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Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.56 by root, Thu Nov 19 01:55:57 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
…		…
326	time, which might affect timers and time-outs.	354	time, which might affect timers and time-outs.
327		355
328	When this is the case, you can call this method, which will update	356	When this is the case, you can call this method, which will update
329	the event loop's idea of "current time".	357	the event loop's idea of "current time".
330		358
		359	A typical example would be a script in a web server (e.g.
		360	"mod_perl") - when mod_perl executes the script, then the event loop
		361	will have the wrong idea about the "current time" (being potentially
		362	far in the past, when the script ran the last time). In that case
		363	you should arrange a call to "AnyEvent->now_update" each time the
		364	web server process wakes up again (e.g. at the start of your script,
		365	or in a handler).
		366
331	Note that updating the time might cause some events to be handled.	367	Note that updating the time might cause some events to be handled.
332		368
333	SIGNAL WATCHERS	369	SIGNAL WATCHERS
		370	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		371
334	You can watch for signals using a signal watcher, "signal" is the signal	372	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	373	name in uppercase and without any "SIG" prefix, "cb" is the Perl
336	callback to be invoked whenever a signal occurs.	374	callback to be invoked whenever a signal occurs.
337		375
338	Although the callback might get passed parameters, their value and	376	Although the callback might get passed parameters, their value and
…		…
343	invocation, and callback invocation will be synchronous. Synchronous	381	invocation, and callback invocation will be synchronous. Synchronous
344	means that it might take a while until the signal gets handled by the	382	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.	383	process, but it is guaranteed not to interrupt any other callbacks.
346		384
347	The main advantage of using these watchers is that you can share a	385	The main advantage of using these watchers is that you can share a
348	signal between multiple watchers.	386	signal between multiple watchers, and AnyEvent will ensure that signals
		387	will not interrupt your program at bad times.
349		388
350	This watcher might use %SIG, so programs overwriting those signals	389	This watcher might use %SIG (depending on the event loop used), so
351	directly will likely not work correctly.	390	programs overwriting those signals directly will likely not work
		391	correctly.
352		392
353	Example: exit on SIGINT	393	Example: exit on SIGINT
354		394
355	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	395	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
356		396
		397	Signal Races, Delays and Workarounds
		398	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		399	callbacks to signals in a generic way, which is a pity, as you cannot do
		400	race-free signal handling in perl, requiring C libraries for this.
		401	AnyEvent will try to do it's best, which means in some cases, signals
		402	will be delayed. The maximum time a signal might be delayed is specified
		403	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		404	can be changed only before the first signal watcher is created, and
		405	should be left alone otherwise. This variable determines how often
		406	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		407	will cause fewer spurious wake-ups, which is better for power and CPU
		408	saving.
		409
		410	All these problems can be avoided by installing the optional
		411	Async::Interrupt module, which works with most event loops. It will not
		412	work with inherently broken event loops such as Event or Event::Lib (and
		413	not with POE currently, as POE does it's own workaround with one-second
		414	latency). For those, you just have to suffer the delays.
		415
357	CHILD PROCESS WATCHERS	416	CHILD PROCESS WATCHERS
		417	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		418
358	You can also watch on a child process exit and catch its exit status.	419	You can also watch on a child process exit and catch its exit status.
359		420
360	The child process is specified by the "pid" argument (if set to 0, it	421	The child process is specified by the "pid" argument (one some backends,
361	watches for any child process exit). The watcher will triggered only	422	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	423	The watcher will be triggered only when the child process has finished
363	on any trace events (stopped/continued).	424	and an exit status is available, not on any trace events
		425	(stopped/continued).
364		426
365	The callback will be called with the pid and exit status (as returned by	427	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	428	waitpid), so unlike other watcher types, you can rely on child watcher
367	callback arguments.	429	callback arguments.
368		430
…		…
373		435
374	There is a slight catch to child watchers, however: you usually start	436	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	437	them after the child process was created, and this means the process
376	could have exited already (and no SIGCHLD will be sent anymore).	438	could have exited already (and no SIGCHLD will be sent anymore).
377		439
378	Not all event models handle this correctly (POE doesn't), but even for	440	Not all event models handle this correctly (neither POE nor IO::Async
		441	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	442	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	443	before the process exits (i.e. before you fork in the first place).
381	place).	444	AnyEvent's pure perl event loop handles all cases correctly regardless
		445	of when you start the watcher.
382		446
383	This means you cannot create a child watcher as the very first thing in	447	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	448	an AnyEvent program, you have to create at least one watcher before
385	you "fork" the child (alternatively, you can call "AnyEvent::detect").	449	you "fork" the child (alternatively, you can call "AnyEvent::detect").
386		450
		451	As most event loops do not support waiting for child events, they will
		452	be emulated by AnyEvent in most cases, in which the latency and race
		453	problems mentioned in the description of signal watchers apply.
		454
387	Example: fork a process and wait for it	455	Example: fork a process and wait for it
388		456
389	my $done = AnyEvent->condvar;	457	my $done = AnyEvent->condvar;
390		458
391	my $pid = fork or exit 5;	459	my $pid = fork or exit 5;
392		460
393	my $w = AnyEvent->child (	461	my $w = AnyEvent->child (
394	pid => $pid,	462	pid => $pid,
395	cb => sub {	463	cb => sub {
396	my ($pid, $status) = @_;	464	my ($pid, $status) = @_;
397	warn "pid $pid exited with status $status";	465	warn "pid $pid exited with status $status";
398	$done->send;	466	$done->send;
399	},	467	},
400	);	468	);
401		469
402	# do something else, then wait for process exit	470	# do something else, then wait for process exit
403	$done->recv;	471	$done->recv;
404		472
		473	IDLE WATCHERS
		474	$w = AnyEvent->idle (cb => <callback>);
		475
		476	Sometimes there is a need to do something, but it is not so important to
		477	do it instantly, but only when there is nothing better to do. This
		478	"nothing better to do" is usually defined to be "no other events need
		479	attention by the event loop".
		480
		481	Idle watchers ideally get invoked when the event loop has nothing better
		482	to do, just before it would block the process to wait for new events.
		483	Instead of blocking, the idle watcher is invoked.
		484
		485	Most event loops unfortunately do not really support idle watchers (only
		486	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		487	will simply call the callback "from time to time".
		488
		489	Example: read lines from STDIN, but only process them when the program
		490	is otherwise idle:
		491
		492	my @lines; # read data
		493	my $idle_w;
		494	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		495	push @lines, scalar <STDIN>;
		496
		497	# start an idle watcher, if not already done
		498	$idle_w \|\|= AnyEvent->idle (cb => sub {
		499	# handle only one line, when there are lines left
		500	if (my $line = shift @lines) {
		501	print "handled when idle: $line";
		502	} else {
		503	# otherwise disable the idle watcher again
		504	undef $idle_w;
		505	}
		506	});
		507	});
		508
405	CONDITION VARIABLES	509	CONDITION VARIABLES
		510	$cv = AnyEvent->condvar;
		511
		512	$cv->send (<list>);
		513	my @res = $cv->recv;
		514
406	If you are familiar with some event loops you will know that all of them	515	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	516	require you to run some blocking "loop", "run" or similar function that
408	will actively watch for new events and call your callbacks.	517	will actively watch for new events and call your callbacks.
409		518
410	AnyEvent is different, it expects somebody else to run the event loop	519	AnyEvent is slightly different: it expects somebody else to run the
411	and will only block when necessary (usually when told by the user).	520	event loop and will only block when necessary (usually when told by the
		521	user).
412		522
413	The instrument to do that is called a "condition variable", so called	523	The instrument to do that is called a "condition variable", so called
414	because they represent a condition that must become true.	524	because they represent a condition that must become true.
415		525
		526	Now is probably a good time to look at the examples further below.
		527
416	Condition variables can be created by calling the "AnyEvent->condvar"	528	Condition variables can be created by calling the "AnyEvent->condvar"
417	method, usually without arguments. The only argument pair allowed is	529	method, usually without arguments. The only argument pair allowed is
418
419	"cb", which specifies a callback to be called when the condition	530	"cb", which specifies a callback to be called when the condition
420	variable becomes true, with the condition variable as the first argument	531	variable becomes true, with the condition variable as the first argument
421	(but not the results).	532	(but not the results).
422		533
423	After creation, the condition variable is "false" until it becomes	534	After creation, the condition variable is "false" until it becomes
…		…
428	Condition variables are similar to callbacks, except that you can	539	Condition variables are similar to callbacks, except that you can
429	optionally wait for them. They can also be called merge points - points	540	optionally wait for them. They can also be called merge points - points
430	in time where multiple outstanding events have been processed. And yet	541	in time where multiple outstanding events have been processed. And yet
431	another way to call them is transactions - each condition variable can	542	another way to call them is transactions - each condition variable can
432	be used to represent a transaction, which finishes at some point and	543	be used to represent a transaction, which finishes at some point and
433	delivers a result.	544	delivers a result. And yet some people know them as "futures" - a
		545	promise to compute/deliver something that you can wait for.
434		546
435	Condition variables are very useful to signal that something has	547	Condition variables are very useful to signal that something has
436	finished, for example, if you write a module that does asynchronous http	548	finished, for example, if you write a module that does asynchronous http
437	requests, then a condition variable would be the ideal candidate to	549	requests, then a condition variable would be the ideal candidate to
438	signal the availability of results. The user can either act when the	550	signal the availability of results. The user can either act when the
…		…
472	after => 1,	584	after => 1,
473	cb => sub { $result_ready->send },	585	cb => sub { $result_ready->send },
474	);	586	);
475		587
476	# this "blocks" (while handling events) till the callback	588	# this "blocks" (while handling events) till the callback
477	# calls send	589	# calls ->send
478	$result_ready->recv;	590	$result_ready->recv;
479		591
480	Example: wait for a timer, but take advantage of the fact that condition	592	Example: wait for a timer, but take advantage of the fact that condition
481	variables are also code references.	593	variables are also callable directly.
482		594
483	my $done = AnyEvent->condvar;	595	my $done = AnyEvent->condvar;
484	my $delay = AnyEvent->timer (after => 5, cb => $done);	596	my $delay = AnyEvent->timer (after => 5, cb => $done);
485	$done->recv;	597	$done->recv;
486		598
…		…
492		604
493	...	605	...
494		606
495	my @info = $couchdb->info->recv;	607	my @info = $couchdb->info->recv;
496		608
497	And this is how you would just ste a callback to be called whenever the	609	And this is how you would just set a callback to be called whenever the
498	results are available:	610	results are available:
499		611
500	$couchdb->info->cb (sub {	612	$couchdb->info->cb (sub {
501	my @info = $_[0]->recv;	613	my @info = $_[0]->recv;
502	});	614	});
…		…
517		629
518	Any arguments passed to the "send" call will be returned by all	630	Any arguments passed to the "send" call will be returned by all
519	future "->recv" calls.	631	future "->recv" calls.
520		632
521	Condition variables are overloaded so one can call them directly (as	633	Condition variables are overloaded so one can call them directly (as
522	a code reference). Calling them directly is the same as calling	634	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	635	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		636
530	$cv->croak ($error)	637	$cv->croak ($error)
531	Similar to send, but causes all call's to "->recv" to invoke	638	Similar to send, but causes all call's to "->recv" to invoke
532	"Carp::croak" with the given error message/object/scalar.	639	"Carp::croak" with the given error message/object/scalar.
533		640
534	This can be used to signal any errors to the condition variable	641	This can be used to signal any errors to the condition variable
535	user/consumer.	642	user/consumer. Doing it this way instead of calling "croak" directly
		643	delays the error detetcion, but has the overwhelmign advantage that
		644	it diagnoses the error at the place where the result is expected,
		645	and not deep in some event clalback without connection to the actual
		646	code causing the problem.
536		647
537	$cv->begin ([group callback])	648	$cv->begin ([group callback])
538	$cv->end	649	$cv->end
539	These two methods are EXPERIMENTAL and MIGHT CHANGE.
540
541	These two methods can be used to combine many transactions/events	650	These two methods can be used to combine many transactions/events
542	into one. For example, a function that pings many hosts in parallel	651	into one. For example, a function that pings many hosts in parallel
543	might want to use a condition variable for the whole process.	652	might want to use a condition variable for the whole process.
544		653
545	Every call to "->begin" will increment a counter, and every call to	654	Every call to "->begin" will increment a counter, and every call to
546	"->end" will decrement it. If the counter reaches 0 in "->end", the	655	"->end" will decrement it. If the counter reaches 0 in "->end", the
547	(last) callback passed to "begin" will be executed. That callback is	656	(last) callback passed to "begin" will be executed, passing the
548	supposed to call "->send", but that is not required. If no	657	condvar as first argument. That callback is supposed to call
		658	"->send", but that is not required. If no group callback was set,
549	callback was set, "send" will be called without any arguments.	659	"send" will be called without any arguments.
550		660
551	Let's clarify this with the ping example:	661	You can think of "$cv->send" giving you an OR condition (one call
		662	sends), while "$cv->begin" and "$cv->end" giving you an AND
		663	condition (all "begin" calls must be "end"'ed before the condvar
		664	sends).
		665
		666	Let's start with a simple example: you have two I/O watchers (for
		667	example, STDOUT and STDERR for a program), and you want to wait for
		668	both streams to close before activating a condvar:
552		669
553	my $cv = AnyEvent->condvar;	670	my $cv = AnyEvent->condvar;
554		671
		672	$cv->begin; # first watcher
		673	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		674	defined sysread $fh1, my $buf, 4096
		675	or $cv->end;
		676	});
		677
		678	$cv->begin; # second watcher
		679	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		680	defined sysread $fh2, my $buf, 4096
		681	or $cv->end;
		682	});
		683
		684	$cv->recv;
		685
		686	This works because for every event source (EOF on file handle),
		687	there is one call to "begin", so the condvar waits for all calls to
		688	"end" before sending.
		689
		690	The ping example mentioned above is slightly more complicated, as
		691	the there are results to be passwd back, and the number of tasks
		692	that are begung can potentially be zero:
		693
		694	my $cv = AnyEvent->condvar;
		695
555	my %result;	696	my %result;
556	$cv->begin (sub { $cv->send (\%result) });	697	$cv->begin (sub { shift->send (\%result) });
557		698
558	for my $host (@list_of_hosts) {	699	for my $host (@list_of_hosts) {
559	$cv->begin;	700	$cv->begin;
560	ping_host_then_call_callback $host, sub {	701	ping_host_then_call_callback $host, sub {
561	$result{$host} = ...;	702	$result{$host} = ...;
…		…
576	the loop, which serves two important purposes: first, it sets the	717	the loop, which serves two important purposes: first, it sets the
577	callback to be called once the counter reaches 0, and second, it	718	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	719	ensures that "send" is called even when "no" hosts are being pinged
579	(the loop doesn't execute once).	720	(the loop doesn't execute once).
580		721
581	This is the general pattern when you "fan out" into multiple	722	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	723	potentially none) subrequests: use an outer "begin"/"end" pair to
583	ensure "end" is called at least once, and then, for each subrequest	724	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	725	for each subrequest you start, call "begin" and for each subrequest
585	"end".	726	you finish, call "end".
586		727
587	METHODS FOR CONSUMERS	728	METHODS FOR CONSUMERS
588	These methods should only be used by the consuming side, i.e. the code	729	These methods should only be used by the consuming side, i.e. the code
589	awaits the condition.	730	awaits the condition.
590		731
…		…
599	function will call "croak".	740	function will call "croak".
600		741
601	In list context, all parameters passed to "send" will be returned,	742	In list context, all parameters passed to "send" will be returned,
602	in scalar context only the first one will be returned.	743	in scalar context only the first one will be returned.
603		744
		745	Note that doing a blocking wait in a callback is not supported by
		746	any event loop, that is, recursive invocation of a blocking "->recv"
		747	is not allowed, and the "recv" call will "croak" if such a condition
		748	is detected. This condition can be slightly loosened by using
		749	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		750	thread that doesn't run the event loop itself.
		751
604	Not all event models support a blocking wait - some die in that case	752	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	753	(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	754	using this from a module, never require a blocking wait*. Instead,
607	the caller decide whether the call will block or not (for example,	755	let the caller decide whether the call will block or not (for
608	by coupling condition variables with some kind of request results	756	example, by coupling condition variables with some kind of request
609	and supporting callbacks so the caller knows that getting the result	757	results and supporting callbacks so the caller knows that getting
610	will not block, while still supporting blocking waits if the caller	758	the result will not block, while still supporting blocking waits if
611	so desires).	759	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		760
624	You can ensure that "-recv" never blocks by setting a callback and	761	You can ensure that "-recv" never blocks by setting a callback and
625	only calling "->recv" from within that callback (or at a later	762	only calling "->recv" from within that callback (or at a later
626	time). This will work even when the event loop does not support	763	time). This will work even when the event loop does not support
627	blocking waits otherwise.	764	blocking waits otherwise.
…		…
632		769
633	$cb = $cv->cb ($cb->($cv))	770	$cb = $cv->cb ($cb->($cv))
634	This is a mutator function that returns the callback set and	771	This is a mutator function that returns the callback set and
635	optionally replaces it before doing so.	772	optionally replaces it before doing so.
636		773
637	The callback will be called when the condition becomes "true", i.e.	774	The callback will be called when the condition becomes (or already
638	when "send" or "croak" are called, with the only argument being the	775	was) "true", i.e. when "send" or "croak" are called (or were
639	condition variable itself. Calling "recv" inside the callback or at	776	called), with the only argument being the condition variable itself.
		777	Calling "recv" inside the callback or at any later time is
640	any later time is guaranteed not to block.	778	guaranteed not to block.
		779
		780	SUPPORTED EVENT LOOPS/BACKENDS
		781	The available backend classes are (every class has its own manpage):
		782
		783	Backends that are autoprobed when no other event loop can be found.
		784	EV is the preferred backend when no other event loop seems to be in
		785	use. If EV is not installed, then AnyEvent will fall back to its own
		786	pure-perl implementation, which is available everywhere as it comes
		787	with AnyEvent itself.
		788
		789	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		790	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		791
		792	Backends that are transparently being picked up when they are used.
		793	These will be used when they are currently loaded when the first
		794	watcher is created, in which case it is assumed that the application
		795	is using them. This means that AnyEvent will automatically pick the
		796	right backend when the main program loads an event module before
		797	anything starts to create watchers. Nothing special needs to be done
		798	by the main program.
		799
		800	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		801	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		802	AnyEvent::Impl::Tk based on Tk, very broken.
		803	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		804	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		805	AnyEvent::Impl::Irssi used when running within irssi.
		806
		807	Backends with special needs.
		808	Qt requires the Qt::Application to be instantiated first, but will
		809	otherwise be picked up automatically. As long as the main program
		810	instantiates the application before any AnyEvent watchers are
		811	created, everything should just work.
		812
		813	AnyEvent::Impl::Qt based on Qt.
		814
		815	Support for IO::Async can only be partial, as it is too broken and
		816	architecturally limited to even support the AnyEvent API. It also is
		817	the only event loop that needs the loop to be set explicitly, so it
		818	can only be used by a main program knowing about AnyEvent. See
		819	AnyEvent::Impl::Async for the gory details.
		820
		821	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		822
		823	Event loops that are indirectly supported via other backends.
		824	Some event loops can be supported via other modules:
		825
		826	There is no direct support for WxWidgets (Wx) or Prima.
		827
		828	WxWidgets has no support for watching file handles. However, you can
		829	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		830	simply polls 20 times per second, which was considered to be too
		831	horrible to even consider for AnyEvent.
		832
		833	Prima is not supported as nobody seems to be using it, but it has a
		834	POE backend, so it can be supported through POE.
		835
		836	AnyEvent knows about both Prima and Wx, however, and will try to
		837	load POE when detecting them, in the hope that POE will pick them
		838	up, in which case everything will be automatic.
641		839
642	GLOBAL VARIABLES AND FUNCTIONS	840	GLOBAL VARIABLES AND FUNCTIONS
		841	These are not normally required to use AnyEvent, but can be useful to
		842	write AnyEvent extension modules.
		843
643	$AnyEvent::MODEL	844	$AnyEvent::MODEL
644	Contains "undef" until the first watcher is being created. Then it	845	Contains "undef" until the first watcher is being created, before
		846	the backend has been autodetected.
		847
645	contains the event model that is being used, which is the name of	848	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	849	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	850	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).	851	other class in the case AnyEvent has been extended at runtime (e.g.
649		852	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		853
671	AnyEvent::detect	854	AnyEvent::detect
672	Returns $AnyEvent::MODEL, forcing autodetection of the event model	855	Returns $AnyEvent::MODEL, forcing autodetection of the event model
673	if necessary. You should only call this function right before you	856	if necessary. You should only call this function right before you
674	would have created an AnyEvent watcher anyway, that is, as late as	857	would have created an AnyEvent watcher anyway, that is, as late as
675	possible at runtime.	858	possible at runtime, and not e.g. while initialising of your module.
		859
		860	If you need to do some initialisation before AnyEvent watchers are
		861	created, use "post_detect".
676		862
677	$guard = AnyEvent::post_detect { BLOCK }	863	$guard = AnyEvent::post_detect { BLOCK }
678	Arranges for the code block to be executed as soon as the event	864	Arranges for the code block to be executed as soon as the event
679	model is autodetected (or immediately if this has already happened).	865	model is autodetected (or immediately if this has already happened).
680		866
		867	The block will be executed after the actual backend has been
		868	detected ($AnyEvent::MODEL is set), but before any watchers have
		869	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		870	other initialisations - see the sources of AnyEvent::Strict or
		871	AnyEvent::AIO to see how this is used.
		872
		873	The most common usage is to create some global watchers, without
		874	forcing event module detection too early, for example, AnyEvent::AIO
		875	creates and installs the global IO::AIO watcher in a "post_detect"
		876	block to avoid autodetecting the event module at load time.
		877
681	If called in scalar or list context, then it creates and returns an	878	If called in scalar or list context, then it creates and returns an
682	object that automatically removes the callback again when it is	879	object that automatically removes the callback again when it is
		880	destroyed (or "undef" when the hook was immediately executed). See
683	destroyed. See Coro::BDB for a case where this is useful.	881	AnyEvent::AIO for a case where this is useful.
		882
		883	Example: Create a watcher for the IO::AIO module and store it in
		884	$WATCHER. Only do so after the event loop is initialised, though.
		885
		886	our WATCHER;
		887
		888	my $guard = AnyEvent::post_detect {
		889	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		890	};
		891
		892	# the \|\|= is important in case post_detect immediately runs the block,
		893	# as to not clobber the newly-created watcher. assigning both watcher and
		894	# post_detect guard to the same variable has the advantage of users being
		895	# able to just C<undef $WATCHER> if the watcher causes them grief.
		896
		897	$WATCHER \|\|= $guard;
684		898
685	@AnyEvent::post_detect	899	@AnyEvent::post_detect
686	If there are any code references in this array (you can "push" to it	900	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	901	before or after loading AnyEvent), then they will called directly
688	after the event loop has been chosen.	902	after the event loop has been chosen.
689		903
690	You should check $AnyEvent::MODEL before adding to this array,	904	You should check $AnyEvent::MODEL before adding to this array,
691	though: if it contains a true value then the event loop has already	905	though: if it is defined then the event loop has already been
692	been detected, and the array will be ignored.	906	detected, and the array will be ignored.
693		907
694	Best use "AnyEvent::post_detect { BLOCK }" instead.	908	Best use "AnyEvent::post_detect { BLOCK }" when your application
		909	allows it,as it takes care of these details.
		910
		911	This variable is mainly useful for modules that can do something
		912	useful when AnyEvent is used and thus want to know when it is
		913	initialised, but do not need to even load it by default. This array
		914	provides the means to hook into AnyEvent passively, without loading
		915	it.
695		916
696	WHAT TO DO IN A MODULE	917	WHAT TO DO IN A MODULE
697	As a module author, you should "use AnyEvent" and call AnyEvent methods	918	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.	919	freely, but you should not load a specific event module or rely on it.
699		920
…		…
750	variable somewhere, waiting for it, and sending it when the program	971	variable somewhere, waiting for it, and sending it when the program
751	should exit cleanly.	972	should exit cleanly.
752		973
753	OTHER MODULES	974	OTHER MODULES
754	The following is a non-exhaustive list of additional modules that use	975	The following is a non-exhaustive list of additional modules that use
755	AnyEvent and can therefore be mixed easily with other AnyEvent modules	976	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	977	AnyEvent modules and other event loops in the same program. Some of the
757	available via CPAN.	978	modules come with AnyEvent, most are available via CPAN.
758		979
759	AnyEvent::Util	980	AnyEvent::Util
760	Contains various utility functions that replace often-used but	981	Contains various utility functions that replace often-used but
761	blocking functions such as "inet_aton" by event-/callback-based	982	blocking functions such as "inet_aton" by event-/callback-based
762	versions.	983	versions.
…		…
768	more.	989	more.
769		990
770	AnyEvent::Handle	991	AnyEvent::Handle
771	Provide read and write buffers, manages watchers for reads and	992	Provide read and write buffers, manages watchers for reads and
772	writes, supports raw and formatted I/O, I/O queued and fully	993	writes, supports raw and formatted I/O, I/O queued and fully
773	transparent and non-blocking SSL/TLS.	994	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
774		995
775	AnyEvent::DNS	996	AnyEvent::DNS
776	Provides rich asynchronous DNS resolver capabilities.	997	Provides rich asynchronous DNS resolver capabilities.
777		998
778	AnyEvent::HTTP	999	AnyEvent::HTTP
…		…
799		1020
800	AnyEvent::GPSD	1021	AnyEvent::GPSD
801	A non-blocking interface to gpsd, a daemon delivering GPS	1022	A non-blocking interface to gpsd, a daemon delivering GPS
802	information.	1023	information.
803		1024
		1025	AnyEvent::IRC
		1026	AnyEvent based IRC client module family (replacing the older
		1027	Net::IRC3).
		1028
		1029	AnyEvent::XMPP
		1030	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1031	older Net::XMPP2>.
		1032
804	AnyEvent::IGS	1033	AnyEvent::IGS
805	A non-blocking interface to the Internet Go Server protocol (used by	1034	A non-blocking interface to the Internet Go Server protocol (used by
806	App::IGS).	1035	App::IGS).
807		1036
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	1037	Net::FCP
816	AnyEvent-based implementation of the Freenet Client Protocol,	1038	AnyEvent-based implementation of the Freenet Client Protocol,
817	birthplace of AnyEvent.	1039	birthplace of AnyEvent.
818		1040
819	Event::ExecFlow	1041	Event::ExecFlow
820	High level API for event-based execution flow control.	1042	High level API for event-based execution flow control.
821		1043
822	Coro	1044	Coro
823	Has special support for AnyEvent via Coro::AnyEvent.	1045	Has special support for AnyEvent via Coro::AnyEvent.
824		1046
825	IO::Lambda	1047	SIMPLIFIED AE API
826	The lambda approach to I/O - don't ask, look there. Can use	1048	Starting with version 5.0, AnyEvent officially supports a second, much
827	AnyEvent.	1049	simpler, API that is designed to reduce the calling, typing and memory
		1050	overhead.
		1051
		1052	See the AE manpage for details.
828		1053
829	ERROR AND EXCEPTION HANDLING	1054	ERROR AND EXCEPTION HANDLING
830	In general, AnyEvent does not do any error handling - it relies on the	1055	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	1056	caller to do that if required. The AnyEvent::Strict module (see also the
832	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1057	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
842	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1067	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
843	Glib uses "install_exception_handler" and so on.	1068	Glib uses "install_exception_handler" and so on.
844		1069
845	ENVIRONMENT VARIABLES	1070	ENVIRONMENT VARIABLES
846	The following environment variables are used by this module or its	1071	The following environment variables are used by this module or its
847	submodules:	1072	submodules.
		1073
		1074	Note that AnyEvent will remove all environment variables starting with
		1075	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1076	enabled.
848		1077
849	"PERL_ANYEVENT_VERBOSE"	1078	"PERL_ANYEVENT_VERBOSE"
850	By default, AnyEvent will be completely silent except in fatal	1079	By default, AnyEvent will be completely silent except in fatal
851	conditions. You can set this environment variable to make AnyEvent	1080	conditions. You can set this environment variable to make AnyEvent
852	more talkative.	1081	more talkative.
…		…
855	conditions, such as not being able to load the event model specified	1084	conditions, such as not being able to load the event model specified
856	by "PERL_ANYEVENT_MODEL".	1085	by "PERL_ANYEVENT_MODEL".
857		1086
858	When set to 2 or higher, cause AnyEvent to report to STDERR which	1087	When set to 2 or higher, cause AnyEvent to report to STDERR which
859	event model it chooses.	1088	event model it chooses.
		1089
		1090	When set to 8 or higher, then AnyEvent will report extra information
		1091	on which optional modules it loads and how it implements certain
		1092	features.
860		1093
861	"PERL_ANYEVENT_STRICT"	1094	"PERL_ANYEVENT_STRICT"
862	AnyEvent does not do much argument checking by default, as thorough	1095	AnyEvent does not do much argument checking by default, as thorough
863	argument checking is very costly. Setting this variable to a true	1096	argument checking is very costly. Setting this variable to a true
864	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1097	value will cause AnyEvent to load "AnyEvent::Strict" and then to
865	thoroughly check the arguments passed to most method calls. If it	1098	thoroughly check the arguments passed to most method calls. If it
866	finds any problems it will croak.	1099	finds any problems, it will croak.
867		1100
868	In other words, enables "strict" mode.	1101	In other words, enables "strict" mode.
869		1102
870	Unlike "use strict", it is definitely recommended ot keep it off in	1103	Unlike "use strict" (or it's modern cousin, "use common::sense", it
871	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1104	is definitely recommended to keep it off in production. Keeping
		1105	"PERL_ANYEVENT_STRICT=1" in your environment while developing
872	while developing programs can be very useful, however.	1106	programs can be very useful, however.
873		1107
874	"PERL_ANYEVENT_MODEL"	1108	"PERL_ANYEVENT_MODEL"
875	This can be used to specify the event model to be used by AnyEvent,	1109	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	1110	before auto detection and -probing kicks in. It must be a string
877	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1111	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
918	EDNS0 in its DNS requests.	1152	EDNS0 in its DNS requests.
919		1153
920	"PERL_ANYEVENT_MAX_FORKS"	1154	"PERL_ANYEVENT_MAX_FORKS"
921	The maximum number of child processes that	1155	The maximum number of child processes that
922	"AnyEvent::Util::fork_call" will create in parallel.	1156	"AnyEvent::Util::fork_call" will create in parallel.
		1157
		1158	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1159	The default value for the "max_outstanding" parameter for the
		1160	default DNS resolver - this is the maximum number of parallel DNS
		1161	requests that are sent to the DNS server.
		1162
		1163	"PERL_ANYEVENT_RESOLV_CONF"
		1164	The file to use instead of /etc/resolv.conf (or OS-specific
		1165	configuration) in the default resolver. When set to the empty
		1166	string, no default config will be used.
		1167
		1168	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1169	When neither "ca_file" nor "ca_path" was specified during
		1170	AnyEvent::TLS context creation, and either of these environment
		1171	variables exist, they will be used to specify CA certificate
		1172	locations instead of a system-dependent default.
		1173
		1174	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1175	When these are set to 1, then the respective modules are not loaded.
		1176	Mostly good for testing AnyEvent itself.
923		1177
924	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1178	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925	This is an advanced topic that you do not normally need to use AnyEvent	1179	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	1180	in a module. This section is only of use to event loop authors who want
927	to provide AnyEvent compatibility.	1181	to provide AnyEvent compatibility.
…		…
982	warn "read: $input\n"; # output what has been read	1236	warn "read: $input\n"; # output what has been read
983	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1237	$cv->send if $input =~ /^q/i; # quit program if /^q/i
984	},	1238	},
985	);	1239	);
986		1240
987	my $time_watcher; # can only be used once
988
989	sub new_timer {
990	$timer = AnyEvent->timer (after => 1, cb => sub {	1241	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
991	warn "timeout\n"; # print 'timeout' about every second	1242	warn "timeout\n"; # print 'timeout' at most every second
992	&new_timer; # and restart the time
993	});
994	}	1243	});
995
996	new_timer; # create first timer
997		1244
998	$cv->recv; # wait until user enters /^q/i	1245	$cv->recv; # wait until user enters /^q/i
999		1246
1000	REAL-WORLD EXAMPLE	1247	REAL-WORLD EXAMPLE
1001	Consider the Net::FCP module. It features (among others) the following	1248	Consider the Net::FCP module. It features (among others) the following
…		…
1128	through AnyEvent. The benchmark creates a lot of timers (with a zero	1375	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,	1376	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.	1377	which it is), lets them fire exactly once and destroys them again.
1131		1378
1132	Source code for this benchmark is found as eg/bench in the AnyEvent	1379	Source code for this benchmark is found as eg/bench in the AnyEvent
1133	distribution.	1380	distribution. It uses the AE interface, which makes a real difference
		1381	for the EV and Perl backends only.
1134		1382
1135	Explanation of the columns	1383	Explanation of the columns
1136	watcher is the number of event watchers created/destroyed. Since	1384	watcher is the number of event watchers created/destroyed. Since
1137	different event models feature vastly different performances, each event	1385	different event models feature vastly different performances, each event
1138	loop was given a number of watchers so that overall runtime is	1386	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	1405	destroy is the time, in microseconds, that it takes to destroy a
1158	single watcher.	1406	single watcher.
1159		1407
1160	Results	1408	Results
1161	name watchers bytes create invoke destroy comment	1409	name watchers bytes create invoke destroy comment
1162	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1410	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	1411	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	1412	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	1413	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	1414	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	1415	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1416	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1417	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	1418	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	1419	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	1420	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	1421	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1172		1422
1173	Discussion	1423	Discussion
1174	The benchmark does not measure scalability of the event loop very	1424	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)	1425	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	1426	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	1437	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	1438	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1189	CPU cycles with POE.	1439	CPU cycles with POE.
1190		1440
1191	"EV" is the sole leader regarding speed and memory use, which are both	1441	"EV" is the sole leader regarding speed and memory use, which are both
1192	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1442	maximal/minimal, respectively. When using the AE API there is zero
		1443	overhead (when going through the AnyEvent API create is about 5-6 times
		1444	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	1445	any other event loop and is still faster than Event natively).
1194	natively.
1195		1446
1196	The pure perl implementation is hit in a few sweet spots (both the	1447	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	1448	constant timeout and the use of a single fd hit optimisations in the
1198	perl interpreter and the backend itself). Nevertheless this shows that	1449	perl interpreter and the backend itself). Nevertheless this shows that
1199	it adds very little overhead in itself. Like any select-based backend	1450	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	1452	few of them active), of course, but this was not subject of this
1202	benchmark.	1453	benchmark.
1203		1454
1204	The "Event" module has a relatively high setup and callback invocation	1455	The "Event" module has a relatively high setup and callback invocation
1205	cost, but overall scores in on the third place.	1456	cost, but overall scores in on the third place.
		1457
		1458	"IO::Async" performs admirably well, about on par with "Event", even
		1459	when using its pure perl backend.
1206		1460
1207	"Glib"'s memory usage is quite a bit higher, but it features a faster	1461	"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".	1462	callback invocation and overall ends up in the same class as "Event".
1209	However, Glib scales extremely badly, doubling the number of watchers	1463	However, Glib scales extremely badly, doubling the number of watchers
1210	increases the processing time by more than a factor of four, making it	1464	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	1520	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	1521	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.	1522	many connections, most of which are idle at any one point in time.
1269		1523
1270	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1524	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1271	distribution.	1525	distribution. It uses the AE interface, which makes a real difference
		1526	for the EV and Perl backends only.
1272		1527
1273	Explanation of the columns	1528	Explanation of the columns
1274	sockets is the number of sockets, and twice the number of "servers"	1529	sockets is the number of sockets, and twice the number of "servers"
1275	(as each server has a read and write socket end).	1530	(as each server has a read and write socket end).
1276		1531
…		…
1281	single "request", that is, reading the token from the pipe and	1536	single "request", that is, reading the token from the pipe and
1282	forwarding it to another server. This includes deleting the old timeout	1537	forwarding it to another server. This includes deleting the old timeout
1283	and creating a new one that moves the timeout into the future.	1538	and creating a new one that moves the timeout into the future.
1284		1539
1285	Results	1540	Results
1286	name sockets create request	1541	name sockets create request
1287	EV 20000 69.01 11.16	1542	EV 20000 62.66 7.99
1288	Perl 20000 73.32 35.87	1543	Perl 20000 68.32 32.64
1289	Event 20000 212.62 257.32	1544	IOAsync 20000 174.06 101.15 epoll
1290	Glib 20000 651.16 1896.30	1545	IOAsync 20000 174.67 610.84 poll
		1546	Event 20000 202.69 242.91
		1547	Glib 20000 557.01 1689.52
1291	POE 20000 349.67 12317.24 uses POE::Loop::Event	1548	POE 20000 341.54 12086.32 uses POE::Loop::Event
1292		1549
1293	Discussion	1550	Discussion
1294	This benchmark does measure scalability and overall performance of the	1551	This benchmark does measure scalability and overall performance of the
1295	particular event loop.	1552	particular event loop.
1296		1553
1297	EV is again fastest. Since it is using epoll on my system, the setup	1554	EV is again fastest. Since it is using epoll on my system, the setup
1298	time is relatively high, though.	1555	time is relatively high, though.
1299		1556
1300	Perl surprisingly comes second. It is much faster than the C-based event	1557	Perl surprisingly comes second. It is much faster than the C-based event
1301	loops Event and Glib.	1558	loops Event and Glib.
		1559
		1560	IO::Async performs very well when using its epoll backend, and still
		1561	quite good compared to Glib when using its pure perl backend.
1302		1562
1303	Event suffers from high setup time as well (look at its code and you	1563	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	1564	will understand why). Callback invocation also has a high overhead
1305	compared to the "$_->() for .."-style loop that the Perl event loop	1565	compared to the "$_->() for .."-style loop that the Perl event loop
1306	uses. Event uses select or poll in basically all documented	1566	uses. Event uses select or poll in basically all documented
…		…
1357		1617
1358	Summary	1618	Summary
1359	* C-based event loops perform very well with small number of watchers,	1619	* C-based event loops perform very well with small number of watchers,
1360	as the management overhead dominates.	1620	as the management overhead dominates.
1361		1621
		1622	THE IO::Lambda BENCHMARK
		1623	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1624	could be misinterpreted to make AnyEvent look bad. In fact, the
		1625	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1626	better (which shouldn't come as a surprise to anybody). As such, the
		1627	benchmark is fine, and mostly shows that the AnyEvent backend from
		1628	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1629	without the extra baggage? To explore this, I wrote the equivalent
		1630	benchmark for AnyEvent.
		1631
		1632	The benchmark itself creates an echo-server, and then, for 500 times,
		1633	connects to the echo server, sends a line, waits for the reply, and then
		1634	creates the next connection. This is a rather bad benchmark, as it
		1635	doesn't test the efficiency of the framework or much non-blocking I/O,
		1636	but it is a benchmark nevertheless.
		1637
		1638	name runtime
		1639	Lambda/select 0.330 sec
		1640	+ optimized 0.122 sec
		1641	Lambda/AnyEvent 0.327 sec
		1642	+ optimized 0.138 sec
		1643	Raw sockets/select 0.077 sec
		1644	POE/select, components 0.662 sec
		1645	POE/select, raw sockets 0.226 sec
		1646	POE/select, optimized 0.404 sec
		1647
		1648	AnyEvent/select/nb 0.085 sec
		1649	AnyEvent/EV/nb 0.068 sec
		1650	+state machine 0.134 sec
		1651
		1652	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1653	benchmarks actually make blocking connects and use 100% blocking I/O,
		1654	defeating the purpose of an event-based solution. All of the newly
		1655	written AnyEvent benchmarks use 100% non-blocking connects (using
		1656	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1657	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1658	connects generally require a lot more bookkeeping and event handling
		1659	than blocking connects (which involve a single syscall only).
		1660
		1661	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1662	offers similar expressive power as POE and IO::Lambda, using
		1663	conventional Perl syntax. This means that both the echo server and the
		1664	client are 100% non-blocking, further placing it at a disadvantage.
		1665
		1666	As you can see, the AnyEvent + EV combination even beats the
		1667	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1668	backend easily beats IO::Lambda and POE.
		1669
		1670	And even the 100% non-blocking version written using the high-level (and
		1671	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1672	higher level ("unoptimised") abstractions by a large margin, even though
		1673	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1674
		1675	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1676	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1677	part of the IO::Lambda distribution and were used without any changes.
		1678
1362	SIGNALS	1679	SIGNALS
1363	AnyEvent currently installs handlers for these signals:	1680	AnyEvent currently installs handlers for these signals:
1364		1681
1365	SIGCHLD	1682	SIGCHLD
1366	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1683	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367	emulation for event loops that do not support them natively. Also,	1684	emulation for event loops that do not support them natively. Also,
1368	some event loops install a similar handler.	1685	some event loops install a similar handler.
		1686
		1687	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1688	then AnyEvent will reset it to default, to avoid losing child exit
		1689	statuses.
1369		1690
1370	SIGPIPE	1691	SIGPIPE
1371	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1692	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1372	"undef" when AnyEvent gets loaded.	1693	"undef" when AnyEvent gets loaded.
1373		1694
…		…
1381	it is that this way, the handler will be restored to defaults on	1702	it is that this way, the handler will be restored to defaults on
1382	exec.	1703	exec.
1383		1704
1384	Feel free to install your own handler, or reset it to defaults.	1705	Feel free to install your own handler, or reset it to defaults.
1385		1706
		1707	RECOMMENDED/OPTIONAL MODULES
		1708	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1709	it's built-in modules) are required to use it.
		1710
		1711	That does not mean that AnyEvent won't take advantage of some additional
		1712	modules if they are installed.
		1713
		1714	This section epxlains which additional modules will be used, and how
		1715	they affect AnyEvent's operetion.
		1716
		1717	Async::Interrupt
		1718	This slightly arcane module is used to implement fast signal
		1719	handling: To my knowledge, there is no way to do completely
		1720	race-free and quick signal handling in pure perl. To ensure that
		1721	signals still get delivered, AnyEvent will start an interval timer
		1722	to wake up perl (and catch the signals) with some delay (default is
		1723	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1724
		1725	If this module is available, then it will be used to implement
		1726	signal catching, which means that signals will not be delayed, and
		1727	the event loop will not be interrupted regularly, which is more
		1728	efficient (And good for battery life on laptops).
		1729
		1730	This affects not just the pure-perl event loop, but also other event
		1731	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1732
		1733	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1734	natively, and either employ their own workarounds (POE) or use
		1735	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1736	Installing Async::Interrupt does nothing for those backends.
		1737
		1738	EV This module isn't really "optional", as it is simply one of the
		1739	backend event loops that AnyEvent can use. However, it is simply the
		1740	best event loop available in terms of features, speed and stability:
		1741	It supports the AnyEvent API optimally, implements all the watcher
		1742	types in XS, does automatic timer adjustments even when no monotonic
		1743	clock is available, can take avdantage of advanced kernel interfaces
		1744	such as "epoll" and "kqueue", and is the fastest backend by far.
		1745	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1746	Glib::EV).
		1747
		1748	Guard
		1749	The guard module, when used, will be used to implement
		1750	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1751	uses a lot less memory), but otherwise doesn't affect guard
		1752	operation much. It is purely used for performance.
		1753
		1754	JSON and JSON::XS
		1755	One of these modules is required when you want to read or write JSON
		1756	data via AnyEvent::Handle. It is also written in pure-perl, but can
		1757	take advantage of the ultra-high-speed JSON::XS module when it is
		1758	installed.
		1759
		1760	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1761	installed.
		1762
		1763	Net::SSLeay
		1764	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1765	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1766	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1767
		1768	Time::HiRes
		1769	This module is part of perl since release 5.008. It will be used
		1770	when the chosen event library does not come with a timing source on
		1771	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1772	additionally use it to try to use a monotonic clock for timing
		1773	stability.
		1774
1386	FORK	1775	FORK
1387	Most event libraries are not fork-safe. The ones who are usually are	1776	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.	1777	because they rely on inefficient but fork-safe "select" or "poll" calls.
1389	Only EV is fully fork-aware.	1778	Only EV is fully fork-aware.
1390		1779
1391	If you have to fork, you must either do so before creating your first	1780	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.	1781	watcher OR you must not use AnyEvent at all in the child OR you must do
		1782	something completely out of the scope of AnyEvent.
1393		1783
1394	SECURITY CONSIDERATIONS	1784	SECURITY CONSIDERATIONS
1395	AnyEvent can be forced to load any event model via	1785	AnyEvent can be forced to load any event model via
1396	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1786	$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	1787	to execute arbitrary code or directly gain access, it can easily be used
…		…
1401		1791
1402	You can make AnyEvent completely ignore this variable by deleting it	1792	You can make AnyEvent completely ignore this variable by deleting it
1403	before the first watcher gets created, e.g. with a "BEGIN" block:	1793	before the first watcher gets created, e.g. with a "BEGIN" block:
1404		1794
1405	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1795	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1406		1796
1407	use AnyEvent;	1797	use AnyEvent;
1408		1798
1409	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1799	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	1800	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),	1801	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1412	and $ENV{PERL_ANYEGENT_STRICT}.	1802	and $ENV{PERL_ANYEVENT_STRICT}.
		1803
		1804	Note that AnyEvent will remove all environment variables starting with
		1805	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1806	enabled.
1413		1807
1414	BUGS	1808	BUGS
1415	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1809	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	1810	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	1811	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,	1818	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1425	Event::Lib, Qt, POE.	1819	Event::Lib, Qt, POE.
1426		1820
1427	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1821	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1428	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1822	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1429	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1823	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1824	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1430		1825
1431	Non-blocking file handles, sockets, TCP clients and servers:	1826	Non-blocking file handles, sockets, TCP clients and servers:
1432	AnyEvent::Handle, AnyEvent::Socket.	1827	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1433		1828
1434	Asynchronous DNS: AnyEvent::DNS.	1829	Asynchronous DNS: AnyEvent::DNS.
1435		1830
1436	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1831	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1437		1832
1438	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1833	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1834	AnyEvent::HTTP.
1439		1835
1440	AUTHOR	1836	AUTHOR
1441	Marc Lehmann <schmorp@schmorp.de>	1837	Marc Lehmann <schmorp@schmorp.de>
1442	http://home.schmorp.de/	1838	http://home.schmorp.de/
1443		1839

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Comparing AnyEvent/README (file contents): Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs. Revision 1.56 by root, Thu Nov 19 01:55:57 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 1.56 by root, Thu Nov 19 01:55:57 2009 UTC