[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 1.52 by root, Fri Aug 14 15:13:20 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 $somple_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		46	AnyEvent::MP::Intro - outdated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
…		…
53		77
54	=item port id - C<noderef#portname>	78	=item port id - C<noderef#portname>
55		79
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
57	separator, and a port name (a printable string of unspecified format). An	81	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	82	exception is the the node port, whose ID is identical to its node
59	reference.	83	reference.
60		84
61	=item node	85	=item node
62		86
63	A node is a single process containing at least one port - the node	87	A node is a single process containing at least one port - the node
…		…
90		114
91	=cut	115	=cut
92		116
93	package AnyEvent::MP;	117	package AnyEvent::MP;
94		118
95	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
96		120
97	use common::sense;	121	use common::sense;
98		122
99	use Carp ();	123	use Carp ();
100		124
101	use AE ();	125	use AE ();
102		126
103	use base "Exporter";	127	use base "Exporter";
104		128
105	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
106	our @EXPORT = qw(	131	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
108	resolve_node	133	resolve_node initialise_node
109	become_slave become_public
110	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
111	port	135	port
112	);	136	);
113		137
114	our $SELF;	138	our $SELF;
115		139
…		…
119	kil $SELF, die => $msg;	143	kil $SELF, die => $msg;
120	}	144	}
121		145
122	=item $thisnode = NODE / $NODE	146	=item $thisnode = NODE / $NODE
123		147
124	The C<NODE> function returns, and the C<$NODE> variable contains	148	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	149	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	150	C<initialise_node>.
127	identifiers become invalid.
128		151
129	=item $noderef = node_of $portid	152	=item $noderef = node_of $port
130		153
131	Extracts and returns the noderef from a portid or a noderef.	154	Extracts and returns the noderef from a port ID or a noderef.
		155
		156	=item initialise_node $noderef, $seednode, $seednode...
		157
		158	=item initialise_node "slave/", $master, $master...
		159
		160	Before a node can talk to other nodes on the network it has to initialise
		161	itself - the minimum a node needs to know is it's own name, and optionally
		162	it should know the noderefs of some other nodes in the network.
		163
		164	This function initialises a node - it must be called exactly once (or
		165	never) before calling other AnyEvent::MP functions.
		166
		167	All arguments (optionally except for the first) are noderefs, which can be
		168	either resolved or unresolved.
		169
		170	The first argument will be looked up in the configuration database first
		171	(if it is C<undef> then the current nodename will be used instead) to find
		172	the relevant configuration profile (see L<aemp>). If none is found then
		173	the default configuration is used. The configuration supplies additional
		174	seed/master nodes and can override the actual noderef.
		175
		176	There are two types of networked nodes, public nodes and slave nodes:
		177
		178	=over 4
		179
		180	=item public nodes
		181
		182	For public nodes, C<$noderef> (supplied either directly to
		183	C<initialise_node> or indirectly via a profile or the nodename) must be a
		184	noderef (possibly unresolved, in which case it will be resolved).
		185
		186	After resolving, the node will bind itself on all endpoints and try to
		187	connect to all additional C<$seednodes> that are specified. Seednodes are
		188	optional and can be used to quickly bootstrap the node into an existing
		189	network.
		190
		191	=item slave nodes
		192
		193	When the C<$noderef> (either as given or overriden by the config file)
		194	is the special string C<slave/>, then the node will become a slave
		195	node. Slave nodes cannot be contacted from outside and will route most of
		196	their traffic to the master node that they attach to.
		197
		198	At least one additional noderef is required (either by specifying it
		199	directly or because it is part of the configuration profile): The node
		200	will try to connect to all of them and will become a slave attached to the
		201	first node it can successfully connect to.
		202
		203	=back
		204
		205	This function will block until all nodes have been resolved and, for slave
		206	nodes, until it has successfully established a connection to a master
		207	server.
		208
		209	Example: become a public node listening on the guessed noderef, or the one
		210	specified via C<aemp> for the current node. This should be the most common
		211	form of invocation for "daemon"-type nodes.
		212
		213	initialise_node;
		214
		215	Example: become a slave node to any of the the seednodes specified via
		216	C<aemp>. This form is often used for commandline clients.
		217
		218	initialise_node "slave/";
		219
		220	Example: become a slave node to any of the specified master servers. This
		221	form is also often used for commandline clients.
		222
		223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		224
		225	Example: become a public node, and try to contact some well-known master
		226	servers to become part of the network.
		227
		228	initialise_node undef, "master1", "master2";
		229
		230	Example: become a public node listening on port C<4041>.
		231
		232	initialise_node 4041;
		233
		234	Example: become a public node, only visible on localhost port 4044.
		235
		236	initialise_node "localhost:4044";
132		237
133	=item $cv = resolve_node $noderef	238	=item $cv = resolve_node $noderef
134		239
135	Takes an unresolved node reference that may contain hostnames and	240	Takes an unresolved node reference that may contain hostnames and
136	abbreviated IDs, resolves all of them and returns a resolved node	241	abbreviated IDs, resolves all of them and returns a resolved node
…		…
168		273
169	Due to some quirks in how perl exports variables, it is impossible to	274	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	275	just export C<$SELF>, all the symbols called C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	276	module, but only C<$SELF> is currently used.
172		277
173	=item snd $portid, type => @data	278	=item snd $port, type => @data
174		279
175	=item snd $portid, @msg	280	=item snd $port, @msg
176		281
177	Send the given message to the given port ID, which can identify either	282	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	283	a local or a remote port, and must be a port ID.
179	stringifies a sa port ID (such as a port object :).
180		284
181	While the message can be about anything, it is highly recommended to use a	285	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	286	string as first element (a port ID, or some word that indicates a request
183	type etc.).	287	type etc.).
184		288
185	The message data effectively becomes read-only after a call to this	289	The message data effectively becomes read-only after a call to this
186	function: modifying any argument is not allowed and can cause many	290	function: modifying any argument is not allowed and can cause many
187	problems.	291	problems.
…		…
190	JSON is used, then only strings, numbers and arrays and hashes consisting	294	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	295	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	296	that Storable can serialise and deserialise is allowed, and for the local
193	node, anything can be passed.	297	node, anything can be passed.
194		298
195	=item kil $portid[, @reason]	299	=item $local_port = port
196		300
197	Kill the specified port with the given C<@reason>.	301	Create a new local port object and returns its port ID. Initially it has
		302	no callbacks set and will throw an error when it receives messages.
198		303
199	If no C<@reason> is specified, then the port is killed "normally" (linked	304	=item $local_port = port { my @msg = @_ }
200	ports will not be kileld, or even notified).
201		305
202	Otherwise, linked ports get killed with the same reason (second form of	306	Creates a new local port, and returns its ID. Semantically the same as
203	C<mon>, see below).	307	creating a port and calling C<rcv $port, $callback> on it.
204		308
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	309	The block will be called for every message received on the port, with the
206	will be reported as reason C<< die => $@ >>.	310	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		311	port to be C<kil>ed. The message will be passed as-is, no extra argument
		312	(i.e. no port ID) will be passed to the callback.
207		313
208	Transport/communication errors are reported as C<< transport_error =>	314	If you want to stop/destroy the port, simply C<kil> it:
209	$message >>.
210		315
211	=item $guard = mon $portid, $cb->(@reason)	316	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, @_);	317	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	}	318	...
		319	kil $SELF;
260	}	320	};
261		321
262	$node->monitor ($port, $cb);	322	=cut
263		323
264	defined wantarray	324	sub rcv($@);
265	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	325
		326	sub _kilme {
		327	die "received message on port without callback";
266	}	328	}
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		329
326	sub port(;&) {	330	sub port(;&) {
327	my $id = "$UNIQ." . $ID++;	331	my $id = "$UNIQ." . $ID++;
328	my $port = "$NODE#$id";	332	my $port = "$NODE#$id";
329		333
330	if (@_) {	334	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		335
371	$port	336	$port
372	}	337	}
373		338
374	=item reg $portid, $name	339	=item rcv $local_port, $callback->(@msg)
375		340
376	Registers the given port under the name C<$name>. If the name already	341	Replaces the default callback on the specified port. There is no way to
377	exists it is replaced.	342	remove the default callback: use C<sub { }> to disable it, or better
		343	C<kil> the port when it is no longer needed.
378		344
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<$portid> while	345	The global C<$SELF> (exported by this module) contains C<$port> while
404	executing the callback.	346	executing the callback. Runtime errors during callback execution will
		347	result in the port being C<kil>ed.
405		348
406	Runtime errors wdurign callback execution will result in the port being	349	The default callback received all messages not matched by a more specific
407	C<kil>ed.	350	C<tag> match.
408		351
409	If the match is an array reference, then it will be matched against the	352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
410	first elements of the message, otherwise only the first element is being
411	matched.
412		353
413	Any element in the match that is specified as C<_any_> (a function	354	Register callbacks to be called on messages starting with the given tag on
414	exported by this module) matches any single element of the message.	355	the given port (and return the port), or unregister it (when C<$callback>
		356	is C<$undef>).
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 $otherport, reply =>
		373	rcv port,
		374	msg1 => sub { ... },
		375	...
		376	;
419		377
420	=cut	378	=cut
421		379
422	sub rcv($@) {	380	sub rcv($@) {
		381	my $port = shift;
423	my ($noderef, $port) = split /#/, shift, 2;	382	my ($noderef, $portid) = split /#/, $port, 2;
424		383
425	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
426	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";	385	or Carp::croak "$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#$port: rcv can only be called on message matching ports, caught";
433		386
434	while (@_) {	387	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;
436
437	if (!ref $match) {	388	if (ref $_[0]) {
438	push @{ $self->{rc0}{$match} }, [$cb];	389	if (my $self = $PORT_DATA{$portid}) {
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	390	"AnyEvent::MP::Port" eq ref $self
440	my ($type, @match) = @$match;	391	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441	@match	392
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	393	$self->[2] = shift;
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	394	} else {
445	push @{ $self->{any} }, [$cb, $match];	395	my $cb = shift;
		396	$PORT{$portid} = sub {
		397	local $SELF = $port;
		398	eval { &$cb }; _self_die if $@;
		399	};
		400	}
		401	} elsif (defined $_[0]) {
		402	my $self = $PORT_DATA{$portid} \|\|= do {
		403	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		404
		405	$PORT{$portid} = sub {
		406	local $SELF = $port;
		407
		408	if (my $cb = $self->[1]{$_[0]}) {
		409	shift;
		410	eval { &$cb }; _self_die if $@;
		411	} else {
		412	&{ $self->[0] };
		413	}
		414	};
		415
		416	$self
		417	};
		418
		419	"AnyEvent::MP::Port" eq ref $self
		420	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		421
		422	my ($tag, $cb) = splice @_, 0, 2;
		423
		424	if (defined $cb) {
		425	$self->[1]{$tag} = $cb;
		426	} else {
		427	delete $self->[1]{$tag};
		428	}
446	}	429	}
447	}	430	}
		431
		432	$port
448	}	433	}
449		434
450	=item $closure = psub { BLOCK }	435	=item $closure = psub { BLOCK }
451		436
452	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	437	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
483	$res	468	$res
484	}	469	}
485	}	470	}
486	}	471	}
487		472
488	=back	473	=item $guard = mon $port, $cb->(@reason)
489		474
490	=head1 FUNCTIONS FOR NODES	475	=item $guard = mon $port, $rcvport
491		476
492	=over 4	477	=item $guard = mon $port
493		478
494	=item become_public $noderef	479	=item $guard = mon $port, $rcvport, @msg
495		480
496	Tells the node to become a public node, i.e. reachable from other nodes.	481	Monitor the given port and do something when the port is killed or
		482	messages to it were lost, and optionally return a guard that can be used
		483	to stop monitoring again.
497		484
498	The first argument is the (unresolved) node reference of the local node	485	C<mon> effectively guarantees that, in the absence of hardware failures,
499	(if missing then the empty string is used).	486	that after starting the monitor, either all messages sent to the port
		487	will arrive, or the monitoring action will be invoked after possible
		488	message loss has been detected. No messages will be lost "in between"
		489	(after the first lost message no further messages will be received by the
		490	port). After the monitoring action was invoked, further messages might get
		491	delivered again.
500		492
501	It is quite common to not specify anything, in which case the local node	493	In the first form (callback), the callback is simply called with any
502	tries to listen on the default port, or to only specify a port number, in	494	number of C<@reason> elements (no @reason means that the port was deleted
503	which case AnyEvent::MP tries to guess the local addresses.	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
		496	C<eval> if unsure.
504		497
		498	In the second form (another port given), the other port (C<$rcvport>)
		499	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		500	"normal" kils nothing happens, while under all other conditions, the other
		501	port is killed with the same reason.
		502
		503	The third form (kill self) is the same as the second form, except that
		504	C<$rvport> defaults to C<$SELF>.
		505
		506	In the last form (message), a message of the form C<@msg, @reason> will be
		507	C<snd>.
		508
		509	As a rule of thumb, monitoring requests should always monitor a port from
		510	a local port (or callback). The reason is that kill messages might get
		511	lost, just like any other message. Another less obvious reason is that
		512	even monitoring requests can get lost (for exmaple, when the connection
		513	to the other node goes down permanently). When monitoring a port locally
		514	these problems do not exist.
		515
		516	Example: call a given callback when C<$port> is killed.
		517
		518	mon $port, sub { warn "port died because of <@_>\n" };
		519
		520	Example: kill ourselves when C<$port> is killed abnormally.
		521
		522	mon $port;
		523
		524	Example: send us a restart message when another C<$port> is killed.
		525
		526	mon $port, $self => "restart";
		527
505	=cut	528	=cut
		529
		530	sub mon {
		531	my ($noderef, $port) = split /#/, shift, 2;
		532
		533	my $node = $NODE{$noderef} \|\| add_node $noderef;
		534
		535	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		536
		537	unless (ref $cb) {
		538	if (@_) {
		539	# send a kill info message
		540	my (@msg) = ($cb, @_);
		541	$cb = sub { snd @msg, @_ };
		542	} else {
		543	# simply kill other port
		544	my $port = $cb;
		545	$cb = sub { kil $port, @_ if @_ };
		546	}
		547	}
		548
		549	$node->monitor ($port, $cb);
		550
		551	defined wantarray
		552	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		553	}
		554
		555	=item $guard = mon_guard $port, $ref, $ref...
		556
		557	Monitors the given C<$port> and keeps the passed references. When the port
		558	is killed, the references will be freed.
		559
		560	Optionally returns a guard that will stop the monitoring.
		561
		562	This function is useful when you create e.g. timers or other watchers and
		563	want to free them when the port gets killed:
		564
		565	$port->rcv (start => sub {
		566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		567	undef $timer if 0.9 < rand;
		568	});
		569	});
		570
		571	=cut
		572
		573	sub mon_guard {
		574	my ($port, @refs) = @_;
		575
		576	#TODO: mon-less form?
		577
		578	mon $port, sub { 0 && @refs }
		579	}
		580
		581	=item kil $port[, @reason]
		582
		583	Kill the specified port with the given C<@reason>.
		584
		585	If no C<@reason> is specified, then the port is killed "normally" (linked
		586	ports will not be kileld, or even notified).
		587
		588	Otherwise, linked ports get killed with the same reason (second form of
		589	C<mon>, see below).
		590
		591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		592	will be reported as reason C<< die => $@ >>.
		593
		594	Transport/communication errors are reported as C<< transport_error =>
		595	$message >>.
		596
		597	=cut
		598
		599	=item $port = spawn $node, $initfunc[, @initdata]
		600
		601	Creates a port on the node C<$node> (which can also be a port ID, in which
		602	case it's the node where that port resides).
		603
		604	The port ID of the newly created port is return immediately, and it is
		605	permissible to immediately start sending messages or monitor the port.
		606
		607	After the port has been created, the init function is
		608	called. This function must be a fully-qualified function name
		609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		610	program, use C<::name>.
		611
		612	If the function doesn't exist, then the node tries to C<require>
		613	the package, then the package above the package and so on (e.g.
		614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		615	exists or it runs out of package names.
		616
		617	The init function is then called with the newly-created port as context
		618	object (C<$SELF>) and the C<@initdata> values as arguments.
		619
		620	A common idiom is to pass your own port, monitor the spawned port, and
		621	in the init function, monitor the original port. This two-way monitoring
		622	ensures that both ports get cleaned up when there is a problem.
		623
		624	Example: spawn a chat server port on C<$othernode>.
		625
		626	# this node, executed from within a port context:
		627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		628	mon $server;
		629
		630	# init function on C<$othernode>
		631	sub connect {
		632	my ($srcport) = @_;
		633
		634	mon $srcport;
		635
		636	rcv $SELF, sub {
		637	...
		638	};
		639	}
		640
		641	=cut
		642
		643	sub _spawn {
		644	my $port = shift;
		645	my $init = shift;
		646
		647	local $SELF = "$NODE#$port";
		648	eval {
		649	&{ load_func $init }
		650	};
		651	_self_die if $@;
		652	}
		653
		654	sub spawn(@) {
		655	my ($noderef, undef) = split /#/, shift, 2;
		656
		657	my $id = "$RUNIQ." . $ID++;
		658
		659	$_[0] =~ /::/
		660	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		661
		662	($NODE{$noderef} \|\| add_node $noderef)
		663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		664
		665	"$noderef#$id"
		666	}
506		667
507	=back	668	=back
508		669
509	=head1 NODE MESSAGES	670	=head1 NODE MESSAGES
510		671
…		…
552		713
553	=back	714	=back
554		715
555	=head1 AnyEvent::MP vs. Distributed Erlang	716	=head1 AnyEvent::MP vs. Distributed Erlang
556		717
557	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	718	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	719	== 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	720	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
560	sample:	721	sample:
561		722
562	http://www.erlang.se/doc/programming_rules.shtml	723	http://www.Erlang.se/doc/programming_rules.shtml
563	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	724	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	725	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	726	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
566		727
567	Despite the similarities, there are also some important differences:	728	Despite the similarities, there are also some important differences:
568		729
569	=over 4	730	=over 4
570		731
…		…
575	convenience functionality.	736	convenience functionality.
576		737
577	This means that AEMP requires a less tightly controlled environment at the	738	This means that AEMP requires a less tightly controlled environment at the
578	cost of longer node references and a slightly higher management overhead.	739	cost of longer node references and a slightly higher management overhead.
579		740
		741	=item Erlang has a "remote ports are like local ports" philosophy, AEMP
		742	uses "local ports are like remote ports".
		743
		744	The failure modes for local ports are quite different (runtime errors
		745	only) then for remote ports - when a local port dies, you I<know> it dies,
		746	when a connection to another node dies, you know nothing about the other
		747	port.
		748
		749	Erlang pretends remote ports are as reliable as local ports, even when
		750	they are not.
		751
		752	AEMP encourages a "treat remote ports differently" philosophy, with local
		753	ports being the special case/exception, where transport errors cannot
		754	occur.
		755
580	=item * Erlang uses processes and a mailbox, AEMP does not queue.	756	=item * Erlang uses processes and a mailbox, AEMP does not queue.
581		757
582	Erlang uses processes that selctively receive messages, and therefore	758	Erlang uses processes that selectively receive messages, and therefore
583	needs a queue. AEMP is event based, queuing messages would serve no useful	759	needs a queue. AEMP is event based, queuing messages would serve no
584	purpose.	760	useful purpose. For the same reason the pattern-matching abilities of
		761	AnyEvent::MP are more limited, as there is little need to be able to
		762	filter messages without dequeing them.
585		763
586	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	764	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
587		765
588	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
589		767
590	Sending messages in erlang is synchronous and blocks the process. AEMP	768	Sending messages in Erlang is synchronous and blocks the process (and
591	sends are immediate, connection establishment is handled in the	769	so does not need a queue that can overflow). AEMP sends are immediate,
592	background.	770	connection establishment is handled in the background.
593		771
594	=item * Erlang can silently lose messages, AEMP cannot.	772	=item * Erlang suffers from silent message loss, AEMP does not.
595		773
596	Erlang makes few guarantees on messages delivery - messages can get lost	774	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,	775	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).	776	and c, and the other side only receives messages a and c).
599		777
600	AEMP guarantees correct ordering, and the guarantee that there are no	778	AEMP guarantees correct ordering, and the guarantee that there are no
601	holes in the message sequence.	779	holes in the message sequence.
602		780
603	=item * In erlang, processes can be declared dead and later be found to be	781	=item * In Erlang, processes can be declared dead and later be found to be
604	alive.	782	alive.
605		783
606	In erlang it can happen that a monitored process is declared dead and	784	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	785	linked processes get killed, but later it turns out that the process is
608	still alive - and can receive messages.	786	still alive - and can receive messages.
609		787
610	In AEMP, when port monitoring detects a port as dead, then that port will	788	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	789	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.	790	and then later sends messages to it, finding it is still alive.
613		791
614	=item * Erlang can send messages to the wrong port, AEMP does not.	792	=item * Erlang can send messages to the wrong port, AEMP does not.
615		793
616	In erlang it is quite possible that a node that restarts reuses a process	794	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	795	known to other nodes for a completely different process, causing messages
618	messages destined for that process to end up in an unrelated process.	796	destined for that process to end up in an unrelated process.
619		797
620	AEMP never reuses port IDs, so old messages or old port IDs floating	798	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.	799	around in the network will not be sent to an unrelated port.
622		800
623	=item * Erlang uses unprotected connections, AEMP uses secure	801	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
627	securely authenticate nodes.	805	securely authenticate nodes.
628		806
629	=item * The AEMP protocol is optimised for both text-based and binary	807	=item * The AEMP protocol is optimised for both text-based and binary
630	communications.	808	communications.
631		809
632	The AEMP protocol, unlike the erlang protocol, supports both	810	The AEMP protocol, unlike the Erlang protocol, supports both
633	language-independent text-only protocols (good for debugging) and binary,	811	language-independent text-only protocols (good for debugging) and binary,
634	language-specific serialisers (e.g. Storable).	812	language-specific serialisers (e.g. Storable).
635		813
636	It has also been carefully designed to be implementable in other languages	814	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	815	with a minimum of work while gracefully degrading fucntionality to make the
638	protocol simple.	816	protocol simple.
639		817
		818	=item * AEMP has more flexible monitoring options than Erlang.
		819
		820	In Erlang, you can chose to receive I<all> exit signals as messages
		821	or I<none>, there is no in-between, so monitoring single processes is
		822	difficult to implement. Monitoring in AEMP is more flexible than in
		823	Erlang, as one can choose between automatic kill, exit message or callback
		824	on a per-process basis.
		825
		826	=item * Erlang tries to hide remote/local connections, AEMP does not.
		827
		828	Monitoring in Erlang is not an indicator of process death/crashes,
		829	as linking is (except linking is unreliable in Erlang).
		830
		831	In AEMP, you don't "look up" registered port names or send to named ports
		832	that might or might not be persistent. Instead, you normally spawn a port
		833	on the remote node. The init function monitors the you, and you monitor
		834	the remote port. Since both monitors are local to the node, they are much
		835	more reliable.
		836
		837	This also saves round-trips and avoids sending messages to the wrong port
		838	(hard to do in Erlang).
		839
		840	=back
		841
		842	=head1 RATIONALE
		843
		844	=over 4
		845
		846	=item Why strings for ports and noderefs, why not objects?
		847
		848	We considered "objects", but found that the actual number of methods
		849	thatc an be called are very low. Since port IDs and noderefs travel over
		850	the network frequently, the serialising/deserialising would add lots of
		851	overhead, as well as having to keep a proxy object.
		852
		853	Strings can easily be printed, easily serialised etc. and need no special
		854	procedures to be "valid".
		855
		856	And a a miniport consists of a single closure stored in a global hash - it
		857	can't become much cheaper.
		858
		859	=item Why favour JSON, why not real serialising format such as Storable?
		860
		861	In fact, any AnyEvent::MP node will happily accept Storable as framing
		862	format, but currently there is no way to make a node use Storable by
		863	default.
		864
		865	The default framing protocol is JSON because a) JSON::XS is many times
		866	faster for small messages and b) most importantly, after years of
		867	experience we found that object serialisation is causing more problems
		868	than it gains: Just like function calls, objects simply do not travel
		869	easily over the network, mostly because they will always be a copy, so you
		870	always have to re-think your design.
		871
		872	Keeping your messages simple, concentrating on data structures rather than
		873	objects, will keep your messages clean, tidy and efficient.
		874
640	=back	875	=back
641		876
642	=head1 SEE ALSO	877	=head1 SEE ALSO
643		878
644	L<AnyEvent>.	879	L<AnyEvent>.

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Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC