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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC

…		…
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's noderef
10	NODE # returns this node's noderef	10	NODE # returns this node's noderef
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node; # -OR-
		17	initialise_node "localhost:4040"; # -OR-
		18	initialise_node "slave/", "localhost:4040"
		19
		20	# ports are message endpoints
		21
		22	# sending messages
13	snd $port, type => data...;	23	snd $port, type => data...;
		24	snd $port, @msg;
		25	snd @msg_with_first_element_being_a_port;
14		26
15	$SELF # receiving/own port id in rcv callbacks	27	# creating/using ports, the simple way
		28	my $somple_port = port { my @msg = @_; 0 };
16		29
17	rcv $port, smartmatch => $cb->($port, @msg);	30	# creating/using ports, type matching
18		31	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		34
24	# more, smarter, matches (_any_ is exported by this module)	35	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	36	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
…		…
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	60	manual page.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
39	so do not use. This was uploaded mainly to reserve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.	64	stay tuned!
41		65
42	=head1 CONCEPTS	66	=head1 CONCEPTS
43		67
44	=over 4	68	=over 4
45		69
…		…
90		114
91	=cut	115	=cut
92		116
93	package AnyEvent::MP;	117	package AnyEvent::MP;
94		118
95	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
96		120
97	use common::sense;	121	use common::sense;
98		122
99	use Carp ();	123	use Carp ();
100		124
101	use AE ();	125	use AE ();
102		126
103	use base "Exporter";	127	use base "Exporter";
104		128
105	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
106	our @EXPORT = qw(	131	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
108	resolve_node initialise_node	133	resolve_node initialise_node
109	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
110	port	135	port
111	);	136	);
112		137
113	our $SELF;	138	our $SELF;
114		139
…		…
123	The C<NODE> function returns, and the C<$NODE> variable contains	148	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	149	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	150	to C<become_public> or C<become_slave>, after which all local port
126	identifiers become invalid.	151	identifiers become invalid.
127		152
128	=item $noderef = node_of $portid	153	=item $noderef = node_of $port
129		154
130	Extracts and returns the noderef from a portid or a noderef.	155	Extracts and returns the noderef from a portid or a noderef.
		156
		157	=item initialise_node $noderef, $seednode, $seednode...
		158
		159	=item initialise_node "slave/", $master, $master...
		160
		161	Before a node can talk to other nodes on the network it has to initialise
		162	itself - the minimum a node needs to know is it's own name, and optionally
		163	it should know the noderefs of some other nodes in the network.
		164
		165	This function initialises a node - it must be called exactly once (or
		166	never) before calling other AnyEvent::MP functions.
		167
		168	All arguments (optionally except for the first) are noderefs, which can be
		169	either resolved or unresolved.
		170
		171	The first argument will be looked up in the configuration database first
		172	(if it is C<undef> then the current nodename will be used instead) to find
		173	the relevant configuration profile (see L<aemp>). If none is found then
		174	the default configuration is used. The configuration supplies additional
		175	seed/master nodes and can override the actual noderef.
		176
		177	There are two types of networked nodes, public nodes and slave nodes:
		178
		179	=over 4
		180
		181	=item public nodes
		182
		183	For public nodes, C<$noderef> (supplied either directly to
		184	C<initialise_node> or indirectly via a profile or the nodename) must be a
		185	noderef (possibly unresolved, in which case it will be resolved).
		186
		187	After resolving, the node will bind itself on all endpoints and try to
		188	connect to all additional C<$seednodes> that are specified. Seednodes are
		189	optional and can be used to quickly bootstrap the node into an existing
		190	network.
		191
		192	=item slave nodes
		193
		194	When the C<$noderef> (either as given or overriden by the config file)
		195	is the special string C<slave/>, then the node will become a slave
		196	node. Slave nodes cannot be contacted from outside and will route most of
		197	their traffic to the master node that they attach to.
		198
		199	At least one additional noderef is required (either by specifying it
		200	directly or because it is part of the configuration profile): The node
		201	will try to connect to all of them and will become a slave attached to the
		202	first node it can successfully connect to.
		203
		204	=back
		205
		206	This function will block until all nodes have been resolved and, for slave
		207	nodes, until it has successfully established a connection to a master
		208	server.
		209
		210	Example: become a public node listening on the guessed noderef, or the one
		211	specified via C<aemp> for the current node. This should be the most common
		212	form of invocation for "daemon"-type nodes.
		213
		214	initialise_node;
		215
		216	Example: become a slave node to any of the the seednodes specified via
		217	C<aemp>. This form is often used for commandline clients.
		218
		219	initialise_node "slave/";
		220
		221	Example: become a slave node to any of the specified master servers. This
		222	form is also often used for commandline clients.
		223
		224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		225
		226	Example: become a public node, and try to contact some well-known master
		227	servers to become part of the network.
		228
		229	initialise_node undef, "master1", "master2";
		230
		231	Example: become a public node listening on port C<4041>.
		232
		233	initialise_node 4041;
		234
		235	Example: become a public node, only visible on localhost port 4044.
		236
		237	initialise_node "localhost:4044";
131		238
132	=item $cv = resolve_node $noderef	239	=item $cv = resolve_node $noderef
133		240
134	Takes an unresolved node reference that may contain hostnames and	241	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	242	abbreviated IDs, resolves all of them and returns a resolved node
…		…
167		274
168	Due to some quirks in how perl exports variables, it is impossible to	275	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	276	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	277	module, but only C<$SELF> is currently used.
171		278
172	=item snd $portid, type => @data	279	=item snd $port, type => @data
173		280
174	=item snd $portid, @msg	281	=item snd $port, @msg
175		282
176	Send the given message to the given port ID, which can identify either	283	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	284	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 :).	285	stringifies a sa port ID (such as a port object :).
179		286
…		…
191	that Storable can serialise and deserialise is allowed, and for the local	298	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	299	node, anything can be passed.
193		300
194	=item $local_port = port	301	=item $local_port = port
195		302
196	Create a new local port object that can be used either as a pattern	303	Create a new local port object and returns its port ID. Initially it has
197	matching port ("full port") or a single-callback port ("miniport"),	304	no callbacks set and will throw an error when it receives messages.
198	depending on how C<rcv> callbacks are bound to the object.
199		305
200	=item $portid = port { my @msg = @_; $finished }	306	=item $local_port = port { my @msg = @_ }
201		307
202	Creates a "mini port", that is, a very lightweight port without any	308	Creates a new local port, and returns its ID. Semantically the same as
203	pattern matching behind it, and returns its ID.	309	creating a port and calling C<rcv $port, $callback> on it.
204		310
205	The block will be called for every message received on the port. When the	311	The block will be called for every message received on the port, with the
206	callback returns a true value its job is considered "done" and the port	312	global variable C<$SELF> set to the port ID. Runtime errors will cause the
207	will be destroyed. Otherwise it will stay alive.	313	port to be C<kil>ed. The message will be passed as-is, no extra argument
		314	(i.e. no port ID) will be passed to the callback.
208		315
209	The message will be passed as-is, no extra argument (i.e. no port id) will	316	If you want to stop/destroy the port, simply C<kil> it:
210	be passed to the callback.
211		317
212	If you need the local port id in the callback, this works nicely:	318	my $port = port {
213		319	my @msg = @_;
214	my $port; $port = port {	320	...
215	snd $otherport, reply => $port;	321	kil $SELF;
216	};	322	};
217		323
218	=cut	324	=cut
		325
		326	sub rcv($@);
		327
		328	sub _kilme {
		329	die "received message on port without callback";
		330	}
219		331
220	sub port(;&) {	332	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	333	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	334	my $port = "$NODE#$id";
223		335
224	if (@_) {	336	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		337
265	$port	338	$port
266	}	339	}
267		340
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)	341	=item rcv $local_port, $callback->(@msg)
286		342
287	Replaces the callback on the specified miniport (or newly created port	343	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:	344	remove the default callback: use C<sub { }> to disable it, or better
		345	C<kil> the port when it is no longer needed.
289		346
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<$portid> while	347	The global C<$SELF> (exported by this module) contains C<$port> while
304	executing the callback.	348	executing the callback. Runtime errors during callback execution will
		349	result in the port being C<kil>ed.
305		350
306	Runtime errors wdurign callback execution will result in the port being	351	The default callback received all messages not matched by a more specific
307	C<kil>ed.	352	C<tag> match.
308		353
309	If the match is an array reference, then it will be matched against the	354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
310	first elements of the message, otherwise only the first element is being
311	matched.
312		355
313	Any element in the match that is specified as C<_any_> (a function	356	Register callbacks to be called on messages starting with the given tag on
314	exported by this module) matches any single element of the message.	357	the given port (and return the port), or unregister it (when C<$callback>
		358	is C<$undef>).
315		359
316	While not required, it is highly recommended that the first matching	360	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	361	element (the tag) has been removed. The callback will use the same
318	also the most efficient match (by far).	362	environment as the default callback (see above).
		363
		364	Example: create a port and bind receivers on it in one go.
		365
		366	my $port = rcv port,
		367	msg1 => sub { ... },
		368	msg2 => sub { ... },
		369	;
		370
		371	Example: create a port, bind receivers and send it in a message elsewhere
		372	in one go:
		373
		374	snd $otherport, reply =>
		375	rcv port,
		376	msg1 => sub { ... },
		377	...
		378	;
319		379
320	=cut	380	=cut
321		381
322	sub rcv($@) {	382	sub rcv($@) {
323	my $portid = shift;	383	my $port = shift;
324	my ($noderef, $port) = split /#/, $port, 2;	384	my ($noderef, $portid) = split /#/, $port, 2;
325		385
326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";	387	or Carp::croak "$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#$port: rcv can only be called on message matching ports, caught";
334		388
335	while (@_) {	389	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;
337
338	if (!ref $match) {	390	if (ref $_[0]) {
339	push @{ $self->{rc0}{$match} }, [$cb];	391	if (my $self = $PORT_DATA{$portid}) {
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	392	"AnyEvent::MP::Port" eq ref $self
341	my ($type, @match) = @$match;	393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
342	@match	394
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	395	$self->[2] = shift;
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {	396	} else {
346	push @{ $self->{any} }, [$cb, $match];	397	my $cb = shift;
		398	$PORT{$portid} = sub {
		399	local $SELF = $port;
		400	eval { &$cb }; _self_die if $@;
		401	};
		402	}
		403	} elsif (defined $_[0]) {
		404	my $self = $PORT_DATA{$portid} \|\|= do {
		405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		406
		407	$PORT{$portid} = sub {
		408	local $SELF = $port;
		409
		410	if (my $cb = $self->[1]{$_[0]}) {
		411	shift;
		412	eval { &$cb }; _self_die if $@;
		413	} else {
		414	&{ $self->[0] };
		415	}
		416	};
		417
		418	$self
		419	};
		420
		421	"AnyEvent::MP::Port" eq ref $self
		422	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		423
		424	my ($tag, $cb) = splice @_, 0, 2;
		425
		426	if (defined $cb) {
		427	$self->[1]{$tag} = $cb;
		428	} else {
		429	delete $self->[1]{$tag};
		430	}
347	}	431	}
348	}	432	}
349		433
350	$portid	434	$port
351	}	435	}
352		436
353	=item $closure = psub { BLOCK }	437	=item $closure = psub { BLOCK }
354		438
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	439	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	470	$res
387	}	471	}
388	}	472	}
389	}	473	}
390		474
391	=item $guard = mon $portid, $cb->(@reason)	475	=item $guard = mon $port, $cb->(@reason)
392		476
393	=item $guard = mon $portid, $otherport	477	=item $guard = mon $port, $rcvport
394		478
		479	=item $guard = mon $port
		480
395	=item $guard = mon $portid, $otherport, @msg	481	=item $guard = mon $port, $rcvport, @msg
396		482
397	Monitor the given port and do something when the port is killed.	483	Monitor the given port and do something when the port is killed or
		484	messages to it were lost, and optionally return a guard that can be used
		485	to stop monitoring again.
398		486
		487	C<mon> effectively guarantees that, in the absence of hardware failures,
		488	that after starting the monitor, either all messages sent to the port
		489	will arrive, or the monitoring action will be invoked after possible
		490	message loss has been detected. No messages will be lost "in between"
		491	(after the first lost message no further messages will be received by the
		492	port). After the monitoring action was invoked, further messages might get
		493	delivered again.
		494
399	In the first form, the callback is simply called with any number	495	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	496	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	497	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	498	C<eval> if unsure.
403		499
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	500	In the second form (another port given), the other port (C<$rcvport>)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
406	under all other conditions, the other port is killed with the same reason.	502	"normal" kils nothing happens, while under all other conditions, the other
		503	port is killed with the same reason.
407		504
		505	The third form (kill self) is the same as the second form, except that
		506	C<$rvport> defaults to C<$SELF>.
		507
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	508	In the last form (message), a message of the form C<@msg, @reason> will be
		509	C<snd>.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for exmaple, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
409		517
410	Example: call a given callback when C<$port> is killed.	518	Example: call a given callback when C<$port> is killed.
411		519
412	mon $port, sub { warn "port died because of <@_>\n" };	520	mon $port, sub { warn "port died because of <@_>\n" };
413		521
414	Example: kill ourselves when C<$port> is killed abnormally.	522	Example: kill ourselves when C<$port> is killed abnormally.
415		523
416	mon $port, $self;	524	mon $port;
417		525
418	Example: send us a restart message another C<$port> is killed.	526	Example: send us a restart message when another C<$port> is killed.
419		527
420	mon $port, $self => "restart";	528	mon $port, $self => "restart";
421		529
422	=cut	530	=cut
423		531
424	sub mon {	532	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	533	my ($noderef, $port) = split /#/, shift, 2;
426		534
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	535	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		536
429	my $cb = shift;	537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		538
431	unless (ref $cb) {	539	unless (ref $cb) {
432	if (@_) {	540	if (@_) {
433	# send a kill info message	541	# send a kill info message
434	my (@msg) = ($cb, @_);	542	my (@msg) = ($cb, @_);
…		…
465	=cut	573	=cut
466		574
467	sub mon_guard {	575	sub mon_guard {
468	my ($port, @refs) = @_;	576	my ($port, @refs) = @_;
469		577
		578	#TODO: mon-less form?
		579
470	mon $port, sub { 0 && @refs }	580	mon $port, sub { 0 && @refs }
471	}	581	}
472		582
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]	583	=item kil $port[, @reason]
484		584
485	Kill the specified port with the given C<@reason>.	585	Kill the specified port with the given C<@reason>.
486		586
487	If no C<@reason> is specified, then the port is killed "normally" (linked	587	If no C<@reason> is specified, then the port is killed "normally" (linked
488	ports will not be kileld, or even notified).	588	ports will not be kileld, or even notified).
…		…
494	will be reported as reason C<< die => $@ >>.	594	will be reported as reason C<< die => $@ >>.
495		595
496	Transport/communication errors are reported as C<< transport_error =>	596	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	597	$message >>.
498		598
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	599	=cut
		600
		601	=item $port = spawn $node, $initfunc[, @initdata]
		602
		603	Creates a port on the node C<$node> (which can also be a port ID, in which
		604	case it's the node where that port resides).
		605
		606	The port ID of the newly created port is return immediately, and it is
		607	permissible to immediately start sending messages or monitor the port.
		608
		609	After the port has been created, the init function is
		610	called. This function must be a fully-qualified function name
		611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		612	program, use C<::name>.
		613
		614	If the function doesn't exist, then the node tries to C<require>
		615	the package, then the package above the package and so on (e.g.
		616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		617	exists or it runs out of package names.
		618
		619	The init function is then called with the newly-created port as context
		620	object (C<$SELF>) and the C<@initdata> values as arguments.
		621
		622	A common idiom is to pass your own port, monitor the spawned port, and
		623	in the init function, monitor the original port. This two-way monitoring
		624	ensures that both ports get cleaned up when there is a problem.
		625
		626	Example: spawn a chat server port on C<$othernode>.
		627
		628	# this node, executed from within a port context:
		629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		630	mon $server;
		631
		632	# init function on C<$othernode>
		633	sub connect {
		634	my ($srcport) = @_;
		635
		636	mon $srcport;
		637
		638	rcv $SELF, sub {
		639	...
		640	};
		641	}
		642
		643	=cut
		644
		645	sub _spawn {
		646	my $port = shift;
		647	my $init = shift;
		648
		649	local $SELF = "$NODE#$port";
		650	eval {
		651	&{ load_func $init }
		652	};
		653	_self_die if $@;
		654	}
		655
		656	sub spawn(@) {
		657	my ($noderef, undef) = split /#/, shift, 2;
		658
		659	my $id = "$RUNIQ." . $ID++;
		660
		661	$_[0] =~ /::/
		662	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		663
		664	($NODE{$noderef} \|\| add_node $noderef)
		665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		666
		667	"$noderef#$id"
		668	}
517		669
518	=back	670	=back
519		671
520	=head1 NODE MESSAGES	672	=head1 NODE MESSAGES
521		673
…		…
563		715
564	=back	716	=back
565		717
566	=head1 AnyEvent::MP vs. Distributed Erlang	718	=head1 AnyEvent::MP vs. Distributed Erlang
567		719
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
569	== aemp node, erlang process == aemp port), so many of the documents and	721	== aemp node, Erlang process == aemp port), so many of the documents and
570	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
571	sample:	723	sample:
572		724
573	http://www.erlang.se/doc/programming_rules.shtml	725	http://www.Erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
575	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
576	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577		729
578	Despite the similarities, there are also some important differences:	730	Despite the similarities, there are also some important differences:
579		731
580	=over 4	732	=over 4
581		733
…		…
592		744
593	Erlang uses processes that selctively receive messages, and therefore	745	Erlang uses processes that selctively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	746	needs a queue. AEMP is event based, queuing messages would serve no useful
595	purpose.	747	purpose.
596		748
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	749	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		750
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		752
601	Sending messages in erlang is synchronous and blocks the process. AEMP	753	Sending messages in Erlang is synchronous and blocks the process. AEMP
602	sends are immediate, connection establishment is handled in the	754	sends are immediate, connection establishment is handled in the
603	background.	755	background.
604		756
605	=item * Erlang can silently lose messages, AEMP cannot.	757	=item * Erlang can silently lose messages, AEMP cannot.
606		758
…		…
609	and c, and the other side only receives messages a and c).	761	and c, and the other side only receives messages a and c).
610		762
611	AEMP guarantees correct ordering, and the guarantee that there are no	763	AEMP guarantees correct ordering, and the guarantee that there are no
612	holes in the message sequence.	764	holes in the message sequence.
613		765
614	=item * In erlang, processes can be declared dead and later be found to be	766	=item * In Erlang, processes can be declared dead and later be found to be
615	alive.	767	alive.
616		768
617	In erlang it can happen that a monitored process is declared dead and	769	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	770	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.	771	still alive - and can receive messages.
620		772
621	In AEMP, when port monitoring detects a port as dead, then that port will	773	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	774	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.	775	and then later sends messages to it, finding it is still alive.
624		776
625	=item * Erlang can send messages to the wrong port, AEMP does not.	777	=item * Erlang can send messages to the wrong port, AEMP does not.
626		778
627	In erlang it is quite possible that a node that restarts reuses a process	779	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	780	ID known to other nodes for a completely different process, causing
629	messages destined for that process to end up in an unrelated process.	781	messages destined for that process to end up in an unrelated process.
630		782
631	AEMP never reuses port IDs, so old messages or old port IDs floating	783	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.	784	around in the network will not be sent to an unrelated port.
…		…
638	securely authenticate nodes.	790	securely authenticate nodes.
639		791
640	=item * The AEMP protocol is optimised for both text-based and binary	792	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	793	communications.
642		794
643	The AEMP protocol, unlike the erlang protocol, supports both	795	The AEMP protocol, unlike the Erlang protocol, supports both
644	language-independent text-only protocols (good for debugging) and binary,	796	language-independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	797	language-specific serialisers (e.g. Storable).
646		798
647	It has also been carefully designed to be implementable in other languages	799	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	800	with a minimum of work while gracefully degrading fucntionality to make the
649	protocol simple.	801	protocol simple.
650		802
		803	=item * AEMP has more flexible monitoring options than Erlang.
		804
		805	In Erlang, you can chose to receive I<all> exit signals as messages
		806	or I<none>, there is no in-between, so monitoring single processes is
		807	difficult to implement. Monitoring in AEMP is more flexible than in
		808	Erlang, as one can choose between automatic kill, exit message or callback
		809	on a per-process basis.
		810
		811	=item * Erlang tries to hide remote/local connections, AEMP does not.
		812
		813	Monitoring in Erlang is not an indicator of process death/crashes,
		814	as linking is (except linking is unreliable in Erlang).
		815
		816	In AEMP, you don't "look up" registered port names or send to named ports
		817	that might or might not be persistent. Instead, you normally spawn a port
		818	on the remote node. The init function monitors the you, and you monitor
		819	the remote port. Since both monitors are local to the node, they are much
		820	more reliable.
		821
		822	This also saves round-trips and avoids sending messages to the wrong port
		823	(hard to do in Erlang).
		824
		825	=back
		826
		827	=head1 RATIONALE
		828
		829	=over 4
		830
		831	=item Why strings for ports and noderefs, why not objects?
		832
		833	We considered "objects", but found that the actual number of methods
		834	thatc an be called are very low. Since port IDs and noderefs travel over
		835	the network frequently, the serialising/deserialising would add lots of
		836	overhead, as well as having to keep a proxy object.
		837
		838	Strings can easily be printed, easily serialised etc. and need no special
		839	procedures to be "valid".
		840
		841	And a a miniport consists of a single closure stored in a global hash - it
		842	can't become much cheaper.
		843
		844	=item Why favour JSON, why not real serialising format such as Storable?
		845
		846	In fact, any AnyEvent::MP node will happily accept Storable as framing
		847	format, but currently there is no way to make a node use Storable by
		848	default.
		849
		850	The default framing protocol is JSON because a) JSON::XS is many times
		851	faster for small messages and b) most importantly, after years of
		852	experience we found that object serialisation is causing more problems
		853	than it gains: Just like function calls, objects simply do not travel
		854	easily over the network, mostly because they will always be a copy, so you
		855	always have to re-think your design.
		856
		857	Keeping your messages simple, concentrating on data structures rather than
		858	objects, will keep your messages clean, tidy and efficient.
		859
651	=back	860	=back
652		861
653	=head1 SEE ALSO	862	=head1 SEE ALSO
654		863
655	L<AnyEvent>.	864	L<AnyEvent>.

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents): Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs. Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC

Diff Legend

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC