FCGI::ProcManager(3)

NAME
 FCGI::ProcManager - functions for managing FastCGI applications.

SYNOPSIS
 # In Object-oriented style.
 use CGI::Fast;
 use FCGI::ProcManager;
 my $proc_manager = FCGI::ProcManager->new({
    n_processes => 10
 });
 $proc_manager->pm_manage();
 while (my $cgi = CGI::Fast->new()) {
   $proc_manager->pm_pre_dispatch();
   # ... handle the request here ...
   $proc_manager->pm_post_dispatch();
 }

 # This style is also supported:
 use CGI::Fast;
 use FCGI::ProcManager qw(pm_manage pm_pre_dispatch
              pm_post_dispatch);
 pm_manage( n_processes => 10 );
 while (my $cgi = CGI::Fast->new()) {
   pm_pre_dispatch();
   #...
   pm_post_dispatch();
 }

DESCRIPTION
FCGI::ProcManager is used to serve as a FastCGI process manager. By re-implementing it in perl, developers can more finely tune performance in their web applications, and can take advantage of copy-on-write semantics prevalent in UNIX kernel process management. The process manager should be invoked before the caller''s request loop

The primary routine, "pm_manage", enters a loop in which it maintains a number of FastCGI servers (via fork(2)), and which reaps those servers when they die (via wait(2)).

"pm_manage" provides too hooks:

 C<managing_init> - called just before the manager enters the manager loop.
 C<handling_init> - called just before a server is returns from C<pm_manage>

It is necessary for the caller, when implementing its request loop, to insert a call to "pm_pre_dispatch" at the top of the loop, and then 7"pm_post_dispatch" at the end of the loop.

  Signal Handling
FCGI::ProcManager attempts to do the right thing for proper shutdowns now.

When it receives a SIGHUP, it sends a SIGTERM to each of its children, and then resumes its normal operations.

When it receives a SIGTERM, it sends a SIGTERM to each of its children, sets an alarm(3) "die timeout" handler, and waits for each of its children to die. If all children die before this timeout, process manager exits with return status 0. If all children do not die by the time the "die timeout" occurs, the process manager sends a SIGKILL to each of the remaining children, and exists with return status 1.

In order to get FastCGI servers to exit upon receiving a signal, it is necessary to use its FAIL_ACCEPT_ON_INTR. See FCGI's description of FAIL_ACCEPT_ON_INTR. Unfortunately, if you want/need to use CGI::Fast, it is currently necessary to run the latest (at the time of writing) development version of FCGI.pm. (>= 0.71_02)

Otherwise, if you don't, there is a loop around accept(2) which prevents os_unix.c OS_Accept() from returning the necessary error when FastCGI servers blocking on accept(2) receive the SIGTERM or SIGHUP.

FCGI::ProcManager uses POSIX::sigaction() to override the default SA_RESTART policy used for perl's %SIG behavior. Specifically, the process manager never uses SA_RESTART, while the child FastCGI servers turn off SA_RESTART around the accept(2) loop, but reinstate it otherwise.

The desired (and implemented) effect is to give a request as big a chance as possible to succeed and to delay their exits until after their request, while allowing the FastCGI servers waiting for new requests to die right away.

METHODS

  new
 class or instance
 (ProcManager) new([hash parameters])

Constructs a new process manager. Takes an option has of initial parameter values, and assigns these to the constructed object HASH, overriding any default values. The default parameter values currently are:

 role         => manager
 start_delay  => 0
 die_timeout  => 60
 pm_title => 'perl-fcgi-pm'

Manager methods

  pm_manage
 instance or export
 (int) pm_manage([hash parameters])

DESCRIPTION:

When this is called by a FastCGI script to manage application servers. It defines a sequence of instructions for a process to enter this method and begin forking off and managing those handlers, and it defines a sequence of instructions to intialize those handlers.

If n_processes < 1, the managing section is subverted, and only the handling sequence is executed.

Either returns the return value of pm_die() and/or pm_abort() (which will not ever return in general), or returns 1 to the calling script to begin handling requests.

  managing_init
 instance
 () managing_init()

DESCRIPTION:

Overrideable method which initializes a process manager. In order to handle signals, manage the PID file, and change the process name properly, any method which overrides this should call SUPER::managing_init().

  pm_die
 instance or export
 () pm_die(string msg[, int exit_status])

DESCRIPTION:

This method is called when a process manager receives a notification to shut itself down. pm_die() attempts to shutdown the process manager gently, sending a SIGTERM to each managed process, waiting die_timeout() seconds to reap each process, and then exit gracefully once all children are reaped, or to abort if all children are not reaped.

  pm_wait
 instance or export
 (int pid) pm_wait()

DESCRIPTION:

This calls wait() which suspends execution until a child has exited. If the process ID returned by wait corresponds to a managed process, pm_notify() is called with the exit status of that process. pm_wait() returns with the return value of wait().

  pm_write_pid_file
 instance or export
 () pm_write_pid_file([string filename])

DESCRIPTION:

Writes current process ID to optionally specified file. If no filename is specified, it uses the value of the "pid_fname" parameter.

  pm_remove_pid_file
 instance or export
 () pm_remove_pid_file()

DESCRIPTION:

Removes optionally specified file. If no filename is specified, it uses the value of the "pid_fname" parameter.

  sig_sub
 instance
 () sig_sub(string name)

DESCRIPTION:

The name of this method is passed to POSIX::sigaction(), and handles signals for the process manager. If $SIG_CODEREF is set, then the input arguments to this are passed to a call to that.

  sig_manager
 instance
 () sig_manager(string name)

DESCRIPTION:

Handles signals of the process manager. Takes as input the name of signal being handled.

Handler methods

  handling_init
 instance or export
 () handling_init()

DESCRIPTION:

  pm_pre_dispatch
 instance or export
 () pm_pre_dispatch()

DESCRIPTION:

  pm_post_dispatch
 instance or export
 () pm_post_dispatch()

DESCRIPTION:

  sig_handler
 instance or export
 () sig_handler()

DESCRIPTION:

Common methods and routines

  self_or_default
 private global
 (ProcManager, @args) self_or_default([ ProcManager, ] @args);

DESCRIPTION:

This is a helper subroutine to acquire or otherwise create a singleton default object if one is not passed in, e.g., a method call.

  pm_change_process_name
 instance or export
 () pm_change_process_name()

DESCRIPTION:

  pm_received_signal
 instance or export
 () pm_received signal()

DESCRIPTION:

parameters

  pm_parameter
 instance or export
 () pm_parameter()

DESCRIPTION:

  n_processes

  no_signals

  pid_fname

  die_timeout

  role

  start_delay
DESCRIPTION:

notification and death

  pm_warn
 instance or export
 () pm_warn()

DESCRIPTION:

  pm_notify
 instance or export
 () pm_notify()

DESCRIPTION:

  pm_exit
 instance or export
 () pm_exit(string msg[, int exit_status])

DESCRIPTION:

  pm_abort
 instance or export
 () pm_abort(string msg[, int exit_status])

DESCRIPTION:

BUGS
No known bugs, but this does not mean no bugs exist.

SEE ALSO
FCGI.

MAINTAINER
Gareth Kirwan <gbjk@thermeon.com>

AUTHOR
James E Jurach Jr.

COPYRIGHT
 FCGI-ProcManager - A Perl FCGI Process Manager
 Copyright (c) 2000, FundsXpress Financial Network, Inc.

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2 of the License, or (at your option) any later version.

 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
 AND EFFORT IS WITH THE YOU.  See the GNU Lesser General Public
 License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA