[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 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	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub { ... });	11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
11		12
		13	# one-shot or repeating timers
12	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
14		16
15	print AnyEvent->now; # prints current event loop time	17	print AnyEvent->now; # prints current event loop time
16	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17		19
		20	# POSIX signal
18	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });	21	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19		22
		23	# child process exit
20	my $w = AnyEvent->child (pid => $pid, cb => sub {	24	my $w = AnyEvent->child (pid => $pid, cb => sub {
21	my ($pid, $status) = @_;	25	my ($pid, $status) = @_;
22	...	26	...
23	});	27	});
		28
		29	# called when event loop idle (if applicable)
		30	my $w = AnyEvent->idle (cb => sub { ... });
24		31
25	my $w = AnyEvent->condvar; # stores whether a condition was flagged	32	my $w = AnyEvent->condvar; # stores whether a condition was flagged
26	$w->send; # wake up current and all future recv's	33	$w->send; # wake up current and all future recv's
27	$w->recv; # enters "main loop" till $condvar gets ->send	34	$w->recv; # enters "main loop" till $condvar gets ->send
28	# use a condvar in callback mode:	35	# use a condvar in callback mode:
30		37
31	INTRODUCTION/TUTORIAL	38	INTRODUCTION/TUTORIAL
32	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
33	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
34	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.
35		49
36	WHY YOU SHOULD USE THIS MODULE (OR NOT)	50	WHY YOU SHOULD USE THIS MODULE (OR NOT)
37	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
38	nowadays. So what is different about AnyEvent?	52	nowadays. So what is different about AnyEvent?
39		53
…		…
159	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,
160	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
161	declared.	175	declared.
162		176
163	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
164	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
165	the following mandatory key-value pairs as arguments:	185	the following mandatory key-value pairs as arguments:
166		186
167	"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
168	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
169	handle). Note that only file handles pointing to things for which	189	handle). Note that only file handles pointing to things for which
170	non-blocking operation makes sense are allowed. This includes sockets,	190	non-blocking operation makes sense are allowed. This includes sockets,
171	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
172	files or block devices.	192	files or block devices.
…		…
196	warn "read: $input\n";	216	warn "read: $input\n";
197	undef $w;	217	undef $w;
198	});	218	});
199		219
200	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
201	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
202	with the following mandatory arguments:	230	with the following mandatory arguments:
203		231
204	"after" specifies after how many seconds (fractional values are	232	"after" specifies after how many seconds (fractional values are
205	supported) the callback should be invoked. "cb" is the callback to	233	supported) the callback should be invoked. "cb" is the callback to
…		…
329	the event loop's idea of "current time".	357	the event loop's idea of "current time".
330		358
331	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.
332		360
333	SIGNAL WATCHERS	361	SIGNAL WATCHERS
		362	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		363
334	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
335	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
336	callback to be invoked whenever a signal occurs.	366	callback to be invoked whenever a signal occurs.
337		367
338	Although the callback might get passed parameters, their value and	368	Although the callback might get passed parameters, their value and
…		…
343	invocation, and callback invocation will be synchronous. Synchronous	373	invocation, and callback invocation will be synchronous. Synchronous
344	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
345	process, but it is guaranteed not to interrupt any other callbacks.	375	process, but it is guaranteed not to interrupt any other callbacks.
346		376
347	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
348	signal between multiple watchers.	378	signal between multiple watchers, and AnyEvent will ensure that signals
		379	will not interrupt your program at bad times.
349		380
350	This watcher might use %SIG, so programs overwriting those signals	381	This watcher might use %SIG (depending on the event loop used), so
351	directly will likely not work correctly.	382	programs overwriting those signals directly will likely not work
		383	correctly.
352		384
353	Example: exit on SIGINT	385	Example: exit on SIGINT
354		386
355	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	387	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
356		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
357	CHILD PROCESS WATCHERS	408	CHILD PROCESS WATCHERS
		409	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		410
358	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.
359		412
360	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,
361	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).
362	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
363	on any trace events (stopped/continued).	416	and an exit status is available, not on any trace events
		417	(stopped/continued).
364		418
365	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
366	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
367	callback arguments.	421	callback arguments.
368		422
…		…
373		427
374	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
375	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
376	could have exited already (and no SIGCHLD will be sent anymore).	430	could have exited already (and no SIGCHLD will be sent anymore).
377		431
378	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
379	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
380	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).
381	place).	436	AnyEvent's pure perl event loop handles all cases correctly regardless
		437	of when you start the watcher.
382		438
383	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
384	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
385	you "fork" the child (alternatively, you can call "AnyEvent::detect").	441	you "fork" the child (alternatively, you can call "AnyEvent::detect").
386		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
387	Example: fork a process and wait for it	447	Example: fork a process and wait for it
388		448
389	my $done = AnyEvent->condvar;	449	my $done = AnyEvent->condvar;
390		450
391	my $pid = fork or exit 5;	451	my $pid = fork or exit 5;
392		452
393	my $w = AnyEvent->child (	453	my $w = AnyEvent->child (
394	pid => $pid,	454	pid => $pid,
395	cb => sub {	455	cb => sub {
396	my ($pid, $status) = @_;	456	my ($pid, $status) = @_;
397	warn "pid $pid exited with status $status";	457	warn "pid $pid exited with status $status";
398	$done->send;	458	$done->send;
399	},	459	},
400	);	460	);
401		461
402	# do something else, then wait for process exit	462	# do something else, then wait for process exit
403	$done->recv;	463	$done->recv;
404		464
		465	IDLE WATCHERS
		466	$w = AnyEvent->idle (cb => <callback>);
		467
		468	Sometimes there is a need to do something, but it is not so important to
		469	do it instantly, but only when there is nothing better to do. This
		470	"nothing better to do" is usually defined to be "no other events need
		471	attention by the event loop".
		472
		473	Idle watchers ideally get invoked when the event loop has nothing better
		474	to do, just before it would block the process to wait for new events.
		475	Instead of blocking, the idle watcher is invoked.
		476
		477	Most event loops unfortunately do not really support idle watchers (only
		478	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		479	will simply call the callback "from time to time".
		480
		481	Example: read lines from STDIN, but only process them when the program
		482	is otherwise idle:
		483
		484	my @lines; # read data
		485	my $idle_w;
		486	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		487	push @lines, scalar <STDIN>;
		488
		489	# start an idle watcher, if not already done
		490	$idle_w \|\|= AnyEvent->idle (cb => sub {
		491	# handle only one line, when there are lines left
		492	if (my $line = shift @lines) {
		493	print "handled when idle: $line";
		494	} else {
		495	# otherwise disable the idle watcher again
		496	undef $idle_w;
		497	}
		498	});
		499	});
		500
405	CONDITION VARIABLES	501	CONDITION VARIABLES
		502	$cv = AnyEvent->condvar;
		503
		504	$cv->send (<list>);
		505	my @res = $cv->recv;
		506
406	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
407	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
408	will actively watch for new events and call your callbacks.	509	will actively watch for new events and call your callbacks.
409		510
410	AnyEvent is different, it expects somebody else to run the event loop	511	AnyEvent is slightly different: it expects somebody else to run the
411	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).
412		514
413	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
414	because they represent a condition that must become true.	516	because they represent a condition that must become true.
415		517
		518	Now is probably a good time to look at the examples further below.
		519
416	Condition variables can be created by calling the "AnyEvent->condvar"	520	Condition variables can be created by calling the "AnyEvent->condvar"
417	method, usually without arguments. The only argument pair allowed is	521	method, usually without arguments. The only argument pair allowed is
418
419	"cb", which specifies a callback to be called when the condition	522	"cb", which specifies a callback to be called when the condition
420	variable becomes true, with the condition variable as the first argument	523	variable becomes true, with the condition variable as the first argument
421	(but not the results).	524	(but not the results).
422		525
423	After creation, the condition variable is "false" until it becomes	526	After creation, the condition variable is "false" until it becomes
…		…
428	Condition variables are similar to callbacks, except that you can	531	Condition variables are similar to callbacks, except that you can
429	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
430	in time where multiple outstanding events have been processed. And yet	533	in time where multiple outstanding events have been processed. And yet
431	another way to call them is transactions - each condition variable can	534	another way to call them is transactions - each condition variable can
432	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
433	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.
434		538
435	Condition variables are very useful to signal that something has	539	Condition variables are very useful to signal that something has
436	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
437	requests, then a condition variable would be the ideal candidate to	541	requests, then a condition variable would be the ideal candidate to
438	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
…		…
472	after => 1,	576	after => 1,
473	cb => sub { $result_ready->send },	577	cb => sub { $result_ready->send },
474	);	578	);
475		579
476	# this "blocks" (while handling events) till the callback	580	# this "blocks" (while handling events) till the callback
477	# calls send	581	# calls ->send
478	$result_ready->recv;	582	$result_ready->recv;
479		583
480	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
481	variables are also code references.	585	variables are also callable directly.
482		586
483	my $done = AnyEvent->condvar;	587	my $done = AnyEvent->condvar;
484	my $delay = AnyEvent->timer (after => 5, cb => $done);	588	my $delay = AnyEvent->timer (after => 5, cb => $done);
485	$done->recv;	589	$done->recv;
486		590
…		…
492		596
493	...	597	...
494		598
495	my @info = $couchdb->info->recv;	599	my @info = $couchdb->info->recv;
496		600
497	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
498	results are available:	602	results are available:
499		603
500	$couchdb->info->cb (sub {	604	$couchdb->info->cb (sub {
501	my @info = $_[0]->recv;	605	my @info = $_[0]->recv;
502	});	606	});
…		…
517		621
518	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
519	future "->recv" calls.	623	future "->recv" calls.
520		624
521	Condition variables are overloaded so one can call them directly (as	625	Condition variables are overloaded so one can call them directly (as
522	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
523	"send". Note, however, that many C-based event loops do not handle	627	calling "send".
524	overloading, so as tempting as it may be, passing a condition
525	variable instead of a callback does not work. Both the pure perl and
526	EV loops support overloading, however, as well as all functions that
527	use perl to invoke a callback (as in AnyEvent::Socket and
528	AnyEvent::DNS for example).
529		628
530	$cv->croak ($error)	629	$cv->croak ($error)
531	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
532	"Carp::croak" with the given error message/object/scalar.	631	"Carp::croak" with the given error message/object/scalar.
533		632
534	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
535	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.
536		639
537	$cv->begin ([group callback])	640	$cv->begin ([group callback])
538	$cv->end	641	$cv->end
539	These two methods are EXPERIMENTAL and MIGHT CHANGE.
540
541	These two methods can be used to combine many transactions/events	642	These two methods can be used to combine many transactions/events
542	into one. For example, a function that pings many hosts in parallel	643	into one. For example, a function that pings many hosts in parallel
543	might want to use a condition variable for the whole process.	644	might want to use a condition variable for the whole process.
544		645
545	Every call to "->begin" will increment a counter, and every call to	646	Every call to "->begin" will increment a counter, and every call to
546	"->end" will decrement it. If the counter reaches 0 in "->end", the	647	"->end" will decrement it. If the counter reaches 0 in "->end", the
547	(last) callback passed to "begin" will be executed. That callback is	648	(last) callback passed to "begin" will be executed, passing the
548	supposed to call "->send", but that is not required. If no	649	condvar as first argument. That callback is supposed to call
		650	"->send", but that is not required. If no group callback was set,
549	callback was set, "send" will be called without any arguments.	651	"send" will be called without any arguments.
550		652
551	Let's clarify this with the ping example:	653	You can think of "$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:
552		661
553	my $cv = AnyEvent->condvar;	662	my $cv = AnyEvent->condvar;
554		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
555	my %result;	688	my %result;
556	$cv->begin (sub { $cv->send (\%result) });	689	$cv->begin (sub { shift->send (\%result) });
557		690
558	for my $host (@list_of_hosts) {	691	for my $host (@list_of_hosts) {
559	$cv->begin;	692	$cv->begin;
560	ping_host_then_call_callback $host, sub {	693	ping_host_then_call_callback $host, sub {
561	$result{$host} = ...;	694	$result{$host} = ...;
…		…
576	the loop, which serves two important purposes: first, it sets the	709	the loop, which serves two important purposes: first, it sets the
577	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
578	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
579	(the loop doesn't execute once).	712	(the loop doesn't execute once).
580		713
581	This is the general pattern when you "fan out" into multiple	714	This is the general pattern when you "fan out" into multiple (but
582	subrequests: use an outer "begin"/"end" pair to set the callback and	715	potentially none) subrequests: use an outer "begin"/"end" pair to
583	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,
584	you start, call "begin" and for each subrequest you finish, call	717	for each subrequest you start, call "begin" and for each subrequest
585	"end".	718	you finish, call "end".
586		719
587	METHODS FOR CONSUMERS	720	METHODS FOR CONSUMERS
588	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
589	awaits the condition.	722	awaits the condition.
590		723
…		…
599	function will call "croak".	732	function will call "croak".
600		733
601	In list context, all parameters passed to "send" will be returned,	734	In list context, all parameters passed to "send" will be returned,
602	in scalar context only the first one will be returned.	735	in scalar context only the first one will be returned.
603		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
604	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
605	(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
606	using this from a module, never require a blocking wait*, but let	746	using this from a module, never require a blocking wait*. Instead,
607	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
608	by coupling condition variables with some kind of request results	748	example, by coupling condition variables with some kind of request
609	and supporting callbacks so the caller knows that getting the result	749	results and supporting callbacks so the caller knows that getting
610	will not block, while still supporting blocking waits if the caller	750	the result will not block, while still supporting blocking waits if
611	so desires).	751	the caller so desires).
612
613	Another reason never to "->recv" in a module is that you cannot
614	sensibly have two "->recv"'s in parallel, as that would require
615	multiple interpreters or coroutines/threads, none of which
616	"AnyEvent" can supply.
617
618	The Coro module, however, can and does supply coroutines and, in
619	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
620	versions and also integrates coroutines into AnyEvent, making
621	blocking "->recv" calls perfectly safe as long as they are done from
622	another coroutine (one that doesn't run the event loop).
623		752
624	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
625	only calling "->recv" from within that callback (or at a later	754	only calling "->recv" from within that callback (or at a later
626	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
627	blocking waits otherwise.	756	blocking waits otherwise.
…		…
632		761
633	$cb = $cv->cb ($cb->($cv))	762	$cb = $cv->cb ($cb->($cv))
634	This is a mutator function that returns the callback set and	763	This is a mutator function that returns the callback set and
635	optionally replaces it before doing so.	764	optionally replaces it before doing so.
636		765
637	The callback will be called when the condition becomes "true", i.e.	766	The callback will be called when the condition becomes (or already
638	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
639	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
640	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.
641		831
642	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
643	$AnyEvent::MODEL	836	$AnyEvent::MODEL
644	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
645	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
646	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
647	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
648	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.
649		844	in rxvt-unicode it will be "urxvt::anyevent").
650	The known classes so far are:
651
652	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
653	AnyEvent::Impl::Event based on Event, second best choice.
654	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
655	AnyEvent::Impl::Glib based on Glib, third-best choice.
656	AnyEvent::Impl::Tk based on Tk, very bad choice.
657	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
658	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
659	AnyEvent::Impl::POE based on POE, not generic enough for full support.
660
661	There is no support for WxWidgets, as WxWidgets has no support for
662	watching file handles. However, you can use WxWidgets through the
663	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
664	second, which was considered to be too horrible to even consider for
665	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
666	using it's adaptor.
667
668	AnyEvent knows about Prima and Wx and will try to use POE when
669	autodetecting them.
670		845
671	AnyEvent::detect	846	AnyEvent::detect
672	Returns $AnyEvent::MODEL, forcing autodetection of the event model	847	Returns $AnyEvent::MODEL, forcing autodetection of the event model
673	if necessary. You should only call this function right before you	848	if necessary. You should only call this function right before you
674	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
675	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".
676		854
677	$guard = AnyEvent::post_detect { BLOCK }	855	$guard = AnyEvent::post_detect { BLOCK }
678	Arranges for the code block to be executed as soon as the event	856	Arranges for the code block to be executed as soon as the event
679	model is autodetected (or immediately if this has already happened).	857	model is autodetected (or immediately if this has already happened).
680		858
		859	The block will be executed after the actual backend has been
		860	detected ($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
681	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
682	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
683	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;
684		890
685	@AnyEvent::post_detect	891	@AnyEvent::post_detect
686	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
687	before or after loading AnyEvent), then they will called directly	893	before or after loading AnyEvent), then they will called directly
688	after the event loop has been chosen.	894	after the event loop has been chosen.
689		895
690	You should check $AnyEvent::MODEL before adding to this array,	896	You should check $AnyEvent::MODEL before adding to this array,
691	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
692	been detected, and the array will be ignored.	898	detected, and the array will be ignored.
693		899
694	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.
695		908
696	WHAT TO DO IN A MODULE	909	WHAT TO DO IN A MODULE
697	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
698	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.
699		912
…		…
750	variable somewhere, waiting for it, and sending it when the program	963	variable somewhere, waiting for it, and sending it when the program
751	should exit cleanly.	964	should exit cleanly.
752		965
753	OTHER MODULES	966	OTHER MODULES
754	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
755	AnyEvent and can therefore be mixed easily with other AnyEvent modules	968	AnyEvent as a client and can therefore be mixed easily with other
756	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
757	available via CPAN.	970	modules come with AnyEvent, most are available via CPAN.
758		971
759	AnyEvent::Util	972	AnyEvent::Util
760	Contains various utility functions that replace often-used but	973	Contains various utility functions that replace often-used but
761	blocking functions such as "inet_aton" by event-/callback-based	974	blocking functions such as "inet_aton" by event-/callback-based
762	versions.	975	versions.
…		…
768	more.	981	more.
769		982
770	AnyEvent::Handle	983	AnyEvent::Handle
771	Provide read and write buffers, manages watchers for reads and	984	Provide read and write buffers, manages watchers for reads and
772	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
773	transparent and non-blocking SSL/TLS.	986	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
774		987
775	AnyEvent::DNS	988	AnyEvent::DNS
776	Provides rich asynchronous DNS resolver capabilities.	989	Provides rich asynchronous DNS resolver capabilities.
777		990
778	AnyEvent::HTTP	991	AnyEvent::HTTP
…		…
799		1012
800	AnyEvent::GPSD	1013	AnyEvent::GPSD
801	A non-blocking interface to gpsd, a daemon delivering GPS	1014	A non-blocking interface to gpsd, a daemon delivering GPS
802	information.	1015	information.
803		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
804	AnyEvent::IGS	1025	AnyEvent::IGS
805	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
806	App::IGS).	1027	App::IGS).
807		1028
808	AnyEvent::IRC
809	AnyEvent based IRC client module family (replacing the older
810	Net::IRC3).
811
812	Net::XMPP2
813	AnyEvent based XMPP (Jabber protocol) module family.
814
815	Net::FCP	1029	Net::FCP
816	AnyEvent-based implementation of the Freenet Client Protocol,	1030	AnyEvent-based implementation of the Freenet Client Protocol,
817	birthplace of AnyEvent.	1031	birthplace of AnyEvent.
818		1032
819	Event::ExecFlow	1033	Event::ExecFlow
820	High level API for event-based execution flow control.	1034	High level API for event-based execution flow control.
821		1035
822	Coro	1036	Coro
823	Has special support for AnyEvent via Coro::AnyEvent.	1037	Has special support for AnyEvent via Coro::AnyEvent.
824		1038
825	IO::Lambda	1039	SIMPLIFIED AE API
826	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
827	AnyEvent.	1041	simpler, API that is designed to reduce the calling, typing and memory
		1042	overhead.
		1043
		1044	See the AE manpage for details.
828		1045
829	ERROR AND EXCEPTION HANDLING	1046	ERROR AND EXCEPTION HANDLING
830	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
831	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
832	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1049	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
842	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1059	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
843	Glib uses "install_exception_handler" and so on.	1060	Glib uses "install_exception_handler" and so on.
844		1061
845	ENVIRONMENT VARIABLES	1062	ENVIRONMENT VARIABLES
846	The following environment variables are used by this module or its	1063	The following environment variables are used by this module or its
847	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.
848		1069
849	"PERL_ANYEVENT_VERBOSE"	1070	"PERL_ANYEVENT_VERBOSE"
850	By default, AnyEvent will be completely silent except in fatal	1071	By default, AnyEvent will be completely silent except in fatal
851	conditions. You can set this environment variable to make AnyEvent	1072	conditions. You can set this environment variable to make AnyEvent
852	more talkative.	1073	more talkative.
…		…
855	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
856	by "PERL_ANYEVENT_MODEL".	1077	by "PERL_ANYEVENT_MODEL".
857		1078
858	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
859	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.
860		1085
861	"PERL_ANYEVENT_STRICT"	1086	"PERL_ANYEVENT_STRICT"
862	AnyEvent does not do much argument checking by default, as thorough	1087	AnyEvent does not do much argument checking by default, as thorough
863	argument checking is very costly. Setting this variable to a true	1088	argument checking is very costly. Setting this variable to a true
864	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1089	value will cause AnyEvent to load "AnyEvent::Strict" and then to
865	thoroughly check the arguments passed to most method calls. If it	1090	thoroughly check the arguments passed to most method calls. If it
866	finds any problems it will croak.	1091	finds any problems, it will croak.
867		1092
868	In other words, enables "strict" mode.	1093	In other words, enables "strict" mode.
869		1094
870	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
871	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
872	while developing programs can be very useful, however.	1098	programs can be very useful, however.
873		1099
874	"PERL_ANYEVENT_MODEL"	1100	"PERL_ANYEVENT_MODEL"
875	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,
876	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
877	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1103	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
918	EDNS0 in its DNS requests.	1144	EDNS0 in its DNS requests.
919		1145
920	"PERL_ANYEVENT_MAX_FORKS"	1146	"PERL_ANYEVENT_MAX_FORKS"
921	The maximum number of child processes that	1147	The maximum number of child processes that
922	"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.
923		1169
924	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1170	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925	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
926	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
927	to provide AnyEvent compatibility.	1173	to provide AnyEvent compatibility.
…		…
982	warn "read: $input\n"; # output what has been read	1228	warn "read: $input\n"; # output what has been read
983	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1229	$cv->send if $input =~ /^q/i; # quit program if /^q/i
984	},	1230	},
985	);	1231	);
986		1232
987	my $time_watcher; # can only be used once
988
989	sub new_timer {
990	$timer = AnyEvent->timer (after => 1, cb => sub {	1233	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
991	warn "timeout\n"; # print 'timeout' about every second	1234	warn "timeout\n"; # print 'timeout' at most every second
992	&new_timer; # and restart the time
993	});
994	}	1235	});
995
996	new_timer; # create first timer
997		1236
998	$cv->recv; # wait until user enters /^q/i	1237	$cv->recv; # wait until user enters /^q/i
999		1238
1000	REAL-WORLD EXAMPLE	1239	REAL-WORLD EXAMPLE
1001	Consider the Net::FCP module. It features (among others) the following	1240	Consider the Net::FCP module. It features (among others) the following
…		…
1128	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
1129	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,
1130	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.
1131		1370
1132	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
1133	distribution.	1372	distribution. It uses the AE interface, which makes a real difference
		1373	for the EV and Perl backends only.
1134		1374
1135	Explanation of the columns	1375	Explanation of the columns
1136	watcher is the number of event watchers created/destroyed. Since	1376	watcher is the number of event watchers created/destroyed. Since
1137	different event models feature vastly different performances, each event	1377	different event models feature vastly different performances, each event
1138	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
…		…
1157	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
1158	single watcher.	1398	single watcher.
1159		1399
1160	Results	1400	Results
1161	name watchers bytes create invoke destroy comment	1401	name watchers bytes create invoke destroy comment
1162	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
1163	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
1164	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
1165	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
1166	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
1167	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
1168	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
1169	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
1170	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
1171	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
1172		1414
1173	Discussion	1415	Discussion
1174	The benchmark does not measure scalability of the event loop very	1416	The benchmark does not measure scalability of the event loop very
1175	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)
1176	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
…		…
1187	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1429	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1188	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
1189	CPU cycles with POE.	1431	CPU cycles with POE.
1190		1432
1191	"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
1192	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
1193	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).
1194	natively.
1195		1438
1196	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
1197	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
1198	perl interpreter and the backend itself). Nevertheless this shows that	1441	perl interpreter and the backend itself). Nevertheless this shows that
1199	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
…		…
1201	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
1202	benchmark.	1445	benchmark.
1203		1446
1204	The "Event" module has a relatively high setup and callback invocation	1447	The "Event" module has a relatively high setup and callback invocation
1205	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.
1206		1452
1207	"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
1208	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".
1209	However, Glib scales extremely badly, doubling the number of watchers	1455	However, Glib scales extremely badly, doubling the number of watchers
1210	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
…		…
1266	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
1267	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
1268	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.
1269		1515
1270	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
1271	distribution.	1517	distribution. It uses the AE interface, which makes a real difference
		1518	for the EV and Perl backends only.
1272		1519
1273	Explanation of the columns	1520	Explanation of the columns
1274	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"
1275	(as each server has a read and write socket end).	1522	(as each server has a read and write socket end).
1276		1523
…		…
1281	single "request", that is, reading the token from the pipe and	1528	single "request", that is, reading the token from the pipe and
1282	forwarding it to another server. This includes deleting the old timeout	1529	forwarding it to another server. This includes deleting the old timeout
1283	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.
1284		1531
1285	Results	1532	Results
1286	name sockets create request	1533	name sockets create request
1287	EV 20000 69.01 11.16	1534	EV 20000 62.66 7.99
1288	Perl 20000 73.32 35.87	1535	Perl 20000 68.32 32.64
1289	Event 20000 212.62 257.32	1536	IOAsync 20000 174.06 101.15 epoll
1290	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
1291	POE 20000 349.67 12317.24 uses POE::Loop::Event	1540	POE 20000 341.54 12086.32 uses POE::Loop::Event
1292		1541
1293	Discussion	1542	Discussion
1294	This benchmark does measure scalability and overall performance of the	1543	This benchmark does measure scalability and overall performance of the
1295	particular event loop.	1544	particular event loop.
1296		1545
1297	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
1298	time is relatively high, though.	1547	time is relatively high, though.
1299		1548
1300	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
1301	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.
1302		1554
1303	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
1304	will understand why). Callback invocation also has a high overhead	1556	will understand why). Callback invocation also has a high overhead
1305	compared to the "$_->() for .."-style loop that the Perl event loop	1557	compared to the "$_->() for .."-style loop that the Perl event loop
1306	uses. Event uses select or poll in basically all documented	1558	uses. Event uses select or poll in basically all documented
…		…
1357		1609
1358	Summary	1610	Summary
1359	* 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,
1360	as the management overhead dominates.	1612	as the management overhead dominates.
1361		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
1362	SIGNALS	1671	SIGNALS
1363	AnyEvent currently installs handlers for these signals:	1672	AnyEvent currently installs handlers for these signals:
1364		1673
1365	SIGCHLD	1674	SIGCHLD
1366	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1675	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367	emulation for event loops that do not support them natively. Also,	1676	emulation for event loops that do not support them natively. Also,
1368	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.
1369		1682
1370	SIGPIPE	1683	SIGPIPE
1371	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
1372	"undef" when AnyEvent gets loaded.	1685	"undef" when AnyEvent gets loaded.
1373		1686
…		…
1381	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
1382	exec.	1695	exec.
1383		1696
1384	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.
1385		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
1386	FORK	1767	FORK
1387	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
1388	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.
1389	Only EV is fully fork-aware.	1770	Only EV is fully fork-aware.
1390		1771
1391	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
1392	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.
1393		1775
1394	SECURITY CONSIDERATIONS	1776	SECURITY CONSIDERATIONS
1395	AnyEvent can be forced to load any event model via	1777	AnyEvent can be forced to load any event model via
1396	$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
1397	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
…		…
1401		1783
1402	You can make AnyEvent completely ignore this variable by deleting it	1784	You can make AnyEvent completely ignore this variable by deleting it
1403	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:
1404		1786
1405	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1787	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1406		1788
1407	use AnyEvent;	1789	use AnyEvent;
1408		1790
1409	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1791	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1410	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
1411	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),
1412	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.
1413		1799
1414	BUGS	1800	BUGS
1415	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
1416	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
1417	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
…		…
1424	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,
1425	Event::Lib, Qt, POE.	1811	Event::Lib, Qt, POE.
1426		1812
1427	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1813	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1428	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1814	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1429	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.
1430		1817
1431	Non-blocking file handles, sockets, TCP clients and servers:	1818	Non-blocking file handles, sockets, TCP clients and servers:
1432	AnyEvent::Handle, AnyEvent::Socket.	1819	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1433		1820
1434	Asynchronous DNS: AnyEvent::DNS.	1821	Asynchronous DNS: AnyEvent::DNS.
1435		1822
1436	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1823	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1437		1824
1438	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1825	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1826	AnyEvent::HTTP.
1439		1827
1440	AUTHOR	1828	AUTHOR
1441	Marc Lehmann <schmorp@schmorp.de>	1829	Marc Lehmann <schmorp@schmorp.de>
1442	http://home.schmorp.de/	1830	http://home.schmorp.de/
1443		1831

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Comparing AnyEvent/README (file contents): Revision 1.37 by root, Mon Apr 20 14:34:18 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 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.54 by root, Tue Sep 1 18:27:46 2009 UTC