[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.43 by root, Thu Jul 9 08:37:06 2009 UTC vs.
Revision 1.62 by root, Sun Jun 6 10:13:57 2010 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 and POE are various supported	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	event 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	# if you prefer function calls, look at the AE manpage for
		11	# an alternative API.
		12
10	# file descriptor readable	13	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });	14	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
12		15
13	# one-shot or repeating timers	16	# one-shot or repeating timers
14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	17	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	18	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
37		40
38	INTRODUCTION/TUTORIAL	41	INTRODUCTION/TUTORIAL
39	This manpage is mainly a reference manual. If you are interested in a	42	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	43	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
41	manpage.	44	manpage.
		45
		46	SUPPORT
		47	There is a mailinglist for discussing all things AnyEvent, and an IRC
		48	channel, too.
		49
		50	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		51	Repository, at <http://anyevent.schmorp.de>, for more info.
42		52
43	WHY YOU SHOULD USE THIS MODULE (OR NOT)	53	WHY YOU SHOULD USE THIS MODULE (OR NOT)
44	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	54	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
45	nowadays. So what is different about AnyEvent?	55	nowadays. So what is different about AnyEvent?
46		56
…		…
166	Note that "my $w; $w =" combination. This is necessary because in Perl,	176	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	177	my variables are only visible after the statement in which they are
168	declared.	178	declared.
169		179
170	I/O WATCHERS	180	I/O WATCHERS
		181	$w = AnyEvent->io (
		182	fh => <filehandle_or_fileno>,
		183	poll => <"r" or "w">,
		184	cb => <callback>,
		185	);
		186
171	You can create an I/O watcher by calling the "AnyEvent->io" method with	187	You can create an I/O watcher by calling the "AnyEvent->io" method with
172	the following mandatory key-value pairs as arguments:	188	the following mandatory key-value pairs as arguments:
173		189
174	"fh" is the Perl file handle (or a naked file descriptor) to watch for	190	"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	191	events (AnyEvent might or might not keep a reference to this file
…		…
203	warn "read: $input\n";	219	warn "read: $input\n";
204	undef $w;	220	undef $w;
205	});	221	});
206		222
207	TIME WATCHERS	223	TIME WATCHERS
		224	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		225
		226	$w = AnyEvent->timer (
		227	after => <fractional_seconds>,
		228	interval => <fractional_seconds>,
		229	cb => <callback>,
		230	);
		231
208	You can create a time watcher by calling the "AnyEvent->timer" method	232	You can create a time watcher by calling the "AnyEvent->timer" method
209	with the following mandatory arguments:	233	with the following mandatory arguments:
210		234
211	"after" specifies after how many seconds (fractional values are	235	"after" specifies after how many seconds (fractional values are
212	supported) the callback should be invoked. "cb" is the callback to	236	supported) the callback should be invoked. "cb" is the callback to
…		…
333	time, which might affect timers and time-outs.	357	time, which might affect timers and time-outs.
334		358
335	When this is the case, you can call this method, which will update	359	When this is the case, you can call this method, which will update
336	the event loop's idea of "current time".	360	the event loop's idea of "current time".
337		361
		362	A typical example would be a script in a web server (e.g.
		363	"mod_perl") - when mod_perl executes the script, then the event loop
		364	will have the wrong idea about the "current time" (being potentially
		365	far in the past, when the script ran the last time). In that case
		366	you should arrange a call to "AnyEvent->now_update" each time the
		367	web server process wakes up again (e.g. at the start of your script,
		368	or in a handler).
		369
338	Note that updating the time might cause some events to be handled.	370	Note that updating the time might cause some events to be handled.
339		371
340	SIGNAL WATCHERS	372	SIGNAL WATCHERS
		373	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		374
341	You can watch for signals using a signal watcher, "signal" is the signal	375	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	376	name in uppercase and without any "SIG" prefix, "cb" is the Perl
343	callback to be invoked whenever a signal occurs.	377	callback to be invoked whenever a signal occurs.
344		378
345	Although the callback might get passed parameters, their value and	379	Although the callback might get passed parameters, their value and
…		…
350	invocation, and callback invocation will be synchronous. Synchronous	384	invocation, and callback invocation will be synchronous. Synchronous
351	means that it might take a while until the signal gets handled by the	385	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.	386	process, but it is guaranteed not to interrupt any other callbacks.
353		387
354	The main advantage of using these watchers is that you can share a	388	The main advantage of using these watchers is that you can share a
355	signal between multiple watchers.	389	signal between multiple watchers, and AnyEvent will ensure that signals
		390	will not interrupt your program at bad times.
356		391
357	This watcher might use %SIG, so programs overwriting those signals	392	This watcher might use %SIG (depending on the event loop used), so
358	directly will likely not work correctly.	393	programs overwriting those signals directly will likely not work
		394	correctly.
359		395
360	Example: exit on SIGINT	396	Example: exit on SIGINT
361		397
362	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	398	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
363		399
		400	Restart Behaviour
		401	While restart behaviour is up to the event loop implementation, most
		402	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		403	pure perl implementation).
		404
		405	Safe/Unsafe Signals
		406	Perl signals can be either "safe" (synchronous to opcode handling) or
		407	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		408	latter might corrupt your memory.
		409
		410	AnyEvent signal handlers are, in addition, synchronous to the event
		411	loop, i.e. they will not interrupt your running perl program but will
		412	only be called as part of the normal event handling (just like timer,
		413	I/O etc. callbacks, too).
		414
		415	Signal Races, Delays and Workarounds
		416	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		417	callbacks to signals in a generic way, which is a pity, as you cannot do
		418	race-free signal handling in perl, requiring C libraries for this.
		419	AnyEvent will try to do it's best, which means in some cases, signals
		420	will be delayed. The maximum time a signal might be delayed is specified
		421	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		422	can be changed only before the first signal watcher is created, and
		423	should be left alone otherwise. This variable determines how often
		424	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		425	will cause fewer spurious wake-ups, which is better for power and CPU
		426	saving.
		427
		428	All these problems can be avoided by installing the optional
		429	Async::Interrupt module, which works with most event loops. It will not
		430	work with inherently broken event loops such as Event or Event::Lib (and
		431	not with POE currently, as POE does it's own workaround with one-second
		432	latency). For those, you just have to suffer the delays.
		433
364	CHILD PROCESS WATCHERS	434	CHILD PROCESS WATCHERS
		435	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		436
365	You can also watch on a child process exit and catch its exit status.	437	You can also watch on a child process exit and catch its exit status.
366		438
367	The child process is specified by the "pid" argument (if set to 0, it	439	The child process is specified by the "pid" argument (one some backends,
368	watches for any child process exit). The watcher will triggered only	440	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	441	The watcher will be triggered only when the child process has finished
370	on any trace events (stopped/continued).	442	and an exit status is available, not on any trace events
		443	(stopped/continued).
371		444
372	The callback will be called with the pid and exit status (as returned by	445	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	446	waitpid), so unlike other watcher types, you can rely on child watcher
374	callback arguments.	447	callback arguments.
375		448
…		…
390	of when you start the watcher.	463	of when you start the watcher.
391		464
392	This means you cannot create a child watcher as the very first thing in	465	This means you cannot create a child watcher as the very first thing in
393	an AnyEvent program, you have to create at least one watcher before	466	an AnyEvent program, you have to create at least one watcher before
394	you "fork" the child (alternatively, you can call "AnyEvent::detect").	467	you "fork" the child (alternatively, you can call "AnyEvent::detect").
		468
		469	As most event loops do not support waiting for child events, they will
		470	be emulated by AnyEvent in most cases, in which the latency and race
		471	problems mentioned in the description of signal watchers apply.
395		472
396	Example: fork a process and wait for it	473	Example: fork a process and wait for it
397		474
398	my $done = AnyEvent->condvar;	475	my $done = AnyEvent->condvar;
399		476
…		…
410		487
411	# do something else, then wait for process exit	488	# do something else, then wait for process exit
412	$done->recv;	489	$done->recv;
413		490
414	IDLE WATCHERS	491	IDLE WATCHERS
415	Sometimes there is a need to do something, but it is not so important to	492	$w = AnyEvent->idle (cb => <callback>);
416	do it instantly, but only when there is nothing better to do. This
417	"nothing better to do" is usually defined to be "no other events need
418	attention by the event loop".
419		493
420	Idle watchers ideally get invoked when the event loop has nothing better	494	Repeatedly invoke the callback after the process becomes idle, until
421	to do, just before it would block the process to wait for new events.	495	either the watcher is destroyed or new events have been detected.
422	Instead of blocking, the idle watcher is invoked.
423		496
424	Most event loops unfortunately do not really support idle watchers (only	497	Idle watchers are useful when there is a need to do something, but it is
		498	not so important (or wise) to do it instantly. The callback will be
		499	invoked only when there is "nothing better to do", which is usually
		500	defined as "all outstanding events have been handled and no new events
		501	have been detected". That means that idle watchers ideally get invoked
		502	when the event loop has just polled for new events but none have been
		503	detected. Instead of blocking to wait for more events, the idle watchers
		504	will be invoked.
		505
		506	Unfortunately, most event loops do not really support idle watchers
425	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent	507	(only EV, Event and Glib do it in a usable fashion) - for the rest,
426	will simply call the callback "from time to time".	508	AnyEvent will simply call the callback "from time to time".
427		509
428	Example: read lines from STDIN, but only process them when the program	510	Example: read lines from STDIN, but only process them when the program
429	is otherwise idle:	511	is otherwise idle:
430		512
431	my @lines; # read data	513	my @lines; # read data
…		…
444	}	526	}
445	});	527	});
446	});	528	});
447		529
448	CONDITION VARIABLES	530	CONDITION VARIABLES
		531	$cv = AnyEvent->condvar;
		532
		533	$cv->send (<list>);
		534	my @res = $cv->recv;
		535
449	If you are familiar with some event loops you will know that all of them	536	If you are familiar with some event loops you will know that all of them
450	require you to run some blocking "loop", "run" or similar function that	537	require you to run some blocking "loop", "run" or similar function that
451	will actively watch for new events and call your callbacks.	538	will actively watch for new events and call your callbacks.
452		539
453	AnyEvent is different, it expects somebody else to run the event loop	540	AnyEvent is slightly different: it expects somebody else to run the
454	and will only block when necessary (usually when told by the user).	541	event loop and will only block when necessary (usually when told by the
		542	user).
455		543
456	The instrument to do that is called a "condition variable", so called	544	The tool to do that is called a "condition variable", so called because
457	because they represent a condition that must become true.	545	they represent a condition that must become true.
		546
		547	Now is probably a good time to look at the examples further below.
458		548
459	Condition variables can be created by calling the "AnyEvent->condvar"	549	Condition variables can be created by calling the "AnyEvent->condvar"
460	method, usually without arguments. The only argument pair allowed is	550	method, usually without arguments. The only argument pair allowed is
461
462	"cb", which specifies a callback to be called when the condition	551	"cb", which specifies a callback to be called when the condition
463	variable becomes true, with the condition variable as the first argument	552	variable becomes true, with the condition variable as the first argument
464	(but not the results).	553	(but not the results).
465		554
466	After creation, the condition variable is "false" until it becomes	555	After creation, the condition variable is "false" until it becomes
467	"true" by calling the "send" method (or calling the condition variable	556	"true" by calling the "send" method (or calling the condition variable
468	as if it were a callback, read about the caveats in the description for	557	as if it were a callback, read about the caveats in the description for
469	the "->send" method).	558	the "->send" method).
470		559
471	Condition variables are similar to callbacks, except that you can	560	Since condition variables are the most complex part of the AnyEvent API,
472	optionally wait for them. They can also be called merge points - points	561	here are some different mental models of what they are - pick the ones
473	in time where multiple outstanding events have been processed. And yet	562	you can connect to:
474	another way to call them is transactions - each condition variable can	563
475	be used to represent a transaction, which finishes at some point and	564	* Condition variables are like callbacks - you can call them (and pass
476	delivers a result.	565	them instead of callbacks). Unlike callbacks however, you can also
		566	wait for them to be called.
		567
		568	* Condition variables are signals - one side can emit or send them,
		569	the other side can wait for them, or install a handler that is
		570	called when the signal fires.
		571
		572	* Condition variables are like "Merge Points" - points in your program
		573	where you merge multiple independent results/control flows into one.
		574
		575	* Condition variables represent a transaction - function that start
		576	some kind of transaction can return them, leaving the caller the
		577	choice between waiting in a blocking fashion, or setting a callback.
		578
		579	* Condition variables represent future values, or promises to deliver
		580	some result, long before the result is available.
477		581
478	Condition variables are very useful to signal that something has	582	Condition variables are very useful to signal that something has
479	finished, for example, if you write a module that does asynchronous http	583	finished, for example, if you write a module that does asynchronous http
480	requests, then a condition variable would be the ideal candidate to	584	requests, then a condition variable would be the ideal candidate to
481	signal the availability of results. The user can either act when the	585	signal the availability of results. The user can either act when the
…		…
502	which eventually calls "-> send", and the "consumer side", which waits	606	which eventually calls "-> send", and the "consumer side", which waits
503	for the send to occur.	607	for the send to occur.
504		608
505	Example: wait for a timer.	609	Example: wait for a timer.
506		610
507	# wait till the result is ready	611	# condition: "wait till the timer is fired"
508	my $result_ready = AnyEvent->condvar;	612	my $timer_fired = AnyEvent->condvar;
509		613
510	# do something such as adding a timer	614	# create the timer - we could wait for, say
511	# or socket watcher the calls $result_ready->send	615	# a handle becomign ready, or even an
512	# when the "result" is ready.	616	# AnyEvent::HTTP request to finish, but
513	# in this case, we simply use a timer:	617	# in this case, we simply use a timer:
514	my $w = AnyEvent->timer (	618	my $w = AnyEvent->timer (
515	after => 1,	619	after => 1,
516	cb => sub { $result_ready->send },	620	cb => sub { $timer_fired->send },
517	);	621	);
518		622
519	# this "blocks" (while handling events) till the callback	623	# this "blocks" (while handling events) till the callback
520	# calls send	624	# calls ->send
521	$result_ready->recv;	625	$timer_fired->recv;
522		626
523	Example: wait for a timer, but take advantage of the fact that condition	627	Example: wait for a timer, but take advantage of the fact that condition
524	variables are also code references.	628	variables are also callable directly.
525		629
526	my $done = AnyEvent->condvar;	630	my $done = AnyEvent->condvar;
527	my $delay = AnyEvent->timer (after => 5, cb => $done);	631	my $delay = AnyEvent->timer (after => 5, cb => $done);
528	$done->recv;	632	$done->recv;
529		633
…		…
535		639
536	...	640	...
537		641
538	my @info = $couchdb->info->recv;	642	my @info = $couchdb->info->recv;
539		643
540	And this is how you would just ste a callback to be called whenever the	644	And this is how you would just set a callback to be called whenever the
541	results are available:	645	results are available:
542		646
543	$couchdb->info->cb (sub {	647	$couchdb->info->cb (sub {
544	my @info = $_[0]->recv;	648	my @info = $_[0]->recv;
545	});	649	});
…		…
560		664
561	Any arguments passed to the "send" call will be returned by all	665	Any arguments passed to the "send" call will be returned by all
562	future "->recv" calls.	666	future "->recv" calls.
563		667
564	Condition variables are overloaded so one can call them directly (as	668	Condition variables are overloaded so one can call them directly (as
565	a code reference). Calling them directly is the same as calling	669	if they were a code reference). Calling them directly is the same as
566	"send". Note, however, that many C-based event loops do not handle	670	calling "send".
567	overloading, so as tempting as it may be, passing a condition
568	variable instead of a callback does not work. Both the pure perl and
569	EV loops support overloading, however, as well as all functions that
570	use perl to invoke a callback (as in AnyEvent::Socket and
571	AnyEvent::DNS for example).
572		671
573	$cv->croak ($error)	672	$cv->croak ($error)
574	Similar to send, but causes all call's to "->recv" to invoke	673	Similar to send, but causes all call's to "->recv" to invoke
575	"Carp::croak" with the given error message/object/scalar.	674	"Carp::croak" with the given error message/object/scalar.
576		675
577	This can be used to signal any errors to the condition variable	676	This can be used to signal any errors to the condition variable
578	user/consumer.	677	user/consumer. Doing it this way instead of calling "croak" directly
		678	delays the error detetcion, but has the overwhelmign advantage that
		679	it diagnoses the error at the place where the result is expected,
		680	and not deep in some event clalback without connection to the actual
		681	code causing the problem.
579		682
580	$cv->begin ([group callback])	683	$cv->begin ([group callback])
581	$cv->end	684	$cv->end
582	These two methods can be used to combine many transactions/events	685	These two methods can be used to combine many transactions/events
583	into one. For example, a function that pings many hosts in parallel	686	into one. For example, a function that pings many hosts in parallel
584	might want to use a condition variable for the whole process.	687	might want to use a condition variable for the whole process.
585		688
586	Every call to "->begin" will increment a counter, and every call to	689	Every call to "->begin" will increment a counter, and every call to
587	"->end" will decrement it. If the counter reaches 0 in "->end", the	690	"->end" will decrement it. If the counter reaches 0 in "->end", the
588	(last) callback passed to "begin" will be executed. That callback is	691	(last) callback passed to "begin" will be executed, passing the
589	supposed to call "->send", but that is not required. If no	692	condvar as first argument. That callback is supposed to call
		693	"->send", but that is not required. If no group callback was set,
590	callback was set, "send" will be called without any arguments.	694	"send" will be called without any arguments.
591		695
592	You can think of "$cv->send" giving you an OR condition (one call	696	You can think of "$cv->send" giving you an OR condition (one call
593	sends), while "$cv->begin" and "$cv->end" giving you an AND	697	sends), while "$cv->begin" and "$cv->end" giving you an AND
594	condition (all "begin" calls must be "end"'ed before the condvar	698	condition (all "begin" calls must be "end"'ed before the condvar
595	sends).	699	sends).
…		…
623	that are begung can potentially be zero:	727	that are begung can potentially be zero:
624		728
625	my $cv = AnyEvent->condvar;	729	my $cv = AnyEvent->condvar;
626		730
627	my %result;	731	my %result;
628	$cv->begin (sub { $cv->send (\%result) });	732	$cv->begin (sub { shift->send (\%result) });
629		733
630	for my $host (@list_of_hosts) {	734	for my $host (@list_of_hosts) {
631	$cv->begin;	735	$cv->begin;
632	ping_host_then_call_callback $host, sub {	736	ping_host_then_call_callback $host, sub {
633	$result{$host} = ...;	737	$result{$host} = ...;
…		…
671	function will call "croak".	775	function will call "croak".
672		776
673	In list context, all parameters passed to "send" will be returned,	777	In list context, all parameters passed to "send" will be returned,
674	in scalar context only the first one will be returned.	778	in scalar context only the first one will be returned.
675		779
		780	Note that doing a blocking wait in a callback is not supported by
		781	any event loop, that is, recursive invocation of a blocking "->recv"
		782	is not allowed, and the "recv" call will "croak" if such a condition
		783	is detected. This condition can be slightly loosened by using
		784	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		785	thread that doesn't run the event loop itself.
		786
676	Not all event models support a blocking wait - some die in that case	787	Not all event models support a blocking wait - some die in that case
677	(programs might want to do that to stay interactive), so *if you are	788	(programs might want to do that to stay interactive), so *if you are
678	using this from a module, never require a blocking wait*, but let	789	using this from a module, never require a blocking wait*. Instead,
679	the caller decide whether the call will block or not (for example,	790	let the caller decide whether the call will block or not (for
680	by coupling condition variables with some kind of request results	791	example, by coupling condition variables with some kind of request
681	and supporting callbacks so the caller knows that getting the result	792	results and supporting callbacks so the caller knows that getting
682	will not block, while still supporting blocking waits if the caller	793	the result will not block, while still supporting blocking waits if
683	so desires).	794	the caller so desires).
684
685	Another reason never to "->recv" in a module is that you cannot
686	sensibly have two "->recv"'s in parallel, as that would require
687	multiple interpreters or coroutines/threads, none of which
688	"AnyEvent" can supply.
689
690	The Coro module, however, can and does supply coroutines and, in
691	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
692	versions and also integrates coroutines into AnyEvent, making
693	blocking "->recv" calls perfectly safe as long as they are done from
694	another coroutine (one that doesn't run the event loop).
695		795
696	You can ensure that "-recv" never blocks by setting a callback and	796	You can ensure that "-recv" never blocks by setting a callback and
697	only calling "->recv" from within that callback (or at a later	797	only calling "->recv" from within that callback (or at a later
698	time). This will work even when the event loop does not support	798	time). This will work even when the event loop does not support
699	blocking waits otherwise.	799	blocking waits otherwise.
…		…
704		804
705	$cb = $cv->cb ($cb->($cv))	805	$cb = $cv->cb ($cb->($cv))
706	This is a mutator function that returns the callback set and	806	This is a mutator function that returns the callback set and
707	optionally replaces it before doing so.	807	optionally replaces it before doing so.
708		808
709	The callback will be called when the condition becomes "true", i.e.	809	The callback will be called when the condition becomes (or already
710	when "send" or "croak" are called, with the only argument being the	810	was) "true", i.e. when "send" or "croak" are called (or were
711	condition variable itself. Calling "recv" inside the callback or at	811	called), with the only argument being the condition variable itself.
		812	Calling "recv" inside the callback or at any later time is
712	any later time is guaranteed not to block.	813	guaranteed not to block.
713		814
714	SUPPORTED EVENT LOOPS/BACKENDS	815	SUPPORTED EVENT LOOPS/BACKENDS
715	The available backend classes are (every class has its own manpage):	816	The available backend classes are (every class has its own manpage):
716		817
717	Backends that are autoprobed when no other event loop can be found.	818	Backends that are autoprobed when no other event loop can be found.
718	EV is the preferred backend when no other event loop seems to be in	819	EV is the preferred backend when no other event loop seems to be in
719	use. If EV is not installed, then AnyEvent will try Event, and,	820	use. If EV is not installed, then AnyEvent will fall back to its own
720	failing that, will fall back to its own pure-perl implementation,	821	pure-perl implementation, which is available everywhere as it comes
721	which is available everywhere as it comes with AnyEvent itself.	822	with AnyEvent itself.
722		823
723	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	824	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
724	AnyEvent::Impl::Event based on Event, very stable, few glitches.
725	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	825	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
726		826
727	Backends that are transparently being picked up when they are used.	827	Backends that are transparently being picked up when they are used.
728	These will be used when they are currently loaded when the first	828	These will be used when they are currently loaded when the first
729	watcher is created, in which case it is assumed that the application	829	watcher is created, in which case it is assumed that the application
730	is using them. This means that AnyEvent will automatically pick the	830	is using them. This means that AnyEvent will automatically pick the
731	right backend when the main program loads an event module before	831	right backend when the main program loads an event module before
732	anything starts to create watchers. Nothing special needs to be done	832	anything starts to create watchers. Nothing special needs to be done
733	by the main program.	833	by the main program.
734		834
		835	AnyEvent::Impl::Event based on Event, very stable, few glitches.
735	AnyEvent::Impl::Glib based on Glib, slow but very stable.	836	AnyEvent::Impl::Glib based on Glib, slow but very stable.
736	AnyEvent::Impl::Tk based on Tk, very broken.	837	AnyEvent::Impl::Tk based on Tk, very broken.
737	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	838	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
738	AnyEvent::Impl::POE based on POE, very slow, some limitations.	839	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		840	AnyEvent::Impl::Irssi used when running within irssi.
739		841
740	Backends with special needs.	842	Backends with special needs.
741	Qt requires the Qt::Application to be instantiated first, but will	843	Qt requires the Qt::Application to be instantiated first, but will
742	otherwise be picked up automatically. As long as the main program	844	otherwise be picked up automatically. As long as the main program
743	instantiates the application before any AnyEvent watchers are	845	instantiates the application before any AnyEvent watchers are
…		…
808	creates and installs the global IO::AIO watcher in a "post_detect"	910	creates and installs the global IO::AIO watcher in a "post_detect"
809	block to avoid autodetecting the event module at load time.	911	block to avoid autodetecting the event module at load time.
810		912
811	If called in scalar or list context, then it creates and returns an	913	If called in scalar or list context, then it creates and returns an
812	object that automatically removes the callback again when it is	914	object that automatically removes the callback again when it is
		915	destroyed (or "undef" when the hook was immediately executed). See
813	destroyed. See Coro::BDB for a case where this is useful.	916	AnyEvent::AIO for a case where this is useful.
		917
		918	Example: Create a watcher for the IO::AIO module and store it in
		919	$WATCHER. Only do so after the event loop is initialised, though.
		920
		921	our WATCHER;
		922
		923	my $guard = AnyEvent::post_detect {
		924	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		925	};
		926
		927	# the \|\|= is important in case post_detect immediately runs the block,
		928	# as to not clobber the newly-created watcher. assigning both watcher and
		929	# post_detect guard to the same variable has the advantage of users being
		930	# able to just C<undef $WATCHER> if the watcher causes them grief.
		931
		932	$WATCHER \|\|= $guard;
814		933
815	@AnyEvent::post_detect	934	@AnyEvent::post_detect
816	If there are any code references in this array (you can "push" to it	935	If there are any code references in this array (you can "push" to it
817	before or after loading AnyEvent), then they will called directly	936	before or after loading AnyEvent), then they will called directly
818	after the event loop has been chosen.	937	after the event loop has been chosen.
…		…
820	You should check $AnyEvent::MODEL before adding to this array,	939	You should check $AnyEvent::MODEL before adding to this array,
821	though: if it is defined then the event loop has already been	940	though: if it is defined then the event loop has already been
822	detected, and the array will be ignored.	941	detected, and the array will be ignored.
823		942
824	Best use "AnyEvent::post_detect { BLOCK }" when your application	943	Best use "AnyEvent::post_detect { BLOCK }" when your application
825	allows it,as it takes care of these details.	944	allows it, as it takes care of these details.
826		945
827	This variable is mainly useful for modules that can do something	946	This variable is mainly useful for modules that can do something
828	useful when AnyEvent is used and thus want to know when it is	947	useful when AnyEvent is used and thus want to know when it is
829	initialised, but do not need to even load it by default. This array	948	initialised, but do not need to even load it by default. This array
830	provides the means to hook into AnyEvent passively, without loading	949	provides the means to hook into AnyEvent passively, without loading
831	it.	950	it.
		951
		952	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		953	together, you could put this into Coro (this is the actual code used
		954	by Coro to accomplish this):
		955
		956	if (defined $AnyEvent::MODEL) {
		957	# AnyEvent already initialised, so load Coro::AnyEvent
		958	require Coro::AnyEvent;
		959	} else {
		960	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		961	# as soon as it is
		962	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		963	}
832		964
833	WHAT TO DO IN A MODULE	965	WHAT TO DO IN A MODULE
834	As a module author, you should "use AnyEvent" and call AnyEvent methods	966	As a module author, you should "use AnyEvent" and call AnyEvent methods
835	freely, but you should not load a specific event module or rely on it.	967	freely, but you should not load a specific event module or rely on it.
836		968
…		…
889		1021
890	OTHER MODULES	1022	OTHER MODULES
891	The following is a non-exhaustive list of additional modules that use	1023	The following is a non-exhaustive list of additional modules that use
892	AnyEvent as a client and can therefore be mixed easily with other	1024	AnyEvent as a client and can therefore be mixed easily with other
893	AnyEvent modules and other event loops in the same program. Some of the	1025	AnyEvent modules and other event loops in the same program. Some of the
894	modules come with AnyEvent, most are available via CPAN.	1026	modules come as part of AnyEvent, the others are available via CPAN.
895		1027
896	AnyEvent::Util	1028	AnyEvent::Util
897	Contains various utility functions that replace often-used but	1029	Contains various utility functions that replace often-used but
898	blocking functions such as "inet_aton" by event-/callback-based	1030	blocking functions such as "inet_aton" by event-/callback-based
899	versions.	1031	versions.
…		…
910	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1042	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
911		1043
912	AnyEvent::DNS	1044	AnyEvent::DNS
913	Provides rich asynchronous DNS resolver capabilities.	1045	Provides rich asynchronous DNS resolver capabilities.
914		1046
		1047	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1048	AnyEvent::IGS, AnyEvent::FCP
		1049	Implement event-based interfaces to the protocols of the same name
		1050	(for the curious, IGS is the International Go Server and FCP is the
		1051	Freenet Client Protocol).
		1052
		1053	AnyEvent::Handle::UDP
		1054	Here be danger!
		1055
		1056	As Pauli would put it, "Not only is it not right, it's not even
		1057	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1058	most notably it's use of a stream-based API with a protocol that
		1059	isn't streamable, that the only way to improve it is to delete it.
		1060
		1061	It features data corruption (but typically only under load) and
		1062	general confusion. On top, the author is not only clueless about UDP
		1063	but also fact-resistant - some gems of his understanding: "connect
		1064	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1065	has datagrams, not packets", "I don't need to implement proper error
		1066	checking as UDP doesn't support error checking" and so on - he
		1067	doesn't even understand what's wrong with his module when it is
		1068	explained to him.
		1069
915	AnyEvent::HTTP	1070	AnyEvent::DBI
916	A simple-to-use HTTP library that is capable of making a lot of	1071	Executes DBI requests asynchronously in a proxy process for you,
917	concurrent HTTP requests.	1072	notifying you in an event-bnased way when the operation is finished.
		1073
		1074	AnyEvent::AIO
		1075	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1076	the toolbox of every event programmer. AnyEvent::AIO transparently
		1077	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1078	event-based file I/O, and much more.
918		1079
919	AnyEvent::HTTPD	1080	AnyEvent::HTTPD
920	Provides a simple web application server framework.	1081	A simple embedded webserver.
921		1082
922	AnyEvent::FastPing	1083	AnyEvent::FastPing
923	The fastest ping in the west.	1084	The fastest ping in the west.
924		1085
925	AnyEvent::DBI
926	Executes DBI requests asynchronously in a proxy process.
927
928	AnyEvent::AIO
929	Truly asynchronous I/O, should be in the toolbox of every event
930	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
931	together.
932
933	AnyEvent::BDB
934	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
935	fuses BDB and AnyEvent together.
936
937	AnyEvent::GPSD
938	A non-blocking interface to gpsd, a daemon delivering GPS
939	information.
940
941	AnyEvent::IRC
942	AnyEvent based IRC client module family (replacing the older
943	Net::IRC3).
944
945	AnyEvent::XMPP
946	AnyEvent based XMPP (Jabber protocol) module family (replacing the
947	older Net::XMPP2>.
948
949	AnyEvent::IGS
950	A non-blocking interface to the Internet Go Server protocol (used by
951	App::IGS).
952
953	Net::FCP
954	AnyEvent-based implementation of the Freenet Client Protocol,
955	birthplace of AnyEvent.
956
957	Event::ExecFlow
958	High level API for event-based execution flow control.
959
960	Coro	1086	Coro
961	Has special support for AnyEvent via Coro::AnyEvent.	1087	Has special support for AnyEvent via Coro::AnyEvent.
		1088
		1089	SIMPLIFIED AE API
		1090	Starting with version 5.0, AnyEvent officially supports a second, much
		1091	simpler, API that is designed to reduce the calling, typing and memory
		1092	overhead by using function call syntax and a fixed number of parameters.
		1093
		1094	See the AE manpage for details.
962		1095
963	ERROR AND EXCEPTION HANDLING	1096	ERROR AND EXCEPTION HANDLING
964	In general, AnyEvent does not do any error handling - it relies on the	1097	In general, AnyEvent does not do any error handling - it relies on the
965	caller to do that if required. The AnyEvent::Strict module (see also the	1098	caller to do that if required. The AnyEvent::Strict module (see also the
966	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1099	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
994	by "PERL_ANYEVENT_MODEL".	1127	by "PERL_ANYEVENT_MODEL".
995		1128
996	When set to 2 or higher, cause AnyEvent to report to STDERR which	1129	When set to 2 or higher, cause AnyEvent to report to STDERR which
997	event model it chooses.	1130	event model it chooses.
998		1131
		1132	When set to 8 or higher, then AnyEvent will report extra information
		1133	on which optional modules it loads and how it implements certain
		1134	features.
		1135
999	"PERL_ANYEVENT_STRICT"	1136	"PERL_ANYEVENT_STRICT"
1000	AnyEvent does not do much argument checking by default, as thorough	1137	AnyEvent does not do much argument checking by default, as thorough
1001	argument checking is very costly. Setting this variable to a true	1138	argument checking is very costly. Setting this variable to a true
1002	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1139	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1003	thoroughly check the arguments passed to most method calls. If it	1140	thoroughly check the arguments passed to most method calls. If it
1004	finds any problems, it will croak.	1141	finds any problems, it will croak.
1005		1142
1006	In other words, enables "strict" mode.	1143	In other words, enables "strict" mode.
1007		1144
1008	Unlike "use strict", it is definitely recommended to keep it off in	1145	Unlike "use strict" (or it's modern cousin, "use common::sense", it
1009	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1146	is definitely recommended to keep it off in production. Keeping
		1147	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1010	while developing programs can be very useful, however.	1148	programs can be very useful, however.
1011		1149
1012	"PERL_ANYEVENT_MODEL"	1150	"PERL_ANYEVENT_MODEL"
1013	This can be used to specify the event model to be used by AnyEvent,	1151	This can be used to specify the event model to be used by AnyEvent,
1014	before auto detection and -probing kicks in. It must be a string	1152	before auto detection and -probing kicks in. It must be a string
1015	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1153	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
1072	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1210	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1073	When neither "ca_file" nor "ca_path" was specified during	1211	When neither "ca_file" nor "ca_path" was specified during
1074	AnyEvent::TLS context creation, and either of these environment	1212	AnyEvent::TLS context creation, and either of these environment
1075	variables exist, they will be used to specify CA certificate	1213	variables exist, they will be used to specify CA certificate
1076	locations instead of a system-dependent default.	1214	locations instead of a system-dependent default.
		1215
		1216	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1217	When these are set to 1, then the respective modules are not loaded.
		1218	Mostly good for testing AnyEvent itself.
1077		1219
1078	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1220	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1079	This is an advanced topic that you do not normally need to use AnyEvent	1221	This is an advanced topic that you do not normally need to use AnyEvent
1080	in a module. This section is only of use to event loop authors who want	1222	in a module. This section is only of use to event loop authors who want
1081	to provide AnyEvent compatibility.	1223	to provide AnyEvent compatibility.
…		…
1136	warn "read: $input\n"; # output what has been read	1278	warn "read: $input\n"; # output what has been read
1137	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1279	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1138	},	1280	},
1139	);	1281	);
1140		1282
1141	my $time_watcher; # can only be used once
1142
1143	sub new_timer {
1144	$timer = AnyEvent->timer (after => 1, cb => sub {	1283	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1145	warn "timeout\n"; # print 'timeout' about every second	1284	warn "timeout\n"; # print 'timeout' at most every second
1146	&new_timer; # and restart the time
1147	});
1148	}	1285	});
1149
1150	new_timer; # create first timer
1151		1286
1152	$cv->recv; # wait until user enters /^q/i	1287	$cv->recv; # wait until user enters /^q/i
1153		1288
1154	REAL-WORLD EXAMPLE	1289	REAL-WORLD EXAMPLE
1155	Consider the Net::FCP module. It features (among others) the following	1290	Consider the Net::FCP module. It features (among others) the following
…		…
1227		1362
1228	The actual code goes further and collects all errors ("die"s,	1363	The actual code goes further and collects all errors ("die"s,
1229	exceptions) that occurred during request processing. The "result" method	1364	exceptions) that occurred during request processing. The "result" method
1230	detects whether an exception as thrown (it is stored inside the $txn	1365	detects whether an exception as thrown (it is stored inside the $txn
1231	object) and just throws the exception, which means connection errors and	1366	object) and just throws the exception, which means connection errors and
1232	other problems get reported tot he code that tries to use the result,	1367	other problems get reported to the code that tries to use the result,
1233	not in a random callback.	1368	not in a random callback.
1234		1369
1235	All of this enables the following usage styles:	1370	All of this enables the following usage styles:
1236		1371
1237	1. Blocking:	1372	1. Blocking:
…		…
1282	through AnyEvent. The benchmark creates a lot of timers (with a zero	1417	through AnyEvent. The benchmark creates a lot of timers (with a zero
1283	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1418	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1284	which it is), lets them fire exactly once and destroys them again.	1419	which it is), lets them fire exactly once and destroys them again.
1285		1420
1286	Source code for this benchmark is found as eg/bench in the AnyEvent	1421	Source code for this benchmark is found as eg/bench in the AnyEvent
1287	distribution.	1422	distribution. It uses the AE interface, which makes a real difference
		1423	for the EV and Perl backends only.
1288		1424
1289	Explanation of the columns	1425	Explanation of the columns
1290	watcher is the number of event watchers created/destroyed. Since	1426	watcher is the number of event watchers created/destroyed. Since
1291	different event models feature vastly different performances, each event	1427	different event models feature vastly different performances, each event
1292	loop was given a number of watchers so that overall runtime is	1428	loop was given a number of watchers so that overall runtime is
…		…
1311	destroy is the time, in microseconds, that it takes to destroy a	1447	destroy is the time, in microseconds, that it takes to destroy a
1312	single watcher.	1448	single watcher.
1313		1449
1314	Results	1450	Results
1315	name watchers bytes create invoke destroy comment	1451	name watchers bytes create invoke destroy comment
1316	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1452	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1317	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1453	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1318	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1454	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1319	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1455	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1320	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1456	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1321	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1457	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1322	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1458	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1323	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1459	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1324	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1460	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1325	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1461	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1326	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1462	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1327	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1463	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1328		1464
1329	Discussion	1465	Discussion
1330	The benchmark does not measure scalability of the event loop very	1466	The benchmark does not measure scalability of the event loop very
1331	well. For example, a select-based event loop (such as the pure perl one)	1467	well. For example, a select-based event loop (such as the pure perl one)
1332	can never compete with an event loop that uses epoll when the number of	1468	can never compete with an event loop that uses epoll when the number of
…		…
1343	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1479	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1344	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1480	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1345	CPU cycles with POE.	1481	CPU cycles with POE.
1346		1482
1347	"EV" is the sole leader regarding speed and memory use, which are both	1483	"EV" is the sole leader regarding speed and memory use, which are both
1348	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1484	maximal/minimal, respectively. When using the AE API there is zero
		1485	overhead (when going through the AnyEvent API create is about 5-6 times
		1486	slower, with other times being equal, so still uses far less memory than
1349	far less memory than any other event loop and is still faster than Event	1487	any other event loop and is still faster than Event natively).
1350	natively.
1351		1488
1352	The pure perl implementation is hit in a few sweet spots (both the	1489	The pure perl implementation is hit in a few sweet spots (both the
1353	constant timeout and the use of a single fd hit optimisations in the	1490	constant timeout and the use of a single fd hit optimisations in the
1354	perl interpreter and the backend itself). Nevertheless this shows that	1491	perl interpreter and the backend itself). Nevertheless this shows that
1355	it adds very little overhead in itself. Like any select-based backend	1492	it adds very little overhead in itself. Like any select-based backend
…		…
1425	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1562	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1426	100 (1%) are active. This mirrors the activity of large servers with	1563	100 (1%) are active. This mirrors the activity of large servers with
1427	many connections, most of which are idle at any one point in time.	1564	many connections, most of which are idle at any one point in time.
1428		1565
1429	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1566	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1430	distribution.	1567	distribution. It uses the AE interface, which makes a real difference
		1568	for the EV and Perl backends only.
1431		1569
1432	Explanation of the columns	1570	Explanation of the columns
1433	sockets is the number of sockets, and twice the number of "servers"	1571	sockets is the number of sockets, and twice the number of "servers"
1434	(as each server has a read and write socket end).	1572	(as each server has a read and write socket end).
1435		1573
…		…
1441	forwarding it to another server. This includes deleting the old timeout	1579	forwarding it to another server. This includes deleting the old timeout
1442	and creating a new one that moves the timeout into the future.	1580	and creating a new one that moves the timeout into the future.
1443		1581
1444	Results	1582	Results
1445	name sockets create request	1583	name sockets create request
1446	EV 20000 69.01 11.16	1584	EV 20000 62.66 7.99
1447	Perl 20000 73.32 35.87	1585	Perl 20000 68.32 32.64
1448	IOAsync 20000 157.00 98.14 epoll	1586	IOAsync 20000 174.06 101.15 epoll
1449	IOAsync 20000 159.31 616.06 poll	1587	IOAsync 20000 174.67 610.84 poll
1450	Event 20000 212.62 257.32	1588	Event 20000 202.69 242.91
1451	Glib 20000 651.16 1896.30	1589	Glib 20000 557.01 1689.52
1452	POE 20000 349.67 12317.24 uses POE::Loop::Event	1590	POE 20000 341.54 12086.32 uses POE::Loop::Event
1453		1591
1454	Discussion	1592	Discussion
1455	This benchmark does measure scalability and overall performance of the	1593	This benchmark does measure scalability and overall performance of the
1456	particular event loop.	1594	particular event loop.
1457		1595
…		…
1570	As you can see, the AnyEvent + EV combination even beats the	1708	As you can see, the AnyEvent + EV combination even beats the
1571	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1709	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1572	backend easily beats IO::Lambda and POE.	1710	backend easily beats IO::Lambda and POE.
1573		1711
1574	And even the 100% non-blocking version written using the high-level (and	1712	And even the 100% non-blocking version written using the high-level (and
1575	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1713	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1576	large margin, even though it does all of DNS, tcp-connect and socket I/O	1714	higher level ("unoptimised") abstractions by a large margin, even though
1577	in a non-blocking way.	1715	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1578		1716
1579	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1717	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1580	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1718	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1581	part of the IO::lambda distribution and were used without any changes.	1719	part of the IO::Lambda distribution and were used without any changes.
1582		1720
1583	SIGNALS	1721	SIGNALS
1584	AnyEvent currently installs handlers for these signals:	1722	AnyEvent currently installs handlers for these signals:
1585		1723
1586	SIGCHLD	1724	SIGCHLD
1587	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1725	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1588	emulation for event loops that do not support them natively. Also,	1726	emulation for event loops that do not support them natively. Also,
1589	some event loops install a similar handler.	1727	some event loops install a similar handler.
1590		1728
1591	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent	1729	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
1592	will reset it to default, to avoid losing child exit statuses.	1730	then AnyEvent will reset it to default, to avoid losing child exit
		1731	statuses.
1593		1732
1594	SIGPIPE	1733	SIGPIPE
1595	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1734	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1596	"undef" when AnyEvent gets loaded.	1735	"undef" when AnyEvent gets loaded.
1597		1736
…		…
1605	it is that this way, the handler will be restored to defaults on	1744	it is that this way, the handler will be restored to defaults on
1606	exec.	1745	exec.
1607		1746
1608	Feel free to install your own handler, or reset it to defaults.	1747	Feel free to install your own handler, or reset it to defaults.
1609		1748
		1749	RECOMMENDED/OPTIONAL MODULES
		1750	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1751	it's built-in modules) are required to use it.
		1752
		1753	That does not mean that AnyEvent won't take advantage of some additional
		1754	modules if they are installed.
		1755
		1756	This section explains which additional modules will be used, and how
		1757	they affect AnyEvent's operation.
		1758
		1759	Async::Interrupt
		1760	This slightly arcane module is used to implement fast signal
		1761	handling: To my knowledge, there is no way to do completely
		1762	race-free and quick signal handling in pure perl. To ensure that
		1763	signals still get delivered, AnyEvent will start an interval timer
		1764	to wake up perl (and catch the signals) with some delay (default is
		1765	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1766
		1767	If this module is available, then it will be used to implement
		1768	signal catching, which means that signals will not be delayed, and
		1769	the event loop will not be interrupted regularly, which is more
		1770	efficient (and good for battery life on laptops).
		1771
		1772	This affects not just the pure-perl event loop, but also other event
		1773	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1774
		1775	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1776	natively, and either employ their own workarounds (POE) or use
		1777	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1778	Installing Async::Interrupt does nothing for those backends.
		1779
		1780	EV This module isn't really "optional", as it is simply one of the
		1781	backend event loops that AnyEvent can use. However, it is simply the
		1782	best event loop available in terms of features, speed and stability:
		1783	It supports the AnyEvent API optimally, implements all the watcher
		1784	types in XS, does automatic timer adjustments even when no monotonic
		1785	clock is available, can take avdantage of advanced kernel interfaces
		1786	such as "epoll" and "kqueue", and is the fastest backend by far.
		1787	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1788	Glib::EV).
		1789
		1790	If you only use backends that rely on another event loop (e.g.
		1791	"Tk"), then this module will do nothing for you.
		1792
		1793	Guard
		1794	The guard module, when used, will be used to implement
		1795	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1796	uses a lot less memory), but otherwise doesn't affect guard
		1797	operation much. It is purely used for performance.
		1798
		1799	JSON and JSON::XS
		1800	One of these modules is required when you want to read or write JSON
		1801	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1802	can take advantage of the ultra-high-speed JSON::XS module when it
		1803	is installed.
		1804
		1805	Net::SSLeay
		1806	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1807	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1808	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1809
		1810	Time::HiRes
		1811	This module is part of perl since release 5.008. It will be used
		1812	when the chosen event library does not come with a timing source on
		1813	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1814	additionally use it to try to use a monotonic clock for timing
		1815	stability.
		1816
1610	FORK	1817	FORK
1611	Most event libraries are not fork-safe. The ones who are usually are	1818	Most event libraries are not fork-safe. The ones who are usually are
1612	because they rely on inefficient but fork-safe "select" or "poll" calls.	1819	because they rely on inefficient but fork-safe "select" or "poll" calls
1613	Only EV is fully fork-aware.	1820	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1821	epoll are usually badly thought-out hacks that are incompatible with
		1822	fork in one way or another. Only EV is fully fork-aware and ensures that
		1823	you continue event-processing in both parent and child (or both, if you
		1824	know what you are doing).
		1825
		1826	This means that, in general, you cannot fork and do event processing in
		1827	the child if the event library was initialised before the fork (which
		1828	usually happens when the first AnyEvent watcher is created, or the
		1829	library is loaded).
1614		1830
1615	If you have to fork, you must either do so before creating your first	1831	If you have to fork, you must either do so before creating your first
1616	watcher OR you must not use AnyEvent at all in the child.	1832	watcher OR you must not use AnyEvent at all in the child OR you must do
		1833	something completely out of the scope of AnyEvent.
		1834
		1835	The problem of doing event processing in the parent and the child is
		1836	much more complicated: even for backends that are fork-aware or
		1837	fork-safe, their behaviour is not usually what you want: fork clones all
		1838	watchers, that means all timers, I/O watchers etc. are active in both
		1839	parent and child, which is almost never what you want. USing "exec" to
		1840	start worker children from some kind of manage rprocess is usually
		1841	preferred, because it is much easier and cleaner, at the expense of
		1842	having to have another binary.
1617		1843
1618	SECURITY CONSIDERATIONS	1844	SECURITY CONSIDERATIONS
1619	AnyEvent can be forced to load any event model via	1845	AnyEvent can be forced to load any event model via
1620	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1846	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1621	to execute arbitrary code or directly gain access, it can easily be used	1847	to execute arbitrary code or directly gain access, it can easily be used
…		…
1653	Event::Lib, Qt, POE.	1879	Event::Lib, Qt, POE.
1654		1880
1655	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1881	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1656	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1882	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1657	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	1883	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1658	AnyEvent::Impl::IOAsync.	1884	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1659		1885
1660	Non-blocking file handles, sockets, TCP clients and servers:	1886	Non-blocking file handles, sockets, TCP clients and servers:
1661	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	1887	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1662		1888
1663	Asynchronous DNS: AnyEvent::DNS.	1889	Asynchronous DNS: AnyEvent::DNS.

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Comparing AnyEvent/README (file contents): Revision 1.43 by root, Thu Jul 9 08:37:06 2009 UTC vs. Revision 1.62 by root, Sun Jun 6 10:13:57 2010 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.43 by root, Thu Jul 9 08:37:06 2009 UTC vs.
Revision 1.62 by root, Sun Jun 6 10:13:57 2010 UTC