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1=head1 => NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops 5EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
6event loops.
6 7
7=head1 SYNOPSIS 8=head1 SYNOPSIS
8 9
9 use AnyEvent; 10 use AnyEvent;
10 11
12 # file descriptor readable
11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { 13 my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
14
15 # one-shot or repeating timers
16 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
17 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
18
19 print AnyEvent->now; # prints current event loop time
20 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
21
22 # POSIX signal
23 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
24
25 # child process exit
26 my $w = AnyEvent->child (pid => $pid, cb => sub {
27 my ($pid, $status) = @_;
12 ... 28 ...
13 }); 29 });
14 30
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 31 # called when event loop idle (if applicable)
16 ... 32 my $w = AnyEvent->idle (cb => sub { ... });
17 });
18 33
19 my $w = AnyEvent->condvar; # stores whether a condition was flagged 34 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->send; # wake up current and all future recv's 35 $w->send; # wake up current and all future recv's
21 $w->recv; # enters "main loop" till $condvar gets ->send 36 $w->recv; # enters "main loop" till $condvar gets ->send
37 # use a condvar in callback mode:
38 $w->cb (sub { $_[0]->recv });
39
40=head1 INTRODUCTION/TUTORIAL
41
42This manpage is mainly a reference manual. If you are interested
43in a tutorial or some gentle introduction, have a look at the
44L<AnyEvent::Intro> manpage.
22 45
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) 46=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 47
25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 48Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26nowadays. So what is different about AnyEvent? 49nowadays. So what is different about AnyEvent?
27 50
28Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of 51Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29policy> and AnyEvent is I<small and efficient>. 52policy> and AnyEvent is I<small and efficient>.
30 53
31First and foremost, I<AnyEvent is not an event model> itself, it only 54First and foremost, I<AnyEvent is not an event model> itself, it only
32interfaces to whatever event model the main program happens to use in a 55interfaces to whatever event model the main program happens to use, in a
33pragmatic way. For event models and certain classes of immortals alike, 56pragmatic way. For event models and certain classes of immortals alike,
34the statement "there can only be one" is a bitter reality: In general, 57the statement "there can only be one" is a bitter reality: In general,
35only one event loop can be active at the same time in a process. AnyEvent 58only one event loop can be active at the same time in a process. AnyEvent
36helps hiding the differences between those event loops. 59cannot change this, but it can hide the differences between those event
60loops.
37 61
38The goal of AnyEvent is to offer module authors the ability to do event 62The goal of AnyEvent is to offer module authors the ability to do event
39programming (waiting for I/O or timer events) without subscribing to a 63programming (waiting for I/O or timer events) without subscribing to a
40religion, a way of living, and most importantly: without forcing your 64religion, a way of living, and most importantly: without forcing your
41module users into the same thing by forcing them to use the same event 65module users into the same thing by forcing them to use the same event
42model you use. 66model you use.
43 67
44For modules like POE or IO::Async (which is a total misnomer as it is 68For modules like POE or IO::Async (which is a total misnomer as it is
45actually doing all I/O I<synchronously>...), using them in your module is 69actually doing all I/O I<synchronously>...), using them in your module is
46like joining a cult: After you joined, you are dependent on them and you 70like joining a cult: After you joined, you are dependent on them and you
47cannot use anything else, as it is simply incompatible to everything that 71cannot use anything else, as they are simply incompatible to everything
48isn't itself. What's worse, all the potential users of your module are 72that isn't them. What's worse, all the potential users of your
49I<also> forced to use the same event loop you use. 73module are I<also> forced to use the same event loop you use.
50 74
51AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works 75AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52fine. AnyEvent + Tk works fine etc. etc. but none of these work together 76fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if 77with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54your module uses one of those, every user of your module has to use it, 78your module uses one of those, every user of your module has to use it,
55too. But if your module uses AnyEvent, it works transparently with all 79too. But if your module uses AnyEvent, it works transparently with all
56event models it supports (including stuff like POE and IO::Async, as long 80event models it supports (including stuff like IO::Async, as long as those
57as those use one of the supported event loops. It is trivial to add new 81use one of the supported event loops. It is trivial to add new event loops
58event loops to AnyEvent, too, so it is future-proof). 82to AnyEvent, too, so it is future-proof).
59 83
60In addition to being free of having to use I<the one and only true event 84In addition to being free of having to use I<the one and only true event
61model>, AnyEvent also is free of bloat and policy: with POE or similar 85model>, AnyEvent also is free of bloat and policy: with POE or similar
62modules, you get an enormous amount of code and strict rules you have to 86modules, you get an enormous amount of code and strict rules you have to
63follow. AnyEvent, on the other hand, is lean and up to the point, by only 87follow. AnyEvent, on the other hand, is lean and up to the point, by only
121These watchers are normal Perl objects with normal Perl lifetime. After 145These watchers are normal Perl objects with normal Perl lifetime. After
122creating a watcher it will immediately "watch" for events and invoke the 146creating a watcher it will immediately "watch" for events and invoke the
123callback when the event occurs (of course, only when the event model 147callback when the event occurs (of course, only when the event model
124is in control). 148is in control).
125 149
150Note that B<callbacks must not permanently change global variables>
151potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
152callbacks must not C<die> >>. The former is good programming practise in
153Perl and the latter stems from the fact that exception handling differs
154widely between event loops.
155
126To disable the watcher you have to destroy it (e.g. by setting the 156To disable the watcher you have to destroy it (e.g. by setting the
127variable you store it in to C<undef> or otherwise deleting all references 157variable you store it in to C<undef> or otherwise deleting all references
128to it). 158to it).
129 159
130All watchers are created by calling a method on the C<AnyEvent> class. 160All watchers are created by calling a method on the C<AnyEvent> class.
132Many watchers either are used with "recursion" (repeating timers for 162Many watchers either are used with "recursion" (repeating timers for
133example), or need to refer to their watcher object in other ways. 163example), or need to refer to their watcher object in other ways.
134 164
135An any way to achieve that is this pattern: 165An any way to achieve that is this pattern:
136 166
137 my $w; $w = AnyEvent->type (arg => value ..., cb => sub { 167 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
138 # you can use $w here, for example to undef it 168 # you can use $w here, for example to undef it
139 undef $w; 169 undef $w;
140 }); 170 });
141 171
142Note that C<my $w; $w => combination. This is necessary because in Perl, 172Note that C<my $w; $w => combination. This is necessary because in Perl,
143my variables are only visible after the statement in which they are 173my variables are only visible after the statement in which they are
144declared. 174declared.
145 175
146=head2 I/O WATCHERS 176=head2 I/O WATCHERS
147 177
148You can create an I/O watcher by calling the C<< AnyEvent->io >> method 178You can create an I/O watcher by calling the C<< AnyEvent->io >> method
149with the following mandatory key-value pairs as arguments: 179with the following mandatory key-value pairs as arguments:
150 180
151C<fh> the Perl I<file handle> (I<not> file descriptor) to watch 181C<fh> is the Perl I<file handle> (I<not> file descriptor) to watch
182for events (AnyEvent might or might not keep a reference to this file
183handle). Note that only file handles pointing to things for which
184non-blocking operation makes sense are allowed. This includes sockets,
185most character devices, pipes, fifos and so on, but not for example files
186or block devices.
187
152for events. C<poll> must be a string that is either C<r> or C<w>, 188C<poll> must be a string that is either C<r> or C<w>, which creates a
153which creates a watcher waiting for "r"eadable or "w"ritable events, 189watcher waiting for "r"eadable or "w"ritable events, respectively.
190
154respectively. C<cb> is the callback to invoke each time the file handle 191C<cb> is the callback to invoke each time the file handle becomes ready.
155becomes ready.
156 192
157Although the callback might get passed parameters, their value and 193Although the callback might get passed parameters, their value and
158presence is undefined and you cannot rely on them. Portable AnyEvent 194presence is undefined and you cannot rely on them. Portable AnyEvent
159callbacks cannot use arguments passed to I/O watcher callbacks. 195callbacks cannot use arguments passed to I/O watcher callbacks.
160 196
164 200
165Some event loops issue spurious readyness notifications, so you should 201Some event loops issue spurious readyness notifications, so you should
166always use non-blocking calls when reading/writing from/to your file 202always use non-blocking calls when reading/writing from/to your file
167handles. 203handles.
168 204
169Example:
170
171 # wait for readability of STDIN, then read a line and disable the watcher 205Example: wait for readability of STDIN, then read a line and disable the
206watcher.
207
172 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 208 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
173 chomp (my $input = <STDIN>); 209 chomp (my $input = <STDIN>);
174 warn "read: $input\n"; 210 warn "read: $input\n";
175 undef $w; 211 undef $w;
176 }); 212 });
186 222
187Although the callback might get passed parameters, their value and 223Although the callback might get passed parameters, their value and
188presence is undefined and you cannot rely on them. Portable AnyEvent 224presence is undefined and you cannot rely on them. Portable AnyEvent
189callbacks cannot use arguments passed to time watcher callbacks. 225callbacks cannot use arguments passed to time watcher callbacks.
190 226
191The timer callback will be invoked at most once: if you want a repeating 227The callback will normally be invoked once only. If you specify another
192timer you have to create a new watcher (this is a limitation by both Tk 228parameter, C<interval>, as a strictly positive number (> 0), then the
193and Glib). 229callback will be invoked regularly at that interval (in fractional
230seconds) after the first invocation. If C<interval> is specified with a
231false value, then it is treated as if it were missing.
194 232
195Example: 233The callback will be rescheduled before invoking the callback, but no
234attempt is done to avoid timer drift in most backends, so the interval is
235only approximate.
196 236
197 # fire an event after 7.7 seconds 237Example: fire an event after 7.7 seconds.
238
198 my $w = AnyEvent->timer (after => 7.7, cb => sub { 239 my $w = AnyEvent->timer (after => 7.7, cb => sub {
199 warn "timeout\n"; 240 warn "timeout\n";
200 }); 241 });
201 242
202 # to cancel the timer: 243 # to cancel the timer:
203 undef $w; 244 undef $w;
204 245
205Example 2:
206
207 # fire an event after 0.5 seconds, then roughly every second 246Example 2: fire an event after 0.5 seconds, then roughly every second.
208 my $w;
209 247
210 my $cb = sub {
211 # cancel the old timer while creating a new one
212 $w = AnyEvent->timer (after => 1, cb => $cb); 248 my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
249 warn "timeout\n";
213 }; 250 };
214
215 # start the "loop" by creating the first watcher
216 $w = AnyEvent->timer (after => 0.5, cb => $cb);
217 251
218=head3 TIMING ISSUES 252=head3 TIMING ISSUES
219 253
220There are two ways to handle timers: based on real time (relative, "fire 254There are two ways to handle timers: based on real time (relative, "fire
221in 10 seconds") and based on wallclock time (absolute, "fire at 12 255in 10 seconds") and based on wallclock time (absolute, "fire at 12
233timers. 267timers.
234 268
235AnyEvent always prefers relative timers, if available, matching the 269AnyEvent always prefers relative timers, if available, matching the
236AnyEvent API. 270AnyEvent API.
237 271
272AnyEvent has two additional methods that return the "current time":
273
274=over 4
275
276=item AnyEvent->time
277
278This returns the "current wallclock time" as a fractional number of
279seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
280return, and the result is guaranteed to be compatible with those).
281
282It progresses independently of any event loop processing, i.e. each call
283will check the system clock, which usually gets updated frequently.
284
285=item AnyEvent->now
286
287This also returns the "current wallclock time", but unlike C<time>, above,
288this value might change only once per event loop iteration, depending on
289the event loop (most return the same time as C<time>, above). This is the
290time that AnyEvent's timers get scheduled against.
291
292I<In almost all cases (in all cases if you don't care), this is the
293function to call when you want to know the current time.>
294
295This function is also often faster then C<< AnyEvent->time >>, and
296thus the preferred method if you want some timestamp (for example,
297L<AnyEvent::Handle> uses this to update it's activity timeouts).
298
299The rest of this section is only of relevance if you try to be very exact
300with your timing, you can skip it without bad conscience.
301
302For a practical example of when these times differ, consider L<Event::Lib>
303and L<EV> and the following set-up:
304
305The event loop is running and has just invoked one of your callback at
306time=500 (assume no other callbacks delay processing). In your callback,
307you wait a second by executing C<sleep 1> (blocking the process for a
308second) and then (at time=501) you create a relative timer that fires
309after three seconds.
310
311With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
312both return C<501>, because that is the current time, and the timer will
313be scheduled to fire at time=504 (C<501> + C<3>).
314
315With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
316time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
317last event processing phase started. With L<EV>, your timer gets scheduled
318to run at time=503 (C<500> + C<3>).
319
320In one sense, L<Event::Lib> is more exact, as it uses the current time
321regardless of any delays introduced by event processing. However, most
322callbacks do not expect large delays in processing, so this causes a
323higher drift (and a lot more system calls to get the current time).
324
325In another sense, L<EV> is more exact, as your timer will be scheduled at
326the same time, regardless of how long event processing actually took.
327
328In either case, if you care (and in most cases, you don't), then you
329can get whatever behaviour you want with any event loop, by taking the
330difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
331account.
332
333=item AnyEvent->now_update
334
335Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
336the current time for each loop iteration (see the discussion of L<<
337AnyEvent->now >>, above).
338
339When a callback runs for a long time (or when the process sleeps), then
340this "current" time will differ substantially from the real time, which
341might affect timers and time-outs.
342
343When this is the case, you can call this method, which will update the
344event loop's idea of "current time".
345
346Note that updating the time I<might> cause some events to be handled.
347
348=back
349
238=head2 SIGNAL WATCHERS 350=head2 SIGNAL WATCHERS
239 351
240You can watch for signals using a signal watcher, C<signal> is the signal 352You can watch for signals using a signal watcher, C<signal> is the signal
241I<name> without any C<SIG> prefix, C<cb> is the Perl callback to 353I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
242be invoked whenever a signal occurs. 354callback to be invoked whenever a signal occurs.
243 355
244Although the callback might get passed parameters, their value and 356Although the callback might get passed parameters, their value and
245presence is undefined and you cannot rely on them. Portable AnyEvent 357presence is undefined and you cannot rely on them. Portable AnyEvent
246callbacks cannot use arguments passed to signal watcher callbacks. 358callbacks cannot use arguments passed to signal watcher callbacks.
247 359
263=head2 CHILD PROCESS WATCHERS 375=head2 CHILD PROCESS WATCHERS
264 376
265You can also watch on a child process exit and catch its exit status. 377You can also watch on a child process exit and catch its exit status.
266 378
267The child process is specified by the C<pid> argument (if set to C<0>, it 379The child process is specified by the C<pid> argument (if set to C<0>, it
268watches for any child process exit). The watcher will trigger as often 380watches for any child process exit). The watcher will triggered only when
269as status change for the child are received. This works by installing a 381the child process has finished and an exit status is available, not on
270signal handler for C<SIGCHLD>. The callback will be called with the pid 382any trace events (stopped/continued).
271and exit status (as returned by waitpid), so unlike other watcher types, 383
272you I<can> rely on child watcher callback arguments. 384The callback will be called with the pid and exit status (as returned by
385waitpid), so unlike other watcher types, you I<can> rely on child watcher
386callback arguments.
387
388This watcher type works by installing a signal handler for C<SIGCHLD>,
389and since it cannot be shared, nothing else should use SIGCHLD or reap
390random child processes (waiting for specific child processes, e.g. inside
391C<system>, is just fine).
273 392
274There is a slight catch to child watchers, however: you usually start them 393There is a slight catch to child watchers, however: you usually start them
275I<after> the child process was created, and this means the process could 394I<after> the child process was created, and this means the process could
276have exited already (and no SIGCHLD will be sent anymore). 395have exited already (and no SIGCHLD will be sent anymore).
277 396
278Not all event models handle this correctly (POE doesn't), but even for 397Not all event models handle this correctly (neither POE nor IO::Async do,
398see their AnyEvent::Impl manpages for details), but even for event models
279event models that I<do> handle this correctly, they usually need to be 399that I<do> handle this correctly, they usually need to be loaded before
280loaded before the process exits (i.e. before you fork in the first place). 400the process exits (i.e. before you fork in the first place). AnyEvent's
401pure perl event loop handles all cases correctly regardless of when you
402start the watcher.
281 403
282This means you cannot create a child watcher as the very first thing in an 404This means you cannot create a child watcher as the very first
283AnyEvent program, you I<have> to create at least one watcher before you 405thing in an AnyEvent program, you I<have> to create at least one
284C<fork> the child (alternatively, you can call C<AnyEvent::detect>). 406watcher before you C<fork> the child (alternatively, you can call
407C<AnyEvent::detect>).
285 408
286Example: fork a process and wait for it 409Example: fork a process and wait for it
287 410
288 my $done = AnyEvent->condvar; 411 my $done = AnyEvent->condvar;
289 412
290 my $pid = fork or exit 5; 413 my $pid = fork or exit 5;
291 414
292 my $w = AnyEvent->child ( 415 my $w = AnyEvent->child (
293 pid => $pid, 416 pid => $pid,
294 cb => sub { 417 cb => sub {
295 my ($pid, $status) = @_; 418 my ($pid, $status) = @_;
296 warn "pid $pid exited with status $status"; 419 warn "pid $pid exited with status $status";
297 $done->send; 420 $done->send;
298 }, 421 },
299 ); 422 );
300 423
301 # do something else, then wait for process exit 424 # do something else, then wait for process exit
302 $done->recv; 425 $done->recv;
426
427=head2 IDLE WATCHERS
428
429Sometimes there is a need to do something, but it is not so important
430to do it instantly, but only when there is nothing better to do. This
431"nothing better to do" is usually defined to be "no other events need
432attention by the event loop".
433
434Idle watchers ideally get invoked when the event loop has nothing
435better to do, just before it would block the process to wait for new
436events. Instead of blocking, the idle watcher is invoked.
437
438Most event loops unfortunately do not really support idle watchers (only
439EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
440will simply call the callback "from time to time".
441
442Example: read lines from STDIN, but only process them when the
443program is otherwise idle:
444
445 my @lines; # read data
446 my $idle_w;
447 my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
448 push @lines, scalar <STDIN>;
449
450 # start an idle watcher, if not already done
451 $idle_w ||= AnyEvent->idle (cb => sub {
452 # handle only one line, when there are lines left
453 if (my $line = shift @lines) {
454 print "handled when idle: $line";
455 } else {
456 # otherwise disable the idle watcher again
457 undef $idle_w;
458 }
459 });
460 });
303 461
304=head2 CONDITION VARIABLES 462=head2 CONDITION VARIABLES
305 463
306If you are familiar with some event loops you will know that all of them 464If you are familiar with some event loops you will know that all of them
307require you to run some blocking "loop", "run" or similar function that 465require you to run some blocking "loop", "run" or similar function that
313The instrument to do that is called a "condition variable", so called 471The instrument to do that is called a "condition variable", so called
314because they represent a condition that must become true. 472because they represent a condition that must become true.
315 473
316Condition variables can be created by calling the C<< AnyEvent->condvar 474Condition variables can be created by calling the C<< AnyEvent->condvar
317>> method, usually without arguments. The only argument pair allowed is 475>> method, usually without arguments. The only argument pair allowed is
476
318C<cb>, which specifies a callback to be called when the condition variable 477C<cb>, which specifies a callback to be called when the condition variable
319becomes true. 478becomes true, with the condition variable as the first argument (but not
479the results).
320 480
321After creation, the condition variable is "false" until it becomes "true" 481After creation, the condition variable is "false" until it becomes "true"
322by calling the C<send> method (or calling the condition variable as if it 482by calling the C<send> method (or calling the condition variable as if it
323were a callback, read about the caveats in the description for the C<< 483were a callback, read about the caveats in the description for the C<<
324->send >> method). 484->send >> method).
380 540
381 my $done = AnyEvent->condvar; 541 my $done = AnyEvent->condvar;
382 my $delay = AnyEvent->timer (after => 5, cb => $done); 542 my $delay = AnyEvent->timer (after => 5, cb => $done);
383 $done->recv; 543 $done->recv;
384 544
545Example: Imagine an API that returns a condvar and doesn't support
546callbacks. This is how you make a synchronous call, for example from
547the main program:
548
549 use AnyEvent::CouchDB;
550
551 ...
552
553 my @info = $couchdb->info->recv;
554
555And this is how you would just ste a callback to be called whenever the
556results are available:
557
558 $couchdb->info->cb (sub {
559 my @info = $_[0]->recv;
560 });
561
385=head3 METHODS FOR PRODUCERS 562=head3 METHODS FOR PRODUCERS
386 563
387These methods should only be used by the producing side, i.e. the 564These methods should only be used by the producing side, i.e. the
388code/module that eventually sends the signal. Note that it is also 565code/module that eventually sends the signal. Note that it is also
389the producer side which creates the condvar in most cases, but it isn't 566the producer side which creates the condvar in most cases, but it isn't
422 599
423=item $cv->begin ([group callback]) 600=item $cv->begin ([group callback])
424 601
425=item $cv->end 602=item $cv->end
426 603
427These two methods are EXPERIMENTAL and MIGHT CHANGE.
428
429These two methods can be used to combine many transactions/events into 604These two methods can be used to combine many transactions/events into
430one. For example, a function that pings many hosts in parallel might want 605one. For example, a function that pings many hosts in parallel might want
431to use a condition variable for the whole process. 606to use a condition variable for the whole process.
432 607
433Every call to C<< ->begin >> will increment a counter, and every call to 608Every call to C<< ->begin >> will increment a counter, and every call to
434C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end 609C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
435>>, the (last) callback passed to C<begin> will be executed. That callback 610>>, the (last) callback passed to C<begin> will be executed. That callback
436is I<supposed> to call C<< ->send >>, but that is not required. If no 611is I<supposed> to call C<< ->send >>, but that is not required. If no
437callback was set, C<send> will be called without any arguments. 612callback was set, C<send> will be called without any arguments.
438 613
439Let's clarify this with the ping example: 614You can think of C<< $cv->send >> giving you an OR condition (one call
615sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
616condition (all C<begin> calls must be C<end>'ed before the condvar sends).
617
618Let's start with a simple example: you have two I/O watchers (for example,
619STDOUT and STDERR for a program), and you want to wait for both streams to
620close before activating a condvar:
621
622 my $cv = AnyEvent->condvar;
623
624 $cv->begin; # first watcher
625 my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
626 defined sysread $fh1, my $buf, 4096
627 or $cv->end;
628 });
629
630 $cv->begin; # second watcher
631 my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
632 defined sysread $fh2, my $buf, 4096
633 or $cv->end;
634 });
635
636 $cv->recv;
637
638This works because for every event source (EOF on file handle), there is
639one call to C<begin>, so the condvar waits for all calls to C<end> before
640sending.
641
642The ping example mentioned above is slightly more complicated, as the
643there are results to be passwd back, and the number of tasks that are
644begung can potentially be zero:
440 645
441 my $cv = AnyEvent->condvar; 646 my $cv = AnyEvent->condvar;
442 647
443 my %result; 648 my %result;
444 $cv->begin (sub { $cv->send (\%result) }); 649 $cv->begin (sub { $cv->send (\%result) });
464loop, which serves two important purposes: first, it sets the callback 669loop, which serves two important purposes: first, it sets the callback
465to be called once the counter reaches C<0>, and second, it ensures that 670to be called once the counter reaches C<0>, and second, it ensures that
466C<send> is called even when C<no> hosts are being pinged (the loop 671C<send> is called even when C<no> hosts are being pinged (the loop
467doesn't execute once). 672doesn't execute once).
468 673
469This is the general pattern when you "fan out" into multiple subrequests: 674This is the general pattern when you "fan out" into multiple (but
470use an outer C<begin>/C<end> pair to set the callback and ensure C<end> 675potentially none) subrequests: use an outer C<begin>/C<end> pair to set
471is called at least once, and then, for each subrequest you start, call 676the callback and ensure C<end> is called at least once, and then, for each
472C<begin> and for each subrequest you finish, call C<end>. 677subrequest you start, call C<begin> and for each subrequest you finish,
678call C<end>.
473 679
474=back 680=back
475 681
476=head3 METHODS FOR CONSUMERS 682=head3 METHODS FOR CONSUMERS
477 683
522=item $bool = $cv->ready 728=item $bool = $cv->ready
523 729
524Returns true when the condition is "true", i.e. whether C<send> or 730Returns true when the condition is "true", i.e. whether C<send> or
525C<croak> have been called. 731C<croak> have been called.
526 732
527=item $cb = $cv->cb ([new callback]) 733=item $cb = $cv->cb ($cb->($cv))
528 734
529This is a mutator function that returns the callback set and optionally 735This is a mutator function that returns the callback set and optionally
530replaces it before doing so. 736replaces it before doing so.
531 737
532The callback will be called when the condition becomes "true", i.e. when 738The callback will be called when the condition becomes "true", i.e. when
533C<send> or C<croak> are called. Calling C<recv> inside the callback 739C<send> or C<croak> are called, with the only argument being the condition
534or at any later time is guaranteed not to block. 740variable itself. Calling C<recv> inside the callback or at any later time
741is guaranteed not to block.
535 742
536=back 743=back
537 744
538=head1 GLOBAL VARIABLES AND FUNCTIONS 745=head1 GLOBAL VARIABLES AND FUNCTIONS
539 746
556 AnyEvent::Impl::Tk based on Tk, very bad choice. 763 AnyEvent::Impl::Tk based on Tk, very bad choice.
557 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). 764 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
558 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 765 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
559 AnyEvent::Impl::POE based on POE, not generic enough for full support. 766 AnyEvent::Impl::POE based on POE, not generic enough for full support.
560 767
768 # warning, support for IO::Async is only partial, as it is too broken
769 # and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
770 AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
771
561There is no support for WxWidgets, as WxWidgets has no support for 772There is no support for WxWidgets, as WxWidgets has no support for
562watching file handles. However, you can use WxWidgets through the 773watching file handles. However, you can use WxWidgets through the
563POE Adaptor, as POE has a Wx backend that simply polls 20 times per 774POE Adaptor, as POE has a Wx backend that simply polls 20 times per
564second, which was considered to be too horrible to even consider for 775second, which was considered to be too horrible to even consider for
565AnyEvent. Likewise, other POE backends can be used by AnyEvent by using 776AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
668=item L<AnyEvent::Util> 879=item L<AnyEvent::Util>
669 880
670Contains various utility functions that replace often-used but blocking 881Contains various utility functions that replace often-used but blocking
671functions such as C<inet_aton> by event-/callback-based versions. 882functions such as C<inet_aton> by event-/callback-based versions.
672 883
673=item L<AnyEvent::Handle>
674
675Provide read and write buffers and manages watchers for reads and writes.
676
677=item L<AnyEvent::Socket> 884=item L<AnyEvent::Socket>
678 885
679Provides various utility functions for (internet protocol) sockets, 886Provides various utility functions for (internet protocol) sockets,
680addresses and name resolution. Also functions to create non-blocking tcp 887addresses and name resolution. Also functions to create non-blocking tcp
681connections or tcp servers, with IPv6 and SRV record support and more. 888connections or tcp servers, with IPv6 and SRV record support and more.
682 889
890=item L<AnyEvent::Handle>
891
892Provide read and write buffers, manages watchers for reads and writes,
893supports raw and formatted I/O, I/O queued and fully transparent and
894non-blocking SSL/TLS.
895
683=item L<AnyEvent::DNS> 896=item L<AnyEvent::DNS>
684 897
685Provides rich asynchronous DNS resolver capabilities. 898Provides rich asynchronous DNS resolver capabilities.
686 899
900=item L<AnyEvent::HTTP>
901
902A simple-to-use HTTP library that is capable of making a lot of concurrent
903HTTP requests.
904
687=item L<AnyEvent::HTTPD> 905=item L<AnyEvent::HTTPD>
688 906
689Provides a simple web application server framework. 907Provides a simple web application server framework.
690 908
691=item L<AnyEvent::FastPing> 909=item L<AnyEvent::FastPing>
692 910
693The fastest ping in the west. 911The fastest ping in the west.
694 912
913=item L<AnyEvent::DBI>
914
915Executes L<DBI> requests asynchronously in a proxy process.
916
917=item L<AnyEvent::AIO>
918
919Truly asynchronous I/O, should be in the toolbox of every event
920programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
921together.
922
923=item L<AnyEvent::BDB>
924
925Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
926L<BDB> and AnyEvent together.
927
928=item L<AnyEvent::GPSD>
929
930A non-blocking interface to gpsd, a daemon delivering GPS information.
931
932=item L<AnyEvent::IGS>
933
934A non-blocking interface to the Internet Go Server protocol (used by
935L<App::IGS>).
936
695=item L<Net::IRC3> 937=item L<AnyEvent::IRC>
696 938
697AnyEvent based IRC client module family. 939AnyEvent based IRC client module family (replacing the older Net::IRC3).
698 940
699=item L<Net::XMPP2> 941=item L<Net::XMPP2>
700 942
701AnyEvent based XMPP (Jabber protocol) module family. 943AnyEvent based XMPP (Jabber protocol) module family.
702 944
711 953
712=item L<Coro> 954=item L<Coro>
713 955
714Has special support for AnyEvent via L<Coro::AnyEvent>. 956Has special support for AnyEvent via L<Coro::AnyEvent>.
715 957
716=item L<AnyEvent::AIO>, L<IO::AIO>
717
718Truly asynchronous I/O, should be in the toolbox of every event
719programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
720together.
721
722=item L<AnyEvent::BDB>, L<BDB>
723
724Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
725IO::AIO and AnyEvent together.
726
727=item L<IO::Lambda> 958=item L<IO::Lambda>
728 959
729The lambda approach to I/O - don't ask, look there. Can use AnyEvent. 960The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
730 961
731=back 962=back
733=cut 964=cut
734 965
735package AnyEvent; 966package AnyEvent;
736 967
737no warnings; 968no warnings;
738use strict; 969use strict qw(vars subs);
739 970
740use Carp; 971use Carp;
741 972
742our $VERSION = '4.05'; 973our $VERSION = 4.8;
743our $MODEL; 974our $MODEL;
744 975
745our $AUTOLOAD; 976our $AUTOLOAD;
746our @ISA; 977our @ISA;
747 978
748our @REGISTRY; 979our @REGISTRY;
749 980
750our $WIN32; 981our $WIN32;
751 982
752BEGIN { 983BEGIN {
753 my $win32 = ! ! ($^O =~ /mswin32/i); 984 eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
754 eval "sub WIN32(){ $win32 }"; 985 eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
986
987 delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
988 if ${^TAINT};
755} 989}
756 990
757our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 991our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
758 992
759our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred 993our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
777 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 1011 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
778 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 1012 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
779 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza 1013 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
780 [Wx:: => AnyEvent::Impl::POE::], 1014 [Wx:: => AnyEvent::Impl::POE::],
781 [Prima:: => AnyEvent::Impl::POE::], 1015 [Prima:: => AnyEvent::Impl::POE::],
1016 # IO::Async is just too broken - we would need workaorunds for its
1017 # byzantine signal and broken child handling, among others.
1018 # IO::Async is rather hard to detect, as it doesn't have any
1019 # obvious default class.
1020# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
1021# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
1022# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
782); 1023);
783 1024
784our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY); 1025our %method = map +($_ => 1),
1026 qw(io timer time now now_update signal child idle condvar one_event DESTROY);
785 1027
786our @post_detect; 1028our @post_detect;
787 1029
788sub post_detect(&) { 1030sub post_detect(&) {
789 my ($cb) = @_; 1031 my ($cb) = @_;
794 1 1036 1
795 } else { 1037 } else {
796 push @post_detect, $cb; 1038 push @post_detect, $cb;
797 1039
798 defined wantarray 1040 defined wantarray
799 ? bless \$cb, "AnyEvent::Util::PostDetect" 1041 ? bless \$cb, "AnyEvent::Util::postdetect"
800 : () 1042 : ()
801 } 1043 }
802} 1044}
803 1045
804sub AnyEvent::Util::PostDetect::DESTROY { 1046sub AnyEvent::Util::postdetect::DESTROY {
805 @post_detect = grep $_ != ${$_[0]}, @post_detect; 1047 @post_detect = grep $_ != ${$_[0]}, @post_detect;
806} 1048}
807 1049
808sub detect() { 1050sub detect() {
809 unless ($MODEL) { 1051 unless ($MODEL) {
846 last; 1088 last;
847 } 1089 }
848 } 1090 }
849 1091
850 $MODEL 1092 $MODEL
851 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib."; 1093 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
852 } 1094 }
853 } 1095 }
854 1096
1097 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
1098
855 unshift @ISA, $MODEL; 1099 unshift @ISA, $MODEL;
856 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 1100
1101 require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
857 1102
858 (shift @post_detect)->() while @post_detect; 1103 (shift @post_detect)->() while @post_detect;
859 } 1104 }
860 1105
861 $MODEL 1106 $MODEL
871 1116
872 my $class = shift; 1117 my $class = shift;
873 $class->$func (@_); 1118 $class->$func (@_);
874} 1119}
875 1120
1121# utility function to dup a filehandle. this is used by many backends
1122# to support binding more than one watcher per filehandle (they usually
1123# allow only one watcher per fd, so we dup it to get a different one).
1124sub _dupfh($$;$$) {
1125 my ($poll, $fh, $r, $w) = @_;
1126
1127 # cygwin requires the fh mode to be matching, unix doesn't
1128 my ($rw, $mode) = $poll eq "r" ? ($r, "<")
1129 : $poll eq "w" ? ($w, ">")
1130 : Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
1131
1132 open my $fh2, "$mode&" . fileno $fh
1133 or die "cannot dup() filehandle: $!,";
1134
1135 # we assume CLOEXEC is already set by perl in all important cases
1136
1137 ($fh2, $rw)
1138}
1139
876package AnyEvent::Base; 1140package AnyEvent::Base;
877 1141
1142# default implementations for many methods
1143
1144BEGIN {
1145 if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
1146 *_time = \&Time::HiRes::time;
1147 # if (eval "use POSIX (); (POSIX::times())...
1148 } else {
1149 *_time = sub { time }; # epic fail
1150 }
1151}
1152
1153sub time { _time }
1154sub now { _time }
1155sub now_update { }
1156
878# default implementation for ->condvar 1157# default implementation for ->condvar
879 1158
880sub condvar { 1159sub condvar {
881 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar:: 1160 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
882} 1161}
883 1162
884# default implementation for ->signal 1163# default implementation for ->signal
885 1164
886our %SIG_CB; 1165our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
1166
1167sub _signal_exec {
1168 sysread $SIGPIPE_R, my $dummy, 4;
1169
1170 while (%SIG_EV) {
1171 for (keys %SIG_EV) {
1172 delete $SIG_EV{$_};
1173 $_->() for values %{ $SIG_CB{$_} || {} };
1174 }
1175 }
1176}
887 1177
888sub signal { 1178sub signal {
889 my (undef, %arg) = @_; 1179 my (undef, %arg) = @_;
890 1180
1181 unless ($SIGPIPE_R) {
1182 require Fcntl;
1183
1184 if (AnyEvent::WIN32) {
1185 require AnyEvent::Util;
1186
1187 ($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
1188 AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
1189 AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
1190 } else {
1191 pipe $SIGPIPE_R, $SIGPIPE_W;
1192 fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
1193 fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
1194
1195 # not strictly required, as $^F is normally 2, but let's make sure...
1196 fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
1197 fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
1198 }
1199
1200 $SIGPIPE_R
1201 or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
1202
1203 $SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
1204 }
1205
891 my $signal = uc $arg{signal} 1206 my $signal = uc $arg{signal}
892 or Carp::croak "required option 'signal' is missing"; 1207 or Carp::croak "required option 'signal' is missing";
893 1208
894 $SIG_CB{$signal}{$arg{cb}} = $arg{cb}; 1209 $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
895 $SIG{$signal} ||= sub { 1210 $SIG{$signal} ||= sub {
896 $_->() for values %{ $SIG_CB{$signal} || {} }; 1211 local $!;
1212 syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
1213 undef $SIG_EV{$signal};
897 }; 1214 };
898 1215
899 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal" 1216 bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
900} 1217}
901 1218
902sub AnyEvent::Base::Signal::DESTROY { 1219sub AnyEvent::Base::signal::DESTROY {
903 my ($signal, $cb) = @{$_[0]}; 1220 my ($signal, $cb) = @{$_[0]};
904 1221
905 delete $SIG_CB{$signal}{$cb}; 1222 delete $SIG_CB{$signal}{$cb};
906 1223
1224 # delete doesn't work with older perls - they then
1225 # print weird messages, or just unconditionally exit
1226 # instead of getting the default action.
907 $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} }; 1227 undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
908} 1228}
909 1229
910# default implementation for ->child 1230# default implementation for ->child
911 1231
912our %PID_CB; 1232our %PID_CB;
913our $CHLD_W; 1233our $CHLD_W;
914our $CHLD_DELAY_W; 1234our $CHLD_DELAY_W;
915our $PID_IDLE;
916our $WNOHANG; 1235our $WNOHANG;
917 1236
918sub _child_wait { 1237sub _sigchld {
919 while (0 < (my $pid = waitpid -1, $WNOHANG)) { 1238 while (0 < (my $pid = waitpid -1, $WNOHANG)) {
920 $_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }), 1239 $_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
921 (values %{ $PID_CB{0} || {} }); 1240 (values %{ $PID_CB{0} || {} });
922 } 1241 }
923
924 undef $PID_IDLE;
925}
926
927sub _sigchld {
928 # make sure we deliver these changes "synchronous" with the event loop.
929 $CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
930 undef $CHLD_DELAY_W;
931 &_child_wait;
932 });
933} 1242}
934 1243
935sub child { 1244sub child {
936 my (undef, %arg) = @_; 1245 my (undef, %arg) = @_;
937 1246
938 defined (my $pid = $arg{pid} + 0) 1247 defined (my $pid = $arg{pid} + 0)
939 or Carp::croak "required option 'pid' is missing"; 1248 or Carp::croak "required option 'pid' is missing";
940 1249
941 $PID_CB{$pid}{$arg{cb}} = $arg{cb}; 1250 $PID_CB{$pid}{$arg{cb}} = $arg{cb};
942 1251
943 unless ($WNOHANG) {
944 $WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1; 1252 $WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
945 }
946 1253
947 unless ($CHLD_W) { 1254 unless ($CHLD_W) {
948 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld); 1255 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
949 # child could be a zombie already, so make at least one round 1256 # child could be a zombie already, so make at least one round
950 &_sigchld; 1257 &_sigchld;
951 } 1258 }
952 1259
953 bless [$pid, $arg{cb}], "AnyEvent::Base::Child" 1260 bless [$pid, $arg{cb}], "AnyEvent::Base::child"
954} 1261}
955 1262
956sub AnyEvent::Base::Child::DESTROY { 1263sub AnyEvent::Base::child::DESTROY {
957 my ($pid, $cb) = @{$_[0]}; 1264 my ($pid, $cb) = @{$_[0]};
958 1265
959 delete $PID_CB{$pid}{$cb}; 1266 delete $PID_CB{$pid}{$cb};
960 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; 1267 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
961 1268
962 undef $CHLD_W unless keys %PID_CB; 1269 undef $CHLD_W unless keys %PID_CB;
1270}
1271
1272# idle emulation is done by simply using a timer, regardless
1273# of whether the process is idle or not, and not letting
1274# the callback use more than 50% of the time.
1275sub idle {
1276 my (undef, %arg) = @_;
1277
1278 my ($cb, $w, $rcb) = $arg{cb};
1279
1280 $rcb = sub {
1281 if ($cb) {
1282 $w = _time;
1283 &$cb;
1284 $w = _time - $w;
1285
1286 # never use more then 50% of the time for the idle watcher,
1287 # within some limits
1288 $w = 0.0001 if $w < 0.0001;
1289 $w = 5 if $w > 5;
1290
1291 $w = AnyEvent->timer (after => $w, cb => $rcb);
1292 } else {
1293 # clean up...
1294 undef $w;
1295 undef $rcb;
1296 }
1297 };
1298
1299 $w = AnyEvent->timer (after => 0.05, cb => $rcb);
1300
1301 bless \\$cb, "AnyEvent::Base::idle"
1302}
1303
1304sub AnyEvent::Base::idle::DESTROY {
1305 undef $${$_[0]};
963} 1306}
964 1307
965package AnyEvent::CondVar; 1308package AnyEvent::CondVar;
966 1309
967our @ISA = AnyEvent::CondVar::Base::; 1310our @ISA = AnyEvent::CondVar::Base::;
1019} 1362}
1020 1363
1021# undocumented/compatibility with pre-3.4 1364# undocumented/compatibility with pre-3.4
1022*broadcast = \&send; 1365*broadcast = \&send;
1023*wait = \&_wait; 1366*wait = \&_wait;
1367
1368=head1 ERROR AND EXCEPTION HANDLING
1369
1370In general, AnyEvent does not do any error handling - it relies on the
1371caller to do that if required. The L<AnyEvent::Strict> module (see also
1372the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
1373checking of all AnyEvent methods, however, which is highly useful during
1374development.
1375
1376As for exception handling (i.e. runtime errors and exceptions thrown while
1377executing a callback), this is not only highly event-loop specific, but
1378also not in any way wrapped by this module, as this is the job of the main
1379program.
1380
1381The pure perl event loop simply re-throws the exception (usually
1382within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
1383$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
1384so on.
1385
1386=head1 ENVIRONMENT VARIABLES
1387
1388The following environment variables are used by this module or its
1389submodules.
1390
1391Note that AnyEvent will remove I<all> environment variables starting with
1392C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
1393enabled.
1394
1395=over 4
1396
1397=item C<PERL_ANYEVENT_VERBOSE>
1398
1399By default, AnyEvent will be completely silent except in fatal
1400conditions. You can set this environment variable to make AnyEvent more
1401talkative.
1402
1403When set to C<1> or higher, causes AnyEvent to warn about unexpected
1404conditions, such as not being able to load the event model specified by
1405C<PERL_ANYEVENT_MODEL>.
1406
1407When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1408model it chooses.
1409
1410=item C<PERL_ANYEVENT_STRICT>
1411
1412AnyEvent does not do much argument checking by default, as thorough
1413argument checking is very costly. Setting this variable to a true value
1414will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1415check the arguments passed to most method calls. If it finds any problems,
1416it will croak.
1417
1418In other words, enables "strict" mode.
1419
1420Unlike C<use strict>, it is definitely recommended to keep it off in
1421production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
1422developing programs can be very useful, however.
1423
1424=item C<PERL_ANYEVENT_MODEL>
1425
1426This can be used to specify the event model to be used by AnyEvent, before
1427auto detection and -probing kicks in. It must be a string consisting
1428entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1429and the resulting module name is loaded and if the load was successful,
1430used as event model. If it fails to load AnyEvent will proceed with
1431auto detection and -probing.
1432
1433This functionality might change in future versions.
1434
1435For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1436could start your program like this:
1437
1438 PERL_ANYEVENT_MODEL=Perl perl ...
1439
1440=item C<PERL_ANYEVENT_PROTOCOLS>
1441
1442Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1443for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1444of auto probing).
1445
1446Must be set to a comma-separated list of protocols or address families,
1447current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1448used, and preference will be given to protocols mentioned earlier in the
1449list.
1450
1451This variable can effectively be used for denial-of-service attacks
1452against local programs (e.g. when setuid), although the impact is likely
1453small, as the program has to handle conenction and other failures anyways.
1454
1455Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1456but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1457- only support IPv4, never try to resolve or contact IPv6
1458addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1459IPv6, but prefer IPv6 over IPv4.
1460
1461=item C<PERL_ANYEVENT_EDNS0>
1462
1463Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1464for DNS. This extension is generally useful to reduce DNS traffic, but
1465some (broken) firewalls drop such DNS packets, which is why it is off by
1466default.
1467
1468Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1469EDNS0 in its DNS requests.
1470
1471=item C<PERL_ANYEVENT_MAX_FORKS>
1472
1473The maximum number of child processes that C<AnyEvent::Util::fork_call>
1474will create in parallel.
1475
1476=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
1477
1478The default value for the C<max_outstanding> parameter for the default DNS
1479resolver - this is the maximum number of parallel DNS requests that are
1480sent to the DNS server.
1481
1482=item C<PERL_ANYEVENT_RESOLV_CONF>
1483
1484The file to use instead of F</etc/resolv.conf> (or OS-specific
1485configuration) in the default resolver. When set to the empty string, no
1486default config will be used.
1487
1488=back
1024 1489
1025=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1490=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1026 1491
1027This is an advanced topic that you do not normally need to use AnyEvent in 1492This is an advanced topic that you do not normally need to use AnyEvent in
1028a module. This section is only of use to event loop authors who want to 1493a module. This section is only of use to event loop authors who want to
1062 1527
1063I<rxvt-unicode> also cheats a bit by not providing blocking access to 1528I<rxvt-unicode> also cheats a bit by not providing blocking access to
1064condition variables: code blocking while waiting for a condition will 1529condition variables: code blocking while waiting for a condition will
1065C<die>. This still works with most modules/usages, and blocking calls must 1530C<die>. This still works with most modules/usages, and blocking calls must
1066not be done in an interactive application, so it makes sense. 1531not be done in an interactive application, so it makes sense.
1067
1068=head1 ENVIRONMENT VARIABLES
1069
1070The following environment variables are used by this module:
1071
1072=over 4
1073
1074=item C<PERL_ANYEVENT_VERBOSE>
1075
1076By default, AnyEvent will be completely silent except in fatal
1077conditions. You can set this environment variable to make AnyEvent more
1078talkative.
1079
1080When set to C<1> or higher, causes AnyEvent to warn about unexpected
1081conditions, such as not being able to load the event model specified by
1082C<PERL_ANYEVENT_MODEL>.
1083
1084When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1085model it chooses.
1086
1087=item C<PERL_ANYEVENT_MODEL>
1088
1089This can be used to specify the event model to be used by AnyEvent, before
1090auto detection and -probing kicks in. It must be a string consisting
1091entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1092and the resulting module name is loaded and if the load was successful,
1093used as event model. If it fails to load AnyEvent will proceed with
1094auto detection and -probing.
1095
1096This functionality might change in future versions.
1097
1098For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1099could start your program like this:
1100
1101 PERL_ANYEVENT_MODEL=Perl perl ...
1102
1103=item C<PERL_ANYEVENT_PROTOCOLS>
1104
1105Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1106for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1107of auto probing).
1108
1109Must be set to a comma-separated list of protocols or address families,
1110current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1111used, and preference will be given to protocols mentioned earlier in the
1112list.
1113
1114This variable can effectively be used for denial-of-service attacks
1115against local programs (e.g. when setuid), although the impact is likely
1116small, as the program has to handle connection errors already-
1117
1118Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1119but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1120- only support IPv4, never try to resolve or contact IPv6
1121addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1122IPv6, but prefer IPv6 over IPv4.
1123
1124=item C<PERL_ANYEVENT_EDNS0>
1125
1126Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1127for DNS. This extension is generally useful to reduce DNS traffic, but
1128some (broken) firewalls drop such DNS packets, which is why it is off by
1129default.
1130
1131Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1132EDNS0 in its DNS requests.
1133
1134=item C<PERL_ANYEVENT_MAX_FORKS>
1135
1136The maximum number of child processes that C<AnyEvent::Util::fork_call>
1137will create in parallel.
1138
1139=back
1140 1532
1141=head1 EXAMPLE PROGRAM 1533=head1 EXAMPLE PROGRAM
1142 1534
1143The following program uses an I/O watcher to read data from STDIN, a timer 1535The following program uses an I/O watcher to read data from STDIN, a timer
1144to display a message once per second, and a condition variable to quit the 1536to display a message once per second, and a condition variable to quit the
1338watcher. 1730watcher.
1339 1731
1340=head3 Results 1732=head3 Results
1341 1733
1342 name watchers bytes create invoke destroy comment 1734 name watchers bytes create invoke destroy comment
1343 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1735 EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1344 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1736 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1345 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1737 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1346 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1738 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1347 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1739 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1348 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers 1740 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1741 IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
1742 IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1349 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1743 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1350 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1744 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1351 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1745 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1352 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1746 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1353 1747
1354=head3 Discussion 1748=head3 Discussion
1355 1749
1356The benchmark does I<not> measure scalability of the event loop very 1750The benchmark does I<not> measure scalability of the event loop very
1357well. For example, a select-based event loop (such as the pure perl one) 1751well. For example, a select-based event loop (such as the pure perl one)
1382performance becomes really bad with lots of file descriptors (and few of 1776performance becomes really bad with lots of file descriptors (and few of
1383them active), of course, but this was not subject of this benchmark. 1777them active), of course, but this was not subject of this benchmark.
1384 1778
1385The C<Event> module has a relatively high setup and callback invocation 1779The C<Event> module has a relatively high setup and callback invocation
1386cost, but overall scores in on the third place. 1780cost, but overall scores in on the third place.
1781
1782C<IO::Async> performs admirably well, about on par with C<Event>, even
1783when using its pure perl backend.
1387 1784
1388C<Glib>'s memory usage is quite a bit higher, but it features a 1785C<Glib>'s memory usage is quite a bit higher, but it features a
1389faster callback invocation and overall ends up in the same class as 1786faster callback invocation and overall ends up in the same class as
1390C<Event>. However, Glib scales extremely badly, doubling the number of 1787C<Event>. However, Glib scales extremely badly, doubling the number of
1391watchers increases the processing time by more than a factor of four, 1788watchers increases the processing time by more than a factor of four,
1469it to another server. This includes deleting the old timeout and creating 1866it to another server. This includes deleting the old timeout and creating
1470a new one that moves the timeout into the future. 1867a new one that moves the timeout into the future.
1471 1868
1472=head3 Results 1869=head3 Results
1473 1870
1474 name sockets create request 1871 name sockets create request
1475 EV 20000 69.01 11.16 1872 EV 20000 69.01 11.16
1476 Perl 20000 73.32 35.87 1873 Perl 20000 73.32 35.87
1874 IOAsync 20000 157.00 98.14 epoll
1875 IOAsync 20000 159.31 616.06 poll
1477 Event 20000 212.62 257.32 1876 Event 20000 212.62 257.32
1478 Glib 20000 651.16 1896.30 1877 Glib 20000 651.16 1896.30
1479 POE 20000 349.67 12317.24 uses POE::Loop::Event 1878 POE 20000 349.67 12317.24 uses POE::Loop::Event
1480 1879
1481=head3 Discussion 1880=head3 Discussion
1482 1881
1483This benchmark I<does> measure scalability and overall performance of the 1882This benchmark I<does> measure scalability and overall performance of the
1484particular event loop. 1883particular event loop.
1486EV is again fastest. Since it is using epoll on my system, the setup time 1885EV is again fastest. Since it is using epoll on my system, the setup time
1487is relatively high, though. 1886is relatively high, though.
1488 1887
1489Perl surprisingly comes second. It is much faster than the C-based event 1888Perl surprisingly comes second. It is much faster than the C-based event
1490loops Event and Glib. 1889loops Event and Glib.
1890
1891IO::Async performs very well when using its epoll backend, and still quite
1892good compared to Glib when using its pure perl backend.
1491 1893
1492Event suffers from high setup time as well (look at its code and you will 1894Event suffers from high setup time as well (look at its code and you will
1493understand why). Callback invocation also has a high overhead compared to 1895understand why). Callback invocation also has a high overhead compared to
1494the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event 1896the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1495uses select or poll in basically all documented configurations. 1897uses select or poll in basically all documented configurations.
1558=item * C-based event loops perform very well with small number of 1960=item * C-based event loops perform very well with small number of
1559watchers, as the management overhead dominates. 1961watchers, as the management overhead dominates.
1560 1962
1561=back 1963=back
1562 1964
1965=head2 THE IO::Lambda BENCHMARK
1966
1967Recently I was told about the benchmark in the IO::Lambda manpage, which
1968could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
1969simply compares IO::Lambda with POE, and IO::Lambda looks better (which
1970shouldn't come as a surprise to anybody). As such, the benchmark is
1971fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
1972very optimal. But how would AnyEvent compare when used without the extra
1973baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
1974
1975The benchmark itself creates an echo-server, and then, for 500 times,
1976connects to the echo server, sends a line, waits for the reply, and then
1977creates the next connection. This is a rather bad benchmark, as it doesn't
1978test the efficiency of the framework or much non-blocking I/O, but it is a
1979benchmark nevertheless.
1980
1981 name runtime
1982 Lambda/select 0.330 sec
1983 + optimized 0.122 sec
1984 Lambda/AnyEvent 0.327 sec
1985 + optimized 0.138 sec
1986 Raw sockets/select 0.077 sec
1987 POE/select, components 0.662 sec
1988 POE/select, raw sockets 0.226 sec
1989 POE/select, optimized 0.404 sec
1990
1991 AnyEvent/select/nb 0.085 sec
1992 AnyEvent/EV/nb 0.068 sec
1993 +state machine 0.134 sec
1994
1995The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
1996benchmarks actually make blocking connects and use 100% blocking I/O,
1997defeating the purpose of an event-based solution. All of the newly
1998written AnyEvent benchmarks use 100% non-blocking connects (using
1999AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
2000resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
2001generally require a lot more bookkeeping and event handling than blocking
2002connects (which involve a single syscall only).
2003
2004The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
2005offers similar expressive power as POE and IO::Lambda, using conventional
2006Perl syntax. This means that both the echo server and the client are 100%
2007non-blocking, further placing it at a disadvantage.
2008
2009As you can see, the AnyEvent + EV combination even beats the
2010hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
2011backend easily beats IO::Lambda and POE.
2012
2013And even the 100% non-blocking version written using the high-level (and
2014slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
2015large margin, even though it does all of DNS, tcp-connect and socket I/O
2016in a non-blocking way.
2017
2018The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
2019F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
2020part of the IO::lambda distribution and were used without any changes.
2021
2022
2023=head1 SIGNALS
2024
2025AnyEvent currently installs handlers for these signals:
2026
2027=over 4
2028
2029=item SIGCHLD
2030
2031A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
2032emulation for event loops that do not support them natively. Also, some
2033event loops install a similar handler.
2034
2035If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent will
2036reset it to default, to avoid losing child exit statuses.
2037
2038=item SIGPIPE
2039
2040A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
2041when AnyEvent gets loaded.
2042
2043The rationale for this is that AnyEvent users usually do not really depend
2044on SIGPIPE delivery (which is purely an optimisation for shell use, or
2045badly-written programs), but C<SIGPIPE> can cause spurious and rare
2046program exits as a lot of people do not expect C<SIGPIPE> when writing to
2047some random socket.
2048
2049The rationale for installing a no-op handler as opposed to ignoring it is
2050that this way, the handler will be restored to defaults on exec.
2051
2052Feel free to install your own handler, or reset it to defaults.
2053
2054=back
2055
2056=cut
2057
2058undef $SIG{CHLD}
2059 if $SIG{CHLD} eq 'IGNORE';
2060
2061$SIG{PIPE} = sub { }
2062 unless defined $SIG{PIPE};
1563 2063
1564=head1 FORK 2064=head1 FORK
1565 2065
1566Most event libraries are not fork-safe. The ones who are usually are 2066Most event libraries are not fork-safe. The ones who are usually are
1567because they rely on inefficient but fork-safe C<select> or C<poll> 2067because they rely on inefficient but fork-safe C<select> or C<poll>
1581specified in the variable. 2081specified in the variable.
1582 2082
1583You can make AnyEvent completely ignore this variable by deleting it 2083You can make AnyEvent completely ignore this variable by deleting it
1584before the first watcher gets created, e.g. with a C<BEGIN> block: 2084before the first watcher gets created, e.g. with a C<BEGIN> block:
1585 2085
1586 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 2086 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1587 2087
1588 use AnyEvent; 2088 use AnyEvent;
1589 2089
1590Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 2090Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1591be used to probe what backend is used and gain other information (which is 2091be used to probe what backend is used and gain other information (which is
1592probably even less useful to an attacker than PERL_ANYEVENT_MODEL). 2092probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
2093$ENV{PERL_ANYEVENT_STRICT}.
2094
2095Note that AnyEvent will remove I<all> environment variables starting with
2096C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
2097enabled.
2098
2099
2100=head1 BUGS
2101
2102Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
2103to work around. If you suffer from memleaks, first upgrade to Perl 5.10
2104and check wether the leaks still show up. (Perl 5.10.0 has other annoying
2105memleaks, such as leaking on C<map> and C<grep> but it is usually not as
2106pronounced).
1593 2107
1594 2108
1595=head1 SEE ALSO 2109=head1 SEE ALSO
1596 2110
1597Utility functions: L<AnyEvent::Util>. 2111Utility functions: L<AnyEvent::Util>.
1614Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>. 2128Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1615 2129
1616 2130
1617=head1 AUTHOR 2131=head1 AUTHOR
1618 2132
1619 Marc Lehmann <schmorp@schmorp.de> 2133 Marc Lehmann <schmorp@schmorp.de>
1620 http://home.schmorp.de/ 2134 http://home.schmorp.de/
1621 2135
1622=cut 2136=cut
1623 2137
16241 21381
1625 2139

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