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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.48 by root, Thu Aug 13 02:59:42 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 miniports
		28	my $miniport = port { my @msg = @_; 0 };
16		29
		30	# creating/using full ports
		31	my $port = port;
17	rcv $port, smartmatch => $cb->($port, @msg);	32	rcv $port, smartmatch => $cb->(@msg);
18
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	34	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		35
24	# more, smarter, matches (_any_ is exported by this module)	36	# more, smarter, matches (_any_ is exported by this module)
25	rcv $port, [child_died => $pid] => sub { ...	37	rcv $port, [child_died => $pid] => sub { ...
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
27		39
		40	# create a port on another node
		41	my $port = spawn $node, $initfunc, @initdata;
		42
		43	# monitoring
		44	mon $port, $cb->(@msg) # callback is invoked on death
		45	mon $port, $otherport # kill otherport on abnormal death
		46	mon $port, $otherport, @msg # send message on death
		47
		48	=head1 CURRENT STATUS
		49
		50	AnyEvent::MP - stable API, should work
		51	AnyEvent::MP::Intro - outdated
		52	AnyEvent::MP::Kernel - WIP
		53	AnyEvent::MP::Transport - mostly stable
		54
		55	stay tuned.
		56
28	=head1 DESCRIPTION	57	=head1 DESCRIPTION
29		58
30	This module (-family) implements a simple message passing framework.	59	This module (-family) implements a simple message passing framework.
31		60
32	Despite its simplicity, you can securely message other processes running	61	Despite its simplicity, you can securely message other processes running
…		…
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	64	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	65	manual page.
37		66
38	At the moment, this module family is severly broken and underdocumented,	67	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 -	68	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.	69	stay tuned!
41		70
42	=head1 CONCEPTS	71	=head1 CONCEPTS
43		72
44	=over 4	73	=over 4
45		74
…		…
90		119
91	=cut	120	=cut
92		121
93	package AnyEvent::MP;	122	package AnyEvent::MP;
94		123
95	use AnyEvent::MP::Base;	124	use AnyEvent::MP::Kernel;
96		125
97	use common::sense;	126	use common::sense;
98		127
99	use Carp ();	128	use Carp ();
100		129
101	use AE ();	130	use AE ();
102		131
103	use base "Exporter";	132	use base "Exporter";
104		133
105	our $VERSION = '0.1';	134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		135
106	our @EXPORT = qw(	136	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	137	NODE $NODE *SELF node_of _any_
108	resolve_node initialise_node	138	resolve_node initialise_node
109	snd rcv mon kil reg psub	139	snd rcv mon kil reg psub spawn
110	port	140	port
111	);	141	);
112		142
113	our $SELF;	143	our $SELF;
114		144
…		…
123	The C<NODE> function returns, and the C<$NODE> variable contains	153	The C<NODE> function returns, and the C<$NODE> variable contains
124	the noderef of the local node. The value is initialised by a call	154	the noderef of the local node. The value is initialised by a call
125	to C<become_public> or C<become_slave>, after which all local port	155	to C<become_public> or C<become_slave>, after which all local port
126	identifiers become invalid.	156	identifiers become invalid.
127		157
128	=item $noderef = node_of $portid	158	=item $noderef = node_of $port
129		159
130	Extracts and returns the noderef from a portid or a noderef.	160	Extracts and returns the noderef from a portid or a noderef.
		161
		162	=item initialise_node $noderef, $seednode, $seednode...
		163
		164	=item initialise_node "slave/", $master, $master...
		165
		166	Before a node can talk to other nodes on the network it has to initialise
		167	itself - the minimum a node needs to know is it's own name, and optionally
		168	it should know the noderefs of some other nodes in the network.
		169
		170	This function initialises a node - it must be called exactly once (or
		171	never) before calling other AnyEvent::MP functions.
		172
		173	All arguments are noderefs, which can be either resolved or unresolved.
		174
		175	There are two types of networked nodes, public nodes and slave nodes:
		176
		177	=over 4
		178
		179	=item public nodes
		180
		181	For public nodes, C<$noderef> must either be a (possibly unresolved)
		182	noderef, in which case it will be resolved, or C<undef> (or missing), in
		183	which case the noderef will be guessed.
		184
		185	Afterwards, the node will bind itself on all endpoints and try to connect
		186	to all additional C<$seednodes> that are specified. Seednodes are optional
		187	and can be used to quickly bootstrap the node into an existing network.
		188
		189	=item slave nodes
		190
		191	When the C<$noderef> is the special string C<slave/>, then the node will
		192	become a slave node. Slave nodes cannot be contacted from outside and will
		193	route most of their traffic to the master node that they attach to.
		194
		195	At least one additional noderef is required: The node will try to connect
		196	to all of them and will become a slave attached to the first node it can
		197	successfully connect to.
		198
		199	=back
		200
		201	This function will block until all nodes have been resolved and, for slave
		202	nodes, until it has successfully established a connection to a master
		203	server.
		204
		205	Example: become a public node listening on the default node.
		206
		207	initialise_node;
		208
		209	Example: become a public node, and try to contact some well-known master
		210	servers to become part of the network.
		211
		212	initialise_node undef, "master1", "master2";
		213
		214	Example: become a public node listening on port C<4041>.
		215
		216	initialise_node 4041;
		217
		218	Example: become a public node, only visible on localhost port 4044.
		219
		220	initialise_node "locahost:4044";
		221
		222	Example: become a slave node to any of the specified master servers.
		223
		224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
131		225
132	=item $cv = resolve_node $noderef	226	=item $cv = resolve_node $noderef
133		227
134	Takes an unresolved node reference that may contain hostnames and	228	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	229	abbreviated IDs, resolves all of them and returns a resolved node
…		…
167		261
168	Due to some quirks in how perl exports variables, it is impossible to	262	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	263	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	264	module, but only C<$SELF> is currently used.
171		265
172	=item snd $portid, type => @data	266	=item snd $port, type => @data
173		267
174	=item snd $portid, @msg	268	=item snd $port, @msg
175		269
176	Send the given message to the given port ID, which can identify either	270	Send the given message to the given port ID, which can identify either
177	a local or a remote port, and can be either a string or soemthignt hat	271	a local or a remote port, and can be either a string or soemthignt hat
178	stringifies a sa port ID (such as a port object :).	272	stringifies a sa port ID (such as a port object :).
179		273
…		…
195		289
196	Create a new local port object that can be used either as a pattern	290	Create a new local port object that can be used either as a pattern
197	matching port ("full port") or a single-callback port ("miniport"),	291	matching port ("full port") or a single-callback port ("miniport"),
198	depending on how C<rcv> callbacks are bound to the object.	292	depending on how C<rcv> callbacks are bound to the object.
199		293
200	=item $portid = port { my @msg = @_; $finished }	294	=item $port = port { my @msg = @_; $finished }
201		295
202	Creates a "mini port", that is, a very lightweight port without any	296	Creates a "miniport", that is, a very lightweight port without any pattern
203	pattern matching behind it, and returns its ID.	297	matching behind it, and returns its ID. Semantically the same as creating
		298	a port and calling C<rcv $port, $callback> on it.
204		299
205	The block will be called for every message received on the port. When the	300	The block will be called for every message received on the port. When the
206	callback returns a true value its job is considered "done" and the port	301	callback returns a true value its job is considered "done" and the port
207	will be destroyed. Otherwise it will stay alive.	302	will be destroyed. Otherwise it will stay alive.
208		303
…		…
215	snd $otherport, reply => $port;	310	snd $otherport, reply => $port;
216	};	311	};
217		312
218	=cut	313	=cut
219		314
		315	sub rcv($@);
		316
220	sub port(;&) {	317	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	318	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	319	my $port = "$NODE#$id";
223		320
224	if (@_) {	321	if (@_) {
		322	rcv $port, shift;
		323	} else {
		324	$PORT{$id} = sub { }; # nop
		325	}
		326
		327	$port
		328	}
		329
		330	=item reg $port, $name
		331
		332	=item reg $name
		333
		334	Registers the given port (or C<$SELF><<< if missing) under the name
		335	C<$name>. If the name already exists it is replaced.
		336
		337	A port can only be registered under one well known name.
		338
		339	A port automatically becomes unregistered when it is killed.
		340
		341	=cut
		342
		343	sub reg(@) {
		344	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
		345
		346	$REG{$_[0]} = $port;
		347	}
		348
		349	=item rcv $port, $callback->(@msg)
		350
		351	Replaces the callback on the specified miniport (after converting it to
		352	one if required).
		353
		354	=item rcv $port, tagstring => $callback->(@msg), ...
		355
		356	=item rcv $port, $smartmatch => $callback->(@msg), ...
		357
		358	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
		359
		360	Register callbacks to be called on matching messages on the given full
		361	port (after converting it to one if required) and return the port.
		362
		363	The callback has to return a true value when its work is done, after
		364	which is will be removed, or a false value in which case it will stay
		365	registered.
		366
		367	The global C<$SELF> (exported by this module) contains C<$port> while
		368	executing the callback.
		369
		370	Runtime errors during callback execution will result in the port being
		371	C<kil>ed.
		372
		373	If the match is an array reference, then it will be matched against the
		374	first elements of the message, otherwise only the first element is being
		375	matched.
		376
		377	Any element in the match that is specified as C<_any_> (a function
		378	exported by this module) matches any single element of the message.
		379
		380	While not required, it is highly recommended that the first matching
		381	element is a string identifying the message. The one-string-only match is
		382	also the most efficient match (by far).
		383
		384	Example: create a port and bind receivers on it in one go.
		385
		386	my $port = rcv port,
		387	msg1 => sub { ...; 0 },
		388	msg2 => sub { ...; 0 },
		389	;
		390
		391	Example: create a port, bind receivers and send it in a message elsewhere
		392	in one go:
		393
		394	snd $otherport, reply =>
		395	rcv port,
		396	msg1 => sub { ...; 0 },
		397	...
		398	;
		399
		400	=cut
		401
		402	sub rcv($@) {
		403	my $port = shift;
		404	my ($noderef, $portid) = split /#/, $port, 2;
		405
		406	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		407	or Carp::croak "$port: rcv can only be called on local ports, caught";
		408
		409	if (@_ == 1) {
225	my $cb = shift;	410	my $cb = shift;
		411	delete $PORT_DATA{$portid};
226	$PORT{$id} = sub {	412	$PORT{$portid} = sub {
227	local $SELF = $port;	413	local $SELF = $port;
228	eval {	414	eval {
229	&$cb	415	&$cb
230	and kil $id;	416	and kil $port;
231	};	417	};
232	_self_die if $@;	418	_self_die if $@;
233	};	419	};
234	} else {	420	} else {
		421	my $self = $PORT_DATA{$portid} \|\|= do {
235	my $self = bless {	422	my $self = bless {
236	id => "$NODE#$id",	423	id => $port,
237	}, "AnyEvent::MP::Port";	424	}, "AnyEvent::MP::Port";
238		425
239	$PORT_DATA{$id} = $self;
240	$PORT{$id} = sub {	426	$PORT{$portid} = sub {
241	local $SELF = $port;	427	local $SELF = $port;
242		428
243	eval {	429	eval {
244	for (@{ $self->{rc0}{$_[0]} }) {	430	for (@{ $self->{rc0}{$_[0]} }) {
245	$_ && &{$_->[0]}	431	$_ && &{$_->[0]}
246	&& undef $_;	432	&& undef $_;
247	}	433	}
248		434
249	for (@{ $self->{rcv}{$_[0]} }) {	435	for (@{ $self->{rcv}{$_[0]} }) {
250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	436	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
251	&& &{$_->[0]}	437	&& &{$_->[0]}
252	&& undef $_;	438	&& undef $_;
253	}	439	}
254		440
255	for (@{ $self->{any} }) {	441	for (@{ $self->{any} }) {
256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	442	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
257	&& &{$_->[0]}	443	&& &{$_->[0]}
258	&& undef $_;	444	&& undef $_;
		445	}
259	}	446	};
		447	_self_die if $@;
260	};	448	};
261	_self_die if $@;	449
		450	$self
262	};	451	};
263	}
264		452
265	$port
266	}
267
268	=item reg $portid, $name
269
270	Registers the given port under the name C<$name>. If the name already
271	exists it is replaced.
272
273	A port can only be registered under one well known name.
274
275	A port automatically becomes unregistered when it is killed.
276
277	=cut
278
279	sub reg(@) {
280	my ($portid, $name) = @_;
281
282	$REG{$name} = $portid;
283	}
284
285	=item rcv $portid, $callback->(@msg)
286
287	Replaces the callback on the specified miniport (or newly created port
288	object, see C<port>). Full ports are configured with the following calls:
289
290	=item rcv $portid, tagstring => $callback->(@msg), ...
291
292	=item rcv $portid, $smartmatch => $callback->(@msg), ...
293
294	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
295
296	Register callbacks to be called on matching messages on the given full
297	port (or newly created port).
298
299	The callback has to return a true value when its work is done, after
300	which is will be removed, or a false value in which case it will stay
301	registered.
302
303	The global C<$SELF> (exported by this module) contains C<$portid> while
304	executing the callback.
305
306	Runtime errors wdurign callback execution will result in the port being
307	C<kil>ed.
308
309	If the match is an array reference, then it will be matched against the
310	first elements of the message, otherwise only the first element is being
311	matched.
312
313	Any element in the match that is specified as C<_any_> (a function
314	exported by this module) matches any single element of the message.
315
316	While not required, it is highly recommended that the first matching
317	element is a string identifying the message. The one-string-only match is
318	also the most efficient match (by far).
319
320	=cut
321
322	sub rcv($@) {
323	my $portid = shift;
324	my ($noderef, $port) = split /#/, $port, 2;
325
326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
328
329	my $self = $PORT_DATA{$port}
330	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
331
332	"AnyEvent::MP::Port" eq ref $self	453	"AnyEvent::MP::Port" eq ref $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";	454	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
334		455
335	while (@_) {	456	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;	457	my ($match, $cb) = splice @_, 0, 2;
337		458
338	if (!ref $match) {	459	if (!ref $match) {
339	push @{ $self->{rc0}{$match} }, [$cb];	460	push @{ $self->{rc0}{$match} }, [$cb];
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	461	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
341	my ($type, @match) = @$match;	462	my ($type, @match) = @$match;
342	@match	463	@match
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	464	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	465	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {	466	} else {
346	push @{ $self->{any} }, [$cb, $match];	467	push @{ $self->{any} }, [$cb, $match];
		468	}
347	}	469	}
348	}	470	}
349		471
350	$portid	472	$port
351	}	473	}
352		474
353	=item $closure = psub { BLOCK }	475	=item $closure = psub { BLOCK }
354		476
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	477	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	508	$res
387	}	509	}
388	}	510	}
389	}	511	}
390		512
391	=item $guard = mon $portid, $cb->(@reason)	513	=item $guard = mon $port, $cb->(@reason)
392		514
393	=item $guard = mon $portid, $otherport	515	=item $guard = mon $port, $rcvport
394		516
		517	=item $guard = mon $port
		518
395	=item $guard = mon $portid, $otherport, @msg	519	=item $guard = mon $port, $rcvport, @msg
396		520
397	Monitor the given port and do something when the port is killed.	521	Monitor the given port and do something when the port is killed or
		522	messages to it were lost, and optionally return a guard that can be used
		523	to stop monitoring again.
398		524
		525	C<mon> effectively guarantees that, in the absence of hardware failures,
		526	that after starting the monitor, either all messages sent to the port
		527	will arrive, or the monitoring action will be invoked after possible
		528	message loss has been detected. No messages will be lost "in between"
		529	(after the first lost message no further messages will be received by the
		530	port). After the monitoring action was invoked, further messages might get
		531	delivered again.
		532
399	In the first form, the callback is simply called with any number	533	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	534	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	535	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	536	C<eval> if unsure.
403		537
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	538	In the second form (another port given), the other port (C<$rcvport>)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	539	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
406	under all other conditions, the other port is killed with the same reason.	540	"normal" kils nothing happens, while under all other conditions, the other
		541	port is killed with the same reason.
407		542
		543	The third form (kill self) is the same as the second form, except that
		544	C<$rvport> defaults to C<$SELF>.
		545
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	546	In the last form (message), a message of the form C<@msg, @reason> will be
		547	C<snd>.
		548
		549	As a rule of thumb, monitoring requests should always monitor a port from
		550	a local port (or callback). The reason is that kill messages might get
		551	lost, just like any other message. Another less obvious reason is that
		552	even monitoring requests can get lost (for exmaple, when the connection
		553	to the other node goes down permanently). When monitoring a port locally
		554	these problems do not exist.
409		555
410	Example: call a given callback when C<$port> is killed.	556	Example: call a given callback when C<$port> is killed.
411		557
412	mon $port, sub { warn "port died because of <@_>\n" };	558	mon $port, sub { warn "port died because of <@_>\n" };
413		559
414	Example: kill ourselves when C<$port> is killed abnormally.	560	Example: kill ourselves when C<$port> is killed abnormally.
415		561
416	mon $port, $self;	562	mon $port;
417		563
418	Example: send us a restart message another C<$port> is killed.	564	Example: send us a restart message when another C<$port> is killed.
419		565
420	mon $port, $self => "restart";	566	mon $port, $self => "restart";
421		567
422	=cut	568	=cut
423		569
424	sub mon {	570	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	571	my ($noderef, $port) = split /#/, shift, 2;
426		572
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	573	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		574
429	my $cb = shift;	575	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		576
431	unless (ref $cb) {	577	unless (ref $cb) {
432	if (@_) {	578	if (@_) {
433	# send a kill info message	579	# send a kill info message
434	my (@msg) = ($cb, @_);	580	my (@msg) = ($cb, @_);
…		…
465	=cut	611	=cut
466		612
467	sub mon_guard {	613	sub mon_guard {
468	my ($port, @refs) = @_;	614	my ($port, @refs) = @_;
469		615
		616	#TODO: mon-less form?
		617
470	mon $port, sub { 0 && @refs }	618	mon $port, sub { 0 && @refs }
471	}	619	}
472		620
473	=item lnk $port1, $port2
474
475	Link two ports. This is simply a shorthand for:
476
477	mon $port1, $port2;
478	mon $port2, $port1;
479
480	It means that if either one is killed abnormally, the other one gets
481	killed as well.
482
483	=item kil $portid[, @reason]	621	=item kil $port[, @reason]
484		622
485	Kill the specified port with the given C<@reason>.	623	Kill the specified port with the given C<@reason>.
486		624
487	If no C<@reason> is specified, then the port is killed "normally" (linked	625	If no C<@reason> is specified, then the port is killed "normally" (linked
488	ports will not be kileld, or even notified).	626	ports will not be kileld, or even notified).
…		…
494	will be reported as reason C<< die => $@ >>.	632	will be reported as reason C<< die => $@ >>.
495		633
496	Transport/communication errors are reported as C<< transport_error =>	634	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	635	$message >>.
498		636
499	=back
500
501	=head1 FUNCTIONS FOR NODES
502
503	=over 4
504
505	=item become_public $noderef
506
507	Tells the node to become a public node, i.e. reachable from other nodes.
508
509	The first argument is the (unresolved) node reference of the local node
510	(if missing then the empty string is used).
511
512	It is quite common to not specify anything, in which case the local node
513	tries to listen on the default port, or to only specify a port number, in
514	which case AnyEvent::MP tries to guess the local addresses.
515
516	=cut	637	=cut
		638
		639	=item $port = spawn $node, $initfunc[, @initdata]
		640
		641	Creates a port on the node C<$node> (which can also be a port ID, in which
		642	case it's the node where that port resides).
		643
		644	The port ID of the newly created port is return immediately, and it is
		645	permissible to immediately start sending messages or monitor the port.
		646
		647	After the port has been created, the init function is
		648	called. This function must be a fully-qualified function name
		649	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		650	program, use C<::name>.
		651
		652	If the function doesn't exist, then the node tries to C<require>
		653	the package, then the package above the package and so on (e.g.
		654	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		655	exists or it runs out of package names.
		656
		657	The init function is then called with the newly-created port as context
		658	object (C<$SELF>) and the C<@initdata> values as arguments.
		659
		660	A common idiom is to pass your own port, monitor the spawned port, and
		661	in the init function, monitor the original port. This two-way monitoring
		662	ensures that both ports get cleaned up when there is a problem.
		663
		664	Example: spawn a chat server port on C<$othernode>.
		665
		666	# this node, executed from within a port context:
		667	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		668	mon $server;
		669
		670	# init function on C<$othernode>
		671	sub connect {
		672	my ($srcport) = @_;
		673
		674	mon $srcport;
		675
		676	rcv $SELF, sub {
		677	...
		678	};
		679	}
		680
		681	=cut
		682
		683	sub _spawn {
		684	my $port = shift;
		685	my $init = shift;
		686
		687	local $SELF = "$NODE#$port";
		688	eval {
		689	&{ load_func $init }
		690	};
		691	_self_die if $@;
		692	}
		693
		694	sub spawn(@) {
		695	my ($noderef, undef) = split /#/, shift, 2;
		696
		697	my $id = "$RUNIQ." . $ID++;
		698
		699	$_[0] =~ /::/
		700	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		701
		702	($NODE{$noderef} \|\| add_node $noderef)
		703	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		704
		705	"$noderef#$id"
		706	}
517		707
518	=back	708	=back
519		709
520	=head1 NODE MESSAGES	710	=head1 NODE MESSAGES
521		711
…		…
563		753
564	=back	754	=back
565		755
566	=head1 AnyEvent::MP vs. Distributed Erlang	756	=head1 AnyEvent::MP vs. Distributed Erlang
567		757
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	758	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
569	== aemp node, erlang process == aemp port), so many of the documents and	759	== aemp node, Erlang process == aemp port), so many of the documents and
570	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	760	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
571	sample:	761	sample:
572		762
573	http://www.erlang.se/doc/programming_rules.shtml	763	http://www.Erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	764	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
575	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	765	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
576	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	766	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577		767
578	Despite the similarities, there are also some important differences:	768	Despite the similarities, there are also some important differences:
579		769
580	=over 4	770	=over 4
581		771
…		…
592		782
593	Erlang uses processes that selctively receive messages, and therefore	783	Erlang uses processes that selctively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	784	needs a queue. AEMP is event based, queuing messages would serve no useful
595	purpose.	785	purpose.
596		786
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	787	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		788
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	789	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		790
601	Sending messages in erlang is synchronous and blocks the process. AEMP	791	Sending messages in Erlang is synchronous and blocks the process. AEMP
602	sends are immediate, connection establishment is handled in the	792	sends are immediate, connection establishment is handled in the
603	background.	793	background.
604		794
605	=item * Erlang can silently lose messages, AEMP cannot.	795	=item * Erlang can silently lose messages, AEMP cannot.
606		796
…		…
609	and c, and the other side only receives messages a and c).	799	and c, and the other side only receives messages a and c).
610		800
611	AEMP guarantees correct ordering, and the guarantee that there are no	801	AEMP guarantees correct ordering, and the guarantee that there are no
612	holes in the message sequence.	802	holes in the message sequence.
613		803
614	=item * In erlang, processes can be declared dead and later be found to be	804	=item * In Erlang, processes can be declared dead and later be found to be
615	alive.	805	alive.
616		806
617	In erlang it can happen that a monitored process is declared dead and	807	In Erlang it can happen that a monitored process is declared dead and
618	linked processes get killed, but later it turns out that the process is	808	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.	809	still alive - and can receive messages.
620		810
621	In AEMP, when port monitoring detects a port as dead, then that port will	811	In AEMP, when port monitoring detects a port as dead, then that port will
622	eventually be killed - it cannot happen that a node detects a port as dead	812	eventually be killed - it cannot happen that a node detects a port as dead
623	and then later sends messages to it, finding it is still alive.	813	and then later sends messages to it, finding it is still alive.
624		814
625	=item * Erlang can send messages to the wrong port, AEMP does not.	815	=item * Erlang can send messages to the wrong port, AEMP does not.
626		816
627	In erlang it is quite possible that a node that restarts reuses a process	817	In Erlang it is quite possible that a node that restarts reuses a process
628	ID known to other nodes for a completely different process, causing	818	ID known to other nodes for a completely different process, causing
629	messages destined for that process to end up in an unrelated process.	819	messages destined for that process to end up in an unrelated process.
630		820
631	AEMP never reuses port IDs, so old messages or old port IDs floating	821	AEMP never reuses port IDs, so old messages or old port IDs floating
632	around in the network will not be sent to an unrelated port.	822	around in the network will not be sent to an unrelated port.
…		…
638	securely authenticate nodes.	828	securely authenticate nodes.
639		829
640	=item * The AEMP protocol is optimised for both text-based and binary	830	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	831	communications.
642		832
643	The AEMP protocol, unlike the erlang protocol, supports both	833	The AEMP protocol, unlike the Erlang protocol, supports both
644	language-independent text-only protocols (good for debugging) and binary,	834	language-independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	835	language-specific serialisers (e.g. Storable).
646		836
647	It has also been carefully designed to be implementable in other languages	837	It has also been carefully designed to be implementable in other languages
648	with a minimum of work while gracefully degrading fucntionality to make the	838	with a minimum of work while gracefully degrading fucntionality to make the
649	protocol simple.	839	protocol simple.
650		840
		841	=item * AEMP has more flexible monitoring options than Erlang.
		842
		843	In Erlang, you can chose to receive I<all> exit signals as messages
		844	or I<none>, there is no in-between, so monitoring single processes is
		845	difficult to implement. Monitoring in AEMP is more flexible than in
		846	Erlang, as one can choose between automatic kill, exit message or callback
		847	on a per-process basis.
		848
		849	=item * Erlang tries to hide remote/local connections, AEMP does not.
		850
		851	Monitoring in Erlang is not an indicator of process death/crashes,
		852	as linking is (except linking is unreliable in Erlang).
		853
		854	In AEMP, you don't "look up" registered port names or send to named ports
		855	that might or might not be persistent. Instead, you normally spawn a port
		856	on the remote node. The init function monitors the you, and you monitor
		857	the remote port. Since both monitors are local to the node, they are much
		858	more reliable.
		859
		860	This also saves round-trips and avoids sending messages to the wrong port
		861	(hard to do in Erlang).
		862
		863	=back
		864
		865	=head1 RATIONALE
		866
		867	=over 4
		868
		869	=item Why strings for ports and noderefs, why not objects?
		870
		871	We considered "objects", but found that the actual number of methods
		872	thatc an be called are very low. Since port IDs and noderefs travel over
		873	the network frequently, the serialising/deserialising would add lots of
		874	overhead, as well as having to keep a proxy object.
		875
		876	Strings can easily be printed, easily serialised etc. and need no special
		877	procedures to be "valid".
		878
		879	And a a miniport consists of a single closure stored in a global hash - it
		880	can't become much cheaper.
		881
		882	=item Why favour JSON, why not real serialising format such as Storable?
		883
		884	In fact, any AnyEvent::MP node will happily accept Storable as framing
		885	format, but currently there is no way to make a node use Storable by
		886	default.
		887
		888	The default framing protocol is JSON because a) JSON::XS is many times
		889	faster for small messages and b) most importantly, after years of
		890	experience we found that object serialisation is causing more problems
		891	than it gains: Just like function calls, objects simply do not travel
		892	easily over the network, mostly because they will always be a copy, so you
		893	always have to re-think your design.
		894
		895	Keeping your messages simple, concentrating on data structures rather than
		896	objects, will keep your messages clean, tidy and efficient.
		897
651	=back	898	=back
652		899
653	=head1 SEE ALSO	900	=head1 SEE ALSO
654		901
655	L<AnyEvent>.	902	L<AnyEvent>.

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Revision 1.48 by root, Thu Aug 13 02:59:42 2009 UTC