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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.35 by root, Thu Aug 6 10:21:48 2009 UTC vs.
Revision 1.62 by root, Thu Aug 27 07:12:48 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 $simple_port = port { my @msg = @_; 0 };
16		29
17	rcv $port, smartmatch => $cb->($port, @msg);	30	# creating/using ports, tagged message 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
27
28	# linking two ports, so they both crash together
29	lnk $port1, $port2;
30		37
31	# monitoring	38	# monitoring
32	mon $port, $cb->(@msg) # callback is invoked on death	39	mon $port, $cb->(@msg) # callback is invoked on death
33	mon $port, $otherport # kill otherport on abnormal death	40	mon $port, $otherport # kill otherport on abnormal death
34	mon $port, $otherport, @msg # send message on death	41	mon $port, $otherport, @msg # send message on death
35		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		46	AnyEvent::MP::Intro - outdated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.
		51
36	=head1 DESCRIPTION	52	=head1 DESCRIPTION
37		53
38	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
39		55
40	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
…		…
43	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>
44	manual page.	60	manual page.
45		61
46	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
47	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 -
48	stay tuned! The basic API should be finished, however.	64	stay tuned!
49		65
50	=head1 CONCEPTS	66	=head1 CONCEPTS
51		67
52	=over 4	68	=over 4
53		69
54	=item port	70	=item port
55		71
56	A port is something you can send messages to (with the C<snd> function).	72	A port is something you can send messages to (with the C<snd> function).
57		73
58	Some ports allow you to register C<rcv> handlers that can match specific	74	Ports allow you to register C<rcv> handlers that can match all or just
59	messages. All C<rcv> handlers will receive messages they match, messages	75	some messages. Messages will not be queued.
60	will not be queued.
61		76
62	=item port id - C<noderef#portname>	77	=item port id - C<noderef#portname>
63		78
64	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
65	separator, and a port name (a printable string of unspecified format). An	80	separator, and a port name (a printable string of unspecified format). An
66	exception is the the node port, whose ID is identical to its node	81	exception is the the node port, whose ID is identical to its node
67	reference.	82	reference.
68		83
69	=item node	84	=item node
70		85
71	A node is a single process containing at least one port - the node	86	A node is a single process containing at least one port - the node port,
72	port. You can send messages to node ports to find existing ports or to	87	which provides nodes to manage each other remotely, and to create new
73	create new ports, among other things.	88	ports.
74		89
75	Nodes are either private (single-process only), slaves (connected to a	90	Nodes are either private (single-process only), slaves (can only talk to
76	master node only) or public nodes (connectable from unrelated nodes).	91	public nodes, but do not need an open port) or public nodes (connectable
		92	from any other node).
77		93
78	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
79		95
80	A node reference is a string that either simply identifies the node (for	96	A node reference is a string that either simply identifies the node (for
81	private and slave nodes), or contains a recipe on how to reach a given	97	private and slave nodes), or contains a recipe on how to reach a given
…		…
98		114
99	=cut	115	=cut
100		116
101	package AnyEvent::MP;	117	package AnyEvent::MP;
102		118
103	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
104		120
105	use common::sense;	121	use common::sense;
106		122
107	use Carp ();	123	use Carp ();
108		124
109	use AE ();	125	use AE ();
110		126
111	use base "Exporter";	127	use base "Exporter";
112		128
113	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
114	our @EXPORT = qw(	131	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of after
116	resolve_node initialise_node	133	resolve_node initialise_node
117	snd rcv mon kil reg psub	134	snd rcv mon mon_guard kil reg psub spawn
118	port	135	port
119	);	136	);
120		137
121	our $SELF;	138	our $SELF;
122		139
…		…
126	kil $SELF, die => $msg;	143	kil $SELF, die => $msg;
127	}	144	}
128		145
129	=item $thisnode = NODE / $NODE	146	=item $thisnode = NODE / $NODE
130		147
131	The C<NODE> function returns, and the C<$NODE> variable contains	148	The C<NODE> function returns, and the C<$NODE> variable contains the
132	the noderef of the local node. The value is initialised by a call	149	noderef of the local node. The value is initialised by a call to
133	to C<become_public> or C<become_slave>, after which all local port	150	C<initialise_node>.
134	identifiers become invalid.
135		151
136	=item $noderef = node_of $port	152	=item $noderef = node_of $port
137		153
138	Extracts and returns the noderef from a portid or a noderef.	154	Extracts and returns the noderef from a port ID or a noderef.
139		155
140	=item initialise_node $noderef, $seednode, $seednode...	156	=item initialise_node $noderef, $seednode, $seednode...
141		157
142	=item initialise_node "slave/", $master, $master...	158	=item initialise_node "slave/", $master, $master...
143		159
…		…
146	it should know the noderefs of some other nodes in the network.	162	it should know the noderefs of some other nodes in the network.
147		163
148	This function initialises a node - it must be called exactly once (or	164	This function initialises a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	165	never) before calling other AnyEvent::MP functions.
150		166
151	All arguments are noderefs, which can be either resolved or unresolved.	167	All arguments (optionally except for the first) are noderefs, which can be
		168	either resolved or unresolved.
		169
		170	The first argument will be looked up in the configuration database first
		171	(if it is C<undef> then the current nodename will be used instead) to find
		172	the relevant configuration profile (see L<aemp>). If none is found then
		173	the default configuration is used. The configuration supplies additional
		174	seed/master nodes and can override the actual noderef.
152		175
153	There are two types of networked nodes, public nodes and slave nodes:	176	There are two types of networked nodes, public nodes and slave nodes:
154		177
155	=over 4	178	=over 4
156		179
157	=item public nodes	180	=item public nodes
158		181
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	182	For public nodes, C<$noderef> (supplied either directly to
160	noderef, in which case it will be resolved, or C<undef> (or missing), in	183	C<initialise_node> or indirectly via a profile or the nodename) must be a
161	which case the noderef will be guessed.	184	noderef (possibly unresolved, in which case it will be resolved).
162		185
163	Afterwards, the node will bind itself on all endpoints and try to connect	186	After resolving, the node will bind itself on all endpoints.
164	to all additional C<$seednodes> that are specified. Seednodes are optional
165	and can be used to quickly bootstrap the node into an existing network.
166		187
167	=item slave nodes	188	=item slave nodes
168		189
169	When the C<$noderef> is the special string C<slave/>, then the node will	190	When the C<$noderef> (either as given or overriden by the config file)
		191	is the special string C<slave/>, then the node will become a slave
170	become a slave node. Slave nodes cannot be contacted from outside and will	192	node. Slave nodes cannot be contacted from outside, and cannot talk to
171	route most of their traffic to the master node that they attach to.	193	each other (at least in this version of AnyEvent::MP).
172		194
173	At least one additional noderef is required: The node will try to connect	195	Slave nodes work by creating connections to all public nodes, using the
174	to all of them and will become a slave attached to the first node it can	196	L<AnyEvent::MP::Global> service.
175	successfully connect to.
176		197
177	=back	198	=back
178		199
179	This function will block until all nodes have been resolved and, for slave	200	After initialising itself, the node will connect to all additional
180	nodes, until it has successfully established a connection to a master	201	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
181	server.	202	optional and can be used to quickly bootstrap the node into an existing
		203	network.
182		204
		205	All the seednodes will also be specially marked to automatically retry
		206	connecting to them indefinitely, so make sure that seednodes are really
		207	reliable and up (this might also change in the future).
		208
183	Example: become a public node listening on the default node.	209	Example: become a public node listening on the guessed noderef, or the one
		210	specified via C<aemp> for the current node. This should be the most common
		211	form of invocation for "daemon"-type nodes.
184		212
185	initialise_node;	213	initialise_node;
		214
		215	Example: become a slave node to any of the the seednodes specified via
		216	C<aemp>. This form is often used for commandline clients.
		217
		218	initialise_node "slave/";
186		219
187	Example: become a public node, and try to contact some well-known master	220	Example: become a public node, and try to contact some well-known master
188	servers to become part of the network.	221	servers to become part of the network.
189		222
190	initialise_node undef, "master1", "master2";	223	initialise_node undef, "master1", "master2";
…		…
193		226
194	initialise_node 4041;	227	initialise_node 4041;
195		228
196	Example: become a public node, only visible on localhost port 4044.	229	Example: become a public node, only visible on localhost port 4044.
197		230
198	initialise_node "locahost:4044";	231	initialise_node "localhost:4044";
199
200	Example: become a slave node to any of the specified master servers.
201
202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
203		232
204	=item $cv = resolve_node $noderef	233	=item $cv = resolve_node $noderef
205		234
206	Takes an unresolved node reference that may contain hostnames and	235	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node	236	abbreviated IDs, resolves all of them and returns a resolved node
…		…
244	=item snd $port, type => @data	273	=item snd $port, type => @data
245		274
246	=item snd $port, @msg	275	=item snd $port, @msg
247		276
248	Send the given message to the given port ID, which can identify either	277	Send the given message to the given port ID, which can identify either
249	a local or a remote port, and can be either a string or soemthignt hat	278	a local or a remote port, and must be a port ID.
250	stringifies a sa port ID (such as a port object :).
251		279
252	While the message can be about anything, it is highly recommended to use a	280	While the message can be about anything, it is highly recommended to use a
253	string as first element (a portid, or some word that indicates a request	281	string as first element (a port ID, or some word that indicates a request
254	type etc.).	282	type etc.).
255		283
256	The message data effectively becomes read-only after a call to this	284	The message data effectively becomes read-only after a call to this
257	function: modifying any argument is not allowed and can cause many	285	function: modifying any argument is not allowed and can cause many
258	problems.	286	problems.
…		…
263	that Storable can serialise and deserialise is allowed, and for the local	291	that Storable can serialise and deserialise is allowed, and for the local
264	node, anything can be passed.	292	node, anything can be passed.
265		293
266	=item $local_port = port	294	=item $local_port = port
267		295
268	Create a new local port object that can be used either as a pattern	296	Create a new local port object and returns its port ID. Initially it has
269	matching port ("full port") or a single-callback port ("miniport"),	297	no callbacks set and will throw an error when it receives messages.
270	depending on how C<rcv> callbacks are bound to the object.
271		298
272	=item $port = port { my @msg = @_; $finished }	299	=item $local_port = port { my @msg = @_ }
273		300
274	Creates a "miniport", that is, a very lightweight port without any pattern	301	Creates a new local port, and returns its ID. Semantically the same as
275	matching behind it, and returns its ID. Semantically the same as creating
276	a port and calling C<rcv $port, $callback> on it.	302	creating a port and calling C<rcv $port, $callback> on it.
277		303
278	The block will be called for every message received on the port. When the	304	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	305	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	306	port to be C<kil>ed. The message will be passed as-is, no extra argument
		307	(i.e. no port ID) will be passed to the callback.
281		308
282	The message will be passed as-is, no extra argument (i.e. no port id) will	309	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		310
285	If you need the local port id in the callback, this works nicely:	311	my $port = port {
286		312	my @msg = @_;
287	my $port; $port = port {	313	...
288	snd $otherport, reply => $port;	314	kil $SELF;
289	};	315	};
290		316
291	=cut	317	=cut
292		318
293	sub rcv($@);	319	sub rcv($@);
		320
		321	sub _kilme {
		322	die "received message on port without callback";
		323	}
294		324
295	sub port(;&) {	325	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	326	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	327	my $port = "$NODE#$id";
298		328
299	if (@_) {	329	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		330
305	$port	331	$port
306	}	332	}
307		333
308	=item reg $port, $name
309
310	Registers the given port under the name C<$name>. If the name already
311	exists it is replaced.
312
313	A port can only be registered under one well known name.
314
315	A port automatically becomes unregistered when it is killed.
316
317	=cut
318
319	sub reg(@) {
320	my ($port, $name) = @_;
321
322	$REG{$name} = $port;
323	}
324
325	=item rcv $port, $callback->(@msg)	334	=item rcv $local_port, $callback->(@msg)
326		335
327	Replaces the callback on the specified miniport (after converting it to	336	Replaces the default callback on the specified port. There is no way to
328	one if required).	337	remove the default callback: use C<sub { }> to disable it, or better
329		338	C<kil> the port when it is no longer needed.
330	=item rcv $port, tagstring => $callback->(@msg), ...
331
332	=item rcv $port, $smartmatch => $callback->(@msg), ...
333
334	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
335
336	Register callbacks to be called on matching messages on the given full
337	port (after converting it to one if required).
338
339	The callback has to return a true value when its work is done, after
340	which is will be removed, or a false value in which case it will stay
341	registered.
342		339
343	The global C<$SELF> (exported by this module) contains C<$port> while	340	The global C<$SELF> (exported by this module) contains C<$port> while
344	executing the callback.	341	executing the callback. Runtime errors during callback execution will
		342	result in the port being C<kil>ed.
345		343
346	Runtime errors wdurign callback execution will result in the port being	344	The default callback received all messages not matched by a more specific
347	C<kil>ed.	345	C<tag> match.
348		346
349	If the match is an array reference, then it will be matched against the	347	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
350	first elements of the message, otherwise only the first element is being
351	matched.
352		348
353	Any element in the match that is specified as C<_any_> (a function	349	Register (or replace) callbacks to be called on messages starting with the
354	exported by this module) matches any single element of the message.	350	given tag on the given port (and return the port), or unregister it (when
		351	C<$callback> is C<$undef> or missing). There can only be one callback
		352	registered for each tag.
355		353
356	While not required, it is highly recommended that the first matching	354	The original message will be passed to the callback, after the first
357	element is a string identifying the message. The one-string-only match is	355	element (the tag) has been removed. The callback will use the same
358	also the most efficient match (by far).	356	environment as the default callback (see above).
		357
		358	Example: create a port and bind receivers on it in one go.
		359
		360	my $port = rcv port,
		361	msg1 => sub { ... },
		362	msg2 => sub { ... },
		363	;
		364
		365	Example: create a port, bind receivers and send it in a message elsewhere
		366	in one go:
		367
		368	snd $otherport, reply =>
		369	rcv port,
		370	msg1 => sub { ... },
		371	...
		372	;
		373
		374	Example: temporarily register a rcv callback for a tag matching some port
		375	(e.g. for a rpc reply) and unregister it after a message was received.
		376
		377	rcv $port, $otherport => sub {
		378	my @reply = @_;
		379
		380	rcv $SELF, $otherport;
		381	};
359		382
360	=cut	383	=cut
361		384
362	sub rcv($@) {	385	sub rcv($@) {
363	my $port = shift;	386	my $port = shift;
364	my ($noderef, $portid) = split /#/, $port, 2;	387	my ($noderef, $portid) = split /#/, $port, 2;
365		388
366	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	389	$NODE{$noderef} == $NODE{""}
367	or Carp::croak "$port: rcv can only be called on local ports, caught";	390	or Carp::croak "$port: rcv can only be called on local ports, caught";
368		391
369	if (@_ == 1) {	392	while (@_) {
		393	if (ref $_[0]) {
		394	if (my $self = $PORT_DATA{$portid}) {
		395	"AnyEvent::MP::Port" eq ref $self
		396	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		397
		398	$self->[2] = shift;
		399	} else {
370	my $cb = shift;	400	my $cb = shift;
371	delete $PORT_DATA{$portid};
372	$PORT{$portid} = sub {	401	$PORT{$portid} = sub {
373	local $SELF = $port;	402	local $SELF = $port;
374	eval {	403	eval { &$cb }; _self_die if $@;
375	&$cb	404	};
376	and kil $port;
377	};	405	}
378	_self_die if $@;	406	} elsif (defined $_[0]) {
379	};
380	} else {
381	my $self = $PORT_DATA{$portid} \|\|= do {	407	my $self = $PORT_DATA{$portid} \|\|= do {
382	my $self = bless {	408	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
383	id => $port,
384	}, "AnyEvent::MP::Port";
385		409
386	$PORT{$portid} = sub {	410	$PORT{$portid} = sub {
387	local $SELF = $port;	411	local $SELF = $port;
388		412
389	eval {
390	for (@{ $self->{rc0}{$_[0]} }) {	413	if (my $cb = $self->[1]{$_[0]}) {
391	$_ && &{$_->[0]}	414	shift;
392	&& undef $_;	415	eval { &$cb }; _self_die if $@;
393	}	416	} else {
394
395	for (@{ $self->{rcv}{$_[0]} }) {
396	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
397	&& &{$_->[0]}	417	&{ $self->[0] };
398	&& undef $_;
399	}
400
401	for (@{ $self->{any} }) {
402	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
403	&& &{$_->[0]}
404	&& undef $_;
405	}	418	}
406	};	419	};
407	_self_die if $@;	420
		421	$self
408	};	422	};
409		423
410	$self
411	};
412
413	"AnyEvent::MP::Port" eq ref $self	424	"AnyEvent::MP::Port" eq ref $self
414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	425	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
415		426
416	while (@_) {
417	my ($match, $cb) = splice @_, 0, 2;	427	my ($tag, $cb) = splice @_, 0, 2;
418		428
419	if (!ref $match) {	429	if (defined $cb) {
420	push @{ $self->{rc0}{$match} }, [$cb];	430	$self->[1]{$tag} = $cb;
421	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
422	my ($type, @match) = @$match;
423	@match
424	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
425	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
426	} else {	431	} else {
427	push @{ $self->{any} }, [$cb, $match];	432	delete $self->[1]{$tag};
428	}	433	}
429	}	434	}
430	}	435	}
431		436
432	$port	437	$port
…		…
470	}	475	}
471	}	476	}
472		477
473	=item $guard = mon $port, $cb->(@reason)	478	=item $guard = mon $port, $cb->(@reason)
474		479
475	=item $guard = mon $port, $otherport	480	=item $guard = mon $port, $rcvport
476		481
		482	=item $guard = mon $port
		483
477	=item $guard = mon $port, $otherport, @msg	484	=item $guard = mon $port, $rcvport, @msg
478		485
479	Monitor the given port and do something when the port is killed.	486	Monitor the given port and do something when the port is killed or
		487	messages to it were lost, and optionally return a guard that can be used
		488	to stop monitoring again.
480		489
		490	C<mon> effectively guarantees that, in the absence of hardware failures,
		491	that after starting the monitor, either all messages sent to the port
		492	will arrive, or the monitoring action will be invoked after possible
		493	message loss has been detected. No messages will be lost "in between"
		494	(after the first lost message no further messages will be received by the
		495	port). After the monitoring action was invoked, further messages might get
		496	delivered again.
		497
		498	Note that monitoring-actions are one-shot: once released, they are removed
		499	and will not trigger again.
		500
481	In the first form, the callback is simply called with any number	501	In the first form (callback), the callback is simply called with any
482	of C<@reason> elements (no @reason means that the port was deleted	502	number of C<@reason> elements (no @reason means that the port was deleted
483	"normally"). Note also that I<< the callback B<must> never die >>, so use	503	"normally"). Note also that I<< the callback B<must> never die >>, so use
484	C<eval> if unsure.	504	C<eval> if unsure.
485		505
486	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	506	In the second form (another port given), the other port (C<$rcvport>)
487	a @reason was specified, i.e. on "normal" kils nothing happens, while	507	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
488	under all other conditions, the other port is killed with the same reason.	508	"normal" kils nothing happens, while under all other conditions, the other
		509	port is killed with the same reason.
489		510
		511	The third form (kill self) is the same as the second form, except that
		512	C<$rvport> defaults to C<$SELF>.
		513
490	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	514	In the last form (message), a message of the form C<@msg, @reason> will be
		515	C<snd>.
		516
		517	As a rule of thumb, monitoring requests should always monitor a port from
		518	a local port (or callback). The reason is that kill messages might get
		519	lost, just like any other message. Another less obvious reason is that
		520	even monitoring requests can get lost (for exmaple, when the connection
		521	to the other node goes down permanently). When monitoring a port locally
		522	these problems do not exist.
491		523
492	Example: call a given callback when C<$port> is killed.	524	Example: call a given callback when C<$port> is killed.
493		525
494	mon $port, sub { warn "port died because of <@_>\n" };	526	mon $port, sub { warn "port died because of <@_>\n" };
495		527
496	Example: kill ourselves when C<$port> is killed abnormally.	528	Example: kill ourselves when C<$port> is killed abnormally.
497		529
498	mon $port, $self;	530	mon $port;
499		531
500	Example: send us a restart message another C<$port> is killed.	532	Example: send us a restart message when another C<$port> is killed.
501		533
502	mon $port, $self => "restart";	534	mon $port, $self => "restart";
503		535
504	=cut	536	=cut
505		537
506	sub mon {	538	sub mon {
507	my ($noderef, $port) = split /#/, shift, 2;	539	my ($noderef, $port) = split /#/, shift, 2;
508		540
509	my $node = $NODE{$noderef} \|\| add_node $noderef;	541	my $node = $NODE{$noderef} \|\| add_node $noderef;
510		542
511	my $cb = shift;	543	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
512		544
513	unless (ref $cb) {	545	unless (ref $cb) {
514	if (@_) {	546	if (@_) {
515	# send a kill info message	547	# send a kill info message
516	my (@msg) = ($cb, @_);	548	my (@msg) = ($cb, @_);
…		…
547	=cut	579	=cut
548		580
549	sub mon_guard {	581	sub mon_guard {
550	my ($port, @refs) = @_;	582	my ($port, @refs) = @_;
551		583
		584	#TODO: mon-less form?
		585
552	mon $port, sub { 0 && @refs }	586	mon $port, sub { 0 && @refs }
553	}	587	}
554
555	=item lnk $port1, $port2
556
557	Link two ports. This is simply a shorthand for:
558
559	mon $port1, $port2;
560	mon $port2, $port1;
561
562	It means that if either one is killed abnormally, the other one gets
563	killed as well.
564		588
565	=item kil $port[, @reason]	589	=item kil $port[, @reason]
566		590
567	Kill the specified port with the given C<@reason>.	591	Kill the specified port with the given C<@reason>.
568		592
…		…
576	will be reported as reason C<< die => $@ >>.	600	will be reported as reason C<< die => $@ >>.
577		601
578	Transport/communication errors are reported as C<< transport_error =>	602	Transport/communication errors are reported as C<< transport_error =>
579	$message >>.	603	$message >>.
580		604
581	=back
582
583	=head1 NODE MESSAGES
584
585	Nodes understand the following messages sent to them. Many of them take
586	arguments called C<@reply>, which will simply be used to compose a reply
587	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
588	the remaining arguments are simply the message data.
589
590	While other messages exist, they are not public and subject to change.
591
592	=over 4
593
594	=cut	605	=cut
595		606
596	=item lookup => $name, @reply	607	=item $port = spawn $node, $initfunc[, @initdata]
597		608
598	Replies with the port ID of the specified well-known port, or C<undef>.	609	Creates a port on the node C<$node> (which can also be a port ID, in which
		610	case it's the node where that port resides).
599		611
600	=item devnull => ...	612	The port ID of the newly created port is return immediately, and it is
		613	permissible to immediately start sending messages or monitor the port.
601		614
602	Generic data sink/CPU heat conversion.	615	After the port has been created, the init function is
		616	called. This function must be a fully-qualified function name
		617	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		618	program, use C<::name>.
603		619
604	=item relay => $port, @msg	620	If the function doesn't exist, then the node tries to C<require>
		621	the package, then the package above the package and so on (e.g.
		622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		623	exists or it runs out of package names.
605		624
606	Simply forwards the message to the given port.	625	The init function is then called with the newly-created port as context
		626	object (C<$SELF>) and the C<@initdata> values as arguments.
607		627
608	=item eval => $string[ @reply]	628	A common idiom is to pass your own port, monitor the spawned port, and
		629	in the init function, monitor the original port. This two-way monitoring
		630	ensures that both ports get cleaned up when there is a problem.
609		631
610	Evaluates the given string. If C<@reply> is given, then a message of the	632	Example: spawn a chat server port on C<$othernode>.
611	form C<@reply, $@, @evalres> is sent.
612		633
613	Example: crash another node.	634	# this node, executed from within a port context:
		635	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		636	mon $server;
614		637
615	snd $othernode, eval => "exit";	638	# init function on C<$othernode>
		639	sub connect {
		640	my ($srcport) = @_;
616		641
617	=item time => @reply	642	mon $srcport;
618		643
619	Replies the the current node time to C<@reply>.	644	rcv $SELF, sub {
		645	...
		646	};
		647	}
620		648
621	Example: tell the current node to send the current time to C<$myport> in a	649	=cut
622	C<timereply> message.
623		650
624	snd $NODE, time => $myport, timereply => 1, 2;	651	sub _spawn {
625	# => snd $myport, timereply => 1, 2, <time>	652	my $port = shift;
		653	my $init = shift;
		654
		655	local $SELF = "$NODE#$port";
		656	eval {
		657	&{ load_func $init }
		658	};
		659	_self_die if $@;
		660	}
		661
		662	sub spawn(@) {
		663	my ($noderef, undef) = split /#/, shift, 2;
		664
		665	my $id = "$RUNIQ." . $ID++;
		666
		667	$_[0] =~ /::/
		668	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		669
		670	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		671
		672	"$noderef#$id"
		673	}
		674
		675	=item after $timeout, @msg
		676
		677	=item after $timeout, $callback
		678
		679	Either sends the given message, or call the given callback, after the
		680	specified number of seconds.
		681
		682	This is simply a utility function that come sin handy at times.
		683
		684	=cut
		685
		686	sub after($@) {
		687	my ($timeout, @action) = @_;
		688
		689	my $t; $t = AE::timer $timeout, 0, sub {
		690	undef $t;
		691	ref $action[0]
		692	? $action[0]()
		693	: snd @action;
		694	};
		695	}
626		696
627	=back	697	=back
628		698
629	=head1 AnyEvent::MP vs. Distributed Erlang	699	=head1 AnyEvent::MP vs. Distributed Erlang
630		700
…		…
649	convenience functionality.	719	convenience functionality.
650		720
651	This means that AEMP requires a less tightly controlled environment at the	721	This means that AEMP requires a less tightly controlled environment at the
652	cost of longer node references and a slightly higher management overhead.	722	cost of longer node references and a slightly higher management overhead.
653		723
		724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		725	uses "local ports are like remote ports".
		726
		727	The failure modes for local ports are quite different (runtime errors
		728	only) then for remote ports - when a local port dies, you I<know> it dies,
		729	when a connection to another node dies, you know nothing about the other
		730	port.
		731
		732	Erlang pretends remote ports are as reliable as local ports, even when
		733	they are not.
		734
		735	AEMP encourages a "treat remote ports differently" philosophy, with local
		736	ports being the special case/exception, where transport errors cannot
		737	occur.
		738
654	=item * Erlang uses processes and a mailbox, AEMP does not queue.	739	=item * Erlang uses processes and a mailbox, AEMP does not queue.
655		740
656	Erlang uses processes that selctively receive messages, and therefore	741	Erlang uses processes that selectively receive messages, and therefore
657	needs a queue. AEMP is event based, queuing messages would serve no useful	742	needs a queue. AEMP is event based, queuing messages would serve no
658	purpose.	743	useful purpose. For the same reason the pattern-matching abilities of
		744	AnyEvent::MP are more limited, as there is little need to be able to
		745	filter messages without dequeing them.
659		746
660	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
661		748
662	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
663		750
664	Sending messages in Erlang is synchronous and blocks the process. AEMP	751	Sending messages in Erlang is synchronous and blocks the process (and
665	sends are immediate, connection establishment is handled in the	752	so does not need a queue that can overflow). AEMP sends are immediate,
666	background.	753	connection establishment is handled in the background.
667		754
668	=item * Erlang can silently lose messages, AEMP cannot.	755	=item * Erlang suffers from silent message loss, AEMP does not.
669		756
670	Erlang makes few guarantees on messages delivery - messages can get lost	757	Erlang makes few guarantees on messages delivery - messages can get lost
671	without any of the processes realising it (i.e. you send messages a, b,	758	without any of the processes realising it (i.e. you send messages a, b,
672	and c, and the other side only receives messages a and c).	759	and c, and the other side only receives messages a and c).
673		760
…		…
685	eventually be killed - it cannot happen that a node detects a port as dead	772	eventually be killed - it cannot happen that a node detects a port as dead
686	and then later sends messages to it, finding it is still alive.	773	and then later sends messages to it, finding it is still alive.
687		774
688	=item * Erlang can send messages to the wrong port, AEMP does not.	775	=item * Erlang can send messages to the wrong port, AEMP does not.
689		776
690	In Erlang it is quite possible that a node that restarts reuses a process	777	In Erlang it is quite likely that a node that restarts reuses a process ID
691	ID known to other nodes for a completely different process, causing	778	known to other nodes for a completely different process, causing messages
692	messages destined for that process to end up in an unrelated process.	779	destined for that process to end up in an unrelated process.
693		780
694	AEMP never reuses port IDs, so old messages or old port IDs floating	781	AEMP never reuses port IDs, so old messages or old port IDs floating
695	around in the network will not be sent to an unrelated port.	782	around in the network will not be sent to an unrelated port.
696		783
697	=item * Erlang uses unprotected connections, AEMP uses secure	784	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
717	or I<none>, there is no in-between, so monitoring single processes is	804	or I<none>, there is no in-between, so monitoring single processes is
718	difficult to implement. Monitoring in AEMP is more flexible than in	805	difficult to implement. Monitoring in AEMP is more flexible than in
719	Erlang, as one can choose between automatic kill, exit message or callback	806	Erlang, as one can choose between automatic kill, exit message or callback
720	on a per-process basis.	807	on a per-process basis.
721		808
722	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	809	=item * Erlang tries to hide remote/local connections, AEMP does not.
723		810
724	Monitoring in Erlang is not an indicator of process death/crashes,	811	Monitoring in Erlang is not an indicator of process death/crashes,
725	as linking is (except linking is unreliable in Erlang). In AEMP, the	812	as linking is (except linking is unreliable in Erlang).
726	semantics of monitoring and linking are identical, linking is simply	813
727	two-way monitoring with automatic kill.	814	In AEMP, you don't "look up" registered port names or send to named ports
		815	that might or might not be persistent. Instead, you normally spawn a port
		816	on the remote node. The init function monitors the you, and you monitor
		817	the remote port. Since both monitors are local to the node, they are much
		818	more reliable.
		819
		820	This also saves round-trips and avoids sending messages to the wrong port
		821	(hard to do in Erlang).
		822
		823	=back
		824
		825	=head1 RATIONALE
		826
		827	=over 4
		828
		829	=item Why strings for ports and noderefs, why not objects?
		830
		831	We considered "objects", but found that the actual number of methods
		832	thatc an be called are very low. Since port IDs and noderefs travel over
		833	the network frequently, the serialising/deserialising would add lots of
		834	overhead, as well as having to keep a proxy object.
		835
		836	Strings can easily be printed, easily serialised etc. and need no special
		837	procedures to be "valid".
		838
		839	And a a miniport consists of a single closure stored in a global hash - it
		840	can't become much cheaper.
		841
		842	=item Why favour JSON, why not real serialising format such as Storable?
		843
		844	In fact, any AnyEvent::MP node will happily accept Storable as framing
		845	format, but currently there is no way to make a node use Storable by
		846	default.
		847
		848	The default framing protocol is JSON because a) JSON::XS is many times
		849	faster for small messages and b) most importantly, after years of
		850	experience we found that object serialisation is causing more problems
		851	than it gains: Just like function calls, objects simply do not travel
		852	easily over the network, mostly because they will always be a copy, so you
		853	always have to re-think your design.
		854
		855	Keeping your messages simple, concentrating on data structures rather than
		856	objects, will keep your messages clean, tidy and efficient.
728		857
729	=back	858	=back
730		859
731	=head1 SEE ALSO	860	=head1 SEE ALSO
732		861

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Revision 1.62 by root, Thu Aug 27 07:12:48 2009 UTC