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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.30 by root, Tue Aug 4 23:35:51 2009 UTC vs.
Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC

…		…
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's noderef
10	NODE # returns this node's noderef	10	NODE # returns this node's noderef
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node; # -OR-
		17	initialise_node "localhost:4040"; # -OR-
		18	initialise_node "slave/", "localhost:4040"
		19
		20	# ports are message endpoints
		21
		22	# sending messages
13	snd $port, type => data...;	23	snd $port, type => data...;
		24	snd $port, @msg;
		25	snd @msg_with_first_element_being_a_port;
14		26
15	$SELF # receiving/own port id in rcv callbacks	27	# creating/using ports, the simple way
		28	my $somple_port = port { my @msg = @_; 0 };
16		29
17	rcv $port, smartmatch => $cb->($port, @msg);	30	# creating/using ports, type matching
18		31	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		34
24	# more, smarter, matches (_any_ is exported by this module)	35	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	36	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
…		…
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	60	manual page.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
39	so do not use. This was uploaded mainly to reserve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.	64	stay tuned!
41		65
42	=head1 CONCEPTS	66	=head1 CONCEPTS
43		67
44	=over 4	68	=over 4
45		69
…		…
90		114
91	=cut	115	=cut
92		116
93	package AnyEvent::MP;	117	package AnyEvent::MP;
94		118
95	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
96		120
97	use common::sense;	121	use common::sense;
98		122
99	use Carp ();	123	use Carp ();
100		124
101	use AE ();	125	use AE ();
102		126
103	use base "Exporter";	127	use base "Exporter";
104		128
105	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
106	our @EXPORT = qw(	131	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
108	resolve_node	133	resolve_node initialise_node
109	become_slave become_public
110	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
111	port	135	port
112	);	136	);
113		137
114	our $SELF;	138	our $SELF;
115		139
…		…
124	The C<NODE> function returns, and the C<$NODE> variable contains	148	The C<NODE> function returns, and the C<$NODE> variable contains
125	the noderef of the local node. The value is initialised by a call	149	the noderef of the local node. The value is initialised by a call
126	to C<become_public> or C<become_slave>, after which all local port	150	to C<become_public> or C<become_slave>, after which all local port
127	identifiers become invalid.	151	identifiers become invalid.
128		152
129	=item $noderef = node_of $portid	153	=item $noderef = node_of $port
130		154
131	Extracts and returns the noderef from a portid or a noderef.	155	Extracts and returns the noderef from a portid or a noderef.
		156
		157	=item initialise_node $noderef, $seednode, $seednode...
		158
		159	=item initialise_node "slave/", $master, $master...
		160
		161	Before a node can talk to other nodes on the network it has to initialise
		162	itself - the minimum a node needs to know is it's own name, and optionally
		163	it should know the noderefs of some other nodes in the network.
		164
		165	This function initialises a node - it must be called exactly once (or
		166	never) before calling other AnyEvent::MP functions.
		167
		168	All arguments (optionally except for the first) are noderefs, which can be
		169	either resolved or unresolved.
		170
		171	The first argument will be looked up in the configuration database first
		172	(if it is C<undef> then the current nodename will be used instead) to find
		173	the relevant configuration profile (see L<aemp>). If none is found then
		174	the default configuration is used. The configuration supplies additional
		175	seed/master nodes and can override the actual noderef.
		176
		177	There are two types of networked nodes, public nodes and slave nodes:
		178
		179	=over 4
		180
		181	=item public nodes
		182
		183	For public nodes, C<$noderef> (supplied either directly to
		184	C<initialise_node> or indirectly via a profile or the nodename) must be a
		185	noderef (possibly unresolved, in which case it will be resolved).
		186
		187	After resolving, the node will bind itself on all endpoints and try to
		188	connect to all additional C<$seednodes> that are specified. Seednodes are
		189	optional and can be used to quickly bootstrap the node into an existing
		190	network.
		191
		192	=item slave nodes
		193
		194	When the C<$noderef> (either as given or overriden by the config file)
		195	is the special string C<slave/>, then the node will become a slave
		196	node. Slave nodes cannot be contacted from outside and will route most of
		197	their traffic to the master node that they attach to.
		198
		199	At least one additional noderef is required (either by specifying it
		200	directly or because it is part of the configuration profile): The node
		201	will try to connect to all of them and will become a slave attached to the
		202	first node it can successfully connect to.
		203
		204	=back
		205
		206	This function will block until all nodes have been resolved and, for slave
		207	nodes, until it has successfully established a connection to a master
		208	server.
		209
		210	Example: become a public node listening on the guessed noderef, or the one
		211	specified via C<aemp> for the current node. This should be the most common
		212	form of invocation for "daemon"-type nodes.
		213
		214	initialise_node;
		215
		216	Example: become a slave node to any of the the seednodes specified via
		217	C<aemp>. This form is often used for commandline clients.
		218
		219	initialise_node "slave/";
		220
		221	Example: become a slave node to any of the specified master servers. This
		222	form is also often used for commandline clients.
		223
		224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		225
		226	Example: become a public node, and try to contact some well-known master
		227	servers to become part of the network.
		228
		229	initialise_node undef, "master1", "master2";
		230
		231	Example: become a public node listening on port C<4041>.
		232
		233	initialise_node 4041;
		234
		235	Example: become a public node, only visible on localhost port 4044.
		236
		237	initialise_node "localhost:4044";
132		238
133	=item $cv = resolve_node $noderef	239	=item $cv = resolve_node $noderef
134		240
135	Takes an unresolved node reference that may contain hostnames and	241	Takes an unresolved node reference that may contain hostnames and
136	abbreviated IDs, resolves all of them and returns a resolved node	242	abbreviated IDs, resolves all of them and returns a resolved node
…		…
168		274
169	Due to some quirks in how perl exports variables, it is impossible to	275	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	276	just export C<$SELF>, all the symbols called C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	277	module, but only C<$SELF> is currently used.
172		278
173	=item snd $portid, type => @data	279	=item snd $port, type => @data
174		280
175	=item snd $portid, @msg	281	=item snd $port, @msg
176		282
177	Send the given message to the given port ID, which can identify either	283	Send the given message to the given port ID, which can identify either
178	a local or a remote port, and can be either a string or soemthignt hat	284	a local or a remote port, and can be either a string or soemthignt hat
179	stringifies a sa port ID (such as a port object :).	285	stringifies a sa port ID (such as a port object :).
180		286
…		…
190	JSON is used, then only strings, numbers and arrays and hashes consisting	296	JSON is used, then only strings, numbers and arrays and hashes consisting
191	of those are allowed (no objects). When Storable is used, then anything	297	of those are allowed (no objects). When Storable is used, then anything
192	that Storable can serialise and deserialise is allowed, and for the local	298	that Storable can serialise and deserialise is allowed, and for the local
193	node, anything can be passed.	299	node, anything can be passed.
194		300
195	=item kil $portid[, @reason]	301	=item $local_port = port
196		302
197	Kill the specified port with the given C<@reason>.	303	Create a new local port object and returns its port ID. Initially it has
		304	no callbacks set and will throw an error when it receives messages.
198		305
199	If no C<@reason> is specified, then the port is killed "normally" (linked	306	=item $local_port = port { my @msg = @_ }
200	ports will not be kileld, or even notified).
201		307
202	Otherwise, linked ports get killed with the same reason (second form of	308	Creates a new local port, and returns its ID. Semantically the same as
203	C<mon>, see below).	309	creating a port and calling C<rcv $port, $callback> on it.
204		310
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	311	The block will be called for every message received on the port, with the
206	will be reported as reason C<< die => $@ >>.	312	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		313	port to be C<kil>ed. The message will be passed as-is, no extra argument
		314	(i.e. no port ID) will be passed to the callback.
207		315
208	Transport/communication errors are reported as C<< transport_error =>	316	If you want to stop/destroy the port, simply C<kil> it:
209	$message >>.
210		317
		318	my $port = port {
		319	my @msg = @_;
		320	...
		321	kil $SELF;
		322	};
		323
		324	=cut
		325
		326	sub rcv($@);
		327
		328	sub _kilme {
		329	die "received message on port without callback";
		330	}
		331
		332	sub port(;&) {
		333	my $id = "$UNIQ." . $ID++;
		334	my $port = "$NODE#$id";
		335
		336	rcv $port, shift \|\| \&_kilme;
		337
		338	$port
		339	}
		340
		341	=item rcv $local_port, $callback->(@msg)
		342
		343	Replaces the default callback on the specified port. There is no way to
		344	remove the default callback: use C<sub { }> to disable it, or better
		345	C<kil> the port when it is no longer needed.
		346
		347	The global C<$SELF> (exported by this module) contains C<$port> while
		348	executing the callback. Runtime errors during callback execution will
		349	result in the port being C<kil>ed.
		350
		351	The default callback received all messages not matched by a more specific
		352	C<tag> match.
		353
		354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		355
		356	Register callbacks to be called on messages starting with the given tag on
		357	the given port (and return the port), or unregister it (when C<$callback>
		358	is C<$undef>).
		359
		360	The original message will be passed to the callback, after the first
		361	element (the tag) has been removed. The callback will use the same
		362	environment as the default callback (see above).
		363
		364	Example: create a port and bind receivers on it in one go.
		365
		366	my $port = rcv port,
		367	msg1 => sub { ... },
		368	msg2 => sub { ... },
		369	;
		370
		371	Example: create a port, bind receivers and send it in a message elsewhere
		372	in one go:
		373
		374	snd $otherport, reply =>
		375	rcv port,
		376	msg1 => sub { ... },
		377	...
		378	;
		379
		380	=cut
		381
		382	sub rcv($@) {
		383	my $port = shift;
		384	my ($noderef, $portid) = split /#/, $port, 2;
		385
		386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		387	or Carp::croak "$port: rcv can only be called on local ports, caught";
		388
		389	while (@_) {
		390	if (ref $_[0]) {
		391	if (my $self = $PORT_DATA{$portid}) {
		392	"AnyEvent::MP::Port" eq ref $self
		393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		394
		395	$self->[2] = shift;
		396	} else {
		397	my $cb = shift;
		398	$PORT{$portid} = sub {
		399	local $SELF = $port;
		400	eval { &$cb }; _self_die if $@;
		401	};
		402	}
		403	} elsif (defined $_[0]) {
		404	my $self = $PORT_DATA{$portid} \|\|= do {
		405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		406
		407	$PORT{$portid} = sub {
		408	local $SELF = $port;
		409
		410	if (my $cb = $self->[1]{$_[0]}) {
		411	shift;
		412	eval { &$cb }; _self_die if $@;
		413	} else {
		414	&{ $self->[0] };
		415	}
		416	};
		417
		418	$self
		419	};
		420
		421	"AnyEvent::MP::Port" eq ref $self
		422	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		423
		424	my ($tag, $cb) = splice @_, 0, 2;
		425
		426	if (defined $cb) {
		427	$self->[1]{$tag} = $cb;
		428	} else {
		429	delete $self->[1]{$tag};
		430	}
		431	}
		432	}
		433
		434	$port
		435	}
		436
		437	=item $closure = psub { BLOCK }
		438
		439	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		440	closure is executed, sets up the environment in the same way as in C<rcv>
		441	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		442
		443	This is useful when you register callbacks from C<rcv> callbacks:
		444
		445	rcv delayed_reply => sub {
		446	my ($delay, @reply) = @_;
		447	my $timer = AE::timer $delay, 0, psub {
		448	snd @reply, $SELF;
		449	};
		450	};
		451
		452	=cut
		453
		454	sub psub(&) {
		455	my $cb = shift;
		456
		457	my $port = $SELF
		458	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		459
		460	sub {
		461	local $SELF = $port;
		462
		463	if (wantarray) {
		464	my @res = eval { &$cb };
		465	_self_die if $@;
		466	@res
		467	} else {
		468	my $res = eval { &$cb };
		469	_self_die if $@;
		470	$res
		471	}
		472	}
		473	}
		474
211	=item $guard = mon $portid, $cb->(@reason)	475	=item $guard = mon $port, $cb->(@reason)
212		476
213	=item $guard = mon $portid, $otherport	477	=item $guard = mon $port, $rcvport
214		478
		479	=item $guard = mon $port
		480
215	=item $guard = mon $portid, $otherport, @msg	481	=item $guard = mon $port, $rcvport, @msg
216		482
217	Monitor the given port and do something when the port is killed.	483	Monitor the given port and do something when the port is killed or
		484	messages to it were lost, and optionally return a guard that can be used
		485	to stop monitoring again.
218		486
		487	C<mon> effectively guarantees that, in the absence of hardware failures,
		488	that after starting the monitor, either all messages sent to the port
		489	will arrive, or the monitoring action will be invoked after possible
		490	message loss has been detected. No messages will be lost "in between"
		491	(after the first lost message no further messages will be received by the
		492	port). After the monitoring action was invoked, further messages might get
		493	delivered again.
		494
219	In the first form, the callback is simply called with any number	495	In the first form (callback), the callback is simply called with any
220	of C<@reason> elements (no @reason means that the port was deleted	496	number of C<@reason> elements (no @reason means that the port was deleted
221	"normally"). Note also that I<< the callback B<must> never die >>, so use	497	"normally"). Note also that I<< the callback B<must> never die >>, so use
222	C<eval> if unsure.	498	C<eval> if unsure.
223		499
224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	500	In the second form (another port given), the other port (C<$rcvport>)
225	a @reason was specified, i.e. on "normal" kils nothing happens, while	501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
226	under all other conditions, the other port is killed with the same reason.	502	"normal" kils nothing happens, while under all other conditions, the other
		503	port is killed with the same reason.
227		504
		505	The third form (kill self) is the same as the second form, except that
		506	C<$rvport> defaults to C<$SELF>.
		507
228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	508	In the last form (message), a message of the form C<@msg, @reason> will be
		509	C<snd>.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for exmaple, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
229		517
230	Example: call a given callback when C<$port> is killed.	518	Example: call a given callback when C<$port> is killed.
231		519
232	mon $port, sub { warn "port died because of <@_>\n" };	520	mon $port, sub { warn "port died because of <@_>\n" };
233		521
234	Example: kill ourselves when C<$port> is killed abnormally.	522	Example: kill ourselves when C<$port> is killed abnormally.
235		523
236	mon $port, $self;	524	mon $port;
237		525
238	Example: send us a restart message another C<$port> is killed.	526	Example: send us a restart message when another C<$port> is killed.
239		527
240	mon $port, $self => "restart";	528	mon $port, $self => "restart";
241		529
242	=cut	530	=cut
243		531
244	sub mon {	532	sub mon {
245	my ($noderef, $port) = split /#/, shift, 2;	533	my ($noderef, $port) = split /#/, shift, 2;
246		534
247	my $node = $NODE{$noderef} \|\| add_node $noderef;	535	my $node = $NODE{$noderef} \|\| add_node $noderef;
248		536
249	my $cb = shift;	537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
250		538
251	unless (ref $cb) {	539	unless (ref $cb) {
252	if (@_) {	540	if (@_) {
253	# send a kill info message	541	# send a kill info message
254	my (@msg) = ($cb, @_);	542	my (@msg) = ($cb, @_);
…		…
285	=cut	573	=cut
286		574
287	sub mon_guard {	575	sub mon_guard {
288	my ($port, @refs) = @_;	576	my ($port, @refs) = @_;
289		577
		578	#TODO: mon-less form?
		579
290	mon $port, sub { 0 && @refs }	580	mon $port, sub { 0 && @refs }
291	}	581	}
292		582
293	=item lnk $port1, $port2	583	=item kil $port[, @reason]
294		584
295	Link two ports. This is simply a shorthand for:	585	Kill the specified port with the given C<@reason>.
296		586
297	mon $port1, $port2;	587	If no C<@reason> is specified, then the port is killed "normally" (linked
298	mon $port2, $port1;	588	ports will not be kileld, or even notified).
299		589
300	It means that if either one is killed abnormally, the other one gets	590	Otherwise, linked ports get killed with the same reason (second form of
301	killed as well.	591	C<mon>, see below).
302		592
303	=item $local_port = port	593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		594	will be reported as reason C<< die => $@ >>.
304		595
305	Create a new local port object that supports message matching.	596	Transport/communication errors are reported as C<< transport_error =>
		597	$message >>.
306		598
307	=item $portid = port { my @msg = @_; $finished }
308
309	Creates a "mini port", that is, a very lightweight port without any
310	pattern matching behind it, and returns its ID.
311
312	The block will be called for every message received on the port. When the
313	callback returns a true value its job is considered "done" and the port
314	will be destroyed. Otherwise it will stay alive.
315
316	The message will be passed as-is, no extra argument (i.e. no port id) will
317	be passed to the callback.
318
319	If you need the local port id in the callback, this works nicely:
320
321	my $port; $port = miniport {
322	snd $otherport, reply => $port;
323	};
324
325	=cut	599	=cut
326		600
327	sub port(;&) {	601	=item $port = spawn $node, $initfunc[, @initdata]
328	my $id = "$UNIQ." . $ID++;
329	my $port = "$NODE#$id";
330		602
331	if (@_) {	603	Creates a port on the node C<$node> (which can also be a port ID, in which
332	my $cb = shift;	604	case it's the node where that port resides).
333	$PORT{$id} = sub {	605
334	local $SELF = $port;	606	The port ID of the newly created port is return immediately, and it is
335	eval {	607	permissible to immediately start sending messages or monitor the port.
336	&$cb	608
337	and kil $id;	609	After the port has been created, the init function is
		610	called. This function must be a fully-qualified function name
		611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		612	program, use C<::name>.
		613
		614	If the function doesn't exist, then the node tries to C<require>
		615	the package, then the package above the package and so on (e.g.
		616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		617	exists or it runs out of package names.
		618
		619	The init function is then called with the newly-created port as context
		620	object (C<$SELF>) and the C<@initdata> values as arguments.
		621
		622	A common idiom is to pass your own port, monitor the spawned port, and
		623	in the init function, monitor the original port. This two-way monitoring
		624	ensures that both ports get cleaned up when there is a problem.
		625
		626	Example: spawn a chat server port on C<$othernode>.
		627
		628	# this node, executed from within a port context:
		629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		630	mon $server;
		631
		632	# init function on C<$othernode>
		633	sub connect {
		634	my ($srcport) = @_;
		635
		636	mon $srcport;
		637
		638	rcv $SELF, sub {
338	};	639	...
339	_self_die if $@;
340	};
341	} else {
342	my $self = bless {
343	id => "$NODE#$id",
344	}, "AnyEvent::MP::Port";
345
346	$PORT_DATA{$id} = $self;
347	$PORT{$id} = sub {
348	local $SELF = $port;
349
350	eval {
351	for (@{ $self->{rc0}{$_[0]} }) {
352	$_ && &{$_->[0]}
353	&& undef $_;
354	}
355
356	for (@{ $self->{rcv}{$_[0]} }) {
357	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
358	&& &{$_->[0]}
359	&& undef $_;
360	}
361
362	for (@{ $self->{any} }) {
363	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
364	&& &{$_->[0]}
365	&& undef $_;
366	}
367	};
368	_self_die if $@;
369	};	640	};
370	}	641	}
371		642
372	$port	643	=cut
		644
		645	sub _spawn {
		646	my $port = shift;
		647	my $init = shift;
		648
		649	local $SELF = "$NODE#$port";
		650	eval {
		651	&{ load_func $init }
		652	};
		653	_self_die if $@;
373	}	654	}
374		655
375	=item reg $portid, $name	656	sub spawn(@) {
		657	my ($noderef, undef) = split /#/, shift, 2;
376		658
377	Registers the given port under the name C<$name>. If the name already	659	my $id = "$RUNIQ." . $ID++;
378	exists it is replaced.
379		660
380	A port can only be registered under one well known name.	661	$_[0] =~ /::/
		662	or Carp::croak "spawn init function must be a fully-qualified name, caught";
381		663
382	A port automatically becomes unregistered when it is killed.	664	($NODE{$noderef} \|\| add_node $noderef)
		665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
383		666
384	=cut	667	"$noderef#$id"
385
386	sub reg(@) {
387	my ($portid, $name) = @_;
388
389	$REG{$name} = $portid;
390	}	668	}
391
392	=item rcv $portid, tagstring => $callback->(@msg), ...
393
394	=item rcv $portid, $smartmatch => $callback->(@msg), ...
395
396	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
397
398	Register callbacks to be called on matching messages on the given port.
399
400	The callback has to return a true value when its work is done, after
401	which is will be removed, or a false value in which case it will stay
402	registered.
403
404	The global C<$SELF> (exported by this module) contains C<$portid> while
405	executing the callback.
406
407	Runtime errors wdurign callback execution will result in the port being
408	C<kil>ed.
409
410	If the match is an array reference, then it will be matched against the
411	first elements of the message, otherwise only the first element is being
412	matched.
413
414	Any element in the match that is specified as C<_any_> (a function
415	exported by this module) matches any single element of the message.
416
417	While not required, it is highly recommended that the first matching
418	element is a string identifying the message. The one-string-only match is
419	also the most efficient match (by far).
420
421	=cut
422
423	sub rcv($@) {
424	my ($noderef, $port) = split /#/, shift, 2;
425
426	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
427	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
428
429	my $self = $PORT_DATA{$port}
430	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
431
432	"AnyEvent::MP::Port" eq ref $self
433	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
434
435	while (@_) {
436	my ($match, $cb) = splice @_, 0, 2;
437
438	if (!ref $match) {
439	push @{ $self->{rc0}{$match} }, [$cb];
440	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
441	my ($type, @match) = @$match;
442	@match
443	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
444	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
445	} else {
446	push @{ $self->{any} }, [$cb, $match];
447	}
448	}
449	}
450
451	=item $closure = psub { BLOCK }
452
453	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
454	closure is executed, sets up the environment in the same way as in C<rcv>
455	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
456
457	This is useful when you register callbacks from C<rcv> callbacks:
458
459	rcv delayed_reply => sub {
460	my ($delay, @reply) = @_;
461	my $timer = AE::timer $delay, 0, psub {
462	snd @reply, $SELF;
463	};
464	};
465
466	=cut
467
468	sub psub(&) {
469	my $cb = shift;
470
471	my $port = $SELF
472	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
473
474	sub {
475	local $SELF = $port;
476
477	if (wantarray) {
478	my @res = eval { &$cb };
479	_self_die if $@;
480	@res
481	} else {
482	my $res = eval { &$cb };
483	_self_die if $@;
484	$res
485	}
486	}
487	}
488
489	=back
490
491	=head1 FUNCTIONS FOR NODES
492
493	=over 4
494
495	=item become_public $noderef
496
497	Tells the node to become a public node, i.e. reachable from other nodes.
498
499	The first argument is the (unresolved) node reference of the local node
500	(if missing then the empty string is used).
501
502	It is quite common to not specify anything, in which case the local node
503	tries to listen on the default port, or to only specify a port number, in
504	which case AnyEvent::MP tries to guess the local addresses.
505
506	=cut
507		669
508	=back	670	=back
509		671
510	=head1 NODE MESSAGES	672	=head1 NODE MESSAGES
511		673
…		…
553		715
554	=back	716	=back
555		717
556	=head1 AnyEvent::MP vs. Distributed Erlang	718	=head1 AnyEvent::MP vs. Distributed Erlang
557		719
558	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
559	== aemp node, erlang process == aemp port), so many of the documents and	721	== aemp node, Erlang process == aemp port), so many of the documents and
560	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
561	sample:	723	sample:
562		724
563	http://www.erlang.se/doc/programming_rules.shtml	725	http://www.Erlang.se/doc/programming_rules.shtml
564	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
565	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
566	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
567		729
568	Despite the similarities, there are also some important differences:	730	Despite the similarities, there are also some important differences:
569		731
570	=over 4	732	=over 4
571		733
…		…
576	convenience functionality.	738	convenience functionality.
577		739
578	This means that AEMP requires a less tightly controlled environment at the	740	This means that AEMP requires a less tightly controlled environment at the
579	cost of longer node references and a slightly higher management overhead.	741	cost of longer node references and a slightly higher management overhead.
580		742
		743	=item Erlang has a "remote ports are like local ports" philosophy, AEMP
		744	uses "local ports are like remote ports".
		745
		746	The failure modes for local ports are quite different (runtime errors
		747	only) then for remote ports - when a local port dies, you I<know> it dies,
		748	when a connection to another node dies, you know nothing about the other
		749	port.
		750
		751	Erlang pretends remote ports are as reliable as local ports, even when
		752	they are not.
		753
		754	AEMP encourages a "treat remote ports differently" philosophy, with local
		755	ports being the special case/exception, where transport errors cannot
		756	occur.
		757
581	=item * Erlang uses processes and a mailbox, AEMP does not queue.	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
582		759
583	Erlang uses processes that selctively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
584	needs a queue. AEMP is event based, queuing messages would serve no useful	761	needs a queue. AEMP is event based, queuing messages would serve no
585	purpose.	762	useful purpose. For the same reason the pattern-matching abilities of
		763	AnyEvent::MP are more limited, as there is little need to be able to
		764	filter messages without dequeing them.
586		765
587	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
588		767
589	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
590		769
591	Sending messages in erlang is synchronous and blocks the process. AEMP	770	Sending messages in Erlang is synchronous and blocks the process (and
592	sends are immediate, connection establishment is handled in the	771	so does not need a queue that can overflow). AEMP sends are immediate,
593	background.	772	connection establishment is handled in the background.
594		773
595	=item * Erlang can silently lose messages, AEMP cannot.	774	=item * Erlang suffers from silent message loss, AEMP does not.
596		775
597	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
598	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
599	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
600		779
601	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that there are no
602	holes in the message sequence.	781	holes in the message sequence.
603		782
604	=item * In erlang, processes can be declared dead and later be found to be	783	=item * In Erlang, processes can be declared dead and later be found to be
605	alive.	784	alive.
606		785
607	In erlang it can happen that a monitored process is declared dead and	786	In Erlang it can happen that a monitored process is declared dead and
608	linked processes get killed, but later it turns out that the process is	787	linked processes get killed, but later it turns out that the process is
609	still alive - and can receive messages.	788	still alive - and can receive messages.
610		789
611	In AEMP, when port monitoring detects a port as dead, then that port will	790	In AEMP, when port monitoring detects a port as dead, then that port will
612	eventually be killed - it cannot happen that a node detects a port as dead	791	eventually be killed - it cannot happen that a node detects a port as dead
613	and then later sends messages to it, finding it is still alive.	792	and then later sends messages to it, finding it is still alive.
614		793
615	=item * Erlang can send messages to the wrong port, AEMP does not.	794	=item * Erlang can send messages to the wrong port, AEMP does not.
616		795
617	In erlang it is quite possible that a node that restarts reuses a process	796	In Erlang it is quite likely that a node that restarts reuses a process ID
618	ID known to other nodes for a completely different process, causing	797	known to other nodes for a completely different process, causing messages
619	messages destined for that process to end up in an unrelated process.	798	destined for that process to end up in an unrelated process.
620		799
621	AEMP never reuses port IDs, so old messages or old port IDs floating	800	AEMP never reuses port IDs, so old messages or old port IDs floating
622	around in the network will not be sent to an unrelated port.	801	around in the network will not be sent to an unrelated port.
623		802
624	=item * Erlang uses unprotected connections, AEMP uses secure	803	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
628	securely authenticate nodes.	807	securely authenticate nodes.
629		808
630	=item * The AEMP protocol is optimised for both text-based and binary	809	=item * The AEMP protocol is optimised for both text-based and binary
631	communications.	810	communications.
632		811
633	The AEMP protocol, unlike the erlang protocol, supports both	812	The AEMP protocol, unlike the Erlang protocol, supports both
634	language-independent text-only protocols (good for debugging) and binary,	813	language-independent text-only protocols (good for debugging) and binary,
635	language-specific serialisers (e.g. Storable).	814	language-specific serialisers (e.g. Storable).
636		815
637	It has also been carefully designed to be implementable in other languages	816	It has also been carefully designed to be implementable in other languages
638	with a minimum of work while gracefully degrading fucntionality to make the	817	with a minimum of work while gracefully degrading fucntionality to make the
639	protocol simple.	818	protocol simple.
640		819
		820	=item * AEMP has more flexible monitoring options than Erlang.
		821
		822	In Erlang, you can chose to receive I<all> exit signals as messages
		823	or I<none>, there is no in-between, so monitoring single processes is
		824	difficult to implement. Monitoring in AEMP is more flexible than in
		825	Erlang, as one can choose between automatic kill, exit message or callback
		826	on a per-process basis.
		827
		828	=item * Erlang tries to hide remote/local connections, AEMP does not.
		829
		830	Monitoring in Erlang is not an indicator of process death/crashes,
		831	as linking is (except linking is unreliable in Erlang).
		832
		833	In AEMP, you don't "look up" registered port names or send to named ports
		834	that might or might not be persistent. Instead, you normally spawn a port
		835	on the remote node. The init function monitors the you, and you monitor
		836	the remote port. Since both monitors are local to the node, they are much
		837	more reliable.
		838
		839	This also saves round-trips and avoids sending messages to the wrong port
		840	(hard to do in Erlang).
		841
		842	=back
		843
		844	=head1 RATIONALE
		845
		846	=over 4
		847
		848	=item Why strings for ports and noderefs, why not objects?
		849
		850	We considered "objects", but found that the actual number of methods
		851	thatc an be called are very low. Since port IDs and noderefs travel over
		852	the network frequently, the serialising/deserialising would add lots of
		853	overhead, as well as having to keep a proxy object.
		854
		855	Strings can easily be printed, easily serialised etc. and need no special
		856	procedures to be "valid".
		857
		858	And a a miniport consists of a single closure stored in a global hash - it
		859	can't become much cheaper.
		860
		861	=item Why favour JSON, why not real serialising format such as Storable?
		862
		863	In fact, any AnyEvent::MP node will happily accept Storable as framing
		864	format, but currently there is no way to make a node use Storable by
		865	default.
		866
		867	The default framing protocol is JSON because a) JSON::XS is many times
		868	faster for small messages and b) most importantly, after years of
		869	experience we found that object serialisation is causing more problems
		870	than it gains: Just like function calls, objects simply do not travel
		871	easily over the network, mostly because they will always be a copy, so you
		872	always have to re-think your design.
		873
		874	Keeping your messages simple, concentrating on data structures rather than
		875	objects, will keep your messages clean, tidy and efficient.
		876
641	=back	877	=back
642		878
643	=head1 SEE ALSO	879	=head1 SEE ALSO
644		880
645	L<AnyEvent>.	881	L<AnyEvent>.

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Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC