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 re-enstate 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()) {
148 $this->{sigaction_no_sa_restart} =
149 POSIX::SigAction->new('FCGI::ProcManager::sig_sub');
150 $this->{sigaction_sa_restart} =
151 POSIX::SigAction->new('FCGI::ProcManager::sig_sub',undef,POSIX::SA_RESTART);
157 =head1 Manager methods
162 (int) pm_manage([hash parameters])
166 When this is called by a FastCGI script to manage application servers. It
167 defines a sequence of instructions for a process to enter this method and
168 begin forking off and managing those handlers, and it defines a sequence of
169 instructions to intialize those handlers.
171 If n_processes < 1, the managing section is subverted, and only the
172 handling sequence is executed.
174 Either returns the return value of pm_die() and/or pm_abort() (which will
175 not ever return in general), or returns 1 to the calling script to begin
181 my ($this,%values) = self_or_default(@_);
182 map { $this->pm_parameter($_,$values{$_}) } keys %values;
184 # skip to handling now if we won't be managing any processes.
185 $this->n_processes() or return;
187 # call the (possibly overloaded) management initialization hook.
188 $this->role("manager");
189 $this->managing_init();
190 $this->pm_notify("initialized");
192 my $manager_pid = $$;
194 MANAGING_LOOP: while (1) {
196 $this->n_processes() > 0 or
197 return $this->pm_die();
199 # while we have fewer servers than we want.
200 PIDS: while (keys(%{$this->{PIDS}}) < $this->n_processes()) {
202 if (my $pid = fork()) {
203 # the manager remembers the server.
204 $this->{PIDS}->{$pid} = { pid=>$pid };
205 $this->pm_notify("server (pid $pid) started");
207 } elsif (! defined $pid) {
208 return $this->pm_abort("fork: $!");
211 $this->{MANAGER_PID} = $manager_pid;
212 # the server exits the managing loop.
216 for (my $s = $this->start_delay(); $s; $s = sleep $s) {};
219 # this should block until the next server dies.
226 # forget any children we had been collecting.
227 delete $this->{PIDS};
229 # call the (possibly overloaded) handling init hook
230 $this->role("server");
231 $this->handling_init();
232 $this->pm_notify("initialized");
245 Overrideable method which initializes a process manager. In order to
246 handle signals, manage the PID file, and change the process name properly,
247 any method which overrides this should call SUPER::managing_init().
254 # begin to handle signals.
255 # We do NOT want SA_RESTART in the process manager.
256 # -- we want start the shutdown sequence immediately upon SIGTERM.
257 unless ($this->no_signals()) {
258 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or
259 $this->pm_warn("sigaction: SIGTERM: $!");
260 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or
261 $this->pm_warn("sigaction: SIGHUP: $!");
262 $SIG_CODEREF = sub { $this->sig_manager(@_) };
265 # change the name of this process as it appears in ps(1) output.
266 $this->pm_change_process_name($this->pm_parameter('pm_title'));
268 $this->pm_write_pid_file();
274 () pm_die(string msg[, int exit_status])
278 This method is called when a process manager receives a notification to
279 shut itself down. pm_die() attempts to shutdown the process manager
280 gently, sending a SIGTERM to each managed process, waiting die_timeout()
281 seconds to reap each process, and then exit gracefully once all children
282 are reaped, or to abort if all children are not reaped.
287 my ($this,$msg,$n) = self_or_default(@_);
289 # stop handling signals.
291 $SIG{HUP} = 'DEFAULT';
292 $SIG{TERM} = 'DEFAULT';
294 $this->pm_remove_pid_file();
296 # prepare to die no matter what.
297 if (defined $this->die_timeout()) {
298 $SIG{ALRM} = sub { $this->pm_abort("wait timeout") };
299 alarm $this->die_timeout();
302 # send a TERM to each of the servers.
303 if (my @pids = keys %{$this->{PIDS}}) {
304 $this->pm_notify("sending TERM to PIDs, @pids");
308 # wait for the servers to die.
309 while (%{$this->{PIDS}}) {
314 $this->pm_exit("dying: ".$msg,$n);
324 This calls wait() which suspends execution until a child has exited.
325 If the process ID returned by wait corresponds to a managed process,
326 pm_notify() is called with the exit status of that process.
327 pm_wait() returns with the return value of wait().
332 my ($this) = self_or_default(@_);
334 # wait for the next server to die.
335 next if (my $pid = wait()) < 0;
337 # notify when one of our servers have died.
338 delete $this->{PIDS}->{$pid} and
339 $this->pm_notify("server (pid $pid) exited with status $?");
344 =head2 pm_write_pid_file
347 () pm_write_pid_file([string filename])
351 Writes current process ID to optionally specified file. If no filename is
352 specified, it uses the value of the C<pid_fname> parameter.
356 sub pm_write_pid_file {
357 my ($this,$fname) = self_or_default(@_);
358 $fname ||= $this->pid_fname() or return;
359 if (!open PIDFILE, ">$fname") {
360 $this->pm_warn("open: $fname: $!");
363 print PIDFILE "$$\n";
367 =head2 pm_remove_pid_file
370 () pm_remove_pid_file()
374 Removes optionally specified file. If no filename is specified, it uses
375 the value of the C<pid_fname> parameter.
379 sub pm_remove_pid_file {
380 my ($this,$fname) = self_or_default(@_);
381 $fname ||= $this->pid_fname() or return;
382 my $ret = unlink($fname) or $this->pm_warn("unlink: $fname: $!");
389 () sig_sub(string name)
393 The name of this method is passed to POSIX::sigaction(), and handles signals
394 for the process manager. If $SIG_CODEREF is set, then the input arguments
395 to this are passed to a call to that.
400 $SIG_CODEREF->(@_) if ref $SIG_CODEREF;
406 () sig_manager(string name)
410 Handles signals of the process manager. Takes as input the name of signal
416 my ($this,$name) = @_;
417 if ($name eq "TERM") {
418 $this->pm_notify("received signal $name");
419 $this->pm_die("safe exit from signal $name");
420 } elsif ($name eq "HUP") {
421 # send a TERM to each of the servers, and pretend like nothing happened..
422 if (my @pids = keys %{$this->{PIDS}}) {
423 $this->pm_notify("sending TERM to PIDs, @pids");
427 $this->pm_notify("ignoring signal $name");
431 =head1 Handler methods
445 # begin to handle signals.
446 # We'll want accept(2) to return -1(EINTR) on caught signal..
447 unless ($this->no_signals()) {
448 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
449 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
450 $SIG_CODEREF = sub { $this->sig_handler(@_) };
453 # change the name of this process as it appears in ps(1) output.
454 $this->pm_change_process_name("perl-fcgi");
457 =head2 pm_pre_dispatch
466 sub pm_pre_dispatch {
467 my ($this) = self_or_default(@_);
469 # Now, we want the request to continue unhindered..
470 unless ($this->no_signals()) {
471 sigaction(SIGTERM, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
472 sigaction(SIGHUP, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
476 =head2 pm_post_dispatch
479 () pm_post_dispatch()
485 sub pm_post_dispatch {
486 my ($this) = self_or_default(@_);
487 if ($this->pm_received_signal("TERM")) {
488 $this->pm_exit("safe exit after SIGTERM");
490 if ($this->pm_received_signal("HUP")) {
491 $this->pm_exit("safe exit after SIGHUP");
493 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
494 $this->pm_exit("safe exit: manager has died");
496 # We'll want accept(2) to return -1(EINTR) on caught signal..
497 unless ($this->no_signals()) {
498 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
499 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
513 my ($this,$name) = @_;
514 $this->pm_received_signal($name,1);
517 =head1 Common methods and routines
519 =head2 self_or_default
522 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
526 This is a helper subroutine to acquire or otherwise create a singleton
527 default object if one is not passed in, e.g., a method call.
531 sub self_or_default {
532 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
533 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
534 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
535 $Q or $Q = $FCGI::ProcManager::Default->new;
538 return wantarray ? @_ : $Q;
541 =head2 pm_change_process_name
544 () pm_change_process_name()
550 sub pm_change_process_name {
551 my ($this,$name) = self_or_default(@_);
555 =head2 pm_received_signal
558 () pm_received signal()
564 sub pm_received_signal {
565 my ($this,$sig,$received) = self_or_default(@_);
566 $sig or return $this->{SIG_RECEIVED};
567 $received and $this->{SIG_RECEIVED}->{$sig}++;
568 return $this->{SIG_RECEIVED}->{$sig};
583 my ($this,$key,$value) = self_or_default(@_);
584 defined $value and $this->{$key} = $value;
585 return $this->{$key};
604 sub n_processes { shift->pm_parameter("n_processes", @_); }
605 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
606 sub no_signals { shift->pm_parameter("no_signals", @_); }
607 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
608 sub role { shift->pm_parameter("role", @_); }
609 sub start_delay { shift->pm_parameter("start_delay", @_); }
611 =head1 notification and death
623 my ($this,$msg) = self_or_default(@_);
624 $this->pm_notify($msg);
637 my ($this,$msg) = self_or_default(@_);
639 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
645 () pm_exit(string msg[, int exit_status])
652 my ($this,$msg,$n) = self_or_default(@_);
655 # if we still have children at this point, something went wrong.
657 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
659 $this->pm_warn($msg);
667 () pm_abort(string msg[, int exit_status])
674 my ($this,$msg,$n) = self_or_default(@_);
676 $this->pm_exit($msg,1);
684 No known bugs, but this does not mean no bugs exist.
692 Gareth Kirwan <gbjk@thermeon.com>
700 FCGI-ProcManager - A Perl FCGI Process Manager
701 Copyright (c) 2000, FundsXpress Financial Network, Inc.
703 This library is free software; you can redistribute it and/or
704 modify it under the terms of the GNU Lesser General Public
705 License as published by the Free Software Foundation; either
706 version 2 of the License, or (at your option) any later version.
708 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
709 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
710 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
711 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
712 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
713 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
714 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
715 License for more details.
717 You should have received a copy of the GNU Lesser General Public
718 License along with this library; if not, write to the Free Software
719 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA