[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.42 by root, Mon Apr 7 19:40:12 2008 UTC vs.
Revision 1.95 by root, Sat Apr 26 11:06:45 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, Coro::EV, Coro::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
14		14
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...	16	...
17	});	17	});
18		18
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	19	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	20	$w->wait; # enters "main loop" till $condvar gets ->broadcast
21	$w->broadcast; # wake up current and all future wait's	21	$w->broadcast; # wake up current and all future wait's
22		22
23	=head1 WHY YOU SHOULD USE THIS MODULE	23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		24
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	26	nowadays. So what is different about AnyEvent?
27		27
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	29	policy> and AnyEvent is I<small and efficient>.
30		30
31	First and foremost, I<AnyEvent is not an event model> itself, it only	31	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	32	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,	33	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	34	the statement "there can only be one" is a bitter reality: In general,
35	helps hiding the differences.	35	only one event loop can be active at the same time in a process. AnyEvent
		36	helps hiding the differences between those event loops.
36		37
37	The goal of AnyEvent is to offer module authors the ability to do event	38	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	39	programming (waiting for I/O or timer events) without subscribing to a
39	religion, a way of living, and most importantly: without forcing your	40	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	41	module users into the same thing by forcing them to use the same event
41	model you use.	42	model you use.
42		43
43	For modules like POE or IO::Async (which is actually doing all I/O	44	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	45	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	46	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	47	cannot use anything else, as it is simply incompatible to everything that
47	itself.	48	isn't itself. What's worse, all the potential users of your module are
		49	I<also> forced to use the same event loop you use.
48		50
49	AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk	51	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	52	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	53	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	54	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	55	too. But if your module uses AnyEvent, it works transparently with all
54	(including stuff like POE and IO::Async).	56	event models it supports (including stuff like POE and IO::Async, as long
		57	as those use one of the supported event loops. It is trivial to add new
		58	event loops to AnyEvent, too, so it is future-proof).
55		59
56	In addition of being free of having to use I<the one and only true event	60	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	61	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	62	modules, you get an enourmous 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	63	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	64	offering the functionality that is necessary, in as thin as a wrapper as
61	technically possible.	65	technically possible.
		66
		67	Of course, if you 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
		69	model, you should I<not> use this module.
62		70
63		71
64	=head1 DESCRIPTION	72	=head1 DESCRIPTION
65		73
66	L<AnyEvent> provides an identical interface to multiple event loops. This	74	L<AnyEvent> provides an identical interface to multiple event loops. This
67	allows module authors to utilise an event loop without forcing module	75	allows module authors to utilise an event loop without forcing module
68	users to use the same event loop (as only a single event loop can coexist	76	users to use the same event loop (as only a single event loop can coexist
69	peacefully at any one time).	77	peacefully at any one time).
70		78
71	The interface itself is vaguely similar but not identical to the Event	79	The interface itself is vaguely similar, but not identical to the L<Event>
72	module.	80	module.
73		81
74	On the first call of any method, the module tries to detect the currently	82	During the first call of any watcher-creation method, the module tries
75	loaded event loop by probing wether any of the following modules is	83	to detect the currently loaded event loop by probing whether one of the
76	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
77	used. If none is found, the module tries to load these modules in the	85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
78	order given. The first one that could be successfully loaded will be	86	L<POE>. The first one found is used. If none are found, the module tries
79	used. If still none could be found, AnyEvent will fall back to a pure-perl	87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
80	event loop, which is also not very efficient.	88	adaptor should always succeed) in the order given. The first one that can
		89	be successfully loaded will be used. If, after this, still none could be
		90	found, AnyEvent will fall back to a pure-perl event loop, which is not
		91	very efficient, but should work everywhere.
81		92
82	Because AnyEvent first checks for modules that are already loaded, loading	93	Because AnyEvent first checks for modules that are already loaded, loading
83	an Event model explicitly before first using AnyEvent will likely make	94	an event model explicitly before first using AnyEvent will likely make
84	that model the default. For example:	95	that model the default. For example:
85		96
86	use Tk;	97	use Tk;
87	use AnyEvent;	98	use AnyEvent;
88		99
89	# .. AnyEvent will likely default to Tk	100	# .. AnyEvent will likely default to Tk
		101
		102	The I<likely> means that, if any module loads another event model and
		103	starts using it, all bets are off. Maybe you should tell their authors to
		104	use AnyEvent so their modules work together with others seamlessly...
90		105
91	The pure-perl implementation of AnyEvent is called	106	The pure-perl implementation of AnyEvent is called
92	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
93	explicitly.	108	explicitly.
94		109
…		…
97	AnyEvent has the central concept of a I<watcher>, which is an object that	112	AnyEvent has the central concept of a I<watcher>, which is an object that
98	stores relevant data for each kind of event you are waiting for, such as	113	stores relevant data for each kind of event you are waiting for, such as
99	the callback to call, the filehandle to watch, etc.	114	the callback to call, the filehandle to watch, etc.
100		115
101	These watchers are normal Perl objects with normal Perl lifetime. After	116	These watchers are normal Perl objects with normal Perl lifetime. After
102	creating a watcher it will immediately "watch" for events and invoke	117	creating a watcher it will immediately "watch" for events and invoke the
		118	callback when the event occurs (of course, only when the event model
		119	is in control).
		120
103	the callback. To disable the watcher you have to destroy it (e.g. by	121	To disable the watcher you have to destroy it (e.g. by setting the
104	setting the variable that stores it to C<undef> or otherwise deleting all	122	variable you store it in to C<undef> or otherwise deleting all references
105	references to it).	123	to it).
106		124
107	All watchers are created by calling a method on the C<AnyEvent> class.	125	All watchers are created by calling a method on the C<AnyEvent> class.
108		126
		127	Many watchers either are used with "recursion" (repeating timers for
		128	example), or need to refer to their watcher object in other ways.
		129
		130	An any way to achieve that is this pattern:
		131
		132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		133	# you can use $w here, for example to undef it
		134	undef $w;
		135	});
		136
		137	Note that C<my $w; $w => combination. This is necessary because in Perl,
		138	my variables are only visible after the statement in which they are
		139	declared.
		140
109	=head2 IO WATCHERS	141	=head2 I/O WATCHERS
110		142
111	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
112	the following mandatory arguments:	144	with the following mandatory key-value pairs as arguments:
113		145
114	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
115	events. C<poll> must be a string that is either C<r> or C<w>, that creates	147	for events. C<poll> must be a string that is either C<r> or C<w>,
116	a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback	148	which creates a watcher waiting for "r"eadable or "w"ritable events,
117	to invoke everytime the filehandle becomes ready.	149	respectively. C<cb> is the callback to invoke each time the file handle
		150	becomes ready.
118		151
119	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	152	Although the callback might get passed parameters, their value and
120	a socket you can have one r + one w, not any more (limitation comes from	153	presence is undefined and you cannot rely on them. Portable AnyEvent
121	Tk - if you are sure you are not using Tk this limitation is gone).	154	callbacks cannot use arguments passed to I/O watcher callbacks.
122		155
123	Filehandles will be kept alive, so as long as the watcher exists, the	156	The I/O watcher might use the underlying file descriptor or a copy of it.
124	filehandle exists, too.	157	You must not close a file handle as long as any watcher is active on the
		158	underlying file descriptor.
		159
		160	Some event loops issue spurious readyness notifications, so you should
		161	always use non-blocking calls when reading/writing from/to your file
		162	handles.
125		163
126	Example:	164	Example:
127		165
128	# wait for readability of STDIN, then read a line and disable the watcher	166	# wait for readability of STDIN, then read a line and disable the watcher
129	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
…		…
135	=head2 TIME WATCHERS	173	=head2 TIME WATCHERS
136		174
137	You can create a time watcher by calling the C<< AnyEvent->timer >>	175	You can create a time watcher by calling the C<< AnyEvent->timer >>
138	method with the following mandatory arguments:	176	method with the following mandatory arguments:
139		177
140	C<after> after how many seconds (fractions are supported) should the timer	178	C<after> specifies after how many seconds (fractional values are
141	activate. C<cb> the callback to invoke.	179	supported) the callback should be invoked. C<cb> is the callback to invoke
		180	in that case.
		181
		182	Although the callback might get passed parameters, their value and
		183	presence is undefined and you cannot rely on them. Portable AnyEvent
		184	callbacks cannot use arguments passed to time watcher callbacks.
142		185
143	The timer callback will be invoked at most once: if you want a repeating	186	The timer callback will be invoked at most once: if you want a repeating
144	timer you have to create a new watcher (this is a limitation by both Tk	187	timer you have to create a new watcher (this is a limitation by both Tk
145	and Glib).	188	and Glib).
146		189
…		…
152	});	195	});
153		196
154	# to cancel the timer:	197	# to cancel the timer:
155	undef $w;	198	undef $w;
156		199
		200	Example 2:
		201
		202	# fire an event after 0.5 seconds, then roughly every second
		203	my $w;
		204
		205	my $cb = sub {
		206	# cancel the old timer while creating a new one
		207	$w = AnyEvent->timer (after => 1, cb => $cb);
		208	};
		209
		210	# start the "loop" by creating the first watcher
		211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		212
		213	=head3 TIMING ISSUES
		214
		215	There are two ways to handle timers: based on real time (relative, "fire
		216	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		217	o'clock").
		218
		219	While most event loops expect timers to specified in a relative way, they
		220	use absolute time internally. This makes a difference when your clock
		221	"jumps", for example, when ntp decides to set your clock backwards from
		222	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		223	fire "after" a second might actually take six years to finally fire.
		224
		225	AnyEvent cannot compensate for this. The only event loop that is conscious
		226	about these issues is L<EV>, which offers both relative (ev_timer, based
		227	on true relative time) and absolute (ev_periodic, based on wallclock time)
		228	timers.
		229
		230	AnyEvent always prefers relative timers, if available, matching the
		231	AnyEvent API.
		232
		233	=head2 SIGNAL WATCHERS
		234
		235	You can watch for signals using a signal watcher, C<signal> is the signal
		236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		237	be invoked whenever a signal occurs.
		238
		239	Although the callback might get passed parameters, their value and
		240	presence is undefined and you cannot rely on them. Portable AnyEvent
		241	callbacks cannot use arguments passed to signal watcher callbacks.
		242
		243	Multiple signal occurances can be clumped together into one callback
		244	invocation, and callback invocation will be synchronous. synchronous means
		245	that it might take a while until the signal gets handled by the process,
		246	but it is guarenteed not to interrupt any other callbacks.
		247
		248	The main advantage of using these watchers is that you can share a signal
		249	between multiple watchers.
		250
		251	This watcher might use C<%SIG>, so programs overwriting those signals
		252	directly will likely not work correctly.
		253
		254	Example: exit on SIGINT
		255
		256	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		257
		258	=head2 CHILD PROCESS WATCHERS
		259
		260	You can also watch on a child process exit and catch its exit status.
		261
		262	The child process is specified by the C<pid> argument (if set to C<0>, it
		263	watches for any child process exit). The watcher will trigger as often
		264	as status change for the child are received. This works by installing a
		265	signal handler for C<SIGCHLD>. The callback will be called with the pid
		266	and exit status (as returned by waitpid), so unlike other watcher types,
		267	you I<can> rely on child watcher callback arguments.
		268
		269	There is a slight catch to child watchers, however: you usually start them
		270	I<after> the child process was created, and this means the process could
		271	have exited already (and no SIGCHLD will be sent anymore).
		272
		273	Not all event models handle this correctly (POE doesn't), but even for
		274	event models that I<do> handle this correctly, they usually need to be
		275	loaded before the process exits (i.e. before you fork in the first place).
		276
		277	This means you cannot create a child watcher as the very first thing in an
		278	AnyEvent program, you I<have> to create at least one watcher before you
		279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		280
		281	Example: fork a process and wait for it
		282
		283	my $done = AnyEvent->condvar;
		284
		285	AnyEvent::detect; # force event module to be initialised
		286
		287	my $pid = fork or exit 5;
		288
		289	my $w = AnyEvent->child (
		290	pid => $pid,
		291	cb => sub {
		292	my ($pid, $status) = @_;
		293	warn "pid $pid exited with status $status";
		294	$done->broadcast;
		295	},
		296	);
		297
		298	# do something else, then wait for process exit
		299	$done->wait;
		300
157	=head2 CONDITION WATCHERS	301	=head2 CONDITION VARIABLES
158		302
159	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	303	Condition variables can be created by calling the C<< AnyEvent->condvar >>
160	method without any arguments.	304	method without any arguments.
161		305
162	A condition watcher watches for a condition - precisely that the C<<	306	A condition variable waits for a condition - precisely that the C<<
163	->broadcast >> method has been called.	307	->broadcast >> method has been called.
164		308
		309	They are very useful to signal that a condition has been fulfilled, for
		310	example, if you write a module that does asynchronous http requests,
		311	then a condition variable would be the ideal candidate to signal the
		312	availability of results.
		313
		314	You can also use condition variables to block your main program until
		315	an event occurs - for example, you could C<< ->wait >> in your main
		316	program until the user clicks the Quit button in your app, which would C<<
		317	->broadcast >> the "quit" event.
		318
165	Note that condition watchers recurse into the event loop - if you have	319	Note that condition variables recurse into the event loop - if you have
166	two watchers that call C<< ->wait >> in a round-robbin fashion, you	320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
167	lose. Therefore, condition watchers are good to export to your caller, but	321	lose. Therefore, condition variables are good to export to your caller, but
168	you should avoid making a blocking wait, at least in callbacks, as this	322	you should avoid making a blocking wait yourself, at least in callbacks,
169	usually asks for trouble.	323	as this asks for trouble.
170		324
171	The watcher has only two methods:	325	This object has two methods:
172		326
173	=over 4	327	=over 4
174		328
175	=item $cv->wait	329	=item $cv->wait
176		330
177	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
178	called on c<$cv>, while servicing other watchers normally.	332	called on c<$cv>, while servicing other watchers normally.
179		333
180	Not all event models support a blocking wait - some die in that case, so
181	if you are using this from a module, never require a blocking wait, but
182	let the caller decide wether the call will block or not (for example,
183	by coupling condition variables with some kind of request results and
184	supporting callbacks so the caller knows that getting the result will not
185	block, while still suppporting blockign waits if the caller so desires).
186
187	You can only wait once on a condition - additional calls will return	334	You can only wait once on a condition - additional calls will return
188	immediately.	335	immediately.
189		336
		337	Not all event models support a blocking wait - some die in that case
		338	(programs might want to do that to stay interactive), so I<if you are
		339	using this from a module, never require a blocking wait>, but let the
		340	caller decide whether the call will block or not (for example, by coupling
		341	condition variables with some kind of request results and supporting
		342	callbacks so the caller knows that getting the result will not block,
		343	while still suppporting blocking waits if the caller so desires).
		344
		345	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		346	sensibly have two C<< ->wait >>'s in parallel, as that would require
		347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		350	from different coroutines, however).
		351
190	=item $cv->broadcast	352	=item $cv->broadcast
191		353
192	Flag the condition as ready - a running C<< ->wait >> and all further	354	Flag the condition as ready - a running C<< ->wait >> and all further
193	calls to C<wait> will return after this method has been called. If nobody	355	calls to C<wait> will (eventually) return after this method has been
194	is waiting the broadcast will be remembered..	356	called. If nobody is waiting the broadcast will be remembered..
		357
		358	=back
195		359
196	Example:	360	Example:
197		361
198	# wait till the result is ready	362	# wait till the result is ready
199	my $result_ready = AnyEvent->condvar;	363	my $result_ready = AnyEvent->condvar;
200		364
201	# do something such as adding a timer	365	# do something such as adding a timer
202	# or socket watcher the calls $result_ready->broadcast	366	# or socket watcher the calls $result_ready->broadcast
203	# when the "result" is ready.	367	# when the "result" is ready.
		368	# in this case, we simply use a timer:
		369	my $w = AnyEvent->timer (
		370	after => 1,
		371	cb => sub { $result_ready->broadcast },
		372	);
204		373
		374	# this "blocks" (while handling events) till the watcher
		375	# calls broadcast
205	$result_ready->wait;	376	$result_ready->wait;
206		377
207	=back	378	=head1 GLOBAL VARIABLES AND FUNCTIONS
208
209	=head2 SIGNAL WATCHERS
210
211	You can listen for signals using a signal watcher, C<signal> is the signal
212	I<name> without any C<SIG> prefix. Multiple signals events can be clumped
213	together into one callback invocation, and callback invocation might or
214	might not be asynchronous.
215
216	These watchers might use C<%SIG>, so programs overwriting those signals
217	directly will likely not work correctly.
218
219	Example: exit on SIGINT
220
221	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
222
223	=head2 CHILD PROCESS WATCHERS
224
225	You can also listen for the status of a child process specified by the
226	C<pid> argument (or any child if the pid argument is 0). The watcher will
227	trigger as often as status change for the child are received. This works
228	by installing a signal handler for C<SIGCHLD>. The callback will be called with
229	the pid and exit status (as returned by waitpid).
230
231	Example: wait for pid 1333
232
233	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
234
235	=head1 GLOBALS
236		379
237	=over 4	380	=over 4
238		381
239	=item $AnyEvent::MODEL	382	=item $AnyEvent::MODEL
240		383
…		…
245	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
246		389
247	The known classes so far are:	390	The known classes so far are:
248		391
249	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
250	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
251	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
252	AnyEvent::Impl::Event based on Event, also second best choice :)	395	AnyEvent::Impl::Event based on Event, second best choice.
253	AnyEvent::Impl::Glib based on Glib, second-best choice.	396	AnyEvent::Impl::Glib based on Glib, third-best choice.
		397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
254	AnyEvent::Impl::Tk based on Tk, very bad choice.	398	AnyEvent::Impl::Tk based on Tk, very bad choice.
255	AnyEvent::Impl::Perl pure-perl implementation, inefficient.	399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		401	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		402
		403	There is no support for WxWidgets, as WxWidgets has no support for
		404	watching file handles. However, you can use WxWidgets through the
		405	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		406	second, which was considered to be too horrible to even consider for
		407	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		408	it's adaptor.
		409
		410	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		411	autodetecting them.
256		412
257	=item AnyEvent::detect	413	=item AnyEvent::detect
258		414
259	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
260	necessary. You should only call this function right before you would have	416	if necessary. You should only call this function right before you would
261	created an AnyEvent watcher anyway, that is, very late at runtime.	417	have created an AnyEvent watcher anyway, that is, as late as possible at
		418	runtime.
262		419
263	=back	420	=back
264		421
265	=head1 WHAT TO DO IN A MODULE	422	=head1 WHAT TO DO IN A MODULE
266		423
267	As a module author, you should "use AnyEvent" and call AnyEvent methods	424	As a module author, you should C<use AnyEvent> and call AnyEvent methods
268	freely, but you should not load a specific event module or rely on it.	425	freely, but you should not load a specific event module or rely on it.
269		426
270	Be careful when you create watchers in the module body - Anyevent will	427	Be careful when you create watchers in the module body - AnyEvent will
271	decide which event module to use as soon as the first method is called, so	428	decide which event module to use as soon as the first method is called, so
272	by calling AnyEvent in your module body you force the user of your module	429	by calling AnyEvent in your module body you force the user of your module
273	to load the event module first.	430	to load the event module first.
274		431
		432	Never call C<< ->wait >> on a condition variable unless you I<know> that
		433	the C<< ->broadcast >> method has been called on it already. This is
		434	because it will stall the whole program, and the whole point of using
		435	events is to stay interactive.
		436
		437	It is fine, however, to call C<< ->wait >> when the user of your module
		438	requests it (i.e. if you create a http request object ad have a method
		439	called C<results> that returns the results, it should call C<< ->wait >>
		440	freely, as the user of your module knows what she is doing. always).
		441
275	=head1 WHAT TO DO IN THE MAIN PROGRAM	442	=head1 WHAT TO DO IN THE MAIN PROGRAM
276		443
277	There will always be a single main program - the only place that should	444	There will always be a single main program - the only place that should
278	dictate which event model to use.	445	dictate which event model to use.
279		446
280	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
281	do anything special and let AnyEvent decide which implementation to chose.	448	do anything special (it does not need to be event-based) and let AnyEvent
		449	decide which implementation to chose if some module relies on it.
282		450
283	If the main program relies on a specific event model (for example, in Gtk2	451	If the main program relies on a specific event model. For example, in
284	programs you have to rely on either Glib or Glib::Event), you should load	452	Gtk2 programs you have to rely on the Glib module. You should load the
285	it before loading AnyEvent or any module that uses it, generally, as early	453	event module before loading AnyEvent or any module that uses it: generally
286	as possible. The reason is that modules might create watchers when they	454	speaking, you should load it as early as possible. The reason is that
287	are loaded, and AnyEvent will decide on the event model to use as soon as	455	modules might create watchers when they are loaded, and AnyEvent will
288	it creates watchers, and it might chose the wrong one unless you load the	456	decide on the event model to use as soon as it creates watchers, and it
289	correct one yourself.	457	might chose the wrong one unless you load the correct one yourself.
290		458
291	You can chose to use a rather inefficient pure-perl implementation by	459	You can chose to use a rather inefficient pure-perl implementation by
292	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
293	generally better.	461	behaviour everywhere, but letting AnyEvent chose is generally better.
294		462
295	=cut	463	=cut
296		464
297	package AnyEvent;	465	package AnyEvent;
298		466
299	no warnings;	467	no warnings;
300	use strict;	468	use strict;
301		469
302	use Carp;	470	use Carp;
303		471
304	our $VERSION = '3.0';	472	our $VERSION = '3.3';
305	our $MODEL;	473	our $MODEL;
306		474
307	our $AUTOLOAD;	475	our $AUTOLOAD;
308	our @ISA;	476	our @ISA;
309		477
…		…
311		479
312	our @REGISTRY;	480	our @REGISTRY;
313		481
314	my @models = (	482	my @models = (
315	[Coro::EV:: => AnyEvent::Impl::CoroEV::],	483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
		484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
316	[EV:: => AnyEvent::Impl::EV::],	485	[EV:: => AnyEvent::Impl::EV::],
317	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
318	[Event:: => AnyEvent::Impl::Event::],	486	[Event:: => AnyEvent::Impl::Event::],
319	[Glib:: => AnyEvent::Impl::Glib::],	487	[Glib:: => AnyEvent::Impl::Glib::],
320	[Tk:: => AnyEvent::Impl::Tk::],	488	[Tk:: => AnyEvent::Impl::Tk::],
		489	[Wx:: => AnyEvent::Impl::POE::],
		490	[Prima:: => AnyEvent::Impl::POE::],
321	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		492	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
322	);	496	);
323		497
324	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
325		499
326	sub detect() {	500	sub detect() {
327	unless ($MODEL) {	501	unless ($MODEL) {
328	no strict 'refs';	502	no strict 'refs';
329		503
		504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		505	my $model = "AnyEvent::Impl::$1";
		506	if (eval "require $model") {
		507	$MODEL = $model;
		508	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		509	} else {
		510	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		511	}
		512	}
		513
330	# check for already loaded models	514	# check for already loaded models
		515	unless ($MODEL) {
331	for (@REGISTRY, @models) {	516	for (@REGISTRY, @models) {
332	my ($package, $model) = @$_;	517	my ($package, $model) = @$_;
333	if (${"$package\::VERSION"} > 0) {	518	if (${"$package\::VERSION"} > 0) {
334	if (eval "require $model") {	519	if (eval "require $model") {
335	$MODEL = $model;	520	$MODEL = $model;
336	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	521	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
337	last;	522	last;
		523	}
338	}	524	}
339	}	525	}
340	}
341		526
342	unless ($MODEL) {	527	unless ($MODEL) {
343	# try to load a model	528	# try to load a model
344		529
345	for (@REGISTRY, @models) {	530	for (@REGISTRY, @models) {
346	my ($package, $model) = @$_;	531	my ($package, $model) = @$_;
347	if (eval "require $package"	532	if (eval "require $package"
348	and ${"$package\::VERSION"} > 0	533	and ${"$package\::VERSION"} > 0
349	and eval "require $model") {	534	and eval "require $model") {
350	$MODEL = $model;	535	$MODEL = $model;
351	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	536	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
352	last;	537	last;
		538	}
353	}	539	}
		540
		541	$MODEL
		542	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) or Glib.";
354	}	543	}
355
356	$MODEL
357	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.";
358	}	544	}
359		545
360	unshift @ISA, $MODEL;	546	unshift @ISA, $MODEL;
361	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
362	}	548	}
…		…
473	undef $CHLD_W unless keys %PID_CB;	659	undef $CHLD_W unless keys %PID_CB;
474	}	660	}
475		661
476	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
477		663
		664	This is an advanced topic that you do not normally need to use AnyEvent in
		665	a module. This section is only of use to event loop authors who want to
		666	provide AnyEvent compatibility.
		667
478	If you need to support another event library which isn't directly	668	If you need to support another event library which isn't directly
479	supported by AnyEvent, you can supply your own interface to it by	669	supported by AnyEvent, you can supply your own interface to it by
480	pushing, before the first watcher gets created, the package name of	670	pushing, before the first watcher gets created, the package name of
481	the event module and the package name of the interface to use onto	671	the event module and the package name of the interface to use onto
482	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	672	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
483	AnyEvent.	673	AnyEvent, so it is reasonably cheap.
484		674
485	Example:	675	Example:
486		676
487	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	677	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
488		678
489	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	679	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
490	package/class when it finds the C<urxvt> package/module is loaded. When	680	package/class when it finds the C<urxvt> package/module is already loaded.
		681
491	AnyEvent is loaded and asked to find a suitable event model, it will	682	When AnyEvent is loaded and asked to find a suitable event model, it
492	first check for the presence of urxvt.	683	will first check for the presence of urxvt by trying to C<use> the
		684	C<urxvt::anyevent> module.
493		685
494	The class should provide implementations for all watcher types (see	686	The class should provide implementations for all watcher types. See
495	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	687	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
496	(Source code) and so on for actual examples, use C<perldoc -m	688	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
497	AnyEvent::Impl::Glib> to see the sources).	689	see the sources.
498		690
		691	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		692	provide suitable (hopefully) replacements.
		693
499	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	694	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
500	uses the above line as-is. An interface isn't included in AnyEvent	695	terminal emulator uses the above line as-is. An interface isn't included
501	because it doesn't make sense outside the embedded interpreter inside	696	in AnyEvent because it doesn't make sense outside the embedded interpreter
502	I<rxvt-unicode>, and it is updated and maintained as part of the	697	inside I<rxvt-unicode>, and it is updated and maintained as part of the
503	I<rxvt-unicode> distribution.	698	I<rxvt-unicode> distribution.
504		699
505	I<rxvt-unicode> also cheats a bit by not providing blocking access to	700	I<rxvt-unicode> also cheats a bit by not providing blocking access to
506	condition variables: code blocking while waiting for a condition will	701	condition variables: code blocking while waiting for a condition will
507	C<die>. This still works with most modules/usages, and blocking calls must	702	C<die>. This still works with most modules/usages, and blocking calls must
508	not be in an interactive application, so it makes sense.	703	not be done in an interactive application, so it makes sense.
509		704
510	=head1 ENVIRONMENT VARIABLES	705	=head1 ENVIRONMENT VARIABLES
511		706
512	The following environment variables are used by this module:	707	The following environment variables are used by this module:
513		708
514	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event	709	=over 4
515	model gets used.
516		710
		711	=item C<PERL_ANYEVENT_VERBOSE>
		712
		713	By default, AnyEvent will be completely silent except in fatal
		714	conditions. You can set this environment variable to make AnyEvent more
		715	talkative.
		716
		717	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		718	conditions, such as not being able to load the event model specified by
		719	C<PERL_ANYEVENT_MODEL>.
		720
		721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		722	model it chooses.
		723
		724	=item C<PERL_ANYEVENT_MODEL>
		725
		726	This can be used to specify the event model to be used by AnyEvent, before
		727	autodetection and -probing kicks in. It must be a string consisting
		728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		729	and the resulting module name is loaded and if the load was successful,
		730	used as event model. If it fails to load AnyEvent will proceed with
		731	autodetection and -probing.
		732
		733	This functionality might change in future versions.
		734
		735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		736	could start your program like this:
		737
		738	PERL_ANYEVENT_MODEL=Perl perl ...
		739
		740	=back
		741
517	=head1 EXAMPLE	742	=head1 EXAMPLE PROGRAM
518		743
519	The following program uses an io watcher to read data from stdin, a timer	744	The following program uses an I/O watcher to read data from STDIN, a timer
520	to display a message once per second, and a condvar to exit the program	745	to display a message once per second, and a condition variable to quit the
521	when the user enters quit:	746	program when the user enters quit:
522		747
523	use AnyEvent;	748	use AnyEvent;
524		749
525	my $cv = AnyEvent->condvar;	750	my $cv = AnyEvent->condvar;
526		751
527	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	752	my $io_watcher = AnyEvent->io (
		753	fh => \*STDIN,
		754	poll => 'r',
		755	cb => sub {
528	warn "io event <$_[0]>\n"; # will always output <r>	756	warn "io event <$_[0]>\n"; # will always output <r>
529	chomp (my $input = <STDIN>); # read a line	757	chomp (my $input = <STDIN>); # read a line
530	warn "read: $input\n"; # output what has been read	758	warn "read: $input\n"; # output what has been read
531	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		760	},
532	});	761	);
533		762
534	my $time_watcher; # can only be used once	763	my $time_watcher; # can only be used once
535		764
536	sub new_timer {	765	sub new_timer {
537	$timer = AnyEvent->timer (after => 1, cb => sub {	766	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
619	$txn->{finished}->wait;	848	$txn->{finished}->wait;
620	return $txn->{result};	849	return $txn->{result};
621		850
622	The actual code goes further and collects all errors (C<die>s, exceptions)	851	The actual code goes further and collects all errors (C<die>s, exceptions)
623	that occured during request processing. The C<result> method detects	852	that occured during request processing. The C<result> method detects
624	wether an exception as thrown (it is stored inside the $txn object)	853	whether an exception as thrown (it is stored inside the $txn object)
625	and just throws the exception, which means connection errors and other	854	and just throws the exception, which means connection errors and other
626	problems get reported tot he code that tries to use the result, not in a	855	problems get reported tot he code that tries to use the result, not in a
627	random callback.	856	random callback.
628		857
629	All of this enables the following usage styles:	858	All of this enables the following usage styles:
630		859
631	1. Blocking:	860	1. Blocking:
632		861
633	my $data = $fcp->client_get ($url);	862	my $data = $fcp->client_get ($url);
634		863
635	2. Blocking, but parallelizing:	864	2. Blocking, but running in parallel:
636		865
637	my @datas = map $_->result,	866	my @datas = map $_->result,
638	map $fcp->txn_client_get ($_),	867	map $fcp->txn_client_get ($_),
639	@urls;	868	@urls;
640		869
641	Both blocking examples work without the module user having to know	870	Both blocking examples work without the module user having to know
642	anything about events.	871	anything about events.
643		872
644	3a. Event-based in a main program, using any support Event module:	873	3a. Event-based in a main program, using any supported event module:
645		874
646	use Event;	875	use EV;
647		876
648	$fcp->txn_client_get ($url)->cb (sub {	877	$fcp->txn_client_get ($url)->cb (sub {
649	my $txn = shift;	878	my $txn = shift;
650	my $data = $txn->result;	879	my $data = $txn->result;
651	...	880	...
652	});	881	});
653		882
654	Event::loop;	883	EV::loop;
655		884
656	3b. The module user could use AnyEvent, too:	885	3b. The module user could use AnyEvent, too:
657		886
658	use AnyEvent;	887	use AnyEvent;
659		888
…		…
664	$quit->broadcast;	893	$quit->broadcast;
665	});	894	});
666		895
667	$quit->wait;	896	$quit->wait;
668		897
		898
		899	=head1 BENCHMARKS
		900
		901	To give you an idea of the performance and overheads that AnyEvent adds
		902	over the event loops themselves and to give you an impression of the speed
		903	of various event loops I prepared some benchmarks.
		904
		905	=head2 BENCHMARKING ANYEVENT OVERHEAD
		906
		907	Here is a benchmark of various supported event models used natively and
		908	through anyevent. The benchmark creates a lot of timers (with a zero
		909	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		910	which it is), lets them fire exactly once and destroys them again.
		911
		912	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		913	distribution.
		914
		915	=head3 Explanation of the columns
		916
		917	I<watcher> is the number of event watchers created/destroyed. Since
		918	different event models feature vastly different performances, each event
		919	loop was given a number of watchers so that overall runtime is acceptable
		920	and similar between tested event loop (and keep them from crashing): Glib
		921	would probably take thousands of years if asked to process the same number
		922	of watchers as EV in this benchmark.
		923
		924	I<bytes> is the number of bytes (as measured by the resident set size,
		925	RSS) consumed by each watcher. This method of measuring captures both C
		926	and Perl-based overheads.
		927
		928	I<create> is the time, in microseconds (millionths of seconds), that it
		929	takes to create a single watcher. The callback is a closure shared between
		930	all watchers, to avoid adding memory overhead. That means closure creation
		931	and memory usage is not included in the figures.
		932
		933	I<invoke> is the time, in microseconds, used to invoke a simple
		934	callback. The callback simply counts down a Perl variable and after it was
		935	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		936	signal the end of this phase.
		937
		938	I<destroy> is the time, in microseconds, that it takes to destroy a single
		939	watcher.
		940
		941	=head3 Results
		942
		943	name watchers bytes create invoke destroy comment
		944	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		945	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		946	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		947	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		948	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		949	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers
		950	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		951	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		952	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		953	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		954
		955	=head3 Discussion
		956
		957	The benchmark does I<not> measure scalability of the event loop very
		958	well. For example, a select-based event loop (such as the pure perl one)
		959	can never compete with an event loop that uses epoll when the number of
		960	file descriptors grows high. In this benchmark, all events become ready at
		961	the same time, so select/poll-based implementations get an unnatural speed
		962	boost.
		963
		964	Also, note that the number of watchers usually has a nonlinear effect on
		965	overall speed, that is, creating twice as many watchers doesn't take twice
		966	the time - usually it takes longer. This puts event loops tested with a
		967	higher number of watchers at a disadvantage.
		968
		969	C<EV> is the sole leader regarding speed and memory use, which are both
		970	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		971	far less memory than any other event loop and is still faster than Event
		972	natively.
		973
		974	The pure perl implementation is hit in a few sweet spots (both the
		975	constant timeout and the use of a single fd hit optimisations in the perl
		976	interpreter and the backend itself). Nevertheless this shows that it
		977	adds very little overhead in itself. Like any select-based backend its
		978	performance becomes really bad with lots of file descriptors (and few of
		979	them active), of course, but this was not subject of this benchmark.
		980
		981	The C<Event> module has a relatively high setup and callback invocation
		982	cost, but overall scores in on the third place.
		983
		984	C<Glib>'s memory usage is quite a bit higher, but it features a
		985	faster callback invocation and overall ends up in the same class as
		986	C<Event>. However, Glib scales extremely badly, doubling the number of
		987	watchers increases the processing time by more than a factor of four,
		988	making it completely unusable when using larger numbers of watchers
		989	(note that only a single file descriptor was used in the benchmark, so
		990	inefficiencies of C<poll> do not account for this).
		991
		992	The C<Tk> adaptor works relatively well. The fact that it crashes with
		993	more than 2000 watchers is a big setback, however, as correctness takes
		994	precedence over speed. Nevertheless, its performance is surprising, as the
		995	file descriptor is dup()ed for each watcher. This shows that the dup()
		996	employed by some adaptors is not a big performance issue (it does incur a
		997	hidden memory cost inside the kernel which is not reflected in the figures
		998	above).
		999
		1000	C<POE>, regardless of underlying event loop (whether using its pure
		1001	perl select-based backend or the Event module, the POE-EV backend
		1002	couldn't be tested because it wasn't working) shows abysmal performance
		1003	and memory usage: Watchers use almost 30 times as much memory as
		1004	EV watchers, and 10 times as much memory as Event (the high memory
		1005	requirements are caused by requiring a session for each watcher). Watcher
		1006	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1007	implementation. The design of the POE adaptor class in AnyEvent can not
		1008	really account for this, as session creation overhead is small compared
		1009	to execution of the state machine, which is coded pretty optimally within
		1010	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		1011
		1012	=head3 Summary
		1013
		1014	=over 4
		1015
		1016	=item * Using EV through AnyEvent is faster than any other event loop
		1017	(even when used without AnyEvent), but most event loops have acceptable
		1018	performance with or without AnyEvent.
		1019
		1020	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1021	the actual event loop, only with extremely fast event loops such as EV
		1022	adds AnyEvent significant overhead.
		1023
		1024	=item * You should avoid POE like the plague if you want performance or
		1025	reasonable memory usage.
		1026
		1027	=back
		1028
		1029	=head2 BENCHMARKING THE LARGE SERVER CASE
		1030
		1031	This benchmark atcually benchmarks the event loop itself. It works by
		1032	creating a number of "servers": each server consists of a socketpair, a
		1033	timeout watcher that gets reset on activity (but never fires), and an I/O
		1034	watcher waiting for input on one side of the socket. Each time the socket
		1035	watcher reads a byte it will write that byte to a random other "server".
		1036
		1037	The effect is that there will be a lot of I/O watchers, only part of which
		1038	are active at any one point (so there is a constant number of active
		1039	fds for each loop iterstaion, but which fds these are is random). The
		1040	timeout is reset each time something is read because that reflects how
		1041	most timeouts work (and puts extra pressure on the event loops).
		1042
		1043	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1044	(1%) are active. This mirrors the activity of large servers with many
		1045	connections, most of which are idle at any one point in time.
		1046
		1047	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1048	distribution.
		1049
		1050	=head3 Explanation of the columns
		1051
		1052	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1053	each server has a read and write socket end).
		1054
		1055	I<create> is the time it takes to create a socketpair (which is
		1056	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1057
		1058	I<request>, the most important value, is the time it takes to handle a
		1059	single "request", that is, reading the token from the pipe and forwarding
		1060	it to another server. This includes deleting the old timeout and creating
		1061	a new one that moves the timeout into the future.
		1062
		1063	=head3 Results
		1064
		1065	name sockets create request
		1066	EV 20000 69.01 11.16
		1067	Perl 20000 75.28 112.76
		1068	Event 20000 212.62 257.32
		1069	Glib 20000 651.16 1896.30
		1070	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1071
		1072	=head3 Discussion
		1073
		1074	This benchmark I<does> measure scalability and overall performance of the
		1075	particular event loop.
		1076
		1077	EV is again fastest. Since it is using epoll on my system, the setup time
		1078	is relatively high, though.
		1079
		1080	Perl surprisingly comes second. It is much faster than the C-based event
		1081	loops Event and Glib.
		1082
		1083	Event suffers from high setup time as well (look at its code and you will
		1084	understand why). Callback invocation also has a high overhead compared to
		1085	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1086	uses select or poll in basically all documented configurations.
		1087
		1088	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1089	clearly fails to perform with many filehandles or in busy servers.
		1090
		1091	POE is still completely out of the picture, taking over 1000 times as long
		1092	as EV, and over 100 times as long as the Perl implementation, even though
		1093	it uses a C-based event loop in this case.
		1094
		1095	=head3 Summary
		1096
		1097	=over 4
		1098
		1099	=item * The pure perl implementation performs extremely well, considering
		1100	that it uses select.
		1101
		1102	=item * Avoid Glib or POE in large projects where performance matters.
		1103
		1104	=back
		1105
		1106	=head2 BENCHMARKING SMALL SERVERS
		1107
		1108	While event loops should scale (and select-based ones do not...) even to
		1109	large servers, most programs we (or I :) actually write have only a few
		1110	I/O watchers.
		1111
		1112	In this benchmark, I use the same benchmark program as in the large server
		1113	case, but it uses only eight "servers", of which three are active at any
		1114	one time. This should reflect performance for a small server relatively
		1115	well.
		1116
		1117	The columns are identical to the previous table.
		1118
		1119	=head3 Results
		1120
		1121	name sockets create request
		1122	EV 16 20.00 6.54
		1123	Event 16 81.27 35.86
		1124	Glib 16 32.63 15.48
		1125	Perl 16 24.62 162.37
		1126	POE 16 261.87 276.28 uses POE::Loop::Event
		1127
		1128	=head3 Discussion
		1129
		1130	The benchmark tries to test the performance of a typical small
		1131	server. While knowing how various event loops perform is interesting, keep
		1132	in mind that their overhead in this case is usually not as important, due
		1133	to the small absolute number of watchers.
		1134
		1135	EV is again fastest.
		1136
		1137	The C-based event loops Event and Glib come in second this time, as the
		1138	overhead of running an iteration is much smaller in C than in Perl (little
		1139	code to execute in the inner loop, and perl's function calling overhead is
		1140	high, and updating all the data structures is costly).
		1141
		1142	The pure perl event loop is much slower, but still competitive.
		1143
		1144	POE also performs much better in this case, but is is stillf ar behind the
		1145	others.
		1146
		1147	=head3 Summary
		1148
		1149	=over 4
		1150
		1151	=item * C-based event loops perform very well with small number of
		1152	watchers, as the management overhead dominates.
		1153
		1154	=back
		1155
		1156
		1157	=head1 FORK
		1158
		1159	Most event libraries are not fork-safe. The ones who are usually are
		1160	because they are so inefficient. Only L<EV> is fully fork-aware.
		1161
		1162	If you have to fork, you must either do so I<before> creating your first
		1163	watcher OR you must not use AnyEvent at all in the child.
		1164
		1165
		1166	=head1 SECURITY CONSIDERATIONS
		1167
		1168	AnyEvent can be forced to load any event model via
		1169	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1170	execute arbitrary code or directly gain access, it can easily be used to
		1171	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1172	will not be active when the program uses a different event model than
		1173	specified in the variable.
		1174
		1175	You can make AnyEvent completely ignore this variable by deleting it
		1176	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1177
		1178	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1179
		1180	use AnyEvent;
		1181
		1182
669	=head1 SEE ALSO	1183	=head1 SEE ALSO
670		1184
671	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	1185	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		1186	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1187	L<Event::Lib>, L<Qt>, L<POE>.
672		1188
		1189	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
673	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	1190	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1191	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1192	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
674		1193
675	Nontrivial usage example: L<Net::FCP>.	1194	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
676		1195
677	=head1	1196
		1197	=head1 AUTHOR
		1198
		1199	Marc Lehmann <schmorp@schmorp.de>
		1200	http://home.schmorp.de/
678		1201
679	=cut	1202	=cut
680		1203
681	1	1204	1
682		1205

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.42 by root, Mon Apr 7 19:40:12 2008 UTC vs.
Revision 1.95 by root, Sat Apr 26 11:06:45 2008 UTC