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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
30	rcv $port, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
31		31
32	# create a port on another node	32	# create a port on another node
33	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
34		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
35	# monitoring	39	# monitoring
36	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
38	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
39		51
40	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
41		53
42	bin/aemp - stable.	54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - explains most concepts.	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.	58	AnyEvent::MP::Global - stable API.
47
48	stay tuned.
49		59
50	=head1 DESCRIPTION	60	=head1 DESCRIPTION
51		61
52	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
53		63
…		…
68		78
69	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
70	some messages. Messages send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
71	anything was listening for them or not.	81	anything was listening for them or not.
72		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
73	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
74		86
75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
76	separator, and a port name (a printable string of unspecified format).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
77		90
78	=item node	91	=item node
79		92
80	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
81	which enables nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
82	ports.	95	ports.
83		96
84	Nodes are either public (have one or more listening ports) or private	97	Nodes are either public (have one or more listening ports) or private
85	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
86	currently.	99	currently, but all nodes can talk to public nodes.
87		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
88	=item node ID - C<[A-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 an 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 these additions:
		236
		237	=over 4
		238
		239	=item norc => $boolean (default false)
		240
		241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		242	be consulted - all configuraiton options must be specified in the
		243	C<configure> call.
		244
		245	=item force => $boolean (default false)
		246
		247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
		250
		251	=item secure => $pass->($nodeid)
		252
		253	In addition to specifying a boolean, you can specify a code reference that
		254	is called for every remote execution attempt - the execution request is
		255	granted iff the callback returns a true value.
		256
		257	See F<semp setsecure> for more info.
		258
		259	=back
		260
189	=over 4	261	=over 4
190		262
191	=item step 1, gathering configuration from profiles	263	=item step 1, gathering configuration from profiles
192		264
193	The function first looks up a profile in the aemp configuration (see the	265	The function first looks up a profile in the aemp configuration (see the
…		…
206	That means that the values specified in the profile have highest priority	278	That means that the values specified in the profile have highest priority
207	and the values specified directly via C<configure> have lowest priority,	279	and the values specified directly via C<configure> have lowest priority,
208	and can only be used to specify defaults.	280	and can only be used to specify defaults.
209		281
210	If the profile specifies a node ID, then this will become the node ID of	282	If the profile specifies a node ID, then this will become the node ID of
211	this process. If not, then the profile name will be used as node ID. The	283	this process. If not, then the profile name will be used as node ID, with
212	special node ID of C<anon/> will be replaced by a random node ID.	284	a unique randoms tring (C</%u>) appended.
		285
		286	The node ID can contain some C<%> sequences that are expanded: C<%n>
		287	is expanded to the local nodename, C<%u> is replaced by a random
		288	strign to make the node unique. For example, the F<aemp> commandline
		289	utility uses C<aemp/%n/%u> as nodename, which might expand to
		290	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
213		291
214	=item step 2, bind listener sockets	292	=item step 2, bind listener sockets
215		293
216	The next step is to look up the binds in the profile, followed by binding	294	The next step is to look up the binds in the profile, followed by binding
217	aemp protocol listeners on all binds specified (it is possible and valid	295	aemp protocol listeners on all binds specified (it is possible and valid
…		…
223	used, meaning the node will bind on a dynamically-assigned port on every	301	used, meaning the node will bind on a dynamically-assigned port on every
224	local IP address it finds.	302	local IP address it finds.
225		303
226	=item step 3, connect to seed nodes	304	=item step 3, connect to seed nodes
227		305
228	As the last step, the seeds list from the profile is passed to the	306	As the last step, the seed ID list from the profile is passed to the
229	L<AnyEvent::MP::Global> module, which will then use it to keep	307	L<AnyEvent::MP::Global> module, which will then use it to keep
230	connectivity with at least one node at any point in time.	308	connectivity with at least one node at any point in time.
231		309
232	=back	310	=back
233		311
234	Example: become a distributed node using the locla node name as profile.	312	Example: become a distributed node using the local node name as profile.
235	This should be the most common form of invocation for "daemon"-type nodes.	313	This should be the most common form of invocation for "daemon"-type nodes.
236		314
237	configure	315	configure
238		316
239	Example: become an anonymous node. This form is often used for commandline	317	Example: become a semi-anonymous node. This form is often used for
240	clients.	318	commandline clients.
241		319
242	configure nodeid => "anon/";	320	configure nodeid => "myscript/%n/%u";
243		321
244	Example: configure a node using a profile called seed, which si suitable	322	Example: configure a node using a profile called seed, which is suitable
245	for a seed node as it binds on all local addresses on a fixed port (4040,	323	for a seed node as it binds on all local addresses on a fixed port (4040,
246	customary for aemp).	324	customary for aemp).
247		325
248	# use the aemp commandline utility	326	# use the aemp commandline utility
249	# aemp profile seed nodeid anon/ binds '*:4040'	327	# aemp profile seed binds '*:4040'
250		328
251	# then use it	329	# then use it
252	configure profile => "seed";	330	configure profile => "seed";
253		331
254	# or simply use aemp from the shell again:	332	# or simply use aemp from the shell again:
…		…
324	sub _kilme {	402	sub _kilme {
325	die "received message on port without callback";	403	die "received message on port without callback";
326	}	404	}
327		405
328	sub port(;&) {	406	sub port(;&) {
329	my $id = "$UNIQ." . $ID++;	407	my $id = $UNIQ . ++$ID;
330	my $port = "$NODE#$id";	408	my $port = "$NODE#$id";
331		409
332	rcv $port, shift \|\| \&_kilme;	410	rcv $port, shift \|\| \&_kilme;
333		411
334	$port	412	$port
…		…
373	msg1 => sub { ... },	451	msg1 => sub { ... },
374	...	452	...
375	;	453	;
376		454
377	Example: temporarily register a rcv callback for a tag matching some port	455	Example: temporarily register a rcv callback for a tag matching some port
378	(e.g. for a rpc reply) and unregister it after a message was received.	456	(e.g. for an rpc reply) and unregister it after a message was received.
379		457
380	rcv $port, $otherport => sub {	458	rcv $port, $otherport => sub {
381	my @reply = @_;	459	my @reply = @_;
382		460
383	rcv $SELF, $otherport;	461	rcv $SELF, $otherport;
…		…
396	if (ref $_[0]) {	474	if (ref $_[0]) {
397	if (my $self = $PORT_DATA{$portid}) {	475	if (my $self = $PORT_DATA{$portid}) {
398	"AnyEvent::MP::Port" eq ref $self	476	"AnyEvent::MP::Port" eq ref $self
399	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	477	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
400		478
401	$self->[2] = shift;	479	$self->[0] = shift;
402	} else {	480	} else {
403	my $cb = shift;	481	my $cb = shift;
404	$PORT{$portid} = sub {	482	$PORT{$portid} = sub {
405	local $SELF = $port;	483	local $SELF = $port;
406	eval { &$cb }; _self_die if $@;	484	eval { &$cb }; _self_die if $@;
407	};	485	};
408	}	486	}
409	} elsif (defined $_[0]) {	487	} elsif (defined $_[0]) {
410	my $self = $PORT_DATA{$portid} \|\|= do {	488	my $self = $PORT_DATA{$portid} \|\|= do {
411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	489	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
412		490
413	$PORT{$portid} = sub {	491	$PORT{$portid} = sub {
414	local $SELF = $port;	492	local $SELF = $port;
415		493
416	if (my $cb = $self->[1]{$_[0]}) {	494	if (my $cb = $self->[1]{$_[0]}) {
…		…
438	}	516	}
439		517
440	$port	518	$port
441	}	519	}
442		520
		521	=item peval $port, $coderef[, @args]
		522
		523	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		524	when the code throews an exception the C<$port> will be killed.
		525
		526	Any remaining args will be passed to the callback. Any return values will
		527	be returned to the caller.
		528
		529	This is useful when you temporarily want to execute code in the context of
		530	a port.
		531
		532	Example: create a port and run some initialisation code in it's context.
		533
		534	my $port = port { ... };
		535
		536	peval $port, sub {
		537	init
		538	or die "unable to init";
		539	};
		540
		541	=cut
		542
		543	sub peval($$) {
		544	local $SELF = shift;
		545	my $cb = shift;
		546
		547	if (wantarray) {
		548	my @res = eval { &$cb };
		549	_self_die if $@;
		550	@res
		551	} else {
		552	my $res = eval { &$cb };
		553	_self_die if $@;
		554	$res
		555	}
		556	}
		557
443	=item $closure = psub { BLOCK }	558	=item $closure = psub { BLOCK }
444		559
445	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	560	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
446	closure is executed, sets up the environment in the same way as in C<rcv>	561	closure is executed, sets up the environment in the same way as in C<rcv>
447	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	562	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		563
		564	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		565	BLOCK }, @_ } >>.
448		566
449	This is useful when you register callbacks from C<rcv> callbacks:	567	This is useful when you register callbacks from C<rcv> callbacks:
450		568
451	rcv delayed_reply => sub {	569	rcv delayed_reply => sub {
452	my ($delay, @reply) = @_;	570	my ($delay, @reply) = @_;
…		…
525	delivered again.	643	delivered again.
526		644
527	Inter-host-connection timeouts and monitoring depend on the transport	645	Inter-host-connection timeouts and monitoring depend on the transport
528	used. The only transport currently implemented is TCP, and AnyEvent::MP	646	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	647	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).	648	non-idle connection, and usually around two hours for idle connections).
531		649
532	This means that monitoring is good for program errors and cleaning up	650	This means that monitoring is good for program errors and cleaning up
533	stuff eventually, but they are no replacement for a timeout when you need	651	stuff eventually, but they are no replacement for a timeout when you need
534	to ensure some maximum latency.	652	to ensure some maximum latency.
535		653
…		…
567	}	685	}
568		686
569	$node->monitor ($port, $cb);	687	$node->monitor ($port, $cb);
570		688
571	defined wantarray	689	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	690	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
573	}	691	}
574		692
575	=item $guard = mon_guard $port, $ref, $ref...	693	=item $guard = mon_guard $port, $ref, $ref...
576		694
577	Monitors the given C<$port> and keeps the passed references. When the port	695	Monitors the given C<$port> and keeps the passed references. When the port
…		…
600		718
601	=item kil $port[, @reason]	719	=item kil $port[, @reason]
602		720
603	Kill the specified port with the given C<@reason>.	721	Kill the specified port with the given C<@reason>.
604		722
605	If no C<@reason> is specified, then the port is killed "normally" (ports	723	If no C<@reason> is specified, then the port is killed "normally" -
606	monitoring other ports will not necessarily die because a port dies	724	monitor callback will be invoked, but the kil will not cause linked ports
607	"normally").	725	(C<mon $mport, $lport> form) to get killed.
608		726
609	Otherwise, linked ports get killed with the same reason (second form of	727	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
610	C<mon>, see above).	728	form) get killed with the same reason.
611		729
612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	730	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
613	will be reported as reason C<< die => $@ >>.	731	will be reported as reason C<< die => $@ >>.
614		732
615	Transport/communication errors are reported as C<< transport_error =>	733	Transport/communication errors are reported as C<< transport_error =>
…		…
681	}	799	}
682		800
683	sub spawn(@) {	801	sub spawn(@) {
684	my ($nodeid, undef) = split /#/, shift, 2;	802	my ($nodeid, undef) = split /#/, shift, 2;
685		803
686	my $id = "$RUNIQ." . $ID++;	804	my $id = $RUNIQ . ++$ID;
687		805
688	$_[0] =~ /::/	806	$_[0] =~ /::/
689	or Carp::croak "spawn init function must be a fully-qualified name, caught";	807	or Carp::croak "spawn init function must be a fully-qualified name, caught";
690		808
691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	809	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
692		810
693	"$nodeid#$id"	811	"$nodeid#$id"
694	}	812	}
		813
695		814
696	=item after $timeout, @msg	815	=item after $timeout, @msg
697		816
698	=item after $timeout, $callback	817	=item after $timeout, $callback
699		818
…		…
715	? $action[0]()	834	? $action[0]()
716	: snd @action;	835	: snd @action;
717	};	836	};
718	}	837	}
719		838
		839	=item cal $port, @msg, $callback[, $timeout]
		840
		841	A simple form of RPC - sends a message to the given C<$port> with the
		842	given contents (C<@msg>), but adds a reply port to the message.
		843
		844	The reply port is created temporarily just for the purpose of receiving
		845	the reply, and will be C<kil>ed when no longer needed.
		846
		847	A reply message sent to the port is passed to the C<$callback> as-is.
		848
		849	If an optional time-out (in seconds) is given and it is not C<undef>,
		850	then the callback will be called without any arguments after the time-out
		851	elapsed and the port is C<kil>ed.
		852
		853	If no time-out is given (or it is C<undef>), then the local port will
		854	monitor the remote port instead, so it eventually gets cleaned-up.
		855
		856	Currently this function returns the temporary port, but this "feature"
		857	might go in future versions unless you can make a convincing case that
		858	this is indeed useful for something.
		859
		860	=cut
		861
		862	sub cal(@) {
		863	my $timeout = ref $_[-1] ? undef : pop;
		864	my $cb = pop;
		865
		866	my $port = port {
		867	undef $timeout;
		868	kil $SELF;
		869	&$cb;
		870	};
		871
		872	if (defined $timeout) {
		873	$timeout = AE::timer $timeout, 0, sub {
		874	undef $timeout;
		875	kil $port;
		876	$cb->();
		877	};
		878	} else {
		879	mon $_[0], sub {
		880	kil $port;
		881	$cb->();
		882	};
		883	}
		884
		885	push @_, $port;
		886	&snd;
		887
		888	$port
		889	}
		890
		891	=back
		892
		893	=head1 DISTRIBUTED DATABASE
		894
		895	AnyEvent::MP comes with a simple distributed database. The database will
		896	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		897	the global nodes for their needs.
		898
		899	The database consists of a two-level hash - a hash contains a hash which
		900	contains values.
		901
		902	The top level hash key is called "family", and the second-level hash key
		903	is called "subkey" or simply "key".
		904
		905	The family must be alphanumeric, i.e. start with a letter and consist
		906	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		907	pretty much like Perl module names.
		908
		909	As the family namespace is global, it is recommended to prefix family names
		910	with the name of the application or module using it.
		911
		912	The subkeys must be non-empty strings, with no further restrictions.
		913
		914	The values should preferably be strings, but other perl scalars should
		915	work as well (such as undef, arrays and hashes).
		916
		917	Every database entry is owned by one node - adding the same family/subkey
		918	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		919	but the result might be nondeterministic, i.e. the key might have
		920	different values on different nodes.
		921
		922	Different subkeys in the same family can be owned by different nodes
		923	without problems, and in fact, this is the common method to create worker
		924	pools. For example, a worker port for image scaling might do this:
		925
		926	db_set my_image_scalers => $port;
		927
		928	And clients looking for an image scaler will want to get the
		929	C<my_image_scalers> keys:
		930
		931	db_keys "my_image_scalers" => 60 => sub {
		932	#d##TODO#
		933
		934	=over
		935
		936	=item db_set $family => $subkey [=> $value]
		937
		938	Sets (or replaces) a key to the database - if C<$value> is omitted,
		939	C<undef> is used instead.
		940
		941	=item db_del $family => $subkey
		942
		943	Deletes a key from the database.
		944
		945	=item $guard = db_reg $family => $subkey [=> $value]
		946
		947	Sets the key on the database and returns a guard. When the guard is
		948	destroyed, the key is deleted from the database. If C<$value> is missing,
		949	then C<undef> is used.
		950
		951	=cut
		952
720	=back	953	=back
721		954
722	=head1 AnyEvent::MP vs. Distributed Erlang	955	=head1 AnyEvent::MP vs. Distributed Erlang
723		956
724	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	957	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
725	== aemp node, Erlang process == aemp port), so many of the documents and	958	== aemp node, Erlang process == aemp port), so many of the documents and
726	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	959	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
727	sample:	960	sample:
728		961
729	http://www.Erlang.se/doc/programming_rules.shtml	962	http://www.erlang.se/doc/programming_rules.shtml
730	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	963	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
731	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	964	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
732	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	965	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
733		966
734	Despite the similarities, there are also some important differences:	967	Despite the similarities, there are also some important differences:
735		968
736	=over 4	969	=over 4
737		970
738	=item * Node IDs are arbitrary strings in AEMP.	971	=item * Node IDs are arbitrary strings in AEMP.
739		972
740	Erlang relies on special naming and DNS to work everywhere in the same	973	Erlang relies on special naming and DNS to work everywhere in the same
741	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	974	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
742	configuration or DNS), but will otherwise discover other odes itself.	975	configuration or DNS), and possibly the addresses of some seed nodes, but
		976	will otherwise discover other nodes (and their IDs) itself.
743		977
744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	978	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
745	uses "local ports are like remote ports".	979	uses "local ports are like remote ports".
746		980
747	The failure modes for local ports are quite different (runtime errors	981	The failure modes for local ports are quite different (runtime errors
…		…
756	ports being the special case/exception, where transport errors cannot	990	ports being the special case/exception, where transport errors cannot
757	occur.	991	occur.
758		992
759	=item * Erlang uses processes and a mailbox, AEMP does not queue.	993	=item * Erlang uses processes and a mailbox, AEMP does not queue.
760		994
761	Erlang uses processes that selectively receive messages, and therefore	995	Erlang uses processes that selectively receive messages out of order, and
762	needs a queue. AEMP is event based, queuing messages would serve no	996	therefore needs a queue. AEMP is event based, queuing messages would serve
763	useful purpose. For the same reason the pattern-matching abilities of	997	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	998	of AnyEvent::MP are more limited, as there is little need to be able to
765	filter messages without dequeuing them.	999	filter messages without dequeuing them.
766		1000
767	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1001	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1002	being event-based, while Erlang is process-based.
		1003
		1004	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1005	top of AEMP and Coro threads.
768		1006
769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1007	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
770		1008
771	Sending messages in Erlang is synchronous and blocks the process (and	1009	Sending messages in Erlang is synchronous and blocks the process until
		1010	a conenction has been established and the message sent (and so does not
772	so does not need a queue that can overflow). AEMP sends are immediate,	1011	need a queue that can overflow). AEMP sends return immediately, connection
773	connection establishment is handled in the background.	1012	establishment is handled in the background.
774		1013
775	=item * Erlang suffers from silent message loss, AEMP does not.	1014	=item * Erlang suffers from silent message loss, AEMP does not.
776		1015
777	Erlang makes few guarantees on messages delivery - messages can get lost	1016	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,	1017	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).	1018	b, and c, and the other side only receives messages a and c).
780		1019
781	AEMP guarantees correct ordering, and the guarantee that after one message	1020	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	1021	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	1022	same port are lost as well, until monitoring raises an error, so there are
784	sequence.	1023	no silent "holes" in the message sequence.
		1024
		1025	If you want your software to be very reliable, you have to cope with
		1026	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1027	simply tries to work better in common error cases, such as when a network
		1028	link goes down.
785		1029
786	=item * Erlang can send messages to the wrong port, AEMP does not.	1030	=item * Erlang can send messages to the wrong port, AEMP does not.
787		1031
788	In Erlang it is quite likely that a node that restarts reuses a process ID	1032	In Erlang it is quite likely that a node that restarts reuses an Erlang
789	known to other nodes for a completely different process, causing messages	1033	process ID known to other nodes for a completely different process,
790	destined for that process to end up in an unrelated process.	1034	causing messages destined for that process to end up in an unrelated
		1035	process.
791		1036
792	AEMP never reuses port IDs, so old messages or old port IDs floating	1037	AEMP does not reuse port IDs, so old messages or old port IDs floating
793	around in the network will not be sent to an unrelated port.	1038	around in the network will not be sent to an unrelated port.
794		1039
795	=item * Erlang uses unprotected connections, AEMP uses secure	1040	=item * Erlang uses unprotected connections, AEMP uses secure
796	authentication and can use TLS.	1041	authentication and can use TLS.
797		1042
…		…
800		1045
801	=item * The AEMP protocol is optimised for both text-based and binary	1046	=item * The AEMP protocol is optimised for both text-based and binary
802	communications.	1047	communications.
803		1048
804	The AEMP protocol, unlike the Erlang protocol, supports both programming	1049	The AEMP protocol, unlike the Erlang protocol, supports both programming
805	language independent text-only protocols (good for debugging) and binary,	1050	language independent text-only protocols (good for debugging), and binary,
806	language-specific serialisers (e.g. Storable). By default, unless TLS is	1051	language-specific serialisers (e.g. Storable). By default, unless TLS is
807	used, the protocol is actually completely text-based.	1052	used, the protocol is actually completely text-based.
808		1053
809	It has also been carefully designed to be implementable in other languages	1054	It has also been carefully designed to be implementable in other languages
810	with a minimum of work while gracefully degrading functionality to make the	1055	with a minimum of work while gracefully degrading functionality to make the
811	protocol simple.	1056	protocol simple.
812		1057
813	=item * AEMP has more flexible monitoring options than Erlang.	1058	=item * AEMP has more flexible monitoring options than Erlang.
814		1059
815	In Erlang, you can chose to receive I<all> exit signals as messages	1060	In Erlang, you can chose to receive I<all> exit signals as messages or
816	or I<none>, there is no in-between, so monitoring single processes is	1061	I<none>, there is no in-between, so monitoring single Erlang processes is
817	difficult to implement. Monitoring in AEMP is more flexible than in	1062	difficult to implement.
818	Erlang, as one can choose between automatic kill, exit message or callback	1063
819	on a per-process basis.	1064	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1065	between automatic kill, exit message or callback on a per-port basis.
820		1066
821	=item * Erlang tries to hide remote/local connections, AEMP does not.	1067	=item * Erlang tries to hide remote/local connections, AEMP does not.
822		1068
823	Monitoring in Erlang is not an indicator of process death/crashes, in the	1069	Monitoring in Erlang is not an indicator of process death/crashes, in the
824	same way as linking is (except linking is unreliable in Erlang).	1070	same way as linking is (except linking is unreliable in Erlang).
…		…
846	overhead, as well as having to keep a proxy object everywhere.	1092	overhead, as well as having to keep a proxy object everywhere.
847		1093
848	Strings can easily be printed, easily serialised etc. and need no special	1094	Strings can easily be printed, easily serialised etc. and need no special
849	procedures to be "valid".	1095	procedures to be "valid".
850		1096
851	And as a result, a miniport consists of a single closure stored in a	1097	And as a result, a port with just a default receiver consists of a single
852	global hash - it can't become much cheaper.	1098	code reference stored in a global hash - it can't become much cheaper.
853		1099
854	=item Why favour JSON, why not a real serialising format such as Storable?	1100	=item Why favour JSON, why not a real serialising format such as Storable?
855		1101
856	In fact, any AnyEvent::MP node will happily accept Storable as framing	1102	In fact, any AnyEvent::MP node will happily accept Storable as framing
857	format, but currently there is no way to make a node use Storable by	1103	format, but currently there is no way to make a node use Storable by
…		…
873		1119
874	L<AnyEvent::MP::Intro> - a gentle introduction.	1120	L<AnyEvent::MP::Intro> - a gentle introduction.
875		1121
876	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1122	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
877		1123
878	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1124	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
879	your applications.	1125	your applications.
		1126
		1127	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
880		1128
881	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1129	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
882	all nodes.	1130	all nodes.
883		1131
884	L<AnyEvent>.	1132	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC vs. Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC