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Revision 1.168 by root, Tue Jul 8 23:53:37 2008 UTC vs.
Revision 1.198 by root, Thu Mar 26 20:17:44 2009 UTC

6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9 use AnyEvent; 9 use AnyEvent;
10 10
11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { 11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });
12 ...
13 });
14 12
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 13 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
14 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
15
16 print AnyEvent->now; # prints current event loop time
17 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
18
19 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
20
21 my $w = AnyEvent->child (pid => $pid, cb => sub {
22 my ($pid, $status) = @_;
16 ... 23 ...
17 }); 24 });
18 25
19 my $w = AnyEvent->condvar; # stores whether a condition was flagged 26 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->send; # wake up current and all future recv's 27 $w->send; # wake up current and all future recv's
21 $w->recv; # enters "main loop" till $condvar gets ->send 28 $w->recv; # enters "main loop" till $condvar gets ->send
29 # use a condvar in callback mode:
30 $w->cb (sub { $_[0]->recv });
22 31
23=head1 INTRODUCTION/TUTORIAL 32=head1 INTRODUCTION/TUTORIAL
24 33
25This manpage is mainly a reference manual. If you are interested 34This manpage is mainly a reference manual. If you are interested
26in a tutorial or some gentle introduction, have a look at the 35in a tutorial or some gentle introduction, have a look at the
128These watchers are normal Perl objects with normal Perl lifetime. After 137These watchers are normal Perl objects with normal Perl lifetime. After
129creating a watcher it will immediately "watch" for events and invoke the 138creating a watcher it will immediately "watch" for events and invoke the
130callback when the event occurs (of course, only when the event model 139callback when the event occurs (of course, only when the event model
131is in control). 140is in control).
132 141
142Note that B<callbacks must not permanently change global variables>
143potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
144callbacks must not C<die> >>. The former is good programming practise in
145Perl and the latter stems from the fact that exception handling differs
146widely between event loops.
147
133To disable the watcher you have to destroy it (e.g. by setting the 148To disable the watcher you have to destroy it (e.g. by setting the
134variable you store it in to C<undef> or otherwise deleting all references 149variable you store it in to C<undef> or otherwise deleting all references
135to it). 150to it).
136 151
137All watchers are created by calling a method on the C<AnyEvent> class. 152All watchers are created by calling a method on the C<AnyEvent> class.
331=head2 CHILD PROCESS WATCHERS 346=head2 CHILD PROCESS WATCHERS
332 347
333You can also watch on a child process exit and catch its exit status. 348You can also watch on a child process exit and catch its exit status.
334 349
335The child process is specified by the C<pid> argument (if set to C<0>, it 350The child process is specified by the C<pid> argument (if set to C<0>, it
336watches for any child process exit). The watcher will trigger as often 351watches for any child process exit). The watcher will triggered only when
337as status change for the child are received. This works by installing a 352the child process has finished and an exit status is available, not on
338signal handler for C<SIGCHLD>. The callback will be called with the pid 353any trace events (stopped/continued).
339and exit status (as returned by waitpid), so unlike other watcher types, 354
340you I<can> rely on child watcher callback arguments. 355The callback will be called with the pid and exit status (as returned by
356waitpid), so unlike other watcher types, you I<can> rely on child watcher
357callback arguments.
358
359This watcher type works by installing a signal handler for C<SIGCHLD>,
360and since it cannot be shared, nothing else should use SIGCHLD or reap
361random child processes (waiting for specific child processes, e.g. inside
362C<system>, is just fine).
341 363
342There is a slight catch to child watchers, however: you usually start them 364There is a slight catch to child watchers, however: you usually start them
343I<after> the child process was created, and this means the process could 365I<after> the child process was created, and this means the process could
344have exited already (and no SIGCHLD will be sent anymore). 366have exited already (and no SIGCHLD will be sent anymore).
345 367
381The instrument to do that is called a "condition variable", so called 403The instrument to do that is called a "condition variable", so called
382because they represent a condition that must become true. 404because they represent a condition that must become true.
383 405
384Condition variables can be created by calling the C<< AnyEvent->condvar 406Condition variables can be created by calling the C<< AnyEvent->condvar
385>> method, usually without arguments. The only argument pair allowed is 407>> method, usually without arguments. The only argument pair allowed is
408
386C<cb>, which specifies a callback to be called when the condition variable 409C<cb>, which specifies a callback to be called when the condition variable
387becomes true. 410becomes true, with the condition variable as the first argument (but not
411the results).
388 412
389After creation, the condition variable is "false" until it becomes "true" 413After creation, the condition variable is "false" until it becomes "true"
390by calling the C<send> method (or calling the condition variable as if it 414by calling the C<send> method (or calling the condition variable as if it
391were a callback, read about the caveats in the description for the C<< 415were a callback, read about the caveats in the description for the C<<
392->send >> method). 416->send >> method).
448 472
449 my $done = AnyEvent->condvar; 473 my $done = AnyEvent->condvar;
450 my $delay = AnyEvent->timer (after => 5, cb => $done); 474 my $delay = AnyEvent->timer (after => 5, cb => $done);
451 $done->recv; 475 $done->recv;
452 476
477Example: Imagine an API that returns a condvar and doesn't support
478callbacks. This is how you make a synchronous call, for example from
479the main program:
480
481 use AnyEvent::CouchDB;
482
483 ...
484
485 my @info = $couchdb->info->recv;
486
487And this is how you would just ste a callback to be called whenever the
488results are available:
489
490 $couchdb->info->cb (sub {
491 my @info = $_[0]->recv;
492 });
493
453=head3 METHODS FOR PRODUCERS 494=head3 METHODS FOR PRODUCERS
454 495
455These methods should only be used by the producing side, i.e. the 496These methods should only be used by the producing side, i.e. the
456code/module that eventually sends the signal. Note that it is also 497code/module that eventually sends the signal. Note that it is also
457the producer side which creates the condvar in most cases, but it isn't 498the producer side which creates the condvar in most cases, but it isn't
590=item $bool = $cv->ready 631=item $bool = $cv->ready
591 632
592Returns true when the condition is "true", i.e. whether C<send> or 633Returns true when the condition is "true", i.e. whether C<send> or
593C<croak> have been called. 634C<croak> have been called.
594 635
595=item $cb = $cv->cb ([new callback]) 636=item $cb = $cv->cb ($cb->($cv))
596 637
597This is a mutator function that returns the callback set and optionally 638This is a mutator function that returns the callback set and optionally
598replaces it before doing so. 639replaces it before doing so.
599 640
600The callback will be called when the condition becomes "true", i.e. when 641The callback will be called when the condition becomes "true", i.e. when
790=item L<AnyEvent::IGS> 831=item L<AnyEvent::IGS>
791 832
792A non-blocking interface to the Internet Go Server protocol (used by 833A non-blocking interface to the Internet Go Server protocol (used by
793L<App::IGS>). 834L<App::IGS>).
794 835
795=item L<Net::IRC3> 836=item L<AnyEvent::IRC>
796 837
797AnyEvent based IRC client module family. 838AnyEvent based IRC client module family (replacing the older Net::IRC3).
798 839
799=item L<Net::XMPP2> 840=item L<Net::XMPP2>
800 841
801AnyEvent based XMPP (Jabber protocol) module family. 842AnyEvent based XMPP (Jabber protocol) module family.
802 843
822=cut 863=cut
823 864
824package AnyEvent; 865package AnyEvent;
825 866
826no warnings; 867no warnings;
827use strict; 868use strict qw(vars subs);
828 869
829use Carp; 870use Carp;
830 871
831our $VERSION = 4.2; 872our $VERSION = 4.341;
832our $MODEL; 873our $MODEL;
833 874
834our $AUTOLOAD; 875our $AUTOLOAD;
835our @ISA; 876our @ISA;
836 877
963 1004
964 my $class = shift; 1005 my $class = shift;
965 $class->$func (@_); 1006 $class->$func (@_);
966} 1007}
967 1008
1009# utility function to dup a filehandle. this is used by many backends
1010# to support binding more than one watcher per filehandle (they usually
1011# allow only one watcher per fd, so we dup it to get a different one).
1012sub _dupfh($$$$) {
1013 my ($poll, $fh, $r, $w) = @_;
1014
1015 # cygwin requires the fh mode to be matching, unix doesn't
1016 my ($rw, $mode) = $poll eq "r" ? ($r, "<")
1017 : $poll eq "w" ? ($w, ">")
1018 : Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
1019
1020 open my $fh2, "$mode&" . fileno $fh
1021 or die "cannot dup() filehandle: $!";
1022
1023 # we assume CLOEXEC is already set by perl in all important cases
1024
1025 ($fh2, $rw)
1026}
1027
968package AnyEvent::Base; 1028package AnyEvent::Base;
969 1029
970# default implementation for now and time 1030# default implementation for now and time
971 1031
972use Time::HiRes (); 1032BEGIN {
1033 if (eval "use Time::HiRes (); time (); 1") {
1034 *_time = \&Time::HiRes::time;
1035 # if (eval "use POSIX (); (POSIX::times())...
1036 } else {
1037 *_time = sub { time }; # epic fail
1038 }
1039}
973 1040
974sub time { Time::HiRes::time } 1041sub time { _time }
975sub now { Time::HiRes::time } 1042sub now { _time }
976 1043
977# default implementation for ->condvar 1044# default implementation for ->condvar
978 1045
979sub condvar { 1046sub condvar {
980 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar:: 1047 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
981} 1048}
982 1049
983# default implementation for ->signal 1050# default implementation for ->signal
984 1051
985our %SIG_CB; 1052our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
1053
1054sub _signal_exec {
1055 sysread $SIGPIPE_R, my $dummy, 4;
1056
1057 while (%SIG_EV) {
1058 for (keys %SIG_EV) {
1059 delete $SIG_EV{$_};
1060 $_->() for values %{ $SIG_CB{$_} || {} };
1061 }
1062 }
1063}
986 1064
987sub signal { 1065sub signal {
988 my (undef, %arg) = @_; 1066 my (undef, %arg) = @_;
989 1067
1068 unless ($SIGPIPE_R) {
1069 if (AnyEvent::WIN32) {
1070 ($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
1071 AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
1072 AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
1073 } else {
1074 pipe $SIGPIPE_R, $SIGPIPE_W;
1075 require Fcntl;
1076 fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
1077 fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
1078 }
1079
1080 $SIGPIPE_R
1081 or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
1082
1083 $SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
1084 }
1085
990 my $signal = uc $arg{signal} 1086 my $signal = uc $arg{signal}
991 or Carp::croak "required option 'signal' is missing"; 1087 or Carp::croak "required option 'signal' is missing";
992 1088
993 $SIG_CB{$signal}{$arg{cb}} = $arg{cb}; 1089 $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
994 $SIG{$signal} ||= sub { 1090 $SIG{$signal} ||= sub {
995 $_->() for values %{ $SIG_CB{$signal} || {} }; 1091 syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
1092 undef $SIG_EV{$signal};
996 }; 1093 };
997 1094
998 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal" 1095 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
999} 1096}
1000 1097
1119 1216
1120# undocumented/compatibility with pre-3.4 1217# undocumented/compatibility with pre-3.4
1121*broadcast = \&send; 1218*broadcast = \&send;
1122*wait = \&_wait; 1219*wait = \&_wait;
1123 1220
1221=head1 ERROR AND EXCEPTION HANDLING
1222
1223In general, AnyEvent does not do any error handling - it relies on the
1224caller to do that if required. The L<AnyEvent::Strict> module (see also
1225the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
1226checking of all AnyEvent methods, however, which is highly useful during
1227development.
1228
1229As for exception handling (i.e. runtime errors and exceptions thrown while
1230executing a callback), this is not only highly event-loop specific, but
1231also not in any way wrapped by this module, as this is the job of the main
1232program.
1233
1234The pure perl event loop simply re-throws the exception (usually
1235within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
1236$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
1237so on.
1238
1239=head1 ENVIRONMENT VARIABLES
1240
1241The following environment variables are used by this module or its
1242submodules:
1243
1244=over 4
1245
1246=item C<PERL_ANYEVENT_VERBOSE>
1247
1248By default, AnyEvent will be completely silent except in fatal
1249conditions. You can set this environment variable to make AnyEvent more
1250talkative.
1251
1252When set to C<1> or higher, causes AnyEvent to warn about unexpected
1253conditions, such as not being able to load the event model specified by
1254C<PERL_ANYEVENT_MODEL>.
1255
1256When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1257model it chooses.
1258
1259=item C<PERL_ANYEVENT_STRICT>
1260
1261AnyEvent does not do much argument checking by default, as thorough
1262argument checking is very costly. Setting this variable to a true value
1263will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1264check the arguments passed to most method calls. If it finds any problems
1265it will croak.
1266
1267In other words, enables "strict" mode.
1268
1269Unlike C<use strict>, it is definitely recommended ot keep it off in
1270production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
1271developing programs can be very useful, however.
1272
1273=item C<PERL_ANYEVENT_MODEL>
1274
1275This can be used to specify the event model to be used by AnyEvent, before
1276auto detection and -probing kicks in. It must be a string consisting
1277entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1278and the resulting module name is loaded and if the load was successful,
1279used as event model. If it fails to load AnyEvent will proceed with
1280auto detection and -probing.
1281
1282This functionality might change in future versions.
1283
1284For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1285could start your program like this:
1286
1287 PERL_ANYEVENT_MODEL=Perl perl ...
1288
1289=item C<PERL_ANYEVENT_PROTOCOLS>
1290
1291Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1292for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1293of auto probing).
1294
1295Must be set to a comma-separated list of protocols or address families,
1296current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1297used, and preference will be given to protocols mentioned earlier in the
1298list.
1299
1300This variable can effectively be used for denial-of-service attacks
1301against local programs (e.g. when setuid), although the impact is likely
1302small, as the program has to handle conenction and other failures anyways.
1303
1304Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1305but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1306- only support IPv4, never try to resolve or contact IPv6
1307addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1308IPv6, but prefer IPv6 over IPv4.
1309
1310=item C<PERL_ANYEVENT_EDNS0>
1311
1312Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1313for DNS. This extension is generally useful to reduce DNS traffic, but
1314some (broken) firewalls drop such DNS packets, which is why it is off by
1315default.
1316
1317Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1318EDNS0 in its DNS requests.
1319
1320=item C<PERL_ANYEVENT_MAX_FORKS>
1321
1322The maximum number of child processes that C<AnyEvent::Util::fork_call>
1323will create in parallel.
1324
1325=back
1326
1124=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1327=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1125 1328
1126This is an advanced topic that you do not normally need to use AnyEvent in 1329This is an advanced topic that you do not normally need to use AnyEvent in
1127a module. This section is only of use to event loop authors who want to 1330a module. This section is only of use to event loop authors who want to
1128provide AnyEvent compatibility. 1331provide AnyEvent compatibility.
1161 1364
1162I<rxvt-unicode> also cheats a bit by not providing blocking access to 1365I<rxvt-unicode> also cheats a bit by not providing blocking access to
1163condition variables: code blocking while waiting for a condition will 1366condition variables: code blocking while waiting for a condition will
1164C<die>. This still works with most modules/usages, and blocking calls must 1367C<die>. This still works with most modules/usages, and blocking calls must
1165not be done in an interactive application, so it makes sense. 1368not be done in an interactive application, so it makes sense.
1166
1167=head1 ENVIRONMENT VARIABLES
1168
1169The following environment variables are used by this module:
1170
1171=over 4
1172
1173=item C<PERL_ANYEVENT_VERBOSE>
1174
1175By default, AnyEvent will be completely silent except in fatal
1176conditions. You can set this environment variable to make AnyEvent more
1177talkative.
1178
1179When set to C<1> or higher, causes AnyEvent to warn about unexpected
1180conditions, such as not being able to load the event model specified by
1181C<PERL_ANYEVENT_MODEL>.
1182
1183When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1184model it chooses.
1185
1186=item C<PERL_ANYEVENT_STRICT>
1187
1188AnyEvent does not do much argument checking by default, as thorough
1189argument checking is very costly. Setting this variable to a true value
1190will cause AnyEvent to thoroughly check the arguments passed to most
1191method calls and croaks if it finds any problems. In other words, enables
1192"strict" mode. Unlike C<use strict> it is definitely recommended ot keep
1193it off in production.
1194
1195=item C<PERL_ANYEVENT_MODEL>
1196
1197This can be used to specify the event model to be used by AnyEvent, before
1198auto detection and -probing kicks in. It must be a string consisting
1199entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1200and the resulting module name is loaded and if the load was successful,
1201used as event model. If it fails to load AnyEvent will proceed with
1202auto detection and -probing.
1203
1204This functionality might change in future versions.
1205
1206For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1207could start your program like this:
1208
1209 PERL_ANYEVENT_MODEL=Perl perl ...
1210
1211=item C<PERL_ANYEVENT_PROTOCOLS>
1212
1213Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1214for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1215of auto probing).
1216
1217Must be set to a comma-separated list of protocols or address families,
1218current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1219used, and preference will be given to protocols mentioned earlier in the
1220list.
1221
1222This variable can effectively be used for denial-of-service attacks
1223against local programs (e.g. when setuid), although the impact is likely
1224small, as the program has to handle connection errors already-
1225
1226Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1227but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1228- only support IPv4, never try to resolve or contact IPv6
1229addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1230IPv6, but prefer IPv6 over IPv4.
1231
1232=item C<PERL_ANYEVENT_EDNS0>
1233
1234Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1235for DNS. This extension is generally useful to reduce DNS traffic, but
1236some (broken) firewalls drop such DNS packets, which is why it is off by
1237default.
1238
1239Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1240EDNS0 in its DNS requests.
1241
1242=item C<PERL_ANYEVENT_MAX_FORKS>
1243
1244The maximum number of child processes that C<AnyEvent::Util::fork_call>
1245will create in parallel.
1246
1247=back
1248 1369
1249=head1 EXAMPLE PROGRAM 1370=head1 EXAMPLE PROGRAM
1250 1371
1251The following program uses an I/O watcher to read data from STDIN, a timer 1372The following program uses an I/O watcher to read data from STDIN, a timer
1252to display a message once per second, and a condition variable to quit the 1373to display a message once per second, and a condition variable to quit the
1446watcher. 1567watcher.
1447 1568
1448=head3 Results 1569=head3 Results
1449 1570
1450 name watchers bytes create invoke destroy comment 1571 name watchers bytes create invoke destroy comment
1451 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1572 EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1452 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1573 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1453 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1574 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1454 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1575 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1455 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1576 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1456 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers 1577 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1457 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1578 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1458 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1579 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1459 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1580 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1460 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1581 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1461 1582
1462=head3 Discussion 1583=head3 Discussion
1463 1584
1464The benchmark does I<not> measure scalability of the event loop very 1585The benchmark does I<not> measure scalability of the event loop very
1465well. For example, a select-based event loop (such as the pure perl one) 1586well. For example, a select-based event loop (such as the pure perl one)
1667watchers, as the management overhead dominates. 1788watchers, as the management overhead dominates.
1668 1789
1669=back 1790=back
1670 1791
1671 1792
1793=head1 SIGNALS
1794
1795AnyEvent currently installs handlers for these signals:
1796
1797=over 4
1798
1799=item SIGCHLD
1800
1801A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
1802emulation for event loops that do not support them natively. Also, some
1803event loops install a similar handler.
1804
1805=item SIGPIPE
1806
1807A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
1808when AnyEvent gets loaded.
1809
1810The rationale for this is that AnyEvent users usually do not really depend
1811on SIGPIPE delivery (which is purely an optimisation for shell use, or
1812badly-written programs), but C<SIGPIPE> can cause spurious and rare
1813program exits as a lot of people do not expect C<SIGPIPE> when writing to
1814some random socket.
1815
1816The rationale for installing a no-op handler as opposed to ignoring it is
1817that this way, the handler will be restored to defaults on exec.
1818
1819Feel free to install your own handler, or reset it to defaults.
1820
1821=back
1822
1823=cut
1824
1825$SIG{PIPE} = sub { }
1826 unless defined $SIG{PIPE};
1827
1828
1672=head1 FORK 1829=head1 FORK
1673 1830
1674Most event libraries are not fork-safe. The ones who are usually are 1831Most event libraries are not fork-safe. The ones who are usually are
1675because they rely on inefficient but fork-safe C<select> or C<poll> 1832because they rely on inefficient but fork-safe C<select> or C<poll>
1676calls. Only L<EV> is fully fork-aware. 1833calls. Only L<EV> is fully fork-aware.
1704=head1 BUGS 1861=head1 BUGS
1705 1862
1706Perl 5.8 has numerous memleaks that sometimes hit this module and are hard 1863Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1707to work around. If you suffer from memleaks, first upgrade to Perl 5.10 1864to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1708and check wether the leaks still show up. (Perl 5.10.0 has other annoying 1865and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1709mamleaks, such as leaking on C<map> and C<grep> but it is usually not as 1866memleaks, such as leaking on C<map> and C<grep> but it is usually not as
1710pronounced). 1867pronounced).
1711 1868
1712 1869
1713=head1 SEE ALSO 1870=head1 SEE ALSO
1714 1871

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