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Revision 1.179 by root, Thu Sep 4 10:58:58 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	Event, Coro, 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 wether 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, and AnyEvent	49	the statement "there can only be one" is a bitter reality: In general,
35	helps hiding the differences.	50	only one event loop can be active at the same time in a process. AnyEvent
		51	cannot change this, but it can hide the differences between those event
		52	loops.
36		53
37	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
38	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
39	religion, a way of living, and most importantly: without forcing your	56	religion, a way of living, and most importantly: without forcing your
40	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
41	model you use.	58	model you use.
42		59
43	For modules like POE or IO::Async (which is actually doing all I/O	60	For modules like POE or IO::Async (which is a total misnomer as it is
44	I<synchronously>...), using them in your module is like joining a	61	actually doing all I/O I<synchronously>...), using them in your module is
45	cult: After you joined, you are dependent on them and you cannot use	62	like joining a cult: After you joined, you are dependent on them and you
46	anything else, as it is simply incompatible to everything that isn't	63	cannot use anything else, as they are simply incompatible to everything
47	itself.	64	that isn't them. What's worse, all the potential users of your
		65	module are I<also> forced to use the same event loop you use.
48		66
49	AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk	67	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	works fine etc. etc. but none of these work together with the rest: POE	68	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51	+ IO::Async? no go. Tk + Event? no go. If your module uses one of	69	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
52	those, every user of your module has to use it, too. If your module	70	your module uses one of those, every user of your module has to use it,
53	uses AnyEvent, it works transparently with all event models it supports	71	too. But if your module uses AnyEvent, it works transparently with all
54	(including stuff like POE and IO::Async).	72	event models it supports (including stuff like IO::Async, as long as those
		73	use one of the supported event loops. It is trivial to add new event loops
		74	to AnyEvent, too, so it is future-proof).
55		75
56	In addition of 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
57	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
58	modules, you get an enourmous amount of code and strict rules you have	78	modules, you get an enormous amount of code and strict rules you have to
59	to follow. AnyEvent, on the other hand, is lean and to the point by only	79	follow. AnyEvent, on the other hand, is lean and up to the point, by only
60	offering the functionality that is useful, in as thin as a wrapper as	80	offering the functionality that is necessary, in as thin as a wrapper as
61	technically possible.	81	technically possible.
62		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
63	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
64	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
65	model, you should I<not> use this module.	91	model, you should I<not> use this module.
66
67		92
68	=head1 DESCRIPTION	93	=head1 DESCRIPTION
69		94
70	L<AnyEvent> provides an identical interface to multiple event loops. This	95	L<AnyEvent> provides an identical interface to multiple event loops. This
71	allows module authors to utilise an event loop without forcing module	96	allows module authors to utilise an event loop without forcing module
72	users to use the same event loop (as only a single event loop can coexist	97	users to use the same event loop (as only a single event loop can coexist
73	peacefully at any one time).	98	peacefully at any one time).
74		99
75	The interface itself is vaguely similar but not identical to the Event	100	The interface itself is vaguely similar, but not identical to the L<Event>
76	module.	101	module.
77		102
78	On the first call of any method, the module tries to detect the currently	103	During the first call of any watcher-creation method, the module tries
79	loaded event loop by probing wether any of the following modules is	104	to detect the currently loaded event loop by probing whether one of the
80	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	105	following modules is already loaded: L<EV>,
81	used. If none is found, the module tries to load these modules in the	106	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
82	order given. The first one that could be successfully loaded will be	107	L<POE>. The first one found is used. If none are found, the module tries
83	used. If still none could be found, AnyEvent will fall back to a pure-perl	108	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
84	event loop, which is also not very efficient.	109	adaptor should always succeed) in the order given. The first one that can
		110	be successfully loaded will be used. If, after this, still none could be
		111	found, AnyEvent will fall back to a pure-perl event loop, which is not
		112	very efficient, but should work everywhere.
85		113
86	Because AnyEvent first checks for modules that are already loaded, loading	114	Because AnyEvent first checks for modules that are already loaded, loading
87	an Event model explicitly before first using AnyEvent will likely make	115	an event model explicitly before first using AnyEvent will likely make
88	that model the default. For example:	116	that model the default. For example:
89		117
90	use Tk;	118	use Tk;
91	use AnyEvent;	119	use AnyEvent;
92		120
93	# .. AnyEvent will likely default to Tk	121	# .. AnyEvent will likely default to Tk
94		122
		123	The I<likely> means that, if any module loads another event model and
		124	starts using it, all bets are off. Maybe you should tell their authors to
		125	use AnyEvent so their modules work together with others seamlessly...
		126
95	The pure-perl implementation of AnyEvent is called	127	The pure-perl implementation of AnyEvent is called
96	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
97	explicitly.	129	explicitly and enjoy the high availability of that event loop :)
98		130
99	=head1 WATCHERS	131	=head1 WATCHERS
100		132
101	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
102	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
103	the callback to call, the filehandle to watch, etc.	135	the callback to call, the file handle to watch, etc.
104		136
105	These watchers are normal Perl objects with normal Perl lifetime. After	137	These watchers are normal Perl objects with normal Perl lifetime. After
106	creating a watcher it will immediately "watch" for events and invoke	138	creating a watcher it will immediately "watch" for events and invoke the
		139	callback when the event occurs (of course, only when the event model
		140	is in control).
		141
107	the callback. To disable the watcher you have to destroy it (e.g. by	142	To disable the watcher you have to destroy it (e.g. by setting the
108	setting the variable that stores it to C<undef> or otherwise deleting all	143	variable you store it in to C<undef> or otherwise deleting all references
109	references to it).	144	to it).
110		145
111	All watchers are created by calling a method on the C<AnyEvent> class.	146	All watchers are created by calling a method on the C<AnyEvent> class.
112		147
		148	Many watchers either are used with "recursion" (repeating timers for
		149	example), or need to refer to their watcher object in other ways.
		150
		151	An any way to achieve that is this pattern:
		152
		153	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		154	# you can use $w here, for example to undef it
		155	undef $w;
		156	});
		157
		158	Note that C<my $w; $w => combination. This is necessary because in Perl,
		159	my variables are only visible after the statement in which they are
		160	declared.
		161
113	=head2 IO WATCHERS	162	=head2 I/O WATCHERS
114		163
115	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	164	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
116	the following mandatory arguments:	165	with the following mandatory key-value pairs as arguments:
117		166
118	C<fh> the Perl I<filehandle> (not filedescriptor) 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>
119	events. C<poll> must be a string that is either C<r> or C<w>, that creates	169	must be a string that is either C<r> or C<w>, which creates a watcher
120	a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback	170	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the
121	to invoke everytime the filehandle becomes ready.	171	callback to invoke each time the file handle becomes ready.
122		172
123	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	173	Although the callback might get passed parameters, their value and
124	a socket you can have one r + one w, not any more (limitation comes from	174	presence is undefined and you cannot rely on them. Portable AnyEvent
125	Tk - if you are sure you are not using Tk this limitation is gone).	175	callbacks cannot use arguments passed to I/O watcher callbacks.
126		176
127	Filehandles will be kept alive, so as long as the watcher exists, the	177	The I/O watcher might use the underlying file descriptor or a copy of it.
128	filehandle exists, too.	178	You must not close a file handle as long as any watcher is active on the
		179	underlying file descriptor.
129		180
130	Example:	181	Some event loops issue spurious readyness notifications, so you should
		182	always use non-blocking calls when reading/writing from/to your file
		183	handles.
131		184
132	# 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
133	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	188	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
134	chomp (my $input = <STDIN>);	189	chomp (my $input = <STDIN>);
135	warn "read: $input\n";	190	warn "read: $input\n";
136	undef $w;	191	undef $w;
137	});	192	});
…		…
139	=head2 TIME WATCHERS	194	=head2 TIME WATCHERS
140		195
141	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 >>
142	method with the following mandatory arguments:	197	method with the following mandatory arguments:
143		198
144	C<after> after how many seconds (fractions are supported) should the timer	199	C<after> specifies after how many seconds (fractional values are
145	activate. C<cb> the callback to invoke.	200	supported) the callback should be invoked. C<cb> is the callback to invoke
		201	in that case.
146		202
147	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
148	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
149	and Glib).	205	callbacks cannot use arguments passed to time watcher callbacks.
150		206
151	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.
152		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
153	# fire an event after 7.7 seconds	217	Example: fire an event after 7.7 seconds.
		218
154	my $w = AnyEvent->timer (after => 7.7, cb => sub {	219	my $w = AnyEvent->timer (after => 7.7, cb => sub {
155	warn "timeout\n";	220	warn "timeout\n";
156	});	221	});
157		222
158	# to cancel the timer:	223	# to cancel the timer:
159	undef $w;	224	undef $w;
160		225
161	=head2 CONDITION WATCHERS	226	Example 2: fire an event after 0.5 seconds, then roughly every second.
162		227
163	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	228	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
164	method without any arguments.	229	warn "timeout\n";
		230	};
165		231
166	A condition watcher watches for a condition - precisely that the C<<	232	=head3 TIMING ISSUES
167	->broadcast >> method has been called.
168		233
169	Note that condition watchers recurse into the event loop - if you have	234	There are two ways to handle timers: based on real time (relative, "fire
170	two watchers that call C<< ->wait >> in a round-robbin fashion, you	235	in 10 seconds") and based on wallclock time (absolute, "fire at 12
171	lose. Therefore, condition watchers are good to export to your caller, but	236	o'clock").
172	you should avoid making a blocking wait, at least in callbacks, as this
173	usually asks for trouble.
174		237
175	The watcher has only two methods:	238	While most event loops expect timers to specified in a relative way, they
		239	use absolute time internally. This makes a difference when your clock
		240	"jumps", for example, when ntp decides to set your clock backwards from
		241	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		242	fire "after" a second might actually take six years to finally fire.
		243
		244	AnyEvent cannot compensate for this. The only event loop that is conscious
		245	about these issues is L<EV>, which offers both relative (ev_timer, based
		246	on true relative time) and absolute (ev_periodic, based on wallclock time)
		247	timers.
		248
		249	AnyEvent always prefers relative timers, if available, matching the
		250	AnyEvent API.
		251
		252	AnyEvent has two additional methods that return the "current time":
176		253
177	=over 4	254	=over 4
178		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
		315	=head2 SIGNAL WATCHERS
		316
		317	You can watch for signals using a signal watcher, C<signal> is the signal
		318	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		319	callback to be invoked whenever a signal occurs.
		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
		325	Multiple signal occurrences can be clumped together into one callback
		326	invocation, and callback invocation will be synchronous. Synchronous means
		327	that it might take a while until the signal gets handled by the process,
		328	but it is guaranteed not to interrupt any other callbacks.
		329
		330	The main advantage of using these watchers is that you can share a signal
		331	between multiple watchers.
		332
		333	This watcher might use C<%SIG>, so programs overwriting those signals
		334	directly will likely not work correctly.
		335
		336	Example: exit on SIGINT
		337
		338	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		339
		340	=head2 CHILD PROCESS WATCHERS
		341
		342	You can also watch on a child process exit and catch its exit status.
		343
		344	The child process is specified by the C<pid> argument (if set to C<0>, it
		345	watches for any child process exit). The watcher will trigger as often
		346	as status change for the child are received. This works by installing a
		347	signal handler for C<SIGCHLD>. The callback will be called with the pid
		348	and exit status (as returned by waitpid), so unlike other watcher types,
		349	you I<can> rely on child watcher callback arguments.
		350
		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).
		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
		369	my $w = AnyEvent->child (
		370	pid => $pid,
		371	cb => sub {
		372	my ($pid, $status) = @_;
		373	warn "pid $pid exited with status $status";
		374	$done->send;
		375	},
		376	);
		377
		378	# do something else, then wait for process exit
		379	$done->recv;
		380
		381	=head2 CONDITION VARIABLES
		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
		393	Condition variables can be created by calling the C<< AnyEvent->condvar
		394	>> method, usually without arguments. The only argument pair allowed is
		395
		396	C<cb>, which specifies a callback to be called when the condition variable
		397	becomes true, with the condition variable as the first argument (but not
		398	the results).
		399
		400	After creation, the condition variable is "false" until it becomes "true"
		401	by calling the C<send> method (or calling the condition variable as if it
		402	were a callback, read about the caveats in the description for the C<<
		403	->send >> method).
		404
		405	Condition variables are similar to callbacks, except that you can
		406	optionally wait for them. They can also be called merge points - points
		407	in time where multiple outstanding events have been processed. And yet
		408	another way to call them is transactions - each condition variable can be
		409	used to represent a transaction, which finishes at some point and delivers
		410	a result.
		411
		412	Condition variables are very useful to signal that something has finished,
		413	for example, if you write a module that does asynchronous http requests,
		414	then a condition variable would be the ideal candidate to signal the
		415	availability of results. The user can either act when the callback is
		416	called or can synchronously C<< ->recv >> for the results.
		417
		418	You can also use them to simulate traditional event loops - for example,
		419	you can block your main program until an event occurs - for example, you
		420	could C<< ->recv >> in your main program until the user clicks the Quit
		421	button of your app, which would C<< ->send >> the "quit" event.
		422
		423	Note that condition variables recurse into the event loop - if you have
		424	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		425	lose. Therefore, condition variables are good to export to your caller, but
		426	you should avoid making a blocking wait yourself, at least in callbacks,
		427	as this asks for trouble.
		428
		429	Condition variables are represented by hash refs in perl, and the keys
		430	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		431	easy (it is often useful to build your own transaction class on top of
		432	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		433	it's C<new> method in your own C<new> method.
		434
		435	There are two "sides" to a condition variable - the "producer side" which
		436	eventually calls C<< -> send >>, and the "consumer side", which waits
		437	for the send to occur.
		438
		439	Example: wait for a timer.
		440
		441	# wait till the result is ready
		442	my $result_ready = AnyEvent->condvar;
		443
		444	# do something such as adding a timer
		445	# or socket watcher the calls $result_ready->send
		446	# when the "result" is ready.
		447	# in this case, we simply use a timer:
		448	my $w = AnyEvent->timer (
		449	after => 1,
		450	cb => sub { $result_ready->send },
		451	);
		452
		453	# this "blocks" (while handling events) till the callback
		454	# calls send
		455	$result_ready->recv;
		456
		457	Example: wait for a timer, but take advantage of the fact that
		458	condition variables are also code references.
		459
		460	my $done = AnyEvent->condvar;
		461	my $delay = AnyEvent->timer (after => 5, cb => $done);
		462	$done->recv;
		463
		464	Example: Imagine an API that returns a condvar and doesn't support
		465	callbacks. This is how you make a synchronous call, for example from
		466	the main program:
		467
		468	use AnyEvent::CouchDB;
		469
		470	...
		471
		472	my @info = $couchdb->info->recv;
		473
		474	And this is how you would just ste a callback to be called whenever the
		475	results are available:
		476
		477	$couchdb->info->cb (sub {
		478	my @info = $_[0]->recv;
		479	});
		480
		481	=head3 METHODS FOR PRODUCERS
		482
		483	These methods should only be used by the producing side, i.e. the
		484	code/module that eventually sends the signal. Note that it is also
		485	the producer side which creates the condvar in most cases, but it isn't
		486	uncommon for the consumer to create it as well.
		487
		488	=over 4
		489
		490	=item $cv->send (...)
		491
		492	Flag the condition as ready - a running C<< ->recv >> and all further
		493	calls to C<recv> will (eventually) return after this method has been
		494	called. If nobody is waiting the send will be remembered.
		495
		496	If a callback has been set on the condition variable, it is called
		497	immediately from within send.
		498
		499	Any arguments passed to the C<send> call will be returned by all
		500	future C<< ->recv >> calls.
		501
		502	Condition variables are overloaded so one can call them directly
		503	(as a code reference). Calling them directly is the same as calling
		504	C<send>. Note, however, that many C-based event loops do not handle
		505	overloading, so as tempting as it may be, passing a condition variable
		506	instead of a callback does not work. Both the pure perl and EV loops
		507	support overloading, however, as well as all functions that use perl to
		508	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		509	example).
		510
		511	=item $cv->croak ($error)
		512
		513	Similar to send, but causes all call's to C<< ->recv >> to invoke
		514	C<Carp::croak> with the given error message/object/scalar.
		515
		516	This can be used to signal any errors to the condition variable
		517	user/consumer.
		518
		519	=item $cv->begin ([group callback])
		520
179	=item $cv->wait	521	=item $cv->end
180		522
181	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	523	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		524
		525	These two methods can be used to combine many transactions/events into
		526	one. For example, a function that pings many hosts in parallel might want
		527	to use a condition variable for the whole process.
		528
		529	Every call to C<< ->begin >> will increment a counter, and every call to
		530	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		531	>>, the (last) callback passed to C<begin> will be executed. That callback
		532	is I<supposed> to call C<< ->send >>, but that is not required. If no
		533	callback was set, C<send> will be called without any arguments.
		534
		535	Let's clarify this with the ping example:
		536
		537	my $cv = AnyEvent->condvar;
		538
		539	my %result;
		540	$cv->begin (sub { $cv->send (\%result) });
		541
		542	for my $host (@list_of_hosts) {
		543	$cv->begin;
		544	ping_host_then_call_callback $host, sub {
		545	$result{$host} = ...;
		546	$cv->end;
		547	};
		548	}
		549
		550	$cv->end;
		551
		552	This code fragment supposedly pings a number of hosts and calls
		553	C<send> after results for all then have have been gathered - in any
		554	order. To achieve this, the code issues a call to C<begin> when it starts
		555	each ping request and calls C<end> when it has received some result for
		556	it. Since C<begin> and C<end> only maintain a counter, the order in which
		557	results arrive is not relevant.
		558
		559	There is an additional bracketing call to C<begin> and C<end> outside the
		560	loop, which serves two important purposes: first, it sets the callback
		561	to be called once the counter reaches C<0>, and second, it ensures that
		562	C<send> is called even when C<no> hosts are being pinged (the loop
		563	doesn't execute once).
		564
		565	This is the general pattern when you "fan out" into multiple subrequests:
		566	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		567	is called at least once, and then, for each subrequest you start, call
		568	C<begin> and for each subrequest you finish, call C<end>.
		569
		570	=back
		571
		572	=head3 METHODS FOR CONSUMERS
		573
		574	These methods should only be used by the consuming side, i.e. the
		575	code awaits the condition.
		576
		577	=over 4
		578
		579	=item $cv->recv
		580
		581	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
182	called on c<$cv>, while servicing other watchers normally.	582	>> methods have been called on c<$cv>, while servicing other watchers
		583	normally.
183		584
184	You can only wait once on a condition - additional calls will return	585	You can only wait once on a condition - additional calls are valid but
185	immediately.	586	will return immediately.
		587
		588	If an error condition has been set by calling C<< ->croak >>, then this
		589	function will call C<croak>.
		590
		591	In list context, all parameters passed to C<send> will be returned,
		592	in scalar context only the first one will be returned.
186		593
187	Not all event models support a blocking wait - some die in that case	594	Not all event models support a blocking wait - some die in that case
188	(programs might want to do that so they stay interactive), so I<if you	595	(programs might want to do that to stay interactive), so I<if you are
189	are using this from a module, never require a blocking wait>, but let the	596	using this from a module, never require a blocking wait>, but let the
190	caller decide wether the call will block or not (for example, by coupling	597	caller decide whether the call will block or not (for example, by coupling
191	condition variables with some kind of request results and supporting	598	condition variables with some kind of request results and supporting
192	callbacks so the caller knows that getting the result will not block,	599	callbacks so the caller knows that getting the result will not block,
193	while still suppporting blocking waits if the caller so desires).	600	while still supporting blocking waits if the caller so desires).
194		601
195	Another reason I<never> to C<< ->wait >> in a module is that you cannot	602	Another reason I<never> to C<< ->recv >> in a module is that you cannot
196	sensibly have two C<< ->wait >>'s in parallel, as that would require	603	sensibly have two C<< ->recv >>'s in parallel, as that would require
197	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	604	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
198	can supply (the coroutine-aware backends C<Coro::EV> and C<Coro::Event>	605	can supply.
199	explicitly support concurrent C<< ->wait >>'s from different coroutines,
200	however).
201		606
202	=item $cv->broadcast	607	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		608	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		609	versions and also integrates coroutines into AnyEvent, making blocking
		610	C<< ->recv >> calls perfectly safe as long as they are done from another
		611	coroutine (one that doesn't run the event loop).
203		612
204	Flag the condition as ready - a running C<< ->wait >> and all further	613	You can ensure that C<< -recv >> never blocks by setting a callback and
205	calls to C<wait> will return after this method has been called. If nobody	614	only calling C<< ->recv >> from within that callback (or at a later
206	is waiting the broadcast will be remembered..	615	time). This will work even when the event loop does not support blocking
		616	waits otherwise.
207		617
208	Example:	618	=item $bool = $cv->ready
209		619
210	# wait till the result is ready	620	Returns true when the condition is "true", i.e. whether C<send> or
211	my $result_ready = AnyEvent->condvar;	621	C<croak> have been called.
212		622
213	# do something such as adding a timer	623	=item $cb = $cv->cb ($cb->($cv))
214	# or socket watcher the calls $result_ready->broadcast
215	# when the "result" is ready.
216		624
217	$result_ready->wait;	625	This is a mutator function that returns the callback set and optionally
		626	replaces it before doing so.
		627
		628	The callback will be called when the condition becomes "true", i.e. when
		629	C<send> or C<croak> are called, with the only argument being the condition
		630	variable itself. Calling C<recv> inside the callback or at any later time
		631	is guaranteed not to block.
218		632
219	=back	633	=back
220		634
221	=head2 SIGNAL WATCHERS	635	=head1 GLOBAL VARIABLES AND FUNCTIONS
222
223	You can listen for signals using a signal watcher, C<signal> is the signal
224	I<name> without any C<SIG> prefix. Multiple signals events can be clumped
225	together into one callback invocation, and callback invocation might or
226	might not be asynchronous.
227
228	These watchers might use C<%SIG>, so programs overwriting those signals
229	directly will likely not work correctly.
230
231	Example: exit on SIGINT
232
233	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
234
235	=head2 CHILD PROCESS WATCHERS
236
237	You can also listen for the status of a child process specified by the
238	C<pid> argument (or any child if the pid argument is 0). The watcher will
239	trigger as often as status change for the child are received. This works
240	by installing a signal handler for C<SIGCHLD>. The callback will be called with
241	the pid and exit status (as returned by waitpid).
242
243	Example: wait for pid 1333
244
245	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
246
247	=head1 GLOBALS
248		636
249	=over 4	637	=over 4
250		638
251	=item $AnyEvent::MODEL	639	=item $AnyEvent::MODEL
252		640
…		…
256	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	644	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
257	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	645	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
258		646
259	The known classes so far are:	647	The known classes so far are:
260		648
261	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
262	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	649	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
263	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
264	AnyEvent::Impl::Event based on Event, also second best choice :)	650	AnyEvent::Impl::Event based on Event, second best choice.
		651	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
265	AnyEvent::Impl::Glib based on Glib, third-best choice.	652	AnyEvent::Impl::Glib based on Glib, third-best choice.
266	AnyEvent::Impl::Tk based on Tk, very bad choice.	653	AnyEvent::Impl::Tk based on Tk, very bad choice.
267	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	654	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		655	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		656	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		657
		658	There is no support for WxWidgets, as WxWidgets has no support for
		659	watching file handles. However, you can use WxWidgets through the
		660	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		661	second, which was considered to be too horrible to even consider for
		662	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		663	it's adaptor.
		664
		665	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		666	autodetecting them.
268		667
269	=item AnyEvent::detect	668	=item AnyEvent::detect
270		669
271	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	670	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
272	necessary. You should only call this function right before you would have	671	if necessary. You should only call this function right before you would
273	created an AnyEvent watcher anyway, that is, very late at runtime.	672	have created an AnyEvent watcher anyway, that is, as late as possible at
		673	runtime.
		674
		675	=item $guard = AnyEvent::post_detect { BLOCK }
		676
		677	Arranges for the code block to be executed as soon as the event model is
		678	autodetected (or immediately if this has already happened).
		679
		680	If called in scalar or list context, then it creates and returns an object
		681	that automatically removes the callback again when it is destroyed. See
		682	L<Coro::BDB> for a case where this is useful.
		683
		684	=item @AnyEvent::post_detect
		685
		686	If there are any code references in this array (you can C<push> to it
		687	before or after loading AnyEvent), then they will called directly after
		688	the event loop has been chosen.
		689
		690	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		691	if it contains a true value then the event loop has already been detected,
		692	and the array will be ignored.
		693
		694	Best use C<AnyEvent::post_detect { BLOCK }> instead.
274		695
275	=back	696	=back
276		697
277	=head1 WHAT TO DO IN A MODULE	698	=head1 WHAT TO DO IN A MODULE
278		699
279	As a module author, you should "use AnyEvent" and call AnyEvent methods	700	As a module author, you should C<use AnyEvent> and call AnyEvent methods
280	freely, but you should not load a specific event module or rely on it.	701	freely, but you should not load a specific event module or rely on it.
281		702
282	Be careful when you create watchers in the module body - Anyevent will	703	Be careful when you create watchers in the module body - AnyEvent will
283	decide which event module to use as soon as the first method is called, so	704	decide which event module to use as soon as the first method is called, so
284	by calling AnyEvent in your module body you force the user of your module	705	by calling AnyEvent in your module body you force the user of your module
285	to load the event module first.	706	to load the event module first.
286		707
		708	Never call C<< ->recv >> on a condition variable unless you I<know> that
		709	the C<< ->send >> method has been called on it already. This is
		710	because it will stall the whole program, and the whole point of using
		711	events is to stay interactive.
		712
		713	It is fine, however, to call C<< ->recv >> when the user of your module
		714	requests it (i.e. if you create a http request object ad have a method
		715	called C<results> that returns the results, it should call C<< ->recv >>
		716	freely, as the user of your module knows what she is doing. always).
		717
287	=head1 WHAT TO DO IN THE MAIN PROGRAM	718	=head1 WHAT TO DO IN THE MAIN PROGRAM
288		719
289	There will always be a single main program - the only place that should	720	There will always be a single main program - the only place that should
290	dictate which event model to use.	721	dictate which event model to use.
291		722
292	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	723	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
293	do anything special and let AnyEvent decide which implementation to chose.	724	do anything special (it does not need to be event-based) and let AnyEvent
		725	decide which implementation to chose if some module relies on it.
294		726
295	If the main program relies on a specific event model (for example, in Gtk2	727	If the main program relies on a specific event model - for example, in
296	programs you have to rely on either Glib or Glib::Event), you should load	728	Gtk2 programs you have to rely on the Glib module - you should load the
297	it before loading AnyEvent or any module that uses it, generally, as early	729	event module before loading AnyEvent or any module that uses it: generally
298	as possible. The reason is that modules might create watchers when they	730	speaking, you should load it as early as possible. The reason is that
299	are loaded, and AnyEvent will decide on the event model to use as soon as	731	modules might create watchers when they are loaded, and AnyEvent will
300	it creates watchers, and it might chose the wrong one unless you load the	732	decide on the event model to use as soon as it creates watchers, and it
301	correct one yourself.	733	might chose the wrong one unless you load the correct one yourself.
302		734
303	You can chose to use a rather inefficient pure-perl implementation by	735	You can chose to use a pure-perl implementation by loading the
304	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	736	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
305	generally better.	737	everywhere, but letting AnyEvent chose the model is generally better.
		738
		739	=head2 MAINLOOP EMULATION
		740
		741	Sometimes (often for short test scripts, or even standalone programs who
		742	only want to use AnyEvent), you do not want to run a specific event loop.
		743
		744	In that case, you can use a condition variable like this:
		745
		746	AnyEvent->condvar->recv;
		747
		748	This has the effect of entering the event loop and looping forever.
		749
		750	Note that usually your program has some exit condition, in which case
		751	it is better to use the "traditional" approach of storing a condition
		752	variable somewhere, waiting for it, and sending it when the program should
		753	exit cleanly.
		754
		755
		756	=head1 OTHER MODULES
		757
		758	The following is a non-exhaustive list of additional modules that use
		759	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		760	in the same program. Some of the modules come with AnyEvent, some are
		761	available via CPAN.
		762
		763	=over 4
		764
		765	=item L<AnyEvent::Util>
		766
		767	Contains various utility functions that replace often-used but blocking
		768	functions such as C<inet_aton> by event-/callback-based versions.
		769
		770	=item L<AnyEvent::Socket>
		771
		772	Provides various utility functions for (internet protocol) sockets,
		773	addresses and name resolution. Also functions to create non-blocking tcp
		774	connections or tcp servers, with IPv6 and SRV record support and more.
		775
		776	=item L<AnyEvent::Handle>
		777
		778	Provide read and write buffers, manages watchers for reads and writes,
		779	supports raw and formatted I/O, I/O queued and fully transparent and
		780	non-blocking SSL/TLS.
		781
		782	=item L<AnyEvent::DNS>
		783
		784	Provides rich asynchronous DNS resolver capabilities.
		785
		786	=item L<AnyEvent::HTTP>
		787
		788	A simple-to-use HTTP library that is capable of making a lot of concurrent
		789	HTTP requests.
		790
		791	=item L<AnyEvent::HTTPD>
		792
		793	Provides a simple web application server framework.
		794
		795	=item L<AnyEvent::FastPing>
		796
		797	The fastest ping in the west.
		798
		799	=item L<AnyEvent::DBI>
		800
		801	Executes L<DBI> requests asynchronously in a proxy process.
		802
		803	=item L<AnyEvent::AIO>
		804
		805	Truly asynchronous I/O, should be in the toolbox of every event
		806	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		807	together.
		808
		809	=item L<AnyEvent::BDB>
		810
		811	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		812	L<BDB> and AnyEvent together.
		813
		814	=item L<AnyEvent::GPSD>
		815
		816	A non-blocking interface to gpsd, a daemon delivering GPS information.
		817
		818	=item L<AnyEvent::IGS>
		819
		820	A non-blocking interface to the Internet Go Server protocol (used by
		821	L<App::IGS>).
		822
		823	=item L<Net::IRC3>
		824
		825	AnyEvent based IRC client module family.
		826
		827	=item L<Net::XMPP2>
		828
		829	AnyEvent based XMPP (Jabber protocol) module family.
		830
		831	=item L<Net::FCP>
		832
		833	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		834	of AnyEvent.
		835
		836	=item L<Event::ExecFlow>
		837
		838	High level API for event-based execution flow control.
		839
		840	=item L<Coro>
		841
		842	Has special support for AnyEvent via L<Coro::AnyEvent>.
		843
		844	=item L<IO::Lambda>
		845
		846	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		847
		848	=back
306		849
307	=cut	850	=cut
308		851
309	package AnyEvent;	852	package AnyEvent;
310		853
311	no warnings;	854	no warnings;
312	use strict;	855	use strict;
313		856
314	use Carp;	857	use Carp;
315		858
316	our $VERSION = '3.0';	859	our $VERSION = 4.233;
317	our $MODEL;	860	our $MODEL;
318		861
319	our $AUTOLOAD;	862	our $AUTOLOAD;
320	our @ISA;	863	our @ISA;
321		864
		865	our @REGISTRY;
		866
		867	our $WIN32;
		868
		869	BEGIN {
		870	my $win32 = ! ! ($^O =~ /mswin32/i);
		871	eval "sub WIN32(){ $win32 }";
		872	}
		873
322	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	874	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
323		875
324	our @REGISTRY;	876	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		877
		878	{
		879	my $idx;
		880	$PROTOCOL{$_} = ++$idx
		881	for reverse split /\s*,\s*/,
		882	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		883	}
325		884
326	my @models = (	885	my @models = (
327	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
328	[EV:: => AnyEvent::Impl::EV::],	886	[EV:: => AnyEvent::Impl::EV::],
329	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
330	[Event:: => AnyEvent::Impl::Event::],	887	[Event:: => AnyEvent::Impl::Event::],
331	[Glib:: => AnyEvent::Impl::Glib::],
332	[Tk:: => AnyEvent::Impl::Tk::],
333	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	888	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		889	# everything below here will not be autoprobed
		890	# as the pureperl backend should work everywhere
		891	# and is usually faster
		892	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		893	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		894	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		895	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		896	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		897	[Wx:: => AnyEvent::Impl::POE::],
		898	[Prima:: => AnyEvent::Impl::POE::],
334	);	899	);
335		900
336	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	901	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		902
		903	our @post_detect;
		904
		905	sub post_detect(&) {
		906	my ($cb) = @_;
		907
		908	if ($MODEL) {
		909	$cb->();
		910
		911	1
		912	} else {
		913	push @post_detect, $cb;
		914
		915	defined wantarray
		916	? bless \$cb, "AnyEvent::Util::PostDetect"
		917	: ()
		918	}
		919	}
		920
		921	sub AnyEvent::Util::PostDetect::DESTROY {
		922	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		923	}
337		924
338	sub detect() {	925	sub detect() {
339	unless ($MODEL) {	926	unless ($MODEL) {
340	no strict 'refs';	927	no strict 'refs';
		928	local $SIG{__DIE__};
		929
		930	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		931	my $model = "AnyEvent::Impl::$1";
		932	if (eval "require $model") {
		933	$MODEL = $model;
		934	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		935	} else {
		936	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		937	}
		938	}
341		939
342	# check for already loaded models	940	# check for already loaded models
		941	unless ($MODEL) {
343	for (@REGISTRY, @models) {	942	for (@REGISTRY, @models) {
344	my ($package, $model) = @$_;	943	my ($package, $model) = @$_;
345	if (${"$package\::VERSION"} > 0) {	944	if (${"$package\::VERSION"} > 0) {
346	if (eval "require $model") {	945	if (eval "require $model") {
347	$MODEL = $model;	946	$MODEL = $model;
348	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	947	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
349	last;	948	last;
		949	}
350	}	950	}
351	}	951	}
		952
		953	unless ($MODEL) {
		954	# try to load a model
		955
		956	for (@REGISTRY, @models) {
		957	my ($package, $model) = @$_;
		958	if (eval "require $package"
		959	and ${"$package\::VERSION"} > 0
		960	and eval "require $model") {
		961	$MODEL = $model;
		962	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		963	last;
		964	}
		965	}
		966
		967	$MODEL
		968	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
		969	}
352	}	970	}
353		971
354	unless ($MODEL) {	972	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
355	# try to load a model
356
357	for (@REGISTRY, @models) {
358	my ($package, $model) = @$_;
359	if (eval "require $package"
360	and ${"$package\::VERSION"} > 0
361	and eval "require $model") {
362	$MODEL = $model;
363	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
364	last;
365	}
366	}
367
368	$MODEL
369	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.";
370	}
371		973
372	unshift @ISA, $MODEL;	974	unshift @ISA, $MODEL;
373	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	975
		976	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		977
		978	(shift @post_detect)->() while @post_detect;
374	}	979	}
375		980
376	$MODEL	981	$MODEL
377	}	982	}
378		983
…		…
386		991
387	my $class = shift;	992	my $class = shift;
388	$class->$func (@_);	993	$class->$func (@_);
389	}	994	}
390		995
		996	# utility function to dup a filehandle. this is used by many backends
		997	# to support binding more than one watcher per filehandle (they usually
		998	# allow only one watcher per fd, so we dup it to get a different one).
		999	sub _dupfh($$$$) {
		1000	my ($poll, $fh, $r, $w) = @_;
		1001
		1002	require Fcntl;
		1003
		1004	# cygwin requires the fh mode to be matching, unix doesn't
		1005	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1006	: $poll eq "w" ? ($w, ">")
		1007	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1008
		1009	open my $fh2, "$mode&" . fileno $fh
		1010	or die "cannot dup() filehandle: $!";
		1011
		1012	# we assume CLOEXEC is already set by perl in all important cases
		1013
		1014	($fh2, $rw)
		1015	}
		1016
391	package AnyEvent::Base;	1017	package AnyEvent::Base;
392		1018
		1019	# default implementation for now and time
		1020
		1021	BEGIN {
		1022	if (eval "use Time::HiRes (); time (); 1") {
		1023	*_time = \&Time::HiRes::time;
		1024	# if (eval "use POSIX (); (POSIX::times())...
		1025	} else {
		1026	*_time = \&CORE::time; # epic fail
		1027	}
		1028	}
		1029
		1030	sub time { _time }
		1031	sub now { _time }
		1032
393	# default implementation for ->condvar, ->wait, ->broadcast	1033	# default implementation for ->condvar
394		1034
395	sub condvar {	1035	sub condvar {
396	bless \my $flag, "AnyEvent::Base::CondVar"	1036	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
397	}
398
399	sub AnyEvent::Base::CondVar::broadcast {
400	${$_[0]}++;
401	}
402
403	sub AnyEvent::Base::CondVar::wait {
404	AnyEvent->one_event while !${$_[0]};
405	}	1037	}
406		1038
407	# default implementation for ->signal	1039	# default implementation for ->signal
408		1040
409	our %SIG_CB;	1041	our %SIG_CB;
…		…
425	sub AnyEvent::Base::Signal::DESTROY {	1057	sub AnyEvent::Base::Signal::DESTROY {
426	my ($signal, $cb) = @{$_[0]};	1058	my ($signal, $cb) = @{$_[0]};
427		1059
428	delete $SIG_CB{$signal}{$cb};	1060	delete $SIG_CB{$signal}{$cb};
429		1061
430	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1062	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
431	}	1063	}
432		1064
433	# default implementation for ->child	1065	# default implementation for ->child
434		1066
435	our %PID_CB;	1067	our %PID_CB;
…		…
462	or Carp::croak "required option 'pid' is missing";	1094	or Carp::croak "required option 'pid' is missing";
463		1095
464	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1096	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
465		1097
466	unless ($WNOHANG) {	1098	unless ($WNOHANG) {
467	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1099	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
468	}	1100	}
469		1101
470	unless ($CHLD_W) {	1102	unless ($CHLD_W) {
471	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1103	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
472	# child could be a zombie already, so make at least one round	1104	# child could be a zombie already, so make at least one round
…		…
483	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1115	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
484		1116
485	undef $CHLD_W unless keys %PID_CB;	1117	undef $CHLD_W unless keys %PID_CB;
486	}	1118	}
487		1119
		1120	package AnyEvent::CondVar;
		1121
		1122	our @ISA = AnyEvent::CondVar::Base::;
		1123
		1124	package AnyEvent::CondVar::Base;
		1125
		1126	use overload
		1127	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1128	fallback => 1;
		1129
		1130	sub _send {
		1131	# nop
		1132	}
		1133
		1134	sub send {
		1135	my $cv = shift;
		1136	$cv->{_ae_sent} = [@_];
		1137	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1138	$cv->_send;
		1139	}
		1140
		1141	sub croak {
		1142	$_[0]{_ae_croak} = $_[1];
		1143	$_[0]->send;
		1144	}
		1145
		1146	sub ready {
		1147	$_[0]{_ae_sent}
		1148	}
		1149
		1150	sub _wait {
		1151	AnyEvent->one_event while !$_[0]{_ae_sent};
		1152	}
		1153
		1154	sub recv {
		1155	$_[0]->_wait;
		1156
		1157	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1158	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1159	}
		1160
		1161	sub cb {
		1162	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1163	$_[0]{_ae_cb}
		1164	}
		1165
		1166	sub begin {
		1167	++$_[0]{_ae_counter};
		1168	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1169	}
		1170
		1171	sub end {
		1172	return if --$_[0]{_ae_counter};
		1173	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1174	}
		1175
		1176	# undocumented/compatibility with pre-3.4
		1177	*broadcast = \&send;
		1178	*wait = \&_wait;
		1179
488	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1180	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1181
		1182	This is an advanced topic that you do not normally need to use AnyEvent in
		1183	a module. This section is only of use to event loop authors who want to
		1184	provide AnyEvent compatibility.
489		1185
490	If you need to support another event library which isn't directly	1186	If you need to support another event library which isn't directly
491	supported by AnyEvent, you can supply your own interface to it by	1187	supported by AnyEvent, you can supply your own interface to it by
492	pushing, before the first watcher gets created, the package name of	1188	pushing, before the first watcher gets created, the package name of
493	the event module and the package name of the interface to use onto	1189	the event module and the package name of the interface to use onto
494	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1190	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
495	AnyEvent.	1191	AnyEvent, so it is reasonably cheap.
496		1192
497	Example:	1193	Example:
498		1194
499	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1195	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
500		1196
501	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1197	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
502	package/class when it finds the C<urxvt> package/module is loaded. When	1198	package/class when it finds the C<urxvt> package/module is already loaded.
		1199
503	AnyEvent is loaded and asked to find a suitable event model, it will	1200	When AnyEvent is loaded and asked to find a suitable event model, it
504	first check for the presence of urxvt.	1201	will first check for the presence of urxvt by trying to C<use> the
		1202	C<urxvt::anyevent> module.
505		1203
506	The class should provide implementations for all watcher types (see	1204	The class should provide implementations for all watcher types. See
507	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1205	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
508	(Source code) and so on for actual examples, use C<perldoc -m	1206	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
509	AnyEvent::Impl::Glib> to see the sources).	1207	see the sources.
510		1208
		1209	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1210	provide suitable (hopefully) replacements.
		1211
511	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1212	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
512	uses the above line as-is. An interface isn't included in AnyEvent	1213	terminal emulator uses the above line as-is. An interface isn't included
513	because it doesn't make sense outside the embedded interpreter inside	1214	in AnyEvent because it doesn't make sense outside the embedded interpreter
514	I<rxvt-unicode>, and it is updated and maintained as part of the	1215	inside I<rxvt-unicode>, and it is updated and maintained as part of the
515	I<rxvt-unicode> distribution.	1216	I<rxvt-unicode> distribution.
516		1217
517	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1218	I<rxvt-unicode> also cheats a bit by not providing blocking access to
518	condition variables: code blocking while waiting for a condition will	1219	condition variables: code blocking while waiting for a condition will
519	C<die>. This still works with most modules/usages, and blocking calls must	1220	C<die>. This still works with most modules/usages, and blocking calls must
520	not be in an interactive application, so it makes sense.	1221	not be done in an interactive application, so it makes sense.
521		1222
522	=head1 ENVIRONMENT VARIABLES	1223	=head1 ENVIRONMENT VARIABLES
523		1224
524	The following environment variables are used by this module:	1225	The following environment variables are used by this module:
525		1226
526	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event	1227	=over 4
527	model gets used.
528		1228
		1229	=item C<PERL_ANYEVENT_VERBOSE>
		1230
		1231	By default, AnyEvent will be completely silent except in fatal
		1232	conditions. You can set this environment variable to make AnyEvent more
		1233	talkative.
		1234
		1235	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1236	conditions, such as not being able to load the event model specified by
		1237	C<PERL_ANYEVENT_MODEL>.
		1238
		1239	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1240	model it chooses.
		1241
		1242	=item C<PERL_ANYEVENT_STRICT>
		1243
		1244	AnyEvent does not do much argument checking by default, as thorough
		1245	argument checking is very costly. Setting this variable to a true value
		1246	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1247	check the arguments passed to most method calls. If it finds any problems
		1248	it will croak.
		1249
		1250	In other words, enables "strict" mode.
		1251
		1252	Unlike C<use strict> it is definitely recommended ot keep it off in
		1253	production.
		1254
		1255	=item C<PERL_ANYEVENT_MODEL>
		1256
		1257	This can be used to specify the event model to be used by AnyEvent, before
		1258	auto detection and -probing kicks in. It must be a string consisting
		1259	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1260	and the resulting module name is loaded and if the load was successful,
		1261	used as event model. If it fails to load AnyEvent will proceed with
		1262	auto detection and -probing.
		1263
		1264	This functionality might change in future versions.
		1265
		1266	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1267	could start your program like this:
		1268
		1269	PERL_ANYEVENT_MODEL=Perl perl ...
		1270
		1271	=item C<PERL_ANYEVENT_PROTOCOLS>
		1272
		1273	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1274	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1275	of auto probing).
		1276
		1277	Must be set to a comma-separated list of protocols or address families,
		1278	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1279	used, and preference will be given to protocols mentioned earlier in the
		1280	list.
		1281
		1282	This variable can effectively be used for denial-of-service attacks
		1283	against local programs (e.g. when setuid), although the impact is likely
		1284	small, as the program has to handle connection errors already-
		1285
		1286	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1287	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1288	- only support IPv4, never try to resolve or contact IPv6
		1289	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1290	IPv6, but prefer IPv6 over IPv4.
		1291
		1292	=item C<PERL_ANYEVENT_EDNS0>
		1293
		1294	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1295	for DNS. This extension is generally useful to reduce DNS traffic, but
		1296	some (broken) firewalls drop such DNS packets, which is why it is off by
		1297	default.
		1298
		1299	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1300	EDNS0 in its DNS requests.
		1301
		1302	=item C<PERL_ANYEVENT_MAX_FORKS>
		1303
		1304	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1305	will create in parallel.
		1306
		1307	=back
		1308
529	=head1 EXAMPLE	1309	=head1 EXAMPLE PROGRAM
530		1310
531	The following program uses an io watcher to read data from stdin, a timer	1311	The following program uses an I/O watcher to read data from STDIN, a timer
532	to display a message once per second, and a condvar to exit the program	1312	to display a message once per second, and a condition variable to quit the
533	when the user enters quit:	1313	program when the user enters quit:
534		1314
535	use AnyEvent;	1315	use AnyEvent;
536		1316
537	my $cv = AnyEvent->condvar;	1317	my $cv = AnyEvent->condvar;
538		1318
539	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	1319	my $io_watcher = AnyEvent->io (
		1320	fh => \*STDIN,
		1321	poll => 'r',
		1322	cb => sub {
540	warn "io event <$_[0]>\n"; # will always output <r>	1323	warn "io event <$_[0]>\n"; # will always output <r>
541	chomp (my $input = <STDIN>); # read a line	1324	chomp (my $input = <STDIN>); # read a line
542	warn "read: $input\n"; # output what has been read	1325	warn "read: $input\n"; # output what has been read
543	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1326	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		1327	},
544	});	1328	);
545		1329
546	my $time_watcher; # can only be used once	1330	my $time_watcher; # can only be used once
547		1331
548	sub new_timer {	1332	sub new_timer {
549	$timer = AnyEvent->timer (after => 1, cb => sub {	1333	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
552	});	1336	});
553	}	1337	}
554		1338
555	new_timer; # create first timer	1339	new_timer; # create first timer
556		1340
557	$cv->wait; # wait until user enters /^q/i	1341	$cv->recv; # wait until user enters /^q/i
558		1342
559	=head1 REAL-WORLD EXAMPLE	1343	=head1 REAL-WORLD EXAMPLE
560		1344
561	Consider the L<Net::FCP> module. It features (among others) the following	1345	Consider the L<Net::FCP> module. It features (among others) the following
562	API calls, which are to freenet what HTTP GET requests are to http:	1346	API calls, which are to freenet what HTTP GET requests are to http:
…		…
612	syswrite $txn->{fh}, $txn->{request}	1396	syswrite $txn->{fh}, $txn->{request}
613	or die "connection or write error";	1397	or die "connection or write error";
614	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1398	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
615		1399
616	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1400	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
617	result and signals any possible waiters that the request ahs finished:	1401	result and signals any possible waiters that the request has finished:
618		1402
619	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1403	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
620		1404
621	if (end-of-file or data complete) {	1405	if (end-of-file or data complete) {
622	$txn->{result} = $txn->{buf};	1406	$txn->{result} = $txn->{buf};
623	$txn->{finished}->broadcast;	1407	$txn->{finished}->send;
624	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1408	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
625	}	1409	}
626		1410
627	The C<result> method, finally, just waits for the finished signal (if the	1411	The C<result> method, finally, just waits for the finished signal (if the
628	request was already finished, it doesn't wait, of course, and returns the	1412	request was already finished, it doesn't wait, of course, and returns the
629	data:	1413	data:
630		1414
631	$txn->{finished}->wait;	1415	$txn->{finished}->recv;
632	return $txn->{result};	1416	return $txn->{result};
633		1417
634	The actual code goes further and collects all errors (C<die>s, exceptions)	1418	The actual code goes further and collects all errors (C<die>s, exceptions)
635	that occured during request processing. The C<result> method detects	1419	that occurred during request processing. The C<result> method detects
636	wether an exception as thrown (it is stored inside the $txn object)	1420	whether an exception as thrown (it is stored inside the $txn object)
637	and just throws the exception, which means connection errors and other	1421	and just throws the exception, which means connection errors and other
638	problems get reported tot he code that tries to use the result, not in a	1422	problems get reported tot he code that tries to use the result, not in a
639	random callback.	1423	random callback.
640		1424
641	All of this enables the following usage styles:	1425	All of this enables the following usage styles:
…		…
671		1455
672	my $quit = AnyEvent->condvar;	1456	my $quit = AnyEvent->condvar;
673		1457
674	$fcp->txn_client_get ($url)->cb (sub {	1458	$fcp->txn_client_get ($url)->cb (sub {
675	...	1459	...
676	$quit->broadcast;	1460	$quit->send;
677	});	1461	});
678		1462
679	$quit->wait;	1463	$quit->recv;
		1464
		1465
		1466	=head1 BENCHMARKS
		1467
		1468	To give you an idea of the performance and overheads that AnyEvent adds
		1469	over the event loops themselves and to give you an impression of the speed
		1470	of various event loops I prepared some benchmarks.
		1471
		1472	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1473
		1474	Here is a benchmark of various supported event models used natively and
		1475	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1476	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1477	which it is), lets them fire exactly once and destroys them again.
		1478
		1479	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1480	distribution.
		1481
		1482	=head3 Explanation of the columns
		1483
		1484	I<watcher> is the number of event watchers created/destroyed. Since
		1485	different event models feature vastly different performances, each event
		1486	loop was given a number of watchers so that overall runtime is acceptable
		1487	and similar between tested event loop (and keep them from crashing): Glib
		1488	would probably take thousands of years if asked to process the same number
		1489	of watchers as EV in this benchmark.
		1490
		1491	I<bytes> is the number of bytes (as measured by the resident set size,
		1492	RSS) consumed by each watcher. This method of measuring captures both C
		1493	and Perl-based overheads.
		1494
		1495	I<create> is the time, in microseconds (millionths of seconds), that it
		1496	takes to create a single watcher. The callback is a closure shared between
		1497	all watchers, to avoid adding memory overhead. That means closure creation
		1498	and memory usage is not included in the figures.
		1499
		1500	I<invoke> is the time, in microseconds, used to invoke a simple
		1501	callback. The callback simply counts down a Perl variable and after it was
		1502	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1503	signal the end of this phase.
		1504
		1505	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1506	watcher.
		1507
		1508	=head3 Results
		1509
		1510	name watchers bytes create invoke destroy comment
		1511	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1512	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1513	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1514	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1515	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1516	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1517	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1518	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1519	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1520	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1521
		1522	=head3 Discussion
		1523
		1524	The benchmark does I<not> measure scalability of the event loop very
		1525	well. For example, a select-based event loop (such as the pure perl one)
		1526	can never compete with an event loop that uses epoll when the number of
		1527	file descriptors grows high. In this benchmark, all events become ready at
		1528	the same time, so select/poll-based implementations get an unnatural speed
		1529	boost.
		1530
		1531	Also, note that the number of watchers usually has a nonlinear effect on
		1532	overall speed, that is, creating twice as many watchers doesn't take twice
		1533	the time - usually it takes longer. This puts event loops tested with a
		1534	higher number of watchers at a disadvantage.
		1535
		1536	To put the range of results into perspective, consider that on the
		1537	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1538	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1539	cycles with POE.
		1540
		1541	C<EV> is the sole leader regarding speed and memory use, which are both
		1542	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1543	far less memory than any other event loop and is still faster than Event
		1544	natively.
		1545
		1546	The pure perl implementation is hit in a few sweet spots (both the
		1547	constant timeout and the use of a single fd hit optimisations in the perl
		1548	interpreter and the backend itself). Nevertheless this shows that it
		1549	adds very little overhead in itself. Like any select-based backend its
		1550	performance becomes really bad with lots of file descriptors (and few of
		1551	them active), of course, but this was not subject of this benchmark.
		1552
		1553	The C<Event> module has a relatively high setup and callback invocation
		1554	cost, but overall scores in on the third place.
		1555
		1556	C<Glib>'s memory usage is quite a bit higher, but it features a
		1557	faster callback invocation and overall ends up in the same class as
		1558	C<Event>. However, Glib scales extremely badly, doubling the number of
		1559	watchers increases the processing time by more than a factor of four,
		1560	making it completely unusable when using larger numbers of watchers
		1561	(note that only a single file descriptor was used in the benchmark, so
		1562	inefficiencies of C<poll> do not account for this).
		1563
		1564	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1565	more than 2000 watchers is a big setback, however, as correctness takes
		1566	precedence over speed. Nevertheless, its performance is surprising, as the
		1567	file descriptor is dup()ed for each watcher. This shows that the dup()
		1568	employed by some adaptors is not a big performance issue (it does incur a
		1569	hidden memory cost inside the kernel which is not reflected in the figures
		1570	above).
		1571
		1572	C<POE>, regardless of underlying event loop (whether using its pure perl
		1573	select-based backend or the Event module, the POE-EV backend couldn't
		1574	be tested because it wasn't working) shows abysmal performance and
		1575	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1576	as EV watchers, and 10 times as much memory as Event (the high memory
		1577	requirements are caused by requiring a session for each watcher). Watcher
		1578	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1579	implementation.
		1580
		1581	The design of the POE adaptor class in AnyEvent can not really account
		1582	for the performance issues, though, as session creation overhead is
		1583	small compared to execution of the state machine, which is coded pretty
		1584	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1585	using multiple sessions is not a good approach, especially regarding
		1586	memory usage, even the author of POE could not come up with a faster
		1587	design).
		1588
		1589	=head3 Summary
		1590
		1591	=over 4
		1592
		1593	=item * Using EV through AnyEvent is faster than any other event loop
		1594	(even when used without AnyEvent), but most event loops have acceptable
		1595	performance with or without AnyEvent.
		1596
		1597	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1598	the actual event loop, only with extremely fast event loops such as EV
		1599	adds AnyEvent significant overhead.
		1600
		1601	=item * You should avoid POE like the plague if you want performance or
		1602	reasonable memory usage.
		1603
		1604	=back
		1605
		1606	=head2 BENCHMARKING THE LARGE SERVER CASE
		1607
		1608	This benchmark actually benchmarks the event loop itself. It works by
		1609	creating a number of "servers": each server consists of a socket pair, a
		1610	timeout watcher that gets reset on activity (but never fires), and an I/O
		1611	watcher waiting for input on one side of the socket. Each time the socket
		1612	watcher reads a byte it will write that byte to a random other "server".
		1613
		1614	The effect is that there will be a lot of I/O watchers, only part of which
		1615	are active at any one point (so there is a constant number of active
		1616	fds for each loop iteration, but which fds these are is random). The
		1617	timeout is reset each time something is read because that reflects how
		1618	most timeouts work (and puts extra pressure on the event loops).
		1619
		1620	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1621	(1%) are active. This mirrors the activity of large servers with many
		1622	connections, most of which are idle at any one point in time.
		1623
		1624	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1625	distribution.
		1626
		1627	=head3 Explanation of the columns
		1628
		1629	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1630	each server has a read and write socket end).
		1631
		1632	I<create> is the time it takes to create a socket pair (which is
		1633	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1634
		1635	I<request>, the most important value, is the time it takes to handle a
		1636	single "request", that is, reading the token from the pipe and forwarding
		1637	it to another server. This includes deleting the old timeout and creating
		1638	a new one that moves the timeout into the future.
		1639
		1640	=head3 Results
		1641
		1642	name sockets create request
		1643	EV 20000 69.01 11.16
		1644	Perl 20000 73.32 35.87
		1645	Event 20000 212.62 257.32
		1646	Glib 20000 651.16 1896.30
		1647	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1648
		1649	=head3 Discussion
		1650
		1651	This benchmark I<does> measure scalability and overall performance of the
		1652	particular event loop.
		1653
		1654	EV is again fastest. Since it is using epoll on my system, the setup time
		1655	is relatively high, though.
		1656
		1657	Perl surprisingly comes second. It is much faster than the C-based event
		1658	loops Event and Glib.
		1659
		1660	Event suffers from high setup time as well (look at its code and you will
		1661	understand why). Callback invocation also has a high overhead compared to
		1662	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1663	uses select or poll in basically all documented configurations.
		1664
		1665	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1666	clearly fails to perform with many filehandles or in busy servers.
		1667
		1668	POE is still completely out of the picture, taking over 1000 times as long
		1669	as EV, and over 100 times as long as the Perl implementation, even though
		1670	it uses a C-based event loop in this case.
		1671
		1672	=head3 Summary
		1673
		1674	=over 4
		1675
		1676	=item * The pure perl implementation performs extremely well.
		1677
		1678	=item * Avoid Glib or POE in large projects where performance matters.
		1679
		1680	=back
		1681
		1682	=head2 BENCHMARKING SMALL SERVERS
		1683
		1684	While event loops should scale (and select-based ones do not...) even to
		1685	large servers, most programs we (or I :) actually write have only a few
		1686	I/O watchers.
		1687
		1688	In this benchmark, I use the same benchmark program as in the large server
		1689	case, but it uses only eight "servers", of which three are active at any
		1690	one time. This should reflect performance for a small server relatively
		1691	well.
		1692
		1693	The columns are identical to the previous table.
		1694
		1695	=head3 Results
		1696
		1697	name sockets create request
		1698	EV 16 20.00 6.54
		1699	Perl 16 25.75 12.62
		1700	Event 16 81.27 35.86
		1701	Glib 16 32.63 15.48
		1702	POE 16 261.87 276.28 uses POE::Loop::Event
		1703
		1704	=head3 Discussion
		1705
		1706	The benchmark tries to test the performance of a typical small
		1707	server. While knowing how various event loops perform is interesting, keep
		1708	in mind that their overhead in this case is usually not as important, due
		1709	to the small absolute number of watchers (that is, you need efficiency and
		1710	speed most when you have lots of watchers, not when you only have a few of
		1711	them).
		1712
		1713	EV is again fastest.
		1714
		1715	Perl again comes second. It is noticeably faster than the C-based event
		1716	loops Event and Glib, although the difference is too small to really
		1717	matter.
		1718
		1719	POE also performs much better in this case, but is is still far behind the
		1720	others.
		1721
		1722	=head3 Summary
		1723
		1724	=over 4
		1725
		1726	=item * C-based event loops perform very well with small number of
		1727	watchers, as the management overhead dominates.
		1728
		1729	=back
		1730
		1731
		1732	=head1 FORK
		1733
		1734	Most event libraries are not fork-safe. The ones who are usually are
		1735	because they rely on inefficient but fork-safe C<select> or C<poll>
		1736	calls. Only L<EV> is fully fork-aware.
		1737
		1738	If you have to fork, you must either do so I<before> creating your first
		1739	watcher OR you must not use AnyEvent at all in the child.
		1740
		1741
		1742	=head1 SECURITY CONSIDERATIONS
		1743
		1744	AnyEvent can be forced to load any event model via
		1745	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1746	execute arbitrary code or directly gain access, it can easily be used to
		1747	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1748	will not be active when the program uses a different event model than
		1749	specified in the variable.
		1750
		1751	You can make AnyEvent completely ignore this variable by deleting it
		1752	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1753
		1754	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1755
		1756	use AnyEvent;
		1757
		1758	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1759	be used to probe what backend is used and gain other information (which is
		1760	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1761	$ENV{PERL_ANYEGENT_STRICT}.
		1762
		1763
		1764	=head1 BUGS
		1765
		1766	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1767	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1768	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1769	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1770	pronounced).
		1771
680		1772
681	=head1 SEE ALSO	1773	=head1 SEE ALSO
682		1774
683	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1775	Utility functions: L<AnyEvent::Util>.
684	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.
685		1776
686	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1777	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		1778	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		1779
687	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	1780	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
688	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.	1781	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		1782	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		1783	L<AnyEvent::Impl::POE>.
689		1784
		1785	Non-blocking file handles, sockets, TCP clients and
		1786	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1787
		1788	Asynchronous DNS: L<AnyEvent::DNS>.
		1789
		1790	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1791
690	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1792	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
691		1793
692	=head1	1794
		1795	=head1 AUTHOR
		1796
		1797	Marc Lehmann <schmorp@schmorp.de>
		1798	http://home.schmorp.de/
693		1799
694	=cut	1800	=cut
695		1801
696	1	1802	1
697		1803

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