On Sun, 2003-02-23 at 10:46, Jim Morrison [Mailing-Lists] wrote: > Having spent the w/e getting to grips with startup.pl's and the such I'm > beginning to discover that it's only possible to share read-only memory > and as soon as you write to memory it splits off.. ..
The situation with forked Apache processes is the same as with any forked process: you have to use some form of IPC to communicate between them. I suggest you look at IPC::MM or IPC::Shareable. IPC::Shareable is more transparent, but IPC::MM has better performance. IPC::MM simply creates a hash in shared memory and lets you write to it. Either of these will allow you to share data between processes. > What I really want to do is to write a module that can be accessed from > any of the child apache processes such that some work can be done at one > stage, and if the second request comes through to another child, that > child can pick up on the work of the first.. That sounds pretty sketchy to me. Why are you trying to do that? There may be a much simpler way to achieve what you're after. > Is there _absolutely_ no way that two children could ever have write > access to the same object? No, not when there are multiple processes involved. The sharing that happens with the modules I mentioned above involves serializing Perl data into a byte stream, putting it into shared memory, and then pulling it back and de-serializing on the other side. > Lastly, coming from a RiscOS background, it was always possible to issue > module interrupts such that one program can call the functions of > another completely separate program.. You have the basic Unix building blocks here: signals, semaphores, shared memory, sockets. > It seems to me I'm missing some pretty basic inter-program communication > stuff.. but then all my experience of calling one linux prog from > another has usually worked by piping something from one to another. You can talk between processes on STDIN (which is what a pipe is doing) if the process you want to talk to is listening on STDIN. Web server processes don't do that. They listen on sockets for requests from outside. - Perrin
