[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 1.57 by root, Sat Aug 15 04:34:34 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	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		46	AnyEvent::MP::Intro - outdated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	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.
		206
		207	=back
		208
		209	This function will block until all nodes have been resolved and, for slave
		210	nodes, until it has successfully established a connection to a master
		211	server.
		212
		213	All the seednodes will also be specially marked to automatically retry
		214	connecting to them infinitely.
		215
		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.
		219
		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";
		231
		232	Example: become a public node, and try to contact some well-known master
		233	servers to become part of the network.
		234
		235	initialise_node undef, "master1", "master2";
		236
		237	Example: become a public node listening on port C<4041>.
		238
		239	initialise_node 4041;
		240
		241	Example: become a public node, only visible on localhost port 4044.
		242
		243	initialise_node "localhost:4044";
132		244
133	=item $cv = resolve_node $noderef	245	=item $cv = resolve_node $noderef
134		246
135	Takes an unresolved node reference that may contain hostnames and	247	Takes an unresolved node reference that may contain hostnames and
136	abbreviated IDs, resolves all of them and returns a resolved node	248	abbreviated IDs, resolves all of them and returns a resolved node
…		…
168		280
169	Due to some quirks in how perl exports variables, it is impossible to	281	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	282	just export C<$SELF>, all the symbols called C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	283	module, but only C<$SELF> is currently used.
172		284
173	=item snd $portid, type => @data	285	=item snd $port, type => @data
174		286
175	=item snd $portid, @msg	287	=item snd $port, @msg
176		288
177	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
178	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.
179	stringifies a sa port ID (such as a port object :).
180		291
181	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
182	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
183	type etc.).	294	type etc.).
184		295
185	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
186	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument is not allowed and can cause many
187	problems.	298	problems.
…		…
190	JSON is used, then only strings, numbers and arrays and hashes consisting	301	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	302	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	303	that Storable can serialise and deserialise is allowed, and for the local
193	node, anything can be passed.	304	node, anything can be passed.
194		305
195	=item kil $portid[, @reason]	306	=item $local_port = port
196		307
197	Kill the specified port with the given C<@reason>.	308	Create a new local port object and returns its port ID. Initially it has
		309	no callbacks set and will throw an error when it receives messages.
198		310
199	If no C<@reason> is specified, then the port is killed "normally" (linked	311	=item $local_port = port { my @msg = @_ }
200	ports will not be kileld, or even notified).
201		312
202	Otherwise, linked ports get killed with the same reason (second form of	313	Creates a new local port, and returns its ID. Semantically the same as
203	C<mon>, see below).	314	creating a port and calling C<rcv $port, $callback> on it.
204		315
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	316	The block will be called for every message received on the port, with the
206	will be reported as reason C<< die => $@ >>.	317	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		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.
207		320
208	Transport/communication errors are reported as C<< transport_error =>	321	If you want to stop/destroy the port, simply C<kil> it:
209	$message >>.
210		322
211	=item $guard = mon $portid, $cb->(@reason)	323	my $port = port {
212		324	my @msg = @_;
213	=item $guard = mon $portid, $otherport	325	...
214		326	kil $SELF;
215	=item $guard = mon $portid, $otherport, @msg	327	};
216
217	Monitor the given port and do something when the port is killed.
218
219	In the first form, the callback is simply called with any number
220	of C<@reason> elements (no @reason means that the port was deleted
221	"normally"). Note also that I<< the callback B<must> never die >>, so use
222	C<eval> if unsure.
223
224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
225	a @reason was specified, i.e. on "normal" kils nothing happens, while
226	under all other conditions, the other port is killed with the same reason.
227
228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
229
230	Example: call a given callback when C<$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, $self => "restart";
241		328
242	=cut	329	=cut
243		330
244	sub mon {	331	sub rcv($@);
245	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);
246		332
247	my $node = $NODE{$noderef} \|\| add_node $noderef;	333	sub _kilme {
248		334	die "received message on port without callback";
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, @_);
254	$cb = sub { snd @msg, @_ };
255	} else {
256	# simply kill other port
257	my $port = $cb;
258	$cb = sub { kil $port, @_ if @_ };
259	}
260	}
261
262	$node->monitor ($port, $cb);
263
264	defined wantarray
265	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
266	}	335	}
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		336
326	sub port(;&) {	337	sub port(;&) {
327	my $id = "$UNIQ." . $ID++;	338	my $id = "$UNIQ." . $ID++;
328	my $port = "$NODE#$id";	339	my $port = "$NODE#$id";
329		340
330	if (@_) {	341	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		342
371	$port	343	$port
372	}	344	}
373		345
374	=item reg $portid, $name	346	=item rcv $local_port, $callback->(@msg)
375		347
376	Registers the given port under the name C<$name>. If the name already	348	Replaces the default callback on the specified port. There is no way to
377	exists it is replaced.	349	remove the default callback: use C<sub { }> to disable it, or better
		350	C<kil> the port when it is no longer needed.
378		351
379	A port can only be registered under one well known name.	352	The global C<$SELF> (exported by this module) contains C<$port> while
		353	executing the callback. Runtime errors during callback execution will
		354	result in the port being C<kil>ed.
380		355
381	A port automatically becomes unregistered when it is killed.	356	The default callback received all messages not matched by a more specific
		357	C<tag> match.
		358
		359	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		360
		361	Register (or replace) callbacks to be called on messages starting with the
		362	given tag on the given port (and return the port), or unregister it (when
		363	C<$callback> is C<$undef> or missing). There can only be one callback
		364	registered for each tag.
		365
		366	The original message will be passed to the callback, after the first
		367	element (the tag) has been removed. The callback will use the same
		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, $otherport;
		393	};
382		394
383	=cut	395	=cut
384		396
385	sub reg(@) {
386	my ($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<$portid> while
404	executing the callback.
405
406	Runtime errors wdurign callback execution will result in the port being
407	C<kil>ed.
408
409	If the match is an array reference, then it will be matched against the
410	first elements of the message, otherwise only the first element is being
411	matched.
412
413	Any element in the match that is specified as C<_any_> (a function
414	exported by this module) matches any single element of the message.
415
416	While not required, it is highly recommended that the first matching
417	element is a string identifying the message. The one-string-only match is
418	also the most efficient match (by far).
419
420	=cut
421
422	sub rcv($@) {	397	sub rcv($@) {
		398	my $port = shift;
423	my ($noderef, $port) = split /#/, shift, 2;	399	my ($noderef, $portid) = split /#/, $port, 2;
424		400
425	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
426	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";	402	or Carp::croak "$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#$port: rcv can only be called on message matching ports, caught";
433		403
434	while (@_) {	404	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;
436
437	if (!ref $match) {	405	if (ref $_[0]) {
438	push @{ $self->{rc0}{$match} }, [$cb];	406	if (my $self = $PORT_DATA{$portid}) {
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	407	"AnyEvent::MP::Port" eq ref $self
440	my ($type, @match) = @$match;	408	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441	@match	409
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	410	$self->[2] = shift;
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	411	} else {
445	push @{ $self->{any} }, [$cb, $match];	412	my $cb = shift;
		413	$PORT{$portid} = sub {
		414	local $SELF = $port;
		415	eval { &$cb }; _self_die if $@;
		416	};
		417	}
		418	} elsif (defined $_[0]) {
		419	my $self = $PORT_DATA{$portid} \|\|= do {
		420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		421
		422	$PORT{$portid} = sub {
		423	local $SELF = $port;
		424
		425	if (my $cb = $self->[1]{$_[0]}) {
		426	shift;
		427	eval { &$cb }; _self_die if $@;
		428	} else {
		429	&{ $self->[0] };
		430	}
		431	};
		432
		433	$self
		434	};
		435
		436	"AnyEvent::MP::Port" eq ref $self
		437	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		438
		439	my ($tag, $cb) = splice @_, 0, 2;
		440
		441	if (defined $cb) {
		442	$self->[1]{$tag} = $cb;
		443	} else {
		444	delete $self->[1]{$tag};
		445	}
446	}	446	}
447	}	447	}
		448
		449	$port
448	}	450	}
449		451
450	=item $closure = psub { BLOCK }	452	=item $closure = psub { BLOCK }
451		453
452	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	454	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
483	$res	485	$res
484	}	486	}
485	}	487	}
486	}	488	}
487		489
		490	=item $guard = mon $port, $cb->(@reason)
		491
		492	=item $guard = mon $port, $rcvport
		493
		494	=item $guard = mon $port
		495
		496	=item $guard = mon $port, $rcvport, @msg
		497
		498	Monitor the given port and do something when the port is killed or
		499	messages to it were lost, and optionally return a guard that can be used
		500	to stop monitoring again.
		501
		502	C<mon> effectively guarantees that, in the absence of hardware failures,
		503	that after starting the monitor, either all messages sent to the port
		504	will arrive, or the monitoring action will be invoked after possible
		505	message loss has been detected. No messages will be lost "in between"
		506	(after the first lost message no further messages will be received by the
		507	port). After the monitoring action was invoked, further messages might get
		508	delivered again.
		509
		510	In the first form (callback), the callback is simply called with any
		511	number of C<@reason> elements (no @reason means that the port was deleted
		512	"normally"). Note also that I<< the callback B<must> never die >>, so use
		513	C<eval> if unsure.
		514
		515	In the second form (another port given), the other port (C<$rcvport>)
		516	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		517	"normal" kils nothing happens, while under all other conditions, the other
		518	port is killed with the same reason.
		519
		520	The third form (kill self) is the same as the second form, except that
		521	C<$rvport> defaults to C<$SELF>.
		522
		523	In the last form (message), a message of the form C<@msg, @reason> will be
		524	C<snd>.
		525
		526	As a rule of thumb, monitoring requests should always monitor a port from
		527	a local port (or callback). The reason is that kill messages might get
		528	lost, just like any other message. Another less obvious reason is that
		529	even monitoring requests can get lost (for exmaple, when the connection
		530	to the other node goes down permanently). When monitoring a port locally
		531	these problems do not exist.
		532
		533	Example: call a given callback when C<$port> is killed.
		534
		535	mon $port, sub { warn "port died because of <@_>\n" };
		536
		537	Example: kill ourselves when C<$port> is killed abnormally.
		538
		539	mon $port;
		540
		541	Example: send us a restart message when another C<$port> is killed.
		542
		543	mon $port, $self => "restart";
		544
		545	=cut
		546
		547	sub mon {
		548	my ($noderef, $port) = split /#/, shift, 2;
		549
		550	my $node = $NODE{$noderef} \|\| add_node $noderef;
		551
		552	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		553
		554	unless (ref $cb) {
		555	if (@_) {
		556	# send a kill info message
		557	my (@msg) = ($cb, @_);
		558	$cb = sub { snd @msg, @_ };
		559	} else {
		560	# simply kill other port
		561	my $port = $cb;
		562	$cb = sub { kil $port, @_ if @_ };
		563	}
		564	}
		565
		566	$node->monitor ($port, $cb);
		567
		568	defined wantarray
		569	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		570	}
		571
		572	=item $guard = mon_guard $port, $ref, $ref...
		573
		574	Monitors the given C<$port> and keeps the passed references. When the port
		575	is killed, the references will be freed.
		576
		577	Optionally returns a guard that will stop the monitoring.
		578
		579	This function is useful when you create e.g. timers or other watchers and
		580	want to free them when the port gets killed:
		581
		582	$port->rcv (start => sub {
		583	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		584	undef $timer if 0.9 < rand;
		585	});
		586	});
		587
		588	=cut
		589
		590	sub mon_guard {
		591	my ($port, @refs) = @_;
		592
		593	#TODO: mon-less form?
		594
		595	mon $port, sub { 0 && @refs }
		596	}
		597
		598	=item kil $port[, @reason]
		599
		600	Kill the specified port with the given C<@reason>.
		601
		602	If no C<@reason> is specified, then the port is killed "normally" (linked
		603	ports will not be kileld, or even notified).
		604
		605	Otherwise, linked ports get killed with the same reason (second form of
		606	C<mon>, see below).
		607
		608	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		609	will be reported as reason C<< die => $@ >>.
		610
		611	Transport/communication errors are reported as C<< transport_error =>
		612	$message >>.
		613
		614	=cut
		615
		616	=item $port = spawn $node, $initfunc[, @initdata]
		617
		618	Creates a port on the node C<$node> (which can also be a port ID, in which
		619	case it's the node where that port resides).
		620
		621	The port ID of the newly created port is return immediately, and it is
		622	permissible to immediately start sending messages or monitor the port.
		623
		624	After the port has been created, the init function is
		625	called. This function must be a fully-qualified function name
		626	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		627	program, use C<::name>.
		628
		629	If the function doesn't exist, then the node tries to C<require>
		630	the package, then the package above the package and so on (e.g.
		631	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		632	exists or it runs out of package names.
		633
		634	The init function is then called with the newly-created port as context
		635	object (C<$SELF>) and the C<@initdata> values as arguments.
		636
		637	A common idiom is to pass your own port, monitor the spawned port, and
		638	in the init function, monitor the original port. This two-way monitoring
		639	ensures that both ports get cleaned up when there is a problem.
		640
		641	Example: spawn a chat server port on C<$othernode>.
		642
		643	# this node, executed from within a port context:
		644	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		645	mon $server;
		646
		647	# init function on C<$othernode>
		648	sub connect {
		649	my ($srcport) = @_;
		650
		651	mon $srcport;
		652
		653	rcv $SELF, sub {
		654	...
		655	};
		656	}
		657
		658	=cut
		659
		660	sub _spawn {
		661	my $port = shift;
		662	my $init = shift;
		663
		664	local $SELF = "$NODE#$port";
		665	eval {
		666	&{ load_func $init }
		667	};
		668	_self_die if $@;
		669	}
		670
		671	sub spawn(@) {
		672	my ($noderef, undef) = split /#/, shift, 2;
		673
		674	my $id = "$RUNIQ." . $ID++;
		675
		676	$_[0] =~ /::/
		677	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		678
		679	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		680
		681	"$noderef#$id"
		682	}
		683
488	=back	684	=back
489		685
490	=head1 FUNCTIONS FOR NODES
491
492	=over 4
493
494	=item become_public $noderef
495
496	Tells the node to become a public node, i.e. reachable from other nodes.
497
498	The first argument is the (unresolved) node reference of the local node
499	(if missing then the empty string is used).
500
501	It is quite common to not specify anything, in which case the local node
502	tries to listen on the default port, or to only specify a port number, in
503	which case AnyEvent::MP tries to guess the local addresses.
504
505	=cut
506
507	=back
508
509	=head1 NODE MESSAGES
510
511	Nodes understand the following messages sent to them. Many of them take
512	arguments called C<@reply>, which will simply be used to compose a reply
513	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
514	the remaining arguments are simply the message data.
515
516	While other messages exist, they are not public and subject to change.
517
518	=over 4
519
520	=cut
521
522	=item lookup => $name, @reply
523
524	Replies with the port ID of the specified well-known port, or C<undef>.
525
526	=item devnull => ...
527
528	Generic data sink/CPU heat conversion.
529
530	=item relay => $port, @msg
531
532	Simply forwards the message to the given port.
533
534	=item eval => $string[ @reply]
535
536	Evaluates the given string. If C<@reply> is given, then a message of the
537	form C<@reply, $@, @evalres> is sent.
538
539	Example: crash another node.
540
541	snd $othernode, eval => "exit";
542
543	=item time => @reply
544
545	Replies the the current node time to C<@reply>.
546
547	Example: tell the current node to send the current time to C<$myport> in a
548	C<timereply> message.
549
550	snd $NODE, time => $myport, timereply => 1, 2;
551	# => snd $myport, timereply => 1, 2, <time>
552
553	=back
554
555	=head1 AnyEvent::MP vs. Distributed Erlang	686	=head1 AnyEvent::MP vs. Distributed Erlang
556		687
557	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	688	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	689	== 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	690	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
560	sample:	691	sample:
561		692
562	http://www.erlang.se/doc/programming_rules.shtml	693	http://www.Erlang.se/doc/programming_rules.shtml
563	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	694	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	695	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	696	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
566		697
567	Despite the similarities, there are also some important differences:	698	Despite the similarities, there are also some important differences:
568		699
569	=over 4	700	=over 4
570		701
…		…
575	convenience functionality.	706	convenience functionality.
576		707
577	This means that AEMP requires a less tightly controlled environment at the	708	This means that AEMP requires a less tightly controlled environment at the
578	cost of longer node references and a slightly higher management overhead.	709	cost of longer node references and a slightly higher management overhead.
579		710
		711	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		712	uses "local ports are like remote ports".
		713
		714	The failure modes for local ports are quite different (runtime errors
		715	only) then for remote ports - when a local port dies, you I<know> it dies,
		716	when a connection to another node dies, you know nothing about the other
		717	port.
		718
		719	Erlang pretends remote ports are as reliable as local ports, even when
		720	they are not.
		721
		722	AEMP encourages a "treat remote ports differently" philosophy, with local
		723	ports being the special case/exception, where transport errors cannot
		724	occur.
		725
580	=item * Erlang uses processes and a mailbox, AEMP does not queue.	726	=item * Erlang uses processes and a mailbox, AEMP does not queue.
581		727
582	Erlang uses processes that selctively receive messages, and therefore	728	Erlang uses processes that selectively receive messages, and therefore
583	needs a queue. AEMP is event based, queuing messages would serve no useful	729	needs a queue. AEMP is event based, queuing messages would serve no
584	purpose.	730	useful purpose. For the same reason the pattern-matching abilities of
		731	AnyEvent::MP are more limited, as there is little need to be able to
		732	filter messages without dequeing them.
585		733
586	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	734	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
587		735
588	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	736	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
589		737
590	Sending messages in erlang is synchronous and blocks the process. AEMP	738	Sending messages in Erlang is synchronous and blocks the process (and
591	sends are immediate, connection establishment is handled in the	739	so does not need a queue that can overflow). AEMP sends are immediate,
592	background.	740	connection establishment is handled in the background.
593		741
594	=item * Erlang can silently lose messages, AEMP cannot.	742	=item * Erlang suffers from silent message loss, AEMP does not.
595		743
596	Erlang makes few guarantees on messages delivery - messages can get lost	744	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,	745	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).	746	and c, and the other side only receives messages a and c).
599		747
600	AEMP guarantees correct ordering, and the guarantee that there are no	748	AEMP guarantees correct ordering, and the guarantee that there are no
601	holes in the message sequence.	749	holes in the message sequence.
602		750
603	=item * In erlang, processes can be declared dead and later be found to be	751	=item * In Erlang, processes can be declared dead and later be found to be
604	alive.	752	alive.
605		753
606	In erlang it can happen that a monitored process is declared dead and	754	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	755	linked processes get killed, but later it turns out that the process is
608	still alive - and can receive messages.	756	still alive - and can receive messages.
609		757
610	In AEMP, when port monitoring detects a port as dead, then that port will	758	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	759	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.	760	and then later sends messages to it, finding it is still alive.
613		761
614	=item * Erlang can send messages to the wrong port, AEMP does not.	762	=item * Erlang can send messages to the wrong port, AEMP does not.
615		763
616	In erlang it is quite possible that a node that restarts reuses a process	764	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	765	known to other nodes for a completely different process, causing messages
618	messages destined for that process to end up in an unrelated process.	766	destined for that process to end up in an unrelated process.
619		767
620	AEMP never reuses port IDs, so old messages or old port IDs floating	768	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.	769	around in the network will not be sent to an unrelated port.
622		770
623	=item * Erlang uses unprotected connections, AEMP uses secure	771	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
627	securely authenticate nodes.	775	securely authenticate nodes.
628		776
629	=item * The AEMP protocol is optimised for both text-based and binary	777	=item * The AEMP protocol is optimised for both text-based and binary
630	communications.	778	communications.
631		779
632	The AEMP protocol, unlike the erlang protocol, supports both	780	The AEMP protocol, unlike the Erlang protocol, supports both
633	language-independent text-only protocols (good for debugging) and binary,	781	language-independent text-only protocols (good for debugging) and binary,
634	language-specific serialisers (e.g. Storable).	782	language-specific serialisers (e.g. Storable).
635		783
636	It has also been carefully designed to be implementable in other languages	784	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	785	with a minimum of work while gracefully degrading fucntionality to make the
638	protocol simple.	786	protocol simple.
639		787
		788	=item * AEMP has more flexible monitoring options than Erlang.
		789
		790	In Erlang, you can chose to receive I<all> exit signals as messages
		791	or I<none>, there is no in-between, so monitoring single processes is
		792	difficult to implement. Monitoring in AEMP is more flexible than in
		793	Erlang, as one can choose between automatic kill, exit message or callback
		794	on a per-process basis.
		795
		796	=item * Erlang tries to hide remote/local connections, AEMP does not.
		797
		798	Monitoring in Erlang is not an indicator of process death/crashes,
		799	as linking is (except linking is unreliable in Erlang).
		800
		801	In AEMP, you don't "look up" registered port names or send to named ports
		802	that might or might not be persistent. Instead, you normally spawn a port
		803	on the remote node. The init function monitors the you, and you monitor
		804	the remote port. Since both monitors are local to the node, they are much
		805	more reliable.
		806
		807	This also saves round-trips and avoids sending messages to the wrong port
		808	(hard to do in Erlang).
		809
		810	=back
		811
		812	=head1 RATIONALE
		813
		814	=over 4
		815
		816	=item Why strings for ports and noderefs, why not objects?
		817
		818	We considered "objects", but found that the actual number of methods
		819	thatc an be called are very low. Since port IDs and noderefs travel over
		820	the network frequently, the serialising/deserialising would add lots of
		821	overhead, as well as having to keep a proxy object.
		822
		823	Strings can easily be printed, easily serialised etc. and need no special
		824	procedures to be "valid".
		825
		826	And a a miniport consists of a single closure stored in a global hash - it
		827	can't become much cheaper.
		828
		829	=item Why favour JSON, why not real serialising format such as Storable?
		830
		831	In fact, any AnyEvent::MP node will happily accept Storable as framing
		832	format, but currently there is no way to make a node use Storable by
		833	default.
		834
		835	The default framing protocol is JSON because a) JSON::XS is many times
		836	faster for small messages and b) most importantly, after years of
		837	experience we found that object serialisation is causing more problems
		838	than it gains: Just like function calls, objects simply do not travel
		839	easily over the network, mostly because they will always be a copy, so you
		840	always have to re-think your design.
		841
		842	Keeping your messages simple, concentrating on data structures rather than
		843	objects, will keep your messages clean, tidy and efficient.
		844
640	=back	845	=back
641		846
642	=head1 SEE ALSO	847	=head1 SEE ALSO
643		848
644	L<AnyEvent>.	849	L<AnyEvent>.

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Revision 1.57 by root, Sat Aug 15 04:34:34 2009 UTC