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Revision 1.173 by root, Mon Jul 21 03:47:22 2008 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });
		12
		13	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		14	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		15
		16	print AnyEvent->now; # prints current event loop time
		17	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		18
		19	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		20
		21	my $w = AnyEvent->child (pid => $pid, cb => sub {
		22	my ($pid, $status) = @_;
12	...	23	...
13	});	24	});
14		25
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...
17	});
18
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	26	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		27	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	28	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	29	# use a condvar in callback mode:
		30	$w->cb (sub { $_[0]->recv });
		31
		32	=head1 INTRODUCTION/TUTORIAL
		33
		34	This manpage is mainly a reference manual. If you are interested
		35	in a tutorial or some gentle introduction, have a look at the
		36	L<AnyEvent::Intro> manpage.
22		37
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	38	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		39
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	40	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	41	nowadays. So what is different about AnyEvent?
27		42
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	43	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	44	policy> and AnyEvent is I<small and efficient>.
30		45
31	First and foremost, I<AnyEvent is not an event model> itself, it only	46	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	47	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	48	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	49	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	50	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	51	cannot change this, but it can hide the differences between those event
		52	loops.
37		53
38	The goal of AnyEvent is to offer module authors the ability to do event	54	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	55	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	56	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	57	module users into the same thing by forcing them to use the same event
42	model you use.	58	model you use.
43		59
44	For modules like POE or IO::Async (which is a total misnomer as it is	60	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	61	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	62	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	63	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	64	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	65	module are I<also> forced to use the same event loop you use.
50		66
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	67	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	68	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	69	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	70	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	71	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	72	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	73	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	74	to AnyEvent, too, so it is future-proof).
59		75
60	In addition to being free of having to use I<the one and only true event	76	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	77	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	78	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	79	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	80	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	81	technically possible.
66		82
		83	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		84	of useful functionality, such as an asynchronous DNS resolver, 100%
		85	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		86	such as Windows) and lots of real-world knowledge and workarounds for
		87	platform bugs and differences.
		88
67	Of course, if you want lots of policy (this can arguably be somewhat	89	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	90	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	91	model, you should I<not> use this module.
70
71		92
72	=head1 DESCRIPTION	93	=head1 DESCRIPTION
73		94
74	L<AnyEvent> provides an identical interface to multiple event loops. This	95	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	96	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	100	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	101	module.
81		102
82	During the first call of any watcher-creation method, the module tries	103	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	104	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	105	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	106	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	107	L<POE>. The first one found is used. If none are found, the module tries
		108	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		109	adaptor should always succeed) in the order given. The first one that can
87	that can be successfully loaded will be used. If, after this, still none	110	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	111	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	112	very efficient, but should work everywhere.
90		113
91	Because AnyEvent first checks for modules that are already loaded, loading	114	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	115	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	116	that model the default. For example:
94		117
…		…
101	starts using it, all bets are off. Maybe you should tell their authors to	124	starts using it, all bets are off. Maybe you should tell their authors to
102	use AnyEvent so their modules work together with others seamlessly...	125	use AnyEvent so their modules work together with others seamlessly...
103		126
104	The pure-perl implementation of AnyEvent is called	127	The pure-perl implementation of AnyEvent is called
105	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	128	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
106	explicitly.	129	explicitly and enjoy the high availability of that event loop :)
107		130
108	=head1 WATCHERS	131	=head1 WATCHERS
109		132
110	AnyEvent has the central concept of a I<watcher>, which is an object that	133	AnyEvent has the central concept of a I<watcher>, which is an object that
111	stores relevant data for each kind of event you are waiting for, such as	134	stores relevant data for each kind of event you are waiting for, such as
112	the callback to call, the filehandle to watch, etc.	135	the callback to call, the file handle to watch, etc.
113		136
114	These watchers are normal Perl objects with normal Perl lifetime. After	137	These watchers are normal Perl objects with normal Perl lifetime. After
115	creating a watcher it will immediately "watch" for events and invoke the	138	creating a watcher it will immediately "watch" for events and invoke the
116	callback when the event occurs (of course, only when the event model	139	callback when the event occurs (of course, only when the event model
117	is in control).	140	is in control).
…		…
125	Many watchers either are used with "recursion" (repeating timers for	148	Many watchers either are used with "recursion" (repeating timers for
126	example), or need to refer to their watcher object in other ways.	149	example), or need to refer to their watcher object in other ways.
127		150
128	An any way to achieve that is this pattern:	151	An any way to achieve that is this pattern:
129		152
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	153	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	154	# you can use $w here, for example to undef it
132	undef $w;	155	undef $w;
133	});	156	});
134		157
135	Note that C<my $w; $w => combination. This is necessary because in Perl,	158	Note that C<my $w; $w => combination. This is necessary because in Perl,
136	my variables are only visible after the statement in which they are	159	my variables are only visible after the statement in which they are
137	declared.	160	declared.
138		161
139	=head2 IO WATCHERS	162	=head2 I/O WATCHERS
140		163
141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	164	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
142	with the following mandatory key-value pairs as arguments:	165	with the following mandatory key-value pairs as arguments:
143		166
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	167	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for events
		168	(AnyEvent might or might not keep a reference to this file handle). C<poll>
145	events. C<poll> must be a string that is either C<r> or C<w>, which	169	must be a string that is either C<r> or C<w>, which creates a watcher
146	creates a watcher waiting for "r"eadable or "w"ritable events,	170	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the
147	respectively. C<cb> is the callback to invoke each time the file handle	171	callback to invoke each time the file handle becomes ready.
148	becomes ready.
149		172
150	File handles will be kept alive, so as long as the watcher exists, the	173	Although the callback might get passed parameters, their value and
151	file handle exists, too.	174	presence is undefined and you cannot rely on them. Portable AnyEvent
		175	callbacks cannot use arguments passed to I/O watcher callbacks.
152		176
		177	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	178	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	179	underlying file descriptor.
155		180
156	Some event loops issue spurious readyness notifications, so you should	181	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	182	always use non-blocking calls when reading/writing from/to your file
158	handles.	183	handles.
159		184
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	185	Example: wait for readability of STDIN, then read a line and disable the
		186	watcher.
		187
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	188	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	189	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	190	warn "read: $input\n";
166	undef $w;	191	undef $w;
167	});	192	});
…		…
170		195
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	196	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	197	method with the following mandatory arguments:
173		198
174	C<after> specifies after how many seconds (fractional values are	199	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	200	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	201	in that case.
177		202
178	The timer callback will be invoked at most once: if you want a repeating	203	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	204	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	205	callbacks cannot use arguments passed to time watcher callbacks.
181		206
182	Example:	207	The callback will normally be invoked once only. If you specify another
		208	parameter, C<interval>, as a strictly positive number (> 0), then the
		209	callback will be invoked regularly at that interval (in fractional
		210	seconds) after the first invocation. If C<interval> is specified with a
		211	false value, then it is treated as if it were missing.
183		212
		213	The callback will be rescheduled before invoking the callback, but no
		214	attempt is done to avoid timer drift in most backends, so the interval is
		215	only approximate.
		216
184	# fire an event after 7.7 seconds	217	Example: fire an event after 7.7 seconds.
		218
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	219	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	220	warn "timeout\n";
187	});	221	});
188		222
189	# to cancel the timer:	223	# to cancel the timer:
190	undef $w;	224	undef $w;
191		225
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	226	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		227
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	228	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		229	warn "timeout\n";
200	};	230	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		231
205	=head3 TIMING ISSUES	232	=head3 TIMING ISSUES
206		233
207	There are two ways to handle timers: based on real time (relative, "fire	234	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	235	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	236	o'clock").
210		237
211	While most event loops expect timers to specified in a relative way, they use	238	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	239	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	240	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	241	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	242	fire "after" a second might actually take six years to finally fire.
216		243
217	AnyEvent cannot compensate for this. The only event loop that is conscious	244	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	245	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	246	on true relative time) and absolute (ev_periodic, based on wallclock time)
		247	timers.
220		248
221	AnyEvent always prefers relative timers, if available, matching the	249	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	250	AnyEvent API.
223		251
		252	AnyEvent has two additional methods that return the "current time":
		253
		254	=over 4
		255
		256	=item AnyEvent->time
		257
		258	This returns the "current wallclock time" as a fractional number of
		259	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		260	return, and the result is guaranteed to be compatible with those).
		261
		262	It progresses independently of any event loop processing, i.e. each call
		263	will check the system clock, which usually gets updated frequently.
		264
		265	=item AnyEvent->now
		266
		267	This also returns the "current wallclock time", but unlike C<time>, above,
		268	this value might change only once per event loop iteration, depending on
		269	the event loop (most return the same time as C<time>, above). This is the
		270	time that AnyEvent's timers get scheduled against.
		271
		272	I<In almost all cases (in all cases if you don't care), this is the
		273	function to call when you want to know the current time.>
		274
		275	This function is also often faster then C<< AnyEvent->time >>, and
		276	thus the preferred method if you want some timestamp (for example,
		277	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		278
		279	The rest of this section is only of relevance if you try to be very exact
		280	with your timing, you can skip it without bad conscience.
		281
		282	For a practical example of when these times differ, consider L<Event::Lib>
		283	and L<EV> and the following set-up:
		284
		285	The event loop is running and has just invoked one of your callback at
		286	time=500 (assume no other callbacks delay processing). In your callback,
		287	you wait a second by executing C<sleep 1> (blocking the process for a
		288	second) and then (at time=501) you create a relative timer that fires
		289	after three seconds.
		290
		291	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		292	both return C<501>, because that is the current time, and the timer will
		293	be scheduled to fire at time=504 (C<501> + C<3>).
		294
		295	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		296	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		297	last event processing phase started. With L<EV>, your timer gets scheduled
		298	to run at time=503 (C<500> + C<3>).
		299
		300	In one sense, L<Event::Lib> is more exact, as it uses the current time
		301	regardless of any delays introduced by event processing. However, most
		302	callbacks do not expect large delays in processing, so this causes a
		303	higher drift (and a lot more system calls to get the current time).
		304
		305	In another sense, L<EV> is more exact, as your timer will be scheduled at
		306	the same time, regardless of how long event processing actually took.
		307
		308	In either case, if you care (and in most cases, you don't), then you
		309	can get whatever behaviour you want with any event loop, by taking the
		310	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		311	account.
		312
		313	=back
		314
224	=head2 SIGNAL WATCHERS	315	=head2 SIGNAL WATCHERS
225		316
226	You can watch for signals using a signal watcher, C<signal> is the signal	317	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	318	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
228	be invoked whenever a signal occurs.	319	callback to be invoked whenever a signal occurs.
229		320
		321	Although the callback might get passed parameters, their value and
		322	presence is undefined and you cannot rely on them. Portable AnyEvent
		323	callbacks cannot use arguments passed to signal watcher callbacks.
		324
230	Multiple signals occurances can be clumped together into one callback	325	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	326	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	327	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	328	but it is guaranteed not to interrupt any other callbacks.
234		329
235	The main advantage of using these watchers is that you can share a signal	330	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	331	between multiple watchers.
237		332
238	This watcher might use C<%SIG>, so programs overwriting those signals	333	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
248		343
249	The child process is specified by the C<pid> argument (if set to C<0>, it	344	The child process is specified by the C<pid> argument (if set to C<0>, it
250	watches for any child process exit). The watcher will trigger as often	345	watches for any child process exit). The watcher will trigger as often
251	as status change for the child are received. This works by installing a	346	as status change for the child are received. This works by installing a
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	347	signal handler for C<SIGCHLD>. The callback will be called with the pid
253	and exit status (as returned by waitpid).	348	and exit status (as returned by waitpid), so unlike other watcher types,
		349	you I<can> rely on child watcher callback arguments.
254		350
255	Example: wait for pid 1333	351	There is a slight catch to child watchers, however: you usually start them
		352	I<after> the child process was created, and this means the process could
		353	have exited already (and no SIGCHLD will be sent anymore).
256		354
		355	Not all event models handle this correctly (POE doesn't), but even for
		356	event models that I<do> handle this correctly, they usually need to be
		357	loaded before the process exits (i.e. before you fork in the first place).
		358
		359	This means you cannot create a child watcher as the very first thing in an
		360	AnyEvent program, you I<have> to create at least one watcher before you
		361	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		362
		363	Example: fork a process and wait for it
		364
		365	my $done = AnyEvent->condvar;
		366
		367	my $pid = fork or exit 5;
		368
257	my $w = AnyEvent->child (	369	my $w = AnyEvent->child (
258	pid => 1333,	370	pid => $pid,
259	cb => sub {	371	cb => sub {
260	my ($pid, $status) = @_;	372	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	373	warn "pid $pid exited with status $status";
		374	$done->send;
262	},	375	},
263	);	376	);
		377
		378	# do something else, then wait for process exit
		379	$done->recv;
264		380
265	=head2 CONDITION VARIABLES	381	=head2 CONDITION VARIABLES
266		382
		383	If you are familiar with some event loops you will know that all of them
		384	require you to run some blocking "loop", "run" or similar function that
		385	will actively watch for new events and call your callbacks.
		386
		387	AnyEvent is different, it expects somebody else to run the event loop and
		388	will only block when necessary (usually when told by the user).
		389
		390	The instrument to do that is called a "condition variable", so called
		391	because they represent a condition that must become true.
		392
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	393	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.
269		394
270	A condition variable waits for a condition - precisely that the C<<	395	>> method, usually without arguments. The only argument pair allowed is
271	->broadcast >> method has been called.
272		396
273	They are very useful to signal that a condition has been fulfilled, for	397	C<cb>, which specifies a callback to be called when the condition variable
		398	becomes true, with the condition variable as the first argument (but not
		399	the results).
		400
		401	After creation, the condition variable is "false" until it becomes "true"
		402	by calling the C<send> method (or calling the condition variable as if it
		403	were a callback, read about the caveats in the description for the C<<
		404	->send >> method).
		405
		406	Condition variables are similar to callbacks, except that you can
		407	optionally wait for them. They can also be called merge points - points
		408	in time where multiple outstanding events have been processed. And yet
		409	another way to call them is transactions - each condition variable can be
		410	used to represent a transaction, which finishes at some point and delivers
		411	a result.
		412
		413	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	414	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	415	then a condition variable would be the ideal candidate to signal the
276	availability of results.	416	availability of results. The user can either act when the callback is
		417	called or can synchronously C<< ->recv >> for the results.
277		418
278	You can also use condition variables to block your main program until	419	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	420	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	421	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	422	button of your app, which would C<< ->send >> the "quit" event.
282		423
283	Note that condition variables recurse into the event loop - if you have	424	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	425	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	426	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	427	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	428	as this asks for trouble.
288		429
289	This object has two methods:	430	Condition variables are represented by hash refs in perl, and the keys
		431	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		432	easy (it is often useful to build your own transaction class on top of
		433	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		434	it's C<new> method in your own C<new> method.
		435
		436	There are two "sides" to a condition variable - the "producer side" which
		437	eventually calls C<< -> send >>, and the "consumer side", which waits
		438	for the send to occur.
		439
		440	Example: wait for a timer.
		441
		442	# wait till the result is ready
		443	my $result_ready = AnyEvent->condvar;
		444
		445	# do something such as adding a timer
		446	# or socket watcher the calls $result_ready->send
		447	# when the "result" is ready.
		448	# in this case, we simply use a timer:
		449	my $w = AnyEvent->timer (
		450	after => 1,
		451	cb => sub { $result_ready->send },
		452	);
		453
		454	# this "blocks" (while handling events) till the callback
		455	# calls send
		456	$result_ready->recv;
		457
		458	Example: wait for a timer, but take advantage of the fact that
		459	condition variables are also code references.
		460
		461	my $done = AnyEvent->condvar;
		462	my $delay = AnyEvent->timer (after => 5, cb => $done);
		463	$done->recv;
		464
		465	Example: Imagine an API that returns a condvar and doesn't support
		466	callbacks. This is how you make a synchronous call, for example from
		467	the main program:
		468
		469	use AnyEvent::CouchDB;
		470
		471	...
		472
		473	my @info = $couchdb->info->recv;
		474
		475	And this is how you would just ste a callback to be called whenever the
		476	results are available:
		477
		478	$couchdb->info->cb (sub {
		479	my @info = $_[0]->recv;
		480	});
		481
		482	=head3 METHODS FOR PRODUCERS
		483
		484	These methods should only be used by the producing side, i.e. the
		485	code/module that eventually sends the signal. Note that it is also
		486	the producer side which creates the condvar in most cases, but it isn't
		487	uncommon for the consumer to create it as well.
290		488
291	=over 4	489	=over 4
292		490
		491	=item $cv->send (...)
		492
		493	Flag the condition as ready - a running C<< ->recv >> and all further
		494	calls to C<recv> will (eventually) return after this method has been
		495	called. If nobody is waiting the send will be remembered.
		496
		497	If a callback has been set on the condition variable, it is called
		498	immediately from within send.
		499
		500	Any arguments passed to the C<send> call will be returned by all
		501	future C<< ->recv >> calls.
		502
		503	Condition variables are overloaded so one can call them directly
		504	(as a code reference). Calling them directly is the same as calling
		505	C<send>. Note, however, that many C-based event loops do not handle
		506	overloading, so as tempting as it may be, passing a condition variable
		507	instead of a callback does not work. Both the pure perl and EV loops
		508	support overloading, however, as well as all functions that use perl to
		509	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		510	example).
		511
		512	=item $cv->croak ($error)
		513
		514	Similar to send, but causes all call's to C<< ->recv >> to invoke
		515	C<Carp::croak> with the given error message/object/scalar.
		516
		517	This can be used to signal any errors to the condition variable
		518	user/consumer.
		519
		520	=item $cv->begin ([group callback])
		521
293	=item $cv->wait	522	=item $cv->end
294		523
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	524	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		525
		526	These two methods can be used to combine many transactions/events into
		527	one. For example, a function that pings many hosts in parallel might want
		528	to use a condition variable for the whole process.
		529
		530	Every call to C<< ->begin >> will increment a counter, and every call to
		531	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		532	>>, the (last) callback passed to C<begin> will be executed. That callback
		533	is I<supposed> to call C<< ->send >>, but that is not required. If no
		534	callback was set, C<send> will be called without any arguments.
		535
		536	Let's clarify this with the ping example:
		537
		538	my $cv = AnyEvent->condvar;
		539
		540	my %result;
		541	$cv->begin (sub { $cv->send (\%result) });
		542
		543	for my $host (@list_of_hosts) {
		544	$cv->begin;
		545	ping_host_then_call_callback $host, sub {
		546	$result{$host} = ...;
		547	$cv->end;
		548	};
		549	}
		550
		551	$cv->end;
		552
		553	This code fragment supposedly pings a number of hosts and calls
		554	C<send> after results for all then have have been gathered - in any
		555	order. To achieve this, the code issues a call to C<begin> when it starts
		556	each ping request and calls C<end> when it has received some result for
		557	it. Since C<begin> and C<end> only maintain a counter, the order in which
		558	results arrive is not relevant.
		559
		560	There is an additional bracketing call to C<begin> and C<end> outside the
		561	loop, which serves two important purposes: first, it sets the callback
		562	to be called once the counter reaches C<0>, and second, it ensures that
		563	C<send> is called even when C<no> hosts are being pinged (the loop
		564	doesn't execute once).
		565
		566	This is the general pattern when you "fan out" into multiple subrequests:
		567	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		568	is called at least once, and then, for each subrequest you start, call
		569	C<begin> and for each subrequest you finish, call C<end>.
		570
		571	=back
		572
		573	=head3 METHODS FOR CONSUMERS
		574
		575	These methods should only be used by the consuming side, i.e. the
		576	code awaits the condition.
		577
		578	=over 4
		579
		580	=item $cv->recv
		581
		582	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
296	called on c<$cv>, while servicing other watchers normally.	583	>> methods have been called on c<$cv>, while servicing other watchers
		584	normally.
297		585
298	You can only wait once on a condition - additional calls will return	586	You can only wait once on a condition - additional calls are valid but
299	immediately.	587	will return immediately.
		588
		589	If an error condition has been set by calling C<< ->croak >>, then this
		590	function will call C<croak>.
		591
		592	In list context, all parameters passed to C<send> will be returned,
		593	in scalar context only the first one will be returned.
300		594
301	Not all event models support a blocking wait - some die in that case	595	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are	596	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the	597	using this from a module, never require a blocking wait>, but let the
304	caller decide whether the call will block or not (for example, by coupling	598	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting	599	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,	600	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).	601	while still supporting blocking waits if the caller so desires).
308		602
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot	603	Another reason I<never> to C<< ->recv >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require	604	sensibly have two C<< ->recv >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	605	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	606	can supply.
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315		607
316	=item $cv->broadcast	608	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		609	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		610	versions and also integrates coroutines into AnyEvent, making blocking
		611	C<< ->recv >> calls perfectly safe as long as they are done from another
		612	coroutine (one that doesn't run the event loop).
317		613
318	Flag the condition as ready - a running C<< ->wait >> and all further	614	You can ensure that C<< -recv >> never blocks by setting a callback and
319	calls to C<wait> will (eventually) return after this method has been	615	only calling C<< ->recv >> from within that callback (or at a later
320	called. If nobody is waiting the broadcast will be remembered..	616	time). This will work even when the event loop does not support blocking
		617	waits otherwise.
		618
		619	=item $bool = $cv->ready
		620
		621	Returns true when the condition is "true", i.e. whether C<send> or
		622	C<croak> have been called.
		623
		624	=item $cb = $cv->cb ($cb->($cv))
		625
		626	This is a mutator function that returns the callback set and optionally
		627	replaces it before doing so.
		628
		629	The callback will be called when the condition becomes "true", i.e. when
		630	C<send> or C<croak> are called, with the only argument being the condition
		631	variable itself. Calling C<recv> inside the callback or at any later time
		632	is guaranteed not to block.
321		633
322	=back	634	=back
323
324	Example:
325
326	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;
328
329	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast
331	# when the "result" is ready.
332	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (
334	after => 1,
335	cb => sub { $result_ready->broadcast },
336	);
337
338	# this "blocks" (while handling events) till the watcher
339	# calls broadcast
340	$result_ready->wait;
341		635
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	636	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		637
344	=over 4	638	=over 4
345		639
…		…
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	645	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	646	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
353		647
354	The known classes so far are:	648	The known classes so far are:
355		649
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	650	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)	651	AnyEvent::Impl::Event based on Event, second best choice.
		652	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
360	AnyEvent::Impl::Glib based on Glib, third-best choice.	653	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.	654	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	655	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		656	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		657	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		658
		659	There is no support for WxWidgets, as WxWidgets has no support for
		660	watching file handles. However, you can use WxWidgets through the
		661	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		662	second, which was considered to be too horrible to even consider for
		663	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		664	it's adaptor.
		665
		666	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		667	autodetecting them.
363		668
364	=item AnyEvent::detect	669	=item AnyEvent::detect
365		670
366	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	671	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
367	if necessary. You should only call this function right before you would	672	if necessary. You should only call this function right before you would
368	have created an AnyEvent watcher anyway, that is, as late as possible at	673	have created an AnyEvent watcher anyway, that is, as late as possible at
369	runtime.	674	runtime.
370		675
		676	=item $guard = AnyEvent::post_detect { BLOCK }
		677
		678	Arranges for the code block to be executed as soon as the event model is
		679	autodetected (or immediately if this has already happened).
		680
		681	If called in scalar or list context, then it creates and returns an object
		682	that automatically removes the callback again when it is destroyed. See
		683	L<Coro::BDB> for a case where this is useful.
		684
		685	=item @AnyEvent::post_detect
		686
		687	If there are any code references in this array (you can C<push> to it
		688	before or after loading AnyEvent), then they will called directly after
		689	the event loop has been chosen.
		690
		691	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		692	if it contains a true value then the event loop has already been detected,
		693	and the array will be ignored.
		694
		695	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		696
371	=back	697	=back
372		698
373	=head1 WHAT TO DO IN A MODULE	699	=head1 WHAT TO DO IN A MODULE
374		700
375	As a module author, you should C<use AnyEvent> and call AnyEvent methods	701	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
378	Be careful when you create watchers in the module body - AnyEvent will	704	Be careful when you create watchers in the module body - AnyEvent will
379	decide which event module to use as soon as the first method is called, so	705	decide which event module to use as soon as the first method is called, so
380	by calling AnyEvent in your module body you force the user of your module	706	by calling AnyEvent in your module body you force the user of your module
381	to load the event module first.	707	to load the event module first.
382		708
383	Never call C<< ->wait >> on a condition variable unless you I<know> that	709	Never call C<< ->recv >> on a condition variable unless you I<know> that
384	the C<< ->broadcast >> method has been called on it already. This is	710	the C<< ->send >> method has been called on it already. This is
385	because it will stall the whole program, and the whole point of using	711	because it will stall the whole program, and the whole point of using
386	events is to stay interactive.	712	events is to stay interactive.
387		713
388	It is fine, however, to call C<< ->wait >> when the user of your module	714	It is fine, however, to call C<< ->recv >> when the user of your module
389	requests it (i.e. if you create a http request object ad have a method	715	requests it (i.e. if you create a http request object ad have a method
390	called C<results> that returns the results, it should call C<< ->wait >>	716	called C<results> that returns the results, it should call C<< ->recv >>
391	freely, as the user of your module knows what she is doing. always).	717	freely, as the user of your module knows what she is doing. always).
392		718
393	=head1 WHAT TO DO IN THE MAIN PROGRAM	719	=head1 WHAT TO DO IN THE MAIN PROGRAM
394		720
395	There will always be a single main program - the only place that should	721	There will always be a single main program - the only place that should
…		…
397		723
398	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	724	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
399	do anything special (it does not need to be event-based) and let AnyEvent	725	do anything special (it does not need to be event-based) and let AnyEvent
400	decide which implementation to chose if some module relies on it.	726	decide which implementation to chose if some module relies on it.
401		727
402	If the main program relies on a specific event model. For example, in	728	If the main program relies on a specific event model - for example, in
403	Gtk2 programs you have to rely on the Glib module. You should load the	729	Gtk2 programs you have to rely on the Glib module - you should load the
404	event module before loading AnyEvent or any module that uses it: generally	730	event module before loading AnyEvent or any module that uses it: generally
405	speaking, you should load it as early as possible. The reason is that	731	speaking, you should load it as early as possible. The reason is that
406	modules might create watchers when they are loaded, and AnyEvent will	732	modules might create watchers when they are loaded, and AnyEvent will
407	decide on the event model to use as soon as it creates watchers, and it	733	decide on the event model to use as soon as it creates watchers, and it
408	might chose the wrong one unless you load the correct one yourself.	734	might chose the wrong one unless you load the correct one yourself.
409		735
410	You can chose to use a rather inefficient pure-perl implementation by	736	You can chose to use a pure-perl implementation by loading the
411	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	737	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
412	behaviour everywhere, but letting AnyEvent chose is generally better.	738	everywhere, but letting AnyEvent chose the model is generally better.
		739
		740	=head2 MAINLOOP EMULATION
		741
		742	Sometimes (often for short test scripts, or even standalone programs who
		743	only want to use AnyEvent), you do not want to run a specific event loop.
		744
		745	In that case, you can use a condition variable like this:
		746
		747	AnyEvent->condvar->recv;
		748
		749	This has the effect of entering the event loop and looping forever.
		750
		751	Note that usually your program has some exit condition, in which case
		752	it is better to use the "traditional" approach of storing a condition
		753	variable somewhere, waiting for it, and sending it when the program should
		754	exit cleanly.
		755
		756
		757	=head1 OTHER MODULES
		758
		759	The following is a non-exhaustive list of additional modules that use
		760	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		761	in the same program. Some of the modules come with AnyEvent, some are
		762	available via CPAN.
		763
		764	=over 4
		765
		766	=item L<AnyEvent::Util>
		767
		768	Contains various utility functions that replace often-used but blocking
		769	functions such as C<inet_aton> by event-/callback-based versions.
		770
		771	=item L<AnyEvent::Socket>
		772
		773	Provides various utility functions for (internet protocol) sockets,
		774	addresses and name resolution. Also functions to create non-blocking tcp
		775	connections or tcp servers, with IPv6 and SRV record support and more.
		776
		777	=item L<AnyEvent::Handle>
		778
		779	Provide read and write buffers, manages watchers for reads and writes,
		780	supports raw and formatted I/O, I/O queued and fully transparent and
		781	non-blocking SSL/TLS.
		782
		783	=item L<AnyEvent::DNS>
		784
		785	Provides rich asynchronous DNS resolver capabilities.
		786
		787	=item L<AnyEvent::HTTP>
		788
		789	A simple-to-use HTTP library that is capable of making a lot of concurrent
		790	HTTP requests.
		791
		792	=item L<AnyEvent::HTTPD>
		793
		794	Provides a simple web application server framework.
		795
		796	=item L<AnyEvent::FastPing>
		797
		798	The fastest ping in the west.
		799
		800	=item L<AnyEvent::DBI>
		801
		802	Executes L<DBI> requests asynchronously in a proxy process.
		803
		804	=item L<AnyEvent::AIO>
		805
		806	Truly asynchronous I/O, should be in the toolbox of every event
		807	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		808	together.
		809
		810	=item L<AnyEvent::BDB>
		811
		812	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		813	L<BDB> and AnyEvent together.
		814
		815	=item L<AnyEvent::GPSD>
		816
		817	A non-blocking interface to gpsd, a daemon delivering GPS information.
		818
		819	=item L<AnyEvent::IGS>
		820
		821	A non-blocking interface to the Internet Go Server protocol (used by
		822	L<App::IGS>).
		823
		824	=item L<Net::IRC3>
		825
		826	AnyEvent based IRC client module family.
		827
		828	=item L<Net::XMPP2>
		829
		830	AnyEvent based XMPP (Jabber protocol) module family.
		831
		832	=item L<Net::FCP>
		833
		834	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		835	of AnyEvent.
		836
		837	=item L<Event::ExecFlow>
		838
		839	High level API for event-based execution flow control.
		840
		841	=item L<Coro>
		842
		843	Has special support for AnyEvent via L<Coro::AnyEvent>.
		844
		845	=item L<IO::Lambda>
		846
		847	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		848
		849	=back
413		850
414	=cut	851	=cut
415		852
416	package AnyEvent;	853	package AnyEvent;
417		854
418	no warnings;	855	no warnings;
419	use strict;	856	use strict;
420		857
421	use Carp;	858	use Carp;
422		859
423	our $VERSION = '3.12';	860	our $VERSION = 4.22;
424	our $MODEL;	861	our $MODEL;
425		862
426	our $AUTOLOAD;	863	our $AUTOLOAD;
427	our @ISA;	864	our @ISA;
428		865
		866	our @REGISTRY;
		867
		868	our $WIN32;
		869
		870	BEGIN {
		871	my $win32 = ! ! ($^O =~ /mswin32/i);
		872	eval "sub WIN32(){ $win32 }";
		873	}
		874
429	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	875	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
430		876
431	our @REGISTRY;	877	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		878
		879	{
		880	my $idx;
		881	$PROTOCOL{$_} = ++$idx
		882	for reverse split /\s*,\s*/,
		883	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		884	}
432		885
433	my @models = (	886	my @models = (
434	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
435	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
436	[EV:: => AnyEvent::Impl::EV::],	887	[EV:: => AnyEvent::Impl::EV::],
437	[Event:: => AnyEvent::Impl::Event::],	888	[Event:: => AnyEvent::Impl::Event::],
438	[Glib:: => AnyEvent::Impl::Glib::],
439	[Tk:: => AnyEvent::Impl::Tk::],
440	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	889	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		890	# everything below here will not be autoprobed
		891	# as the pureperl backend should work everywhere
		892	# and is usually faster
		893	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		894	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		895	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		896	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		897	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		898	[Wx:: => AnyEvent::Impl::POE::],
		899	[Prima:: => AnyEvent::Impl::POE::],
441	);	900	);
442		901
443	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	902	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		903
		904	our @post_detect;
		905
		906	sub post_detect(&) {
		907	my ($cb) = @_;
		908
		909	if ($MODEL) {
		910	$cb->();
		911
		912	1
		913	} else {
		914	push @post_detect, $cb;
		915
		916	defined wantarray
		917	? bless \$cb, "AnyEvent::Util::PostDetect"
		918	: ()
		919	}
		920	}
		921
		922	sub AnyEvent::Util::PostDetect::DESTROY {
		923	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		924	}
444		925
445	sub detect() {	926	sub detect() {
446	unless ($MODEL) {	927	unless ($MODEL) {
447	no strict 'refs';	928	no strict 'refs';
		929	local $SIG{__DIE__};
		930
		931	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		932	my $model = "AnyEvent::Impl::$1";
		933	if (eval "require $model") {
		934	$MODEL = $model;
		935	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		936	} else {
		937	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		938	}
		939	}
448		940
449	# check for already loaded models	941	# check for already loaded models
		942	unless ($MODEL) {
450	for (@REGISTRY, @models) {	943	for (@REGISTRY, @models) {
451	my ($package, $model) = @$_;	944	my ($package, $model) = @$_;
452	if (${"$package\::VERSION"} > 0) {	945	if (${"$package\::VERSION"} > 0) {
453	if (eval "require $model") {	946	if (eval "require $model") {
454	$MODEL = $model;	947	$MODEL = $model;
455	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	948	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
456	last;	949	last;
		950	}
457	}	951	}
458	}	952	}
		953
		954	unless ($MODEL) {
		955	# try to load a model
		956
		957	for (@REGISTRY, @models) {
		958	my ($package, $model) = @$_;
		959	if (eval "require $package"
		960	and ${"$package\::VERSION"} > 0
		961	and eval "require $model") {
		962	$MODEL = $model;
		963	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		964	last;
		965	}
		966	}
		967
		968	$MODEL
		969	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
		970	}
459	}	971	}
460		972
461	unless ($MODEL) {	973	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
462	# try to load a model
463
464	for (@REGISTRY, @models) {
465	my ($package, $model) = @$_;
466	if (eval "require $package"
467	and ${"$package\::VERSION"} > 0
468	and eval "require $model") {
469	$MODEL = $model;
470	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
471	last;
472	}
473	}
474
475	$MODEL
476	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event), Glib or Tk.";
477	}
478		974
479	unshift @ISA, $MODEL;	975	unshift @ISA, $MODEL;
480	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	976
		977	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		978
		979	(shift @post_detect)->() while @post_detect;
481	}	980	}
482		981
483	$MODEL	982	$MODEL
484	}	983	}
485		984
…		…
493		992
494	my $class = shift;	993	my $class = shift;
495	$class->$func (@_);	994	$class->$func (@_);
496	}	995	}
497		996
		997	# utility function to dup a filehandle. this is used by many backends
		998	# to support binding more than one watcher per filehandle (they usually
		999	# allow only one watcher per fd, so we dup it to get a different one).
		1000	sub _dupfh($$$$) {
		1001	my ($poll, $fh, $r, $w) = @_;
		1002
		1003	require Fcntl;
		1004
		1005	# cygwin requires the fh mode to be matching, unix doesn't
		1006	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1007	: $poll eq "w" ? ($w, ">")
		1008	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1009
		1010	open my $fh2, "$mode&" . fileno $fh
		1011	or die "cannot dup() filehandle: $!";
		1012
		1013	# we assume CLOEXEC is already set by perl in all important cases
		1014
		1015	($fh2, $rw)
		1016	}
		1017
498	package AnyEvent::Base;	1018	package AnyEvent::Base;
499		1019
		1020	# default implementation for now and time
		1021
		1022	use Time::HiRes ();
		1023
		1024	sub time { Time::HiRes::time }
		1025	sub now { Time::HiRes::time }
		1026
500	# default implementation for ->condvar, ->wait, ->broadcast	1027	# default implementation for ->condvar
501		1028
502	sub condvar {	1029	sub condvar {
503	bless \my $flag, "AnyEvent::Base::CondVar"	1030	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
504	}
505
506	sub AnyEvent::Base::CondVar::broadcast {
507	${$_[0]}++;
508	}
509
510	sub AnyEvent::Base::CondVar::wait {
511	AnyEvent->one_event while !${$_[0]};
512	}	1031	}
513		1032
514	# default implementation for ->signal	1033	# default implementation for ->signal
515		1034
516	our %SIG_CB;	1035	our %SIG_CB;
…		…
532	sub AnyEvent::Base::Signal::DESTROY {	1051	sub AnyEvent::Base::Signal::DESTROY {
533	my ($signal, $cb) = @{$_[0]};	1052	my ($signal, $cb) = @{$_[0]};
534		1053
535	delete $SIG_CB{$signal}{$cb};	1054	delete $SIG_CB{$signal}{$cb};
536		1055
537	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1056	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
538	}	1057	}
539		1058
540	# default implementation for ->child	1059	# default implementation for ->child
541		1060
542	our %PID_CB;	1061	our %PID_CB;
…		…
569	or Carp::croak "required option 'pid' is missing";	1088	or Carp::croak "required option 'pid' is missing";
570		1089
571	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1090	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
572		1091
573	unless ($WNOHANG) {	1092	unless ($WNOHANG) {
574	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1093	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
575	}	1094	}
576		1095
577	unless ($CHLD_W) {	1096	unless ($CHLD_W) {
578	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1097	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
579	# child could be a zombie already, so make at least one round	1098	# child could be a zombie already, so make at least one round
…		…
589	delete $PID_CB{$pid}{$cb};	1108	delete $PID_CB{$pid}{$cb};
590	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1109	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
591		1110
592	undef $CHLD_W unless keys %PID_CB;	1111	undef $CHLD_W unless keys %PID_CB;
593	}	1112	}
		1113
		1114	package AnyEvent::CondVar;
		1115
		1116	our @ISA = AnyEvent::CondVar::Base::;
		1117
		1118	package AnyEvent::CondVar::Base;
		1119
		1120	use overload
		1121	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1122	fallback => 1;
		1123
		1124	sub _send {
		1125	# nop
		1126	}
		1127
		1128	sub send {
		1129	my $cv = shift;
		1130	$cv->{_ae_sent} = [@_];
		1131	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1132	$cv->_send;
		1133	}
		1134
		1135	sub croak {
		1136	$_[0]{_ae_croak} = $_[1];
		1137	$_[0]->send;
		1138	}
		1139
		1140	sub ready {
		1141	$_[0]{_ae_sent}
		1142	}
		1143
		1144	sub _wait {
		1145	AnyEvent->one_event while !$_[0]{_ae_sent};
		1146	}
		1147
		1148	sub recv {
		1149	$_[0]->_wait;
		1150
		1151	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1152	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1153	}
		1154
		1155	sub cb {
		1156	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1157	$_[0]{_ae_cb}
		1158	}
		1159
		1160	sub begin {
		1161	++$_[0]{_ae_counter};
		1162	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1163	}
		1164
		1165	sub end {
		1166	return if --$_[0]{_ae_counter};
		1167	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1168	}
		1169
		1170	# undocumented/compatibility with pre-3.4
		1171	*broadcast = \&send;
		1172	*wait = \&_wait;
594		1173
595	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1174	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
596		1175
597	This is an advanced topic that you do not normally need to use AnyEvent in	1176	This is an advanced topic that you do not normally need to use AnyEvent in
598	a module. This section is only of use to event loop authors who want to	1177	a module. This section is only of use to event loop authors who want to
…		…
637		1216
638	=head1 ENVIRONMENT VARIABLES	1217	=head1 ENVIRONMENT VARIABLES
639		1218
640	The following environment variables are used by this module:	1219	The following environment variables are used by this module:
641		1220
642	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, cause AnyEvent to	1221	=over 4
643	report to STDERR which event model it chooses.	1222
		1223	=item C<PERL_ANYEVENT_VERBOSE>
		1224
		1225	By default, AnyEvent will be completely silent except in fatal
		1226	conditions. You can set this environment variable to make AnyEvent more
		1227	talkative.
		1228
		1229	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1230	conditions, such as not being able to load the event model specified by
		1231	C<PERL_ANYEVENT_MODEL>.
		1232
		1233	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1234	model it chooses.
		1235
		1236	=item C<PERL_ANYEVENT_STRICT>
		1237
		1238	AnyEvent does not do much argument checking by default, as thorough
		1239	argument checking is very costly. Setting this variable to a true value
		1240	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1241	check the arguments passed to most method calls. If it finds any problems
		1242	it will croak.
		1243
		1244	In other words, enables "strict" mode.
		1245
		1246	Unlike C<use strict> it is definitely recommended ot keep it off in
		1247	production.
		1248
		1249	=item C<PERL_ANYEVENT_MODEL>
		1250
		1251	This can be used to specify the event model to be used by AnyEvent, before
		1252	auto detection and -probing kicks in. It must be a string consisting
		1253	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1254	and the resulting module name is loaded and if the load was successful,
		1255	used as event model. If it fails to load AnyEvent will proceed with
		1256	auto detection and -probing.
		1257
		1258	This functionality might change in future versions.
		1259
		1260	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1261	could start your program like this:
		1262
		1263	PERL_ANYEVENT_MODEL=Perl perl ...
		1264
		1265	=item C<PERL_ANYEVENT_PROTOCOLS>
		1266
		1267	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1268	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1269	of auto probing).
		1270
		1271	Must be set to a comma-separated list of protocols or address families,
		1272	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1273	used, and preference will be given to protocols mentioned earlier in the
		1274	list.
		1275
		1276	This variable can effectively be used for denial-of-service attacks
		1277	against local programs (e.g. when setuid), although the impact is likely
		1278	small, as the program has to handle connection errors already-
		1279
		1280	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1281	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1282	- only support IPv4, never try to resolve or contact IPv6
		1283	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1284	IPv6, but prefer IPv6 over IPv4.
		1285
		1286	=item C<PERL_ANYEVENT_EDNS0>
		1287
		1288	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1289	for DNS. This extension is generally useful to reduce DNS traffic, but
		1290	some (broken) firewalls drop such DNS packets, which is why it is off by
		1291	default.
		1292
		1293	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1294	EDNS0 in its DNS requests.
		1295
		1296	=item C<PERL_ANYEVENT_MAX_FORKS>
		1297
		1298	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1299	will create in parallel.
		1300
		1301	=back
644		1302
645	=head1 EXAMPLE PROGRAM	1303	=head1 EXAMPLE PROGRAM
646		1304
647	The following program uses an IO watcher to read data from STDIN, a timer	1305	The following program uses an I/O watcher to read data from STDIN, a timer
648	to display a message once per second, and a condition variable to quit the	1306	to display a message once per second, and a condition variable to quit the
649	program when the user enters quit:	1307	program when the user enters quit:
650		1308
651	use AnyEvent;	1309	use AnyEvent;
652		1310
…		…
657	poll => 'r',	1315	poll => 'r',
658	cb => sub {	1316	cb => sub {
659	warn "io event <$_[0]>\n"; # will always output <r>	1317	warn "io event <$_[0]>\n"; # will always output <r>
660	chomp (my $input = <STDIN>); # read a line	1318	chomp (my $input = <STDIN>); # read a line
661	warn "read: $input\n"; # output what has been read	1319	warn "read: $input\n"; # output what has been read
662	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1320	$cv->send if $input =~ /^q/i; # quit program if /^q/i
663	},	1321	},
664	);	1322	);
665		1323
666	my $time_watcher; # can only be used once	1324	my $time_watcher; # can only be used once
667		1325
…		…
672	});	1330	});
673	}	1331	}
674		1332
675	new_timer; # create first timer	1333	new_timer; # create first timer
676		1334
677	$cv->wait; # wait until user enters /^q/i	1335	$cv->recv; # wait until user enters /^q/i
678		1336
679	=head1 REAL-WORLD EXAMPLE	1337	=head1 REAL-WORLD EXAMPLE
680		1338
681	Consider the L<Net::FCP> module. It features (among others) the following	1339	Consider the L<Net::FCP> module. It features (among others) the following
682	API calls, which are to freenet what HTTP GET requests are to http:	1340	API calls, which are to freenet what HTTP GET requests are to http:
…		…
732	syswrite $txn->{fh}, $txn->{request}	1390	syswrite $txn->{fh}, $txn->{request}
733	or die "connection or write error";	1391	or die "connection or write error";
734	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1392	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
735		1393
736	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1394	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
737	result and signals any possible waiters that the request ahs finished:	1395	result and signals any possible waiters that the request has finished:
738		1396
739	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1397	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
740		1398
741	if (end-of-file or data complete) {	1399	if (end-of-file or data complete) {
742	$txn->{result} = $txn->{buf};	1400	$txn->{result} = $txn->{buf};
743	$txn->{finished}->broadcast;	1401	$txn->{finished}->send;
744	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1402	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
745	}	1403	}
746		1404
747	The C<result> method, finally, just waits for the finished signal (if the	1405	The C<result> method, finally, just waits for the finished signal (if the
748	request was already finished, it doesn't wait, of course, and returns the	1406	request was already finished, it doesn't wait, of course, and returns the
749	data:	1407	data:
750		1408
751	$txn->{finished}->wait;	1409	$txn->{finished}->recv;
752	return $txn->{result};	1410	return $txn->{result};
753		1411
754	The actual code goes further and collects all errors (C<die>s, exceptions)	1412	The actual code goes further and collects all errors (C<die>s, exceptions)
755	that occured during request processing. The C<result> method detects	1413	that occurred during request processing. The C<result> method detects
756	whether an exception as thrown (it is stored inside the $txn object)	1414	whether an exception as thrown (it is stored inside the $txn object)
757	and just throws the exception, which means connection errors and other	1415	and just throws the exception, which means connection errors and other
758	problems get reported tot he code that tries to use the result, not in a	1416	problems get reported tot he code that tries to use the result, not in a
759	random callback.	1417	random callback.
760		1418
…		…
791		1449
792	my $quit = AnyEvent->condvar;	1450	my $quit = AnyEvent->condvar;
793		1451
794	$fcp->txn_client_get ($url)->cb (sub {	1452	$fcp->txn_client_get ($url)->cb (sub {
795	...	1453	...
796	$quit->broadcast;	1454	$quit->send;
797	});	1455	});
798		1456
799	$quit->wait;	1457	$quit->recv;
		1458
		1459
		1460	=head1 BENCHMARKS
		1461
		1462	To give you an idea of the performance and overheads that AnyEvent adds
		1463	over the event loops themselves and to give you an impression of the speed
		1464	of various event loops I prepared some benchmarks.
		1465
		1466	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1467
		1468	Here is a benchmark of various supported event models used natively and
		1469	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1470	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1471	which it is), lets them fire exactly once and destroys them again.
		1472
		1473	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1474	distribution.
		1475
		1476	=head3 Explanation of the columns
		1477
		1478	I<watcher> is the number of event watchers created/destroyed. Since
		1479	different event models feature vastly different performances, each event
		1480	loop was given a number of watchers so that overall runtime is acceptable
		1481	and similar between tested event loop (and keep them from crashing): Glib
		1482	would probably take thousands of years if asked to process the same number
		1483	of watchers as EV in this benchmark.
		1484
		1485	I<bytes> is the number of bytes (as measured by the resident set size,
		1486	RSS) consumed by each watcher. This method of measuring captures both C
		1487	and Perl-based overheads.
		1488
		1489	I<create> is the time, in microseconds (millionths of seconds), that it
		1490	takes to create a single watcher. The callback is a closure shared between
		1491	all watchers, to avoid adding memory overhead. That means closure creation
		1492	and memory usage is not included in the figures.
		1493
		1494	I<invoke> is the time, in microseconds, used to invoke a simple
		1495	callback. The callback simply counts down a Perl variable and after it was
		1496	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1497	signal the end of this phase.
		1498
		1499	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1500	watcher.
		1501
		1502	=head3 Results
		1503
		1504	name watchers bytes create invoke destroy comment
		1505	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1506	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1507	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1508	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1509	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1510	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1511	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1512	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1513	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1514	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1515
		1516	=head3 Discussion
		1517
		1518	The benchmark does I<not> measure scalability of the event loop very
		1519	well. For example, a select-based event loop (such as the pure perl one)
		1520	can never compete with an event loop that uses epoll when the number of
		1521	file descriptors grows high. In this benchmark, all events become ready at
		1522	the same time, so select/poll-based implementations get an unnatural speed
		1523	boost.
		1524
		1525	Also, note that the number of watchers usually has a nonlinear effect on
		1526	overall speed, that is, creating twice as many watchers doesn't take twice
		1527	the time - usually it takes longer. This puts event loops tested with a
		1528	higher number of watchers at a disadvantage.
		1529
		1530	To put the range of results into perspective, consider that on the
		1531	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1532	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1533	cycles with POE.
		1534
		1535	C<EV> is the sole leader regarding speed and memory use, which are both
		1536	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1537	far less memory than any other event loop and is still faster than Event
		1538	natively.
		1539
		1540	The pure perl implementation is hit in a few sweet spots (both the
		1541	constant timeout and the use of a single fd hit optimisations in the perl
		1542	interpreter and the backend itself). Nevertheless this shows that it
		1543	adds very little overhead in itself. Like any select-based backend its
		1544	performance becomes really bad with lots of file descriptors (and few of
		1545	them active), of course, but this was not subject of this benchmark.
		1546
		1547	The C<Event> module has a relatively high setup and callback invocation
		1548	cost, but overall scores in on the third place.
		1549
		1550	C<Glib>'s memory usage is quite a bit higher, but it features a
		1551	faster callback invocation and overall ends up in the same class as
		1552	C<Event>. However, Glib scales extremely badly, doubling the number of
		1553	watchers increases the processing time by more than a factor of four,
		1554	making it completely unusable when using larger numbers of watchers
		1555	(note that only a single file descriptor was used in the benchmark, so
		1556	inefficiencies of C<poll> do not account for this).
		1557
		1558	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1559	more than 2000 watchers is a big setback, however, as correctness takes
		1560	precedence over speed. Nevertheless, its performance is surprising, as the
		1561	file descriptor is dup()ed for each watcher. This shows that the dup()
		1562	employed by some adaptors is not a big performance issue (it does incur a
		1563	hidden memory cost inside the kernel which is not reflected in the figures
		1564	above).
		1565
		1566	C<POE>, regardless of underlying event loop (whether using its pure perl
		1567	select-based backend or the Event module, the POE-EV backend couldn't
		1568	be tested because it wasn't working) shows abysmal performance and
		1569	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1570	as EV watchers, and 10 times as much memory as Event (the high memory
		1571	requirements are caused by requiring a session for each watcher). Watcher
		1572	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1573	implementation.
		1574
		1575	The design of the POE adaptor class in AnyEvent can not really account
		1576	for the performance issues, though, as session creation overhead is
		1577	small compared to execution of the state machine, which is coded pretty
		1578	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1579	using multiple sessions is not a good approach, especially regarding
		1580	memory usage, even the author of POE could not come up with a faster
		1581	design).
		1582
		1583	=head3 Summary
		1584
		1585	=over 4
		1586
		1587	=item * Using EV through AnyEvent is faster than any other event loop
		1588	(even when used without AnyEvent), but most event loops have acceptable
		1589	performance with or without AnyEvent.
		1590
		1591	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1592	the actual event loop, only with extremely fast event loops such as EV
		1593	adds AnyEvent significant overhead.
		1594
		1595	=item * You should avoid POE like the plague if you want performance or
		1596	reasonable memory usage.
		1597
		1598	=back
		1599
		1600	=head2 BENCHMARKING THE LARGE SERVER CASE
		1601
		1602	This benchmark actually benchmarks the event loop itself. It works by
		1603	creating a number of "servers": each server consists of a socket pair, a
		1604	timeout watcher that gets reset on activity (but never fires), and an I/O
		1605	watcher waiting for input on one side of the socket. Each time the socket
		1606	watcher reads a byte it will write that byte to a random other "server".
		1607
		1608	The effect is that there will be a lot of I/O watchers, only part of which
		1609	are active at any one point (so there is a constant number of active
		1610	fds for each loop iteration, but which fds these are is random). The
		1611	timeout is reset each time something is read because that reflects how
		1612	most timeouts work (and puts extra pressure on the event loops).
		1613
		1614	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1615	(1%) are active. This mirrors the activity of large servers with many
		1616	connections, most of which are idle at any one point in time.
		1617
		1618	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1619	distribution.
		1620
		1621	=head3 Explanation of the columns
		1622
		1623	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1624	each server has a read and write socket end).
		1625
		1626	I<create> is the time it takes to create a socket pair (which is
		1627	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1628
		1629	I<request>, the most important value, is the time it takes to handle a
		1630	single "request", that is, reading the token from the pipe and forwarding
		1631	it to another server. This includes deleting the old timeout and creating
		1632	a new one that moves the timeout into the future.
		1633
		1634	=head3 Results
		1635
		1636	name sockets create request
		1637	EV 20000 69.01 11.16
		1638	Perl 20000 73.32 35.87
		1639	Event 20000 212.62 257.32
		1640	Glib 20000 651.16 1896.30
		1641	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1642
		1643	=head3 Discussion
		1644
		1645	This benchmark I<does> measure scalability and overall performance of the
		1646	particular event loop.
		1647
		1648	EV is again fastest. Since it is using epoll on my system, the setup time
		1649	is relatively high, though.
		1650
		1651	Perl surprisingly comes second. It is much faster than the C-based event
		1652	loops Event and Glib.
		1653
		1654	Event suffers from high setup time as well (look at its code and you will
		1655	understand why). Callback invocation also has a high overhead compared to
		1656	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1657	uses select or poll in basically all documented configurations.
		1658
		1659	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1660	clearly fails to perform with many filehandles or in busy servers.
		1661
		1662	POE is still completely out of the picture, taking over 1000 times as long
		1663	as EV, and over 100 times as long as the Perl implementation, even though
		1664	it uses a C-based event loop in this case.
		1665
		1666	=head3 Summary
		1667
		1668	=over 4
		1669
		1670	=item * The pure perl implementation performs extremely well.
		1671
		1672	=item * Avoid Glib or POE in large projects where performance matters.
		1673
		1674	=back
		1675
		1676	=head2 BENCHMARKING SMALL SERVERS
		1677
		1678	While event loops should scale (and select-based ones do not...) even to
		1679	large servers, most programs we (or I :) actually write have only a few
		1680	I/O watchers.
		1681
		1682	In this benchmark, I use the same benchmark program as in the large server
		1683	case, but it uses only eight "servers", of which three are active at any
		1684	one time. This should reflect performance for a small server relatively
		1685	well.
		1686
		1687	The columns are identical to the previous table.
		1688
		1689	=head3 Results
		1690
		1691	name sockets create request
		1692	EV 16 20.00 6.54
		1693	Perl 16 25.75 12.62
		1694	Event 16 81.27 35.86
		1695	Glib 16 32.63 15.48
		1696	POE 16 261.87 276.28 uses POE::Loop::Event
		1697
		1698	=head3 Discussion
		1699
		1700	The benchmark tries to test the performance of a typical small
		1701	server. While knowing how various event loops perform is interesting, keep
		1702	in mind that their overhead in this case is usually not as important, due
		1703	to the small absolute number of watchers (that is, you need efficiency and
		1704	speed most when you have lots of watchers, not when you only have a few of
		1705	them).
		1706
		1707	EV is again fastest.
		1708
		1709	Perl again comes second. It is noticeably faster than the C-based event
		1710	loops Event and Glib, although the difference is too small to really
		1711	matter.
		1712
		1713	POE also performs much better in this case, but is is still far behind the
		1714	others.
		1715
		1716	=head3 Summary
		1717
		1718	=over 4
		1719
		1720	=item * C-based event loops perform very well with small number of
		1721	watchers, as the management overhead dominates.
		1722
		1723	=back
		1724
		1725
		1726	=head1 FORK
		1727
		1728	Most event libraries are not fork-safe. The ones who are usually are
		1729	because they rely on inefficient but fork-safe C<select> or C<poll>
		1730	calls. Only L<EV> is fully fork-aware.
		1731
		1732	If you have to fork, you must either do so I<before> creating your first
		1733	watcher OR you must not use AnyEvent at all in the child.
		1734
		1735
		1736	=head1 SECURITY CONSIDERATIONS
		1737
		1738	AnyEvent can be forced to load any event model via
		1739	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1740	execute arbitrary code or directly gain access, it can easily be used to
		1741	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1742	will not be active when the program uses a different event model than
		1743	specified in the variable.
		1744
		1745	You can make AnyEvent completely ignore this variable by deleting it
		1746	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1747
		1748	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1749
		1750	use AnyEvent;
		1751
		1752	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1753	be used to probe what backend is used and gain other information (which is
		1754	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1755	$ENV{PERL_ANYEGENT_STRICT}.
		1756
		1757
		1758	=head1 BUGS
		1759
		1760	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1761	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1762	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1763	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1764	pronounced).
		1765
800		1766
801	=head1 SEE ALSO	1767	=head1 SEE ALSO
802		1768
803	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1769	Utility functions: L<AnyEvent::Util>.
804	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.
805		1770
806	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1771	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		1772	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		1773
807	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	1774	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
808	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.	1775	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		1776	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		1777	L<AnyEvent::Impl::POE>.
809		1778
		1779	Non-blocking file handles, sockets, TCP clients and
		1780	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1781
		1782	Asynchronous DNS: L<AnyEvent::DNS>.
		1783
		1784	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1785
810	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1786	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
		1787
811		1788
812	=head1 AUTHOR	1789	=head1 AUTHOR
813		1790
814	Marc Lehmann <schmorp@schmorp.de>	1791	Marc Lehmann <schmorp@schmorp.de>
815	http://home.schmorp.de/	1792	http://home.schmorp.de/
816		1793
817	=cut	1794	=cut
818		1795
819	1	1796	1
820		1797

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