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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.38 by root, Sun Nov 25 14:08:12 2007 UTC vs.
Revision 1.76 by root, Fri Apr 25 08:41:38 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.
		70
22		71
23	=head1 DESCRIPTION	72	=head1 DESCRIPTION
24		73
25	L<AnyEvent> provides an identical interface to multiple event loops. This	74	L<AnyEvent> provides an identical interface to multiple event loops. This
26	allows module authors to utilise an event loop without forcing module	75	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	76	users to use the same event loop (as only a single event loop can coexist
28	peacefully at any one time).	77	peacefully at any one time).
29		78
30	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>
31	module.	80	module.
32		81
33	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
34	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
35	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>,
36	used. If none is found, the module tries to load these modules in the	85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
37	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
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	87	to load these modules (excluding Event::Lib, Qt and POE as the pure perl
39	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.
40		92
41	Because AnyEvent first checks for modules that are already loaded, loading	93	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	94	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	95	that model the default. For example:
44		96
45	use Tk;	97	use Tk;
46	use AnyEvent;	98	use AnyEvent;
47		99
48	# .. 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...
49		105
50	The pure-perl implementation of AnyEvent is called	106	The pure-perl implementation of AnyEvent is called
51	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
52	explicitly.	108	explicitly.
53		109
…		…
56	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
57	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
58	the callback to call, the filehandle to watch, etc.	114	the callback to call, the filehandle to watch, etc.
59		115
60	These watchers are normal Perl objects with normal Perl lifetime. After	116	These watchers are normal Perl objects with normal Perl lifetime. After
61	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
62	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
63	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
64	references to it).	123	to it).
65		124
66	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.
67		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
68	=head2 IO WATCHERS	141	=head2 IO WATCHERS
69		142
70	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
71	the following mandatory arguments:	144	with the following mandatory key-value pairs as arguments:
72		145
73	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 for
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	147	events. C<poll> must be a string that is either C<r> or C<w>, which
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback	148	creates a watcher waiting for "r"eadable or "w"ritable events,
76	to invoke everytime the filehandle becomes ready.	149	respectively. C<cb> is the callback to invoke each time the file handle
		150	becomes ready.
77		151
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	152	As long as the I/O watcher exists it will keep the file descriptor or a
79	a socket you can have one r + one w, not any more (limitation comes from	153	copy of it alive/open.
80	Tk - if you are sure you are not using Tk this limitation is gone).
81		154
82	Filehandles will be kept alive, so as long as the watcher exists, the	155	It is not allowed to close a file handle as long as any watcher is active
83	filehandle exists, too.	156	on the underlying file descriptor.
		157
		158	Some event loops issue spurious readyness notifications, so you should
		159	always use non-blocking calls when reading/writing from/to your file
		160	handles.
84		161
85	Example:	162	Example:
86		163
87	# wait for readability of STDIN, then read a line and disable the watcher	164	# 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 {	165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
…		…
94	=head2 TIME WATCHERS	171	=head2 TIME WATCHERS
95		172
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	173	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	174	method with the following mandatory arguments:
98		175
99	C<after> after how many seconds (fractions are supported) should the timer	176	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	177	supported) should the timer activate. C<cb> the callback to invoke in that
		178	case.
101		179
102	The timer callback will be invoked at most once: if you want a repeating	180	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	181	timer you have to create a new watcher (this is a limitation by both Tk
104	and Glib).	182	and Glib).
105		183
…		…
111	});	189	});
112		190
113	# to cancel the timer:	191	# to cancel the timer:
114	undef $w;	192	undef $w;
115		193
		194	Example 2:
		195
		196	# fire an event after 0.5 seconds, then roughly every second
		197	my $w;
		198
		199	my $cb = sub {
		200	# cancel the old timer while creating a new one
		201	$w = AnyEvent->timer (after => 1, cb => $cb);
		202	};
		203
		204	# start the "loop" by creating the first watcher
		205	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		206
		207	=head3 TIMING ISSUES
		208
		209	There are two ways to handle timers: based on real time (relative, "fire
		210	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		211	o'clock").
		212
		213	While most event loops expect timers to specified in a relative way, they
		214	use absolute time internally. This makes a difference when your clock
		215	"jumps", for example, when ntp decides to set your clock backwards from
		216	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		217	fire "after" a second might actually take six years to finally fire.
		218
		219	AnyEvent cannot compensate for this. The only event loop that is conscious
		220	about these issues is L<EV>, which offers both relative (ev_timer, based
		221	on true relative time) and absolute (ev_periodic, based on wallclock time)
		222	timers.
		223
		224	AnyEvent always prefers relative timers, if available, matching the
		225	AnyEvent API.
		226
		227	=head2 SIGNAL WATCHERS
		228
		229	You can watch for signals using a signal watcher, C<signal> is the signal
		230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		231	be invoked whenever a signal occurs.
		232
		233	Multiple signal occurances can be clumped together into one callback
		234	invocation, and callback invocation will be synchronous. synchronous means
		235	that it might take a while until the signal gets handled by the process,
		236	but it is guarenteed not to interrupt any other callbacks.
		237
		238	The main advantage of using these watchers is that you can share a signal
		239	between multiple watchers.
		240
		241	This watcher might use C<%SIG>, so programs overwriting those signals
		242	directly will likely not work correctly.
		243
		244	Example: exit on SIGINT
		245
		246	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		247
		248	=head2 CHILD PROCESS WATCHERS
		249
		250	You can also watch on a child process exit and catch its exit status.
		251
		252	The child process is specified by the C<pid> argument (if set to C<0>, it
		253	watches for any child process exit). The watcher will trigger as often
		254	as status change for the child are received. This works by installing a
		255	signal handler for C<SIGCHLD>. The callback will be called with the pid
		256	and exit status (as returned by waitpid).
		257
		258	Example: wait for pid 1333
		259
		260	my $w = AnyEvent->child (
		261	pid => 1333,
		262	cb => sub {
		263	my ($pid, $status) = @_;
		264	warn "pid $pid exited with status $status";
		265	},
		266	);
		267
116	=head2 CONDITION WATCHERS	268	=head2 CONDITION VARIABLES
117		269
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	270	Condition variables can be created by calling the C<< AnyEvent->condvar >>
119	method without any arguments.	271	method without any arguments.
120		272
121	A condition watcher watches for a condition - precisely that the C<<	273	A condition variable waits for a condition - precisely that the C<<
122	->broadcast >> method has been called.	274	->broadcast >> method has been called.
123		275
124	The watcher has only two methods:	276	They are very useful to signal that a condition has been fulfilled, for
		277	example, if you write a module that does asynchronous http requests,
		278	then a condition variable would be the ideal candidate to signal the
		279	availability of results.
		280
		281	You can also use condition variables to block your main program until
		282	an event occurs - for example, you could C<< ->wait >> in your main
		283	program until the user clicks the Quit button in your app, which would C<<
		284	->broadcast >> the "quit" event.
		285
		286	Note that condition variables recurse into the event loop - if you have
		287	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		288	lose. Therefore, condition variables are good to export to your caller, but
		289	you should avoid making a blocking wait yourself, at least in callbacks,
		290	as this asks for trouble.
		291
		292	This object has two methods:
125		293
126	=over 4	294	=over 4
127		295
128	=item $cv->wait	296	=item $cv->wait
129		297
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
131	called on c<$cv>, while servicing other watchers normally.	299	called on c<$cv>, while servicing other watchers normally.
132		300
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	301	You can only wait once on a condition - additional calls will return
141	immediately.	302	immediately.
142		303
		304	Not all event models support a blocking wait - some die in that case
		305	(programs might want to do that to stay interactive), so I<if you are
		306	using this from a module, never require a blocking wait>, but let the
		307	caller decide whether the call will block or not (for example, by coupling
		308	condition variables with some kind of request results and supporting
		309	callbacks so the caller knows that getting the result will not block,
		310	while still suppporting blocking waits if the caller so desires).
		311
		312	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		313	sensibly have two C<< ->wait >>'s in parallel, as that would require
		314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		317	from different coroutines, however).
		318
143	=item $cv->broadcast	319	=item $cv->broadcast
144		320
145	Flag the condition as ready - a running C<< ->wait >> and all further	321	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	322	calls to C<wait> will (eventually) return after this method has been
147	is waiting the broadcast will be remembered..	323	called. If nobody is waiting the broadcast will be remembered..
		324
		325	=back
148		326
149	Example:	327	Example:
150		328
151	# wait till the result is ready	329	# wait till the result is ready
152	my $result_ready = AnyEvent->condvar;	330	my $result_ready = AnyEvent->condvar;
153		331
154	# do something such as adding a timer	332	# do something such as adding a timer
155	# or socket watcher the calls $result_ready->broadcast	333	# or socket watcher the calls $result_ready->broadcast
156	# when the "result" is ready.	334	# when the "result" is ready.
		335	# in this case, we simply use a timer:
		336	my $w = AnyEvent->timer (
		337	after => 1,
		338	cb => sub { $result_ready->broadcast },
		339	);
157		340
		341	# this "blocks" (while handling events) till the watcher
		342	# calls broadcast
158	$result_ready->wait;	343	$result_ready->wait;
159		344
160	=back	345	=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 (or any child if the pid argument is 0). The watcher will
180	trigger as often as status change for the child are received. This works
181	by installing a signal handler for C<SIGCHLD>. The callback will be called with
182	the pid and exit status (as returned by waitpid).
183
184	Example: wait for pid 1333
185
186	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
187
188	=head1 GLOBALS
189		346
190	=over 4	347	=over 4
191		348
192	=item $AnyEvent::MODEL	349	=item $AnyEvent::MODEL
193		350
…		…
198	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
199		356
200	The known classes so far are:	357	The known classes so far are:
201		358
202	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
203	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
204	AnyEvent::Impl::Coro based on Coro::Event, second best choice.
205	AnyEvent::Impl::Event based on Event, also second best choice :)	362	AnyEvent::Impl::Event based on Event, second best choice.
206	AnyEvent::Impl::Glib based on Glib, second-best choice.	363	AnyEvent::Impl::Glib based on Glib, third-best choice.
207	AnyEvent::Impl::Tk based on Tk, very bad choice.	364	AnyEvent::Impl::Tk based on Tk, very bad choice.
208	AnyEvent::Impl::Perl pure-perl implementation, inefficient.	365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		369
		370	There is no support for WxWidgets, as WxWidgets has no support for
		371	watching file handles. However, you can use WxWidgets through the
		372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		373	second, which was considered to be too horrible to even consider for
		374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		375	it's adaptor.
		376
		377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		378	autodetecting them.
209		379
210	=item AnyEvent::detect	380	=item AnyEvent::detect
211		381
212	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
213	necessary. You should only call this function right before you would have	383	if necessary. You should only call this function right before you would
214	created an AnyEvent watcher anyway, that is, very late at runtime.	384	have created an AnyEvent watcher anyway, that is, as late as possible at
		385	runtime.
215		386
216	=back	387	=back
217		388
218	=head1 WHAT TO DO IN A MODULE	389	=head1 WHAT TO DO IN A MODULE
219		390
220	As a module author, you should "use AnyEvent" and call AnyEvent methods	391	As a module author, you should C<use AnyEvent> and call AnyEvent methods
221	freely, but you should not load a specific event module or rely on it.	392	freely, but you should not load a specific event module or rely on it.
222		393
223	Be careful when you create watchers in the module body - Anyevent will	394	Be careful when you create watchers in the module body - AnyEvent will
224	decide which event module to use as soon as the first method is called, so	395	decide which event module to use as soon as the first method is called, so
225	by calling AnyEvent in your module body you force the user of your module	396	by calling AnyEvent in your module body you force the user of your module
226	to load the event module first.	397	to load the event module first.
227		398
		399	Never call C<< ->wait >> on a condition variable unless you I<know> that
		400	the C<< ->broadcast >> method has been called on it already. This is
		401	because it will stall the whole program, and the whole point of using
		402	events is to stay interactive.
		403
		404	It is fine, however, to call C<< ->wait >> when the user of your module
		405	requests it (i.e. if you create a http request object ad have a method
		406	called C<results> that returns the results, it should call C<< ->wait >>
		407	freely, as the user of your module knows what she is doing. always).
		408
228	=head1 WHAT TO DO IN THE MAIN PROGRAM	409	=head1 WHAT TO DO IN THE MAIN PROGRAM
229		410
230	There will always be a single main program - the only place that should	411	There will always be a single main program - the only place that should
231	dictate which event model to use.	412	dictate which event model to use.
232		413
233	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	414	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
234	do anything special and let AnyEvent decide which implementation to chose.	415	do anything special (it does not need to be event-based) and let AnyEvent
		416	decide which implementation to chose if some module relies on it.
235		417
236	If the main program relies on a specific event model (for example, in Gtk2	418	If the main program relies on a specific event model. For example, in
237	programs you have to rely on either Glib or Glib::Event), you should load	419	Gtk2 programs you have to rely on the Glib module. You should load the
238	it before loading AnyEvent or any module that uses it, generally, as early	420	event module before loading AnyEvent or any module that uses it: generally
239	as possible. The reason is that modules might create watchers when they	421	speaking, you should load it as early as possible. The reason is that
240	are loaded, and AnyEvent will decide on the event model to use as soon as	422	modules might create watchers when they are loaded, and AnyEvent will
241	it creates watchers, and it might chose the wrong one unless you load the	423	decide on the event model to use as soon as it creates watchers, and it
242	correct one yourself.	424	might chose the wrong one unless you load the correct one yourself.
243		425
244	You can chose to use a rather inefficient pure-perl implementation by	426	You can chose to use a rather inefficient pure-perl implementation by
245	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
246	generally better.	428	behaviour everywhere, but letting AnyEvent chose is generally better.
247		429
248	=cut	430	=cut
249		431
250	package AnyEvent;	432	package AnyEvent;
251		433
252	no warnings;	434	no warnings;
253	use strict;	435	use strict;
254		436
255	use Carp;	437	use Carp;
256		438
257	our $VERSION = '2.8';	439	our $VERSION = '3.3';
258	our $MODEL;	440	our $MODEL;
259		441
260	our $AUTOLOAD;	442	our $AUTOLOAD;
261	our @ISA;	443	our @ISA;
262		444
…		…
264		446
265	our @REGISTRY;	447	our @REGISTRY;
266		448
267	my @models = (	449	my @models = (
268	[Coro::EV:: => AnyEvent::Impl::CoroEV::],	450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
		451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
269	[EV:: => AnyEvent::Impl::EV::],	452	[EV:: => AnyEvent::Impl::EV::],
270	[Coro::Event:: => AnyEvent::Impl::Coro::],
271	[Event:: => AnyEvent::Impl::Event::],	453	[Event:: => AnyEvent::Impl::Event::],
272	[Glib:: => AnyEvent::Impl::Glib::],	454	[Glib:: => AnyEvent::Impl::Glib::],
273	[Tk:: => AnyEvent::Impl::Tk::],	455	[Tk:: => AnyEvent::Impl::Tk::],
		456	[Wx:: => AnyEvent::Impl::POE::],
		457	[Prima:: => AnyEvent::Impl::POE::],
274	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		459	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
275	);	463	);
276		464
277	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
278		466
279	sub detect() {	467	sub detect() {
280	unless ($MODEL) {	468	unless ($MODEL) {
281	no strict 'refs';	469	no strict 'refs';
282		470
		471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		472	my $model = "AnyEvent::Impl::$1";
		473	if (eval "require $model") {
		474	$MODEL = $model;
		475	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		476	} else {
		477	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		478	}
		479	}
		480
283	# check for already loaded models	481	# check for already loaded models
		482	unless ($MODEL) {
284	for (@REGISTRY, @models) {	483	for (@REGISTRY, @models) {
285	my ($package, $model) = @$_;	484	my ($package, $model) = @$_;
286	if (${"$package\::VERSION"} > 0) {	485	if (${"$package\::VERSION"} > 0) {
287	if (eval "require $model") {	486	if (eval "require $model") {
288	$MODEL = $model;	487	$MODEL = $model;
289	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
290	last;	489	last;
		490	}
291	}	491	}
292	}	492	}
293	}
294		493
295	unless ($MODEL) {	494	unless ($MODEL) {
296	# try to load a model	495	# try to load a model
297		496
298	for (@REGISTRY, @models) {	497	for (@REGISTRY, @models) {
299	my ($package, $model) = @$_;	498	my ($package, $model) = @$_;
300	if (eval "require $package"	499	if (eval "require $package"
301	and ${"$package\::VERSION"} > 0	500	and ${"$package\::VERSION"} > 0
302	and eval "require $model") {	501	and eval "require $model") {
303	$MODEL = $model;	502	$MODEL = $model;
304	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	503	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
305	last;	504	last;
		505	}
306	}	506	}
		507
		508	$MODEL
		509	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.";
307	}	510	}
308
309	$MODEL
310	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.";
311	}	511	}
312		512
313	unshift @ISA, $MODEL;	513	unshift @ISA, $MODEL;
314	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
315	}	515	}
…		…
426	undef $CHLD_W unless keys %PID_CB;	626	undef $CHLD_W unless keys %PID_CB;
427	}	627	}
428		628
429	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
430		630
		631	This is an advanced topic that you do not normally need to use AnyEvent in
		632	a module. This section is only of use to event loop authors who want to
		633	provide AnyEvent compatibility.
		634
431	If you need to support another event library which isn't directly	635	If you need to support another event library which isn't directly
432	supported by AnyEvent, you can supply your own interface to it by	636	supported by AnyEvent, you can supply your own interface to it by
433	pushing, before the first watcher gets created, the package name of	637	pushing, before the first watcher gets created, the package name of
434	the event module and the package name of the interface to use onto	638	the event module and the package name of the interface to use onto
435	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	639	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
436	AnyEvent.	640	AnyEvent, so it is reasonably cheap.
437		641
438	Example:	642	Example:
439		643
440	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	644	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
441		645
442	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	646	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
443	package/class when it finds the C<urxvt> package/module is loaded. When	647	package/class when it finds the C<urxvt> package/module is already loaded.
		648
444	AnyEvent is loaded and asked to find a suitable event model, it will	649	When AnyEvent is loaded and asked to find a suitable event model, it
445	first check for the presence of urxvt.	650	will first check for the presence of urxvt by trying to C<use> the
		651	C<urxvt::anyevent> module.
446		652
447	The class should provide implementations for all watcher types (see	653	The class should provide implementations for all watcher types. See
448	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	654	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
449	(Source code) and so on for actual examples, use C<perldoc -m	655	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
450	AnyEvent::Impl::Glib> to see the sources).	656	see the sources.
451		657
		658	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		659	provide suitable (hopefully) replacements.
		660
452	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	661	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
453	uses the above line as-is. An interface isn't included in AnyEvent	662	terminal emulator uses the above line as-is. An interface isn't included
454	because it doesn't make sense outside the embedded interpreter inside	663	in AnyEvent because it doesn't make sense outside the embedded interpreter
455	I<rxvt-unicode>, and it is updated and maintained as part of the	664	inside I<rxvt-unicode>, and it is updated and maintained as part of the
456	I<rxvt-unicode> distribution.	665	I<rxvt-unicode> distribution.
457		666
458	I<rxvt-unicode> also cheats a bit by not providing blocking access to	667	I<rxvt-unicode> also cheats a bit by not providing blocking access to
459	condition variables: code blocking while waiting for a condition will	668	condition variables: code blocking while waiting for a condition will
460	C<die>. This still works with most modules/usages, and blocking calls must	669	C<die>. This still works with most modules/usages, and blocking calls must
461	not be in an interactive application, so it makes sense.	670	not be done in an interactive application, so it makes sense.
462		671
463	=head1 ENVIRONMENT VARIABLES	672	=head1 ENVIRONMENT VARIABLES
464		673
465	The following environment variables are used by this module:	674	The following environment variables are used by this module:
466		675
467	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event	676	=over 4
468	model gets used.
469		677
		678	=item C<PERL_ANYEVENT_VERBOSE>
		679
		680	By default, AnyEvent will be completely silent except in fatal
		681	conditions. You can set this environment variable to make AnyEvent more
		682	talkative.
		683
		684	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		685	conditions, such as not being able to load the event model specified by
		686	C<PERL_ANYEVENT_MODEL>.
		687
		688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		689	model it chooses.
		690
		691	=item C<PERL_ANYEVENT_MODEL>
		692
		693	This can be used to specify the event model to be used by AnyEvent, before
		694	autodetection and -probing kicks in. It must be a string consisting
		695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		696	and the resulting module name is loaded and if the load was successful,
		697	used as event model. If it fails to load AnyEvent will proceed with
		698	autodetection and -probing.
		699
		700	This functionality might change in future versions.
		701
		702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		703	could start your program like this:
		704
		705	PERL_ANYEVENT_MODEL=Perl perl ...
		706
		707	=back
		708
470	=head1 EXAMPLE	709	=head1 EXAMPLE PROGRAM
471		710
472	The following program uses an io watcher to read data from stdin, a timer	711	The following program uses an IO watcher to read data from STDIN, a timer
473	to display a message once per second, and a condvar to exit the program	712	to display a message once per second, and a condition variable to quit the
474	when the user enters quit:	713	program when the user enters quit:
475		714
476	use AnyEvent;	715	use AnyEvent;
477		716
478	my $cv = AnyEvent->condvar;	717	my $cv = AnyEvent->condvar;
479		718
480	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	719	my $io_watcher = AnyEvent->io (
		720	fh => \*STDIN,
		721	poll => 'r',
		722	cb => sub {
481	warn "io event <$_[0]>\n"; # will always output <r>	723	warn "io event <$_[0]>\n"; # will always output <r>
482	chomp (my $input = <STDIN>); # read a line	724	chomp (my $input = <STDIN>); # read a line
483	warn "read: $input\n"; # output what has been read	725	warn "read: $input\n"; # output what has been read
484	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		727	},
485	});	728	);
486		729
487	my $time_watcher; # can only be used once	730	my $time_watcher; # can only be used once
488		731
489	sub new_timer {	732	sub new_timer {
490	$timer = AnyEvent->timer (after => 1, cb => sub {	733	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
572	$txn->{finished}->wait;	815	$txn->{finished}->wait;
573	return $txn->{result};	816	return $txn->{result};
574		817
575	The actual code goes further and collects all errors (C<die>s, exceptions)	818	The actual code goes further and collects all errors (C<die>s, exceptions)
576	that occured during request processing. The C<result> method detects	819	that occured during request processing. The C<result> method detects
577	wether an exception as thrown (it is stored inside the $txn object)	820	whether an exception as thrown (it is stored inside the $txn object)
578	and just throws the exception, which means connection errors and other	821	and just throws the exception, which means connection errors and other
579	problems get reported tot he code that tries to use the result, not in a	822	problems get reported tot he code that tries to use the result, not in a
580	random callback.	823	random callback.
581		824
582	All of this enables the following usage styles:	825	All of this enables the following usage styles:
583		826
584	1. Blocking:	827	1. Blocking:
585		828
586	my $data = $fcp->client_get ($url);	829	my $data = $fcp->client_get ($url);
587		830
588	2. Blocking, but parallelizing:	831	2. Blocking, but running in parallel:
589		832
590	my @datas = map $_->result,	833	my @datas = map $_->result,
591	map $fcp->txn_client_get ($_),	834	map $fcp->txn_client_get ($_),
592	@urls;	835	@urls;
593		836
594	Both blocking examples work without the module user having to know	837	Both blocking examples work without the module user having to know
595	anything about events.	838	anything about events.
596		839
597	3a. Event-based in a main program, using any support Event module:	840	3a. Event-based in a main program, using any supported event module:
598		841
599	use Event;	842	use EV;
600		843
601	$fcp->txn_client_get ($url)->cb (sub {	844	$fcp->txn_client_get ($url)->cb (sub {
602	my $txn = shift;	845	my $txn = shift;
603	my $data = $txn->result;	846	my $data = $txn->result;
604	...	847	...
605	});	848	});
606		849
607	Event::loop;	850	EV::loop;
608		851
609	3b. The module user could use AnyEvent, too:	852	3b. The module user could use AnyEvent, too:
610		853
611	use AnyEvent;	854	use AnyEvent;
612		855
…		…
617	$quit->broadcast;	860	$quit->broadcast;
618	});	861	});
619		862
620	$quit->wait;	863	$quit->wait;
621		864
		865
		866	=head1 BENCHMARK
		867
		868	To give you an idea of the performance and overheads that AnyEvent adds
		869	over the event loops themselves (and to give you an impression of the
		870	speed of various event loops), here is a benchmark of various supported
		871	event models natively and with anyevent. The benchmark creates a lot of
		872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to
		873	become writable, which it is), lets them fire exactly once and destroys
		874	them again.
		875
		876	=head2 Explanation of the columns
		877
		878	I<watcher> is the number of event watchers created/destroyed. Since
		879	different event models feature vastly different performances, each event
		880	loop was given a number of watchers so that overall runtime is acceptable
		881	and similar between tested event loop (and keep them from crashing): Glib
		882	would probably take thousands of years if asked to process the same number
		883	of watchers as EV in this benchmark.
		884
		885	I<bytes> is the number of bytes (as measured by the resident set size,
		886	RSS) consumed by each watcher. This method of measuring captures both C
		887	and Perl-based overheads.
		888
		889	I<create> is the time, in microseconds (millionths of seconds), that it
		890	takes to create a single watcher. The callback is a closure shared between
		891	all watchers, to avoid adding memory overhead. That means closure creation
		892	and memory usage is not included in the figures.
		893
		894	I<invoke> is the time, in microseconds, used to invoke a simple
		895	callback. The callback simply counts down a Perl variable and after it was
		896	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		897	signal the end of this phase.
		898
		899	I<destroy> is the time, in microseconds, that it takes to destroy a single
		900	watcher.
		901
		902	=head2 Results
		903
		904	name watchers bytes create invoke destroy comment
		905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		906	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
		907	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
		908	Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation
		909	Event/Event 16000 523 28.05 21.38 0.86 Event native interface
		910	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
		911	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
		912	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
		913	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event
		914	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
		915
		916	=head2 Discussion
		917
		918	The benchmark does I<not> measure scalability of the event loop very
		919	well. For example, a select-based event loop (such as the pure perl one)
		920	can never compete with an event loop that uses epoll when the number of
		921	file descriptors grows high. In this benchmark, only a single filehandle
		922	is used (although some of the AnyEvent adaptors dup() its file descriptor
		923	to worka round bugs).
		924
		925	C<EV> is the sole leader regarding speed and memory use, which are both
		926	maximal/minimal, respectively. Even when going through AnyEvent, there are
		927	only two event loops that use slightly less memory (the C<Event> module
		928	natively and the pure perl backend), and no faster event models, not even
		929	C<Event> natively.
		930
		931	The pure perl implementation is hit in a few sweet spots (both the
		932	zero timeout and the use of a single fd hit optimisations in the perl
		933	interpreter and the backend itself). Nevertheless tis shows that it
		934	adds very little overhead in itself. Like any select-based backend its
		935	performance becomes really bad with lots of file descriptors, of course,
		936	but this was not subject of this benchmark.
		937
		938	The C<Event> module has a relatively high setup and callback invocation cost,
		939	but overall scores on the third place.
		940
		941	C<Glib>'s memory usage is quite a bit bit higher, but it features a
		942	faster callback invocation and overall ends up in the same class as
		943	C<Event>. However, Glib scales extremely badly, doubling the number of
		944	watchers increases the processing time by more than a factor of four,
		945	making it completely unusable when using larger numbers of watchers
		946	(note that only a single file descriptor was used in the benchmark, so
		947	inefficiencies of C<poll> do not account for this).
		948
		949	The C<Tk> adaptor works relatively well. The fact that it crashes with
		950	more than 2000 watchers is a big setback, however, as correctness takes
		951	precedence over speed. Nevertheless, its performance is surprising, as the
		952	file descriptor is dup()ed for each watcher. This shows that the dup()
		953	employed by some adaptors is not a big performance issue (it does incur a
		954	hidden memory cost inside the kernel, though, that is not reflected in the
		955	figures above).
		956
		957	C<POE>, regardless of underlying event loop (wether using its pure perl
		958	select-based backend or the Event module) shows abysmal performance and
		959	memory usage: Watchers use almost 30 times as much memory as EV watchers,
		960	and 10 times as much memory as both Event or EV via AnyEvent. Watcher
		961	invocation is almost 700 times slower than with AnyEvent's pure perl
		962	implementation. The design of the POE adaptor class in AnyEvent can not
		963	really account for this, as session creation overhead is small compared
		964	to execution of the state machine, which is coded pretty optimally within
		965	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		966
		967	=head2 Summary
		968
		969	Using EV through AnyEvent is faster than any other event loop, but most
		970	event loops have acceptable performance with or without AnyEvent.
		971
		972	The overhead AnyEvent adds is usually much smaller than the overhead of
		973	the actual event loop, only with extremely fast event loops such as the EV
		974	adds AnyEvent significant overhead.
		975
		976	And you should simply avoid POE like the plague if you want performance or
		977	reasonable memory usage.
		978
		979
		980	=head1 FORK
		981
		982	Most event libraries are not fork-safe. The ones who are usually are
		983	because they are so inefficient. Only L<EV> is fully fork-aware.
		984
		985	If you have to fork, you must either do so I<before> creating your first
		986	watcher OR you must not use AnyEvent at all in the child.
		987
		988
		989	=head1 SECURITY CONSIDERATIONS
		990
		991	AnyEvent can be forced to load any event model via
		992	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		993	execute arbitrary code or directly gain access, it can easily be used to
		994	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		995	will not be active when the program uses a different event model than
		996	specified in the variable.
		997
		998	You can make AnyEvent completely ignore this variable by deleting it
		999	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1000
		1001	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1002
		1003	use AnyEvent;
		1004
		1005
622	=head1 SEE ALSO	1006	=head1 SEE ALSO
623		1007
624	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	1008	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		1009	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1010	L<Event::Lib>, L<Qt>, L<POE>.
625		1011
		1012	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
626	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	1013	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1014	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1015	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
627		1016
628	Nontrivial usage example: L<Net::FCP>.	1017	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
629		1018
630	=head1	1019
		1020	=head1 AUTHOR
		1021
		1022	Marc Lehmann <schmorp@schmorp.de>
		1023	http://home.schmorp.de/
631		1024
632	=cut	1025	=cut
633		1026
634	1	1027	1
635		1028

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.38 by root, Sun Nov 25 14:08:12 2007 UTC vs. Revision 1.76 by root, Fri Apr 25 08:41:38 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.38 by root, Sun Nov 25 14:08:12 2007 UTC vs.
Revision 1.76 by root, Fri Apr 25 08:41:38 2008 UTC