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.
35 # In Object-oriented style.
37 use FCGI::ProcManager;
38 my $proc_manager = FCGI::ProcManager->new({
41 $proc_manager->pm_manage();
42 while (my $cgi = CGI::Fast->new()) {
43 $proc_manager->pm_pre_dispatch();
44 # ... handle the request here ...
45 $proc_manager->pm_post_dispatch();
48 # This style is also supported:
50 use FCGI::ProcManager qw(pm_manage pm_pre_dispatch
52 pm_manage( n_processes => 10 );
53 while (my $cgi = CGI::Fast->new()) {
61 FCGI::ProcManager is used to serve as a FastCGI process manager. By
62 re-implementing it in perl, developers can more finely tune performance in
63 their web applications, and can take advantage of copy-on-write semantics
64 prevalent in UNIX kernel process management. The process manager should
65 be invoked before the caller''s request loop
67 The primary routine, C<pm_manage>, enters a loop in which it maintains a
68 number of FastCGI servers (via fork(2)), and which reaps those servers
69 when they die (via wait(2)).
71 C<pm_manage> provides too hooks:
73 C<managing_init> - called just before the manager enters the manager loop.
74 C<handling_init> - called just before a server is returns from C<pm_manage>
76 It is necessary for the caller, when implementing its request loop, to
77 insert a call to C<pm_pre_dispatch> at the top of the loop, and then
78 7C<pm_post_dispatch> at the end of the loop.
80 =head2 Signal Handling
82 FCGI::ProcManager attempts to do the right thing for proper shutdowns now.
84 When it receives a SIGHUP, it sends a SIGTERM to each of its children, and
85 then resumes its normal operations.
87 When it receives a SIGTERM, it sends a SIGTERM to each of its children, sets
88 an alarm(3) "die timeout" handler, and waits for each of its children to
89 die. If all children die before this timeout, process manager exits with
90 return status 0. If all children do not die by the time the "die timeout"
91 occurs, the process manager sends a SIGKILL to each of the remaining
92 children, and exists with return status 1.
94 In order to get FastCGI servers to exit upon receiving a signal, it is
95 necessary to use its FAIL_ACCEPT_ON_INTR. See FCGI.pm's description of
96 FAIL_ACCEPT_ON_INTR. Unfortunately, if you want/need to use CGI::Fast, it
97 appears currently necessary to modify your installation of FCGI.pm, with
98 something like the following:
101 --- FCGI.pm 2001/03/09 01:44:00 1.1.1.3
102 +++ FCGI.pm 2001/03/09 01:47:32 1.2
104 *FAIL_ACCEPT_ON_INTR = sub() { 1 };
106 sub Request(;***$$$) {
107 - my @defaults = (\*STDIN, \*STDOUT, \*STDERR, \%ENV, 0, 0);
108 + my @defaults = (\*STDIN, \*STDOUT, \*STDERR, \%ENV, 0, FAIL_ACCEPT_ON_INTR());
109 splice @defaults,0,@_,@_;
114 Otherwise, if you don't, there is a loop around accept(2) which prevents
115 os_unix.c OS_Accept() from returning the necessary error when FastCGI
116 servers blocking on accept(2) receive the SIGTERM or SIGHUP.
118 FCGI::ProcManager uses POSIX::sigaction() to override the default SA_RESTART
119 policy used for perl's %SIG behavior. Specifically, the process manager
120 never uses SA_RESTART, while the child FastCGI servers turn off SA_RESTART
121 around the accept(2) loop, but re-enstate it otherwise.
123 The desired (and implemented) effect is to give a request as big a chance as
124 possible to succeed and to delay their exits until after their request,
125 while allowing the FastCGI servers waiting for new requests to die right
133 (ProcManager) new([hash parameters])
135 Constructs a new process manager. Takes an option has of initial parameter
136 values, and assigns these to the constructed object HASH, overriding any
137 default values. The default parameter values currently are:
142 pm_title => 'perl-fcgi-pm'
147 my ($proto,$init) = @_;
154 pm_title => 'perl-fcgi-pm',
157 bless $this, ref($proto)||$proto;
161 # initialize signal constructions.
162 unless ($this->no_signals()) {
163 $this->{sigaction_no_sa_restart} =
164 POSIX::SigAction->new('FCGI::ProcManager::sig_sub');
165 $this->{sigaction_sa_restart} =
166 POSIX::SigAction->new('FCGI::ProcManager::sig_sub',undef,POSIX::SA_RESTART);
172 =head1 Manager methods
177 (int) pm_manage([hash parameters])
181 When this is called by a FastCGI script to manage application servers. It
182 defines a sequence of instructions for a process to enter this method and
183 begin forking off and managing those handlers, and it defines a sequence of
184 instructions to intialize those handlers.
186 If n_processes < 1, the managing section is subverted, and only the
187 handling sequence is executed.
189 Either returns the return value of pm_die() and/or pm_abort() (which will
190 not ever return in general), or returns 1 to the calling script to begin
196 my ($this,%values) = self_or_default(@_);
197 map { $this->pm_parameter($_,$values{$_}) } keys %values;
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; $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 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or
274 $this->pm_warn("sigaction: SIGTERM: $!");
275 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or
276 $this->pm_warn("sigaction: SIGHUP: $!");
277 $SIG_CODEREF = sub { $this->sig_manager(@_) };
280 # change the name of this process as it appears in ps(1) output.
281 $this->pm_change_process_name($this->pm_parameter('pm_title'));
283 $this->pm_write_pid_file();
289 () pm_die(string msg[, int exit_status])
293 This method is called when a process manager receives a notification to
294 shut itself down. pm_die() attempts to shutdown the process manager
295 gently, sending a SIGTERM to each managed process, waiting die_timeout()
296 seconds to reap each process, and then exit gracefully once all children
297 are reaped, or to abort if all children are not reaped.
302 my ($this,$msg,$n) = self_or_default(@_);
304 # stop handling signals.
306 $SIG{HUP} = 'DEFAULT';
307 $SIG{TERM} = 'DEFAULT';
309 $this->pm_remove_pid_file();
311 # prepare to die no matter what.
312 if (defined $this->die_timeout()) {
313 $SIG{ALRM} = sub { $this->pm_abort("wait timeout") };
314 alarm $this->die_timeout();
317 # send a TERM to each of the servers.
318 if (my @pids = keys %{$this->{PIDS}}) {
319 $this->pm_notify("sending TERM to PIDs, @pids");
323 # wait for the servers to die.
324 while (%{$this->{PIDS}}) {
329 $this->pm_exit("dying: ".$msg,$n);
339 This calls wait() which suspends execution until a child has exited.
340 If the process ID returned by wait corresponds to a managed process,
341 pm_notify() is called with the exit status of that process.
342 pm_wait() returns with the return value of wait().
347 my ($this) = self_or_default(@_);
349 # wait for the next server to die.
350 next if (my $pid = wait()) < 0;
352 # notify when one of our servers have died.
353 delete $this->{PIDS}->{$pid} and
354 $this->pm_notify("server (pid $pid) exited with status $?");
359 =head2 pm_write_pid_file
362 () pm_write_pid_file([string filename])
366 Writes current process ID to optionally specified file. If no filename is
367 specified, it uses the value of the C<pid_fname> parameter.
371 sub pm_write_pid_file {
372 my ($this,$fname) = self_or_default(@_);
373 $fname ||= $this->pid_fname() or return;
374 if (!open PIDFILE, ">$fname") {
375 $this->pm_warn("open: $fname: $!");
378 print PIDFILE "$$\n";
382 =head2 pm_remove_pid_file
385 () pm_remove_pid_file()
389 Removes optionally specified file. If no filename is specified, it uses
390 the value of the C<pid_fname> parameter.
394 sub pm_remove_pid_file {
395 my ($this,$fname) = self_or_default(@_);
396 $fname ||= $this->pid_fname() or return;
397 my $ret = unlink($fname) or $this->pm_warn("unlink: $fname: $!");
404 () sig_sub(string name)
408 The name of this method is passed to POSIX::sigaction(), and handles signals
409 for the process manager. If $SIG_CODEREF is set, then the input arguments
410 to this are passed to a call to that.
415 $SIG_CODEREF->(@_) if ref $SIG_CODEREF;
421 () sig_manager(string name)
425 Handles signals of the process manager. Takes as input the name of signal
431 my ($this,$name) = @_;
432 if ($name eq "TERM") {
433 $this->pm_notify("received signal $name");
434 $this->pm_die("safe exit from signal $name");
435 } elsif ($name eq "HUP") {
436 # send a TERM to each of the servers, and pretend like nothing happened..
437 if (my @pids = keys %{$this->{PIDS}}) {
438 $this->pm_notify("sending TERM to PIDs, @pids");
442 $this->pm_notify("ignoring signal $name");
446 =head1 Handler methods
460 # begin to handle signals.
461 # We'll want accept(2) to return -1(EINTR) on caught signal..
462 unless ($this->no_signals()) {
463 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
464 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
465 $SIG_CODEREF = sub { $this->sig_handler(@_) };
468 # change the name of this process as it appears in ps(1) output.
469 $this->pm_change_process_name("perl-fcgi");
472 =head2 pm_pre_dispatch
481 sub pm_pre_dispatch {
482 my ($this) = self_or_default(@_);
484 # Now, we want the request to continue unhindered..
485 unless ($this->no_signals()) {
486 sigaction(SIGTERM, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
487 sigaction(SIGHUP, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
491 =head2 pm_post_dispatch
494 () pm_post_dispatch()
500 sub pm_post_dispatch {
501 my ($this) = self_or_default(@_);
502 if ($this->pm_received_signal("TERM")) {
503 $this->pm_exit("safe exit after SIGTERM");
505 if ($this->pm_received_signal("HUP")) {
506 $this->pm_exit("safe exit after SIGHUP");
508 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
509 $this->pm_exit("safe exit: manager has died");
511 # We'll want accept(2) to return -1(EINTR) on caught signal..
512 unless ($this->no_signals()) {
513 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
514 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
528 my ($this,$name) = @_;
529 $this->pm_received_signal($name,1);
532 =head1 Common methods and routines
534 =head2 self_or_default
537 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
541 This is a helper subroutine to acquire or otherwise create a singleton
542 default object if one is not passed in, e.g., a method call.
546 sub self_or_default {
547 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
548 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
549 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
550 $Q or $Q = $FCGI::ProcManager::Default->new;
553 return wantarray ? @_ : $Q;
556 =head2 pm_change_process_name
559 () pm_change_process_name()
565 sub pm_change_process_name {
566 my ($this,$name) = self_or_default(@_);
570 =head2 pm_received_signal
573 () pm_received signal()
579 sub pm_received_signal {
580 my ($this,$sig,$received) = self_or_default(@_);
581 $sig or return $this->{SIG_RECEIVED};
582 $received and $this->{SIG_RECEIVED}->{$sig}++;
583 return $this->{SIG_RECEIVED}->{$sig};
598 my ($this,$key,$value) = self_or_default(@_);
599 defined $value and $this->{$key} = $value;
600 return $this->{$key};
619 sub n_processes { shift->pm_parameter("n_processes", @_); }
620 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
621 sub no_signals { shift->pm_parameter("no_signals", @_); }
622 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
623 sub role { shift->pm_parameter("role", @_); }
624 sub start_delay { shift->pm_parameter("start_delay", @_); }
626 =head1 notification and death
638 my ($this,$msg) = self_or_default(@_);
639 $this->pm_notify($msg);
652 my ($this,$msg) = self_or_default(@_);
654 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
660 () pm_exit(string msg[, int exit_status])
667 my ($this,$msg,$n) = self_or_default(@_);
670 # if we still have children at this point, something went wrong.
672 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
674 $this->pm_warn($msg);
682 () pm_abort(string msg[, int exit_status])
689 my ($this,$msg,$n) = self_or_default(@_);
691 $this->pm_exit($msg,1);
699 No known bugs, but this does not mean no bugs exist.
707 Gareth Kirwan <gbjk@thermeon.com>
715 FCGI-ProcManager - A Perl FCGI Process Manager
716 Copyright (c) 2000, FundsXpress Financial Network, Inc.
718 This library is free software; you can redistribute it and/or
719 modify it under the terms of the GNU Lesser General Public
720 License as published by the Free Software Foundation; either
721 version 2 of the License, or (at your option) any later version.
723 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
724 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
725 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
726 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
727 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
728 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
729 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
730 License for more details.
732 You should have received a copy of the GNU Lesser General Public
733 License along with this library; if not, write to the Free Software
734 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA