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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs.
Revision 1.55 by root, Fri Aug 14 23:17:17 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		46	AnyEvent::MP::Intro - outdated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 (connected to a
76	master node only) or public nodes (connectable from unrelated nodes).	91	master node only) or public nodes (connectable from unrelated nodes).
77		92
78	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
…		…
98		113
99	=cut	114	=cut
100		115
101	package AnyEvent::MP;	116	package AnyEvent::MP;
102		117
103	use AnyEvent::MP::Base;	118	use AnyEvent::MP::Kernel;
104		119
105	use common::sense;	120	use common::sense;
106		121
107	use Carp ();	122	use Carp ();
108		123
109	use AE ();	124	use AE ();
110		125
111	use base "Exporter";	126	use base "Exporter";
112		127
113	our $VERSION = '0.1';	128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		129
114	our @EXPORT = qw(	130	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	131	NODE $NODE *SELF node_of _any_
116	resolve_node initialise_node	132	resolve_node initialise_node
117	snd rcv mon kil reg psub	133	snd rcv mon kil reg psub spawn
118	port	134	port
119	);	135	);
120		136
121	our $SELF;	137	our $SELF;
122		138
…		…
126	kil $SELF, die => $msg;	142	kil $SELF, die => $msg;
127	}	143	}
128		144
129	=item $thisnode = NODE / $NODE	145	=item $thisnode = NODE / $NODE
130		146
131	The C<NODE> function returns, and the C<$NODE> variable contains	147	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	148	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	149	C<initialise_node>.
134	identifiers become invalid.
135		150
136	=item $noderef = node_of $port	151	=item $noderef = node_of $port
137		152
138	Extracts and returns the noderef from a portid or a noderef.	153	Extracts and returns the noderef from a port ID or a noderef.
139		154
140	=item initialise_node $noderef, $seednode, $seednode...	155	=item initialise_node $noderef, $seednode, $seednode...
141		156
142	=item initialise_node "slave/", $master, $master...	157	=item initialise_node "slave/", $master, $master...
143		158
…		…
146	it should know the noderefs of some other nodes in the network.	161	it should know the noderefs of some other nodes in the network.
147		162
148	This function initialises a node - it must be called exactly once (or	163	This function initialises a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	164	never) before calling other AnyEvent::MP functions.
150		165
151	All arguments are noderefs, which can be either resolved or unresolved.	166	All arguments (optionally except for the first) are noderefs, which can be
		167	either resolved or unresolved.
		168
		169	The first argument will be looked up in the configuration database first
		170	(if it is C<undef> then the current nodename will be used instead) to find
		171	the relevant configuration profile (see L<aemp>). If none is found then
		172	the default configuration is used. The configuration supplies additional
		173	seed/master nodes and can override the actual noderef.
152		174
153	There are two types of networked nodes, public nodes and slave nodes:	175	There are two types of networked nodes, public nodes and slave nodes:
154		176
155	=over 4	177	=over 4
156		178
157	=item public nodes	179	=item public nodes
158		180
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	181	For public nodes, C<$noderef> (supplied either directly to
160	noderef, in which case it will be resolved, or C<undef> (or missing), in	182	C<initialise_node> or indirectly via a profile or the nodename) must be a
161	which case the noderef will be guessed.	183	noderef (possibly unresolved, in which case it will be resolved).
162		184
163	Afterwards, the node will bind itself on all endpoints and try to connect	185	After resolving, the node will bind itself on all endpoints and try to
164	to all additional C<$seednodes> that are specified. Seednodes are optional	186	connect to all additional C<$seednodes> that are specified. Seednodes are
165	and can be used to quickly bootstrap the node into an existing network.	187	optional and can be used to quickly bootstrap the node into an existing
		188	network.
166		189
167	=item slave nodes	190	=item slave nodes
168		191
169	When the C<$noderef> is the special string C<slave/>, then the node will	192	When the C<$noderef> (either as given or overriden by the config file)
		193	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	194	node. Slave nodes cannot be contacted from outside and will route most of
171	route most of their traffic to the master node that they attach to.	195	their traffic to the master node that they attach to.
172		196
173	At least one additional noderef is required: The node will try to connect	197	At least one additional noderef is required (either by specifying it
174	to all of them and will become a slave attached to the first node it can	198	directly or because it is part of the configuration profile): The node
175	successfully connect to.	199	will try to connect to all of them and will become a slave attached to the
		200	first node it can successfully connect to.
176		201
177	=back	202	=back
178		203
179	This function will block until all nodes have been resolved and, for slave	204	This function will block until all nodes have been resolved and, for slave
180	nodes, until it has successfully established a connection to a master	205	nodes, until it has successfully established a connection to a master
181	server.	206	server.
182		207
183	Example: become a public node listening on the default node.	208	Example: become a public node listening on the guessed noderef, or the one
		209	specified via C<aemp> for the current node. This should be the most common
		210	form of invocation for "daemon"-type nodes.
184		211
185	initialise_node;	212	initialise_node;
		213
		214	Example: become a slave node to any of the the seednodes specified via
		215	C<aemp>. This form is often used for commandline clients.
		216
		217	initialise_node "slave/";
		218
		219	Example: become a slave node to any of the specified master servers. This
		220	form is also often used for commandline clients.
		221
		222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
186		223
187	Example: become a public node, and try to contact some well-known master	224	Example: become a public node, and try to contact some well-known master
188	servers to become part of the network.	225	servers to become part of the network.
189		226
190	initialise_node undef, "master1", "master2";	227	initialise_node undef, "master1", "master2";
…		…
193		230
194	initialise_node 4041;	231	initialise_node 4041;
195		232
196	Example: become a public node, only visible on localhost port 4044.	233	Example: become a public node, only visible on localhost port 4044.
197		234
198	initialise_node "locahost:4044";	235	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		236
204	=item $cv = resolve_node $noderef	237	=item $cv = resolve_node $noderef
205		238
206	Takes an unresolved node reference that may contain hostnames and	239	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node	240	abbreviated IDs, resolves all of them and returns a resolved node
…		…
244	=item snd $port, type => @data	277	=item snd $port, type => @data
245		278
246	=item snd $port, @msg	279	=item snd $port, @msg
247		280
248	Send the given message to the given port ID, which can identify either	281	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	282	a local or a remote port, and must be a port ID.
250	stringifies a sa port ID (such as a port object :).
251		283
252	While the message can be about anything, it is highly recommended to use a	284	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	285	string as first element (a port ID, or some word that indicates a request
254	type etc.).	286	type etc.).
255		287
256	The message data effectively becomes read-only after a call to this	288	The message data effectively becomes read-only after a call to this
257	function: modifying any argument is not allowed and can cause many	289	function: modifying any argument is not allowed and can cause many
258	problems.	290	problems.
…		…
263	that Storable can serialise and deserialise is allowed, and for the local	295	that Storable can serialise and deserialise is allowed, and for the local
264	node, anything can be passed.	296	node, anything can be passed.
265		297
266	=item $local_port = port	298	=item $local_port = port
267		299
268	Create a new local port object that can be used either as a pattern	300	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"),	301	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		302
272	=item $port = port { my @msg = @_; $finished }	303	=item $local_port = port { my @msg = @_ }
273		304
274	Creates a "miniport", that is, a very lightweight port without any pattern	305	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.	306	creating a port and calling C<rcv $port, $callback> on it.
277		307
278	The block will be called for every message received on the port. When the	308	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	309	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	310	port to be C<kil>ed. The message will be passed as-is, no extra argument
		311	(i.e. no port ID) will be passed to the callback.
281		312
282	The message will be passed as-is, no extra argument (i.e. no port id) will	313	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		314
285	If you need the local port id in the callback, this works nicely:	315	my $port = port {
286		316	my @msg = @_;
287	my $port; $port = port {	317	...
288	snd $otherport, reply => $port;	318	kil $SELF;
289	};	319	};
290		320
291	=cut	321	=cut
292		322
293	sub rcv($@);	323	sub rcv($@);
		324
		325	sub _kilme {
		326	die "received message on port without callback";
		327	}
294		328
295	sub port(;&) {	329	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	330	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	331	my $port = "$NODE#$id";
298		332
299	if (@_) {	333	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		334
305	$port	335	$port
306	}	336	}
307		337
308	=item reg $port, $name
309
310	=item reg $name
311
312	Registers the given port (or C<$SELF><<< if missing) under the name
313	C<$name>. If the name already exists it is replaced.
314
315	A port can only be registered under one well known name.
316
317	A port automatically becomes unregistered when it is killed.
318
319	=cut
320
321	sub reg(@) {
322	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
323
324	$REG{$_[0]} = $port;
325	}
326
327	=item rcv $port, $callback->(@msg)	338	=item rcv $local_port, $callback->(@msg)
328		339
329	Replaces the callback on the specified miniport (after converting it to	340	Replaces the default callback on the specified port. There is no way to
330	one if required).	341	remove the default callback: use C<sub { }> to disable it, or better
331		342	C<kil> the port when it is no longer needed.
332	=item rcv $port, tagstring => $callback->(@msg), ...
333
334	=item rcv $port, $smartmatch => $callback->(@msg), ...
335
336	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
337
338	Register callbacks to be called on matching messages on the given full
339	port (after converting it to one if required) and return the port.
340
341	The callback has to return a true value when its work is done, after
342	which is will be removed, or a false value in which case it will stay
343	registered.
344		343
345	The global C<$SELF> (exported by this module) contains C<$port> while	344	The global C<$SELF> (exported by this module) contains C<$port> while
346	executing the callback.	345	executing the callback. Runtime errors during callback execution will
		346	result in the port being C<kil>ed.
347		347
348	Runtime errors wdurign callback execution will result in the port being	348	The default callback received all messages not matched by a more specific
349	C<kil>ed.	349	C<tag> match.
350		350
351	If the match is an array reference, then it will be matched against the	351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352	first elements of the message, otherwise only the first element is being
353	matched.
354		352
355	Any element in the match that is specified as C<_any_> (a function	353	Register (or replace) callbacks to be called on messages starting with the
356	exported by this module) matches any single element of the message.	354	given tag on the given port (and return the port), or unregister it (when
		355	C<$callback> is C<$undef> or missing). There can only be one callback
		356	registered for each tag.
357		357
358	While not required, it is highly recommended that the first matching	358	The original message will be passed to the callback, after the first
359	element is a string identifying the message. The one-string-only match is	359	element (the tag) has been removed. The callback will use the same
360	also the most efficient match (by far).	360	environment as the default callback (see above).
361		361
362	Example: create a port and bind receivers on it in one go.	362	Example: create a port and bind receivers on it in one go.
363		363
364	my $port = rcv port,	364	my $port = rcv port,
365	msg1 => sub { ...; 0 },	365	msg1 => sub { ... },
366	msg2 => sub { ...; 0 },	366	msg2 => sub { ... },
367	;	367	;
368		368
369	Example: create a port, bind receivers and send it in a message elsewhere	369	Example: create a port, bind receivers and send it in a message elsewhere
370	in one go:	370	in one go:
371		371
372	snd $otherport, reply =>	372	snd $otherport, reply =>
373	rcv port,	373	rcv port,
374	msg1 => sub { ...; 0 },	374	msg1 => sub { ... },
375	...	375	...
376	;	376	;
		377
		378	Example: temporarily register a rcv callback for a tag matching some port
		379	(e.g. for a rpc reply) and unregister it after a message was received.
		380
		381	rcv $port, $otherport => sub {
		382	my @reply = @_;
		383
		384	rcv $SELF, $otherport;
		385	};
377		386
378	=cut	387	=cut
379		388
380	sub rcv($@) {	389	sub rcv($@) {
381	my $port = shift;	390	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	391	my ($noderef, $portid) = split /#/, $port, 2;
383		392
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	394	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		395
387	if (@_ == 1) {	396	while (@_) {
		397	if (ref $_[0]) {
		398	if (my $self = $PORT_DATA{$portid}) {
		399	"AnyEvent::MP::Port" eq ref $self
		400	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		401
		402	$self->[2] = shift;
		403	} else {
388	my $cb = shift;	404	my $cb = shift;
389	delete $PORT_DATA{$portid};
390	$PORT{$portid} = sub {	405	$PORT{$portid} = sub {
391	local $SELF = $port;	406	local $SELF = $port;
392	eval {	407	eval { &$cb }; _self_die if $@;
393	&$cb	408	};
394	and kil $port;
395	};	409	}
396	_self_die if $@;	410	} elsif (defined $_[0]) {
397	};
398	} else {
399	my $self = $PORT_DATA{$portid} \|\|= do {	411	my $self = $PORT_DATA{$portid} \|\|= do {
400	my $self = bless {	412	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
401	id => $port,
402	}, "AnyEvent::MP::Port";
403		413
404	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
405	local $SELF = $port;	415	local $SELF = $port;
406		416
407	eval {
408	for (@{ $self->{rc0}{$_[0]} }) {	417	if (my $cb = $self->[1]{$_[0]}) {
409	$_ && &{$_->[0]}	418	shift;
410	&& undef $_;	419	eval { &$cb }; _self_die if $@;
411	}	420	} else {
412
413	for (@{ $self->{rcv}{$_[0]} }) {
414	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
415	&& &{$_->[0]}	421	&{ $self->[0] };
416	&& undef $_;
417	}
418
419	for (@{ $self->{any} }) {
420	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
421	&& &{$_->[0]}
422	&& undef $_;
423	}	422	}
424	};	423	};
425	_self_die if $@;	424
		425	$self
426	};	426	};
427		427
428	$self
429	};
430
431	"AnyEvent::MP::Port" eq ref $self	428	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	429	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
433		430
434	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;	431	my ($tag, $cb) = splice @_, 0, 2;
436		432
437	if (!ref $match) {	433	if (defined $cb) {
438	push @{ $self->{rc0}{$match} }, [$cb];	434	$self->[1]{$tag} = $cb;
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440	my ($type, @match) = @$match;
441	@match
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	435	} else {
445	push @{ $self->{any} }, [$cb, $match];	436	delete $self->[1]{$tag};
446	}	437	}
447	}	438	}
448	}	439	}
449		440
450	$port	441	$port
…		…
494		485
495	=item $guard = mon $port	486	=item $guard = mon $port
496		487
497	=item $guard = mon $port, $rcvport, @msg	488	=item $guard = mon $port, $rcvport, @msg
498		489
499	Monitor the given port and do something when the port is killed, and	490	Monitor the given port and do something when the port is killed or
500	optionally return a guard that can be used to stop monitoring again.	491	messages to it were lost, and optionally return a guard that can be used
		492	to stop monitoring again.
		493
		494	C<mon> effectively guarantees that, in the absence of hardware failures,
		495	that after starting the monitor, either all messages sent to the port
		496	will arrive, or the monitoring action will be invoked after possible
		497	message loss has been detected. No messages will be lost "in between"
		498	(after the first lost message no further messages will be received by the
		499	port). After the monitoring action was invoked, further messages might get
		500	delivered again.
501		501
502	In the first form (callback), the callback is simply called with any	502	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	503	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	504	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	505	C<eval> if unsure.
506		506
507	In the second form (another port given), the other port (C<$rcvport)	507	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	509	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	510	port is killed with the same reason.
511		511
512	The third form (kill self) is the same as the second form, except that	512	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	513	C<$rvport> defaults to C<$SELF>.
514		514
515	In the last form (message), a message of the form C<@msg, @reason> will be	515	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	516	C<snd>.
517		517
		518	As a rule of thumb, monitoring requests should always monitor a port from
		519	a local port (or callback). The reason is that kill messages might get
		520	lost, just like any other message. Another less obvious reason is that
		521	even monitoring requests can get lost (for exmaple, when the connection
		522	to the other node goes down permanently). When monitoring a port locally
		523	these problems do not exist.
		524
518	Example: call a given callback when C<$port> is killed.	525	Example: call a given callback when C<$port> is killed.
519		526
520	mon $port, sub { warn "port died because of <@_>\n" };	527	mon $port, sub { warn "port died because of <@_>\n" };
521		528
522	Example: kill ourselves when C<$port> is killed abnormally.	529	Example: kill ourselves when C<$port> is killed abnormally.
…		…
532	sub mon {	539	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	540	my ($noderef, $port) = split /#/, shift, 2;
534		541
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	542	my $node = $NODE{$noderef} \|\| add_node $noderef;
536		543
537	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	544	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		545
539	unless (ref $cb) {	546	unless (ref $cb) {
540	if (@_) {	547	if (@_) {
541	# send a kill info message	548	# send a kill info message
542	my (@msg) = @_;	549	my (@msg) = ($cb, @_);
543	$cb = sub { snd @msg, @_ };	550	$cb = sub { snd @msg, @_ };
544	} else {	551	} else {
545	# simply kill other port	552	# simply kill other port
546	my $port = $cb;	553	my $port = $cb;
547	$cb = sub { kil $port, @_ if @_ };	554	$cb = sub { kil $port, @_ if @_ };
…		…
578	#TODO: mon-less form?	585	#TODO: mon-less form?
579		586
580	mon $port, sub { 0 && @refs }	587	mon $port, sub { 0 && @refs }
581	}	588	}
582		589
583	=item lnk $port1, $port2
584
585	=item lnk $otherport
586
587	Link two ports. This is simply a shorthand for:
588
589	mon $port1, $port2;
590	mon $port2, $port1;
591
592	It means that if either one is killed abnormally, the other one gets
593	killed as well.
594
595	The one-argument form assumes that one port is C<$SELF>.
596
597	=cut
598
599	sub lnk {
600	my $port1 = shift;
601	my $port2 = @_ ? shift : $SELF \|\| Carp::croak 'lnk: called with one argument only, but $SELF not set,';
602
603	mon $port1, $port2;
604	mon $port2, $port1;
605	}
606
607	=item kil $port[, @reason]	590	=item kil $port[, @reason]
608		591
609	Kill the specified port with the given C<@reason>.	592	Kill the specified port with the given C<@reason>.
610		593
611	If no C<@reason> is specified, then the port is killed "normally" (linked	594	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	601	will be reported as reason C<< die => $@ >>.
619		602
620	Transport/communication errors are reported as C<< transport_error =>	603	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	604	$message >>.
		605
		606	=cut
		607
		608	=item $port = spawn $node, $initfunc[, @initdata]
		609
		610	Creates a port on the node C<$node> (which can also be a port ID, in which
		611	case it's the node where that port resides).
		612
		613	The port ID of the newly created port is return immediately, and it is
		614	permissible to immediately start sending messages or monitor the port.
		615
		616	After the port has been created, the init function is
		617	called. This function must be a fully-qualified function name
		618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		619	program, use C<::name>.
		620
		621	If the function doesn't exist, then the node tries to C<require>
		622	the package, then the package above the package and so on (e.g.
		623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		624	exists or it runs out of package names.
		625
		626	The init function is then called with the newly-created port as context
		627	object (C<$SELF>) and the C<@initdata> values as arguments.
		628
		629	A common idiom is to pass your own port, monitor the spawned port, and
		630	in the init function, monitor the original port. This two-way monitoring
		631	ensures that both ports get cleaned up when there is a problem.
		632
		633	Example: spawn a chat server port on C<$othernode>.
		634
		635	# this node, executed from within a port context:
		636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		637	mon $server;
		638
		639	# init function on C<$othernode>
		640	sub connect {
		641	my ($srcport) = @_;
		642
		643	mon $srcport;
		644
		645	rcv $SELF, sub {
		646	...
		647	};
		648	}
		649
		650	=cut
		651
		652	sub _spawn {
		653	my $port = shift;
		654	my $init = shift;
		655
		656	local $SELF = "$NODE#$port";
		657	eval {
		658	&{ load_func $init }
		659	};
		660	_self_die if $@;
		661	}
		662
		663	sub spawn(@) {
		664	my ($noderef, undef) = split /#/, shift, 2;
		665
		666	my $id = "$RUNIQ." . $ID++;
		667
		668	$_[0] =~ /::/
		669	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		670
		671	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		672
		673	"$noderef#$id"
		674	}
622		675
623	=back	676	=back
624		677
625	=head1 NODE MESSAGES	678	=head1 NODE MESSAGES
626		679
…		…
691	convenience functionality.	744	convenience functionality.
692		745
693	This means that AEMP requires a less tightly controlled environment at the	746	This means that AEMP requires a less tightly controlled environment at the
694	cost of longer node references and a slightly higher management overhead.	747	cost of longer node references and a slightly higher management overhead.
695		748
		749	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		750	uses "local ports are like remote ports".
		751
		752	The failure modes for local ports are quite different (runtime errors
		753	only) then for remote ports - when a local port dies, you I<know> it dies,
		754	when a connection to another node dies, you know nothing about the other
		755	port.
		756
		757	Erlang pretends remote ports are as reliable as local ports, even when
		758	they are not.
		759
		760	AEMP encourages a "treat remote ports differently" philosophy, with local
		761	ports being the special case/exception, where transport errors cannot
		762	occur.
		763
696	=item * Erlang uses processes and a mailbox, AEMP does not queue.	764	=item * Erlang uses processes and a mailbox, AEMP does not queue.
697		765
698	Erlang uses processes that selctively receive messages, and therefore	766	Erlang uses processes that selectively receive messages, and therefore
699	needs a queue. AEMP is event based, queuing messages would serve no useful	767	needs a queue. AEMP is event based, queuing messages would serve no
700	purpose.	768	useful purpose. For the same reason the pattern-matching abilities of
		769	AnyEvent::MP are more limited, as there is little need to be able to
		770	filter messages without dequeing them.
701		771
702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	772	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
703		773
704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	774	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
705		775
706	Sending messages in Erlang is synchronous and blocks the process. AEMP	776	Sending messages in Erlang is synchronous and blocks the process (and
707	sends are immediate, connection establishment is handled in the	777	so does not need a queue that can overflow). AEMP sends are immediate,
708	background.	778	connection establishment is handled in the background.
709		779
710	=item * Erlang can silently lose messages, AEMP cannot.	780	=item * Erlang suffers from silent message loss, AEMP does not.
711		781
712	Erlang makes few guarantees on messages delivery - messages can get lost	782	Erlang makes few guarantees on messages delivery - messages can get lost
713	without any of the processes realising it (i.e. you send messages a, b,	783	without any of the processes realising it (i.e. you send messages a, b,
714	and c, and the other side only receives messages a and c).	784	and c, and the other side only receives messages a and c).
715		785
…		…
727	eventually be killed - it cannot happen that a node detects a port as dead	797	eventually be killed - it cannot happen that a node detects a port as dead
728	and then later sends messages to it, finding it is still alive.	798	and then later sends messages to it, finding it is still alive.
729		799
730	=item * Erlang can send messages to the wrong port, AEMP does not.	800	=item * Erlang can send messages to the wrong port, AEMP does not.
731		801
732	In Erlang it is quite possible that a node that restarts reuses a process	802	In Erlang it is quite likely that a node that restarts reuses a process ID
733	ID known to other nodes for a completely different process, causing	803	known to other nodes for a completely different process, causing messages
734	messages destined for that process to end up in an unrelated process.	804	destined for that process to end up in an unrelated process.
735		805
736	AEMP never reuses port IDs, so old messages or old port IDs floating	806	AEMP never reuses port IDs, so old messages or old port IDs floating
737	around in the network will not be sent to an unrelated port.	807	around in the network will not be sent to an unrelated port.
738		808
739	=item * Erlang uses unprotected connections, AEMP uses secure	809	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
759	or I<none>, there is no in-between, so monitoring single processes is	829	or I<none>, there is no in-between, so monitoring single processes is
760	difficult to implement. Monitoring in AEMP is more flexible than in	830	difficult to implement. Monitoring in AEMP is more flexible than in
761	Erlang, as one can choose between automatic kill, exit message or callback	831	Erlang, as one can choose between automatic kill, exit message or callback
762	on a per-process basis.	832	on a per-process basis.
763		833
764	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	834	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		835
766	Monitoring in Erlang is not an indicator of process death/crashes,	836	Monitoring in Erlang is not an indicator of process death/crashes,
767	as linking is (except linking is unreliable in Erlang). In AEMP, the	837	as linking is (except linking is unreliable in Erlang).
768	semantics of monitoring and linking are identical, linking is simply	838
769	two-way monitoring with automatic kill.	839	In AEMP, you don't "look up" registered port names or send to named ports
		840	that might or might not be persistent. Instead, you normally spawn a port
		841	on the remote node. The init function monitors the you, and you monitor
		842	the remote port. Since both monitors are local to the node, they are much
		843	more reliable.
		844
		845	This also saves round-trips and avoids sending messages to the wrong port
		846	(hard to do in Erlang).
		847
		848	=back
		849
		850	=head1 RATIONALE
		851
		852	=over 4
		853
		854	=item Why strings for ports and noderefs, why not objects?
		855
		856	We considered "objects", but found that the actual number of methods
		857	thatc an be called are very low. Since port IDs and noderefs travel over
		858	the network frequently, the serialising/deserialising would add lots of
		859	overhead, as well as having to keep a proxy object.
		860
		861	Strings can easily be printed, easily serialised etc. and need no special
		862	procedures to be "valid".
		863
		864	And a a miniport consists of a single closure stored in a global hash - it
		865	can't become much cheaper.
		866
		867	=item Why favour JSON, why not real serialising format such as Storable?
		868
		869	In fact, any AnyEvent::MP node will happily accept Storable as framing
		870	format, but currently there is no way to make a node use Storable by
		871	default.
		872
		873	The default framing protocol is JSON because a) JSON::XS is many times
		874	faster for small messages and b) most importantly, after years of
		875	experience we found that object serialisation is causing more problems
		876	than it gains: Just like function calls, objects simply do not travel
		877	easily over the network, mostly because they will always be a copy, so you
		878	always have to re-think your design.
		879
		880	Keeping your messages simple, concentrating on data structures rather than
		881	objects, will keep your messages clean, tidy and efficient.
770		882
771	=back	883	=back
772		884
773	=head1 SEE ALSO	885	=head1 SEE ALSO
774		886

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Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC