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 1.36 by root, Fri Mar 27 10:49:50 2009 UTC

… …
132 These watchers are normal Perl objects with normal Perl lifetime. After 132 These watchers are normal Perl objects with normal Perl lifetime. After
133 creating a watcher it will immediately "watch" for events and invoke the 133 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 134 callback when the event occurs (of course, only when the event model is
135 in control). 135 in control).
136 136
137 Note that callbacks must not permanently change global variables
138 potentially in use by the event loop (such as $_ or $[) and that
139 callbacks must not "die". The former is good programming practise in
140 Perl and the latter stems from the fact that exception handling differs
141 widely between event loops.
142
137 To disable the watcher you have to destroy it (e.g. by setting the 143 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 144 variable you store it in to "undef" or otherwise deleting all references
139 to it). 145 to it).
140 146
141 All watchers are created by calling a method on the "AnyEvent" class. 147 All watchers are created by calling a method on the "AnyEvent" class.
… …
156 162
157 I/O WATCHERS 163 I/O WATCHERS
158 You can create an I/O watcher by calling the "AnyEvent->io" method with 164 You can create an I/O watcher by calling the "AnyEvent->io" method with
159 the following mandatory key-value pairs as arguments: 165 the following mandatory key-value pairs as arguments:
160 166
161 "fh" the Perl *file handle* (*not* file descriptor) to watch for events 167 "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). 168 events (AnyEvent might or might not keep a reference to this file
169 handle). Note that only file handles pointing to things for which
170 non-blocking operation makes sense are allowed. This includes sockets,
171 most character devices, pipes, fifos and so on, but not for example
172 files or block devices.
173
163 "poll" must be a string that is either "r" or "w", which creates a 174 "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" 175 watcher waiting for "r"eadable or "w"ritable events, respectively.
176
165 is the callback to invoke each time the file handle becomes ready. 177 "cb" is the callback to invoke each time the file handle becomes ready.
166 178
167 Although the callback might get passed parameters, their value and 179 Although the callback might get passed parameters, their value and
168 presence is undefined and you cannot rely on them. Portable AnyEvent 180 presence is undefined and you cannot rely on them. Portable AnyEvent
169 callbacks cannot use arguments passed to I/O watcher callbacks. 181 callbacks cannot use arguments passed to I/O watcher callbacks.
170 182
… …
330 342
331 CHILD PROCESS WATCHERS 343 CHILD PROCESS WATCHERS
332 You can also watch on a child process exit and catch its exit status. 344 You can also watch on a child process exit and catch its exit status.
333 345
334 The child process is specified by the "pid" argument (if set to 0, it 346 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 347 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 348 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 349 on any trace events (stopped/continued).
338 and exit status (as returned by waitpid), so unlike other watcher types, 350
339 you *can* rely on child watcher callback arguments. 351 The callback will be called with the pid and exit status (as returned by
352 waitpid), so unlike other watcher types, you *can* rely on child watcher
353 callback arguments.
354
355 This watcher type works by installing a signal handler for "SIGCHLD",
356 and since it cannot be shared, nothing else should use SIGCHLD or reap
357 random child processes (waiting for specific child processes, e.g.
358 inside "system", is just fine).
340 359
341 There is a slight catch to child watchers, however: you usually start 360 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 361 them *after* the child process was created, and this means the process
343 could have exited already (and no SIGCHLD will be sent anymore). 362 could have exited already (and no SIGCHLD will be sent anymore).
344 363
… …
770 789
771 AnyEvent::IGS 790 AnyEvent::IGS
772 A non-blocking interface to the Internet Go Server protocol (used by 791 A non-blocking interface to the Internet Go Server protocol (used by
773 App::IGS). 792 App::IGS).
774 793
794 AnyEvent::IRC
795 AnyEvent based IRC client module family (replacing the older
775 Net::IRC3 796 Net::IRC3).
776 AnyEvent based IRC client module family.
777 797
778 Net::XMPP2 798 Net::XMPP2
779 AnyEvent based XMPP (Jabber protocol) module family. 799 AnyEvent based XMPP (Jabber protocol) module family.
780 800
781 Net::FCP 801 Net::FCP
… …
790 810
791 IO::Lambda 811 IO::Lambda
792 The lambda approach to I/O - don't ask, look there. Can use 812 The lambda approach to I/O - don't ask, look there. Can use
793 AnyEvent. 813 AnyEvent.
794 814
795SUPPLYING YOUR OWN EVENT MODEL INTERFACE 815ERROR AND EXCEPTION HANDLING
796 This is an advanced topic that you do not normally need to use AnyEvent 816 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 817 caller to do that if required. The AnyEvent::Strict module (see also the
798 to provide AnyEvent compatibility. 818 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
819 checking of all AnyEvent methods, however, which is highly useful during
820 development.
799 821
800 If you need to support another event library which isn't directly 822 As for exception handling (i.e. runtime errors and exceptions thrown
801 supported by AnyEvent, you can supply your own interface to it by 823 while executing a callback), this is not only highly event-loop
802 pushing, before the first watcher gets created, the package name of the 824 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 825 job of the main program.
804 @AnyEvent::REGISTRY. You can do that before and even without loading
805 AnyEvent, so it is reasonably cheap.
806 826
807 Example: 827 The pure perl event loop simply re-throws the exception (usually within
808 828 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
809 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 829 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.
837 830
838ENVIRONMENT VARIABLES 831ENVIRONMENT VARIABLES
839 The following environment variables are used by this module: 832 The following environment variables are used by this module or its
833 submodules:
840 834
841 "PERL_ANYEVENT_VERBOSE" 835 "PERL_ANYEVENT_VERBOSE"
842 By default, AnyEvent will be completely silent except in fatal 836 By default, AnyEvent will be completely silent except in fatal
843 conditions. You can set this environment variable to make AnyEvent 837 conditions. You can set this environment variable to make AnyEvent
844 more talkative. 838 more talkative.
… …
857 thoroughly check the arguments passed to most method calls. If it 851 thoroughly check the arguments passed to most method calls. If it
858 finds any problems it will croak. 852 finds any problems it will croak.
859 853
860 In other words, enables "strict" mode. 854 In other words, enables "strict" mode.
861 855
862 Unlike "use strict" it is definitely recommended ot keep it off in 856 Unlike "use strict", it is definitely recommended ot keep it off in
863 production. 857 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
858 while developing programs can be very useful, however.
864 859
865 "PERL_ANYEVENT_MODEL" 860 "PERL_ANYEVENT_MODEL"
866 This can be used to specify the event model to be used by AnyEvent, 861 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 862 before auto detection and -probing kicks in. It must be a string
868 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 863 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
… …
887 mentioned will be used, and preference will be given to protocols 882 mentioned will be used, and preference will be given to protocols
888 mentioned earlier in the list. 883 mentioned earlier in the list.
889 884
890 This variable can effectively be used for denial-of-service attacks 885 This variable can effectively be used for denial-of-service attacks
891 against local programs (e.g. when setuid), although the impact is 886 against local programs (e.g. when setuid), although the impact is
892 likely small, as the program has to handle connection errors 887 likely small, as the program has to handle conenction and other
893 already- 888 failures anyways.
894 889
895 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over 890 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
896 IPv6, but support both and try to use both. 891 IPv6, but support both and try to use both.
897 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to 892 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
898 resolve or contact IPv6 addresses. 893 resolve or contact IPv6 addresses.
… …
909 EDNS0 in its DNS requests. 904 EDNS0 in its DNS requests.
910 905
911 "PERL_ANYEVENT_MAX_FORKS" 906 "PERL_ANYEVENT_MAX_FORKS"
912 The maximum number of child processes that 907 The maximum number of child processes that
913 "AnyEvent::Util::fork_call" will create in parallel. 908 "AnyEvent::Util::fork_call" will create in parallel.
909
910SUPPLYING YOUR OWN EVENT MODEL INTERFACE
911 This is an advanced topic that you do not normally need to use AnyEvent
912 in a module. This section is only of use to event loop authors who want
913 to provide AnyEvent compatibility.
914
915 If you need to support another event library which isn't directly
916 supported by AnyEvent, you can supply your own interface to it by
917 pushing, before the first watcher gets created, the package name of the
918 event module and the package name of the interface to use onto
919 @AnyEvent::REGISTRY. You can do that before and even without loading
920 AnyEvent, so it is reasonably cheap.
921
922 Example:
923
924 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
925
926 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
927 package/class when it finds the "urxvt" package/module is already
928 loaded.
929
930 When AnyEvent is loaded and asked to find a suitable event model, it
931 will first check for the presence of urxvt by trying to "use" the
932 "urxvt::anyevent" module.
933
934 The class should provide implementations for all watcher types. See
935 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
936 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
937 the sources.
938
939 If you don't provide "signal" and "child" watchers than AnyEvent will
940 provide suitable (hopefully) replacements.
941
942 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
943 terminal emulator uses the above line as-is. An interface isn't included
944 in AnyEvent because it doesn't make sense outside the embedded
945 interpreter inside *rxvt-unicode*, and it is updated and maintained as
946 part of the *rxvt-unicode* distribution.
947
948 *rxvt-unicode* also cheats a bit by not providing blocking access to
949 condition variables: code blocking while waiting for a condition will
950 "die". This still works with most modules/usages, and blocking calls
951 must not be done in an interactive application, so it makes sense.
914 952
915EXAMPLE PROGRAM 953EXAMPLE PROGRAM
916 The following program uses an I/O watcher to read data from STDIN, a 954 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 955 timer to display a message once per second, and a condition variable to
918 quit the program when the user enters quit: 956 quit the program when the user enters quit:
… …
1105 *destroy* is the time, in microseconds, that it takes to destroy a 1143 *destroy* is the time, in microseconds, that it takes to destroy a
1106 single watcher. 1144 single watcher.
1107 1145
1108 Results 1146 Results
1109 name watchers bytes create invoke destroy comment 1147 name watchers bytes create invoke destroy comment
1110 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1148 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 1149 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 1150 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 1151 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 1152 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 1153 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 1154 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 1155 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 1156 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 1157 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1120 1158
1121 Discussion 1159 Discussion
1122 The benchmark does *not* measure scalability of the event loop very 1160 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) 1161 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 1162 can never compete with an event loop that uses epoll when the number of
… …
1305 1343
1306 Summary 1344 Summary
1307 * C-based event loops perform very well with small number of watchers, 1345 * C-based event loops perform very well with small number of watchers,
1308 as the management overhead dominates. 1346 as the management overhead dominates.
1309 1347
1348SIGNALS
1349 AnyEvent currently installs handlers for these signals:
1350
1351 SIGCHLD
1352 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1353 emulation for event loops that do not support them natively. Also,
1354 some event loops install a similar handler.
1355
1356 SIGPIPE
1357 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1358 "undef" when AnyEvent gets loaded.
1359
1360 The rationale for this is that AnyEvent users usually do not really
1361 depend on SIGPIPE delivery (which is purely an optimisation for
1362 shell use, or badly-written programs), but "SIGPIPE" can cause
1363 spurious and rare program exits as a lot of people do not expect
1364 "SIGPIPE" when writing to some random socket.
1365
1366 The rationale for installing a no-op handler as opposed to ignoring
1367 it is that this way, the handler will be restored to defaults on
1368 exec.
1369
1370 Feel free to install your own handler, or reset it to defaults.
1371
1310FORK 1372FORK
1311 Most event libraries are not fork-safe. The ones who are usually are 1373 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. 1374 because they rely on inefficient but fork-safe "select" or "poll" calls.
1313 Only EV is fully fork-aware. 1375 Only EV is fully fork-aware.
1314 1376
… …
1337 1399
1338BUGS 1400BUGS
1339 Perl 5.8 has numerous memleaks that sometimes hit this module and are 1401 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 1402 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 1403 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 1404 annoying memleaks, such as leaking on "map" and "grep" but it is usually
1343 not as pronounced). 1405 not as pronounced).
1344 1406
1345SEE ALSO 1407SEE ALSO
1346 Utility functions: AnyEvent::Util. 1408 Utility functions: AnyEvent::Util.
1347 1409

Diff Legend

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