[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.59 by root, Tue Jan 5 10:45:25 2010 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, 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	Restart Behaviour
		398	While restart behaviour is up to the event loop implementation, most
		399	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		400	pure perl implementation).
		401
		402	Safe/Unsafe Signals
		403	Perl signals can be either "safe" (synchronous to opcode handling) or
		404	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		405	latter might corrupt your memory.
		406
		407	AnyEvent signal handlers are, in addition, synchronous to the event
		408	loop, i.e. they will not interrupt your running perl program but will
		409	only be called as part of the normal event handling (just like timer,
		410	I/O etc. callbacks, too).
		411
		412	Signal Races, Delays and Workarounds
		413	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		414	callbacks to signals in a generic way, which is a pity, as you cannot do
		415	race-free signal handling in perl, requiring C libraries for this.
		416	AnyEvent will try to do it's best, which means in some cases, signals
		417	will be delayed. The maximum time a signal might be delayed is specified
		418	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		419	can be changed only before the first signal watcher is created, and
		420	should be left alone otherwise. This variable determines how often
		421	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		422	will cause fewer spurious wake-ups, which is better for power and CPU
		423	saving.
		424
		425	All these problems can be avoided by installing the optional
		426	Async::Interrupt module, which works with most event loops. It will not
		427	work with inherently broken event loops such as Event or Event::Lib (and
		428	not with POE currently, as POE does it's own workaround with one-second
		429	latency). For those, you just have to suffer the delays.
		430
357	CHILD PROCESS WATCHERS	431	CHILD PROCESS WATCHERS
		432	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		433
358	You can also watch on a child process exit and catch its exit status.	434	You can also watch on a child process exit and catch its exit status.
359		435
360	The child process is specified by the "pid" argument (if set to 0, it	436	The child process is specified by the "pid" argument (one some backends,
361	watches for any child process exit). The watcher will triggered only	437	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	438	The watcher will be triggered only when the child process has finished
363	on any trace events (stopped/continued).	439	and an exit status is available, not on any trace events
		440	(stopped/continued).
364		441
365	The callback will be called with the pid and exit status (as returned by	442	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	443	waitpid), so unlike other watcher types, you can rely on child watcher
367	callback arguments.	444	callback arguments.
368		445
…		…
373		450
374	There is a slight catch to child watchers, however: you usually start	451	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	452	them after the child process was created, and this means the process
376	could have exited already (and no SIGCHLD will be sent anymore).	453	could have exited already (and no SIGCHLD will be sent anymore).
377		454
378	Not all event models handle this correctly (POE doesn't), but even for	455	Not all event models handle this correctly (neither POE nor IO::Async
		456	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	457	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	458	before the process exits (i.e. before you fork in the first place).
381	place).	459	AnyEvent's pure perl event loop handles all cases correctly regardless
		460	of when you start the watcher.
382		461
383	This means you cannot create a child watcher as the very first thing in	462	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	463	an AnyEvent program, you have to create at least one watcher before
385	you "fork" the child (alternatively, you can call "AnyEvent::detect").	464	you "fork" the child (alternatively, you can call "AnyEvent::detect").
386		465
		466	As most event loops do not support waiting for child events, they will
		467	be emulated by AnyEvent in most cases, in which the latency and race
		468	problems mentioned in the description of signal watchers apply.
		469
387	Example: fork a process and wait for it	470	Example: fork a process and wait for it
388		471
389	my $done = AnyEvent->condvar;	472	my $done = AnyEvent->condvar;
390		473
391	my $pid = fork or exit 5;	474	my $pid = fork or exit 5;
392		475
393	my $w = AnyEvent->child (	476	my $w = AnyEvent->child (
394	pid => $pid,	477	pid => $pid,
395	cb => sub {	478	cb => sub {
396	my ($pid, $status) = @_;	479	my ($pid, $status) = @_;
397	warn "pid $pid exited with status $status";	480	warn "pid $pid exited with status $status";
398	$done->send;	481	$done->send;
399	},	482	},
400	);	483	);
401		484
402	# do something else, then wait for process exit	485	# do something else, then wait for process exit
403	$done->recv;	486	$done->recv;
404		487
		488	IDLE WATCHERS
		489	$w = AnyEvent->idle (cb => <callback>);
		490
		491	Repeatedly invoke the callback after the process becomes idle, until
		492	either the watcher is destroyed or new events have been detected.
		493
		494	Idle watchers are useful when there is a need to do something, but it is
		495	not so important (or wise) to do it instantly. The callback will be
		496	invoked only when there is "nothing better to do", which is usually
		497	defined as "all outstanding events have been handled and no new events
		498	have been detected". That means that idle watchers ideally get invoked
		499	when the event loop has just polled for new events but none have been
		500	detected. Instead of blocking to wait for more events, the idle watchers
		501	will be invoked.
		502
		503	Unfortunately, most event loops do not really support idle watchers
		504	(only EV, Event and Glib do it in a usable fashion) - for the rest,
		505	AnyEvent will simply call the callback "from time to time".
		506
		507	Example: read lines from STDIN, but only process them when the program
		508	is otherwise idle:
		509
		510	my @lines; # read data
		511	my $idle_w;
		512	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		513	push @lines, scalar <STDIN>;
		514
		515	# start an idle watcher, if not already done
		516	$idle_w \|\|= AnyEvent->idle (cb => sub {
		517	# handle only one line, when there are lines left
		518	if (my $line = shift @lines) {
		519	print "handled when idle: $line";
		520	} else {
		521	# otherwise disable the idle watcher again
		522	undef $idle_w;
		523	}
		524	});
		525	});
		526
405	CONDITION VARIABLES	527	CONDITION VARIABLES
		528	$cv = AnyEvent->condvar;
		529
		530	$cv->send (<list>);
		531	my @res = $cv->recv;
		532
406	If you are familiar with some event loops you will know that all of them	533	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	534	require you to run some blocking "loop", "run" or similar function that
408	will actively watch for new events and call your callbacks.	535	will actively watch for new events and call your callbacks.
409		536
410	AnyEvent is different, it expects somebody else to run the event loop	537	AnyEvent is slightly different: it expects somebody else to run the
411	and will only block when necessary (usually when told by the user).	538	event loop and will only block when necessary (usually when told by the
		539	user).
412		540
413	The instrument to do that is called a "condition variable", so called	541	The instrument to do that is called a "condition variable", so called
414	because they represent a condition that must become true.	542	because they represent a condition that must become true.
415		543
		544	Now is probably a good time to look at the examples further below.
		545
416	Condition variables can be created by calling the "AnyEvent->condvar"	546	Condition variables can be created by calling the "AnyEvent->condvar"
417	method, usually without arguments. The only argument pair allowed is	547	method, usually without arguments. The only argument pair allowed is
418
419	"cb", which specifies a callback to be called when the condition	548	"cb", which specifies a callback to be called when the condition
420	variable becomes true, with the condition variable as the first argument	549	variable becomes true, with the condition variable as the first argument
421	(but not the results).	550	(but not the results).
422		551
423	After creation, the condition variable is "false" until it becomes	552	After creation, the condition variable is "false" until it becomes
…		…
428	Condition variables are similar to callbacks, except that you can	557	Condition variables are similar to callbacks, except that you can
429	optionally wait for them. They can also be called merge points - points	558	optionally wait for them. They can also be called merge points - points
430	in time where multiple outstanding events have been processed. And yet	559	in time where multiple outstanding events have been processed. And yet
431	another way to call them is transactions - each condition variable can	560	another way to call them is transactions - each condition variable can
432	be used to represent a transaction, which finishes at some point and	561	be used to represent a transaction, which finishes at some point and
433	delivers a result.	562	delivers a result. And yet some people know them as "futures" - a
		563	promise to compute/deliver something that you can wait for.
434		564
435	Condition variables are very useful to signal that something has	565	Condition variables are very useful to signal that something has
436	finished, for example, if you write a module that does asynchronous http	566	finished, for example, if you write a module that does asynchronous http
437	requests, then a condition variable would be the ideal candidate to	567	requests, then a condition variable would be the ideal candidate to
438	signal the availability of results. The user can either act when the	568	signal the availability of results. The user can either act when the
…		…
472	after => 1,	602	after => 1,
473	cb => sub { $result_ready->send },	603	cb => sub { $result_ready->send },
474	);	604	);
475		605
476	# this "blocks" (while handling events) till the callback	606	# this "blocks" (while handling events) till the callback
477	# calls send	607	# calls ->send
478	$result_ready->recv;	608	$result_ready->recv;
479		609
480	Example: wait for a timer, but take advantage of the fact that condition	610	Example: wait for a timer, but take advantage of the fact that condition
481	variables are also code references.	611	variables are also callable directly.
482		612
483	my $done = AnyEvent->condvar;	613	my $done = AnyEvent->condvar;
484	my $delay = AnyEvent->timer (after => 5, cb => $done);	614	my $delay = AnyEvent->timer (after => 5, cb => $done);
485	$done->recv;	615	$done->recv;
486		616
…		…
492		622
493	...	623	...
494		624
495	my @info = $couchdb->info->recv;	625	my @info = $couchdb->info->recv;
496		626
497	And this is how you would just ste a callback to be called whenever the	627	And this is how you would just set a callback to be called whenever the
498	results are available:	628	results are available:
499		629
500	$couchdb->info->cb (sub {	630	$couchdb->info->cb (sub {
501	my @info = $_[0]->recv;	631	my @info = $_[0]->recv;
502	});	632	});
…		…
517		647
518	Any arguments passed to the "send" call will be returned by all	648	Any arguments passed to the "send" call will be returned by all
519	future "->recv" calls.	649	future "->recv" calls.
520		650
521	Condition variables are overloaded so one can call them directly (as	651	Condition variables are overloaded so one can call them directly (as
522	a code reference). Calling them directly is the same as calling	652	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	653	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		654
530	$cv->croak ($error)	655	$cv->croak ($error)
531	Similar to send, but causes all call's to "->recv" to invoke	656	Similar to send, but causes all call's to "->recv" to invoke
532	"Carp::croak" with the given error message/object/scalar.	657	"Carp::croak" with the given error message/object/scalar.
533		658
534	This can be used to signal any errors to the condition variable	659	This can be used to signal any errors to the condition variable
535	user/consumer.	660	user/consumer. Doing it this way instead of calling "croak" directly
		661	delays the error detetcion, but has the overwhelmign advantage that
		662	it diagnoses the error at the place where the result is expected,
		663	and not deep in some event clalback without connection to the actual
		664	code causing the problem.
536		665
537	$cv->begin ([group callback])	666	$cv->begin ([group callback])
538	$cv->end	667	$cv->end
539	These two methods are EXPERIMENTAL and MIGHT CHANGE.
540
541	These two methods can be used to combine many transactions/events	668	These two methods can be used to combine many transactions/events
542	into one. For example, a function that pings many hosts in parallel	669	into one. For example, a function that pings many hosts in parallel
543	might want to use a condition variable for the whole process.	670	might want to use a condition variable for the whole process.
544		671
545	Every call to "->begin" will increment a counter, and every call to	672	Every call to "->begin" will increment a counter, and every call to
546	"->end" will decrement it. If the counter reaches 0 in "->end", the	673	"->end" will decrement it. If the counter reaches 0 in "->end", the
547	(last) callback passed to "begin" will be executed. That callback is	674	(last) callback passed to "begin" will be executed, passing the
548	supposed to call "->send", but that is not required. If no	675	condvar as first argument. That callback is supposed to call
		676	"->send", but that is not required. If no group callback was set,
549	callback was set, "send" will be called without any arguments.	677	"send" will be called without any arguments.
550		678
551	Let's clarify this with the ping example:	679	You can think of "$cv->send" giving you an OR condition (one call
		680	sends), while "$cv->begin" and "$cv->end" giving you an AND
		681	condition (all "begin" calls must be "end"'ed before the condvar
		682	sends).
		683
		684	Let's start with a simple example: you have two I/O watchers (for
		685	example, STDOUT and STDERR for a program), and you want to wait for
		686	both streams to close before activating a condvar:
552		687
553	my $cv = AnyEvent->condvar;	688	my $cv = AnyEvent->condvar;
554		689
		690	$cv->begin; # first watcher
		691	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		692	defined sysread $fh1, my $buf, 4096
		693	or $cv->end;
		694	});
		695
		696	$cv->begin; # second watcher
		697	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		698	defined sysread $fh2, my $buf, 4096
		699	or $cv->end;
		700	});
		701
		702	$cv->recv;
		703
		704	This works because for every event source (EOF on file handle),
		705	there is one call to "begin", so the condvar waits for all calls to
		706	"end" before sending.
		707
		708	The ping example mentioned above is slightly more complicated, as
		709	the there are results to be passwd back, and the number of tasks
		710	that are begung can potentially be zero:
		711
		712	my $cv = AnyEvent->condvar;
		713
555	my %result;	714	my %result;
556	$cv->begin (sub { $cv->send (\%result) });	715	$cv->begin (sub { shift->send (\%result) });
557		716
558	for my $host (@list_of_hosts) {	717	for my $host (@list_of_hosts) {
559	$cv->begin;	718	$cv->begin;
560	ping_host_then_call_callback $host, sub {	719	ping_host_then_call_callback $host, sub {
561	$result{$host} = ...;	720	$result{$host} = ...;
…		…
576	the loop, which serves two important purposes: first, it sets the	735	the loop, which serves two important purposes: first, it sets the
577	callback to be called once the counter reaches 0, and second, it	736	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	737	ensures that "send" is called even when "no" hosts are being pinged
579	(the loop doesn't execute once).	738	(the loop doesn't execute once).
580		739
581	This is the general pattern when you "fan out" into multiple	740	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	741	potentially none) subrequests: use an outer "begin"/"end" pair to
583	ensure "end" is called at least once, and then, for each subrequest	742	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	743	for each subrequest you start, call "begin" and for each subrequest
585	"end".	744	you finish, call "end".
586		745
587	METHODS FOR CONSUMERS	746	METHODS FOR CONSUMERS
588	These methods should only be used by the consuming side, i.e. the code	747	These methods should only be used by the consuming side, i.e. the code
589	awaits the condition.	748	awaits the condition.
590		749
…		…
599	function will call "croak".	758	function will call "croak".
600		759
601	In list context, all parameters passed to "send" will be returned,	760	In list context, all parameters passed to "send" will be returned,
602	in scalar context only the first one will be returned.	761	in scalar context only the first one will be returned.
603		762
		763	Note that doing a blocking wait in a callback is not supported by
		764	any event loop, that is, recursive invocation of a blocking "->recv"
		765	is not allowed, and the "recv" call will "croak" if such a condition
		766	is detected. This condition can be slightly loosened by using
		767	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		768	thread that doesn't run the event loop itself.
		769
604	Not all event models support a blocking wait - some die in that case	770	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	771	(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	772	using this from a module, never require a blocking wait*. Instead,
607	the caller decide whether the call will block or not (for example,	773	let the caller decide whether the call will block or not (for
608	by coupling condition variables with some kind of request results	774	example, by coupling condition variables with some kind of request
609	and supporting callbacks so the caller knows that getting the result	775	results and supporting callbacks so the caller knows that getting
610	will not block, while still supporting blocking waits if the caller	776	the result will not block, while still supporting blocking waits if
611	so desires).	777	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		778
624	You can ensure that "-recv" never blocks by setting a callback and	779	You can ensure that "-recv" never blocks by setting a callback and
625	only calling "->recv" from within that callback (or at a later	780	only calling "->recv" from within that callback (or at a later
626	time). This will work even when the event loop does not support	781	time). This will work even when the event loop does not support
627	blocking waits otherwise.	782	blocking waits otherwise.
…		…
632		787
633	$cb = $cv->cb ($cb->($cv))	788	$cb = $cv->cb ($cb->($cv))
634	This is a mutator function that returns the callback set and	789	This is a mutator function that returns the callback set and
635	optionally replaces it before doing so.	790	optionally replaces it before doing so.
636		791
637	The callback will be called when the condition becomes "true", i.e.	792	The callback will be called when the condition becomes (or already
638	when "send" or "croak" are called, with the only argument being the	793	was) "true", i.e. when "send" or "croak" are called (or were
639	condition variable itself. Calling "recv" inside the callback or at	794	called), with the only argument being the condition variable itself.
		795	Calling "recv" inside the callback or at any later time is
640	any later time is guaranteed not to block.	796	guaranteed not to block.
		797
		798	SUPPORTED EVENT LOOPS/BACKENDS
		799	The available backend classes are (every class has its own manpage):
		800
		801	Backends that are autoprobed when no other event loop can be found.
		802	EV is the preferred backend when no other event loop seems to be in
		803	use. If EV is not installed, then AnyEvent will fall back to its own
		804	pure-perl implementation, which is available everywhere as it comes
		805	with AnyEvent itself.
		806
		807	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		808	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		809
		810	Backends that are transparently being picked up when they are used.
		811	These will be used when they are currently loaded when the first
		812	watcher is created, in which case it is assumed that the application
		813	is using them. This means that AnyEvent will automatically pick the
		814	right backend when the main program loads an event module before
		815	anything starts to create watchers. Nothing special needs to be done
		816	by the main program.
		817
		818	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		819	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		820	AnyEvent::Impl::Tk based on Tk, very broken.
		821	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		822	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		823	AnyEvent::Impl::Irssi used when running within irssi.
		824
		825	Backends with special needs.
		826	Qt requires the Qt::Application to be instantiated first, but will
		827	otherwise be picked up automatically. As long as the main program
		828	instantiates the application before any AnyEvent watchers are
		829	created, everything should just work.
		830
		831	AnyEvent::Impl::Qt based on Qt.
		832
		833	Support for IO::Async can only be partial, as it is too broken and
		834	architecturally limited to even support the AnyEvent API. It also is
		835	the only event loop that needs the loop to be set explicitly, so it
		836	can only be used by a main program knowing about AnyEvent. See
		837	AnyEvent::Impl::Async for the gory details.
		838
		839	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		840
		841	Event loops that are indirectly supported via other backends.
		842	Some event loops can be supported via other modules:
		843
		844	There is no direct support for WxWidgets (Wx) or Prima.
		845
		846	WxWidgets has no support for watching file handles. However, you can
		847	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		848	simply polls 20 times per second, which was considered to be too
		849	horrible to even consider for AnyEvent.
		850
		851	Prima is not supported as nobody seems to be using it, but it has a
		852	POE backend, so it can be supported through POE.
		853
		854	AnyEvent knows about both Prima and Wx, however, and will try to
		855	load POE when detecting them, in the hope that POE will pick them
		856	up, in which case everything will be automatic.
641		857
642	GLOBAL VARIABLES AND FUNCTIONS	858	GLOBAL VARIABLES AND FUNCTIONS
		859	These are not normally required to use AnyEvent, but can be useful to
		860	write AnyEvent extension modules.
		861
643	$AnyEvent::MODEL	862	$AnyEvent::MODEL
644	Contains "undef" until the first watcher is being created. Then it	863	Contains "undef" until the first watcher is being created, before
		864	the backend has been autodetected.
		865
645	contains the event model that is being used, which is the name of	866	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	867	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	868	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).	869	other class in the case AnyEvent has been extended at runtime (e.g.
649		870	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		871
671	AnyEvent::detect	872	AnyEvent::detect
672	Returns $AnyEvent::MODEL, forcing autodetection of the event model	873	Returns $AnyEvent::MODEL, forcing autodetection of the event model
673	if necessary. You should only call this function right before you	874	if necessary. You should only call this function right before you
674	would have created an AnyEvent watcher anyway, that is, as late as	875	would have created an AnyEvent watcher anyway, that is, as late as
675	possible at runtime.	876	possible at runtime, and not e.g. while initialising of your module.
		877
		878	If you need to do some initialisation before AnyEvent watchers are
		879	created, use "post_detect".
676		880
677	$guard = AnyEvent::post_detect { BLOCK }	881	$guard = AnyEvent::post_detect { BLOCK }
678	Arranges for the code block to be executed as soon as the event	882	Arranges for the code block to be executed as soon as the event
679	model is autodetected (or immediately if this has already happened).	883	model is autodetected (or immediately if this has already happened).
680		884
		885	The block will be executed after the actual backend has been
		886	detected ($AnyEvent::MODEL is set), but before any watchers have
		887	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		888	other initialisations - see the sources of AnyEvent::Strict or
		889	AnyEvent::AIO to see how this is used.
		890
		891	The most common usage is to create some global watchers, without
		892	forcing event module detection too early, for example, AnyEvent::AIO
		893	creates and installs the global IO::AIO watcher in a "post_detect"
		894	block to avoid autodetecting the event module at load time.
		895
681	If called in scalar or list context, then it creates and returns an	896	If called in scalar or list context, then it creates and returns an
682	object that automatically removes the callback again when it is	897	object that automatically removes the callback again when it is
		898	destroyed (or "undef" when the hook was immediately executed). See
683	destroyed. See Coro::BDB for a case where this is useful.	899	AnyEvent::AIO for a case where this is useful.
		900
		901	Example: Create a watcher for the IO::AIO module and store it in
		902	$WATCHER. Only do so after the event loop is initialised, though.
		903
		904	our WATCHER;
		905
		906	my $guard = AnyEvent::post_detect {
		907	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		908	};
		909
		910	# the \|\|= is important in case post_detect immediately runs the block,
		911	# as to not clobber the newly-created watcher. assigning both watcher and
		912	# post_detect guard to the same variable has the advantage of users being
		913	# able to just C<undef $WATCHER> if the watcher causes them grief.
		914
		915	$WATCHER \|\|= $guard;
684		916
685	@AnyEvent::post_detect	917	@AnyEvent::post_detect
686	If there are any code references in this array (you can "push" to it	918	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	919	before or after loading AnyEvent), then they will called directly
688	after the event loop has been chosen.	920	after the event loop has been chosen.
689		921
690	You should check $AnyEvent::MODEL before adding to this array,	922	You should check $AnyEvent::MODEL before adding to this array,
691	though: if it contains a true value then the event loop has already	923	though: if it is defined then the event loop has already been
692	been detected, and the array will be ignored.	924	detected, and the array will be ignored.
693		925
694	Best use "AnyEvent::post_detect { BLOCK }" instead.	926	Best use "AnyEvent::post_detect { BLOCK }" when your application
		927	allows it, as it takes care of these details.
		928
		929	This variable is mainly useful for modules that can do something
		930	useful when AnyEvent is used and thus want to know when it is
		931	initialised, but do not need to even load it by default. This array
		932	provides the means to hook into AnyEvent passively, without loading
		933	it.
		934
		935	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		936	together, you could put this into Coro (this is the actual code used
		937	by Coro to accomplish this):
		938
		939	if (defined $AnyEvent::MODEL) {
		940	# AnyEvent already initialised, so load Coro::AnyEvent
		941	require Coro::AnyEvent;
		942	} else {
		943	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		944	# as soon as it is
		945	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		946	}
695		947
696	WHAT TO DO IN A MODULE	948	WHAT TO DO IN A MODULE
697	As a module author, you should "use AnyEvent" and call AnyEvent methods	949	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.	950	freely, but you should not load a specific event module or rely on it.
699		951
…		…
750	variable somewhere, waiting for it, and sending it when the program	1002	variable somewhere, waiting for it, and sending it when the program
751	should exit cleanly.	1003	should exit cleanly.
752		1004
753	OTHER MODULES	1005	OTHER MODULES
754	The following is a non-exhaustive list of additional modules that use	1006	The following is a non-exhaustive list of additional modules that use
755	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1007	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	1008	AnyEvent modules and other event loops in the same program. Some of the
757	available via CPAN.	1009	modules come with AnyEvent, most are available via CPAN.
758		1010
759	AnyEvent::Util	1011	AnyEvent::Util
760	Contains various utility functions that replace often-used but	1012	Contains various utility functions that replace often-used but
761	blocking functions such as "inet_aton" by event-/callback-based	1013	blocking functions such as "inet_aton" by event-/callback-based
762	versions.	1014	versions.
…		…
768	more.	1020	more.
769		1021
770	AnyEvent::Handle	1022	AnyEvent::Handle
771	Provide read and write buffers, manages watchers for reads and	1023	Provide read and write buffers, manages watchers for reads and
772	writes, supports raw and formatted I/O, I/O queued and fully	1024	writes, supports raw and formatted I/O, I/O queued and fully
773	transparent and non-blocking SSL/TLS.	1025	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
774		1026
775	AnyEvent::DNS	1027	AnyEvent::DNS
776	Provides rich asynchronous DNS resolver capabilities.	1028	Provides rich asynchronous DNS resolver capabilities.
777		1029
778	AnyEvent::HTTP	1030	AnyEvent::HTTP
…		…
799		1051
800	AnyEvent::GPSD	1052	AnyEvent::GPSD
801	A non-blocking interface to gpsd, a daemon delivering GPS	1053	A non-blocking interface to gpsd, a daemon delivering GPS
802	information.	1054	information.
803		1055
		1056	AnyEvent::IRC
		1057	AnyEvent based IRC client module family (replacing the older
		1058	Net::IRC3).
		1059
		1060	AnyEvent::XMPP
		1061	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1062	older Net::XMPP2>.
		1063
804	AnyEvent::IGS	1064	AnyEvent::IGS
805	A non-blocking interface to the Internet Go Server protocol (used by	1065	A non-blocking interface to the Internet Go Server protocol (used by
806	App::IGS).	1066	App::IGS).
807		1067
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	1068	Net::FCP
816	AnyEvent-based implementation of the Freenet Client Protocol,	1069	AnyEvent-based implementation of the Freenet Client Protocol,
817	birthplace of AnyEvent.	1070	birthplace of AnyEvent.
818		1071
819	Event::ExecFlow	1072	Event::ExecFlow
820	High level API for event-based execution flow control.	1073	High level API for event-based execution flow control.
821		1074
822	Coro	1075	Coro
823	Has special support for AnyEvent via Coro::AnyEvent.	1076	Has special support for AnyEvent via Coro::AnyEvent.
824		1077
825	IO::Lambda	1078	SIMPLIFIED AE API
826	The lambda approach to I/O - don't ask, look there. Can use	1079	Starting with version 5.0, AnyEvent officially supports a second, much
827	AnyEvent.	1080	simpler, API that is designed to reduce the calling, typing and memory
		1081	overhead.
		1082
		1083	See the AE manpage for details.
828		1084
829	ERROR AND EXCEPTION HANDLING	1085	ERROR AND EXCEPTION HANDLING
830	In general, AnyEvent does not do any error handling - it relies on the	1086	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	1087	caller to do that if required. The AnyEvent::Strict module (see also the
832	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1088	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
842	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1098	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
843	Glib uses "install_exception_handler" and so on.	1099	Glib uses "install_exception_handler" and so on.
844		1100
845	ENVIRONMENT VARIABLES	1101	ENVIRONMENT VARIABLES
846	The following environment variables are used by this module or its	1102	The following environment variables are used by this module or its
847	submodules:	1103	submodules.
		1104
		1105	Note that AnyEvent will remove all environment variables starting with
		1106	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1107	enabled.
848		1108
849	"PERL_ANYEVENT_VERBOSE"	1109	"PERL_ANYEVENT_VERBOSE"
850	By default, AnyEvent will be completely silent except in fatal	1110	By default, AnyEvent will be completely silent except in fatal
851	conditions. You can set this environment variable to make AnyEvent	1111	conditions. You can set this environment variable to make AnyEvent
852	more talkative.	1112	more talkative.
…		…
855	conditions, such as not being able to load the event model specified	1115	conditions, such as not being able to load the event model specified
856	by "PERL_ANYEVENT_MODEL".	1116	by "PERL_ANYEVENT_MODEL".
857		1117
858	When set to 2 or higher, cause AnyEvent to report to STDERR which	1118	When set to 2 or higher, cause AnyEvent to report to STDERR which
859	event model it chooses.	1119	event model it chooses.
		1120
		1121	When set to 8 or higher, then AnyEvent will report extra information
		1122	on which optional modules it loads and how it implements certain
		1123	features.
860		1124
861	"PERL_ANYEVENT_STRICT"	1125	"PERL_ANYEVENT_STRICT"
862	AnyEvent does not do much argument checking by default, as thorough	1126	AnyEvent does not do much argument checking by default, as thorough
863	argument checking is very costly. Setting this variable to a true	1127	argument checking is very costly. Setting this variable to a true
864	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1128	value will cause AnyEvent to load "AnyEvent::Strict" and then to
865	thoroughly check the arguments passed to most method calls. If it	1129	thoroughly check the arguments passed to most method calls. If it
866	finds any problems it will croak.	1130	finds any problems, it will croak.
867		1131
868	In other words, enables "strict" mode.	1132	In other words, enables "strict" mode.
869		1133
870	Unlike "use strict", it is definitely recommended ot keep it off in	1134	Unlike "use strict" (or it's modern cousin, "use common::sense", it
871	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1135	is definitely recommended to keep it off in production. Keeping
		1136	"PERL_ANYEVENT_STRICT=1" in your environment while developing
872	while developing programs can be very useful, however.	1137	programs can be very useful, however.
873		1138
874	"PERL_ANYEVENT_MODEL"	1139	"PERL_ANYEVENT_MODEL"
875	This can be used to specify the event model to be used by AnyEvent,	1140	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	1141	before auto detection and -probing kicks in. It must be a string
877	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1142	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
918	EDNS0 in its DNS requests.	1183	EDNS0 in its DNS requests.
919		1184
920	"PERL_ANYEVENT_MAX_FORKS"	1185	"PERL_ANYEVENT_MAX_FORKS"
921	The maximum number of child processes that	1186	The maximum number of child processes that
922	"AnyEvent::Util::fork_call" will create in parallel.	1187	"AnyEvent::Util::fork_call" will create in parallel.
		1188
		1189	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1190	The default value for the "max_outstanding" parameter for the
		1191	default DNS resolver - this is the maximum number of parallel DNS
		1192	requests that are sent to the DNS server.
		1193
		1194	"PERL_ANYEVENT_RESOLV_CONF"
		1195	The file to use instead of /etc/resolv.conf (or OS-specific
		1196	configuration) in the default resolver. When set to the empty
		1197	string, no default config will be used.
		1198
		1199	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1200	When neither "ca_file" nor "ca_path" was specified during
		1201	AnyEvent::TLS context creation, and either of these environment
		1202	variables exist, they will be used to specify CA certificate
		1203	locations instead of a system-dependent default.
		1204
		1205	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1206	When these are set to 1, then the respective modules are not loaded.
		1207	Mostly good for testing AnyEvent itself.
923		1208
924	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1209	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925	This is an advanced topic that you do not normally need to use AnyEvent	1210	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	1211	in a module. This section is only of use to event loop authors who want
927	to provide AnyEvent compatibility.	1212	to provide AnyEvent compatibility.
…		…
982	warn "read: $input\n"; # output what has been read	1267	warn "read: $input\n"; # output what has been read
983	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1268	$cv->send if $input =~ /^q/i; # quit program if /^q/i
984	},	1269	},
985	);	1270	);
986		1271
987	my $time_watcher; # can only be used once
988
989	sub new_timer {
990	$timer = AnyEvent->timer (after => 1, cb => sub {	1272	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
991	warn "timeout\n"; # print 'timeout' about every second	1273	warn "timeout\n"; # print 'timeout' at most every second
992	&new_timer; # and restart the time
993	});
994	}	1274	});
995
996	new_timer; # create first timer
997		1275
998	$cv->recv; # wait until user enters /^q/i	1276	$cv->recv; # wait until user enters /^q/i
999		1277
1000	REAL-WORLD EXAMPLE	1278	REAL-WORLD EXAMPLE
1001	Consider the Net::FCP module. It features (among others) the following	1279	Consider the Net::FCP module. It features (among others) the following
…		…
1128	through AnyEvent. The benchmark creates a lot of timers (with a zero	1406	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,	1407	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.	1408	which it is), lets them fire exactly once and destroys them again.
1131		1409
1132	Source code for this benchmark is found as eg/bench in the AnyEvent	1410	Source code for this benchmark is found as eg/bench in the AnyEvent
1133	distribution.	1411	distribution. It uses the AE interface, which makes a real difference
		1412	for the EV and Perl backends only.
1134		1413
1135	Explanation of the columns	1414	Explanation of the columns
1136	watcher is the number of event watchers created/destroyed. Since	1415	watcher is the number of event watchers created/destroyed. Since
1137	different event models feature vastly different performances, each event	1416	different event models feature vastly different performances, each event
1138	loop was given a number of watchers so that overall runtime is	1417	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	1436	destroy is the time, in microseconds, that it takes to destroy a
1158	single watcher.	1437	single watcher.
1159		1438
1160	Results	1439	Results
1161	name watchers bytes create invoke destroy comment	1440	name watchers bytes create invoke destroy comment
1162	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1441	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	1442	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	1443	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	1444	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	1445	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	1446	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1447	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1448	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	1449	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	1450	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	1451	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	1452	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1172		1453
1173	Discussion	1454	Discussion
1174	The benchmark does not measure scalability of the event loop very	1455	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)	1456	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	1457	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	1468	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	1469	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1189	CPU cycles with POE.	1470	CPU cycles with POE.
1190		1471
1191	"EV" is the sole leader regarding speed and memory use, which are both	1472	"EV" is the sole leader regarding speed and memory use, which are both
1192	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1473	maximal/minimal, respectively. When using the AE API there is zero
		1474	overhead (when going through the AnyEvent API create is about 5-6 times
		1475	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	1476	any other event loop and is still faster than Event natively).
1194	natively.
1195		1477
1196	The pure perl implementation is hit in a few sweet spots (both the	1478	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	1479	constant timeout and the use of a single fd hit optimisations in the
1198	perl interpreter and the backend itself). Nevertheless this shows that	1480	perl interpreter and the backend itself). Nevertheless this shows that
1199	it adds very little overhead in itself. Like any select-based backend	1481	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	1483	few of them active), of course, but this was not subject of this
1202	benchmark.	1484	benchmark.
1203		1485
1204	The "Event" module has a relatively high setup and callback invocation	1486	The "Event" module has a relatively high setup and callback invocation
1205	cost, but overall scores in on the third place.	1487	cost, but overall scores in on the third place.
		1488
		1489	"IO::Async" performs admirably well, about on par with "Event", even
		1490	when using its pure perl backend.
1206		1491
1207	"Glib"'s memory usage is quite a bit higher, but it features a faster	1492	"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".	1493	callback invocation and overall ends up in the same class as "Event".
1209	However, Glib scales extremely badly, doubling the number of watchers	1494	However, Glib scales extremely badly, doubling the number of watchers
1210	increases the processing time by more than a factor of four, making it	1495	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	1551	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	1552	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.	1553	many connections, most of which are idle at any one point in time.
1269		1554
1270	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1555	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1271	distribution.	1556	distribution. It uses the AE interface, which makes a real difference
		1557	for the EV and Perl backends only.
1272		1558
1273	Explanation of the columns	1559	Explanation of the columns
1274	sockets is the number of sockets, and twice the number of "servers"	1560	sockets is the number of sockets, and twice the number of "servers"
1275	(as each server has a read and write socket end).	1561	(as each server has a read and write socket end).
1276		1562
…		…
1281	single "request", that is, reading the token from the pipe and	1567	single "request", that is, reading the token from the pipe and
1282	forwarding it to another server. This includes deleting the old timeout	1568	forwarding it to another server. This includes deleting the old timeout
1283	and creating a new one that moves the timeout into the future.	1569	and creating a new one that moves the timeout into the future.
1284		1570
1285	Results	1571	Results
1286	name sockets create request	1572	name sockets create request
1287	EV 20000 69.01 11.16	1573	EV 20000 62.66 7.99
1288	Perl 20000 73.32 35.87	1574	Perl 20000 68.32 32.64
1289	Event 20000 212.62 257.32	1575	IOAsync 20000 174.06 101.15 epoll
1290	Glib 20000 651.16 1896.30	1576	IOAsync 20000 174.67 610.84 poll
		1577	Event 20000 202.69 242.91
		1578	Glib 20000 557.01 1689.52
1291	POE 20000 349.67 12317.24 uses POE::Loop::Event	1579	POE 20000 341.54 12086.32 uses POE::Loop::Event
1292		1580
1293	Discussion	1581	Discussion
1294	This benchmark does measure scalability and overall performance of the	1582	This benchmark does measure scalability and overall performance of the
1295	particular event loop.	1583	particular event loop.
1296		1584
1297	EV is again fastest. Since it is using epoll on my system, the setup	1585	EV is again fastest. Since it is using epoll on my system, the setup
1298	time is relatively high, though.	1586	time is relatively high, though.
1299		1587
1300	Perl surprisingly comes second. It is much faster than the C-based event	1588	Perl surprisingly comes second. It is much faster than the C-based event
1301	loops Event and Glib.	1589	loops Event and Glib.
		1590
		1591	IO::Async performs very well when using its epoll backend, and still
		1592	quite good compared to Glib when using its pure perl backend.
1302		1593
1303	Event suffers from high setup time as well (look at its code and you	1594	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	1595	will understand why). Callback invocation also has a high overhead
1305	compared to the "$_->() for .."-style loop that the Perl event loop	1596	compared to the "$_->() for .."-style loop that the Perl event loop
1306	uses. Event uses select or poll in basically all documented	1597	uses. Event uses select or poll in basically all documented
…		…
1357		1648
1358	Summary	1649	Summary
1359	* C-based event loops perform very well with small number of watchers,	1650	* C-based event loops perform very well with small number of watchers,
1360	as the management overhead dominates.	1651	as the management overhead dominates.
1361		1652
		1653	THE IO::Lambda BENCHMARK
		1654	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1655	could be misinterpreted to make AnyEvent look bad. In fact, the
		1656	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1657	better (which shouldn't come as a surprise to anybody). As such, the
		1658	benchmark is fine, and mostly shows that the AnyEvent backend from
		1659	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1660	without the extra baggage? To explore this, I wrote the equivalent
		1661	benchmark for AnyEvent.
		1662
		1663	The benchmark itself creates an echo-server, and then, for 500 times,
		1664	connects to the echo server, sends a line, waits for the reply, and then
		1665	creates the next connection. This is a rather bad benchmark, as it
		1666	doesn't test the efficiency of the framework or much non-blocking I/O,
		1667	but it is a benchmark nevertheless.
		1668
		1669	name runtime
		1670	Lambda/select 0.330 sec
		1671	+ optimized 0.122 sec
		1672	Lambda/AnyEvent 0.327 sec
		1673	+ optimized 0.138 sec
		1674	Raw sockets/select 0.077 sec
		1675	POE/select, components 0.662 sec
		1676	POE/select, raw sockets 0.226 sec
		1677	POE/select, optimized 0.404 sec
		1678
		1679	AnyEvent/select/nb 0.085 sec
		1680	AnyEvent/EV/nb 0.068 sec
		1681	+state machine 0.134 sec
		1682
		1683	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1684	benchmarks actually make blocking connects and use 100% blocking I/O,
		1685	defeating the purpose of an event-based solution. All of the newly
		1686	written AnyEvent benchmarks use 100% non-blocking connects (using
		1687	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1688	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1689	connects generally require a lot more bookkeeping and event handling
		1690	than blocking connects (which involve a single syscall only).
		1691
		1692	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1693	offers similar expressive power as POE and IO::Lambda, using
		1694	conventional Perl syntax. This means that both the echo server and the
		1695	client are 100% non-blocking, further placing it at a disadvantage.
		1696
		1697	As you can see, the AnyEvent + EV combination even beats the
		1698	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1699	backend easily beats IO::Lambda and POE.
		1700
		1701	And even the 100% non-blocking version written using the high-level (and
		1702	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1703	higher level ("unoptimised") abstractions by a large margin, even though
		1704	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1705
		1706	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1707	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1708	part of the IO::Lambda distribution and were used without any changes.
		1709
1362	SIGNALS	1710	SIGNALS
1363	AnyEvent currently installs handlers for these signals:	1711	AnyEvent currently installs handlers for these signals:
1364		1712
1365	SIGCHLD	1713	SIGCHLD
1366	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1714	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367	emulation for event loops that do not support them natively. Also,	1715	emulation for event loops that do not support them natively. Also,
1368	some event loops install a similar handler.	1716	some event loops install a similar handler.
		1717
		1718	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1719	then AnyEvent will reset it to default, to avoid losing child exit
		1720	statuses.
1369		1721
1370	SIGPIPE	1722	SIGPIPE
1371	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1723	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1372	"undef" when AnyEvent gets loaded.	1724	"undef" when AnyEvent gets loaded.
1373		1725
…		…
1381	it is that this way, the handler will be restored to defaults on	1733	it is that this way, the handler will be restored to defaults on
1382	exec.	1734	exec.
1383		1735
1384	Feel free to install your own handler, or reset it to defaults.	1736	Feel free to install your own handler, or reset it to defaults.
1385		1737
		1738	RECOMMENDED/OPTIONAL MODULES
		1739	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1740	it's built-in modules) are required to use it.
		1741
		1742	That does not mean that AnyEvent won't take advantage of some additional
		1743	modules if they are installed.
		1744
		1745	This section explains which additional modules will be used, and how
		1746	they affect AnyEvent's operation.
		1747
		1748	Async::Interrupt
		1749	This slightly arcane module is used to implement fast signal
		1750	handling: To my knowledge, there is no way to do completely
		1751	race-free and quick signal handling in pure perl. To ensure that
		1752	signals still get delivered, AnyEvent will start an interval timer
		1753	to wake up perl (and catch the signals) with some delay (default is
		1754	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1755
		1756	If this module is available, then it will be used to implement
		1757	signal catching, which means that signals will not be delayed, and
		1758	the event loop will not be interrupted regularly, which is more
		1759	efficient (and good for battery life on laptops).
		1760
		1761	This affects not just the pure-perl event loop, but also other event
		1762	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1763
		1764	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1765	natively, and either employ their own workarounds (POE) or use
		1766	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1767	Installing Async::Interrupt does nothing for those backends.
		1768
		1769	EV This module isn't really "optional", as it is simply one of the
		1770	backend event loops that AnyEvent can use. However, it is simply the
		1771	best event loop available in terms of features, speed and stability:
		1772	It supports the AnyEvent API optimally, implements all the watcher
		1773	types in XS, does automatic timer adjustments even when no monotonic
		1774	clock is available, can take avdantage of advanced kernel interfaces
		1775	such as "epoll" and "kqueue", and is the fastest backend by far.
		1776	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1777	Glib::EV).
		1778
		1779	Guard
		1780	The guard module, when used, will be used to implement
		1781	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1782	uses a lot less memory), but otherwise doesn't affect guard
		1783	operation much. It is purely used for performance.
		1784
		1785	JSON and JSON::XS
		1786	One of these modules is required when you want to read or write JSON
		1787	data via AnyEvent::Handle. It is also written in pure-perl, but can
		1788	take advantage of the ultra-high-speed JSON::XS module when it is
		1789	installed.
		1790
		1791	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1792	installed.
		1793
		1794	Net::SSLeay
		1795	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1796	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1797	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1798
		1799	Time::HiRes
		1800	This module is part of perl since release 5.008. It will be used
		1801	when the chosen event library does not come with a timing source on
		1802	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1803	additionally use it to try to use a monotonic clock for timing
		1804	stability.
		1805
1386	FORK	1806	FORK
1387	Most event libraries are not fork-safe. The ones who are usually are	1807	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.	1808	because they rely on inefficient but fork-safe "select" or "poll" calls
1389	Only EV is fully fork-aware.	1809	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1810	epoll are usually badly thought-out hacks that are incompatible with
		1811	fork in one way or another. Only EV is fully fork-aware and ensures that
		1812	you continue event-processing in both parent and child (or both, if you
		1813	know what you are doing).
		1814
		1815	This means that, in general, you cannot fork and do event processing in
		1816	the child if the event library was initialised before the fork (which
		1817	usually happens when the first AnyEvent watcher is created, or the
		1818	library is loaded).
1390		1819
1391	If you have to fork, you must either do so before creating your first	1820	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.	1821	watcher OR you must not use AnyEvent at all in the child OR you must do
		1822	something completely out of the scope of AnyEvent.
		1823
		1824	The problem of doing event processing in the parent and the child is
		1825	much more complicated: even for backends that are fork-aware or
		1826	fork-safe, their behaviour is not usually what you want: fork clones all
		1827	watchers, that means all timers, I/O watchers etc. are active in both
		1828	parent and child, which is almost never what you want. USing "exec" to
		1829	start worker children from some kind of manage rprocess is usually
		1830	preferred, because it is much easier and cleaner, at the expense of
		1831	having to have another binary.
1393		1832
1394	SECURITY CONSIDERATIONS	1833	SECURITY CONSIDERATIONS
1395	AnyEvent can be forced to load any event model via	1834	AnyEvent can be forced to load any event model via
1396	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1835	$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	1836	to execute arbitrary code or directly gain access, it can easily be used
…		…
1401		1840
1402	You can make AnyEvent completely ignore this variable by deleting it	1841	You can make AnyEvent completely ignore this variable by deleting it
1403	before the first watcher gets created, e.g. with a "BEGIN" block:	1842	before the first watcher gets created, e.g. with a "BEGIN" block:
1404		1843
1405	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1844	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1406		1845
1407	use AnyEvent;	1846	use AnyEvent;
1408		1847
1409	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1848	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	1849	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),	1850	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1412	and $ENV{PERL_ANYEGENT_STRICT}.	1851	and $ENV{PERL_ANYEVENT_STRICT}.
		1852
		1853	Note that AnyEvent will remove all environment variables starting with
		1854	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1855	enabled.
1413		1856
1414	BUGS	1857	BUGS
1415	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1858	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	1859	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	1860	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,	1867	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1425	Event::Lib, Qt, POE.	1868	Event::Lib, Qt, POE.
1426		1869
1427	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1870	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1428	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1871	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1429	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1872	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1873	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1430		1874
1431	Non-blocking file handles, sockets, TCP clients and servers:	1875	Non-blocking file handles, sockets, TCP clients and servers:
1432	AnyEvent::Handle, AnyEvent::Socket.	1876	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1433		1877
1434	Asynchronous DNS: AnyEvent::DNS.	1878	Asynchronous DNS: AnyEvent::DNS.
1435		1879
1436	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1880	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1437		1881
1438	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1882	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1883	AnyEvent::HTTP.
1439		1884
1440	AUTHOR	1885	AUTHOR
1441	Marc Lehmann <schmorp@schmorp.de>	1886	Marc Lehmann <schmorp@schmorp.de>
1442	http://home.schmorp.de/	1887	http://home.schmorp.de/
1443		1888

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Comparing AnyEvent/README (file contents): Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs. Revision 1.59 by root, Tue Jan 5 10:45:25 2010 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 1.59 by root, Tue Jan 5 10:45:25 2010 UTC