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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.78 by root, Thu Sep 3 20:16:36 2009 UTC vs.
Revision 1.128 by root, Sun Mar 4 14:28:44 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
30	rcv $port, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
31		31
32	# create a port on another node	32	# create a port on another node
33	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
34		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
35	# monitoring	39	# monitoring
36	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
38	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
39		51
40	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
41		53
42	bin/aemp - stable.	54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - explains most concepts.	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - stable API, 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
…		…
61		71
62	=over 4	72	=over 4
63		73
64	=item port	74	=item port
65		75
66	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
67		78
68	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
69	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
70	anything was listening for them or not.	81	anything was listening for them or not.
71		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
72	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
73		86
74	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<#>)
75	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).
76		90
77	=item node	91	=item node
78		92
79	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,
80	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
81	ports.	95	ports.
82		96
83	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
84	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
85	currently.	99	currently, but all nodes can talk to public nodes.
86		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
87	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
88		104
89	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
90	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
91	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
92	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
93		109
94	=item binds - C<ip:port>	110	=item binds - C<ip:port>
95		111
96	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
97	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
98	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
99	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.
100		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
101	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
102		150
103	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
104	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.
105	network. This node is called a seed.
106		153
107	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
108	are expected to be long-running, and at least one of those should always
109	be available. When nodes run out of connections (e.g. due to a network
110	error), they try to re-establish connections to some seednodes again to
111	join the network.
112		155
113	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
114	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).
115		170
116	=back	171	=back
117		172
118	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
119		174
…		…
121		176
122	=cut	177	=cut
123		178
124	package AnyEvent::MP;	179	package AnyEvent::MP;
125		180
		181	use AnyEvent::MP::Config ();
126	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
127		184
128	use common::sense;	185	use common::sense;
129		186
130	use Carp ();	187	use Carp ();
131		188
132	use AE ();	189	use AE ();
		190	use Guard ();
133		191
134	use base "Exporter";	192	use base "Exporter";
135		193
136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
137		195
138	our @EXPORT = qw(	196	our @EXPORT = qw(
139	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
140	configure	198	configure
141	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
142	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
143	);	203	);
144		204
145	our $SELF;	205	our $SELF;
146		206
147	sub _self_die() {	207	sub _self_die() {
…		…
170	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
171		231
172	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
173	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
174		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
175	=over 4	262	=over 4
176		263
177	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
178		265
179	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
…		…
192	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
193	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
194	and can only be used to specify defaults.	281	and can only be used to specify defaults.
195		282
196	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
197	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
198	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>.
199		292
200	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
201		294
202	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
203	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
…		…
209	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
210	local IP address it finds.	303	local IP address it finds.
211		304
212	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
213		306
214	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
215	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
216	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
217		310
218	=back	311	=back
219		312
220	Example: become a distributed node using the locla node name as profile.	313	Example: become a distributed node using the local node name as profile.
221	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.
222		315
223	configure	316	configure
224		317
225	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
226	clients.	319	commandline clients.
227		320
228	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
229		322
230	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
231	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,
232	customary for aemp).	325	customary for aemp).
233		326
234	# use the aemp commandline utility	327	# use the aemp commandline utility
235	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
236		329
237	# then use it	330	# then use it
238	configure profile => "seed";	331	configure profile => "seed";
239		332
240	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
310	sub _kilme {	403	sub _kilme {
311	die "received message on port without callback";	404	die "received message on port without callback";
312	}	405	}
313		406
314	sub port(;&) {	407	sub port(;&) {
315	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
316	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
317		410
318	rcv $port, shift \|\| \&_kilme;	411	rcv $port, shift \|\| \&_kilme;
319		412
320	$port	413	$port
…		…
359	msg1 => sub { ... },	452	msg1 => sub { ... },
360	...	453	...
361	;	454	;
362		455
363	Example: temporarily register a rcv callback for a tag matching some port	456	Example: temporarily register a rcv callback for a tag matching some port
364	(e.g. for a rpc reply) and unregister it after a message was received.	457	(e.g. for an rpc reply) and unregister it after a message was received.
365		458
366	rcv $port, $otherport => sub {	459	rcv $port, $otherport => sub {
367	my @reply = @_;	460	my @reply = @_;
368		461
369	rcv $SELF, $otherport;	462	rcv $SELF, $otherport;
…		…
382	if (ref $_[0]) {	475	if (ref $_[0]) {
383	if (my $self = $PORT_DATA{$portid}) {	476	if (my $self = $PORT_DATA{$portid}) {
384	"AnyEvent::MP::Port" eq ref $self	477	"AnyEvent::MP::Port" eq ref $self
385	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	478	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
386		479
387	$self->[2] = shift;	480	$self->[0] = shift;
388	} else {	481	} else {
389	my $cb = shift;	482	my $cb = shift;
390	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
391	local $SELF = $port;	484	local $SELF = $port;
392	eval { &$cb }; _self_die if $@;	485	eval { &$cb }; _self_die if $@;
393	};	486	};
394	}	487	}
395	} elsif (defined $_[0]) {	488	} elsif (defined $_[0]) {
396	my $self = $PORT_DATA{$portid} \|\|= do {	489	my $self = $PORT_DATA{$portid} \|\|= do {
397	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	490	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
398		491
399	$PORT{$portid} = sub {	492	$PORT{$portid} = sub {
400	local $SELF = $port;	493	local $SELF = $port;
401		494
402	if (my $cb = $self->[1]{$_[0]}) {	495	if (my $cb = $self->[1]{$_[0]}) {
…		…
424	}	517	}
425		518
426	$port	519	$port
427	}	520	}
428		521
		522	=item peval $port, $coderef[, @args]
		523
		524	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		525	when the code throews an exception the C<$port> will be killed.
		526
		527	Any remaining args will be passed to the callback. Any return values will
		528	be returned to the caller.
		529
		530	This is useful when you temporarily want to execute code in the context of
		531	a port.
		532
		533	Example: create a port and run some initialisation code in it's context.
		534
		535	my $port = port { ... };
		536
		537	peval $port, sub {
		538	init
		539	or die "unable to init";
		540	};
		541
		542	=cut
		543
		544	sub peval($$) {
		545	local $SELF = shift;
		546	my $cb = shift;
		547
		548	if (wantarray) {
		549	my @res = eval { &$cb };
		550	_self_die if $@;
		551	@res
		552	} else {
		553	my $res = eval { &$cb };
		554	_self_die if $@;
		555	$res
		556	}
		557	}
		558
429	=item $closure = psub { BLOCK }	559	=item $closure = psub { BLOCK }
430		560
431	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	561	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
432	closure is executed, sets up the environment in the same way as in C<rcv>	562	closure is executed, sets up the environment in the same way as in C<rcv>
433	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	563	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		564
		565	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		566	BLOCK }, @_ } >>.
434		567
435	This is useful when you register callbacks from C<rcv> callbacks:	568	This is useful when you register callbacks from C<rcv> callbacks:
436		569
437	rcv delayed_reply => sub {	570	rcv delayed_reply => sub {
438	my ($delay, @reply) = @_;	571	my ($delay, @reply) = @_;
…		…
474		607
475	Monitor the given port and do something when the port is killed or	608	Monitor the given port and do something when the port is killed or
476	messages to it were lost, and optionally return a guard that can be used	609	messages to it were lost, and optionally return a guard that can be used
477	to stop monitoring again.	610	to stop monitoring again.
478		611
		612	In the first form (callback), the callback is simply called with any
		613	number of C<@reason> elements (no @reason means that the port was deleted
		614	"normally"). Note also that I<< the callback B<must> never die >>, so use
		615	C<eval> if unsure.
		616
		617	In the second form (another port given), the other port (C<$rcvport>)
		618	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		619	"normal" kils nothing happens, while under all other conditions, the other
		620	port is killed with the same reason.
		621
		622	The third form (kill self) is the same as the second form, except that
		623	C<$rvport> defaults to C<$SELF>.
		624
		625	In the last form (message), a message of the form C<@msg, @reason> will be
		626	C<snd>.
		627
		628	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		629	alert was raised), they are removed and will not trigger again.
		630
		631	As a rule of thumb, monitoring requests should always monitor a port from
		632	a local port (or callback). The reason is that kill messages might get
		633	lost, just like any other message. Another less obvious reason is that
		634	even monitoring requests can get lost (for example, when the connection
		635	to the other node goes down permanently). When monitoring a port locally
		636	these problems do not exist.
		637
479	C<mon> effectively guarantees that, in the absence of hardware failures,	638	C<mon> effectively guarantees that, in the absence of hardware failures,
480	after starting the monitor, either all messages sent to the port will	639	after starting the monitor, either all messages sent to the port will
481	arrive, or the monitoring action will be invoked after possible message	640	arrive, or the monitoring action will be invoked after possible message
482	loss has been detected. No messages will be lost "in between" (after	641	loss has been detected. No messages will be lost "in between" (after
483	the first lost message no further messages will be received by the	642	the first lost message no further messages will be received by the
484	port). After the monitoring action was invoked, further messages might get	643	port). After the monitoring action was invoked, further messages might get
485	delivered again.	644	delivered again.
486		645
487	Note that monitoring-actions are one-shot: once messages are lost (and a	646	Inter-host-connection timeouts and monitoring depend on the transport
488	monitoring alert was raised), they are removed and will not trigger again.	647	used. The only transport currently implemented is TCP, and AnyEvent::MP
		648	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		649	non-idle connection, and usually around two hours for idle connections).
489		650
490	In the first form (callback), the callback is simply called with any	651	This means that monitoring is good for program errors and cleaning up
491	number of C<@reason> elements (no @reason means that the port was deleted	652	stuff eventually, but they are no replacement for a timeout when you need
492	"normally"). Note also that I<< the callback B<must> never die >>, so use	653	to ensure some maximum latency.
493	C<eval> if unsure.
494
495	In the second form (another port given), the other port (C<$rcvport>)
496	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
497	"normal" kils nothing happens, while under all other conditions, the other
498	port is killed with the same reason.
499
500	The third form (kill self) is the same as the second form, except that
501	C<$rvport> defaults to C<$SELF>.
502
503	In the last form (message), a message of the form C<@msg, @reason> will be
504	C<snd>.
505
506	As a rule of thumb, monitoring requests should always monitor a port from
507	a local port (or callback). The reason is that kill messages might get
508	lost, just like any other message. Another less obvious reason is that
509	even monitoring requests can get lost (for example, when the connection
510	to the other node goes down permanently). When monitoring a port locally
511	these problems do not exist.
512		654
513	Example: call a given callback when C<$port> is killed.	655	Example: call a given callback when C<$port> is killed.
514		656
515	mon $port, sub { warn "port died because of <@_>\n" };	657	mon $port, sub { warn "port died because of <@_>\n" };
516		658
…		…
544	}	686	}
545		687
546	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
547		689
548	defined wantarray	690	defined wantarray
549	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
550	}	692	}
551		693
552	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
553		695
554	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
…		…
577		719
578	=item kil $port[, @reason]	720	=item kil $port[, @reason]
579		721
580	Kill the specified port with the given C<@reason>.	722	Kill the specified port with the given C<@reason>.
581		723
582	If no C<@reason> is specified, then the port is killed "normally" (ports	724	If no C<@reason> is specified, then the port is killed "normally" -
583	monitoring other ports will not necessarily die because a port dies	725	monitor callback will be invoked, but the kil will not cause linked ports
584	"normally").	726	(C<mon $mport, $lport> form) to get killed.
585		727
586	Otherwise, linked ports get killed with the same reason (second form of	728	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
587	C<mon>, see above).	729	form) get killed with the same reason.
588		730
589	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	731	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
590	will be reported as reason C<< die => $@ >>.	732	will be reported as reason C<< die => $@ >>.
591		733
592	Transport/communication errors are reported as C<< transport_error =>	734	Transport/communication errors are reported as C<< transport_error =>
…		…
611	the package, then the package above the package and so on (e.g.	753	the package, then the package above the package and so on (e.g.
612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	754	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
613	exists or it runs out of package names.	755	exists or it runs out of package names.
614		756
615	The init function is then called with the newly-created port as context	757	The init function is then called with the newly-created port as context
616	object (C<$SELF>) and the C<@initdata> values as arguments.	758	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		759	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		760	the port might not get created.
617		761
618	A common idiom is to pass a local port, immediately monitor the spawned	762	A common idiom is to pass a local port, immediately monitor the spawned
619	port, and in the remote init function, immediately monitor the passed	763	port, and in the remote init function, immediately monitor the passed
620	local port. This two-way monitoring ensures that both ports get cleaned up	764	local port. This two-way monitoring ensures that both ports get cleaned up
621	when there is a problem.	765	when there is a problem.
622		766
		767	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		768	caller before C<spawn> returns (by delaying invocation when spawn is
		769	called for the local node).
		770
623	Example: spawn a chat server port on C<$othernode>.	771	Example: spawn a chat server port on C<$othernode>.
624		772
625	# this node, executed from within a port context:	773	# this node, executed from within a port context:
626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	774	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
627	mon $server;	775	mon $server;
…		…
641		789
642	sub _spawn {	790	sub _spawn {
643	my $port = shift;	791	my $port = shift;
644	my $init = shift;	792	my $init = shift;
645		793
		794	# rcv will create the actual port
646	local $SELF = "$NODE#$port";	795	local $SELF = "$NODE#$port";
647	eval {	796	eval {
648	&{ load_func $init }	797	&{ load_func $init }
649	};	798	};
650	_self_die if $@;	799	_self_die if $@;
651	}	800	}
652		801
653	sub spawn(@) {	802	sub spawn(@) {
654	my ($nodeid, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
655		804
656	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
657		806
658	$_[0] =~ /::/	807	$_[0] =~ /::/
659	or Carp::croak "spawn init function must be a fully-qualified name, caught";	808	or Carp::croak "spawn init function must be a fully-qualified name, caught";
660		809
661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
662		811
663	"$nodeid#$id"	812	"$nodeid#$id"
664	}	813	}
		814
665		815
666	=item after $timeout, @msg	816	=item after $timeout, @msg
667		817
668	=item after $timeout, $callback	818	=item after $timeout, $callback
669		819
…		…
685	? $action[0]()	835	? $action[0]()
686	: snd @action;	836	: snd @action;
687	};	837	};
688	}	838	}
689		839
		840	=item cal $port, @msg, $callback[, $timeout]
		841
		842	A simple form of RPC - sends a message to the given C<$port> with the
		843	given contents (C<@msg>), but adds a reply port to the message.
		844
		845	The reply port is created temporarily just for the purpose of receiving
		846	the reply, and will be C<kil>ed when no longer needed.
		847
		848	A reply message sent to the port is passed to the C<$callback> as-is.
		849
		850	If an optional time-out (in seconds) is given and it is not C<undef>,
		851	then the callback will be called without any arguments after the time-out
		852	elapsed and the port is C<kil>ed.
		853
		854	If no time-out is given (or it is C<undef>), then the local port will
		855	monitor the remote port instead, so it eventually gets cleaned-up.
		856
		857	Currently this function returns the temporary port, but this "feature"
		858	might go in future versions unless you can make a convincing case that
		859	this is indeed useful for something.
		860
		861	=cut
		862
		863	sub cal(@) {
		864	my $timeout = ref $_[-1] ? undef : pop;
		865	my $cb = pop;
		866
		867	my $port = port {
		868	undef $timeout;
		869	kil $SELF;
		870	&$cb;
		871	};
		872
		873	if (defined $timeout) {
		874	$timeout = AE::timer $timeout, 0, sub {
		875	undef $timeout;
		876	kil $port;
		877	$cb->();
		878	};
		879	} else {
		880	mon $_[0], sub {
		881	kil $port;
		882	$cb->();
		883	};
		884	}
		885
		886	push @_, $port;
		887	&snd;
		888
		889	$port
		890	}
		891
		892	=back
		893
		894	=head1 DISTRIBUTED DATABASE
		895
		896	AnyEvent::MP comes with a simple distributed database. The database will
		897	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		898	the global nodes for their needs.
		899
		900	The database consists of a two-level hash - a hash contains a hash which
		901	contains values.
		902
		903	The top level hash key is called "family", and the second-level hash key
		904	is called "subkey" or simply "key".
		905
		906	The family must be alphanumeric, i.e. start with a letter and consist
		907	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		908	pretty much like Perl module names.
		909
		910	As the family namespace is global, it is recommended to prefix family names
		911	with the name of the application or module using it.
		912
		913	The subkeys must be non-empty strings, with no further restrictions.
		914
		915	The values should preferably be strings, but other perl scalars should
		916	work as well (such as undef, arrays and hashes).
		917
		918	Every database entry is owned by one node - adding the same family/subkey
		919	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		920	but the result might be nondeterministic, i.e. the key might have
		921	different values on different nodes.
		922
		923	Different subkeys in the same family can be owned by different nodes
		924	without problems, and in fact, this is the common method to create worker
		925	pools. For example, a worker port for image scaling might do this:
		926
		927	db_set my_image_scalers => $port;
		928
		929	And clients looking for an image scaler will want to get the
		930	C<my_image_scalers> keys:
		931
		932	db_keys "my_image_scalers" => 60 => sub {
		933	#d##TODO#
		934
		935	=over
		936
		937	=item db_set $family => $subkey [=> $value]
		938
		939	Sets (or replaces) a key to the database - if C<$value> is omitted,
		940	C<undef> is used instead.
		941
		942	=item db_del $family => $subkey
		943
		944	Deletes a key from the database.
		945
		946	=item $guard = db_reg $family => $subkey [=> $value]
		947
		948	Sets the key on the database and returns a guard. When the guard is
		949	destroyed, the key is deleted from the database. If C<$value> is missing,
		950	then C<undef> is used.
		951
		952	=item $guard = db_mon $family => $cb->($familyhash, \@subkeys...)
		953
		954	Creates a monitor on the given database family. Each time a key is set or
		955	or is deleted the callback is called with a hash containing the database
		956	family and an arrayref with subkeys that have changed.
		957
		958	Specifically, if one of the passed subkeys exists in the $familyhash, then
		959	it is currently set to the value in the $familyhash. Otherwise, it has
		960	been deleted.
		961
		962	The first call will be with the current contents of the family and all
		963	keys, as if they were just added.
		964
		965	It is possible that the callback is called with a change event even though
		966	the subkey is already present and the value has not changed.
		967
		968	The monitoring stops when the guard object is destroyed.
		969
		970	Example: on every change to the family "mygroup", print out all keys.
		971
		972	my $guard = db_mon mygroup => sub {
		973	my ($family, $keys) = @_;
		974	print "mygroup members: ", (join " ", keys %$family), "\n";
		975	};
		976
		977	Exmaple: wait until the family "My::Module::workers" is non-empty.
		978
		979	my $guard; $guard = db_mon My::Module::workers => sub {
		980	my ($family, $keys) = @_;
		981	return unless %$family;
		982	undef $guard;
		983	print "My::Module::workers now nonempty\n";
		984	};
		985
		986	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		987
		988	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		989	my ($family, $keys) = @_;
		990
		991	for (@$keys) {
		992	print "$_: ",
		993	(exists $family->{$_}
		994	? $family->{$_}
		995	: "(deleted)"),
		996	"\n";
		997	}
		998	};
		999
		1000	=cut
		1001
690	=back	1002	=back
691		1003
692	=head1 AnyEvent::MP vs. Distributed Erlang	1004	=head1 AnyEvent::MP vs. Distributed Erlang
693		1005
694	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1006	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
695	== aemp node, Erlang process == aemp port), so many of the documents and	1007	== aemp node, Erlang process == aemp port), so many of the documents and
696	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1008	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
697	sample:	1009	sample:
698		1010
699	http://www.Erlang.se/doc/programming_rules.shtml	1011	http://www.erlang.se/doc/programming_rules.shtml
700	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1012	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
701	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1013	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
702	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1014	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
703		1015
704	Despite the similarities, there are also some important differences:	1016	Despite the similarities, there are also some important differences:
705		1017
706	=over 4	1018	=over 4
707		1019
708	=item * Node IDs are arbitrary strings in AEMP.	1020	=item * Node IDs are arbitrary strings in AEMP.
709		1021
710	Erlang relies on special naming and DNS to work everywhere in the same	1022	Erlang relies on special naming and DNS to work everywhere in the same
711	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1023	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
712	configuration or DNS), but will otherwise discover other odes itself.	1024	configuration or DNS), and possibly the addresses of some seed nodes, but
		1025	will otherwise discover other nodes (and their IDs) itself.
713		1026
714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1027	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
715	uses "local ports are like remote ports".	1028	uses "local ports are like remote ports".
716		1029
717	The failure modes for local ports are quite different (runtime errors	1030	The failure modes for local ports are quite different (runtime errors
…		…
726	ports being the special case/exception, where transport errors cannot	1039	ports being the special case/exception, where transport errors cannot
727	occur.	1040	occur.
728		1041
729	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1042	=item * Erlang uses processes and a mailbox, AEMP does not queue.
730		1043
731	Erlang uses processes that selectively receive messages, and therefore	1044	Erlang uses processes that selectively receive messages out of order, and
732	needs a queue. AEMP is event based, queuing messages would serve no	1045	therefore needs a queue. AEMP is event based, queuing messages would serve
733	useful purpose. For the same reason the pattern-matching abilities of	1046	no useful purpose. For the same reason the pattern-matching abilities
734	AnyEvent::MP are more limited, as there is little need to be able to	1047	of AnyEvent::MP are more limited, as there is little need to be able to
735	filter messages without dequeuing them.	1048	filter messages without dequeuing them.
736		1049
737	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1050	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1051	being event-based, while Erlang is process-based.
		1052
		1053	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1054	top of AEMP and Coro threads.
738		1055
739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1056	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
740		1057
741	Sending messages in Erlang is synchronous and blocks the process (and	1058	Sending messages in Erlang is synchronous and blocks the process until
		1059	a conenction has been established and the message sent (and so does not
742	so does not need a queue that can overflow). AEMP sends are immediate,	1060	need a queue that can overflow). AEMP sends return immediately, connection
743	connection establishment is handled in the background.	1061	establishment is handled in the background.
744		1062
745	=item * Erlang suffers from silent message loss, AEMP does not.	1063	=item * Erlang suffers from silent message loss, AEMP does not.
746		1064
747	Erlang makes few guarantees on messages delivery - messages can get lost	1065	Erlang implements few guarantees on messages delivery - messages can get
748	without any of the processes realising it (i.e. you send messages a, b,	1066	lost without any of the processes realising it (i.e. you send messages a,
749	and c, and the other side only receives messages a and c).	1067	b, and c, and the other side only receives messages a and c).
750		1068
751	AEMP guarantees correct ordering, and the guarantee that after one message	1069	AEMP guarantees (modulo hardware errors) correct ordering, and the
752	is lost, all following ones sent to the same port are lost as well, until	1070	guarantee that after one message is lost, all following ones sent to the
753	monitoring raises an error, so there are no silent "holes" in the message	1071	same port are lost as well, until monitoring raises an error, so there are
754	sequence.	1072	no silent "holes" in the message sequence.
		1073
		1074	If you want your software to be very reliable, you have to cope with
		1075	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1076	simply tries to work better in common error cases, such as when a network
		1077	link goes down.
755		1078
756	=item * Erlang can send messages to the wrong port, AEMP does not.	1079	=item * Erlang can send messages to the wrong port, AEMP does not.
757		1080
758	In Erlang it is quite likely that a node that restarts reuses a process ID	1081	In Erlang it is quite likely that a node that restarts reuses an Erlang
759	known to other nodes for a completely different process, causing messages	1082	process ID known to other nodes for a completely different process,
760	destined for that process to end up in an unrelated process.	1083	causing messages destined for that process to end up in an unrelated
		1084	process.
761		1085
762	AEMP never reuses port IDs, so old messages or old port IDs floating	1086	AEMP does not reuse port IDs, so old messages or old port IDs floating
763	around in the network will not be sent to an unrelated port.	1087	around in the network will not be sent to an unrelated port.
764		1088
765	=item * Erlang uses unprotected connections, AEMP uses secure	1089	=item * Erlang uses unprotected connections, AEMP uses secure
766	authentication and can use TLS.	1090	authentication and can use TLS.
767		1091
…		…
770		1094
771	=item * The AEMP protocol is optimised for both text-based and binary	1095	=item * The AEMP protocol is optimised for both text-based and binary
772	communications.	1096	communications.
773		1097
774	The AEMP protocol, unlike the Erlang protocol, supports both programming	1098	The AEMP protocol, unlike the Erlang protocol, supports both programming
775	language independent text-only protocols (good for debugging) and binary,	1099	language independent text-only protocols (good for debugging), and binary,
776	language-specific serialisers (e.g. Storable). By default, unless TLS is	1100	language-specific serialisers (e.g. Storable). By default, unless TLS is
777	used, the protocol is actually completely text-based.	1101	used, the protocol is actually completely text-based.
778		1102
779	It has also been carefully designed to be implementable in other languages	1103	It has also been carefully designed to be implementable in other languages
780	with a minimum of work while gracefully degrading functionality to make the	1104	with a minimum of work while gracefully degrading functionality to make the
781	protocol simple.	1105	protocol simple.
782		1106
783	=item * AEMP has more flexible monitoring options than Erlang.	1107	=item * AEMP has more flexible monitoring options than Erlang.
784		1108
785	In Erlang, you can chose to receive I<all> exit signals as messages	1109	In Erlang, you can chose to receive I<all> exit signals as messages or
786	or I<none>, there is no in-between, so monitoring single processes is	1110	I<none>, there is no in-between, so monitoring single Erlang processes is
787	difficult to implement. Monitoring in AEMP is more flexible than in	1111	difficult to implement.
788	Erlang, as one can choose between automatic kill, exit message or callback	1112
789	on a per-process basis.	1113	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1114	between automatic kill, exit message or callback on a per-port basis.
790		1115
791	=item * Erlang tries to hide remote/local connections, AEMP does not.	1116	=item * Erlang tries to hide remote/local connections, AEMP does not.
792		1117
793	Monitoring in Erlang is not an indicator of process death/crashes, in the	1118	Monitoring in Erlang is not an indicator of process death/crashes, in the
794	same way as linking is (except linking is unreliable in Erlang).	1119	same way as linking is (except linking is unreliable in Erlang).
…		…
816	overhead, as well as having to keep a proxy object everywhere.	1141	overhead, as well as having to keep a proxy object everywhere.
817		1142
818	Strings can easily be printed, easily serialised etc. and need no special	1143	Strings can easily be printed, easily serialised etc. and need no special
819	procedures to be "valid".	1144	procedures to be "valid".
820		1145
821	And as a result, a miniport consists of a single closure stored in a	1146	And as a result, a port with just a default receiver consists of a single
822	global hash - it can't become much cheaper.	1147	code reference stored in a global hash - it can't become much cheaper.
823		1148
824	=item Why favour JSON, why not a real serialising format such as Storable?	1149	=item Why favour JSON, why not a real serialising format such as Storable?
825		1150
826	In fact, any AnyEvent::MP node will happily accept Storable as framing	1151	In fact, any AnyEvent::MP node will happily accept Storable as framing
827	format, but currently there is no way to make a node use Storable by	1152	format, but currently there is no way to make a node use Storable by
…		…
843		1168
844	L<AnyEvent::MP::Intro> - a gentle introduction.	1169	L<AnyEvent::MP::Intro> - a gentle introduction.
845		1170
846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1171	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
847		1172
848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1173	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
849	your applications.	1174	your applications.
		1175
		1176	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1177
		1178	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1179	all nodes.
850		1180
851	L<AnyEvent>.	1181	L<AnyEvent>.
852		1182
853	=head1 AUTHOR	1183	=head1 AUTHOR
854		1184

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.78 by root, Thu Sep 3 20:16:36 2009 UTC vs. Revision 1.128 by root, Sun Mar 4 14:28:44 2012 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.78 by root, Thu Sep 3 20:16:36 2009 UTC vs.
Revision 1.128 by root, Sun Mar 4 14:28:44 2012 UTC