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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.28 by root, Sat Oct 27 15:10:09 2007 UTC vs.
Revision 1.99 by root, Sun Apr 27 17:09:33 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 {
…		…
94	=head2 TIME WATCHERS	192	=head2 TIME WATCHERS
95		193
96	You can create a time 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
160	=back	397	=head1 GLOBAL VARIABLES AND FUNCTIONS
161
162	=head2 SIGNAL WATCHERS
163
164	You can listen for signals using a signal watcher, C<signal> is the signal
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped
166	together into one callback invocation, and callback invocation might or
167	might not be asynchronous.
168
169	These watchers might use C<%SIG>, so programs overwriting those signals
170	directly will likely not work correctly.
171
172	Example: exit on SIGINT
173
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175
176	=head2 CHILD PROCESS WATCHERS
177
178	You can also listen for the status of a child process specified by the
179	C<pid> argument. The watcher will only trigger once. This works by
180	installing a signal handler for C<SIGCHLD>.
181
182	Example: wait for pid 1333
183
184	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
185
186	=head1 GLOBALS
187		398
188	=over 4	399	=over 4
189		400
190	=item $AnyEvent::MODEL	401	=item $AnyEvent::MODEL
191		402
…		…
195	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	406	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
196	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	407	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
197		408
198	The known classes so far are:	409	The known classes so far are:
199		410
200	AnyEvent::Impl::Coro based on Coro::Event, best choice.	411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
201	EV::AnyEvent based on EV (an interface to libevent)	413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
202	AnyEvent::Impl::Event based on Event, also best choice :)	414	AnyEvent::Impl::Event based on Event, second best choice.
203	AnyEvent::Impl::Glib based on Glib, second-best choice.	415	AnyEvent::Impl::Glib based on Glib, third-best choice.
		416	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
204	AnyEvent::Impl::Tk based on Tk, very bad choice.	417	AnyEvent::Impl::Tk based on Tk, very bad choice.
205	AnyEvent::Impl::Perl pure-perl implementation, inefficient.	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.
206		431
207	=item AnyEvent::detect	432	=item AnyEvent::detect
208		433
209	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
210	necessary. You should only call this function right before you would have	435	if necessary. You should only call this function right before you would
211	created an AnyEvent watcher anyway, that is, very late at runtime.	436	have created an AnyEvent watcher anyway, that is, as late as possible at
		437	runtime.
212		438
213	=back	439	=back
214		440
215	=head1 WHAT TO DO IN A MODULE	441	=head1 WHAT TO DO IN A MODULE
216		442
217	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
218	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.
219		445
220	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
221	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
222	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
223	to load the event module first.	449	to load the event module first.
224		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
225	=head1 WHAT TO DO IN THE MAIN PROGRAM	461	=head1 WHAT TO DO IN THE MAIN PROGRAM
226		462
227	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
228	dictate which event model to use.	464	dictate which event model to use.
229		465
230	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
231	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.
232		469
233	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
234	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
235	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
236	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
237	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
238	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
239	correct one yourself.	476	might chose the wrong one unless you load the correct one yourself.
240		477
241	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
242	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
243	generally better.	480	behaviour everywhere, but letting AnyEvent chose is generally better.
244		481
245	=cut	482	=cut
246		483
247	package AnyEvent;	484	package AnyEvent;
248		485
249	no warnings;	486	no warnings;
250	use strict;	487	use strict;
251		488
252	use Carp;	489	use Carp;
253		490
254	our $VERSION = '2.55';	491	our $VERSION = '3.3';
255	our $MODEL;	492	our $MODEL;
256		493
257	our $AUTOLOAD;	494	our $AUTOLOAD;
258	our @ISA;	495	our @ISA;
259		496
260	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	497	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
261		498
262	our @REGISTRY;	499	our @REGISTRY;
263		500
264	my @models = (	501	my @models = (
		502	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
265	[Coro::Event:: => AnyEvent::Impl::Coro::],	503	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
266	[EV:: => EV::AnyEvent::],	504	[EV:: => AnyEvent::Impl::EV::],
267	[Event:: => AnyEvent::Impl::Event::],	505	[Event:: => AnyEvent::Impl::Event::],
268	[Glib:: => AnyEvent::Impl::Glib::],	506	[Glib:: => AnyEvent::Impl::Glib::],
269	[Tk:: => AnyEvent::Impl::Tk::],	507	[Tk:: => AnyEvent::Impl::Tk::],
		508	[Wx:: => AnyEvent::Impl::POE::],
		509	[Prima:: => AnyEvent::Impl::POE::],
270	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	510	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		511	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		512	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		513	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		514	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
271	);	515	);
272		516
273	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	517	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
274		518
275	sub detect() {	519	sub detect() {
276	unless ($MODEL) {	520	unless ($MODEL) {
277	no strict 'refs';	521	no strict 'refs';
278		522
		523	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		524	my $model = "AnyEvent::Impl::$1";
		525	if (eval "require $model") {
		526	$MODEL = $model;
		527	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		528	} else {
		529	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		530	}
		531	}
		532
279	# check for already loaded models	533	# check for already loaded models
		534	unless ($MODEL) {
280	for (@REGISTRY, @models) {	535	for (@REGISTRY, @models) {
281	my ($package, $model) = @$_;	536	my ($package, $model) = @$_;
282	if (${"$package\::VERSION"} > 0) {	537	if (${"$package\::VERSION"} > 0) {
283	if (eval "require $model") {	538	if (eval "require $model") {
284	$MODEL = $model;	539	$MODEL = $model;
285	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	540	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
286	last;	541	last;
		542	}
287	}	543	}
288	}	544	}
289	}
290		545
291	unless ($MODEL) {	546	unless ($MODEL) {
292	# try to load a model	547	# try to load a model
293		548
294	for (@REGISTRY, @models) {	549	for (@REGISTRY, @models) {
295	my ($package, $model) = @$_;	550	my ($package, $model) = @$_;
296	if (eval "require $package"	551	if (eval "require $package"
297	and ${"$package\::VERSION"} > 0	552	and ${"$package\::VERSION"} > 0
298	and eval "require $model") {	553	and eval "require $model") {
299	$MODEL = $model;	554	$MODEL = $model;
300	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	555	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
301	last;	556	last;
		557	}
302	}	558	}
		559
		560	$MODEL
		561	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.";
303	}	562	}
304
305	$MODEL
306	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
307	}	563	}
308		564
309	unshift @ISA, $MODEL;	565	unshift @ISA, $MODEL;
310	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	566	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
311	}	567	}
…		…
369		625
370	# default implementation for ->child	626	# default implementation for ->child
371		627
372	our %PID_CB;	628	our %PID_CB;
373	our $CHLD_W;	629	our $CHLD_W;
		630	our $CHLD_DELAY_W;
374	our $PID_IDLE;	631	our $PID_IDLE;
375	our $WNOHANG;	632	our $WNOHANG;
376		633
377	sub _child_wait {	634	sub _child_wait {
378	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	635	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
379	$_->() for values %{ (delete $PID_CB{$pid}) \|\| {} };	636	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		637	(values %{ $PID_CB{0} \|\| {} });
380	}	638	}
381		639
382	undef $PID_IDLE;	640	undef $PID_IDLE;
383	}	641	}
384		642
		643	sub _sigchld {
		644	# make sure we deliver these changes "synchronous" with the event loop.
		645	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		646	undef $CHLD_DELAY_W;
		647	&_child_wait;
		648	});
		649	}
		650
385	sub child {	651	sub child {
386	my (undef, %arg) = @_;	652	my (undef, %arg) = @_;
387		653
388	my $pid = uc $arg{pid}	654	defined (my $pid = $arg{pid} + 0)
389	or Carp::croak "required option 'pid' is missing";	655	or Carp::croak "required option 'pid' is missing";
390		656
391	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	657	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
392		658
393	unless ($WNOHANG) {	659	unless ($WNOHANG) {
394	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;	660	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
395	}	661	}
396		662
397	unless ($CHLD_W) {	663	unless ($CHLD_W) {
398	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait);	664	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
399	# child could be a zombie already	665	# child could be a zombie already, so make at least one round
400	$PID_IDLE \|\|= AnyEvent->timer (after => 0, cb => \&_child_wait);	666	&_sigchld;
401	}	667	}
402		668
403	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	669	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
404	}	670	}
405		671
…		…
411		677
412	undef $CHLD_W unless keys %PID_CB;	678	undef $CHLD_W unless keys %PID_CB;
413	}	679	}
414		680
415	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	681	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		682
		683	This is an advanced topic that you do not normally need to use AnyEvent in
		684	a module. This section is only of use to event loop authors who want to
		685	provide AnyEvent compatibility.
416		686
417	If you need to support another event library which isn't directly	687	If you need to support another event library which isn't directly
418	supported by AnyEvent, you can supply your own interface to it by	688	supported by AnyEvent, you can supply your own interface to it by
419	pushing, before the first watcher gets created, the package name of	689	pushing, before the first watcher gets created, the package name of
420	the event module and the package name of the interface to use onto	690	the event module and the package name of the interface to use onto
421	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	691	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
422	AnyEvent.	692	AnyEvent, so it is reasonably cheap.
423		693
424	Example:	694	Example:
425		695
426	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	696	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
427		697
428	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	698	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
429	package/class when it finds the C<urxvt> package/module is loaded. When	699	package/class when it finds the C<urxvt> package/module is already loaded.
		700
430	AnyEvent is loaded and asked to find a suitable event model, it will	701	When AnyEvent is loaded and asked to find a suitable event model, it
431	first check for the presence of urxvt.	702	will first check for the presence of urxvt by trying to C<use> the
		703	C<urxvt::anyevent> module.
432		704
433	The class should provide implementations for all watcher types (see	705	The class should provide implementations for all watcher types. See
434	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	706	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
435	(Source code) and so on for actual examples, use C<perldoc -m	707	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
436	AnyEvent::Impl::Glib> to see the sources).	708	see the sources.
437		709
		710	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		711	provide suitable (hopefully) replacements.
		712
438	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	713	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
439	uses the above line as-is. An interface isn't included in AnyEvent	714	terminal emulator uses the above line as-is. An interface isn't included
440	because it doesn't make sense outside the embedded interpreter inside	715	in AnyEvent because it doesn't make sense outside the embedded interpreter
441	I<rxvt-unicode>, and it is updated and maintained as part of the	716	inside I<rxvt-unicode>, and it is updated and maintained as part of the
442	I<rxvt-unicode> distribution.	717	I<rxvt-unicode> distribution.
443		718
444	I<rxvt-unicode> also cheats a bit by not providing blocking access to	719	I<rxvt-unicode> also cheats a bit by not providing blocking access to
445	condition variables: code blocking while waiting for a condition will	720	condition variables: code blocking while waiting for a condition will
446	C<die>. This still works with most modules/usages, and blocking calls must	721	C<die>. This still works with most modules/usages, and blocking calls must
447	not be in an interactive application, so it makes sense.	722	not be done in an interactive application, so it makes sense.
448		723
449	=head1 ENVIRONMENT VARIABLES	724	=head1 ENVIRONMENT VARIABLES
450		725
451	The following environment variables are used by this module:	726	The following environment variables are used by this module:
452		727
453	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event	728	=over 4
454	model gets used.
455		729
		730	=item C<PERL_ANYEVENT_VERBOSE>
		731
		732	By default, AnyEvent will be completely silent except in fatal
		733	conditions. You can set this environment variable to make AnyEvent more
		734	talkative.
		735
		736	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		737	conditions, such as not being able to load the event model specified by
		738	C<PERL_ANYEVENT_MODEL>.
		739
		740	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		741	model it chooses.
		742
		743	=item C<PERL_ANYEVENT_MODEL>
		744
		745	This can be used to specify the event model to be used by AnyEvent, before
		746	autodetection and -probing kicks in. It must be a string consisting
		747	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		748	and the resulting module name is loaded and if the load was successful,
		749	used as event model. If it fails to load AnyEvent will proceed with
		750	autodetection and -probing.
		751
		752	This functionality might change in future versions.
		753
		754	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		755	could start your program like this:
		756
		757	PERL_ANYEVENT_MODEL=Perl perl ...
		758
		759	=back
		760
456	=head1 EXAMPLE	761	=head1 EXAMPLE PROGRAM
457		762
458	The following program uses an io watcher to read data from stdin, a timer	763	The following program uses an I/O watcher to read data from STDIN, a timer
459	to display a message once per second, and a condvar to exit the program	764	to display a message once per second, and a condition variable to quit the
460	when the user enters quit:	765	program when the user enters quit:
461		766
462	use AnyEvent;	767	use AnyEvent;
463		768
464	my $cv = AnyEvent->condvar;	769	my $cv = AnyEvent->condvar;
465		770
466	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	771	my $io_watcher = AnyEvent->io (
		772	fh => \*STDIN,
		773	poll => 'r',
		774	cb => sub {
467	warn "io event <$_[0]>\n"; # will always output <r>	775	warn "io event <$_[0]>\n"; # will always output <r>
468	chomp (my $input = <STDIN>); # read a line	776	chomp (my $input = <STDIN>); # read a line
469	warn "read: $input\n"; # output what has been read	777	warn "read: $input\n"; # output what has been read
470	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	778	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		779	},
471	});	780	);
472		781
473	my $time_watcher; # can only be used once	782	my $time_watcher; # can only be used once
474		783
475	sub new_timer {	784	sub new_timer {
476	$timer = AnyEvent->timer (after => 1, cb => sub {	785	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
558	$txn->{finished}->wait;	867	$txn->{finished}->wait;
559	return $txn->{result};	868	return $txn->{result};
560		869
561	The actual code goes further and collects all errors (C<die>s, exceptions)	870	The actual code goes further and collects all errors (C<die>s, exceptions)
562	that occured during request processing. The C<result> method detects	871	that occured during request processing. The C<result> method detects
563	wether an exception as thrown (it is stored inside the $txn object)	872	whether an exception as thrown (it is stored inside the $txn object)
564	and just throws the exception, which means connection errors and other	873	and just throws the exception, which means connection errors and other
565	problems get reported tot he code that tries to use the result, not in a	874	problems get reported tot he code that tries to use the result, not in a
566	random callback.	875	random callback.
567		876
568	All of this enables the following usage styles:	877	All of this enables the following usage styles:
569		878
570	1. Blocking:	879	1. Blocking:
571		880
572	my $data = $fcp->client_get ($url);	881	my $data = $fcp->client_get ($url);
573		882
574	2. Blocking, but parallelizing:	883	2. Blocking, but running in parallel:
575		884
576	my @datas = map $_->result,	885	my @datas = map $_->result,
577	map $fcp->txn_client_get ($_),	886	map $fcp->txn_client_get ($_),
578	@urls;	887	@urls;
579		888
580	Both blocking examples work without the module user having to know	889	Both blocking examples work without the module user having to know
581	anything about events.	890	anything about events.
582		891
583	3a. Event-based in a main program, using any support Event module:	892	3a. Event-based in a main program, using any supported event module:
584		893
585	use Event;	894	use EV;
586		895
587	$fcp->txn_client_get ($url)->cb (sub {	896	$fcp->txn_client_get ($url)->cb (sub {
588	my $txn = shift;	897	my $txn = shift;
589	my $data = $txn->result;	898	my $data = $txn->result;
590	...	899	...
591	});	900	});
592		901
593	Event::loop;	902	EV::loop;
594		903
595	3b. The module user could use AnyEvent, too:	904	3b. The module user could use AnyEvent, too:
596		905
597	use AnyEvent;	906	use AnyEvent;
598		907
…		…
603	$quit->broadcast;	912	$quit->broadcast;
604	});	913	});
605		914
606	$quit->wait;	915	$quit->wait;
607		916
		917
		918	=head1 BENCHMARKS
		919
		920	To give you an idea of the performance and overheads that AnyEvent adds
		921	over the event loops themselves and to give you an impression of the speed
		922	of various event loops I prepared some benchmarks.
		923
		924	=head2 BENCHMARKING ANYEVENT OVERHEAD
		925
		926	Here is a benchmark of various supported event models used natively and
		927	through anyevent. The benchmark creates a lot of timers (with a zero
		928	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		929	which it is), lets them fire exactly once and destroys them again.
		930
		931	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		932	distribution.
		933
		934	=head3 Explanation of the columns
		935
		936	I<watcher> is the number of event watchers created/destroyed. Since
		937	different event models feature vastly different performances, each event
		938	loop was given a number of watchers so that overall runtime is acceptable
		939	and similar between tested event loop (and keep them from crashing): Glib
		940	would probably take thousands of years if asked to process the same number
		941	of watchers as EV in this benchmark.
		942
		943	I<bytes> is the number of bytes (as measured by the resident set size,
		944	RSS) consumed by each watcher. This method of measuring captures both C
		945	and Perl-based overheads.
		946
		947	I<create> is the time, in microseconds (millionths of seconds), that it
		948	takes to create a single watcher. The callback is a closure shared between
		949	all watchers, to avoid adding memory overhead. That means closure creation
		950	and memory usage is not included in the figures.
		951
		952	I<invoke> is the time, in microseconds, used to invoke a simple
		953	callback. The callback simply counts down a Perl variable and after it was
		954	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		955	signal the end of this phase.
		956
		957	I<destroy> is the time, in microseconds, that it takes to destroy a single
		958	watcher.
		959
		960	=head3 Results
		961
		962	name watchers bytes create invoke destroy comment
		963	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		964	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		965	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		966	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		967	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		968	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		969	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		970	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		971	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		972	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		973
		974	=head3 Discussion
		975
		976	The benchmark does I<not> measure scalability of the event loop very
		977	well. For example, a select-based event loop (such as the pure perl one)
		978	can never compete with an event loop that uses epoll when the number of
		979	file descriptors grows high. In this benchmark, all events become ready at
		980	the same time, so select/poll-based implementations get an unnatural speed
		981	boost.
		982
		983	Also, note that the number of watchers usually has a nonlinear effect on
		984	overall speed, that is, creating twice as many watchers doesn't take twice
		985	the time - usually it takes longer. This puts event loops tested with a
		986	higher number of watchers at a disadvantage.
		987
		988	To put the range of results into perspective, consider that on the
		989	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		990	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		991	cycles with POE.
		992
		993	C<EV> is the sole leader regarding speed and memory use, which are both
		994	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		995	far less memory than any other event loop and is still faster than Event
		996	natively.
		997
		998	The pure perl implementation is hit in a few sweet spots (both the
		999	constant timeout and the use of a single fd hit optimisations in the perl
		1000	interpreter and the backend itself). Nevertheless this shows that it
		1001	adds very little overhead in itself. Like any select-based backend its
		1002	performance becomes really bad with lots of file descriptors (and few of
		1003	them active), of course, but this was not subject of this benchmark.
		1004
		1005	The C<Event> module has a relatively high setup and callback invocation
		1006	cost, but overall scores in on the third place.
		1007
		1008	C<Glib>'s memory usage is quite a bit higher, but it features a
		1009	faster callback invocation and overall ends up in the same class as
		1010	C<Event>. However, Glib scales extremely badly, doubling the number of
		1011	watchers increases the processing time by more than a factor of four,
		1012	making it completely unusable when using larger numbers of watchers
		1013	(note that only a single file descriptor was used in the benchmark, so
		1014	inefficiencies of C<poll> do not account for this).
		1015
		1016	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1017	more than 2000 watchers is a big setback, however, as correctness takes
		1018	precedence over speed. Nevertheless, its performance is surprising, as the
		1019	file descriptor is dup()ed for each watcher. This shows that the dup()
		1020	employed by some adaptors is not a big performance issue (it does incur a
		1021	hidden memory cost inside the kernel which is not reflected in the figures
		1022	above).
		1023
		1024	C<POE>, regardless of underlying event loop (whether using its pure
		1025	perl select-based backend or the Event module, the POE-EV backend
		1026	couldn't be tested because it wasn't working) shows abysmal performance
		1027	and memory usage: Watchers use almost 30 times as much memory as
		1028	EV watchers, and 10 times as much memory as Event (the high memory
		1029	requirements are caused by requiring a session for each watcher). Watcher
		1030	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1031	implementation. The design of the POE adaptor class in AnyEvent can not
		1032	really account for this, as session creation overhead is small compared
		1033	to execution of the state machine, which is coded pretty optimally within
		1034	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		1035
		1036	=head3 Summary
		1037
		1038	=over 4
		1039
		1040	=item * Using EV through AnyEvent is faster than any other event loop
		1041	(even when used without AnyEvent), but most event loops have acceptable
		1042	performance with or without AnyEvent.
		1043
		1044	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1045	the actual event loop, only with extremely fast event loops such as EV
		1046	adds AnyEvent significant overhead.
		1047
		1048	=item * You should avoid POE like the plague if you want performance or
		1049	reasonable memory usage.
		1050
		1051	=back
		1052
		1053	=head2 BENCHMARKING THE LARGE SERVER CASE
		1054
		1055	This benchmark atcually benchmarks the event loop itself. It works by
		1056	creating a number of "servers": each server consists of a socketpair, a
		1057	timeout watcher that gets reset on activity (but never fires), and an I/O
		1058	watcher waiting for input on one side of the socket. Each time the socket
		1059	watcher reads a byte it will write that byte to a random other "server".
		1060
		1061	The effect is that there will be a lot of I/O watchers, only part of which
		1062	are active at any one point (so there is a constant number of active
		1063	fds for each loop iterstaion, but which fds these are is random). The
		1064	timeout is reset each time something is read because that reflects how
		1065	most timeouts work (and puts extra pressure on the event loops).
		1066
		1067	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1068	(1%) are active. This mirrors the activity of large servers with many
		1069	connections, most of which are idle at any one point in time.
		1070
		1071	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1072	distribution.
		1073
		1074	=head3 Explanation of the columns
		1075
		1076	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1077	each server has a read and write socket end).
		1078
		1079	I<create> is the time it takes to create a socketpair (which is
		1080	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1081
		1082	I<request>, the most important value, is the time it takes to handle a
		1083	single "request", that is, reading the token from the pipe and forwarding
		1084	it to another server. This includes deleting the old timeout and creating
		1085	a new one that moves the timeout into the future.
		1086
		1087	=head3 Results
		1088
		1089	name sockets create request
		1090	EV 20000 69.01 11.16
		1091	Perl 20000 73.32 35.87
		1092	Event 20000 212.62 257.32
		1093	Glib 20000 651.16 1896.30
		1094	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1095
		1096	=head3 Discussion
		1097
		1098	This benchmark I<does> measure scalability and overall performance of the
		1099	particular event loop.
		1100
		1101	EV is again fastest. Since it is using epoll on my system, the setup time
		1102	is relatively high, though.
		1103
		1104	Perl surprisingly comes second. It is much faster than the C-based event
		1105	loops Event and Glib.
		1106
		1107	Event suffers from high setup time as well (look at its code and you will
		1108	understand why). Callback invocation also has a high overhead compared to
		1109	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1110	uses select or poll in basically all documented configurations.
		1111
		1112	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1113	clearly fails to perform with many filehandles or in busy servers.
		1114
		1115	POE is still completely out of the picture, taking over 1000 times as long
		1116	as EV, and over 100 times as long as the Perl implementation, even though
		1117	it uses a C-based event loop in this case.
		1118
		1119	=head3 Summary
		1120
		1121	=over 4
		1122
		1123	=item * The pure perl implementation performs extremely well, considering
		1124	that it uses select.
		1125
		1126	=item * Avoid Glib or POE in large projects where performance matters.
		1127
		1128	=back
		1129
		1130	=head2 BENCHMARKING SMALL SERVERS
		1131
		1132	While event loops should scale (and select-based ones do not...) even to
		1133	large servers, most programs we (or I :) actually write have only a few
		1134	I/O watchers.
		1135
		1136	In this benchmark, I use the same benchmark program as in the large server
		1137	case, but it uses only eight "servers", of which three are active at any
		1138	one time. This should reflect performance for a small server relatively
		1139	well.
		1140
		1141	The columns are identical to the previous table.
		1142
		1143	=head3 Results
		1144
		1145	name sockets create request
		1146	EV 16 20.00 6.54
		1147	Perl 16 25.75 12.62
		1148	Event 16 81.27 35.86
		1149	Glib 16 32.63 15.48
		1150	POE 16 261.87 276.28 uses POE::Loop::Event
		1151
		1152	=head3 Discussion
		1153
		1154	The benchmark tries to test the performance of a typical small
		1155	server. While knowing how various event loops perform is interesting, keep
		1156	in mind that their overhead in this case is usually not as important, due
		1157	to the small absolute number of watchers (that is, you need efficiency and
		1158	speed most when you have lots of watchers, not when you only have a few of
		1159	them).
		1160
		1161	EV is again fastest.
		1162
		1163	The C-based event loops Event and Glib come in second this time, as the
		1164	overhead of running an iteration is much smaller in C than in Perl (little
		1165	code to execute in the inner loop, and perl's function calling overhead is
		1166	high, and updating all the data structures is costly).
		1167
		1168	The pure perl event loop is much slower, but still competitive.
		1169
		1170	POE also performs much better in this case, but is is still far behind the
		1171	others.
		1172
		1173	=head3 Summary
		1174
		1175	=over 4
		1176
		1177	=item * C-based event loops perform very well with small number of
		1178	watchers, as the management overhead dominates.
		1179
		1180	=back
		1181
		1182
		1183	=head1 FORK
		1184
		1185	Most event libraries are not fork-safe. The ones who are usually are
		1186	because they are so inefficient. Only L<EV> is fully fork-aware.
		1187
		1188	If you have to fork, you must either do so I<before> creating your first
		1189	watcher OR you must not use AnyEvent at all in the child.
		1190
		1191
		1192	=head1 SECURITY CONSIDERATIONS
		1193
		1194	AnyEvent can be forced to load any event model via
		1195	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1196	execute arbitrary code or directly gain access, it can easily be used to
		1197	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1198	will not be active when the program uses a different event model than
		1199	specified in the variable.
		1200
		1201	You can make AnyEvent completely ignore this variable by deleting it
		1202	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1203
		1204	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1205
		1206	use AnyEvent;
		1207
		1208
608	=head1 SEE ALSO	1209	=head1 SEE ALSO
609		1210
610	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	1211	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		1212	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1213	L<Event::Lib>, L<Qt>, L<POE>.
611		1214
		1215	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
612	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	1216	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1217	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1218	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
613		1219
614	Nontrivial usage example: L<Net::FCP>.	1220	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
615		1221
616	=head1	1222
		1223	=head1 AUTHOR
		1224
		1225	Marc Lehmann <schmorp@schmorp.de>
		1226	http://home.schmorp.de/
617		1227
618	=cut	1228	=cut
619		1229
620	1	1230	1
621		1231

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.28 by root, Sat Oct 27 15:10:09 2007 UTC vs. Revision 1.99 by root, Sun Apr 27 17:09:33 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.28 by root, Sat Oct 27 15:10:09 2007 UTC vs.
Revision 1.99 by root, Sun Apr 27 17:09:33 2008 UTC