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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 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 these 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	=item secure => $pass->($nodeid)
		252
		253	In addition to specifying a boolean, you can specify a code reference that
		254	is called for every remote execution attempt - the execution request is
		255	granted iff the callback returns a true value.
		256
		257	See F<semp setsecure> for more info.
		258
		259	=back
		260
176	=over 4	261	=over 4
177		262
178	=item step 1, gathering configuration from profiles	263	=item step 1, gathering configuration from profiles
179		264
180	The function first looks up a profile in the aemp configuration (see the	265	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	278	That means that the values specified in the profile have highest priority
194	and the values specified directly via C<configure> have lowest priority,	279	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	280	and can only be used to specify defaults.
196		281
197	If the profile specifies a node ID, then this will become the node ID of	282	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	283	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.	284	a unique randoms tring (C</%u>) appended.
		285
		286	The node ID can contain some C<%> sequences that are expanded: C<%n>
		287	is expanded to the local nodename, C<%u> is replaced by a random
		288	strign to make the node unique. For example, the F<aemp> commandline
		289	utility uses C<aemp/%n/%u> as nodename, which might expand to
		290	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
200		291
201	=item step 2, bind listener sockets	292	=item step 2, bind listener sockets
202		293
203	The next step is to look up the binds in the profile, followed by binding	294	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	295	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	301	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	302	local IP address it finds.
212		303
213	=item step 3, connect to seed nodes	304	=item step 3, connect to seed nodes
214		305
215	As the last step, the seeds list from the profile is passed to the	306	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	307	L<AnyEvent::MP::Global> module, which will then use it to keep
217	connectivity with at least one node at any point in time.	308	connectivity with at least one node at any point in time.
218		309
219	=back	310	=back
220		311
221	Example: become a distributed node using the locla node name as profile.	312	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.	313	This should be the most common form of invocation for "daemon"-type nodes.
223		314
224	configure	315	configure
225		316
226	Example: become an anonymous node. This form is often used for commandline	317	Example: become a semi-anonymous node. This form is often used for
227	clients.	318	commandline clients.
228		319
229	configure nodeid => "anon/";	320	configure nodeid => "myscript/%n/%u";
230		321
231	Example: configure a node using a profile called seed, which si suitable	322	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,	323	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	324	customary for aemp).
234		325
235	# use the aemp commandline utility	326	# use the aemp commandline utility
236	# aemp profile seed nodeid anon/ binds '*:4040'	327	# aemp profile seed binds '*:4040'
237		328
238	# then use it	329	# then use it
239	configure profile => "seed";	330	configure profile => "seed";
240		331
241	# or simply use aemp from the shell again:	332	# or simply use aemp from the shell again:
…		…
311	sub _kilme {	402	sub _kilme {
312	die "received message on port without callback";	403	die "received message on port without callback";
313	}	404	}
314		405
315	sub port(;&) {	406	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	407	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	408	my $port = "$NODE#$id";
318		409
319	rcv $port, shift \|\| \&_kilme;	410	rcv $port, shift \|\| \&_kilme;
320		411
321	$port	412	$port
…		…
360	msg1 => sub { ... },	451	msg1 => sub { ... },
361	...	452	...
362	;	453	;
363		454
364	Example: temporarily register a rcv callback for a tag matching some port	455	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.	456	(e.g. for an rpc reply) and unregister it after a message was received.
366		457
367	rcv $port, $otherport => sub {	458	rcv $port, $otherport => sub {
368	my @reply = @_;	459	my @reply = @_;
369		460
370	rcv $SELF, $otherport;	461	rcv $SELF, $otherport;
…		…
383	if (ref $_[0]) {	474	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	475	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	476	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	477	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387		478
388	$self->[2] = shift;	479	$self->[0] = shift;
389	} else {	480	} else {
390	my $cb = shift;	481	my $cb = shift;
391	$PORT{$portid} = sub {	482	$PORT{$portid} = sub {
392	local $SELF = $port;	483	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	484	eval { &$cb }; _self_die if $@;
394	};	485	};
395	}	486	}
396	} elsif (defined $_[0]) {	487	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	488	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	489	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		490
400	$PORT{$portid} = sub {	491	$PORT{$portid} = sub {
401	local $SELF = $port;	492	local $SELF = $port;
402		493
403	if (my $cb = $self->[1]{$_[0]}) {	494	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	516	}
426		517
427	$port	518	$port
428	}	519	}
429		520
		521	=item peval $port, $coderef[, @args]
		522
		523	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		524	when the code throews an exception the C<$port> will be killed.
		525
		526	Any remaining args will be passed to the callback. Any return values will
		527	be returned to the caller.
		528
		529	This is useful when you temporarily want to execute code in the context of
		530	a port.
		531
		532	Example: create a port and run some initialisation code in it's context.
		533
		534	my $port = port { ... };
		535
		536	peval $port, sub {
		537	init
		538	or die "unable to init";
		539	};
		540
		541	=cut
		542
		543	sub peval($$) {
		544	local $SELF = shift;
		545	my $cb = shift;
		546
		547	if (wantarray) {
		548	my @res = eval { &$cb };
		549	_self_die if $@;
		550	@res
		551	} else {
		552	my $res = eval { &$cb };
		553	_self_die if $@;
		554	$res
		555	}
		556	}
		557
430	=item $closure = psub { BLOCK }	558	=item $closure = psub { BLOCK }
431		559
432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	560	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>	561	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.	562	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		563
		564	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		565	BLOCK }, @_ } >>.
435		566
436	This is useful when you register callbacks from C<rcv> callbacks:	567	This is useful when you register callbacks from C<rcv> callbacks:
437		568
438	rcv delayed_reply => sub {	569	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	570	my ($delay, @reply) = @_;
…		…
512	delivered again.	643	delivered again.
513		644
514	Inter-host-connection timeouts and monitoring depend on the transport	645	Inter-host-connection timeouts and monitoring depend on the transport
515	used. The only transport currently implemented is TCP, and AnyEvent::MP	646	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	647	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).	648	non-idle connection, and usually around two hours for idle connections).
518		649
519	This means that monitoring is good for program errors and cleaning up	650	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	651	stuff eventually, but they are no replacement for a timeout when you need
521	to ensure some maximum latency.	652	to ensure some maximum latency.
522		653
…		…
554	}	685	}
555		686
556	$node->monitor ($port, $cb);	687	$node->monitor ($port, $cb);
557		688
558	defined wantarray	689	defined wantarray
559	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	690	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
560	}	691	}
561		692
562	=item $guard = mon_guard $port, $ref, $ref...	693	=item $guard = mon_guard $port, $ref, $ref...
563		694
564	Monitors the given C<$port> and keeps the passed references. When the port	695	Monitors the given C<$port> and keeps the passed references. When the port
…		…
587		718
588	=item kil $port[, @reason]	719	=item kil $port[, @reason]
589		720
590	Kill the specified port with the given C<@reason>.	721	Kill the specified port with the given C<@reason>.
591		722
592	If no C<@reason> is specified, then the port is killed "normally" (ports	723	If no C<@reason> is specified, then the port is killed "normally" -
593	monitoring other ports will not necessarily die because a port dies	724	monitor callback will be invoked, but the kil will not cause linked ports
594	"normally").	725	(C<mon $mport, $lport> form) to get killed.
595		726
596	Otherwise, linked ports get killed with the same reason (second form of	727	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
597	C<mon>, see above).	728	form) get killed with the same reason.
598		729
599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	730	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
600	will be reported as reason C<< die => $@ >>.	731	will be reported as reason C<< die => $@ >>.
601		732
602	Transport/communication errors are reported as C<< transport_error =>	733	Transport/communication errors are reported as C<< transport_error =>
…		…
668	}	799	}
669		800
670	sub spawn(@) {	801	sub spawn(@) {
671	my ($nodeid, undef) = split /#/, shift, 2;	802	my ($nodeid, undef) = split /#/, shift, 2;
672		803
673	my $id = "$RUNIQ." . $ID++;	804	my $id = $RUNIQ . ++$ID;
674		805
675	$_[0] =~ /::/	806	$_[0] =~ /::/
676	or Carp::croak "spawn init function must be a fully-qualified name, caught";	807	or Carp::croak "spawn init function must be a fully-qualified name, caught";
677		808
678	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	809	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679		810
680	"$nodeid#$id"	811	"$nodeid#$id"
681	}	812	}
		813
682		814
683	=item after $timeout, @msg	815	=item after $timeout, @msg
684		816
685	=item after $timeout, $callback	817	=item after $timeout, $callback
686		818
…		…
702	? $action[0]()	834	? $action[0]()
703	: snd @action;	835	: snd @action;
704	};	836	};
705	}	837	}
706		838
		839	=item cal $port, @msg, $callback[, $timeout]
		840
		841	A simple form of RPC - sends a message to the given C<$port> with the
		842	given contents (C<@msg>), but adds a reply port to the message.
		843
		844	The reply port is created temporarily just for the purpose of receiving
		845	the reply, and will be C<kil>ed when no longer needed.
		846
		847	A reply message sent to the port is passed to the C<$callback> as-is.
		848
		849	If an optional time-out (in seconds) is given and it is not C<undef>,
		850	then the callback will be called without any arguments after the time-out
		851	elapsed and the port is C<kil>ed.
		852
		853	If no time-out is given (or it is C<undef>), then the local port will
		854	monitor the remote port instead, so it eventually gets cleaned-up.
		855
		856	Currently this function returns the temporary port, but this "feature"
		857	might go in future versions unless you can make a convincing case that
		858	this is indeed useful for something.
		859
		860	=cut
		861
		862	sub cal(@) {
		863	my $timeout = ref $_[-1] ? undef : pop;
		864	my $cb = pop;
		865
		866	my $port = port {
		867	undef $timeout;
		868	kil $SELF;
		869	&$cb;
		870	};
		871
		872	if (defined $timeout) {
		873	$timeout = AE::timer $timeout, 0, sub {
		874	undef $timeout;
		875	kil $port;
		876	$cb->();
		877	};
		878	} else {
		879	mon $_[0], sub {
		880	kil $port;
		881	$cb->();
		882	};
		883	}
		884
		885	push @_, $port;
		886	&snd;
		887
		888	$port
		889	}
		890
		891	=back
		892
		893	=head1 DISTRIBUTED DATABASE
		894
		895	AnyEvent::MP comes with a simple distributed database. The database will
		896	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		897	the global nodes for their needs.
		898
		899	The database consists of a two-level hash - a hash contains a hash which
		900	contains values.
		901
		902	The top level hash key is called "family", and the second-level hash key
		903	is called "subkey" or simply "key".
		904
		905	The family must be alphanumeric, i.e. start with a letter and consist
		906	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		907	pretty much like Perl module names.
		908
		909	As the family namespace is global, it is recommended to prefix family names
		910	with the name of the application or module using it.
		911
		912	The subkeys must be non-empty strings, with no further restrictions.
		913
		914	The values should preferably be strings, but other perl scalars should
		915	work as well (such as undef, arrays and hashes).
		916
		917	Every database entry is owned by one node - adding the same family/subkey
		918	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		919	but the result might be nondeterministic, i.e. the key might have
		920	different values on different nodes.
		921
		922	Different subkeys in the same family can be owned by different nodes
		923	without problems, and in fact, this is the common method to create worker
		924	pools. For example, a worker port for image scaling might do this:
		925
		926	db_set my_image_scalers => $port;
		927
		928	And clients looking for an image scaler will want to get the
		929	C<my_image_scalers> keys:
		930
		931	db_keys "my_image_scalers" => 60 => sub {
		932	#d##TODO#
		933
		934	=over
		935
		936	=item db_set $family => $subkey [=> $value]
		937
		938	Sets (or replaces) a key to the database - if C<$value> is omitted,
		939	C<undef> is used instead.
		940
		941	=item db_del $family => $subkey
		942
		943	Deletes a key from the database.
		944
		945	=item $guard = db_reg $family => $subkey [=> $value]
		946
		947	Sets the key on the database and returns a guard. When the guard is
		948	destroyed, the key is deleted from the database. If C<$value> is missing,
		949	then C<undef> is used.
		950
		951	=cut
		952
707	=back	953	=back
708		954
709	=head1 AnyEvent::MP vs. Distributed Erlang	955	=head1 AnyEvent::MP vs. Distributed Erlang
710		956
711	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	957	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
712	== aemp node, Erlang process == aemp port), so many of the documents and	958	== aemp node, Erlang process == aemp port), so many of the documents and
713	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	959	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
714	sample:	960	sample:
715		961
716	http://www.Erlang.se/doc/programming_rules.shtml	962	http://www.erlang.se/doc/programming_rules.shtml
717	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	963	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
718	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	964	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
719	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	965	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
720		966
721	Despite the similarities, there are also some important differences:	967	Despite the similarities, there are also some important differences:
722		968
723	=over 4	969	=over 4
724		970
725	=item * Node IDs are arbitrary strings in AEMP.	971	=item * Node IDs are arbitrary strings in AEMP.
726		972
727	Erlang relies on special naming and DNS to work everywhere in the same	973	Erlang relies on special naming and DNS to work everywhere in the same
728	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	974	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
729	configuration or DNS), but will otherwise discover other odes itself.	975	configuration or DNS), and possibly the addresses of some seed nodes, but
		976	will otherwise discover other nodes (and their IDs) itself.
730		977
731	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	978	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
732	uses "local ports are like remote ports".	979	uses "local ports are like remote ports".
733		980
734	The failure modes for local ports are quite different (runtime errors	981	The failure modes for local ports are quite different (runtime errors
…		…
743	ports being the special case/exception, where transport errors cannot	990	ports being the special case/exception, where transport errors cannot
744	occur.	991	occur.
745		992
746	=item * Erlang uses processes and a mailbox, AEMP does not queue.	993	=item * Erlang uses processes and a mailbox, AEMP does not queue.
747		994
748	Erlang uses processes that selectively receive messages, and therefore	995	Erlang uses processes that selectively receive messages out of order, and
749	needs a queue. AEMP is event based, queuing messages would serve no	996	therefore needs a queue. AEMP is event based, queuing messages would serve
750	useful purpose. For the same reason the pattern-matching abilities of	997	no useful purpose. For the same reason the pattern-matching abilities
751	AnyEvent::MP are more limited, as there is little need to be able to	998	of AnyEvent::MP are more limited, as there is little need to be able to
752	filter messages without dequeuing them.	999	filter messages without dequeuing them.
753		1000
754	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1001	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1002	being event-based, while Erlang is process-based.
		1003
		1004	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1005	top of AEMP and Coro threads.
755		1006
756	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1007	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
757		1008
758	Sending messages in Erlang is synchronous and blocks the process (and	1009	Sending messages in Erlang is synchronous and blocks the process until
		1010	a conenction has been established and the message sent (and so does not
759	so does not need a queue that can overflow). AEMP sends are immediate,	1011	need a queue that can overflow). AEMP sends return immediately, connection
760	connection establishment is handled in the background.	1012	establishment is handled in the background.
761		1013
762	=item * Erlang suffers from silent message loss, AEMP does not.	1014	=item * Erlang suffers from silent message loss, AEMP does not.
763		1015
764	Erlang makes few guarantees on messages delivery - messages can get lost	1016	Erlang implements few guarantees on messages delivery - messages can get
765	without any of the processes realising it (i.e. you send messages a, b,	1017	lost without any of the processes realising it (i.e. you send messages a,
766	and c, and the other side only receives messages a and c).	1018	b, and c, and the other side only receives messages a and c).
767		1019
768	AEMP guarantees correct ordering, and the guarantee that after one message	1020	AEMP guarantees (modulo hardware errors) correct ordering, and the
769	is lost, all following ones sent to the same port are lost as well, until	1021	guarantee that after one message is lost, all following ones sent to the
770	monitoring raises an error, so there are no silent "holes" in the message	1022	same port are lost as well, until monitoring raises an error, so there are
771	sequence.	1023	no silent "holes" in the message sequence.
		1024
		1025	If you want your software to be very reliable, you have to cope with
		1026	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1027	simply tries to work better in common error cases, such as when a network
		1028	link goes down.
772		1029
773	=item * Erlang can send messages to the wrong port, AEMP does not.	1030	=item * Erlang can send messages to the wrong port, AEMP does not.
774		1031
775	In Erlang it is quite likely that a node that restarts reuses a process ID	1032	In Erlang it is quite likely that a node that restarts reuses an Erlang
776	known to other nodes for a completely different process, causing messages	1033	process ID known to other nodes for a completely different process,
777	destined for that process to end up in an unrelated process.	1034	causing messages destined for that process to end up in an unrelated
		1035	process.
778		1036
779	AEMP never reuses port IDs, so old messages or old port IDs floating	1037	AEMP does not reuse port IDs, so old messages or old port IDs floating
780	around in the network will not be sent to an unrelated port.	1038	around in the network will not be sent to an unrelated port.
781		1039
782	=item * Erlang uses unprotected connections, AEMP uses secure	1040	=item * Erlang uses unprotected connections, AEMP uses secure
783	authentication and can use TLS.	1041	authentication and can use TLS.
784		1042
…		…
787		1045
788	=item * The AEMP protocol is optimised for both text-based and binary	1046	=item * The AEMP protocol is optimised for both text-based and binary
789	communications.	1047	communications.
790		1048
791	The AEMP protocol, unlike the Erlang protocol, supports both programming	1049	The AEMP protocol, unlike the Erlang protocol, supports both programming
792	language independent text-only protocols (good for debugging) and binary,	1050	language independent text-only protocols (good for debugging), and binary,
793	language-specific serialisers (e.g. Storable). By default, unless TLS is	1051	language-specific serialisers (e.g. Storable). By default, unless TLS is
794	used, the protocol is actually completely text-based.	1052	used, the protocol is actually completely text-based.
795		1053
796	It has also been carefully designed to be implementable in other languages	1054	It has also been carefully designed to be implementable in other languages
797	with a minimum of work while gracefully degrading functionality to make the	1055	with a minimum of work while gracefully degrading functionality to make the
798	protocol simple.	1056	protocol simple.
799		1057
800	=item * AEMP has more flexible monitoring options than Erlang.	1058	=item * AEMP has more flexible monitoring options than Erlang.
801		1059
802	In Erlang, you can chose to receive I<all> exit signals as messages	1060	In Erlang, you can chose to receive I<all> exit signals as messages or
803	or I<none>, there is no in-between, so monitoring single processes is	1061	I<none>, there is no in-between, so monitoring single Erlang processes is
804	difficult to implement. Monitoring in AEMP is more flexible than in	1062	difficult to implement.
805	Erlang, as one can choose between automatic kill, exit message or callback	1063
806	on a per-process basis.	1064	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1065	between automatic kill, exit message or callback on a per-port basis.
807		1066
808	=item * Erlang tries to hide remote/local connections, AEMP does not.	1067	=item * Erlang tries to hide remote/local connections, AEMP does not.
809		1068
810	Monitoring in Erlang is not an indicator of process death/crashes, in the	1069	Monitoring in Erlang is not an indicator of process death/crashes, in the
811	same way as linking is (except linking is unreliable in Erlang).	1070	same way as linking is (except linking is unreliable in Erlang).
…		…
833	overhead, as well as having to keep a proxy object everywhere.	1092	overhead, as well as having to keep a proxy object everywhere.
834		1093
835	Strings can easily be printed, easily serialised etc. and need no special	1094	Strings can easily be printed, easily serialised etc. and need no special
836	procedures to be "valid".	1095	procedures to be "valid".
837		1096
838	And as a result, a miniport consists of a single closure stored in a	1097	And as a result, a port with just a default receiver consists of a single
839	global hash - it can't become much cheaper.	1098	code reference stored in a global hash - it can't become much cheaper.
840		1099
841	=item Why favour JSON, why not a real serialising format such as Storable?	1100	=item Why favour JSON, why not a real serialising format such as Storable?
842		1101
843	In fact, any AnyEvent::MP node will happily accept Storable as framing	1102	In fact, any AnyEvent::MP node will happily accept Storable as framing
844	format, but currently there is no way to make a node use Storable by	1103	format, but currently there is no way to make a node use Storable by
…		…
860		1119
861	L<AnyEvent::MP::Intro> - a gentle introduction.	1120	L<AnyEvent::MP::Intro> - a gentle introduction.
862		1121
863	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1122	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
864		1123
865	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1124	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
866	your applications.	1125	your applications.
		1126
		1127	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
867		1128
868	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1129	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
869	all nodes.	1130	all nodes.
870		1131
871	L<AnyEvent>.	1132	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC vs. Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC