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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs.
Revision 1.51 by root, Fri Aug 14 14:07:44 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, type 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		46	AnyEvent::MP::Intro - outdated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
…		…
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 initialise_node	133	resolve_node initialise_node
109	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
110	port	135	port
111	);	136	);
112		137
113	our $SELF;	138	our $SELF;
114		139
…		…
127		152
128	=item $noderef = node_of $port	153	=item $noderef = node_of $port
129		154
130	Extracts and returns the noderef from a portid or a noderef.	155	Extracts and returns the noderef from a portid or a noderef.
131		156
		157	=item initialise_node $noderef, $seednode, $seednode...
		158
		159	=item initialise_node "slave/", $master, $master...
		160
		161	Before a node can talk to other nodes on the network it has to initialise
		162	itself - the minimum a node needs to know is it's own name, and optionally
		163	it should know the noderefs of some other nodes in the network.
		164
		165	This function initialises a node - it must be called exactly once (or
		166	never) before calling other AnyEvent::MP functions.
		167
		168	All arguments (optionally except for the first) are noderefs, which can be
		169	either resolved or unresolved.
		170
		171	The first argument will be looked up in the configuration database first
		172	(if it is C<undef> then the current nodename will be used instead) to find
		173	the relevant configuration profile (see L<aemp>). If none is found then
		174	the default configuration is used. The configuration supplies additional
		175	seed/master nodes and can override the actual noderef.
		176
		177	There are two types of networked nodes, public nodes and slave nodes:
		178
		179	=over 4
		180
		181	=item public nodes
		182
		183	For public nodes, C<$noderef> (supplied either directly to
		184	C<initialise_node> or indirectly via a profile or the nodename) must be a
		185	noderef (possibly unresolved, in which case it will be resolved).
		186
		187	After resolving, the node will bind itself on all endpoints and try to
		188	connect to all additional C<$seednodes> that are specified. Seednodes are
		189	optional and can be used to quickly bootstrap the node into an existing
		190	network.
		191
		192	=item slave nodes
		193
		194	When the C<$noderef> (either as given or overriden by the config file)
		195	is the special string C<slave/>, then the node will become a slave
		196	node. Slave nodes cannot be contacted from outside and will route most of
		197	their traffic to the master node that they attach to.
		198
		199	At least one additional noderef is required (either by specifying it
		200	directly or because it is part of the configuration profile): The node
		201	will try to connect to all of them and will become a slave attached to the
		202	first node it can successfully connect to.
		203
		204	=back
		205
		206	This function will block until all nodes have been resolved and, for slave
		207	nodes, until it has successfully established a connection to a master
		208	server.
		209
		210	Example: become a public node listening on the guessed noderef, or the one
		211	specified via C<aemp> for the current node. This should be the most common
		212	form of invocation for "daemon"-type nodes.
		213
		214	initialise_node;
		215
		216	Example: become a slave node to any of the the seednodes specified via
		217	C<aemp>. This form is often used for commandline clients.
		218
		219	initialise_node "slave/";
		220
		221	Example: become a slave node to any of the specified master servers. This
		222	form is also often used for commandline clients.
		223
		224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		225
		226	Example: become a public node, and try to contact some well-known master
		227	servers to become part of the network.
		228
		229	initialise_node undef, "master1", "master2";
		230
		231	Example: become a public node listening on port C<4041>.
		232
		233	initialise_node 4041;
		234
		235	Example: become a public node, only visible on localhost port 4044.
		236
		237	initialise_node "localhost:4044";
		238
132	=item $cv = resolve_node $noderef	239	=item $cv = resolve_node $noderef
133		240
134	Takes an unresolved node reference that may contain hostnames and	241	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	242	abbreviated IDs, resolves all of them and returns a resolved node
136	reference.	243	reference.
…		…
191	that Storable can serialise and deserialise is allowed, and for the local	298	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	299	node, anything can be passed.
193		300
194	=item $local_port = port	301	=item $local_port = port
195		302
196	Create a new local port object that can be used either as a pattern	303	Create a new local port object and returns its port ID. Initially it has
197	matching port ("full port") or a single-callback port ("miniport"),	304	no callbacks set and will throw an error when it receives messages.
198	depending on how C<rcv> callbacks are bound to the object.
199		305
200	=item $port = port { my @msg = @_; $finished }	306	=item $local_port = port { my @msg = @_ }
201		307
202	Creates a "miniport", that is, a very lightweight port without any pattern	308	Creates a new local port, and returns its ID. Semantically the same as
203	matching behind it, and returns its ID. Semantically the same as creating
204	a port and calling C<rcv $port, $callback> on it.	309	creating a port and calling C<rcv $port, $callback> on it.
205		310
206	The block will be called for every message received on the port. When the	311	The block will be called for every message received on the port, with the
207	callback returns a true value its job is considered "done" and the port	312	global variable C<$SELF> set to the port ID. Runtime errors will cause the
208	will be destroyed. Otherwise it will stay alive.	313	port to be C<kil>ed. The message will be passed as-is, no extra argument
		314	(i.e. no port ID) will be passed to the callback.
209		315
210	The message will be passed as-is, no extra argument (i.e. no port id) will	316	If you want to stop/destroy the port, simply C<kil> it:
211	be passed to the callback.
212		317
213	If you need the local port id in the callback, this works nicely:	318	my $port = port {
214		319	my @msg = @_;
215	my $port; $port = port {	320	...
216	snd $otherport, reply => $port;	321	kil $SELF;
217	};	322	};
218		323
219	=cut	324	=cut
220		325
221	sub rcv($@);	326	sub rcv($@);
		327
		328	sub _kilme {
		329	die "received message on port without callback";
		330	}
222		331
223	sub port(;&) {	332	sub port(;&) {
224	my $id = "$UNIQ." . $ID++;	333	my $id = "$UNIQ." . $ID++;
225	my $port = "$NODE#$id";	334	my $port = "$NODE#$id";
226		335
227	if (@_) {	336	rcv $port, shift \|\| \&_kilme;
228	rcv $port, shift;
229	} else {
230	$PORT{$id} = sub { }; # nop
231	}
232		337
233	$port	338	$port
234	}	339	}
235		340
236	=item reg $port, $name
237
238	Registers the given port under the name C<$name>. If the name already
239	exists it is replaced.
240
241	A port can only be registered under one well known name.
242
243	A port automatically becomes unregistered when it is killed.
244
245	=cut
246
247	sub reg(@) {
248	my ($port, $name) = @_;
249
250	$REG{$name} = $port;
251	}
252
253	=item rcv $port, $callback->(@msg)	341	=item rcv $local_port, $callback->(@msg)
254		342
255	Replaces the callback on the specified miniport (after converting it to	343	Replaces the default callback on the specified port. There is no way to
256	one if required).	344	remove the default callback: use C<sub { }> to disable it, or better
257		345	C<kil> the port when it is no longer needed.
258	=item rcv $port, tagstring => $callback->(@msg), ...
259
260	=item rcv $port, $smartmatch => $callback->(@msg), ...
261
262	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
263
264	Register callbacks to be called on matching messages on the given full
265	port (after converting it to one if required).
266
267	The callback has to return a true value when its work is done, after
268	which is will be removed, or a false value in which case it will stay
269	registered.
270		346
271	The global C<$SELF> (exported by this module) contains C<$port> while	347	The global C<$SELF> (exported by this module) contains C<$port> while
272	executing the callback.	348	executing the callback. Runtime errors during callback execution will
		349	result in the port being C<kil>ed.
273		350
274	Runtime errors wdurign callback execution will result in the port being	351	The default callback received all messages not matched by a more specific
275	C<kil>ed.	352	C<tag> match.
276		353
277	If the match is an array reference, then it will be matched against the	354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
278	first elements of the message, otherwise only the first element is being
279	matched.
280		355
281	Any element in the match that is specified as C<_any_> (a function	356	Register callbacks to be called on messages starting with the given tag on
282	exported by this module) matches any single element of the message.	357	the given port (and return the port), or unregister it (when C<$callback>
		358	is C<$undef>).
283		359
284	While not required, it is highly recommended that the first matching	360	The original message will be passed to the callback, after the first
285	element is a string identifying the message. The one-string-only match is	361	element (the tag) has been removed. The callback will use the same
286	also the most efficient match (by far).	362	environment as the default callback (see above).
		363
		364	Example: create a port and bind receivers on it in one go.
		365
		366	my $port = rcv port,
		367	msg1 => sub { ... },
		368	msg2 => sub { ... },
		369	;
		370
		371	Example: create a port, bind receivers and send it in a message elsewhere
		372	in one go:
		373
		374	snd $otherport, reply =>
		375	rcv port,
		376	msg1 => sub { ... },
		377	...
		378	;
287		379
288	=cut	380	=cut
289		381
290	sub rcv($@) {	382	sub rcv($@) {
291	my $port = shift;	383	my $port = shift;
292	my ($noderef, $portid) = split /#/, $port, 2;	384	my ($noderef, $portid) = split /#/, $port, 2;
293		385
294	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
295	or Carp::croak "$port: rcv can only be called on local ports, caught";	387	or Carp::croak "$port: rcv can only be called on local ports, caught";
296		388
297	if (@_ == 1) {	389	while (@_) {
		390	if (ref $_[0]) {
		391	if (my $self = $PORT_DATA{$portid}) {
		392	"AnyEvent::MP::Port" eq ref $self
		393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		394
		395	$self->[2] = shift;
		396	} else {
298	my $cb = shift;	397	my $cb = shift;
299	delete $PORT_DATA{$portid};
300	$PORT{$portid} = sub {	398	$PORT{$portid} = sub {
301	local $SELF = $port;	399	local $SELF = $port;
302	eval {	400	eval { &$cb }; _self_die if $@;
303	&$cb	401	};
304	and kil $port;
305	};	402	}
306	_self_die if $@;	403	} elsif (defined $_[0]) {
307	};
308	} else {
309	my $self = $PORT_DATA{$portid} \|\|= do {	404	my $self = $PORT_DATA{$portid} \|\|= do {
310	my $self = bless {	405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
311	id => $port,
312	}, "AnyEvent::MP::Port";
313		406
314	$PORT{$portid} = sub {	407	$PORT{$portid} = sub {
315	local $SELF = $port;	408	local $SELF = $port;
316		409
317	eval {
318	for (@{ $self->{rc0}{$_[0]} }) {	410	if (my $cb = $self->[1]{$_[0]}) {
319	$_ && &{$_->[0]}	411	shift;
320	&& undef $_;	412	eval { &$cb }; _self_die if $@;
321	}	413	} else {
322
323	for (@{ $self->{rcv}{$_[0]} }) {
324	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
325	&& &{$_->[0]}	414	&{ $self->[0] };
326	&& undef $_;
327	}
328
329	for (@{ $self->{any} }) {
330	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
331	&& &{$_->[0]}
332	&& undef $_;
333	}	415	}
334	};	416	};
335	_self_die if $@;	417
		418	$self
336	};	419	};
337		420
338	$self
339	};
340
341	"AnyEvent::MP::Port" eq ref $self	421	"AnyEvent::MP::Port" eq ref $self
342	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	422	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
343		423
344	while (@_) {
345	my ($match, $cb) = splice @_, 0, 2;	424	my ($tag, $cb) = splice @_, 0, 2;
346		425
347	if (!ref $match) {	426	if (defined $cb) {
348	push @{ $self->{rc0}{$match} }, [$cb];	427	$self->[1]{$tag} = $cb;
349	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
350	my ($type, @match) = @$match;
351	@match
352	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
353	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
354	} else {	428	} else {
355	push @{ $self->{any} }, [$cb, $match];	429	delete $self->[1]{$tag};
356	}	430	}
357	}	431	}
358	}	432	}
359		433
360	$port	434	$port
…		…
398	}	472	}
399	}	473	}
400		474
401	=item $guard = mon $port, $cb->(@reason)	475	=item $guard = mon $port, $cb->(@reason)
402		476
403	=item $guard = mon $port, $otherport	477	=item $guard = mon $port, $rcvport
404		478
		479	=item $guard = mon $port
		480
405	=item $guard = mon $port, $otherport, @msg	481	=item $guard = mon $port, $rcvport, @msg
406		482
407	Monitor the given port and do something when the port is killed.	483	Monitor the given port and do something when the port is killed or
		484	messages to it were lost, and optionally return a guard that can be used
		485	to stop monitoring again.
408		486
		487	C<mon> effectively guarantees that, in the absence of hardware failures,
		488	that after starting the monitor, either all messages sent to the port
		489	will arrive, or the monitoring action will be invoked after possible
		490	message loss has been detected. No messages will be lost "in between"
		491	(after the first lost message no further messages will be received by the
		492	port). After the monitoring action was invoked, further messages might get
		493	delivered again.
		494
409	In the first form, the callback is simply called with any number	495	In the first form (callback), the callback is simply called with any
410	of C<@reason> elements (no @reason means that the port was deleted	496	number of C<@reason> elements (no @reason means that the port was deleted
411	"normally"). Note also that I<< the callback B<must> never die >>, so use	497	"normally"). Note also that I<< the callback B<must> never die >>, so use
412	C<eval> if unsure.	498	C<eval> if unsure.
413		499
414	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	500	In the second form (another port given), the other port (C<$rcvport>)
415	a @reason was specified, i.e. on "normal" kils nothing happens, while	501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
416	under all other conditions, the other port is killed with the same reason.	502	"normal" kils nothing happens, while under all other conditions, the other
		503	port is killed with the same reason.
417		504
		505	The third form (kill self) is the same as the second form, except that
		506	C<$rvport> defaults to C<$SELF>.
		507
418	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	508	In the last form (message), a message of the form C<@msg, @reason> will be
		509	C<snd>.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for exmaple, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
419		517
420	Example: call a given callback when C<$port> is killed.	518	Example: call a given callback when C<$port> is killed.
421		519
422	mon $port, sub { warn "port died because of <@_>\n" };	520	mon $port, sub { warn "port died because of <@_>\n" };
423		521
424	Example: kill ourselves when C<$port> is killed abnormally.	522	Example: kill ourselves when C<$port> is killed abnormally.
425		523
426	mon $port, $self;	524	mon $port;
427		525
428	Example: send us a restart message another C<$port> is killed.	526	Example: send us a restart message when another C<$port> is killed.
429		527
430	mon $port, $self => "restart";	528	mon $port, $self => "restart";
431		529
432	=cut	530	=cut
433		531
434	sub mon {	532	sub mon {
435	my ($noderef, $port) = split /#/, shift, 2;	533	my ($noderef, $port) = split /#/, shift, 2;
436		534
437	my $node = $NODE{$noderef} \|\| add_node $noderef;	535	my $node = $NODE{$noderef} \|\| add_node $noderef;
438		536
439	my $cb = shift;	537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
440		538
441	unless (ref $cb) {	539	unless (ref $cb) {
442	if (@_) {	540	if (@_) {
443	# send a kill info message	541	# send a kill info message
444	my (@msg) = ($cb, @_);	542	my (@msg) = ($cb, @_);
…		…
475	=cut	573	=cut
476		574
477	sub mon_guard {	575	sub mon_guard {
478	my ($port, @refs) = @_;	576	my ($port, @refs) = @_;
479		577
		578	#TODO: mon-less form?
		579
480	mon $port, sub { 0 && @refs }	580	mon $port, sub { 0 && @refs }
481	}	581	}
482		582
483	=item lnk $port1, $port2
484
485	Link two ports. This is simply a shorthand for:
486
487	mon $port1, $port2;
488	mon $port2, $port1;
489
490	It means that if either one is killed abnormally, the other one gets
491	killed as well.
492
493	=item kil $port[, @reason]	583	=item kil $port[, @reason]
494		584
495	Kill the specified port with the given C<@reason>.	585	Kill the specified port with the given C<@reason>.
496		586
497	If no C<@reason> is specified, then the port is killed "normally" (linked	587	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
504	will be reported as reason C<< die => $@ >>.	594	will be reported as reason C<< die => $@ >>.
505		595
506	Transport/communication errors are reported as C<< transport_error =>	596	Transport/communication errors are reported as C<< transport_error =>
507	$message >>.	597	$message >>.
508		598
509	=back
510
511	=head1 FUNCTIONS FOR NODES
512
513	=over 4
514
515	=item initialise_node $noderef, $seednode, $seednode...
516
517	=item initialise_node "slave/", $master, $master...
518
519	Initialises a node - must be called exactly once before calling other
520	AnyEvent::MP functions when talking to other nodes is required.
521
522	All arguments are noderefs, which can be either resolved or unresolved.
523
524	There are two types of networked nodes, public nodes and slave nodes:
525
526	=over 4
527
528	=item public nodes
529
530	For public nodes, C<$noderef> must either be a (possibly unresolved)
531	noderef, in which case it will be resolved, or C<undef> (or missing), in
532	which case the noderef will be guessed.
533
534	Afterwards, the node will bind itself on all endpoints and try to connect
535	to all additional C<$seednodes> that are specified. Seednodes are optional
536	and can be used to quickly bootstrap the node into an existing network.
537
538	=item slave nodes
539
540	When the C<$noderef> is the special string C<slave/>, then the node will
541	become a slave node. Slave nodes cannot be contacted from outside and will
542	route most of their traffic to the master node that they attach to.
543
544	At least one additional noderef is required: The node will try to connect
545	to all of them and will become a slave attached to the first node it can
546	successfully connect to.
547
548	=back
549
550	This function will block until all nodes have been resolved and, for slave
551	nodes, until it has successfully established a connection to a master
552	server.
553
554	Example: become a public node listening on the default node.
555
556	initialise_node;
557
558	Example: become a public node, and try to contact some well-known master
559	servers to become part of the network.
560
561	initialise_node undef, "master1", "master2";
562
563	Example: become a public node listening on port C<4041>.
564
565	initialise_node 4041;
566
567	Example: become a public node, only visible on localhost port 4044.
568
569	initialise_node "locahost:4044";
570
571	Example: become a slave node to any of the specified master servers.
572
573	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
574
575	=cut	599	=cut
		600
		601	=item $port = spawn $node, $initfunc[, @initdata]
		602
		603	Creates a port on the node C<$node> (which can also be a port ID, in which
		604	case it's the node where that port resides).
		605
		606	The port ID of the newly created port is return immediately, and it is
		607	permissible to immediately start sending messages or monitor the port.
		608
		609	After the port has been created, the init function is
		610	called. This function must be a fully-qualified function name
		611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		612	program, use C<::name>.
		613
		614	If the function doesn't exist, then the node tries to C<require>
		615	the package, then the package above the package and so on (e.g.
		616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		617	exists or it runs out of package names.
		618
		619	The init function is then called with the newly-created port as context
		620	object (C<$SELF>) and the C<@initdata> values as arguments.
		621
		622	A common idiom is to pass your own port, monitor the spawned port, and
		623	in the init function, monitor the original port. This two-way monitoring
		624	ensures that both ports get cleaned up when there is a problem.
		625
		626	Example: spawn a chat server port on C<$othernode>.
		627
		628	# this node, executed from within a port context:
		629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		630	mon $server;
		631
		632	# init function on C<$othernode>
		633	sub connect {
		634	my ($srcport) = @_;
		635
		636	mon $srcport;
		637
		638	rcv $SELF, sub {
		639	...
		640	};
		641	}
		642
		643	=cut
		644
		645	sub _spawn {
		646	my $port = shift;
		647	my $init = shift;
		648
		649	local $SELF = "$NODE#$port";
		650	eval {
		651	&{ load_func $init }
		652	};
		653	_self_die if $@;
		654	}
		655
		656	sub spawn(@) {
		657	my ($noderef, undef) = split /#/, shift, 2;
		658
		659	my $id = "$RUNIQ." . $ID++;
		660
		661	$_[0] =~ /::/
		662	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		663
		664	($NODE{$noderef} \|\| add_node $noderef)
		665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		666
		667	"$noderef#$id"
		668	}
576		669
577	=back	670	=back
578		671
579	=head1 NODE MESSAGES	672	=head1 NODE MESSAGES
580		673
…		…
622		715
623	=back	716	=back
624		717
625	=head1 AnyEvent::MP vs. Distributed Erlang	718	=head1 AnyEvent::MP vs. Distributed Erlang
626		719
627	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
628	== aemp node, erlang process == aemp port), so many of the documents and	721	== aemp node, Erlang process == aemp port), so many of the documents and
629	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
630	sample:	723	sample:
631		724
632	http://www.erlang.se/doc/programming_rules.shtml	725	http://www.Erlang.se/doc/programming_rules.shtml
633	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
634	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
635	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
636		729
637	Despite the similarities, there are also some important differences:	730	Despite the similarities, there are also some important differences:
638		731
639	=over 4	732	=over 4
640		733
…		…
645	convenience functionality.	738	convenience functionality.
646		739
647	This means that AEMP requires a less tightly controlled environment at the	740	This means that AEMP requires a less tightly controlled environment at the
648	cost of longer node references and a slightly higher management overhead.	741	cost of longer node references and a slightly higher management overhead.
649		742
		743	=item Erlang has a "remote ports are like local ports" philosophy, AEMP
		744	uses "local ports are like remote ports".
		745
		746	The failure modes for local ports are quite different (runtime errors
		747	only) then for remote ports - when a local port dies, you I<know> it dies,
		748	when a connection to another node dies, you know nothing about the other
		749	port.
		750
		751	Erlang pretends remote ports are as reliable as local ports, even when
		752	they are not.
		753
		754	AEMP encourages a "treat remote ports differently" philosophy, with local
		755	ports being the special case/exception, where transport errors cannot
		756	occur.
		757
650	=item * Erlang uses processes and a mailbox, AEMP does not queue.	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
651		759
652	Erlang uses processes that selctively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
653	needs a queue. AEMP is event based, queuing messages would serve no useful	761	needs a queue. AEMP is event based, queuing messages would serve no
654	purpose.	762	useful purpose. For the same reason the pattern-matching abilities of
		763	AnyEvent::MP are more limited, as there is little need to be able to
		764	filter messages without dequeing them.
655		765
656	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
657		767
658	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
659		769
660	Sending messages in erlang is synchronous and blocks the process. AEMP	770	Sending messages in Erlang is synchronous and blocks the process (and
661	sends are immediate, connection establishment is handled in the	771	so does not need a queue that can overflow). AEMP sends are immediate,
662	background.	772	connection establishment is handled in the background.
663		773
664	=item * Erlang can silently lose messages, AEMP cannot.	774	=item * Erlang suffers from silent message loss, AEMP does not.
665		775
666	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
667	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
668	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
669		779
670	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that there are no
671	holes in the message sequence.	781	holes in the message sequence.
672		782
673	=item * In erlang, processes can be declared dead and later be found to be	783	=item * In Erlang, processes can be declared dead and later be found to be
674	alive.	784	alive.
675		785
676	In erlang it can happen that a monitored process is declared dead and	786	In Erlang it can happen that a monitored process is declared dead and
677	linked processes get killed, but later it turns out that the process is	787	linked processes get killed, but later it turns out that the process is
678	still alive - and can receive messages.	788	still alive - and can receive messages.
679		789
680	In AEMP, when port monitoring detects a port as dead, then that port will	790	In AEMP, when port monitoring detects a port as dead, then that port will
681	eventually be killed - it cannot happen that a node detects a port as dead	791	eventually be killed - it cannot happen that a node detects a port as dead
682	and then later sends messages to it, finding it is still alive.	792	and then later sends messages to it, finding it is still alive.
683		793
684	=item * Erlang can send messages to the wrong port, AEMP does not.	794	=item * Erlang can send messages to the wrong port, AEMP does not.
685		795
686	In erlang it is quite possible that a node that restarts reuses a process	796	In Erlang it is quite likely that a node that restarts reuses a process ID
687	ID known to other nodes for a completely different process, causing	797	known to other nodes for a completely different process, causing messages
688	messages destined for that process to end up in an unrelated process.	798	destined for that process to end up in an unrelated process.
689		799
690	AEMP never reuses port IDs, so old messages or old port IDs floating	800	AEMP never reuses port IDs, so old messages or old port IDs floating
691	around in the network will not be sent to an unrelated port.	801	around in the network will not be sent to an unrelated port.
692		802
693	=item * Erlang uses unprotected connections, AEMP uses secure	803	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
697	securely authenticate nodes.	807	securely authenticate nodes.
698		808
699	=item * The AEMP protocol is optimised for both text-based and binary	809	=item * The AEMP protocol is optimised for both text-based and binary
700	communications.	810	communications.
701		811
702	The AEMP protocol, unlike the erlang protocol, supports both	812	The AEMP protocol, unlike the Erlang protocol, supports both
703	language-independent text-only protocols (good for debugging) and binary,	813	language-independent text-only protocols (good for debugging) and binary,
704	language-specific serialisers (e.g. Storable).	814	language-specific serialisers (e.g. Storable).
705		815
706	It has also been carefully designed to be implementable in other languages	816	It has also been carefully designed to be implementable in other languages
707	with a minimum of work while gracefully degrading fucntionality to make the	817	with a minimum of work while gracefully degrading fucntionality to make the
708	protocol simple.	818	protocol simple.
709		819
		820	=item * AEMP has more flexible monitoring options than Erlang.
		821
		822	In Erlang, you can chose to receive I<all> exit signals as messages
		823	or I<none>, there is no in-between, so monitoring single processes is
		824	difficult to implement. Monitoring in AEMP is more flexible than in
		825	Erlang, as one can choose between automatic kill, exit message or callback
		826	on a per-process basis.
		827
		828	=item * Erlang tries to hide remote/local connections, AEMP does not.
		829
		830	Monitoring in Erlang is not an indicator of process death/crashes,
		831	as linking is (except linking is unreliable in Erlang).
		832
		833	In AEMP, you don't "look up" registered port names or send to named ports
		834	that might or might not be persistent. Instead, you normally spawn a port
		835	on the remote node. The init function monitors the you, and you monitor
		836	the remote port. Since both monitors are local to the node, they are much
		837	more reliable.
		838
		839	This also saves round-trips and avoids sending messages to the wrong port
		840	(hard to do in Erlang).
		841
		842	=back
		843
		844	=head1 RATIONALE
		845
		846	=over 4
		847
		848	=item Why strings for ports and noderefs, why not objects?
		849
		850	We considered "objects", but found that the actual number of methods
		851	thatc an be called are very low. Since port IDs and noderefs travel over
		852	the network frequently, the serialising/deserialising would add lots of
		853	overhead, as well as having to keep a proxy object.
		854
		855	Strings can easily be printed, easily serialised etc. and need no special
		856	procedures to be "valid".
		857
		858	And a a miniport consists of a single closure stored in a global hash - it
		859	can't become much cheaper.
		860
		861	=item Why favour JSON, why not real serialising format such as Storable?
		862
		863	In fact, any AnyEvent::MP node will happily accept Storable as framing
		864	format, but currently there is no way to make a node use Storable by
		865	default.
		866
		867	The default framing protocol is JSON because a) JSON::XS is many times
		868	faster for small messages and b) most importantly, after years of
		869	experience we found that object serialisation is causing more problems
		870	than it gains: Just like function calls, objects simply do not travel
		871	easily over the network, mostly because they will always be a copy, so you
		872	always have to re-think your design.
		873
		874	Keeping your messages simple, concentrating on data structures rather than
		875	objects, will keep your messages clean, tidy and efficient.
		876
710	=back	877	=back
711		878
712	=head1 SEE ALSO	879	=head1 SEE ALSO
713		880
714	L<AnyEvent>.	881	L<AnyEvent>.

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Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC