[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 1.49 by root, Thu Aug 13 15:29:58 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		51	AnyEvent::MP::Intro - outdated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, $master...
		165
		166	Before a node can talk to other nodes on the network it has to initialise
		167	itself - the minimum a node needs to know is it's own name, and optionally
		168	it should know the noderefs of some other nodes in the network.
		169
		170	This function initialises a node - it must be called exactly once (or
		171	never) before calling other AnyEvent::MP functions.
		172
		173	All arguments (optionally except for the first) are noderefs, which can be
		174	either resolved or unresolved.
		175
		176	The first argument will be looked up in the configuration database first
		177	(if it is C<undef> then the current nodename will be used instead) to find
		178	the relevant configuration profile (see L<aemp>). If none is found then
		179	the default configuration is used. The configuration supplies additional
		180	seed/master nodes and can override the actual noderef.
		181
		182	There are two types of networked nodes, public nodes and slave nodes:
		183
		184	=over 4
		185
		186	=item public nodes
		187
		188	For public nodes, C<$noderef> (supplied either directly to
		189	C<initialise_node> or indirectly via a profile or the nodename) must be a
		190	noderef (possibly unresolved, in which case it will be resolved).
		191
		192	After resolving, the node will bind itself on all endpoints and try to
		193	connect to all additional C<$seednodes> that are specified. Seednodes are
		194	optional and can be used to quickly bootstrap the node into an existing
		195	network.
		196
		197	=item slave nodes
		198
		199	When the C<$noderef> (either as given or overriden by the config file)
		200	is the special string C<slave/>, then the node will become a slave
		201	node. Slave nodes cannot be contacted from outside and will route most of
		202	their traffic to the master node that they attach to.
		203
		204	At least one additional noderef is required (either by specifying it
		205	directly or because it is part of the configuration profile): The node
		206	will try to connect to all of them and will become a slave attached to the
		207	first node it can successfully connect to.
		208
		209	=back
		210
		211	This function will block until all nodes have been resolved and, for slave
		212	nodes, until it has successfully established a connection to a master
		213	server.
		214
		215	Example: become a public node listening on the guessed noderef, or the one
		216	specified via C<aemp> for the current node. This should be the most common
		217	form of invocation for "daemon"-type nodes.
		218
		219	initialise_node;
		220
		221	Example: become a slave node to any of the the seednodes specified via
		222	C<aemp>. This form is often used for commandline clients.
		223
		224	initialise_node "slave/";
		225
		226	Example: become a slave node to any of the specified master servers. This
		227	form is also often used for commandline clients.
		228
		229	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		230
		231	Example: become a public node, and try to contact some well-known master
		232	servers to become part of the network.
		233
		234	initialise_node undef, "master1", "master2";
		235
		236	Example: become a public node listening on port C<4041>.
		237
		238	initialise_node 4041;
		239
		240	Example: become a public node, only visible on localhost port 4044.
		241
		242	initialise_node "localhost:4044";
131		243
132	=item $cv = resolve_node $noderef	244	=item $cv = resolve_node $noderef
133		245
134	Takes an unresolved node reference that may contain hostnames and	246	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	247	abbreviated IDs, resolves all of them and returns a resolved node
…		…
167		279
168	Due to some quirks in how perl exports variables, it is impossible to	280	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	281	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	282	module, but only C<$SELF> is currently used.
171		283
172	=item snd $portid, type => @data	284	=item snd $port, type => @data
173		285
174	=item snd $portid, @msg	286	=item snd $port, @msg
175		287
176	Send the given message to the given port ID, which can identify either	288	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	289	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 :).	290	stringifies a sa port ID (such as a port object :).
179		291
…		…
195		307
196	Create a new local port object that can be used either as a pattern	308	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"),	309	matching port ("full port") or a single-callback port ("miniport"),
198	depending on how C<rcv> callbacks are bound to the object.	310	depending on how C<rcv> callbacks are bound to the object.
199		311
200	=item $portid = port { my @msg = @_; $finished }	312	=item $port = port { my @msg = @_; $finished }
201		313
202	Creates a "mini port", that is, a very lightweight port without any	314	Creates a "miniport", that is, a very lightweight port without any pattern
203	pattern matching behind it, and returns its ID.	315	matching behind it, and returns its ID. Semantically the same as creating
		316	a port and calling C<rcv $port, $callback> on it.
204		317
205	The block will be called for every message received on the port. When the	318	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	319	callback returns a true value its job is considered "done" and the port
207	will be destroyed. Otherwise it will stay alive.	320	will be destroyed. Otherwise it will stay alive.
208		321
…		…
215	snd $otherport, reply => $port;	328	snd $otherport, reply => $port;
216	};	329	};
217		330
218	=cut	331	=cut
219		332
		333	sub rcv($@);
		334
220	sub port(;&) {	335	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	336	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	337	my $port = "$NODE#$id";
223		338
224	if (@_) {	339	if (@_) {
		340	rcv $port, shift;
		341	} else {
		342	$PORT{$id} = sub { }; # nop
		343	}
		344
		345	$port
		346	}
		347
		348	=item reg $port, $name
		349
		350	=item reg $name
		351
		352	Registers the given port (or C<$SELF><<< if missing) under the name
		353	C<$name>. If the name already exists it is replaced.
		354
		355	A port can only be registered under one well known name.
		356
		357	A port automatically becomes unregistered when it is killed.
		358
		359	=cut
		360
		361	sub reg(@) {
		362	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
		363
		364	$REG{$_[0]} = $port;
		365	}
		366
		367	=item rcv $port, $callback->(@msg)
		368
		369	Replaces the callback on the specified miniport (after converting it to
		370	one if required).
		371
		372	=item rcv $port, tagstring => $callback->(@msg), ...
		373
		374	=item rcv $port, $smartmatch => $callback->(@msg), ...
		375
		376	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
		377
		378	Register callbacks to be called on matching messages on the given full
		379	port (after converting it to one if required) and return the port.
		380
		381	The callback has to return a true value when its work is done, after
		382	which is will be removed, or a false value in which case it will stay
		383	registered.
		384
		385	The global C<$SELF> (exported by this module) contains C<$port> while
		386	executing the callback.
		387
		388	Runtime errors during callback execution will result in the port being
		389	C<kil>ed.
		390
		391	If the match is an array reference, then it will be matched against the
		392	first elements of the message, otherwise only the first element is being
		393	matched.
		394
		395	Any element in the match that is specified as C<_any_> (a function
		396	exported by this module) matches any single element of the message.
		397
		398	While not required, it is highly recommended that the first matching
		399	element is a string identifying the message. The one-string-only match is
		400	also the most efficient match (by far).
		401
		402	Example: create a port and bind receivers on it in one go.
		403
		404	my $port = rcv port,
		405	msg1 => sub { ...; 0 },
		406	msg2 => sub { ...; 0 },
		407	;
		408
		409	Example: create a port, bind receivers and send it in a message elsewhere
		410	in one go:
		411
		412	snd $otherport, reply =>
		413	rcv port,
		414	msg1 => sub { ...; 0 },
		415	...
		416	;
		417
		418	=cut
		419
		420	sub rcv($@) {
		421	my $port = shift;
		422	my ($noderef, $portid) = split /#/, $port, 2;
		423
		424	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		425	or Carp::croak "$port: rcv can only be called on local ports, caught";
		426
		427	if (@_ == 1) {
225	my $cb = shift;	428	my $cb = shift;
		429	delete $PORT_DATA{$portid};
226	$PORT{$id} = sub {	430	$PORT{$portid} = sub {
227	local $SELF = $port;	431	local $SELF = $port;
228	eval {	432	eval {
229	&$cb	433	&$cb
230	and kil $id;	434	and kil $port;
231	};	435	};
232	_self_die if $@;	436	_self_die if $@;
233	};	437	};
234	} else {	438	} else {
		439	my $self = $PORT_DATA{$portid} \|\|= do {
235	my $self = bless {	440	my $self = bless {
236	id => "$NODE#$id",	441	id => $port,
237	}, "AnyEvent::MP::Port";	442	}, "AnyEvent::MP::Port";
238		443
239	$PORT_DATA{$id} = $self;
240	$PORT{$id} = sub {	444	$PORT{$portid} = sub {
241	local $SELF = $port;	445	local $SELF = $port;
242		446
243	eval {	447	eval {
244	for (@{ $self->{rc0}{$_[0]} }) {	448	for (@{ $self->{rc0}{$_[0]} }) {
245	$_ && &{$_->[0]}	449	$_ && &{$_->[0]}
246	&& undef $_;	450	&& undef $_;
247	}	451	}
248		452
249	for (@{ $self->{rcv}{$_[0]} }) {	453	for (@{ $self->{rcv}{$_[0]} }) {
250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	454	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
251	&& &{$_->[0]}	455	&& &{$_->[0]}
252	&& undef $_;	456	&& undef $_;
253	}	457	}
254		458
255	for (@{ $self->{any} }) {	459	for (@{ $self->{any} }) {
256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	460	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
257	&& &{$_->[0]}	461	&& &{$_->[0]}
258	&& undef $_;	462	&& undef $_;
		463	}
259	}	464	};
		465	_self_die if $@;
260	};	466	};
261	_self_die if $@;	467
		468	$self
262	};	469	};
263	}
264		470
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	471	"AnyEvent::MP::Port" eq ref $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";	472	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
334		473
335	while (@_) {	474	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;	475	my ($match, $cb) = splice @_, 0, 2;
337		476
338	if (!ref $match) {	477	if (!ref $match) {
339	push @{ $self->{rc0}{$match} }, [$cb];	478	push @{ $self->{rc0}{$match} }, [$cb];
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	479	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
341	my ($type, @match) = @$match;	480	my ($type, @match) = @$match;
342	@match	481	@match
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	482	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	483	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {	484	} else {
346	push @{ $self->{any} }, [$cb, $match];	485	push @{ $self->{any} }, [$cb, $match];
		486	}
347	}	487	}
348	}	488	}
349		489
350	$portid	490	$port
351	}	491	}
352		492
353	=item $closure = psub { BLOCK }	493	=item $closure = psub { BLOCK }
354		494
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	495	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	526	$res
387	}	527	}
388	}	528	}
389	}	529	}
390		530
391	=item $guard = mon $portid, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason)
392		532
393	=item $guard = mon $portid, $otherport	533	=item $guard = mon $port, $rcvport
394		534
		535	=item $guard = mon $port
		536
395	=item $guard = mon $portid, $otherport, @msg	537	=item $guard = mon $port, $rcvport, @msg
396		538
397	Monitor the given port and do something when the port is killed.	539	Monitor the given port and do something when the port is killed or
		540	messages to it were lost, and optionally return a guard that can be used
		541	to stop monitoring again.
398		542
		543	C<mon> effectively guarantees that, in the absence of hardware failures,
		544	that after starting the monitor, either all messages sent to the port
		545	will arrive, or the monitoring action will be invoked after possible
		546	message loss has been detected. No messages will be lost "in between"
		547	(after the first lost message no further messages will be received by the
		548	port). After the monitoring action was invoked, further messages might get
		549	delivered again.
		550
399	In the first form, the callback is simply called with any number	551	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	552	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	553	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	554	C<eval> if unsure.
403		555
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	556	In the second form (another port given), the other port (C<$rcvport>)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	557	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.	558	"normal" kils nothing happens, while under all other conditions, the other
		559	port is killed with the same reason.
407		560
		561	The third form (kill self) is the same as the second form, except that
		562	C<$rvport> defaults to C<$SELF>.
		563
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	564	In the last form (message), a message of the form C<@msg, @reason> will be
		565	C<snd>.
		566
		567	As a rule of thumb, monitoring requests should always monitor a port from
		568	a local port (or callback). The reason is that kill messages might get
		569	lost, just like any other message. Another less obvious reason is that
		570	even monitoring requests can get lost (for exmaple, when the connection
		571	to the other node goes down permanently). When monitoring a port locally
		572	these problems do not exist.
409		573
410	Example: call a given callback when C<$port> is killed.	574	Example: call a given callback when C<$port> is killed.
411		575
412	mon $port, sub { warn "port died because of <@_>\n" };	576	mon $port, sub { warn "port died because of <@_>\n" };
413		577
414	Example: kill ourselves when C<$port> is killed abnormally.	578	Example: kill ourselves when C<$port> is killed abnormally.
415		579
416	mon $port, $self;	580	mon $port;
417		581
418	Example: send us a restart message another C<$port> is killed.	582	Example: send us a restart message when another C<$port> is killed.
419		583
420	mon $port, $self => "restart";	584	mon $port, $self => "restart";
421		585
422	=cut	586	=cut
423		587
424	sub mon {	588	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	589	my ($noderef, $port) = split /#/, shift, 2;
426		590
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	591	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		592
429	my $cb = shift;	593	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		594
431	unless (ref $cb) {	595	unless (ref $cb) {
432	if (@_) {	596	if (@_) {
433	# send a kill info message	597	# send a kill info message
434	my (@msg) = ($cb, @_);	598	my (@msg) = ($cb, @_);
…		…
465	=cut	629	=cut
466		630
467	sub mon_guard {	631	sub mon_guard {
468	my ($port, @refs) = @_;	632	my ($port, @refs) = @_;
469		633
		634	#TODO: mon-less form?
		635
470	mon $port, sub { 0 && @refs }	636	mon $port, sub { 0 && @refs }
471	}	637	}
472		638
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]	639	=item kil $port[, @reason]
484		640
485	Kill the specified port with the given C<@reason>.	641	Kill the specified port with the given C<@reason>.
486		642
487	If no C<@reason> is specified, then the port is killed "normally" (linked	643	If no C<@reason> is specified, then the port is killed "normally" (linked
488	ports will not be kileld, or even notified).	644	ports will not be kileld, or even notified).
…		…
494	will be reported as reason C<< die => $@ >>.	650	will be reported as reason C<< die => $@ >>.
495		651
496	Transport/communication errors are reported as C<< transport_error =>	652	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	653	$message >>.
498		654
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	655	=cut
		656
		657	=item $port = spawn $node, $initfunc[, @initdata]
		658
		659	Creates a port on the node C<$node> (which can also be a port ID, in which
		660	case it's the node where that port resides).
		661
		662	The port ID of the newly created port is return immediately, and it is
		663	permissible to immediately start sending messages or monitor the port.
		664
		665	After the port has been created, the init function is
		666	called. This function must be a fully-qualified function name
		667	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		668	program, use C<::name>.
		669
		670	If the function doesn't exist, then the node tries to C<require>
		671	the package, then the package above the package and so on (e.g.
		672	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		673	exists or it runs out of package names.
		674
		675	The init function is then called with the newly-created port as context
		676	object (C<$SELF>) and the C<@initdata> values as arguments.
		677
		678	A common idiom is to pass your own port, monitor the spawned port, and
		679	in the init function, monitor the original port. This two-way monitoring
		680	ensures that both ports get cleaned up when there is a problem.
		681
		682	Example: spawn a chat server port on C<$othernode>.
		683
		684	# this node, executed from within a port context:
		685	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		686	mon $server;
		687
		688	# init function on C<$othernode>
		689	sub connect {
		690	my ($srcport) = @_;
		691
		692	mon $srcport;
		693
		694	rcv $SELF, sub {
		695	...
		696	};
		697	}
		698
		699	=cut
		700
		701	sub _spawn {
		702	my $port = shift;
		703	my $init = shift;
		704
		705	local $SELF = "$NODE#$port";
		706	eval {
		707	&{ load_func $init }
		708	};
		709	_self_die if $@;
		710	}
		711
		712	sub spawn(@) {
		713	my ($noderef, undef) = split /#/, shift, 2;
		714
		715	my $id = "$RUNIQ." . $ID++;
		716
		717	$_[0] =~ /::/
		718	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		719
		720	($NODE{$noderef} \|\| add_node $noderef)
		721	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		722
		723	"$noderef#$id"
		724	}
517		725
518	=back	726	=back
519		727
520	=head1 NODE MESSAGES	728	=head1 NODE MESSAGES
521		729
…		…
563		771
564	=back	772	=back
565		773
566	=head1 AnyEvent::MP vs. Distributed Erlang	774	=head1 AnyEvent::MP vs. Distributed Erlang
567		775
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	776	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	777	== 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	778	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
571	sample:	779	sample:
572		780
573	http://www.erlang.se/doc/programming_rules.shtml	781	http://www.Erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	782	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	783	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	784	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577		785
578	Despite the similarities, there are also some important differences:	786	Despite the similarities, there are also some important differences:
579		787
580	=over 4	788	=over 4
581		789
…		…
592		800
593	Erlang uses processes that selctively receive messages, and therefore	801	Erlang uses processes that selctively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	802	needs a queue. AEMP is event based, queuing messages would serve no useful
595	purpose.	803	purpose.
596		804
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	805	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		806
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	807	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		808
601	Sending messages in erlang is synchronous and blocks the process. AEMP	809	Sending messages in Erlang is synchronous and blocks the process. AEMP
602	sends are immediate, connection establishment is handled in the	810	sends are immediate, connection establishment is handled in the
603	background.	811	background.
604		812
605	=item * Erlang can silently lose messages, AEMP cannot.	813	=item * Erlang can silently lose messages, AEMP cannot.
606		814
…		…
609	and c, and the other side only receives messages a and c).	817	and c, and the other side only receives messages a and c).
610		818
611	AEMP guarantees correct ordering, and the guarantee that there are no	819	AEMP guarantees correct ordering, and the guarantee that there are no
612	holes in the message sequence.	820	holes in the message sequence.
613		821
614	=item * In erlang, processes can be declared dead and later be found to be	822	=item * In Erlang, processes can be declared dead and later be found to be
615	alive.	823	alive.
616		824
617	In erlang it can happen that a monitored process is declared dead and	825	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	826	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.	827	still alive - and can receive messages.
620		828
621	In AEMP, when port monitoring detects a port as dead, then that port will	829	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	830	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.	831	and then later sends messages to it, finding it is still alive.
624		832
625	=item * Erlang can send messages to the wrong port, AEMP does not.	833	=item * Erlang can send messages to the wrong port, AEMP does not.
626		834
627	In erlang it is quite possible that a node that restarts reuses a process	835	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	836	ID known to other nodes for a completely different process, causing
629	messages destined for that process to end up in an unrelated process.	837	messages destined for that process to end up in an unrelated process.
630		838
631	AEMP never reuses port IDs, so old messages or old port IDs floating	839	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.	840	around in the network will not be sent to an unrelated port.
…		…
638	securely authenticate nodes.	846	securely authenticate nodes.
639		847
640	=item * The AEMP protocol is optimised for both text-based and binary	848	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	849	communications.
642		850
643	The AEMP protocol, unlike the erlang protocol, supports both	851	The AEMP protocol, unlike the Erlang protocol, supports both
644	language-independent text-only protocols (good for debugging) and binary,	852	language-independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	853	language-specific serialisers (e.g. Storable).
646		854
647	It has also been carefully designed to be implementable in other languages	855	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	856	with a minimum of work while gracefully degrading fucntionality to make the
649	protocol simple.	857	protocol simple.
650		858
		859	=item * AEMP has more flexible monitoring options than Erlang.
		860
		861	In Erlang, you can chose to receive I<all> exit signals as messages
		862	or I<none>, there is no in-between, so monitoring single processes is
		863	difficult to implement. Monitoring in AEMP is more flexible than in
		864	Erlang, as one can choose between automatic kill, exit message or callback
		865	on a per-process basis.
		866
		867	=item * Erlang tries to hide remote/local connections, AEMP does not.
		868
		869	Monitoring in Erlang is not an indicator of process death/crashes,
		870	as linking is (except linking is unreliable in Erlang).
		871
		872	In AEMP, you don't "look up" registered port names or send to named ports
		873	that might or might not be persistent. Instead, you normally spawn a port
		874	on the remote node. The init function monitors the you, and you monitor
		875	the remote port. Since both monitors are local to the node, they are much
		876	more reliable.
		877
		878	This also saves round-trips and avoids sending messages to the wrong port
		879	(hard to do in Erlang).
		880
		881	=back
		882
		883	=head1 RATIONALE
		884
		885	=over 4
		886
		887	=item Why strings for ports and noderefs, why not objects?
		888
		889	We considered "objects", but found that the actual number of methods
		890	thatc an be called are very low. Since port IDs and noderefs travel over
		891	the network frequently, the serialising/deserialising would add lots of
		892	overhead, as well as having to keep a proxy object.
		893
		894	Strings can easily be printed, easily serialised etc. and need no special
		895	procedures to be "valid".
		896
		897	And a a miniport consists of a single closure stored in a global hash - it
		898	can't become much cheaper.
		899
		900	=item Why favour JSON, why not real serialising format such as Storable?
		901
		902	In fact, any AnyEvent::MP node will happily accept Storable as framing
		903	format, but currently there is no way to make a node use Storable by
		904	default.
		905
		906	The default framing protocol is JSON because a) JSON::XS is many times
		907	faster for small messages and b) most importantly, after years of
		908	experience we found that object serialisation is causing more problems
		909	than it gains: Just like function calls, objects simply do not travel
		910	easily over the network, mostly because they will always be a copy, so you
		911	always have to re-think your design.
		912
		913	Keeping your messages simple, concentrating on data structures rather than
		914	objects, will keep your messages clean, tidy and efficient.
		915
651	=back	916	=back
652		917
653	=head1 SEE ALSO	918	=head1 SEE ALSO
654		919
655	L<AnyEvent>.	920	L<AnyEvent>.

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Revision 1.49 by root, Thu Aug 13 15:29:58 2009 UTC