1 package FCGI::ProcManager;
3 # Copyright (c) 2000, FundsXpress Financial Network, Inc.
4 # This library is free software released under the GNU Lesser General
5 # Public License, Version 2.1. Please read the important licensing and
6 # disclaimer information included below.
8 # $Id: ProcManager.pm,v 1.23 2001/04/23 16:10:11 muaddie Exp $
12 use POSIX qw(:signal_h);
14 use vars qw($VERSION @ISA @EXPORT_OK %EXPORT_TAGS $Q $SIG_CODEREF);
18 @EXPORT_OK = qw(pm_manage pm_die pm_wait
19 pm_write_pid_file pm_remove_pid_file
20 pm_pre_dispatch pm_post_dispatch
21 pm_change_process_name pm_received_signal pm_parameter
22 pm_warn pm_notify pm_abort pm_exit
24 $EXPORT_TAGS{all} = \@EXPORT_OK;
25 $FCGI::ProcManager::Default = 'FCGI::ProcManager';
30 FCGI::ProcManager - functions for managing FastCGI applications.
34 # In Object-oriented style.
36 use FCGI::ProcManager;
37 my $proc_manager = FCGI::ProcManager->new({
40 $proc_manager->pm_manage();
41 while (my $cgi = CGI::Fast->new()) {
42 $proc_manager->pm_pre_dispatch();
43 # ... handle the request here ...
44 $proc_manager->pm_post_dispatch();
47 # This style is also supported:
49 use FCGI::ProcManager qw(pm_manage pm_pre_dispatch
51 pm_manage( n_processes => 10 );
52 while (my $cgi = CGI::Fast->new()) {
60 FCGI::ProcManager is used to serve as a FastCGI process manager. By
61 re-implementing it in perl, developers can more finely tune performance in
62 their web applications, and can take advantage of copy-on-write semantics
63 prevalent in UNIX kernel process management. The process manager should
64 be invoked before the caller''s request loop
66 The primary routine, C<pm_manage>, enters a loop in which it maintains a
67 number of FastCGI servers (via fork(2)), and which reaps those servers
68 when they die (via wait(2)).
70 C<pm_manage> provides too hooks:
72 C<managing_init> - called just before the manager enters the manager loop.
73 C<handling_init> - called just before a server is returns from C<pm_manage>
75 It is necessary for the caller, when implementing its request loop, to
76 insert a call to C<pm_pre_dispatch> at the top of the loop, and then
77 7C<pm_post_dispatch> at the end of the loop.
79 =head2 Signal Handling
81 FCGI::ProcManager attempts to do the right thing for proper shutdowns now.
83 When it receives a SIGHUP, it sends a SIGTERM to each of its children, and
84 then resumes its normal operations.
86 When it receives a SIGTERM, it sends a SIGTERM to each of its children, sets
87 an alarm(3) "die timeout" handler, and waits for each of its children to
88 die. If all children die before this timeout, process manager exits with
89 return status 0. If all children do not die by the time the "die timeout"
90 occurs, the process manager sends a SIGKILL to each of the remaining
91 children, and exists with return status 1.
93 In order to get FastCGI servers to exit upon receiving a signal, it is
94 necessary to use its FAIL_ACCEPT_ON_INTR. See L<FCGI>'s description of
95 FAIL_ACCEPT_ON_INTR. Unfortunately, if you want/need to use L<CGI::Fast>, it
96 is currently necessary to run the latest (at the time of writing) development
97 version of FCGI.pm. (>= 0.71_02)
99 Otherwise, if you don't, there is a loop around accept(2) which prevents
100 os_unix.c OS_Accept() from returning the necessary error when FastCGI
101 servers blocking on accept(2) receive the SIGTERM or SIGHUP.
103 FCGI::ProcManager uses POSIX::sigaction() to override the default SA_RESTART
104 policy used for perl's %SIG behavior. Specifically, the process manager
105 never uses SA_RESTART, while the child FastCGI servers turn off SA_RESTART
106 around the accept(2) loop, but reinstate it otherwise.
108 The desired (and implemented) effect is to give a request as big a chance as
109 possible to succeed and to delay their exits until after their request,
110 while allowing the FastCGI servers waiting for new requests to die right
118 (ProcManager) new([hash parameters])
120 Constructs a new process manager. Takes an option has of initial parameter
121 values, and assigns these to the constructed object HASH, overriding any
122 default values. The default parameter values currently are:
127 pm_title => 'perl-fcgi-pm'
132 my ($proto,$init) = @_;
139 pm_title => 'perl-fcgi-pm',
142 bless $this, ref($proto)||$proto;
146 # initialize signal constructions.
147 unless ($this->no_signals() or $^O eq 'Win32') {
148 $this->{sigaction_no_sa_restart} =
149 POSIX::SigAction->new('FCGI::ProcManager::sig_sub');
150 $this->{sigaction_sa_restart} =
151 POSIX::SigAction->new('FCGI::ProcManager::sig_sub',undef,POSIX::SA_RESTART);
157 sub _set_signal_handler {
158 my ($this, $signal, $restart);
160 if ($^O eq 'Win32') {
161 $SIG{$signal} = 'FCGI::ProcManager::sig_sub';
164 sigaction(&{"POSIX::SIG$signal"}(), $restart ? $this->{sigaction_sa_restart} : $this->{sigaction_no_sa_restart})
165 or $this->pm_warn("sigaction: SIG$signal: $!");
169 =head1 Manager methods
174 (int) pm_manage([hash parameters])
178 When this is called by a FastCGI script to manage application servers. It
179 defines a sequence of instructions for a process to enter this method and
180 begin forking off and managing those handlers, and it defines a sequence of
181 instructions to intialize those handlers.
183 If n_processes < 1, the managing section is subverted, and only the
184 handling sequence is executed.
186 Either returns the return value of pm_die() and/or pm_abort() (which will
187 not ever return in general), or returns 1 to the calling script to begin
193 my ($this,%values) = self_or_default(@_);
194 map { $this->pm_parameter($_,$values{$_}) } keys %values;
196 local $SIG{CHLD}; # Replace the SIGCHLD default handler in case
197 # somebody shit on it whilst loading code.
199 # skip to handling now if we won't be managing any processes.
200 $this->n_processes() or return;
202 # call the (possibly overloaded) management initialization hook.
203 $this->role("manager");
204 $this->managing_init();
205 $this->pm_notify("initialized");
207 my $manager_pid = $$;
209 MANAGING_LOOP: while (1) {
211 $this->n_processes() > 0 or
212 return $this->pm_die();
214 # while we have fewer servers than we want.
215 PIDS: while (keys(%{$this->{PIDS}}) < $this->n_processes()) {
217 if (my $pid = fork()) {
218 # the manager remembers the server.
219 $this->{PIDS}->{$pid} = { pid=>$pid };
220 $this->pm_notify("server (pid $pid) started");
222 } elsif (! defined $pid) {
223 return $this->pm_abort("fork: $!");
226 $this->{MANAGER_PID} = $manager_pid;
227 # the server exits the managing loop.
231 for (my $s = $this->start_delay(); $s > 0; $s -= sleep $s) {};
234 # this should block until the next server dies.
241 # forget any children we had been collecting.
242 delete $this->{PIDS};
244 # call the (possibly overloaded) handling init hook
245 $this->role("server");
246 $this->handling_init();
247 $this->pm_notify("initialized");
260 Overrideable method which initializes a process manager. In order to
261 handle signals, manage the PID file, and change the process name properly,
262 any method which overrides this should call SUPER::managing_init().
269 # begin to handle signals.
270 # We do NOT want SA_RESTART in the process manager.
271 # -- we want start the shutdown sequence immediately upon SIGTERM.
272 unless ($this->no_signals()) {
273 $this->_set_signal_handler('TERM', 0);
274 $this->_set_signal_handler('HUP', 0);
275 $SIG_CODEREF = sub { $this->sig_manager(@_) };
278 # change the name of this process as it appears in ps(1) output.
279 $this->pm_change_process_name($this->pm_parameter('pm_title'));
281 $this->pm_write_pid_file();
287 () pm_die(string msg[, int exit_status])
291 This method is called when a process manager receives a notification to
292 shut itself down. pm_die() attempts to shutdown the process manager
293 gently, sending a SIGTERM to each managed process, waiting die_timeout()
294 seconds to reap each process, and then exit gracefully once all children
295 are reaped, or to abort if all children are not reaped.
300 my ($this,$msg,$n) = self_or_default(@_);
302 # stop handling signals.
304 $SIG{HUP} = 'DEFAULT';
305 $SIG{TERM} = 'DEFAULT';
307 $this->pm_remove_pid_file();
309 # prepare to die no matter what.
310 if (defined $this->die_timeout()) {
311 $SIG{ALRM} = sub { $this->pm_abort("wait timeout") };
312 alarm $this->die_timeout();
315 # send a TERM to each of the servers.
316 if (my @pids = keys %{$this->{PIDS}}) {
317 $this->pm_notify("sending TERM to PIDs, @pids");
321 # wait for the servers to die.
322 while (%{$this->{PIDS}}) {
327 $this->pm_exit("dying: ".$msg,$n);
337 This calls wait() which suspends execution until a child has exited.
338 If the process ID returned by wait corresponds to a managed process,
339 pm_notify() is called with the exit status of that process.
340 pm_wait() returns with the return value of wait().
345 my ($this) = self_or_default(@_);
347 # wait for the next server to die.
348 return if ((my $pid = wait()) < 0);
350 # notify when one of our servers have died.
351 delete $this->{PIDS}->{$pid} and
352 $this->pm_notify("server (pid $pid) exited with status $?");
357 =head2 pm_write_pid_file
360 () pm_write_pid_file([string filename])
364 Writes current process ID to optionally specified file. If no filename is
365 specified, it uses the value of the C<pid_fname> parameter.
369 sub pm_write_pid_file {
370 my ($this,$fname) = self_or_default(@_);
371 $fname ||= $this->pid_fname() or return;
373 if (!open $PIDFILE, ">$fname") {
374 $this->pm_warn("open: $fname: $!");
377 print $PIDFILE "$$\n" or die "Could not print PID: $!";
378 close $PIDFILE or die "Could not close PID file: $!";
381 =head2 pm_remove_pid_file
384 () pm_remove_pid_file()
388 Removes optionally specified file. If no filename is specified, it uses
389 the value of the C<pid_fname> parameter.
393 sub pm_remove_pid_file {
394 my ($this,$fname) = self_or_default(@_);
395 $fname ||= $this->pid_fname() or return;
396 my $ret = unlink($fname) or $this->pm_warn("unlink: $fname: $!");
403 () sig_sub(string name)
407 The name of this method is passed to POSIX::sigaction(), and handles signals
408 for the process manager. If $SIG_CODEREF is set, then the input arguments
409 to this are passed to a call to that.
414 $SIG_CODEREF->(@_) if ref $SIG_CODEREF;
420 () sig_manager(string name)
424 Handles signals of the process manager. Takes as input the name of signal
430 my ($this,$name) = @_;
431 if ($name eq "TERM") {
432 $this->pm_notify("received signal $name");
433 $this->pm_die("safe exit from signal $name");
434 } elsif ($name eq "HUP") {
435 # send a TERM to each of the servers, and pretend like nothing happened..
436 if (my @pids = keys %{$this->{PIDS}}) {
437 $this->pm_notify("sending TERM to PIDs, @pids");
441 $this->pm_notify("ignoring signal $name");
445 =head1 Handler methods
459 # begin to handle signals.
460 # We'll want accept(2) to return -1(EINTR) on caught signal..
461 unless ($this->no_signals()) {
462 $this->_set_signal_handler('TERM', 0);
463 $this->_set_signal_handler('HUP', 0);
464 $SIG_CODEREF = sub { $this->sig_handler(@_) };
467 # change the name of this process as it appears in ps(1) output.
468 $this->pm_change_process_name("perl-fcgi");
470 # Re-srand in case someone called rand before the fork, so that
471 # children get different random numbers.
475 =head2 pm_pre_dispatch
484 sub pm_pre_dispatch {
485 my ($this) = self_or_default(@_);
487 # Now, we want the request to continue unhindered..
488 unless ($this->no_signals()) {
489 $this->_set_signal_handler('TERM', 1);
490 $this->_set_signal_handler('HUP', 1);
494 =head2 pm_post_dispatch
497 () pm_post_dispatch()
503 sub pm_post_dispatch {
504 my ($this) = self_or_default(@_);
505 if ($this->pm_received_signal("TERM")) {
506 $this->pm_exit("safe exit after SIGTERM");
508 if ($this->pm_received_signal("HUP")) {
509 $this->pm_exit("safe exit after SIGHUP");
511 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
512 $this->pm_exit("safe exit: manager has died");
514 # We'll want accept(2) to return -1(EINTR) on caught signal..
515 unless ($this->no_signals()) {
516 $this->_set_signal_handler('TERM', 0);
517 $this->_set_signal_handler('HUP', 0);
531 my ($this,$name) = @_;
532 $this->pm_received_signal($name,1);
535 =head1 Common methods and routines
537 =head2 self_or_default
540 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
544 This is a helper subroutine to acquire or otherwise create a singleton
545 default object if one is not passed in, e.g., a method call.
549 sub self_or_default {
550 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
551 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
552 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
553 $Q or $Q = $FCGI::ProcManager::Default->new;
556 return wantarray ? @_ : $Q;
559 =head2 pm_change_process_name
562 () pm_change_process_name()
568 sub pm_change_process_name {
569 my ($this,$name) = self_or_default(@_);
573 =head2 pm_received_signal
576 () pm_received signal()
582 sub pm_received_signal {
583 my ($this,$sig,$received) = self_or_default(@_);
584 $sig or return $this->{SIG_RECEIVED};
585 $received and $this->{SIG_RECEIVED}->{$sig}++;
586 return $this->{SIG_RECEIVED}->{$sig};
601 my ($this,$key,$value) = self_or_default(@_);
602 defined $value and $this->{$key} = $value;
603 return $this->{$key};
622 sub n_processes { shift->pm_parameter("n_processes", @_); }
623 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
624 sub no_signals { shift->pm_parameter("no_signals", @_); }
625 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
626 sub role { shift->pm_parameter("role", @_); }
627 sub start_delay { shift->pm_parameter("start_delay", @_); }
629 =head1 notification and death
641 my ($this,$msg) = self_or_default(@_);
642 $this->pm_notify($msg);
655 my ($this,$msg) = self_or_default(@_);
657 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
663 () pm_exit(string msg[, int exit_status])
670 my ($this,$msg,$n) = self_or_default(@_);
673 # if we still have children at this point, something went wrong.
675 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
677 $this->pm_warn($msg);
685 () pm_abort(string msg[, int exit_status])
692 my ($this,$msg,$n) = self_or_default(@_);
694 $this->pm_exit($msg,1);
702 No known bugs, but this does not mean no bugs exist.
710 Gareth Kirwan <gbjk@thermeon.com>
718 FCGI-ProcManager - A Perl FCGI Process Manager
719 Copyright (c) 2000, FundsXpress Financial Network, Inc.
721 This library is free software; you can redistribute it and/or
722 modify it under the terms of the GNU Lesser General Public
723 License as published by the Free Software Foundation; either
724 version 2 of the License, or (at your option) any later version.
726 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
727 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
728 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
729 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
730 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
731 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
732 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
733 License for more details.
735 You should have received a copy of the GNU Lesser General Public
736 License along with this library; if not, write to the Free Software
737 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA