Thank you Jason. I registered on Skype (rene.heymans). You can try around noon your time (6PM mine). Till then. Regards, René
On Saturday, August 2, 2014 9:16:29 PM UTC+2, Jason Garber wrote: > > We can do a gotomeeting. Perhaps around lunchtime eastern on Sunday? > On Aug 2, 2014 2:08 PM, <[email protected] <javascript:>> wrote: > >> Hello Jason, >> >> Thank you very much for your kind and swift offer. I'll do it gladly ... >> but I need to set-up Skype on my station :-( and register a Skype account. >> I'm an old-timer and my only contact is Gmail. I have no G+, no Facebook, >> no Twitter, ... >> >> What is your preferred day and time for a Skype call. >> I live in the Paris-Luxembourg-Brussels time zone. For instance it is now >> Saturday Aug. 2, 20:05. >> >> When you say privately, I suppose a one-to-one call on Skype and I >> suppose I can easily find your name there. >> >> Have a nice Sunday and thanks again, >> >> René >> >> On Saturday, August 2, 2014 6:35:33 PM UTC+2, Jason Garber wrote: >>> >>> Hi Rene, >>> >>> I offer to do a skype call with you to review all of this as I have been >>> there done that and have a crisp understanding of all the working parts. >>> >>> Contact me privately if you want to do this. >>> >>> Thanks, >>> Jason >>> On Aug 2, 2014 12:32 PM, <[email protected]> wrote: >>> >>>> Dear Graham & al., >>>> >>>> Congratulations for your software and documentation. I have however >>>> some difficulties as outlined in the subject caption. >>>> >>>> I'm building a case study for an application on an intranet within a >>>> company where the users would interact with their browser communicating >>>> with the Apache2/mod_wsgi server (daemon mode + multi-threads). >>>> >>>> However I'm afraid I'm misunderstanding some important underlying >>>> concepts of the architecture. Please allow me to give an example and to >>>> give you my thoughts - which could go wrong somewhere. >>>> >>>> *Part 1:* >>>> >>>> I wrote a simple HTML page with a one field input form. >>>> >>>> In my `environment` dictionary, I have, among other key/value pairs, >>>> the following: >>>> >>>> REQUEST_METHOD: POST >>>> REQUEST_URI: /core/my-wsgi-app >>>> mod_wsgi.callable_object: application >>>> >>>> The first two values come obviously from my html <form >>>> action="core/my-wsgi-app" method="post">...</form>, and the third value is >>>> the default value in the configuration directive (WSGICallableObject >>>> application). >>>> >>>> In my my-wsgi-app script, I have of course: >>>> >>>> def application (environment, start_response): >>>> [my code here] >>>> return [response_body] >>>> >>>> So all is fine and works well but there is something I don't get (I >>>> mean I haven't fully assimilated), certainly in a multi-users, >>>> multi-threads, ... environment. The main question is about the >>>> WSGICallableObject. >>>> >>>> >>>> The documentation (https://code.google.com/p/modwsgi/wiki/ >>>> ConfigurationDirectives#WSGICallableObject) says "*The >>>> WSGICallableObject directive can be used to override the name of the >>>> Python >>>> callable object in the script file which is used as the entry point into >>>> the WSGI application.*" [underlining is mine]. For me the WSGI >>>> application is the whole application: when finished the target application >>>> I'm case studying could serve one hundred users, delivering thousands of >>>> pages built dynamically over hundreds of SQL tables, ... Am I right in >>>> thinking than one entry point would be fit for such purpose. The size of >>>> the application is such that I already opted for a daemon configuration >>>> with multi-threads (I do not wish to have users waiting in a single queue >>>> because one of them is building a page that takes seconds to assemble). >>>> >>>> Having one single callable object seems to give me these only 4 options: >>>> >>>> 1) Have only one single REQUEST_URI, say /core/my-wsgi-app, where only >>>> one callable object (function, class, ...) is used under the one and same >>>> name (application). In such case that callable object is the one and only >>>> full single entry point to the overall application (thousands of pages >>>> built dynamically) and I must care for checking, authorisation, parsing, >>>> dispatching, ... and finally assembling the response and returning it. I'm >>>> wondering if this single script/callable-object could become a bottleneck. >>>> It is the concern I've just expressed. Of course, Python can handle >>>> hundreds of function calls and instance calls. This option makes me doubt >>>> I >>>> fully understand the mechanism. I call this option N to 1. >>>> >>>> 2) Have various REQUEST_URI (even one per page if need be) and in each >>>> called script, there would be one callable object with the same name >>>> ("application" as defined in the WSGICallableObject directive). In >>>> that case, I could create a callable instance of a base class but that >>>> instance should bear the application name and use the two positional >>>> arguments passed by mod_wsgi. This option, if used exclusively, seems to >>>> me >>>> like a normal "CGI static serving", i.e. one request activates one script >>>> (the whole logic and dynamism is in the script). This point too makes me >>>> doubt I understand the real nature of WSGI. I call this option N to N. >>>> >>>> 3) One could combine option 1 and 2 to create more dynamism without >>>> risking the potential (?) bottleneck of option 1 when used alone. I call >>>> this option N to M (<<N) >>>> >>>> 4) There seems to be a possibility to define the WSGICallableObject >>>> per directory. My understanding is that the REQUEST_URI belonging to a >>>> directory (and its sub-directories) would use that callable object name. >>>> This means for instance that any URI of the form /core/section-1/abc would >>>> have a callable object Application_1, while any URI under >>>> /core/section-N/... would have a callable object Application_N. I haven't >>>> tried this directive yet so I may misunderstand its role. >>>> >>>> This is my overall understanding but I'm afraid I'm missing something >>>> fundamental [please note that I'm not an English speaker and I might have >>>> missed subtleties in the documentation which is quite dense]. I tried to >>>> picture this in a diagram but I'm not sure I got it right: >>>> >>>> M (html requests) -> 1 (http server) -> N x P (mod_wsgi daemons x >>>> threads) -> X? (Python instance(s) / one per daemon ? I don't know) -> M >>>> (calls to one object in one URI or to many objects - named the same - in >>>> many URI ? ) and back to the user via the same route. >>>> >>>> I assume that one user html request generates ultimately one call to a >>>> callable object (give or take) : that's why I use M in toth cases. Is this >>>> assumption correct ? My dilemma is that I can't understand the spread of >>>> the load between the 2 extremes: one URI containing the `application` >>>> callable object (that is eventually called hundreds of times per second) >>>> or >>>> many hundreds URI each containing a callable object named `application` >>>> that all get called much less frequently. >>>> >>>> *Part 2:* >>>> >>>> As a consequence of this hazy understanding of mine, I wonder why can't >>>> the name of the callable object be chosen on demand ? >>>> >>>> If I refer to PEP3333 (http://legacy.python.org/dev/peps/pep-3333/) I >>>> understand that: >>>> " >>>> *A server or gateway must invoke the application object using >>>> positional (not keyword) arguments. (E.g. by calling result = >>>> application(environ, start_response)*" >>>> >>>> So my guess is that, still referring to the example at the top, one >>>> thread in mod_wsgi loads (I wouldn't call this an import) the >>>> /core/my-wsgi-app script and calls application(environment, >>>> start_response) >>>> that has been defined in it. Is this the correct mechanism ? >>>> >>>> Could we imagine that mod_wsgi would sometime call my_App (arg1, arg2), >>>> some other time call your_App (req, resp) or call Small_app (in, out) >>>> where >>>> my_App, your_App, Small_app would be defined because mod_wsgi would be >>>> able >>>> to set dynamically the WSGICallableObject . Imagine that in the >>>> WSGIImportScript script file, we would have: >>>> >>>> def my_App (param1, param2): >>>> [code here] >>>> return [my_Response] >>>> >>>> def your_App (param1, param2): >>>> [code here] >>>> return [your_Response] >>>> >>>> def Small_app (param1, param2): >>>> [code here] >>>> return [Small_response] >>>> >>>> all the functions would be ready to be called. >>>> >>>> I suppose that in any case we are limited: >>>> >>>> A) by the HTTP protocol (URI given via the action attribute, the >>>> POST, GET, OPTIONS, ... from the method attribute and the key/value pairs >>>> from the various input fields); and >>>> >>>> B) by directives we could give to configure mod_wsgi. I guess it is >>>> not the role neither the intend to build some "user logic" within mod_wsgi. >>>> >>>> *Conclusions:* >>>> >>>> 1) Am I correct in my understanding of mod_wsgi as expressed here above >>>> (Part 1) ? Beware that I could be out of my depth, i.e. talking about >>>> something I don't properly understand. In that case please correct me or >>>> complement my view. >>>> >>>> 2) Do we need to dynamically choose the callable object name for the >>>> sake of dynamism and multiplicity ? >>>> >>>> -> If not, the current set-up is enough. In which case is the >>>> preceding point ( 1) ) complete and correct ? >>>> >>>> -> If yes, how to do it simply and elegantly ? >>>> >>>> => Idea 1: create an extra key/value pair (e.g. >>>> wsgi_callable_object=my_application). It seems cumbersome to me. >>>> >>>> => Idea 2: if the URI were to have the form >>>> /core/my-wsgi-app/_my_application then mod_wsgi could provide: >>>> REQUEST_URI: /core/my-wsgi-app >>>> mod_wsgi.callable_object: my_application >>>> in the 'environment` dictionary because it would strip the >>>> trailing part beginning with an underscore provided it is told to do so by >>>> a directive; >>>> otherwise it would behave as now and deliver: >>>> REQUEST_URI: /core/my-wsgi-app/_my_application >>>> mod_wsgi.callable_object: application >>>> >>>> *Thanks:* >>>> >>>> I do realize this is an unusual post (maybe it should find its way in >>>> the group working on the documentation) but I would be very happy if some >>>> of you could answer / feedback to me. In any case I do thank you all in >>>> advance. >>>> >>>> René >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "modwsgi" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at http://groups.google.com/group/modwsgi. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> -- >> You received this message because you are subscribed to the Google Groups >> "modwsgi" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] <javascript:>. >> To post to this group, send email to [email protected] >> <javascript:>. >> Visit this group at http://groups.google.com/group/modwsgi. >> For more options, visit https://groups.google.com/d/optout. >> > -- You received this message because you are subscribed to the Google Groups "modwsgi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/modwsgi. For more options, visit https://groups.google.com/d/optout.
