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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.42 by root, Mon Apr 7 19:40:12 2008 UTC vs.
Revision 1.65 by root, Fri Apr 25 06:58:12 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	Event, Coro, Glib, Tk, Perl - various supported event loops	5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
14		14
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...	16	...
17	});	17	});
18		18
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	19	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	20	$w->wait; # enters "main loop" till $condvar gets ->broadcast
21	$w->broadcast; # wake up current and all future wait's	21	$w->broadcast; # wake up current and all future wait's
22		22
23	=head1 WHY YOU SHOULD USE THIS MODULE	23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		24
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	26	nowadays. So what is different about AnyEvent?
27		27
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	29	policy> and AnyEvent is I<small and efficient>.
30		30
31	First and foremost, I<AnyEvent is not an event model> itself, it only	31	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	32	interfaces to whatever event model the main program happens to use in a
33	pragmatic way. For event models and certain classes of immortals alike,	33	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality, and AnyEvent	34	the statement "there can only be one" is a bitter reality: In general,
35	helps hiding the differences.	35	only one event loop can be active at the same time in a process. AnyEvent
		36	helps hiding the differences between those event loops.
36		37
37	The goal of AnyEvent is to offer module authors the ability to do event	38	The goal of AnyEvent is to offer module authors the ability to do event
38	programming (waiting for I/O or timer events) without subscribing to a	39	programming (waiting for I/O or timer events) without subscribing to a
39	religion, a way of living, and most importantly: without forcing your	40	religion, a way of living, and most importantly: without forcing your
40	module users into the same thing by forcing them to use the same event	41	module users into the same thing by forcing them to use the same event
41	model you use.	42	model you use.
42		43
43	For modules like POE or IO::Async (which is actually doing all I/O	44	For modules like POE or IO::Async (which is a total misnomer as it is
44	I<synchronously>...), using them in your module is like joining a	45	actually doing all I/O I<synchronously>...), using them in your module is
45	cult: After you joined, you are dependent on them and you cannot use	46	like joining a cult: After you joined, you are dependent on them and you
46	anything else, as it is simply incompatible to everything that isn't	47	cannot use anything else, as it is simply incompatible to everything that
47	itself.	48	isn't itself. What's worse, all the potential users of your module are
		49	I<also> forced to use the same event loop you use.
48		50
49	AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk	51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	works fine etc. etc. but none of these work together with the rest: POE	52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51	+ IO::Async? no go. Tk + Event? no go. If your module uses one of	53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if
52	those, every user of your module has to use it, too. If your module	54	your module uses one of those, every user of your module has to use it,
53	uses AnyEvent, it works transparently with all event models it supports	55	too. But if your module uses AnyEvent, it works transparently with all
54	(including stuff like POE and IO::Async).	56	event models it supports (including stuff like POE and IO::Async, as long
		57	as those use one of the supported event loops. It is trivial to add new
		58	event loops to AnyEvent, too, so it is future-proof).
55		59
56	In addition of being free of having to use I<the one and only true event	60	In addition to being free of having to use I<the one and only true event
57	model>, AnyEvent also is free of bloat and policy: with POE or similar	61	model>, AnyEvent also is free of bloat and policy: with POE or similar
58	modules, you get an enourmous amount of code and strict rules you have	62	modules, you get an enourmous amount of code and strict rules you have to
59	to follow. AnyEvent, on the other hand, is lean and to the point by only	63	follow. AnyEvent, on the other hand, is lean and up to the point, by only
60	offering the functionality that is useful, in as thin as a wrapper as	64	offering the functionality that is necessary, in as thin as a wrapper as
61	technically possible.	65	technically possible.
		66
		67	Of course, if you want lots of policy (this can arguably be somewhat
		68	useful) and you want to force your users to use the one and only event
		69	model, you should I<not> use this module.
62		70
63		71
64	=head1 DESCRIPTION	72	=head1 DESCRIPTION
65		73
66	L<AnyEvent> provides an identical interface to multiple event loops. This	74	L<AnyEvent> provides an identical interface to multiple event loops. This
67	allows module authors to utilise an event loop without forcing module	75	allows module authors to utilise an event loop without forcing module
68	users to use the same event loop (as only a single event loop can coexist	76	users to use the same event loop (as only a single event loop can coexist
69	peacefully at any one time).	77	peacefully at any one time).
70		78
71	The interface itself is vaguely similar but not identical to the Event	79	The interface itself is vaguely similar, but not identical to the L<Event>
72	module.	80	module.
73		81
74	On the first call of any method, the module tries to detect the currently	82	During the first call of any watcher-creation method, the module tries
75	loaded event loop by probing wether any of the following modules is	83	to detect the currently loaded event loop by probing whether one of the
76	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
77	used. If none is found, the module tries to load these modules in the	85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
78	order given. The first one that could be successfully loaded will be	86	L<POE>. The first one found is used. If none are found, the module tries
79	used. If still none could be found, AnyEvent will fall back to a pure-perl	87	to load these modules (excluding Event::Lib, Qt and POE as the pure perl
80	event loop, which is also not very efficient.	88	adaptor should always succeed) in the order given. The first one that can
		89	be successfully loaded will be used. If, after this, still none could be
		90	found, AnyEvent will fall back to a pure-perl event loop, which is not
		91	very efficient, but should work everywhere.
81		92
82	Because AnyEvent first checks for modules that are already loaded, loading	93	Because AnyEvent first checks for modules that are already loaded, loading
83	an Event model explicitly before first using AnyEvent will likely make	94	an event model explicitly before first using AnyEvent will likely make
84	that model the default. For example:	95	that model the default. For example:
85		96
86	use Tk;	97	use Tk;
87	use AnyEvent;	98	use AnyEvent;
88		99
89	# .. AnyEvent will likely default to Tk	100	# .. AnyEvent will likely default to Tk
		101
		102	The I<likely> means that, if any module loads another event model and
		103	starts using it, all bets are off. Maybe you should tell their authors to
		104	use AnyEvent so their modules work together with others seamlessly...
90		105
91	The pure-perl implementation of AnyEvent is called	106	The pure-perl implementation of AnyEvent is called
92	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
93	explicitly.	108	explicitly.
94		109
…		…
97	AnyEvent has the central concept of a I<watcher>, which is an object that	112	AnyEvent has the central concept of a I<watcher>, which is an object that
98	stores relevant data for each kind of event you are waiting for, such as	113	stores relevant data for each kind of event you are waiting for, such as
99	the callback to call, the filehandle to watch, etc.	114	the callback to call, the filehandle to watch, etc.
100		115
101	These watchers are normal Perl objects with normal Perl lifetime. After	116	These watchers are normal Perl objects with normal Perl lifetime. After
102	creating a watcher it will immediately "watch" for events and invoke	117	creating a watcher it will immediately "watch" for events and invoke the
		118	callback when the event occurs (of course, only when the event model
		119	is in control).
		120
103	the callback. To disable the watcher you have to destroy it (e.g. by	121	To disable the watcher you have to destroy it (e.g. by setting the
104	setting the variable that stores it to C<undef> or otherwise deleting all	122	variable you store it in to C<undef> or otherwise deleting all references
105	references to it).	123	to it).
106		124
107	All watchers are created by calling a method on the C<AnyEvent> class.	125	All watchers are created by calling a method on the C<AnyEvent> class.
108		126
		127	Many watchers either are used with "recursion" (repeating timers for
		128	example), or need to refer to their watcher object in other ways.
		129
		130	An any way to achieve that is this pattern:
		131
		132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		133	# you can use $w here, for example to undef it
		134	undef $w;
		135	});
		136
		137	Note that C<my $w; $w => combination. This is necessary because in Perl,
		138	my variables are only visible after the statement in which they are
		139	declared.
		140
109	=head2 IO WATCHERS	141	=head2 IO WATCHERS
110		142
111	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
112	the following mandatory arguments:	144	with the following mandatory key-value pairs as arguments:
113		145
114	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
115	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
116	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,
117	to invoke everytime the filehandle becomes ready.	149	respectively. C<cb> is the callback to invoke each time the file handle
		150	becomes ready.
118		151
119	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	152	As long as the I/O watcher exists it will keep the file descriptor or a
120	a socket you can have one r + one w, not any more (limitation comes from	153	copy of it alive/open.
121	Tk - if you are sure you are not using Tk this limitation is gone).
122		154
123	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
124	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.
125		161
126	Example:	162	Example:
127		163
128	# 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
129	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
…		…
135	=head2 TIME WATCHERS	171	=head2 TIME WATCHERS
136		172
137	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 >>
138	method with the following mandatory arguments:	174	method with the following mandatory arguments:
139		175
140	C<after> after how many seconds (fractions are supported) should the timer	176	C<after> specifies after how many seconds (fractional values are
141	activate. C<cb> the callback to invoke.	177	supported) should the timer activate. C<cb> the callback to invoke in that
		178	case.
142		179
143	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
144	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
145	and Glib).	182	and Glib).
146		183
…		…
152	});	189	});
153		190
154	# to cancel the timer:	191	# to cancel the timer:
155	undef $w;	192	undef $w;
156		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
157	=head2 CONDITION WATCHERS	268	=head2 CONDITION VARIABLES
158		269
159	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	270	Condition variables can be created by calling the C<< AnyEvent->condvar >>
160	method without any arguments.	271	method without any arguments.
161		272
162	A condition watcher watches for a condition - precisely that the C<<	273	A condition variable waits for a condition - precisely that the C<<
163	->broadcast >> method has been called.	274	->broadcast >> method has been called.
164		275
		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
165	Note that condition watchers recurse into the event loop - if you have	286	Note that condition variables recurse into the event loop - if you have
166	two watchers that call C<< ->wait >> in a round-robbin fashion, you	287	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
167	lose. Therefore, condition watchers are good to export to your caller, but	288	lose. Therefore, condition variables are good to export to your caller, but
168	you should avoid making a blocking wait, at least in callbacks, as this	289	you should avoid making a blocking wait yourself, at least in callbacks,
169	usually asks for trouble.	290	as this asks for trouble.
170		291
171	The watcher has only two methods:	292	This object has two methods:
172		293
173	=over 4	294	=over 4
174		295
175	=item $cv->wait	296	=item $cv->wait
176		297
177	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
178	called on c<$cv>, while servicing other watchers normally.	299	called on c<$cv>, while servicing other watchers normally.
179		300
180	Not all event models support a blocking wait - some die in that case, so
181	if you are using this from a module, never require a blocking wait, but
182	let the caller decide wether the call will block or not (for example,
183	by coupling condition variables with some kind of request results and
184	supporting callbacks so the caller knows that getting the result will not
185	block, while still suppporting blockign waits if the caller so desires).
186
187	You can only wait once on a condition - additional calls will return	301	You can only wait once on a condition - additional calls will return
188	immediately.	302	immediately.
189		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
190	=item $cv->broadcast	319	=item $cv->broadcast
191		320
192	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
193	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
194	is waiting the broadcast will be remembered..	323	called. If nobody is waiting the broadcast will be remembered..
		324
		325	=back
195		326
196	Example:	327	Example:
197		328
198	# wait till the result is ready	329	# wait till the result is ready
199	my $result_ready = AnyEvent->condvar;	330	my $result_ready = AnyEvent->condvar;
200		331
201	# do something such as adding a timer	332	# do something such as adding a timer
202	# or socket watcher the calls $result_ready->broadcast	333	# or socket watcher the calls $result_ready->broadcast
203	# 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	);
204		340
		341	# this "blocks" (while handling events) till the watcher
		342	# calls broadcast
205	$result_ready->wait;	343	$result_ready->wait;
206		344
207	=back	345	=head1 GLOBAL VARIABLES AND FUNCTIONS
208
209	=head2 SIGNAL WATCHERS
210
211	You can listen for signals using a signal watcher, C<signal> is the signal
212	I<name> without any C<SIG> prefix. Multiple signals events can be clumped
213	together into one callback invocation, and callback invocation might or
214	might not be asynchronous.
215
216	These watchers might use C<%SIG>, so programs overwriting those signals
217	directly will likely not work correctly.
218
219	Example: exit on SIGINT
220
221	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
222
223	=head2 CHILD PROCESS WATCHERS
224
225	You can also listen for the status of a child process specified by the
226	C<pid> argument (or any child if the pid argument is 0). The watcher will
227	trigger as often as status change for the child are received. This works
228	by installing a signal handler for C<SIGCHLD>. The callback will be called with
229	the pid and exit status (as returned by waitpid).
230
231	Example: wait for pid 1333
232
233	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
234
235	=head1 GLOBALS
236		346
237	=over 4	347	=over 4
238		348
239	=item $AnyEvent::MODEL	349	=item $AnyEvent::MODEL
240		350
…		…
245	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
246		356
247	The known classes so far are:	357	The known classes so far are:
248		358
249	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
250	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
251	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
252	AnyEvent::Impl::Event based on Event, also second best choice :)	362	AnyEvent::Impl::Event based on Event, second best choice.
253	AnyEvent::Impl::Glib based on Glib, second-best choice.	363	AnyEvent::Impl::Glib based on Glib, third-best choice.
254	AnyEvent::Impl::Tk based on Tk, very bad choice.	364	AnyEvent::Impl::Tk based on Tk, very bad choice.
255	AnyEvent::Impl::Perl pure-perl implementation, inefficient.	365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		369
		370	There is no support for WxWidgets, as WxWidgets has no support for
		371	watching file handles. However, you can use WxWidgets through the
		372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		373	second, which was considered to be too horrible to even consider for
		374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		375	it's adaptor.
		376
		377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		378	autodetecting them.
256		379
257	=item AnyEvent::detect	380	=item AnyEvent::detect
258		381
259	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
260	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
261	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.
262		386
263	=back	387	=back
264		388
265	=head1 WHAT TO DO IN A MODULE	389	=head1 WHAT TO DO IN A MODULE
266		390
267	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
268	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.
269		393
270	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
271	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
272	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
273	to load the event module first.	397	to load the event module first.
274		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
275	=head1 WHAT TO DO IN THE MAIN PROGRAM	409	=head1 WHAT TO DO IN THE MAIN PROGRAM
276		410
277	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
278	dictate which event model to use.	412	dictate which event model to use.
279		413
280	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
281	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.
282		417
283	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
284	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
285	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
286	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
287	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
288	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
289	correct one yourself.	424	might chose the wrong one unless you load the correct one yourself.
290		425
291	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
292	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
293	generally better.	428	behaviour everywhere, but letting AnyEvent chose is generally better.
294		429
295	=cut	430	=cut
296		431
297	package AnyEvent;	432	package AnyEvent;
298		433
299	no warnings;	434	no warnings;
300	use strict;	435	use strict;
301		436
302	use Carp;	437	use Carp;
303		438
304	our $VERSION = '3.0';	439	our $VERSION = '3.3';
305	our $MODEL;	440	our $MODEL;
306		441
307	our $AUTOLOAD;	442	our $AUTOLOAD;
308	our @ISA;	443	our @ISA;
309		444
…		…
311		446
312	our @REGISTRY;	447	our @REGISTRY;
313		448
314	my @models = (	449	my @models = (
315	[Coro::EV:: => AnyEvent::Impl::CoroEV::],	450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
		451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
316	[EV:: => AnyEvent::Impl::EV::],	452	[EV:: => AnyEvent::Impl::EV::],
317	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
318	[Event:: => AnyEvent::Impl::Event::],	453	[Event:: => AnyEvent::Impl::Event::],
319	[Glib:: => AnyEvent::Impl::Glib::],	454	[Glib:: => AnyEvent::Impl::Glib::],
320	[Tk:: => AnyEvent::Impl::Tk::],	455	[Tk:: => AnyEvent::Impl::Tk::],
		456	[Wx:: => AnyEvent::Impl::POE::],
		457	[Prima:: => AnyEvent::Impl::POE::],
321	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		459	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
322	);	463	);
323		464
324	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
325		466
326	sub detect() {	467	sub detect() {
327	unless ($MODEL) {	468	unless ($MODEL) {
328	no strict 'refs';	469	no strict 'refs';
329		470
		471	if ($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 $verbose;
		478	}
		479	}
		480
330	# check for already loaded models	481	# check for already loaded models
		482	unless ($MODEL) {
331	for (@REGISTRY, @models) {	483	for (@REGISTRY, @models) {
332	my ($package, $model) = @$_;	484	my ($package, $model) = @$_;
333	if (${"$package\::VERSION"} > 0) {	485	if (${"$package\::VERSION"} > 0) {
334	if (eval "require $model") {	486	if (eval "require $model") {
335	$MODEL = $model;	487	$MODEL = $model;
336	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
337	last;	489	last;
		490	}
338	}	491	}
339	}	492	}
340	}
341		493
342	unless ($MODEL) {	494	unless ($MODEL) {
343	# try to load a model	495	# try to load a model
344		496
345	for (@REGISTRY, @models) {	497	for (@REGISTRY, @models) {
346	my ($package, $model) = @$_;	498	my ($package, $model) = @$_;
347	if (eval "require $package"	499	if (eval "require $package"
348	and ${"$package\::VERSION"} > 0	500	and ${"$package\::VERSION"} > 0
349	and eval "require $model") {	501	and eval "require $model") {
350	$MODEL = $model;	502	$MODEL = $model;
351	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	503	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
352	last;	504	last;
		505	}
353	}	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.";
354	}	510	}
355
356	$MODEL
357	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event), Glib or Tk.";
358	}	511	}
359		512
360	unshift @ISA, $MODEL;	513	unshift @ISA, $MODEL;
361	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
362	}	515	}
…		…
473	undef $CHLD_W unless keys %PID_CB;	626	undef $CHLD_W unless keys %PID_CB;
474	}	627	}
475		628
476	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
477		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
478	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
479	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
480	pushing, before the first watcher gets created, the package name of	637	pushing, before the first watcher gets created, the package name of
481	the event module and the package name of the interface to use onto	638	the event module and the package name of the interface to use onto
482	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	639	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
483	AnyEvent.	640	AnyEvent, so it is reasonably cheap.
484		641
485	Example:	642	Example:
486		643
487	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	644	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
488		645
489	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	646	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
490	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
491	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
492	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.
493		652
494	The class should provide implementations for all watcher types (see	653	The class should provide implementations for all watcher types. See
495	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	654	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
496	(Source code) and so on for actual examples, use C<perldoc -m	655	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
497	AnyEvent::Impl::Glib> to see the sources).	656	see the sources.
498		657
		658	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		659	provide suitable (hopefully) replacements.
		660
499	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)
500	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
501	because it doesn't make sense outside the embedded interpreter inside	663	in AnyEvent because it doesn't make sense outside the embedded interpreter
502	I<rxvt-unicode>, and it is updated and maintained as part of the	664	inside I<rxvt-unicode>, and it is updated and maintained as part of the
503	I<rxvt-unicode> distribution.	665	I<rxvt-unicode> distribution.
504		666
505	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
506	condition variables: code blocking while waiting for a condition will	668	condition variables: code blocking while waiting for a condition will
507	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
508	not be in an interactive application, so it makes sense.	670	not be done in an interactive application, so it makes sense.
509		671
510	=head1 ENVIRONMENT VARIABLES	672	=head1 ENVIRONMENT VARIABLES
511		673
512	The following environment variables are used by this module:	674	The following environment variables are used by this module:
513		675
514	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event	676	=over 4
515	model gets used.
516		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
517	=head1 EXAMPLE	709	=head1 EXAMPLE PROGRAM
518		710
519	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
520	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
521	when the user enters quit:	713	program when the user enters quit:
522		714
523	use AnyEvent;	715	use AnyEvent;
524		716
525	my $cv = AnyEvent->condvar;	717	my $cv = AnyEvent->condvar;
526		718
527	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	719	my $io_watcher = AnyEvent->io (
		720	fh => \*STDIN,
		721	poll => 'r',
		722	cb => sub {
528	warn "io event <$_[0]>\n"; # will always output <r>	723	warn "io event <$_[0]>\n"; # will always output <r>
529	chomp (my $input = <STDIN>); # read a line	724	chomp (my $input = <STDIN>); # read a line
530	warn "read: $input\n"; # output what has been read	725	warn "read: $input\n"; # output what has been read
531	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		727	},
532	});	728	);
533		729
534	my $time_watcher; # can only be used once	730	my $time_watcher; # can only be used once
535		731
536	sub new_timer {	732	sub new_timer {
537	$timer = AnyEvent->timer (after => 1, cb => sub {	733	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
619	$txn->{finished}->wait;	815	$txn->{finished}->wait;
620	return $txn->{result};	816	return $txn->{result};
621		817
622	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)
623	that occured during request processing. The C<result> method detects	819	that occured during request processing. The C<result> method detects
624	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)
625	and just throws the exception, which means connection errors and other	821	and just throws the exception, which means connection errors and other
626	problems get reported tot he code that tries to use the result, not in a	822	problems get reported tot he code that tries to use the result, not in a
627	random callback.	823	random callback.
628		824
629	All of this enables the following usage styles:	825	All of this enables the following usage styles:
630		826
631	1. Blocking:	827	1. Blocking:
632		828
633	my $data = $fcp->client_get ($url);	829	my $data = $fcp->client_get ($url);
634		830
635	2. Blocking, but parallelizing:	831	2. Blocking, but running in parallel:
636		832
637	my @datas = map $_->result,	833	my @datas = map $_->result,
638	map $fcp->txn_client_get ($_),	834	map $fcp->txn_client_get ($_),
639	@urls;	835	@urls;
640		836
641	Both blocking examples work without the module user having to know	837	Both blocking examples work without the module user having to know
642	anything about events.	838	anything about events.
643		839
644	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:
645		841
646	use Event;	842	use EV;
647		843
648	$fcp->txn_client_get ($url)->cb (sub {	844	$fcp->txn_client_get ($url)->cb (sub {
649	my $txn = shift;	845	my $txn = shift;
650	my $data = $txn->result;	846	my $data = $txn->result;
651	...	847	...
652	});	848	});
653		849
654	Event::loop;	850	EV::loop;
655		851
656	3b. The module user could use AnyEvent, too:	852	3b. The module user could use AnyEvent, too:
657		853
658	use AnyEvent;	854	use AnyEvent;
659		855
…		…
664	$quit->broadcast;	860	$quit->broadcast;
665	});	861	});
666		862
667	$quit->wait;	863	$quit->wait;
668		864
		865
		866	=head1 BENCHMARK
		867
		868	To give you an idea of the performance and overheads that AnyEvent adds
		869	over the backends directly, here is a benchmark of various supported event
		870	models natively and with anyevent. The benchmark creates a lot of timers
		871	(with a zero timeout) and io events (watching STDOUT, a pty, to become
		872	writable), lets them fire exactly once and destroys them again.
		873
		874	Explanation of the fields:
		875
		876	I<watcher> is the number of event watchers created/destroyed. Sicne
		877	different event models have vastly different performance each backend was
		878	handed a number of watchers so that overall runtime is acceptable and
		879	similar to all backends (and keep them from crashing).
		880
		881	I<bytes> is the number of bytes (as measured by resident set size) used by
		882	each watcher.
		883
		884	I<create> is the time, in microseconds, to create a single watcher.
		885
		886	I<invoke> is the time, in microseconds, used to invoke a simple callback
		887	that simply counts down.
		888
		889	I<destroy> is the time, in microseconds, to destroy a single watcher.
		890
		891	name watcher bytes create invoke destroy comment
		892	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		893	EV/Any 100000 610 3.52 0.91 0.75
		894	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
		895	Perl/Any 10000 654 4.64 1.22 0.77 pure perl implementation
		896	Event/Event 10000 523 28.05 21.38 5.22 Event native interface
		897	Event/Any 10000 943 34.43 20.48 1.39
		898	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
		899	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
		900	POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select
		901	POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event
		902
		903	Discussion: The benchmark does I<not> bench scalability of the
		904	backend. For example a select-based backend (such as the pureperl one) can
		905	never compete with a backend using epoll. In this benchmark, only a single
		906	filehandle is used.
		907
		908	EV is the sole leader regarding speed and memory use, which are both
		909	maximal/minimal. Even when going through AnyEvent, there is only one event
		910	loop that uses less memory (the Event module natively), and no faster
		911	event model.
		912
		913	The pure perl implementation is hit in a few sweet spots (both the
		914	zero timeout and the use of a single fd hit optimisations in the perl
		915	interpreter and the backend itself), but it shows that it adds very little
		916	overhead in itself. Like any select-based backend it's performance becomes
		917	really bad with lots of file descriptors.
		918
		919	The Event module has a relatively high setup and callback invocation cost,
		920	but overall scores on the third place.
		921
		922	Glib has a little higher memory cost, a bit fster callback invocation and
		923	has a similar speed as Event.
		924
		925	The Tk backend works relatively well, the fact that it crashes with
		926	more than 2000 watchers is a big setback, however, as correctness takes
		927	precedence over speed.
		928
		929	POE, regardless of backend (wether it's pure perl select backend or the
		930	Event backend) shows abysmal performance and memory usage: Watchers use
		931	almost 30 times as much memory as EV watchers, and 10 times as much memory
		932	as both Event or EV via AnyEvent.
		933
		934	Summary: using EV through AnyEvent is faster than any other event
		935	loop. The overhead AnyEvent adds can be very small, and you should avoid
		936	POE like the plague if you want performance or reasonable memory usage.
		937
		938
		939	=head1 FORK
		940
		941	Most event libraries are not fork-safe. The ones who are usually are
		942	because they are so inefficient. Only L<EV> is fully fork-aware.
		943
		944	If you have to fork, you must either do so I<before> creating your first
		945	watcher OR you must not use AnyEvent at all in the child.
		946
		947
		948	=head1 SECURITY CONSIDERATIONS
		949
		950	AnyEvent can be forced to load any event model via
		951	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		952	execute arbitrary code or directly gain access, it can easily be used to
		953	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		954	will not be active when the program uses a different event model than
		955	specified in the variable.
		956
		957	You can make AnyEvent completely ignore this variable by deleting it
		958	before the first watcher gets created, e.g. with a C<BEGIN> block:
		959
		960	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		961
		962	use AnyEvent;
		963
		964
669	=head1 SEE ALSO	965	=head1 SEE ALSO
670		966
671	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	967	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		968	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		969	L<Event::Lib>, L<Qt>, L<POE>.
672		970
		971	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
673	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	972	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		973	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		974	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
674		975
675	Nontrivial usage example: L<Net::FCP>.	976	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
676		977
677	=head1	978
		979	=head1 AUTHOR
		980
		981	Marc Lehmann <schmorp@schmorp.de>
		982	http://home.schmorp.de/
678		983
679	=cut	984	=cut
680		985
681	1	986	1
682		987

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.42 by root, Mon Apr 7 19:40:12 2008 UTC vs. Revision 1.65 by root, Fri Apr 25 06:58:12 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.42 by root, Mon Apr 7 19:40:12 2008 UTC vs.
Revision 1.65 by root, Fri Apr 25 06:58:12 2008 UTC