[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 1.130 by root, Fri Mar 9 17:05:26 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 $port, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
38	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @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
		202	db_mon db_family db_keys db_values
157	);	203	);
158		204
159	our $SELF;	205	our $SELF;
160		206
161	sub _self_die() {	207	sub _self_die() {
…		…
184	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
185		231
186	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
187	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
188		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
189	=over 4	262	=over 4
190		263
191	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
192		265
193	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
…		…
206	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
207	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
208	and can only be used to specify defaults.	281	and can only be used to specify defaults.
209		282
210	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
211	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
212	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>.
213		292
214	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
215		294
216	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
217	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
…		…
223	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
224	local IP address it finds.	303	local IP address it finds.
225		304
226	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
227		306
228	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
229	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
230	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
231		310
232	=back	311	=back
233		312
234	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.
235	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.
236		315
237	configure	316	configure
238		317
239	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
240	clients.	319	commandline clients.
241		320
242	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
243		322
244	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
245	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,
246	customary for aemp).	325	customary for aemp).
247		326
248	# use the aemp commandline utility	327	# use the aemp commandline utility
249	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
250		329
251	# then use it	330	# then use it
252	configure profile => "seed";	331	configure profile => "seed";
253		332
254	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
324	sub _kilme {	403	sub _kilme {
325	die "received message on port without callback";	404	die "received message on port without callback";
326	}	405	}
327		406
328	sub port(;&) {	407	sub port(;&) {
329	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
330	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
331		410
332	rcv $port, shift \|\| \&_kilme;	411	rcv $port, shift \|\| \&_kilme;
333		412
334	$port	413	$port
…		…
373	msg1 => sub { ... },	452	msg1 => sub { ... },
374	...	453	...
375	;	454	;
376		455
377	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
378	(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.
379		458
380	rcv $port, $otherport => sub {	459	rcv $port, $otherport => sub {
381	my @reply = @_;	460	my @reply = @_;
382		461
383	rcv $SELF, $otherport;	462	rcv $SELF, $otherport;
…		…
396	if (ref $_[0]) {	475	if (ref $_[0]) {
397	if (my $self = $PORT_DATA{$portid}) {	476	if (my $self = $PORT_DATA{$portid}) {
398	"AnyEvent::MP::Port" eq ref $self	477	"AnyEvent::MP::Port" eq ref $self
399	or Carp::croak "$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";
400		479
401	$self->[2] = shift;	480	$self->[0] = shift;
402	} else {	481	} else {
403	my $cb = shift;	482	my $cb = shift;
404	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
405	local $SELF = $port;	484	local $SELF = $port;
406	eval { &$cb }; _self_die if $@;	485	eval { &$cb }; _self_die if $@;
407	};	486	};
408	}	487	}
409	} elsif (defined $_[0]) {	488	} elsif (defined $_[0]) {
410	my $self = $PORT_DATA{$portid} \|\|= do {	489	my $self = $PORT_DATA{$portid} \|\|= do {
411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	490	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
412		491
413	$PORT{$portid} = sub {	492	$PORT{$portid} = sub {
414	local $SELF = $port;	493	local $SELF = $port;
415		494
416	if (my $cb = $self->[1]{$_[0]}) {	495	if (my $cb = $self->[1]{$_[0]}) {
…		…
438	}	517	}
439		518
440	$port	519	$port
441	}	520	}
442		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
443	=item $closure = psub { BLOCK }	559	=item $closure = psub { BLOCK }
444		560
445	Remembers C<$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
446	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>
447	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 $SELF, sub {
		566	BLOCK }, @_ } >>.
448		567
449	This is useful when you register callbacks from C<rcv> callbacks:	568	This is useful when you register callbacks from C<rcv> callbacks:
450		569
451	rcv delayed_reply => sub {	570	rcv delayed_reply => sub {
452	my ($delay, @reply) = @_;	571	my ($delay, @reply) = @_;
…		…
525	delivered again.	644	delivered again.
526		645
527	Inter-host-connection timeouts and monitoring depend on the transport	646	Inter-host-connection timeouts and monitoring depend on the transport
528	used. The only transport currently implemented is TCP, and AnyEvent::MP	647	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	648	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).	649	non-idle connection, and usually around two hours for idle connections).
531		650
532	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
533	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
534	to ensure some maximum latency.	653	to ensure some maximum latency.
535		654
…		…
567	}	686	}
568		687
569	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
570		689
571	defined wantarray	690	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
573	}	692	}
574		693
575	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
576		695
577	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
…		…
600		719
601	=item kil $port[, @reason]	720	=item kil $port[, @reason]
602		721
603	Kill the specified port with the given C<@reason>.	722	Kill the specified port with the given C<@reason>.
604		723
605	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" -
606	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
607	"normally").	726	(C<mon $mport, $lport> form) to get killed.
608		727
609	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>
610	C<mon>, see above).	729	form) get killed with the same reason.
611		730
612	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
613	will be reported as reason C<< die => $@ >>.	732	will be reported as reason C<< die => $@ >>.
614		733
615	Transport/communication errors are reported as C<< transport_error =>	734	Transport/communication errors are reported as C<< transport_error =>
…		…
681	}	800	}
682		801
683	sub spawn(@) {	802	sub spawn(@) {
684	my ($nodeid, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
685		804
686	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
687		806
688	$_[0] =~ /::/	807	$_[0] =~ /::/
689	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";
690		809
691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
692		811
693	"$nodeid#$id"	812	"$nodeid#$id"
694	}	813	}
		814
695		815
696	=item after $timeout, @msg	816	=item after $timeout, @msg
697		817
698	=item after $timeout, $callback	818	=item after $timeout, $callback
699		819
…		…
715	? $action[0]()	835	? $action[0]()
716	: snd @action;	836	: snd @action;
717	};	837	};
718	}	838	}
719		839
		840	#=item $cb2 = timeout $seconds, $cb[, @args]
		841
		842	=item cal $port, @msg, $callback[, $timeout]
		843
		844	A simple form of RPC - sends a message to the given C<$port> with the
		845	given contents (C<@msg>), but adds a reply port to the message.
		846
		847	The reply port is created temporarily just for the purpose of receiving
		848	the reply, and will be C<kil>ed when no longer needed.
		849
		850	A reply message sent to the port is passed to the C<$callback> as-is.
		851
		852	If an optional time-out (in seconds) is given and it is not C<undef>,
		853	then the callback will be called without any arguments after the time-out
		854	elapsed and the port is C<kil>ed.
		855
		856	If no time-out is given (or it is C<undef>), then the local port will
		857	monitor the remote port instead, so it eventually gets cleaned-up.
		858
		859	Currently this function returns the temporary port, but this "feature"
		860	might go in future versions unless you can make a convincing case that
		861	this is indeed useful for something.
		862
		863	=cut
		864
		865	sub cal(@) {
		866	my $timeout = ref $_[-1] ? undef : pop;
		867	my $cb = pop;
		868
		869	my $port = port {
		870	undef $timeout;
		871	kil $SELF;
		872	&$cb;
		873	};
		874
		875	if (defined $timeout) {
		876	$timeout = AE::timer $timeout, 0, sub {
		877	undef $timeout;
		878	kil $port;
		879	$cb->();
		880	};
		881	} else {
		882	mon $_[0], sub {
		883	kil $port;
		884	$cb->();
		885	};
		886	}
		887
		888	push @_, $port;
		889	&snd;
		890
		891	$port
		892	}
		893
		894	=back
		895
		896	=head1 DISTRIBUTED DATABASE
		897
		898	AnyEvent::MP comes with a simple distributed database. The database will
		899	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		900	the global nodes for their needs.
		901
		902	The database consists of a two-level hash - a hash contains a hash which
		903	contains values.
		904
		905	The top level hash key is called "family", and the second-level hash key
		906	is called "subkey" or simply "key".
		907
		908	The family must be alphanumeric, i.e. start with a letter and consist
		909	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		910	pretty much like Perl module names.
		911
		912	As the family namespace is global, it is recommended to prefix family names
		913	with the name of the application or module using it.
		914
		915	The subkeys must be non-empty strings, with no further restrictions.
		916
		917	The values should preferably be strings, but other perl scalars should
		918	work as well (such as undef, arrays and hashes).
		919
		920	Every database entry is owned by one node - adding the same family/subkey
		921	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		922	but the result might be nondeterministic, i.e. the key might have
		923	different values on different nodes.
		924
		925	Different subkeys in the same family can be owned by different nodes
		926	without problems, and in fact, this is the common method to create worker
		927	pools. For example, a worker port for image scaling might do this:
		928
		929	db_set my_image_scalers => $port;
		930
		931	And clients looking for an image scaler will want to get the
		932	C<my_image_scalers> keys from time to time:
		933
		934	db_keys my_image_scalers => sub {
		935	@ports = @{ $_[0] };
		936	};
		937
		938	Or better yet, they want to monitor the database family, so they always
		939	have a reasonable up-to-date copy:
		940
		941	db_mon my_image_scalers => sub {
		942	@ports = keys %{ $_[0] };
		943	};
		944
		945	In general, you can set or delete single subkeys, but query and monitor
		946	whole families only.
		947
		948	If you feel the need to monitor or query a single subkey, try giving it
		949	it's own family.
		950
		951	=over
		952
		953	=item db_set $family => $subkey [=> $value]
		954
		955	Sets (or replaces) a key to the database - if C<$value> is omitted,
		956	C<undef> is used instead.
		957
		958	=item db_del $family => $subkey...
		959
		960	Deletes one or more subkeys from the database family.
		961
		962	=item $guard = db_reg $family => $subkey [=> $value]
		963
		964	Sets the key on the database and returns a guard. When the guard is
		965	destroyed, the key is deleted from the database. If C<$value> is missing,
		966	then C<undef> is used.
		967
		968	=item db_family $family => $cb->(\%familyhash)
		969
		970	Queries the named database C<$family> and call the callback with the
		971	family represented as a hash. You can keep and freely modify the hash.
		972
		973	=item db_keys $family => $cb->(\@keys)
		974
		975	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		976	them as array reference to the callback.
		977
		978	=item db_values $family => $cb->(\@values)
		979
		980	Same as C<db_family>, except it only queries the family I<values> and passes them
		981	as array reference to the callback.
		982
		983	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		984
		985	Creates a monitor on the given database family. Each time a key is set
		986	or or is deleted the callback is called with a hash containing the
		987	database family and three lists of added, changed and deleted subkeys,
		988	respectively. If no keys have changed then the array reference might be
		989	C<undef> or even missing.
		990
		991	The family hash reference and the key arrays belong to AnyEvent::MP and
		992	B<must not be modified or stored> by the callback. When in doubt, make a
		993	copy.
		994
		995	As soon as possible after the monitoring starts, the callback will be
		996	called with the intiial contents of the family, even if it is empty,
		997	i.e. there will always be a timely call to the callback with the current
		998	contents.
		999
		1000	It is possible that the callback is called with a change event even though
		1001	the subkey is already present and the value has not changed.
		1002
		1003	The monitoring stops when the guard object is destroyed.
		1004
		1005	Example: on every change to the family "mygroup", print out all keys.
		1006
		1007	my $guard = db_mon mygroup => sub {
		1008	my ($family, $a, $c, $d) = @_;
		1009	print "mygroup members: ", (join " ", keys %$family), "\n";
		1010	};
		1011
		1012	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1013
		1014	my $guard; $guard = db_mon My::Module::workers => sub {
		1015	my ($family, $a, $c, $d) = @_;
		1016	return unless %$family;
		1017	undef $guard;
		1018	print "My::Module::workers now nonempty\n";
		1019	};
		1020
		1021	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1022
		1023	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1024	my ($family, $a, $c, $d) = @_;
		1025
		1026	print "+$_=$family->{$_}\n" for @$a;
		1027	print "*$_=$family->{$_}\n" for @$c;
		1028	print "-$_=$family->{$_}\n" for @$d;
		1029	};
		1030
		1031	=cut
		1032
720	=back	1033	=back
721		1034
722	=head1 AnyEvent::MP vs. Distributed Erlang	1035	=head1 AnyEvent::MP vs. Distributed Erlang
723		1036
724	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1037	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	1038	== 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	1039	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
727	sample:	1040	sample:
728		1041
729	http://www.Erlang.se/doc/programming_rules.shtml	1042	http://www.erlang.se/doc/programming_rules.shtml
730	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1043	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	1044	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	1045	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
733		1046
734	Despite the similarities, there are also some important differences:	1047	Despite the similarities, there are also some important differences:
735		1048
736	=over 4	1049	=over 4
737		1050
738	=item * Node IDs are arbitrary strings in AEMP.	1051	=item * Node IDs are arbitrary strings in AEMP.
739		1052
740	Erlang relies on special naming and DNS to work everywhere in the same	1053	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	1054	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.	1055	configuration or DNS), and possibly the addresses of some seed nodes, but
		1056	will otherwise discover other nodes (and their IDs) itself.
743		1057
744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1058	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
745	uses "local ports are like remote ports".	1059	uses "local ports are like remote ports".
746		1060
747	The failure modes for local ports are quite different (runtime errors	1061	The failure modes for local ports are quite different (runtime errors
…		…
756	ports being the special case/exception, where transport errors cannot	1070	ports being the special case/exception, where transport errors cannot
757	occur.	1071	occur.
758		1072
759	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1073	=item * Erlang uses processes and a mailbox, AEMP does not queue.
760		1074
761	Erlang uses processes that selectively receive messages, and therefore	1075	Erlang uses processes that selectively receive messages out of order, and
762	needs a queue. AEMP is event based, queuing messages would serve no	1076	therefore needs a queue. AEMP is event based, queuing messages would serve
763	useful purpose. For the same reason the pattern-matching abilities of	1077	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	1078	of AnyEvent::MP are more limited, as there is little need to be able to
765	filter messages without dequeuing them.	1079	filter messages without dequeuing them.
766		1080
767	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1081	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1082	being event-based, while Erlang is process-based.
		1083
		1084	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1085	top of AEMP and Coro threads.
768		1086
769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1087	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
770		1088
771	Sending messages in Erlang is synchronous and blocks the process (and	1089	Sending messages in Erlang is synchronous and blocks the process until
		1090	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,	1091	need a queue that can overflow). AEMP sends return immediately, connection
773	connection establishment is handled in the background.	1092	establishment is handled in the background.
774		1093
775	=item * Erlang suffers from silent message loss, AEMP does not.	1094	=item * Erlang suffers from silent message loss, AEMP does not.
776		1095
777	Erlang makes few guarantees on messages delivery - messages can get lost	1096	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,	1097	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).	1098	b, and c, and the other side only receives messages a and c).
780		1099
781	AEMP guarantees correct ordering, and the guarantee that after one message	1100	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	1101	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	1102	same port are lost as well, until monitoring raises an error, so there are
784	sequence.	1103	no silent "holes" in the message sequence.
		1104
		1105	If you want your software to be very reliable, you have to cope with
		1106	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1107	simply tries to work better in common error cases, such as when a network
		1108	link goes down.
785		1109
786	=item * Erlang can send messages to the wrong port, AEMP does not.	1110	=item * Erlang can send messages to the wrong port, AEMP does not.
787		1111
788	In Erlang it is quite likely that a node that restarts reuses a process ID	1112	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	1113	process ID known to other nodes for a completely different process,
790	destined for that process to end up in an unrelated process.	1114	causing messages destined for that process to end up in an unrelated
		1115	process.
791		1116
792	AEMP never reuses port IDs, so old messages or old port IDs floating	1117	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.	1118	around in the network will not be sent to an unrelated port.
794		1119
795	=item * Erlang uses unprotected connections, AEMP uses secure	1120	=item * Erlang uses unprotected connections, AEMP uses secure
796	authentication and can use TLS.	1121	authentication and can use TLS.
797		1122
…		…
800		1125
801	=item * The AEMP protocol is optimised for both text-based and binary	1126	=item * The AEMP protocol is optimised for both text-based and binary
802	communications.	1127	communications.
803		1128
804	The AEMP protocol, unlike the Erlang protocol, supports both programming	1129	The AEMP protocol, unlike the Erlang protocol, supports both programming
805	language independent text-only protocols (good for debugging) and binary,	1130	language independent text-only protocols (good for debugging), and binary,
806	language-specific serialisers (e.g. Storable). By default, unless TLS is	1131	language-specific serialisers (e.g. Storable). By default, unless TLS is
807	used, the protocol is actually completely text-based.	1132	used, the protocol is actually completely text-based.
808		1133
809	It has also been carefully designed to be implementable in other languages	1134	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	1135	with a minimum of work while gracefully degrading functionality to make the
811	protocol simple.	1136	protocol simple.
812		1137
813	=item * AEMP has more flexible monitoring options than Erlang.	1138	=item * AEMP has more flexible monitoring options than Erlang.
814		1139
815	In Erlang, you can chose to receive I<all> exit signals as messages	1140	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	1141	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	1142	difficult to implement.
818	Erlang, as one can choose between automatic kill, exit message or callback	1143
819	on a per-process basis.	1144	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1145	between automatic kill, exit message or callback on a per-port basis.
820		1146
821	=item * Erlang tries to hide remote/local connections, AEMP does not.	1147	=item * Erlang tries to hide remote/local connections, AEMP does not.
822		1148
823	Monitoring in Erlang is not an indicator of process death/crashes, in the	1149	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).	1150	same way as linking is (except linking is unreliable in Erlang).
…		…
846	overhead, as well as having to keep a proxy object everywhere.	1172	overhead, as well as having to keep a proxy object everywhere.
847		1173
848	Strings can easily be printed, easily serialised etc. and need no special	1174	Strings can easily be printed, easily serialised etc. and need no special
849	procedures to be "valid".	1175	procedures to be "valid".
850		1176
851	And as a result, a miniport consists of a single closure stored in a	1177	And as a result, a port with just a default receiver consists of a single
852	global hash - it can't become much cheaper.	1178	code reference stored in a global hash - it can't become much cheaper.
853		1179
854	=item Why favour JSON, why not a real serialising format such as Storable?	1180	=item Why favour JSON, why not a real serialising format such as Storable?
855		1181
856	In fact, any AnyEvent::MP node will happily accept Storable as framing	1182	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	1183	format, but currently there is no way to make a node use Storable by
…		…
873		1199
874	L<AnyEvent::MP::Intro> - a gentle introduction.	1200	L<AnyEvent::MP::Intro> - a gentle introduction.
875		1201
876	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1202	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
877		1203
878	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1204	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
879	your applications.	1205	your applications.
		1206
		1207	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
880		1208
881	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1209	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
882	all nodes.	1210	all nodes.
883		1211
884	L<AnyEvent>.	1212	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 1.130 by root, Fri Mar 9 17:05:26 2012 UTC

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Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC vs.
Revision 1.130 by root, Fri Mar 9 17:05:26 2012 UTC