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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.91 by root, Tue Sep 22 09:54:42 2009 UTC vs.
Revision 1.136 by root, Wed Mar 21 15:22:16 2012 UTC

…		…
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 $localport, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
37	mon $localport, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
38	mon $localport, $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.
…		…
66		78
67	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
68	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
69	anything was listening for them or not.	81	anything was listening for them or not.
70		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
71	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
72		86
73	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<#>)
74	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).
75		90
76	=item node	91	=item node
77		92
78	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,
79	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
80	ports.	95	ports.
81		96
82	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
83	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
84	currently.	99	currently, but all nodes can talk to public nodes.
85		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
87		104
88	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
89	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
90	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
91	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
92		109
93	=item binds - C<ip:port>	110	=item binds - C<ip:port>
94		111
95	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
96	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
97	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
98	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.
99		119
100	=item seed nodes	120	=item seed nodes
101		121
102	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
103	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
104	network. This node is called a seed.	124	network. These other nodes are called "seed nodes".
105		125
106	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
107	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
108	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.
109		129
110	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
111	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
112	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.
113		135
114	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
115	should always be available. They should also be relatively responsive - a	137	should always be available. They should also be relatively responsive - a
116	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.
117		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
118	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
119		150
120	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
121	TCP port) of nodes thta should be used as seed nodes.	152	TCP port) of nodes that should be used as seed nodes.
122		153
123	The nodes listening on those endpoints are expected to be long-running,	154	=item global nodes
124	and at least one of those should always be available. When nodes run out	155
125	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
126	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).
127		170
128	=back	171	=back
129		172
130	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
131		174
…		…
133		176
134	=cut	177	=cut
135		178
136	package AnyEvent::MP;	179	package AnyEvent::MP;
137		180
		181	use AnyEvent::MP::Config ();
138	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
139		184
140	use common::sense;	185	use common::sense;
141		186
142	use Carp ();	187	use Carp ();
143		188
144	use AE ();	189	use AE ();
		190	use Guard ();
145		191
146	use base "Exporter";	192	use base "Exporter";
147		193
148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
149		195
150	our @EXPORT = qw(	196	our @EXPORT = qw(
151	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
152	configure	198	configure
153	snd rcv mon mon_guard kil psub spawn cal	199	snd rcv mon mon_guard kil psub peval spawn cal
154	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
155	);	203	);
156		204
157	our $SELF;	205	our $SELF;
158		206
159	sub _self_die() {	207	sub _self_die() {
…		…
182	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
183		231
184	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
185	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
186		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
187	=over 4	267	=over 4
188		268
189	=item step 1, gathering configuration from profiles	269	=item step 1, gathering configuration from profiles
190		270
191	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
…		…
204	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
205	and the values specified directly via C<configure> have lowest priority,	285	and the values specified directly via C<configure> have lowest priority,
206	and can only be used to specify defaults.	286	and can only be used to specify defaults.
207		287
208	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
209	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
210	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>.
211		297
212	=item step 2, bind listener sockets	298	=item step 2, bind listener sockets
213		299
214	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
215	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
…		…
221	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
222	local IP address it finds.	308	local IP address it finds.
223		309
224	=item step 3, connect to seed nodes	310	=item step 3, connect to seed nodes
225		311
226	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
227	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
228	connectivity with at least one node at any point in time.	314	connectivity with at least one node at any point in time.
229		315
230	=back	316	=back
231		317
232	Example: become a distributed node using the local node name as profile.	318	Example: become a distributed node using the local node name as profile.
233	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.
234		320
235	configure	321	configure
236		322
237	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
238	clients.	324	commandline clients.
239		325
240	configure nodeid => "anon/";	326	configure nodeid => "myscript/%n/%u";
241		327
242	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
243	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,
244	customary for aemp).	330	customary for aemp).
245		331
246	# use the aemp commandline utility	332	# use the aemp commandline utility
247	# aemp profile seed nodeid anon/ binds '*:4040'	333	# aemp profile seed binds '*:4040'
248		334
249	# then use it	335	# then use it
250	configure profile => "seed";	336	configure profile => "seed";
251		337
252	# or simply use aemp from the shell again:	338	# or simply use aemp from the shell again:
…		…
317		403
318	=cut	404	=cut
319		405
320	sub rcv($@);	406	sub rcv($@);
321		407
322	sub _kilme {	408	my $KILME = sub {
323	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
324	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
325		412
326	sub port(;&) {	413	sub port(;&) {
327	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
328	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
329		416
330	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
331		418
332	$port	419	$port
333	}	420	}
334		421
335	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
340		427
341	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
342	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
343	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
344		431
345	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
346	C<tag> match.	433	C<tag> match.
347		434
348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
349		436
350	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
…		…
371	msg1 => sub { ... },	458	msg1 => sub { ... },
372	...	459	...
373	;	460	;
374		461
375	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
376	(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.
377		464
378	rcv $port, $otherport => sub {	465	rcv $port, $otherport => sub {
379	my @reply = @_;	466	my @reply = @_;
380		467
381	rcv $SELF, $otherport;	468	rcv $SELF, $otherport;
…		…
394	if (ref $_[0]) {	481	if (ref $_[0]) {
395	if (my $self = $PORT_DATA{$portid}) {	482	if (my $self = $PORT_DATA{$portid}) {
396	"AnyEvent::MP::Port" eq ref $self	483	"AnyEvent::MP::Port" eq ref $self
397	or Carp::croak "$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";
398		485
399	$self->[2] = shift;	486	$self->[0] = shift;
400	} else {	487	} else {
401	my $cb = shift;	488	my $cb = shift;
402	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
403	local $SELF = $port;	490	local $SELF = $port;
404	eval { &$cb }; _self_die if $@;	491	eval { &$cb }; _self_die if $@;
405	};	492	};
406	}	493	}
407	} elsif (defined $_[0]) {	494	} elsif (defined $_[0]) {
408	my $self = $PORT_DATA{$portid} \|\|= do {	495	my $self = $PORT_DATA{$portid} \|\|= do {
409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	496	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
410		497
411	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
412	local $SELF = $port;	499	local $SELF = $port;
413		500
414	if (my $cb = $self->[1]{$_[0]}) {	501	if (my $cb = $self->[1]{$_[0]}) {
…		…
436	}	523	}
437		524
438	$port	525	$port
439	}	526	}
440		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
441	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
442		566
443	Remembers C<$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
444	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>
445	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 $SELF, sub {
		572	BLOCK }, @_ } >>.
446		573
447	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
448		575
449	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
450	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
523	delivered again.	650	delivered again.
524		651
525	Inter-host-connection timeouts and monitoring depend on the transport	652	Inter-host-connection timeouts and monitoring depend on the transport
526	used. The only transport currently implemented is TCP, and AnyEvent::MP	653	used. The only transport currently implemented is TCP, and AnyEvent::MP
527	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
528	non-idle connection, and usually around two hours for idle conenctions).	655	non-idle connection, and usually around two hours for idle connections).
529		656
530	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
531	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
532	to ensure some maximum latency.	659	to ensure some maximum latency.
533		660
…		…
565	}	692	}
566		693
567	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
568		695
569	defined wantarray	696	defined wantarray
570	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
571	}	698	}
572		699
573	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
574		701
575	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
…		…
598		725
599	=item kil $port[, @reason]	726	=item kil $port[, @reason]
600		727
601	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
602		729
603	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" -
604	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
605	"normally").	732	(C<mon $mport, $lport> form) to get killed.
606		733
607	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>
608	C<mon>, see above).	735	form) get killed with the same reason.
609		736
610	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
611	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
612		739
613	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
614	$message >>.	741	$message >>.
615		742
616	=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: $!";
617		754
618	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
619		756
620	Creates a port on the node C<$node> (which can also be a port ID, in which	757	Creates a port on the node C<$node> (which can also be a port ID, in which
621	case it's the node where that port resides).	758	case it's the node where that port resides).
…		…
679	}	816	}
680		817
681	sub spawn(@) {	818	sub spawn(@) {
682	my ($nodeid, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
683		820
684	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
685		822
686	$_[0] =~ /::/	823	$_[0] =~ /::/
687	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";
688		825
689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
690		827
691	"$nodeid#$id"	828	"$nodeid#$id"
692	}	829	}
		830
693		831
694	=item after $timeout, @msg	832	=item after $timeout, @msg
695		833
696	=item after $timeout, $callback	834	=item after $timeout, $callback
697		835
…		…
713	? $action[0]()	851	? $action[0]()
714	: snd @action;	852	: snd @action;
715	};	853	};
716	}	854	}
717		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
		857
718	=item cal $port, @msg, $callback[, $timeout]	858	=item cal $port, @msg, $callback[, $timeout]
719		859
720	A simple form of RPC - sends a message to the given C<$port> with the	860	A simple form of RPC - sends a message to the given C<$port> with the
721	given contents (C<@msg>), but adds a reply port to the message.	861	given contents (C<@msg>), but adds a reply port to the message.
722		862
…		…
727		867
728	If an optional time-out (in seconds) is given and it is not C<undef>,	868	If an optional time-out (in seconds) is given and it is not C<undef>,
729	then the callback will be called without any arguments after the time-out	869	then the callback will be called without any arguments after the time-out
730	elapsed and the port is C<kil>ed.	870	elapsed and the port is C<kil>ed.
731		871
732	If no time-out is given, then the local port will monitor the remote port	872	If no time-out is given (or it is C<undef>), then the local port will
733	instead, so it eventually gets cleaned-up.	873	monitor the remote port instead, so it eventually gets cleaned-up.
734		874
735	Currently this function returns the temporary port, but this "feature"	875	Currently this function returns the temporary port, but this "feature"
736	might go in future versions unless you can make a convincing case that	876	might go in future versions unless you can make a convincing case that
737	this is indeed useful for something.	877	this is indeed useful for something.
738		878
…		…
767	$port	907	$port
768	}	908	}
769		909
770	=back	910	=back
771		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 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	=item db_del $family => $subkey...
		980
		981	Deletes one or more subkeys from the database family.
		982
		983	=item $guard = db_reg $family => $subkey [=> $value]
		984
		985	Sets the key on the database and returns a guard. When the guard is
		986	destroyed, the key is deleted from the database. If C<$value> is missing,
		987	then C<undef> is used.
		988
		989	=item db_family $family => $cb->(\%familyhash)
		990
		991	Queries the named database C<$family> and call the callback with the
		992	family represented as a hash. You can keep and freely modify the hash.
		993
		994	=item db_keys $family => $cb->(\@keys)
		995
		996	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		997	them as array reference to the callback.
		998
		999	=item db_values $family => $cb->(\@values)
		1000
		1001	Same as C<db_family>, except it only queries the family I<values> and passes them
		1002	as array reference to the callback.
		1003
		1004	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1005
		1006	Creates a monitor on the given database family. Each time a key is set
		1007	or or is deleted the callback is called with a hash containing the
		1008	database family and three lists of added, changed and deleted subkeys,
		1009	respectively. If no keys have changed then the array reference might be
		1010	C<undef> or even missing.
		1011
		1012	If not called in void context, a guard object is returned that, when
		1013	destroyed, stops the monitor.
		1014
		1015	The family hash reference and the key arrays belong to AnyEvent::MP and
		1016	B<must not be modified or stored> by the callback. When in doubt, make a
		1017	copy.
		1018
		1019	As soon as possible after the monitoring starts, the callback will be
		1020	called with the intiial contents of the family, even if it is empty,
		1021	i.e. there will always be a timely call to the callback with the current
		1022	contents.
		1023
		1024	It is possible that the callback is called with a change event even though
		1025	the subkey is already present and the value has not changed.
		1026
		1027	The monitoring stops when the guard object is destroyed.
		1028
		1029	Example: on every change to the family "mygroup", print out all keys.
		1030
		1031	my $guard = db_mon mygroup => sub {
		1032	my ($family, $a, $c, $d) = @_;
		1033	print "mygroup members: ", (join " ", keys %$family), "\n";
		1034	};
		1035
		1036	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1037
		1038	my $guard; $guard = db_mon My::Module::workers => sub {
		1039	my ($family, $a, $c, $d) = @_;
		1040	return unless %$family;
		1041	undef $guard;
		1042	print "My::Module::workers now nonempty\n";
		1043	};
		1044
		1045	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1046
		1047	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1048	my ($family, $a, $c, $d) = @_;
		1049
		1050	print "+$_=$family->{$_}\n" for @$a;
		1051	print "*$_=$family->{$_}\n" for @$c;
		1052	print "-$_=$family->{$_}\n" for @$d;
		1053	};
		1054
		1055	=cut
		1056
		1057	=back
		1058
772	=head1 AnyEvent::MP vs. Distributed Erlang	1059	=head1 AnyEvent::MP vs. Distributed Erlang
773		1060
774	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1061	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
775	== aemp node, Erlang process == aemp port), so many of the documents and	1062	== aemp node, Erlang process == aemp port), so many of the documents and
776	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1063	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
777	sample:	1064	sample:
778		1065
779	http://www.Erlang.se/doc/programming_rules.shtml	1066	http://www.erlang.se/doc/programming_rules.shtml
780	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1067	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
781	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1068	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
782	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1069	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
783		1070
784	Despite the similarities, there are also some important differences:	1071	Despite the similarities, there are also some important differences:
785		1072
786	=over 4	1073	=over 4
787		1074
788	=item * Node IDs are arbitrary strings in AEMP.	1075	=item * Node IDs are arbitrary strings in AEMP.
789		1076
790	Erlang relies on special naming and DNS to work everywhere in the same	1077	Erlang relies on special naming and DNS to work everywhere in the same
791	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1078	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
792	configuration or DNS), but will otherwise discover other odes itself.	1079	configuration or DNS), and possibly the addresses of some seed nodes, but
		1080	will otherwise discover other nodes (and their IDs) itself.
793		1081
794	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1082	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
795	uses "local ports are like remote ports".	1083	uses "local ports are like remote ports".
796		1084
797	The failure modes for local ports are quite different (runtime errors	1085	The failure modes for local ports are quite different (runtime errors
…		…
806	ports being the special case/exception, where transport errors cannot	1094	ports being the special case/exception, where transport errors cannot
807	occur.	1095	occur.
808		1096
809	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1097	=item * Erlang uses processes and a mailbox, AEMP does not queue.
810		1098
811	Erlang uses processes that selectively receive messages, and therefore	1099	Erlang uses processes that selectively receive messages out of order, and
812	needs a queue. AEMP is event based, queuing messages would serve no	1100	therefore needs a queue. AEMP is event based, queuing messages would serve
813	useful purpose. For the same reason the pattern-matching abilities of	1101	no useful purpose. For the same reason the pattern-matching abilities
814	AnyEvent::MP are more limited, as there is little need to be able to	1102	of AnyEvent::MP are more limited, as there is little need to be able to
815	filter messages without dequeuing them.	1103	filter messages without dequeuing them.
816		1104
817	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1105	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1106	being event-based, while Erlang is process-based.
		1107
		1108	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1109	top of AEMP and Coro threads.
818		1110
819	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1111	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
820		1112
821	Sending messages in Erlang is synchronous and blocks the process (and	1113	Sending messages in Erlang is synchronous and blocks the process until
		1114	a conenction has been established and the message sent (and so does not
822	so does not need a queue that can overflow). AEMP sends are immediate,	1115	need a queue that can overflow). AEMP sends return immediately, connection
823	connection establishment is handled in the background.	1116	establishment is handled in the background.
824		1117
825	=item * Erlang suffers from silent message loss, AEMP does not.	1118	=item * Erlang suffers from silent message loss, AEMP does not.
826		1119
827	Erlang makes few guarantees on messages delivery - messages can get lost	1120	Erlang implements few guarantees on messages delivery - messages can get
828	without any of the processes realising it (i.e. you send messages a, b,	1121	lost without any of the processes realising it (i.e. you send messages a,
829	and c, and the other side only receives messages a and c).	1122	b, and c, and the other side only receives messages a and c).
830		1123
831	AEMP guarantees correct ordering, and the guarantee that after one message	1124	AEMP guarantees (modulo hardware errors) correct ordering, and the
832	is lost, all following ones sent to the same port are lost as well, until	1125	guarantee that after one message is lost, all following ones sent to the
833	monitoring raises an error, so there are no silent "holes" in the message	1126	same port are lost as well, until monitoring raises an error, so there are
834	sequence.	1127	no silent "holes" in the message sequence.
		1128
		1129	If you want your software to be very reliable, you have to cope with
		1130	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1131	simply tries to work better in common error cases, such as when a network
		1132	link goes down.
835		1133
836	=item * Erlang can send messages to the wrong port, AEMP does not.	1134	=item * Erlang can send messages to the wrong port, AEMP does not.
837		1135
838	In Erlang it is quite likely that a node that restarts reuses a process ID	1136	In Erlang it is quite likely that a node that restarts reuses an Erlang
839	known to other nodes for a completely different process, causing messages	1137	process ID known to other nodes for a completely different process,
840	destined for that process to end up in an unrelated process.	1138	causing messages destined for that process to end up in an unrelated
		1139	process.
841		1140
842	AEMP never reuses port IDs, so old messages or old port IDs floating	1141	AEMP does not reuse port IDs, so old messages or old port IDs floating
843	around in the network will not be sent to an unrelated port.	1142	around in the network will not be sent to an unrelated port.
844		1143
845	=item * Erlang uses unprotected connections, AEMP uses secure	1144	=item * Erlang uses unprotected connections, AEMP uses secure
846	authentication and can use TLS.	1145	authentication and can use TLS.
847		1146
…		…
850		1149
851	=item * The AEMP protocol is optimised for both text-based and binary	1150	=item * The AEMP protocol is optimised for both text-based and binary
852	communications.	1151	communications.
853		1152
854	The AEMP protocol, unlike the Erlang protocol, supports both programming	1153	The AEMP protocol, unlike the Erlang protocol, supports both programming
855	language independent text-only protocols (good for debugging) and binary,	1154	language independent text-only protocols (good for debugging), and binary,
856	language-specific serialisers (e.g. Storable). By default, unless TLS is	1155	language-specific serialisers (e.g. Storable). By default, unless TLS is
857	used, the protocol is actually completely text-based.	1156	used, the protocol is actually completely text-based.
858		1157
859	It has also been carefully designed to be implementable in other languages	1158	It has also been carefully designed to be implementable in other languages
860	with a minimum of work while gracefully degrading functionality to make the	1159	with a minimum of work while gracefully degrading functionality to make the
861	protocol simple.	1160	protocol simple.
862		1161
863	=item * AEMP has more flexible monitoring options than Erlang.	1162	=item * AEMP has more flexible monitoring options than Erlang.
864		1163
865	In Erlang, you can chose to receive I<all> exit signals as messages	1164	In Erlang, you can chose to receive I<all> exit signals as messages or
866	or I<none>, there is no in-between, so monitoring single processes is	1165	I<none>, there is no in-between, so monitoring single Erlang processes is
867	difficult to implement. Monitoring in AEMP is more flexible than in	1166	difficult to implement.
868	Erlang, as one can choose between automatic kill, exit message or callback	1167
869	on a per-process basis.	1168	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1169	between automatic kill, exit message or callback on a per-port basis.
870		1170
871	=item * Erlang tries to hide remote/local connections, AEMP does not.	1171	=item * Erlang tries to hide remote/local connections, AEMP does not.
872		1172
873	Monitoring in Erlang is not an indicator of process death/crashes, in the	1173	Monitoring in Erlang is not an indicator of process death/crashes, in the
874	same way as linking is (except linking is unreliable in Erlang).	1174	same way as linking is (except linking is unreliable in Erlang).
…		…
896	overhead, as well as having to keep a proxy object everywhere.	1196	overhead, as well as having to keep a proxy object everywhere.
897		1197
898	Strings can easily be printed, easily serialised etc. and need no special	1198	Strings can easily be printed, easily serialised etc. and need no special
899	procedures to be "valid".	1199	procedures to be "valid".
900		1200
901	And as a result, a miniport consists of a single closure stored in a	1201	And as a result, a port with just a default receiver consists of a single
902	global hash - it can't become much cheaper.	1202	code reference stored in a global hash - it can't become much cheaper.
903		1203
904	=item Why favour JSON, why not a real serialising format such as Storable?	1204	=item Why favour JSON, why not a real serialising format such as Storable?
905		1205
906	In fact, any AnyEvent::MP node will happily accept Storable as framing	1206	In fact, any AnyEvent::MP node will happily accept Storable as framing
907	format, but currently there is no way to make a node use Storable by	1207	format, but currently there is no way to make a node use Storable by
…		…
923		1223
924	L<AnyEvent::MP::Intro> - a gentle introduction.	1224	L<AnyEvent::MP::Intro> - a gentle introduction.
925		1225
926	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1226	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
927		1227
928	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1228	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
929	your applications.	1229	your applications.
		1230
		1231	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
930		1232
931	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1233	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
932	all nodes.	1234	all nodes.
933		1235
934	L<AnyEvent>.	1236	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.91 by root, Tue Sep 22 09:54:42 2009 UTC vs. Revision 1.136 by root, Wed Mar 21 15:22:16 2012 UTC

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Revision 1.91 by root, Tue Sep 22 09:54:42 2009 UTC vs.
Revision 1.136 by root, Wed Mar 21 15:22:16 2012 UTC