[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 1.61 by root, Wed Apr 28 14:15:55 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	# if you prefer function calls, look at the L<AE> manpage for
		11	# an alternative API.
		12
		13	# file handle or descriptor readable
10	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub { ... });	14	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
11		15
		16	# one-shot or repeating timers
12	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	17	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	18	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
14		19
15	print AnyEvent->now; # prints current event loop time	20	print AnyEvent->now; # prints current event loop time
16	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	21	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17		22
		23	# POSIX signal
18	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });	24	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19		25
		26	# child process exit
20	my $w = AnyEvent->child (pid => $pid, cb => sub {	27	my $w = AnyEvent->child (pid => $pid, cb => sub {
21	my ($pid, $status) = @_;	28	my ($pid, $status) = @_;
22	...	29	...
23	});	30	});
		31
		32	# called when event loop idle (if applicable)
		33	my $w = AnyEvent->idle (cb => sub { ... });
24		34
25	my $w = AnyEvent->condvar; # stores whether a condition was flagged	35	my $w = AnyEvent->condvar; # stores whether a condition was flagged
26	$w->send; # wake up current and all future recv's	36	$w->send; # wake up current and all future recv's
27	$w->recv; # enters "main loop" till $condvar gets ->send	37	$w->recv; # enters "main loop" till $condvar gets ->send
28	# use a condvar in callback mode:	38	# use a condvar in callback mode:
30		40
31	INTRODUCTION/TUTORIAL	41	INTRODUCTION/TUTORIAL
32	This manpage is mainly a reference manual. If you are interested in a	42	This manpage is mainly a reference manual. If you are interested in a
33	tutorial or some gentle introduction, have a look at the AnyEvent::Intro	43	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
34	manpage.	44	manpage.
		45
		46	SUPPORT
		47	There is a mailinglist for discussing all things AnyEvent, and an IRC
		48	channel, too.
		49
		50	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		51	Repository, at <http://anyevent.schmorp.de>, for more info.
35		52
36	WHY YOU SHOULD USE THIS MODULE (OR NOT)	53	WHY YOU SHOULD USE THIS MODULE (OR NOT)
37	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	54	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
38	nowadays. So what is different about AnyEvent?	55	nowadays. So what is different about AnyEvent?
39		56
…		…
159	Note that "my $w; $w =" combination. This is necessary because in Perl,	176	Note that "my $w; $w =" combination. This is necessary because in Perl,
160	my variables are only visible after the statement in which they are	177	my variables are only visible after the statement in which they are
161	declared.	178	declared.
162		179
163	I/O WATCHERS	180	I/O WATCHERS
		181	$w = AnyEvent->io (
		182	fh => <filehandle_or_fileno>,
		183	poll => <"r" or "w">,
		184	cb => <callback>,
		185	);
		186
164	You can create an I/O watcher by calling the "AnyEvent->io" method with	187	You can create an I/O watcher by calling the "AnyEvent->io" method with
165	the following mandatory key-value pairs as arguments:	188	the following mandatory key-value pairs as arguments:
166		189
167	"fh" is the Perl file handle (not file descriptor) to watch for	190	"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	191	events (AnyEvent might or might not keep a reference to this file
169	handle). Note that only file handles pointing to things for which	192	handle). Note that only file handles pointing to things for which
170	non-blocking operation makes sense are allowed. This includes sockets,	193	non-blocking operation makes sense are allowed. This includes sockets,
171	most character devices, pipes, fifos and so on, but not for example	194	most character devices, pipes, fifos and so on, but not for example
172	files or block devices.	195	files or block devices.
…		…
196	warn "read: $input\n";	219	warn "read: $input\n";
197	undef $w;	220	undef $w;
198	});	221	});
199		222
200	TIME WATCHERS	223	TIME WATCHERS
		224	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		225
		226	$w = AnyEvent->timer (
		227	after => <fractional_seconds>,
		228	interval => <fractional_seconds>,
		229	cb => <callback>,
		230	);
		231
201	You can create a time watcher by calling the "AnyEvent->timer" method	232	You can create a time watcher by calling the "AnyEvent->timer" method
202	with the following mandatory arguments:	233	with the following mandatory arguments:
203		234
204	"after" specifies after how many seconds (fractional values are	235	"after" specifies after how many seconds (fractional values are
205	supported) the callback should be invoked. "cb" is the callback to	236	supported) the callback should be invoked. "cb" is the callback to
…		…
326	time, which might affect timers and time-outs.	357	time, which might affect timers and time-outs.
327		358
328	When this is the case, you can call this method, which will update	359	When this is the case, you can call this method, which will update
329	the event loop's idea of "current time".	360	the event loop's idea of "current time".
330		361
		362	A typical example would be a script in a web server (e.g.
		363	"mod_perl") - when mod_perl executes the script, then the event loop
		364	will have the wrong idea about the "current time" (being potentially
		365	far in the past, when the script ran the last time). In that case
		366	you should arrange a call to "AnyEvent->now_update" each time the
		367	web server process wakes up again (e.g. at the start of your script,
		368	or in a handler).
		369
331	Note that updating the time might cause some events to be handled.	370	Note that updating the time might cause some events to be handled.
332		371
333	SIGNAL WATCHERS	372	SIGNAL WATCHERS
		373	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		374
334	You can watch for signals using a signal watcher, "signal" is the signal	375	You can watch for signals using a signal watcher, "signal" is the signal
335	name in uppercase and without any "SIG" prefix, "cb" is the Perl	376	name in uppercase and without any "SIG" prefix, "cb" is the Perl
336	callback to be invoked whenever a signal occurs.	377	callback to be invoked whenever a signal occurs.
337		378
338	Although the callback might get passed parameters, their value and	379	Although the callback might get passed parameters, their value and
…		…
343	invocation, and callback invocation will be synchronous. Synchronous	384	invocation, and callback invocation will be synchronous. Synchronous
344	means that it might take a while until the signal gets handled by the	385	means that it might take a while until the signal gets handled by the
345	process, but it is guaranteed not to interrupt any other callbacks.	386	process, but it is guaranteed not to interrupt any other callbacks.
346		387
347	The main advantage of using these watchers is that you can share a	388	The main advantage of using these watchers is that you can share a
348	signal between multiple watchers.	389	signal between multiple watchers, and AnyEvent will ensure that signals
		390	will not interrupt your program at bad times.
349		391
350	This watcher might use %SIG, so programs overwriting those signals	392	This watcher might use %SIG (depending on the event loop used), so
351	directly will likely not work correctly.	393	programs overwriting those signals directly will likely not work
		394	correctly.
352		395
353	Example: exit on SIGINT	396	Example: exit on SIGINT
354		397
355	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	398	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
356		399
		400	Restart Behaviour
		401	While restart behaviour is up to the event loop implementation, most
		402	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		403	pure perl implementation).
		404
		405	Safe/Unsafe Signals
		406	Perl signals can be either "safe" (synchronous to opcode handling) or
		407	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		408	latter might corrupt your memory.
		409
		410	AnyEvent signal handlers are, in addition, synchronous to the event
		411	loop, i.e. they will not interrupt your running perl program but will
		412	only be called as part of the normal event handling (just like timer,
		413	I/O etc. callbacks, too).
		414
		415	Signal Races, Delays and Workarounds
		416	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		417	callbacks to signals in a generic way, which is a pity, as you cannot do
		418	race-free signal handling in perl, requiring C libraries for this.
		419	AnyEvent will try to do it's best, which means in some cases, signals
		420	will be delayed. The maximum time a signal might be delayed is specified
		421	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		422	can be changed only before the first signal watcher is created, and
		423	should be left alone otherwise. This variable determines how often
		424	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		425	will cause fewer spurious wake-ups, which is better for power and CPU
		426	saving.
		427
		428	All these problems can be avoided by installing the optional
		429	Async::Interrupt module, which works with most event loops. It will not
		430	work with inherently broken event loops such as Event or Event::Lib (and
		431	not with POE currently, as POE does it's own workaround with one-second
		432	latency). For those, you just have to suffer the delays.
		433
357	CHILD PROCESS WATCHERS	434	CHILD PROCESS WATCHERS
		435	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		436
358	You can also watch on a child process exit and catch its exit status.	437	You can also watch on a child process exit and catch its exit status.
359		438
360	The child process is specified by the "pid" argument (if set to 0, it	439	The child process is specified by the "pid" argument (one some backends,
361	watches for any child process exit). The watcher will triggered only	440	using 0 watches for any child process exit, on others this will croak).
362	when the child process has finished and an exit status is available, not	441	The watcher will be triggered only when the child process has finished
363	on any trace events (stopped/continued).	442	and an exit status is available, not on any trace events
		443	(stopped/continued).
364		444
365	The callback will be called with the pid and exit status (as returned by	445	The callback will be called with the pid and exit status (as returned by
366	waitpid), so unlike other watcher types, you can rely on child watcher	446	waitpid), so unlike other watcher types, you can rely on child watcher
367	callback arguments.	447	callback arguments.
368		448
…		…
373		453
374	There is a slight catch to child watchers, however: you usually start	454	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	455	them after the child process was created, and this means the process
376	could have exited already (and no SIGCHLD will be sent anymore).	456	could have exited already (and no SIGCHLD will be sent anymore).
377		457
378	Not all event models handle this correctly (POE doesn't), but even for	458	Not all event models handle this correctly (neither POE nor IO::Async
		459	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	460	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	461	before the process exits (i.e. before you fork in the first place).
381	place).	462	AnyEvent's pure perl event loop handles all cases correctly regardless
		463	of when you start the watcher.
382		464
383	This means you cannot create a child watcher as the very first thing in	465	This means you cannot create a child watcher as the very first thing in
384	an AnyEvent program, you have to create at least one watcher before	466	an AnyEvent program, you have to create at least one watcher before
385	you "fork" the child (alternatively, you can call "AnyEvent::detect").	467	you "fork" the child (alternatively, you can call "AnyEvent::detect").
		468
		469	As most event loops do not support waiting for child events, they will
		470	be emulated by AnyEvent in most cases, in which the latency and race
		471	problems mentioned in the description of signal watchers apply.
386		472
387	Example: fork a process and wait for it	473	Example: fork a process and wait for it
388		474
389	my $done = AnyEvent->condvar;	475	my $done = AnyEvent->condvar;
390		476
…		…
400	);	486	);
401		487
402	# do something else, then wait for process exit	488	# do something else, then wait for process exit
403	$done->recv;	489	$done->recv;
404		490
		491	IDLE WATCHERS
		492	$w = AnyEvent->idle (cb => <callback>);
		493
		494	Repeatedly invoke the callback after the process becomes idle, until
		495	either the watcher is destroyed or new events have been detected.
		496
		497	Idle watchers are useful when there is a need to do something, but it is
		498	not so important (or wise) to do it instantly. The callback will be
		499	invoked only when there is "nothing better to do", which is usually
		500	defined as "all outstanding events have been handled and no new events
		501	have been detected". That means that idle watchers ideally get invoked
		502	when the event loop has just polled for new events but none have been
		503	detected. Instead of blocking to wait for more events, the idle watchers
		504	will be invoked.
		505
		506	Unfortunately, most event loops do not really support idle watchers
		507	(only EV, Event and Glib do it in a usable fashion) - for the rest,
		508	AnyEvent will simply call the callback "from time to time".
		509
		510	Example: read lines from STDIN, but only process them when the program
		511	is otherwise idle:
		512
		513	my @lines; # read data
		514	my $idle_w;
		515	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		516	push @lines, scalar <STDIN>;
		517
		518	# start an idle watcher, if not already done
		519	$idle_w \|\|= AnyEvent->idle (cb => sub {
		520	# handle only one line, when there are lines left
		521	if (my $line = shift @lines) {
		522	print "handled when idle: $line";
		523	} else {
		524	# otherwise disable the idle watcher again
		525	undef $idle_w;
		526	}
		527	});
		528	});
		529
405	CONDITION VARIABLES	530	CONDITION VARIABLES
		531	$cv = AnyEvent->condvar;
		532
		533	$cv->send (<list>);
		534	my @res = $cv->recv;
		535
406	If you are familiar with some event loops you will know that all of them	536	If you are familiar with some event loops you will know that all of them
407	require you to run some blocking "loop", "run" or similar function that	537	require you to run some blocking "loop", "run" or similar function that
408	will actively watch for new events and call your callbacks.	538	will actively watch for new events and call your callbacks.
409		539
410	AnyEvent is different, it expects somebody else to run the event loop	540	AnyEvent is slightly different: it expects somebody else to run the
411	and will only block when necessary (usually when told by the user).	541	event loop and will only block when necessary (usually when told by the
		542	user).
412		543
413	The instrument to do that is called a "condition variable", so called	544	The instrument to do that is called a "condition variable", so called
414	because they represent a condition that must become true.	545	because they represent a condition that must become true.
415		546
		547	Now is probably a good time to look at the examples further below.
		548
416	Condition variables can be created by calling the "AnyEvent->condvar"	549	Condition variables can be created by calling the "AnyEvent->condvar"
417	method, usually without arguments. The only argument pair allowed is	550	method, usually without arguments. The only argument pair allowed is
418
419	"cb", which specifies a callback to be called when the condition	551	"cb", which specifies a callback to be called when the condition
420	variable becomes true, with the condition variable as the first argument	552	variable becomes true, with the condition variable as the first argument
421	(but not the results).	553	(but not the results).
422		554
423	After creation, the condition variable is "false" until it becomes	555	After creation, the condition variable is "false" until it becomes
…		…
428	Condition variables are similar to callbacks, except that you can	560	Condition variables are similar to callbacks, except that you can
429	optionally wait for them. They can also be called merge points - points	561	optionally wait for them. They can also be called merge points - points
430	in time where multiple outstanding events have been processed. And yet	562	in time where multiple outstanding events have been processed. And yet
431	another way to call them is transactions - each condition variable can	563	another way to call them is transactions - each condition variable can
432	be used to represent a transaction, which finishes at some point and	564	be used to represent a transaction, which finishes at some point and
433	delivers a result.	565	delivers a result. And yet some people know them as "futures" - a
		566	promise to compute/deliver something that you can wait for.
434		567
435	Condition variables are very useful to signal that something has	568	Condition variables are very useful to signal that something has
436	finished, for example, if you write a module that does asynchronous http	569	finished, for example, if you write a module that does asynchronous http
437	requests, then a condition variable would be the ideal candidate to	570	requests, then a condition variable would be the ideal candidate to
438	signal the availability of results. The user can either act when the	571	signal the availability of results. The user can either act when the
…		…
459	which eventually calls "-> send", and the "consumer side", which waits	592	which eventually calls "-> send", and the "consumer side", which waits
460	for the send to occur.	593	for the send to occur.
461		594
462	Example: wait for a timer.	595	Example: wait for a timer.
463		596
464	# wait till the result is ready	597	# condition: "wait till the timer is fired"
465	my $result_ready = AnyEvent->condvar;	598	my $timer_fired = AnyEvent->condvar;
466		599
467	# do something such as adding a timer	600	# create the timer - we could wait for, say
468	# or socket watcher the calls $result_ready->send	601	# a handle becomign ready, or even an
469	# when the "result" is ready.	602	# AnyEvent::HTTP request to finish, but
470	# in this case, we simply use a timer:	603	# in this case, we simply use a timer:
471	my $w = AnyEvent->timer (	604	my $w = AnyEvent->timer (
472	after => 1,	605	after => 1,
473	cb => sub { $result_ready->send },	606	cb => sub { $timer_fired->send },
474	);	607	);
475		608
476	# this "blocks" (while handling events) till the callback	609	# this "blocks" (while handling events) till the callback
477	# calls send	610	# calls ->send
478	$result_ready->recv;	611	$timer_fired->recv;
479		612
480	Example: wait for a timer, but take advantage of the fact that condition	613	Example: wait for a timer, but take advantage of the fact that condition
481	variables are also code references.	614	variables are also callable directly.
482		615
483	my $done = AnyEvent->condvar;	616	my $done = AnyEvent->condvar;
484	my $delay = AnyEvent->timer (after => 5, cb => $done);	617	my $delay = AnyEvent->timer (after => 5, cb => $done);
485	$done->recv;	618	$done->recv;
486		619
…		…
492		625
493	...	626	...
494		627
495	my @info = $couchdb->info->recv;	628	my @info = $couchdb->info->recv;
496		629
497	And this is how you would just ste a callback to be called whenever the	630	And this is how you would just set a callback to be called whenever the
498	results are available:	631	results are available:
499		632
500	$couchdb->info->cb (sub {	633	$couchdb->info->cb (sub {
501	my @info = $_[0]->recv;	634	my @info = $_[0]->recv;
502	});	635	});
…		…
517		650
518	Any arguments passed to the "send" call will be returned by all	651	Any arguments passed to the "send" call will be returned by all
519	future "->recv" calls.	652	future "->recv" calls.
520		653
521	Condition variables are overloaded so one can call them directly (as	654	Condition variables are overloaded so one can call them directly (as
522	a code reference). Calling them directly is the same as calling	655	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	656	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		657
530	$cv->croak ($error)	658	$cv->croak ($error)
531	Similar to send, but causes all call's to "->recv" to invoke	659	Similar to send, but causes all call's to "->recv" to invoke
532	"Carp::croak" with the given error message/object/scalar.	660	"Carp::croak" with the given error message/object/scalar.
533		661
534	This can be used to signal any errors to the condition variable	662	This can be used to signal any errors to the condition variable
535	user/consumer.	663	user/consumer. Doing it this way instead of calling "croak" directly
		664	delays the error detetcion, but has the overwhelmign advantage that
		665	it diagnoses the error at the place where the result is expected,
		666	and not deep in some event clalback without connection to the actual
		667	code causing the problem.
536		668
537	$cv->begin ([group callback])	669	$cv->begin ([group callback])
538	$cv->end	670	$cv->end
539	These two methods are EXPERIMENTAL and MIGHT CHANGE.
540
541	These two methods can be used to combine many transactions/events	671	These two methods can be used to combine many transactions/events
542	into one. For example, a function that pings many hosts in parallel	672	into one. For example, a function that pings many hosts in parallel
543	might want to use a condition variable for the whole process.	673	might want to use a condition variable for the whole process.
544		674
545	Every call to "->begin" will increment a counter, and every call to	675	Every call to "->begin" will increment a counter, and every call to
546	"->end" will decrement it. If the counter reaches 0 in "->end", the	676	"->end" will decrement it. If the counter reaches 0 in "->end", the
547	(last) callback passed to "begin" will be executed. That callback is	677	(last) callback passed to "begin" will be executed, passing the
548	supposed to call "->send", but that is not required. If no	678	condvar as first argument. That callback is supposed to call
		679	"->send", but that is not required. If no group callback was set,
549	callback was set, "send" will be called without any arguments.	680	"send" will be called without any arguments.
550		681
551	Let's clarify this with the ping example:	682	You can think of "$cv->send" giving you an OR condition (one call
		683	sends), while "$cv->begin" and "$cv->end" giving you an AND
		684	condition (all "begin" calls must be "end"'ed before the condvar
		685	sends).
		686
		687	Let's start with a simple example: you have two I/O watchers (for
		688	example, STDOUT and STDERR for a program), and you want to wait for
		689	both streams to close before activating a condvar:
552		690
553	my $cv = AnyEvent->condvar;	691	my $cv = AnyEvent->condvar;
554		692
		693	$cv->begin; # first watcher
		694	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		695	defined sysread $fh1, my $buf, 4096
		696	or $cv->end;
		697	});
		698
		699	$cv->begin; # second watcher
		700	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		701	defined sysread $fh2, my $buf, 4096
		702	or $cv->end;
		703	});
		704
		705	$cv->recv;
		706
		707	This works because for every event source (EOF on file handle),
		708	there is one call to "begin", so the condvar waits for all calls to
		709	"end" before sending.
		710
		711	The ping example mentioned above is slightly more complicated, as
		712	the there are results to be passwd back, and the number of tasks
		713	that are begung can potentially be zero:
		714
		715	my $cv = AnyEvent->condvar;
		716
555	my %result;	717	my %result;
556	$cv->begin (sub { $cv->send (\%result) });	718	$cv->begin (sub { shift->send (\%result) });
557		719
558	for my $host (@list_of_hosts) {	720	for my $host (@list_of_hosts) {
559	$cv->begin;	721	$cv->begin;
560	ping_host_then_call_callback $host, sub {	722	ping_host_then_call_callback $host, sub {
561	$result{$host} = ...;	723	$result{$host} = ...;
…		…
576	the loop, which serves two important purposes: first, it sets the	738	the loop, which serves two important purposes: first, it sets the
577	callback to be called once the counter reaches 0, and second, it	739	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	740	ensures that "send" is called even when "no" hosts are being pinged
579	(the loop doesn't execute once).	741	(the loop doesn't execute once).
580		742
581	This is the general pattern when you "fan out" into multiple	743	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	744	potentially none) subrequests: use an outer "begin"/"end" pair to
583	ensure "end" is called at least once, and then, for each subrequest	745	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	746	for each subrequest you start, call "begin" and for each subrequest
585	"end".	747	you finish, call "end".
586		748
587	METHODS FOR CONSUMERS	749	METHODS FOR CONSUMERS
588	These methods should only be used by the consuming side, i.e. the code	750	These methods should only be used by the consuming side, i.e. the code
589	awaits the condition.	751	awaits the condition.
590		752
…		…
599	function will call "croak".	761	function will call "croak".
600		762
601	In list context, all parameters passed to "send" will be returned,	763	In list context, all parameters passed to "send" will be returned,
602	in scalar context only the first one will be returned.	764	in scalar context only the first one will be returned.
603		765
		766	Note that doing a blocking wait in a callback is not supported by
		767	any event loop, that is, recursive invocation of a blocking "->recv"
		768	is not allowed, and the "recv" call will "croak" if such a condition
		769	is detected. This condition can be slightly loosened by using
		770	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		771	thread that doesn't run the event loop itself.
		772
604	Not all event models support a blocking wait - some die in that case	773	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	774	(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	775	using this from a module, never require a blocking wait*. Instead,
607	the caller decide whether the call will block or not (for example,	776	let the caller decide whether the call will block or not (for
608	by coupling condition variables with some kind of request results	777	example, by coupling condition variables with some kind of request
609	and supporting callbacks so the caller knows that getting the result	778	results and supporting callbacks so the caller knows that getting
610	will not block, while still supporting blocking waits if the caller	779	the result will not block, while still supporting blocking waits if
611	so desires).	780	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		781
624	You can ensure that "-recv" never blocks by setting a callback and	782	You can ensure that "-recv" never blocks by setting a callback and
625	only calling "->recv" from within that callback (or at a later	783	only calling "->recv" from within that callback (or at a later
626	time). This will work even when the event loop does not support	784	time). This will work even when the event loop does not support
627	blocking waits otherwise.	785	blocking waits otherwise.
…		…
632		790
633	$cb = $cv->cb ($cb->($cv))	791	$cb = $cv->cb ($cb->($cv))
634	This is a mutator function that returns the callback set and	792	This is a mutator function that returns the callback set and
635	optionally replaces it before doing so.	793	optionally replaces it before doing so.
636		794
637	The callback will be called when the condition becomes "true", i.e.	795	The callback will be called when the condition becomes (or already
638	when "send" or "croak" are called, with the only argument being the	796	was) "true", i.e. when "send" or "croak" are called (or were
639	condition variable itself. Calling "recv" inside the callback or at	797	called), with the only argument being the condition variable itself.
		798	Calling "recv" inside the callback or at any later time is
640	any later time is guaranteed not to block.	799	guaranteed not to block.
		800
		801	SUPPORTED EVENT LOOPS/BACKENDS
		802	The available backend classes are (every class has its own manpage):
		803
		804	Backends that are autoprobed when no other event loop can be found.
		805	EV is the preferred backend when no other event loop seems to be in
		806	use. If EV is not installed, then AnyEvent will fall back to its own
		807	pure-perl implementation, which is available everywhere as it comes
		808	with AnyEvent itself.
		809
		810	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		811	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		812
		813	Backends that are transparently being picked up when they are used.
		814	These will be used when they are currently loaded when the first
		815	watcher is created, in which case it is assumed that the application
		816	is using them. This means that AnyEvent will automatically pick the
		817	right backend when the main program loads an event module before
		818	anything starts to create watchers. Nothing special needs to be done
		819	by the main program.
		820
		821	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		822	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		823	AnyEvent::Impl::Tk based on Tk, very broken.
		824	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		825	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		826	AnyEvent::Impl::Irssi used when running within irssi.
		827
		828	Backends with special needs.
		829	Qt requires the Qt::Application to be instantiated first, but will
		830	otherwise be picked up automatically. As long as the main program
		831	instantiates the application before any AnyEvent watchers are
		832	created, everything should just work.
		833
		834	AnyEvent::Impl::Qt based on Qt.
		835
		836	Support for IO::Async can only be partial, as it is too broken and
		837	architecturally limited to even support the AnyEvent API. It also is
		838	the only event loop that needs the loop to be set explicitly, so it
		839	can only be used by a main program knowing about AnyEvent. See
		840	AnyEvent::Impl::Async for the gory details.
		841
		842	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		843
		844	Event loops that are indirectly supported via other backends.
		845	Some event loops can be supported via other modules:
		846
		847	There is no direct support for WxWidgets (Wx) or Prima.
		848
		849	WxWidgets has no support for watching file handles. However, you can
		850	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		851	simply polls 20 times per second, which was considered to be too
		852	horrible to even consider for AnyEvent.
		853
		854	Prima is not supported as nobody seems to be using it, but it has a
		855	POE backend, so it can be supported through POE.
		856
		857	AnyEvent knows about both Prima and Wx, however, and will try to
		858	load POE when detecting them, in the hope that POE will pick them
		859	up, in which case everything will be automatic.
641		860
642	GLOBAL VARIABLES AND FUNCTIONS	861	GLOBAL VARIABLES AND FUNCTIONS
		862	These are not normally required to use AnyEvent, but can be useful to
		863	write AnyEvent extension modules.
		864
643	$AnyEvent::MODEL	865	$AnyEvent::MODEL
644	Contains "undef" until the first watcher is being created. Then it	866	Contains "undef" until the first watcher is being created, before
		867	the backend has been autodetected.
		868
645	contains the event model that is being used, which is the name of	869	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	870	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	871	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).	872	other class in the case AnyEvent has been extended at runtime (e.g.
649		873	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		874
671	AnyEvent::detect	875	AnyEvent::detect
672	Returns $AnyEvent::MODEL, forcing autodetection of the event model	876	Returns $AnyEvent::MODEL, forcing autodetection of the event model
673	if necessary. You should only call this function right before you	877	if necessary. You should only call this function right before you
674	would have created an AnyEvent watcher anyway, that is, as late as	878	would have created an AnyEvent watcher anyway, that is, as late as
675	possible at runtime.	879	possible at runtime, and not e.g. while initialising of your module.
		880
		881	If you need to do some initialisation before AnyEvent watchers are
		882	created, use "post_detect".
676		883
677	$guard = AnyEvent::post_detect { BLOCK }	884	$guard = AnyEvent::post_detect { BLOCK }
678	Arranges for the code block to be executed as soon as the event	885	Arranges for the code block to be executed as soon as the event
679	model is autodetected (or immediately if this has already happened).	886	model is autodetected (or immediately if this has already happened).
680		887
		888	The block will be executed after the actual backend has been
		889	detected ($AnyEvent::MODEL is set), but before any watchers have
		890	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		891	other initialisations - see the sources of AnyEvent::Strict or
		892	AnyEvent::AIO to see how this is used.
		893
		894	The most common usage is to create some global watchers, without
		895	forcing event module detection too early, for example, AnyEvent::AIO
		896	creates and installs the global IO::AIO watcher in a "post_detect"
		897	block to avoid autodetecting the event module at load time.
		898
681	If called in scalar or list context, then it creates and returns an	899	If called in scalar or list context, then it creates and returns an
682	object that automatically removes the callback again when it is	900	object that automatically removes the callback again when it is
		901	destroyed (or "undef" when the hook was immediately executed). See
683	destroyed. See Coro::BDB for a case where this is useful.	902	AnyEvent::AIO for a case where this is useful.
		903
		904	Example: Create a watcher for the IO::AIO module and store it in
		905	$WATCHER. Only do so after the event loop is initialised, though.
		906
		907	our WATCHER;
		908
		909	my $guard = AnyEvent::post_detect {
		910	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		911	};
		912
		913	# the \|\|= is important in case post_detect immediately runs the block,
		914	# as to not clobber the newly-created watcher. assigning both watcher and
		915	# post_detect guard to the same variable has the advantage of users being
		916	# able to just C<undef $WATCHER> if the watcher causes them grief.
		917
		918	$WATCHER \|\|= $guard;
684		919
685	@AnyEvent::post_detect	920	@AnyEvent::post_detect
686	If there are any code references in this array (you can "push" to it	921	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	922	before or after loading AnyEvent), then they will called directly
688	after the event loop has been chosen.	923	after the event loop has been chosen.
689		924
690	You should check $AnyEvent::MODEL before adding to this array,	925	You should check $AnyEvent::MODEL before adding to this array,
691	though: if it contains a true value then the event loop has already	926	though: if it is defined then the event loop has already been
692	been detected, and the array will be ignored.	927	detected, and the array will be ignored.
693		928
694	Best use "AnyEvent::post_detect { BLOCK }" instead.	929	Best use "AnyEvent::post_detect { BLOCK }" when your application
		930	allows it, as it takes care of these details.
		931
		932	This variable is mainly useful for modules that can do something
		933	useful when AnyEvent is used and thus want to know when it is
		934	initialised, but do not need to even load it by default. This array
		935	provides the means to hook into AnyEvent passively, without loading
		936	it.
		937
		938	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		939	together, you could put this into Coro (this is the actual code used
		940	by Coro to accomplish this):
		941
		942	if (defined $AnyEvent::MODEL) {
		943	# AnyEvent already initialised, so load Coro::AnyEvent
		944	require Coro::AnyEvent;
		945	} else {
		946	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		947	# as soon as it is
		948	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		949	}
695		950
696	WHAT TO DO IN A MODULE	951	WHAT TO DO IN A MODULE
697	As a module author, you should "use AnyEvent" and call AnyEvent methods	952	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.	953	freely, but you should not load a specific event module or rely on it.
699		954
…		…
750	variable somewhere, waiting for it, and sending it when the program	1005	variable somewhere, waiting for it, and sending it when the program
751	should exit cleanly.	1006	should exit cleanly.
752		1007
753	OTHER MODULES	1008	OTHER MODULES
754	The following is a non-exhaustive list of additional modules that use	1009	The following is a non-exhaustive list of additional modules that use
755	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1010	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	1011	AnyEvent modules and other event loops in the same program. Some of the
757	available via CPAN.	1012	modules come with AnyEvent, most are available via CPAN.
758		1013
759	AnyEvent::Util	1014	AnyEvent::Util
760	Contains various utility functions that replace often-used but	1015	Contains various utility functions that replace often-used but
761	blocking functions such as "inet_aton" by event-/callback-based	1016	blocking functions such as "inet_aton" by event-/callback-based
762	versions.	1017	versions.
…		…
768	more.	1023	more.
769		1024
770	AnyEvent::Handle	1025	AnyEvent::Handle
771	Provide read and write buffers, manages watchers for reads and	1026	Provide read and write buffers, manages watchers for reads and
772	writes, supports raw and formatted I/O, I/O queued and fully	1027	writes, supports raw and formatted I/O, I/O queued and fully
773	transparent and non-blocking SSL/TLS.	1028	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
774		1029
775	AnyEvent::DNS	1030	AnyEvent::DNS
776	Provides rich asynchronous DNS resolver capabilities.	1031	Provides rich asynchronous DNS resolver capabilities.
777		1032
778	AnyEvent::HTTP	1033	AnyEvent::HTTP
…		…
799		1054
800	AnyEvent::GPSD	1055	AnyEvent::GPSD
801	A non-blocking interface to gpsd, a daemon delivering GPS	1056	A non-blocking interface to gpsd, a daemon delivering GPS
802	information.	1057	information.
803		1058
		1059	AnyEvent::IRC
		1060	AnyEvent based IRC client module family (replacing the older
		1061	Net::IRC3).
		1062
		1063	AnyEvent::XMPP
		1064	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1065	older Net::XMPP2>.
		1066
804	AnyEvent::IGS	1067	AnyEvent::IGS
805	A non-blocking interface to the Internet Go Server protocol (used by	1068	A non-blocking interface to the Internet Go Server protocol (used by
806	App::IGS).	1069	App::IGS).
807		1070
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	1071	Net::FCP
816	AnyEvent-based implementation of the Freenet Client Protocol,	1072	AnyEvent-based implementation of the Freenet Client Protocol,
817	birthplace of AnyEvent.	1073	birthplace of AnyEvent.
818		1074
819	Event::ExecFlow	1075	Event::ExecFlow
820	High level API for event-based execution flow control.	1076	High level API for event-based execution flow control.
821		1077
822	Coro	1078	Coro
823	Has special support for AnyEvent via Coro::AnyEvent.	1079	Has special support for AnyEvent via Coro::AnyEvent.
824		1080
825	IO::Lambda	1081	SIMPLIFIED AE API
826	The lambda approach to I/O - don't ask, look there. Can use	1082	Starting with version 5.0, AnyEvent officially supports a second, much
827	AnyEvent.	1083	simpler, API that is designed to reduce the calling, typing and memory
		1084	overhead by using function call syntax and a fixed number of parameters.
		1085
		1086	See the AE manpage for details.
828		1087
829	ERROR AND EXCEPTION HANDLING	1088	ERROR AND EXCEPTION HANDLING
830	In general, AnyEvent does not do any error handling - it relies on the	1089	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	1090	caller to do that if required. The AnyEvent::Strict module (see also the
832	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1091	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
842	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1101	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
843	Glib uses "install_exception_handler" and so on.	1102	Glib uses "install_exception_handler" and so on.
844		1103
845	ENVIRONMENT VARIABLES	1104	ENVIRONMENT VARIABLES
846	The following environment variables are used by this module or its	1105	The following environment variables are used by this module or its
847	submodules:	1106	submodules.
		1107
		1108	Note that AnyEvent will remove all environment variables starting with
		1109	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1110	enabled.
848		1111
849	"PERL_ANYEVENT_VERBOSE"	1112	"PERL_ANYEVENT_VERBOSE"
850	By default, AnyEvent will be completely silent except in fatal	1113	By default, AnyEvent will be completely silent except in fatal
851	conditions. You can set this environment variable to make AnyEvent	1114	conditions. You can set this environment variable to make AnyEvent
852	more talkative.	1115	more talkative.
…		…
855	conditions, such as not being able to load the event model specified	1118	conditions, such as not being able to load the event model specified
856	by "PERL_ANYEVENT_MODEL".	1119	by "PERL_ANYEVENT_MODEL".
857		1120
858	When set to 2 or higher, cause AnyEvent to report to STDERR which	1121	When set to 2 or higher, cause AnyEvent to report to STDERR which
859	event model it chooses.	1122	event model it chooses.
		1123
		1124	When set to 8 or higher, then AnyEvent will report extra information
		1125	on which optional modules it loads and how it implements certain
		1126	features.
860		1127
861	"PERL_ANYEVENT_STRICT"	1128	"PERL_ANYEVENT_STRICT"
862	AnyEvent does not do much argument checking by default, as thorough	1129	AnyEvent does not do much argument checking by default, as thorough
863	argument checking is very costly. Setting this variable to a true	1130	argument checking is very costly. Setting this variable to a true
864	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1131	value will cause AnyEvent to load "AnyEvent::Strict" and then to
865	thoroughly check the arguments passed to most method calls. If it	1132	thoroughly check the arguments passed to most method calls. If it
866	finds any problems it will croak.	1133	finds any problems, it will croak.
867		1134
868	In other words, enables "strict" mode.	1135	In other words, enables "strict" mode.
869		1136
870	Unlike "use strict", it is definitely recommended ot keep it off in	1137	Unlike "use strict" (or it's modern cousin, "use common::sense", it
871	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1138	is definitely recommended to keep it off in production. Keeping
		1139	"PERL_ANYEVENT_STRICT=1" in your environment while developing
872	while developing programs can be very useful, however.	1140	programs can be very useful, however.
873		1141
874	"PERL_ANYEVENT_MODEL"	1142	"PERL_ANYEVENT_MODEL"
875	This can be used to specify the event model to be used by AnyEvent,	1143	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	1144	before auto detection and -probing kicks in. It must be a string
877	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1145	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
918	EDNS0 in its DNS requests.	1186	EDNS0 in its DNS requests.
919		1187
920	"PERL_ANYEVENT_MAX_FORKS"	1188	"PERL_ANYEVENT_MAX_FORKS"
921	The maximum number of child processes that	1189	The maximum number of child processes that
922	"AnyEvent::Util::fork_call" will create in parallel.	1190	"AnyEvent::Util::fork_call" will create in parallel.
		1191
		1192	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1193	The default value for the "max_outstanding" parameter for the
		1194	default DNS resolver - this is the maximum number of parallel DNS
		1195	requests that are sent to the DNS server.
		1196
		1197	"PERL_ANYEVENT_RESOLV_CONF"
		1198	The file to use instead of /etc/resolv.conf (or OS-specific
		1199	configuration) in the default resolver. When set to the empty
		1200	string, no default config will be used.
		1201
		1202	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1203	When neither "ca_file" nor "ca_path" was specified during
		1204	AnyEvent::TLS context creation, and either of these environment
		1205	variables exist, they will be used to specify CA certificate
		1206	locations instead of a system-dependent default.
		1207
		1208	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1209	When these are set to 1, then the respective modules are not loaded.
		1210	Mostly good for testing AnyEvent itself.
923		1211
924	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1212	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925	This is an advanced topic that you do not normally need to use AnyEvent	1213	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	1214	in a module. This section is only of use to event loop authors who want
927	to provide AnyEvent compatibility.	1215	to provide AnyEvent compatibility.
…		…
982	warn "read: $input\n"; # output what has been read	1270	warn "read: $input\n"; # output what has been read
983	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1271	$cv->send if $input =~ /^q/i; # quit program if /^q/i
984	},	1272	},
985	);	1273	);
986		1274
987	my $time_watcher; # can only be used once
988
989	sub new_timer {
990	$timer = AnyEvent->timer (after => 1, cb => sub {	1275	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
991	warn "timeout\n"; # print 'timeout' about every second	1276	warn "timeout\n"; # print 'timeout' at most every second
992	&new_timer; # and restart the time
993	});
994	}	1277	});
995
996	new_timer; # create first timer
997		1278
998	$cv->recv; # wait until user enters /^q/i	1279	$cv->recv; # wait until user enters /^q/i
999		1280
1000	REAL-WORLD EXAMPLE	1281	REAL-WORLD EXAMPLE
1001	Consider the Net::FCP module. It features (among others) the following	1282	Consider the Net::FCP module. It features (among others) the following
…		…
1073		1354
1074	The actual code goes further and collects all errors ("die"s,	1355	The actual code goes further and collects all errors ("die"s,
1075	exceptions) that occurred during request processing. The "result" method	1356	exceptions) that occurred during request processing. The "result" method
1076	detects whether an exception as thrown (it is stored inside the $txn	1357	detects whether an exception as thrown (it is stored inside the $txn
1077	object) and just throws the exception, which means connection errors and	1358	object) and just throws the exception, which means connection errors and
1078	other problems get reported tot he code that tries to use the result,	1359	other problems get reported to the code that tries to use the result,
1079	not in a random callback.	1360	not in a random callback.
1080		1361
1081	All of this enables the following usage styles:	1362	All of this enables the following usage styles:
1082		1363
1083	1. Blocking:	1364	1. Blocking:
…		…
1128	through AnyEvent. The benchmark creates a lot of timers (with a zero	1409	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,	1410	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.	1411	which it is), lets them fire exactly once and destroys them again.
1131		1412
1132	Source code for this benchmark is found as eg/bench in the AnyEvent	1413	Source code for this benchmark is found as eg/bench in the AnyEvent
1133	distribution.	1414	distribution. It uses the AE interface, which makes a real difference
		1415	for the EV and Perl backends only.
1134		1416
1135	Explanation of the columns	1417	Explanation of the columns
1136	watcher is the number of event watchers created/destroyed. Since	1418	watcher is the number of event watchers created/destroyed. Since
1137	different event models feature vastly different performances, each event	1419	different event models feature vastly different performances, each event
1138	loop was given a number of watchers so that overall runtime is	1420	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	1439	destroy is the time, in microseconds, that it takes to destroy a
1158	single watcher.	1440	single watcher.
1159		1441
1160	Results	1442	Results
1161	name watchers bytes create invoke destroy comment	1443	name watchers bytes create invoke destroy comment
1162	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1444	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	1445	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	1446	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	1447	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	1448	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	1449	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1450	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1451	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	1452	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	1453	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	1454	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	1455	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1172		1456
1173	Discussion	1457	Discussion
1174	The benchmark does not measure scalability of the event loop very	1458	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)	1459	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	1460	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	1471	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	1472	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1189	CPU cycles with POE.	1473	CPU cycles with POE.
1190		1474
1191	"EV" is the sole leader regarding speed and memory use, which are both	1475	"EV" is the sole leader regarding speed and memory use, which are both
1192	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1476	maximal/minimal, respectively. When using the AE API there is zero
		1477	overhead (when going through the AnyEvent API create is about 5-6 times
		1478	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	1479	any other event loop and is still faster than Event natively).
1194	natively.
1195		1480
1196	The pure perl implementation is hit in a few sweet spots (both the	1481	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	1482	constant timeout and the use of a single fd hit optimisations in the
1198	perl interpreter and the backend itself). Nevertheless this shows that	1483	perl interpreter and the backend itself). Nevertheless this shows that
1199	it adds very little overhead in itself. Like any select-based backend	1484	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	1486	few of them active), of course, but this was not subject of this
1202	benchmark.	1487	benchmark.
1203		1488
1204	The "Event" module has a relatively high setup and callback invocation	1489	The "Event" module has a relatively high setup and callback invocation
1205	cost, but overall scores in on the third place.	1490	cost, but overall scores in on the third place.
		1491
		1492	"IO::Async" performs admirably well, about on par with "Event", even
		1493	when using its pure perl backend.
1206		1494
1207	"Glib"'s memory usage is quite a bit higher, but it features a faster	1495	"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".	1496	callback invocation and overall ends up in the same class as "Event".
1209	However, Glib scales extremely badly, doubling the number of watchers	1497	However, Glib scales extremely badly, doubling the number of watchers
1210	increases the processing time by more than a factor of four, making it	1498	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	1554	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	1555	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.	1556	many connections, most of which are idle at any one point in time.
1269		1557
1270	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1558	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1271	distribution.	1559	distribution. It uses the AE interface, which makes a real difference
		1560	for the EV and Perl backends only.
1272		1561
1273	Explanation of the columns	1562	Explanation of the columns
1274	sockets is the number of sockets, and twice the number of "servers"	1563	sockets is the number of sockets, and twice the number of "servers"
1275	(as each server has a read and write socket end).	1564	(as each server has a read and write socket end).
1276		1565
…		…
1281	single "request", that is, reading the token from the pipe and	1570	single "request", that is, reading the token from the pipe and
1282	forwarding it to another server. This includes deleting the old timeout	1571	forwarding it to another server. This includes deleting the old timeout
1283	and creating a new one that moves the timeout into the future.	1572	and creating a new one that moves the timeout into the future.
1284		1573
1285	Results	1574	Results
1286	name sockets create request	1575	name sockets create request
1287	EV 20000 69.01 11.16	1576	EV 20000 62.66 7.99
1288	Perl 20000 73.32 35.87	1577	Perl 20000 68.32 32.64
1289	Event 20000 212.62 257.32	1578	IOAsync 20000 174.06 101.15 epoll
1290	Glib 20000 651.16 1896.30	1579	IOAsync 20000 174.67 610.84 poll
		1580	Event 20000 202.69 242.91
		1581	Glib 20000 557.01 1689.52
1291	POE 20000 349.67 12317.24 uses POE::Loop::Event	1582	POE 20000 341.54 12086.32 uses POE::Loop::Event
1292		1583
1293	Discussion	1584	Discussion
1294	This benchmark does measure scalability and overall performance of the	1585	This benchmark does measure scalability and overall performance of the
1295	particular event loop.	1586	particular event loop.
1296		1587
1297	EV is again fastest. Since it is using epoll on my system, the setup	1588	EV is again fastest. Since it is using epoll on my system, the setup
1298	time is relatively high, though.	1589	time is relatively high, though.
1299		1590
1300	Perl surprisingly comes second. It is much faster than the C-based event	1591	Perl surprisingly comes second. It is much faster than the C-based event
1301	loops Event and Glib.	1592	loops Event and Glib.
		1593
		1594	IO::Async performs very well when using its epoll backend, and still
		1595	quite good compared to Glib when using its pure perl backend.
1302		1596
1303	Event suffers from high setup time as well (look at its code and you	1597	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	1598	will understand why). Callback invocation also has a high overhead
1305	compared to the "$_->() for .."-style loop that the Perl event loop	1599	compared to the "$_->() for .."-style loop that the Perl event loop
1306	uses. Event uses select or poll in basically all documented	1600	uses. Event uses select or poll in basically all documented
…		…
1357		1651
1358	Summary	1652	Summary
1359	* C-based event loops perform very well with small number of watchers,	1653	* C-based event loops perform very well with small number of watchers,
1360	as the management overhead dominates.	1654	as the management overhead dominates.
1361		1655
		1656	THE IO::Lambda BENCHMARK
		1657	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1658	could be misinterpreted to make AnyEvent look bad. In fact, the
		1659	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1660	better (which shouldn't come as a surprise to anybody). As such, the
		1661	benchmark is fine, and mostly shows that the AnyEvent backend from
		1662	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1663	without the extra baggage? To explore this, I wrote the equivalent
		1664	benchmark for AnyEvent.
		1665
		1666	The benchmark itself creates an echo-server, and then, for 500 times,
		1667	connects to the echo server, sends a line, waits for the reply, and then
		1668	creates the next connection. This is a rather bad benchmark, as it
		1669	doesn't test the efficiency of the framework or much non-blocking I/O,
		1670	but it is a benchmark nevertheless.
		1671
		1672	name runtime
		1673	Lambda/select 0.330 sec
		1674	+ optimized 0.122 sec
		1675	Lambda/AnyEvent 0.327 sec
		1676	+ optimized 0.138 sec
		1677	Raw sockets/select 0.077 sec
		1678	POE/select, components 0.662 sec
		1679	POE/select, raw sockets 0.226 sec
		1680	POE/select, optimized 0.404 sec
		1681
		1682	AnyEvent/select/nb 0.085 sec
		1683	AnyEvent/EV/nb 0.068 sec
		1684	+state machine 0.134 sec
		1685
		1686	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1687	benchmarks actually make blocking connects and use 100% blocking I/O,
		1688	defeating the purpose of an event-based solution. All of the newly
		1689	written AnyEvent benchmarks use 100% non-blocking connects (using
		1690	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1691	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1692	connects generally require a lot more bookkeeping and event handling
		1693	than blocking connects (which involve a single syscall only).
		1694
		1695	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1696	offers similar expressive power as POE and IO::Lambda, using
		1697	conventional Perl syntax. This means that both the echo server and the
		1698	client are 100% non-blocking, further placing it at a disadvantage.
		1699
		1700	As you can see, the AnyEvent + EV combination even beats the
		1701	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1702	backend easily beats IO::Lambda and POE.
		1703
		1704	And even the 100% non-blocking version written using the high-level (and
		1705	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1706	higher level ("unoptimised") abstractions by a large margin, even though
		1707	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1708
		1709	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1710	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1711	part of the IO::Lambda distribution and were used without any changes.
		1712
1362	SIGNALS	1713	SIGNALS
1363	AnyEvent currently installs handlers for these signals:	1714	AnyEvent currently installs handlers for these signals:
1364		1715
1365	SIGCHLD	1716	SIGCHLD
1366	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1717	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367	emulation for event loops that do not support them natively. Also,	1718	emulation for event loops that do not support them natively. Also,
1368	some event loops install a similar handler.	1719	some event loops install a similar handler.
		1720
		1721	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1722	then AnyEvent will reset it to default, to avoid losing child exit
		1723	statuses.
1369		1724
1370	SIGPIPE	1725	SIGPIPE
1371	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1726	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1372	"undef" when AnyEvent gets loaded.	1727	"undef" when AnyEvent gets loaded.
1373		1728
…		…
1381	it is that this way, the handler will be restored to defaults on	1736	it is that this way, the handler will be restored to defaults on
1382	exec.	1737	exec.
1383		1738
1384	Feel free to install your own handler, or reset it to defaults.	1739	Feel free to install your own handler, or reset it to defaults.
1385		1740
		1741	RECOMMENDED/OPTIONAL MODULES
		1742	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1743	it's built-in modules) are required to use it.
		1744
		1745	That does not mean that AnyEvent won't take advantage of some additional
		1746	modules if they are installed.
		1747
		1748	This section explains which additional modules will be used, and how
		1749	they affect AnyEvent's operation.
		1750
		1751	Async::Interrupt
		1752	This slightly arcane module is used to implement fast signal
		1753	handling: To my knowledge, there is no way to do completely
		1754	race-free and quick signal handling in pure perl. To ensure that
		1755	signals still get delivered, AnyEvent will start an interval timer
		1756	to wake up perl (and catch the signals) with some delay (default is
		1757	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1758
		1759	If this module is available, then it will be used to implement
		1760	signal catching, which means that signals will not be delayed, and
		1761	the event loop will not be interrupted regularly, which is more
		1762	efficient (and good for battery life on laptops).
		1763
		1764	This affects not just the pure-perl event loop, but also other event
		1765	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1766
		1767	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1768	natively, and either employ their own workarounds (POE) or use
		1769	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1770	Installing Async::Interrupt does nothing for those backends.
		1771
		1772	EV This module isn't really "optional", as it is simply one of the
		1773	backend event loops that AnyEvent can use. However, it is simply the
		1774	best event loop available in terms of features, speed and stability:
		1775	It supports the AnyEvent API optimally, implements all the watcher
		1776	types in XS, does automatic timer adjustments even when no monotonic
		1777	clock is available, can take avdantage of advanced kernel interfaces
		1778	such as "epoll" and "kqueue", and is the fastest backend by far.
		1779	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1780	Glib::EV).
		1781
		1782	If you only use backends that rely on another event loop (e.g.
		1783	"Tk"), then this module will do nothing for you.
		1784
		1785	Guard
		1786	The guard module, when used, will be used to implement
		1787	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1788	uses a lot less memory), but otherwise doesn't affect guard
		1789	operation much. It is purely used for performance.
		1790
		1791	JSON and JSON::XS
		1792	One of these modules is required when you want to read or write JSON
		1793	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1794	can take advantage of the ultra-high-speed JSON::XS module when it
		1795	is installed.
		1796
		1797	Net::SSLeay
		1798	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1799	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1800	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1801
		1802	Time::HiRes
		1803	This module is part of perl since release 5.008. It will be used
		1804	when the chosen event library does not come with a timing source on
		1805	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1806	additionally use it to try to use a monotonic clock for timing
		1807	stability.
		1808
1386	FORK	1809	FORK
1387	Most event libraries are not fork-safe. The ones who are usually are	1810	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.	1811	because they rely on inefficient but fork-safe "select" or "poll" calls
1389	Only EV is fully fork-aware.	1812	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1813	epoll are usually badly thought-out hacks that are incompatible with
		1814	fork in one way or another. Only EV is fully fork-aware and ensures that
		1815	you continue event-processing in both parent and child (or both, if you
		1816	know what you are doing).
		1817
		1818	This means that, in general, you cannot fork and do event processing in
		1819	the child if the event library was initialised before the fork (which
		1820	usually happens when the first AnyEvent watcher is created, or the
		1821	library is loaded).
1390		1822
1391	If you have to fork, you must either do so before creating your first	1823	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.	1824	watcher OR you must not use AnyEvent at all in the child OR you must do
		1825	something completely out of the scope of AnyEvent.
		1826
		1827	The problem of doing event processing in the parent and the child is
		1828	much more complicated: even for backends that are fork-aware or
		1829	fork-safe, their behaviour is not usually what you want: fork clones all
		1830	watchers, that means all timers, I/O watchers etc. are active in both
		1831	parent and child, which is almost never what you want. USing "exec" to
		1832	start worker children from some kind of manage rprocess is usually
		1833	preferred, because it is much easier and cleaner, at the expense of
		1834	having to have another binary.
1393		1835
1394	SECURITY CONSIDERATIONS	1836	SECURITY CONSIDERATIONS
1395	AnyEvent can be forced to load any event model via	1837	AnyEvent can be forced to load any event model via
1396	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1838	$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	1839	to execute arbitrary code or directly gain access, it can easily be used
…		…
1407	use AnyEvent;	1849	use AnyEvent;
1408		1850
1409	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1851	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	1852	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),	1853	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1412	and $ENV{PERL_ANYEGENT_STRICT}.	1854	and $ENV{PERL_ANYEVENT_STRICT}.
		1855
		1856	Note that AnyEvent will remove all environment variables starting with
		1857	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1858	enabled.
1413		1859
1414	BUGS	1860	BUGS
1415	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1861	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	1862	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	1863	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,	1870	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1425	Event::Lib, Qt, POE.	1871	Event::Lib, Qt, POE.
1426		1872
1427	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1873	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1428	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1874	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1429	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1875	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1876	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1430		1877
1431	Non-blocking file handles, sockets, TCP clients and servers:	1878	Non-blocking file handles, sockets, TCP clients and servers:
1432	AnyEvent::Handle, AnyEvent::Socket.	1879	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1433		1880
1434	Asynchronous DNS: AnyEvent::DNS.	1881	Asynchronous DNS: AnyEvent::DNS.
1435		1882
1436	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1883	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1437		1884
1438	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1885	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1886	AnyEvent::HTTP.
1439		1887
1440	AUTHOR	1888	AUTHOR
1441	Marc Lehmann <schmorp@schmorp.de>	1889	Marc Lehmann <schmorp@schmorp.de>
1442	http://home.schmorp.de/	1890	http://home.schmorp.de/
1443		1891

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Comparing AnyEvent/README (file contents): Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs. Revision 1.61 by root, Wed Apr 28 14:15:55 2010 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.61 by root, Wed Apr 28 14:15:55 2010 UTC