[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.46 by root, Sat Jul 18 05:19:09 2009 UTC vs.
Revision 1.60 by root, Mon Apr 12 02:50:31 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 and POE are various supported	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	event 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
10	# file descriptor readable	13	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });	14	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
12		15
13	# one-shot or repeating timers	16	# one-shot or repeating timers
14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	17	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	18	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
37		40
38	INTRODUCTION/TUTORIAL	41	INTRODUCTION/TUTORIAL
39	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
40	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
41	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.
42		52
43	WHY YOU SHOULD USE THIS MODULE (OR NOT)	53	WHY YOU SHOULD USE THIS MODULE (OR NOT)
44	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
45	nowadays. So what is different about AnyEvent?	55	nowadays. So what is different about AnyEvent?
46		56
…		…
166	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,
167	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
168	declared.	178	declared.
169		179
170	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
171	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
172	the following mandatory key-value pairs as arguments:	188	the following mandatory key-value pairs as arguments:
173		189
174	"fh" is the Perl file handle (or a naked file descriptor) to watch for	190	"fh" is the Perl file handle (or a naked file descriptor) to watch for
175	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
…		…
203	warn "read: $input\n";	219	warn "read: $input\n";
204	undef $w;	220	undef $w;
205	});	221	});
206		222
207	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
208	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
209	with the following mandatory arguments:	233	with the following mandatory arguments:
210		234
211	"after" specifies after how many seconds (fractional values are	235	"after" specifies after how many seconds (fractional values are
212	supported) the callback should be invoked. "cb" is the callback to	236	supported) the callback should be invoked. "cb" is the callback to
…		…
333	time, which might affect timers and time-outs.	357	time, which might affect timers and time-outs.
334		358
335	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
336	the event loop's idea of "current time".	360	the event loop's idea of "current time".
337		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
338	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.
339		371
340	SIGNAL WATCHERS	372	SIGNAL WATCHERS
		373	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		374
341	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
342	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
343	callback to be invoked whenever a signal occurs.	377	callback to be invoked whenever a signal occurs.
344		378
345	Although the callback might get passed parameters, their value and	379	Although the callback might get passed parameters, their value and
…		…
357		391
358	This watcher might use %SIG (depending on the event loop used), so	392	This watcher might use %SIG (depending on the event loop used), so
359	programs overwriting those signals directly will likely not work	393	programs overwriting those signals directly will likely not work
360	correctly.	394	correctly.
361		395
		396	Example: exit on SIGINT
		397
		398	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		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
362	Also note that many event loops (e.g. Glib, Tk, Qt, IO::Async) do not	416	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
363	support attaching callbacks to signals, which is a pity, as you cannot	417	callbacks to signals in a generic way, which is a pity, as you cannot do
364	do race-free signal handling in perl. AnyEvent will try to do it's best,	418	race-free signal handling in perl, requiring C libraries for this.
365	but in some cases, signals will be delayed. The maximum time a signal	419	AnyEvent will try to do it's best, which means in some cases, signals
366	might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default:	420	will be delayed. The maximum time a signal might be delayed is specified
367	10 seconds). This variable can be changed only before the first signal	421	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
368	watcher is created, and should be left alone otherwise. Higher values	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
369	will cause fewer spurious wake-ups, which is better for power and CPU	425	will cause fewer spurious wake-ups, which is better for power and CPU
		426	saving.
		427
370	saving. All these problems can be avoided by installing the optional	428	All these problems can be avoided by installing the optional
371	Async::Interrupt module.	429	Async::Interrupt module, which works with most event loops. It will not
372		430	work with inherently broken event loops such as Event or Event::Lib (and
373	Example: exit on SIGINT	431	not with POE currently, as POE does it's own workaround with one-second
374		432	latency). For those, you just have to suffer the delays.
375	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
376		433
377	CHILD PROCESS WATCHERS	434	CHILD PROCESS WATCHERS
		435	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		436
378	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.
379		438
380	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,
381	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).
382	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
383	on any trace events (stopped/continued).	442	and an exit status is available, not on any trace events
		443	(stopped/continued).
384		444
385	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
386	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
387	callback arguments.	447	callback arguments.
388		448
…		…
427		487
428	# do something else, then wait for process exit	488	# do something else, then wait for process exit
429	$done->recv;	489	$done->recv;
430		490
431	IDLE WATCHERS	491	IDLE WATCHERS
432	Sometimes there is a need to do something, but it is not so important to	492	$w = AnyEvent->idle (cb => <callback>);
433	do it instantly, but only when there is nothing better to do. This
434	"nothing better to do" is usually defined to be "no other events need
435	attention by the event loop".
436		493
437	Idle watchers ideally get invoked when the event loop has nothing better	494	Repeatedly invoke the callback after the process becomes idle, until
438	to do, just before it would block the process to wait for new events.	495	either the watcher is destroyed or new events have been detected.
439	Instead of blocking, the idle watcher is invoked.
440		496
441	Most event loops unfortunately do not really support idle watchers (only	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
442	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent	507	(only EV, Event and Glib do it in a usable fashion) - for the rest,
443	will simply call the callback "from time to time".	508	AnyEvent will simply call the callback "from time to time".
444		509
445	Example: read lines from STDIN, but only process them when the program	510	Example: read lines from STDIN, but only process them when the program
446	is otherwise idle:	511	is otherwise idle:
447		512
448	my @lines; # read data	513	my @lines; # read data
…		…
461	}	526	}
462	});	527	});
463	});	528	});
464		529
465	CONDITION VARIABLES	530	CONDITION VARIABLES
		531	$cv = AnyEvent->condvar;
		532
		533	$cv->send (<list>);
		534	my @res = $cv->recv;
		535
466	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
467	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
468	will actively watch for new events and call your callbacks.	538	will actively watch for new events and call your callbacks.
469		539
470	AnyEvent is slightly different: it expects somebody else to run the	540	AnyEvent is slightly different: it expects somebody else to run the
…		…
490	Condition variables are similar to callbacks, except that you can	560	Condition variables are similar to callbacks, except that you can
491	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
492	in time where multiple outstanding events have been processed. And yet	562	in time where multiple outstanding events have been processed. And yet
493	another way to call them is transactions - each condition variable can	563	another way to call them is transactions - each condition variable can
494	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
495	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.
496		567
497	Condition variables are very useful to signal that something has	568	Condition variables are very useful to signal that something has
498	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
499	requests, then a condition variable would be the ideal candidate to	570	requests, then a condition variable would be the ideal candidate to
500	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
…		…
521	which eventually calls "-> send", and the "consumer side", which waits	592	which eventually calls "-> send", and the "consumer side", which waits
522	for the send to occur.	593	for the send to occur.
523		594
524	Example: wait for a timer.	595	Example: wait for a timer.
525		596
526	# wait till the result is ready	597	# condition: "wait till the timer is fired"
527	my $result_ready = AnyEvent->condvar;	598	my $timer_fired = AnyEvent->condvar;
528		599
529	# do something such as adding a timer	600	# create the timer - we could wait for, say
530	# or socket watcher the calls $result_ready->send	601	# a handle becomign ready, or even an
531	# when the "result" is ready.	602	# AnyEvent::HTTP request to finish, but
532	# in this case, we simply use a timer:	603	# in this case, we simply use a timer:
533	my $w = AnyEvent->timer (	604	my $w = AnyEvent->timer (
534	after => 1,	605	after => 1,
535	cb => sub { $result_ready->send },	606	cb => sub { $timer_fired->send },
536	);	607	);
537		608
538	# this "blocks" (while handling events) till the callback	609	# this "blocks" (while handling events) till the callback
539	# calls -<send	610	# calls ->send
540	$result_ready->recv;	611	$timer_fired->recv;
541		612
542	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
543	variables are also callable directly.	614	variables are also callable directly.
544		615
545	my $done = AnyEvent->condvar;	616	my $done = AnyEvent->condvar;
…		…
601	into one. For example, a function that pings many hosts in parallel	672	into one. For example, a function that pings many hosts in parallel
602	might want to use a condition variable for the whole process.	673	might want to use a condition variable for the whole process.
603		674
604	Every call to "->begin" will increment a counter, and every call to	675	Every call to "->begin" will increment a counter, and every call to
605	"->end" will decrement it. If the counter reaches 0 in "->end", the	676	"->end" will decrement it. If the counter reaches 0 in "->end", the
606	(last) callback passed to "begin" will be executed. That callback is	677	(last) callback passed to "begin" will be executed, passing the
607	supposed to call "->send", but that is not required. If no	678	condvar as first argument. That callback is supposed to call
		679	"->send", but that is not required. If no group callback was set,
608	callback was set, "send" will be called without any arguments.	680	"send" will be called without any arguments.
609		681
610	You can think of "$cv->send" giving you an OR condition (one call	682	You can think of "$cv->send" giving you an OR condition (one call
611	sends), while "$cv->begin" and "$cv->end" giving you an AND	683	sends), while "$cv->begin" and "$cv->end" giving you an AND
612	condition (all "begin" calls must be "end"'ed before the condvar	684	condition (all "begin" calls must be "end"'ed before the condvar
613	sends).	685	sends).
…		…
641	that are begung can potentially be zero:	713	that are begung can potentially be zero:
642		714
643	my $cv = AnyEvent->condvar;	715	my $cv = AnyEvent->condvar;
644		716
645	my %result;	717	my %result;
646	$cv->begin (sub { $cv->send (\%result) });	718	$cv->begin (sub { shift->send (\%result) });
647		719
648	for my $host (@list_of_hosts) {	720	for my $host (@list_of_hosts) {
649	$cv->begin;	721	$cv->begin;
650	ping_host_then_call_callback $host, sub {	722	ping_host_then_call_callback $host, sub {
651	$result{$host} = ...;	723	$result{$host} = ...;
…		…
718		790
719	$cb = $cv->cb ($cb->($cv))	791	$cb = $cv->cb ($cb->($cv))
720	This is a mutator function that returns the callback set and	792	This is a mutator function that returns the callback set and
721	optionally replaces it before doing so.	793	optionally replaces it before doing so.
722		794
723	The callback will be called when the condition becomes "true", i.e.	795	The callback will be called when the condition becomes (or already
724	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
725	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
726	any later time is guaranteed not to block.	799	guaranteed not to block.
727		800
728	SUPPORTED EVENT LOOPS/BACKENDS	801	SUPPORTED EVENT LOOPS/BACKENDS
729	The available backend classes are (every class has its own manpage):	802	The available backend classes are (every class has its own manpage):
730		803
731	Backends that are autoprobed when no other event loop can be found.	804	Backends that are autoprobed when no other event loop can be found.
732	EV is the preferred backend when no other event loop seems to be in	805	EV is the preferred backend when no other event loop seems to be in
733	use. If EV is not installed, then AnyEvent will try Event, and,	806	use. If EV is not installed, then AnyEvent will fall back to its own
734	failing that, will fall back to its own pure-perl implementation,	807	pure-perl implementation, which is available everywhere as it comes
735	which is available everywhere as it comes with AnyEvent itself.	808	with AnyEvent itself.
736		809
737	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	810	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
738	AnyEvent::Impl::Event based on Event, very stable, few glitches.
739	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	811	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
740		812
741	Backends that are transparently being picked up when they are used.	813	Backends that are transparently being picked up when they are used.
742	These will be used when they are currently loaded when the first	814	These will be used when they are currently loaded when the first
743	watcher is created, in which case it is assumed that the application	815	watcher is created, in which case it is assumed that the application
744	is using them. This means that AnyEvent will automatically pick the	816	is using them. This means that AnyEvent will automatically pick the
745	right backend when the main program loads an event module before	817	right backend when the main program loads an event module before
746	anything starts to create watchers. Nothing special needs to be done	818	anything starts to create watchers. Nothing special needs to be done
747	by the main program.	819	by the main program.
748		820
		821	AnyEvent::Impl::Event based on Event, very stable, few glitches.
749	AnyEvent::Impl::Glib based on Glib, slow but very stable.	822	AnyEvent::Impl::Glib based on Glib, slow but very stable.
750	AnyEvent::Impl::Tk based on Tk, very broken.	823	AnyEvent::Impl::Tk based on Tk, very broken.
751	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	824	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
752	AnyEvent::Impl::POE based on POE, very slow, some limitations.	825	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		826	AnyEvent::Impl::Irssi used when running within irssi.
753		827
754	Backends with special needs.	828	Backends with special needs.
755	Qt requires the Qt::Application to be instantiated first, but will	829	Qt requires the Qt::Application to be instantiated first, but will
756	otherwise be picked up automatically. As long as the main program	830	otherwise be picked up automatically. As long as the main program
757	instantiates the application before any AnyEvent watchers are	831	instantiates the application before any AnyEvent watchers are
…		…
822	creates and installs the global IO::AIO watcher in a "post_detect"	896	creates and installs the global IO::AIO watcher in a "post_detect"
823	block to avoid autodetecting the event module at load time.	897	block to avoid autodetecting the event module at load time.
824		898
825	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
826	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
827	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;
828		919
829	@AnyEvent::post_detect	920	@AnyEvent::post_detect
830	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
831	before or after loading AnyEvent), then they will called directly	922	before or after loading AnyEvent), then they will called directly
832	after the event loop has been chosen.	923	after the event loop has been chosen.
…		…
834	You should check $AnyEvent::MODEL before adding to this array,	925	You should check $AnyEvent::MODEL before adding to this array,
835	though: if it is defined then the event loop has already been	926	though: if it is defined then the event loop has already been
836	detected, and the array will be ignored.	927	detected, and the array will be ignored.
837		928
838	Best use "AnyEvent::post_detect { BLOCK }" when your application	929	Best use "AnyEvent::post_detect { BLOCK }" when your application
839	allows it,as it takes care of these details.	930	allows it, as it takes care of these details.
840		931
841	This variable is mainly useful for modules that can do something	932	This variable is mainly useful for modules that can do something
842	useful when AnyEvent is used and thus want to know when it is	933	useful when AnyEvent is used and thus want to know when it is
843	initialised, but do not need to even load it by default. This array	934	initialised, but do not need to even load it by default. This array
844	provides the means to hook into AnyEvent passively, without loading	935	provides the means to hook into AnyEvent passively, without loading
845	it.	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	}
846		950
847	WHAT TO DO IN A MODULE	951	WHAT TO DO IN A MODULE
848	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
849	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.
850		954
…		…
971	Event::ExecFlow	1075	Event::ExecFlow
972	High level API for event-based execution flow control.	1076	High level API for event-based execution flow control.
973		1077
974	Coro	1078	Coro
975	Has special support for AnyEvent via Coro::AnyEvent.	1079	Has special support for AnyEvent via Coro::AnyEvent.
		1080
		1081	SIMPLIFIED AE API
		1082	Starting with version 5.0, AnyEvent officially supports a second, much
		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.
976		1087
977	ERROR AND EXCEPTION HANDLING	1088	ERROR AND EXCEPTION HANDLING
978	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
979	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
980	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1091	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
1159	warn "read: $input\n"; # output what has been read	1270	warn "read: $input\n"; # output what has been read
1160	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1271	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1161	},	1272	},
1162	);	1273	);
1163		1274
1164	my $time_watcher; # can only be used once
1165
1166	sub new_timer {
1167	$timer = AnyEvent->timer (after => 1, cb => sub {	1275	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1168	warn "timeout\n"; # print 'timeout' about every second	1276	warn "timeout\n"; # print 'timeout' at most every second
1169	&new_timer; # and restart the time
1170	});
1171	}	1277	});
1172
1173	new_timer; # create first timer
1174		1278
1175	$cv->recv; # wait until user enters /^q/i	1279	$cv->recv; # wait until user enters /^q/i
1176		1280
1177	REAL-WORLD EXAMPLE	1281	REAL-WORLD EXAMPLE
1178	Consider the Net::FCP module. It features (among others) the following	1282	Consider the Net::FCP module. It features (among others) the following
…		…
1250		1354
1251	The actual code goes further and collects all errors ("die"s,	1355	The actual code goes further and collects all errors ("die"s,
1252	exceptions) that occurred during request processing. The "result" method	1356	exceptions) that occurred during request processing. The "result" method
1253	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
1254	object) and just throws the exception, which means connection errors and	1358	object) and just throws the exception, which means connection errors and
1255	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,
1256	not in a random callback.	1360	not in a random callback.
1257		1361
1258	All of this enables the following usage styles:	1362	All of this enables the following usage styles:
1259		1363
1260	1. Blocking:	1364	1. Blocking:
…		…
1305	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
1306	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,
1307	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.
1308		1412
1309	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
1310	distribution.	1414	distribution. It uses the AE interface, which makes a real difference
		1415	for the EV and Perl backends only.
1311		1416
1312	Explanation of the columns	1417	Explanation of the columns
1313	watcher is the number of event watchers created/destroyed. Since	1418	watcher is the number of event watchers created/destroyed. Since
1314	different event models feature vastly different performances, each event	1419	different event models feature vastly different performances, each event
1315	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
…		…
1334	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
1335	single watcher.	1440	single watcher.
1336		1441
1337	Results	1442	Results
1338	name watchers bytes create invoke destroy comment	1443	name watchers bytes create invoke destroy comment
1339	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
1340	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
1341	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
1342	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
1343	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
1344	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
1345	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1450	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1346	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1451	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1347	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
1348	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
1349	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
1350	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
1351		1456
1352	Discussion	1457	Discussion
1353	The benchmark does not measure scalability of the event loop very	1458	The benchmark does not measure scalability of the event loop very
1354	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)
1355	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
…		…
1366	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1471	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1367	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
1368	CPU cycles with POE.	1473	CPU cycles with POE.
1369		1474
1370	"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
1371	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
1372	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).
1373	natively.
1374		1480
1375	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
1376	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
1377	perl interpreter and the backend itself). Nevertheless this shows that	1483	perl interpreter and the backend itself). Nevertheless this shows that
1378	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
…		…
1448	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
1449	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
1450	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.
1451		1557
1452	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
1453	distribution.	1559	distribution. It uses the AE interface, which makes a real difference
		1560	for the EV and Perl backends only.
1454		1561
1455	Explanation of the columns	1562	Explanation of the columns
1456	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"
1457	(as each server has a read and write socket end).	1564	(as each server has a read and write socket end).
1458		1565
…		…
1464	forwarding it to another server. This includes deleting the old timeout	1571	forwarding it to another server. This includes deleting the old timeout
1465	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.
1466		1573
1467	Results	1574	Results
1468	name sockets create request	1575	name sockets create request
1469	EV 20000 69.01 11.16	1576	EV 20000 62.66 7.99
1470	Perl 20000 73.32 35.87	1577	Perl 20000 68.32 32.64
1471	IOAsync 20000 157.00 98.14 epoll	1578	IOAsync 20000 174.06 101.15 epoll
1472	IOAsync 20000 159.31 616.06 poll	1579	IOAsync 20000 174.67 610.84 poll
1473	Event 20000 212.62 257.32	1580	Event 20000 202.69 242.91
1474	Glib 20000 651.16 1896.30	1581	Glib 20000 557.01 1689.52
1475	POE 20000 349.67 12317.24 uses POE::Loop::Event	1582	POE 20000 341.54 12086.32 uses POE::Loop::Event
1476		1583
1477	Discussion	1584	Discussion
1478	This benchmark does measure scalability and overall performance of the	1585	This benchmark does measure scalability and overall performance of the
1479	particular event loop.	1586	particular event loop.
1480		1587
…		…
1593	As you can see, the AnyEvent + EV combination even beats the	1700	As you can see, the AnyEvent + EV combination even beats the
1594	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1701	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1595	backend easily beats IO::Lambda and POE.	1702	backend easily beats IO::Lambda and POE.
1596		1703
1597	And even the 100% non-blocking version written using the high-level (and	1704	And even the 100% non-blocking version written using the high-level (and
1598	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1705	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1599	large margin, even though it does all of DNS, tcp-connect and socket I/O	1706	higher level ("unoptimised") abstractions by a large margin, even though
1600	in a non-blocking way.	1707	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1601		1708
1602	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1709	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1603	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1710	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1604	part of the IO::lambda distribution and were used without any changes.	1711	part of the IO::Lambda distribution and were used without any changes.
1605		1712
1606	SIGNALS	1713	SIGNALS
1607	AnyEvent currently installs handlers for these signals:	1714	AnyEvent currently installs handlers for these signals:
1608		1715
1609	SIGCHLD	1716	SIGCHLD
…		…
1636	it's built-in modules) are required to use it.	1743	it's built-in modules) are required to use it.
1637		1744
1638	That does not mean that AnyEvent won't take advantage of some additional	1745	That does not mean that AnyEvent won't take advantage of some additional
1639	modules if they are installed.	1746	modules if they are installed.
1640		1747
1641	This section epxlains which additional modules will be used, and how	1748	This section explains which additional modules will be used, and how
1642	they affect AnyEvent's operetion.	1749	they affect AnyEvent's operation.
1643		1750
1644	Async::Interrupt	1751	Async::Interrupt
1645	This slightly arcane module is used to implement fast signal	1752	This slightly arcane module is used to implement fast signal
1646	handling: To my knowledge, there is no way to do completely	1753	handling: To my knowledge, there is no way to do completely
1647	race-free and quick signal handling in pure perl. To ensure that	1754	race-free and quick signal handling in pure perl. To ensure that
1648	signals still get delivered, AnyEvent will start an interval timer	1755	signals still get delivered, AnyEvent will start an interval timer
1649	to wake up perl (and catch the signals) with soemd elay (default is	1756	to wake up perl (and catch the signals) with some delay (default is
1650	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).	1757	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1651		1758
1652	If this module is available, then it will be used to implement	1759	If this module is available, then it will be used to implement
1653	signal catching, which means that signals will not be delayed, and	1760	signal catching, which means that signals will not be delayed, and
1654	the event loop will not be interrupted regularly, which is more	1761	the event loop will not be interrupted regularly, which is more
1655	efficient (And good for battery life on laptops).	1762	efficient (and good for battery life on laptops).
1656		1763
1657	This affects not just the pure-perl event loop, but also other event	1764	This affects not just the pure-perl event loop, but also other event
1658	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).	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.
1659		1771
1660	EV This module isn't really "optional", as it is simply one of the	1772	EV This module isn't really "optional", as it is simply one of the
1661	backend event loops that AnyEvent can use. However, it is simply the	1773	backend event loops that AnyEvent can use. However, it is simply the
1662	best event loop available in terms of features, speed and stability:	1774	best event loop available in terms of features, speed and stability:
1663	It supports the AnyEvent API optimally, implements all the watcher	1775	It supports the AnyEvent API optimally, implements all the watcher
…		…
1665	clock is available, can take avdantage of advanced kernel interfaces	1777	clock is available, can take avdantage of advanced kernel interfaces
1666	such as "epoll" and "kqueue", and is the fastest backend by far.	1778	such as "epoll" and "kqueue", and is the fastest backend by far.
1667	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and	1779	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1668	Glib::EV).	1780	Glib::EV).
1669		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
1670	Guard	1785	Guard
1671	The guard module, when used, will be used to implement	1786	The guard module, when used, will be used to implement
1672	"AnyEvent::Util::guard". This speeds up guards considerably (and	1787	"AnyEvent::Util::guard". This speeds up guards considerably (and
1673	uses a lot less memory), but otherwise doesn't affect guard	1788	uses a lot less memory), but otherwise doesn't affect guard
1674	operation much. It is purely used for performance.	1789	operation much. It is purely used for performance.
1675		1790
1676	JSON and JSON::XS	1791	JSON and JSON::XS
1677	This module is required when you want to read or write JSON data via	1792	One of these modules is required when you want to read or write JSON
1678	AnyEvent::Handle. It is also written in pure-perl, but can take	1793	data via AnyEvent::Handle. JSON is also written in pure-perl, but
1679	advantage of the ulta-high-speed JSON::XS module when it is	1794	can take advantage of the ultra-high-speed JSON::XS module when it
1680	installed.	1795	is installed.
1681
1682	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1683	installed.
1684		1796
1685	Net::SSLeay	1797	Net::SSLeay
1686	Implementing TLS/SSL in Perl is certainly interesting, but not very	1798	Implementing TLS/SSL in Perl is certainly interesting, but not very
1687	worthwhile: If this module is installed, then AnyEvent::Handle (with	1799	worthwhile: If this module is installed, then AnyEvent::Handle (with
1688	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	1800	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
…		…
1694	additionally use it to try to use a monotonic clock for timing	1806	additionally use it to try to use a monotonic clock for timing
1695	stability.	1807	stability.
1696		1808
1697	FORK	1809	FORK
1698	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
1699	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
1700	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).
1701		1822
1702	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
1703	watcher OR you must not use AnyEvent at all in the child OR you must do	1824	watcher OR you must not use AnyEvent at all in the child OR you must do
1704	something completely out of the scope of AnyEvent.	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.
1705		1835
1706	SECURITY CONSIDERATIONS	1836	SECURITY CONSIDERATIONS
1707	AnyEvent can be forced to load any event model via	1837	AnyEvent can be forced to load any event model via
1708	$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
1709	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
…		…
1741	Event::Lib, Qt, POE.	1871	Event::Lib, Qt, POE.
1742		1872
1743	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1873	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1744	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1874	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1745	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	1875	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1746	AnyEvent::Impl::IOAsync.	1876	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1747		1877
1748	Non-blocking file handles, sockets, TCP clients and servers:	1878	Non-blocking file handles, sockets, TCP clients and servers:
1749	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	1879	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1750		1880
1751	Asynchronous DNS: AnyEvent::DNS.	1881	Asynchronous DNS: AnyEvent::DNS.

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/README (file contents): Revision 1.46 by root, Sat Jul 18 05:19:09 2009 UTC vs. Revision 1.60 by root, Mon Apr 12 02:50:31 2010 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.46 by root, Sat Jul 18 05:19:09 2009 UTC vs.
Revision 1.60 by root, Mon Apr 12 02:50:31 2010 UTC