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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.81 by root, Mon Sep 7 18:33:44 2009 UTC vs.
Revision 1.137 by root, Wed Mar 21 23:48:39 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-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 => $pass->(@msg)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every code execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	Most of the time the callback should look only at
		259	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		260	actual message (which can be about anything, and is mostly provided for
		261	diagnostic purposes).
		262
		263	See F<semp setsecure> for more info.
		264
		265	=back
		266
176	=over 4	267	=over 4
177		268
178	=item step 1, gathering configuration from profiles	269	=item step 1, gathering configuration from profiles
179		270
180	The function first looks up a profile in the aemp configuration (see the	271	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	284	That means that the values specified in the profile have highest priority
194	and the values specified directly via C<configure> have lowest priority,	285	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	286	and can only be used to specify defaults.
196		287
197	If the profile specifies a node ID, then this will become the node ID of	288	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	289	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.	290	a unique randoms tring (C</%u>) appended.
		291
		292	The node ID can contain some C<%> sequences that are expanded: C<%n>
		293	is expanded to the local nodename, C<%u> is replaced by a random
		294	strign to make the node unique. For example, the F<aemp> commandline
		295	utility uses C<aemp/%n/%u> as nodename, which might expand to
		296	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
200		297
201	=item step 2, bind listener sockets	298	=item step 2, bind listener sockets
202		299
203	The next step is to look up the binds in the profile, followed by binding	300	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	301	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	307	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	308	local IP address it finds.
212		309
213	=item step 3, connect to seed nodes	310	=item step 3, connect to seed nodes
214		311
215	As the last step, the seeds list from the profile is passed to the	312	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	313	L<AnyEvent::MP::Global> module, which will then use it to keep
217	connectivity with at least one node at any point in time.	314	connectivity with at least one node at any point in time.
218		315
219	=back	316	=back
220		317
221	Example: become a distributed node using the locla node name as profile.	318	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.	319	This should be the most common form of invocation for "daemon"-type nodes.
223		320
224	configure	321	configure
225		322
226	Example: become an anonymous node. This form is often used for commandline	323	Example: become a semi-anonymous node. This form is often used for
227	clients.	324	commandline clients.
228		325
229	configure nodeid => "anon/";	326	configure nodeid => "myscript/%n/%u";
230		327
231	Example: configure a node using a profile called seed, which si suitable	328	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,	329	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	330	customary for aemp).
234		331
235	# use the aemp commandline utility	332	# use the aemp commandline utility
236	# aemp profile seed nodeid anon/ binds '*:4040'	333	# aemp profile seed binds '*:4040'
237		334
238	# then use it	335	# then use it
239	configure profile => "seed";	336	configure profile => "seed";
240		337
241	# or simply use aemp from the shell again:	338	# or simply use aemp from the shell again:
…		…
306		403
307	=cut	404	=cut
308		405
309	sub rcv($@);	406	sub rcv($@);
310		407
311	sub _kilme {	408	my $KILME = sub {
312	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
313	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
314		412
315	sub port(;&) {	413	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
318		416
319	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
320		418
321	$port	419	$port
322	}	420	}
323		421
324	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
329		427
330	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
331	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
332	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
333		431
334	The default callback received all messages not matched by a more specific	432	The default callback receives all messages not matched by a more specific
335	C<tag> match.	433	C<tag> match.
336		434
337	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
338		436
339	Register (or replace) callbacks to be called on messages starting with the	437	Register (or replace) callbacks to be called on messages starting with the
…		…
360	msg1 => sub { ... },	458	msg1 => sub { ... },
361	...	459	...
362	;	460	;
363		461
364	Example: temporarily register a rcv callback for a tag matching some port	462	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.	463	(e.g. for an rpc reply) and unregister it after a message was received.
366		464
367	rcv $port, $otherport => sub {	465	rcv $port, $otherport => sub {
368	my @reply = @_;	466	my @reply = @_;
369		467
370	rcv $SELF, $otherport;	468	rcv $SELF, $otherport;
…		…
383	if (ref $_[0]) {	481	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	482	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	483	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	484	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387		485
388	$self->[2] = shift;	486	$self->[0] = shift;
389	} else {	487	} else {
390	my $cb = shift;	488	my $cb = shift;
391	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
392	local $SELF = $port;	490	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	491	eval { &$cb }; _self_die if $@;
394	};	492	};
395	}	493	}
396	} elsif (defined $_[0]) {	494	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	495	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	496	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		497
400	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
401	local $SELF = $port;	499	local $SELF = $port;
402		500
403	if (my $cb = $self->[1]{$_[0]}) {	501	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	523	}
426		524
427	$port	525	$port
428	}	526	}
429		527
		528	=item peval $port, $coderef[, @args]
		529
		530	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		531	when the code throews an exception the C<$port> will be killed.
		532
		533	Any remaining args will be passed to the callback. Any return values will
		534	be returned to the caller.
		535
		536	This is useful when you temporarily want to execute code in the context of
		537	a port.
		538
		539	Example: create a port and run some initialisation code in it's context.
		540
		541	my $port = port { ... };
		542
		543	peval $port, sub {
		544	init
		545	or die "unable to init";
		546	};
		547
		548	=cut
		549
		550	sub peval($$) {
		551	local $SELF = shift;
		552	my $cb = shift;
		553
		554	if (wantarray) {
		555	my @res = eval { &$cb };
		556	_self_die if $@;
		557	@res
		558	} else {
		559	my $res = eval { &$cb };
		560	_self_die if $@;
		561	$res
		562	}
		563	}
		564
430	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
431		566
432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	567	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>	568	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.	569	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		570
		571	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		572	BLOCK }, @_ } >>.
435		573
436	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
437		575
438	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
512	delivered again.	650	delivered again.
513		651
514	Inter-host-connection timeouts and monitoring depend on the transport	652	Inter-host-connection timeouts and monitoring depend on the transport
515	used. The only transport currently implemented is TCP, and AnyEvent::MP	653	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	654	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).	655	non-idle connection, and usually around two hours for idle connections).
518		656
519	This means that monitoring is good for program errors and cleaning up	657	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	658	stuff eventually, but they are no replacement for a timeout when you need
521	to ensure some maximum latency.	659	to ensure some maximum latency.
522		660
…		…
554	}	692	}
555		693
556	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
557		695
558	defined wantarray	696	defined wantarray
559	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
560	}	698	}
561		699
562	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
563		701
564	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
…		…
587		725
588	=item kil $port[, @reason]	726	=item kil $port[, @reason]
589		727
590	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
591		729
592	If no C<@reason> is specified, then the port is killed "normally" (ports	730	If no C<@reason> is specified, then the port is killed "normally" -
593	monitoring other ports will not necessarily die because a port dies	731	monitor callback will be invoked, but the kil will not cause linked ports
594	"normally").	732	(C<mon $mport, $lport> form) to get killed.
595		733
596	Otherwise, linked ports get killed with the same reason (second form of	734	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
597	C<mon>, see above).	735	form) get killed with the same reason.
598		736
599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	737	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
600	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
601		739
602	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
603	$message >>.	741	$message >>.
604		742
605	=cut	743	Common idioms:
		744
		745	# silently remove yourself, do not kill linked ports
		746	kil $SELF;
		747
		748	# report a failure in some detail
		749	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		750
		751	# do not waste much time with killing, just die when something goes wrong
		752	open my $fh, "<file"
		753	or die "file: $!";
606		754
607	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
608		756
609	Creates a port on the node C<$node> (which can also be a port ID, in which	757	Creates a port on the node C<$node> (which can also be a port ID, in which
610	case it's the node where that port resides).	758	case it's the node where that port resides).
…		…
621	the package, then the package above the package and so on (e.g.	769	the package, then the package above the package and so on (e.g.
622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	770	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
623	exists or it runs out of package names.	771	exists or it runs out of package names.
624		772
625	The init function is then called with the newly-created port as context	773	The init function is then called with the newly-created port as context
626	object (C<$SELF>) and the C<@initdata> values as arguments.	774	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		775	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		776	the port might not get created.
627		777
628	A common idiom is to pass a local port, immediately monitor the spawned	778	A common idiom is to pass a local port, immediately monitor the spawned
629	port, and in the remote init function, immediately monitor the passed	779	port, and in the remote init function, immediately monitor the passed
630	local port. This two-way monitoring ensures that both ports get cleaned up	780	local port. This two-way monitoring ensures that both ports get cleaned up
631	when there is a problem.	781	when there is a problem.
…		…
655		805
656	sub _spawn {	806	sub _spawn {
657	my $port = shift;	807	my $port = shift;
658	my $init = shift;	808	my $init = shift;
659		809
		810	# rcv will create the actual port
660	local $SELF = "$NODE#$port";	811	local $SELF = "$NODE#$port";
661	eval {	812	eval {
662	&{ load_func $init }	813	&{ load_func $init }
663	};	814	};
664	_self_die if $@;	815	_self_die if $@;
665	}	816	}
666		817
667	sub spawn(@) {	818	sub spawn(@) {
668	my ($nodeid, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
669		820
670	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
671		822
672	$_[0] =~ /::/	823	$_[0] =~ /::/
673	or Carp::croak "spawn init function must be a fully-qualified name, caught";	824	or Carp::croak "spawn init function must be a fully-qualified name, caught";
674		825
675	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
676		827
677	"$nodeid#$id"	828	"$nodeid#$id"
678	}	829	}
		830
679		831
680	=item after $timeout, @msg	832	=item after $timeout, @msg
681		833
682	=item after $timeout, $callback	834	=item after $timeout, $callback
683		835
…		…
699	? $action[0]()	851	? $action[0]()
700	: snd @action;	852	: snd @action;
701	};	853	};
702	}	854	}
703		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
		857
		858	=item cal $port, @msg, $callback[, $timeout]
		859
		860	A simple form of RPC - sends a message to the given C<$port> with the
		861	given contents (C<@msg>), but adds a reply port to the message.
		862
		863	The reply port is created temporarily just for the purpose of receiving
		864	the reply, and will be C<kil>ed when no longer needed.
		865
		866	A reply message sent to the port is passed to the C<$callback> as-is.
		867
		868	If an optional time-out (in seconds) is given and it is not C<undef>,
		869	then the callback will be called without any arguments after the time-out
		870	elapsed and the port is C<kil>ed.
		871
		872	If no time-out is given (or it is C<undef>), then the local port will
		873	monitor the remote port instead, so it eventually gets cleaned-up.
		874
		875	Currently this function returns the temporary port, but this "feature"
		876	might go in future versions unless you can make a convincing case that
		877	this is indeed useful for something.
		878
		879	=cut
		880
		881	sub cal(@) {
		882	my $timeout = ref $_[-1] ? undef : pop;
		883	my $cb = pop;
		884
		885	my $port = port {
		886	undef $timeout;
		887	kil $SELF;
		888	&$cb;
		889	};
		890
		891	if (defined $timeout) {
		892	$timeout = AE::timer $timeout, 0, sub {
		893	undef $timeout;
		894	kil $port;
		895	$cb->();
		896	};
		897	} else {
		898	mon $_[0], sub {
		899	kil $port;
		900	$cb->();
		901	};
		902	}
		903
		904	push @_, $port;
		905	&snd;
		906
		907	$port
		908	}
		909
		910	=back
		911
		912	=head1 DISTRIBUTED DATABASE
		913
		914	AnyEvent::MP comes with a simple distributed database. The database will
		915	be mirrored asynchronously on all global nodes. Other nodes bind to one
		916	of the global nodes for their needs. Every node has a "local database"
		917	which contains all the values that are set locally. All local databases
		918	are merged together to form the global database, which can be queried.
		919
		920	The database structure is that of a two-level hash - the database hash
		921	contains hashes which contain values, similarly to a perl hash of hashes,
		922	i.e.:
		923
		924	$DATABASE{$family}{$subkey} = $value
		925
		926	The top level hash key is called "family", and the second-level hash key
		927	is called "subkey" or simply "key".
		928
		929	The family must be alphanumeric, i.e. start with a letter and consist
		930	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		931	pretty much like Perl module names.
		932
		933	As the family namespace is global, it is recommended to prefix family names
		934	with the name of the application or module using it.
		935
		936	The subkeys must be non-empty strings, with no further restrictions.
		937
		938	The values should preferably be strings, but other perl scalars should
		939	work as well (such as C<undef>, arrays and hashes).
		940
		941	Every database entry is owned by one node - adding the same family/subkey
		942	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		943	but the result might be nondeterministic, i.e. the key might have
		944	different values on different nodes.
		945
		946	Different subkeys in the same family can be owned by different nodes
		947	without problems, and in fact, this is the common method to create worker
		948	pools. For example, a worker port for image scaling might do this:
		949
		950	db_set my_image_scalers => $port;
		951
		952	And clients looking for an image scaler will want to get the
		953	C<my_image_scalers> keys from time to time:
		954
		955	db_keys my_image_scalers => sub {
		956	@ports = @{ $_[0] };
		957	};
		958
		959	Or better yet, they want to monitor the database family, so they always
		960	have a reasonable up-to-date copy:
		961
		962	db_mon my_image_scalers => sub {
		963	@ports = keys %{ $_[0] };
		964	};
		965
		966	In general, you can set or delete single subkeys, but query and monitor
		967	whole families only.
		968
		969	If you feel the need to monitor or query a single subkey, try giving it
		970	it's own family.
		971
		972	=over
		973
		974	=item $guard = db_set $family => $subkey [=> $value]
		975
		976	Sets (or replaces) a key to the database - if C<$value> is omitted,
		977	C<undef> is used instead.
		978
		979	When called in non-void context, C<db_set> returns a guard that
		980	automatically calls C<db_del> when it is destroyed.
		981
		982	=item db_del $family => $subkey...
		983
		984	Deletes one or more subkeys from the database family.
		985
		986	=item $guard = db_reg $family => $port => $value
		987
		988	=item $guard = db_reg $family => $port
		989
		990	=item $guard = db_reg $family
		991
		992	Registers a port in the given family and optionally returns a guard to
		993	remove it.
		994
		995	This function basically does the same as:
		996
		997	db_set $family => $port => $value
		998
		999	Except that the port is monitored and automatically removed from the
		1000	database family when it is kil'ed.
		1001
		1002	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1003	C<$SELF> is used.
		1004
		1005	This function is most useful to register a port in some port group (which
		1006	is just another name for a database family), and have it removed when the
		1007	port is gone. This works best when the port is a local port.
		1008
		1009	=cut
		1010
		1011	sub db_reg($$;$) {
		1012	my $family = shift;
		1013	my $port = @_ ? shift : $SELF;
		1014
		1015	my $clr = sub { db_del $family => $port };
		1016	mon $port, $clr;
		1017
		1018	db_set $family => $port => $_[0];
		1019
		1020	defined wantarray
		1021	and &Guard::guard ($clr)
		1022	}
		1023
		1024	=item db_family $family => $cb->(\%familyhash)
		1025
		1026	Queries the named database C<$family> and call the callback with the
		1027	family represented as a hash. You can keep and freely modify the hash.
		1028
		1029	=item db_keys $family => $cb->(\@keys)
		1030
		1031	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1032	them as array reference to the callback.
		1033
		1034	=item db_values $family => $cb->(\@values)
		1035
		1036	Same as C<db_family>, except it only queries the family I<values> and passes them
		1037	as array reference to the callback.
		1038
		1039	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1040
		1041	Creates a monitor on the given database family. Each time a key is set
		1042	or or is deleted the callback is called with a hash containing the
		1043	database family and three lists of added, changed and deleted subkeys,
		1044	respectively. If no keys have changed then the array reference might be
		1045	C<undef> or even missing.
		1046
		1047	If not called in void context, a guard object is returned that, when
		1048	destroyed, stops the monitor.
		1049
		1050	The family hash reference and the key arrays belong to AnyEvent::MP and
		1051	B<must not be modified or stored> by the callback. When in doubt, make a
		1052	copy.
		1053
		1054	As soon as possible after the monitoring starts, the callback will be
		1055	called with the intiial contents of the family, even if it is empty,
		1056	i.e. there will always be a timely call to the callback with the current
		1057	contents.
		1058
		1059	It is possible that the callback is called with a change event even though
		1060	the subkey is already present and the value has not changed.
		1061
		1062	The monitoring stops when the guard object is destroyed.
		1063
		1064	Example: on every change to the family "mygroup", print out all keys.
		1065
		1066	my $guard = db_mon mygroup => sub {
		1067	my ($family, $a, $c, $d) = @_;
		1068	print "mygroup members: ", (join " ", keys %$family), "\n";
		1069	};
		1070
		1071	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1072
		1073	my $guard; $guard = db_mon My::Module::workers => sub {
		1074	my ($family, $a, $c, $d) = @_;
		1075	return unless %$family;
		1076	undef $guard;
		1077	print "My::Module::workers now nonempty\n";
		1078	};
		1079
		1080	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1081
		1082	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1083	my ($family, $a, $c, $d) = @_;
		1084
		1085	print "+$_=$family->{$_}\n" for @$a;
		1086	print "*$_=$family->{$_}\n" for @$c;
		1087	print "-$_=$family->{$_}\n" for @$d;
		1088	};
		1089
		1090	=cut
		1091
704	=back	1092	=back
705		1093
706	=head1 AnyEvent::MP vs. Distributed Erlang	1094	=head1 AnyEvent::MP vs. Distributed Erlang
707		1095
708	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1096	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
709	== aemp node, Erlang process == aemp port), so many of the documents and	1097	== aemp node, Erlang process == aemp port), so many of the documents and
710	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1098	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
711	sample:	1099	sample:
712		1100
713	http://www.Erlang.se/doc/programming_rules.shtml	1101	http://www.erlang.se/doc/programming_rules.shtml
714	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1102	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
715	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1103	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
716	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1104	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
717		1105
718	Despite the similarities, there are also some important differences:	1106	Despite the similarities, there are also some important differences:
719		1107
720	=over 4	1108	=over 4
721		1109
722	=item * Node IDs are arbitrary strings in AEMP.	1110	=item * Node IDs are arbitrary strings in AEMP.
723		1111
724	Erlang relies on special naming and DNS to work everywhere in the same	1112	Erlang relies on special naming and DNS to work everywhere in the same
725	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1113	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
726	configuration or DNS), but will otherwise discover other odes itself.	1114	configuration or DNS), and possibly the addresses of some seed nodes, but
		1115	will otherwise discover other nodes (and their IDs) itself.
727		1116
728	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1117	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
729	uses "local ports are like remote ports".	1118	uses "local ports are like remote ports".
730		1119
731	The failure modes for local ports are quite different (runtime errors	1120	The failure modes for local ports are quite different (runtime errors
…		…
740	ports being the special case/exception, where transport errors cannot	1129	ports being the special case/exception, where transport errors cannot
741	occur.	1130	occur.
742		1131
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1132	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		1133
745	Erlang uses processes that selectively receive messages, and therefore	1134	Erlang uses processes that selectively receive messages out of order, and
746	needs a queue. AEMP is event based, queuing messages would serve no	1135	therefore needs a queue. AEMP is event based, queuing messages would serve
747	useful purpose. For the same reason the pattern-matching abilities of	1136	no useful purpose. For the same reason the pattern-matching abilities
748	AnyEvent::MP are more limited, as there is little need to be able to	1137	of AnyEvent::MP are more limited, as there is little need to be able to
749	filter messages without dequeuing them.	1138	filter messages without dequeuing them.
750		1139
751	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1140	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1141	being event-based, while Erlang is process-based.
		1142
		1143	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1144	top of AEMP and Coro threads.
752		1145
753	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1146	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
754		1147
755	Sending messages in Erlang is synchronous and blocks the process (and	1148	Sending messages in Erlang is synchronous and blocks the process until
		1149	a conenction has been established and the message sent (and so does not
756	so does not need a queue that can overflow). AEMP sends are immediate,	1150	need a queue that can overflow). AEMP sends return immediately, connection
757	connection establishment is handled in the background.	1151	establishment is handled in the background.
758		1152
759	=item * Erlang suffers from silent message loss, AEMP does not.	1153	=item * Erlang suffers from silent message loss, AEMP does not.
760		1154
761	Erlang makes few guarantees on messages delivery - messages can get lost	1155	Erlang implements few guarantees on messages delivery - messages can get
762	without any of the processes realising it (i.e. you send messages a, b,	1156	lost without any of the processes realising it (i.e. you send messages a,
763	and c, and the other side only receives messages a and c).	1157	b, and c, and the other side only receives messages a and c).
764		1158
765	AEMP guarantees correct ordering, and the guarantee that after one message	1159	AEMP guarantees (modulo hardware errors) correct ordering, and the
766	is lost, all following ones sent to the same port are lost as well, until	1160	guarantee that after one message is lost, all following ones sent to the
767	monitoring raises an error, so there are no silent "holes" in the message	1161	same port are lost as well, until monitoring raises an error, so there are
768	sequence.	1162	no silent "holes" in the message sequence.
		1163
		1164	If you want your software to be very reliable, you have to cope with
		1165	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1166	simply tries to work better in common error cases, such as when a network
		1167	link goes down.
769		1168
770	=item * Erlang can send messages to the wrong port, AEMP does not.	1169	=item * Erlang can send messages to the wrong port, AEMP does not.
771		1170
772	In Erlang it is quite likely that a node that restarts reuses a process ID	1171	In Erlang it is quite likely that a node that restarts reuses an Erlang
773	known to other nodes for a completely different process, causing messages	1172	process ID known to other nodes for a completely different process,
774	destined for that process to end up in an unrelated process.	1173	causing messages destined for that process to end up in an unrelated
		1174	process.
775		1175
776	AEMP never reuses port IDs, so old messages or old port IDs floating	1176	AEMP does not reuse port IDs, so old messages or old port IDs floating
777	around in the network will not be sent to an unrelated port.	1177	around in the network will not be sent to an unrelated port.
778		1178
779	=item * Erlang uses unprotected connections, AEMP uses secure	1179	=item * Erlang uses unprotected connections, AEMP uses secure
780	authentication and can use TLS.	1180	authentication and can use TLS.
781		1181
…		…
784		1184
785	=item * The AEMP protocol is optimised for both text-based and binary	1185	=item * The AEMP protocol is optimised for both text-based and binary
786	communications.	1186	communications.
787		1187
788	The AEMP protocol, unlike the Erlang protocol, supports both programming	1188	The AEMP protocol, unlike the Erlang protocol, supports both programming
789	language independent text-only protocols (good for debugging) and binary,	1189	language independent text-only protocols (good for debugging), and binary,
790	language-specific serialisers (e.g. Storable). By default, unless TLS is	1190	language-specific serialisers (e.g. Storable). By default, unless TLS is
791	used, the protocol is actually completely text-based.	1191	used, the protocol is actually completely text-based.
792		1192
793	It has also been carefully designed to be implementable in other languages	1193	It has also been carefully designed to be implementable in other languages
794	with a minimum of work while gracefully degrading functionality to make the	1194	with a minimum of work while gracefully degrading functionality to make the
795	protocol simple.	1195	protocol simple.
796		1196
797	=item * AEMP has more flexible monitoring options than Erlang.	1197	=item * AEMP has more flexible monitoring options than Erlang.
798		1198
799	In Erlang, you can chose to receive I<all> exit signals as messages	1199	In Erlang, you can chose to receive I<all> exit signals as messages or
800	or I<none>, there is no in-between, so monitoring single processes is	1200	I<none>, there is no in-between, so monitoring single Erlang processes is
801	difficult to implement. Monitoring in AEMP is more flexible than in	1201	difficult to implement.
802	Erlang, as one can choose between automatic kill, exit message or callback	1202
803	on a per-process basis.	1203	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1204	between automatic kill, exit message or callback on a per-port basis.
804		1205
805	=item * Erlang tries to hide remote/local connections, AEMP does not.	1206	=item * Erlang tries to hide remote/local connections, AEMP does not.
806		1207
807	Monitoring in Erlang is not an indicator of process death/crashes, in the	1208	Monitoring in Erlang is not an indicator of process death/crashes, in the
808	same way as linking is (except linking is unreliable in Erlang).	1209	same way as linking is (except linking is unreliable in Erlang).
…		…
830	overhead, as well as having to keep a proxy object everywhere.	1231	overhead, as well as having to keep a proxy object everywhere.
831		1232
832	Strings can easily be printed, easily serialised etc. and need no special	1233	Strings can easily be printed, easily serialised etc. and need no special
833	procedures to be "valid".	1234	procedures to be "valid".
834		1235
835	And as a result, a miniport consists of a single closure stored in a	1236	And as a result, a port with just a default receiver consists of a single
836	global hash - it can't become much cheaper.	1237	code reference stored in a global hash - it can't become much cheaper.
837		1238
838	=item Why favour JSON, why not a real serialising format such as Storable?	1239	=item Why favour JSON, why not a real serialising format such as Storable?
839		1240
840	In fact, any AnyEvent::MP node will happily accept Storable as framing	1241	In fact, any AnyEvent::MP node will happily accept Storable as framing
841	format, but currently there is no way to make a node use Storable by	1242	format, but currently there is no way to make a node use Storable by
…		…
851	Keeping your messages simple, concentrating on data structures rather than	1252	Keeping your messages simple, concentrating on data structures rather than
852	objects, will keep your messages clean, tidy and efficient.	1253	objects, will keep your messages clean, tidy and efficient.
853		1254
854	=back	1255	=back
855		1256
		1257	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1258
		1259	AEMP version 2 has three major incompatible changes compared to version 1:
		1260
		1261	=over 4
		1262
		1263	=item AnyEvent::MP::Global no longer has group management functions.
		1264
		1265	AnyEvent::MP now comes with a distributed database that is more
		1266	powerful. It's database families map closely to ports, but the API has
		1267	minor differences:
		1268
		1269	grp_reg $group, $port # old
		1270	db_reg $group, $port # new
		1271
		1272	$list = grp_get $group # old
		1273	db_keys $group, sub { my $list = shift } # new
		1274
		1275	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1276	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1277
		1278	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get>
		1279	is no longer instant, because the local node might not have a copy of
		1280	the group. This can be partially remedied by using C<db_mon> to keep an
		1281	updated copy of the group:
		1282
		1283	my $local_group_copy;
		1284	db_mon $group => sub { $local_group_copy = shift };
		1285
		1286	# no keys %$local_group_copy always returns the most up-to-date
		1287	# list of ports in the group.
		1288
		1289	C<grp_mon> can almost be replaced by C<db_mon>:
		1290
		1291	db_mon $group => sub {
		1292	my ($ports, $add, $chg, $lde) = @_;
		1293	$ports = [keys %$ports];
		1294
		1295	# now $ports, $add and $del are the same as
		1296	# were originally passed by grp_mon.
		1297	...
		1298	};
		1299
		1300	=item Nodes not longer connect to all other nodes.
		1301
		1302	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1303	module, which in turn would create connections to all other nodes in the
		1304	network (helped by the seed nodes).
		1305
		1306	In version 2.x, global nodes still connect to all other global nodes, but
		1307	other nodes don't - now every node either is a global node itself, or
		1308	attaches itself to another global node.
		1309
		1310	If a node isn't a global node itself, then it attaches itself to one
		1311	of its seed nodes. If that seed node isn't a global node yet, it will
		1312	automatically be upgraded to a global node.
		1313
		1314	So in many cases, nothing needs to be changed - one just has to make sure
		1315	that all seed nodes are meshed together with the other seed nodes (as with
		1316	AEMP 1.x), and other nodes specify them as seed nodes.
		1317
		1318	Not opening a connection to every other node is usually an advantage,
		1319	except when you need the lower latency of an already established
		1320	connection. To ensure a node establishes a connection to another node,
		1321	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1322	create the connection (And notify you when the connection fails).
		1323
		1324	=item Listener-less nodes are gone.
		1325
		1326	And are not coming back, at least not in their old form.
		1327
		1328	There are vague plans to implement some form of routing domains, which
		1329	might or might not bring back listener-less nodes, but don't count on it.
		1330
		1331	The fact that most connections are now optional somewhat mitigates this,
		1332	as a node can be effectively unreachable from the outside without any
		1333	problems, as long as it isn't a global node and only reaches out to other
		1334	nodes (as opposed to being contacted from other nodes).
		1335
		1336	=back
		1337
856	=head1 SEE ALSO	1338	=head1 SEE ALSO
857		1339
858	L<AnyEvent::MP::Intro> - a gentle introduction.	1340	L<AnyEvent::MP::Intro> - a gentle introduction.
859		1341
860	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1342	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
861		1343
862	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1344	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
863	your applications.	1345	your applications.
		1346
		1347	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
864		1348
865	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1349	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
866	all nodes.	1350	all nodes.
867		1351
868	L<AnyEvent>.	1352	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.81 by root, Mon Sep 7 18:33:44 2009 UTC vs. Revision 1.137 by root, Wed Mar 21 23:48:39 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.81 by root, Mon Sep 7 18:33:44 2009 UTC vs.
Revision 1.137 by root, Wed Mar 21 23:48:39 2012 UTC