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Comparing AnyEvent/README (file contents):
Revision 1.38 by root, Sun Apr 26 18:12:53 2009 UTC vs.
Revision 1.54 by root, Tue Sep 1 18:27:46 2009 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	loops	5	Qt and POE are various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
10	# file descriptor readable	10	# file descriptor readable
37		37
38	INTRODUCTION/TUTORIAL	38	INTRODUCTION/TUTORIAL
39	This manpage is mainly a reference manual. If you are interested in a	39	This manpage is mainly a reference manual. If you are interested in a
40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro	40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
41	manpage.	41	manpage.
		42
		43	SUPPORT
		44	There is a mailinglist for discussing all things AnyEvent, and an IRC
		45	channel, too.
		46
		47	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		48	Repository, at <http://anyevent.schmorp.de>, for more info.
42		49
43	WHY YOU SHOULD USE THIS MODULE (OR NOT)	50	WHY YOU SHOULD USE THIS MODULE (OR NOT)
44	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	51	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
45	nowadays. So what is different about AnyEvent?	52	nowadays. So what is different about AnyEvent?
46		53
…		…
166	Note that "my $w; $w =" combination. This is necessary because in Perl,	173	Note that "my $w; $w =" combination. This is necessary because in Perl,
167	my variables are only visible after the statement in which they are	174	my variables are only visible after the statement in which they are
168	declared.	175	declared.
169		176
170	I/O WATCHERS	177	I/O WATCHERS
		178	$w = AnyEvent->io (
		179	fh => <filehandle_or_fileno>,
		180	poll => <"r" or "w">,
		181	cb => <callback>,
		182	);
		183
171	You can create an I/O watcher by calling the "AnyEvent->io" method with	184	You can create an I/O watcher by calling the "AnyEvent->io" method with
172	the following mandatory key-value pairs as arguments:	185	the following mandatory key-value pairs as arguments:
173		186
174	"fh" is the Perl file handle (not file descriptor) to watch for	187	"fh" is the Perl file handle (or a naked file descriptor) to watch for
175	events (AnyEvent might or might not keep a reference to this file	188	events (AnyEvent might or might not keep a reference to this file
176	handle). Note that only file handles pointing to things for which	189	handle). Note that only file handles pointing to things for which
177	non-blocking operation makes sense are allowed. This includes sockets,	190	non-blocking operation makes sense are allowed. This includes sockets,
178	most character devices, pipes, fifos and so on, but not for example	191	most character devices, pipes, fifos and so on, but not for example
179	files or block devices.	192	files or block devices.
…		…
203	warn "read: $input\n";	216	warn "read: $input\n";
204	undef $w;	217	undef $w;
205	});	218	});
206		219
207	TIME WATCHERS	220	TIME WATCHERS
		221	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		222
		223	$w = AnyEvent->timer (
		224	after => <fractional_seconds>,
		225	interval => <fractional_seconds>,
		226	cb => <callback>,
		227	);
		228
208	You can create a time watcher by calling the "AnyEvent->timer" method	229	You can create a time watcher by calling the "AnyEvent->timer" method
209	with the following mandatory arguments:	230	with the following mandatory arguments:
210		231
211	"after" specifies after how many seconds (fractional values are	232	"after" specifies after how many seconds (fractional values are
212	supported) the callback should be invoked. "cb" is the callback to	233	supported) the callback should be invoked. "cb" is the callback to
…		…
336	the event loop's idea of "current time".	357	the event loop's idea of "current time".
337		358
338	Note that updating the time might cause some events to be handled.	359	Note that updating the time might cause some events to be handled.
339		360
340	SIGNAL WATCHERS	361	SIGNAL WATCHERS
		362	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		363
341	You can watch for signals using a signal watcher, "signal" is the signal	364	You can watch for signals using a signal watcher, "signal" is the signal
342	name in uppercase and without any "SIG" prefix, "cb" is the Perl	365	name in uppercase and without any "SIG" prefix, "cb" is the Perl
343	callback to be invoked whenever a signal occurs.	366	callback to be invoked whenever a signal occurs.
344		367
345	Although the callback might get passed parameters, their value and	368	Although the callback might get passed parameters, their value and
…		…
350	invocation, and callback invocation will be synchronous. Synchronous	373	invocation, and callback invocation will be synchronous. Synchronous
351	means that it might take a while until the signal gets handled by the	374	means that it might take a while until the signal gets handled by the
352	process, but it is guaranteed not to interrupt any other callbacks.	375	process, but it is guaranteed not to interrupt any other callbacks.
353		376
354	The main advantage of using these watchers is that you can share a	377	The main advantage of using these watchers is that you can share a
355	signal between multiple watchers.	378	signal between multiple watchers, and AnyEvent will ensure that signals
		379	will not interrupt your program at bad times.
356		380
357	This watcher might use %SIG, so programs overwriting those signals	381	This watcher might use %SIG (depending on the event loop used), so
358	directly will likely not work correctly.	382	programs overwriting those signals directly will likely not work
		383	correctly.
359		384
360	Example: exit on SIGINT	385	Example: exit on SIGINT
361		386
362	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	387	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
363		388
		389	Signal Races, Delays and Workarounds
		390	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		391	callbacks to signals in a generic way, which is a pity, as you cannot do
		392	race-free signal handling in perl, requiring C libraries for this.
		393	AnyEvent will try to do it's best, which means in some cases, signals
		394	will be delayed. The maximum time a signal might be delayed is specified
		395	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		396	can be changed only before the first signal watcher is created, and
		397	should be left alone otherwise. This variable determines how often
		398	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		399	will cause fewer spurious wake-ups, which is better for power and CPU
		400	saving.
		401
		402	All these problems can be avoided by installing the optional
		403	Async::Interrupt module, which works with most event loops. It will not
		404	work with inherently broken event loops such as Event or Event::Lib (and
		405	not with POE currently, as POE does it's own workaround with one-second
		406	latency). For those, you just have to suffer the delays.
		407
364	CHILD PROCESS WATCHERS	408	CHILD PROCESS WATCHERS
		409	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		410
365	You can also watch on a child process exit and catch its exit status.	411	You can also watch on a child process exit and catch its exit status.
366		412
367	The child process is specified by the "pid" argument (if set to 0, it	413	The child process is specified by the "pid" argument (one some backends,
368	watches for any child process exit). The watcher will triggered only	414	using 0 watches for any child process exit, on others this will croak).
369	when the child process has finished and an exit status is available, not	415	The watcher will be triggered only when the child process has finished
370	on any trace events (stopped/continued).	416	and an exit status is available, not on any trace events
		417	(stopped/continued).
371		418
372	The callback will be called with the pid and exit status (as returned by	419	The callback will be called with the pid and exit status (as returned by
373	waitpid), so unlike other watcher types, you can rely on child watcher	420	waitpid), so unlike other watcher types, you can rely on child watcher
374	callback arguments.	421	callback arguments.
375		422
…		…
380		427
381	There is a slight catch to child watchers, however: you usually start	428	There is a slight catch to child watchers, however: you usually start
382	them after the child process was created, and this means the process	429	them after the child process was created, and this means the process
383	could have exited already (and no SIGCHLD will be sent anymore).	430	could have exited already (and no SIGCHLD will be sent anymore).
384		431
385	Not all event models handle this correctly (POE doesn't), but even for	432	Not all event models handle this correctly (neither POE nor IO::Async
		433	do, see their AnyEvent::Impl manpages for details), but even for event
386	event models that do handle this correctly, they usually need to be	434	models that do handle this correctly, they usually need to be loaded
387	loaded before the process exits (i.e. before you fork in the first	435	before the process exits (i.e. before you fork in the first place).
388	place).	436	AnyEvent's pure perl event loop handles all cases correctly regardless
		437	of when you start the watcher.
389		438
390	This means you cannot create a child watcher as the very first thing in	439	This means you cannot create a child watcher as the very first thing in
391	an AnyEvent program, you have to create at least one watcher before	440	an AnyEvent program, you have to create at least one watcher before
392	you "fork" the child (alternatively, you can call "AnyEvent::detect").	441	you "fork" the child (alternatively, you can call "AnyEvent::detect").
393		442
		443	As most event loops do not support waiting for child events, they will
		444	be emulated by AnyEvent in most cases, in which the latency and race
		445	problems mentioned in the description of signal watchers apply.
		446
394	Example: fork a process and wait for it	447	Example: fork a process and wait for it
395		448
396	my $done = AnyEvent->condvar;	449	my $done = AnyEvent->condvar;
397		450
398	my $pid = fork or exit 5;	451	my $pid = fork or exit 5;
399		452
400	my $w = AnyEvent->child (	453	my $w = AnyEvent->child (
401	pid => $pid,	454	pid => $pid,
402	cb => sub {	455	cb => sub {
403	my ($pid, $status) = @_;	456	my ($pid, $status) = @_;
404	warn "pid $pid exited with status $status";	457	warn "pid $pid exited with status $status";
405	$done->send;	458	$done->send;
406	},	459	},
407	);	460	);
408		461
409	# do something else, then wait for process exit	462	# do something else, then wait for process exit
410	$done->recv;	463	$done->recv;
411		464
412	IDLE WATCHERS	465	IDLE WATCHERS
		466	$w = AnyEvent->idle (cb => <callback>);
		467
413	Sometimes there is a need to do something, but it is not so important to	468	Sometimes there is a need to do something, but it is not so important to
414	do it instantly, but only when there is nothing better to do. This	469	do it instantly, but only when there is nothing better to do. This
415	"nothing better to do" is usually defined to be "no other events need	470	"nothing better to do" is usually defined to be "no other events need
416	attention by the event loop".	471	attention by the event loop".
417		472
…		…
442	}	497	}
443	});	498	});
444	});	499	});
445		500
446	CONDITION VARIABLES	501	CONDITION VARIABLES
		502	$cv = AnyEvent->condvar;
		503
		504	$cv->send (<list>);
		505	my @res = $cv->recv;
		506
447	If you are familiar with some event loops you will know that all of them	507	If you are familiar with some event loops you will know that all of them
448	require you to run some blocking "loop", "run" or similar function that	508	require you to run some blocking "loop", "run" or similar function that
449	will actively watch for new events and call your callbacks.	509	will actively watch for new events and call your callbacks.
450		510
451	AnyEvent is different, it expects somebody else to run the event loop	511	AnyEvent is slightly different: it expects somebody else to run the
452	and will only block when necessary (usually when told by the user).	512	event loop and will only block when necessary (usually when told by the
		513	user).
453		514
454	The instrument to do that is called a "condition variable", so called	515	The instrument to do that is called a "condition variable", so called
455	because they represent a condition that must become true.	516	because they represent a condition that must become true.
456		517
		518	Now is probably a good time to look at the examples further below.
		519
457	Condition variables can be created by calling the "AnyEvent->condvar"	520	Condition variables can be created by calling the "AnyEvent->condvar"
458	method, usually without arguments. The only argument pair allowed is	521	method, usually without arguments. The only argument pair allowed is
459
460	"cb", which specifies a callback to be called when the condition	522	"cb", which specifies a callback to be called when the condition
461	variable becomes true, with the condition variable as the first argument	523	variable becomes true, with the condition variable as the first argument
462	(but not the results).	524	(but not the results).
463		525
464	After creation, the condition variable is "false" until it becomes	526	After creation, the condition variable is "false" until it becomes
…		…
469	Condition variables are similar to callbacks, except that you can	531	Condition variables are similar to callbacks, except that you can
470	optionally wait for them. They can also be called merge points - points	532	optionally wait for them. They can also be called merge points - points
471	in time where multiple outstanding events have been processed. And yet	533	in time where multiple outstanding events have been processed. And yet
472	another way to call them is transactions - each condition variable can	534	another way to call them is transactions - each condition variable can
473	be used to represent a transaction, which finishes at some point and	535	be used to represent a transaction, which finishes at some point and
474	delivers a result.	536	delivers a result. And yet some people know them as "futures" - a
		537	promise to compute/deliver something that you can wait for.
475		538
476	Condition variables are very useful to signal that something has	539	Condition variables are very useful to signal that something has
477	finished, for example, if you write a module that does asynchronous http	540	finished, for example, if you write a module that does asynchronous http
478	requests, then a condition variable would be the ideal candidate to	541	requests, then a condition variable would be the ideal candidate to
479	signal the availability of results. The user can either act when the	542	signal the availability of results. The user can either act when the
…		…
513	after => 1,	576	after => 1,
514	cb => sub { $result_ready->send },	577	cb => sub { $result_ready->send },
515	);	578	);
516		579
517	# this "blocks" (while handling events) till the callback	580	# this "blocks" (while handling events) till the callback
518	# calls send	581	# calls ->send
519	$result_ready->recv;	582	$result_ready->recv;
520		583
521	Example: wait for a timer, but take advantage of the fact that condition	584	Example: wait for a timer, but take advantage of the fact that condition
522	variables are also code references.	585	variables are also callable directly.
523		586
524	my $done = AnyEvent->condvar;	587	my $done = AnyEvent->condvar;
525	my $delay = AnyEvent->timer (after => 5, cb => $done);	588	my $delay = AnyEvent->timer (after => 5, cb => $done);
526	$done->recv;	589	$done->recv;
527		590
…		…
533		596
534	...	597	...
535		598
536	my @info = $couchdb->info->recv;	599	my @info = $couchdb->info->recv;
537		600
538	And this is how you would just ste a callback to be called whenever the	601	And this is how you would just set a callback to be called whenever the
539	results are available:	602	results are available:
540		603
541	$couchdb->info->cb (sub {	604	$couchdb->info->cb (sub {
542	my @info = $_[0]->recv;	605	my @info = $_[0]->recv;
543	});	606	});
…		…
558		621
559	Any arguments passed to the "send" call will be returned by all	622	Any arguments passed to the "send" call will be returned by all
560	future "->recv" calls.	623	future "->recv" calls.
561		624
562	Condition variables are overloaded so one can call them directly (as	625	Condition variables are overloaded so one can call them directly (as
563	a code reference). Calling them directly is the same as calling	626	if they were a code reference). Calling them directly is the same as
564	"send". Note, however, that many C-based event loops do not handle	627	calling "send".
565	overloading, so as tempting as it may be, passing a condition
566	variable instead of a callback does not work. Both the pure perl and
567	EV loops support overloading, however, as well as all functions that
568	use perl to invoke a callback (as in AnyEvent::Socket and
569	AnyEvent::DNS for example).
570		628
571	$cv->croak ($error)	629	$cv->croak ($error)
572	Similar to send, but causes all call's to "->recv" to invoke	630	Similar to send, but causes all call's to "->recv" to invoke
573	"Carp::croak" with the given error message/object/scalar.	631	"Carp::croak" with the given error message/object/scalar.
574		632
575	This can be used to signal any errors to the condition variable	633	This can be used to signal any errors to the condition variable
576	user/consumer.	634	user/consumer. Doing it this way instead of calling "croak" directly
		635	delays the error detetcion, but has the overwhelmign advantage that
		636	it diagnoses the error at the place where the result is expected,
		637	and not deep in some event clalback without connection to the actual
		638	code causing the problem.
577		639
578	$cv->begin ([group callback])	640	$cv->begin ([group callback])
579	$cv->end	641	$cv->end
580	These two methods are EXPERIMENTAL and MIGHT CHANGE.
581
582	These two methods can be used to combine many transactions/events	642	These two methods can be used to combine many transactions/events
583	into one. For example, a function that pings many hosts in parallel	643	into one. For example, a function that pings many hosts in parallel
584	might want to use a condition variable for the whole process.	644	might want to use a condition variable for the whole process.
585		645
586	Every call to "->begin" will increment a counter, and every call to	646	Every call to "->begin" will increment a counter, and every call to
587	"->end" will decrement it. If the counter reaches 0 in "->end", the	647	"->end" will decrement it. If the counter reaches 0 in "->end", the
588	(last) callback passed to "begin" will be executed. That callback is	648	(last) callback passed to "begin" will be executed, passing the
589	supposed to call "->send", but that is not required. If no	649	condvar as first argument. That callback is supposed to call
		650	"->send", but that is not required. If no group callback was set,
590	callback was set, "send" will be called without any arguments.	651	"send" will be called without any arguments.
591		652
592	Let's clarify this with the ping example:	653	You can think of "$cv->send" giving you an OR condition (one call
		654	sends), while "$cv->begin" and "$cv->end" giving you an AND
		655	condition (all "begin" calls must be "end"'ed before the condvar
		656	sends).
		657
		658	Let's start with a simple example: you have two I/O watchers (for
		659	example, STDOUT and STDERR for a program), and you want to wait for
		660	both streams to close before activating a condvar:
593		661
594	my $cv = AnyEvent->condvar;	662	my $cv = AnyEvent->condvar;
595		663
		664	$cv->begin; # first watcher
		665	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		666	defined sysread $fh1, my $buf, 4096
		667	or $cv->end;
		668	});
		669
		670	$cv->begin; # second watcher
		671	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		672	defined sysread $fh2, my $buf, 4096
		673	or $cv->end;
		674	});
		675
		676	$cv->recv;
		677
		678	This works because for every event source (EOF on file handle),
		679	there is one call to "begin", so the condvar waits for all calls to
		680	"end" before sending.
		681
		682	The ping example mentioned above is slightly more complicated, as
		683	the there are results to be passwd back, and the number of tasks
		684	that are begung can potentially be zero:
		685
		686	my $cv = AnyEvent->condvar;
		687
596	my %result;	688	my %result;
597	$cv->begin (sub { $cv->send (\%result) });	689	$cv->begin (sub { shift->send (\%result) });
598		690
599	for my $host (@list_of_hosts) {	691	for my $host (@list_of_hosts) {
600	$cv->begin;	692	$cv->begin;
601	ping_host_then_call_callback $host, sub {	693	ping_host_then_call_callback $host, sub {
602	$result{$host} = ...;	694	$result{$host} = ...;
…		…
617	the loop, which serves two important purposes: first, it sets the	709	the loop, which serves two important purposes: first, it sets the
618	callback to be called once the counter reaches 0, and second, it	710	callback to be called once the counter reaches 0, and second, it
619	ensures that "send" is called even when "no" hosts are being pinged	711	ensures that "send" is called even when "no" hosts are being pinged
620	(the loop doesn't execute once).	712	(the loop doesn't execute once).
621		713
622	This is the general pattern when you "fan out" into multiple	714	This is the general pattern when you "fan out" into multiple (but
623	subrequests: use an outer "begin"/"end" pair to set the callback and	715	potentially none) subrequests: use an outer "begin"/"end" pair to
624	ensure "end" is called at least once, and then, for each subrequest	716	set the callback and ensure "end" is called at least once, and then,
625	you start, call "begin" and for each subrequest you finish, call	717	for each subrequest you start, call "begin" and for each subrequest
626	"end".	718	you finish, call "end".
627		719
628	METHODS FOR CONSUMERS	720	METHODS FOR CONSUMERS
629	These methods should only be used by the consuming side, i.e. the code	721	These methods should only be used by the consuming side, i.e. the code
630	awaits the condition.	722	awaits the condition.
631		723
…		…
640	function will call "croak".	732	function will call "croak".
641		733
642	In list context, all parameters passed to "send" will be returned,	734	In list context, all parameters passed to "send" will be returned,
643	in scalar context only the first one will be returned.	735	in scalar context only the first one will be returned.
644		736
		737	Note that doing a blocking wait in a callback is not supported by
		738	any event loop, that is, recursive invocation of a blocking "->recv"
		739	is not allowed, and the "recv" call will "croak" if such a condition
		740	is detected. This condition can be slightly loosened by using
		741	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		742	thread that doesn't run the event loop itself.
		743
645	Not all event models support a blocking wait - some die in that case	744	Not all event models support a blocking wait - some die in that case
646	(programs might want to do that to stay interactive), so *if you are	745	(programs might want to do that to stay interactive), so *if you are
647	using this from a module, never require a blocking wait*, but let	746	using this from a module, never require a blocking wait*. Instead,
648	the caller decide whether the call will block or not (for example,	747	let the caller decide whether the call will block or not (for
649	by coupling condition variables with some kind of request results	748	example, by coupling condition variables with some kind of request
650	and supporting callbacks so the caller knows that getting the result	749	results and supporting callbacks so the caller knows that getting
651	will not block, while still supporting blocking waits if the caller	750	the result will not block, while still supporting blocking waits if
652	so desires).	751	the caller so desires).
653
654	Another reason never to "->recv" in a module is that you cannot
655	sensibly have two "->recv"'s in parallel, as that would require
656	multiple interpreters or coroutines/threads, none of which
657	"AnyEvent" can supply.
658
659	The Coro module, however, can and does supply coroutines and, in
660	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
661	versions and also integrates coroutines into AnyEvent, making
662	blocking "->recv" calls perfectly safe as long as they are done from
663	another coroutine (one that doesn't run the event loop).
664		752
665	You can ensure that "-recv" never blocks by setting a callback and	753	You can ensure that "-recv" never blocks by setting a callback and
666	only calling "->recv" from within that callback (or at a later	754	only calling "->recv" from within that callback (or at a later
667	time). This will work even when the event loop does not support	755	time). This will work even when the event loop does not support
668	blocking waits otherwise.	756	blocking waits otherwise.
…		…
673		761
674	$cb = $cv->cb ($cb->($cv))	762	$cb = $cv->cb ($cb->($cv))
675	This is a mutator function that returns the callback set and	763	This is a mutator function that returns the callback set and
676	optionally replaces it before doing so.	764	optionally replaces it before doing so.
677		765
678	The callback will be called when the condition becomes "true", i.e.	766	The callback will be called when the condition becomes (or already
679	when "send" or "croak" are called, with the only argument being the	767	was) "true", i.e. when "send" or "croak" are called (or were
680	condition variable itself. Calling "recv" inside the callback or at	768	called), with the only argument being the condition variable itself.
		769	Calling "recv" inside the callback or at any later time is
681	any later time is guaranteed not to block.	770	guaranteed not to block.
		771
		772	SUPPORTED EVENT LOOPS/BACKENDS
		773	The available backend classes are (every class has its own manpage):
		774
		775	Backends that are autoprobed when no other event loop can be found.
		776	EV is the preferred backend when no other event loop seems to be in
		777	use. If EV is not installed, then AnyEvent will fall back to its own
		778	pure-perl implementation, which is available everywhere as it comes
		779	with AnyEvent itself.
		780
		781	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		782	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		783
		784	Backends that are transparently being picked up when they are used.
		785	These will be used when they are currently loaded when the first
		786	watcher is created, in which case it is assumed that the application
		787	is using them. This means that AnyEvent will automatically pick the
		788	right backend when the main program loads an event module before
		789	anything starts to create watchers. Nothing special needs to be done
		790	by the main program.
		791
		792	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		793	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		794	AnyEvent::Impl::Tk based on Tk, very broken.
		795	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		796	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		797	AnyEvent::Impl::Irssi used when running within irssi.
		798
		799	Backends with special needs.
		800	Qt requires the Qt::Application to be instantiated first, but will
		801	otherwise be picked up automatically. As long as the main program
		802	instantiates the application before any AnyEvent watchers are
		803	created, everything should just work.
		804
		805	AnyEvent::Impl::Qt based on Qt.
		806
		807	Support for IO::Async can only be partial, as it is too broken and
		808	architecturally limited to even support the AnyEvent API. It also is
		809	the only event loop that needs the loop to be set explicitly, so it
		810	can only be used by a main program knowing about AnyEvent. See
		811	AnyEvent::Impl::Async for the gory details.
		812
		813	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		814
		815	Event loops that are indirectly supported via other backends.
		816	Some event loops can be supported via other modules:
		817
		818	There is no direct support for WxWidgets (Wx) or Prima.
		819
		820	WxWidgets has no support for watching file handles. However, you can
		821	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		822	simply polls 20 times per second, which was considered to be too
		823	horrible to even consider for AnyEvent.
		824
		825	Prima is not supported as nobody seems to be using it, but it has a
		826	POE backend, so it can be supported through POE.
		827
		828	AnyEvent knows about both Prima and Wx, however, and will try to
		829	load POE when detecting them, in the hope that POE will pick them
		830	up, in which case everything will be automatic.
682		831
683	GLOBAL VARIABLES AND FUNCTIONS	832	GLOBAL VARIABLES AND FUNCTIONS
		833	These are not normally required to use AnyEvent, but can be useful to
		834	write AnyEvent extension modules.
		835
684	$AnyEvent::MODEL	836	$AnyEvent::MODEL
685	Contains "undef" until the first watcher is being created. Then it	837	Contains "undef" until the first watcher is being created, before
		838	the backend has been autodetected.
		839
686	contains the event model that is being used, which is the name of	840	Afterwards it contains the event model that is being used, which is
687	the Perl class implementing the model. This class is usually one of	841	the name of the Perl class implementing the model. This class is
688	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	842	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
689	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	843	other class in the case AnyEvent has been extended at runtime (e.g.
690		844	in rxvt-unicode it will be "urxvt::anyevent").
691	The known classes so far are:
692
693	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
694	AnyEvent::Impl::Event based on Event, second best choice.
695	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
696	AnyEvent::Impl::Glib based on Glib, third-best choice.
697	AnyEvent::Impl::Tk based on Tk, very bad choice.
698	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
699	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
700	AnyEvent::Impl::POE based on POE, not generic enough for full support.
701
702	There is no support for WxWidgets, as WxWidgets has no support for
703	watching file handles. However, you can use WxWidgets through the
704	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
705	second, which was considered to be too horrible to even consider for
706	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
707	using it's adaptor.
708
709	AnyEvent knows about Prima and Wx and will try to use POE when
710	autodetecting them.
711		845
712	AnyEvent::detect	846	AnyEvent::detect
713	Returns $AnyEvent::MODEL, forcing autodetection of the event model	847	Returns $AnyEvent::MODEL, forcing autodetection of the event model
714	if necessary. You should only call this function right before you	848	if necessary. You should only call this function right before you
715	would have created an AnyEvent watcher anyway, that is, as late as	849	would have created an AnyEvent watcher anyway, that is, as late as
716	possible at runtime.	850	possible at runtime, and not e.g. while initialising of your module.
		851
		852	If you need to do some initialisation before AnyEvent watchers are
		853	created, use "post_detect".
717		854
718	$guard = AnyEvent::post_detect { BLOCK }	855	$guard = AnyEvent::post_detect { BLOCK }
719	Arranges for the code block to be executed as soon as the event	856	Arranges for the code block to be executed as soon as the event
720	model is autodetected (or immediately if this has already happened).	857	model is autodetected (or immediately if this has already happened).
721		858
		859	The block will be executed after the actual backend has been
		860	detected ($AnyEvent::MODEL is set), but before any watchers have
		861	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		862	other initialisations - see the sources of AnyEvent::Strict or
		863	AnyEvent::AIO to see how this is used.
		864
		865	The most common usage is to create some global watchers, without
		866	forcing event module detection too early, for example, AnyEvent::AIO
		867	creates and installs the global IO::AIO watcher in a "post_detect"
		868	block to avoid autodetecting the event module at load time.
		869
722	If called in scalar or list context, then it creates and returns an	870	If called in scalar or list context, then it creates and returns an
723	object that automatically removes the callback again when it is	871	object that automatically removes the callback again when it is
		872	destroyed (or "undef" when the hook was immediately executed). See
724	destroyed. See Coro::BDB for a case where this is useful.	873	AnyEvent::AIO for a case where this is useful.
		874
		875	Example: Create a watcher for the IO::AIO module and store it in
		876	$WATCHER. Only do so after the event loop is initialised, though.
		877
		878	our WATCHER;
		879
		880	my $guard = AnyEvent::post_detect {
		881	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		882	};
		883
		884	# the \|\|= is important in case post_detect immediately runs the block,
		885	# as to not clobber the newly-created watcher. assigning both watcher and
		886	# post_detect guard to the same variable has the advantage of users being
		887	# able to just C<undef $WATCHER> if the watcher causes them grief.
		888
		889	$WATCHER \|\|= $guard;
725		890
726	@AnyEvent::post_detect	891	@AnyEvent::post_detect
727	If there are any code references in this array (you can "push" to it	892	If there are any code references in this array (you can "push" to it
728	before or after loading AnyEvent), then they will called directly	893	before or after loading AnyEvent), then they will called directly
729	after the event loop has been chosen.	894	after the event loop has been chosen.
730		895
731	You should check $AnyEvent::MODEL before adding to this array,	896	You should check $AnyEvent::MODEL before adding to this array,
732	though: if it contains a true value then the event loop has already	897	though: if it is defined then the event loop has already been
733	been detected, and the array will be ignored.	898	detected, and the array will be ignored.
734		899
735	Best use "AnyEvent::post_detect { BLOCK }" instead.	900	Best use "AnyEvent::post_detect { BLOCK }" when your application
		901	allows it,as it takes care of these details.
		902
		903	This variable is mainly useful for modules that can do something
		904	useful when AnyEvent is used and thus want to know when it is
		905	initialised, but do not need to even load it by default. This array
		906	provides the means to hook into AnyEvent passively, without loading
		907	it.
736		908
737	WHAT TO DO IN A MODULE	909	WHAT TO DO IN A MODULE
738	As a module author, you should "use AnyEvent" and call AnyEvent methods	910	As a module author, you should "use AnyEvent" and call AnyEvent methods
739	freely, but you should not load a specific event module or rely on it.	911	freely, but you should not load a specific event module or rely on it.
740		912
…		…
791	variable somewhere, waiting for it, and sending it when the program	963	variable somewhere, waiting for it, and sending it when the program
792	should exit cleanly.	964	should exit cleanly.
793		965
794	OTHER MODULES	966	OTHER MODULES
795	The following is a non-exhaustive list of additional modules that use	967	The following is a non-exhaustive list of additional modules that use
796	AnyEvent and can therefore be mixed easily with other AnyEvent modules	968	AnyEvent as a client and can therefore be mixed easily with other
797	in the same program. Some of the modules come with AnyEvent, some are	969	AnyEvent modules and other event loops in the same program. Some of the
798	available via CPAN.	970	modules come with AnyEvent, most are available via CPAN.
799		971
800	AnyEvent::Util	972	AnyEvent::Util
801	Contains various utility functions that replace often-used but	973	Contains various utility functions that replace often-used but
802	blocking functions such as "inet_aton" by event-/callback-based	974	blocking functions such as "inet_aton" by event-/callback-based
803	versions.	975	versions.
…		…
809	more.	981	more.
810		982
811	AnyEvent::Handle	983	AnyEvent::Handle
812	Provide read and write buffers, manages watchers for reads and	984	Provide read and write buffers, manages watchers for reads and
813	writes, supports raw and formatted I/O, I/O queued and fully	985	writes, supports raw and formatted I/O, I/O queued and fully
814	transparent and non-blocking SSL/TLS.	986	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
815		987
816	AnyEvent::DNS	988	AnyEvent::DNS
817	Provides rich asynchronous DNS resolver capabilities.	989	Provides rich asynchronous DNS resolver capabilities.
818		990
819	AnyEvent::HTTP	991	AnyEvent::HTTP
…		…
840		1012
841	AnyEvent::GPSD	1013	AnyEvent::GPSD
842	A non-blocking interface to gpsd, a daemon delivering GPS	1014	A non-blocking interface to gpsd, a daemon delivering GPS
843	information.	1015	information.
844		1016
		1017	AnyEvent::IRC
		1018	AnyEvent based IRC client module family (replacing the older
		1019	Net::IRC3).
		1020
		1021	AnyEvent::XMPP
		1022	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1023	older Net::XMPP2>.
		1024
845	AnyEvent::IGS	1025	AnyEvent::IGS
846	A non-blocking interface to the Internet Go Server protocol (used by	1026	A non-blocking interface to the Internet Go Server protocol (used by
847	App::IGS).	1027	App::IGS).
848		1028
849	AnyEvent::IRC
850	AnyEvent based IRC client module family (replacing the older
851	Net::IRC3).
852
853	Net::XMPP2
854	AnyEvent based XMPP (Jabber protocol) module family.
855
856	Net::FCP	1029	Net::FCP
857	AnyEvent-based implementation of the Freenet Client Protocol,	1030	AnyEvent-based implementation of the Freenet Client Protocol,
858	birthplace of AnyEvent.	1031	birthplace of AnyEvent.
859		1032
860	Event::ExecFlow	1033	Event::ExecFlow
861	High level API for event-based execution flow control.	1034	High level API for event-based execution flow control.
862		1035
863	Coro	1036	Coro
864	Has special support for AnyEvent via Coro::AnyEvent.	1037	Has special support for AnyEvent via Coro::AnyEvent.
865		1038
866	IO::Lambda	1039	SIMPLIFIED AE API
867	The lambda approach to I/O - don't ask, look there. Can use	1040	Starting with version 5.0, AnyEvent officially supports a second, much
868	AnyEvent.	1041	simpler, API that is designed to reduce the calling, typing and memory
		1042	overhead.
		1043
		1044	See the AE manpage for details.
869		1045
870	ERROR AND EXCEPTION HANDLING	1046	ERROR AND EXCEPTION HANDLING
871	In general, AnyEvent does not do any error handling - it relies on the	1047	In general, AnyEvent does not do any error handling - it relies on the
872	caller to do that if required. The AnyEvent::Strict module (see also the	1048	caller to do that if required. The AnyEvent::Strict module (see also the
873	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1049	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
883	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1059	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
884	Glib uses "install_exception_handler" and so on.	1060	Glib uses "install_exception_handler" and so on.
885		1061
886	ENVIRONMENT VARIABLES	1062	ENVIRONMENT VARIABLES
887	The following environment variables are used by this module or its	1063	The following environment variables are used by this module or its
888	submodules:	1064	submodules.
		1065
		1066	Note that AnyEvent will remove all environment variables starting with
		1067	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1068	enabled.
889		1069
890	"PERL_ANYEVENT_VERBOSE"	1070	"PERL_ANYEVENT_VERBOSE"
891	By default, AnyEvent will be completely silent except in fatal	1071	By default, AnyEvent will be completely silent except in fatal
892	conditions. You can set this environment variable to make AnyEvent	1072	conditions. You can set this environment variable to make AnyEvent
893	more talkative.	1073	more talkative.
…		…
896	conditions, such as not being able to load the event model specified	1076	conditions, such as not being able to load the event model specified
897	by "PERL_ANYEVENT_MODEL".	1077	by "PERL_ANYEVENT_MODEL".
898		1078
899	When set to 2 or higher, cause AnyEvent to report to STDERR which	1079	When set to 2 or higher, cause AnyEvent to report to STDERR which
900	event model it chooses.	1080	event model it chooses.
		1081
		1082	When set to 8 or higher, then AnyEvent will report extra information
		1083	on which optional modules it loads and how it implements certain
		1084	features.
901		1085
902	"PERL_ANYEVENT_STRICT"	1086	"PERL_ANYEVENT_STRICT"
903	AnyEvent does not do much argument checking by default, as thorough	1087	AnyEvent does not do much argument checking by default, as thorough
904	argument checking is very costly. Setting this variable to a true	1088	argument checking is very costly. Setting this variable to a true
905	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1089	value will cause AnyEvent to load "AnyEvent::Strict" and then to
906	thoroughly check the arguments passed to most method calls. If it	1090	thoroughly check the arguments passed to most method calls. If it
907	finds any problems it will croak.	1091	finds any problems, it will croak.
908		1092
909	In other words, enables "strict" mode.	1093	In other words, enables "strict" mode.
910		1094
911	Unlike "use strict", it is definitely recommended ot keep it off in	1095	Unlike "use strict" (or it's modern cousin, "use common::sense", it
912	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1096	is definitely recommended to keep it off in production. Keeping
		1097	"PERL_ANYEVENT_STRICT=1" in your environment while developing
913	while developing programs can be very useful, however.	1098	programs can be very useful, however.
914		1099
915	"PERL_ANYEVENT_MODEL"	1100	"PERL_ANYEVENT_MODEL"
916	This can be used to specify the event model to be used by AnyEvent,	1101	This can be used to specify the event model to be used by AnyEvent,
917	before auto detection and -probing kicks in. It must be a string	1102	before auto detection and -probing kicks in. It must be a string
918	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1103	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
959	EDNS0 in its DNS requests.	1144	EDNS0 in its DNS requests.
960		1145
961	"PERL_ANYEVENT_MAX_FORKS"	1146	"PERL_ANYEVENT_MAX_FORKS"
962	The maximum number of child processes that	1147	The maximum number of child processes that
963	"AnyEvent::Util::fork_call" will create in parallel.	1148	"AnyEvent::Util::fork_call" will create in parallel.
		1149
		1150	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1151	The default value for the "max_outstanding" parameter for the
		1152	default DNS resolver - this is the maximum number of parallel DNS
		1153	requests that are sent to the DNS server.
		1154
		1155	"PERL_ANYEVENT_RESOLV_CONF"
		1156	The file to use instead of /etc/resolv.conf (or OS-specific
		1157	configuration) in the default resolver. When set to the empty
		1158	string, no default config will be used.
		1159
		1160	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1161	When neither "ca_file" nor "ca_path" was specified during
		1162	AnyEvent::TLS context creation, and either of these environment
		1163	variables exist, they will be used to specify CA certificate
		1164	locations instead of a system-dependent default.
		1165
		1166	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1167	When these are set to 1, then the respective modules are not loaded.
		1168	Mostly good for testing AnyEvent itself.
964		1169
965	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1170	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
966	This is an advanced topic that you do not normally need to use AnyEvent	1171	This is an advanced topic that you do not normally need to use AnyEvent
967	in a module. This section is only of use to event loop authors who want	1172	in a module. This section is only of use to event loop authors who want
968	to provide AnyEvent compatibility.	1173	to provide AnyEvent compatibility.
…		…
1023	warn "read: $input\n"; # output what has been read	1228	warn "read: $input\n"; # output what has been read
1024	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1229	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1025	},	1230	},
1026	);	1231	);
1027		1232
1028	my $time_watcher; # can only be used once
1029
1030	sub new_timer {
1031	$timer = AnyEvent->timer (after => 1, cb => sub {	1233	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1032	warn "timeout\n"; # print 'timeout' about every second	1234	warn "timeout\n"; # print 'timeout' at most every second
1033	&new_timer; # and restart the time
1034	});
1035	}	1235	});
1036
1037	new_timer; # create first timer
1038		1236
1039	$cv->recv; # wait until user enters /^q/i	1237	$cv->recv; # wait until user enters /^q/i
1040		1238
1041	REAL-WORLD EXAMPLE	1239	REAL-WORLD EXAMPLE
1042	Consider the Net::FCP module. It features (among others) the following	1240	Consider the Net::FCP module. It features (among others) the following
…		…
1169	through AnyEvent. The benchmark creates a lot of timers (with a zero	1367	through AnyEvent. The benchmark creates a lot of timers (with a zero
1170	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1368	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1171	which it is), lets them fire exactly once and destroys them again.	1369	which it is), lets them fire exactly once and destroys them again.
1172		1370
1173	Source code for this benchmark is found as eg/bench in the AnyEvent	1371	Source code for this benchmark is found as eg/bench in the AnyEvent
1174	distribution.	1372	distribution. It uses the AE interface, which makes a real difference
		1373	for the EV and Perl backends only.
1175		1374
1176	Explanation of the columns	1375	Explanation of the columns
1177	watcher is the number of event watchers created/destroyed. Since	1376	watcher is the number of event watchers created/destroyed. Since
1178	different event models feature vastly different performances, each event	1377	different event models feature vastly different performances, each event
1179	loop was given a number of watchers so that overall runtime is	1378	loop was given a number of watchers so that overall runtime is
…		…
1198	destroy is the time, in microseconds, that it takes to destroy a	1397	destroy is the time, in microseconds, that it takes to destroy a
1199	single watcher.	1398	single watcher.
1200		1399
1201	Results	1400	Results
1202	name watchers bytes create invoke destroy comment	1401	name watchers bytes create invoke destroy comment
1203	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1402	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1204	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1403	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1205	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1404	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1206	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1405	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1207	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1406	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1208	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1407	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1408	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1409	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1209	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1410	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1210	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1411	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1211	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1412	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1212	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1413	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1213		1414
1214	Discussion	1415	Discussion
1215	The benchmark does not measure scalability of the event loop very	1416	The benchmark does not measure scalability of the event loop very
1216	well. For example, a select-based event loop (such as the pure perl one)	1417	well. For example, a select-based event loop (such as the pure perl one)
1217	can never compete with an event loop that uses epoll when the number of	1418	can never compete with an event loop that uses epoll when the number of
…		…
1228	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1429	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1229	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1430	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1230	CPU cycles with POE.	1431	CPU cycles with POE.
1231		1432
1232	"EV" is the sole leader regarding speed and memory use, which are both	1433	"EV" is the sole leader regarding speed and memory use, which are both
1233	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1434	maximal/minimal, respectively. When using the AE API there is zero
		1435	overhead (when going through the AnyEvent API create is about 5-6 times
		1436	slower, with other times being equal, so still uses far less memory than
1234	far less memory than any other event loop and is still faster than Event	1437	any other event loop and is still faster than Event natively).
1235	natively.
1236		1438
1237	The pure perl implementation is hit in a few sweet spots (both the	1439	The pure perl implementation is hit in a few sweet spots (both the
1238	constant timeout and the use of a single fd hit optimisations in the	1440	constant timeout and the use of a single fd hit optimisations in the
1239	perl interpreter and the backend itself). Nevertheless this shows that	1441	perl interpreter and the backend itself). Nevertheless this shows that
1240	it adds very little overhead in itself. Like any select-based backend	1442	it adds very little overhead in itself. Like any select-based backend
…		…
1242	few of them active), of course, but this was not subject of this	1444	few of them active), of course, but this was not subject of this
1243	benchmark.	1445	benchmark.
1244		1446
1245	The "Event" module has a relatively high setup and callback invocation	1447	The "Event" module has a relatively high setup and callback invocation
1246	cost, but overall scores in on the third place.	1448	cost, but overall scores in on the third place.
		1449
		1450	"IO::Async" performs admirably well, about on par with "Event", even
		1451	when using its pure perl backend.
1247		1452
1248	"Glib"'s memory usage is quite a bit higher, but it features a faster	1453	"Glib"'s memory usage is quite a bit higher, but it features a faster
1249	callback invocation and overall ends up in the same class as "Event".	1454	callback invocation and overall ends up in the same class as "Event".
1250	However, Glib scales extremely badly, doubling the number of watchers	1455	However, Glib scales extremely badly, doubling the number of watchers
1251	increases the processing time by more than a factor of four, making it	1456	increases the processing time by more than a factor of four, making it
…		…
1307	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1512	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1308	100 (1%) are active. This mirrors the activity of large servers with	1513	100 (1%) are active. This mirrors the activity of large servers with
1309	many connections, most of which are idle at any one point in time.	1514	many connections, most of which are idle at any one point in time.
1310		1515
1311	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1516	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1312	distribution.	1517	distribution. It uses the AE interface, which makes a real difference
		1518	for the EV and Perl backends only.
1313		1519
1314	Explanation of the columns	1520	Explanation of the columns
1315	sockets is the number of sockets, and twice the number of "servers"	1521	sockets is the number of sockets, and twice the number of "servers"
1316	(as each server has a read and write socket end).	1522	(as each server has a read and write socket end).
1317		1523
…		…
1322	single "request", that is, reading the token from the pipe and	1528	single "request", that is, reading the token from the pipe and
1323	forwarding it to another server. This includes deleting the old timeout	1529	forwarding it to another server. This includes deleting the old timeout
1324	and creating a new one that moves the timeout into the future.	1530	and creating a new one that moves the timeout into the future.
1325		1531
1326	Results	1532	Results
1327	name sockets create request	1533	name sockets create request
1328	EV 20000 69.01 11.16	1534	EV 20000 62.66 7.99
1329	Perl 20000 73.32 35.87	1535	Perl 20000 68.32 32.64
1330	Event 20000 212.62 257.32	1536	IOAsync 20000 174.06 101.15 epoll
1331	Glib 20000 651.16 1896.30	1537	IOAsync 20000 174.67 610.84 poll
		1538	Event 20000 202.69 242.91
		1539	Glib 20000 557.01 1689.52
1332	POE 20000 349.67 12317.24 uses POE::Loop::Event	1540	POE 20000 341.54 12086.32 uses POE::Loop::Event
1333		1541
1334	Discussion	1542	Discussion
1335	This benchmark does measure scalability and overall performance of the	1543	This benchmark does measure scalability and overall performance of the
1336	particular event loop.	1544	particular event loop.
1337		1545
1338	EV is again fastest. Since it is using epoll on my system, the setup	1546	EV is again fastest. Since it is using epoll on my system, the setup
1339	time is relatively high, though.	1547	time is relatively high, though.
1340		1548
1341	Perl surprisingly comes second. It is much faster than the C-based event	1549	Perl surprisingly comes second. It is much faster than the C-based event
1342	loops Event and Glib.	1550	loops Event and Glib.
		1551
		1552	IO::Async performs very well when using its epoll backend, and still
		1553	quite good compared to Glib when using its pure perl backend.
1343		1554
1344	Event suffers from high setup time as well (look at its code and you	1555	Event suffers from high setup time as well (look at its code and you
1345	will understand why). Callback invocation also has a high overhead	1556	will understand why). Callback invocation also has a high overhead
1346	compared to the "$_->() for .."-style loop that the Perl event loop	1557	compared to the "$_->() for .."-style loop that the Perl event loop
1347	uses. Event uses select or poll in basically all documented	1558	uses. Event uses select or poll in basically all documented
…		…
1398		1609
1399	Summary	1610	Summary
1400	* C-based event loops perform very well with small number of watchers,	1611	* C-based event loops perform very well with small number of watchers,
1401	as the management overhead dominates.	1612	as the management overhead dominates.
1402		1613
		1614	THE IO::Lambda BENCHMARK
		1615	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1616	could be misinterpreted to make AnyEvent look bad. In fact, the
		1617	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1618	better (which shouldn't come as a surprise to anybody). As such, the
		1619	benchmark is fine, and mostly shows that the AnyEvent backend from
		1620	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1621	without the extra baggage? To explore this, I wrote the equivalent
		1622	benchmark for AnyEvent.
		1623
		1624	The benchmark itself creates an echo-server, and then, for 500 times,
		1625	connects to the echo server, sends a line, waits for the reply, and then
		1626	creates the next connection. This is a rather bad benchmark, as it
		1627	doesn't test the efficiency of the framework or much non-blocking I/O,
		1628	but it is a benchmark nevertheless.
		1629
		1630	name runtime
		1631	Lambda/select 0.330 sec
		1632	+ optimized 0.122 sec
		1633	Lambda/AnyEvent 0.327 sec
		1634	+ optimized 0.138 sec
		1635	Raw sockets/select 0.077 sec
		1636	POE/select, components 0.662 sec
		1637	POE/select, raw sockets 0.226 sec
		1638	POE/select, optimized 0.404 sec
		1639
		1640	AnyEvent/select/nb 0.085 sec
		1641	AnyEvent/EV/nb 0.068 sec
		1642	+state machine 0.134 sec
		1643
		1644	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1645	benchmarks actually make blocking connects and use 100% blocking I/O,
		1646	defeating the purpose of an event-based solution. All of the newly
		1647	written AnyEvent benchmarks use 100% non-blocking connects (using
		1648	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1649	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1650	connects generally require a lot more bookkeeping and event handling
		1651	than blocking connects (which involve a single syscall only).
		1652
		1653	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1654	offers similar expressive power as POE and IO::Lambda, using
		1655	conventional Perl syntax. This means that both the echo server and the
		1656	client are 100% non-blocking, further placing it at a disadvantage.
		1657
		1658	As you can see, the AnyEvent + EV combination even beats the
		1659	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1660	backend easily beats IO::Lambda and POE.
		1661
		1662	And even the 100% non-blocking version written using the high-level (and
		1663	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1664	higher level ("unoptimised") abstractions by a large margin, even though
		1665	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1666
		1667	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1668	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1669	part of the IO::Lambda distribution and were used without any changes.
		1670
1403	SIGNALS	1671	SIGNALS
1404	AnyEvent currently installs handlers for these signals:	1672	AnyEvent currently installs handlers for these signals:
1405		1673
1406	SIGCHLD	1674	SIGCHLD
1407	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1675	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1408	emulation for event loops that do not support them natively. Also,	1676	emulation for event loops that do not support them natively. Also,
1409	some event loops install a similar handler.	1677	some event loops install a similar handler.
		1678
		1679	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1680	then AnyEvent will reset it to default, to avoid losing child exit
		1681	statuses.
1410		1682
1411	SIGPIPE	1683	SIGPIPE
1412	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1684	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1413	"undef" when AnyEvent gets loaded.	1685	"undef" when AnyEvent gets loaded.
1414		1686
…		…
1422	it is that this way, the handler will be restored to defaults on	1694	it is that this way, the handler will be restored to defaults on
1423	exec.	1695	exec.
1424		1696
1425	Feel free to install your own handler, or reset it to defaults.	1697	Feel free to install your own handler, or reset it to defaults.
1426		1698
		1699	RECOMMENDED/OPTIONAL MODULES
		1700	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1701	it's built-in modules) are required to use it.
		1702
		1703	That does not mean that AnyEvent won't take advantage of some additional
		1704	modules if they are installed.
		1705
		1706	This section epxlains which additional modules will be used, and how
		1707	they affect AnyEvent's operetion.
		1708
		1709	Async::Interrupt
		1710	This slightly arcane module is used to implement fast signal
		1711	handling: To my knowledge, there is no way to do completely
		1712	race-free and quick signal handling in pure perl. To ensure that
		1713	signals still get delivered, AnyEvent will start an interval timer
		1714	to wake up perl (and catch the signals) with some delay (default is
		1715	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1716
		1717	If this module is available, then it will be used to implement
		1718	signal catching, which means that signals will not be delayed, and
		1719	the event loop will not be interrupted regularly, which is more
		1720	efficient (And good for battery life on laptops).
		1721
		1722	This affects not just the pure-perl event loop, but also other event
		1723	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1724
		1725	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1726	natively, and either employ their own workarounds (POE) or use
		1727	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1728	Installing Async::Interrupt does nothing for those backends.
		1729
		1730	EV This module isn't really "optional", as it is simply one of the
		1731	backend event loops that AnyEvent can use. However, it is simply the
		1732	best event loop available in terms of features, speed and stability:
		1733	It supports the AnyEvent API optimally, implements all the watcher
		1734	types in XS, does automatic timer adjustments even when no monotonic
		1735	clock is available, can take avdantage of advanced kernel interfaces
		1736	such as "epoll" and "kqueue", and is the fastest backend by far.
		1737	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1738	Glib::EV).
		1739
		1740	Guard
		1741	The guard module, when used, will be used to implement
		1742	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1743	uses a lot less memory), but otherwise doesn't affect guard
		1744	operation much. It is purely used for performance.
		1745
		1746	JSON and JSON::XS
		1747	This module is required when you want to read or write JSON data via
		1748	AnyEvent::Handle. It is also written in pure-perl, but can take
		1749	advantage of the ultra-high-speed JSON::XS module when it is
		1750	installed.
		1751
		1752	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1753	installed.
		1754
		1755	Net::SSLeay
		1756	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1757	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1758	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1759
		1760	Time::HiRes
		1761	This module is part of perl since release 5.008. It will be used
		1762	when the chosen event library does not come with a timing source on
		1763	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1764	additionally use it to try to use a monotonic clock for timing
		1765	stability.
		1766
1427	FORK	1767	FORK
1428	Most event libraries are not fork-safe. The ones who are usually are	1768	Most event libraries are not fork-safe. The ones who are usually are
1429	because they rely on inefficient but fork-safe "select" or "poll" calls.	1769	because they rely on inefficient but fork-safe "select" or "poll" calls.
1430	Only EV is fully fork-aware.	1770	Only EV is fully fork-aware.
1431		1771
1432	If you have to fork, you must either do so before creating your first	1772	If you have to fork, you must either do so before creating your first
1433	watcher OR you must not use AnyEvent at all in the child.	1773	watcher OR you must not use AnyEvent at all in the child OR you must do
		1774	something completely out of the scope of AnyEvent.
1434		1775
1435	SECURITY CONSIDERATIONS	1776	SECURITY CONSIDERATIONS
1436	AnyEvent can be forced to load any event model via	1777	AnyEvent can be forced to load any event model via
1437	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1778	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1438	to execute arbitrary code or directly gain access, it can easily be used	1779	to execute arbitrary code or directly gain access, it can easily be used
…		…
1442		1783
1443	You can make AnyEvent completely ignore this variable by deleting it	1784	You can make AnyEvent completely ignore this variable by deleting it
1444	before the first watcher gets created, e.g. with a "BEGIN" block:	1785	before the first watcher gets created, e.g. with a "BEGIN" block:
1445		1786
1446	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1787	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1447		1788
1448	use AnyEvent;	1789	use AnyEvent;
1449		1790
1450	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1791	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1451	be used to probe what backend is used and gain other information (which	1792	be used to probe what backend is used and gain other information (which
1452	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),	1793	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1453	and $ENV{PERL_ANYEGENT_STRICT}.	1794	and $ENV{PERL_ANYEVENT_STRICT}.
		1795
		1796	Note that AnyEvent will remove all environment variables starting with
		1797	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1798	enabled.
1454		1799
1455	BUGS	1800	BUGS
1456	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1801	Perl 5.8 has numerous memleaks that sometimes hit this module and are
1457	hard to work around. If you suffer from memleaks, first upgrade to Perl	1802	hard to work around. If you suffer from memleaks, first upgrade to Perl
1458	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1803	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
…		…
1465	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1810	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1466	Event::Lib, Qt, POE.	1811	Event::Lib, Qt, POE.
1467		1812
1468	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1813	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1469	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1814	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1470	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1815	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1816	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1471		1817
1472	Non-blocking file handles, sockets, TCP clients and servers:	1818	Non-blocking file handles, sockets, TCP clients and servers:
1473	AnyEvent::Handle, AnyEvent::Socket.	1819	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1474		1820
1475	Asynchronous DNS: AnyEvent::DNS.	1821	Asynchronous DNS: AnyEvent::DNS.
1476		1822
1477	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1823	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1478		1824
1479	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1825	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1826	AnyEvent::HTTP.
1480		1827
1481	AUTHOR	1828	AUTHOR
1482	Marc Lehmann <schmorp@schmorp.de>	1829	Marc Lehmann <schmorp@schmorp.de>
1483	http://home.schmorp.de/	1830	http://home.schmorp.de/
1484		1831

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Comparing AnyEvent/README (file contents): Revision 1.38 by root, Sun Apr 26 18:12:53 2009 UTC vs. Revision 1.54 by root, Tue Sep 1 18:27:46 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.38 by root, Sun Apr 26 18:12:53 2009 UTC vs.
Revision 1.54 by root, Tue Sep 1 18:27:46 2009 UTC