as it can:
def action(self): def long_func(): yield "some data right away" # do something that take a long time yield "some more data" # etc. resp = Response() resp.content = long_func() return resp
Note that if you need access to the special vars request, session, c, or g in your generator function, you should bring the actual object into scope for the function. This is because the iterator could likely be executing outside the Pylons environment during which the special var proxies will not proxy. So:
I just gave this a try and it didn't give me the result I was expecting. The code I tried is:
def index(self): req = request.current_obj() def long_func(): env = req.environ yield 'I am starting now' #simulate a very long process for i in range(10000): print i yield 'I should be finishing now' res = Response() res.content = long_func() return res
I know that this really does not do anything, I am just trying to get the use-case to work. What I expected to see in the browser was first the "I am starting now" statement, followed by by the print stuff in the cmd window followed by the last statement being sent to the browser. Instead it looks like either its all being sent at once, or the browser is waiting for the page to finish before anything gets rendered. Do you know of any way to test to see which is it? Jose
Ben Bangert wrote: > On Aug 15, 2006, at 11:07 PM, jose wrote:
> > Is it possible to send intermediate content to a browser with pylons? > > the use-case is if I have a long process I would like to send some > > content to the browser, run my long process and then send the rest of > > the content in real-time. Currently an action waits for the must > > return the Response, meaning that all the content is sent all at once > > rather then incremental. > > Thanks for any and all help
> You'll want to return a generator as your response like so:
> Note that you need to bring special vars like request, c, g, and > session into scope for the generator closure so that they'll be > available when the generator is used for the response.
jose wrote: > I just gave this a try and it didn't give me the result I was > expecting. The code I tried is:
> def index(self): > req = request.current_obj() > def long_func(): > env = req.environ > yield 'I am starting now' > #simulate a very long process > for i in range(10000): > print i > yield 'I should be finishing now' > res = Response() > res.content = long_func() > return res
> I know that this really does not do anything, I am just trying to get > the use-case to work. What I expected to see in the browser was first > the "I am starting now" statement, followed by by the print stuff in > the cmd window followed by the last statement being sent to the > browser. Instead it looks like either its all being sent at once, or > the browser is waiting for the page to finish before anything gets > rendered. Do you know of any way to test to see which is it?
If you really want to send out content over time, you need to use the writer that start_response returns; the iterator allows for incremental production of a response, but it's up to the server exactly when/how to send it out and it might be buffered.
I don't know if Pylons normally gives access to the writer start_response returns?
I just tried this code as well and it gave me the same result. The page did not show any of the text until the whole request was finished. I am using the paster serve server.
Could it be that I have a version that is before Ben removed all the explicit list() calls?
If so, what is the easy_install command to run to upgrade to the right version?
jose wrote: > I just gave this a try and it didn't give me the result I was > expecting. The code I tried is:
> def index(self): > req = request.current_obj() > def long_func(): > env = req.environ > yield 'I am starting now' > #simulate a very long process > for i in range(10000): > print i > yield 'I should be finishing now' > res = Response() > res.content = long_func() > return res > > > return the Response, meaning that all the content is sent all at once > > > rather then incremental. > > > Thanks for any and all help
I know that Response is actually paste.wsgiwrappers.WSGIResponse, but it'd be great if it'd accept an iterator as content parameter so last three lines could be replaced by
> I just tried this code as well and it gave me the same result. The > page did not show any of the text until the whole request was finished. > I am using the paster serve server.
> Could it be that I have a version that is before Ben removed all the > explicit list() calls?
> If so, what is the easy_install command to run to upgrade to the right > version?
Ah, yes. There was the update, I believe that made it into 0.9.1 though. I should mention that due to how debug mode catches the info should an exception be caught, you can only send a stream when debug mode is off.
Try uncommenting the set debug = false
At the bottom of the development.ini file, and let me know if the iterator works.
That did it. After uncommenting that line and restarting the paster server the following function (slightly modified from the previous example to send all items to the browser) worked as expected sending each yield statement output to the browser immediately.
def test(self): import time req = request.current_obj() def long_func(): env = req.environ yield 'I am starting now' for i in range(100): yield "<br>%s" % i time.sleep(.1) yield 'I should be finishing now' res = Response() res.content = long_func() return res
Ben Bangert wrote: > I should mention that due to how debug mode catches the info > should an exception be caught, you can only send a stream when debug > mode is off.
> Try uncommenting the > set debug = false
> At the bottom of the development.ini file, and let me know if the > iterator works.
