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()) {
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 local $SIG{CHLD}; # Replace the SIGCHLD default handler in case
185 # somebody shit on it whilst loading code.
187 # skip to handling now if we won't be managing any processes.
188 $this->n_processes() or return;
190 # call the (possibly overloaded) management initialization hook.
191 $this->role("manager");
192 $this->managing_init();
193 $this->pm_notify("initialized");
195 my $manager_pid = $$;
197 MANAGING_LOOP: while (1) {
199 $this->n_processes() > 0 or
200 return $this->pm_die();
202 # while we have fewer servers than we want.
203 PIDS: while (keys(%{$this->{PIDS}}) < $this->n_processes()) {
205 if (my $pid = fork()) {
206 # the manager remembers the server.
207 $this->{PIDS}->{$pid} = { pid=>$pid };
208 $this->pm_notify("server (pid $pid) started");
210 } elsif (! defined $pid) {
211 return $this->pm_abort("fork: $!");
214 $this->{MANAGER_PID} = $manager_pid;
215 # the server exits the managing loop.
219 for (my $s = $this->start_delay(); $s > 0; $s -= sleep $s) {};
222 # this should block until the next server dies.
229 # forget any children we had been collecting.
230 delete $this->{PIDS};
232 # call the (possibly overloaded) handling init hook
233 $this->role("server");
234 $this->handling_init();
235 $this->pm_notify("initialized");
248 Overrideable method which initializes a process manager. In order to
249 handle signals, manage the PID file, and change the process name properly,
250 any method which overrides this should call SUPER::managing_init().
257 # begin to handle signals.
258 # We do NOT want SA_RESTART in the process manager.
259 # -- we want start the shutdown sequence immediately upon SIGTERM.
260 unless ($this->no_signals()) {
261 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or
262 $this->pm_warn("sigaction: SIGTERM: $!");
263 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or
264 $this->pm_warn("sigaction: SIGHUP: $!");
265 $SIG_CODEREF = sub { $this->sig_manager(@_) };
268 # change the name of this process as it appears in ps(1) output.
269 $this->pm_change_process_name($this->pm_parameter('pm_title'));
271 $this->pm_write_pid_file();
277 () pm_die(string msg[, int exit_status])
281 This method is called when a process manager receives a notification to
282 shut itself down. pm_die() attempts to shutdown the process manager
283 gently, sending a SIGTERM to each managed process, waiting die_timeout()
284 seconds to reap each process, and then exit gracefully once all children
285 are reaped, or to abort if all children are not reaped.
290 my ($this,$msg,$n) = self_or_default(@_);
292 # stop handling signals.
294 $SIG{HUP} = 'DEFAULT';
295 $SIG{TERM} = 'DEFAULT';
297 $this->pm_remove_pid_file();
299 # prepare to die no matter what.
300 if (defined $this->die_timeout()) {
301 $SIG{ALRM} = sub { $this->pm_abort("wait timeout") };
302 alarm $this->die_timeout();
305 # send a TERM to each of the servers.
306 if (my @pids = keys %{$this->{PIDS}}) {
307 $this->pm_notify("sending TERM to PIDs, @pids");
311 # wait for the servers to die.
312 while (%{$this->{PIDS}}) {
317 $this->pm_exit("dying: ".$msg,$n);
327 This calls wait() which suspends execution until a child has exited.
328 If the process ID returned by wait corresponds to a managed process,
329 pm_notify() is called with the exit status of that process.
330 pm_wait() returns with the return value of wait().
335 my ($this) = self_or_default(@_);
337 # wait for the next server to die.
338 return if ((my $pid = wait()) < 0);
340 # notify when one of our servers have died.
341 delete $this->{PIDS}->{$pid} and
342 $this->pm_notify("server (pid $pid) exited with status $?");
347 =head2 pm_write_pid_file
350 () pm_write_pid_file([string filename])
354 Writes current process ID to optionally specified file. If no filename is
355 specified, it uses the value of the C<pid_fname> parameter.
359 sub pm_write_pid_file {
360 my ($this,$fname) = self_or_default(@_);
361 $fname ||= $this->pid_fname() or return;
363 if (!open $PIDFILE, ">$fname") {
364 $this->pm_warn("open: $fname: $!");
367 print $PIDFILE "$$\n" or die "Could not print PID: $!";
368 close $PIDFILE or die "Could not close PID file: $!";
371 =head2 pm_remove_pid_file
374 () pm_remove_pid_file()
378 Removes optionally specified file. If no filename is specified, it uses
379 the value of the C<pid_fname> parameter.
383 sub pm_remove_pid_file {
384 my ($this,$fname) = self_or_default(@_);
385 $fname ||= $this->pid_fname() or return;
386 my $ret = unlink($fname) or $this->pm_warn("unlink: $fname: $!");
393 () sig_sub(string name)
397 The name of this method is passed to POSIX::sigaction(), and handles signals
398 for the process manager. If $SIG_CODEREF is set, then the input arguments
399 to this are passed to a call to that.
404 $SIG_CODEREF->(@_) if ref $SIG_CODEREF;
410 () sig_manager(string name)
414 Handles signals of the process manager. Takes as input the name of signal
420 my ($this,$name) = @_;
421 if ($name eq "TERM") {
422 $this->pm_notify("received signal $name");
423 $this->pm_die("safe exit from signal $name");
424 } elsif ($name eq "HUP") {
425 # send a TERM to each of the servers, and pretend like nothing happened..
426 if (my @pids = keys %{$this->{PIDS}}) {
427 $this->pm_notify("sending TERM to PIDs, @pids");
431 $this->pm_notify("ignoring signal $name");
435 =head1 Handler methods
449 # begin to handle signals.
450 # We'll want accept(2) to return -1(EINTR) on caught signal..
451 unless ($this->no_signals()) {
452 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
453 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
454 $SIG_CODEREF = sub { $this->sig_handler(@_) };
457 # change the name of this process as it appears in ps(1) output.
458 $this->pm_change_process_name("perl-fcgi");
461 =head2 pm_pre_dispatch
470 sub pm_pre_dispatch {
471 my ($this) = self_or_default(@_);
473 # Now, we want the request to continue unhindered..
474 unless ($this->no_signals()) {
475 sigaction(SIGTERM, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
476 sigaction(SIGHUP, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
480 =head2 pm_post_dispatch
483 () pm_post_dispatch()
489 sub pm_post_dispatch {
490 my ($this) = self_or_default(@_);
491 if ($this->pm_received_signal("TERM")) {
492 $this->pm_exit("safe exit after SIGTERM");
494 if ($this->pm_received_signal("HUP")) {
495 $this->pm_exit("safe exit after SIGHUP");
497 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
498 $this->pm_exit("safe exit: manager has died");
500 # We'll want accept(2) to return -1(EINTR) on caught signal..
501 unless ($this->no_signals()) {
502 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
503 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
517 my ($this,$name) = @_;
518 $this->pm_received_signal($name,1);
521 =head1 Common methods and routines
523 =head2 self_or_default
526 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
530 This is a helper subroutine to acquire or otherwise create a singleton
531 default object if one is not passed in, e.g., a method call.
535 sub self_or_default {
536 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
537 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
538 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
539 $Q or $Q = $FCGI::ProcManager::Default->new;
542 return wantarray ? @_ : $Q;
545 =head2 pm_change_process_name
548 () pm_change_process_name()
554 sub pm_change_process_name {
555 my ($this,$name) = self_or_default(@_);
559 =head2 pm_received_signal
562 () pm_received signal()
568 sub pm_received_signal {
569 my ($this,$sig,$received) = self_or_default(@_);
570 $sig or return $this->{SIG_RECEIVED};
571 $received and $this->{SIG_RECEIVED}->{$sig}++;
572 return $this->{SIG_RECEIVED}->{$sig};
587 my ($this,$key,$value) = self_or_default(@_);
588 defined $value and $this->{$key} = $value;
589 return $this->{$key};
608 sub n_processes { shift->pm_parameter("n_processes", @_); }
609 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
610 sub no_signals { shift->pm_parameter("no_signals", @_); }
611 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
612 sub role { shift->pm_parameter("role", @_); }
613 sub start_delay { shift->pm_parameter("start_delay", @_); }
615 =head1 notification and death
627 my ($this,$msg) = self_or_default(@_);
628 $this->pm_notify($msg);
641 my ($this,$msg) = self_or_default(@_);
643 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
649 () pm_exit(string msg[, int exit_status])
656 my ($this,$msg,$n) = self_or_default(@_);
659 # if we still have children at this point, something went wrong.
661 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
663 $this->pm_warn($msg);
671 () pm_abort(string msg[, int exit_status])
678 my ($this,$msg,$n) = self_or_default(@_);
680 $this->pm_exit($msg,1);
688 No known bugs, but this does not mean no bugs exist.
696 Gareth Kirwan <gbjk@thermeon.com>
704 FCGI-ProcManager - A Perl FCGI Process Manager
705 Copyright (c) 2000, FundsXpress Financial Network, Inc.
707 This library is free software; you can redistribute it and/or
708 modify it under the terms of the GNU Lesser General Public
709 License as published by the Free Software Foundation; either
710 version 2 of the License, or (at your option) any later version.
712 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
713 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
714 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
715 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
716 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
717 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
718 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
719 License for more details.
721 You should have received a copy of the GNU Lesser General Public
722 License along with this library; if not, write to the Free Software
723 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA