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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.15 by root, Mon Oct 30 20:55:05 2006 UTC vs.
Revision 1.100 by elmex, Sun Apr 27 19:15:43 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
		71	#TODO#
		72
		73	Net::IRC3
		74	AnyEvent::HTTPD
		75	AnyEvent::DNS
		76	IO::AnyEvent
		77	Net::FPing
		78	Net::XMPP2
		79	Coro
		80
		81	AnyEvent::IRC
		82	AnyEvent::HTTPD
		83	AnyEvent::DNS
		84	AnyEvent::Handle
		85	AnyEvent::Socket
		86	AnyEvent::FPing
		87	AnyEvent::XMPP
		88	AnyEvent::SNMP
		89	Coro
22		90
23	=head1 DESCRIPTION	91	=head1 DESCRIPTION
24		92
25	L<AnyEvent> provides an identical interface to multiple event loops. This	93	L<AnyEvent> provides an identical interface to multiple event loops. This
26	allows module authors to utilise an event loop without forcing module	94	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	95	users to use the same event loop (as only a single event loop can coexist
28	peacefully at any one time).	96	peacefully at any one time).
29		97
30	The interface itself is vaguely similar but not identical to the Event	98	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	99	module.
32		100
33	On the first call of any method, the module tries to detect the currently	101	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	102	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	103	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	104	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
37	order given. The first one that could be successfully loaded will be	105	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	106	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
39	event loop, which is also not very efficient.	107	adaptor should always succeed) in the order given. The first one that can
		108	be successfully loaded will be used. If, after this, still none could be
		109	found, AnyEvent will fall back to a pure-perl event loop, which is not
		110	very efficient, but should work everywhere.
40		111
41	Because AnyEvent first checks for modules that are already loaded, loading	112	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	113	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	114	that model the default. For example:
44		115
45	use Tk;	116	use Tk;
46	use AnyEvent;	117	use AnyEvent;
47		118
48	# .. AnyEvent will likely default to Tk	119	# .. AnyEvent will likely default to Tk
		120
		121	The I<likely> means that, if any module loads another event model and
		122	starts using it, all bets are off. Maybe you should tell their authors to
		123	use AnyEvent so their modules work together with others seamlessly...
49		124
50	The pure-perl implementation of AnyEvent is called	125	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	126	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	127	explicitly.
53		128
…		…
56	AnyEvent has the central concept of a I<watcher>, which is an object that	131	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	132	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	133	the callback to call, the filehandle to watch, etc.
59		134
60	These watchers are normal Perl objects with normal Perl lifetime. After	135	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	136	creating a watcher it will immediately "watch" for events and invoke the
		137	callback when the event occurs (of course, only when the event model
		138	is in control).
		139
62	the callback. To disable the watcher you have to destroy it (e.g. by	140	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	141	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	142	to it).
65		143
66	All watchers are created by calling a method on the C<AnyEvent> class.	144	All watchers are created by calling a method on the C<AnyEvent> class.
67		145
		146	Many watchers either are used with "recursion" (repeating timers for
		147	example), or need to refer to their watcher object in other ways.
		148
		149	An any way to achieve that is this pattern:
		150
		151	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		152	# you can use $w here, for example to undef it
		153	undef $w;
		154	});
		155
		156	Note that C<my $w; $w => combination. This is necessary because in Perl,
		157	my variables are only visible after the statement in which they are
		158	declared.
		159
68	=head2 IO WATCHERS	160	=head2 I/O WATCHERS
69		161
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	162	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	163	with the following mandatory key-value pairs as arguments:
72		164
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	165	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	166	for events. C<poll> must be a string that is either C<r> or C<w>,
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback	167	which creates a watcher waiting for "r"eadable or "w"ritable events,
76	to invoke everytime the filehandle becomes ready.	168	respectively. C<cb> is the callback to invoke each time the file handle
		169	becomes ready.
77		170
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	171	Although the callback might get passed parameters, their value and
79	a socket you can have one r + one w, not any more (limitation comes from	172	presence is undefined and you cannot rely on them. Portable AnyEvent
80	Tk - if you are sure you are not using Tk this limitation is gone).	173	callbacks cannot use arguments passed to I/O watcher callbacks.
81		174
82	Filehandles will be kept alive, so as long as the watcher exists, the	175	The I/O watcher might use the underlying file descriptor or a copy of it.
83	filehandle exists, too.	176	You must not close a file handle as long as any watcher is active on the
		177	underlying file descriptor.
		178
		179	Some event loops issue spurious readyness notifications, so you should
		180	always use non-blocking calls when reading/writing from/to your file
		181	handles.
84		182
85	Example:	183	Example:
86		184
87	# wait for readability of STDIN, then read a line and disable the watcher	185	# 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 {	186	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	187	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	188	warn "read: $input\n";
91	undef $w;	189	undef $w;
92	});	190	});
93		191
94	=head2 TIMER WATCHERS	192	=head2 TIME WATCHERS
95		193
96	You can create a timer watcher by calling the C<< AnyEvent->timer >>	194	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	195	method with the following mandatory arguments:
98		196
99	C<after> after how many seconds (fractions are supported) should the timer	197	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	198	supported) the callback should be invoked. C<cb> is the callback to invoke
		199	in that case.
		200
		201	Although the callback might get passed parameters, their value and
		202	presence is undefined and you cannot rely on them. Portable AnyEvent
		203	callbacks cannot use arguments passed to time watcher callbacks.
101		204
102	The timer callback will be invoked at most once: if you want a repeating	205	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	206	timer you have to create a new watcher (this is a limitation by both Tk
104	and Glib).	207	and Glib).
105		208
…		…
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	212	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	213	warn "timeout\n";
111	});	214	});
112		215
113	# to cancel the timer:	216	# to cancel the timer:
114	undef $w	217	undef $w;
115		218
		219	Example 2:
		220
		221	# fire an event after 0.5 seconds, then roughly every second
		222	my $w;
		223
		224	my $cb = sub {
		225	# cancel the old timer while creating a new one
		226	$w = AnyEvent->timer (after => 1, cb => $cb);
		227	};
		228
		229	# start the "loop" by creating the first watcher
		230	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		231
		232	=head3 TIMING ISSUES
		233
		234	There are two ways to handle timers: based on real time (relative, "fire
		235	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		236	o'clock").
		237
		238	While most event loops expect timers to specified in a relative way, they
		239	use absolute time internally. This makes a difference when your clock
		240	"jumps", for example, when ntp decides to set your clock backwards from
		241	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		242	fire "after" a second might actually take six years to finally fire.
		243
		244	AnyEvent cannot compensate for this. The only event loop that is conscious
		245	about these issues is L<EV>, which offers both relative (ev_timer, based
		246	on true relative time) and absolute (ev_periodic, based on wallclock time)
		247	timers.
		248
		249	AnyEvent always prefers relative timers, if available, matching the
		250	AnyEvent API.
		251
		252	=head2 SIGNAL WATCHERS
		253
		254	You can watch for signals using a signal watcher, C<signal> is the signal
		255	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		256	be invoked whenever a signal occurs.
		257
		258	Although the callback might get passed parameters, their value and
		259	presence is undefined and you cannot rely on them. Portable AnyEvent
		260	callbacks cannot use arguments passed to signal watcher callbacks.
		261
		262	Multiple signal occurances can be clumped together into one callback
		263	invocation, and callback invocation will be synchronous. synchronous means
		264	that it might take a while until the signal gets handled by the process,
		265	but it is guarenteed not to interrupt any other callbacks.
		266
		267	The main advantage of using these watchers is that you can share a signal
		268	between multiple watchers.
		269
		270	This watcher might use C<%SIG>, so programs overwriting those signals
		271	directly will likely not work correctly.
		272
		273	Example: exit on SIGINT
		274
		275	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		276
		277	=head2 CHILD PROCESS WATCHERS
		278
		279	You can also watch on a child process exit and catch its exit status.
		280
		281	The child process is specified by the C<pid> argument (if set to C<0>, it
		282	watches for any child process exit). The watcher will trigger as often
		283	as status change for the child are received. This works by installing a
		284	signal handler for C<SIGCHLD>. The callback will be called with the pid
		285	and exit status (as returned by waitpid), so unlike other watcher types,
		286	you I<can> rely on child watcher callback arguments.
		287
		288	There is a slight catch to child watchers, however: you usually start them
		289	I<after> the child process was created, and this means the process could
		290	have exited already (and no SIGCHLD will be sent anymore).
		291
		292	Not all event models handle this correctly (POE doesn't), but even for
		293	event models that I<do> handle this correctly, they usually need to be
		294	loaded before the process exits (i.e. before you fork in the first place).
		295
		296	This means you cannot create a child watcher as the very first thing in an
		297	AnyEvent program, you I<have> to create at least one watcher before you
		298	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		299
		300	Example: fork a process and wait for it
		301
		302	my $done = AnyEvent->condvar;
		303
		304	AnyEvent::detect; # force event module to be initialised
		305
		306	my $pid = fork or exit 5;
		307
		308	my $w = AnyEvent->child (
		309	pid => $pid,
		310	cb => sub {
		311	my ($pid, $status) = @_;
		312	warn "pid $pid exited with status $status";
		313	$done->broadcast;
		314	},
		315	);
		316
		317	# do something else, then wait for process exit
		318	$done->wait;
		319
116	=head2 CONDITION WATCHERS	320	=head2 CONDITION VARIABLES
117		321
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	322	Condition variables can be created by calling the C<< AnyEvent->condvar >>
119	method without any arguments.	323	method without any arguments.
120		324
121	A condition watcher watches for a condition - precisely that the C<<	325	A condition variable waits for a condition - precisely that the C<<
122	->broadcast >> method has been called.	326	->broadcast >> method has been called.
123		327
124	The watcher has only two methods:	328	They are very useful to signal that a condition has been fulfilled, for
		329	example, if you write a module that does asynchronous http requests,
		330	then a condition variable would be the ideal candidate to signal the
		331	availability of results.
		332
		333	You can also use condition variables to block your main program until
		334	an event occurs - for example, you could C<< ->wait >> in your main
		335	program until the user clicks the Quit button in your app, which would C<<
		336	->broadcast >> the "quit" event.
		337
		338	Note that condition variables recurse into the event loop - if you have
		339	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		340	lose. Therefore, condition variables are good to export to your caller, but
		341	you should avoid making a blocking wait yourself, at least in callbacks,
		342	as this asks for trouble.
		343
		344	This object has two methods:
125		345
126	=over 4	346	=over 4
127		347
128	=item $cv->wait	348	=item $cv->wait
129		349
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	350	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
131	called on c<$cv>, while servicing other watchers normally.	351	called on c<$cv>, while servicing other watchers normally.
132		352
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	353	You can only wait once on a condition - additional calls will return
141	immediately.	354	immediately.
142		355
		356	Not all event models support a blocking wait - some die in that case
		357	(programs might want to do that to stay interactive), so I<if you are
		358	using this from a module, never require a blocking wait>, but let the
		359	caller decide whether the call will block or not (for example, by coupling
		360	condition variables with some kind of request results and supporting
		361	callbacks so the caller knows that getting the result will not block,
		362	while still suppporting blocking waits if the caller so desires).
		363
		364	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		365	sensibly have two C<< ->wait >>'s in parallel, as that would require
		366	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		367	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		368	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		369	from different coroutines, however).
		370
143	=item $cv->broadcast	371	=item $cv->broadcast
144		372
145	Flag the condition as ready - a running C<< ->wait >> and all further	373	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	374	calls to C<wait> will (eventually) return after this method has been
147	is waiting the broadcast will be remembered..	375	called. If nobody is waiting the broadcast will be remembered..
		376
		377	=back
148		378
149	Example:	379	Example:
150		380
151	# wait till the result is ready	381	# wait till the result is ready
152	my $result_ready = AnyEvent->condvar;	382	my $result_ready = AnyEvent->condvar;
153		383
154	# do something such as adding a timer	384	# do something such as adding a timer
155	# or socket watcher the calls $result_ready->broadcast	385	# or socket watcher the calls $result_ready->broadcast
156	# when the "result" is ready.	386	# when the "result" is ready.
		387	# in this case, we simply use a timer:
		388	my $w = AnyEvent->timer (
		389	after => 1,
		390	cb => sub { $result_ready->broadcast },
		391	);
157		392
		393	# this "blocks" (while handling events) till the watcher
		394	# calls broadcast
158	$result_ready->wait;	395	$result_ready->wait;
159		396
		397	=head1 GLOBAL VARIABLES AND FUNCTIONS
		398
		399	=over 4
		400
		401	=item $AnyEvent::MODEL
		402
		403	Contains C<undef> until the first watcher is being created. Then it
		404	contains the event model that is being used, which is the name of the
		405	Perl class implementing the model. This class is usually one of the
		406	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
		407	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
		408
		409	The known classes so far are:
		410
		411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
		414	AnyEvent::Impl::Event based on Event, second best choice.
		415	AnyEvent::Impl::Glib based on Glib, third-best choice.
		416	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		417	AnyEvent::Impl::Tk based on Tk, very bad choice.
		418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		420	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		421
		422	There is no support for WxWidgets, as WxWidgets has no support for
		423	watching file handles. However, you can use WxWidgets through the
		424	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		425	second, which was considered to be too horrible to even consider for
		426	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		427	it's adaptor.
		428
		429	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		430	autodetecting them.
		431
		432	=item AnyEvent::detect
		433
		434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
		435	if necessary. You should only call this function right before you would
		436	have created an AnyEvent watcher anyway, that is, as late as possible at
		437	runtime.
		438
160	=back	439	=back
161		440
162	=head1 WHAT TO DO IN A MODULE	441	=head1 WHAT TO DO IN A MODULE
163		442
164	As a module author, you should "use AnyEvent" and call AnyEvent methods	443	As a module author, you should C<use AnyEvent> and call AnyEvent methods
165	freely, but you should not load a specific event module or rely on it.	444	freely, but you should not load a specific event module or rely on it.
166		445
167	Be careful when you create watchers in the module body - Anyevent will	446	Be careful when you create watchers in the module body - AnyEvent will
168	decide which event module to use as soon as the first method is called, so	447	decide which event module to use as soon as the first method is called, so
169	by calling AnyEvent in your module body you force the user of your module	448	by calling AnyEvent in your module body you force the user of your module
170	to load the event module first.	449	to load the event module first.
171		450
		451	Never call C<< ->wait >> on a condition variable unless you I<know> that
		452	the C<< ->broadcast >> method has been called on it already. This is
		453	because it will stall the whole program, and the whole point of using
		454	events is to stay interactive.
		455
		456	It is fine, however, to call C<< ->wait >> when the user of your module
		457	requests it (i.e. if you create a http request object ad have a method
		458	called C<results> that returns the results, it should call C<< ->wait >>
		459	freely, as the user of your module knows what she is doing. always).
		460
172	=head1 WHAT TO DO IN THE MAIN PROGRAM	461	=head1 WHAT TO DO IN THE MAIN PROGRAM
173		462
174	There will always be a single main program - the only place that should	463	There will always be a single main program - the only place that should
175	dictate which event model to use.	464	dictate which event model to use.
176		465
177	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	466	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
178	do anything special and let AnyEvent decide which implementation to chose.	467	do anything special (it does not need to be event-based) and let AnyEvent
		468	decide which implementation to chose if some module relies on it.
179		469
180	If the main program relies on a specific event model (for example, in Gtk2	470	If the main program relies on a specific event model. For example, in
181	programs you have to rely on either Glib or Glib::Event), you should load	471	Gtk2 programs you have to rely on the Glib module. You should load the
182	it before loading AnyEvent or any module that uses it, generally, as early	472	event module before loading AnyEvent or any module that uses it: generally
183	as possible. The reason is that modules might create watchers when they	473	speaking, you should load it as early as possible. The reason is that
184	are loaded, and AnyEvent will decide on the event model to use as soon as	474	modules might create watchers when they are loaded, and AnyEvent will
185	it creates watchers, and it might chose the wrong one unless you load the	475	decide on the event model to use as soon as it creates watchers, and it
186	correct one yourself.	476	might chose the wrong one unless you load the correct one yourself.
187		477
188	You can chose to use a rather inefficient pure-perl implementation by	478	You can chose to use a rather inefficient pure-perl implementation by
189	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
190	generally better.	480	behaviour everywhere, but letting AnyEvent chose is generally better.
		481
		482	=head1 OTHER MODULES
		483
		484	L<AnyEvent> itself comes with useful utility modules:
		485
		486	To make it easier to do non-blocking IO the modules L<AnyEvent::Handle>
		487	and L<AnyEvent::Socket> are provided. L<AnyEvent::Handle> provides
		488	read and write buffers and manages watchers for reads and writes.
		489	L<AnyEvent::Socket> provides means to do non-blocking connects.
		490
		491	Aside from those there are these modules that support AnyEvent (and use it
		492	for non-blocking IO):
		493
		494	=over 4
		495
		496	=item L<AnyEvent::FastPing>
		497
		498	=item L<Net::IRC3>
		499
		500	=item L<Net::XMPP2>
		501
		502	=back
191		503
192	=cut	504	=cut
193		505
194	package AnyEvent;	506	package AnyEvent;
195		507
196	no warnings;	508	no warnings;
197	use strict 'vars';	509	use strict;
		510
198	use Carp;	511	use Carp;
199		512
200	our $VERSION = '2.0';	513	our $VERSION = '3.3';
201	our $MODEL;	514	our $MODEL;
202		515
203	our $AUTOLOAD;	516	our $AUTOLOAD;
204	our @ISA;	517	our @ISA;
205		518
206	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	519	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
207		520
208	our @REGISTRY;	521	our @REGISTRY;
209		522
210	my @models = (	523	my @models = (
		524	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
211	[Coro::Event:: => AnyEvent::Impl::Coro::],	525	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
		526	[EV:: => AnyEvent::Impl::EV::],
212	[Event:: => AnyEvent::Impl::Event::],	527	[Event:: => AnyEvent::Impl::Event::],
213	[Glib:: => AnyEvent::Impl::Glib::],	528	[Glib:: => AnyEvent::Impl::Glib::],
214	[Tk:: => AnyEvent::Impl::Tk::],	529	[Tk:: => AnyEvent::Impl::Tk::],
		530	[Wx:: => AnyEvent::Impl::POE::],
		531	[Prima:: => AnyEvent::Impl::POE::],
215	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	532	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		533	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		534	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		535	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		536	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
216	);	537	);
217		538
218	our %method = map +($_ => 1), qw(io timer condvar broadcast wait DESTROY);	539	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
219		540
220	sub AUTOLOAD {	541	sub detect() {
221	$AUTOLOAD =~ s/.*://;
222
223	$method{$AUTOLOAD}
224	or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
225
226	unless ($MODEL) {	542	unless ($MODEL) {
		543	no strict 'refs';
		544
		545	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		546	my $model = "AnyEvent::Impl::$1";
		547	if (eval "require $model") {
		548	$MODEL = $model;
		549	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		550	} else {
		551	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		552	}
		553	}
		554
227	# check for already loaded models	555	# check for already loaded models
		556	unless ($MODEL) {
228	for (@REGISTRY, @models) {	557	for (@REGISTRY, @models) {
229	my ($package, $model) = @$_;	558	my ($package, $model) = @$_;
230	if (${"$package\::VERSION"} > 0) {	559	if (${"$package\::VERSION"} > 0) {
231	if (eval "require $model") {	560	if (eval "require $model") {
232	$MODEL = $model;	561	$MODEL = $model;
233	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	562	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
234	last;	563	last;
		564	}
235	}	565	}
236	}	566	}
		567
		568	unless ($MODEL) {
		569	# try to load a model
		570
		571	for (@REGISTRY, @models) {
		572	my ($package, $model) = @$_;
		573	if (eval "require $package"
		574	and ${"$package\::VERSION"} > 0
		575	and eval "require $model") {
		576	$MODEL = $model;
		577	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		578	last;
		579	}
		580	}
		581
		582	$MODEL
		583	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";
		584	}
237	}	585	}
238		586
239	unless ($MODEL) {	587	unshift @ISA, $MODEL;
240	# try to load a model	588	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
241
242	for (@REGISTRY, @models) {
243	my ($package, $model) = @$_;
244	if (eval "require $model") {
245	$MODEL = $model;
246	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
247	last;
248	}
249	}
250
251	$MODEL
252	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk.";
253	}
254	}	589	}
255		590
256	@ISA = $MODEL;	591	$MODEL
		592	}
		593
		594	sub AUTOLOAD {
		595	(my $func = $AUTOLOAD) =~ s/.*://;
		596
		597	$method{$func}
		598	or croak "$func: not a valid method for AnyEvent objects";
		599
		600	detect unless $MODEL;
257		601
258	my $class = shift;	602	my $class = shift;
259	$class->$AUTOLOAD (@_);	603	$class->$func (@_);
260	}	604	}
261		605
		606	package AnyEvent::Base;
		607
		608	# default implementation for ->condvar, ->wait, ->broadcast
		609
		610	sub condvar {
		611	bless \my $flag, "AnyEvent::Base::CondVar"
		612	}
		613
		614	sub AnyEvent::Base::CondVar::broadcast {
		615	${$_[0]}++;
		616	}
		617
		618	sub AnyEvent::Base::CondVar::wait {
		619	AnyEvent->one_event while !${$_[0]};
		620	}
		621
		622	# default implementation for ->signal
		623
		624	our %SIG_CB;
		625
		626	sub signal {
		627	my (undef, %arg) = @_;
		628
		629	my $signal = uc $arg{signal}
		630	or Carp::croak "required option 'signal' is missing";
		631
		632	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		633	$SIG{$signal} \|\|= sub {
		634	$_->() for values %{ $SIG_CB{$signal} \|\| {} };
		635	};
		636
		637	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
		638	}
		639
		640	sub AnyEvent::Base::Signal::DESTROY {
		641	my ($signal, $cb) = @{$_[0]};
		642
		643	delete $SIG_CB{$signal}{$cb};
		644
		645	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
		646	}
		647
		648	# default implementation for ->child
		649
		650	our %PID_CB;
		651	our $CHLD_W;
		652	our $CHLD_DELAY_W;
		653	our $PID_IDLE;
		654	our $WNOHANG;
		655
		656	sub _child_wait {
		657	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		658	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		659	(values %{ $PID_CB{0} \|\| {} });
		660	}
		661
		662	undef $PID_IDLE;
		663	}
		664
		665	sub _sigchld {
		666	# make sure we deliver these changes "synchronous" with the event loop.
		667	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		668	undef $CHLD_DELAY_W;
		669	&_child_wait;
		670	});
		671	}
		672
		673	sub child {
		674	my (undef, %arg) = @_;
		675
		676	defined (my $pid = $arg{pid} + 0)
		677	or Carp::croak "required option 'pid' is missing";
		678
		679	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
		680
		681	unless ($WNOHANG) {
		682	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
		683	}
		684
		685	unless ($CHLD_W) {
		686	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
		687	# child could be a zombie already, so make at least one round
		688	&_sigchld;
		689	}
		690
		691	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
		692	}
		693
		694	sub AnyEvent::Base::Child::DESTROY {
		695	my ($pid, $cb) = @{$_[0]};
		696
		697	delete $PID_CB{$pid}{$cb};
		698	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		699
		700	undef $CHLD_W unless keys %PID_CB;
		701	}
		702
262	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	703	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		704
		705	This is an advanced topic that you do not normally need to use AnyEvent in
		706	a module. This section is only of use to event loop authors who want to
		707	provide AnyEvent compatibility.
263		708
264	If you need to support another event library which isn't directly	709	If you need to support another event library which isn't directly
265	supported by AnyEvent, you can supply your own interface to it by	710	supported by AnyEvent, you can supply your own interface to it by
266	pushing, before the first watcher gets created, the package name of	711	pushing, before the first watcher gets created, the package name of
267	the event module and the package name of the interface to use onto	712	the event module and the package name of the interface to use onto
268	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	713	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
269	AnyEvent.	714	AnyEvent, so it is reasonably cheap.
270		715
271	Example:	716	Example:
272		717
273	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	718	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
274		719
275	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	720	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
276	package/class when it finds the C<urxvt> package/module is loaded. When	721	package/class when it finds the C<urxvt> package/module is already loaded.
		722
277	AnyEvent is loaded and asked to find a suitable event model, it will	723	When AnyEvent is loaded and asked to find a suitable event model, it
278	first check for the presence of urxvt.	724	will first check for the presence of urxvt by trying to C<use> the
		725	C<urxvt::anyevent> module.
279		726
280	The class should prove implementations for all watcher types (see	727	The class should provide implementations for all watcher types. See
281	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	728	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
282	(Source code) and so on for actual examples, use C<perldoc -m	729	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
283	AnyEvent::Impl::Glib> to see the sources).	730	see the sources.
284		731
		732	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		733	provide suitable (hopefully) replacements.
		734
285	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	735	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
286	uses the above line as-is. An interface isn't included in AnyEvent	736	terminal emulator uses the above line as-is. An interface isn't included
287	because it doesn't make sense outside the embedded interpreter inside	737	in AnyEvent because it doesn't make sense outside the embedded interpreter
288	I<rxvt-unicode>, and it is updated and maintained as part of the	738	inside I<rxvt-unicode>, and it is updated and maintained as part of the
289	I<rxvt-unicode> distribution.	739	I<rxvt-unicode> distribution.
290		740
291	I<rxvt-unicode> also cheats a bit by not providing blocking access to	741	I<rxvt-unicode> also cheats a bit by not providing blocking access to
292	condition variables: code blocking while waiting for a condition will	742	condition variables: code blocking while waiting for a condition will
293	C<die>. This still works with most modules/usages, and blocking calls must	743	C<die>. This still works with most modules/usages, and blocking calls must
294	not be in an interactive appliation, so it makes sense.	744	not be done in an interactive application, so it makes sense.
295		745
296	=head1 ENVIRONMENT VARIABLES	746	=head1 ENVIRONMENT VARIABLES
297		747
298	The following environment variables are used by this module:	748	The following environment variables are used by this module:
299		749
300	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event	750	=over 4
301	model gets used.
302		751
		752	=item C<PERL_ANYEVENT_VERBOSE>
		753
		754	By default, AnyEvent will be completely silent except in fatal
		755	conditions. You can set this environment variable to make AnyEvent more
		756	talkative.
		757
		758	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		759	conditions, such as not being able to load the event model specified by
		760	C<PERL_ANYEVENT_MODEL>.
		761
		762	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		763	model it chooses.
		764
		765	=item C<PERL_ANYEVENT_MODEL>
		766
		767	This can be used to specify the event model to be used by AnyEvent, before
		768	autodetection and -probing kicks in. It must be a string consisting
		769	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		770	and the resulting module name is loaded and if the load was successful,
		771	used as event model. If it fails to load AnyEvent will proceed with
		772	autodetection and -probing.
		773
		774	This functionality might change in future versions.
		775
		776	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		777	could start your program like this:
		778
		779	PERL_ANYEVENT_MODEL=Perl perl ...
		780
		781	=back
		782
303	=head1 EXAMPLE	783	=head1 EXAMPLE PROGRAM
304		784
305	The following program uses an io watcher to read data from stdin, a timer	785	The following program uses an I/O watcher to read data from STDIN, a timer
306	to display a message once per second, and a condvar to exit the program	786	to display a message once per second, and a condition variable to quit the
307	when the user enters quit:	787	program when the user enters quit:
308		788
309	use AnyEvent;	789	use AnyEvent;
310		790
311	my $cv = AnyEvent->condvar;	791	my $cv = AnyEvent->condvar;
312		792
313	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	793	my $io_watcher = AnyEvent->io (
		794	fh => \*STDIN,
		795	poll => 'r',
		796	cb => sub {
314	warn "io event <$_[0]>\n"; # will always output <r>	797	warn "io event <$_[0]>\n"; # will always output <r>
315	chomp (my $input = <STDIN>); # read a line	798	chomp (my $input = <STDIN>); # read a line
316	warn "read: $input\n"; # output what has been read	799	warn "read: $input\n"; # output what has been read
317	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	800	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		801	},
318	});	802	);
319		803
320	my $time_watcher; # can only be used once	804	my $time_watcher; # can only be used once
321		805
322	sub new_timer {	806	sub new_timer {
323	$timer = AnyEvent->timer (after => 1, cb => sub {	807	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
405	$txn->{finished}->wait;	889	$txn->{finished}->wait;
406	return $txn->{result};	890	return $txn->{result};
407		891
408	The actual code goes further and collects all errors (C<die>s, exceptions)	892	The actual code goes further and collects all errors (C<die>s, exceptions)
409	that occured during request processing. The C<result> method detects	893	that occured during request processing. The C<result> method detects
410	wether an exception as thrown (it is stored inside the $txn object)	894	whether an exception as thrown (it is stored inside the $txn object)
411	and just throws the exception, which means connection errors and other	895	and just throws the exception, which means connection errors and other
412	problems get reported tot he code that tries to use the result, not in a	896	problems get reported tot he code that tries to use the result, not in a
413	random callback.	897	random callback.
414		898
415	All of this enables the following usage styles:	899	All of this enables the following usage styles:
416		900
417	1. Blocking:	901	1. Blocking:
418		902
419	my $data = $fcp->client_get ($url);	903	my $data = $fcp->client_get ($url);
420		904
421	2. Blocking, but parallelizing:	905	2. Blocking, but running in parallel:
422		906
423	my @datas = map $_->result,	907	my @datas = map $_->result,
424	map $fcp->txn_client_get ($_),	908	map $fcp->txn_client_get ($_),
425	@urls;	909	@urls;
426		910
427	Both blocking examples work without the module user having to know	911	Both blocking examples work without the module user having to know
428	anything about events.	912	anything about events.
429		913
430	3a. Event-based in a main program, using any support Event module:	914	3a. Event-based in a main program, using any supported event module:
431		915
432	use Event;	916	use EV;
433		917
434	$fcp->txn_client_get ($url)->cb (sub {	918	$fcp->txn_client_get ($url)->cb (sub {
435	my $txn = shift;	919	my $txn = shift;
436	my $data = $txn->result;	920	my $data = $txn->result;
437	...	921	...
438	});	922	});
439		923
440	Event::loop;	924	EV::loop;
441		925
442	3b. The module user could use AnyEvent, too:	926	3b. The module user could use AnyEvent, too:
443		927
444	use AnyEvent;	928	use AnyEvent;
445		929
…		…
450	$quit->broadcast;	934	$quit->broadcast;
451	});	935	});
452		936
453	$quit->wait;	937	$quit->wait;
454		938
		939
		940	=head1 BENCHMARKS
		941
		942	To give you an idea of the performance and overheads that AnyEvent adds
		943	over the event loops themselves and to give you an impression of the speed
		944	of various event loops I prepared some benchmarks.
		945
		946	=head2 BENCHMARKING ANYEVENT OVERHEAD
		947
		948	Here is a benchmark of various supported event models used natively and
		949	through anyevent. The benchmark creates a lot of timers (with a zero
		950	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		951	which it is), lets them fire exactly once and destroys them again.
		952
		953	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		954	distribution.
		955
		956	=head3 Explanation of the columns
		957
		958	I<watcher> is the number of event watchers created/destroyed. Since
		959	different event models feature vastly different performances, each event
		960	loop was given a number of watchers so that overall runtime is acceptable
		961	and similar between tested event loop (and keep them from crashing): Glib
		962	would probably take thousands of years if asked to process the same number
		963	of watchers as EV in this benchmark.
		964
		965	I<bytes> is the number of bytes (as measured by the resident set size,
		966	RSS) consumed by each watcher. This method of measuring captures both C
		967	and Perl-based overheads.
		968
		969	I<create> is the time, in microseconds (millionths of seconds), that it
		970	takes to create a single watcher. The callback is a closure shared between
		971	all watchers, to avoid adding memory overhead. That means closure creation
		972	and memory usage is not included in the figures.
		973
		974	I<invoke> is the time, in microseconds, used to invoke a simple
		975	callback. The callback simply counts down a Perl variable and after it was
		976	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		977	signal the end of this phase.
		978
		979	I<destroy> is the time, in microseconds, that it takes to destroy a single
		980	watcher.
		981
		982	=head3 Results
		983
		984	name watchers bytes create invoke destroy comment
		985	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		986	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		987	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		988	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		989	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		990	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		991	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		992	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		993	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		994	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		995
		996	=head3 Discussion
		997
		998	The benchmark does I<not> measure scalability of the event loop very
		999	well. For example, a select-based event loop (such as the pure perl one)
		1000	can never compete with an event loop that uses epoll when the number of
		1001	file descriptors grows high. In this benchmark, all events become ready at
		1002	the same time, so select/poll-based implementations get an unnatural speed
		1003	boost.
		1004
		1005	Also, note that the number of watchers usually has a nonlinear effect on
		1006	overall speed, that is, creating twice as many watchers doesn't take twice
		1007	the time - usually it takes longer. This puts event loops tested with a
		1008	higher number of watchers at a disadvantage.
		1009
		1010	To put the range of results into perspective, consider that on the
		1011	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1012	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1013	cycles with POE.
		1014
		1015	C<EV> is the sole leader regarding speed and memory use, which are both
		1016	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1017	far less memory than any other event loop and is still faster than Event
		1018	natively.
		1019
		1020	The pure perl implementation is hit in a few sweet spots (both the
		1021	constant timeout and the use of a single fd hit optimisations in the perl
		1022	interpreter and the backend itself). Nevertheless this shows that it
		1023	adds very little overhead in itself. Like any select-based backend its
		1024	performance becomes really bad with lots of file descriptors (and few of
		1025	them active), of course, but this was not subject of this benchmark.
		1026
		1027	The C<Event> module has a relatively high setup and callback invocation
		1028	cost, but overall scores in on the third place.
		1029
		1030	C<Glib>'s memory usage is quite a bit higher, but it features a
		1031	faster callback invocation and overall ends up in the same class as
		1032	C<Event>. However, Glib scales extremely badly, doubling the number of
		1033	watchers increases the processing time by more than a factor of four,
		1034	making it completely unusable when using larger numbers of watchers
		1035	(note that only a single file descriptor was used in the benchmark, so
		1036	inefficiencies of C<poll> do not account for this).
		1037
		1038	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1039	more than 2000 watchers is a big setback, however, as correctness takes
		1040	precedence over speed. Nevertheless, its performance is surprising, as the
		1041	file descriptor is dup()ed for each watcher. This shows that the dup()
		1042	employed by some adaptors is not a big performance issue (it does incur a
		1043	hidden memory cost inside the kernel which is not reflected in the figures
		1044	above).
		1045
		1046	C<POE>, regardless of underlying event loop (whether using its pure
		1047	perl select-based backend or the Event module, the POE-EV backend
		1048	couldn't be tested because it wasn't working) shows abysmal performance
		1049	and memory usage: Watchers use almost 30 times as much memory as
		1050	EV watchers, and 10 times as much memory as Event (the high memory
		1051	requirements are caused by requiring a session for each watcher). Watcher
		1052	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1053	implementation. The design of the POE adaptor class in AnyEvent can not
		1054	really account for this, as session creation overhead is small compared
		1055	to execution of the state machine, which is coded pretty optimally within
		1056	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		1057
		1058	=head3 Summary
		1059
		1060	=over 4
		1061
		1062	=item * Using EV through AnyEvent is faster than any other event loop
		1063	(even when used without AnyEvent), but most event loops have acceptable
		1064	performance with or without AnyEvent.
		1065
		1066	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1067	the actual event loop, only with extremely fast event loops such as EV
		1068	adds AnyEvent significant overhead.
		1069
		1070	=item * You should avoid POE like the plague if you want performance or
		1071	reasonable memory usage.
		1072
		1073	=back
		1074
		1075	=head2 BENCHMARKING THE LARGE SERVER CASE
		1076
		1077	This benchmark atcually benchmarks the event loop itself. It works by
		1078	creating a number of "servers": each server consists of a socketpair, a
		1079	timeout watcher that gets reset on activity (but never fires), and an I/O
		1080	watcher waiting for input on one side of the socket. Each time the socket
		1081	watcher reads a byte it will write that byte to a random other "server".
		1082
		1083	The effect is that there will be a lot of I/O watchers, only part of which
		1084	are active at any one point (so there is a constant number of active
		1085	fds for each loop iterstaion, but which fds these are is random). The
		1086	timeout is reset each time something is read because that reflects how
		1087	most timeouts work (and puts extra pressure on the event loops).
		1088
		1089	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1090	(1%) are active. This mirrors the activity of large servers with many
		1091	connections, most of which are idle at any one point in time.
		1092
		1093	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1094	distribution.
		1095
		1096	=head3 Explanation of the columns
		1097
		1098	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1099	each server has a read and write socket end).
		1100
		1101	I<create> is the time it takes to create a socketpair (which is
		1102	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1103
		1104	I<request>, the most important value, is the time it takes to handle a
		1105	single "request", that is, reading the token from the pipe and forwarding
		1106	it to another server. This includes deleting the old timeout and creating
		1107	a new one that moves the timeout into the future.
		1108
		1109	=head3 Results
		1110
		1111	name sockets create request
		1112	EV 20000 69.01 11.16
		1113	Perl 20000 73.32 35.87
		1114	Event 20000 212.62 257.32
		1115	Glib 20000 651.16 1896.30
		1116	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1117
		1118	=head3 Discussion
		1119
		1120	This benchmark I<does> measure scalability and overall performance of the
		1121	particular event loop.
		1122
		1123	EV is again fastest. Since it is using epoll on my system, the setup time
		1124	is relatively high, though.
		1125
		1126	Perl surprisingly comes second. It is much faster than the C-based event
		1127	loops Event and Glib.
		1128
		1129	Event suffers from high setup time as well (look at its code and you will
		1130	understand why). Callback invocation also has a high overhead compared to
		1131	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1132	uses select or poll in basically all documented configurations.
		1133
		1134	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1135	clearly fails to perform with many filehandles or in busy servers.
		1136
		1137	POE is still completely out of the picture, taking over 1000 times as long
		1138	as EV, and over 100 times as long as the Perl implementation, even though
		1139	it uses a C-based event loop in this case.
		1140
		1141	=head3 Summary
		1142
		1143	=over 4
		1144
		1145	=item * The pure perl implementation performs extremely well, considering
		1146	that it uses select.
		1147
		1148	=item * Avoid Glib or POE in large projects where performance matters.
		1149
		1150	=back
		1151
		1152	=head2 BENCHMARKING SMALL SERVERS
		1153
		1154	While event loops should scale (and select-based ones do not...) even to
		1155	large servers, most programs we (or I :) actually write have only a few
		1156	I/O watchers.
		1157
		1158	In this benchmark, I use the same benchmark program as in the large server
		1159	case, but it uses only eight "servers", of which three are active at any
		1160	one time. This should reflect performance for a small server relatively
		1161	well.
		1162
		1163	The columns are identical to the previous table.
		1164
		1165	=head3 Results
		1166
		1167	name sockets create request
		1168	EV 16 20.00 6.54
		1169	Perl 16 25.75 12.62
		1170	Event 16 81.27 35.86
		1171	Glib 16 32.63 15.48
		1172	POE 16 261.87 276.28 uses POE::Loop::Event
		1173
		1174	=head3 Discussion
		1175
		1176	The benchmark tries to test the performance of a typical small
		1177	server. While knowing how various event loops perform is interesting, keep
		1178	in mind that their overhead in this case is usually not as important, due
		1179	to the small absolute number of watchers (that is, you need efficiency and
		1180	speed most when you have lots of watchers, not when you only have a few of
		1181	them).
		1182
		1183	EV is again fastest.
		1184
		1185	The C-based event loops Event and Glib come in second this time, as the
		1186	overhead of running an iteration is much smaller in C than in Perl (little
		1187	code to execute in the inner loop, and perl's function calling overhead is
		1188	high, and updating all the data structures is costly).
		1189
		1190	The pure perl event loop is much slower, but still competitive.
		1191
		1192	POE also performs much better in this case, but is is still far behind the
		1193	others.
		1194
		1195	=head3 Summary
		1196
		1197	=over 4
		1198
		1199	=item * C-based event loops perform very well with small number of
		1200	watchers, as the management overhead dominates.
		1201
		1202	=back
		1203
		1204
		1205	=head1 FORK
		1206
		1207	Most event libraries are not fork-safe. The ones who are usually are
		1208	because they are so inefficient. Only L<EV> is fully fork-aware.
		1209
		1210	If you have to fork, you must either do so I<before> creating your first
		1211	watcher OR you must not use AnyEvent at all in the child.
		1212
		1213
		1214	=head1 SECURITY CONSIDERATIONS
		1215
		1216	AnyEvent can be forced to load any event model via
		1217	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1218	execute arbitrary code or directly gain access, it can easily be used to
		1219	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1220	will not be active when the program uses a different event model than
		1221	specified in the variable.
		1222
		1223	You can make AnyEvent completely ignore this variable by deleting it
		1224	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1225
		1226	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1227
		1228	use AnyEvent;
		1229
		1230
455	=head1 SEE ALSO	1231	=head1 SEE ALSO
456		1232
457	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	1233	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		1234	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1235	L<Event::Lib>, L<Qt>, L<POE>.
458		1236
		1237	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
459	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	1238	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1239	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1240	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
460		1241
461	Nontrivial usage example: L<Net::FCP>.	1242	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
462		1243
463	=head1	1244
		1245	=head1 AUTHOR
		1246
		1247	Marc Lehmann <schmorp@schmorp.de>
		1248	http://home.schmorp.de/
464		1249
465	=cut	1250	=cut
466		1251
467	1	1252	1
468		1253

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.15 by root, Mon Oct 30 20:55:05 2006 UTC vs. Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.15 by root, Mon Oct 30 20:55:05 2006 UTC vs.
Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC