Thanks for the answer - I was aware that I don't have to do this to handle ajax requests in general. The application I'm building needs to send and receive a sequence of messages from the client in a specific order, so I thought it would be easier to handle it in one thread/ process. It is however probably better to do it statelessly as you say, so I'll probably have to rewrite the code somewhat.
Out of curiosity though, what is the right way to start a subprocess in web2py? On 19 Mai, 22:00, Yarko Tymciurak <[email protected]> wrote: > On May 19, 2:14 pm, amoygard <[email protected]> wrote: > > > Hi, > > > I'm pretty new to web2py and web application frameworks. I'm trying to > > create a new background process in controller to handle incoming ajax > > data from a user. > > You are trying to do too much: remember: the web is "stateless" --- > when _anything_ comes in from a client that gets directed to your URL, > (this is just an example flow, so you can get the general idea): > > - somewhere, a DNS server replaces the URI name with a destination > address; > - the destination server (let's say apache) tries to sort out, and > direct to the correct app (in this case, web2py); > - web2py's main() parses the path part of the URI to decide how to > route internally > - if it finds a matching app/controller, main() will set up the > execution environment to prepare the call: > - i.e., your models are "executed" so that the table definitions, > etc. are all in the environment, and then your controller file > - the function in your controller is called with this execution > environment (this is the thread that you are trying to make, and > should not bother) > > The controller function does it's stuff with the request, and returns > (to main()) the response - sometimes nothing, sometimes a dict. of > stuff; > Main takes the return values from the controller, and processes > appropriately, most often getting the view, parsing the template, > creating the resulting view, and sending it back to the client. > > When an ajax call is made, you can see an example > athttp://www.web2py.com/book/default/section/10/3, and explanation of > what this does. > > The general point: you call a controller with a request (even in the > case of an ajax call); > The response goes back to the caller. > > Lots of stuff happens for you - you don't need to write the entire web > server underpinnings; just worry about the logic you want to > implement so server and client can converse / exchange information. > > Hope this helps. > > Regards, > - Yarko > > > > > I'm using the module multiprocessing for this. > > However, when I start the new process, a new instance of web2py server > > is started? I'm assuming this has something to do with forking (which > > I don't know much about). Is there an easy workaround? Or should I > > preferrably do this some other way, for instance with threads? > > > Code is as follows (controller calls function 'someinit' in a module > > in module-folder): > > > def tekstpr(mstring,conn): > > print mstring > > conn.send("hello") > > > def someinit(userid): > > from multiprocessing import Pipe, Process > > parent_conn, child_conn = Pipe() > > p = Process(target=tekstpr,args=("I'm alive!",child_conn)) > > session.procpipe = parent_conn > > p.start() > > session.procpipe.poll(300) > > return session.procpipe.recv()
