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:
146 my ($proto,$init) = @_;
155 bless $this, ref($proto)||$proto;
159 # initialize signal constructions.
160 unless ($this->no_signals()) {
161 $this->{sigaction_no_sa_restart} =
162 POSIX::SigAction->new('FCGI::ProcManager::sig_sub');
163 $this->{sigaction_sa_restart} =
164 POSIX::SigAction->new('FCGI::ProcManager::sig_sub',undef,POSIX::SA_RESTART);
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 # skip to handling now if we won't be managing any processes.
198 $this->n_processes() or return;
200 # call the (possibly overloaded) management initialization hook.
201 $this->role("manager");
202 $this->managing_init();
203 $this->pm_notify("initialized");
205 my $manager_pid = $$;
207 MANAGING_LOOP: while (1) {
209 $this->n_processes() > 0 or
210 return $this->pm_die();
212 # while we have fewer servers than we want.
213 PIDS: while (keys(%{$this->{PIDS}}) < $this->n_processes()) {
215 if (my $pid = fork()) {
216 # the manager remembers the server.
217 $this->{PIDS}->{$pid} = { pid=>$pid };
218 $this->pm_notify("server (pid $pid) started");
220 } elsif (! defined $pid) {
221 return $this->pm_abort("fork: $!");
224 $this->{MANAGER_PID} = $manager_pid;
225 # the server exits the managing loop.
229 for (my $s = $this->start_delay(); $s; $s = sleep $s) {};
232 # this should block until the next server dies.
239 # forget any children we had been collecting.
240 delete $this->{PIDS};
242 # call the (possibly overloaded) handling init hook
243 $this->role("server");
244 $this->handling_init();
245 $this->pm_notify("initialized");
258 Overrideable method which initializes a process manager. In order to
259 handle signals, manage the PID file, and change the process name properly,
260 any method which overrides this should call SUPER::managing_init().
267 # begin to handle signals.
268 # We do NOT want SA_RESTART in the process manager.
269 # -- we want start the shutdown sequence immediately upon SIGTERM.
270 unless ($this->no_signals()) {
271 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or
272 $this->pm_warn("sigaction: SIGTERM: $!");
273 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or
274 $this->pm_warn("sigaction: SIGHUP: $!");
275 $SIG_CODEREF = sub { $this->sig_manager(@_) };
278 # change the name of this process as it appears in ps(1) output.
279 $this->pm_change_process_name("perl-fcgi-pm");
281 $this->pm_write_pid_file();
287 () pm_die(string msg[, int exit_status])
291 This method is called when a process manager receives a notification to
292 shut itself down. pm_die() attempts to shutdown the process manager
293 gently, sending a SIGTERM to each managed process, waiting die_timeout()
294 seconds to reap each process, and then exit gracefully once all children
295 are reaped, or to abort if all children are not reaped.
300 my ($this,$msg,$n) = self_or_default(@_);
302 # stop handling signals.
304 $SIG{HUP} = 'DEFAULT';
305 $SIG{TERM} = 'DEFAULT';
307 $this->pm_remove_pid_file();
309 # prepare to die no matter what.
310 if (defined $this->die_timeout()) {
311 $SIG{ALRM} = sub { $this->pm_abort("wait timeout") };
312 alarm $this->die_timeout();
315 # send a TERM to each of the servers.
316 if (my @pids = keys %{$this->{PIDS}}) {
317 $this->pm_notify("sending TERM to PIDs, @pids");
321 # wait for the servers to die.
322 while (%{$this->{PIDS}}) {
327 $this->pm_exit("dying: ".$msg,$n);
337 This calls wait() which suspends execution until a child has exited.
338 If the process ID returned by wait corresponds to a managed process,
339 pm_notify() is called with the exit status of that process.
340 pm_wait() returns with the return value of wait().
345 my ($this) = self_or_default(@_);
347 # wait for the next server to die.
348 next if (my $pid = wait()) < 0;
350 # notify when one of our servers have died.
351 delete $this->{PIDS}->{$pid} and
352 $this->pm_notify("server (pid $pid) exited with status $?");
357 =head2 pm_write_pid_file
360 () pm_write_pid_file([string filename])
364 Writes current process ID to optionally specified file. If no filename is
365 specified, it uses the value of the C<pid_fname> parameter.
369 sub pm_write_pid_file {
370 my ($this,$fname) = self_or_default(@_);
371 $fname ||= $this->pid_fname() or return;
372 if (!open PIDFILE, ">$fname") {
373 $this->pm_warn("open: $fname: $!");
376 print PIDFILE "$$\n";
380 =head2 pm_remove_pid_file
383 () pm_remove_pid_file()
387 Removes optionally specified file. If no filename is specified, it uses
388 the value of the C<pid_fname> parameter.
392 sub pm_remove_pid_file {
393 my ($this,$fname) = self_or_default(@_);
394 $fname ||= $this->pid_fname() or return;
395 my $ret = unlink($fname) or $this->pm_warn("unlink: $fname: $!");
402 () sig_sub(string name)
406 The name of this method is passed to POSIX::sigaction(), and handles signals
407 for the process manager. If $SIG_CODEREF is set, then the input arguments
408 to this are passed to a call to that.
413 $SIG_CODEREF->(@_) if ref $SIG_CODEREF;
419 () sig_manager(string name)
423 Handles signals of the process manager. Takes as input the name of signal
429 my ($this,$name) = @_;
430 if ($name eq "TERM") {
431 $this->pm_notify("received signal $name");
432 $this->pm_die("safe exit from signal $name");
433 } elsif ($name eq "HUP") {
434 # send a TERM to each of the servers, and pretend like nothing happened..
435 if (my @pids = keys %{$this->{PIDS}}) {
436 $this->pm_notify("sending TERM to PIDs, @pids");
440 $this->pm_notify("ignoring signal $name");
444 =head1 Handler methods
458 # begin to handle signals.
459 # We'll want accept(2) to return -1(EINTR) on caught signal..
460 unless ($this->no_signals()) {
461 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
462 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
463 $SIG_CODEREF = sub { $this->sig_handler(@_) };
466 # change the name of this process as it appears in ps(1) output.
467 $this->pm_change_process_name("perl-fcgi");
470 =head2 pm_pre_dispatch
479 sub pm_pre_dispatch {
480 my ($this) = self_or_default(@_);
482 # Now, we want the request to continue unhindered..
483 unless ($this->no_signals()) {
484 sigaction(SIGTERM, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
485 sigaction(SIGHUP, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
489 =head2 pm_post_dispatch
492 () pm_post_dispatch()
498 sub pm_post_dispatch {
499 my ($this) = self_or_default(@_);
500 if ($this->pm_received_signal("TERM")) {
501 $this->pm_exit("safe exit after SIGTERM");
503 if ($this->pm_received_signal("HUP")) {
504 $this->pm_exit("safe exit after SIGHUP");
506 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
507 $this->pm_exit("safe exit: manager has died");
509 # We'll want accept(2) to return -1(EINTR) on caught signal..
510 unless ($this->no_signals()) {
511 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
512 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
526 my ($this,$name) = @_;
527 $this->pm_received_signal($name,1);
530 =head1 Common methods and routines
532 =head2 self_or_default
535 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
539 This is a helper subroutine to acquire or otherwise create a singleton
540 default object if one is not passed in, e.g., a method call.
544 sub self_or_default {
545 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
546 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
547 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
548 $Q or $Q = $FCGI::ProcManager::Default->new;
551 return wantarray ? @_ : $Q;
554 =head2 pm_change_process_name
557 () pm_change_process_name()
563 sub pm_change_process_name {
564 my ($this,$name) = self_or_default(@_);
568 =head2 pm_received_signal
571 () pm_received signal()
577 sub pm_received_signal {
578 my ($this,$sig,$received) = self_or_default(@_);
579 $sig or return $this->{SIG_RECEIVED};
580 $received and $this->{SIG_RECEIVED}->{$sig}++;
581 return $this->{SIG_RECEIVED}->{$sig};
596 my ($this,$key,$value) = self_or_default(@_);
597 defined $value and $this->{$key} = $value;
598 return $this->{$key};
617 sub n_processes { shift->pm_parameter("n_processes", @_); }
618 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
619 sub no_signals { shift->pm_parameter("no_signals", @_); }
620 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
621 sub role { shift->pm_parameter("role", @_); }
622 sub start_delay { shift->pm_parameter("start_delay", @_); }
624 =head1 notification and death
636 my ($this,$msg) = self_or_default(@_);
637 $this->pm_notify($msg);
650 my ($this,$msg) = self_or_default(@_);
652 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
658 () pm_exit(string msg[, int exit_status])
665 my ($this,$msg,$n) = self_or_default(@_);
668 # if we still have children at this point, something went wrong.
670 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
672 $this->pm_warn($msg);
680 () pm_abort(string msg[, int exit_status])
687 my ($this,$msg,$n) = self_or_default(@_);
689 $this->pm_exit($msg,1);
697 No known bugs, but this does not mean no bugs exist.
705 Gareth Kirwan <gbjk@thermeon.com>
713 FCGI-ProcManager - A Perl FCGI Process Manager
714 Copyright (c) 2000, FundsXpress Financial Network, Inc.
716 This library is free software; you can redistribute it and/or
717 modify it under the terms of the GNU Lesser General Public
718 License as published by the Free Software Foundation; either
719 version 2 of the License, or (at your option) any later version.
721 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
722 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
723 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
724 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
725 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
726 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
727 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
728 License for more details.
730 You should have received a copy of the GNU Lesser General Public
731 License along with this library; if not, write to the Free Software
732 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA