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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.35 by root, Thu Aug 6 10:21:48 2009 UTC vs.
Revision 1.52 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
27
28	# linking two ports, so they both crash together
29	lnk $port1, $port2;
30		37
31	# monitoring	38	# monitoring
32	mon $port, $cb->(@msg) # callback is invoked on death	39	mon $port, $cb->(@msg) # callback is invoked on death
33	mon $port, $otherport # kill otherport on abnormal death	40	mon $port, $otherport # kill otherport on abnormal death
34	mon $port, $otherport, @msg # send message on death	41	mon $port, $otherport, @msg # send message on death
35		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
		51
36	=head1 DESCRIPTION	52	=head1 DESCRIPTION
37		53
38	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
39		55
40	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
…		…
43	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
44	manual page.	60	manual page.
45		61
46	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
47	so do not use. This was uploaded mainly to reserve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
48	stay tuned! The basic API should be finished, however.	64	stay tuned!
49		65
50	=head1 CONCEPTS	66	=head1 CONCEPTS
51		67
52	=over 4	68	=over 4
53		69
…		…
98		114
99	=cut	115	=cut
100		116
101	package AnyEvent::MP;	117	package AnyEvent::MP;
102		118
103	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
104		120
105	use common::sense;	121	use common::sense;
106		122
107	use Carp ();	123	use Carp ();
108		124
109	use AE ();	125	use AE ();
110		126
111	use base "Exporter";	127	use base "Exporter";
112		128
113	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
114	our @EXPORT = qw(	131	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
116	resolve_node initialise_node	133	resolve_node initialise_node
117	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
118	port	135	port
119	);	136	);
120		137
121	our $SELF;	138	our $SELF;
122		139
…		…
126	kil $SELF, die => $msg;	143	kil $SELF, die => $msg;
127	}	144	}
128		145
129	=item $thisnode = NODE / $NODE	146	=item $thisnode = NODE / $NODE
130		147
131	The C<NODE> function returns, and the C<$NODE> variable contains	148	The C<NODE> function returns, and the C<$NODE> variable contains the
132	the noderef of the local node. The value is initialised by a call	149	noderef of the local node. The value is initialised by a call to
133	to C<become_public> or C<become_slave>, after which all local port	150	C<initialise_node>.
134	identifiers become invalid.
135		151
136	=item $noderef = node_of $port	152	=item $noderef = node_of $port
137		153
138	Extracts and returns the noderef from a portid or a noderef.	154	Extracts and returns the noderef from a port ID or a noderef.
139		155
140	=item initialise_node $noderef, $seednode, $seednode...	156	=item initialise_node $noderef, $seednode, $seednode...
141		157
142	=item initialise_node "slave/", $master, $master...	158	=item initialise_node "slave/", $master, $master...
143		159
…		…
146	it should know the noderefs of some other nodes in the network.	162	it should know the noderefs of some other nodes in the network.
147		163
148	This function initialises a node - it must be called exactly once (or	164	This function initialises a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	165	never) before calling other AnyEvent::MP functions.
150		166
151	All arguments are noderefs, which can be either resolved or unresolved.	167	All arguments (optionally except for the first) are noderefs, which can be
		168	either resolved or unresolved.
		169
		170	The first argument will be looked up in the configuration database first
		171	(if it is C<undef> then the current nodename will be used instead) to find
		172	the relevant configuration profile (see L<aemp>). If none is found then
		173	the default configuration is used. The configuration supplies additional
		174	seed/master nodes and can override the actual noderef.
152		175
153	There are two types of networked nodes, public nodes and slave nodes:	176	There are two types of networked nodes, public nodes and slave nodes:
154		177
155	=over 4	178	=over 4
156		179
157	=item public nodes	180	=item public nodes
158		181
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	182	For public nodes, C<$noderef> (supplied either directly to
160	noderef, in which case it will be resolved, or C<undef> (or missing), in	183	C<initialise_node> or indirectly via a profile or the nodename) must be a
161	which case the noderef will be guessed.	184	noderef (possibly unresolved, in which case it will be resolved).
162		185
163	Afterwards, the node will bind itself on all endpoints and try to connect	186	After resolving, the node will bind itself on all endpoints and try to
164	to all additional C<$seednodes> that are specified. Seednodes are optional	187	connect to all additional C<$seednodes> that are specified. Seednodes are
165	and can be used to quickly bootstrap the node into an existing network.	188	optional and can be used to quickly bootstrap the node into an existing
		189	network.
166		190
167	=item slave nodes	191	=item slave nodes
168		192
169	When the C<$noderef> is the special string C<slave/>, then the node will	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
170	become a slave node. Slave nodes cannot be contacted from outside and will	195	node. Slave nodes cannot be contacted from outside and will route most of
171	route most of their traffic to the master node that they attach to.	196	their traffic to the master node that they attach to.
172		197
173	At least one additional noderef is required: The node will try to connect	198	At least one additional noderef is required (either by specifying it
174	to all of them and will become a slave attached to the first node it can	199	directly or because it is part of the configuration profile): The node
175	successfully connect to.	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.
176		202
177	=back	203	=back
178		204
179	This function will block until all nodes have been resolved and, for slave	205	This function will block until all nodes have been resolved and, for slave
180	nodes, until it has successfully established a connection to a master	206	nodes, until it has successfully established a connection to a master
181	server.	207	server.
182		208
183	Example: become a public node listening on the default node.	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.
184		212
185	initialise_node;	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";
186		224
187	Example: become a public node, and try to contact some well-known master	225	Example: become a public node, and try to contact some well-known master
188	servers to become part of the network.	226	servers to become part of the network.
189		227
190	initialise_node undef, "master1", "master2";	228	initialise_node undef, "master1", "master2";
…		…
193		231
194	initialise_node 4041;	232	initialise_node 4041;
195		233
196	Example: become a public node, only visible on localhost port 4044.	234	Example: become a public node, only visible on localhost port 4044.
197		235
198	initialise_node "locahost:4044";	236	initialise_node "localhost:4044";
199
200	Example: become a slave node to any of the specified master servers.
201
202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
203		237
204	=item $cv = resolve_node $noderef	238	=item $cv = resolve_node $noderef
205		239
206	Takes an unresolved node reference that may contain hostnames and	240	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node	241	abbreviated IDs, resolves all of them and returns a resolved node
…		…
244	=item snd $port, type => @data	278	=item snd $port, type => @data
245		279
246	=item snd $port, @msg	280	=item snd $port, @msg
247		281
248	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
249	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.
250	stringifies a sa port ID (such as a port object :).
251		284
252	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
253	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
254	type etc.).	287	type etc.).
255		288
256	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
257	function: modifying any argument is not allowed and can cause many	290	function: modifying any argument is not allowed and can cause many
258	problems.	291	problems.
…		…
263	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
264	node, anything can be passed.	297	node, anything can be passed.
265		298
266	=item $local_port = port	299	=item $local_port = port
267		300
268	Create a new local port object that can be used either as a pattern	301	Create a new local port object and returns its port ID. Initially it has
269	matching port ("full port") or a single-callback port ("miniport"),	302	no callbacks set and will throw an error when it receives messages.
270	depending on how C<rcv> callbacks are bound to the object.
271		303
272	=item $port = port { my @msg = @_; $finished }	304	=item $local_port = port { my @msg = @_ }
273		305
274	Creates a "miniport", that is, a very lightweight port without any pattern	306	Creates a new local port, and returns its ID. Semantically the same as
275	matching behind it, and returns its ID. Semantically the same as creating
276	a port and calling C<rcv $port, $callback> on it.	307	creating a port and calling C<rcv $port, $callback> on it.
277		308
278	The block will be called for every message received on the port. When the	309	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	310	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	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.
281		313
282	The message will be passed as-is, no extra argument (i.e. no port id) will	314	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		315
285	If you need the local port id in the callback, this works nicely:	316	my $port = port {
286		317	my @msg = @_;
287	my $port; $port = port {	318	...
288	snd $otherport, reply => $port;	319	kil $SELF;
289	};	320	};
290		321
291	=cut	322	=cut
292		323
293	sub rcv($@);	324	sub rcv($@);
		325
		326	sub _kilme {
		327	die "received message on port without callback";
		328	}
294		329
295	sub port(;&) {	330	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	331	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	332	my $port = "$NODE#$id";
298		333
299	if (@_) {	334	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		335
305	$port	336	$port
306	}	337	}
307		338
308	=item reg $port, $name
309
310	Registers the given port under the name C<$name>. If the name already
311	exists it is replaced.
312
313	A port can only be registered under one well known name.
314
315	A port automatically becomes unregistered when it is killed.
316
317	=cut
318
319	sub reg(@) {
320	my ($port, $name) = @_;
321
322	$REG{$name} = $port;
323	}
324
325	=item rcv $port, $callback->(@msg)	339	=item rcv $local_port, $callback->(@msg)
326		340
327	Replaces the callback on the specified miniport (after converting it to	341	Replaces the default callback on the specified port. There is no way to
328	one if required).	342	remove the default callback: use C<sub { }> to disable it, or better
329		343	C<kil> the port when it is no longer needed.
330	=item rcv $port, tagstring => $callback->(@msg), ...
331
332	=item rcv $port, $smartmatch => $callback->(@msg), ...
333
334	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
335
336	Register callbacks to be called on matching messages on the given full
337	port (after converting it to one if required).
338
339	The callback has to return a true value when its work is done, after
340	which is will be removed, or a false value in which case it will stay
341	registered.
342		344
343	The global C<$SELF> (exported by this module) contains C<$port> while	345	The global C<$SELF> (exported by this module) contains C<$port> while
344	executing the callback.	346	executing the callback. Runtime errors during callback execution will
		347	result in the port being C<kil>ed.
345		348
346	Runtime errors wdurign callback execution will result in the port being	349	The default callback received all messages not matched by a more specific
347	C<kil>ed.	350	C<tag> match.
348		351
349	If the match is an array reference, then it will be matched against the	352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
350	first elements of the message, otherwise only the first element is being
351	matched.
352		353
353	Any element in the match that is specified as C<_any_> (a function	354	Register callbacks to be called on messages starting with the given tag on
354	exported by this module) matches any single element of the message.	355	the given port (and return the port), or unregister it (when C<$callback>
		356	is C<$undef>).
355		357
356	While not required, it is highly recommended that the first matching	358	The original message will be passed to the callback, after the first
357	element is a string identifying the message. The one-string-only match is	359	element (the tag) has been removed. The callback will use the same
358	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 $otherport, reply =>
		373	rcv port,
		374	msg1 => sub { ... },
		375	...
		376	;
359		377
360	=cut	378	=cut
361		379
362	sub rcv($@) {	380	sub rcv($@) {
363	my $port = shift;	381	my $port = shift;
364	my ($noderef, $portid) = split /#/, $port, 2;	382	my ($noderef, $portid) = split /#/, $port, 2;
365		383
366	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
367	or Carp::croak "$port: rcv can only be called on local ports, caught";	385	or Carp::croak "$port: rcv can only be called on local ports, caught";
368		386
369	if (@_ == 1) {	387	while (@_) {
		388	if (ref $_[0]) {
		389	if (my $self = $PORT_DATA{$portid}) {
		390	"AnyEvent::MP::Port" eq ref $self
		391	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		392
		393	$self->[2] = shift;
		394	} else {
370	my $cb = shift;	395	my $cb = shift;
371	delete $PORT_DATA{$portid};
372	$PORT{$portid} = sub {	396	$PORT{$portid} = sub {
373	local $SELF = $port;	397	local $SELF = $port;
374	eval {	398	eval { &$cb }; _self_die if $@;
375	&$cb	399	};
376	and kil $port;
377	};	400	}
378	_self_die if $@;	401	} elsif (defined $_[0]) {
379	};
380	} else {
381	my $self = $PORT_DATA{$portid} \|\|= do {	402	my $self = $PORT_DATA{$portid} \|\|= do {
382	my $self = bless {	403	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
383	id => $port,
384	}, "AnyEvent::MP::Port";
385		404
386	$PORT{$portid} = sub {	405	$PORT{$portid} = sub {
387	local $SELF = $port;	406	local $SELF = $port;
388		407
389	eval {
390	for (@{ $self->{rc0}{$_[0]} }) {	408	if (my $cb = $self->[1]{$_[0]}) {
391	$_ && &{$_->[0]}	409	shift;
392	&& undef $_;	410	eval { &$cb }; _self_die if $@;
393	}	411	} else {
394
395	for (@{ $self->{rcv}{$_[0]} }) {
396	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
397	&& &{$_->[0]}	412	&{ $self->[0] };
398	&& undef $_;
399	}
400
401	for (@{ $self->{any} }) {
402	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
403	&& &{$_->[0]}
404	&& undef $_;
405	}	413	}
406	};	414	};
407	_self_die if $@;	415
		416	$self
408	};	417	};
409		418
410	$self
411	};
412
413	"AnyEvent::MP::Port" eq ref $self	419	"AnyEvent::MP::Port" eq ref $self
414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	420	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
415		421
416	while (@_) {
417	my ($match, $cb) = splice @_, 0, 2;	422	my ($tag, $cb) = splice @_, 0, 2;
418		423
419	if (!ref $match) {	424	if (defined $cb) {
420	push @{ $self->{rc0}{$match} }, [$cb];	425	$self->[1]{$tag} = $cb;
421	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
422	my ($type, @match) = @$match;
423	@match
424	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
425	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
426	} else {	426	} else {
427	push @{ $self->{any} }, [$cb, $match];	427	delete $self->[1]{$tag};
428	}	428	}
429	}	429	}
430	}	430	}
431		431
432	$port	432	$port
…		…
470	}	470	}
471	}	471	}
472		472
473	=item $guard = mon $port, $cb->(@reason)	473	=item $guard = mon $port, $cb->(@reason)
474		474
475	=item $guard = mon $port, $otherport	475	=item $guard = mon $port, $rcvport
476		476
		477	=item $guard = mon $port
		478
477	=item $guard = mon $port, $otherport, @msg	479	=item $guard = mon $port, $rcvport, @msg
478		480
479	Monitor the given port and do something when the port is killed.	481	Monitor the given port and do something when the port is killed or
		482	messages to it were lost, and optionally return a guard that can be used
		483	to stop monitoring again.
480		484
		485	C<mon> effectively guarantees that, in the absence of hardware failures,
		486	that after starting the monitor, either all messages sent to the port
		487	will arrive, or the monitoring action will be invoked after possible
		488	message loss has been detected. No messages will be lost "in between"
		489	(after the first lost message no further messages will be received by the
		490	port). After the monitoring action was invoked, further messages might get
		491	delivered again.
		492
481	In the first form, the callback is simply called with any number	493	In the first form (callback), the callback is simply called with any
482	of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
483	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
484	C<eval> if unsure.	496	C<eval> if unsure.
485		497
486	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	498	In the second form (another port given), the other port (C<$rcvport>)
487	a @reason was specified, i.e. on "normal" kils nothing happens, while	499	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
488	under all other conditions, the other port is killed with the same reason.	500	"normal" kils nothing happens, while under all other conditions, the other
		501	port is killed with the same reason.
489		502
		503	The third form (kill self) is the same as the second form, except that
		504	C<$rvport> defaults to C<$SELF>.
		505
490	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	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.
491		515
492	Example: call a given callback when C<$port> is killed.	516	Example: call a given callback when C<$port> is killed.
493		517
494	mon $port, sub { warn "port died because of <@_>\n" };	518	mon $port, sub { warn "port died because of <@_>\n" };
495		519
496	Example: kill ourselves when C<$port> is killed abnormally.	520	Example: kill ourselves when C<$port> is killed abnormally.
497		521
498	mon $port, $self;	522	mon $port;
499		523
500	Example: send us a restart message another C<$port> is killed.	524	Example: send us a restart message when another C<$port> is killed.
501		525
502	mon $port, $self => "restart";	526	mon $port, $self => "restart";
503		527
504	=cut	528	=cut
505		529
506	sub mon {	530	sub mon {
507	my ($noderef, $port) = split /#/, shift, 2;	531	my ($noderef, $port) = split /#/, shift, 2;
508		532
509	my $node = $NODE{$noderef} \|\| add_node $noderef;	533	my $node = $NODE{$noderef} \|\| add_node $noderef;
510		534
511	my $cb = shift;	535	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
512		536
513	unless (ref $cb) {	537	unless (ref $cb) {
514	if (@_) {	538	if (@_) {
515	# send a kill info message	539	# send a kill info message
516	my (@msg) = ($cb, @_);	540	my (@msg) = ($cb, @_);
…		…
547	=cut	571	=cut
548		572
549	sub mon_guard {	573	sub mon_guard {
550	my ($port, @refs) = @_;	574	my ($port, @refs) = @_;
551		575
		576	#TODO: mon-less form?
		577
552	mon $port, sub { 0 && @refs }	578	mon $port, sub { 0 && @refs }
553	}	579	}
554		580
555	=item lnk $port1, $port2
556
557	Link two ports. This is simply a shorthand for:
558
559	mon $port1, $port2;
560	mon $port2, $port1;
561
562	It means that if either one is killed abnormally, the other one gets
563	killed as well.
564
565	=item kil $port[, @reason]	581	=item kil $port[, @reason]
566		582
567	Kill the specified port with the given C<@reason>.	583	Kill the specified port with the given C<@reason>.
568		584
569	If no C<@reason> is specified, then the port is killed "normally" (linked	585	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
575	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
576	will be reported as reason C<< die => $@ >>.	592	will be reported as reason C<< die => $@ >>.
577		593
578	Transport/communication errors are reported as C<< transport_error =>	594	Transport/communication errors are reported as C<< transport_error =>
579	$message >>.	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	}
580		667
581	=back	668	=back
582		669
583	=head1 NODE MESSAGES	670	=head1 NODE MESSAGES
584		671
…		…
649	convenience functionality.	736	convenience functionality.
650		737
651	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
652	cost of longer node references and a slightly higher management overhead.	739	cost of longer node references and a slightly higher management overhead.
653		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
654	=item * Erlang uses processes and a mailbox, AEMP does not queue.	756	=item * Erlang uses processes and a mailbox, AEMP does not queue.
655		757
656	Erlang uses processes that selctively receive messages, and therefore	758	Erlang uses processes that selectively receive messages, and therefore
657	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
658	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.
659		763
660	(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).
661		765
662	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
663		767
664	Sending messages in Erlang is synchronous and blocks the process. AEMP	768	Sending messages in Erlang is synchronous and blocks the process (and
665	sends are immediate, connection establishment is handled in the	769	so does not need a queue that can overflow). AEMP sends are immediate,
666	background.	770	connection establishment is handled in the background.
667		771
668	=item * Erlang can silently lose messages, AEMP cannot.	772	=item * Erlang suffers from silent message loss, AEMP does not.
669		773
670	Erlang makes few guarantees on messages delivery - messages can get lost	774	Erlang makes few guarantees on messages delivery - messages can get lost
671	without any of the processes realising it (i.e. you send messages a, b,	775	without any of the processes realising it (i.e. you send messages a, b,
672	and c, and the other side only receives messages a and c).	776	and c, and the other side only receives messages a and c).
673		777
…		…
685	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
686	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.
687		791
688	=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.
689		793
690	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
691	ID known to other nodes for a completely different process, causing	795	known to other nodes for a completely different process, causing messages
692	messages destined for that process to end up in an unrelated process.	796	destined for that process to end up in an unrelated process.
693		797
694	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
695	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.
696		800
697	=item * Erlang uses unprotected connections, AEMP uses secure	801	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
717	or I<none>, there is no in-between, so monitoring single processes is	821	or I<none>, there is no in-between, so monitoring single processes is
718	difficult to implement. Monitoring in AEMP is more flexible than in	822	difficult to implement. Monitoring in AEMP is more flexible than in
719	Erlang, as one can choose between automatic kill, exit message or callback	823	Erlang, as one can choose between automatic kill, exit message or callback
720	on a per-process basis.	824	on a per-process basis.
721		825
722	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	826	=item * Erlang tries to hide remote/local connections, AEMP does not.
723		827
724	Monitoring in Erlang is not an indicator of process death/crashes,	828	Monitoring in Erlang is not an indicator of process death/crashes,
725	as linking is (except linking is unreliable in Erlang). In AEMP, the	829	as linking is (except linking is unreliable in Erlang).
726	semantics of monitoring and linking are identical, linking is simply	830
727	two-way monitoring with automatic kill.	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.
728		874
729	=back	875	=back
730		876
731	=head1 SEE ALSO	877	=head1 SEE ALSO
732		878

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