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Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC vs.
Revision 1.72 by root, Tue Dec 17 16:43:15 2013 UTC

262 262
263 Example 2: fire an event after 0.5 seconds, then roughly every second. 263 Example 2: fire an event after 0.5 seconds, then roughly every second.
264 264
265 my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { 265 my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
266 warn "timeout\n"; 266 warn "timeout\n";
267 }; 267 });
268 268
269 TIMING ISSUES 269 TIMING ISSUES
270 There are two ways to handle timers: based on real time (relative, "fire 270 There are two ways to handle timers: based on real time (relative, "fire
271 in 10 seconds") and based on wallclock time (absolute, "fire at 12 271 in 10 seconds") and based on wallclock time (absolute, "fire at 12
272 o'clock"). 272 o'clock").
403 will not restart syscalls (that includes Async::Interrupt and AnyEvent's 403 will not restart syscalls (that includes Async::Interrupt and AnyEvent's
404 pure perl implementation). 404 pure perl implementation).
405 405
406 Safe/Unsafe Signals 406 Safe/Unsafe Signals
407 Perl signals can be either "safe" (synchronous to opcode handling) or 407 Perl signals can be either "safe" (synchronous to opcode handling) or
408 "unsafe" (asynchronous) - the former might get delayed indefinitely, the 408 "unsafe" (asynchronous) - the former might delay signal delivery
409 latter might corrupt your memory. 409 indefinitely, the latter might corrupt your memory.
410 410
411 AnyEvent signal handlers are, in addition, synchronous to the event 411 AnyEvent signal handlers are, in addition, synchronous to the event
412 loop, i.e. they will not interrupt your running perl program but will 412 loop, i.e. they will not interrupt your running perl program but will
413 only be called as part of the normal event handling (just like timer, 413 only be called as part of the normal event handling (just like timer,
414 I/O etc. callbacks, too). 414 I/O etc. callbacks, too).
416 Signal Races, Delays and Workarounds 416 Signal Races, Delays and Workarounds
417 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching 417 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
418 callbacks to signals in a generic way, which is a pity, as you cannot do 418 callbacks to signals in a generic way, which is a pity, as you cannot do
419 race-free signal handling in perl, requiring C libraries for this. 419 race-free signal handling in perl, requiring C libraries for this.
420 AnyEvent will try to do its best, which means in some cases, signals 420 AnyEvent will try to do its best, which means in some cases, signals
421 will be delayed. The maximum time a signal might be delayed is specified 421 will be delayed. The maximum time a signal might be delayed is 10
422 in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable 422 seconds by default, but can be overriden via
423 can be changed only before the first signal watcher is created, and 423 $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
424 should be left alone otherwise. This variable determines how often 424 - see the "ENVIRONMENT VARIABLES" section for details.
425 AnyEvent polls for signals (in case a wake-up was missed). Higher values
426 will cause fewer spurious wake-ups, which is better for power and CPU
427 saving.
428 425
429 All these problems can be avoided by installing the optional 426 All these problems can be avoided by installing the optional
430 Async::Interrupt module, which works with most event loops. It will not 427 Async::Interrupt module, which works with most event loops. It will not
431 work with inherently broken event loops such as Event or Event::Lib (and 428 work with inherently broken event loops such as Event or Event::Lib (and
432 not with POE currently, as POE does its own workaround with one-second
433 latency). For those, you just have to suffer the delays. 429 not with POE currently). For those, you just have to suffer the delays.
434 430
435 CHILD PROCESS WATCHERS 431 CHILD PROCESS WATCHERS
436 $w = AnyEvent->child (pid => <process id>, cb => <callback>); 432 $w = AnyEvent->child (pid => <process id>, cb => <callback>);
437 433
438 You can also watch for a child process exit and catch its exit status. 434 You can also watch for a child process exit and catch its exit status.
473 469
474 Example: fork a process and wait for it 470 Example: fork a process and wait for it
475 471
476 my $done = AnyEvent->condvar; 472 my $done = AnyEvent->condvar;
477 473
474 # this forks and immediately calls exit in the child. this
475 # normally has all sorts of bad consequences for your parent,
476 # so take this as an example only. always fork and exec,
477 # or call POSIX::_exit, in real code.
478 my $pid = fork or exit 5; 478 my $pid = fork or exit 5;
479 479
480 my $w = AnyEvent->child ( 480 my $w = AnyEvent->child (
481 pid => $pid, 481 pid => $pid,
482 cb => sub { 482 cb => sub {
722 This works because for every event source (EOF on file handle), 722 This works because for every event source (EOF on file handle),
723 there is one call to "begin", so the condvar waits for all calls to 723 there is one call to "begin", so the condvar waits for all calls to
724 "end" before sending. 724 "end" before sending.
725 725
726 The ping example mentioned above is slightly more complicated, as 726 The ping example mentioned above is slightly more complicated, as
727 the there are results to be passwd back, and the number of tasks 727 the there are results to be passed back, and the number of tasks
728 that are begun can potentially be zero: 728 that are begun can potentially be zero:
729 729
730 my $cv = AnyEvent->condvar; 730 my $cv = AnyEvent->condvar;
731 731
732 my %result; 732 my %result;
740 }; 740 };
741 } 741 }
742 742
743 $cv->end; 743 $cv->end;
744 744
745 ...
746
747 my $results = $cv->recv;
748
745 This code fragment supposedly pings a number of hosts and calls 749 This code fragment supposedly pings a number of hosts and calls
746 "send" after results for all then have have been gathered - in any 750 "send" after results for all then have have been gathered - in any
747 order. To achieve this, the code issues a call to "begin" when it 751 order. To achieve this, the code issues a call to "begin" when it
748 starts each ping request and calls "end" when it has received some 752 starts each ping request and calls "end" when it has received some
749 result for it. Since "begin" and "end" only maintain a counter, the 753 result for it. Since "begin" and "end" only maintain a counter, the
778 In list context, all parameters passed to "send" will be returned, 782 In list context, all parameters passed to "send" will be returned,
779 in scalar context only the first one will be returned. 783 in scalar context only the first one will be returned.
780 784
781 Note that doing a blocking wait in a callback is not supported by 785 Note that doing a blocking wait in a callback is not supported by
782 any event loop, that is, recursive invocation of a blocking "->recv" 786 any event loop, that is, recursive invocation of a blocking "->recv"
783 is not allowed, and the "recv" call will "croak" if such a condition 787 is not allowed and the "recv" call will "croak" if such a condition
784 is detected. This condition can be slightly loosened by using 788 is detected. This requirement can be dropped by relying on
785 Coro::AnyEvent, which allows you to do a blocking "->recv" from any 789 Coro::AnyEvent , which allows you to do a blocking "->recv" from any
786 thread that doesn't run the event loop itself. 790 thread that doesn't run the event loop itself. Coro::AnyEvent is
791 loaded automatically when Coro is used with AnyEvent, so code does
792 not need to do anything special to take advantage of that: any code
793 that would normally block your program because it calls "recv", be
794 executed in an "async" thread instead without blocking other
795 threads.
787 796
788 Not all event models support a blocking wait - some die in that case 797 Not all event models support a blocking wait - some die in that case
789 (programs might want to do that to stay interactive), so *if you are 798 (programs might want to do that to stay interactive), so *if you are
790 using this from a module, never require a blocking wait*. Instead, 799 using this from a module, never require a blocking wait*. Instead,
791 let the caller decide whether the call will block or not (for 800 let the caller decide whether the call will block or not (for
839 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 848 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
840 AnyEvent::Impl::POE based on POE, very slow, some limitations. 849 AnyEvent::Impl::POE based on POE, very slow, some limitations.
841 AnyEvent::Impl::Irssi used when running within irssi. 850 AnyEvent::Impl::Irssi used when running within irssi.
842 AnyEvent::Impl::IOAsync based on IO::Async. 851 AnyEvent::Impl::IOAsync based on IO::Async.
843 AnyEvent::Impl::Cocoa based on Cocoa::EventLoop. 852 AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
844 AnyEvent::Impl::FLTK2 based on FLTK (fltk 2 binding). 853 AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
845 854
846 Backends with special needs. 855 Backends with special needs.
847 Qt requires the Qt::Application to be instantiated first, but will 856 Qt requires the Qt::Application to be instantiated first, but will
848 otherwise be picked up automatically. As long as the main program 857 otherwise be picked up automatically. As long as the main program
849 instantiates the application before any AnyEvent watchers are 858 instantiates the application before any AnyEvent watchers are
1005 if $some_error_condition; 1014 if $some_error_condition;
1006 1015
1007 AnyEvent::log $level, $msg[, @args] 1016 AnyEvent::log $level, $msg[, @args]
1008 Log the given $msg at the given $level. 1017 Log the given $msg at the given $level.
1009 1018
1019 If AnyEvent::Log is not loaded then this function makes a simple
1020 test to see whether the message will be logged. If the test succeeds
1010 Loads AnyEvent::Log on first use and calls "AnyEvent::Log::log" - 1021 it will load AnyEvent::Log and call "AnyEvent::Log::log" -
1011 consequently, look at the AnyEvent::Log documentation for details. 1022 consequently, look at the AnyEvent::Log documentation for details.
1023
1024 If the test fails it will simply return. Right now this happens when
1025 a numerical loglevel is used and it is larger than the level
1026 specified via $ENV{PERL_ANYEVENT_VERBOSE}.
1012 1027
1013 If you want to sprinkle loads of logging calls around your code, 1028 If you want to sprinkle loads of logging calls around your code,
1014 consider creating a logger callback with the "AnyEvent::Log::logger" 1029 consider creating a logger callback with the "AnyEvent::Log::logger"
1015 function. 1030 function, which can reduce typing, codesize and can reduce the
1031 logging overhead enourmously.
1016 1032
1017WHAT TO DO IN A MODULE 1033WHAT TO DO IN A MODULE
1018 As a module author, you should "use AnyEvent" and call AnyEvent methods 1034 As a module author, you should "use AnyEvent" and call AnyEvent methods
1019 freely, but you should not load a specific event module or rely on it. 1035 freely, but you should not load a specific event module or rely on it.
1020 1036
1079 modules come as part of AnyEvent, the others are available via CPAN (see 1095 modules come as part of AnyEvent, the others are available via CPAN (see
1080 <http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer 1096 <http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
1081 non-exhaustive list), and the list is heavily biased towards modules of 1097 non-exhaustive list), and the list is heavily biased towards modules of
1082 the AnyEvent author himself :) 1098 the AnyEvent author himself :)
1083 1099
1084 AnyEvent::Util 1100 AnyEvent::Util (part of the AnyEvent distribution)
1085 Contains various utility functions that replace often-used blocking 1101 Contains various utility functions that replace often-used blocking
1086 functions such as "inet_aton" with event/callback-based versions. 1102 functions such as "inet_aton" with event/callback-based versions.
1087 1103
1088 AnyEvent::Socket 1104 AnyEvent::Socket (part of the AnyEvent distribution)
1089 Provides various utility functions for (internet protocol) sockets, 1105 Provides various utility functions for (internet protocol) sockets,
1090 addresses and name resolution. Also functions to create non-blocking 1106 addresses and name resolution. Also functions to create non-blocking
1091 tcp connections or tcp servers, with IPv6 and SRV record support and 1107 tcp connections or tcp servers, with IPv6 and SRV record support and
1092 more. 1108 more.
1093 1109
1094 AnyEvent::Handle 1110 AnyEvent::Handle (part of the AnyEvent distribution)
1095 Provide read and write buffers, manages watchers for reads and 1111 Provide read and write buffers, manages watchers for reads and
1096 writes, supports raw and formatted I/O, I/O queued and fully 1112 writes, supports raw and formatted I/O, I/O queued and fully
1097 transparent and non-blocking SSL/TLS (via AnyEvent::TLS). 1113 transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
1098 1114
1099 AnyEvent::DNS 1115 AnyEvent::DNS (part of the AnyEvent distribution)
1100 Provides rich asynchronous DNS resolver capabilities. 1116 Provides rich asynchronous DNS resolver capabilities.
1101 1117
1102 AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, 1118 AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
1103 AnyEvent::IGS, AnyEvent::FCP 1119 AnyEvent::IGS, AnyEvent::FCP
1104 Implement event-based interfaces to the protocols of the same name 1120 Implement event-based interfaces to the protocols of the same name
1105 (for the curious, IGS is the International Go Server and FCP is the 1121 (for the curious, IGS is the International Go Server and FCP is the
1106 Freenet Client Protocol). 1122 Freenet Client Protocol).
1107 1123
1108 AnyEvent::Handle::UDP 1124 AnyEvent::AIO (part of the AnyEvent distribution)
1109 Here be danger!
1110
1111 As Pauli would put it, "Not only is it not right, it's not even
1112 wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
1113 most notably its use of a stream-based API with a protocol that
1114 isn't streamable, that the only way to improve it is to delete it.
1115
1116 It features data corruption (but typically only under load) and
1117 general confusion. On top, the author is not only clueless about UDP
1118 but also fact-resistant - some gems of his understanding: "connect
1119 doesn't work with UDP", "UDP packets are not IP packets", "UDP only
1120 has datagrams, not packets", "I don't need to implement proper error
1121 checking as UDP doesn't support error checking" and so on - he
1122 doesn't even understand what's wrong with his module when it is
1123 explained to him.
1124
1125 AnyEvent::DBI
1126 Executes DBI requests asynchronously in a proxy process for you,
1127 notifying you in an event-based way when the operation is finished.
1128
1129 AnyEvent::AIO
1130 Truly asynchronous (as opposed to non-blocking) I/O, should be in 1125 Truly asynchronous (as opposed to non-blocking) I/O, should be in
1131 the toolbox of every event programmer. AnyEvent::AIO transparently 1126 the toolbox of every event programmer. AnyEvent::AIO transparently
1132 fuses IO::AIO and AnyEvent together, giving AnyEvent access to 1127 fuses IO::AIO and AnyEvent together, giving AnyEvent access to
1133 event-based file I/O, and much more. 1128 event-based file I/O, and much more.
1134 1129
1130 AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
1131 AnyEvent::Fork::Remote
1132 These let you safely fork new subprocesses, either locally or
1133 remotely (e.g.v ia ssh), using some RPC protocol or not, without the
1134 limitations normally imposed by fork (AnyEvent works fine for
1135 example). Dynamically-resized worker pools are obviously included as
1136 well.
1137
1138 And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
1139 just to exec external programs can easily beat using "fork" and
1140 "exec" (or even "system") in most programs.
1141
1142 AnyEvent::Filesys::Notify
1143 AnyEvent is good for non-blocking stuff, but it can't detect file or
1144 path changes (e.g. "watch this directory for new files", "watch this
1145 file for changes"). The AnyEvent::Filesys::Notify module promises to
1146 do just that in a portbale fashion, supporting inotify on GNU/Linux
1147 and some weird, without doubt broken, stuff on OS X to monitor
1148 files. It can fall back to blocking scans at regular intervals
1149 transparently on other platforms, so it's about as portable as it
1150 gets.
1151
1152 (I haven't used it myself, but it seems the biggest problem with it
1153 is it quite bad performance).
1154
1135 AnyEvent::HTTPD 1155 AnyEvent::DBI
1136 A simple embedded webserver. 1156 Executes DBI requests asynchronously in a proxy process for you,
1157 notifying you in an event-based way when the operation is finished.
1137 1158
1138 AnyEvent::FastPing 1159 AnyEvent::FastPing
1139 The fastest ping in the west. 1160 The fastest ping in the west.
1140 1161
1141 Coro 1162 Coro
1142 Has special support for AnyEvent via Coro::AnyEvent. 1163 Has special support for AnyEvent via Coro::AnyEvent, which allows
1164 you to simply invert the flow control - don't call us, we will call
1165 you:
1166
1167 async {
1168 Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
1169 print "5 seconds later!\n";
1170
1171 Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
1172 my $line = <STDIN>; # works for ttys
1173
1174 AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
1175 my ($body, $hdr) = Coro::rouse_wait;
1176 };
1143 1177
1144SIMPLIFIED AE API 1178SIMPLIFIED AE API
1145 Starting with version 5.0, AnyEvent officially supports a second, much 1179 Starting with version 5.0, AnyEvent officially supports a second, much
1146 simpler, API that is designed to reduce the calling, typing and memory 1180 simpler, API that is designed to reduce the calling, typing and memory
1147 overhead by using function call syntax and a fixed number of parameters. 1181 overhead by using function call syntax and a fixed number of parameters.
1163 The pure perl event loop simply re-throws the exception (usually within 1197 The pure perl event loop simply re-throws the exception (usually within
1164 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", 1198 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1165 Glib uses "install_exception_handler" and so on. 1199 Glib uses "install_exception_handler" and so on.
1166 1200
1167ENVIRONMENT VARIABLES 1201ENVIRONMENT VARIABLES
1168 The following environment variables are used by this module or its 1202 AnyEvent supports a number of environment variables that tune the
1169 submodules. 1203 runtime behaviour. They are usually evaluated when AnyEvent is loaded,
1204 initialised, or a submodule that uses them is loaded. Many of them also
1205 cause AnyEvent to load additional modules - for example,
1206 "PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
1207 loaded.
1170 1208
1171 Note that AnyEvent will remove *all* environment variables starting with 1209 All the environment variables documented here start with
1172 "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is 1210 "PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1173 enabled. 1211 Other modules are encouraged (but by no means required) to use
1212 "PERL_ANYEVENT_SUBMODULE" if they have registered the
1213 AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
1214 AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
1215 should not access env variables starting with "AE_", see below).
1216
1217 All variables can also be set via the "AE_" prefix, that is, instead of
1218 setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
1219 there is a clash btween anyevent and another program that uses
1220 "AE_something" you can set the corresponding "PERL_ANYEVENT_something"
1221 variable to the empty string, as those variables take precedence.
1222
1223 When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
1224 their "PERL_ANYEVENT_xxx" counterpart unless that variable already
1225 exists. If taint mode is on, then AnyEvent will remove *all* environment
1226 variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
1227 "undef" or the empty string, if the corresaponding "AE_" variable is
1228 set).
1229
1230 The exact algorithm is currently:
1231
1232 1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
1233 2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
1234 3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
1235
1236 This ensures that child processes will not see the "AE_" variables.
1237
1238 The following environment variables are currently known to AnyEvent:
1174 1239
1175 "PERL_ANYEVENT_VERBOSE" 1240 "PERL_ANYEVENT_VERBOSE"
1176 By default, AnyEvent will be completely silent except in fatal 1241 By default, AnyEvent will log messages with loglevel 4 ("error") or
1177 conditions. You can set this environment variable to make AnyEvent 1242 higher (see AnyEvent::Log). You can set this environment variable to
1178 more talkative. 1243 a numerical loglevel to make AnyEvent more (or less) talkative.
1179 1244
1245 If you want to do more than just set the global logging level you
1246 should have a look at "PERL_ANYEVENT_LOG", which allows much more
1247 complex specifications.
1248
1249 When set to 0 ("off"), then no messages whatsoever will be logged
1250 with everything else at defaults.
1251
1180 When set to 5 or higher, causes AnyEvent to warn about unexpected 1252 When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1181 conditions, such as not being able to load the event model specified 1253 conditions, such as not being able to load the event model specified
1182 by "PERL_ANYEVENT_MODEL". 1254 by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
1255 - this is the minimum recommended level for use during development.
1183 1256
1184 When set to 7 or higher, cause AnyEvent to report to STDERR which 1257 When set to 7 or higher (info), AnyEvent reports which event model
1185 event model it chooses. 1258 it chooses.
1186 1259
1187 When set to 8 or higher, then AnyEvent will report extra information 1260 When set to 8 or higher (debug), then AnyEvent will report extra
1188 on which optional modules it loads and how it implements certain 1261 information on which optional modules it loads and how it implements
1189 features. 1262 certain features.
1263
1264 "PERL_ANYEVENT_LOG"
1265 Accepts rather complex logging specifications. For example, you
1266 could log all "debug" messages of some module to stderr, warnings
1267 and above to stderr, and errors and above to syslog, with:
1268
1269 PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
1270
1271 For the rather extensive details, see AnyEvent::Log.
1272
1273 This variable is evaluated when AnyEvent (or AnyEvent::Log) is
1274 loaded, so will take effect even before AnyEvent has initialised
1275 itself.
1276
1277 Note that specifying this environment variable causes the
1278 AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
1279 does not, so only using the latter saves a few hundred kB of memory
1280 unless a module explicitly needs the extra features of
1281 AnyEvent::Log.
1190 1282
1191 "PERL_ANYEVENT_STRICT" 1283 "PERL_ANYEVENT_STRICT"
1192 AnyEvent does not do much argument checking by default, as thorough 1284 AnyEvent does not do much argument checking by default, as thorough
1193 argument checking is very costly. Setting this variable to a true 1285 argument checking is very costly. Setting this variable to a true
1194 value will cause AnyEvent to load "AnyEvent::Strict" and then to 1286 value will cause AnyEvent to load "AnyEvent::Strict" and then to
1201 is definitely recommended to keep it off in production. Keeping 1293 is definitely recommended to keep it off in production. Keeping
1202 "PERL_ANYEVENT_STRICT=1" in your environment while developing 1294 "PERL_ANYEVENT_STRICT=1" in your environment while developing
1203 programs can be very useful, however. 1295 programs can be very useful, however.
1204 1296
1205 "PERL_ANYEVENT_DEBUG_SHELL" 1297 "PERL_ANYEVENT_DEBUG_SHELL"
1206 If this env variable is set, then its contents will be interpreted 1298 If this env variable is nonempty, then its contents will be
1207 by "AnyEvent::Socket::parse_hostport" (after replacing every 1299 interpreted by "AnyEvent::Socket::parse_hostport" and
1208 occurance of $$ by the process pid) and an "AnyEvent::Debug::shell" 1300 "AnyEvent::Debug::shell" (after replacing every occurance of $$ by
1209 is bound on that port. The shell object is saved in 1301 the process pid). The shell object is saved in
1210 $AnyEvent::Debug::SHELL. 1302 $AnyEvent::Debug::SHELL.
1211 1303
1212 This takes place when the first watcher is created. 1304 This happens when the first watcher is created.
1213 1305
1214 For example, to bind a debug shell on a unix domain socket in 1306 For example, to bind a debug shell on a unix domain socket in
1215 /tmp/debug<pid>.sock, you could use this: 1307 /tmp/debug<pid>.sock, you could use this:
1216 1308
1217 PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog 1309 PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
1310 # connect with e.g.: socat readline /tmp/debug123.sock
1218 1311
1312 Or to bind to tcp port 4545 on localhost:
1313
1314 PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
1315 # connect with e.g.: telnet localhost 4545
1316
1219 Note that creating sockets in /tmp is very unsafe on multiuser 1317 Note that creating sockets in /tmp or on localhost is very unsafe on
1220 systems. 1318 multiuser systems.
1221 1319
1222 "PERL_ANYEVENT_DEBUG_WRAP" 1320 "PERL_ANYEVENT_DEBUG_WRAP"
1223 Can be set to 0, 1 or 2 and enables wrapping of all watchers for 1321 Can be set to 0, 1 or 2 and enables wrapping of all watchers for
1224 debugging purposes. See "AnyEvent::Debug::wrap" for details. 1322 debugging purposes. See "AnyEvent::Debug::wrap" for details.
1225 1323
1240 1338
1241 For example, to force the pure perl model (AnyEvent::Loop::Perl) you 1339 For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1242 could start your program like this: 1340 could start your program like this:
1243 1341
1244 PERL_ANYEVENT_MODEL=Perl perl ... 1342 PERL_ANYEVENT_MODEL=Perl perl ...
1343
1344 "PERL_ANYEVENT_IO_MODEL"
1345 The current file I/O model - see AnyEvent::IO for more info.
1346
1347 At the moment, only "Perl" (small, pure-perl, synchronous) and
1348 "IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
1349 if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1245 1350
1246 "PERL_ANYEVENT_PROTOCOLS" 1351 "PERL_ANYEVENT_PROTOCOLS"
1247 Used by both AnyEvent::DNS and AnyEvent::Socket to determine 1352 Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1248 preferences for IPv4 or IPv6. The default is unspecified (and might 1353 preferences for IPv4 or IPv6. The default is unspecified (and might
1249 change, or be the result of auto probing). 1354 change, or be the result of auto probing).
1263 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to 1368 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1264 resolve or contact IPv6 addresses. 1369 resolve or contact IPv6 addresses.
1265 "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but 1370 "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1266 prefer IPv6 over IPv4. 1371 prefer IPv6 over IPv4.
1267 1372
1373 "PERL_ANYEVENT_HOSTS"
1374 This variable, if specified, overrides the /etc/hosts file used by
1375 AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
1376 read from that file instead.
1377
1268 "PERL_ANYEVENT_EDNS0" 1378 "PERL_ANYEVENT_EDNS0"
1269 Used by AnyEvent::DNS to decide whether to use the EDNS0 extension 1379 Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1270 for DNS. This extension is generally useful to reduce DNS traffic, 1380 for DNS. This extension is generally useful to reduce DNS traffic,
1271 but some (broken) firewalls drop such DNS packets, which is why it 1381 especially when DNSSEC is involved, but some (broken) firewalls drop
1272 is off by default. 1382 such DNS packets, which is why it is off by default.
1273 1383
1274 Setting this variable to 1 will cause AnyEvent::DNS to announce 1384 Setting this variable to 1 will cause AnyEvent::DNS to announce
1275 EDNS0 in its DNS requests. 1385 EDNS0 in its DNS requests.
1276 1386
1277 "PERL_ANYEVENT_MAX_FORKS" 1387 "PERL_ANYEVENT_MAX_FORKS"
1281 "PERL_ANYEVENT_MAX_OUTSTANDING_DNS" 1391 "PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1282 The default value for the "max_outstanding" parameter for the 1392 The default value for the "max_outstanding" parameter for the
1283 default DNS resolver - this is the maximum number of parallel DNS 1393 default DNS resolver - this is the maximum number of parallel DNS
1284 requests that are sent to the DNS server. 1394 requests that are sent to the DNS server.
1285 1395
1396 "PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
1397 Perl has inherently racy signal handling (you can basically choose
1398 between losing signals and memory corruption) - pure perl event
1399 loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
1400 available) therefore have to poll regularly to avoid losing signals.
1401
1402 Some event loops are racy, but don't poll regularly, and some event
1403 loops are written in C but are still racy. For those event loops,
1404 AnyEvent installs a timer that regularly wakes up the event loop.
1405
1406 By default, the interval for this timer is 10 seconds, but you can
1407 override this delay with this environment variable (or by setting
1408 the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
1409 watchers).
1410
1411 Lower values increase CPU (and energy) usage, higher values can
1412 introduce long delays when reaping children or waiting for signals.
1413
1414 The AnyEvent::Async module, if available, will be used to avoid this
1415 polling (with most event loops).
1416
1286 "PERL_ANYEVENT_RESOLV_CONF" 1417 "PERL_ANYEVENT_RESOLV_CONF"
1287 The file to use instead of /etc/resolv.conf (or OS-specific 1418 The absolute path to a resolv.conf-style file to use instead of
1288 configuration) in the default resolver. When set to the empty 1419 /etc/resolv.conf (or the OS-specific configuration) in the default
1289 string, no default config will be used. 1420 resolver, or the empty string to select the default configuration.
1290 1421
1291 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". 1422 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1292 When neither "ca_file" nor "ca_path" was specified during 1423 When neither "ca_file" nor "ca_path" was specified during
1293 AnyEvent::TLS context creation, and either of these environment 1424 AnyEvent::TLS context creation, and either of these environment
1294 variables exist, they will be used to specify CA certificate 1425 variables are nonempty, they will be used to specify CA certificate
1295 locations instead of a system-dependent default. 1426 locations instead of a system-dependent default.
1296 1427
1297 "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT" 1428 "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1298 When these are set to 1, then the respective modules are not loaded. 1429 When these are set to 1, then the respective modules are not loaded.
1299 Mostly good for testing AnyEvent itself. 1430 Mostly good for testing AnyEvent itself.
1892 This module is part of perl since release 5.008. It will be used 2023 This module is part of perl since release 5.008. It will be used
1893 when the chosen event library does not come with a timing source of 2024 when the chosen event library does not come with a timing source of
1894 its own. The pure-perl event loop (AnyEvent::Loop) will additionally 2025 its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1895 load it to try to use a monotonic clock for timing stability. 2026 load it to try to use a monotonic clock for timing stability.
1896 2027
2028 AnyEvent::AIO (and IO::AIO)
2029 The default implementation of AnyEvent::IO is to do I/O
2030 synchronously, stopping programs while they access the disk, which
2031 is fine for a lot of programs.
2032
2033 Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
2034 switch to a true asynchronous implementation, so event processing
2035 can continue even while waiting for disk I/O.
2036
1897FORK 2037FORK
1898 Most event libraries are not fork-safe. The ones who are usually are 2038 Most event libraries are not fork-safe. The ones who are usually are
1899 because they rely on inefficient but fork-safe "select" or "poll" calls 2039 because they rely on inefficient but fork-safe "select" or "poll" calls
1900 - higher performance APIs such as BSD's kqueue or the dreaded Linux 2040 - higher performance APIs such as BSD's kqueue or the dreaded Linux
1901 epoll are usually badly thought-out hacks that are incompatible with 2041 epoll are usually badly thought-out hacks that are incompatible with
1908 usually happens when the first AnyEvent watcher is created, or the 2048 usually happens when the first AnyEvent watcher is created, or the
1909 library is loaded). 2049 library is loaded).
1910 2050
1911 If you have to fork, you must either do so *before* creating your first 2051 If you have to fork, you must either do so *before* creating your first
1912 watcher OR you must not use AnyEvent at all in the child OR you must do 2052 watcher OR you must not use AnyEvent at all in the child OR you must do
1913 something completely out of the scope of AnyEvent. 2053 something completely out of the scope of AnyEvent (see below).
1914 2054
1915 The problem of doing event processing in the parent *and* the child is 2055 The problem of doing event processing in the parent *and* the child is
1916 much more complicated: even for backends that *are* fork-aware or 2056 much more complicated: even for backends that *are* fork-aware or
1917 fork-safe, their behaviour is not usually what you want: fork clones all 2057 fork-safe, their behaviour is not usually what you want: fork clones all
1918 watchers, that means all timers, I/O watchers etc. are active in both 2058 watchers, that means all timers, I/O watchers etc. are active in both
1919 parent and child, which is almost never what you want. USing "exec" to 2059 parent and child, which is almost never what you want. Using "exec" to
1920 start worker children from some kind of manage rprocess is usually 2060 start worker children from some kind of manage prrocess is usually
1921 preferred, because it is much easier and cleaner, at the expense of 2061 preferred, because it is much easier and cleaner, at the expense of
1922 having to have another binary. 2062 having to have another binary.
2063
2064 In addition to logical problems with fork, there are also implementation
2065 problems. For example, on POSIX systems, you cannot fork at all in Perl
2066 code if a thread (I am talking of pthreads here) was ever created in the
2067 process, and this is just the tip of the iceberg. In general, using fork
2068 from Perl is difficult, and attempting to use fork without an exec to
2069 implement some kind of parallel processing is almost certainly doomed.
2070
2071 To safely fork and exec, you should use a module such as Proc::FastSpawn
2072 that let's you safely fork and exec new processes.
2073
2074 If you want to do multiprocessing using processes, you can look at the
2075 AnyEvent::Fork module (and some related modules such as
2076 AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
2077 This module allows you to safely create subprocesses without any
2078 limitations - you can use X11 toolkits or AnyEvent in the children
2079 created by AnyEvent::Fork safely and without any special precautions.
1923 2080
1924SECURITY CONSIDERATIONS 2081SECURITY CONSIDERATIONS
1925 AnyEvent can be forced to load any event model via 2082 AnyEvent can be forced to load any event model via
1926 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used 2083 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1927 to execute arbitrary code or directly gain access, it can easily be used 2084 to execute arbitrary code or directly gain access, it can easily be used
1972 AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK. 2129 AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
1973 2130
1974 Non-blocking handles, pipes, stream sockets, TCP clients and servers: 2131 Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1975 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. 2132 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1976 2133
2134 Asynchronous File I/O: AnyEvent::IO.
2135
1977 Asynchronous DNS: AnyEvent::DNS. 2136 Asynchronous DNS: AnyEvent::DNS.
1978 2137
1979 Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event. 2138 Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1980 2139
1981 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC, 2140 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1982 AnyEvent::HTTP. 2141 AnyEvent::HTTP.
1983 2142
1984AUTHOR 2143AUTHOR
1985 Marc Lehmann <schmorp@schmorp.de> 2144 Marc Lehmann <schmorp@schmorp.de>
1986 http://home.schmorp.de/ 2145 http://anyevent.schmorp.de
1987 2146

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