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Comparing AnyEvent/README (file contents):
Revision 1.36 by root, Fri Mar 27 10:49:50 2009 UTC vs.
Revision 1.50 by root, Sat Aug 1 09:14:54 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
…		…
314	In either case, if you care (and in most cases, you don't), then you	342	In either case, if you care (and in most cases, you don't), then you
315	can get whatever behaviour you want with any event loop, by taking	343	can get whatever behaviour you want with any event loop, by taking
316	the difference between "AnyEvent->time" and "AnyEvent->now" into	344	the difference between "AnyEvent->time" and "AnyEvent->now" into
317	account.	345	account.
318		346
		347	AnyEvent->now_update
		348	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
		349	current time for each loop iteration (see the discussion of
		350	AnyEvent->now, above).
		351
		352	When a callback runs for a long time (or when the process sleeps),
		353	then this "current" time will differ substantially from the real
		354	time, which might affect timers and time-outs.
		355
		356	When this is the case, you can call this method, which will update
		357	the event loop's idea of "current time".
		358
		359	Note that updating the time might cause some events to be handled.
		360
319	SIGNAL WATCHERS	361	SIGNAL WATCHERS
		362	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		363
320	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
321	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
322	callback to be invoked whenever a signal occurs.	366	callback to be invoked whenever a signal occurs.
323		367
324	Although the callback might get passed parameters, their value and	368	Although the callback might get passed parameters, their value and
…		…
329	invocation, and callback invocation will be synchronous. Synchronous	373	invocation, and callback invocation will be synchronous. Synchronous
330	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
331	process, but it is guaranteed not to interrupt any other callbacks.	375	process, but it is guaranteed not to interrupt any other callbacks.
332		376
333	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
334	signal between multiple watchers.	378	signal between multiple watchers, and AnyEvent will ensure that signals
		379	will not interrupt your program at bad times.
335		380
336	This watcher might use %SIG, so programs overwriting those signals	381	This watcher might use %SIG (depending on the event loop used), so
337	directly will likely not work correctly.	382	programs overwriting those signals directly will likely not work
		383	correctly.
338		384
339	Example: exit on SIGINT	385	Example: exit on SIGINT
340		386
341	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	387	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
342		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
343	CHILD PROCESS WATCHERS	408	CHILD PROCESS WATCHERS
		409	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		410
344	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.
345		412
346	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,
347	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).
348	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
349	on any trace events (stopped/continued).	416	and an exit status is available, not on any trace events
		417	(stopped/continued).
350		418
351	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
352	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
353	callback arguments.	421	callback arguments.
354		422
…		…
359		427
360	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
361	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
362	could have exited already (and no SIGCHLD will be sent anymore).	430	could have exited already (and no SIGCHLD will be sent anymore).
363		431
364	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
365	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
366	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).
367	place).	436	AnyEvent's pure perl event loop handles all cases correctly regardless
		437	of when you start the watcher.
368		438
369	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
370	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
371	you "fork" the child (alternatively, you can call "AnyEvent::detect").	441	you "fork" the child (alternatively, you can call "AnyEvent::detect").
372		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
373	Example: fork a process and wait for it	447	Example: fork a process and wait for it
374		448
375	my $done = AnyEvent->condvar;	449	my $done = AnyEvent->condvar;
376		450
377	my $pid = fork or exit 5;	451	my $pid = fork or exit 5;
378		452
379	my $w = AnyEvent->child (	453	my $w = AnyEvent->child (
380	pid => $pid,	454	pid => $pid,
381	cb => sub {	455	cb => sub {
382	my ($pid, $status) = @_;	456	my ($pid, $status) = @_;
383	warn "pid $pid exited with status $status";	457	warn "pid $pid exited with status $status";
384	$done->send;	458	$done->send;
385	},	459	},
386	);	460	);
387		461
388	# do something else, then wait for process exit	462	# do something else, then wait for process exit
389	$done->recv;	463	$done->recv;
390		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
391	CONDITION VARIABLES	501	CONDITION VARIABLES
		502	$cv = AnyEvent->condvar;
		503
		504	$cv->send (<list>);
		505	my @res = $cv->recv;
		506
392	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
393	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
394	will actively watch for new events and call your callbacks.	509	will actively watch for new events and call your callbacks.
395		510
396	AnyEvent is different, it expects somebody else to run the event loop	511	AnyEvent is slightly different: it expects somebody else to run the
397	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).
398		514
399	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
400	because they represent a condition that must become true.	516	because they represent a condition that must become true.
401		517
		518	Now is probably a good time to look at the examples further below.
		519
402	Condition variables can be created by calling the "AnyEvent->condvar"	520	Condition variables can be created by calling the "AnyEvent->condvar"
403	method, usually without arguments. The only argument pair allowed is	521	method, usually without arguments. The only argument pair allowed is
404
405	"cb", which specifies a callback to be called when the condition	522	"cb", which specifies a callback to be called when the condition
406	variable becomes true, with the condition variable as the first argument	523	variable becomes true, with the condition variable as the first argument
407	(but not the results).	524	(but not the results).
408		525
409	After creation, the condition variable is "false" until it becomes	526	After creation, the condition variable is "false" until it becomes
…		…
414	Condition variables are similar to callbacks, except that you can	531	Condition variables are similar to callbacks, except that you can
415	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
416	in time where multiple outstanding events have been processed. And yet	533	in time where multiple outstanding events have been processed. And yet
417	another way to call them is transactions - each condition variable can	534	another way to call them is transactions - each condition variable can
418	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
419	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.
420		538
421	Condition variables are very useful to signal that something has	539	Condition variables are very useful to signal that something has
422	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
423	requests, then a condition variable would be the ideal candidate to	541	requests, then a condition variable would be the ideal candidate to
424	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
…		…
458	after => 1,	576	after => 1,
459	cb => sub { $result_ready->send },	577	cb => sub { $result_ready->send },
460	);	578	);
461		579
462	# this "blocks" (while handling events) till the callback	580	# this "blocks" (while handling events) till the callback
463	# calls send	581	# calls -<send
464	$result_ready->recv;	582	$result_ready->recv;
465		583
466	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
467	variables are also code references.	585	variables are also callable directly.
468		586
469	my $done = AnyEvent->condvar;	587	my $done = AnyEvent->condvar;
470	my $delay = AnyEvent->timer (after => 5, cb => $done);	588	my $delay = AnyEvent->timer (after => 5, cb => $done);
471	$done->recv;	589	$done->recv;
472		590
…		…
478		596
479	...	597	...
480		598
481	my @info = $couchdb->info->recv;	599	my @info = $couchdb->info->recv;
482		600
483	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
484	results are available:	602	results are available:
485		603
486	$couchdb->info->cb (sub {	604	$couchdb->info->cb (sub {
487	my @info = $_[0]->recv;	605	my @info = $_[0]->recv;
488	});	606	});
…		…
503		621
504	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
505	future "->recv" calls.	623	future "->recv" calls.
506		624
507	Condition variables are overloaded so one can call them directly (as	625	Condition variables are overloaded so one can call them directly (as
508	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
509	"send". Note, however, that many C-based event loops do not handle	627	calling "send".
510	overloading, so as tempting as it may be, passing a condition
511	variable instead of a callback does not work. Both the pure perl and
512	EV loops support overloading, however, as well as all functions that
513	use perl to invoke a callback (as in AnyEvent::Socket and
514	AnyEvent::DNS for example).
515		628
516	$cv->croak ($error)	629	$cv->croak ($error)
517	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
518	"Carp::croak" with the given error message/object/scalar.	631	"Carp::croak" with the given error message/object/scalar.
519		632
520	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
521	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.
522		639
523	$cv->begin ([group callback])	640	$cv->begin ([group callback])
524	$cv->end	641	$cv->end
525	These two methods are EXPERIMENTAL and MIGHT CHANGE.
526
527	These two methods can be used to combine many transactions/events	642	These two methods can be used to combine many transactions/events
528	into one. For example, a function that pings many hosts in parallel	643	into one. For example, a function that pings many hosts in parallel
529	might want to use a condition variable for the whole process.	644	might want to use a condition variable for the whole process.
530		645
531	Every call to "->begin" will increment a counter, and every call to	646	Every call to "->begin" will increment a counter, and every call to
532	"->end" will decrement it. If the counter reaches 0 in "->end", the	647	"->end" will decrement it. If the counter reaches 0 in "->end", the
533	(last) callback passed to "begin" will be executed. That callback is	648	(last) callback passed to "begin" will be executed. That callback is
534	supposed to call "->send", but that is not required. If no	649	supposed to call "->send", but that is not required. If no
535	callback was set, "send" will be called without any arguments.	650	callback was set, "send" will be called without any arguments.
536		651
537	Let's clarify this with the ping example:	652	You can think of "$cv->send" giving you an OR condition (one call
		653	sends), while "$cv->begin" and "$cv->end" giving you an AND
		654	condition (all "begin" calls must be "end"'ed before the condvar
		655	sends).
		656
		657	Let's start with a simple example: you have two I/O watchers (for
		658	example, STDOUT and STDERR for a program), and you want to wait for
		659	both streams to close before activating a condvar:
		660
		661	my $cv = AnyEvent->condvar;
		662
		663	$cv->begin; # first watcher
		664	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		665	defined sysread $fh1, my $buf, 4096
		666	or $cv->end;
		667	});
		668
		669	$cv->begin; # second watcher
		670	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		671	defined sysread $fh2, my $buf, 4096
		672	or $cv->end;
		673	});
		674
		675	$cv->recv;
		676
		677	This works because for every event source (EOF on file handle),
		678	there is one call to "begin", so the condvar waits for all calls to
		679	"end" before sending.
		680
		681	The ping example mentioned above is slightly more complicated, as
		682	the there are results to be passwd back, and the number of tasks
		683	that are begung can potentially be zero:
538		684
539	my $cv = AnyEvent->condvar;	685	my $cv = AnyEvent->condvar;
540		686
541	my %result;	687	my %result;
542	$cv->begin (sub { $cv->send (\%result) });	688	$cv->begin (sub { $cv->send (\%result) });
…		…
562	the loop, which serves two important purposes: first, it sets the	708	the loop, which serves two important purposes: first, it sets the
563	callback to be called once the counter reaches 0, and second, it	709	callback to be called once the counter reaches 0, and second, it
564	ensures that "send" is called even when "no" hosts are being pinged	710	ensures that "send" is called even when "no" hosts are being pinged
565	(the loop doesn't execute once).	711	(the loop doesn't execute once).
566		712
567	This is the general pattern when you "fan out" into multiple	713	This is the general pattern when you "fan out" into multiple (but
568	subrequests: use an outer "begin"/"end" pair to set the callback and	714	potentially none) subrequests: use an outer "begin"/"end" pair to
569	ensure "end" is called at least once, and then, for each subrequest	715	set the callback and ensure "end" is called at least once, and then,
570	you start, call "begin" and for each subrequest you finish, call	716	for each subrequest you start, call "begin" and for each subrequest
571	"end".	717	you finish, call "end".
572		718
573	METHODS FOR CONSUMERS	719	METHODS FOR CONSUMERS
574	These methods should only be used by the consuming side, i.e. the code	720	These methods should only be used by the consuming side, i.e. the code
575	awaits the condition.	721	awaits the condition.
576		722
…		…
585	function will call "croak".	731	function will call "croak".
586		732
587	In list context, all parameters passed to "send" will be returned,	733	In list context, all parameters passed to "send" will be returned,
588	in scalar context only the first one will be returned.	734	in scalar context only the first one will be returned.
589		735
		736	Note that doing a blocking wait in a callback is not supported by
		737	any event loop, that is, recursive invocation of a blocking "->recv"
		738	is not allowed, and the "recv" call will "croak" if such a condition
		739	is detected. This condition can be slightly loosened by using
		740	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		741	thread that doesn't run the event loop itself.
		742
590	Not all event models support a blocking wait - some die in that case	743	Not all event models support a blocking wait - some die in that case
591	(programs might want to do that to stay interactive), so *if you are	744	(programs might want to do that to stay interactive), so *if you are
592	using this from a module, never require a blocking wait*, but let	745	using this from a module, never require a blocking wait*. Instead,
593	the caller decide whether the call will block or not (for example,	746	let the caller decide whether the call will block or not (for
594	by coupling condition variables with some kind of request results	747	example, by coupling condition variables with some kind of request
595	and supporting callbacks so the caller knows that getting the result	748	results and supporting callbacks so the caller knows that getting
596	will not block, while still supporting blocking waits if the caller	749	the result will not block, while still supporting blocking waits if
597	so desires).	750	the caller so desires).
598
599	Another reason never to "->recv" in a module is that you cannot
600	sensibly have two "->recv"'s in parallel, as that would require
601	multiple interpreters or coroutines/threads, none of which
602	"AnyEvent" can supply.
603
604	The Coro module, however, can and does supply coroutines and, in
605	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
606	versions and also integrates coroutines into AnyEvent, making
607	blocking "->recv" calls perfectly safe as long as they are done from
608	another coroutine (one that doesn't run the event loop).
609		751
610	You can ensure that "-recv" never blocks by setting a callback and	752	You can ensure that "-recv" never blocks by setting a callback and
611	only calling "->recv" from within that callback (or at a later	753	only calling "->recv" from within that callback (or at a later
612	time). This will work even when the event loop does not support	754	time). This will work even when the event loop does not support
613	blocking waits otherwise.	755	blocking waits otherwise.
…		…
618		760
619	$cb = $cv->cb ($cb->($cv))	761	$cb = $cv->cb ($cb->($cv))
620	This is a mutator function that returns the callback set and	762	This is a mutator function that returns the callback set and
621	optionally replaces it before doing so.	763	optionally replaces it before doing so.
622		764
623	The callback will be called when the condition becomes "true", i.e.	765	The callback will be called when the condition becomes (or already
624	when "send" or "croak" are called, with the only argument being the	766	was) "true", i.e. when "send" or "croak" are called (or were
625	condition variable itself. Calling "recv" inside the callback or at	767	called), with the only argument being the condition variable itself.
		768	Calling "recv" inside the callback or at any later time is
626	any later time is guaranteed not to block.	769	guaranteed not to block.
		770
		771	SUPPORTED EVENT LOOPS/BACKENDS
		772	The available backend classes are (every class has its own manpage):
		773
		774	Backends that are autoprobed when no other event loop can be found.
		775	EV is the preferred backend when no other event loop seems to be in
		776	use. If EV is not installed, then AnyEvent will try Event, and,
		777	failing that, will fall back to its own pure-perl implementation,
		778	which is available everywhere as it comes with AnyEvent itself.
		779
		780	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		781	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		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::Glib based on Glib, slow but very stable.
		793	AnyEvent::Impl::Tk based on Tk, very broken.
		794	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		795	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		796	AnyEvent::Impl::Irssi used when running within irssi.
		797
		798	Backends with special needs.
		799	Qt requires the Qt::Application to be instantiated first, but will
		800	otherwise be picked up automatically. As long as the main program
		801	instantiates the application before any AnyEvent watchers are
		802	created, everything should just work.
		803
		804	AnyEvent::Impl::Qt based on Qt.
		805
		806	Support for IO::Async can only be partial, as it is too broken and
		807	architecturally limited to even support the AnyEvent API. It also is
		808	the only event loop that needs the loop to be set explicitly, so it
		809	can only be used by a main program knowing about AnyEvent. See
		810	AnyEvent::Impl::Async for the gory details.
		811
		812	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		813
		814	Event loops that are indirectly supported via other backends.
		815	Some event loops can be supported via other modules:
		816
		817	There is no direct support for WxWidgets (Wx) or Prima.
		818
		819	WxWidgets has no support for watching file handles. However, you can
		820	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		821	simply polls 20 times per second, which was considered to be too
		822	horrible to even consider for AnyEvent.
		823
		824	Prima is not supported as nobody seems to be using it, but it has a
		825	POE backend, so it can be supported through POE.
		826
		827	AnyEvent knows about both Prima and Wx, however, and will try to
		828	load POE when detecting them, in the hope that POE will pick them
		829	up, in which case everything will be automatic.
627		830
628	GLOBAL VARIABLES AND FUNCTIONS	831	GLOBAL VARIABLES AND FUNCTIONS
		832	These are not normally required to use AnyEvent, but can be useful to
		833	write AnyEvent extension modules.
		834
629	$AnyEvent::MODEL	835	$AnyEvent::MODEL
630	Contains "undef" until the first watcher is being created. Then it	836	Contains "undef" until the first watcher is being created, before
		837	the backend has been autodetected.
		838
631	contains the event model that is being used, which is the name of	839	Afterwards it contains the event model that is being used, which is
632	the Perl class implementing the model. This class is usually one of	840	the name of the Perl class implementing the model. This class is
633	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	841	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
634	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	842	other class in the case AnyEvent has been extended at runtime (e.g.
635		843	in rxvt-unicode it will be "urxvt::anyevent").
636	The known classes so far are:
637
638	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
639	AnyEvent::Impl::Event based on Event, second best choice.
640	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
641	AnyEvent::Impl::Glib based on Glib, third-best choice.
642	AnyEvent::Impl::Tk based on Tk, very bad choice.
643	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
644	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
645	AnyEvent::Impl::POE based on POE, not generic enough for full support.
646
647	There is no support for WxWidgets, as WxWidgets has no support for
648	watching file handles. However, you can use WxWidgets through the
649	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
650	second, which was considered to be too horrible to even consider for
651	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
652	using it's adaptor.
653
654	AnyEvent knows about Prima and Wx and will try to use POE when
655	autodetecting them.
656		844
657	AnyEvent::detect	845	AnyEvent::detect
658	Returns $AnyEvent::MODEL, forcing autodetection of the event model	846	Returns $AnyEvent::MODEL, forcing autodetection of the event model
659	if necessary. You should only call this function right before you	847	if necessary. You should only call this function right before you
660	would have created an AnyEvent watcher anyway, that is, as late as	848	would have created an AnyEvent watcher anyway, that is, as late as
661	possible at runtime.	849	possible at runtime, and not e.g. while initialising of your module.
		850
		851	If you need to do some initialisation before AnyEvent watchers are
		852	created, use "post_detect".
662		853
663	$guard = AnyEvent::post_detect { BLOCK }	854	$guard = AnyEvent::post_detect { BLOCK }
664	Arranges for the code block to be executed as soon as the event	855	Arranges for the code block to be executed as soon as the event
665	model is autodetected (or immediately if this has already happened).	856	model is autodetected (or immediately if this has already happened).
666		857
		858	The block will be executed after the actual backend has been
		859	detected ($AnyEvent::MODEL is set), but before any watchers have
		860	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		861	other initialisations - see the sources of AnyEvent::Strict or
		862	AnyEvent::AIO to see how this is used.
		863
		864	The most common usage is to create some global watchers, without
		865	forcing event module detection too early, for example, AnyEvent::AIO
		866	creates and installs the global IO::AIO watcher in a "post_detect"
		867	block to avoid autodetecting the event module at load time.
		868
667	If called in scalar or list context, then it creates and returns an	869	If called in scalar or list context, then it creates and returns an
668	object that automatically removes the callback again when it is	870	object that automatically removes the callback again when it is
		871	destroyed (or "undef" when the hook was immediately executed). See
669	destroyed. See Coro::BDB for a case where this is useful.	872	AnyEvent::AIO for a case where this is useful.
		873
		874	Example: Create a watcher for the IO::AIO module and store it in
		875	$WATCHER. Only do so after the event loop is initialised, though.
		876
		877	our WATCHER;
		878
		879	my $guard = AnyEvent::post_detect {
		880	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		881	};
		882
		883	# the \|\|= is important in case post_detect immediately runs the block,
		884	# as to not clobber the newly-created watcher. assigning both watcher and
		885	# post_detect guard to the same variable has the advantage of users being
		886	# able to just C<undef $WATCHER> if the watcher causes them grief.
		887
		888	$WATCHER \|\|= $guard;
670		889
671	@AnyEvent::post_detect	890	@AnyEvent::post_detect
672	If there are any code references in this array (you can "push" to it	891	If there are any code references in this array (you can "push" to it
673	before or after loading AnyEvent), then they will called directly	892	before or after loading AnyEvent), then they will called directly
674	after the event loop has been chosen.	893	after the event loop has been chosen.
675		894
676	You should check $AnyEvent::MODEL before adding to this array,	895	You should check $AnyEvent::MODEL before adding to this array,
677	though: if it contains a true value then the event loop has already	896	though: if it is defined then the event loop has already been
678	been detected, and the array will be ignored.	897	detected, and the array will be ignored.
679		898
680	Best use "AnyEvent::post_detect { BLOCK }" instead.	899	Best use "AnyEvent::post_detect { BLOCK }" when your application
		900	allows it,as it takes care of these details.
		901
		902	This variable is mainly useful for modules that can do something
		903	useful when AnyEvent is used and thus want to know when it is
		904	initialised, but do not need to even load it by default. This array
		905	provides the means to hook into AnyEvent passively, without loading
		906	it.
681		907
682	WHAT TO DO IN A MODULE	908	WHAT TO DO IN A MODULE
683	As a module author, you should "use AnyEvent" and call AnyEvent methods	909	As a module author, you should "use AnyEvent" and call AnyEvent methods
684	freely, but you should not load a specific event module or rely on it.	910	freely, but you should not load a specific event module or rely on it.
685		911
…		…
736	variable somewhere, waiting for it, and sending it when the program	962	variable somewhere, waiting for it, and sending it when the program
737	should exit cleanly.	963	should exit cleanly.
738		964
739	OTHER MODULES	965	OTHER MODULES
740	The following is a non-exhaustive list of additional modules that use	966	The following is a non-exhaustive list of additional modules that use
741	AnyEvent and can therefore be mixed easily with other AnyEvent modules	967	AnyEvent as a client and can therefore be mixed easily with other
742	in the same program. Some of the modules come with AnyEvent, some are	968	AnyEvent modules and other event loops in the same program. Some of the
743	available via CPAN.	969	modules come with AnyEvent, most are available via CPAN.
744		970
745	AnyEvent::Util	971	AnyEvent::Util
746	Contains various utility functions that replace often-used but	972	Contains various utility functions that replace often-used but
747	blocking functions such as "inet_aton" by event-/callback-based	973	blocking functions such as "inet_aton" by event-/callback-based
748	versions.	974	versions.
…		…
754	more.	980	more.
755		981
756	AnyEvent::Handle	982	AnyEvent::Handle
757	Provide read and write buffers, manages watchers for reads and	983	Provide read and write buffers, manages watchers for reads and
758	writes, supports raw and formatted I/O, I/O queued and fully	984	writes, supports raw and formatted I/O, I/O queued and fully
759	transparent and non-blocking SSL/TLS.	985	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
760		986
761	AnyEvent::DNS	987	AnyEvent::DNS
762	Provides rich asynchronous DNS resolver capabilities.	988	Provides rich asynchronous DNS resolver capabilities.
763		989
764	AnyEvent::HTTP	990	AnyEvent::HTTP
…		…
785		1011
786	AnyEvent::GPSD	1012	AnyEvent::GPSD
787	A non-blocking interface to gpsd, a daemon delivering GPS	1013	A non-blocking interface to gpsd, a daemon delivering GPS
788	information.	1014	information.
789		1015
		1016	AnyEvent::IRC
		1017	AnyEvent based IRC client module family (replacing the older
		1018	Net::IRC3).
		1019
		1020	AnyEvent::XMPP
		1021	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1022	older Net::XMPP2>.
		1023
790	AnyEvent::IGS	1024	AnyEvent::IGS
791	A non-blocking interface to the Internet Go Server protocol (used by	1025	A non-blocking interface to the Internet Go Server protocol (used by
792	App::IGS).	1026	App::IGS).
793		1027
794	AnyEvent::IRC
795	AnyEvent based IRC client module family (replacing the older
796	Net::IRC3).
797
798	Net::XMPP2
799	AnyEvent based XMPP (Jabber protocol) module family.
800
801	Net::FCP	1028	Net::FCP
802	AnyEvent-based implementation of the Freenet Client Protocol,	1029	AnyEvent-based implementation of the Freenet Client Protocol,
803	birthplace of AnyEvent.	1030	birthplace of AnyEvent.
804		1031
805	Event::ExecFlow	1032	Event::ExecFlow
806	High level API for event-based execution flow control.	1033	High level API for event-based execution flow control.
807		1034
808	Coro	1035	Coro
809	Has special support for AnyEvent via Coro::AnyEvent.	1036	Has special support for AnyEvent via Coro::AnyEvent.
810
811	IO::Lambda
812	The lambda approach to I/O - don't ask, look there. Can use
813	AnyEvent.
814		1037
815	ERROR AND EXCEPTION HANDLING	1038	ERROR AND EXCEPTION HANDLING
816	In general, AnyEvent does not do any error handling - it relies on the	1039	In general, AnyEvent does not do any error handling - it relies on the
817	caller to do that if required. The AnyEvent::Strict module (see also the	1040	caller to do that if required. The AnyEvent::Strict module (see also the
818	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1041	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
828	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1051	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
829	Glib uses "install_exception_handler" and so on.	1052	Glib uses "install_exception_handler" and so on.
830		1053
831	ENVIRONMENT VARIABLES	1054	ENVIRONMENT VARIABLES
832	The following environment variables are used by this module or its	1055	The following environment variables are used by this module or its
833	submodules:	1056	submodules.
		1057
		1058	Note that AnyEvent will remove all environment variables starting with
		1059	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1060	enabled.
834		1061
835	"PERL_ANYEVENT_VERBOSE"	1062	"PERL_ANYEVENT_VERBOSE"
836	By default, AnyEvent will be completely silent except in fatal	1063	By default, AnyEvent will be completely silent except in fatal
837	conditions. You can set this environment variable to make AnyEvent	1064	conditions. You can set this environment variable to make AnyEvent
838	more talkative.	1065	more talkative.
…		…
841	conditions, such as not being able to load the event model specified	1068	conditions, such as not being able to load the event model specified
842	by "PERL_ANYEVENT_MODEL".	1069	by "PERL_ANYEVENT_MODEL".
843		1070
844	When set to 2 or higher, cause AnyEvent to report to STDERR which	1071	When set to 2 or higher, cause AnyEvent to report to STDERR which
845	event model it chooses.	1072	event model it chooses.
		1073
		1074	When set to 8 or higher, then AnyEvent will report extra information
		1075	on which optional modules it loads and how it implements certain
		1076	features.
846		1077
847	"PERL_ANYEVENT_STRICT"	1078	"PERL_ANYEVENT_STRICT"
848	AnyEvent does not do much argument checking by default, as thorough	1079	AnyEvent does not do much argument checking by default, as thorough
849	argument checking is very costly. Setting this variable to a true	1080	argument checking is very costly. Setting this variable to a true
850	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1081	value will cause AnyEvent to load "AnyEvent::Strict" and then to
851	thoroughly check the arguments passed to most method calls. If it	1082	thoroughly check the arguments passed to most method calls. If it
852	finds any problems it will croak.	1083	finds any problems, it will croak.
853		1084
854	In other words, enables "strict" mode.	1085	In other words, enables "strict" mode.
855		1086
856	Unlike "use strict", it is definitely recommended ot keep it off in	1087	Unlike "use strict" (or it's modern cousin, "use common::sense", it
857	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1088	is definitely recommended to keep it off in production. Keeping
		1089	"PERL_ANYEVENT_STRICT=1" in your environment while developing
858	while developing programs can be very useful, however.	1090	programs can be very useful, however.
859		1091
860	"PERL_ANYEVENT_MODEL"	1092	"PERL_ANYEVENT_MODEL"
861	This can be used to specify the event model to be used by AnyEvent,	1093	This can be used to specify the event model to be used by AnyEvent,
862	before auto detection and -probing kicks in. It must be a string	1094	before auto detection and -probing kicks in. It must be a string
863	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1095	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
904	EDNS0 in its DNS requests.	1136	EDNS0 in its DNS requests.
905		1137
906	"PERL_ANYEVENT_MAX_FORKS"	1138	"PERL_ANYEVENT_MAX_FORKS"
907	The maximum number of child processes that	1139	The maximum number of child processes that
908	"AnyEvent::Util::fork_call" will create in parallel.	1140	"AnyEvent::Util::fork_call" will create in parallel.
		1141
		1142	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1143	The default value for the "max_outstanding" parameter for the
		1144	default DNS resolver - this is the maximum number of parallel DNS
		1145	requests that are sent to the DNS server.
		1146
		1147	"PERL_ANYEVENT_RESOLV_CONF"
		1148	The file to use instead of /etc/resolv.conf (or OS-specific
		1149	configuration) in the default resolver. When set to the empty
		1150	string, no default config will be used.
		1151
		1152	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1153	When neither "ca_file" nor "ca_path" was specified during
		1154	AnyEvent::TLS context creation, and either of these environment
		1155	variables exist, they will be used to specify CA certificate
		1156	locations instead of a system-dependent default.
		1157
		1158	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1159	When these are set to 1, then the respective modules are not loaded.
		1160	Mostly good for testing AnyEvent itself.
909		1161
910	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1162	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
911	This is an advanced topic that you do not normally need to use AnyEvent	1163	This is an advanced topic that you do not normally need to use AnyEvent
912	in a module. This section is only of use to event loop authors who want	1164	in a module. This section is only of use to event loop authors who want
913	to provide AnyEvent compatibility.	1165	to provide AnyEvent compatibility.
…		…
1149	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1401	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1150	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1402	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1151	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1403	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1152	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1404	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1153	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1405	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1406	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1407	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1154	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1408	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1155	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1409	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1156	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1410	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1157	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1411	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1158		1412
…		…
1187	few of them active), of course, but this was not subject of this	1441	few of them active), of course, but this was not subject of this
1188	benchmark.	1442	benchmark.
1189		1443
1190	The "Event" module has a relatively high setup and callback invocation	1444	The "Event" module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	1445	cost, but overall scores in on the third place.
		1446
		1447	"IO::Async" performs admirably well, about on par with "Event", even
		1448	when using its pure perl backend.
1192		1449
1193	"Glib"'s memory usage is quite a bit higher, but it features a faster	1450	"Glib"'s memory usage is quite a bit higher, but it features a faster
1194	callback invocation and overall ends up in the same class as "Event".	1451	callback invocation and overall ends up in the same class as "Event".
1195	However, Glib scales extremely badly, doubling the number of watchers	1452	However, Glib scales extremely badly, doubling the number of watchers
1196	increases the processing time by more than a factor of four, making it	1453	increases the processing time by more than a factor of four, making it
…		…
1267	single "request", that is, reading the token from the pipe and	1524	single "request", that is, reading the token from the pipe and
1268	forwarding it to another server. This includes deleting the old timeout	1525	forwarding it to another server. This includes deleting the old timeout
1269	and creating a new one that moves the timeout into the future.	1526	and creating a new one that moves the timeout into the future.
1270		1527
1271	Results	1528	Results
1272	name sockets create request	1529	name sockets create request
1273	EV 20000 69.01 11.16	1530	EV 20000 69.01 11.16
1274	Perl 20000 73.32 35.87	1531	Perl 20000 73.32 35.87
		1532	IOAsync 20000 157.00 98.14 epoll
		1533	IOAsync 20000 159.31 616.06 poll
1275	Event 20000 212.62 257.32	1534	Event 20000 212.62 257.32
1276	Glib 20000 651.16 1896.30	1535	Glib 20000 651.16 1896.30
1277	POE 20000 349.67 12317.24 uses POE::Loop::Event	1536	POE 20000 349.67 12317.24 uses POE::Loop::Event
1278		1537
1279	Discussion	1538	Discussion
1280	This benchmark does measure scalability and overall performance of the	1539	This benchmark does measure scalability and overall performance of the
1281	particular event loop.	1540	particular event loop.
1282		1541
1283	EV is again fastest. Since it is using epoll on my system, the setup	1542	EV is again fastest. Since it is using epoll on my system, the setup
1284	time is relatively high, though.	1543	time is relatively high, though.
1285		1544
1286	Perl surprisingly comes second. It is much faster than the C-based event	1545	Perl surprisingly comes second. It is much faster than the C-based event
1287	loops Event and Glib.	1546	loops Event and Glib.
		1547
		1548	IO::Async performs very well when using its epoll backend, and still
		1549	quite good compared to Glib when using its pure perl backend.
1288		1550
1289	Event suffers from high setup time as well (look at its code and you	1551	Event suffers from high setup time as well (look at its code and you
1290	will understand why). Callback invocation also has a high overhead	1552	will understand why). Callback invocation also has a high overhead
1291	compared to the "$_->() for .."-style loop that the Perl event loop	1553	compared to the "$_->() for .."-style loop that the Perl event loop
1292	uses. Event uses select or poll in basically all documented	1554	uses. Event uses select or poll in basically all documented
…		…
1343		1605
1344	Summary	1606	Summary
1345	* C-based event loops perform very well with small number of watchers,	1607	* C-based event loops perform very well with small number of watchers,
1346	as the management overhead dominates.	1608	as the management overhead dominates.
1347		1609
		1610	THE IO::Lambda BENCHMARK
		1611	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1612	could be misinterpreted to make AnyEvent look bad. In fact, the
		1613	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1614	better (which shouldn't come as a surprise to anybody). As such, the
		1615	benchmark is fine, and mostly shows that the AnyEvent backend from
		1616	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1617	without the extra baggage? To explore this, I wrote the equivalent
		1618	benchmark for AnyEvent.
		1619
		1620	The benchmark itself creates an echo-server, and then, for 500 times,
		1621	connects to the echo server, sends a line, waits for the reply, and then
		1622	creates the next connection. This is a rather bad benchmark, as it
		1623	doesn't test the efficiency of the framework or much non-blocking I/O,
		1624	but it is a benchmark nevertheless.
		1625
		1626	name runtime
		1627	Lambda/select 0.330 sec
		1628	+ optimized 0.122 sec
		1629	Lambda/AnyEvent 0.327 sec
		1630	+ optimized 0.138 sec
		1631	Raw sockets/select 0.077 sec
		1632	POE/select, components 0.662 sec
		1633	POE/select, raw sockets 0.226 sec
		1634	POE/select, optimized 0.404 sec
		1635
		1636	AnyEvent/select/nb 0.085 sec
		1637	AnyEvent/EV/nb 0.068 sec
		1638	+state machine 0.134 sec
		1639
		1640	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1641	benchmarks actually make blocking connects and use 100% blocking I/O,
		1642	defeating the purpose of an event-based solution. All of the newly
		1643	written AnyEvent benchmarks use 100% non-blocking connects (using
		1644	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1645	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1646	connects generally require a lot more bookkeeping and event handling
		1647	than blocking connects (which involve a single syscall only).
		1648
		1649	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1650	offers similar expressive power as POE and IO::Lambda, using
		1651	conventional Perl syntax. This means that both the echo server and the
		1652	client are 100% non-blocking, further placing it at a disadvantage.
		1653
		1654	As you can see, the AnyEvent + EV combination even beats the
		1655	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1656	backend easily beats IO::Lambda and POE.
		1657
		1658	And even the 100% non-blocking version written using the high-level (and
		1659	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
		1660	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1661	in a non-blocking way.
		1662
		1663	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1664	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1665	part of the IO::lambda distribution and were used without any changes.
		1666
1348	SIGNALS	1667	SIGNALS
1349	AnyEvent currently installs handlers for these signals:	1668	AnyEvent currently installs handlers for these signals:
1350		1669
1351	SIGCHLD	1670	SIGCHLD
1352	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1671	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1353	emulation for event loops that do not support them natively. Also,	1672	emulation for event loops that do not support them natively. Also,
1354	some event loops install a similar handler.	1673	some event loops install a similar handler.
		1674
		1675	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1676	then AnyEvent will reset it to default, to avoid losing child exit
		1677	statuses.
1355		1678
1356	SIGPIPE	1679	SIGPIPE
1357	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1680	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1358	"undef" when AnyEvent gets loaded.	1681	"undef" when AnyEvent gets loaded.
1359		1682
…		…
1367	it is that this way, the handler will be restored to defaults on	1690	it is that this way, the handler will be restored to defaults on
1368	exec.	1691	exec.
1369		1692
1370	Feel free to install your own handler, or reset it to defaults.	1693	Feel free to install your own handler, or reset it to defaults.
1371		1694
		1695	RECOMMENDED/OPTIONAL MODULES
		1696	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1697	it's built-in modules) are required to use it.
		1698
		1699	That does not mean that AnyEvent won't take advantage of some additional
		1700	modules if they are installed.
		1701
		1702	This section epxlains which additional modules will be used, and how
		1703	they affect AnyEvent's operetion.
		1704
		1705	Async::Interrupt
		1706	This slightly arcane module is used to implement fast signal
		1707	handling: To my knowledge, there is no way to do completely
		1708	race-free and quick signal handling in pure perl. To ensure that
		1709	signals still get delivered, AnyEvent will start an interval timer
		1710	to wake up perl (and catch the signals) with some delay (default is
		1711	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1712
		1713	If this module is available, then it will be used to implement
		1714	signal catching, which means that signals will not be delayed, and
		1715	the event loop will not be interrupted regularly, which is more
		1716	efficient (And good for battery life on laptops).
		1717
		1718	This affects not just the pure-perl event loop, but also other event
		1719	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1720
		1721	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1722	natively, and either employ their own workarounds (POE) or use
		1723	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1724	Installing Async::Interrupt does nothing for those backends.
		1725
		1726	EV This module isn't really "optional", as it is simply one of the
		1727	backend event loops that AnyEvent can use. However, it is simply the
		1728	best event loop available in terms of features, speed and stability:
		1729	It supports the AnyEvent API optimally, implements all the watcher
		1730	types in XS, does automatic timer adjustments even when no monotonic
		1731	clock is available, can take avdantage of advanced kernel interfaces
		1732	such as "epoll" and "kqueue", and is the fastest backend by far.
		1733	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1734	Glib::EV).
		1735
		1736	Guard
		1737	The guard module, when used, will be used to implement
		1738	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1739	uses a lot less memory), but otherwise doesn't affect guard
		1740	operation much. It is purely used for performance.
		1741
		1742	JSON and JSON::XS
		1743	This module is required when you want to read or write JSON data via
		1744	AnyEvent::Handle. It is also written in pure-perl, but can take
		1745	advantage of the ultra-high-speed JSON::XS module when it is
		1746	installed.
		1747
		1748	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1749	installed.
		1750
		1751	Net::SSLeay
		1752	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1753	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1754	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1755
		1756	Time::HiRes
		1757	This module is part of perl since release 5.008. It will be used
		1758	when the chosen event library does not come with a timing source on
		1759	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1760	additionally use it to try to use a monotonic clock for timing
		1761	stability.
		1762
1372	FORK	1763	FORK
1373	Most event libraries are not fork-safe. The ones who are usually are	1764	Most event libraries are not fork-safe. The ones who are usually are
1374	because they rely on inefficient but fork-safe "select" or "poll" calls.	1765	because they rely on inefficient but fork-safe "select" or "poll" calls.
1375	Only EV is fully fork-aware.	1766	Only EV is fully fork-aware.
1376		1767
1377	If you have to fork, you must either do so before creating your first	1768	If you have to fork, you must either do so before creating your first
1378	watcher OR you must not use AnyEvent at all in the child.	1769	watcher OR you must not use AnyEvent at all in the child OR you must do
		1770	something completely out of the scope of AnyEvent.
1379		1771
1380	SECURITY CONSIDERATIONS	1772	SECURITY CONSIDERATIONS
1381	AnyEvent can be forced to load any event model via	1773	AnyEvent can be forced to load any event model via
1382	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1774	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1383	to execute arbitrary code or directly gain access, it can easily be used	1775	to execute arbitrary code or directly gain access, it can easily be used
…		…
1387		1779
1388	You can make AnyEvent completely ignore this variable by deleting it	1780	You can make AnyEvent completely ignore this variable by deleting it
1389	before the first watcher gets created, e.g. with a "BEGIN" block:	1781	before the first watcher gets created, e.g. with a "BEGIN" block:
1390		1782
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1783	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		1784
1393	use AnyEvent;	1785	use AnyEvent;
1394		1786
1395	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1787	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1396	be used to probe what backend is used and gain other information (which	1788	be used to probe what backend is used and gain other information (which
1397	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),	1789	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1398	and $ENV{PERL_ANYEGENT_STRICT}.	1790	and $ENV{PERL_ANYEVENT_STRICT}.
		1791
		1792	Note that AnyEvent will remove all environment variables starting with
		1793	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1794	enabled.
1399		1795
1400	BUGS	1796	BUGS
1401	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1797	Perl 5.8 has numerous memleaks that sometimes hit this module and are
1402	hard to work around. If you suffer from memleaks, first upgrade to Perl	1798	hard to work around. If you suffer from memleaks, first upgrade to Perl
1403	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1799	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
…		…
1410	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1806	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1411	Event::Lib, Qt, POE.	1807	Event::Lib, Qt, POE.
1412		1808
1413	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1809	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1414	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1810	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1415	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1811	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1812	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1416		1813
1417	Non-blocking file handles, sockets, TCP clients and servers:	1814	Non-blocking file handles, sockets, TCP clients and servers:
1418	AnyEvent::Handle, AnyEvent::Socket.	1815	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1419		1816
1420	Asynchronous DNS: AnyEvent::DNS.	1817	Asynchronous DNS: AnyEvent::DNS.
1421		1818
1422	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1819	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1423		1820
1424	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1821	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1822	AnyEvent::HTTP.
1425		1823
1426	AUTHOR	1824	AUTHOR
1427	Marc Lehmann <schmorp@schmorp.de>	1825	Marc Lehmann <schmorp@schmorp.de>
1428	http://home.schmorp.de/	1826	http://home.schmorp.de/
1429		1827

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Comparing AnyEvent/README (file contents): Revision 1.36 by root, Fri Mar 27 10:49:50 2009 UTC vs. Revision 1.50 by root, Sat Aug 1 09:14:54 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.36 by root, Fri Mar 27 10:49:50 2009 UTC vs.
Revision 1.50 by root, Sat Aug 1 09:14:54 2009 UTC