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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.29 by root, Tue Aug 4 23:16:57 2009 UTC vs.
Revision 1.54 by root, Fri Aug 14 16:15:37 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	37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
…		…
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	60	manual page.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
39	so do not use. This was uploaded mainly to reserve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.	64	stay tuned!
41		65
42	=head1 CONCEPTS	66	=head1 CONCEPTS
43		67
44	=over 4	68	=over 4
45		69
46	=item port	70	=item port
47		71
48	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).
49		73
50	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
51	messages. All C<rcv> handlers will receive messages they match, messages	75	some messages. Messages will not be queued.
52	will not be queued.
53		76
54	=item port id - C<noderef#portname>	77	=item port id - C<noderef#portname>
55		78
56	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
57	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
58	exception is the the node port, whose ID is identical to it's node	81	exception is the the node port, whose ID is identical to its node
59	reference.	82	reference.
60		83
61	=item node	84	=item node
62		85
63	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,
64	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
65	create new ports, among other things.	88	ports.
66		89
67	Nodes are either private (single-process only), slaves (connected to a	90	Nodes are either private (single-process only), slaves (connected to a
68	master node only) or public nodes (connectable from unrelated nodes).	91	master node only) or public nodes (connectable from unrelated nodes).
69		92
70	=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>
…		…
90		113
91	=cut	114	=cut
92		115
93	package AnyEvent::MP;	116	package AnyEvent::MP;
94		117
95	use AnyEvent::MP::Base;	118	use AnyEvent::MP::Kernel;
96		119
97	use common::sense;	120	use common::sense;
98		121
99	use Carp ();	122	use Carp ();
100		123
101	use AE ();	124	use AE ();
102		125
103	use base "Exporter";	126	use base "Exporter";
104		127
105	our $VERSION = '0.1';	128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		129
106	our @EXPORT = qw(	130	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	131	NODE $NODE *SELF node_of _any_
108	resolve_node	132	resolve_node initialise_node
109	become_slave become_public
110	snd rcv mon kil reg psub	133	snd rcv mon kil reg psub spawn
111	port	134	port
112	);	135	);
113		136
114	our $SELF;	137	our $SELF;
115		138
…		…
119	kil $SELF, die => $msg;	142	kil $SELF, die => $msg;
120	}	143	}
121		144
122	=item $thisnode = NODE / $NODE	145	=item $thisnode = NODE / $NODE
123		146
124	The C<NODE> function returns, and the C<$NODE> variable contains	147	The C<NODE> function returns, and the C<$NODE> variable contains the
125	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
126	to C<become_public> or C<become_slave>, after which all local port	149	C<initialise_node>.
127	identifiers become invalid.
128		150
129	=item $noderef = node_of $portid	151	=item $noderef = node_of $port
130		152
131	Extracts and returns the noderef from a portid or a noderef.	153	Extracts and returns the noderef from a port ID or a noderef.
		154
		155	=item initialise_node $noderef, $seednode, $seednode...
		156
		157	=item initialise_node "slave/", $master, $master...
		158
		159	Before a node can talk to other nodes on the network it has to initialise
		160	itself - the minimum a node needs to know is it's own name, and optionally
		161	it should know the noderefs of some other nodes in the network.
		162
		163	This function initialises a node - it must be called exactly once (or
		164	never) before calling other AnyEvent::MP functions.
		165
		166	All arguments (optionally except for the first) are noderefs, which can be
		167	either resolved or unresolved.
		168
		169	The first argument will be looked up in the configuration database first
		170	(if it is C<undef> then the current nodename will be used instead) to find
		171	the relevant configuration profile (see L<aemp>). If none is found then
		172	the default configuration is used. The configuration supplies additional
		173	seed/master nodes and can override the actual noderef.
		174
		175	There are two types of networked nodes, public nodes and slave nodes:
		176
		177	=over 4
		178
		179	=item public nodes
		180
		181	For public nodes, C<$noderef> (supplied either directly to
		182	C<initialise_node> or indirectly via a profile or the nodename) must be a
		183	noderef (possibly unresolved, in which case it will be resolved).
		184
		185	After resolving, the node will bind itself on all endpoints and try to
		186	connect to all additional C<$seednodes> that are specified. Seednodes are
		187	optional and can be used to quickly bootstrap the node into an existing
		188	network.
		189
		190	=item slave nodes
		191
		192	When the C<$noderef> (either as given or overriden by the config file)
		193	is the special string C<slave/>, then the node will become a slave
		194	node. Slave nodes cannot be contacted from outside and will route most of
		195	their traffic to the master node that they attach to.
		196
		197	At least one additional noderef is required (either by specifying it
		198	directly or because it is part of the configuration profile): The node
		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	=back
		203
		204	This function will block until all nodes have been resolved and, for slave
		205	nodes, until it has successfully established a connection to a master
		206	server.
		207
		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.
		211
		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";
		223
		224	Example: become a public node, and try to contact some well-known master
		225	servers to become part of the network.
		226
		227	initialise_node undef, "master1", "master2";
		228
		229	Example: become a public node listening on port C<4041>.
		230
		231	initialise_node 4041;
		232
		233	Example: become a public node, only visible on localhost port 4044.
		234
		235	initialise_node "localhost:4044";
132		236
133	=item $cv = resolve_node $noderef	237	=item $cv = resolve_node $noderef
134		238
135	Takes an unresolved node reference that may contain hostnames and	239	Takes an unresolved node reference that may contain hostnames and
136	abbreviated IDs, resolves all of them and returns a resolved node	240	abbreviated IDs, resolves all of them and returns a resolved node
…		…
168		272
169	Due to some quirks in how perl exports variables, it is impossible to	273	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	274	just export C<$SELF>, all the symbols called C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	275	module, but only C<$SELF> is currently used.
172		276
173	=item snd $portid, type => @data	277	=item snd $port, type => @data
174		278
175	=item snd $portid, @msg	279	=item snd $port, @msg
176		280
177	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
178	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.
179	stringifies a sa port ID (such as a port object :).
180		283
181	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
182	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
183	type etc.).	286	type etc.).
184		287
185	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
186	function: modifying any argument is not allowed and can cause many	289	function: modifying any argument is not allowed and can cause many
187	problems.	290	problems.
…		…
190	JSON is used, then only strings, numbers and arrays and hashes consisting	293	JSON is used, then only strings, numbers and arrays and hashes consisting
191	of those are allowed (no objects). When Storable is used, then anything	294	of those are allowed (no objects). When Storable is used, then anything
192	that Storable can serialise and deserialise is allowed, and for the local	295	that Storable can serialise and deserialise is allowed, and for the local
193	node, anything can be passed.	296	node, anything can be passed.
194		297
195	=item kil $portid[, @reason]	298	=item $local_port = port
196		299
197	Kill the specified port with the given C<@reason>.	300	Create a new local port object and returns its port ID. Initially it has
		301	no callbacks set and will throw an error when it receives messages.
198		302
199	If no C<@reason> is specified, then the port is killed "normally" (linked	303	=item $local_port = port { my @msg = @_ }
200	ports will not be kileld, or even notified).
201		304
202	Otherwise, linked ports get killed with the same reason (second form of	305	Creates a new local port, and returns its ID. Semantically the same as
203	C<mon>, see below).	306	creating a port and calling C<rcv $port, $callback> on it.
204		307
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	308	The block will be called for every message received on the port, with the
206	will be reported as reason C<< die => $@ >>.	309	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		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.
207		312
208	Transport/communication errors are reported as C<< transport_error =>	313	If you want to stop/destroy the port, simply C<kil> it:
209	$message >>.
210		314
211	=item $guard = mon $portid, $cb->(@reason)	315	my $port = port {
212
213	=item $guard = mon $portid, $otherport
214
215	=item $guard = mon $portid, $otherport, @msg
216
217	Monitor the given port and do something when the port is killed.
218
219	In the first form, the callback is simply called with any number
220	of C<@reason> elements (no @reason means that the port was deleted
221	"normally"). Note also that I<< the callback B<must> never die >>, so use
222	C<eval> if unsure.
223
224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
225	a @reason was specified, i.e. on "normal" kils nothing happens, while
226	under all other conditions, the other port is killed with the same reason.
227
228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
229
230	Example: call a given callback when C<$port> is killed.
231
232	mon $port, sub { warn "port died because of <@_>\n" };
233
234	Example: kill ourselves when C<$port> is killed abnormally.
235
236	mon $port, $self;
237
238	Example: send us a restart message another C<$port> is killed.
239
240	mon $port, $self => "restart";
241
242	=cut
243
244	sub mon {
245	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);
246
247	my $node = $NODE{$noderef} \|\| add_node $noderef;
248
249	#TODO: ports must not be references
250	if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {
251	if (@_) {
252	# send a kill info message
253	my (@msg) = ($cb, @_);	316	my @msg = @_;
254	$cb = sub { snd @msg, @_ };
255	} else {
256	# simply kill other port
257	my $port = $cb;
258	$cb = sub { kil $port, @_ if @_ };
259	}	317	...
		318	kil $SELF;
260	}	319	};
261		320
262	$node->monitor ($port, $cb);	321	=cut
263		322
264	defined wantarray	323	sub rcv($@);
265	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	324
		325	sub _kilme {
		326	die "received message on port without callback";
266	}	327	}
267
268	=item $guard = mon_guard $port, $ref, $ref...
269
270	Monitors the given C<$port> and keeps the passed references. When the port
271	is killed, the references will be freed.
272
273	Optionally returns a guard that will stop the monitoring.
274
275	This function is useful when you create e.g. timers or other watchers and
276	want to free them when the port gets killed:
277
278	$port->rcv (start => sub {
279	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
280	undef $timer if 0.9 < rand;
281	});
282	});
283
284	=cut
285
286	sub mon_guard {
287	my ($port, @refs) = @_;
288
289	mon $port, sub { 0 && @refs }
290	}
291
292	=item lnk $port1, $port2
293
294	Link two ports. This is simply a shorthand for:
295
296	mon $port1, $port2;
297	mon $port2, $port1;
298
299	It means that if either one is killed abnormally, the other one gets
300	killed as well.
301
302	=item $local_port = port
303
304	Create a new local port object that supports message matching.
305
306	=item $portid = port { my @msg = @_; $finished }
307
308	Creates a "mini port", that is, a very lightweight port without any
309	pattern matching behind it, and returns its ID.
310
311	The block will be called for every message received on the port. When the
312	callback returns a true value its job is considered "done" and the port
313	will be destroyed. Otherwise it will stay alive.
314
315	The message will be passed as-is, no extra argument (i.e. no port id) will
316	be passed to the callback.
317
318	If you need the local port id in the callback, this works nicely:
319
320	my $port; $port = miniport {
321	snd $otherport, reply => $port;
322	};
323
324	=cut
325		328
326	sub port(;&) {	329	sub port(;&) {
327	my $id = "$UNIQ." . $ID++;	330	my $id = "$UNIQ." . $ID++;
328	my $port = "$NODE#$id";	331	my $port = "$NODE#$id";
329		332
330	if (@_) {	333	rcv $port, shift \|\| \&_kilme;
331	my $cb = shift;
332	$PORT{$id} = sub {
333	local $SELF = $port;
334	eval {
335	&$cb
336	and kil $id;
337	};
338	_self_die if $@;
339	};
340	} else {
341	my $self = bless {
342	id => "$NODE#$id",
343	}, "AnyEvent::MP::Port";
344
345	$PORT_DATA{$id} = $self;
346	$PORT{$id} = sub {
347	local $SELF = $port;
348
349	eval {
350	for (@{ $self->{rc0}{$_[0]} }) {
351	$_ && &{$_->[0]}
352	&& undef $_;
353	}
354
355	for (@{ $self->{rcv}{$_[0]} }) {
356	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
357	&& &{$_->[0]}
358	&& undef $_;
359	}
360
361	for (@{ $self->{any} }) {
362	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
363	&& &{$_->[0]}
364	&& undef $_;
365	}
366	};
367	_self_die if $@;
368	};
369	}
370		334
371	$port	335	$port
372	}	336	}
373		337
374	=item reg $portid, $name	338	=item rcv $local_port, $callback->(@msg)
375		339
376	Registers the given port under the name C<$name>. If the name already	340	Replaces the default callback on the specified port. There is no way to
377	exists it is replaced.	341	remove the default callback: use C<sub { }> to disable it, or better
		342	C<kil> the port when it is no longer needed.
378		343
379	A port can only be registered under one well known name.
380
381	A port automatically becomes unregistered when it is killed.
382
383	=cut
384
385	sub reg(@) {
386	my ($portid, $name) = @_;
387
388	$REG{$name} = $portid;
389	}
390
391	=item rcv $portid, tagstring => $callback->(@msg), ...
392
393	=item rcv $portid, $smartmatch => $callback->(@msg), ...
394
395	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
396
397	Register callbacks to be called on matching messages on the given port.
398
399	The callback has to return a true value when its work is done, after
400	which is will be removed, or a false value in which case it will stay
401	registered.
402
403	The global C<$SELF> (exported by this module) contains C<$portid> while	344	The global C<$SELF> (exported by this module) contains C<$port> while
404	executing the callback.	345	executing the callback. Runtime errors during callback execution will
		346	result in the port being C<kil>ed.
405		347
406	Runtime errors wdurign callback execution will result in the port being	348	The default callback received all messages not matched by a more specific
407	C<kil>ed.	349	C<tag> match.
408		350
409	If the match is an array reference, then it will be matched against the	351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
410	first elements of the message, otherwise only the first element is being
411	matched.
412		352
413	Any element in the match that is specified as C<_any_> (a function	353	Register (or replace) callbacks to be called on messages starting with the
414	exported by this module) matches any single element of the message.	354	given tag on the given port (and return the port), or unregister it (when
		355	C<$callback> is C<$undef> or missing). There can only be one callback
		356	registered for each tag.
415		357
416	While not required, it is highly recommended that the first matching	358	The original message will be passed to the callback, after the first
417	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
418	also the most efficient match (by far).	360	environment as the default callback (see above).
		361
		362	Example: create a port and bind receivers on it in one go.
		363
		364	my $port = rcv port,
		365	msg1 => sub { ... },
		366	msg2 => sub { ... },
		367	;
		368
		369	Example: create a port, bind receivers and send it in a message elsewhere
		370	in one go:
		371
		372	snd $otherport, reply =>
		373	rcv port,
		374	msg1 => sub { ... },
		375	...
		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, $otherport;
		385	};
419		386
420	=cut	387	=cut
421		388
422	sub rcv($@) {	389	sub rcv($@) {
		390	my $port = shift;
423	my ($noderef, $port) = split /#/, shift, 2;	391	my ($noderef, $portid) = split /#/, $port, 2;
424		392
425	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
426	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";	394	or Carp::croak "$port: rcv can only be called on local ports, caught";
427
428	my $self = $PORT_DATA{$port}
429	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
430
431	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
433		395
434	while (@_) {	396	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;
436
437	if (!ref $match) {	397	if (ref $_[0]) {
438	push @{ $self->{rc0}{$match} }, [$cb];	398	if (my $self = $PORT_DATA{$portid}) {
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	399	"AnyEvent::MP::Port" eq ref $self
440	my ($type, @match) = @$match;	400	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441	@match	401
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	402	$self->[2] = shift;
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	403	} else {
445	push @{ $self->{any} }, [$cb, $match];	404	my $cb = shift;
		405	$PORT{$portid} = sub {
		406	local $SELF = $port;
		407	eval { &$cb }; _self_die if $@;
		408	};
		409	}
		410	} elsif (defined $_[0]) {
		411	my $self = $PORT_DATA{$portid} \|\|= do {
		412	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		413
		414	$PORT{$portid} = sub {
		415	local $SELF = $port;
		416
		417	if (my $cb = $self->[1]{$_[0]}) {
		418	shift;
		419	eval { &$cb }; _self_die if $@;
		420	} else {
		421	&{ $self->[0] };
		422	}
		423	};
		424
		425	$self
		426	};
		427
		428	"AnyEvent::MP::Port" eq ref $self
		429	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		430
		431	my ($tag, $cb) = splice @_, 0, 2;
		432
		433	if (defined $cb) {
		434	$self->[1]{$tag} = $cb;
		435	} else {
		436	delete $self->[1]{$tag};
		437	}
446	}	438	}
447	}	439	}
		440
		441	$port
448	}	442	}
449		443
450	=item $closure = psub { BLOCK }	444	=item $closure = psub { BLOCK }
451		445
452	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	446	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
483	$res	477	$res
484	}	478	}
485	}	479	}
486	}	480	}
487		481
488	=back	482	=item $guard = mon $port, $cb->(@reason)
489		483
490	=head1 FUNCTIONS FOR NODES	484	=item $guard = mon $port, $rcvport
491		485
492	=over 4	486	=item $guard = mon $port
493		487
494	=item become_public $noderef	488	=item $guard = mon $port, $rcvport, @msg
495		489
496	Tells the node to become a public node, i.e. reachable from other nodes.	490	Monitor the given port and do something when the port is killed or
		491	messages to it were lost, and optionally return a guard that can be used
		492	to stop monitoring again.
497		493
498	The first argument is the (unresolved) node reference of the local node	494	C<mon> effectively guarantees that, in the absence of hardware failures,
499	(if missing then the empty string is used).	495	that after starting the monitor, either all messages sent to the port
		496	will arrive, or the monitoring action will be invoked after possible
		497	message loss has been detected. No messages will be lost "in between"
		498	(after the first lost message no further messages will be received by the
		499	port). After the monitoring action was invoked, further messages might get
		500	delivered again.
500		501
501	It is quite common to not specify anything, in which case the local node	502	In the first form (callback), the callback is simply called with any
502	tries to listen on the default port, or to only specify a port number, in	503	number of C<@reason> elements (no @reason means that the port was deleted
503	which case AnyEvent::MP tries to guess the local addresses.	504	"normally"). Note also that I<< the callback B<must> never die >>, so use
		505	C<eval> if unsure.
504		506
		507	In the second form (another port given), the other port (C<$rcvport>)
		508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		509	"normal" kils nothing happens, while under all other conditions, the other
		510	port is killed with the same reason.
		511
		512	The third form (kill self) is the same as the second form, except that
		513	C<$rvport> defaults to C<$SELF>.
		514
		515	In the last form (message), a message of the form C<@msg, @reason> will be
		516	C<snd>.
		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
		525	Example: call a given callback when C<$port> is killed.
		526
		527	mon $port, sub { warn "port died because of <@_>\n" };
		528
		529	Example: kill ourselves when C<$port> is killed abnormally.
		530
		531	mon $port;
		532
		533	Example: send us a restart message when another C<$port> is killed.
		534
		535	mon $port, $self => "restart";
		536
505	=cut	537	=cut
		538
		539	sub mon {
		540	my ($noderef, $port) = split /#/, shift, 2;
		541
		542	my $node = $NODE{$noderef} \|\| add_node $noderef;
		543
		544	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		545
		546	unless (ref $cb) {
		547	if (@_) {
		548	# send a kill info message
		549	my (@msg) = ($cb, @_);
		550	$cb = sub { snd @msg, @_ };
		551	} else {
		552	# simply kill other port
		553	my $port = $cb;
		554	$cb = sub { kil $port, @_ if @_ };
		555	}
		556	}
		557
		558	$node->monitor ($port, $cb);
		559
		560	defined wantarray
		561	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		562	}
		563
		564	=item $guard = mon_guard $port, $ref, $ref...
		565
		566	Monitors the given C<$port> and keeps the passed references. When the port
		567	is killed, the references will be freed.
		568
		569	Optionally returns a guard that will stop the monitoring.
		570
		571	This function is useful when you create e.g. timers or other watchers and
		572	want to free them when the port gets killed:
		573
		574	$port->rcv (start => sub {
		575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		576	undef $timer if 0.9 < rand;
		577	});
		578	});
		579
		580	=cut
		581
		582	sub mon_guard {
		583	my ($port, @refs) = @_;
		584
		585	#TODO: mon-less form?
		586
		587	mon $port, sub { 0 && @refs }
		588	}
		589
		590	=item kil $port[, @reason]
		591
		592	Kill the specified port with the given C<@reason>.
		593
		594	If no C<@reason> is specified, then the port is killed "normally" (linked
		595	ports will not be kileld, or even notified).
		596
		597	Otherwise, linked ports get killed with the same reason (second form of
		598	C<mon>, see below).
		599
		600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		601	will be reported as reason C<< die => $@ >>.
		602
		603	Transport/communication errors are reported as C<< transport_error =>
		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	$_[0] =~ /::/
		669	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		670
		671	($NODE{$noderef} \|\| add_node $noderef)
		672	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		673
		674	"$noderef#$id"
		675	}
506		676
507	=back	677	=back
508		678
509	=head1 NODE MESSAGES	679	=head1 NODE MESSAGES
510		680
…		…
552		722
553	=back	723	=back
554		724
555	=head1 AnyEvent::MP vs. Distributed Erlang	725	=head1 AnyEvent::MP vs. Distributed Erlang
556		726
557	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	727	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
558	== aemp node, erlang process == aemp port), so many of the documents and	728	== aemp node, Erlang process == aemp port), so many of the documents and
559	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	729	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
560	sample:	730	sample:
561		731
562	http://www.erlang.se/doc/programming_rules.shtml	732	http://www.Erlang.se/doc/programming_rules.shtml
563	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	733	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
564	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	734	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
565	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	735	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
566		736
567	Despite the similarities, there are also some important differences:	737	Despite the similarities, there are also some important differences:
568		738
569	=over 4	739	=over 4
570		740
…		…
575	convenience functionality.	745	convenience functionality.
576		746
577	This means that AEMP requires a less tightly controlled environment at the	747	This means that AEMP requires a less tightly controlled environment at the
578	cost of longer node references and a slightly higher management overhead.	748	cost of longer node references and a slightly higher management overhead.
579		749
		750	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		751	uses "local ports are like remote ports".
		752
		753	The failure modes for local ports are quite different (runtime errors
		754	only) then for remote ports - when a local port dies, you I<know> it dies,
		755	when a connection to another node dies, you know nothing about the other
		756	port.
		757
		758	Erlang pretends remote ports are as reliable as local ports, even when
		759	they are not.
		760
		761	AEMP encourages a "treat remote ports differently" philosophy, with local
		762	ports being the special case/exception, where transport errors cannot
		763	occur.
		764
580	=item * Erlang uses processes and a mailbox, AEMP does not queue.	765	=item * Erlang uses processes and a mailbox, AEMP does not queue.
581		766
582	Erlang uses processes that selctively receive messages, and therefore	767	Erlang uses processes that selectively receive messages, and therefore
583	needs a queue. AEMP is event based, queuing messages would serve no useful	768	needs a queue. AEMP is event based, queuing messages would serve no
584	purpose.	769	useful purpose. For the same reason the pattern-matching abilities of
		770	AnyEvent::MP are more limited, as there is little need to be able to
		771	filter messages without dequeing them.
585		772
586	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
587		774
588	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
589		776
590	Sending messages in erlang is synchronous and blocks the process. AEMP	777	Sending messages in Erlang is synchronous and blocks the process (and
591	sends are immediate, connection establishment is handled in the	778	so does not need a queue that can overflow). AEMP sends are immediate,
592	background.	779	connection establishment is handled in the background.
593		780
594	=item * Erlang can silently lose messages, AEMP cannot.	781	=item * Erlang suffers from silent message loss, AEMP does not.
595		782
596	Erlang makes few guarantees on messages delivery - messages can get lost	783	Erlang makes few guarantees on messages delivery - messages can get lost
597	without any of the processes realising it (i.e. you send messages a, b,	784	without any of the processes realising it (i.e. you send messages a, b,
598	and c, and the other side only receives messages a and c).	785	and c, and the other side only receives messages a and c).
599		786
600	AEMP guarantees correct ordering, and the guarantee that there are no	787	AEMP guarantees correct ordering, and the guarantee that there are no
601	holes in the message sequence.	788	holes in the message sequence.
602		789
603	=item * In erlang, processes can be declared dead and later be found to be	790	=item * In Erlang, processes can be declared dead and later be found to be
604	alive.	791	alive.
605		792
606	In erlang it can happen that a monitored process is declared dead and	793	In Erlang it can happen that a monitored process is declared dead and
607	linked processes get killed, but later it turns out that the process is	794	linked processes get killed, but later it turns out that the process is
608	still alive - and can receive messages.	795	still alive - and can receive messages.
609		796
610	In AEMP, when port monitoring detects a port as dead, then that port will	797	In AEMP, when port monitoring detects a port as dead, then that port will
611	eventually be killed - it cannot happen that a node detects a port as dead	798	eventually be killed - it cannot happen that a node detects a port as dead
612	and then later sends messages to it, finding it is still alive.	799	and then later sends messages to it, finding it is still alive.
613		800
614	=item * Erlang can send messages to the wrong port, AEMP does not.	801	=item * Erlang can send messages to the wrong port, AEMP does not.
615		802
616	In erlang it is quite possible that a node that restarts reuses a process	803	In Erlang it is quite likely that a node that restarts reuses a process ID
617	ID known to other nodes for a completely different process, causing	804	known to other nodes for a completely different process, causing messages
618	messages destined for that process to end up in an unrelated process.	805	destined for that process to end up in an unrelated process.
619		806
620	AEMP never reuses port IDs, so old messages or old port IDs floating	807	AEMP never reuses port IDs, so old messages or old port IDs floating
621	around in the network will not be sent to an unrelated port.	808	around in the network will not be sent to an unrelated port.
622		809
623	=item * Erlang uses unprotected connections, AEMP uses secure	810	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
627	securely authenticate nodes.	814	securely authenticate nodes.
628		815
629	=item * The AEMP protocol is optimised for both text-based and binary	816	=item * The AEMP protocol is optimised for both text-based and binary
630	communications.	817	communications.
631		818
632	The AEMP protocol, unlike the erlang protocol, supports both	819	The AEMP protocol, unlike the Erlang protocol, supports both
633	language-independent text-only protocols (good for debugging) and binary,	820	language-independent text-only protocols (good for debugging) and binary,
634	language-specific serialisers (e.g. Storable).	821	language-specific serialisers (e.g. Storable).
635		822
636	It has also been carefully designed to be implementable in other languages	823	It has also been carefully designed to be implementable in other languages
637	with a minimum of work while gracefully degrading fucntionality to make the	824	with a minimum of work while gracefully degrading fucntionality to make the
638	protocol simple.	825	protocol simple.
639		826
		827	=item * AEMP has more flexible monitoring options than Erlang.
		828
		829	In Erlang, you can chose to receive I<all> exit signals as messages
		830	or I<none>, there is no in-between, so monitoring single processes is
		831	difficult to implement. Monitoring in AEMP is more flexible than in
		832	Erlang, as one can choose between automatic kill, exit message or callback
		833	on a per-process basis.
		834
		835	=item * Erlang tries to hide remote/local connections, AEMP does not.
		836
		837	Monitoring in Erlang is not an indicator of process death/crashes,
		838	as linking is (except linking is unreliable in Erlang).
		839
		840	In AEMP, you don't "look up" registered port names or send to named ports
		841	that might or might not be persistent. Instead, you normally spawn a port
		842	on the remote node. The init function monitors the you, and you monitor
		843	the remote port. Since both monitors are local to the node, they are much
		844	more reliable.
		845
		846	This also saves round-trips and avoids sending messages to the wrong port
		847	(hard to do in Erlang).
		848
		849	=back
		850
		851	=head1 RATIONALE
		852
		853	=over 4
		854
		855	=item Why strings for ports and noderefs, why not objects?
		856
		857	We considered "objects", but found that the actual number of methods
		858	thatc an be called are very low. Since port IDs and noderefs travel over
		859	the network frequently, the serialising/deserialising would add lots of
		860	overhead, as well as having to keep a proxy object.
		861
		862	Strings can easily be printed, easily serialised etc. and need no special
		863	procedures to be "valid".
		864
		865	And a a miniport consists of a single closure stored in a global hash - it
		866	can't become much cheaper.
		867
		868	=item Why favour JSON, why not real serialising format such as Storable?
		869
		870	In fact, any AnyEvent::MP node will happily accept Storable as framing
		871	format, but currently there is no way to make a node use Storable by
		872	default.
		873
		874	The default framing protocol is JSON because a) JSON::XS is many times
		875	faster for small messages and b) most importantly, after years of
		876	experience we found that object serialisation is causing more problems
		877	than it gains: Just like function calls, objects simply do not travel
		878	easily over the network, mostly because they will always be a copy, so you
		879	always have to re-think your design.
		880
		881	Keeping your messages simple, concentrating on data structures rather than
		882	objects, will keep your messages clean, tidy and efficient.
		883
640	=back	884	=back
641		885
642	=head1 SEE ALSO	886	=head1 SEE ALSO
643		887
644	L<AnyEvent>.	888	L<AnyEvent>.

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Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC