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 FCGI.pm's description of
95 FAIL_ACCEPT_ON_INTR. Unfortunately, if you want/need to use CGI::Fast, it
96 appears currently necessary to modify your installation of FCGI.pm, with
97 something like the following:
100 --- FCGI.pm 2001/03/09 01:44:00 1.1.1.3
101 +++ FCGI.pm 2001/03/09 01:47:32 1.2
103 *FAIL_ACCEPT_ON_INTR = sub() { 1 };
105 sub Request(;***$$$) {
106 - my @defaults = (\*STDIN, \*STDOUT, \*STDERR, \%ENV, 0, 0);
107 + my @defaults = (\*STDIN, \*STDOUT, \*STDERR, \%ENV, 0, FAIL_ACCEPT_ON_INTR());
108 splice @defaults,0,@_,@_;
113 Otherwise, if you don't, there is a loop around accept(2) which prevents
114 os_unix.c OS_Accept() from returning the necessary error when FastCGI
115 servers blocking on accept(2) receive the SIGTERM or SIGHUP.
117 FCGI::ProcManager uses POSIX::sigaction() to override the default SA_RESTART
118 policy used for perl's %SIG behavior. Specifically, the process manager
119 never uses SA_RESTART, while the child FastCGI servers turn off SA_RESTART
120 around the accept(2) loop, but re-enstate it otherwise.
122 The desired (and implemented) effect is to give a request as big a chance as
123 possible to succeed and to delay their exits until after their request,
124 while allowing the FastCGI servers waiting for new requests to die right
132 (ProcManager) new([hash parameters])
134 Constructs a new process manager. Takes an option has of initial parameter
135 values, and assigns these to the constructed object HASH, overriding any
136 default values. The default parameter values currently are:
141 pm_title => 'perl-fcgi-pm'
146 my ($proto,$init) = @_;
153 pm_title => 'perl-fcgi-pm',
156 bless $this, ref($proto)||$proto;
160 # initialize signal constructions.
161 unless ($this->no_signals()) {
162 $this->{sigaction_no_sa_restart} =
163 POSIX::SigAction->new('FCGI::ProcManager::sig_sub');
164 $this->{sigaction_sa_restart} =
165 POSIX::SigAction->new('FCGI::ProcManager::sig_sub',undef,POSIX::SA_RESTART);
171 =head1 Manager methods
176 (int) pm_manage([hash parameters])
180 When this is called by a FastCGI script to manage application servers. It
181 defines a sequence of instructions for a process to enter this method and
182 begin forking off and managing those handlers, and it defines a sequence of
183 instructions to intialize those handlers.
185 If n_processes < 1, the managing section is subverted, and only the
186 handling sequence is executed.
188 Either returns the return value of pm_die() and/or pm_abort() (which will
189 not ever return in general), or returns 1 to the calling script to begin
195 my ($this,%values) = self_or_default(@_);
196 map { $this->pm_parameter($_,$values{$_}) } keys %values;
198 # skip to handling now if we won't be managing any processes.
199 $this->n_processes() or return;
201 # call the (possibly overloaded) management initialization hook.
202 $this->role("manager");
203 $this->managing_init();
204 $this->pm_notify("initialized");
206 my $manager_pid = $$;
208 MANAGING_LOOP: while (1) {
210 $this->n_processes() > 0 or
211 return $this->pm_die();
213 # while we have fewer servers than we want.
214 PIDS: while (keys(%{$this->{PIDS}}) < $this->n_processes()) {
216 if (my $pid = fork()) {
217 # the manager remembers the server.
218 $this->{PIDS}->{$pid} = { pid=>$pid };
219 $this->pm_notify("server (pid $pid) started");
221 } elsif (! defined $pid) {
222 return $this->pm_abort("fork: $!");
225 $this->{MANAGER_PID} = $manager_pid;
226 # the server exits the managing loop.
230 for (my $s = $this->start_delay(); $s; $s = sleep $s) {};
233 # this should block until the next server dies.
240 # forget any children we had been collecting.
241 delete $this->{PIDS};
243 # call the (possibly overloaded) handling init hook
244 $this->role("server");
245 $this->handling_init();
246 $this->pm_notify("initialized");
259 Overrideable method which initializes a process manager. In order to
260 handle signals, manage the PID file, and change the process name properly,
261 any method which overrides this should call SUPER::managing_init().
268 # begin to handle signals.
269 # We do NOT want SA_RESTART in the process manager.
270 # -- we want start the shutdown sequence immediately upon SIGTERM.
271 unless ($this->no_signals()) {
272 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or
273 $this->pm_warn("sigaction: SIGTERM: $!");
274 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or
275 $this->pm_warn("sigaction: SIGHUP: $!");
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 next 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 ||= $this->pid_fname() or return;
373 if (!open PIDFILE, ">$fname") {
374 $this->pm_warn("open: $fname: $!");
377 print PIDFILE "$$\n";
381 =head2 pm_remove_pid_file
384 () pm_remove_pid_file()
388 Removes optionally specified file. If no filename is specified, it uses
389 the value of the C<pid_fname> parameter.
393 sub pm_remove_pid_file {
394 my ($this,$fname) = self_or_default(@_);
395 $fname ||= $this->pid_fname() or return;
396 my $ret = unlink($fname) or $this->pm_warn("unlink: $fname: $!");
403 () sig_sub(string name)
407 The name of this method is passed to POSIX::sigaction(), and handles signals
408 for the process manager. If $SIG_CODEREF is set, then the input arguments
409 to this are passed to a call to that.
414 $SIG_CODEREF->(@_) if ref $SIG_CODEREF;
420 () sig_manager(string name)
424 Handles signals of the process manager. Takes as input the name of signal
430 my ($this,$name) = @_;
431 if ($name eq "TERM") {
432 $this->pm_notify("received signal $name");
433 $this->pm_die("safe exit from signal $name");
434 } elsif ($name eq "HUP") {
435 # send a TERM to each of the servers, and pretend like nothing happened..
436 if (my @pids = keys %{$this->{PIDS}}) {
437 $this->pm_notify("sending TERM to PIDs, @pids");
441 $this->pm_notify("ignoring signal $name");
445 =head1 Handler methods
459 # begin to handle signals.
460 # We'll want accept(2) to return -1(EINTR) on caught signal..
461 unless ($this->no_signals()) {
462 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
463 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
464 $SIG_CODEREF = sub { $this->sig_handler(@_) };
467 # change the name of this process as it appears in ps(1) output.
468 $this->pm_change_process_name("perl-fcgi");
471 =head2 pm_pre_dispatch
480 sub pm_pre_dispatch {
481 my ($this) = self_or_default(@_);
483 # Now, we want the request to continue unhindered..
484 unless ($this->no_signals()) {
485 sigaction(SIGTERM, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
486 sigaction(SIGHUP, $this->{sigaction_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
490 =head2 pm_post_dispatch
493 () pm_post_dispatch()
499 sub pm_post_dispatch {
500 my ($this) = self_or_default(@_);
501 if ($this->pm_received_signal("TERM")) {
502 $this->pm_exit("safe exit after SIGTERM");
504 if ($this->pm_received_signal("HUP")) {
505 $this->pm_exit("safe exit after SIGHUP");
507 if ($this->{MANAGER_PID} and getppid() != $this->{MANAGER_PID}) {
508 $this->pm_exit("safe exit: manager has died");
510 # We'll want accept(2) to return -1(EINTR) on caught signal..
511 unless ($this->no_signals()) {
512 sigaction(SIGTERM, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGTERM: $!");
513 sigaction(SIGHUP, $this->{sigaction_no_sa_restart}) or $this->pm_warn("sigaction: SIGHUP: $!");
527 my ($this,$name) = @_;
528 $this->pm_received_signal($name,1);
531 =head1 Common methods and routines
533 =head2 self_or_default
536 (ProcManager, @args) self_or_default([ ProcManager, ] @args);
540 This is a helper subroutine to acquire or otherwise create a singleton
541 default object if one is not passed in, e.g., a method call.
545 sub self_or_default {
546 return @_ if defined $_[0] and !ref $_[0] and $_[0] eq 'FCGI::ProcManager';
547 if (!defined $_[0] or (ref($_[0]) ne 'FCGI::ProcManager' and
548 !UNIVERSAL::isa($_[0],'FCGI::ProcManager'))) {
549 $Q or $Q = $FCGI::ProcManager::Default->new;
552 return wantarray ? @_ : $Q;
555 =head2 pm_change_process_name
558 () pm_change_process_name()
564 sub pm_change_process_name {
565 my ($this,$name) = self_or_default(@_);
569 =head2 pm_received_signal
572 () pm_received signal()
578 sub pm_received_signal {
579 my ($this,$sig,$received) = self_or_default(@_);
580 $sig or return $this->{SIG_RECEIVED};
581 $received and $this->{SIG_RECEIVED}->{$sig}++;
582 return $this->{SIG_RECEIVED}->{$sig};
597 my ($this,$key,$value) = self_or_default(@_);
598 defined $value and $this->{$key} = $value;
599 return $this->{$key};
618 sub n_processes { shift->pm_parameter("n_processes", @_); }
619 sub pid_fname { shift->pm_parameter("pid_fname", @_); }
620 sub no_signals { shift->pm_parameter("no_signals", @_); }
621 sub die_timeout { shift->pm_parameter("die_timeout", @_); }
622 sub role { shift->pm_parameter("role", @_); }
623 sub start_delay { shift->pm_parameter("start_delay", @_); }
625 =head1 notification and death
637 my ($this,$msg) = self_or_default(@_);
638 $this->pm_notify($msg);
651 my ($this,$msg) = self_or_default(@_);
653 print STDERR "FastCGI: ".$this->role()." (pid $$): ".$msg;
659 () pm_exit(string msg[, int exit_status])
666 my ($this,$msg,$n) = self_or_default(@_);
669 # if we still have children at this point, something went wrong.
671 kill "KILL", keys %{$this->{PIDS}} if $this->{PIDS};
673 $this->pm_warn($msg);
681 () pm_abort(string msg[, int exit_status])
688 my ($this,$msg,$n) = self_or_default(@_);
690 $this->pm_exit($msg,1);
698 No known bugs, but this does not mean no bugs exist.
706 Gareth Kirwan <gbjk@thermeon.com>
714 FCGI-ProcManager - A Perl FCGI Process Manager
715 Copyright (c) 2000, FundsXpress Financial Network, Inc.
717 This library is free software; you can redistribute it and/or
718 modify it under the terms of the GNU Lesser General Public
719 License as published by the Free Software Foundation; either
720 version 2 of the License, or (at your option) any later version.
722 BECAUSE THIS LIBRARY IS LICENSED FREE OF CHARGE, THIS LIBRARY IS
723 BEING PROVIDED "AS IS WITH ALL FAULTS," WITHOUT ANY WARRANTIES
724 OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
725 LIMITATION, ANY IMPLIED WARRANTIES OF TITLE, NONINFRINGEMENT,
726 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND THE
727 ENTIRE RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY,
728 AND EFFORT IS WITH THE YOU. See the GNU Lesser General Public
729 License for more details.
731 You should have received a copy of the GNU Lesser General Public
732 License along with this library; if not, write to the Free Software
733 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA