[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 1.128 by root, Sun Mar 4 14:28:44 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
		202	db_mon db_family db_keys db_values
144	);	203	);
145		204
146	our $SELF;	205	our $SELF;
147		206
148	sub _self_die() {	207	sub _self_die() {
…		…
171	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
172		231
173	This function configures a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
175		234
		235	The key/value pairs are basically the same ones as documented for the
		236	F<aemp> command line utility (sans the set/del prefix), with these additions:
		237
		238	=over 4
		239
		240	=item norc => $boolean (default false)
		241
		242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		243	be consulted - all configuraiton options must be specified in the
		244	C<configure> call.
		245
		246	=item force => $boolean (default false)
		247
		248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
		251
		252	=item secure => $pass->($nodeid)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every remote execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	See F<semp setsecure> for more info.
		259
		260	=back
		261
176	=over 4	262	=over 4
177		263
178	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
179		265
180	The function first looks up a profile in the aemp configuration (see the	266	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	279	That means that the values specified in the profile have highest priority
194	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	281	and can only be used to specify defaults.
196		282
197	If the profile specifies a node ID, then this will become the node ID of	283	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	284	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.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
200		292
201	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
202		294
203	The next step is to look up the binds in the profile, followed by binding	295	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	296	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	302	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	303	local IP address it finds.
212		304
213	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
214		306
215	As the last step, the seeds list from the profile is passed to the	307	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	308	L<AnyEvent::MP::Global> module, which will then use it to keep
217	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
218		310
219	=back	311	=back
220		312
221	Example: become a distributed node using the locla node name as profile.	313	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.	314	This should be the most common form of invocation for "daemon"-type nodes.
223		315
224	configure	316	configure
225		317
226	Example: become an anonymous node. This form is often used for commandline	318	Example: become a semi-anonymous node. This form is often used for
227	clients.	319	commandline clients.
228		320
229	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
230		322
231	Example: configure a node using a profile called seed, which si suitable	323	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,	324	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	325	customary for aemp).
234		326
235	# use the aemp commandline utility	327	# use the aemp commandline utility
236	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
237		329
238	# then use it	330	# then use it
239	configure profile => "seed";	331	configure profile => "seed";
240		332
241	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
311	sub _kilme {	403	sub _kilme {
312	die "received message on port without callback";	404	die "received message on port without callback";
313	}	405	}
314		406
315	sub port(;&) {	407	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
318		410
319	rcv $port, shift \|\| \&_kilme;	411	rcv $port, shift \|\| \&_kilme;
320		412
321	$port	413	$port
…		…
360	msg1 => sub { ... },	452	msg1 => sub { ... },
361	...	453	...
362	;	454	;
363		455
364	Example: temporarily register a rcv callback for a tag matching some port	456	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.	457	(e.g. for an rpc reply) and unregister it after a message was received.
366		458
367	rcv $port, $otherport => sub {	459	rcv $port, $otherport => sub {
368	my @reply = @_;	460	my @reply = @_;
369		461
370	rcv $SELF, $otherport;	462	rcv $SELF, $otherport;
…		…
383	if (ref $_[0]) {	475	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	476	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	477	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	478	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387		479
388	$self->[2] = shift;	480	$self->[0] = shift;
389	} else {	481	} else {
390	my $cb = shift;	482	my $cb = shift;
391	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
392	local $SELF = $port;	484	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	485	eval { &$cb }; _self_die if $@;
394	};	486	};
395	}	487	}
396	} elsif (defined $_[0]) {	488	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	489	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	490	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		491
400	$PORT{$portid} = sub {	492	$PORT{$portid} = sub {
401	local $SELF = $port;	493	local $SELF = $port;
402		494
403	if (my $cb = $self->[1]{$_[0]}) {	495	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	517	}
426		518
427	$port	519	$port
428	}	520	}
429		521
		522	=item peval $port, $coderef[, @args]
		523
		524	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		525	when the code throews an exception the C<$port> will be killed.
		526
		527	Any remaining args will be passed to the callback. Any return values will
		528	be returned to the caller.
		529
		530	This is useful when you temporarily want to execute code in the context of
		531	a port.
		532
		533	Example: create a port and run some initialisation code in it's context.
		534
		535	my $port = port { ... };
		536
		537	peval $port, sub {
		538	init
		539	or die "unable to init";
		540	};
		541
		542	=cut
		543
		544	sub peval($$) {
		545	local $SELF = shift;
		546	my $cb = shift;
		547
		548	if (wantarray) {
		549	my @res = eval { &$cb };
		550	_self_die if $@;
		551	@res
		552	} else {
		553	my $res = eval { &$cb };
		554	_self_die if $@;
		555	$res
		556	}
		557	}
		558
430	=item $closure = psub { BLOCK }	559	=item $closure = psub { BLOCK }
431		560
432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	561	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>	562	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.	563	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		564
		565	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		566	BLOCK }, @_ } >>.
435		567
436	This is useful when you register callbacks from C<rcv> callbacks:	568	This is useful when you register callbacks from C<rcv> callbacks:
437		569
438	rcv delayed_reply => sub {	570	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	571	my ($delay, @reply) = @_;
…		…
512	delivered again.	644	delivered again.
513		645
514	Inter-host-connection timeouts and monitoring depend on the transport	646	Inter-host-connection timeouts and monitoring depend on the transport
515	used. The only transport currently implemented is TCP, and AnyEvent::MP	647	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	648	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).	649	non-idle connection, and usually around two hours for idle connections).
518		650
519	This means that monitoring is good for program errors and cleaning up	651	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	652	stuff eventually, but they are no replacement for a timeout when you need
521	to ensure some maximum latency.	653	to ensure some maximum latency.
522		654
…		…
554	}	686	}
555		687
556	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
557		689
558	defined wantarray	690	defined wantarray
559	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
560	}	692	}
561		693
562	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
563		695
564	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
…		…
587		719
588	=item kil $port[, @reason]	720	=item kil $port[, @reason]
589		721
590	Kill the specified port with the given C<@reason>.	722	Kill the specified port with the given C<@reason>.
591		723
592	If no C<@reason> is specified, then the port is killed "normally" (ports	724	If no C<@reason> is specified, then the port is killed "normally" -
593	monitoring other ports will not necessarily die because a port dies	725	monitor callback will be invoked, but the kil will not cause linked ports
594	"normally").	726	(C<mon $mport, $lport> form) to get killed.
595		727
596	Otherwise, linked ports get killed with the same reason (second form of	728	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
597	C<mon>, see above).	729	form) get killed with the same reason.
598		730
599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	731	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
600	will be reported as reason C<< die => $@ >>.	732	will be reported as reason C<< die => $@ >>.
601		733
602	Transport/communication errors are reported as C<< transport_error =>	734	Transport/communication errors are reported as C<< transport_error =>
…		…
668	}	800	}
669		801
670	sub spawn(@) {	802	sub spawn(@) {
671	my ($nodeid, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
672		804
673	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
674		806
675	$_[0] =~ /::/	807	$_[0] =~ /::/
676	or Carp::croak "spawn init function must be a fully-qualified name, caught";	808	or Carp::croak "spawn init function must be a fully-qualified name, caught";
677		809
678	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679		811
680	"$nodeid#$id"	812	"$nodeid#$id"
681	}	813	}
		814
682		815
683	=item after $timeout, @msg	816	=item after $timeout, @msg
684		817
685	=item after $timeout, $callback	818	=item after $timeout, $callback
686		819
…		…
702	? $action[0]()	835	? $action[0]()
703	: snd @action;	836	: snd @action;
704	};	837	};
705	}	838	}
706		839
		840	=item cal $port, @msg, $callback[, $timeout]
		841
		842	A simple form of RPC - sends a message to the given C<$port> with the
		843	given contents (C<@msg>), but adds a reply port to the message.
		844
		845	The reply port is created temporarily just for the purpose of receiving
		846	the reply, and will be C<kil>ed when no longer needed.
		847
		848	A reply message sent to the port is passed to the C<$callback> as-is.
		849
		850	If an optional time-out (in seconds) is given and it is not C<undef>,
		851	then the callback will be called without any arguments after the time-out
		852	elapsed and the port is C<kil>ed.
		853
		854	If no time-out is given (or it is C<undef>), then the local port will
		855	monitor the remote port instead, so it eventually gets cleaned-up.
		856
		857	Currently this function returns the temporary port, but this "feature"
		858	might go in future versions unless you can make a convincing case that
		859	this is indeed useful for something.
		860
		861	=cut
		862
		863	sub cal(@) {
		864	my $timeout = ref $_[-1] ? undef : pop;
		865	my $cb = pop;
		866
		867	my $port = port {
		868	undef $timeout;
		869	kil $SELF;
		870	&$cb;
		871	};
		872
		873	if (defined $timeout) {
		874	$timeout = AE::timer $timeout, 0, sub {
		875	undef $timeout;
		876	kil $port;
		877	$cb->();
		878	};
		879	} else {
		880	mon $_[0], sub {
		881	kil $port;
		882	$cb->();
		883	};
		884	}
		885
		886	push @_, $port;
		887	&snd;
		888
		889	$port
		890	}
		891
		892	=back
		893
		894	=head1 DISTRIBUTED DATABASE
		895
		896	AnyEvent::MP comes with a simple distributed database. The database will
		897	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		898	the global nodes for their needs.
		899
		900	The database consists of a two-level hash - a hash contains a hash which
		901	contains values.
		902
		903	The top level hash key is called "family", and the second-level hash key
		904	is called "subkey" or simply "key".
		905
		906	The family must be alphanumeric, i.e. start with a letter and consist
		907	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		908	pretty much like Perl module names.
		909
		910	As the family namespace is global, it is recommended to prefix family names
		911	with the name of the application or module using it.
		912
		913	The subkeys must be non-empty strings, with no further restrictions.
		914
		915	The values should preferably be strings, but other perl scalars should
		916	work as well (such as undef, arrays and hashes).
		917
		918	Every database entry is owned by one node - adding the same family/subkey
		919	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		920	but the result might be nondeterministic, i.e. the key might have
		921	different values on different nodes.
		922
		923	Different subkeys in the same family can be owned by different nodes
		924	without problems, and in fact, this is the common method to create worker
		925	pools. For example, a worker port for image scaling might do this:
		926
		927	db_set my_image_scalers => $port;
		928
		929	And clients looking for an image scaler will want to get the
		930	C<my_image_scalers> keys:
		931
		932	db_keys "my_image_scalers" => 60 => sub {
		933	#d##TODO#
		934
		935	=over
		936
		937	=item db_set $family => $subkey [=> $value]
		938
		939	Sets (or replaces) a key to the database - if C<$value> is omitted,
		940	C<undef> is used instead.
		941
		942	=item db_del $family => $subkey
		943
		944	Deletes a key from the database.
		945
		946	=item $guard = db_reg $family => $subkey [=> $value]
		947
		948	Sets the key on the database and returns a guard. When the guard is
		949	destroyed, the key is deleted from the database. If C<$value> is missing,
		950	then C<undef> is used.
		951
		952	=item $guard = db_mon $family => $cb->($familyhash, \@subkeys...)
		953
		954	Creates a monitor on the given database family. Each time a key is set or
		955	or is deleted the callback is called with a hash containing the database
		956	family and an arrayref with subkeys that have changed.
		957
		958	Specifically, if one of the passed subkeys exists in the $familyhash, then
		959	it is currently set to the value in the $familyhash. Otherwise, it has
		960	been deleted.
		961
		962	The first call will be with the current contents of the family and all
		963	keys, as if they were just added.
		964
		965	It is possible that the callback is called with a change event even though
		966	the subkey is already present and the value has not changed.
		967
		968	The monitoring stops when the guard object is destroyed.
		969
		970	Example: on every change to the family "mygroup", print out all keys.
		971
		972	my $guard = db_mon mygroup => sub {
		973	my ($family, $keys) = @_;
		974	print "mygroup members: ", (join " ", keys %$family), "\n";
		975	};
		976
		977	Exmaple: wait until the family "My::Module::workers" is non-empty.
		978
		979	my $guard; $guard = db_mon My::Module::workers => sub {
		980	my ($family, $keys) = @_;
		981	return unless %$family;
		982	undef $guard;
		983	print "My::Module::workers now nonempty\n";
		984	};
		985
		986	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		987
		988	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		989	my ($family, $keys) = @_;
		990
		991	for (@$keys) {
		992	print "$_: ",
		993	(exists $family->{$_}
		994	? $family->{$_}
		995	: "(deleted)"),
		996	"\n";
		997	}
		998	};
		999
		1000	=cut
		1001
707	=back	1002	=back
708		1003
709	=head1 AnyEvent::MP vs. Distributed Erlang	1004	=head1 AnyEvent::MP vs. Distributed Erlang
710		1005
711	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1006	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	1007	== 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	1008	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
714	sample:	1009	sample:
715		1010
716	http://www.Erlang.se/doc/programming_rules.shtml	1011	http://www.erlang.se/doc/programming_rules.shtml
717	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1012	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	1013	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	1014	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
720		1015
721	Despite the similarities, there are also some important differences:	1016	Despite the similarities, there are also some important differences:
722		1017
723	=over 4	1018	=over 4
724		1019
725	=item * Node IDs are arbitrary strings in AEMP.	1020	=item * Node IDs are arbitrary strings in AEMP.
726		1021
727	Erlang relies on special naming and DNS to work everywhere in the same	1022	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	1023	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.	1024	configuration or DNS), and possibly the addresses of some seed nodes, but
		1025	will otherwise discover other nodes (and their IDs) itself.
730		1026
731	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1027	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
732	uses "local ports are like remote ports".	1028	uses "local ports are like remote ports".
733		1029
734	The failure modes for local ports are quite different (runtime errors	1030	The failure modes for local ports are quite different (runtime errors
…		…
743	ports being the special case/exception, where transport errors cannot	1039	ports being the special case/exception, where transport errors cannot
744	occur.	1040	occur.
745		1041
746	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1042	=item * Erlang uses processes and a mailbox, AEMP does not queue.
747		1043
748	Erlang uses processes that selectively receive messages, and therefore	1044	Erlang uses processes that selectively receive messages out of order, and
749	needs a queue. AEMP is event based, queuing messages would serve no	1045	therefore needs a queue. AEMP is event based, queuing messages would serve
750	useful purpose. For the same reason the pattern-matching abilities of	1046	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	1047	of AnyEvent::MP are more limited, as there is little need to be able to
752	filter messages without dequeuing them.	1048	filter messages without dequeuing them.
753		1049
754	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1050	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1051	being event-based, while Erlang is process-based.
		1052
		1053	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1054	top of AEMP and Coro threads.
755		1055
756	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1056	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
757		1057
758	Sending messages in Erlang is synchronous and blocks the process (and	1058	Sending messages in Erlang is synchronous and blocks the process until
		1059	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,	1060	need a queue that can overflow). AEMP sends return immediately, connection
760	connection establishment is handled in the background.	1061	establishment is handled in the background.
761		1062
762	=item * Erlang suffers from silent message loss, AEMP does not.	1063	=item * Erlang suffers from silent message loss, AEMP does not.
763		1064
764	Erlang makes few guarantees on messages delivery - messages can get lost	1065	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,	1066	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).	1067	b, and c, and the other side only receives messages a and c).
767		1068
768	AEMP guarantees correct ordering, and the guarantee that after one message	1069	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	1070	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	1071	same port are lost as well, until monitoring raises an error, so there are
771	sequence.	1072	no silent "holes" in the message sequence.
		1073
		1074	If you want your software to be very reliable, you have to cope with
		1075	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1076	simply tries to work better in common error cases, such as when a network
		1077	link goes down.
772		1078
773	=item * Erlang can send messages to the wrong port, AEMP does not.	1079	=item * Erlang can send messages to the wrong port, AEMP does not.
774		1080
775	In Erlang it is quite likely that a node that restarts reuses a process ID	1081	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	1082	process ID known to other nodes for a completely different process,
777	destined for that process to end up in an unrelated process.	1083	causing messages destined for that process to end up in an unrelated
		1084	process.
778		1085
779	AEMP never reuses port IDs, so old messages or old port IDs floating	1086	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.	1087	around in the network will not be sent to an unrelated port.
781		1088
782	=item * Erlang uses unprotected connections, AEMP uses secure	1089	=item * Erlang uses unprotected connections, AEMP uses secure
783	authentication and can use TLS.	1090	authentication and can use TLS.
784		1091
…		…
787		1094
788	=item * The AEMP protocol is optimised for both text-based and binary	1095	=item * The AEMP protocol is optimised for both text-based and binary
789	communications.	1096	communications.
790		1097
791	The AEMP protocol, unlike the Erlang protocol, supports both programming	1098	The AEMP protocol, unlike the Erlang protocol, supports both programming
792	language independent text-only protocols (good for debugging) and binary,	1099	language independent text-only protocols (good for debugging), and binary,
793	language-specific serialisers (e.g. Storable). By default, unless TLS is	1100	language-specific serialisers (e.g. Storable). By default, unless TLS is
794	used, the protocol is actually completely text-based.	1101	used, the protocol is actually completely text-based.
795		1102
796	It has also been carefully designed to be implementable in other languages	1103	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	1104	with a minimum of work while gracefully degrading functionality to make the
798	protocol simple.	1105	protocol simple.
799		1106
800	=item * AEMP has more flexible monitoring options than Erlang.	1107	=item * AEMP has more flexible monitoring options than Erlang.
801		1108
802	In Erlang, you can chose to receive I<all> exit signals as messages	1109	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	1110	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	1111	difficult to implement.
805	Erlang, as one can choose between automatic kill, exit message or callback	1112
806	on a per-process basis.	1113	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1114	between automatic kill, exit message or callback on a per-port basis.
807		1115
808	=item * Erlang tries to hide remote/local connections, AEMP does not.	1116	=item * Erlang tries to hide remote/local connections, AEMP does not.
809		1117
810	Monitoring in Erlang is not an indicator of process death/crashes, in the	1118	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).	1119	same way as linking is (except linking is unreliable in Erlang).
…		…
833	overhead, as well as having to keep a proxy object everywhere.	1141	overhead, as well as having to keep a proxy object everywhere.
834		1142
835	Strings can easily be printed, easily serialised etc. and need no special	1143	Strings can easily be printed, easily serialised etc. and need no special
836	procedures to be "valid".	1144	procedures to be "valid".
837		1145
838	And as a result, a miniport consists of a single closure stored in a	1146	And as a result, a port with just a default receiver consists of a single
839	global hash - it can't become much cheaper.	1147	code reference stored in a global hash - it can't become much cheaper.
840		1148
841	=item Why favour JSON, why not a real serialising format such as Storable?	1149	=item Why favour JSON, why not a real serialising format such as Storable?
842		1150
843	In fact, any AnyEvent::MP node will happily accept Storable as framing	1151	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	1152	format, but currently there is no way to make a node use Storable by
…		…
860		1168
861	L<AnyEvent::MP::Intro> - a gentle introduction.	1169	L<AnyEvent::MP::Intro> - a gentle introduction.
862		1170
863	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1171	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
864		1172
865	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1173	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
866	your applications.	1174	your applications.
		1175
		1176	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
867		1177
868	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1178	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
869	all nodes.	1179	all nodes.
870		1180
871	L<AnyEvent>.	1181	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 1.128 by root, Sun Mar 4 14:28:44 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 1.128 by root, Sun Mar 4 14:28:44 2012 UTC