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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs.
Revision 1.57 by root, Sat Aug 15 04:34:34 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 $simple_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		46	AnyEvent::MP::Intro - outdated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
46	=item port	70	=item port
47		71
48	A port is something you can send messages to (with the C<snd> function).	72	A port is something you can send messages to (with the C<snd> function).
49		73
50	Some ports allow you to register C<rcv> handlers that can match specific	74	Ports allow you to register C<rcv> handlers that can match all or just
51	messages. All C<rcv> handlers will receive messages they match, messages	75	some messages. Messages will not be queued.
52	will not be queued.
53		76
54	=item port id - C<noderef#portname>	77	=item port id - C<noderef#portname>
55		78
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
57	separator, and a port name (a printable string of unspecified format). An	80	separator, and a port name (a printable string of unspecified format). An
58	exception is the the node port, whose ID is identical to its node	81	exception is the the node port, whose ID is identical to its node
59	reference.	82	reference.
60		83
61	=item node	84	=item node
62		85
63	A node is a single process containing at least one port - the node	86	A node is a single process containing at least one port - the node port,
64	port. You can send messages to node ports to find existing ports or to	87	which provides nodes to manage each other remotely, and to create new
65	create new ports, among other things.	88	ports.
66		89
67	Nodes are either private (single-process only), slaves (connected to a	90	Nodes are either private (single-process only), slaves (connected to a
68	master node only) or public nodes (connectable from unrelated nodes).	91	master node only) or public nodes (connectable from unrelated nodes).
69		92
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
…		…
90		113
91	=cut	114	=cut
92		115
93	package AnyEvent::MP;	116	package AnyEvent::MP;
94		117
95	use AnyEvent::MP::Base;	118	use AnyEvent::MP::Kernel;
96		119
97	use common::sense;	120	use common::sense;
98		121
99	use Carp ();	122	use Carp ();
100		123
101	use AE ();	124	use AE ();
102		125
103	use base "Exporter";	126	use base "Exporter";
104		127
105	our $VERSION = '0.1';	128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		129
106	our @EXPORT = qw(	130	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	131	NODE $NODE *SELF node_of _any_
108	resolve_node initialise_node	132	resolve_node initialise_node
109	snd rcv mon kil reg psub	133	snd rcv mon kil reg psub spawn
110	port	134	port
111	);	135	);
112		136
113	our $SELF;	137	our $SELF;
114		138
…		…
118	kil $SELF, die => $msg;	142	kil $SELF, die => $msg;
119	}	143	}
120		144
121	=item $thisnode = NODE / $NODE	145	=item $thisnode = NODE / $NODE
122		146
123	The C<NODE> function returns, and the C<$NODE> variable contains	147	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	148	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	149	C<initialise_node>.
126	identifiers become invalid.
127		150
128	=item $noderef = node_of $port	151	=item $noderef = node_of $port
129		152
130	Extracts and returns the noderef from a portid or a noderef.	153	Extracts and returns the noderef from a port ID or a noderef.
		154
		155	=item initialise_node $noderef, $seednode, $seednode...
		156
		157	=item initialise_node "slave/", $master, $master...
		158
		159	Before a node can talk to other nodes on the network it has to initialise
		160	itself - the minimum a node needs to know is it's own name, and optionally
		161	it should know the noderefs of some other nodes in the network.
		162
		163	This function initialises a node - it must be called exactly once (or
		164	never) before calling other AnyEvent::MP functions.
		165
		166	All arguments (optionally except for the first) are noderefs, which can be
		167	either resolved or unresolved.
		168
		169	The first argument will be looked up in the configuration database first
		170	(if it is C<undef> then the current nodename will be used instead) to find
		171	the relevant configuration profile (see L<aemp>). If none is found then
		172	the default configuration is used. The configuration supplies additional
		173	seed/master nodes and can override the actual noderef.
		174
		175	There are two types of networked nodes, public nodes and slave nodes:
		176
		177	=over 4
		178
		179	=item public nodes
		180
		181	For public nodes, C<$noderef> (supplied either directly to
		182	C<initialise_node> or indirectly via a profile or the nodename) must be a
		183	noderef (possibly unresolved, in which case it will be resolved).
		184
		185	After resolving, the node will bind itself on all endpoints and try to
		186	connect to all additional C<$seednodes> that are specified. Seednodes are
		187	optional and can be used to quickly bootstrap the node into an existing
		188	network.
		189
		190	=item slave nodes
		191
		192	When the C<$noderef> (either as given or overriden by the config file)
		193	is the special string C<slave/>, then the node will become a slave
		194	node. Slave nodes cannot be contacted from outside and will route most of
		195	their traffic to the master node that they attach to.
		196
		197	At least one additional noderef is required (either by specifying it
		198	directly or because it is part of the configuration profile): The node
		199	will try to connect to all of them and will become a slave attached to the
		200	first node it can successfully connect to.
		201
		202	Note that slave nodes cannot change their name, and consequently, their
		203	master, so if the master goes down, the slave node will not function well
		204	anymore until it can re-establish conenciton to its master. This makes
		205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.
		206
		207	=back
		208
		209	This function will block until all nodes have been resolved and, for slave
		210	nodes, until it has successfully established a connection to a master
		211	server.
		212
		213	All the seednodes will also be specially marked to automatically retry
		214	connecting to them infinitely.
		215
		216	Example: become a public node listening on the guessed noderef, or the one
		217	specified via C<aemp> for the current node. This should be the most common
		218	form of invocation for "daemon"-type nodes.
		219
		220	initialise_node;
		221
		222	Example: become a slave node to any of the the seednodes specified via
		223	C<aemp>. This form is often used for commandline clients.
		224
		225	initialise_node "slave/";
		226
		227	Example: become a slave node to any of the specified master servers. This
		228	form is also often used for commandline clients.
		229
		230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		231
		232	Example: become a public node, and try to contact some well-known master
		233	servers to become part of the network.
		234
		235	initialise_node undef, "master1", "master2";
		236
		237	Example: become a public node listening on port C<4041>.
		238
		239	initialise_node 4041;
		240
		241	Example: become a public node, only visible on localhost port 4044.
		242
		243	initialise_node "localhost:4044";
131		244
132	=item $cv = resolve_node $noderef	245	=item $cv = resolve_node $noderef
133		246
134	Takes an unresolved node reference that may contain hostnames and	247	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	248	abbreviated IDs, resolves all of them and returns a resolved node
…		…
172	=item snd $port, type => @data	285	=item snd $port, type => @data
173		286
174	=item snd $port, @msg	287	=item snd $port, @msg
175		288
176	Send the given message to the given port ID, which can identify either	289	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	290	a local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		291
180	While the message can be about anything, it is highly recommended to use a	292	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	293	string as first element (a port ID, or some word that indicates a request
182	type etc.).	294	type etc.).
183		295
184	The message data effectively becomes read-only after a call to this	296	The message data effectively becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument is not allowed and can cause many
186	problems.	298	problems.
…		…
191	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	304	node, anything can be passed.
193		305
194	=item $local_port = port	306	=item $local_port = port
195		307
196	Create a new local port object that can be used either as a pattern	308	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"),	309	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		310
200	=item $port = port { my @msg = @_; $finished }	311	=item $local_port = port { my @msg = @_ }
201		312
202	Creates a "miniport", that is, a very lightweight port without any pattern	313	Creates a new local port, and returns its ID. Semantically the same as
203	matching behind it, and returns its ID. Semantically the same as creating
204	a port and calling C<rcv $port, $callback> on it.	314	creating a port and calling C<rcv $port, $callback> on it.
205		315
206	The block will be called for every message received on the port. When the	316	The block will be called for every message received on the port, with the
207	callback returns a true value its job is considered "done" and the port	317	global variable C<$SELF> set to the port ID. Runtime errors will cause the
208	will be destroyed. Otherwise it will stay alive.	318	port to be C<kil>ed. The message will be passed as-is, no extra argument
		319	(i.e. no port ID) will be passed to the callback.
209		320
210	The message will be passed as-is, no extra argument (i.e. no port id) will	321	If you want to stop/destroy the port, simply C<kil> it:
211	be passed to the callback.
212		322
213	If you need the local port id in the callback, this works nicely:	323	my $port = port {
214		324	my @msg = @_;
215	my $port; $port = port {	325	...
216	snd $otherport, reply => $port;	326	kil $SELF;
217	};	327	};
218		328
219	=cut	329	=cut
220		330
221	sub rcv($@);	331	sub rcv($@);
		332
		333	sub _kilme {
		334	die "received message on port without callback";
		335	}
222		336
223	sub port(;&) {	337	sub port(;&) {
224	my $id = "$UNIQ." . $ID++;	338	my $id = "$UNIQ." . $ID++;
225	my $port = "$NODE#$id";	339	my $port = "$NODE#$id";
226		340
227	if (@_) {	341	rcv $port, shift \|\| \&_kilme;
228	rcv $port, shift;
229	} else {
230	$PORT{$id} = sub { }; # nop
231	}
232		342
233	$port	343	$port
234	}	344	}
235		345
236	=item reg $port, $name
237
238	Registers the given port under the name C<$name>. If the name already
239	exists it is replaced.
240
241	A port can only be registered under one well known name.
242
243	A port automatically becomes unregistered when it is killed.
244
245	=cut
246
247	sub reg(@) {
248	my ($port, $name) = @_;
249
250	$REG{$name} = $port;
251	}
252
253	=item rcv $port, $callback->(@msg)	346	=item rcv $local_port, $callback->(@msg)
254		347
255	Replaces the callback on the specified miniport (after converting it to	348	Replaces the default callback on the specified port. There is no way to
256	one if required).	349	remove the default callback: use C<sub { }> to disable it, or better
257		350	C<kil> the port when it is no longer needed.
258	=item rcv $port, tagstring => $callback->(@msg), ...
259
260	=item rcv $port, $smartmatch => $callback->(@msg), ...
261
262	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
263
264	Register callbacks to be called on matching messages on the given full
265	port (after converting it to one if required).
266
267	The callback has to return a true value when its work is done, after
268	which is will be removed, or a false value in which case it will stay
269	registered.
270		351
271	The global C<$SELF> (exported by this module) contains C<$port> while	352	The global C<$SELF> (exported by this module) contains C<$port> while
272	executing the callback.	353	executing the callback. Runtime errors during callback execution will
		354	result in the port being C<kil>ed.
273		355
274	Runtime errors wdurign callback execution will result in the port being	356	The default callback received all messages not matched by a more specific
275	C<kil>ed.	357	C<tag> match.
276		358
277	If the match is an array reference, then it will be matched against the	359	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
278	first elements of the message, otherwise only the first element is being
279	matched.
280		360
281	Any element in the match that is specified as C<_any_> (a function	361	Register (or replace) callbacks to be called on messages starting with the
282	exported by this module) matches any single element of the message.	362	given tag on the given port (and return the port), or unregister it (when
		363	C<$callback> is C<$undef> or missing). There can only be one callback
		364	registered for each tag.
283		365
284	While not required, it is highly recommended that the first matching	366	The original message will be passed to the callback, after the first
285	element is a string identifying the message. The one-string-only match is	367	element (the tag) has been removed. The callback will use the same
286	also the most efficient match (by far).	368	environment as the default callback (see above).
		369
		370	Example: create a port and bind receivers on it in one go.
		371
		372	my $port = rcv port,
		373	msg1 => sub { ... },
		374	msg2 => sub { ... },
		375	;
		376
		377	Example: create a port, bind receivers and send it in a message elsewhere
		378	in one go:
		379
		380	snd $otherport, reply =>
		381	rcv port,
		382	msg1 => sub { ... },
		383	...
		384	;
		385
		386	Example: temporarily register a rcv callback for a tag matching some port
		387	(e.g. for a rpc reply) and unregister it after a message was received.
		388
		389	rcv $port, $otherport => sub {
		390	my @reply = @_;
		391
		392	rcv $SELF, $otherport;
		393	};
287		394
288	=cut	395	=cut
289		396
290	sub rcv($@) {	397	sub rcv($@) {
291	my $port = shift;	398	my $port = shift;
292	my ($noderef, $portid) = split /#/, $port, 2;	399	my ($noderef, $portid) = split /#/, $port, 2;
293		400
294	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
295	or Carp::croak "$port: rcv can only be called on local ports, caught";	402	or Carp::croak "$port: rcv can only be called on local ports, caught";
296		403
297	if (@_ == 1) {	404	while (@_) {
		405	if (ref $_[0]) {
		406	if (my $self = $PORT_DATA{$portid}) {
		407	"AnyEvent::MP::Port" eq ref $self
		408	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		409
		410	$self->[2] = shift;
		411	} else {
298	my $cb = shift;	412	my $cb = shift;
299	delete $PORT_DATA{$portid};
300	$PORT{$portid} = sub {	413	$PORT{$portid} = sub {
301	local $SELF = $port;	414	local $SELF = $port;
302	eval {	415	eval { &$cb }; _self_die if $@;
303	&$cb	416	};
304	and kil $port;
305	};	417	}
306	_self_die if $@;	418	} elsif (defined $_[0]) {
307	};
308	} else {
309	my $self = $PORT_DATA{$portid} \|\|= do {	419	my $self = $PORT_DATA{$portid} \|\|= do {
310	my $self = bless {	420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
311	id => $port,
312	}, "AnyEvent::MP::Port";
313		421
314	$PORT{$portid} = sub {	422	$PORT{$portid} = sub {
315	local $SELF = $port;	423	local $SELF = $port;
316		424
317	eval {
318	for (@{ $self->{rc0}{$_[0]} }) {	425	if (my $cb = $self->[1]{$_[0]}) {
319	$_ && &{$_->[0]}	426	shift;
320	&& undef $_;	427	eval { &$cb }; _self_die if $@;
321	}	428	} else {
322
323	for (@{ $self->{rcv}{$_[0]} }) {
324	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
325	&& &{$_->[0]}	429	&{ $self->[0] };
326	&& undef $_;
327	}
328
329	for (@{ $self->{any} }) {
330	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
331	&& &{$_->[0]}
332	&& undef $_;
333	}	430	}
334	};	431	};
335	_self_die if $@;	432
		433	$self
336	};	434	};
337		435
338	$self
339	};
340
341	"AnyEvent::MP::Port" eq ref $self	436	"AnyEvent::MP::Port" eq ref $self
342	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	437	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
343		438
344	while (@_) {
345	my ($match, $cb) = splice @_, 0, 2;	439	my ($tag, $cb) = splice @_, 0, 2;
346		440
347	if (!ref $match) {	441	if (defined $cb) {
348	push @{ $self->{rc0}{$match} }, [$cb];	442	$self->[1]{$tag} = $cb;
349	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
350	my ($type, @match) = @$match;
351	@match
352	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
353	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
354	} else {	443	} else {
355	push @{ $self->{any} }, [$cb, $match];	444	delete $self->[1]{$tag};
356	}	445	}
357	}	446	}
358	}	447	}
359		448
360	$port	449	$port
…		…
398	}	487	}
399	}	488	}
400		489
401	=item $guard = mon $port, $cb->(@reason)	490	=item $guard = mon $port, $cb->(@reason)
402		491
403	=item $guard = mon $port, $otherport	492	=item $guard = mon $port, $rcvport
404		493
		494	=item $guard = mon $port
		495
405	=item $guard = mon $port, $otherport, @msg	496	=item $guard = mon $port, $rcvport, @msg
406		497
407	Monitor the given port and do something when the port is killed.	498	Monitor the given port and do something when the port is killed or
		499	messages to it were lost, and optionally return a guard that can be used
		500	to stop monitoring again.
408		501
		502	C<mon> effectively guarantees that, in the absence of hardware failures,
		503	that after starting the monitor, either all messages sent to the port
		504	will arrive, or the monitoring action will be invoked after possible
		505	message loss has been detected. No messages will be lost "in between"
		506	(after the first lost message no further messages will be received by the
		507	port). After the monitoring action was invoked, further messages might get
		508	delivered again.
		509
409	In the first form, the callback is simply called with any number	510	In the first form (callback), the callback is simply called with any
410	of C<@reason> elements (no @reason means that the port was deleted	511	number of C<@reason> elements (no @reason means that the port was deleted
411	"normally"). Note also that I<< the callback B<must> never die >>, so use	512	"normally"). Note also that I<< the callback B<must> never die >>, so use
412	C<eval> if unsure.	513	C<eval> if unsure.
413		514
414	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	515	In the second form (another port given), the other port (C<$rcvport>)
415	a @reason was specified, i.e. on "normal" kils nothing happens, while	516	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
416	under all other conditions, the other port is killed with the same reason.	517	"normal" kils nothing happens, while under all other conditions, the other
		518	port is killed with the same reason.
417		519
		520	The third form (kill self) is the same as the second form, except that
		521	C<$rvport> defaults to C<$SELF>.
		522
418	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	523	In the last form (message), a message of the form C<@msg, @reason> will be
		524	C<snd>.
		525
		526	As a rule of thumb, monitoring requests should always monitor a port from
		527	a local port (or callback). The reason is that kill messages might get
		528	lost, just like any other message. Another less obvious reason is that
		529	even monitoring requests can get lost (for exmaple, when the connection
		530	to the other node goes down permanently). When monitoring a port locally
		531	these problems do not exist.
419		532
420	Example: call a given callback when C<$port> is killed.	533	Example: call a given callback when C<$port> is killed.
421		534
422	mon $port, sub { warn "port died because of <@_>\n" };	535	mon $port, sub { warn "port died because of <@_>\n" };
423		536
424	Example: kill ourselves when C<$port> is killed abnormally.	537	Example: kill ourselves when C<$port> is killed abnormally.
425		538
426	mon $port, $self;	539	mon $port;
427		540
428	Example: send us a restart message another C<$port> is killed.	541	Example: send us a restart message when another C<$port> is killed.
429		542
430	mon $port, $self => "restart";	543	mon $port, $self => "restart";
431		544
432	=cut	545	=cut
433		546
434	sub mon {	547	sub mon {
435	my ($noderef, $port) = split /#/, shift, 2;	548	my ($noderef, $port) = split /#/, shift, 2;
436		549
437	my $node = $NODE{$noderef} \|\| add_node $noderef;	550	my $node = $NODE{$noderef} \|\| add_node $noderef;
438		551
439	my $cb = shift;	552	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
440		553
441	unless (ref $cb) {	554	unless (ref $cb) {
442	if (@_) {	555	if (@_) {
443	# send a kill info message	556	# send a kill info message
444	my (@msg) = ($cb, @_);	557	my (@msg) = ($cb, @_);
…		…
475	=cut	588	=cut
476		589
477	sub mon_guard {	590	sub mon_guard {
478	my ($port, @refs) = @_;	591	my ($port, @refs) = @_;
479		592
		593	#TODO: mon-less form?
		594
480	mon $port, sub { 0 && @refs }	595	mon $port, sub { 0 && @refs }
481	}	596	}
482		597
483	=item lnk $port1, $port2
484
485	Link two ports. This is simply a shorthand for:
486
487	mon $port1, $port2;
488	mon $port2, $port1;
489
490	It means that if either one is killed abnormally, the other one gets
491	killed as well.
492
493	=item kil $port[, @reason]	598	=item kil $port[, @reason]
494		599
495	Kill the specified port with the given C<@reason>.	600	Kill the specified port with the given C<@reason>.
496		601
497	If no C<@reason> is specified, then the port is killed "normally" (linked	602	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
504	will be reported as reason C<< die => $@ >>.	609	will be reported as reason C<< die => $@ >>.
505		610
506	Transport/communication errors are reported as C<< transport_error =>	611	Transport/communication errors are reported as C<< transport_error =>
507	$message >>.	612	$message >>.
508		613
		614	=cut
		615
		616	=item $port = spawn $node, $initfunc[, @initdata]
		617
		618	Creates a port on the node C<$node> (which can also be a port ID, in which
		619	case it's the node where that port resides).
		620
		621	The port ID of the newly created port is return immediately, and it is
		622	permissible to immediately start sending messages or monitor the port.
		623
		624	After the port has been created, the init function is
		625	called. This function must be a fully-qualified function name
		626	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		627	program, use C<::name>.
		628
		629	If the function doesn't exist, then the node tries to C<require>
		630	the package, then the package above the package and so on (e.g.
		631	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		632	exists or it runs out of package names.
		633
		634	The init function is then called with the newly-created port as context
		635	object (C<$SELF>) and the C<@initdata> values as arguments.
		636
		637	A common idiom is to pass your own port, monitor the spawned port, and
		638	in the init function, monitor the original port. This two-way monitoring
		639	ensures that both ports get cleaned up when there is a problem.
		640
		641	Example: spawn a chat server port on C<$othernode>.
		642
		643	# this node, executed from within a port context:
		644	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		645	mon $server;
		646
		647	# init function on C<$othernode>
		648	sub connect {
		649	my ($srcport) = @_;
		650
		651	mon $srcport;
		652
		653	rcv $SELF, sub {
		654	...
		655	};
		656	}
		657
		658	=cut
		659
		660	sub _spawn {
		661	my $port = shift;
		662	my $init = shift;
		663
		664	local $SELF = "$NODE#$port";
		665	eval {
		666	&{ load_func $init }
		667	};
		668	_self_die if $@;
		669	}
		670
		671	sub spawn(@) {
		672	my ($noderef, undef) = split /#/, shift, 2;
		673
		674	my $id = "$RUNIQ." . $ID++;
		675
		676	$_[0] =~ /::/
		677	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		678
		679	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		680
		681	"$noderef#$id"
		682	}
		683
509	=back	684	=back
510		685
511	=head1 FUNCTIONS FOR NODES
512
513	=over 4
514
515	=item initialise_node $noderef, $seednode, $seednode...
516
517	=item initialise_node "slave/", $master, $master...
518
519	Initialises a node - must be called exactly once before calling other
520	AnyEvent::MP functions when talking to other nodes is required.
521
522	All arguments are noderefs, which can be either resolved or unresolved.
523
524	There are two types of networked nodes, public nodes and slave nodes:
525
526	=over 4
527
528	=item public nodes
529
530	For public nodes, C<$noderef> must either be a (possibly unresolved)
531	noderef, in which case it will be resolved, or C<undef> (or missing), in
532	which case the noderef will be guessed.
533
534	Afterwards, the node will bind itself on all endpoints and try to connect
535	to all additional C<$seednodes> that are specified. Seednodes are optional
536	and can be used to quickly bootstrap the node into an existing network.
537
538	=item slave nodes
539
540	When the C<$noderef> is the special string C<slave/>, then the node will
541	become a slave node. Slave nodes cannot be contacted from outside and will
542	route most of their traffic to the master node that they attach to.
543
544	At least one additional noderef is required: The node will try to connect
545	to all of them and will become a slave attached to the first node it can
546	successfully connect to.
547
548	=back
549
550	This function will block until all nodes have been resolved and, for slave
551	nodes, until it has successfully established a connection to a master
552	server.
553
554	Example: become a public node listening on the default node.
555
556	initialise_node;
557
558	Example: become a public node, and try to contact some well-known master
559	servers to become part of the network.
560
561	initialise_node undef, "master1", "master2";
562
563	Example: become a public node listening on port C<4041>.
564
565	initialise_node 4041;
566
567	Example: become a public node, only visible on localhost port 4044.
568
569	initialise_node "locahost:4044";
570
571	Example: become a slave node to any of the specified master servers.
572
573	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
574
575	=cut
576
577	=back
578
579	=head1 NODE MESSAGES
580
581	Nodes understand the following messages sent to them. Many of them take
582	arguments called C<@reply>, which will simply be used to compose a reply
583	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
584	the remaining arguments are simply the message data.
585
586	While other messages exist, they are not public and subject to change.
587
588	=over 4
589
590	=cut
591
592	=item lookup => $name, @reply
593
594	Replies with the port ID of the specified well-known port, or C<undef>.
595
596	=item devnull => ...
597
598	Generic data sink/CPU heat conversion.
599
600	=item relay => $port, @msg
601
602	Simply forwards the message to the given port.
603
604	=item eval => $string[ @reply]
605
606	Evaluates the given string. If C<@reply> is given, then a message of the
607	form C<@reply, $@, @evalres> is sent.
608
609	Example: crash another node.
610
611	snd $othernode, eval => "exit";
612
613	=item time => @reply
614
615	Replies the the current node time to C<@reply>.
616
617	Example: tell the current node to send the current time to C<$myport> in a
618	C<timereply> message.
619
620	snd $NODE, time => $myport, timereply => 1, 2;
621	# => snd $myport, timereply => 1, 2, <time>
622
623	=back
624
625	=head1 AnyEvent::MP vs. Distributed Erlang	686	=head1 AnyEvent::MP vs. Distributed Erlang
626		687
627	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	688	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
628	== aemp node, erlang process == aemp port), so many of the documents and	689	== aemp node, Erlang process == aemp port), so many of the documents and
629	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	690	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
630	sample:	691	sample:
631		692
632	http://www.erlang.se/doc/programming_rules.shtml	693	http://www.Erlang.se/doc/programming_rules.shtml
633	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	694	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
634	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	695	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
635	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	696	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
636		697
637	Despite the similarities, there are also some important differences:	698	Despite the similarities, there are also some important differences:
638		699
639	=over 4	700	=over 4
640		701
…		…
645	convenience functionality.	706	convenience functionality.
646		707
647	This means that AEMP requires a less tightly controlled environment at the	708	This means that AEMP requires a less tightly controlled environment at the
648	cost of longer node references and a slightly higher management overhead.	709	cost of longer node references and a slightly higher management overhead.
649		710
		711	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		712	uses "local ports are like remote ports".
		713
		714	The failure modes for local ports are quite different (runtime errors
		715	only) then for remote ports - when a local port dies, you I<know> it dies,
		716	when a connection to another node dies, you know nothing about the other
		717	port.
		718
		719	Erlang pretends remote ports are as reliable as local ports, even when
		720	they are not.
		721
		722	AEMP encourages a "treat remote ports differently" philosophy, with local
		723	ports being the special case/exception, where transport errors cannot
		724	occur.
		725
650	=item * Erlang uses processes and a mailbox, AEMP does not queue.	726	=item * Erlang uses processes and a mailbox, AEMP does not queue.
651		727
652	Erlang uses processes that selctively receive messages, and therefore	728	Erlang uses processes that selectively receive messages, and therefore
653	needs a queue. AEMP is event based, queuing messages would serve no useful	729	needs a queue. AEMP is event based, queuing messages would serve no
654	purpose.	730	useful purpose. For the same reason the pattern-matching abilities of
		731	AnyEvent::MP are more limited, as there is little need to be able to
		732	filter messages without dequeing them.
655		733
656	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	734	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
657		735
658	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	736	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
659		737
660	Sending messages in erlang is synchronous and blocks the process. AEMP	738	Sending messages in Erlang is synchronous and blocks the process (and
661	sends are immediate, connection establishment is handled in the	739	so does not need a queue that can overflow). AEMP sends are immediate,
662	background.	740	connection establishment is handled in the background.
663		741
664	=item * Erlang can silently lose messages, AEMP cannot.	742	=item * Erlang suffers from silent message loss, AEMP does not.
665		743
666	Erlang makes few guarantees on messages delivery - messages can get lost	744	Erlang makes few guarantees on messages delivery - messages can get lost
667	without any of the processes realising it (i.e. you send messages a, b,	745	without any of the processes realising it (i.e. you send messages a, b,
668	and c, and the other side only receives messages a and c).	746	and c, and the other side only receives messages a and c).
669		747
670	AEMP guarantees correct ordering, and the guarantee that there are no	748	AEMP guarantees correct ordering, and the guarantee that there are no
671	holes in the message sequence.	749	holes in the message sequence.
672		750
673	=item * In erlang, processes can be declared dead and later be found to be	751	=item * In Erlang, processes can be declared dead and later be found to be
674	alive.	752	alive.
675		753
676	In erlang it can happen that a monitored process is declared dead and	754	In Erlang it can happen that a monitored process is declared dead and
677	linked processes get killed, but later it turns out that the process is	755	linked processes get killed, but later it turns out that the process is
678	still alive - and can receive messages.	756	still alive - and can receive messages.
679		757
680	In AEMP, when port monitoring detects a port as dead, then that port will	758	In AEMP, when port monitoring detects a port as dead, then that port will
681	eventually be killed - it cannot happen that a node detects a port as dead	759	eventually be killed - it cannot happen that a node detects a port as dead
682	and then later sends messages to it, finding it is still alive.	760	and then later sends messages to it, finding it is still alive.
683		761
684	=item * Erlang can send messages to the wrong port, AEMP does not.	762	=item * Erlang can send messages to the wrong port, AEMP does not.
685		763
686	In erlang it is quite possible that a node that restarts reuses a process	764	In Erlang it is quite likely that a node that restarts reuses a process ID
687	ID known to other nodes for a completely different process, causing	765	known to other nodes for a completely different process, causing messages
688	messages destined for that process to end up in an unrelated process.	766	destined for that process to end up in an unrelated process.
689		767
690	AEMP never reuses port IDs, so old messages or old port IDs floating	768	AEMP never reuses port IDs, so old messages or old port IDs floating
691	around in the network will not be sent to an unrelated port.	769	around in the network will not be sent to an unrelated port.
692		770
693	=item * Erlang uses unprotected connections, AEMP uses secure	771	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
697	securely authenticate nodes.	775	securely authenticate nodes.
698		776
699	=item * The AEMP protocol is optimised for both text-based and binary	777	=item * The AEMP protocol is optimised for both text-based and binary
700	communications.	778	communications.
701		779
702	The AEMP protocol, unlike the erlang protocol, supports both	780	The AEMP protocol, unlike the Erlang protocol, supports both
703	language-independent text-only protocols (good for debugging) and binary,	781	language-independent text-only protocols (good for debugging) and binary,
704	language-specific serialisers (e.g. Storable).	782	language-specific serialisers (e.g. Storable).
705		783
706	It has also been carefully designed to be implementable in other languages	784	It has also been carefully designed to be implementable in other languages
707	with a minimum of work while gracefully degrading fucntionality to make the	785	with a minimum of work while gracefully degrading fucntionality to make the
708	protocol simple.	786	protocol simple.
709		787
		788	=item * AEMP has more flexible monitoring options than Erlang.
		789
		790	In Erlang, you can chose to receive I<all> exit signals as messages
		791	or I<none>, there is no in-between, so monitoring single processes is
		792	difficult to implement. Monitoring in AEMP is more flexible than in
		793	Erlang, as one can choose between automatic kill, exit message or callback
		794	on a per-process basis.
		795
		796	=item * Erlang tries to hide remote/local connections, AEMP does not.
		797
		798	Monitoring in Erlang is not an indicator of process death/crashes,
		799	as linking is (except linking is unreliable in Erlang).
		800
		801	In AEMP, you don't "look up" registered port names or send to named ports
		802	that might or might not be persistent. Instead, you normally spawn a port
		803	on the remote node. The init function monitors the you, and you monitor
		804	the remote port. Since both monitors are local to the node, they are much
		805	more reliable.
		806
		807	This also saves round-trips and avoids sending messages to the wrong port
		808	(hard to do in Erlang).
		809
		810	=back
		811
		812	=head1 RATIONALE
		813
		814	=over 4
		815
		816	=item Why strings for ports and noderefs, why not objects?
		817
		818	We considered "objects", but found that the actual number of methods
		819	thatc an be called are very low. Since port IDs and noderefs travel over
		820	the network frequently, the serialising/deserialising would add lots of
		821	overhead, as well as having to keep a proxy object.
		822
		823	Strings can easily be printed, easily serialised etc. and need no special
		824	procedures to be "valid".
		825
		826	And a a miniport consists of a single closure stored in a global hash - it
		827	can't become much cheaper.
		828
		829	=item Why favour JSON, why not real serialising format such as Storable?
		830
		831	In fact, any AnyEvent::MP node will happily accept Storable as framing
		832	format, but currently there is no way to make a node use Storable by
		833	default.
		834
		835	The default framing protocol is JSON because a) JSON::XS is many times
		836	faster for small messages and b) most importantly, after years of
		837	experience we found that object serialisation is causing more problems
		838	than it gains: Just like function calls, objects simply do not travel
		839	easily over the network, mostly because they will always be a copy, so you
		840	always have to re-think your design.
		841
		842	Keeping your messages simple, concentrating on data structures rather than
		843	objects, will keep your messages clean, tidy and efficient.
		844
710	=back	845	=back
711		846
712	=head1 SEE ALSO	847	=head1 SEE ALSO
713		848
714	L<AnyEvent>.	849	L<AnyEvent>.

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Revision 1.57 by root, Sat Aug 15 04:34:34 2009 UTC