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

…		…
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's noderef
10	NODE # returns this node's noderef	10	NODE # returns this node's noderef
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node; # -OR-
		17	initialise_node "localhost:4040"; # -OR-
		18	initialise_node "slave/", "localhost:4040"
		19
		20	# ports are message endpoints
		21
		22	# sending messages
13	snd $port, type => data...;	23	snd $port, type => data...;
		24	snd $port, @msg;
		25	snd @msg_with_first_element_being_a_port;
14		26
15	$SELF # receiving/own port id in rcv callbacks	27	# creating/using ports, the simple way
		28	my $somple_port = port { my @msg = @_; 0 };
16		29
17	rcv $port, smartmatch => $cb->($port, @msg);	30	# creating/using ports, tagged message matching
18		31	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		34
24	# more, smarter, matches (_any_ is exported by this module)	35	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	36	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
…		…
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	60	manual page.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
39	so do not use. This was uploaded mainly to reserve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.	64	stay tuned!
41		65
42	=head1 CONCEPTS	66	=head1 CONCEPTS
43		67
44	=over 4	68	=over 4
45		69
…		…
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
…		…
118	kil $SELF, die => $msg;	143	kil $SELF, die => $msg;
119	}	144	}
120		145
121	=item $thisnode = NODE / $NODE	146	=item $thisnode = NODE / $NODE
122		147
123	The C<NODE> function returns, and the C<$NODE> variable contains	148	The C<NODE> function returns, and the C<$NODE> variable contains the
124	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
125	to C<become_public> or C<become_slave>, after which all local port	150	C<initialise_node>.
126	identifiers become invalid.
127		151
128	=item $noderef = node_of $portid	152	=item $noderef = node_of $port
129		153
130	Extracts and returns the noderef from a portid or a noderef.	154	Extracts and returns the noderef from a port ID or a noderef.
		155
		156	=item initialise_node $noderef, $seednode, $seednode...
		157
		158	=item initialise_node "slave/", $master, $master...
		159
		160	Before a node can talk to other nodes on the network it has to initialise
		161	itself - the minimum a node needs to know is it's own name, and optionally
		162	it should know the noderefs of some other nodes in the network.
		163
		164	This function initialises a node - it must be called exactly once (or
		165	never) before calling other AnyEvent::MP functions.
		166
		167	All arguments (optionally except for the first) are noderefs, which can be
		168	either resolved or unresolved.
		169
		170	The first argument will be looked up in the configuration database first
		171	(if it is C<undef> then the current nodename will be used instead) to find
		172	the relevant configuration profile (see L<aemp>). If none is found then
		173	the default configuration is used. The configuration supplies additional
		174	seed/master nodes and can override the actual noderef.
		175
		176	There are two types of networked nodes, public nodes and slave nodes:
		177
		178	=over 4
		179
		180	=item public nodes
		181
		182	For public nodes, C<$noderef> (supplied either directly to
		183	C<initialise_node> or indirectly via a profile or the nodename) must be a
		184	noderef (possibly unresolved, in which case it will be resolved).
		185
		186	After resolving, the node will bind itself on all endpoints and try to
		187	connect to all additional C<$seednodes> that are specified. Seednodes are
		188	optional and can be used to quickly bootstrap the node into an existing
		189	network.
		190
		191	=item slave nodes
		192
		193	When the C<$noderef> (either as given or overriden by the config file)
		194	is the special string C<slave/>, then the node will become a slave
		195	node. Slave nodes cannot be contacted from outside and will route most of
		196	their traffic to the master node that they attach to.
		197
		198	At least one additional noderef is required (either by specifying it
		199	directly or because it is part of the configuration profile): The node
		200	will try to connect to all of them and will become a slave attached to the
		201	first node it can successfully connect to.
		202
		203	=back
		204
		205	This function will block until all nodes have been resolved and, for slave
		206	nodes, until it has successfully established a connection to a master
		207	server.
		208
		209	Example: become a public node listening on the guessed noderef, or the one
		210	specified via C<aemp> for the current node. This should be the most common
		211	form of invocation for "daemon"-type nodes.
		212
		213	initialise_node;
		214
		215	Example: become a slave node to any of the the seednodes specified via
		216	C<aemp>. This form is often used for commandline clients.
		217
		218	initialise_node "slave/";
		219
		220	Example: become a slave node to any of the specified master servers. This
		221	form is also often used for commandline clients.
		222
		223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		224
		225	Example: become a public node, and try to contact some well-known master
		226	servers to become part of the network.
		227
		228	initialise_node undef, "master1", "master2";
		229
		230	Example: become a public node listening on port C<4041>.
		231
		232	initialise_node 4041;
		233
		234	Example: become a public node, only visible on localhost port 4044.
		235
		236	initialise_node "localhost:4044";
131		237
132	=item $cv = resolve_node $noderef	238	=item $cv = resolve_node $noderef
133		239
134	Takes an unresolved node reference that may contain hostnames and	240	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	241	abbreviated IDs, resolves all of them and returns a resolved node
…		…
167		273
168	Due to some quirks in how perl exports variables, it is impossible to	274	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	275	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	276	module, but only C<$SELF> is currently used.
171		277
172	=item snd $portid, type => @data	278	=item snd $port, type => @data
173		279
174	=item snd $portid, @msg	280	=item snd $port, @msg
175		281
176	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
177	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.
178	stringifies a sa port ID (such as a port object :).
179		284
180	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
181	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
182	type etc.).	287	type etc.).
183		288
184	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
185	function: modifying any argument is not allowed and can cause many	290	function: modifying any argument is not allowed and can cause many
186	problems.	291	problems.
…		…
191	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
192	node, anything can be passed.	297	node, anything can be passed.
193		298
194	=item $local_port = port	299	=item $local_port = port
195		300
196	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
197	matching port ("full port") or a single-callback port ("miniport"),	302	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		303
200	=item $portid = port { my @msg = @_; $finished }	304	=item $local_port = port { my @msg = @_ }
201		305
202	Creates a "mini port", that is, a very lightweight port without any	306	Creates a new local port, and returns its ID. Semantically the same as
203	pattern matching behind it, and returns its ID.	307	creating a port and calling C<rcv $port, $callback> on it.
204		308
205	The block will be called for every message received on the port. When the	309	The block will be called for every message received on the port, with the
206	callback returns a true value its job is considered "done" and the port	310	global variable C<$SELF> set to the port ID. Runtime errors will cause the
207	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.
208		313
209	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:
210	be passed to the callback.
211		315
212	If you need the local port id in the callback, this works nicely:	316	my $port = port {
213		317	my @msg = @_;
214	my $port; $port = port {	318	...
215	snd $otherport, reply => $port;	319	kil $SELF;
216	};	320	};
217		321
218	=cut	322	=cut
		323
		324	sub rcv($@);
		325
		326	sub _kilme {
		327	die "received message on port without callback";
		328	}
219		329
220	sub port(;&) {	330	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	331	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	332	my $port = "$NODE#$id";
223		333
224	if (@_) {	334	rcv $port, shift \|\| \&_kilme;
225	my $cb = shift;
226	$PORT{$id} = sub {
227	local $SELF = $port;
228	eval {
229	&$cb
230	and kil $id;
231	};
232	_self_die if $@;
233	};
234	} else {
235	my $self = bless {
236	id => "$NODE#$id",
237	}, "AnyEvent::MP::Port";
238
239	$PORT_DATA{$id} = $self;
240	$PORT{$id} = sub {
241	local $SELF = $port;
242
243	eval {
244	for (@{ $self->{rc0}{$_[0]} }) {
245	$_ && &{$_->[0]}
246	&& undef $_;
247	}
248
249	for (@{ $self->{rcv}{$_[0]} }) {
250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
251	&& &{$_->[0]}
252	&& undef $_;
253	}
254
255	for (@{ $self->{any} }) {
256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
257	&& &{$_->[0]}
258	&& undef $_;
259	}
260	};
261	_self_die if $@;
262	};
263	}
264		335
265	$port	336	$port
266	}	337	}
267		338
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)	339	=item rcv $local_port, $callback->(@msg)
286		340
287	Replaces the callback on the specified miniport (or newly created port	341	Replaces the default callback on the specified port. There is no way to
288	object, see C<port>). Full ports are configured with the following calls:	342	remove the default callback: use C<sub { }> to disable it, or better
		343	C<kil> the port when it is no longer needed.
289		344
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<$portid> while	345	The global C<$SELF> (exported by this module) contains C<$port> while
304	executing the callback.	346	executing the callback. Runtime errors during callback execution will
		347	result in the port being C<kil>ed.
305		348
306	Runtime errors wdurign callback execution will result in the port being	349	The default callback received all messages not matched by a more specific
307	C<kil>ed.	350	C<tag> match.
308		351
309	If the match is an array reference, then it will be matched against the	352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
310	first elements of the message, otherwise only the first element is being
311	matched.
312		353
313	Any element in the match that is specified as C<_any_> (a function	354	Register callbacks to be called on messages starting with the given tag on
314	exported by this module) matches any single element of the message.	355	the given port (and return the port), or unregister it (when C<$callback>
		356	is C<$undef>).
315		357
316	While not required, it is highly recommended that the first matching	358	The original message will be passed to the callback, after the first
317	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
318	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 $otherport, reply =>
		373	rcv port,
		374	msg1 => sub { ... },
		375	...
		376	;
319		377
320	=cut	378	=cut
321		379
322	sub rcv($@) {	380	sub rcv($@) {
323	my $portid = shift;	381	my $port = shift;
324	my ($noderef, $port) = split /#/, $port, 2;	382	my ($noderef, $portid) = split /#/, $port, 2;
325		383
326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";	385	or Carp::croak "$port: rcv can only be called on local ports, caught";
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 $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
334		386
335	while (@_) {	387	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;
337
338	if (!ref $match) {	388	if (ref $_[0]) {
339	push @{ $self->{rc0}{$match} }, [$cb];	389	if (my $self = $PORT_DATA{$portid}) {
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	390	"AnyEvent::MP::Port" eq ref $self
341	my ($type, @match) = @$match;	391	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
342	@match	392
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	393	$self->[2] = shift;
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {	394	} else {
346	push @{ $self->{any} }, [$cb, $match];	395	my $cb = shift;
		396	$PORT{$portid} = sub {
		397	local $SELF = $port;
		398	eval { &$cb }; _self_die if $@;
		399	};
		400	}
		401	} elsif (defined $_[0]) {
		402	my $self = $PORT_DATA{$portid} \|\|= do {
		403	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		404
		405	$PORT{$portid} = sub {
		406	local $SELF = $port;
		407
		408	if (my $cb = $self->[1]{$_[0]}) {
		409	shift;
		410	eval { &$cb }; _self_die if $@;
		411	} else {
		412	&{ $self->[0] };
		413	}
		414	};
		415
		416	$self
		417	};
		418
		419	"AnyEvent::MP::Port" eq ref $self
		420	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		421
		422	my ($tag, $cb) = splice @_, 0, 2;
		423
		424	if (defined $cb) {
		425	$self->[1]{$tag} = $cb;
		426	} else {
		427	delete $self->[1]{$tag};
		428	}
347	}	429	}
348	}	430	}
349		431
350	$portid	432	$port
351	}	433	}
352		434
353	=item $closure = psub { BLOCK }	435	=item $closure = psub { BLOCK }
354		436
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	437	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	468	$res
387	}	469	}
388	}	470	}
389	}	471	}
390		472
391	=item $guard = mon $portid, $cb->(@reason)	473	=item $guard = mon $port, $cb->(@reason)
392		474
393	=item $guard = mon $portid, $otherport	475	=item $guard = mon $port, $rcvport
394		476
		477	=item $guard = mon $port
		478
395	=item $guard = mon $portid, $otherport, @msg	479	=item $guard = mon $port, $rcvport, @msg
396		480
397	Monitor the given port and do something when the port is killed.	481	Monitor the given port and do something when the port is killed or
		482	messages to it were lost, and optionally return a guard that can be used
		483	to stop monitoring again.
398		484
		485	C<mon> effectively guarantees that, in the absence of hardware failures,
		486	that after starting the monitor, either all messages sent to the port
		487	will arrive, or the monitoring action will be invoked after possible
		488	message loss has been detected. No messages will be lost "in between"
		489	(after the first lost message no further messages will be received by the
		490	port). After the monitoring action was invoked, further messages might get
		491	delivered again.
		492
399	In the first form, the callback is simply called with any number	493	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	496	C<eval> if unsure.
403		497
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	498	In the second form (another port given), the other port (C<$rcvport>)
405	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
406	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.
407		502
		503	The third form (kill self) is the same as the second form, except that
		504	C<$rvport> defaults to C<$SELF>.
		505
408	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.
409		515
410	Example: call a given callback when C<$port> is killed.	516	Example: call a given callback when C<$port> is killed.
411		517
412	mon $port, sub { warn "port died because of <@_>\n" };	518	mon $port, sub { warn "port died because of <@_>\n" };
413		519
414	Example: kill ourselves when C<$port> is killed abnormally.	520	Example: kill ourselves when C<$port> is killed abnormally.
415		521
416	mon $port, $self;	522	mon $port;
417		523
418	Example: send us a restart message another C<$port> is killed.	524	Example: send us a restart message when another C<$port> is killed.
419		525
420	mon $port, $self => "restart";	526	mon $port, $self => "restart";
421		527
422	=cut	528	=cut
423		529
424	sub mon {	530	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	531	my ($noderef, $port) = split /#/, shift, 2;
426		532
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	533	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		534
429	my $cb = shift;	535	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		536
431	unless (ref $cb) {	537	unless (ref $cb) {
432	if (@_) {	538	if (@_) {
433	# send a kill info message	539	# send a kill info message
434	my (@msg) = ($cb, @_);	540	my (@msg) = ($cb, @_);
…		…
465	=cut	571	=cut
466		572
467	sub mon_guard {	573	sub mon_guard {
468	my ($port, @refs) = @_;	574	my ($port, @refs) = @_;
469		575
		576	#TODO: mon-less form?
		577
470	mon $port, sub { 0 && @refs }	578	mon $port, sub { 0 && @refs }
471	}	579	}
472		580
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]	581	=item kil $port[, @reason]
484		582
485	Kill the specified port with the given C<@reason>.	583	Kill the specified port with the given C<@reason>.
486		584
487	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
488	ports will not be kileld, or even notified).	586	ports will not be kileld, or even notified).
…		…
494	will be reported as reason C<< die => $@ >>.	592	will be reported as reason C<< die => $@ >>.
495		593
496	Transport/communication errors are reported as C<< transport_error =>	594	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	595	$message >>.
498		596
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	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	}
517		667
518	=back	668	=back
519		669
520	=head1 NODE MESSAGES	670	=head1 NODE MESSAGES
521		671
…		…
563		713
564	=back	714	=back
565		715
566	=head1 AnyEvent::MP vs. Distributed Erlang	716	=head1 AnyEvent::MP vs. Distributed Erlang
567		717
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	718	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
569	== aemp node, erlang process == aemp port), so many of the documents and	719	== aemp node, Erlang process == aemp port), so many of the documents and
570	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	720	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
571	sample:	721	sample:
572		722
573	http://www.erlang.se/doc/programming_rules.shtml	723	http://www.Erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	724	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
575	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	725	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
576	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	726	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577		727
578	Despite the similarities, there are also some important differences:	728	Despite the similarities, there are also some important differences:
579		729
580	=over 4	730	=over 4
581		731
…		…
586	convenience functionality.	736	convenience functionality.
587		737
588	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
589	cost of longer node references and a slightly higher management overhead.	739	cost of longer node references and a slightly higher management overhead.
590		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
591	=item * Erlang uses processes and a mailbox, AEMP does not queue.	756	=item * Erlang uses processes and a mailbox, AEMP does not queue.
592		757
593	Erlang uses processes that selctively receive messages, and therefore	758	Erlang uses processes that selectively receive messages, and therefore
594	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
595	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.
596		763
597	(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).
598		765
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		767
601	Sending messages in erlang is synchronous and blocks the process. AEMP	768	Sending messages in Erlang is synchronous and blocks the process (and
602	sends are immediate, connection establishment is handled in the	769	so does not need a queue that can overflow). AEMP sends are immediate,
603	background.	770	connection establishment is handled in the background.
604		771
605	=item * Erlang can silently lose messages, AEMP cannot.	772	=item * Erlang suffers from silent message loss, AEMP does not.
606		773
607	Erlang makes few guarantees on messages delivery - messages can get lost	774	Erlang makes few guarantees on messages delivery - messages can get lost
608	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,
609	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).
610		777
611	AEMP guarantees correct ordering, and the guarantee that there are no	778	AEMP guarantees correct ordering, and the guarantee that there are no
612	holes in the message sequence.	779	holes in the message sequence.
613		780
614	=item * In erlang, processes can be declared dead and later be found to be	781	=item * In Erlang, processes can be declared dead and later be found to be
615	alive.	782	alive.
616		783
617	In erlang it can happen that a monitored process is declared dead and	784	In Erlang it can happen that a monitored process is declared dead and
618	linked processes get killed, but later it turns out that the process is	785	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.	786	still alive - and can receive messages.
620		787
621	In AEMP, when port monitoring detects a port as dead, then that port will	788	In AEMP, when port monitoring detects a port as dead, then that port will
622	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
623	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.
624		791
625	=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.
626		793
627	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
628	ID known to other nodes for a completely different process, causing	795	known to other nodes for a completely different process, causing messages
629	messages destined for that process to end up in an unrelated process.	796	destined for that process to end up in an unrelated process.
630		797
631	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
632	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.
633		800
634	=item * Erlang uses unprotected connections, AEMP uses secure	801	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
638	securely authenticate nodes.	805	securely authenticate nodes.
639		806
640	=item * The AEMP protocol is optimised for both text-based and binary	807	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	808	communications.
642		809
643	The AEMP protocol, unlike the erlang protocol, supports both	810	The AEMP protocol, unlike the Erlang protocol, supports both
644	language-independent text-only protocols (good for debugging) and binary,	811	language-independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	812	language-specific serialisers (e.g. Storable).
646		813
647	It has also been carefully designed to be implementable in other languages	814	It has also been carefully designed to be implementable in other languages
648	with a minimum of work while gracefully degrading fucntionality to make the	815	with a minimum of work while gracefully degrading fucntionality to make the
649	protocol simple.	816	protocol simple.
650		817
		818	=item * AEMP has more flexible monitoring options than Erlang.
		819
		820	In Erlang, you can chose to receive I<all> exit signals as messages
		821	or I<none>, there is no in-between, so monitoring single processes is
		822	difficult to implement. Monitoring in AEMP is more flexible than in
		823	Erlang, as one can choose between automatic kill, exit message or callback
		824	on a per-process basis.
		825
		826	=item * Erlang tries to hide remote/local connections, AEMP does not.
		827
		828	Monitoring in Erlang is not an indicator of process death/crashes,
		829	as linking is (except linking is unreliable in Erlang).
		830
		831	In AEMP, you don't "look up" registered port names or send to named ports
		832	that might or might not be persistent. Instead, you normally spawn a port
		833	on the remote node. The init function monitors the you, and you monitor
		834	the remote port. Since both monitors are local to the node, they are much
		835	more reliable.
		836
		837	This also saves round-trips and avoids sending messages to the wrong port
		838	(hard to do in Erlang).
		839
		840	=back
		841
		842	=head1 RATIONALE
		843
		844	=over 4
		845
		846	=item Why strings for ports and noderefs, why not objects?
		847
		848	We considered "objects", but found that the actual number of methods
		849	thatc an be called are very low. Since port IDs and noderefs travel over
		850	the network frequently, the serialising/deserialising would add lots of
		851	overhead, as well as having to keep a proxy object.
		852
		853	Strings can easily be printed, easily serialised etc. and need no special
		854	procedures to be "valid".
		855
		856	And a a miniport consists of a single closure stored in a global hash - it
		857	can't become much cheaper.
		858
		859	=item Why favour JSON, why not real serialising format such as Storable?
		860
		861	In fact, any AnyEvent::MP node will happily accept Storable as framing
		862	format, but currently there is no way to make a node use Storable by
		863	default.
		864
		865	The default framing protocol is JSON because a) JSON::XS is many times
		866	faster for small messages and b) most importantly, after years of
		867	experience we found that object serialisation is causing more problems
		868	than it gains: Just like function calls, objects simply do not travel
		869	easily over the network, mostly because they will always be a copy, so you
		870	always have to re-think your design.
		871
		872	Keeping your messages simple, concentrating on data structures rather than
		873	objects, will keep your messages clean, tidy and efficient.
		874
651	=back	875	=back
652		876
653	=head1 SEE ALSO	877	=head1 SEE ALSO
654		878
655	L<AnyEvent>.	879	L<AnyEvent>.

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