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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.93 by root, Tue Sep 22 14:14:29 2009 UTC vs.
Revision 1.134 by root, Mon Mar 12 14:47:23 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 => $pass->($nodeid)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every remote execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	See F<semp setsecure> for more info.
		259
		260	=back
		261
187	=over 4	262	=over 4
188		263
189	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
190		265
191	The function first looks up a profile in the aemp configuration (see the	266	The function first looks up a profile in the aemp configuration (see the
…		…
204	That means that the values specified in the profile have highest priority	279	That means that the values specified in the profile have highest priority
205	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
206	and can only be used to specify defaults.	281	and can only be used to specify defaults.
207		282
208	If the profile specifies a node ID, then this will become the node ID of	283	If the profile specifies a node ID, then this will become the node ID of
209	this process. If not, then the profile name will be used as node ID. The	284	this process. If not, then the profile name will be used as node ID, with
210	special node ID of C<anon/> will be replaced by a random node ID.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
211		292
212	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
213		294
214	The next step is to look up the binds in the profile, followed by binding	295	The next step is to look up the binds in the profile, followed by binding
215	aemp protocol listeners on all binds specified (it is possible and valid	296	aemp protocol listeners on all binds specified (it is possible and valid
…		…
221	used, meaning the node will bind on a dynamically-assigned port on every	302	used, meaning the node will bind on a dynamically-assigned port on every
222	local IP address it finds.	303	local IP address it finds.
223		304
224	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
225		306
226	As the last step, the seeds list from the profile is passed to the	307	As the last step, the seed ID list from the profile is passed to the
227	L<AnyEvent::MP::Global> module, which will then use it to keep	308	L<AnyEvent::MP::Global> module, which will then use it to keep
228	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
229		310
230	=back	311	=back
231		312
232	Example: become a distributed node using the local node name as profile.	313	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.	314	This should be the most common form of invocation for "daemon"-type nodes.
234		315
235	configure	316	configure
236		317
237	Example: become an anonymous node. This form is often used for commandline	318	Example: become a semi-anonymous node. This form is often used for
238	clients.	319	commandline clients.
239		320
240	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
241		322
242	Example: configure a node using a profile called seed, which si suitable	323	Example: configure a node using a profile called seed, which is suitable
243	for a seed node as it binds on all local addresses on a fixed port (4040,	324	for a seed node as it binds on all local addresses on a fixed port (4040,
244	customary for aemp).	325	customary for aemp).
245		326
246	# use the aemp commandline utility	327	# use the aemp commandline utility
247	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
248		329
249	# then use it	330	# then use it
250	configure profile => "seed";	331	configure profile => "seed";
251		332
252	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
317		398
318	=cut	399	=cut
319		400
320	sub rcv($@);	401	sub rcv($@);
321		402
322	sub _kilme {	403	my $KILME = sub {
323	die "received message on port without callback";	404	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
324	}	405	kil $SELF, unhandled_message => "missing (tag or fallback) callback for message '$tag'";
		406	};
325		407
326	sub port(;&) {	408	sub port(;&) {
327	my $id = "$UNIQ." . $ID++;	409	my $id = $UNIQ . ++$ID;
328	my $port = "$NODE#$id";	410	my $port = "$NODE#$id";
329		411
330	rcv $port, shift \|\| \&_kilme;	412	rcv $port, shift \|\| $KILME;
331		413
332	$port	414	$port
333	}	415	}
334		416
335	=item rcv $local_port, $callback->(@msg)	417	=item rcv $local_port, $callback->(@msg)
…		…
340		422
341	The global C<$SELF> (exported by this module) contains C<$port> while	423	The global C<$SELF> (exported by this module) contains C<$port> while
342	executing the callback. Runtime errors during callback execution will	424	executing the callback. Runtime errors during callback execution will
343	result in the port being C<kil>ed.	425	result in the port being C<kil>ed.
344		426
345	The default callback received all messages not matched by a more specific	427	The default callback receives all messages not matched by a more specific
346	C<tag> match.	428	C<tag> match.
347		429
348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	430	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
349		431
350	Register (or replace) callbacks to be called on messages starting with the	432	Register (or replace) callbacks to be called on messages starting with the
…		…
371	msg1 => sub { ... },	453	msg1 => sub { ... },
372	...	454	...
373	;	455	;
374		456
375	Example: temporarily register a rcv callback for a tag matching some port	457	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.	458	(e.g. for an rpc reply) and unregister it after a message was received.
377		459
378	rcv $port, $otherport => sub {	460	rcv $port, $otherport => sub {
379	my @reply = @_;	461	my @reply = @_;
380		462
381	rcv $SELF, $otherport;	463	rcv $SELF, $otherport;
…		…
394	if (ref $_[0]) {	476	if (ref $_[0]) {
395	if (my $self = $PORT_DATA{$portid}) {	477	if (my $self = $PORT_DATA{$portid}) {
396	"AnyEvent::MP::Port" eq ref $self	478	"AnyEvent::MP::Port" eq ref $self
397	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	479	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
398		480
399	$self->[2] = shift;	481	$self->[0] = shift;
400	} else {	482	} else {
401	my $cb = shift;	483	my $cb = shift;
402	$PORT{$portid} = sub {	484	$PORT{$portid} = sub {
403	local $SELF = $port;	485	local $SELF = $port;
404	eval { &$cb }; _self_die if $@;	486	eval { &$cb }; _self_die if $@;
405	};	487	};
406	}	488	}
407	} elsif (defined $_[0]) {	489	} elsif (defined $_[0]) {
408	my $self = $PORT_DATA{$portid} \|\|= do {	490	my $self = $PORT_DATA{$portid} \|\|= do {
409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	491	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
410		492
411	$PORT{$portid} = sub {	493	$PORT{$portid} = sub {
412	local $SELF = $port;	494	local $SELF = $port;
413		495
414	if (my $cb = $self->[1]{$_[0]}) {	496	if (my $cb = $self->[1]{$_[0]}) {
…		…
436	}	518	}
437		519
438	$port	520	$port
439	}	521	}
440		522
		523	=item peval $port, $coderef[, @args]
		524
		525	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		526	when the code throews an exception the C<$port> will be killed.
		527
		528	Any remaining args will be passed to the callback. Any return values will
		529	be returned to the caller.
		530
		531	This is useful when you temporarily want to execute code in the context of
		532	a port.
		533
		534	Example: create a port and run some initialisation code in it's context.
		535
		536	my $port = port { ... };
		537
		538	peval $port, sub {
		539	init
		540	or die "unable to init";
		541	};
		542
		543	=cut
		544
		545	sub peval($$) {
		546	local $SELF = shift;
		547	my $cb = shift;
		548
		549	if (wantarray) {
		550	my @res = eval { &$cb };
		551	_self_die if $@;
		552	@res
		553	} else {
		554	my $res = eval { &$cb };
		555	_self_die if $@;
		556	$res
		557	}
		558	}
		559
441	=item $closure = psub { BLOCK }	560	=item $closure = psub { BLOCK }
442		561
443	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	562	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>	563	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.	564	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		565
		566	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		567	BLOCK }, @_ } >>.
446		568
447	This is useful when you register callbacks from C<rcv> callbacks:	569	This is useful when you register callbacks from C<rcv> callbacks:
448		570
449	rcv delayed_reply => sub {	571	rcv delayed_reply => sub {
450	my ($delay, @reply) = @_;	572	my ($delay, @reply) = @_;
…		…
523	delivered again.	645	delivered again.
524		646
525	Inter-host-connection timeouts and monitoring depend on the transport	647	Inter-host-connection timeouts and monitoring depend on the transport
526	used. The only transport currently implemented is TCP, and AnyEvent::MP	648	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	649	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).	650	non-idle connection, and usually around two hours for idle connections).
529		651
530	This means that monitoring is good for program errors and cleaning up	652	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	653	stuff eventually, but they are no replacement for a timeout when you need
532	to ensure some maximum latency.	654	to ensure some maximum latency.
533		655
…		…
565	}	687	}
566		688
567	$node->monitor ($port, $cb);	689	$node->monitor ($port, $cb);
568		690
569	defined wantarray	691	defined wantarray
570	and $cb += 0
571	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	692	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
572	}	693	}
573		694
574	=item $guard = mon_guard $port, $ref, $ref...	695	=item $guard = mon_guard $port, $ref, $ref...
575		696
576	Monitors the given C<$port> and keeps the passed references. When the port	697	Monitors the given C<$port> and keeps the passed references. When the port
…		…
599		720
600	=item kil $port[, @reason]	721	=item kil $port[, @reason]
601		722
602	Kill the specified port with the given C<@reason>.	723	Kill the specified port with the given C<@reason>.
603		724
604	If no C<@reason> is specified, then the port is killed "normally" (ports	725	If no C<@reason> is specified, then the port is killed "normally" -
605	monitoring other ports will not necessarily die because a port dies	726	monitor callback will be invoked, but the kil will not cause linked ports
606	"normally").	727	(C<mon $mport, $lport> form) to get killed.
607		728
608	Otherwise, linked ports get killed with the same reason (second form of	729	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
609	C<mon>, see above).	730	form) get killed with the same reason.
610		731
611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	732	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
612	will be reported as reason C<< die => $@ >>.	733	will be reported as reason C<< die => $@ >>.
613		734
614	Transport/communication errors are reported as C<< transport_error =>	735	Transport/communication errors are reported as C<< transport_error =>
615	$message >>.	736	$message >>.
616		737
617	=cut	738	Common idioms:
		739
		740	# silently remove yourself, do not kill linked ports
		741	kil $SELF;
		742
		743	# report a failure in some detail
		744	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		745
		746	# do not waste much time with killing, just die when something goes wrong
		747	open my $fh, "<file"
		748	or die "file: $!";
618		749
619	=item $port = spawn $node, $initfunc[, @initdata]	750	=item $port = spawn $node, $initfunc[, @initdata]
620		751
621	Creates a port on the node C<$node> (which can also be a port ID, in which	752	Creates a port on the node C<$node> (which can also be a port ID, in which
622	case it's the node where that port resides).	753	case it's the node where that port resides).
…		…
680	}	811	}
681		812
682	sub spawn(@) {	813	sub spawn(@) {
683	my ($nodeid, undef) = split /#/, shift, 2;	814	my ($nodeid, undef) = split /#/, shift, 2;
684		815
685	my $id = "$RUNIQ." . $ID++;	816	my $id = $RUNIQ . ++$ID;
686		817
687	$_[0] =~ /::/	818	$_[0] =~ /::/
688	or Carp::croak "spawn init function must be a fully-qualified name, caught";	819	or Carp::croak "spawn init function must be a fully-qualified name, caught";
689		820
690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	821	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
691		822
692	"$nodeid#$id"	823	"$nodeid#$id"
693	}	824	}
		825
694		826
695	=item after $timeout, @msg	827	=item after $timeout, @msg
696		828
697	=item after $timeout, $callback	829	=item after $timeout, $callback
698		830
…		…
714	? $action[0]()	846	? $action[0]()
715	: snd @action;	847	: snd @action;
716	};	848	};
717	}	849	}
718		850
		851	#=item $cb2 = timeout $seconds, $cb[, @args]
		852
719	=item cal $port, @msg, $callback[, $timeout]	853	=item cal $port, @msg, $callback[, $timeout]
720		854
721	A simple form of RPC - sends a message to the given C<$port> with the	855	A simple form of RPC - sends a message to the given C<$port> with the
722	given contents (C<@msg>), but adds a reply port to the message.	856	given contents (C<@msg>), but adds a reply port to the message.
723		857
…		…
728		862
729	If an optional time-out (in seconds) is given and it is not C<undef>,	863	If an optional time-out (in seconds) is given and it is not C<undef>,
730	then the callback will be called without any arguments after the time-out	864	then the callback will be called without any arguments after the time-out
731	elapsed and the port is C<kil>ed.	865	elapsed and the port is C<kil>ed.
732		866
733	If no time-out is given, then the local port will monitor the remote port	867	If no time-out is given (or it is C<undef>), then the local port will
734	instead, so it eventually gets cleaned-up.	868	monitor the remote port instead, so it eventually gets cleaned-up.
735		869
736	Currently this function returns the temporary port, but this "feature"	870	Currently this function returns the temporary port, but this "feature"
737	might go in future versions unless you can make a convincing case that	871	might go in future versions unless you can make a convincing case that
738	this is indeed useful for something.	872	this is indeed useful for something.
739		873
…		…
768	$port	902	$port
769	}	903	}
770		904
771	=back	905	=back
772		906
		907	=head1 DISTRIBUTED DATABASE
		908
		909	AnyEvent::MP comes with a simple distributed database. The database will
		910	be mirrored asynchronously on all global nodes. Other nodes bind to one
		911	of the global nodes for their needs. Every node has a "local database"
		912	which contains all the values that are set locally. All local databases
		913	are merged together to form the global database, which can be queried.
		914
		915	The database structure is that of a two-level hash - the database hash
		916	contains hashes which contain values, similarly to a perl hash of hashes,
		917	i.e.:
		918
		919	$DATABASE{$family}{$subkey} = $value
		920
		921	The top level hash key is called "family", and the second-level hash key
		922	is called "subkey" or simply "key".
		923
		924	The family must be alphanumeric, i.e. start with a letter and consist
		925	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		926	pretty much like Perl module names.
		927
		928	As the family namespace is global, it is recommended to prefix family names
		929	with the name of the application or module using it.
		930
		931	The subkeys must be non-empty strings, with no further restrictions.
		932
		933	The values should preferably be strings, but other perl scalars should
		934	work as well (such as C<undef>, arrays and hashes).
		935
		936	Every database entry is owned by one node - adding the same family/subkey
		937	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		938	but the result might be nondeterministic, i.e. the key might have
		939	different values on different nodes.
		940
		941	Different subkeys in the same family can be owned by different nodes
		942	without problems, and in fact, this is the common method to create worker
		943	pools. For example, a worker port for image scaling might do this:
		944
		945	db_set my_image_scalers => $port;
		946
		947	And clients looking for an image scaler will want to get the
		948	C<my_image_scalers> keys from time to time:
		949
		950	db_keys my_image_scalers => sub {
		951	@ports = @{ $_[0] };
		952	};
		953
		954	Or better yet, they want to monitor the database family, so they always
		955	have a reasonable up-to-date copy:
		956
		957	db_mon my_image_scalers => sub {
		958	@ports = keys %{ $_[0] };
		959	};
		960
		961	In general, you can set or delete single subkeys, but query and monitor
		962	whole families only.
		963
		964	If you feel the need to monitor or query a single subkey, try giving it
		965	it's own family.
		966
		967	=over
		968
		969	=item db_set $family => $subkey [=> $value]
		970
		971	Sets (or replaces) a key to the database - if C<$value> is omitted,
		972	C<undef> is used instead.
		973
		974	=item db_del $family => $subkey...
		975
		976	Deletes one or more subkeys from the database family.
		977
		978	=item $guard = db_reg $family => $subkey [=> $value]
		979
		980	Sets the key on the database and returns a guard. When the guard is
		981	destroyed, the key is deleted from the database. If C<$value> is missing,
		982	then C<undef> is used.
		983
		984	=item db_family $family => $cb->(\%familyhash)
		985
		986	Queries the named database C<$family> and call the callback with the
		987	family represented as a hash. You can keep and freely modify the hash.
		988
		989	=item db_keys $family => $cb->(\@keys)
		990
		991	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		992	them as array reference to the callback.
		993
		994	=item db_values $family => $cb->(\@values)
		995
		996	Same as C<db_family>, except it only queries the family I<values> and passes them
		997	as array reference to the callback.
		998
		999	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1000
		1001	Creates a monitor on the given database family. Each time a key is set
		1002	or or is deleted the callback is called with a hash containing the
		1003	database family and three lists of added, changed and deleted subkeys,
		1004	respectively. If no keys have changed then the array reference might be
		1005	C<undef> or even missing.
		1006
		1007	If not called in void context, a guard object is returned that, when
		1008	destroyed, stops the monitor.
		1009
		1010	The family hash reference and the key arrays belong to AnyEvent::MP and
		1011	B<must not be modified or stored> by the callback. When in doubt, make a
		1012	copy.
		1013
		1014	As soon as possible after the monitoring starts, the callback will be
		1015	called with the intiial contents of the family, even if it is empty,
		1016	i.e. there will always be a timely call to the callback with the current
		1017	contents.
		1018
		1019	It is possible that the callback is called with a change event even though
		1020	the subkey is already present and the value has not changed.
		1021
		1022	The monitoring stops when the guard object is destroyed.
		1023
		1024	Example: on every change to the family "mygroup", print out all keys.
		1025
		1026	my $guard = db_mon mygroup => sub {
		1027	my ($family, $a, $c, $d) = @_;
		1028	print "mygroup members: ", (join " ", keys %$family), "\n";
		1029	};
		1030
		1031	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1032
		1033	my $guard; $guard = db_mon My::Module::workers => sub {
		1034	my ($family, $a, $c, $d) = @_;
		1035	return unless %$family;
		1036	undef $guard;
		1037	print "My::Module::workers now nonempty\n";
		1038	};
		1039
		1040	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1041
		1042	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1043	my ($family, $a, $c, $d) = @_;
		1044
		1045	print "+$_=$family->{$_}\n" for @$a;
		1046	print "*$_=$family->{$_}\n" for @$c;
		1047	print "-$_=$family->{$_}\n" for @$d;
		1048	};
		1049
		1050	=cut
		1051
		1052	=back
		1053
773	=head1 AnyEvent::MP vs. Distributed Erlang	1054	=head1 AnyEvent::MP vs. Distributed Erlang
774		1055
775	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1056	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
776	== aemp node, Erlang process == aemp port), so many of the documents and	1057	== aemp node, Erlang process == aemp port), so many of the documents and
777	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1058	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
778	sample:	1059	sample:
779		1060
780	http://www.Erlang.se/doc/programming_rules.shtml	1061	http://www.erlang.se/doc/programming_rules.shtml
781	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1062	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
782	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1063	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
783	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1064	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
784		1065
785	Despite the similarities, there are also some important differences:	1066	Despite the similarities, there are also some important differences:
786		1067
787	=over 4	1068	=over 4
788		1069
789	=item * Node IDs are arbitrary strings in AEMP.	1070	=item * Node IDs are arbitrary strings in AEMP.
790		1071
791	Erlang relies on special naming and DNS to work everywhere in the same	1072	Erlang relies on special naming and DNS to work everywhere in the same
792	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1073	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
793	configuration or DNS), but will otherwise discover other odes itself.	1074	configuration or DNS), and possibly the addresses of some seed nodes, but
		1075	will otherwise discover other nodes (and their IDs) itself.
794		1076
795	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1077	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
796	uses "local ports are like remote ports".	1078	uses "local ports are like remote ports".
797		1079
798	The failure modes for local ports are quite different (runtime errors	1080	The failure modes for local ports are quite different (runtime errors
…		…
807	ports being the special case/exception, where transport errors cannot	1089	ports being the special case/exception, where transport errors cannot
808	occur.	1090	occur.
809		1091
810	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1092	=item * Erlang uses processes and a mailbox, AEMP does not queue.
811		1093
812	Erlang uses processes that selectively receive messages, and therefore	1094	Erlang uses processes that selectively receive messages out of order, and
813	needs a queue. AEMP is event based, queuing messages would serve no	1095	therefore needs a queue. AEMP is event based, queuing messages would serve
814	useful purpose. For the same reason the pattern-matching abilities of	1096	no useful purpose. For the same reason the pattern-matching abilities
815	AnyEvent::MP are more limited, as there is little need to be able to	1097	of AnyEvent::MP are more limited, as there is little need to be able to
816	filter messages without dequeuing them.	1098	filter messages without dequeuing them.
817		1099
818	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1100	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1101	being event-based, while Erlang is process-based.
		1102
		1103	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1104	top of AEMP and Coro threads.
819		1105
820	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1106	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
821		1107
822	Sending messages in Erlang is synchronous and blocks the process (and	1108	Sending messages in Erlang is synchronous and blocks the process until
		1109	a conenction has been established and the message sent (and so does not
823	so does not need a queue that can overflow). AEMP sends are immediate,	1110	need a queue that can overflow). AEMP sends return immediately, connection
824	connection establishment is handled in the background.	1111	establishment is handled in the background.
825		1112
826	=item * Erlang suffers from silent message loss, AEMP does not.	1113	=item * Erlang suffers from silent message loss, AEMP does not.
827		1114
828	Erlang makes few guarantees on messages delivery - messages can get lost	1115	Erlang implements few guarantees on messages delivery - messages can get
829	without any of the processes realising it (i.e. you send messages a, b,	1116	lost without any of the processes realising it (i.e. you send messages a,
830	and c, and the other side only receives messages a and c).	1117	b, and c, and the other side only receives messages a and c).
831		1118
832	AEMP guarantees correct ordering, and the guarantee that after one message	1119	AEMP guarantees (modulo hardware errors) correct ordering, and the
833	is lost, all following ones sent to the same port are lost as well, until	1120	guarantee that after one message is lost, all following ones sent to the
834	monitoring raises an error, so there are no silent "holes" in the message	1121	same port are lost as well, until monitoring raises an error, so there are
835	sequence.	1122	no silent "holes" in the message sequence.
		1123
		1124	If you want your software to be very reliable, you have to cope with
		1125	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1126	simply tries to work better in common error cases, such as when a network
		1127	link goes down.
836		1128
837	=item * Erlang can send messages to the wrong port, AEMP does not.	1129	=item * Erlang can send messages to the wrong port, AEMP does not.
838		1130
839	In Erlang it is quite likely that a node that restarts reuses a process ID	1131	In Erlang it is quite likely that a node that restarts reuses an Erlang
840	known to other nodes for a completely different process, causing messages	1132	process ID known to other nodes for a completely different process,
841	destined for that process to end up in an unrelated process.	1133	causing messages destined for that process to end up in an unrelated
		1134	process.
842		1135
843	AEMP never reuses port IDs, so old messages or old port IDs floating	1136	AEMP does not reuse port IDs, so old messages or old port IDs floating
844	around in the network will not be sent to an unrelated port.	1137	around in the network will not be sent to an unrelated port.
845		1138
846	=item * Erlang uses unprotected connections, AEMP uses secure	1139	=item * Erlang uses unprotected connections, AEMP uses secure
847	authentication and can use TLS.	1140	authentication and can use TLS.
848		1141
…		…
851		1144
852	=item * The AEMP protocol is optimised for both text-based and binary	1145	=item * The AEMP protocol is optimised for both text-based and binary
853	communications.	1146	communications.
854		1147
855	The AEMP protocol, unlike the Erlang protocol, supports both programming	1148	The AEMP protocol, unlike the Erlang protocol, supports both programming
856	language independent text-only protocols (good for debugging) and binary,	1149	language independent text-only protocols (good for debugging), and binary,
857	language-specific serialisers (e.g. Storable). By default, unless TLS is	1150	language-specific serialisers (e.g. Storable). By default, unless TLS is
858	used, the protocol is actually completely text-based.	1151	used, the protocol is actually completely text-based.
859		1152
860	It has also been carefully designed to be implementable in other languages	1153	It has also been carefully designed to be implementable in other languages
861	with a minimum of work while gracefully degrading functionality to make the	1154	with a minimum of work while gracefully degrading functionality to make the
862	protocol simple.	1155	protocol simple.
863		1156
864	=item * AEMP has more flexible monitoring options than Erlang.	1157	=item * AEMP has more flexible monitoring options than Erlang.
865		1158
866	In Erlang, you can chose to receive I<all> exit signals as messages	1159	In Erlang, you can chose to receive I<all> exit signals as messages or
867	or I<none>, there is no in-between, so monitoring single processes is	1160	I<none>, there is no in-between, so monitoring single Erlang processes is
868	difficult to implement. Monitoring in AEMP is more flexible than in	1161	difficult to implement.
869	Erlang, as one can choose between automatic kill, exit message or callback	1162
870	on a per-process basis.	1163	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1164	between automatic kill, exit message or callback on a per-port basis.
871		1165
872	=item * Erlang tries to hide remote/local connections, AEMP does not.	1166	=item * Erlang tries to hide remote/local connections, AEMP does not.
873		1167
874	Monitoring in Erlang is not an indicator of process death/crashes, in the	1168	Monitoring in Erlang is not an indicator of process death/crashes, in the
875	same way as linking is (except linking is unreliable in Erlang).	1169	same way as linking is (except linking is unreliable in Erlang).
…		…
897	overhead, as well as having to keep a proxy object everywhere.	1191	overhead, as well as having to keep a proxy object everywhere.
898		1192
899	Strings can easily be printed, easily serialised etc. and need no special	1193	Strings can easily be printed, easily serialised etc. and need no special
900	procedures to be "valid".	1194	procedures to be "valid".
901		1195
902	And as a result, a miniport consists of a single closure stored in a	1196	And as a result, a port with just a default receiver consists of a single
903	global hash - it can't become much cheaper.	1197	code reference stored in a global hash - it can't become much cheaper.
904		1198
905	=item Why favour JSON, why not a real serialising format such as Storable?	1199	=item Why favour JSON, why not a real serialising format such as Storable?
906		1200
907	In fact, any AnyEvent::MP node will happily accept Storable as framing	1201	In fact, any AnyEvent::MP node will happily accept Storable as framing
908	format, but currently there is no way to make a node use Storable by	1202	format, but currently there is no way to make a node use Storable by
…		…
924		1218
925	L<AnyEvent::MP::Intro> - a gentle introduction.	1219	L<AnyEvent::MP::Intro> - a gentle introduction.
926		1220
927	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1221	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
928		1222
929	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1223	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
930	your applications.	1224	your applications.
		1225
		1226	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
931		1227
932	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1228	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
933	all nodes.	1229	all nodes.
934		1230
935	L<AnyEvent>.	1231	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.93 by root, Tue Sep 22 14:14:29 2009 UTC vs. Revision 1.134 by root, Mon Mar 12 14:47:23 2012 UTC

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Revision 1.93 by root, Tue Sep 22 14:14:29 2009 UTC vs.
Revision 1.134 by root, Mon Mar 12 14:47:23 2012 UTC