[ViewVC] Diff of: cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.80 by root, Fri Sep 4 22:30:29 2009 UTC vs.
Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
30	rcv $port, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
31		31
32	# create a port on another node	32	# create a port on another node
33	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
34		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
35	# monitoring	39	# monitoring
36	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
38	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
39		51
40	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
41		53
42	bin/aemp - stable.	54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - explains most concepts.	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.	58	AnyEvent::MP::Global - stable API.
47
48	stay tuned.
49		59
50	=head1 DESCRIPTION	60	=head1 DESCRIPTION
51		61
52	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
53		63
…		…
68		78
69	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
70	some messages. Messages send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
71	anything was listening for them or not.	81	anything was listening for them or not.
72		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
73	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
74		86
75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
76	separator, and a port name (a printable string of unspecified format).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
77		90
78	=item node	91	=item node
79		92
80	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
81	which enables nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
82	ports.	95	ports.
83		96
84	Nodes are either public (have one or more listening ports) or private	97	Nodes are either public (have one or more listening ports) or private
85	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
86	currently.	99	currently, but all nodes can talk to public nodes.
87		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
88	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
89		104
90	A node ID is a string that uniquely identifies the node within a	105	A node ID is a string that uniquely identifies the node within a
91	network. Depending on the configuration used, node IDs can look like a	106	network. Depending on the configuration used, node IDs can look like a
92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
93	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
94		109
95	=item binds - C<ip:port>	110	=item binds - C<ip:port>
96		111
97	Nodes can only talk to each other by creating some kind of connection to	112	Nodes can only talk to each other by creating some kind of connection to
98	each other. To do this, nodes should listen on one or more local transport	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
99	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
100	be used, which specify TCP ports to listen on.	117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
101		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
102	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
103		150
104	When a node starts, it knows nothing about the network. To teach the node	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
105	about the network it first has to contact some other node within the	152	TCP port) of nodes that should be used as seed nodes.
106	network. This node is called a seed.
107		153
108	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
109	are expected to be long-running, and at least one of those should always
110	be available. When nodes run out of connections (e.g. due to a network
111	error), they try to re-establish connections to some seednodes again to
112	join the network.
113		155
114	Apart from being sued for seeding, seednodes are not special in any way -	156	An AEMP network needs a discovery service - nodes need to know how to
115	every public node can be a seednode.	157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
116		170
117	=back	171	=back
118		172
119	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
120		174
…		…
122		176
123	=cut	177	=cut
124		178
125	package AnyEvent::MP;	179	package AnyEvent::MP;
126		180
		181	use AnyEvent::MP::Config ();
127	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
128		184
129	use common::sense;	185	use common::sense;
130		186
131	use Carp ();	187	use Carp ();
132		188
133	use AE ();	189	use AE ();
		190	use Guard ();
134		191
135	use base "Exporter";	192	use base "Exporter";
136		193
137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
138		195
139	our @EXPORT = qw(	196	our @EXPORT = qw(
140	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
141	configure	198	configure
142	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
143	port	200	port
		201	db_set db_del db_reg
144	);	202	);
145		203
146	our $SELF;	204	our $SELF;
147		205
148	sub _self_die() {	206	sub _self_die() {
…		…
171	some other nodes in the network to discover other nodes.	229	some other nodes in the network to discover other nodes.
172		230
173	This function configures a node - it must be called exactly once (or	231	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
175		233
		234	The key/value pairs are basically the same ones as documented for the
		235	F<aemp> command line utility (sans the set/del prefix), with two additions:
		236
		237	=over 4
		238
		239	=item norc => $boolean (default false)
		240
		241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		242	be consulted - all configuraiton options must be specified in the
		243	C<configure> call.
		244
		245	=item force => $boolean (default false)
		246
		247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
		250
		251	=back
		252
176	=over 4	253	=over 4
177		254
178	=item step 1, gathering configuration from profiles	255	=item step 1, gathering configuration from profiles
179		256
180	The function first looks up a profile in the aemp configuration (see the	257	The function first looks up a profile in the aemp configuration (see the
…		…
193	That means that the values specified in the profile have highest priority	270	That means that the values specified in the profile have highest priority
194	and the values specified directly via C<configure> have lowest priority,	271	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	272	and can only be used to specify defaults.
196		273
197	If the profile specifies a node ID, then this will become the node ID of	274	If the profile specifies a node ID, then this will become the node ID of
198	this process. If not, then the profile name will be used as node ID. The	275	this process. If not, then the profile name will be used as node ID, with
199	special node ID of C<anon/> will be replaced by a random node ID.	276	a unique randoms tring (C</%u>) appended.
		277
		278	The node ID can contain some C<%> sequences that are expanded: C<%n>
		279	is expanded to the local nodename, C<%u> is replaced by a random
		280	strign to make the node unique. For example, the F<aemp> commandline
		281	utility uses C<aemp/%n/%u> as nodename, which might expand to
		282	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
200		283
201	=item step 2, bind listener sockets	284	=item step 2, bind listener sockets
202		285
203	The next step is to look up the binds in the profile, followed by binding	286	The next step is to look up the binds in the profile, followed by binding
204	aemp protocol listeners on all binds specified (it is possible and valid	287	aemp protocol listeners on all binds specified (it is possible and valid
…		…
210	used, meaning the node will bind on a dynamically-assigned port on every	293	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	294	local IP address it finds.
212		295
213	=item step 3, connect to seed nodes	296	=item step 3, connect to seed nodes
214		297
215	As the last step, the seeds list from the profile is passed to the	298	As the last step, the seed ID list from the profile is passed to the
216	L<AnyEvent::MP::Global> module, which will then use it to keep	299	L<AnyEvent::MP::Global> module, which will then use it to keep
217	connectivity with at least one node at any point in time.	300	connectivity with at least one node at any point in time.
218		301
219	=back	302	=back
220		303
221	Example: become a distributed node using the locla node name as profile.	304	Example: become a distributed node using the local node name as profile.
222	This should be the most common form of invocation for "daemon"-type nodes.	305	This should be the most common form of invocation for "daemon"-type nodes.
223		306
224	configure	307	configure
225		308
226	Example: become an anonymous node. This form is often used for commandline	309	Example: become a semi-anonymous node. This form is often used for
227	clients.	310	commandline clients.
228		311
229	configure nodeid => "anon/";	312	configure nodeid => "myscript/%n/%u";
230		313
231	Example: configure a node using a profile called seed, which si suitable	314	Example: configure a node using a profile called seed, which is suitable
232	for a seed node as it binds on all local addresses on a fixed port (4040,	315	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	316	customary for aemp).
234		317
235	# use the aemp commandline utility	318	# use the aemp commandline utility
236	# aemp profile seed nodeid anon/ binds '*:4040'	319	# aemp profile seed binds '*:4040'
237		320
238	# then use it	321	# then use it
239	configure profile => "seed";	322	configure profile => "seed";
240		323
241	# or simply use aemp from the shell again:	324	# or simply use aemp from the shell again:
…		…
311	sub _kilme {	394	sub _kilme {
312	die "received message on port without callback";	395	die "received message on port without callback";
313	}	396	}
314		397
315	sub port(;&) {	398	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	399	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	400	my $port = "$NODE#$id";
318		401
319	rcv $port, shift \|\| \&_kilme;	402	rcv $port, shift \|\| \&_kilme;
320		403
321	$port	404	$port
…		…
360	msg1 => sub { ... },	443	msg1 => sub { ... },
361	...	444	...
362	;	445	;
363		446
364	Example: temporarily register a rcv callback for a tag matching some port	447	Example: temporarily register a rcv callback for a tag matching some port
365	(e.g. for a rpc reply) and unregister it after a message was received.	448	(e.g. for an rpc reply) and unregister it after a message was received.
366		449
367	rcv $port, $otherport => sub {	450	rcv $port, $otherport => sub {
368	my @reply = @_;	451	my @reply = @_;
369		452
370	rcv $SELF, $otherport;	453	rcv $SELF, $otherport;
…		…
383	if (ref $_[0]) {	466	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	467	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	468	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	469	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387		470
388	$self->[2] = shift;	471	$self->[0] = shift;
389	} else {	472	} else {
390	my $cb = shift;	473	my $cb = shift;
391	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
392	local $SELF = $port;	475	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	476	eval { &$cb }; _self_die if $@;
394	};	477	};
395	}	478	}
396	} elsif (defined $_[0]) {	479	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	480	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	481	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		482
400	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
401	local $SELF = $port;	484	local $SELF = $port;
402		485
403	if (my $cb = $self->[1]{$_[0]}) {	486	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	508	}
426		509
427	$port	510	$port
428	}	511	}
429		512
		513	=item peval $port, $coderef[, @args]
		514
		515	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		516	when the code throews an exception the C<$port> will be killed.
		517
		518	Any remaining args will be passed to the callback. Any return values will
		519	be returned to the caller.
		520
		521	This is useful when you temporarily want to execute code in the context of
		522	a port.
		523
		524	Example: create a port and run some initialisation code in it's context.
		525
		526	my $port = port { ... };
		527
		528	peval $port, sub {
		529	init
		530	or die "unable to init";
		531	};
		532
		533	=cut
		534
		535	sub peval($$) {
		536	local $SELF = shift;
		537	my $cb = shift;
		538
		539	if (wantarray) {
		540	my @res = eval { &$cb };
		541	_self_die if $@;
		542	@res
		543	} else {
		544	my $res = eval { &$cb };
		545	_self_die if $@;
		546	$res
		547	}
		548	}
		549
430	=item $closure = psub { BLOCK }	550	=item $closure = psub { BLOCK }
431		551
432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	552	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
433	closure is executed, sets up the environment in the same way as in C<rcv>	553	closure is executed, sets up the environment in the same way as in C<rcv>
434	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	554	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		555
		556	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		557	BLOCK }, @_ } >>.
435		558
436	This is useful when you register callbacks from C<rcv> callbacks:	559	This is useful when you register callbacks from C<rcv> callbacks:
437		560
438	rcv delayed_reply => sub {	561	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	562	my ($delay, @reply) = @_;
…		…
512	delivered again.	635	delivered again.
513		636
514	Inter-host-connection timeouts and monitoring depend on the transport	637	Inter-host-connection timeouts and monitoring depend on the transport
515	used. The only transport currently implemented is TCP, and AnyEvent::MP	638	used. The only transport currently implemented is TCP, and AnyEvent::MP
516	relies on TCP to detect node-downs (this can take 10-15 minutes on a	639	relies on TCP to detect node-downs (this can take 10-15 minutes on a
517	non-idle connection, and usually around two hours for idle conenctions).	640	non-idle connection, and usually around two hours for idle connections).
518		641
519	This means that monitoring is good for program errors and cleaning up	642	This means that monitoring is good for program errors and cleaning up
520	stuff eventually, but they are no replacement for a timeout when you need	643	stuff eventually, but they are no replacement for a timeout when you need
521	to ensure some maximum latency.	644	to ensure some maximum latency.
522		645
…		…
554	}	677	}
555		678
556	$node->monitor ($port, $cb);	679	$node->monitor ($port, $cb);
557		680
558	defined wantarray	681	defined wantarray
559	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	682	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
560	}	683	}
561		684
562	=item $guard = mon_guard $port, $ref, $ref...	685	=item $guard = mon_guard $port, $ref, $ref...
563		686
564	Monitors the given C<$port> and keeps the passed references. When the port	687	Monitors the given C<$port> and keeps the passed references. When the port
…		…
587		710
588	=item kil $port[, @reason]	711	=item kil $port[, @reason]
589		712
590	Kill the specified port with the given C<@reason>.	713	Kill the specified port with the given C<@reason>.
591		714
592	If no C<@reason> is specified, then the port is killed "normally" (ports	715	If no C<@reason> is specified, then the port is killed "normally" -
593	monitoring other ports will not necessarily die because a port dies	716	monitor callback will be invoked, but the kil will not cause linked ports
594	"normally").	717	(C<mon $mport, $lport> form) to get killed.
595		718
596	Otherwise, linked ports get killed with the same reason (second form of	719	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
597	C<mon>, see above).	720	form) get killed with the same reason.
598		721
599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	722	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
600	will be reported as reason C<< die => $@ >>.	723	will be reported as reason C<< die => $@ >>.
601		724
602	Transport/communication errors are reported as C<< transport_error =>	725	Transport/communication errors are reported as C<< transport_error =>
…		…
621	the package, then the package above the package and so on (e.g.	744	the package, then the package above the package and so on (e.g.
622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	745	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
623	exists or it runs out of package names.	746	exists or it runs out of package names.
624		747
625	The init function is then called with the newly-created port as context	748	The init function is then called with the newly-created port as context
626	object (C<$SELF>) and the C<@initdata> values as arguments.	749	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		750	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		751	the port might not get created.
627		752
628	A common idiom is to pass a local port, immediately monitor the spawned	753	A common idiom is to pass a local port, immediately monitor the spawned
629	port, and in the remote init function, immediately monitor the passed	754	port, and in the remote init function, immediately monitor the passed
630	local port. This two-way monitoring ensures that both ports get cleaned up	755	local port. This two-way monitoring ensures that both ports get cleaned up
631	when there is a problem.	756	when there is a problem.
…		…
655		780
656	sub _spawn {	781	sub _spawn {
657	my $port = shift;	782	my $port = shift;
658	my $init = shift;	783	my $init = shift;
659		784
		785	# rcv will create the actual port
660	local $SELF = "$NODE#$port";	786	local $SELF = "$NODE#$port";
661	eval {	787	eval {
662	&{ load_func $init }	788	&{ load_func $init }
663	};	789	};
664	_self_die if $@;	790	_self_die if $@;
665	}	791	}
666		792
667	sub spawn(@) {	793	sub spawn(@) {
668	my ($nodeid, undef) = split /#/, shift, 2;	794	my ($nodeid, undef) = split /#/, shift, 2;
669		795
670	my $id = "$RUNIQ." . $ID++;	796	my $id = $RUNIQ . ++$ID;
671		797
672	$_[0] =~ /::/	798	$_[0] =~ /::/
673	or Carp::croak "spawn init function must be a fully-qualified name, caught";	799	or Carp::croak "spawn init function must be a fully-qualified name, caught";
674		800
675	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	801	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
676		802
677	"$nodeid#$id"	803	"$nodeid#$id"
678	}	804	}
		805
679		806
680	=item after $timeout, @msg	807	=item after $timeout, @msg
681		808
682	=item after $timeout, $callback	809	=item after $timeout, $callback
683		810
…		…
699	? $action[0]()	826	? $action[0]()
700	: snd @action;	827	: snd @action;
701	};	828	};
702	}	829	}
703		830
		831	=item cal $port, @msg, $callback[, $timeout]
		832
		833	A simple form of RPC - sends a message to the given C<$port> with the
		834	given contents (C<@msg>), but adds a reply port to the message.
		835
		836	The reply port is created temporarily just for the purpose of receiving
		837	the reply, and will be C<kil>ed when no longer needed.
		838
		839	A reply message sent to the port is passed to the C<$callback> as-is.
		840
		841	If an optional time-out (in seconds) is given and it is not C<undef>,
		842	then the callback will be called without any arguments after the time-out
		843	elapsed and the port is C<kil>ed.
		844
		845	If no time-out is given (or it is C<undef>), then the local port will
		846	monitor the remote port instead, so it eventually gets cleaned-up.
		847
		848	Currently this function returns the temporary port, but this "feature"
		849	might go in future versions unless you can make a convincing case that
		850	this is indeed useful for something.
		851
		852	=cut
		853
		854	sub cal(@) {
		855	my $timeout = ref $_[-1] ? undef : pop;
		856	my $cb = pop;
		857
		858	my $port = port {
		859	undef $timeout;
		860	kil $SELF;
		861	&$cb;
		862	};
		863
		864	if (defined $timeout) {
		865	$timeout = AE::timer $timeout, 0, sub {
		866	undef $timeout;
		867	kil $port;
		868	$cb->();
		869	};
		870	} else {
		871	mon $_[0], sub {
		872	kil $port;
		873	$cb->();
		874	};
		875	}
		876
		877	push @_, $port;
		878	&snd;
		879
		880	$port
		881	}
		882
		883	=back
		884
		885	=head1 DISTRIBUTED DATABASE
		886
		887	AnyEvent::MP comes with a simple distributed database. The database will
		888	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		889	the global nodes for their needs.
		890
		891	The database consists of a two-level hash - a hash contains a hash which
		892	contains values.
		893
		894	The top level hash key is called "family", and the second-level hash key
		895	is called "subkey" or simply "key".
		896
		897	The family must be alphanumeric, i.e. start with a letter and consist
		898	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		899	pretty much like Perl module names.
		900
		901	As the family namespace is global, it is recommended to prefix family names
		902	with the name of the application or module using it.
		903
		904	The subkeys must be non-empty strings, with no further restrictions.
		905
		906	The values should preferably be strings, but other perl scalars should
		907	work as well (such as undef, arrays and hashes).
		908
		909	Every database entry is owned by one node - adding the same family/subkey
		910	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		911	but the result might be nondeterministic, i.e. the key might have
		912	different values on different nodes.
		913
		914	Different subkeys in the same family can be owned by different nodes
		915	without problems, and in fact, this is the common method to create worker
		916	pools. For example, a worker port for image scaling might do this:
		917
		918	db_set my_image_scalers => $port;
		919
		920	And clients looking for an image scaler will want to get the
		921	C<my_image_scalers> keys:
		922
		923	db_keys "my_image_scalers" => 60 => sub {
		924	#d##TODO#
		925
		926	=over
		927
		928	=item db_set $family => $subkey [=> $value]
		929
		930	Sets (or replaces) a key to the database - if C<$value> is omitted,
		931	C<undef> is used instead.
		932
		933	=item db_del $family => $subkey
		934
		935	Deletes a key from the database.
		936
		937	=item $guard = db_reg $family => $subkey [=> $value]
		938
		939	Sets the key on the database and returns a guard. When the guard is
		940	destroyed, the key is deleted from the database. If C<$value> is missing,
		941	then C<undef> is used.
		942
		943	=cut
		944
704	=back	945	=back
705		946
706	=head1 AnyEvent::MP vs. Distributed Erlang	947	=head1 AnyEvent::MP vs. Distributed Erlang
707		948
708	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	949	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
709	== aemp node, Erlang process == aemp port), so many of the documents and	950	== aemp node, Erlang process == aemp port), so many of the documents and
710	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	951	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
711	sample:	952	sample:
712		953
713	http://www.Erlang.se/doc/programming_rules.shtml	954	http://www.erlang.se/doc/programming_rules.shtml
714	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	955	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
715	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	956	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
716	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	957	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
717		958
718	Despite the similarities, there are also some important differences:	959	Despite the similarities, there are also some important differences:
719		960
720	=over 4	961	=over 4
721		962
722	=item * Node IDs are arbitrary strings in AEMP.	963	=item * Node IDs are arbitrary strings in AEMP.
723		964
724	Erlang relies on special naming and DNS to work everywhere in the same	965	Erlang relies on special naming and DNS to work everywhere in the same
725	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	966	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
726	configuration or DNS), but will otherwise discover other odes itself.	967	configuration or DNS), and possibly the addresses of some seed nodes, but
		968	will otherwise discover other nodes (and their IDs) itself.
727		969
728	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	970	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
729	uses "local ports are like remote ports".	971	uses "local ports are like remote ports".
730		972
731	The failure modes for local ports are quite different (runtime errors	973	The failure modes for local ports are quite different (runtime errors
…		…
740	ports being the special case/exception, where transport errors cannot	982	ports being the special case/exception, where transport errors cannot
741	occur.	983	occur.
742		984
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	985	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		986
745	Erlang uses processes that selectively receive messages, and therefore	987	Erlang uses processes that selectively receive messages out of order, and
746	needs a queue. AEMP is event based, queuing messages would serve no	988	therefore needs a queue. AEMP is event based, queuing messages would serve
747	useful purpose. For the same reason the pattern-matching abilities of	989	no useful purpose. For the same reason the pattern-matching abilities
748	AnyEvent::MP are more limited, as there is little need to be able to	990	of AnyEvent::MP are more limited, as there is little need to be able to
749	filter messages without dequeuing them.	991	filter messages without dequeuing them.
750		992
751	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	993	This is not a philosophical difference, but simply stems from AnyEvent::MP
		994	being event-based, while Erlang is process-based.
		995
		996	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		997	top of AEMP and Coro threads.
752		998
753	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	999	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
754		1000
755	Sending messages in Erlang is synchronous and blocks the process (and	1001	Sending messages in Erlang is synchronous and blocks the process until
		1002	a conenction has been established and the message sent (and so does not
756	so does not need a queue that can overflow). AEMP sends are immediate,	1003	need a queue that can overflow). AEMP sends return immediately, connection
757	connection establishment is handled in the background.	1004	establishment is handled in the background.
758		1005
759	=item * Erlang suffers from silent message loss, AEMP does not.	1006	=item * Erlang suffers from silent message loss, AEMP does not.
760		1007
761	Erlang makes few guarantees on messages delivery - messages can get lost	1008	Erlang implements few guarantees on messages delivery - messages can get
762	without any of the processes realising it (i.e. you send messages a, b,	1009	lost without any of the processes realising it (i.e. you send messages a,
763	and c, and the other side only receives messages a and c).	1010	b, and c, and the other side only receives messages a and c).
764		1011
765	AEMP guarantees correct ordering, and the guarantee that after one message	1012	AEMP guarantees (modulo hardware errors) correct ordering, and the
766	is lost, all following ones sent to the same port are lost as well, until	1013	guarantee that after one message is lost, all following ones sent to the
767	monitoring raises an error, so there are no silent "holes" in the message	1014	same port are lost as well, until monitoring raises an error, so there are
768	sequence.	1015	no silent "holes" in the message sequence.
		1016
		1017	If you want your software to be very reliable, you have to cope with
		1018	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1019	simply tries to work better in common error cases, such as when a network
		1020	link goes down.
769		1021
770	=item * Erlang can send messages to the wrong port, AEMP does not.	1022	=item * Erlang can send messages to the wrong port, AEMP does not.
771		1023
772	In Erlang it is quite likely that a node that restarts reuses a process ID	1024	In Erlang it is quite likely that a node that restarts reuses an Erlang
773	known to other nodes for a completely different process, causing messages	1025	process ID known to other nodes for a completely different process,
774	destined for that process to end up in an unrelated process.	1026	causing messages destined for that process to end up in an unrelated
		1027	process.
775		1028
776	AEMP never reuses port IDs, so old messages or old port IDs floating	1029	AEMP does not reuse port IDs, so old messages or old port IDs floating
777	around in the network will not be sent to an unrelated port.	1030	around in the network will not be sent to an unrelated port.
778		1031
779	=item * Erlang uses unprotected connections, AEMP uses secure	1032	=item * Erlang uses unprotected connections, AEMP uses secure
780	authentication and can use TLS.	1033	authentication and can use TLS.
781		1034
…		…
784		1037
785	=item * The AEMP protocol is optimised for both text-based and binary	1038	=item * The AEMP protocol is optimised for both text-based and binary
786	communications.	1039	communications.
787		1040
788	The AEMP protocol, unlike the Erlang protocol, supports both programming	1041	The AEMP protocol, unlike the Erlang protocol, supports both programming
789	language independent text-only protocols (good for debugging) and binary,	1042	language independent text-only protocols (good for debugging), and binary,
790	language-specific serialisers (e.g. Storable). By default, unless TLS is	1043	language-specific serialisers (e.g. Storable). By default, unless TLS is
791	used, the protocol is actually completely text-based.	1044	used, the protocol is actually completely text-based.
792		1045
793	It has also been carefully designed to be implementable in other languages	1046	It has also been carefully designed to be implementable in other languages
794	with a minimum of work while gracefully degrading functionality to make the	1047	with a minimum of work while gracefully degrading functionality to make the
795	protocol simple.	1048	protocol simple.
796		1049
797	=item * AEMP has more flexible monitoring options than Erlang.	1050	=item * AEMP has more flexible monitoring options than Erlang.
798		1051
799	In Erlang, you can chose to receive I<all> exit signals as messages	1052	In Erlang, you can chose to receive I<all> exit signals as messages or
800	or I<none>, there is no in-between, so monitoring single processes is	1053	I<none>, there is no in-between, so monitoring single Erlang processes is
801	difficult to implement. Monitoring in AEMP is more flexible than in	1054	difficult to implement.
802	Erlang, as one can choose between automatic kill, exit message or callback	1055
803	on a per-process basis.	1056	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1057	between automatic kill, exit message or callback on a per-port basis.
804		1058
805	=item * Erlang tries to hide remote/local connections, AEMP does not.	1059	=item * Erlang tries to hide remote/local connections, AEMP does not.
806		1060
807	Monitoring in Erlang is not an indicator of process death/crashes, in the	1061	Monitoring in Erlang is not an indicator of process death/crashes, in the
808	same way as linking is (except linking is unreliable in Erlang).	1062	same way as linking is (except linking is unreliable in Erlang).
…		…
830	overhead, as well as having to keep a proxy object everywhere.	1084	overhead, as well as having to keep a proxy object everywhere.
831		1085
832	Strings can easily be printed, easily serialised etc. and need no special	1086	Strings can easily be printed, easily serialised etc. and need no special
833	procedures to be "valid".	1087	procedures to be "valid".
834		1088
835	And as a result, a miniport consists of a single closure stored in a	1089	And as a result, a port with just a default receiver consists of a single
836	global hash - it can't become much cheaper.	1090	code reference stored in a global hash - it can't become much cheaper.
837		1091
838	=item Why favour JSON, why not a real serialising format such as Storable?	1092	=item Why favour JSON, why not a real serialising format such as Storable?
839		1093
840	In fact, any AnyEvent::MP node will happily accept Storable as framing	1094	In fact, any AnyEvent::MP node will happily accept Storable as framing
841	format, but currently there is no way to make a node use Storable by	1095	format, but currently there is no way to make a node use Storable by
…		…
857		1111
858	L<AnyEvent::MP::Intro> - a gentle introduction.	1112	L<AnyEvent::MP::Intro> - a gentle introduction.
859		1113
860	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1114	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
861		1115
862	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1116	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
863	your applications.	1117	your applications.
		1118
		1119	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1120
		1121	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1122	all nodes.
864		1123
865	L<AnyEvent>.	1124	L<AnyEvent>.
866		1125
867	=head1 AUTHOR	1126	=head1 AUTHOR
868		1127

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Revision 1.80 by root, Fri Sep 4 22:30:29 2009 UTC vs.
Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC