[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 1.59 by root, Mon Aug 17 03:56:34 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		46	AnyEvent::MP::Intro - outdated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 after
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.
		201
		202	Note that slave nodes cannot change their name, and consequently, their
		203	master, so if the master goes down, the slave node will not function well
		204	anymore until it can re-establish conenciton to its master. This makes
		205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.
176		206
177	=back	207	=back
178		208
179	This function will block until all nodes have been resolved and, for slave	209	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	210	nodes, until it has successfully established a connection to a master
181	server.	211	server.
182		212
		213	All the seednodes will also be specially marked to automatically retry
		214	connecting to them infinitely.
		215
183	Example: become a public node listening on the default node.	216	Example: become a public node listening on the guessed noderef, or the one
		217	specified via C<aemp> for the current node. This should be the most common
		218	form of invocation for "daemon"-type nodes.
184		219
185	initialise_node;	220	initialise_node;
		221
		222	Example: become a slave node to any of the the seednodes specified via
		223	C<aemp>. This form is often used for commandline clients.
		224
		225	initialise_node "slave/";
		226
		227	Example: become a slave node to any of the specified master servers. This
		228	form is also often used for commandline clients.
		229
		230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
186		231
187	Example: become a public node, and try to contact some well-known master	232	Example: become a public node, and try to contact some well-known master
188	servers to become part of the network.	233	servers to become part of the network.
189		234
190	initialise_node undef, "master1", "master2";	235	initialise_node undef, "master1", "master2";
…		…
193		238
194	initialise_node 4041;	239	initialise_node 4041;
195		240
196	Example: become a public node, only visible on localhost port 4044.	241	Example: become a public node, only visible on localhost port 4044.
197		242
198	initialise_node "locahost:4044";	243	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		244
204	=item $cv = resolve_node $noderef	245	=item $cv = resolve_node $noderef
205		246
206	Takes an unresolved node reference that may contain hostnames and	247	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node	248	abbreviated IDs, resolves all of them and returns a resolved node
…		…
244	=item snd $port, type => @data	285	=item snd $port, type => @data
245		286
246	=item snd $port, @msg	287	=item snd $port, @msg
247		288
248	Send the given message to the given port ID, which can identify either	289	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	290	a local or a remote port, and must be a port ID.
250	stringifies a sa port ID (such as a port object :).
251		291
252	While the message can be about anything, it is highly recommended to use a	292	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	293	string as first element (a port ID, or some word that indicates a request
254	type etc.).	294	type etc.).
255		295
256	The message data effectively becomes read-only after a call to this	296	The message data effectively becomes read-only after a call to this
257	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument is not allowed and can cause many
258	problems.	298	problems.
…		…
263	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
264	node, anything can be passed.	304	node, anything can be passed.
265		305
266	=item $local_port = port	306	=item $local_port = port
267		307
268	Create a new local port object that can be used either as a pattern	308	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"),	309	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		310
272	=item $port = port { my @msg = @_; $finished }	311	=item $local_port = port { my @msg = @_ }
273		312
274	Creates a "miniport", that is, a very lightweight port without any pattern	313	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.	314	creating a port and calling C<rcv $port, $callback> on it.
277		315
278	The block will be called for every message received on the port. When the	316	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	317	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	318	port to be C<kil>ed. The message will be passed as-is, no extra argument
		319	(i.e. no port ID) will be passed to the callback.
281		320
282	The message will be passed as-is, no extra argument (i.e. no port id) will	321	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		322
285	If you need the local port id in the callback, this works nicely:	323	my $port = port {
286		324	my @msg = @_;
287	my $port; $port = port {	325	...
288	snd $otherport, reply => $port;	326	kil $SELF;
289	};	327	};
290		328
291	=cut	329	=cut
292		330
293	sub rcv($@);	331	sub rcv($@);
		332
		333	sub _kilme {
		334	die "received message on port without callback";
		335	}
294		336
295	sub port(;&) {	337	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	338	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	339	my $port = "$NODE#$id";
298		340
299	if (@_) {	341	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		342
305	$port	343	$port
306	}	344	}
307		345
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)	346	=item rcv $local_port, $callback->(@msg)
326		347
327	Replaces the callback on the specified miniport (after converting it to	348	Replaces the default callback on the specified port. There is no way to
328	one if required).	349	remove the default callback: use C<sub { }> to disable it, or better
329		350	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...] => $callback->(@msg), ...
335
336	Register callbacks to be called on matching messages on the given full
337	port (after converting it to one if required).
338
339	The callback has to return a true value when its work is done, after
340	which is will be removed, or a false value in which case it will stay
341	registered.
342		351
343	The global C<$SELF> (exported by this module) contains C<$port> while	352	The global C<$SELF> (exported by this module) contains C<$port> while
344	executing the callback.	353	executing the callback. Runtime errors during callback execution will
		354	result in the port being C<kil>ed.
345		355
346	Runtime errors wdurign callback execution will result in the port being	356	The default callback received all messages not matched by a more specific
347	C<kil>ed.	357	C<tag> match.
348		358
349	If the match is an array reference, then it will be matched against the	359	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
350	first elements of the message, otherwise only the first element is being
351	matched.
352		360
353	Any element in the match that is specified as C<_any_> (a function	361	Register (or replace) callbacks to be called on messages starting with the
354	exported by this module) matches any single element of the message.	362	given tag on the given port (and return the port), or unregister it (when
		363	C<$callback> is C<$undef> or missing). There can only be one callback
		364	registered for each tag.
355		365
356	While not required, it is highly recommended that the first matching	366	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	367	element (the tag) has been removed. The callback will use the same
358	also the most efficient match (by far).	368	environment as the default callback (see above).
		369
		370	Example: create a port and bind receivers on it in one go.
		371
		372	my $port = rcv port,
		373	msg1 => sub { ... },
		374	msg2 => sub { ... },
		375	;
		376
		377	Example: create a port, bind receivers and send it in a message elsewhere
		378	in one go:
		379
		380	snd $otherport, reply =>
		381	rcv port,
		382	msg1 => sub { ... },
		383	...
		384	;
		385
		386	Example: temporarily register a rcv callback for a tag matching some port
		387	(e.g. for a rpc reply) and unregister it after a message was received.
		388
		389	rcv $port, $otherport => sub {
		390	my @reply = @_;
		391
		392	rcv $SELF, $otherport;
		393	};
359		394
360	=cut	395	=cut
361		396
362	sub rcv($@) {	397	sub rcv($@) {
363	my $port = shift;	398	my $port = shift;
364	my ($noderef, $portid) = split /#/, $port, 2;	399	my ($noderef, $portid) = split /#/, $port, 2;
365		400
366	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	401	$NODE{$noderef} == $NODE{""}
367	or Carp::croak "$port: rcv can only be called on local ports, caught";	402	or Carp::croak "$port: rcv can only be called on local ports, caught";
368		403
369	if (@_ == 1) {	404	while (@_) {
		405	if (ref $_[0]) {
		406	if (my $self = $PORT_DATA{$portid}) {
		407	"AnyEvent::MP::Port" eq ref $self
		408	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		409
		410	$self->[2] = shift;
		411	} else {
370	my $cb = shift;	412	my $cb = shift;
371	delete $PORT_DATA{$portid};
372	$PORT{$portid} = sub {	413	$PORT{$portid} = sub {
373	local $SELF = $port;	414	local $SELF = $port;
374	eval {	415	eval { &$cb }; _self_die if $@;
375	&$cb	416	};
376	and kil $port;
377	};	417	}
378	_self_die if $@;	418	} elsif (defined $_[0]) {
379	};
380	} else {
381	my $self = $PORT_DATA{$portid} \|\|= do {	419	my $self = $PORT_DATA{$portid} \|\|= do {
382	my $self = bless {	420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
383	id => $port,
384	}, "AnyEvent::MP::Port";
385		421
386	$PORT{$portid} = sub {	422	$PORT{$portid} = sub {
387	local $SELF = $port;	423	local $SELF = $port;
388		424
389	eval {
390	for (@{ $self->{rc0}{$_[0]} }) {	425	if (my $cb = $self->[1]{$_[0]}) {
391	$_ && &{$_->[0]}	426	shift;
392	&& undef $_;	427	eval { &$cb }; _self_die if $@;
393	}	428	} else {
394
395	for (@{ $self->{rcv}{$_[0]} }) {
396	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
397	&& &{$_->[0]}	429	&{ $self->[0] };
398	&& undef $_;
399	}
400
401	for (@{ $self->{any} }) {
402	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
403	&& &{$_->[0]}
404	&& undef $_;
405	}	430	}
406	};	431	};
407	_self_die if $@;	432
		433	$self
408	};	434	};
409		435
410	$self
411	};
412
413	"AnyEvent::MP::Port" eq ref $self	436	"AnyEvent::MP::Port" eq ref $self
414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	437	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
415		438
416	while (@_) {
417	my ($match, $cb) = splice @_, 0, 2;	439	my ($tag, $cb) = splice @_, 0, 2;
418		440
419	if (!ref $match) {	441	if (defined $cb) {
420	push @{ $self->{rc0}{$match} }, [$cb];	442	$self->[1]{$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 {	443	} else {
427	push @{ $self->{any} }, [$cb, $match];	444	delete $self->[1]{$tag};
428	}	445	}
429	}	446	}
430	}	447	}
431		448
432	$port	449	$port
…		…
470	}	487	}
471	}	488	}
472		489
473	=item $guard = mon $port, $cb->(@reason)	490	=item $guard = mon $port, $cb->(@reason)
474		491
475	=item $guard = mon $port, $otherport	492	=item $guard = mon $port, $rcvport
476		493
		494	=item $guard = mon $port
		495
477	=item $guard = mon $port, $otherport, @msg	496	=item $guard = mon $port, $rcvport, @msg
478		497
479	Monitor the given port and do something when the port is killed.	498	Monitor the given port and do something when the port is killed or
		499	messages to it were lost, and optionally return a guard that can be used
		500	to stop monitoring again.
480		501
		502	C<mon> effectively guarantees that, in the absence of hardware failures,
		503	that after starting the monitor, either all messages sent to the port
		504	will arrive, or the monitoring action will be invoked after possible
		505	message loss has been detected. No messages will be lost "in between"
		506	(after the first lost message no further messages will be received by the
		507	port). After the monitoring action was invoked, further messages might get
		508	delivered again.
		509
		510	Note that monitoring-actions are one-shot: once released, they are removed
		511	and will not trigger again.
		512
481	In the first form, the callback is simply called with any number	513	In the first form (callback), the callback is simply called with any
482	of C<@reason> elements (no @reason means that the port was deleted	514	number of C<@reason> elements (no @reason means that the port was deleted
483	"normally"). Note also that I<< the callback B<must> never die >>, so use	515	"normally"). Note also that I<< the callback B<must> never die >>, so use
484	C<eval> if unsure.	516	C<eval> if unsure.
485		517
486	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	518	In the second form (another port given), the other port (C<$rcvport>)
487	a @reason was specified, i.e. on "normal" kils nothing happens, while	519	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.	520	"normal" kils nothing happens, while under all other conditions, the other
		521	port is killed with the same reason.
489		522
		523	The third form (kill self) is the same as the second form, except that
		524	C<$rvport> defaults to C<$SELF>.
		525
490	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	526	In the last form (message), a message of the form C<@msg, @reason> will be
		527	C<snd>.
		528
		529	As a rule of thumb, monitoring requests should always monitor a port from
		530	a local port (or callback). The reason is that kill messages might get
		531	lost, just like any other message. Another less obvious reason is that
		532	even monitoring requests can get lost (for exmaple, when the connection
		533	to the other node goes down permanently). When monitoring a port locally
		534	these problems do not exist.
491		535
492	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
493		537
494	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
495		539
496	Example: kill ourselves when C<$port> is killed abnormally.	540	Example: kill ourselves when C<$port> is killed abnormally.
497		541
498	mon $port, $self;	542	mon $port;
499		543
500	Example: send us a restart message another C<$port> is killed.	544	Example: send us a restart message when another C<$port> is killed.
501		545
502	mon $port, $self => "restart";	546	mon $port, $self => "restart";
503		547
504	=cut	548	=cut
505		549
506	sub mon {	550	sub mon {
507	my ($noderef, $port) = split /#/, shift, 2;	551	my ($noderef, $port) = split /#/, shift, 2;
508		552
509	my $node = $NODE{$noderef} \|\| add_node $noderef;	553	my $node = $NODE{$noderef} \|\| add_node $noderef;
510		554
511	my $cb = shift;	555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
512		556
513	unless (ref $cb) {	557	unless (ref $cb) {
514	if (@_) {	558	if (@_) {
515	# send a kill info message	559	# send a kill info message
516	my (@msg) = ($cb, @_);	560	my (@msg) = ($cb, @_);
…		…
547	=cut	591	=cut
548		592
549	sub mon_guard {	593	sub mon_guard {
550	my ($port, @refs) = @_;	594	my ($port, @refs) = @_;
551		595
		596	#TODO: mon-less form?
		597
552	mon $port, sub { 0 && @refs }	598	mon $port, sub { 0 && @refs }
553	}	599	}
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		600
565	=item kil $port[, @reason]	601	=item kil $port[, @reason]
566		602
567	Kill the specified port with the given C<@reason>.	603	Kill the specified port with the given C<@reason>.
568		604
…		…
576	will be reported as reason C<< die => $@ >>.	612	will be reported as reason C<< die => $@ >>.
577		613
578	Transport/communication errors are reported as C<< transport_error =>	614	Transport/communication errors are reported as C<< transport_error =>
579	$message >>.	615	$message >>.
580		616
581	=back
582
583	=head1 NODE MESSAGES
584
585	Nodes understand the following messages sent to them. Many of them take
586	arguments called C<@reply>, which will simply be used to compose a reply
587	message - C<$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	617	=cut
595		618
596	=item lookup => $name, @reply	619	=item $port = spawn $node, $initfunc[, @initdata]
597		620
598	Replies with the port ID of the specified well-known port, or C<undef>.	621	Creates a port on the node C<$node> (which can also be a port ID, in which
		622	case it's the node where that port resides).
599		623
600	=item devnull => ...	624	The port ID of the newly created port is return immediately, and it is
		625	permissible to immediately start sending messages or monitor the port.
601		626
602	Generic data sink/CPU heat conversion.	627	After the port has been created, the init function is
		628	called. This function must be a fully-qualified function name
		629	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		630	program, use C<::name>.
603		631
604	=item relay => $port, @msg	632	If the function doesn't exist, then the node tries to C<require>
		633	the package, then the package above the package and so on (e.g.
		634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		635	exists or it runs out of package names.
605		636
606	Simply forwards the message to the given port.	637	The init function is then called with the newly-created port as context
		638	object (C<$SELF>) and the C<@initdata> values as arguments.
607		639
608	=item eval => $string[ @reply]	640	A common idiom is to pass your own port, monitor the spawned port, and
		641	in the init function, monitor the original port. This two-way monitoring
		642	ensures that both ports get cleaned up when there is a problem.
609		643
610	Evaluates the given string. If C<@reply> is given, then a message of the	644	Example: spawn a chat server port on C<$othernode>.
611	form C<@reply, $@, @evalres> is sent.
612		645
613	Example: crash another node.	646	# this node, executed from within a port context:
		647	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		648	mon $server;
614		649
615	snd $othernode, eval => "exit";	650	# init function on C<$othernode>
		651	sub connect {
		652	my ($srcport) = @_;
616		653
617	=item time => @reply	654	mon $srcport;
618		655
619	Replies the the current node time to C<@reply>.	656	rcv $SELF, sub {
		657	...
		658	};
		659	}
620		660
621	Example: tell the current node to send the current time to C<$myport> in a	661	=cut
622	C<timereply> message.
623		662
624	snd $NODE, time => $myport, timereply => 1, 2;	663	sub _spawn {
625	# => snd $myport, timereply => 1, 2, <time>	664	my $port = shift;
		665	my $init = shift;
		666
		667	local $SELF = "$NODE#$port";
		668	eval {
		669	&{ load_func $init }
		670	};
		671	_self_die if $@;
		672	}
		673
		674	sub spawn(@) {
		675	my ($noderef, undef) = split /#/, shift, 2;
		676
		677	my $id = "$RUNIQ." . $ID++;
		678
		679	$_[0] =~ /::/
		680	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		681
		682	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		683
		684	"$noderef#$id"
		685	}
		686
		687	=item after $timeout, @msg
		688
		689	=item after $timeout, $callback
		690
		691	Either sends the given message, or call the given callback, after the
		692	specified number of seconds.
		693
		694	This is simply a utility function that come sin handy at times.
		695
		696	=cut
		697
		698	sub after($@) {
		699	my ($timeout, @action) = @_;
		700
		701	my $t; $t = AE::timer $timeout, 0, sub {
		702	undef $t;
		703	ref $action[0]
		704	? $action[0]()
		705	: snd @action;
		706	};
		707	}
626		708
627	=back	709	=back
628		710
629	=head1 AnyEvent::MP vs. Distributed Erlang	711	=head1 AnyEvent::MP vs. Distributed Erlang
630		712
…		…
649	convenience functionality.	731	convenience functionality.
650		732
651	This means that AEMP requires a less tightly controlled environment at the	733	This means that AEMP requires a less tightly controlled environment at the
652	cost of longer node references and a slightly higher management overhead.	734	cost of longer node references and a slightly higher management overhead.
653		735
		736	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		737	uses "local ports are like remote ports".
		738
		739	The failure modes for local ports are quite different (runtime errors
		740	only) then for remote ports - when a local port dies, you I<know> it dies,
		741	when a connection to another node dies, you know nothing about the other
		742	port.
		743
		744	Erlang pretends remote ports are as reliable as local ports, even when
		745	they are not.
		746
		747	AEMP encourages a "treat remote ports differently" philosophy, with local
		748	ports being the special case/exception, where transport errors cannot
		749	occur.
		750
654	=item * Erlang uses processes and a mailbox, AEMP does not queue.	751	=item * Erlang uses processes and a mailbox, AEMP does not queue.
655		752
656	Erlang uses processes that selctively receive messages, and therefore	753	Erlang uses processes that selectively receive messages, and therefore
657	needs a queue. AEMP is event based, queuing messages would serve no useful	754	needs a queue. AEMP is event based, queuing messages would serve no
658	purpose.	755	useful purpose. For the same reason the pattern-matching abilities of
		756	AnyEvent::MP are more limited, as there is little need to be able to
		757	filter messages without dequeing them.
659		758
660	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	759	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
661		760
662	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	761	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
663		762
664	Sending messages in Erlang is synchronous and blocks the process. AEMP	763	Sending messages in Erlang is synchronous and blocks the process (and
665	sends are immediate, connection establishment is handled in the	764	so does not need a queue that can overflow). AEMP sends are immediate,
666	background.	765	connection establishment is handled in the background.
667		766
668	=item * Erlang can silently lose messages, AEMP cannot.	767	=item * Erlang suffers from silent message loss, AEMP does not.
669		768
670	Erlang makes few guarantees on messages delivery - messages can get lost	769	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,	770	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).	771	and c, and the other side only receives messages a and c).
673		772
…		…
685	eventually be killed - it cannot happen that a node detects a port as dead	784	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.	785	and then later sends messages to it, finding it is still alive.
687		786
688	=item * Erlang can send messages to the wrong port, AEMP does not.	787	=item * Erlang can send messages to the wrong port, AEMP does not.
689		788
690	In Erlang it is quite possible that a node that restarts reuses a process	789	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	790	known to other nodes for a completely different process, causing messages
692	messages destined for that process to end up in an unrelated process.	791	destined for that process to end up in an unrelated process.
693		792
694	AEMP never reuses port IDs, so old messages or old port IDs floating	793	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.	794	around in the network will not be sent to an unrelated port.
696		795
697	=item * Erlang uses unprotected connections, AEMP uses secure	796	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
717	or I<none>, there is no in-between, so monitoring single processes is	816	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	817	difficult to implement. Monitoring in AEMP is more flexible than in
719	Erlang, as one can choose between automatic kill, exit message or callback	818	Erlang, as one can choose between automatic kill, exit message or callback
720	on a per-process basis.	819	on a per-process basis.
721		820
722	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	821	=item * Erlang tries to hide remote/local connections, AEMP does not.
723		822
724	Monitoring in Erlang is not an indicator of process death/crashes,	823	Monitoring in Erlang is not an indicator of process death/crashes,
725	as linking is (except linking is unreliable in Erlang). In AEMP, the	824	as linking is (except linking is unreliable in Erlang).
726	semantics of monitoring and linking are identical, linking is simply	825
727	two-way monitoring with automatic kill.	826	In AEMP, you don't "look up" registered port names or send to named ports
		827	that might or might not be persistent. Instead, you normally spawn a port
		828	on the remote node. The init function monitors the you, and you monitor
		829	the remote port. Since both monitors are local to the node, they are much
		830	more reliable.
		831
		832	This also saves round-trips and avoids sending messages to the wrong port
		833	(hard to do in Erlang).
		834
		835	=back
		836
		837	=head1 RATIONALE
		838
		839	=over 4
		840
		841	=item Why strings for ports and noderefs, why not objects?
		842
		843	We considered "objects", but found that the actual number of methods
		844	thatc an be called are very low. Since port IDs and noderefs travel over
		845	the network frequently, the serialising/deserialising would add lots of
		846	overhead, as well as having to keep a proxy object.
		847
		848	Strings can easily be printed, easily serialised etc. and need no special
		849	procedures to be "valid".
		850
		851	And a a miniport consists of a single closure stored in a global hash - it
		852	can't become much cheaper.
		853
		854	=item Why favour JSON, why not real serialising format such as Storable?
		855
		856	In fact, any AnyEvent::MP node will happily accept Storable as framing
		857	format, but currently there is no way to make a node use Storable by
		858	default.
		859
		860	The default framing protocol is JSON because a) JSON::XS is many times
		861	faster for small messages and b) most importantly, after years of
		862	experience we found that object serialisation is causing more problems
		863	than it gains: Just like function calls, objects simply do not travel
		864	easily over the network, mostly because they will always be a copy, so you
		865	always have to re-think your design.
		866
		867	Keeping your messages simple, concentrating on data structures rather than
		868	objects, will keep your messages clean, tidy and efficient.
728		869
729	=back	870	=back
730		871
731	=head1 SEE ALSO	872	=head1 SEE ALSO
732		873

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Revision 1.59 by root, Mon Aug 17 03:56:34 2009 UTC