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 $this->pm_change_process_name("perl-fcgi");
460 # Re-srand in case someone called rand before the fork, so that
461 # children get different random numbers.
465 =head2 pm_pre_dispatch
474 sub pm_pre_dispatch {
475 my ($this) = self_or_default(@_);
477 # Now, we want the request to continue unhindered..
478 unless ($this->no_signals()) {
479 sigaction(SIGTERM, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
480 sigaction(SIGHUP, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
484 =head2 pm_post_dispatch
487 () pm_post_dispatch()
493 sub pm_post_dispatch {
494 my ($this) = self_or_default(@_);
495 if ($this->pm_received_signal("TERM")) {
496 $this->pm_exit("safe exit after SIGTERM");
498 if ($this->pm_received_signal("HUP")) {
499 $this->pm_exit("safe exit after SIGHUP");
501 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
502 $this->pm_exit("safe exit: manager has died");
504 # We'll want accept(2) to return -1(EINTR) on caught signal..
505 unless ($this->no_signals()) {
506 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
507 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
521 my ($this,$name) = @_;
522 $this->pm_received_signal($name,1);
525 =head1 Common methods and routines
527 =head2 self_or_default
530 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
534 This is a helper subroutine to acquire or otherwise create a singleton
535 default object if one is not passed in, e.g., a method call.
539 sub self_or_default {
540 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
541 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
542 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
543 $Q or $Q = $FCGI::ProcManager::Default->new;
546 return wantarray ? @_ : $Q;
549 =head2 pm_change_process_name
552 () pm_change_process_name()
558 sub pm_change_process_name {
559 my ($this,$name) = self_or_default(@_);
563 =head2 pm_received_signal
566 () pm_received signal()
572 sub pm_received_signal {
573 my ($this,$sig,$received) = self_or_default(@_);
574 $sig or return $this->{SIG_RECEIVED};
575 $received and $this->{SIG_RECEIVED}->{$sig}++;
576 return $this->{SIG_RECEIVED}->{$sig};
591 my ($this,$key,$value) = self_or_default(@_);
592 defined $value and $this->{$key} = $value;
593 return $this->{$key};
612 sub n_processes { shift->pm_parameter("n_processes", @_); }
613 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
614 sub no_signals { shift->pm_parameter("no_signals", @_); }
615 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
616 sub role { shift->pm_parameter("role", @_); }
617 sub start_delay { shift->pm_parameter("start_delay", @_); }
619 =head1 notification and death
631 my ($this,$msg) = self_or_default(@_);
632 $this->pm_notify($msg);
645 my ($this,$msg) = self_or_default(@_);
647 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
653 () pm_exit(string msg[, int exit_status])
660 my ($this,$msg,$n) = self_or_default(@_);
663 # if we still have children at this point, something went wrong.
665 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
667 $this->pm_warn($msg);
675 () pm_abort(string msg[, int exit_status])
682 my ($this,$msg,$n) = self_or_default(@_);
684 $this->pm_exit($msg,1);
692 No known bugs, but this does not mean no bugs exist.
700 Gareth Kirwan <gbjk@thermeon.com>
708 FCGI-ProcManager - A Perl FCGI Process Manager
709 Copyright (c) 2000, FundsXpress Financial Network, Inc.
711 This library is free software; you can redistribute it and/or
712 modify it under the terms of the GNU Lesser General Public
713 License as published by the Free Software Foundation; either
714 version 2 of the License, or (at your option) any later version.
716 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
717 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
718 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
719 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
720 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
721 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
722 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
723 License for more details.
725 You should have received a copy of the GNU Lesser General Public
726 License along with this library; if not, write to the Free Software
727 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA