Re: forking

Stanley Gambarin (gambarin@openmarket.com)
Fri, 25 Oct 1996 16:38:01 -0400 

Message-Id: <199610252038.QAA23868@u4-138.openmarket.com>
To: Andrew Savige <andrew.savige@sb.com.au>
Subject: Re: forking 
In-Reply-To: Your message of "Wed, 23 Oct 1996 13:47:37 +1000."
             <2.2.32.19961023034737.0067dad0@sb.com.au> 
Date: Fri, 25 Oct 1996 16:38:01 -0400
From: Stanley Gambarin <gambarin@openmarket.com>

> [Stuff removed]
> What I am trying to do is to have responder immediately
> fork a new process to handle the (possibly lengthy) request,
> then wait for the next request and so on.  Is fast-cgi
> designed to work this way?  If not, what is the recommended
> way of writing a remote responder?
> 
> To give you a more precise idea of what I am doing, here
> is a rough map of the responder code;
> 
>    while (FCGI_Accept() >= 0) {
>       if ((pid = fork()) < 0) {
>          error
>       } else if (pid == 0) {
>          /* child */
>          printf("Content-type: text/plain\r\n\r\n");
>          printf("this is a test\n");
>          sleep(2);  /* simulate a lengthy request */
>          FCGI_Finish();
>          exit(0);
>       }
>       /* parent continues */
>    }
> 
> The child's response works, but the parent then exits
> the FCGI_Accept() loop (maybe FCGI_Accept() also calls
> FCGX_Finish() and that causes a problem?).
> 
> Please help.
> 
> -- Andrew
> Andrew Savige        andrews@sb.com.au
> 
	The current design of FastCGI does not permit dynamic number of 
processors (via fork or otherwise).  Thus you must configure the number
of processors statically, using -processes parameter for AppClass directive.
Since all of the processes listen to the same socket, if one of them is busy,
performing lengthy computation or I/O, the others can take over with identical
functionality.  
	The alternative is to provide dynamic process allocation with either
threads or on-demand FastCGI apps.  Both alternatives are currently not 
implemented, but there are some design notes in the mod_fastcgi.c

-- 

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