[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.63 by root, Wed Oct 13 19:49:46 2010 UTC vs.
Revision 1.73 by root, Fri Sep 5 22:24:12 2014 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - the DBI of event loop programming	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,	4	EV, Event, Glib, Tk, UV, Perl, Event::Lib, Irssi, rxvt-unicode,
5	Qt and POE are various supported event loops/environments.	5	IO::Async, Qt, FLTK and POE are various supported event
		6	loops/environments.
6		7
7	SYNOPSIS	8	SYNOPSIS
8	use AnyEvent;	9	use AnyEvent;
9		10
10	# if you prefer function calls, look at the AE manpage for	11	# if you prefer function calls, look at the AE manpage for
80	that isn't them. What's worse, all the potential users of your module	81	that isn't them. What's worse, all the potential users of your module
81	are also forced to use the same event loop you use.	82	are also forced to use the same event loop you use.
82		83
83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	84	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	85	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your	86	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
86	module uses one of those, every user of your module has to use it, too.	87	uses one of those, every user of your module has to use it, too. But if
87	But if your module uses AnyEvent, it works transparently with all event	88	your module uses AnyEvent, it works transparently with all event models
88	models it supports (including stuff like IO::Async, as long as those use	89	it supports (including stuff like IO::Async, as long as those use one of
89	one of the supported event loops. It is easy to add new event loops to	90	the supported event loops. It is easy to add new event loops to
90	AnyEvent, too, so it is future-proof).	91	AnyEvent, too, so it is future-proof).
91		92
92	In addition to being free of having to use *the one and only true event	93	In addition to being free of having to use *the one and only true event
93	model*, AnyEvent also is free of bloat and policy: with POE or similar	94	model*, AnyEvent also is free of bloat and policy: with POE or similar
94	modules, you get an enormous amount of code and strict rules you have to	95	modules, you get an enormous amount of code and strict rules you have to
…		…
115	The interface itself is vaguely similar, but not identical to the Event	116	The interface itself is vaguely similar, but not identical to the Event
116	module.	117	module.
117		118
118	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
119	to detect the currently loaded event loop by probing whether one of the	120	to detect the currently loaded event loop by probing whether one of the
120	following modules is already loaded: EV, AnyEvent::Impl::Perl, Event,	121	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
121	Glib, Tk, Event::Lib, Qt, POE. The first one found is used. If none are	122	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
122	detected, the module tries to load the first four modules in the order	123	detected, the module tries to load the first four modules in the order
123	given; but note that if EV is not available, the pure-perl	124	given; but note that if EV is not available, the pure-perl
124	AnyEvent::Impl::Perl should always work, so the other two are not	125	AnyEvent::Loop should always work, so the other two are not normally
125	normally tried.	126	tried.
126		127
127	Because AnyEvent first checks for modules that are already loaded,	128	Because AnyEvent first checks for modules that are already loaded,
128	loading an event model explicitly before first using AnyEvent will	129	loading an event model explicitly before first using AnyEvent will
129	likely make that model the default. For example:	130	likely make that model the default. For example:
130		131
…		…
136	The likely means that, if any module loads another event model and	137	The likely means that, if any module loads another event model and
137	starts using it, all bets are off - this case should be very rare	138	starts using it, all bets are off - this case should be very rare
138	though, as very few modules hardcode event loops without announcing this	139	though, as very few modules hardcode event loops without announcing this
139	very loudly.	140	very loudly.
140		141
141	The pure-perl implementation of AnyEvent is called	142	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
142	"AnyEvent::Impl::Perl". Like other event modules you can load it	143	Like other event modules you can load it explicitly and enjoy the high
143	explicitly and enjoy the high availability of that event loop :)	144	availability of that event loop :)
144		145
145	WATCHERS	146	WATCHERS
146	AnyEvent has the central concept of a watcher, which is an object that	147	AnyEvent has the central concept of a watcher, which is an object that
147	stores relevant data for each kind of event you are waiting for, such as	148	stores relevant data for each kind of event you are waiting for, such as
148	the callback to call, the file handle to watch, etc.	149	the callback to call, the file handle to watch, etc.
…		…
262		263
263	Example 2: fire an event after 0.5 seconds, then roughly every second.	264	Example 2: fire an event after 0.5 seconds, then roughly every second.
264		265
265	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {	266	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
266	warn "timeout\n";	267	warn "timeout\n";
267	};	268	});
268		269
269	TIMING ISSUES	270	TIMING ISSUES
270	There are two ways to handle timers: based on real time (relative, "fire	271	There are two ways to handle timers: based on real time (relative, "fire
271	in 10 seconds") and based on wallclock time (absolute, "fire at 12	272	in 10 seconds") and based on wallclock time (absolute, "fire at 12
272	o'clock").	273	o'clock").
…		…
347	can get whatever behaviour you want with any event loop, by taking	348	can get whatever behaviour you want with any event loop, by taking
348	the difference between "AnyEvent->time" and "AnyEvent->now" into	349	the difference between "AnyEvent->time" and "AnyEvent->now" into
349	account.	350	account.
350		351
351	AnyEvent->now_update	352	AnyEvent->now_update
352	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the	353	Some event loops (such as EV or AnyEvent::Loop) cache the current
353	current time for each loop iteration (see the discussion of	354	time for each loop iteration (see the discussion of AnyEvent->now,
354	AnyEvent->now, above).	355	above).
355		356
356	When a callback runs for a long time (or when the process sleeps),	357	When a callback runs for a long time (or when the process sleeps),
357	then this "current" time will differ substantially from the real	358	then this "current" time will differ substantially from the real
358	time, which might affect timers and time-outs.	359	time, which might affect timers and time-outs.
359		360
…		…
403	will not restart syscalls (that includes Async::Interrupt and AnyEvent's	404	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
404	pure perl implementation).	405	pure perl implementation).
405		406
406	Safe/Unsafe Signals	407	Safe/Unsafe Signals
407	Perl signals can be either "safe" (synchronous to opcode handling) or	408	Perl signals can be either "safe" (synchronous to opcode handling) or
408	"unsafe" (asynchronous) - the former might get delayed indefinitely, the	409	"unsafe" (asynchronous) - the former might delay signal delivery
409	latter might corrupt your memory.	410	indefinitely, the latter might corrupt your memory.
410		411
411	AnyEvent signal handlers are, in addition, synchronous to the event	412	AnyEvent signal handlers are, in addition, synchronous to the event
412	loop, i.e. they will not interrupt your running perl program but will	413	loop, i.e. they will not interrupt your running perl program but will
413	only be called as part of the normal event handling (just like timer,	414	only be called as part of the normal event handling (just like timer,
414	I/O etc. callbacks, too).	415	I/O etc. callbacks, too).
…		…
416	Signal Races, Delays and Workarounds	417	Signal Races, Delays and Workarounds
417	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching	418	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
418	callbacks to signals in a generic way, which is a pity, as you cannot do	419	callbacks to signals in a generic way, which is a pity, as you cannot do
419	race-free signal handling in perl, requiring C libraries for this.	420	race-free signal handling in perl, requiring C libraries for this.
420	AnyEvent will try to do its best, which means in some cases, signals	421	AnyEvent will try to do its best, which means in some cases, signals
421	will be delayed. The maximum time a signal might be delayed is specified	422	will be delayed. The maximum time a signal might be delayed is 10
422	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable	423	seconds by default, but can be overriden via
423	can be changed only before the first signal watcher is created, and	424	$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
424	should be left alone otherwise. This variable determines how often	425	- see the "ENVIRONMENT VARIABLES" section for details.
425	AnyEvent polls for signals (in case a wake-up was missed). Higher values
426	will cause fewer spurious wake-ups, which is better for power and CPU
427	saving.
428		426
429	All these problems can be avoided by installing the optional	427	All these problems can be avoided by installing the optional
430	Async::Interrupt module, which works with most event loops. It will not	428	Async::Interrupt module, which works with most event loops. It will not
431	work with inherently broken event loops such as Event or Event::Lib (and	429	work with inherently broken event loops such as Event or Event::Lib (and
432	not with POE currently, as POE does its own workaround with one-second
433	latency). For those, you just have to suffer the delays.	430	not with POE currently). For those, you just have to suffer the delays.
434		431
435	CHILD PROCESS WATCHERS	432	CHILD PROCESS WATCHERS
436	$w = AnyEvent->child (pid => <process id>, cb => <callback>);	433	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
437		434
438	You can also watch for a child process exit and catch its exit status.	435	You can also watch for a child process exit and catch its exit status.
…		…
466	This means you cannot create a child watcher as the very first thing in	463	This means you cannot create a child watcher as the very first thing in
467	an AnyEvent program, you have to create at least one watcher before	464	an AnyEvent program, you have to create at least one watcher before
468	you "fork" the child (alternatively, you can call "AnyEvent::detect").	465	you "fork" the child (alternatively, you can call "AnyEvent::detect").
469		466
470	As most event loops do not support waiting for child events, they will	467	As most event loops do not support waiting for child events, they will
471	be emulated by AnyEvent in most cases, in which the latency and race	468	be emulated by AnyEvent in most cases, in which case the latency and
472	problems mentioned in the description of signal watchers apply.	469	race problems mentioned in the description of signal watchers apply.
473		470
474	Example: fork a process and wait for it	471	Example: fork a process and wait for it
475		472
476	my $done = AnyEvent->condvar;	473	my $done = AnyEvent->condvar;
477		474
		475	# this forks and immediately calls exit in the child. this
		476	# normally has all sorts of bad consequences for your parent,
		477	# so take this as an example only. always fork and exec,
		478	# or call POSIX::_exit, in real code.
478	my $pid = fork or exit 5;	479	my $pid = fork or exit 5;
479		480
480	my $w = AnyEvent->child (	481	my $w = AnyEvent->child (
481	pid => $pid,	482	pid => $pid,
482	cb => sub {	483	cb => sub {
…		…
722	This works because for every event source (EOF on file handle),	723	This works because for every event source (EOF on file handle),
723	there is one call to "begin", so the condvar waits for all calls to	724	there is one call to "begin", so the condvar waits for all calls to
724	"end" before sending.	725	"end" before sending.
725		726
726	The ping example mentioned above is slightly more complicated, as	727	The ping example mentioned above is slightly more complicated, as
727	the there are results to be passwd back, and the number of tasks	728	the there are results to be passed back, and the number of tasks
728	that are begun can potentially be zero:	729	that are begun can potentially be zero:
729		730
730	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
731		732
732	my %result;	733	my %result;
…		…
740	};	741	};
741	}	742	}
742		743
743	$cv->end;	744	$cv->end;
744		745
		746	...
		747
		748	my $results = $cv->recv;
		749
745	This code fragment supposedly pings a number of hosts and calls	750	This code fragment supposedly pings a number of hosts and calls
746	"send" after results for all then have have been gathered - in any	751	"send" after results for all then have have been gathered - in any
747	order. To achieve this, the code issues a call to "begin" when it	752	order. To achieve this, the code issues a call to "begin" when it
748	starts each ping request and calls "end" when it has received some	753	starts each ping request and calls "end" when it has received some
749	result for it. Since "begin" and "end" only maintain a counter, the	754	result for it. Since "begin" and "end" only maintain a counter, the
…		…
778	In list context, all parameters passed to "send" will be returned,	783	In list context, all parameters passed to "send" will be returned,
779	in scalar context only the first one will be returned.	784	in scalar context only the first one will be returned.
780		785
781	Note that doing a blocking wait in a callback is not supported by	786	Note that doing a blocking wait in a callback is not supported by
782	any event loop, that is, recursive invocation of a blocking "->recv"	787	any event loop, that is, recursive invocation of a blocking "->recv"
783	is not allowed, and the "recv" call will "croak" if such a condition	788	is not allowed and the "recv" call will "croak" if such a condition
784	is detected. This condition can be slightly loosened by using	789	is detected. This requirement can be dropped by relying on
785	Coro::AnyEvent, which allows you to do a blocking "->recv" from any	790	Coro::AnyEvent , which allows you to do a blocking "->recv" from any
786	thread that doesn't run the event loop itself.	791	thread that doesn't run the event loop itself. Coro::AnyEvent is
		792	loaded automatically when Coro is used with AnyEvent, so code does
		793	not need to do anything special to take advantage of that: any code
		794	that would normally block your program because it calls "recv", be
		795	executed in an "async" thread instead without blocking other
		796	threads.
787		797
788	Not all event models support a blocking wait - some die in that case	798	Not all event models support a blocking wait - some die in that case
789	(programs might want to do that to stay interactive), so *if you are	799	(programs might want to do that to stay interactive), so *if you are
790	using this from a module, never require a blocking wait*. Instead,	800	using this from a module, never require a blocking wait*. Instead,
791	let the caller decide whether the call will block or not (for	801	let the caller decide whether the call will block or not (for
…		…
821	use. If EV is not installed, then AnyEvent will fall back to its own	831	use. If EV is not installed, then AnyEvent will fall back to its own
822	pure-perl implementation, which is available everywhere as it comes	832	pure-perl implementation, which is available everywhere as it comes
823	with AnyEvent itself.	833	with AnyEvent itself.
824		834
825	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	835	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
826	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	836	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
827		837
828	Backends that are transparently being picked up when they are used.	838	Backends that are transparently being picked up when they are used.
829	These will be used if they are already loaded when the first watcher	839	These will be used if they are already loaded when the first watcher
830	is created, in which case it is assumed that the application is	840	is created, in which case it is assumed that the application is
831	using them. This means that AnyEvent will automatically pick the	841	using them. This means that AnyEvent will automatically pick the
…		…
834	by the main program.	844	by the main program.
835		845
836	AnyEvent::Impl::Event based on Event, very stable, few glitches.	846	AnyEvent::Impl::Event based on Event, very stable, few glitches.
837	AnyEvent::Impl::Glib based on Glib, slow but very stable.	847	AnyEvent::Impl::Glib based on Glib, slow but very stable.
838	AnyEvent::Impl::Tk based on Tk, very broken.	848	AnyEvent::Impl::Tk based on Tk, very broken.
		849	AnyEvent::Impl::UV based on UV, innovated square wheels.
839	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	850	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
840	AnyEvent::Impl::POE based on POE, very slow, some limitations.	851	AnyEvent::Impl::POE based on POE, very slow, some limitations.
841	AnyEvent::Impl::Irssi used when running within irssi.	852	AnyEvent::Impl::Irssi used when running within irssi.
		853	AnyEvent::Impl::IOAsync based on IO::Async.
		854	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		855	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
842		856
843	Backends with special needs.	857	Backends with special needs.
844	Qt requires the Qt::Application to be instantiated first, but will	858	Qt requires the Qt::Application to be instantiated first, but will
845	otherwise be picked up automatically. As long as the main program	859	otherwise be picked up automatically. As long as the main program
846	instantiates the application before any AnyEvent watchers are	860	instantiates the application before any AnyEvent watchers are
847	created, everything should just work.	861	created, everything should just work.
848		862
849	AnyEvent::Impl::Qt based on Qt.	863	AnyEvent::Impl::Qt based on Qt.
850
851	Support for IO::Async can only be partial, as it is too broken and
852	architecturally limited to even support the AnyEvent API. It also is
853	the only event loop that needs the loop to be set explicitly, so it
854	can only be used by a main program knowing about AnyEvent. See
855	AnyEvent::Impl::IOAsync for the gory details.
856
857	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
858		864
859	Event loops that are indirectly supported via other backends.	865	Event loops that are indirectly supported via other backends.
860	Some event loops can be supported via other modules:	866	Some event loops can be supported via other modules:
861		867
862	There is no direct support for WxWidgets (Wx) or Prima.	868	There is no direct support for WxWidgets (Wx) or Prima.
…		…
891	Returns $AnyEvent::MODEL, forcing autodetection of the event model	897	Returns $AnyEvent::MODEL, forcing autodetection of the event model
892	if necessary. You should only call this function right before you	898	if necessary. You should only call this function right before you
893	would have created an AnyEvent watcher anyway, that is, as late as	899	would have created an AnyEvent watcher anyway, that is, as late as
894	possible at runtime, and not e.g. during initialisation of your	900	possible at runtime, and not e.g. during initialisation of your
895	module.	901	module.
		902
		903	The effect of calling this function is as if a watcher had been
		904	created (specifically, actions that happen "when the first watcher
		905	is created" happen when calling detetc as well).
896		906
897	If you need to do some initialisation before AnyEvent watchers are	907	If you need to do some initialisation before AnyEvent watchers are
898	created, use "post_detect".	908	created, use "post_detect".
899		909
900	$guard = AnyEvent::post_detect { BLOCK }	910	$guard = AnyEvent::post_detect { BLOCK }
…		…
962	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent	972	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
963	# as soon as it is	973	# as soon as it is
964	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };	974	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
965	}	975	}
966		976
		977	AnyEvent::postpone { BLOCK }
		978	Arranges for the block to be executed as soon as possible, but not
		979	before the call itself returns. In practise, the block will be
		980	executed just before the event loop polls for new events, or shortly
		981	afterwards.
		982
		983	This function never returns anything (to make the "return postpone {
		984	... }" idiom more useful.
		985
		986	To understand the usefulness of this function, consider a function
		987	that asynchronously does something for you and returns some
		988	transaction object or guard to let you cancel the operation. For
		989	example, "AnyEvent::Socket::tcp_connect":
		990
		991	# start a connection attempt unless one is active
		992	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		993	delete $self->{connect_guard};
		994	...
		995	};
		996
		997	Imagine that this function could instantly call the callback, for
		998	example, because it detects an obvious error such as a negative port
		999	number. Invoking the callback before the function returns causes
		1000	problems however: the callback will be called and will try to delete
		1001	the guard object. But since the function hasn't returned yet, there
		1002	is nothing to delete. When the function eventually returns it will
		1003	assign the guard object to "$self->{connect_guard}", where it will
		1004	likely never be deleted, so the program thinks it is still trying to
		1005	connect.
		1006
		1007	This is where "AnyEvent::postpone" should be used. Instead of
		1008	calling the callback directly on error:
		1009
		1010	$cb->(undef), return # signal error to callback, BAD!
		1011	if $some_error_condition;
		1012
		1013	It should use "postpone":
		1014
		1015	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1016	if $some_error_condition;
		1017
		1018	AnyEvent::log $level, $msg[, @args]
		1019	Log the given $msg at the given $level.
		1020
		1021	If AnyEvent::Log is not loaded then this function makes a simple
		1022	test to see whether the message will be logged. If the test succeeds
		1023	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1024	consequently, look at the AnyEvent::Log documentation for details.
		1025
		1026	If the test fails it will simply return. Right now this happens when
		1027	a numerical loglevel is used and it is larger than the level
		1028	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1029
		1030	If you want to sprinkle loads of logging calls around your code,
		1031	consider creating a logger callback with the "AnyEvent::Log::logger"
		1032	function, which can reduce typing, codesize and can reduce the
		1033	logging overhead enourmously.
		1034
967	WHAT TO DO IN A MODULE	1035	WHAT TO DO IN A MODULE
968	As a module author, you should "use AnyEvent" and call AnyEvent methods	1036	As a module author, you should "use AnyEvent" and call AnyEvent methods
969	freely, but you should not load a specific event module or rely on it.	1037	freely, but you should not load a specific event module or rely on it.
970		1038
971	Be careful when you create watchers in the module body - AnyEvent will	1039	Be careful when you create watchers in the module body - AnyEvent will
…		…
1001	will decide on the event model to use as soon as it creates watchers,	1069	will decide on the event model to use as soon as it creates watchers,
1002	and it might choose the wrong one unless you load the correct one	1070	and it might choose the wrong one unless you load the correct one
1003	yourself.	1071	yourself.
1004		1072
1005	You can chose to use a pure-perl implementation by loading the	1073	You can chose to use a pure-perl implementation by loading the
1006	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1074	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
1007	everywhere, but letting AnyEvent chose the model is generally better.	1075	but letting AnyEvent chose the model is generally better.
1008		1076
1009	MAINLOOP EMULATION	1077	MAINLOOP EMULATION
1010	Sometimes (often for short test scripts, or even standalone programs who	1078	Sometimes (often for short test scripts, or even standalone programs who
1011	only want to use AnyEvent), you do not want to run a specific event	1079	only want to use AnyEvent), you do not want to run a specific event
1012	loop.	1080	loop.
…		…
1024		1092
1025	OTHER MODULES	1093	OTHER MODULES
1026	The following is a non-exhaustive list of additional modules that use	1094	The following is a non-exhaustive list of additional modules that use
1027	AnyEvent as a client and can therefore be mixed easily with other	1095	AnyEvent as a client and can therefore be mixed easily with other
1028	AnyEvent modules and other event loops in the same program. Some of the	1096	AnyEvent modules and other event loops in the same program. Some of the
1029	modules come as part of AnyEvent, the others are available via CPAN.	1097	modules come as part of AnyEvent, the others are available via CPAN (see
		1098	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1099	non-exhaustive list), and the list is heavily biased towards modules of
		1100	the AnyEvent author himself :)
1030		1101
1031	AnyEvent::Util	1102	AnyEvent::Util (part of the AnyEvent distribution)
1032	Contains various utility functions that replace often-used blocking	1103	Contains various utility functions that replace often-used blocking
1033	functions such as "inet_aton" with event/callback-based versions.	1104	functions such as "inet_aton" with event/callback-based versions.
1034		1105
1035	AnyEvent::Socket	1106	AnyEvent::Socket (part of the AnyEvent distribution)
1036	Provides various utility functions for (internet protocol) sockets,	1107	Provides various utility functions for (internet protocol) sockets,
1037	addresses and name resolution. Also functions to create non-blocking	1108	addresses and name resolution. Also functions to create non-blocking
1038	tcp connections or tcp servers, with IPv6 and SRV record support and	1109	tcp connections or tcp servers, with IPv6 and SRV record support and
1039	more.	1110	more.
1040		1111
1041	AnyEvent::Handle	1112	AnyEvent::Handle (part of the AnyEvent distribution)
1042	Provide read and write buffers, manages watchers for reads and	1113	Provide read and write buffers, manages watchers for reads and
1043	writes, supports raw and formatted I/O, I/O queued and fully	1114	writes, supports raw and formatted I/O, I/O queued and fully
1044	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).	1115	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
1045		1116
1046	AnyEvent::DNS	1117	AnyEvent::DNS (part of the AnyEvent distribution)
1047	Provides rich asynchronous DNS resolver capabilities.	1118	Provides rich asynchronous DNS resolver capabilities.
1048		1119
1049	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,	1120	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
1050	AnyEvent::IGS, AnyEvent::FCP	1121	AnyEvent::IGS, AnyEvent::FCP
1051	Implement event-based interfaces to the protocols of the same name	1122	Implement event-based interfaces to the protocols of the same name
1052	(for the curious, IGS is the International Go Server and FCP is the	1123	(for the curious, IGS is the International Go Server and FCP is the
1053	Freenet Client Protocol).	1124	Freenet Client Protocol).
1054		1125
1055	AnyEvent::Handle::UDP	1126	AnyEvent::AIO (part of the AnyEvent distribution)
1056	Here be danger!
1057
1058	As Pauli would put it, "Not only is it not right, it's not even
1059	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
1060	most notably its use of a stream-based API with a protocol that
1061	isn't streamable, that the only way to improve it is to delete it.
1062
1063	It features data corruption (but typically only under load) and
1064	general confusion. On top, the author is not only clueless about UDP
1065	but also fact-resistant - some gems of his understanding: "connect
1066	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
1067	has datagrams, not packets", "I don't need to implement proper error
1068	checking as UDP doesn't support error checking" and so on - he
1069	doesn't even understand what's wrong with his module when it is
1070	explained to him.
1071
1072	AnyEvent::DBI
1073	Executes DBI requests asynchronously in a proxy process for you,
1074	notifying you in an event-based way when the operation is finished.
1075
1076	AnyEvent::AIO
1077	Truly asynchronous (as opposed to non-blocking) I/O, should be in	1127	Truly asynchronous (as opposed to non-blocking) I/O, should be in
1078	the toolbox of every event programmer. AnyEvent::AIO transparently	1128	the toolbox of every event programmer. AnyEvent::AIO transparently
1079	fuses IO::AIO and AnyEvent together, giving AnyEvent access to	1129	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
1080	event-based file I/O, and much more.	1130	event-based file I/O, and much more.
1081		1131
		1132	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1133	AnyEvent::Fork::Remote
		1134	These let you safely fork new subprocesses, either locally or
		1135	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1136	limitations normally imposed by fork (AnyEvent works fine for
		1137	example). Dynamically-resized worker pools are obviously included as
		1138	well.
		1139
		1140	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1141	just to exec external programs can easily beat using "fork" and
		1142	"exec" (or even "system") in most programs.
		1143
		1144	AnyEvent::Filesys::Notify
		1145	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1146	path changes (e.g. "watch this directory for new files", "watch this
		1147	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1148	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1149	and some weird, without doubt broken, stuff on OS X to monitor
		1150	files. It can fall back to blocking scans at regular intervals
		1151	transparently on other platforms, so it's about as portable as it
		1152	gets.
		1153
		1154	(I haven't used it myself, but it seems the biggest problem with it
		1155	is it quite bad performance).
		1156
1082	AnyEvent::HTTPD	1157	AnyEvent::DBI
1083	A simple embedded webserver.	1158	Executes DBI requests asynchronously in a proxy process for you,
		1159	notifying you in an event-based way when the operation is finished.
1084		1160
1085	AnyEvent::FastPing	1161	AnyEvent::FastPing
1086	The fastest ping in the west.	1162	The fastest ping in the west.
1087		1163
1088	Coro	1164	Coro
1089	Has special support for AnyEvent via Coro::AnyEvent.	1165	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1166	you to simply invert the flow control - don't call us, we will call
		1167	you:
		1168
		1169	async {
		1170	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1171	print "5 seconds later!\n";
		1172
		1173	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1174	my $line = <STDIN>; # works for ttys
		1175
		1176	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1177	my ($body, $hdr) = Coro::rouse_wait;
		1178	};
1090		1179
1091	SIMPLIFIED AE API	1180	SIMPLIFIED AE API
1092	Starting with version 5.0, AnyEvent officially supports a second, much	1181	Starting with version 5.0, AnyEvent officially supports a second, much
1093	simpler, API that is designed to reduce the calling, typing and memory	1182	simpler, API that is designed to reduce the calling, typing and memory
1094	overhead by using function call syntax and a fixed number of parameters.	1183	overhead by using function call syntax and a fixed number of parameters.
…		…
1110	The pure perl event loop simply re-throws the exception (usually within	1199	The pure perl event loop simply re-throws the exception (usually within
1111	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1200	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1112	Glib uses "install_exception_handler" and so on.	1201	Glib uses "install_exception_handler" and so on.
1113		1202
1114	ENVIRONMENT VARIABLES	1203	ENVIRONMENT VARIABLES
1115	The following environment variables are used by this module or its	1204	AnyEvent supports a number of environment variables that tune the
1116	submodules.	1205	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1206	initialised, or a submodule that uses them is loaded. Many of them also
		1207	cause AnyEvent to load additional modules - for example,
		1208	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1209	loaded.
1117		1210
1118	Note that AnyEvent will remove all environment variables starting with	1211	All the environment variables documented here start with
1119	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1212	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1120	enabled.	1213	Other modules are encouraged (but by no means required) to use
		1214	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1215	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1216	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1217	should not access env variables starting with "AE_", see below).
		1218
		1219	All variables can also be set via the "AE_" prefix, that is, instead of
		1220	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1221	there is a clash btween anyevent and another program that uses
		1222	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1223	variable to the empty string, as those variables take precedence.
		1224
		1225	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1226	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1227	exists. If taint mode is on, then AnyEvent will remove all environment
		1228	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1229	"undef" or the empty string, if the corresaponding "AE_" variable is
		1230	set).
		1231
		1232	The exact algorithm is currently:
		1233
		1234	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1235	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1236	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1237
		1238	This ensures that child processes will not see the "AE_" variables.
		1239
		1240	The following environment variables are currently known to AnyEvent:
1121		1241
1122	"PERL_ANYEVENT_VERBOSE"	1242	"PERL_ANYEVENT_VERBOSE"
1123	By default, AnyEvent will be completely silent except in fatal	1243	By default, AnyEvent will log messages with loglevel 4 ("error") or
1124	conditions. You can set this environment variable to make AnyEvent	1244	higher (see AnyEvent::Log). You can set this environment variable to
1125	more talkative.	1245	a numerical loglevel to make AnyEvent more (or less) talkative.
1126		1246
		1247	If you want to do more than just set the global logging level you
		1248	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1249	complex specifications.
		1250
		1251	When set to 0 ("off"), then no messages whatsoever will be logged
		1252	with everything else at defaults.
		1253
1127	When set to 1 or higher, causes AnyEvent to warn about unexpected	1254	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1128	conditions, such as not being able to load the event model specified	1255	conditions, such as not being able to load the event model specified
1129	by "PERL_ANYEVENT_MODEL".	1256	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1257	- this is the minimum recommended level for use during development.
1130		1258
1131	When set to 2 or higher, cause AnyEvent to report to STDERR which	1259	When set to 7 or higher (info), AnyEvent reports which event model
1132	event model it chooses.	1260	it chooses.
1133		1261
1134	When set to 8 or higher, then AnyEvent will report extra information	1262	When set to 8 or higher (debug), then AnyEvent will report extra
1135	on which optional modules it loads and how it implements certain	1263	information on which optional modules it loads and how it implements
1136	features.	1264	certain features.
		1265
		1266	"PERL_ANYEVENT_LOG"
		1267	Accepts rather complex logging specifications. For example, you
		1268	could log all "debug" messages of some module to stderr, warnings
		1269	and above to stderr, and errors and above to syslog, with:
		1270
		1271	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1272
		1273	For the rather extensive details, see AnyEvent::Log.
		1274
		1275	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1276	loaded, so will take effect even before AnyEvent has initialised
		1277	itself.
		1278
		1279	Note that specifying this environment variable causes the
		1280	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1281	does not, so only using the latter saves a few hundred kB of memory
		1282	unless a module explicitly needs the extra features of
		1283	AnyEvent::Log.
1137		1284
1138	"PERL_ANYEVENT_STRICT"	1285	"PERL_ANYEVENT_STRICT"
1139	AnyEvent does not do much argument checking by default, as thorough	1286	AnyEvent does not do much argument checking by default, as thorough
1140	argument checking is very costly. Setting this variable to a true	1287	argument checking is very costly. Setting this variable to a true
1141	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1288	value will cause AnyEvent to load "AnyEvent::Strict" and then to
…		…
1147	Unlike "use strict" (or its modern cousin, "use common::sense", it	1294	Unlike "use strict" (or its modern cousin, "use common::sense", it
1148	is definitely recommended to keep it off in production. Keeping	1295	is definitely recommended to keep it off in production. Keeping
1149	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1296	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1150	programs can be very useful, however.	1297	programs can be very useful, however.
1151		1298
		1299	"PERL_ANYEVENT_DEBUG_SHELL"
		1300	If this env variable is nonempty, then its contents will be
		1301	interpreted by "AnyEvent::Socket::parse_hostport" and
		1302	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1303	the process pid). The shell object is saved in
		1304	$AnyEvent::Debug::SHELL.
		1305
		1306	This happens when the first watcher is created.
		1307
		1308	For example, to bind a debug shell on a unix domain socket in
		1309	/tmp/debug<pid>.sock, you could use this:
		1310
		1311	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1312	# connect with e.g.: socat readline /tmp/debug123.sock
		1313
		1314	Or to bind to tcp port 4545 on localhost:
		1315
		1316	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1317	# connect with e.g.: telnet localhost 4545
		1318
		1319	Note that creating sockets in /tmp or on localhost is very unsafe on
		1320	multiuser systems.
		1321
		1322	"PERL_ANYEVENT_DEBUG_WRAP"
		1323	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1324	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1325
1152	"PERL_ANYEVENT_MODEL"	1326	"PERL_ANYEVENT_MODEL"
1153	This can be used to specify the event model to be used by AnyEvent,	1327	This can be used to specify the event model to be used by AnyEvent,
1154	before auto detection and -probing kicks in. It must be a string	1328	before auto detection and -probing kicks in.
1155	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1329
1156	gets prepended and the resulting module name is loaded and if the	1330	It normally is a string consisting entirely of ASCII letters (e.g.
1157	load was successful, used as event model. If it fails to load	1331	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1332	the resulting module name is loaded and - if the load was successful
		1333	- used as event model backend. If it fails to load then AnyEvent
1158	AnyEvent will proceed with auto detection and -probing.	1334	will proceed with auto detection and -probing.
1159		1335
1160	This functionality might change in future versions.	1336	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1337	then nothing gets prepended and the module name is used as-is (hint:
		1338	"::" at the end of a string designates a module name and quotes it
		1339	appropriately).
1161		1340
1162	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1341	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1163	could start your program like this:	1342	could start your program like this:
1164		1343
1165	PERL_ANYEVENT_MODEL=Perl perl ...	1344	PERL_ANYEVENT_MODEL=Perl perl ...
		1345
		1346	"PERL_ANYEVENT_IO_MODEL"
		1347	The current file I/O model - see AnyEvent::IO for more info.
		1348
		1349	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1350	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1351	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1166		1352
1167	"PERL_ANYEVENT_PROTOCOLS"	1353	"PERL_ANYEVENT_PROTOCOLS"
1168	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1354	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1169	preferences for IPv4 or IPv6. The default is unspecified (and might	1355	preferences for IPv4 or IPv6. The default is unspecified (and might
1170	change, or be the result of auto probing).	1356	change, or be the result of auto probing).
…		…
1174	mentioned will be used, and preference will be given to protocols	1360	mentioned will be used, and preference will be given to protocols
1175	mentioned earlier in the list.	1361	mentioned earlier in the list.
1176		1362
1177	This variable can effectively be used for denial-of-service attacks	1363	This variable can effectively be used for denial-of-service attacks
1178	against local programs (e.g. when setuid), although the impact is	1364	against local programs (e.g. when setuid), although the impact is
1179	likely small, as the program has to handle conenction and other	1365	likely small, as the program has to handle connection and other
1180	failures anyways.	1366	failures anyways.
1181		1367
1182	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1368	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
1183	IPv6, but support both and try to use both.	1369	IPv6, but support both and try to use both.
1184	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1370	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1185	resolve or contact IPv6 addresses.	1371	resolve or contact IPv6 addresses.
1186	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1372	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1187	prefer IPv6 over IPv4.	1373	prefer IPv6 over IPv4.
1188		1374
		1375	"PERL_ANYEVENT_HOSTS"
		1376	This variable, if specified, overrides the /etc/hosts file used by
		1377	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1378	read from that file instead.
		1379
1189	"PERL_ANYEVENT_EDNS0"	1380	"PERL_ANYEVENT_EDNS0"
1190	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1381	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1191	for DNS. This extension is generally useful to reduce DNS traffic,	1382	for DNS. This extension is generally useful to reduce DNS traffic,
1192	but some (broken) firewalls drop such DNS packets, which is why it	1383	especially when DNSSEC is involved, but some (broken) firewalls drop
1193	is off by default.	1384	such DNS packets, which is why it is off by default.
1194		1385
1195	Setting this variable to 1 will cause AnyEvent::DNS to announce	1386	Setting this variable to 1 will cause AnyEvent::DNS to announce
1196	EDNS0 in its DNS requests.	1387	EDNS0 in its DNS requests.
1197		1388
1198	"PERL_ANYEVENT_MAX_FORKS"	1389	"PERL_ANYEVENT_MAX_FORKS"
…		…
1202	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1393	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1203	The default value for the "max_outstanding" parameter for the	1394	The default value for the "max_outstanding" parameter for the
1204	default DNS resolver - this is the maximum number of parallel DNS	1395	default DNS resolver - this is the maximum number of parallel DNS
1205	requests that are sent to the DNS server.	1396	requests that are sent to the DNS server.
1206		1397
		1398	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1399	Perl has inherently racy signal handling (you can basically choose
		1400	between losing signals and memory corruption) - pure perl event
		1401	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1402	available) therefore have to poll regularly to avoid losing signals.
		1403
		1404	Some event loops are racy, but don't poll regularly, and some event
		1405	loops are written in C but are still racy. For those event loops,
		1406	AnyEvent installs a timer that regularly wakes up the event loop.
		1407
		1408	By default, the interval for this timer is 10 seconds, but you can
		1409	override this delay with this environment variable (or by setting
		1410	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1411	watchers).
		1412
		1413	Lower values increase CPU (and energy) usage, higher values can
		1414	introduce long delays when reaping children or waiting for signals.
		1415
		1416	The AnyEvent::Async module, if available, will be used to avoid this
		1417	polling (with most event loops).
		1418
1207	"PERL_ANYEVENT_RESOLV_CONF"	1419	"PERL_ANYEVENT_RESOLV_CONF"
1208	The file to use instead of /etc/resolv.conf (or OS-specific	1420	The absolute path to a resolv.conf-style file to use instead of
1209	configuration) in the default resolver. When set to the empty	1421	/etc/resolv.conf (or the OS-specific configuration) in the default
1210	string, no default config will be used.	1422	resolver, or the empty string to select the default configuration.
1211		1423
1212	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1424	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1213	When neither "ca_file" nor "ca_path" was specified during	1425	When neither "ca_file" nor "ca_path" was specified during
1214	AnyEvent::TLS context creation, and either of these environment	1426	AnyEvent::TLS context creation, and either of these environment
1215	variables exist, they will be used to specify CA certificate	1427	variables are nonempty, they will be used to specify CA certificate
1216	locations instead of a system-dependent default.	1428	locations instead of a system-dependent default.
1217		1429
1218	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1430	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1219	When these are set to 1, then the respective modules are not loaded.	1431	When these are set to 1, then the respective modules are not loaded.
1220	Mostly good for testing AnyEvent itself.	1432	Mostly good for testing AnyEvent itself.
…		…
1540	when used without AnyEvent), but most event loops have acceptable	1752	when used without AnyEvent), but most event loops have acceptable
1541	performance with or without AnyEvent.	1753	performance with or without AnyEvent.
1542		1754
1543	* The overhead AnyEvent adds is usually much smaller than the overhead	1755	* The overhead AnyEvent adds is usually much smaller than the overhead
1544	of the actual event loop, only with extremely fast event loops such	1756	of the actual event loop, only with extremely fast event loops such
1545	as EV adds AnyEvent significant overhead.	1757	as EV does AnyEvent add significant overhead.
1546		1758
1547	* You should avoid POE like the plague if you want performance or	1759	* You should avoid POE like the plague if you want performance or
1548	reasonable memory usage.	1760	reasonable memory usage.
1549		1761
1550	BENCHMARKING THE LARGE SERVER CASE	1762	BENCHMARKING THE LARGE SERVER CASE
…		…
1810	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2022	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1811		2023
1812	Time::HiRes	2024	Time::HiRes
1813	This module is part of perl since release 5.008. It will be used	2025	This module is part of perl since release 5.008. It will be used
1814	when the chosen event library does not come with a timing source of	2026	when the chosen event library does not come with a timing source of
1815	its own. The pure-perl event loop (AnyEvent::Impl::Perl) will	2027	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1816	additionally use it to try to use a monotonic clock for timing	2028	load it to try to use a monotonic clock for timing stability.
1817	stability.	2029
		2030	AnyEvent::AIO (and IO::AIO)
		2031	The default implementation of AnyEvent::IO is to do I/O
		2032	synchronously, stopping programs while they access the disk, which
		2033	is fine for a lot of programs.
		2034
		2035	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2036	switch to a true asynchronous implementation, so event processing
		2037	can continue even while waiting for disk I/O.
1818		2038
1819	FORK	2039	FORK
1820	Most event libraries are not fork-safe. The ones who are usually are	2040	Most event libraries are not fork-safe. The ones who are usually are
1821	because they rely on inefficient but fork-safe "select" or "poll" calls	2041	because they rely on inefficient but fork-safe "select" or "poll" calls
1822	- higher performance APIs such as BSD's kqueue or the dreaded Linux	2042	- higher performance APIs such as BSD's kqueue or the dreaded Linux
…		…
1830	usually happens when the first AnyEvent watcher is created, or the	2050	usually happens when the first AnyEvent watcher is created, or the
1831	library is loaded).	2051	library is loaded).
1832		2052
1833	If you have to fork, you must either do so before creating your first	2053	If you have to fork, you must either do so before creating your first
1834	watcher OR you must not use AnyEvent at all in the child OR you must do	2054	watcher OR you must not use AnyEvent at all in the child OR you must do
1835	something completely out of the scope of AnyEvent.	2055	something completely out of the scope of AnyEvent (see below).
1836		2056
1837	The problem of doing event processing in the parent and the child is	2057	The problem of doing event processing in the parent and the child is
1838	much more complicated: even for backends that are fork-aware or	2058	much more complicated: even for backends that are fork-aware or
1839	fork-safe, their behaviour is not usually what you want: fork clones all	2059	fork-safe, their behaviour is not usually what you want: fork clones all
1840	watchers, that means all timers, I/O watchers etc. are active in both	2060	watchers, that means all timers, I/O watchers etc. are active in both
1841	parent and child, which is almost never what you want. USing "exec" to	2061	parent and child, which is almost never what you want. Using "exec" to
1842	start worker children from some kind of manage rprocess is usually	2062	start worker children from some kind of manage prrocess is usually
1843	preferred, because it is much easier and cleaner, at the expense of	2063	preferred, because it is much easier and cleaner, at the expense of
1844	having to have another binary.	2064	having to have another binary.
		2065
		2066	In addition to logical problems with fork, there are also implementation
		2067	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2068	code if a thread (I am talking of pthreads here) was ever created in the
		2069	process, and this is just the tip of the iceberg. In general, using fork
		2070	from Perl is difficult, and attempting to use fork without an exec to
		2071	implement some kind of parallel processing is almost certainly doomed.
		2072
		2073	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2074	that let's you safely fork and exec new processes.
		2075
		2076	If you want to do multiprocessing using processes, you can look at the
		2077	AnyEvent::Fork module (and some related modules such as
		2078	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2079	This module allows you to safely create subprocesses without any
		2080	limitations - you can use X11 toolkits or AnyEvent in the children
		2081	created by AnyEvent::Fork safely and without any special precautions.
1845		2082
1846	SECURITY CONSIDERATIONS	2083	SECURITY CONSIDERATIONS
1847	AnyEvent can be forced to load any event model via	2084	AnyEvent can be forced to load any event model via
1848	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2085	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1849	to execute arbitrary code or directly gain access, it can easily be used	2086	to execute arbitrary code or directly gain access, it can easily be used
…		…
1877	SEE ALSO	2114	SEE ALSO
1878	Tutorial/Introduction: AnyEvent::Intro.	2115	Tutorial/Introduction: AnyEvent::Intro.
1879		2116
1880	FAQ: AnyEvent::FAQ.	2117	FAQ: AnyEvent::FAQ.
1881		2118
1882	Utility functions: AnyEvent::Util.	2119	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2120	(simply logging).
1883		2121
1884	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2122	Development/Debugging: AnyEvent::Strict (stricter checking),
1885	Event::Lib, Qt, POE.	2123	AnyEvent::Debug (interactive shell, watcher tracing).
		2124
		2125	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2126	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK.
1886		2127
1887	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2128	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1888	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2129	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1889	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2130	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1890	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.	2131	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
1891		2132
1892	Non-blocking file handles, sockets, TCP clients and servers:	2133	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1893	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2134	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
		2135
		2136	Asynchronous File I/O: AnyEvent::IO.
1894		2137
1895	Asynchronous DNS: AnyEvent::DNS.	2138	Asynchronous DNS: AnyEvent::DNS.
1896		2139
1897	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.	2140	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1898		2141
1899	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,	2142	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1900	AnyEvent::HTTP.	2143	AnyEvent::HTTP.
1901		2144
1902	AUTHOR	2145	AUTHOR
1903	Marc Lehmann <schmorp@schmorp.de>	2146	Marc Lehmann <schmorp@schmorp.de>
1904	http://home.schmorp.de/	2147	http://anyevent.schmorp.de
1905		2148

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Revision 1.63 by root, Wed Oct 13 19:49:46 2010 UTC vs.
Revision 1.73 by root, Fri Sep 5 22:24:12 2014 UTC