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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.83 by root, Tue Sep 8 01:38:16 2009 UTC vs.
Revision 1.125 by root, Sat Mar 3 13:07:19 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
102	=item seed nodes	120	=item seed nodes
103		121
104	When a node starts, it knows nothing about the network. To teach the node	122	When a node starts, it knows nothing about the network it is in - it
105	about the network it first has to contact some other node within the	123	needs to connect to at least one other node that is already in the
106	network. This node is called a seed.	124	network. These other nodes are called "seed nodes".
107		125
108	Apart from the fact that other nodes know them as seed nodes and they have	126	Seed nodes themselves are not special - they are seed nodes only because
109	to have fixed listening addresses, seed nodes are perfectly normal nodes -	127	some other node I<uses> them as such, but any node can be used as seed
110	any node can function as a seed node for others.	128	node for other nodes, and eahc node cna use a different set of seed nodes.
111		129
112	In addition to discovering the network, seed nodes are also used to	130	In addition to discovering the network, seed nodes are also used to
113	maintain the network and to connect nodes that otherwise would have	131	maintain the network - all nodes using the same seed node form are part of
114	trouble connecting. They form the backbone of the AnyEvent::MP network.	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.
115		135
116	Seed nodes are expected to be long-running, and at least one seed node	136	Seed nodes are expected to be long-running, and at least one seed node
117	should always be available.	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.
118		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
119	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
120		150
121	Seeds are transport endpoint(s) (usually a hostname/IP address and a	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
122	TCP port) of nodes thta should be used as seed nodes.	152	TCP port) of nodes that should be used as seed nodes.
123		153
124	The nodes listening on those endpoints are expected to be long-running,	154	=item global nodes
125	and at least one of those should always be available. When nodes run out	155
126	of connections (e.g. due to a network error), they try to re-establish	156	An AEMP network needs a discovery service - nodes need to know how to
127	connections to some seednodes again to join the network.	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).
128		170
129	=back	171	=back
130		172
131	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
132		174
…		…
134		176
135	=cut	177	=cut
136		178
137	package AnyEvent::MP;	179	package AnyEvent::MP;
138		180
		181	use AnyEvent::MP::Config ();
139	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
140		184
141	use common::sense;	185	use common::sense;
142		186
143	use Carp ();	187	use Carp ();
144		188
145	use AE ();	189	use AE ();
		190	use Guard ();
146		191
147	use base "Exporter";	192	use base "Exporter";
148		193
149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
150		195
151	our @EXPORT = qw(	196	our @EXPORT = qw(
152	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
153	configure	198	configure
154	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
155	port	200	port
		201	db_set db_del db_reg
156	);	202	);
157		203
158	our $SELF;	204	our $SELF;
159		205
160	sub _self_die() {	206	sub _self_die() {
…		…
183	some other nodes in the network to discover other nodes.	229	some other nodes in the network to discover other nodes.
184		230
185	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
186	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
187		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
188	=over 4	253	=over 4
189		254
190	=item step 1, gathering configuration from profiles	255	=item step 1, gathering configuration from profiles
191		256
192	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
…		…
205	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
206	and the values specified directly via C<configure> have lowest priority,	271	and the values specified directly via C<configure> have lowest priority,
207	and can only be used to specify defaults.	272	and can only be used to specify defaults.
208		273
209	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
210	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
211	special node ID of C<anon/> will be replaced by a random node ID.	276	a slash (C</>) attached.
		277
		278	If the node ID (or profile name) ends with a slash (C</>), then a random
		279	string is appended to make it unique.
212		280
213	=item step 2, bind listener sockets	281	=item step 2, bind listener sockets
214		282
215	The next step is to look up the binds in the profile, followed by binding	283	The next step is to look up the binds in the profile, followed by binding
216	aemp protocol listeners on all binds specified (it is possible and valid	284	aemp protocol listeners on all binds specified (it is possible and valid
…		…
222	used, meaning the node will bind on a dynamically-assigned port on every	290	used, meaning the node will bind on a dynamically-assigned port on every
223	local IP address it finds.	291	local IP address it finds.
224		292
225	=item step 3, connect to seed nodes	293	=item step 3, connect to seed nodes
226		294
227	As the last step, the seeds list from the profile is passed to the	295	As the last step, the seed ID list from the profile is passed to the
228	L<AnyEvent::MP::Global> module, which will then use it to keep	296	L<AnyEvent::MP::Global> module, which will then use it to keep
229	connectivity with at least one node at any point in time.	297	connectivity with at least one node at any point in time.
230		298
231	=back	299	=back
232		300
233	Example: become a distributed node using the locla node name as profile.	301	Example: become a distributed node using the local node name as profile.
234	This should be the most common form of invocation for "daemon"-type nodes.	302	This should be the most common form of invocation for "daemon"-type nodes.
235		303
236	configure	304	configure
237		305
238	Example: become an anonymous node. This form is often used for commandline	306	Example: become an anonymous node. This form is often used for commandline
239	clients.	307	clients.
240		308
241	configure nodeid => "anon/";	309	configure nodeid => "anon/";
242		310
243	Example: configure a node using a profile called seed, which si suitable	311	Example: configure a node using a profile called seed, which is suitable
244	for a seed node as it binds on all local addresses on a fixed port (4040,	312	for a seed node as it binds on all local addresses on a fixed port (4040,
245	customary for aemp).	313	customary for aemp).
246		314
247	# use the aemp commandline utility	315	# use the aemp commandline utility
248	# aemp profile seed nodeid anon/ binds '*:4040'	316	# aemp profile seed binds '*:4040'
249		317
250	# then use it	318	# then use it
251	configure profile => "seed";	319	configure profile => "seed";
252		320
253	# or simply use aemp from the shell again:	321	# or simply use aemp from the shell again:
…		…
323	sub _kilme {	391	sub _kilme {
324	die "received message on port without callback";	392	die "received message on port without callback";
325	}	393	}
326		394
327	sub port(;&) {	395	sub port(;&) {
328	my $id = "$UNIQ." . $ID++;	396	my $id = $UNIQ . ++$ID;
329	my $port = "$NODE#$id";	397	my $port = "$NODE#$id";
330		398
331	rcv $port, shift \|\| \&_kilme;	399	rcv $port, shift \|\| \&_kilme;
332		400
333	$port	401	$port
…		…
372	msg1 => sub { ... },	440	msg1 => sub { ... },
373	...	441	...
374	;	442	;
375		443
376	Example: temporarily register a rcv callback for a tag matching some port	444	Example: temporarily register a rcv callback for a tag matching some port
377	(e.g. for a rpc reply) and unregister it after a message was received.	445	(e.g. for an rpc reply) and unregister it after a message was received.
378		446
379	rcv $port, $otherport => sub {	447	rcv $port, $otherport => sub {
380	my @reply = @_;	448	my @reply = @_;
381		449
382	rcv $SELF, $otherport;	450	rcv $SELF, $otherport;
…		…
395	if (ref $_[0]) {	463	if (ref $_[0]) {
396	if (my $self = $PORT_DATA{$portid}) {	464	if (my $self = $PORT_DATA{$portid}) {
397	"AnyEvent::MP::Port" eq ref $self	465	"AnyEvent::MP::Port" eq ref $self
398	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	466	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
399		467
400	$self->[2] = shift;	468	$self->[0] = shift;
401	} else {	469	} else {
402	my $cb = shift;	470	my $cb = shift;
403	$PORT{$portid} = sub {	471	$PORT{$portid} = sub {
404	local $SELF = $port;	472	local $SELF = $port;
405	eval { &$cb }; _self_die if $@;	473	eval { &$cb }; _self_die if $@;
406	};	474	};
407	}	475	}
408	} elsif (defined $_[0]) {	476	} elsif (defined $_[0]) {
409	my $self = $PORT_DATA{$portid} \|\|= do {	477	my $self = $PORT_DATA{$portid} \|\|= do {
410	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	478	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
411		479
412	$PORT{$portid} = sub {	480	$PORT{$portid} = sub {
413	local $SELF = $port;	481	local $SELF = $port;
414		482
415	if (my $cb = $self->[1]{$_[0]}) {	483	if (my $cb = $self->[1]{$_[0]}) {
…		…
437	}	505	}
438		506
439	$port	507	$port
440	}	508	}
441		509
		510	=item peval $port, $coderef[, @args]
		511
		512	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		513	when the code throews an exception the C<$port> will be killed.
		514
		515	Any remaining args will be passed to the callback. Any return values will
		516	be returned to the caller.
		517
		518	This is useful when you temporarily want to execute code in the context of
		519	a port.
		520
		521	Example: create a port and run some initialisation code in it's context.
		522
		523	my $port = port { ... };
		524
		525	peval $port, sub {
		526	init
		527	or die "unable to init";
		528	};
		529
		530	=cut
		531
		532	sub peval($$) {
		533	local $SELF = shift;
		534	my $cb = shift;
		535
		536	if (wantarray) {
		537	my @res = eval { &$cb };
		538	_self_die if $@;
		539	@res
		540	} else {
		541	my $res = eval { &$cb };
		542	_self_die if $@;
		543	$res
		544	}
		545	}
		546
442	=item $closure = psub { BLOCK }	547	=item $closure = psub { BLOCK }
443		548
444	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	549	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
445	closure is executed, sets up the environment in the same way as in C<rcv>	550	closure is executed, sets up the environment in the same way as in C<rcv>
446	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	551	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		552
		553	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		554	BLOCK }, @_ } >>.
447		555
448	This is useful when you register callbacks from C<rcv> callbacks:	556	This is useful when you register callbacks from C<rcv> callbacks:
449		557
450	rcv delayed_reply => sub {	558	rcv delayed_reply => sub {
451	my ($delay, @reply) = @_;	559	my ($delay, @reply) = @_;
…		…
524	delivered again.	632	delivered again.
525		633
526	Inter-host-connection timeouts and monitoring depend on the transport	634	Inter-host-connection timeouts and monitoring depend on the transport
527	used. The only transport currently implemented is TCP, and AnyEvent::MP	635	used. The only transport currently implemented is TCP, and AnyEvent::MP
528	relies on TCP to detect node-downs (this can take 10-15 minutes on a	636	relies on TCP to detect node-downs (this can take 10-15 minutes on a
529	non-idle connection, and usually around two hours for idle conenctions).	637	non-idle connection, and usually around two hours for idle connections).
530		638
531	This means that monitoring is good for program errors and cleaning up	639	This means that monitoring is good for program errors and cleaning up
532	stuff eventually, but they are no replacement for a timeout when you need	640	stuff eventually, but they are no replacement for a timeout when you need
533	to ensure some maximum latency.	641	to ensure some maximum latency.
534		642
…		…
566	}	674	}
567		675
568	$node->monitor ($port, $cb);	676	$node->monitor ($port, $cb);
569		677
570	defined wantarray	678	defined wantarray
571	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	679	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
572	}	680	}
573		681
574	=item $guard = mon_guard $port, $ref, $ref...	682	=item $guard = mon_guard $port, $ref, $ref...
575		683
576	Monitors the given C<$port> and keeps the passed references. When the port	684	Monitors the given C<$port> and keeps the passed references. When the port
…		…
599		707
600	=item kil $port[, @reason]	708	=item kil $port[, @reason]
601		709
602	Kill the specified port with the given C<@reason>.	710	Kill the specified port with the given C<@reason>.
603		711
604	If no C<@reason> is specified, then the port is killed "normally" (ports	712	If no C<@reason> is specified, then the port is killed "normally" -
605	monitoring other ports will not necessarily die because a port dies	713	monitor callback will be invoked, but the kil will not cause linked ports
606	"normally").	714	(C<mon $mport, $lport> form) to get killed.
607		715
608	Otherwise, linked ports get killed with the same reason (second form of	716	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
609	C<mon>, see above).	717	form) get killed with the same reason.
610		718
611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	719	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
612	will be reported as reason C<< die => $@ >>.	720	will be reported as reason C<< die => $@ >>.
613		721
614	Transport/communication errors are reported as C<< transport_error =>	722	Transport/communication errors are reported as C<< transport_error =>
…		…
680	}	788	}
681		789
682	sub spawn(@) {	790	sub spawn(@) {
683	my ($nodeid, undef) = split /#/, shift, 2;	791	my ($nodeid, undef) = split /#/, shift, 2;
684		792
685	my $id = "$RUNIQ." . $ID++;	793	my $id = $RUNIQ . ++$ID;
686		794
687	$_[0] =~ /::/	795	$_[0] =~ /::/
688	or Carp::croak "spawn init function must be a fully-qualified name, caught";	796	or Carp::croak "spawn init function must be a fully-qualified name, caught";
689		797
690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	798	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
691		799
692	"$nodeid#$id"	800	"$nodeid#$id"
693	}	801	}
		802
694		803
695	=item after $timeout, @msg	804	=item after $timeout, @msg
696		805
697	=item after $timeout, $callback	806	=item after $timeout, $callback
698		807
…		…
714	? $action[0]()	823	? $action[0]()
715	: snd @action;	824	: snd @action;
716	};	825	};
717	}	826	}
718		827
		828	=item cal $port, @msg, $callback[, $timeout]
		829
		830	A simple form of RPC - sends a message to the given C<$port> with the
		831	given contents (C<@msg>), but adds a reply port to the message.
		832
		833	The reply port is created temporarily just for the purpose of receiving
		834	the reply, and will be C<kil>ed when no longer needed.
		835
		836	A reply message sent to the port is passed to the C<$callback> as-is.
		837
		838	If an optional time-out (in seconds) is given and it is not C<undef>,
		839	then the callback will be called without any arguments after the time-out
		840	elapsed and the port is C<kil>ed.
		841
		842	If no time-out is given (or it is C<undef>), then the local port will
		843	monitor the remote port instead, so it eventually gets cleaned-up.
		844
		845	Currently this function returns the temporary port, but this "feature"
		846	might go in future versions unless you can make a convincing case that
		847	this is indeed useful for something.
		848
		849	=cut
		850
		851	sub cal(@) {
		852	my $timeout = ref $_[-1] ? undef : pop;
		853	my $cb = pop;
		854
		855	my $port = port {
		856	undef $timeout;
		857	kil $SELF;
		858	&$cb;
		859	};
		860
		861	if (defined $timeout) {
		862	$timeout = AE::timer $timeout, 0, sub {
		863	undef $timeout;
		864	kil $port;
		865	$cb->();
		866	};
		867	} else {
		868	mon $_[0], sub {
		869	kil $port;
		870	$cb->();
		871	};
		872	}
		873
		874	push @_, $port;
		875	&snd;
		876
		877	$port
		878	}
		879
		880	=back
		881
		882	=head1 DISTRIBUTED DATABASE
		883
		884	AnyEvent::MP comes with a simple distributed database. The database will
		885	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		886	the global nodes for their needs.
		887
		888	The database consists of a two-level hash - a hash contains a hash which
		889	contains values.
		890
		891	The top level hash key is called "family", and the second-level hash key
		892	is simply called "key".
		893
		894	The family must be alphanumeric, i.e. start with a letter and consist
		895	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		896	pretty much like Perl module names.
		897
		898	As the family namespace is global, it is recommended to prefix family names
		899	with the name of the application or module using it.
		900
		901	The keys must be strings, with no other limitations.
		902
		903	The values should preferably be strings, but other perl scalars should
		904	work as well (such as undef, arrays and hashes).
		905
		906	Every database entry is owned by one node - adding the same family/key
		907	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		908	but the result might be nondeterministic, i.e. the key might have
		909	different values on different nodes.
		910
		911	=item db_set $family => $key => $value
		912
		913	Sets (or replaces) a key to the database.
		914
		915	=item db_del $family => $key
		916
		917	Deletes a key from the database.
		918
		919	=item $guard = db_reg $family => $key [=> $value]
		920
		921	Sets the key on the database and returns a guard. When the guard is
		922	destroyed, the key is deleted from the database. If C<$value> is missing,
		923	then C<undef> is used.
		924
		925	=cut
		926
719	=back	927	=back
720		928
721	=head1 AnyEvent::MP vs. Distributed Erlang	929	=head1 AnyEvent::MP vs. Distributed Erlang
722		930
723	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	931	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
724	== aemp node, Erlang process == aemp port), so many of the documents and	932	== aemp node, Erlang process == aemp port), so many of the documents and
725	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	933	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
726	sample:	934	sample:
727		935
728	http://www.Erlang.se/doc/programming_rules.shtml	936	http://www.erlang.se/doc/programming_rules.shtml
729	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	937	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
730	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	938	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
731	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	939	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
732		940
733	Despite the similarities, there are also some important differences:	941	Despite the similarities, there are also some important differences:
734		942
735	=over 4	943	=over 4
736		944
737	=item * Node IDs are arbitrary strings in AEMP.	945	=item * Node IDs are arbitrary strings in AEMP.
738		946
739	Erlang relies on special naming and DNS to work everywhere in the same	947	Erlang relies on special naming and DNS to work everywhere in the same
740	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	948	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
741	configuration or DNS), but will otherwise discover other odes itself.	949	configuration or DNS), and possibly the addresses of some seed nodes, but
		950	will otherwise discover other nodes (and their IDs) itself.
742		951
743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	952	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
744	uses "local ports are like remote ports".	953	uses "local ports are like remote ports".
745		954
746	The failure modes for local ports are quite different (runtime errors	955	The failure modes for local ports are quite different (runtime errors
…		…
755	ports being the special case/exception, where transport errors cannot	964	ports being the special case/exception, where transport errors cannot
756	occur.	965	occur.
757		966
758	=item * Erlang uses processes and a mailbox, AEMP does not queue.	967	=item * Erlang uses processes and a mailbox, AEMP does not queue.
759		968
760	Erlang uses processes that selectively receive messages, and therefore	969	Erlang uses processes that selectively receive messages out of order, and
761	needs a queue. AEMP is event based, queuing messages would serve no	970	therefore needs a queue. AEMP is event based, queuing messages would serve
762	useful purpose. For the same reason the pattern-matching abilities of	971	no useful purpose. For the same reason the pattern-matching abilities
763	AnyEvent::MP are more limited, as there is little need to be able to	972	of AnyEvent::MP are more limited, as there is little need to be able to
764	filter messages without dequeuing them.	973	filter messages without dequeuing them.
765		974
766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	975	This is not a philosophical difference, but simply stems from AnyEvent::MP
		976	being event-based, while Erlang is process-based.
		977
		978	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		979	top of AEMP and Coro threads.
767		980
768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	981	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
769		982
770	Sending messages in Erlang is synchronous and blocks the process (and	983	Sending messages in Erlang is synchronous and blocks the process until
		984	a conenction has been established and the message sent (and so does not
771	so does not need a queue that can overflow). AEMP sends are immediate,	985	need a queue that can overflow). AEMP sends return immediately, connection
772	connection establishment is handled in the background.	986	establishment is handled in the background.
773		987
774	=item * Erlang suffers from silent message loss, AEMP does not.	988	=item * Erlang suffers from silent message loss, AEMP does not.
775		989
776	Erlang makes few guarantees on messages delivery - messages can get lost	990	Erlang implements few guarantees on messages delivery - messages can get
777	without any of the processes realising it (i.e. you send messages a, b,	991	lost without any of the processes realising it (i.e. you send messages a,
778	and c, and the other side only receives messages a and c).	992	b, and c, and the other side only receives messages a and c).
779		993
780	AEMP guarantees correct ordering, and the guarantee that after one message	994	AEMP guarantees (modulo hardware errors) correct ordering, and the
781	is lost, all following ones sent to the same port are lost as well, until	995	guarantee that after one message is lost, all following ones sent to the
782	monitoring raises an error, so there are no silent "holes" in the message	996	same port are lost as well, until monitoring raises an error, so there are
783	sequence.	997	no silent "holes" in the message sequence.
		998
		999	If you want your software to be very reliable, you have to cope with
		1000	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1001	simply tries to work better in common error cases, such as when a network
		1002	link goes down.
784		1003
785	=item * Erlang can send messages to the wrong port, AEMP does not.	1004	=item * Erlang can send messages to the wrong port, AEMP does not.
786		1005
787	In Erlang it is quite likely that a node that restarts reuses a process ID	1006	In Erlang it is quite likely that a node that restarts reuses an Erlang
788	known to other nodes for a completely different process, causing messages	1007	process ID known to other nodes for a completely different process,
789	destined for that process to end up in an unrelated process.	1008	causing messages destined for that process to end up in an unrelated
		1009	process.
790		1010
791	AEMP never reuses port IDs, so old messages or old port IDs floating	1011	AEMP does not reuse port IDs, so old messages or old port IDs floating
792	around in the network will not be sent to an unrelated port.	1012	around in the network will not be sent to an unrelated port.
793		1013
794	=item * Erlang uses unprotected connections, AEMP uses secure	1014	=item * Erlang uses unprotected connections, AEMP uses secure
795	authentication and can use TLS.	1015	authentication and can use TLS.
796		1016
…		…
799		1019
800	=item * The AEMP protocol is optimised for both text-based and binary	1020	=item * The AEMP protocol is optimised for both text-based and binary
801	communications.	1021	communications.
802		1022
803	The AEMP protocol, unlike the Erlang protocol, supports both programming	1023	The AEMP protocol, unlike the Erlang protocol, supports both programming
804	language independent text-only protocols (good for debugging) and binary,	1024	language independent text-only protocols (good for debugging), and binary,
805	language-specific serialisers (e.g. Storable). By default, unless TLS is	1025	language-specific serialisers (e.g. Storable). By default, unless TLS is
806	used, the protocol is actually completely text-based.	1026	used, the protocol is actually completely text-based.
807		1027
808	It has also been carefully designed to be implementable in other languages	1028	It has also been carefully designed to be implementable in other languages
809	with a minimum of work while gracefully degrading functionality to make the	1029	with a minimum of work while gracefully degrading functionality to make the
810	protocol simple.	1030	protocol simple.
811		1031
812	=item * AEMP has more flexible monitoring options than Erlang.	1032	=item * AEMP has more flexible monitoring options than Erlang.
813		1033
814	In Erlang, you can chose to receive I<all> exit signals as messages	1034	In Erlang, you can chose to receive I<all> exit signals as messages or
815	or I<none>, there is no in-between, so monitoring single processes is	1035	I<none>, there is no in-between, so monitoring single Erlang processes is
816	difficult to implement. Monitoring in AEMP is more flexible than in	1036	difficult to implement.
817	Erlang, as one can choose between automatic kill, exit message or callback	1037
818	on a per-process basis.	1038	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1039	between automatic kill, exit message or callback on a per-port basis.
819		1040
820	=item * Erlang tries to hide remote/local connections, AEMP does not.	1041	=item * Erlang tries to hide remote/local connections, AEMP does not.
821		1042
822	Monitoring in Erlang is not an indicator of process death/crashes, in the	1043	Monitoring in Erlang is not an indicator of process death/crashes, in the
823	same way as linking is (except linking is unreliable in Erlang).	1044	same way as linking is (except linking is unreliable in Erlang).
…		…
845	overhead, as well as having to keep a proxy object everywhere.	1066	overhead, as well as having to keep a proxy object everywhere.
846		1067
847	Strings can easily be printed, easily serialised etc. and need no special	1068	Strings can easily be printed, easily serialised etc. and need no special
848	procedures to be "valid".	1069	procedures to be "valid".
849		1070
850	And as a result, a miniport consists of a single closure stored in a	1071	And as a result, a port with just a default receiver consists of a single
851	global hash - it can't become much cheaper.	1072	code reference stored in a global hash - it can't become much cheaper.
852		1073
853	=item Why favour JSON, why not a real serialising format such as Storable?	1074	=item Why favour JSON, why not a real serialising format such as Storable?
854		1075
855	In fact, any AnyEvent::MP node will happily accept Storable as framing	1076	In fact, any AnyEvent::MP node will happily accept Storable as framing
856	format, but currently there is no way to make a node use Storable by	1077	format, but currently there is no way to make a node use Storable by
…		…
872		1093
873	L<AnyEvent::MP::Intro> - a gentle introduction.	1094	L<AnyEvent::MP::Intro> - a gentle introduction.
874		1095
875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1096	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
876		1097
877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1098	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
878	your applications.	1099	your applications.
		1100
		1101	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
879		1102
880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1103	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
881	all nodes.	1104	all nodes.
882		1105
883	L<AnyEvent>.	1106	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.83 by root, Tue Sep 8 01:38:16 2009 UTC vs. Revision 1.125 by root, Sat Mar 3 13:07:19 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.83 by root, Tue Sep 8 01:38:16 2009 UTC vs.
Revision 1.125 by root, Sat Mar 3 13:07:19 2012 UTC