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Steve Holden
steve at holdenweb.com
Sat Oct 7 03:41:13 EDT 2006
Andreas Klauer wrote: > On Sat, Oct 07, 2006 at 09:18:13AM +1000, Graham Dumpleton wrote: > >>Before I try and address that I would ask why you are trying to perhaps >>reinvent the wheel as others have already solved this problem. > > > It's probably hard not to reinvent the wheel when what you want is > something as trivial as a telnet web application frontend, um, thingy. > I want it to be small, lightweight, and specifically adapted for my needs, > that is the sole reason why I am doing it. > I think perhaps your first problem is that assumption of triviality. I find it's more useful to describe a problem as trivial after I have solved it with less than ten lines of code. Until then I'd prefer to describe the level of difficulty as "unknown". > >>Back to your threads. The problem with using Apache/mod_python when >>you want to preserve some state between requests is not threads but >>processes. This is because when using prefork or worker Apache MPMs >>on UNIX systems, subsequent requests can be directed to different Apache >>child processes. As a result, if one child process had initiated a >>telnet connection, when a subsequent request arrives and it ends up being >>processed by a different child process, it will not have access to >>the open connection. On Win32 boxes this isn't a problem, as there is only one >>Apache process and all requests are handled by it. > > > Thank you for this clarification. I could not find that information > anywhere although I was desparately looking for it. All I found was > persistence this and persistence that and I noticed that there was > no real persistence at all (at least the way I understand it). > > Unless I missed the explanation somewhere, maybe this should go to > some obvious place like the FAQ? > It's a fairly usual condition in web systems: the persistence referred to is usually persistence of session state data rather than persistence of process and network connection state. > >>Also, even if there were some way, Apache is allowed to shutdown >>specific child processes at any time, so you would loose any open >>connection anyway. > > > Especially this part is worth mentioning. Thanks. So there really > is no way but to use some daemon independent from Apache. > Correct. > Thanks for all the replies. :-) > > Although that means I will need to write a daemon for almost anything > that needs persistence (databases don't except for performance reasons). > If you want to persist a network connection across multiple web client interactions then you have indeed summed up your situation quite succinctly. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://holdenweb.blogspot.com Recent Ramblings http://del.icio.us/steve.holden
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