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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.24 by root, Sun Mar 25 00:14:32 2007 UTC vs.
Revision 1.102 by root, Sun Apr 27 21:16:26 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
		23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		24
		25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		26	nowadays. So what is different about AnyEvent?
		27
		28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		29	policy> and AnyEvent is I<small and efficient>.
		30
		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
		33	pragmatic way. For event models and certain classes of immortals alike,
		34	the statement "there can only be one" is a bitter reality: In general,
		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.
		37
		38	The goal of AnyEvent is to offer module authors the ability to do event
		39	programming (waiting for I/O or timer events) without subscribing to a
		40	religion, a way of living, and most importantly: without forcing your
		41	module users into the same thing by forcing them to use the same event
		42	model you use.
		43
		44	For modules like POE or IO::Async (which is a total misnomer as it is
		45	actually doing all I/O I<synchronously>...), using them in your module is
		46	like joining a cult: After you joined, you are dependent on them and you
		47	cannot use anything else, as it is simply incompatible to everything that
		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.
		50
		51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if
		54	your module uses one of those, every user of your module has to use it,
		55	too. But if your module uses AnyEvent, it works transparently with all
		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).
		59
		60	In addition to being free of having to use I<the one and only true event
		61	model>, AnyEvent also is free of bloat and policy: with POE or similar
		62	modules, you get an enourmous amount of code and strict rules you have to
		63	follow. AnyEvent, on the other hand, is lean and up to the point, by only
		64	offering the functionality that is necessary, in as thin as a wrapper as
		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.
22		70
23	=head1 DESCRIPTION	71	=head1 DESCRIPTION
24		72
25	L<AnyEvent> provides an identical interface to multiple event loops. This	73	L<AnyEvent> provides an identical interface to multiple event loops. This
26	allows module authors to utilise an event loop without forcing module	74	allows module authors to utilise an event loop without forcing module
27	users to use the same event loop (as only a single event loop can coexist	75	users to use the same event loop (as only a single event loop can coexist
28	peacefully at any one time).	76	peacefully at any one time).
29		77
30	The interface itself is vaguely similar but not identical to the Event	78	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	79	module.
32		80
33	On the first call of any method, the module tries to detect the currently	81	During the first call of any watcher-creation method, the module tries
34	loaded event loop by probing wether any of the following modules is	82	to detect the currently loaded event loop by probing whether one of the
35	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	83	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
36	used. If none is found, the module tries to load these modules in the	84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
37	order given. The first one that could be successfully loaded will be	85	L<POE>. The first one found is used. If none are found, the module tries
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
39	event loop, which is also not very efficient.	87	adaptor should always succeed) in the order given. The first one that can
		88	be successfully loaded will be used. If, after this, still none could be
		89	found, AnyEvent will fall back to a pure-perl event loop, which is not
		90	very efficient, but should work everywhere.
40		91
41	Because AnyEvent first checks for modules that are already loaded, loading	92	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	93	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	94	that model the default. For example:
44		95
45	use Tk;	96	use Tk;
46	use AnyEvent;	97	use AnyEvent;
47		98
48	# .. AnyEvent will likely default to Tk	99	# .. AnyEvent will likely default to Tk
		100
		101	The I<likely> means that, if any module loads another event model and
		102	starts using it, all bets are off. Maybe you should tell their authors to
		103	use AnyEvent so their modules work together with others seamlessly...
49		104
50	The pure-perl implementation of AnyEvent is called	105	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	107	explicitly.
53		108
…		…
56	AnyEvent has the central concept of a I<watcher>, which is an object that	111	AnyEvent has the central concept of a I<watcher>, which is an object that
57	stores relevant data for each kind of event you are waiting for, such as	112	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	113	the callback to call, the filehandle to watch, etc.
59		114
60	These watchers are normal Perl objects with normal Perl lifetime. After	115	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	116	creating a watcher it will immediately "watch" for events and invoke the
		117	callback when the event occurs (of course, only when the event model
		118	is in control).
		119
62	the callback. To disable the watcher you have to destroy it (e.g. by	120	To disable the watcher you have to destroy it (e.g. by setting the
63	setting the variable that stores it to C<undef> or otherwise deleting all	121	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	122	to it).
65		123
66	All watchers are created by calling a method on the C<AnyEvent> class.	124	All watchers are created by calling a method on the C<AnyEvent> class.
67		125
		126	Many watchers either are used with "recursion" (repeating timers for
		127	example), or need to refer to their watcher object in other ways.
		128
		129	An any way to achieve that is this pattern:
		130
		131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		132	# you can use $w here, for example to undef it
		133	undef $w;
		134	});
		135
		136	Note that C<my $w; $w => combination. This is necessary because in Perl,
		137	my variables are only visible after the statement in which they are
		138	declared.
		139
68	=head2 IO WATCHERS	140	=head2 I/O WATCHERS
69		141
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	143	with the following mandatory key-value pairs as arguments:
72		144
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	146	for events. C<poll> must be a string that is either C<r> or C<w>,
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback	147	which creates a watcher waiting for "r"eadable or "w"ritable events,
76	to invoke everytime the filehandle becomes ready.	148	respectively. C<cb> is the callback to invoke each time the file handle
		149	becomes ready.
77		150
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	151	Although the callback might get passed parameters, their value and
79	a socket you can have one r + one w, not any more (limitation comes from	152	presence is undefined and you cannot rely on them. Portable AnyEvent
80	Tk - if you are sure you are not using Tk this limitation is gone).	153	callbacks cannot use arguments passed to I/O watcher callbacks.
81		154
82	Filehandles will be kept alive, so as long as the watcher exists, the	155	The I/O watcher might use the underlying file descriptor or a copy of it.
83	filehandle exists, too.	156	You must not close a file handle as long as any watcher is active on the
		157	underlying file descriptor.
		158
		159	Some event loops issue spurious readyness notifications, so you should
		160	always use non-blocking calls when reading/writing from/to your file
		161	handles.
84		162
85	Example:	163	Example:
86		164
87	# wait for readability of STDIN, then read a line and disable the watcher	165	# wait for readability of STDIN, then read a line and disable the watcher
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
…		…
94	=head2 TIME WATCHERS	172	=head2 TIME WATCHERS
95		173
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	174	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	175	method with the following mandatory arguments:
98		176
99	C<after> after how many seconds (fractions are supported) should the timer	177	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	178	supported) the callback should be invoked. C<cb> is the callback to invoke
		179	in that case.
		180
		181	Although the callback might get passed parameters, their value and
		182	presence is undefined and you cannot rely on them. Portable AnyEvent
		183	callbacks cannot use arguments passed to time watcher callbacks.
101		184
102	The timer callback will be invoked at most once: if you want a repeating	185	The timer callback will be invoked at most once: if you want a repeating
103	timer you have to create a new watcher (this is a limitation by both Tk	186	timer you have to create a new watcher (this is a limitation by both Tk
104	and Glib).	187	and Glib).
105		188
…		…
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	192	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	193	warn "timeout\n";
111	});	194	});
112		195
113	# to cancel the timer:	196	# to cancel the timer:
114	undef $w	197	undef $w;
115		198
		199	Example 2:
		200
		201	# fire an event after 0.5 seconds, then roughly every second
		202	my $w;
		203
		204	my $cb = sub {
		205	# cancel the old timer while creating a new one
		206	$w = AnyEvent->timer (after => 1, cb => $cb);
		207	};
		208
		209	# start the "loop" by creating the first watcher
		210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		211
		212	=head3 TIMING ISSUES
		213
		214	There are two ways to handle timers: based on real time (relative, "fire
		215	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		216	o'clock").
		217
		218	While most event loops expect timers to specified in a relative way, they
		219	use absolute time internally. This makes a difference when your clock
		220	"jumps", for example, when ntp decides to set your clock backwards from
		221	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		222	fire "after" a second might actually take six years to finally fire.
		223
		224	AnyEvent cannot compensate for this. The only event loop that is conscious
		225	about these issues is L<EV>, which offers both relative (ev_timer, based
		226	on true relative time) and absolute (ev_periodic, based on wallclock time)
		227	timers.
		228
		229	AnyEvent always prefers relative timers, if available, matching the
		230	AnyEvent API.
		231
		232	=head2 SIGNAL WATCHERS
		233
		234	You can watch for signals using a signal watcher, C<signal> is the signal
		235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		236	be invoked whenever a signal occurs.
		237
		238	Although the callback might get passed parameters, their value and
		239	presence is undefined and you cannot rely on them. Portable AnyEvent
		240	callbacks cannot use arguments passed to signal watcher callbacks.
		241
		242	Multiple signal occurances can be clumped together into one callback
		243	invocation, and callback invocation will be synchronous. synchronous means
		244	that it might take a while until the signal gets handled by the process,
		245	but it is guarenteed not to interrupt any other callbacks.
		246
		247	The main advantage of using these watchers is that you can share a signal
		248	between multiple watchers.
		249
		250	This watcher might use C<%SIG>, so programs overwriting those signals
		251	directly will likely not work correctly.
		252
		253	Example: exit on SIGINT
		254
		255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		256
		257	=head2 CHILD PROCESS WATCHERS
		258
		259	You can also watch on a child process exit and catch its exit status.
		260
		261	The child process is specified by the C<pid> argument (if set to C<0>, it
		262	watches for any child process exit). The watcher will trigger as often
		263	as status change for the child are received. This works by installing a
		264	signal handler for C<SIGCHLD>. The callback will be called with the pid
		265	and exit status (as returned by waitpid), so unlike other watcher types,
		266	you I<can> rely on child watcher callback arguments.
		267
		268	There is a slight catch to child watchers, however: you usually start them
		269	I<after> the child process was created, and this means the process could
		270	have exited already (and no SIGCHLD will be sent anymore).
		271
		272	Not all event models handle this correctly (POE doesn't), but even for
		273	event models that I<do> handle this correctly, they usually need to be
		274	loaded before the process exits (i.e. before you fork in the first place).
		275
		276	This means you cannot create a child watcher as the very first thing in an
		277	AnyEvent program, you I<have> to create at least one watcher before you
		278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		279
		280	Example: fork a process and wait for it
		281
		282	my $done = AnyEvent->condvar;
		283
		284	AnyEvent::detect; # force event module to be initialised
		285
		286	my $pid = fork or exit 5;
		287
		288	my $w = AnyEvent->child (
		289	pid => $pid,
		290	cb => sub {
		291	my ($pid, $status) = @_;
		292	warn "pid $pid exited with status $status";
		293	$done->broadcast;
		294	},
		295	);
		296
		297	# do something else, then wait for process exit
		298	$done->wait;
		299
116	=head2 CONDITION WATCHERS	300	=head2 CONDITION VARIABLES
117		301
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	302	Condition variables can be created by calling the C<< AnyEvent->condvar >>
119	method without any arguments.	303	method without any arguments.
120		304
121	A condition watcher watches for a condition - precisely that the C<<	305	A condition variable waits for a condition - precisely that the C<<
122	->broadcast >> method has been called.	306	->broadcast >> method has been called.
123		307
124	The watcher has only two methods:	308	They are very useful to signal that a condition has been fulfilled, for
		309	example, if you write a module that does asynchronous http requests,
		310	then a condition variable would be the ideal candidate to signal the
		311	availability of results.
		312
		313	You can also use condition variables to block your main program until
		314	an event occurs - for example, you could C<< ->wait >> in your main
		315	program until the user clicks the Quit button in your app, which would C<<
		316	->broadcast >> the "quit" event.
		317
		318	Note that condition variables recurse into the event loop - if you have
		319	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		320	lose. Therefore, condition variables are good to export to your caller, but
		321	you should avoid making a blocking wait yourself, at least in callbacks,
		322	as this asks for trouble.
		323
		324	This object has two methods:
125		325
126	=over 4	326	=over 4
127		327
128	=item $cv->wait	328	=item $cv->wait
129		329
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	330	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
131	called on c<$cv>, while servicing other watchers normally.	331	called on c<$cv>, while servicing other watchers normally.
132		332
133	Not all event models support a blocking wait - some die in that case, so
134	if you are using this from a module, never require a blocking wait, but
135	let the caller decide wether the call will block or not (for example,
136	by coupling condition variables with some kind of request results and
137	supporting callbacks so the caller knows that getting the result will not
138	block, while still suppporting blockign waits if the caller so desires).
139
140	You can only wait once on a condition - additional calls will return	333	You can only wait once on a condition - additional calls will return
141	immediately.	334	immediately.
142		335
		336	Not all event models support a blocking wait - some die in that case
		337	(programs might want to do that to stay interactive), so I<if you are
		338	using this from a module, never require a blocking wait>, but let the
		339	caller decide whether the call will block or not (for example, by coupling
		340	condition variables with some kind of request results and supporting
		341	callbacks so the caller knows that getting the result will not block,
		342	while still suppporting blocking waits if the caller so desires).
		343
		344	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		345	sensibly have two C<< ->wait >>'s in parallel, as that would require
		346	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		347	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		348	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		349	from different coroutines, however).
		350
143	=item $cv->broadcast	351	=item $cv->broadcast
144		352
145	Flag the condition as ready - a running C<< ->wait >> and all further	353	Flag the condition as ready - a running C<< ->wait >> and all further
146	calls to C<wait> will return after this method has been called. If nobody	354	calls to C<wait> will (eventually) return after this method has been
147	is waiting the broadcast will be remembered..	355	called. If nobody is waiting the broadcast will be remembered..
		356
		357	=back
148		358
149	Example:	359	Example:
150		360
151	# wait till the result is ready	361	# wait till the result is ready
152	my $result_ready = AnyEvent->condvar;	362	my $result_ready = AnyEvent->condvar;
153		363
154	# do something such as adding a timer	364	# do something such as adding a timer
155	# or socket watcher the calls $result_ready->broadcast	365	# or socket watcher the calls $result_ready->broadcast
156	# when the "result" is ready.	366	# when the "result" is ready.
		367	# in this case, we simply use a timer:
		368	my $w = AnyEvent->timer (
		369	after => 1,
		370	cb => sub { $result_ready->broadcast },
		371	);
157		372
		373	# this "blocks" (while handling events) till the watcher
		374	# calls broadcast
158	$result_ready->wait;	375	$result_ready->wait;
159		376
160	=back	377	=head1 GLOBAL VARIABLES AND FUNCTIONS
161
162	=head2 SIGNAL WATCHERS
163
164	You can listen for signals using a signal watcher, C<signal> is the signal
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped
166	together into one callback invocation, and callback invocation might or
167	might not be asynchronous.
168
169	These watchers might use C<%SIG>, so programs overwriting those signals
170	directly will likely not work correctly.
171
172	Example: exit on SIGINT
173
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175
176	=head2 CHILD PROCESS WATCHERS
177
178	You can also listen for the status of a child process specified by the
179	C<pid> argument. The watcher will only trigger once. This works by
180	installing a signal handler for C<SIGCHLD>.
181
182	Example: wait for pid 1333
183
184	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
185
186	=head1 GLOBALS
187		378
188	=over 4	379	=over 4
189		380
190	=item $AnyEvent::MODEL	381	=item $AnyEvent::MODEL
191		382
…		…
195	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	386	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
196	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	387	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
197		388
198	The known classes so far are:	389	The known classes so far are:
199		390
200	AnyEvent::Impl::Coro based on Coro::Event, best choise.	391	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		392	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		393	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
201	AnyEvent::Impl::Event based on Event, also best choice :)	394	AnyEvent::Impl::Event based on Event, second best choice.
202	AnyEvent::Impl::Glib based on Glib, second-best choice.	395	AnyEvent::Impl::Glib based on Glib, third-best choice.
		396	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
203	AnyEvent::Impl::Tk based on Tk, very bad choice.	397	AnyEvent::Impl::Tk based on Tk, very bad choice.
204	AnyEvent::Impl::Perl pure-perl implementation, inefficient.	398	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		399	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		400	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		401
		402	There is no support for WxWidgets, as WxWidgets has no support for
		403	watching file handles. However, you can use WxWidgets through the
		404	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		405	second, which was considered to be too horrible to even consider for
		406	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		407	it's adaptor.
		408
		409	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		410	autodetecting them.
205		411
206	=item AnyEvent::detect	412	=item AnyEvent::detect
207		413
208	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	414	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
209	necessary. You should only call this function right before you would have	415	if necessary. You should only call this function right before you would
210	created an AnyEvent watcher anyway, that is, very late at runtime.	416	have created an AnyEvent watcher anyway, that is, as late as possible at
		417	runtime.
211		418
212	=back	419	=back
213		420
214	=head1 WHAT TO DO IN A MODULE	421	=head1 WHAT TO DO IN A MODULE
215		422
216	As a module author, you should "use AnyEvent" and call AnyEvent methods	423	As a module author, you should C<use AnyEvent> and call AnyEvent methods
217	freely, but you should not load a specific event module or rely on it.	424	freely, but you should not load a specific event module or rely on it.
218		425
219	Be careful when you create watchers in the module body - Anyevent will	426	Be careful when you create watchers in the module body - AnyEvent will
220	decide which event module to use as soon as the first method is called, so	427	decide which event module to use as soon as the first method is called, so
221	by calling AnyEvent in your module body you force the user of your module	428	by calling AnyEvent in your module body you force the user of your module
222	to load the event module first.	429	to load the event module first.
223		430
		431	Never call C<< ->wait >> on a condition variable unless you I<know> that
		432	the C<< ->broadcast >> method has been called on it already. This is
		433	because it will stall the whole program, and the whole point of using
		434	events is to stay interactive.
		435
		436	It is fine, however, to call C<< ->wait >> when the user of your module
		437	requests it (i.e. if you create a http request object ad have a method
		438	called C<results> that returns the results, it should call C<< ->wait >>
		439	freely, as the user of your module knows what she is doing. always).
		440
224	=head1 WHAT TO DO IN THE MAIN PROGRAM	441	=head1 WHAT TO DO IN THE MAIN PROGRAM
225		442
226	There will always be a single main program - the only place that should	443	There will always be a single main program - the only place that should
227	dictate which event model to use.	444	dictate which event model to use.
228		445
229	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	446	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
230	do anything special and let AnyEvent decide which implementation to chose.	447	do anything special (it does not need to be event-based) and let AnyEvent
		448	decide which implementation to chose if some module relies on it.
231		449
232	If the main program relies on a specific event model (for example, in Gtk2	450	If the main program relies on a specific event model. For example, in
233	programs you have to rely on either Glib or Glib::Event), you should load	451	Gtk2 programs you have to rely on the Glib module. You should load the
234	it before loading AnyEvent or any module that uses it, generally, as early	452	event module before loading AnyEvent or any module that uses it: generally
235	as possible. The reason is that modules might create watchers when they	453	speaking, you should load it as early as possible. The reason is that
236	are loaded, and AnyEvent will decide on the event model to use as soon as	454	modules might create watchers when they are loaded, and AnyEvent will
237	it creates watchers, and it might chose the wrong one unless you load the	455	decide on the event model to use as soon as it creates watchers, and it
238	correct one yourself.	456	might chose the wrong one unless you load the correct one yourself.
239		457
240	You can chose to use a rather inefficient pure-perl implementation by	458	You can chose to use a rather inefficient pure-perl implementation by
241	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	459	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
242	generally better.	460	behaviour everywhere, but letting AnyEvent chose is generally better.
		461
		462	=head1 OTHER MODULES
		463
		464	The following is a non-exhaustive list of additional modules that use
		465	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		466	in the same program. Some of the modules come with AnyEvent, some are
		467	available via CPAN.
		468
		469	=over 4
		470
		471	=item L<AnyEvent::Util>
		472
		473	Contains various utility functions that replace often-used but blocking
		474	functions such as C<inet_aton> by event-/callback-based versions.
		475
		476	=item L<AnyEvent::Handle>
		477
		478	Provide read and write buffers and manages watchers for reads and writes.
		479
		480	=item L<AnyEvent::Socket>
		481
		482	Provides a means to do non-blocking connects, accepts etc.
		483
		484	=item L<AnyEvent::HTTPD>
		485
		486	Provides a simple web application server framework.
		487
		488	=item L<AnyEvent::DNS>
		489
		490	Provides asynchronous DNS resolver capabilities, beyond what
		491	L<AnyEvent::Util> offers.
		492
		493	=item L<AnyEvent::FastPing>
		494
		495	The fastest ping in the west.
		496
		497	=item L<Net::IRC3>
		498
		499	AnyEvent based IRC client module family.
		500
		501	=item L<Net::XMPP2>
		502
		503	AnyEvent based XMPP (Jabber protocol) module family.
		504
		505	=item L<Net::FCP>
		506
		507	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		508	of AnyEvent.
		509
		510	=item L<Event::ExecFlow>
		511
		512	High level API for event-based execution flow control.
		513
		514	=item L<Coro>
		515
		516	Has special support for AnyEvent.
		517
		518	=item L<IO::Lambda>
		519
		520	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		521
		522	=item L<IO::AIO>
		523
		524	Truly asynchronous I/O, should be in the toolbox of every event
		525	programmer. Can be trivially made to use AnyEvent.
		526
		527	=item L<BDB>
		528
		529	Truly asynchronous Berkeley DB access. Can be trivially made to use
		530	AnyEvent.
		531
		532	=back
243		533
244	=cut	534	=cut
245		535
246	package AnyEvent;	536	package AnyEvent;
247		537
248	no warnings;	538	no warnings;
249	use strict;	539	use strict;
250		540
251	use Carp;	541	use Carp;
252		542
253	our $VERSION = '2.52';	543	our $VERSION = '3.3';
254	our $MODEL;	544	our $MODEL;
255		545
256	our $AUTOLOAD;	546	our $AUTOLOAD;
257	our @ISA;	547	our @ISA;
258		548
259	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	549	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
260		550
261	our @REGISTRY;	551	our @REGISTRY;
262		552
263	my @models = (	553	my @models = (
		554	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
264	[Coro::Event:: => AnyEvent::Impl::Coro::],	555	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
		556	[EV:: => AnyEvent::Impl::EV::],
265	[Event:: => AnyEvent::Impl::Event::],	557	[Event:: => AnyEvent::Impl::Event::],
266	[Glib:: => AnyEvent::Impl::Glib::],	558	[Glib:: => AnyEvent::Impl::Glib::],
267	[Tk:: => AnyEvent::Impl::Tk::],	559	[Tk:: => AnyEvent::Impl::Tk::],
		560	[Wx:: => AnyEvent::Impl::POE::],
		561	[Prima:: => AnyEvent::Impl::POE::],
268	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	562	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		563	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		564	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		565	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		566	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
269	);	567	);
270		568
271	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	569	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
272		570
273	sub detect() {	571	sub detect() {
274	unless ($MODEL) {	572	unless ($MODEL) {
275	no strict 'refs';	573	no strict 'refs';
276		574
		575	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		576	my $model = "AnyEvent::Impl::$1";
		577	if (eval "require $model") {
		578	$MODEL = $model;
		579	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		580	} else {
		581	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		582	}
		583	}
		584
277	# check for already loaded models	585	# check for already loaded models
		586	unless ($MODEL) {
278	for (@REGISTRY, @models) {	587	for (@REGISTRY, @models) {
279	my ($package, $model) = @$_;	588	my ($package, $model) = @$_;
280	if (${"$package\::VERSION"} > 0) {	589	if (${"$package\::VERSION"} > 0) {
281	if (eval "require $model") {	590	if (eval "require $model") {
282	$MODEL = $model;	591	$MODEL = $model;
283	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	592	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
284	last;	593	last;
		594	}
285	}	595	}
286	}	596	}
287	}
288		597
289	unless ($MODEL) {	598	unless ($MODEL) {
290	# try to load a model	599	# try to load a model
291		600
292	for (@REGISTRY, @models) {	601	for (@REGISTRY, @models) {
293	my ($package, $model) = @$_;	602	my ($package, $model) = @$_;
294	if (eval "require $package"	603	if (eval "require $package"
295	and ${"$package\::VERSION"} > 0	604	and ${"$package\::VERSION"} > 0
296	and eval "require $model") {	605	and eval "require $model") {
297	$MODEL = $model;	606	$MODEL = $model;
298	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	607	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
299	last;	608	last;
		609	}
300	}	610	}
		611
		612	$MODEL
		613	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.";
301	}	614	}
302
303	$MODEL
304	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
305	}	615	}
306		616
307	unshift @ISA, $MODEL;	617	unshift @ISA, $MODEL;
308	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	618	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
309	}	619	}
…		…
367		677
368	# default implementation for ->child	678	# default implementation for ->child
369		679
370	our %PID_CB;	680	our %PID_CB;
371	our $CHLD_W;	681	our $CHLD_W;
		682	our $CHLD_DELAY_W;
372	our $PID_IDLE;	683	our $PID_IDLE;
373	our $WNOHANG;	684	our $WNOHANG;
374		685
375	sub _child_wait {	686	sub _child_wait {
376	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	687	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
377	$_->() for values %{ (delete $PID_CB{$pid}) \|\| {} };	688	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		689	(values %{ $PID_CB{0} \|\| {} });
378	}	690	}
379		691
380	undef $PID_IDLE;	692	undef $PID_IDLE;
381	}	693	}
382		694
		695	sub _sigchld {
		696	# make sure we deliver these changes "synchronous" with the event loop.
		697	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		698	undef $CHLD_DELAY_W;
		699	&_child_wait;
		700	});
		701	}
		702
383	sub child {	703	sub child {
384	my (undef, %arg) = @_;	704	my (undef, %arg) = @_;
385		705
386	my $pid = uc $arg{pid}	706	defined (my $pid = $arg{pid} + 0)
387	or Carp::croak "required option 'pid' is missing";	707	or Carp::croak "required option 'pid' is missing";
388		708
389	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	709	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
390		710
391	unless ($WNOHANG) {	711	unless ($WNOHANG) {
392	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;	712	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
393	}	713	}
394		714
395	unless ($CHLD_W) {	715	unless ($CHLD_W) {
396	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait);	716	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
397	# child could be a zombie already	717	# child could be a zombie already, so make at least one round
398	$PID_IDLE \|\|= AnyEvent->timer (after => 0, cb => \&_child_wait);	718	&_sigchld;
399	}	719	}
400		720
401	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	721	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
402	}	722	}
403		723
…		…
409		729
410	undef $CHLD_W unless keys %PID_CB;	730	undef $CHLD_W unless keys %PID_CB;
411	}	731	}
412		732
413	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	733	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		734
		735	This is an advanced topic that you do not normally need to use AnyEvent in
		736	a module. This section is only of use to event loop authors who want to
		737	provide AnyEvent compatibility.
414		738
415	If you need to support another event library which isn't directly	739	If you need to support another event library which isn't directly
416	supported by AnyEvent, you can supply your own interface to it by	740	supported by AnyEvent, you can supply your own interface to it by
417	pushing, before the first watcher gets created, the package name of	741	pushing, before the first watcher gets created, the package name of
418	the event module and the package name of the interface to use onto	742	the event module and the package name of the interface to use onto
419	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	743	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
420	AnyEvent.	744	AnyEvent, so it is reasonably cheap.
421		745
422	Example:	746	Example:
423		747
424	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	748	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
425		749
426	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	750	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
427	package/class when it finds the C<urxvt> package/module is loaded. When	751	package/class when it finds the C<urxvt> package/module is already loaded.
		752
428	AnyEvent is loaded and asked to find a suitable event model, it will	753	When AnyEvent is loaded and asked to find a suitable event model, it
429	first check for the presence of urxvt.	754	will first check for the presence of urxvt by trying to C<use> the
		755	C<urxvt::anyevent> module.
430		756
431	The class should provide implementations for all watcher types (see	757	The class should provide implementations for all watcher types. See
432	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	758	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
433	(Source code) and so on for actual examples, use C<perldoc -m	759	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
434	AnyEvent::Impl::Glib> to see the sources).	760	see the sources.
435		761
		762	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		763	provide suitable (hopefully) replacements.
		764
436	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	765	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
437	uses the above line as-is. An interface isn't included in AnyEvent	766	terminal emulator uses the above line as-is. An interface isn't included
438	because it doesn't make sense outside the embedded interpreter inside	767	in AnyEvent because it doesn't make sense outside the embedded interpreter
439	I<rxvt-unicode>, and it is updated and maintained as part of the	768	inside I<rxvt-unicode>, and it is updated and maintained as part of the
440	I<rxvt-unicode> distribution.	769	I<rxvt-unicode> distribution.
441		770
442	I<rxvt-unicode> also cheats a bit by not providing blocking access to	771	I<rxvt-unicode> also cheats a bit by not providing blocking access to
443	condition variables: code blocking while waiting for a condition will	772	condition variables: code blocking while waiting for a condition will
444	C<die>. This still works with most modules/usages, and blocking calls must	773	C<die>. This still works with most modules/usages, and blocking calls must
445	not be in an interactive appliation, so it makes sense.	774	not be done in an interactive application, so it makes sense.
446		775
447	=head1 ENVIRONMENT VARIABLES	776	=head1 ENVIRONMENT VARIABLES
448		777
449	The following environment variables are used by this module:	778	The following environment variables are used by this module:
450		779
451	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event	780	=over 4
452	model gets used.
453		781
		782	=item C<PERL_ANYEVENT_VERBOSE>
		783
		784	By default, AnyEvent will be completely silent except in fatal
		785	conditions. You can set this environment variable to make AnyEvent more
		786	talkative.
		787
		788	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		789	conditions, such as not being able to load the event model specified by
		790	C<PERL_ANYEVENT_MODEL>.
		791
		792	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		793	model it chooses.
		794
		795	=item C<PERL_ANYEVENT_MODEL>
		796
		797	This can be used to specify the event model to be used by AnyEvent, before
		798	autodetection and -probing kicks in. It must be a string consisting
		799	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		800	and the resulting module name is loaded and if the load was successful,
		801	used as event model. If it fails to load AnyEvent will proceed with
		802	autodetection and -probing.
		803
		804	This functionality might change in future versions.
		805
		806	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		807	could start your program like this:
		808
		809	PERL_ANYEVENT_MODEL=Perl perl ...
		810
		811	=back
		812
454	=head1 EXAMPLE	813	=head1 EXAMPLE PROGRAM
455		814
456	The following program uses an io watcher to read data from stdin, a timer	815	The following program uses an I/O watcher to read data from STDIN, a timer
457	to display a message once per second, and a condvar to exit the program	816	to display a message once per second, and a condition variable to quit the
458	when the user enters quit:	817	program when the user enters quit:
459		818
460	use AnyEvent;	819	use AnyEvent;
461		820
462	my $cv = AnyEvent->condvar;	821	my $cv = AnyEvent->condvar;
463		822
464	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	823	my $io_watcher = AnyEvent->io (
		824	fh => \*STDIN,
		825	poll => 'r',
		826	cb => sub {
465	warn "io event <$_[0]>\n"; # will always output <r>	827	warn "io event <$_[0]>\n"; # will always output <r>
466	chomp (my $input = <STDIN>); # read a line	828	chomp (my $input = <STDIN>); # read a line
467	warn "read: $input\n"; # output what has been read	829	warn "read: $input\n"; # output what has been read
468	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	830	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		831	},
469	});	832	);
470		833
471	my $time_watcher; # can only be used once	834	my $time_watcher; # can only be used once
472		835
473	sub new_timer {	836	sub new_timer {
474	$timer = AnyEvent->timer (after => 1, cb => sub {	837	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
556	$txn->{finished}->wait;	919	$txn->{finished}->wait;
557	return $txn->{result};	920	return $txn->{result};
558		921
559	The actual code goes further and collects all errors (C<die>s, exceptions)	922	The actual code goes further and collects all errors (C<die>s, exceptions)
560	that occured during request processing. The C<result> method detects	923	that occured during request processing. The C<result> method detects
561	wether an exception as thrown (it is stored inside the $txn object)	924	whether an exception as thrown (it is stored inside the $txn object)
562	and just throws the exception, which means connection errors and other	925	and just throws the exception, which means connection errors and other
563	problems get reported tot he code that tries to use the result, not in a	926	problems get reported tot he code that tries to use the result, not in a
564	random callback.	927	random callback.
565		928
566	All of this enables the following usage styles:	929	All of this enables the following usage styles:
567		930
568	1. Blocking:	931	1. Blocking:
569		932
570	my $data = $fcp->client_get ($url);	933	my $data = $fcp->client_get ($url);
571		934
572	2. Blocking, but parallelizing:	935	2. Blocking, but running in parallel:
573		936
574	my @datas = map $_->result,	937	my @datas = map $_->result,
575	map $fcp->txn_client_get ($_),	938	map $fcp->txn_client_get ($_),
576	@urls;	939	@urls;
577		940
578	Both blocking examples work without the module user having to know	941	Both blocking examples work without the module user having to know
579	anything about events.	942	anything about events.
580		943
581	3a. Event-based in a main program, using any support Event module:	944	3a. Event-based in a main program, using any supported event module:
582		945
583	use Event;	946	use EV;
584		947
585	$fcp->txn_client_get ($url)->cb (sub {	948	$fcp->txn_client_get ($url)->cb (sub {
586	my $txn = shift;	949	my $txn = shift;
587	my $data = $txn->result;	950	my $data = $txn->result;
588	...	951	...
589	});	952	});
590		953
591	Event::loop;	954	EV::loop;
592		955
593	3b. The module user could use AnyEvent, too:	956	3b. The module user could use AnyEvent, too:
594		957
595	use AnyEvent;	958	use AnyEvent;
596		959
…		…
601	$quit->broadcast;	964	$quit->broadcast;
602	});	965	});
603		966
604	$quit->wait;	967	$quit->wait;
605		968
		969
		970	=head1 BENCHMARKS
		971
		972	To give you an idea of the performance and overheads that AnyEvent adds
		973	over the event loops themselves and to give you an impression of the speed
		974	of various event loops I prepared some benchmarks.
		975
		976	=head2 BENCHMARKING ANYEVENT OVERHEAD
		977
		978	Here is a benchmark of various supported event models used natively and
		979	through anyevent. The benchmark creates a lot of timers (with a zero
		980	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		981	which it is), lets them fire exactly once and destroys them again.
		982
		983	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		984	distribution.
		985
		986	=head3 Explanation of the columns
		987
		988	I<watcher> is the number of event watchers created/destroyed. Since
		989	different event models feature vastly different performances, each event
		990	loop was given a number of watchers so that overall runtime is acceptable
		991	and similar between tested event loop (and keep them from crashing): Glib
		992	would probably take thousands of years if asked to process the same number
		993	of watchers as EV in this benchmark.
		994
		995	I<bytes> is the number of bytes (as measured by the resident set size,
		996	RSS) consumed by each watcher. This method of measuring captures both C
		997	and Perl-based overheads.
		998
		999	I<create> is the time, in microseconds (millionths of seconds), that it
		1000	takes to create a single watcher. The callback is a closure shared between
		1001	all watchers, to avoid adding memory overhead. That means closure creation
		1002	and memory usage is not included in the figures.
		1003
		1004	I<invoke> is the time, in microseconds, used to invoke a simple
		1005	callback. The callback simply counts down a Perl variable and after it was
		1006	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		1007	signal the end of this phase.
		1008
		1009	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1010	watcher.
		1011
		1012	=head3 Results
		1013
		1014	name watchers bytes create invoke destroy comment
		1015	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1016	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1017	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1018	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1019	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1020	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1021	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1022	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1023	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1024	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1025
		1026	=head3 Discussion
		1027
		1028	The benchmark does I<not> measure scalability of the event loop very
		1029	well. For example, a select-based event loop (such as the pure perl one)
		1030	can never compete with an event loop that uses epoll when the number of
		1031	file descriptors grows high. In this benchmark, all events become ready at
		1032	the same time, so select/poll-based implementations get an unnatural speed
		1033	boost.
		1034
		1035	Also, note that the number of watchers usually has a nonlinear effect on
		1036	overall speed, that is, creating twice as many watchers doesn't take twice
		1037	the time - usually it takes longer. This puts event loops tested with a
		1038	higher number of watchers at a disadvantage.
		1039
		1040	To put the range of results into perspective, consider that on the
		1041	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1042	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1043	cycles with POE.
		1044
		1045	C<EV> is the sole leader regarding speed and memory use, which are both
		1046	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1047	far less memory than any other event loop and is still faster than Event
		1048	natively.
		1049
		1050	The pure perl implementation is hit in a few sweet spots (both the
		1051	constant timeout and the use of a single fd hit optimisations in the perl
		1052	interpreter and the backend itself). Nevertheless this shows that it
		1053	adds very little overhead in itself. Like any select-based backend its
		1054	performance becomes really bad with lots of file descriptors (and few of
		1055	them active), of course, but this was not subject of this benchmark.
		1056
		1057	The C<Event> module has a relatively high setup and callback invocation
		1058	cost, but overall scores in on the third place.
		1059
		1060	C<Glib>'s memory usage is quite a bit higher, but it features a
		1061	faster callback invocation and overall ends up in the same class as
		1062	C<Event>. However, Glib scales extremely badly, doubling the number of
		1063	watchers increases the processing time by more than a factor of four,
		1064	making it completely unusable when using larger numbers of watchers
		1065	(note that only a single file descriptor was used in the benchmark, so
		1066	inefficiencies of C<poll> do not account for this).
		1067
		1068	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1069	more than 2000 watchers is a big setback, however, as correctness takes
		1070	precedence over speed. Nevertheless, its performance is surprising, as the
		1071	file descriptor is dup()ed for each watcher. This shows that the dup()
		1072	employed by some adaptors is not a big performance issue (it does incur a
		1073	hidden memory cost inside the kernel which is not reflected in the figures
		1074	above).
		1075
		1076	C<POE>, regardless of underlying event loop (whether using its pure
		1077	perl select-based backend or the Event module, the POE-EV backend
		1078	couldn't be tested because it wasn't working) shows abysmal performance
		1079	and memory usage: Watchers use almost 30 times as much memory as
		1080	EV watchers, and 10 times as much memory as Event (the high memory
		1081	requirements are caused by requiring a session for each watcher). Watcher
		1082	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1083	implementation. The design of the POE adaptor class in AnyEvent can not
		1084	really account for this, as session creation overhead is small compared
		1085	to execution of the state machine, which is coded pretty optimally within
		1086	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		1087
		1088	=head3 Summary
		1089
		1090	=over 4
		1091
		1092	=item * Using EV through AnyEvent is faster than any other event loop
		1093	(even when used without AnyEvent), but most event loops have acceptable
		1094	performance with or without AnyEvent.
		1095
		1096	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1097	the actual event loop, only with extremely fast event loops such as EV
		1098	adds AnyEvent significant overhead.
		1099
		1100	=item * You should avoid POE like the plague if you want performance or
		1101	reasonable memory usage.
		1102
		1103	=back
		1104
		1105	=head2 BENCHMARKING THE LARGE SERVER CASE
		1106
		1107	This benchmark atcually benchmarks the event loop itself. It works by
		1108	creating a number of "servers": each server consists of a socketpair, a
		1109	timeout watcher that gets reset on activity (but never fires), and an I/O
		1110	watcher waiting for input on one side of the socket. Each time the socket
		1111	watcher reads a byte it will write that byte to a random other "server".
		1112
		1113	The effect is that there will be a lot of I/O watchers, only part of which
		1114	are active at any one point (so there is a constant number of active
		1115	fds for each loop iterstaion, but which fds these are is random). The
		1116	timeout is reset each time something is read because that reflects how
		1117	most timeouts work (and puts extra pressure on the event loops).
		1118
		1119	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1120	(1%) are active. This mirrors the activity of large servers with many
		1121	connections, most of which are idle at any one point in time.
		1122
		1123	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1124	distribution.
		1125
		1126	=head3 Explanation of the columns
		1127
		1128	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1129	each server has a read and write socket end).
		1130
		1131	I<create> is the time it takes to create a socketpair (which is
		1132	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1133
		1134	I<request>, the most important value, is the time it takes to handle a
		1135	single "request", that is, reading the token from the pipe and forwarding
		1136	it to another server. This includes deleting the old timeout and creating
		1137	a new one that moves the timeout into the future.
		1138
		1139	=head3 Results
		1140
		1141	name sockets create request
		1142	EV 20000 69.01 11.16
		1143	Perl 20000 73.32 35.87
		1144	Event 20000 212.62 257.32
		1145	Glib 20000 651.16 1896.30
		1146	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1147
		1148	=head3 Discussion
		1149
		1150	This benchmark I<does> measure scalability and overall performance of the
		1151	particular event loop.
		1152
		1153	EV is again fastest. Since it is using epoll on my system, the setup time
		1154	is relatively high, though.
		1155
		1156	Perl surprisingly comes second. It is much faster than the C-based event
		1157	loops Event and Glib.
		1158
		1159	Event suffers from high setup time as well (look at its code and you will
		1160	understand why). Callback invocation also has a high overhead compared to
		1161	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1162	uses select or poll in basically all documented configurations.
		1163
		1164	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1165	clearly fails to perform with many filehandles or in busy servers.
		1166
		1167	POE is still completely out of the picture, taking over 1000 times as long
		1168	as EV, and over 100 times as long as the Perl implementation, even though
		1169	it uses a C-based event loop in this case.
		1170
		1171	=head3 Summary
		1172
		1173	=over 4
		1174
		1175	=item * The pure perl implementation performs extremely well, considering
		1176	that it uses select.
		1177
		1178	=item * Avoid Glib or POE in large projects where performance matters.
		1179
		1180	=back
		1181
		1182	=head2 BENCHMARKING SMALL SERVERS
		1183
		1184	While event loops should scale (and select-based ones do not...) even to
		1185	large servers, most programs we (or I :) actually write have only a few
		1186	I/O watchers.
		1187
		1188	In this benchmark, I use the same benchmark program as in the large server
		1189	case, but it uses only eight "servers", of which three are active at any
		1190	one time. This should reflect performance for a small server relatively
		1191	well.
		1192
		1193	The columns are identical to the previous table.
		1194
		1195	=head3 Results
		1196
		1197	name sockets create request
		1198	EV 16 20.00 6.54
		1199	Perl 16 25.75 12.62
		1200	Event 16 81.27 35.86
		1201	Glib 16 32.63 15.48
		1202	POE 16 261.87 276.28 uses POE::Loop::Event
		1203
		1204	=head3 Discussion
		1205
		1206	The benchmark tries to test the performance of a typical small
		1207	server. While knowing how various event loops perform is interesting, keep
		1208	in mind that their overhead in this case is usually not as important, due
		1209	to the small absolute number of watchers (that is, you need efficiency and
		1210	speed most when you have lots of watchers, not when you only have a few of
		1211	them).
		1212
		1213	EV is again fastest.
		1214
		1215	Perl again comes second. It is noticably faster than the C-based event
		1216	loops Event and Glib, although the difference is too small to really
		1217	matter.
		1218
		1219	POE also performs much better in this case, but is is still far behind the
		1220	others.
		1221
		1222	=head3 Summary
		1223
		1224	=over 4
		1225
		1226	=item * C-based event loops perform very well with small number of
		1227	watchers, as the management overhead dominates.
		1228
		1229	=back
		1230
		1231
		1232	=head1 FORK
		1233
		1234	Most event libraries are not fork-safe. The ones who are usually are
		1235	because they are so inefficient. Only L<EV> is fully fork-aware.
		1236
		1237	If you have to fork, you must either do so I<before> creating your first
		1238	watcher OR you must not use AnyEvent at all in the child.
		1239
		1240
		1241	=head1 SECURITY CONSIDERATIONS
		1242
		1243	AnyEvent can be forced to load any event model via
		1244	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1245	execute arbitrary code or directly gain access, it can easily be used to
		1246	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1247	will not be active when the program uses a different event model than
		1248	specified in the variable.
		1249
		1250	You can make AnyEvent completely ignore this variable by deleting it
		1251	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1252
		1253	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1254
		1255	use AnyEvent;
		1256
		1257
606	=head1 SEE ALSO	1258	=head1 SEE ALSO
607		1259
608	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	1260	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		1261	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1262	L<Event::Lib>, L<Qt>, L<POE>.
609		1263
		1264	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
610	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	1265	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1266	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1267	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
611		1268
612	Nontrivial usage example: L<Net::FCP>.	1269	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
613		1270
614	=head1	1271
		1272	=head1 AUTHOR
		1273
		1274	Marc Lehmann <schmorp@schmorp.de>
		1275	http://home.schmorp.de/
615		1276
616	=cut	1277	=cut
617		1278
618	1	1279	1
619		1280

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.24 by root, Sun Mar 25 00:14:32 2007 UTC vs.
Revision 1.102 by root, Sun Apr 27 21:16:26 2008 UTC