ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/AnyEvent/README
(Generate patch)

Comparing AnyEvent/README (file contents):
Revision 1.29 by root, Tue Jul 29 10:20:33 2008 UTC vs.
Revision 1.40 by root, Tue Jun 23 23:37:32 2009 UTC

1NAME 1NAME
2 AnyEvent - provide framework for multiple event loops 2 AnyEvent - provide framework for multiple event loops
3 3
4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event 4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
5 loops 5 event loops.
6 6
7SYNOPSIS 7SYNOPSIS
8 use AnyEvent; 8 use AnyEvent;
9 9
10 # file descriptor readable
10 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... }); 11 my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
11 12
13 # one-shot or repeating timers
12 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); 14 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... 15 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
14 16
15 print AnyEvent->now; # prints current event loop time 17 print AnyEvent->now; # prints current event loop time
16 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. 18 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17 19
20 # POSIX signal
18 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); 21 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19 22
23 # child process exit
20 my $w = AnyEvent->child (pid => $pid, cb => sub { 24 my $w = AnyEvent->child (pid => $pid, cb => sub {
21 my ($pid, $status) = @_; 25 my ($pid, $status) = @_;
22 ... 26 ...
23 }); 27 });
28
29 # called when event loop idle (if applicable)
30 my $w = AnyEvent->idle (cb => sub { ... });
24 31
25 my $w = AnyEvent->condvar; # stores whether a condition was flagged 32 my $w = AnyEvent->condvar; # stores whether a condition was flagged
26 $w->send; # wake up current and all future recv's 33 $w->send; # wake up current and all future recv's
27 $w->recv; # enters "main loop" till $condvar gets ->send 34 $w->recv; # enters "main loop" till $condvar gets ->send
28 # use a condvar in callback mode: 35 # use a condvar in callback mode:
… …
132 These watchers are normal Perl objects with normal Perl lifetime. After 139 These watchers are normal Perl objects with normal Perl lifetime. After
133 creating a watcher it will immediately "watch" for events and invoke the 140 creating a watcher it will immediately "watch" for events and invoke the
134 callback when the event occurs (of course, only when the event model is 141 callback when the event occurs (of course, only when the event model is
135 in control). 142 in control).
136 143
144 Note that callbacks must not permanently change global variables
145 potentially in use by the event loop (such as $_ or $[) and that
146 callbacks must not "die". The former is good programming practise in
147 Perl and the latter stems from the fact that exception handling differs
148 widely between event loops.
149
137 To disable the watcher you have to destroy it (e.g. by setting the 150 To disable the watcher you have to destroy it (e.g. by setting the
138 variable you store it in to "undef" or otherwise deleting all references 151 variable you store it in to "undef" or otherwise deleting all references
139 to it). 152 to it).
140 153
141 All watchers are created by calling a method on the "AnyEvent" class. 154 All watchers are created by calling a method on the "AnyEvent" class.
… …
156 169
157 I/O WATCHERS 170 I/O WATCHERS
158 You can create an I/O watcher by calling the "AnyEvent->io" method with 171 You can create an I/O watcher by calling the "AnyEvent->io" method with
159 the following mandatory key-value pairs as arguments: 172 the following mandatory key-value pairs as arguments:
160 173
161 "fh" the Perl *file handle* (*not* file descriptor) to watch for events 174 "fh" is the Perl *file handle* (*not* file descriptor) to watch for
162 (AnyEvent might or might not keep a reference to this file handle). 175 events (AnyEvent might or might not keep a reference to this file
176 handle). Note that only file handles pointing to things for which
177 non-blocking operation makes sense are allowed. This includes sockets,
178 most character devices, pipes, fifos and so on, but not for example
179 files or block devices.
180
163 "poll" must be a string that is either "r" or "w", which creates a 181 "poll" must be a string that is either "r" or "w", which creates a
164 watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" 182 watcher waiting for "r"eadable or "w"ritable events, respectively.
183
165 is the callback to invoke each time the file handle becomes ready. 184 "cb" is the callback to invoke each time the file handle becomes ready.
166 185
167 Although the callback might get passed parameters, their value and 186 Although the callback might get passed parameters, their value and
168 presence is undefined and you cannot rely on them. Portable AnyEvent 187 presence is undefined and you cannot rely on them. Portable AnyEvent
169 callbacks cannot use arguments passed to I/O watcher callbacks. 188 callbacks cannot use arguments passed to I/O watcher callbacks.
170 189
… …
302 In either case, if you care (and in most cases, you don't), then you 321 In either case, if you care (and in most cases, you don't), then you
303 can get whatever behaviour you want with any event loop, by taking 322 can get whatever behaviour you want with any event loop, by taking
304 the difference between "AnyEvent->time" and "AnyEvent->now" into 323 the difference between "AnyEvent->time" and "AnyEvent->now" into
305 account. 324 account.
306 325
326 AnyEvent->now_update
327 Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
328 current time for each loop iteration (see the discussion of
329 AnyEvent->now, above).
330
331 When a callback runs for a long time (or when the process sleeps),
332 then this "current" time will differ substantially from the real
333 time, which might affect timers and time-outs.
334
335 When this is the case, you can call this method, which will update
336 the event loop's idea of "current time".
337
338 Note that updating the time *might* cause some events to be handled.
339
307 SIGNAL WATCHERS 340 SIGNAL WATCHERS
308 You can watch for signals using a signal watcher, "signal" is the signal 341 You can watch for signals using a signal watcher, "signal" is the signal
309 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl 342 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
310 callback to be invoked whenever a signal occurs. 343 callback to be invoked whenever a signal occurs.
311 344
… …
330 363
331 CHILD PROCESS WATCHERS 364 CHILD PROCESS WATCHERS
332 You can also watch on a child process exit and catch its exit status. 365 You can also watch on a child process exit and catch its exit status.
333 366
334 The child process is specified by the "pid" argument (if set to 0, it 367 The child process is specified by the "pid" argument (if set to 0, it
335 watches for any child process exit). The watcher will trigger as often 368 watches for any child process exit). The watcher will triggered only
336 as status change for the child are received. This works by installing a 369 when the child process has finished and an exit status is available, not
337 signal handler for "SIGCHLD". The callback will be called with the pid 370 on any trace events (stopped/continued).
338 and exit status (as returned by waitpid), so unlike other watcher types, 371
339 you *can* rely on child watcher callback arguments. 372 The callback will be called with the pid and exit status (as returned by
373 waitpid), so unlike other watcher types, you *can* rely on child watcher
374 callback arguments.
375
376 This watcher type works by installing a signal handler for "SIGCHLD",
377 and since it cannot be shared, nothing else should use SIGCHLD or reap
378 random child processes (waiting for specific child processes, e.g.
379 inside "system", is just fine).
340 380
341 There is a slight catch to child watchers, however: you usually start 381 There is a slight catch to child watchers, however: you usually start
342 them *after* the child process was created, and this means the process 382 them *after* the child process was created, and this means the process
343 could have exited already (and no SIGCHLD will be sent anymore). 383 could have exited already (and no SIGCHLD will be sent anymore).
344 384
… …
352 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 392 you "fork" the child (alternatively, you can call "AnyEvent::detect").
353 393
354 Example: fork a process and wait for it 394 Example: fork a process and wait for it
355 395
356 my $done = AnyEvent->condvar; 396 my $done = AnyEvent->condvar;
357 397
358 my $pid = fork or exit 5; 398 my $pid = fork or exit 5;
359 399
360 my $w = AnyEvent->child ( 400 my $w = AnyEvent->child (
361 pid => $pid, 401 pid => $pid,
362 cb => sub { 402 cb => sub {
363 my ($pid, $status) = @_; 403 my ($pid, $status) = @_;
364 warn "pid $pid exited with status $status"; 404 warn "pid $pid exited with status $status";
365 $done->send; 405 $done->send;
366 }, 406 },
367 ); 407 );
368 408
369 # do something else, then wait for process exit 409 # do something else, then wait for process exit
370 $done->recv; 410 $done->recv;
411
412 IDLE WATCHERS
413 Sometimes there is a need to do something, but it is not so important to
414 do it instantly, but only when there is nothing better to do. This
415 "nothing better to do" is usually defined to be "no other events need
416 attention by the event loop".
417
418 Idle watchers ideally get invoked when the event loop has nothing better
419 to do, just before it would block the process to wait for new events.
420 Instead of blocking, the idle watcher is invoked.
421
422 Most event loops unfortunately do not really support idle watchers (only
423 EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
424 will simply call the callback "from time to time".
425
426 Example: read lines from STDIN, but only process them when the program
427 is otherwise idle:
428
429 my @lines; # read data
430 my $idle_w;
431 my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
432 push @lines, scalar <STDIN>;
433
434 # start an idle watcher, if not already done
435 $idle_w ||= AnyEvent->idle (cb => sub {
436 # handle only one line, when there are lines left
437 if (my $line = shift @lines) {
438 print "handled when idle: $line";
439 } else {
440 # otherwise disable the idle watcher again
441 undef $idle_w;
442 }
443 });
444 });
371 445
372 CONDITION VARIABLES 446 CONDITION VARIABLES
373 If you are familiar with some event loops you will know that all of them 447 If you are familiar with some event loops you will know that all of them
374 require you to run some blocking "loop", "run" or similar function that 448 require you to run some blocking "loop", "run" or similar function that
375 will actively watch for new events and call your callbacks. 449 will actively watch for new events and call your callbacks.
… …
770 844
771 AnyEvent::IGS 845 AnyEvent::IGS
772 A non-blocking interface to the Internet Go Server protocol (used by 846 A non-blocking interface to the Internet Go Server protocol (used by
773 App::IGS). 847 App::IGS).
774 848
849 AnyEvent::IRC
850 AnyEvent based IRC client module family (replacing the older
775 Net::IRC3 851 Net::IRC3).
776 AnyEvent based IRC client module family.
777 852
778 Net::XMPP2 853 Net::XMPP2
779 AnyEvent based XMPP (Jabber protocol) module family. 854 AnyEvent based XMPP (Jabber protocol) module family.
780 855
781 Net::FCP 856 Net::FCP
… …
790 865
791 IO::Lambda 866 IO::Lambda
792 The lambda approach to I/O - don't ask, look there. Can use 867 The lambda approach to I/O - don't ask, look there. Can use
793 AnyEvent. 868 AnyEvent.
794 869
795SUPPLYING YOUR OWN EVENT MODEL INTERFACE 870ERROR AND EXCEPTION HANDLING
796 This is an advanced topic that you do not normally need to use AnyEvent 871 In general, AnyEvent does not do any error handling - it relies on the
797 in a module. This section is only of use to event loop authors who want 872 caller to do that if required. The AnyEvent::Strict module (see also the
798 to provide AnyEvent compatibility. 873 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
874 checking of all AnyEvent methods, however, which is highly useful during
875 development.
799 876
800 If you need to support another event library which isn't directly 877 As for exception handling (i.e. runtime errors and exceptions thrown
801 supported by AnyEvent, you can supply your own interface to it by 878 while executing a callback), this is not only highly event-loop
802 pushing, before the first watcher gets created, the package name of the 879 specific, but also not in any way wrapped by this module, as this is the
803 event module and the package name of the interface to use onto 880 job of the main program.
804 @AnyEvent::REGISTRY. You can do that before and even without loading
805 AnyEvent, so it is reasonably cheap.
806 881
807 Example: 882 The pure perl event loop simply re-throws the exception (usually within
808 883 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
809 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 884 Glib uses "install_exception_handler" and so on.
810
811 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
812 package/class when it finds the "urxvt" package/module is already
813 loaded.
814
815 When AnyEvent is loaded and asked to find a suitable event model, it
816 will first check for the presence of urxvt by trying to "use" the
817 "urxvt::anyevent" module.
818
819 The class should provide implementations for all watcher types. See
820 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
821 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
822 the sources.
823
824 If you don't provide "signal" and "child" watchers than AnyEvent will
825 provide suitable (hopefully) replacements.
826
827 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
828 terminal emulator uses the above line as-is. An interface isn't included
829 in AnyEvent because it doesn't make sense outside the embedded
830 interpreter inside *rxvt-unicode*, and it is updated and maintained as
831 part of the *rxvt-unicode* distribution.
832
833 *rxvt-unicode* also cheats a bit by not providing blocking access to
834 condition variables: code blocking while waiting for a condition will
835 "die". This still works with most modules/usages, and blocking calls
836 must not be done in an interactive application, so it makes sense.
837 885
838ENVIRONMENT VARIABLES 886ENVIRONMENT VARIABLES
839 The following environment variables are used by this module: 887 The following environment variables are used by this module or its
888 submodules.
889
890 Note that AnyEvent will remove *all* environment variables starting with
891 "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
892 enabled.
840 893
841 "PERL_ANYEVENT_VERBOSE" 894 "PERL_ANYEVENT_VERBOSE"
842 By default, AnyEvent will be completely silent except in fatal 895 By default, AnyEvent will be completely silent except in fatal
843 conditions. You can set this environment variable to make AnyEvent 896 conditions. You can set this environment variable to make AnyEvent
844 more talkative. 897 more talkative.
… …
857 thoroughly check the arguments passed to most method calls. If it 910 thoroughly check the arguments passed to most method calls. If it
858 finds any problems it will croak. 911 finds any problems it will croak.
859 912
860 In other words, enables "strict" mode. 913 In other words, enables "strict" mode.
861 914
862 Unlike "use strict" it is definitely recommended ot keep it off in 915 Unlike "use strict", it is definitely recommended ot keep it off in
863 production. 916 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
917 while developing programs can be very useful, however.
864 918
865 "PERL_ANYEVENT_MODEL" 919 "PERL_ANYEVENT_MODEL"
866 This can be used to specify the event model to be used by AnyEvent, 920 This can be used to specify the event model to be used by AnyEvent,
867 before auto detection and -probing kicks in. It must be a string 921 before auto detection and -probing kicks in. It must be a string
868 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 922 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
… …
887 mentioned will be used, and preference will be given to protocols 941 mentioned will be used, and preference will be given to protocols
888 mentioned earlier in the list. 942 mentioned earlier in the list.
889 943
890 This variable can effectively be used for denial-of-service attacks 944 This variable can effectively be used for denial-of-service attacks
891 against local programs (e.g. when setuid), although the impact is 945 against local programs (e.g. when setuid), although the impact is
892 likely small, as the program has to handle connection errors 946 likely small, as the program has to handle conenction and other
893 already- 947 failures anyways.
894 948
895 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over 949 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
896 IPv6, but support both and try to use both. 950 IPv6, but support both and try to use both.
897 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to 951 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
898 resolve or contact IPv6 addresses. 952 resolve or contact IPv6 addresses.
… …
909 EDNS0 in its DNS requests. 963 EDNS0 in its DNS requests.
910 964
911 "PERL_ANYEVENT_MAX_FORKS" 965 "PERL_ANYEVENT_MAX_FORKS"
912 The maximum number of child processes that 966 The maximum number of child processes that
913 "AnyEvent::Util::fork_call" will create in parallel. 967 "AnyEvent::Util::fork_call" will create in parallel.
968
969SUPPLYING YOUR OWN EVENT MODEL INTERFACE
970 This is an advanced topic that you do not normally need to use AnyEvent
971 in a module. This section is only of use to event loop authors who want
972 to provide AnyEvent compatibility.
973
974 If you need to support another event library which isn't directly
975 supported by AnyEvent, you can supply your own interface to it by
976 pushing, before the first watcher gets created, the package name of the
977 event module and the package name of the interface to use onto
978 @AnyEvent::REGISTRY. You can do that before and even without loading
979 AnyEvent, so it is reasonably cheap.
980
981 Example:
982
983 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
984
985 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
986 package/class when it finds the "urxvt" package/module is already
987 loaded.
988
989 When AnyEvent is loaded and asked to find a suitable event model, it
990 will first check for the presence of urxvt by trying to "use" the
991 "urxvt::anyevent" module.
992
993 The class should provide implementations for all watcher types. See
994 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
995 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
996 the sources.
997
998 If you don't provide "signal" and "child" watchers than AnyEvent will
999 provide suitable (hopefully) replacements.
1000
1001 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
1002 terminal emulator uses the above line as-is. An interface isn't included
1003 in AnyEvent because it doesn't make sense outside the embedded
1004 interpreter inside *rxvt-unicode*, and it is updated and maintained as
1005 part of the *rxvt-unicode* distribution.
1006
1007 *rxvt-unicode* also cheats a bit by not providing blocking access to
1008 condition variables: code blocking while waiting for a condition will
1009 "die". This still works with most modules/usages, and blocking calls
1010 must not be done in an interactive application, so it makes sense.
914 1011
915EXAMPLE PROGRAM 1012EXAMPLE PROGRAM
916 The following program uses an I/O watcher to read data from STDIN, a 1013 The following program uses an I/O watcher to read data from STDIN, a
917 timer to display a message once per second, and a condition variable to 1014 timer to display a message once per second, and a condition variable to
918 quit the program when the user enters quit: 1015 quit the program when the user enters quit:
… …
1105 *destroy* is the time, in microseconds, that it takes to destroy a 1202 *destroy* is the time, in microseconds, that it takes to destroy a
1106 single watcher. 1203 single watcher.
1107 1204
1108 Results 1205 Results
1109 name watchers bytes create invoke destroy comment 1206 name watchers bytes create invoke destroy comment
1110 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1207 EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1111 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1208 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1112 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1209 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1113 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1210 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1114 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1211 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1115 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers 1212 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1116 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1213 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1117 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1214 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1118 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1215 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1119 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1216 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1120 1217
1121 Discussion 1218 Discussion
1122 The benchmark does *not* measure scalability of the event loop very 1219 The benchmark does *not* measure scalability of the event loop very
1123 well. For example, a select-based event loop (such as the pure perl one) 1220 well. For example, a select-based event loop (such as the pure perl one)
1124 can never compete with an event loop that uses epoll when the number of 1221 can never compete with an event loop that uses epoll when the number of
… …
1305 1402
1306 Summary 1403 Summary
1307 * C-based event loops perform very well with small number of watchers, 1404 * C-based event loops perform very well with small number of watchers,
1308 as the management overhead dominates. 1405 as the management overhead dominates.
1309 1406
1407 THE IO::Lambda BENCHMARK
1408 Recently I was told about the benchmark in the IO::Lambda manpage, which
1409 could be misinterpreted to make AnyEvent look bad. In fact, the
1410 benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
1411 better (which shouldn't come as a surprise to anybody). As such, the
1412 benchmark is fine, and shows that the AnyEvent backend from IO::Lambda
1413 isn't very optimal. But how would AnyEvent compare when used without the
1414 extra baggage? To explore this, I wrote the equivalent benchmark for
1415 AnyEvent.
1416
1417 The benchmark itself creates an echo-server, and then, for 500 times,
1418 connects to the echo server, sends a line, waits for the reply, and then
1419 creates the next connection. This is a rather bad benchmark, as it
1420 doesn't test the efficiency of the framework, but it is a benchmark
1421 nevertheless.
1422
1423 name runtime
1424 Lambda/select 0.330 sec
1425 + optimized 0.122 sec
1426 Lambda/AnyEvent 0.327 sec
1427 + optimized 0.138 sec
1428 Raw sockets/select 0.077 sec
1429 POE/select, components 0.662 sec
1430 POE/select, raw sockets 0.226 sec
1431 POE/select, optimized 0.404 sec
1432
1433 AnyEvent/select/nb 0.085 sec
1434 AnyEvent/EV/nb 0.068 sec
1435 +state machine 0.134 sec
1436
1437 The benchmark is also a bit unfair (my fault) - the IO::Lambda
1438 benchmarks actually make blocking connects and use 100% blocking I/O,
1439 defeating the purpose of an event-based solution. All of the newly
1440 written AnyEvent benchmarks use 100% non-blocking connects (using
1441 AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
1442 resolver), so AnyEvent is at a disadvantage here as non-blocking
1443 connects generally require a lot more bookkeeping and event handling
1444 than blocking connects (which involve a single syscall only).
1445
1446 The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
1447 offers similar expressive power as POE and IO::Lambda (using
1448 conventional Perl syntax), which means both the echo server and the
1449 client are 100% non-blocking w.r.t. I/O, further placing it at a
1450 disadvantage.
1451
1452 As you can see, AnyEvent + EV even beats the hand-optimised "raw sockets
1453 benchmark", while AnyEvent + its pure perl backend easily beats
1454 IO::Lambda and POE.
1455
1456 And even the 100% non-blocking version written using the high-level (and
1457 slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda, even
1458 thought it does all of DNS, tcp-connect and socket I/O in a non-blocking
1459 way.
1460
1461 The two AnyEvent benchmarks can be found as eg/ae0.pl and eg/ae2.pl in
1462 the AnyEvent distribution, the remaining benchmarks are part of the
1463 IO::lambda distribution and were used without any changes.
1464
1465SIGNALS
1466 AnyEvent currently installs handlers for these signals:
1467
1468 SIGCHLD
1469 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1470 emulation for event loops that do not support them natively. Also,
1471 some event loops install a similar handler.
1472
1473 SIGPIPE
1474 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1475 "undef" when AnyEvent gets loaded.
1476
1477 The rationale for this is that AnyEvent users usually do not really
1478 depend on SIGPIPE delivery (which is purely an optimisation for
1479 shell use, or badly-written programs), but "SIGPIPE" can cause
1480 spurious and rare program exits as a lot of people do not expect
1481 "SIGPIPE" when writing to some random socket.
1482
1483 The rationale for installing a no-op handler as opposed to ignoring
1484 it is that this way, the handler will be restored to defaults on
1485 exec.
1486
1487 Feel free to install your own handler, or reset it to defaults.
1488
1310FORK 1489FORK
1311 Most event libraries are not fork-safe. The ones who are usually are 1490 Most event libraries are not fork-safe. The ones who are usually are
1312 because they rely on inefficient but fork-safe "select" or "poll" calls. 1491 because they rely on inefficient but fork-safe "select" or "poll" calls.
1313 Only EV is fully fork-aware. 1492 Only EV is fully fork-aware.
1314 1493
… …
1325 1504
1326 You can make AnyEvent completely ignore this variable by deleting it 1505 You can make AnyEvent completely ignore this variable by deleting it
1327 before the first watcher gets created, e.g. with a "BEGIN" block: 1506 before the first watcher gets created, e.g. with a "BEGIN" block:
1328 1507
1329 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1508 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1330 1509
1331 use AnyEvent; 1510 use AnyEvent;
1332 1511
1333 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1512 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1334 be used to probe what backend is used and gain other information (which 1513 be used to probe what backend is used and gain other information (which
1335 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), 1514 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1336 and $ENV{PERL_ANYEGENT_STRICT}. 1515 and $ENV{PERL_ANYEVENT_STRICT}.
1337 1516
1338BUGS 1517BUGS
1339 Perl 5.8 has numerous memleaks that sometimes hit this module and are 1518 Perl 5.8 has numerous memleaks that sometimes hit this module and are
1340 hard to work around. If you suffer from memleaks, first upgrade to Perl 1519 hard to work around. If you suffer from memleaks, first upgrade to Perl
1341 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other 1520 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1342 annoying mamleaks, such as leaking on "map" and "grep" but it is usually 1521 annoying memleaks, such as leaking on "map" and "grep" but it is usually
1343 not as pronounced). 1522 not as pronounced).
1344 1523
1345SEE ALSO 1524SEE ALSO
1346 Utility functions: AnyEvent::Util. 1525 Utility functions: AnyEvent::Util.
1347 1526

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines