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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.85 by root, Tue Sep 8 01:54:13 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-Z_][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. They should also be relatively responsive - a	137	should always be available. They should also be relatively responsive - a
118	seed node that blocks for long periods will slow down everybody else.	138	seed node that blocks for long periods will slow down everybody else.
119		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
120	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
121		150
122	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
123	TCP port) of nodes thta should be used as seed nodes.	152	TCP port) of nodes that should be used as seed nodes.
124		153
125	The nodes listening on those endpoints are expected to be long-running,	154	=item global nodes
126	and at least one of those should always be available. When nodes run out	155
127	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
128	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).
129		170
130	=back	171	=back
131		172
132	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
133		174
…		…
135		176
136	=cut	177	=cut
137		178
138	package AnyEvent::MP;	179	package AnyEvent::MP;
139		180
		181	use AnyEvent::MP::Config ();
140	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
141		184
142	use common::sense;	185	use common::sense;
143		186
144	use Carp ();	187	use Carp ();
145		188
146	use AE ();	189	use AE ();
		190	use Guard ();
147		191
148	use base "Exporter";	192	use base "Exporter";
149		193
150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
151		195
152	our @EXPORT = qw(	196	our @EXPORT = qw(
153	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
154	configure	198	configure
155	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
156	port	200	port
		201	db_set db_del db_reg
157	);	202	);
158		203
159	our $SELF;	204	our $SELF;
160		205
161	sub _self_die() {	206	sub _self_die() {
…		…
184	some other nodes in the network to discover other nodes.	229	some other nodes in the network to discover other nodes.
185		230
186	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
187	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
188		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
189	=over 4	253	=over 4
190		254
191	=item step 1, gathering configuration from profiles	255	=item step 1, gathering configuration from profiles
192		256
193	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
…		…
206	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
207	and the values specified directly via C<configure> have lowest priority,	271	and the values specified directly via C<configure> have lowest priority,
208	and can only be used to specify defaults.	272	and can only be used to specify defaults.
209		273
210	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
211	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
212	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>.
213		283
214	=item step 2, bind listener sockets	284	=item step 2, bind listener sockets
215		285
216	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
217	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
…		…
223	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
224	local IP address it finds.	294	local IP address it finds.
225		295
226	=item step 3, connect to seed nodes	296	=item step 3, connect to seed nodes
227		297
228	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
229	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
230	connectivity with at least one node at any point in time.	300	connectivity with at least one node at any point in time.
231		301
232	=back	302	=back
233		303
234	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.
235	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.
236		306
237	configure	307	configure
238		308
239	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
240	clients.	310	commandline clients.
241		311
242	configure nodeid => "anon/";	312	configure nodeid => "myscript/%n/%u";
243		313
244	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
245	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,
246	customary for aemp).	316	customary for aemp).
247		317
248	# use the aemp commandline utility	318	# use the aemp commandline utility
249	# aemp profile seed nodeid anon/ binds '*:4040'	319	# aemp profile seed binds '*:4040'
250		320
251	# then use it	321	# then use it
252	configure profile => "seed";	322	configure profile => "seed";
253		323
254	# or simply use aemp from the shell again:	324	# or simply use aemp from the shell again:
…		…
324	sub _kilme {	394	sub _kilme {
325	die "received message on port without callback";	395	die "received message on port without callback";
326	}	396	}
327		397
328	sub port(;&) {	398	sub port(;&) {
329	my $id = "$UNIQ." . $ID++;	399	my $id = $UNIQ . ++$ID;
330	my $port = "$NODE#$id";	400	my $port = "$NODE#$id";
331		401
332	rcv $port, shift \|\| \&_kilme;	402	rcv $port, shift \|\| \&_kilme;
333		403
334	$port	404	$port
…		…
373	msg1 => sub { ... },	443	msg1 => sub { ... },
374	...	444	...
375	;	445	;
376		446
377	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
378	(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.
379		449
380	rcv $port, $otherport => sub {	450	rcv $port, $otherport => sub {
381	my @reply = @_;	451	my @reply = @_;
382		452
383	rcv $SELF, $otherport;	453	rcv $SELF, $otherport;
…		…
396	if (ref $_[0]) {	466	if (ref $_[0]) {
397	if (my $self = $PORT_DATA{$portid}) {	467	if (my $self = $PORT_DATA{$portid}) {
398	"AnyEvent::MP::Port" eq ref $self	468	"AnyEvent::MP::Port" eq ref $self
399	or Carp::croak "$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";
400		470
401	$self->[2] = shift;	471	$self->[0] = shift;
402	} else {	472	} else {
403	my $cb = shift;	473	my $cb = shift;
404	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
405	local $SELF = $port;	475	local $SELF = $port;
406	eval { &$cb }; _self_die if $@;	476	eval { &$cb }; _self_die if $@;
407	};	477	};
408	}	478	}
409	} elsif (defined $_[0]) {	479	} elsif (defined $_[0]) {
410	my $self = $PORT_DATA{$portid} \|\|= do {	480	my $self = $PORT_DATA{$portid} \|\|= do {
411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	481	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
412		482
413	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
414	local $SELF = $port;	484	local $SELF = $port;
415		485
416	if (my $cb = $self->[1]{$_[0]}) {	486	if (my $cb = $self->[1]{$_[0]}) {
…		…
438	}	508	}
439		509
440	$port	510	$port
441	}	511	}
442		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
443	=item $closure = psub { BLOCK }	550	=item $closure = psub { BLOCK }
444		551
445	Remembers C<$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
446	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>
447	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 $SELF, sub {
		557	BLOCK }, @_ } >>.
448		558
449	This is useful when you register callbacks from C<rcv> callbacks:	559	This is useful when you register callbacks from C<rcv> callbacks:
450		560
451	rcv delayed_reply => sub {	561	rcv delayed_reply => sub {
452	my ($delay, @reply) = @_;	562	my ($delay, @reply) = @_;
…		…
525	delivered again.	635	delivered again.
526		636
527	Inter-host-connection timeouts and monitoring depend on the transport	637	Inter-host-connection timeouts and monitoring depend on the transport
528	used. The only transport currently implemented is TCP, and AnyEvent::MP	638	used. The only transport currently implemented is TCP, and AnyEvent::MP
529	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
530	non-idle connection, and usually around two hours for idle conenctions).	640	non-idle connection, and usually around two hours for idle connections).
531		641
532	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
533	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
534	to ensure some maximum latency.	644	to ensure some maximum latency.
535		645
…		…
567	}	677	}
568		678
569	$node->monitor ($port, $cb);	679	$node->monitor ($port, $cb);
570		680
571	defined wantarray	681	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	682	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
573	}	683	}
574		684
575	=item $guard = mon_guard $port, $ref, $ref...	685	=item $guard = mon_guard $port, $ref, $ref...
576		686
577	Monitors the given C<$port> and keeps the passed references. When the port	687	Monitors the given C<$port> and keeps the passed references. When the port
…		…
600		710
601	=item kil $port[, @reason]	711	=item kil $port[, @reason]
602		712
603	Kill the specified port with the given C<@reason>.	713	Kill the specified port with the given C<@reason>.
604		714
605	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" -
606	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
607	"normally").	717	(C<mon $mport, $lport> form) to get killed.
608		718
609	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>
610	C<mon>, see above).	720	form) get killed with the same reason.
611		721
612	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
613	will be reported as reason C<< die => $@ >>.	723	will be reported as reason C<< die => $@ >>.
614		724
615	Transport/communication errors are reported as C<< transport_error =>	725	Transport/communication errors are reported as C<< transport_error =>
…		…
681	}	791	}
682		792
683	sub spawn(@) {	793	sub spawn(@) {
684	my ($nodeid, undef) = split /#/, shift, 2;	794	my ($nodeid, undef) = split /#/, shift, 2;
685		795
686	my $id = "$RUNIQ." . $ID++;	796	my $id = $RUNIQ . ++$ID;
687		797
688	$_[0] =~ /::/	798	$_[0] =~ /::/
689	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";
690		800
691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	801	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
692		802
693	"$nodeid#$id"	803	"$nodeid#$id"
694	}	804	}
		805
695		806
696	=item after $timeout, @msg	807	=item after $timeout, @msg
697		808
698	=item after $timeout, $callback	809	=item after $timeout, $callback
699		810
…		…
715	? $action[0]()	826	? $action[0]()
716	: snd @action;	827	: snd @action;
717	};	828	};
718	}	829	}
719		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
720	=back	945	=back
721		946
722	=head1 AnyEvent::MP vs. Distributed Erlang	947	=head1 AnyEvent::MP vs. Distributed Erlang
723		948
724	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
725	== 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
726	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
727	sample:	952	sample:
728		953
729	http://www.Erlang.se/doc/programming_rules.shtml	954	http://www.erlang.se/doc/programming_rules.shtml
730	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
731	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
732	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
733		958
734	Despite the similarities, there are also some important differences:	959	Despite the similarities, there are also some important differences:
735		960
736	=over 4	961	=over 4
737		962
738	=item * Node IDs are arbitrary strings in AEMP.	963	=item * Node IDs are arbitrary strings in AEMP.
739		964
740	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
741	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
742	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.
743		969
744	=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
745	uses "local ports are like remote ports".	971	uses "local ports are like remote ports".
746		972
747	The failure modes for local ports are quite different (runtime errors	973	The failure modes for local ports are quite different (runtime errors
…		…
756	ports being the special case/exception, where transport errors cannot	982	ports being the special case/exception, where transport errors cannot
757	occur.	983	occur.
758		984
759	=item * Erlang uses processes and a mailbox, AEMP does not queue.	985	=item * Erlang uses processes and a mailbox, AEMP does not queue.
760		986
761	Erlang uses processes that selectively receive messages, and therefore	987	Erlang uses processes that selectively receive messages out of order, and
762	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
763	useful purpose. For the same reason the pattern-matching abilities of	989	no useful purpose. For the same reason the pattern-matching abilities
764	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
765	filter messages without dequeuing them.	991	filter messages without dequeuing them.
766		992
767	(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.
768		998
769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	999	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
770		1000
771	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
772	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
773	connection establishment is handled in the background.	1004	establishment is handled in the background.
774		1005
775	=item * Erlang suffers from silent message loss, AEMP does not.	1006	=item * Erlang suffers from silent message loss, AEMP does not.
776		1007
777	Erlang makes few guarantees on messages delivery - messages can get lost	1008	Erlang implements few guarantees on messages delivery - messages can get
778	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,
779	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).
780		1011
781	AEMP guarantees correct ordering, and the guarantee that after one message	1012	AEMP guarantees (modulo hardware errors) correct ordering, and the
782	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
783	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
784	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.
785		1021
786	=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.
787		1023
788	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
789	known to other nodes for a completely different process, causing messages	1025	process ID known to other nodes for a completely different process,
790	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.
791		1028
792	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
793	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.
794		1031
795	=item * Erlang uses unprotected connections, AEMP uses secure	1032	=item * Erlang uses unprotected connections, AEMP uses secure
796	authentication and can use TLS.	1033	authentication and can use TLS.
797		1034
…		…
800		1037
801	=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
802	communications.	1039	communications.
803		1040
804	The AEMP protocol, unlike the Erlang protocol, supports both programming	1041	The AEMP protocol, unlike the Erlang protocol, supports both programming
805	language independent text-only protocols (good for debugging) and binary,	1042	language independent text-only protocols (good for debugging), and binary,
806	language-specific serialisers (e.g. Storable). By default, unless TLS is	1043	language-specific serialisers (e.g. Storable). By default, unless TLS is
807	used, the protocol is actually completely text-based.	1044	used, the protocol is actually completely text-based.
808		1045
809	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
810	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
811	protocol simple.	1048	protocol simple.
812		1049
813	=item * AEMP has more flexible monitoring options than Erlang.	1050	=item * AEMP has more flexible monitoring options than Erlang.
814		1051
815	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
816	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
817	difficult to implement. Monitoring in AEMP is more flexible than in	1054	difficult to implement.
818	Erlang, as one can choose between automatic kill, exit message or callback	1055
819	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.
820		1058
821	=item * Erlang tries to hide remote/local connections, AEMP does not.	1059	=item * Erlang tries to hide remote/local connections, AEMP does not.
822		1060
823	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
824	same way as linking is (except linking is unreliable in Erlang).	1062	same way as linking is (except linking is unreliable in Erlang).
…		…
846	overhead, as well as having to keep a proxy object everywhere.	1084	overhead, as well as having to keep a proxy object everywhere.
847		1085
848	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
849	procedures to be "valid".	1087	procedures to be "valid".
850		1088
851	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
852	global hash - it can't become much cheaper.	1090	code reference stored in a global hash - it can't become much cheaper.
853		1091
854	=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?
855		1093
856	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
857	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
…		…
873		1111
874	L<AnyEvent::MP::Intro> - a gentle introduction.	1112	L<AnyEvent::MP::Intro> - a gentle introduction.
875		1113
876	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1114	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
877		1115
878	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1116	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
879	your applications.	1117	your applications.
		1118
		1119	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
880		1120
881	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1121	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
882	all nodes.	1122	all nodes.
883		1123
884	L<AnyEvent>.	1124	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.85 by root, Tue Sep 8 01:54:13 2009 UTC vs. Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.85 by root, Tue Sep 8 01:54:13 2009 UTC vs.
Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC