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16 }); 16 });
17 17
18 my $w = AnyEvent->condvar; # stores whether a condition was flagged 18 my $w = AnyEvent->condvar; # stores whether a condition was flagged
19 $w->send; # wake up current and all future recv's 19 $w->send; # wake up current and all future recv's
20 $w->recv; # enters "main loop" till $condvar gets ->send 20 $w->recv; # enters "main loop" till $condvar gets ->send
21
22INTRODUCTION/TUTORIAL
23 This manpage is mainly a reference manual. If you are interested in a
24 tutorial or some gentle introduction, have a look at the AnyEvent::Intro
25 manpage.
21 26
22WHY YOU SHOULD USE THIS MODULE (OR NOT) 27WHY YOU SHOULD USE THIS MODULE (OR NOT)
23 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 28 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24 nowadays. So what is different about AnyEvent? 29 nowadays. So what is different about AnyEvent?
25 30
46 that isn't itself. What's worse, all the potential users of your module 51 that isn't itself. What's worse, all the potential users of your module
47 are *also* forced to use the same event loop you use. 52 are *also* forced to use the same event loop you use.
48 53
49 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works 54 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50 fine. AnyEvent + Tk works fine etc. etc. but none of these work together 55 fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51 with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if your 56 with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your
52 module uses one of those, every user of your module has to use it, too. 57 module uses one of those, every user of your module has to use it, too.
53 But if your module uses AnyEvent, it works transparently with all event 58 But if your module uses AnyEvent, it works transparently with all event
54 models it supports (including stuff like POE and IO::Async, as long as 59 models it supports (including stuff like POE and IO::Async, as long as
55 those use one of the supported event loops. It is trivial to add new 60 those use one of the supported event loops. It is trivial to add new
56 event loops to AnyEvent, too, so it is future-proof). 61 event loops to AnyEvent, too, so it is future-proof).
57 62
58 In addition to being free of having to use *the one and only true event 63 In addition to being free of having to use *the one and only true event
59 model*, AnyEvent also is free of bloat and policy: with POE or similar 64 model*, AnyEvent also is free of bloat and policy: with POE or similar
60 modules, you get an enourmous amount of code and strict rules you have 65 modules, you get an enormous amount of code and strict rules you have to
61 to follow. AnyEvent, on the other hand, is lean and up to the point, by 66 follow. AnyEvent, on the other hand, is lean and up to the point, by
62 only offering the functionality that is necessary, in as thin as a 67 only offering the functionality that is necessary, in as thin as a
63 wrapper as technically possible. 68 wrapper as technically possible.
64 69
70 Of course, AnyEvent comes with a big (and fully optional!) toolbox of
71 useful functionality, such as an asynchronous DNS resolver, 100%
72 non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
73 such as Windows) and lots of real-world knowledge and workarounds for
74 platform bugs and differences.
75
65 Of course, if you want lots of policy (this can arguably be somewhat 76 Now, if you *do want* lots of policy (this can arguably be somewhat
66 useful) and you want to force your users to use the one and only event 77 useful) and you want to force your users to use the one and only event
67 model, you should *not* use this module. 78 model, you should *not* use this module.
68 79
69DESCRIPTION 80DESCRIPTION
70 AnyEvent provides an identical interface to multiple event loops. This 81 AnyEvent provides an identical interface to multiple event loops. This
99 starts using it, all bets are off. Maybe you should tell their authors 110 starts using it, all bets are off. Maybe you should tell their authors
100 to use AnyEvent so their modules work together with others seamlessly... 111 to use AnyEvent so their modules work together with others seamlessly...
101 112
102 The pure-perl implementation of AnyEvent is called 113 The pure-perl implementation of AnyEvent is called
103 "AnyEvent::Impl::Perl". Like other event modules you can load it 114 "AnyEvent::Impl::Perl". Like other event modules you can load it
104 explicitly. 115 explicitly and enjoy the high availability of that event loop :)
105 116
106WATCHERS 117WATCHERS
107 AnyEvent has the central concept of a *watcher*, which is an object that 118 AnyEvent has the central concept of a *watcher*, which is an object that
108 stores relevant data for each kind of event you are waiting for, such as 119 stores relevant data for each kind of event you are waiting for, such as
109 the callback to call, the filehandle to watch, etc. 120 the callback to call, the file handle to watch, etc.
110 121
111 These watchers are normal Perl objects with normal Perl lifetime. After 122 These watchers are normal Perl objects with normal Perl lifetime. After
112 creating a watcher it will immediately "watch" for events and invoke the 123 creating a watcher it will immediately "watch" for events and invoke the
113 callback when the event occurs (of course, only when the event model is 124 callback when the event occurs (of course, only when the event model is
114 in control). 125 in control).
122 Many watchers either are used with "recursion" (repeating timers for 133 Many watchers either are used with "recursion" (repeating timers for
123 example), or need to refer to their watcher object in other ways. 134 example), or need to refer to their watcher object in other ways.
124 135
125 An any way to achieve that is this pattern: 136 An any way to achieve that is this pattern:
126 137
127 my $w; $w = AnyEvent->type (arg => value ..., cb => sub { 138 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
128 # you can use $w here, for example to undef it 139 # you can use $w here, for example to undef it
129 undef $w; 140 undef $w;
130 }); 141 });
131 142
132 Note that "my $w; $w =" combination. This is necessary because in Perl, 143 Note that "my $w; $w =" combination. This is necessary because in Perl,
133 my variables are only visible after the statement in which they are 144 my variables are only visible after the statement in which they are
134 declared. 145 declared.
135 146
220 on wallclock time) timers. 231 on wallclock time) timers.
221 232
222 AnyEvent always prefers relative timers, if available, matching the 233 AnyEvent always prefers relative timers, if available, matching the
223 AnyEvent API. 234 AnyEvent API.
224 235
236 AnyEvent has two additional methods that return the "current time":
237
238 AnyEvent->time
239 This returns the "current wallclock time" as a fractional number of
240 seconds since the Epoch (the same thing as "time" or
241 "Time::HiRes::time" return, and the result is guaranteed to be
242 compatible with those).
243
244 It progresses independently of any event loop processing, i.e. each
245 call will check the system clock, which usually gets updated
246 frequently.
247
248 AnyEvent->now
249 This also returns the "current wallclock time", but unlike "time",
250 above, this value might change only once per event loop iteration,
251 depending on the event loop (most return the same time as "time",
252 above). This is the time that AnyEvent's timers get scheduled
253 against.
254
255 *In almost all cases (in all cases if you don't care), this is the
256 function to call when you want to know the current time.*
257
258 This function is also often faster then "AnyEvent->time", and thus
259 the preferred method if you want some timestamp (for example,
260 AnyEvent::Handle uses this to update it's activity timeouts).
261
262 The rest of this section is only of relevance if you try to be very
263 exact with your timing, you can skip it without bad conscience.
264
265 For a practical example of when these times differ, consider
266 Event::Lib and EV and the following set-up:
267
268 The event loop is running and has just invoked one of your callback
269 at time=500 (assume no other callbacks delay processing). In your
270 callback, you wait a second by executing "sleep 1" (blocking the
271 process for a second) and then (at time=501) you create a relative
272 timer that fires after three seconds.
273
274 With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both
275 return 501, because that is the current time, and the timer will be
276 scheduled to fire at time=504 (501 + 3).
277
278 With EV, "AnyEvent->time" returns 501 (as that is the current time),
279 but "AnyEvent->now" returns 500, as that is the time the last event
280 processing phase started. With EV, your timer gets scheduled to run
281 at time=503 (500 + 3).
282
283 In one sense, Event::Lib is more exact, as it uses the current time
284 regardless of any delays introduced by event processing. However,
285 most callbacks do not expect large delays in processing, so this
286 causes a higher drift (and a lot more system calls to get the
287 current time).
288
289 In another sense, EV is more exact, as your timer will be scheduled
290 at the same time, regardless of how long event processing actually
291 took.
292
293 In either case, if you care (and in most cases, you don't), then you
294 can get whatever behaviour you want with any event loop, by taking
295 the difference between "AnyEvent->time" and "AnyEvent->now" into
296 account.
297
225 SIGNAL WATCHERS 298 SIGNAL WATCHERS
226 You can watch for signals using a signal watcher, "signal" is the signal 299 You can watch for signals using a signal watcher, "signal" is the signal
227 *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked 300 *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked
228 whenever a signal occurs. 301 whenever a signal occurs.
229 302
230 Although the callback might get passed parameters, their value and 303 Although the callback might get passed parameters, their value and
231 presence is undefined and you cannot rely on them. Portable AnyEvent 304 presence is undefined and you cannot rely on them. Portable AnyEvent
232 callbacks cannot use arguments passed to signal watcher callbacks. 305 callbacks cannot use arguments passed to signal watcher callbacks.
233 306
234 Multiple signal occurances can be clumped together into one callback 307 Multiple signal occurrences can be clumped together into one callback
235 invocation, and callback invocation will be synchronous. synchronous 308 invocation, and callback invocation will be synchronous. Synchronous
236 means that it might take a while until the signal gets handled by the 309 means that it might take a while until the signal gets handled by the
237 process, but it is guarenteed not to interrupt any other callbacks. 310 process, but it is guaranteed not to interrupt any other callbacks.
238 311
239 The main advantage of using these watchers is that you can share a 312 The main advantage of using these watchers is that you can share a
240 signal between multiple watchers. 313 signal between multiple watchers.
241 314
242 This watcher might use %SIG, so programs overwriting those signals 315 This watcher might use %SIG, so programs overwriting those signals
269 an AnyEvent program, you *have* to create at least one watcher before 342 an AnyEvent program, you *have* to create at least one watcher before
270 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 343 you "fork" the child (alternatively, you can call "AnyEvent::detect").
271 344
272 Example: fork a process and wait for it 345 Example: fork a process and wait for it
273 346
274 my $done = AnyEvent->condvar; 347 my $done = AnyEvent->condvar;
275 348
276 my $pid = fork or exit 5; 349 my $pid = fork or exit 5;
277 350
278 my $w = AnyEvent->child ( 351 my $w = AnyEvent->child (
279 pid => $pid, 352 pid => $pid,
280 cb => sub { 353 cb => sub {
281 my ($pid, $status) = @_; 354 my ($pid, $status) = @_;
282 warn "pid $pid exited with status $status"; 355 warn "pid $pid exited with status $status";
283 $done->send; 356 $done->send;
284 }, 357 },
285 ); 358 );
286 359
287 # do something else, then wait for process exit 360 # do something else, then wait for process exit
288 $done->recv; 361 $done->recv;
289 362
290 CONDITION VARIABLES 363 CONDITION VARIABLES
291 If you are familiar with some event loops you will know that all of them 364 If you are familiar with some event loops you will know that all of them
292 require you to run some blocking "loop", "run" or similar function that 365 require you to run some blocking "loop", "run" or similar function that
293 will actively watch for new events and call your callbacks. 366 will actively watch for new events and call your callbacks.
301 Condition variables can be created by calling the "AnyEvent->condvar" 374 Condition variables can be created by calling the "AnyEvent->condvar"
302 method, usually without arguments. The only argument pair allowed is 375 method, usually without arguments. The only argument pair allowed is
303 "cb", which specifies a callback to be called when the condition 376 "cb", which specifies a callback to be called when the condition
304 variable becomes true. 377 variable becomes true.
305 378
306 After creation, the conditon variable is "false" until it becomes "true" 379 After creation, the condition variable is "false" until it becomes
380 "true" by calling the "send" method (or calling the condition variable
381 as if it were a callback, read about the caveats in the description for
307 by calling the "send" method. 382 the "->send" method).
308 383
309 Condition variables are similar to callbacks, except that you can 384 Condition variables are similar to callbacks, except that you can
310 optionally wait for them. They can also be called merge points - points 385 optionally wait for them. They can also be called merge points - points
311 in time where multiple outstandign events have been processed. And yet 386 in time where multiple outstanding events have been processed. And yet
312 another way to call them is transations - each condition variable can be 387 another way to call them is transactions - each condition variable can
313 used to represent a transaction, which finishes at some point and 388 be used to represent a transaction, which finishes at some point and
314 delivers a result. 389 delivers a result.
315 390
316 Condition variables are very useful to signal that something has 391 Condition variables are very useful to signal that something has
317 finished, for example, if you write a module that does asynchronous http 392 finished, for example, if you write a module that does asynchronous http
318 requests, then a condition variable would be the ideal candidate to 393 requests, then a condition variable would be the ideal candidate to
323 you can block your main program until an event occurs - for example, you 398 you can block your main program until an event occurs - for example, you
324 could "->recv" in your main program until the user clicks the Quit 399 could "->recv" in your main program until the user clicks the Quit
325 button of your app, which would "->send" the "quit" event. 400 button of your app, which would "->send" the "quit" event.
326 401
327 Note that condition variables recurse into the event loop - if you have 402 Note that condition variables recurse into the event loop - if you have
328 two pieces of code that call "->recv" in a round-robbin fashion, you 403 two pieces of code that call "->recv" in a round-robin fashion, you
329 lose. Therefore, condition variables are good to export to your caller, 404 lose. Therefore, condition variables are good to export to your caller,
330 but you should avoid making a blocking wait yourself, at least in 405 but you should avoid making a blocking wait yourself, at least in
331 callbacks, as this asks for trouble. 406 callbacks, as this asks for trouble.
332 407
333 Condition variables are represented by hash refs in perl, and the keys 408 Condition variables are represented by hash refs in perl, and the keys
338 413
339 There are two "sides" to a condition variable - the "producer side" 414 There are two "sides" to a condition variable - the "producer side"
340 which eventually calls "-> send", and the "consumer side", which waits 415 which eventually calls "-> send", and the "consumer side", which waits
341 for the send to occur. 416 for the send to occur.
342 417
343 Example: 418 Example: wait for a timer.
344 419
345 # wait till the result is ready 420 # wait till the result is ready
346 my $result_ready = AnyEvent->condvar; 421 my $result_ready = AnyEvent->condvar;
347 422
348 # do something such as adding a timer 423 # do something such as adding a timer
356 431
357 # this "blocks" (while handling events) till the callback 432 # this "blocks" (while handling events) till the callback
358 # calls send 433 # calls send
359 $result_ready->recv; 434 $result_ready->recv;
360 435
436 Example: wait for a timer, but take advantage of the fact that condition
437 variables are also code references.
438
439 my $done = AnyEvent->condvar;
440 my $delay = AnyEvent->timer (after => 5, cb => $done);
441 $done->recv;
442
361 METHODS FOR PRODUCERS 443 METHODS FOR PRODUCERS
362 These methods should only be used by the producing side, i.e. the 444 These methods should only be used by the producing side, i.e. the
363 code/module that eventually sends the signal. Note that it is also the 445 code/module that eventually sends the signal. Note that it is also the
364 producer side which creates the condvar in most cases, but it isn't 446 producer side which creates the condvar in most cases, but it isn't
365 uncommon for the consumer to create it as well. 447 uncommon for the consumer to create it as well.
372 If a callback has been set on the condition variable, it is called 454 If a callback has been set on the condition variable, it is called
373 immediately from within send. 455 immediately from within send.
374 456
375 Any arguments passed to the "send" call will be returned by all 457 Any arguments passed to the "send" call will be returned by all
376 future "->recv" calls. 458 future "->recv" calls.
459
460 Condition variables are overloaded so one can call them directly (as
461 a code reference). Calling them directly is the same as calling
462 "send". Note, however, that many C-based event loops do not handle
463 overloading, so as tempting as it may be, passing a condition
464 variable instead of a callback does not work. Both the pure perl and
465 EV loops support overloading, however, as well as all functions that
466 use perl to invoke a callback (as in AnyEvent::Socket and
467 AnyEvent::DNS for example).
377 468
378 $cv->croak ($error) 469 $cv->croak ($error)
379 Similar to send, but causes all call's to "->recv" to invoke 470 Similar to send, but causes all call's to "->recv" to invoke
380 "Carp::croak" with the given error message/object/scalar. 471 "Carp::croak" with the given error message/object/scalar.
381 472
427 (the loop doesn't execute once). 518 (the loop doesn't execute once).
428 519
429 This is the general pattern when you "fan out" into multiple 520 This is the general pattern when you "fan out" into multiple
430 subrequests: use an outer "begin"/"end" pair to set the callback and 521 subrequests: use an outer "begin"/"end" pair to set the callback and
431 ensure "end" is called at least once, and then, for each subrequest 522 ensure "end" is called at least once, and then, for each subrequest
432 you start, call "begin" and for eahc subrequest you finish, call 523 you start, call "begin" and for each subrequest you finish, call
433 "end". 524 "end".
434 525
435 METHODS FOR CONSUMERS 526 METHODS FOR CONSUMERS
436 These methods should only be used by the consuming side, i.e. the code 527 These methods should only be used by the consuming side, i.e. the code
437 awaits the condition. 528 awaits the condition.
453 (programs might want to do that to stay interactive), so *if you are 544 (programs might want to do that to stay interactive), so *if you are
454 using this from a module, never require a blocking wait*, but let 545 using this from a module, never require a blocking wait*, but let
455 the caller decide whether the call will block or not (for example, 546 the caller decide whether the call will block or not (for example,
456 by coupling condition variables with some kind of request results 547 by coupling condition variables with some kind of request results
457 and supporting callbacks so the caller knows that getting the result 548 and supporting callbacks so the caller knows that getting the result
458 will not block, while still suppporting blocking waits if the caller 549 will not block, while still supporting blocking waits if the caller
459 so desires). 550 so desires).
460 551
461 Another reason *never* to "->recv" in a module is that you cannot 552 Another reason *never* to "->recv" in a module is that you cannot
462 sensibly have two "->recv"'s in parallel, as that would require 553 sensibly have two "->recv"'s in parallel, as that would require
463 multiple interpreters or coroutines/threads, none of which 554 multiple interpreters or coroutines/threads, none of which
481 $cb = $cv->cb ([new callback]) 572 $cb = $cv->cb ([new callback])
482 This is a mutator function that returns the callback set and 573 This is a mutator function that returns the callback set and
483 optionally replaces it before doing so. 574 optionally replaces it before doing so.
484 575
485 The callback will be called when the condition becomes "true", i.e. 576 The callback will be called when the condition becomes "true", i.e.
486 when "send" or "croak" are called. Calling "recv" inside the 577 when "send" or "croak" are called, with the only argument being the
578 condition variable itself. Calling "recv" inside the callback or at
487 callback or at any later time is guaranteed not to block. 579 any later time is guaranteed not to block.
488 580
489GLOBAL VARIABLES AND FUNCTIONS 581GLOBAL VARIABLES AND FUNCTIONS
490 $AnyEvent::MODEL 582 $AnyEvent::MODEL
491 Contains "undef" until the first watcher is being created. Then it 583 Contains "undef" until the first watcher is being created. Then it
492 contains the event model that is being used, which is the name of 584 contains the event model that is being used, which is the name of
566 If it doesn't care, it can just "use AnyEvent" and use it itself, or not 658 If it doesn't care, it can just "use AnyEvent" and use it itself, or not
567 do anything special (it does not need to be event-based) and let 659 do anything special (it does not need to be event-based) and let
568 AnyEvent decide which implementation to chose if some module relies on 660 AnyEvent decide which implementation to chose if some module relies on
569 it. 661 it.
570 662
571 If the main program relies on a specific event model. For example, in 663 If the main program relies on a specific event model - for example, in
572 Gtk2 programs you have to rely on the Glib module. You should load the 664 Gtk2 programs you have to rely on the Glib module - you should load the
573 event module before loading AnyEvent or any module that uses it: 665 event module before loading AnyEvent or any module that uses it:
574 generally speaking, you should load it as early as possible. The reason 666 generally speaking, you should load it as early as possible. The reason
575 is that modules might create watchers when they are loaded, and AnyEvent 667 is that modules might create watchers when they are loaded, and AnyEvent
576 will decide on the event model to use as soon as it creates watchers, 668 will decide on the event model to use as soon as it creates watchers,
577 and it might chose the wrong one unless you load the correct one 669 and it might chose the wrong one unless you load the correct one
578 yourself. 670 yourself.
579 671
580 You can chose to use a rather inefficient pure-perl implementation by 672 You can chose to use a pure-perl implementation by loading the
581 loading the "AnyEvent::Impl::Perl" module, which gives you similar 673 "AnyEvent::Impl::Perl" module, which gives you similar behaviour
582 behaviour everywhere, but letting AnyEvent chose is generally better. 674 everywhere, but letting AnyEvent chose the model is generally better.
675
676 MAINLOOP EMULATION
677 Sometimes (often for short test scripts, or even standalone programs who
678 only want to use AnyEvent), you do not want to run a specific event
679 loop.
680
681 In that case, you can use a condition variable like this:
682
683 AnyEvent->condvar->recv;
684
685 This has the effect of entering the event loop and looping forever.
686
687 Note that usually your program has some exit condition, in which case it
688 is better to use the "traditional" approach of storing a condition
689 variable somewhere, waiting for it, and sending it when the program
690 should exit cleanly.
583 691
584OTHER MODULES 692OTHER MODULES
585 The following is a non-exhaustive list of additional modules that use 693 The following is a non-exhaustive list of additional modules that use
586 AnyEvent and can therefore be mixed easily with other AnyEvent modules 694 AnyEvent and can therefore be mixed easily with other AnyEvent modules
587 in the same program. Some of the modules come with AnyEvent, some are 695 in the same program. Some of the modules come with AnyEvent, some are
594 702
595 AnyEvent::Handle 703 AnyEvent::Handle
596 Provide read and write buffers and manages watchers for reads and 704 Provide read and write buffers and manages watchers for reads and
597 writes. 705 writes.
598 706
707 AnyEvent::Socket
708 Provides various utility functions for (internet protocol) sockets,
709 addresses and name resolution. Also functions to create non-blocking
710 tcp connections or tcp servers, with IPv6 and SRV record support and
711 more.
712
713 AnyEvent::DNS
714 Provides rich asynchronous DNS resolver capabilities.
715
599 AnyEvent::HTTPD 716 AnyEvent::HTTPD
600 Provides a simple web application server framework. 717 Provides a simple web application server framework.
601
602 AnyEvent::DNS
603 Provides asynchronous DNS resolver capabilities, beyond what
604 AnyEvent::Util offers.
605 718
606 AnyEvent::FastPing 719 AnyEvent::FastPing
607 The fastest ping in the west. 720 The fastest ping in the west.
608 721
609 Net::IRC3 722 Net::IRC3
693 When set to 2 or higher, cause AnyEvent to report to STDERR which 806 When set to 2 or higher, cause AnyEvent to report to STDERR which
694 event model it chooses. 807 event model it chooses.
695 808
696 "PERL_ANYEVENT_MODEL" 809 "PERL_ANYEVENT_MODEL"
697 This can be used to specify the event model to be used by AnyEvent, 810 This can be used to specify the event model to be used by AnyEvent,
698 before autodetection and -probing kicks in. It must be a string 811 before auto detection and -probing kicks in. It must be a string
699 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 812 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
700 gets prepended and the resulting module name is loaded and if the 813 gets prepended and the resulting module name is loaded and if the
701 load was successful, used as event model. If it fails to load 814 load was successful, used as event model. If it fails to load
702 AnyEvent will proceed with autodetection and -probing. 815 AnyEvent will proceed with auto detection and -probing.
703 816
704 This functionality might change in future versions. 817 This functionality might change in future versions.
705 818
706 For example, to force the pure perl model (AnyEvent::Impl::Perl) you 819 For example, to force the pure perl model (AnyEvent::Impl::Perl) you
707 could start your program like this: 820 could start your program like this:
708 821
709 PERL_ANYEVENT_MODEL=Perl perl ... 822 PERL_ANYEVENT_MODEL=Perl perl ...
823
824 "PERL_ANYEVENT_PROTOCOLS"
825 Used by both AnyEvent::DNS and AnyEvent::Socket to determine
826 preferences for IPv4 or IPv6. The default is unspecified (and might
827 change, or be the result of auto probing).
828
829 Must be set to a comma-separated list of protocols or address
830 families, current supported: "ipv4" and "ipv6". Only protocols
831 mentioned will be used, and preference will be given to protocols
832 mentioned earlier in the list.
833
834 This variable can effectively be used for denial-of-service attacks
835 against local programs (e.g. when setuid), although the impact is
836 likely small, as the program has to handle connection errors
837 already-
838
839 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
840 IPv6, but support both and try to use both.
841 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
842 resolve or contact IPv6 addresses.
843 "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
844 prefer IPv6 over IPv4.
845
846 "PERL_ANYEVENT_EDNS0"
847 Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
848 for DNS. This extension is generally useful to reduce DNS traffic,
849 but some (broken) firewalls drop such DNS packets, which is why it
850 is off by default.
851
852 Setting this variable to 1 will cause AnyEvent::DNS to announce
853 EDNS0 in its DNS requests.
854
855 "PERL_ANYEVENT_MAX_FORKS"
856 The maximum number of child processes that
857 "AnyEvent::Util::fork_call" will create in parallel.
710 858
711EXAMPLE PROGRAM 859EXAMPLE PROGRAM
712 The following program uses an I/O watcher to read data from STDIN, a 860 The following program uses an I/O watcher to read data from STDIN, a
713 timer to display a message once per second, and a condition variable to 861 timer to display a message once per second, and a condition variable to
714 quit the program when the user enters quit: 862 quit the program when the user enters quit:
722 poll => 'r', 870 poll => 'r',
723 cb => sub { 871 cb => sub {
724 warn "io event <$_[0]>\n"; # will always output <r> 872 warn "io event <$_[0]>\n"; # will always output <r>
725 chomp (my $input = <STDIN>); # read a line 873 chomp (my $input = <STDIN>); # read a line
726 warn "read: $input\n"; # output what has been read 874 warn "read: $input\n"; # output what has been read
727 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 875 $cv->send if $input =~ /^q/i; # quit program if /^q/i
728 }, 876 },
729 ); 877 );
730 878
731 my $time_watcher; # can only be used once 879 my $time_watcher; # can only be used once
732 880
737 }); 885 });
738 } 886 }
739 887
740 new_timer; # create first timer 888 new_timer; # create first timer
741 889
742 $cv->wait; # wait until user enters /^q/i 890 $cv->recv; # wait until user enters /^q/i
743 891
744REAL-WORLD EXAMPLE 892REAL-WORLD EXAMPLE
745 Consider the Net::FCP module. It features (among others) the following 893 Consider the Net::FCP module. It features (among others) the following
746 API calls, which are to freenet what HTTP GET requests are to http: 894 API calls, which are to freenet what HTTP GET requests are to http:
747 895
796 syswrite $txn->{fh}, $txn->{request} 944 syswrite $txn->{fh}, $txn->{request}
797 or die "connection or write error"; 945 or die "connection or write error";
798 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); 946 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799 947
800 Again, "fh_ready_r" waits till all data has arrived, and then stores the 948 Again, "fh_ready_r" waits till all data has arrived, and then stores the
801 result and signals any possible waiters that the request ahs finished: 949 result and signals any possible waiters that the request has finished:
802 950
803 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; 951 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804 952
805 if (end-of-file or data complete) { 953 if (end-of-file or data complete) {
806 $txn->{result} = $txn->{buf}; 954 $txn->{result} = $txn->{buf};
807 $txn->{finished}->broadcast; 955 $txn->{finished}->send;
808 $txb->{cb}->($txn) of $txn->{cb}; # also call callback 956 $txb->{cb}->($txn) of $txn->{cb}; # also call callback
809 } 957 }
810 958
811 The "result" method, finally, just waits for the finished signal (if the 959 The "result" method, finally, just waits for the finished signal (if the
812 request was already finished, it doesn't wait, of course, and returns 960 request was already finished, it doesn't wait, of course, and returns
813 the data: 961 the data:
814 962
815 $txn->{finished}->wait; 963 $txn->{finished}->recv;
816 return $txn->{result}; 964 return $txn->{result};
817 965
818 The actual code goes further and collects all errors ("die"s, 966 The actual code goes further and collects all errors ("die"s,
819 exceptions) that occured during request processing. The "result" method 967 exceptions) that occurred during request processing. The "result" method
820 detects whether an exception as thrown (it is stored inside the $txn 968 detects whether an exception as thrown (it is stored inside the $txn
821 object) and just throws the exception, which means connection errors and 969 object) and just throws the exception, which means connection errors and
822 other problems get reported tot he code that tries to use the result, 970 other problems get reported tot he code that tries to use the result,
823 not in a random callback. 971 not in a random callback.
824 972
855 1003
856 my $quit = AnyEvent->condvar; 1004 my $quit = AnyEvent->condvar;
857 1005
858 $fcp->txn_client_get ($url)->cb (sub { 1006 $fcp->txn_client_get ($url)->cb (sub {
859 ... 1007 ...
860 $quit->broadcast; 1008 $quit->send;
861 }); 1009 });
862 1010
863 $quit->wait; 1011 $quit->recv;
864 1012
865BENCHMARKS 1013BENCHMARKS
866 To give you an idea of the performance and overheads that AnyEvent adds 1014 To give you an idea of the performance and overheads that AnyEvent adds
867 over the event loops themselves and to give you an impression of the 1015 over the event loops themselves and to give you an impression of the
868 speed of various event loops I prepared some benchmarks. 1016 speed of various event loops I prepared some benchmarks.
869 1017
870 BENCHMARKING ANYEVENT OVERHEAD 1018 BENCHMARKING ANYEVENT OVERHEAD
871 Here is a benchmark of various supported event models used natively and 1019 Here is a benchmark of various supported event models used natively and
872 through anyevent. The benchmark creates a lot of timers (with a zero 1020 through AnyEvent. The benchmark creates a lot of timers (with a zero
873 timeout) and I/O watchers (watching STDOUT, a pty, to become writable, 1021 timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
874 which it is), lets them fire exactly once and destroys them again. 1022 which it is), lets them fire exactly once and destroys them again.
875 1023
876 Source code for this benchmark is found as eg/bench in the AnyEvent 1024 Source code for this benchmark is found as eg/bench in the AnyEvent
877 distribution. 1025 distribution.
893 between all watchers, to avoid adding memory overhead. That means 1041 between all watchers, to avoid adding memory overhead. That means
894 closure creation and memory usage is not included in the figures. 1042 closure creation and memory usage is not included in the figures.
895 1043
896 *invoke* is the time, in microseconds, used to invoke a simple callback. 1044 *invoke* is the time, in microseconds, used to invoke a simple callback.
897 The callback simply counts down a Perl variable and after it was invoked 1045 The callback simply counts down a Perl variable and after it was invoked
898 "watcher" times, it would "->broadcast" a condvar once to signal the end 1046 "watcher" times, it would "->send" a condvar once to signal the end of
899 of this phase. 1047 this phase.
900 1048
901 *destroy* is the time, in microseconds, that it takes to destroy a 1049 *destroy* is the time, in microseconds, that it takes to destroy a
902 single watcher. 1050 single watcher.
903 1051
904 Results 1052 Results
992 1140
993 * You should avoid POE like the plague if you want performance or 1141 * You should avoid POE like the plague if you want performance or
994 reasonable memory usage. 1142 reasonable memory usage.
995 1143
996 BENCHMARKING THE LARGE SERVER CASE 1144 BENCHMARKING THE LARGE SERVER CASE
997 This benchmark atcually benchmarks the event loop itself. It works by 1145 This benchmark actually benchmarks the event loop itself. It works by
998 creating a number of "servers": each server consists of a socketpair, a 1146 creating a number of "servers": each server consists of a socket pair, a
999 timeout watcher that gets reset on activity (but never fires), and an 1147 timeout watcher that gets reset on activity (but never fires), and an
1000 I/O watcher waiting for input on one side of the socket. Each time the 1148 I/O watcher waiting for input on one side of the socket. Each time the
1001 socket watcher reads a byte it will write that byte to a random other 1149 socket watcher reads a byte it will write that byte to a random other
1002 "server". 1150 "server".
1003 1151
1004 The effect is that there will be a lot of I/O watchers, only part of 1152 The effect is that there will be a lot of I/O watchers, only part of
1005 which are active at any one point (so there is a constant number of 1153 which are active at any one point (so there is a constant number of
1006 active fds for each loop iterstaion, but which fds these are is random). 1154 active fds for each loop iteration, but which fds these are is random).
1007 The timeout is reset each time something is read because that reflects 1155 The timeout is reset each time something is read because that reflects
1008 how most timeouts work (and puts extra pressure on the event loops). 1156 how most timeouts work (and puts extra pressure on the event loops).
1009 1157
1010 In this benchmark, we use 10000 socketpairs (20000 sockets), of which 1158 In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1011 100 (1%) are active. This mirrors the activity of large servers with 1159 100 (1%) are active. This mirrors the activity of large servers with
1012 many connections, most of which are idle at any one point in time. 1160 many connections, most of which are idle at any one point in time.
1013 1161
1014 Source code for this benchmark is found as eg/bench2 in the AnyEvent 1162 Source code for this benchmark is found as eg/bench2 in the AnyEvent
1015 distribution. 1163 distribution.
1016 1164
1017 Explanation of the columns 1165 Explanation of the columns
1018 *sockets* is the number of sockets, and twice the number of "servers" 1166 *sockets* is the number of sockets, and twice the number of "servers"
1019 (as each server has a read and write socket end). 1167 (as each server has a read and write socket end).
1020 1168
1021 *create* is the time it takes to create a socketpair (which is 1169 *create* is the time it takes to create a socket pair (which is
1022 nontrivial) and two watchers: an I/O watcher and a timeout watcher. 1170 nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1023 1171
1024 *request*, the most important value, is the time it takes to handle a 1172 *request*, the most important value, is the time it takes to handle a
1025 single "request", that is, reading the token from the pipe and 1173 single "request", that is, reading the token from the pipe and
1026 forwarding it to another server. This includes deleting the old timeout 1174 forwarding it to another server. This includes deleting the old timeout
1090 and speed most when you have lots of watchers, not when you only have a 1238 and speed most when you have lots of watchers, not when you only have a
1091 few of them). 1239 few of them).
1092 1240
1093 EV is again fastest. 1241 EV is again fastest.
1094 1242
1095 Perl again comes second. It is noticably faster than the C-based event 1243 Perl again comes second. It is noticeably faster than the C-based event
1096 loops Event and Glib, although the difference is too small to really 1244 loops Event and Glib, although the difference is too small to really
1097 matter. 1245 matter.
1098 1246
1099 POE also performs much better in this case, but is is still far behind 1247 POE also performs much better in this case, but is is still far behind
1100 the others. 1248 the others.
1120 model than specified in the variable. 1268 model than specified in the variable.
1121 1269
1122 You can make AnyEvent completely ignore this variable by deleting it 1270 You can make AnyEvent completely ignore this variable by deleting it
1123 before the first watcher gets created, e.g. with a "BEGIN" block: 1271 before the first watcher gets created, e.g. with a "BEGIN" block:
1124 1272
1125 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1273 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1126 1274
1127 use AnyEvent; 1275 use AnyEvent;
1128 1276
1129 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1277 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1130 be used to probe what backend is used and gain other information (which 1278 be used to probe what backend is used and gain other information (which
1131 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL). 1279 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
1132 1280
1133SEE ALSO 1281SEE ALSO
1282 Utility functions: AnyEvent::Util.
1283
1134 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, 1284 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1135 Event::Lib, Qt, POE. 1285 Event::Lib, Qt, POE.
1136 1286
1137 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, 1287 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1138 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, 1288 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1139 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. 1289 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.
1140 1290
1291 Non-blocking file handles, sockets, TCP clients and servers:
1292 AnyEvent::Handle, AnyEvent::Socket.
1293
1294 Asynchronous DNS: AnyEvent::DNS.
1295
1141 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1296 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1142 1297
1143 Nontrivial usage examples: Net::FCP, Net::XMPP2. 1298 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
1144 1299
1145AUTHOR 1300AUTHOR
1146 Marc Lehmann <schmorp@schmorp.de> 1301 Marc Lehmann <schmorp@schmorp.de>
1147 http://home.schmorp.de/ 1302 http://home.schmorp.de/
1148 1303

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