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);
17 $VERSION = eval $VERSION;
19 @EXPORT_OK = qw(pm_manage pm_die pm_wait
20 pm_write_pid_file pm_remove_pid_file
21 pm_pre_dispatch pm_post_dispatch
22 pm_change_process_name pm_received_signal pm_parameter
23 pm_warn pm_notify pm_abort pm_exit
25 $EXPORT_TAGS{all} = \@EXPORT_OK;
26 $FCGI::ProcManager::Default = 'FCGI::ProcManager';
31 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 L<FCGI>'s description of
96 FAIL_ACCEPT_ON_INTR. Unfortunately, if you want/need to use L<CGI::Fast>, it
97 is currently necessary to run the latest (at the time of writing) development
98 version of FCGI.pm. (>= 0.71_02)
100 Otherwise, if you don't, there is a loop around accept(2) which prevents
101 os_unix.c OS_Accept() from returning the necessary error when FastCGI
102 servers blocking on accept(2) receive the SIGTERM or SIGHUP.
104 FCGI::ProcManager uses POSIX::sigaction() to override the default SA_RESTART
105 policy used for perl's %SIG behavior. Specifically, the process manager
106 never uses SA_RESTART, while the child FastCGI servers turn off SA_RESTART
107 around the accept(2) loop, but reinstate it otherwise.
109 The desired (and implemented) effect is to give a request as big a chance as
110 possible to succeed and to delay their exits until after their request,
111 while allowing the FastCGI servers waiting for new requests to die right
119 (ProcManager) new([hash parameters])
121 Constructs a new process manager. Takes an option has of initial parameter
122 values, and assigns these to the constructed object HASH, overriding any
123 default values. The default parameter values currently are:
128 pm_title => 'perl-fcgi-pm'
133 my ($proto,$init) = @_;
140 pm_title => 'perl-fcgi-pm',
143 bless $this, ref($proto)||$proto;
147 # initialize signal constructions.
148 unless ($this->no_signals() or $^O eq 'Win32') {
149 $this->{sigaction_no_sa_restart} =
150 POSIX::SigAction->new('FCGI::ProcManager::sig_sub');
151 $this->{sigaction_sa_restart} =
152 POSIX::SigAction->new('FCGI::ProcManager::sig_sub',undef,POSIX::SA_RESTART);
158 sub _set_signal_handler {
159 my ($this, $signal, $restart);
161 if ($^O eq 'Win32') {
162 $SIG{$signal} = 'FCGI::ProcManager::sig_sub';
165 sigaction(&{"POSIX::SIG$signal"}(), $restart ? $this->{sigaction_sa_restart} : $this->{sigaction_no_sa_restart})
166 or $this->pm_warn("sigaction: SIG$signal: $!");
170 =head1 Manager methods
175 (int) pm_manage([hash parameters])
179 When this is called by a FastCGI script to manage application servers. It
180 defines a sequence of instructions for a process to enter this method and
181 begin forking off and managing those handlers, and it defines a sequence of
182 instructions to intialize those handlers.
184 If n_processes < 1, the managing section is subverted, and only the
185 handling sequence is executed.
187 Either returns the return value of pm_die() and/or pm_abort() (which will
188 not ever return in general), or returns 1 to the calling script to begin
194 my ($this,%values) = self_or_default(@_);
195 map { $this->pm_parameter($_,$values{$_}) } keys %values;
197 local $SIG{CHLD}; # Replace the SIGCHLD default handler in case
198 # somebody shit on it whilst loading code.
200 # skip to handling now if we won't be managing any processes.
201 $this->n_processes() or return;
203 # call the (possibly overloaded) management initialization hook.
204 $this->role("manager");
205 $this->managing_init();
206 $this->pm_notify("initialized");
208 my $manager_pid = $$;
210 MANAGING_LOOP: while (1) {
212 $this->n_processes() > 0 or
213 return $this->pm_die();
215 # while we have fewer servers than we want.
216 PIDS: while (keys(%{$this->{PIDS}}) < $this->n_processes()) {
218 if (my $pid = fork()) {
219 # the manager remembers the server.
220 $this->{PIDS}->{$pid} = { pid=>$pid };
221 $this->pm_notify("server (pid $pid) started");
223 } elsif (! defined $pid) {
224 return $this->pm_abort("fork: $!");
227 $this->{MANAGER_PID} = $manager_pid;
228 # the server exits the managing loop.
232 for (my $s = $this->start_delay(); $s > 0; $s -= sleep $s) {};
235 # this should block until the next server dies.
242 # forget any children we had been collecting.
243 delete $this->{PIDS};
245 # call the (possibly overloaded) handling init hook
246 $this->role("server");
247 $this->handling_init();
248 $this->pm_notify("initialized");
261 Overrideable method which initializes a process manager. In order to
262 handle signals, manage the PID file, and change the process name properly,
263 any method which overrides this should call SUPER::managing_init().
270 # begin to handle signals.
271 # We do NOT want SA_RESTART in the process manager.
272 # -- we want start the shutdown sequence immediately upon SIGTERM.
273 unless ($this->no_signals()) {
274 $this->_set_signal_handler('TERM', 0);
275 $this->_set_signal_handler('HUP', 0);
276 $SIG_CODEREF = sub { $this->sig_manager(@_) };
279 # change the name of this process as it appears in ps(1) output.
280 $this->pm_change_process_name($this->pm_parameter('pm_title'));
282 $this->pm_write_pid_file();
288 () pm_die(string msg[, int exit_status])
292 This method is called when a process manager receives a notification to
293 shut itself down. pm_die() attempts to shutdown the process manager
294 gently, sending a SIGTERM to each managed process, waiting die_timeout()
295 seconds to reap each process, and then exit gracefully once all children
296 are reaped, or to abort if all children are not reaped.
301 my ($this,$msg,$n) = self_or_default(@_);
303 # stop handling signals.
305 $SIG{HUP} = 'DEFAULT';
306 $SIG{TERM} = 'DEFAULT';
308 $this->pm_remove_pid_file();
310 # prepare to die no matter what.
311 if (defined $this->die_timeout()) {
312 $SIG{ALRM} = sub { $this->pm_abort("wait timeout") };
313 alarm $this->die_timeout();
316 # send a TERM to each of the servers.
317 if (my @pids = keys %{$this->{PIDS}}) {
318 $this->pm_notify("sending TERM to PIDs, @pids");
322 # wait for the servers to die.
323 while (%{$this->{PIDS}}) {
328 $this->pm_exit("dying: ".$msg,$n);
338 This calls wait() which suspends execution until a child has exited.
339 If the process ID returned by wait corresponds to a managed process,
340 pm_notify() is called with the exit status of that process.
341 pm_wait() returns with the return value of wait().
346 my ($this) = self_or_default(@_);
348 # wait for the next server to die.
349 return if ((my $pid = wait()) < 0);
351 # notify when one of our servers have died.
352 delete $this->{PIDS}->{$pid} and
353 $this->pm_notify("server (pid $pid) exited with status $?");
358 =head2 pm_write_pid_file
361 () pm_write_pid_file([string filename])
365 Writes current process ID to optionally specified file. If no filename is
366 specified, it uses the value of the C<pid_fname> parameter.
370 sub pm_write_pid_file {
371 my ($this,$fname) = self_or_default(@_);
372 $fname ||= $this->pid_fname() or return;
374 if (!open $PIDFILE, ">$fname") {
375 $this->pm_warn("open: $fname: $!");
378 print $PIDFILE "$$\n" or die "Could not print PID: $!";
379 close $PIDFILE or die "Could not close PID file: $!";
382 =head2 pm_remove_pid_file
385 () pm_remove_pid_file()
389 Removes optionally specified file. If no filename is specified, it uses
390 the value of the C<pid_fname> parameter.
394 sub pm_remove_pid_file {
395 my ($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 $this->_set_signal_handler('TERM', 0);
464 $this->_set_signal_handler('HUP', 0);
465 $SIG_CODEREF = sub { $this->sig_handler(@_) };
468 # change the name of this process as it appears in ps(1) output.
469 $this->pm_change_process_name("perl-fcgi");
471 # Re-srand in case someone called rand before the fork, so that
472 # children get different random numbers.
476 =head2 pm_pre_dispatch
485 sub pm_pre_dispatch {
486 my ($this) = self_or_default(@_);
488 # Now, we want the request to continue unhindered..
489 unless ($this->no_signals()) {
490 $this->_set_signal_handler('TERM', 1);
491 $this->_set_signal_handler('HUP', 1);
495 =head2 pm_post_dispatch
498 () pm_post_dispatch()
504 sub pm_post_dispatch {
505 my ($this) = self_or_default(@_);
506 if ($this->pm_received_signal("TERM")) {
507 $this->pm_exit("safe exit after SIGTERM");
509 if ($this->pm_received_signal("HUP")) {
510 $this->pm_exit("safe exit after SIGHUP");
512 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
513 $this->pm_exit("safe exit: manager has died");
515 # We'll want accept(2) to return -1(EINTR) on caught signal..
516 unless ($this->no_signals()) {
517 $this->_set_signal_handler('TERM', 0);
518 $this->_set_signal_handler('HUP', 0);
532 my ($this,$name) = @_;
533 $this->pm_received_signal($name,1);
536 =head1 Common methods and routines
538 =head2 self_or_default
541 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
545 This is a helper subroutine to acquire or otherwise create a singleton
546 default object if one is not passed in, e.g., a method call.
550 sub self_or_default {
551 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
552 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
553 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
554 $Q or $Q = $FCGI::ProcManager::Default->new;
557 return wantarray ? @_ : $Q;
560 =head2 pm_change_process_name
563 () pm_change_process_name()
569 sub pm_change_process_name {
570 my ($this,$name) = self_or_default(@_);
574 =head2 pm_received_signal
577 () pm_received signal()
583 sub pm_received_signal {
584 my ($this,$sig,$received) = self_or_default(@_);
585 $sig or return $this->{SIG_RECEIVED};
586 $received and $this->{SIG_RECEIVED}->{$sig}++;
587 return $this->{SIG_RECEIVED}->{$sig};
602 my ($this,$key,$value) = self_or_default(@_);
603 defined $value and $this->{$key} = $value;
604 return $this->{$key};
623 sub n_processes { shift->pm_parameter("n_processes", @_); }
624 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
625 sub no_signals { shift->pm_parameter("no_signals", @_); }
626 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
627 sub role { shift->pm_parameter("role", @_); }
628 sub start_delay { shift->pm_parameter("start_delay", @_); }
630 =head1 notification and death
642 my ($this,$msg) = self_or_default(@_);
643 $this->pm_notify($msg);
656 my ($this,$msg) = self_or_default(@_);
658 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
664 () pm_exit(string msg[, int exit_status])
671 my ($this,$msg,$n) = self_or_default(@_);
674 # if we still have children at this point, something went wrong.
676 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
678 $this->pm_warn($msg);
686 () pm_abort(string msg[, int exit_status])
693 my ($this,$msg,$n) = self_or_default(@_);
695 $this->pm_exit($msg,1);
703 No known bugs, but this does not mean no bugs exist.
711 Gareth Kirwan <gbjk@thermeon.com>
719 FCGI-ProcManager - A Perl FCGI Process Manager
720 Copyright (c) 2000, FundsXpress Financial Network, Inc.
722 This library is free software; you can redistribute it and/or
723 modify it under the terms of the GNU Lesser General Public
724 License as published by the Free Software Foundation; either
725 version 2 of the License, or (at your option) any later version.
727 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
728 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
729 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
730 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
731 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
732 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
733 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
734 License for more details.
736 You should have received a copy of the GNU Lesser General Public
737 License along with this library; if not, write to the Free Software
738 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA