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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.27 by root, Tue Aug 4 22:13:45 2009 UTC vs.
Revision 1.51 by root, Fri Aug 14 14:07:44 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		46	AnyEvent::MP::Intro - outdated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
46	=item port	70	=item port
47		71
48	A port is something you can send messages to with the C<snd> function, and	72	A port is something you can send messages to (with the C<snd> function).
49	you can register C<rcv> handlers with. All C<rcv> handlers will receive	73
50	messages they match, messages will not be queued.	74	Some ports allow you to register C<rcv> handlers that can match specific
		75	messages. All C<rcv> handlers will receive messages they match, messages
		76	will not be queued.
51		77
52	=item port id - C<noderef#portname>	78	=item port id - C<noderef#portname>
53		79
54	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
55	by a port name (a printable string of unspecified format).	81	separator, and a port name (a printable string of unspecified format). An
		82	exception is the the node port, whose ID is identical to its node
		83	reference.
56		84
57	=item node	85	=item node
58		86
59	A node is a single process containing at least one port - the node	87	A node is a single process containing at least one port - the node
60	port. You can send messages to node ports to let them create new ports,	88	port. You can send messages to node ports to find existing ports or to
61	among other things.	89	create new ports, among other things.
62		90
63	Initially, nodes are either private (single-process only) or hidden	91	Nodes are either private (single-process only), slaves (connected to a
64	(connected to a master node only). Only when they epxlicitly "become	92	master node only) or public nodes (connectable from unrelated nodes).
65	public" can you send them messages from unrelated other nodes.
66		93
67	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
68		95
69	A noderef is a string that either uniquely identifies a given node (for	96	A node reference is a string that either simply identifies the node (for
70	private and hidden nodes), or contains a recipe on how to reach a given	97	private and slave nodes), or contains a recipe on how to reach a given
71	node (for public nodes).	98	node (for public nodes).
72		99
		100	This recipe is simply a comma-separated list of C<address:port> pairs (for
		101	TCP/IP, other protocols might look different).
		102
		103	Node references come in two flavours: resolved (containing only numerical
		104	addresses) or unresolved (where hostnames are used instead of addresses).
		105
		106	Before using an unresolved node reference in a message you first have to
		107	resolve it.
		108
73	=back	109	=back
74		110
75	=head1 VARIABLES/FUNCTIONS	111	=head1 VARIABLES/FUNCTIONS
76		112
77	=over 4	113	=over 4
78		114
79	=cut	115	=cut
80		116
81	package AnyEvent::MP;	117	package AnyEvent::MP;
82		118
83	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
84		120
85	use common::sense;	121	use common::sense;
86		122
87	use Carp ();	123	use Carp ();
88		124
89	use AE ();	125	use AE ();
90		126
91	use base "Exporter";	127	use base "Exporter";
92		128
93	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
94	our @EXPORT = qw(	131	our @EXPORT = qw(
95	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
96	become_slave become_public	133	resolve_node initialise_node
97	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
98	port	135	port
99	);	136	);
100		137
101	our $SELF;	138	our $SELF;
102		139
…		…
111	The C<NODE> function returns, and the C<$NODE> variable contains	148	The C<NODE> function returns, and the C<$NODE> variable contains
112	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
113	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
114	identifiers become invalid.	151	identifiers become invalid.
115		152
116	=item $noderef = node_of $portid	153	=item $noderef = node_of $port
117		154
118	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";
		238
		239	=item $cv = resolve_node $noderef
		240
		241	Takes an unresolved node reference that may contain hostnames and
		242	abbreviated IDs, resolves all of them and returns a resolved node
		243	reference.
		244
		245	In addition to C<address:port> pairs allowed in resolved noderefs, the
		246	following forms are supported:
		247
		248	=over 4
		249
		250	=item the empty string
		251
		252	An empty-string component gets resolved as if the default port (4040) was
		253	specified.
		254
		255	=item naked port numbers (e.g. C<1234>)
		256
		257	These are resolved by prepending the local nodename and a colon, to be
		258	further resolved.
		259
		260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		261
		262	These are resolved by using AnyEvent::DNS to resolve them, optionally
		263	looking up SRV records for the C<aemp=4040> port, if no port was
		264	specified.
		265
		266	=back
119		267
120	=item $SELF	268	=item $SELF
121		269
122	Contains the current port id while executing C<rcv> callbacks or C<psub>	270	Contains the current port id while executing C<rcv> callbacks or C<psub>
123	blocks.	271	blocks.
…		…
126		274
127	Due to some quirks in how perl exports variables, it is impossible to	275	Due to some quirks in how perl exports variables, it is impossible to
128	just export C<$SELF>, all the symbols called C<SELF> are exported by this	276	just export C<$SELF>, all the symbols called C<SELF> are exported by this
129	module, but only C<$SELF> is currently used.	277	module, but only C<$SELF> is currently used.
130		278
131	=item snd $portid, type => @data	279	=item snd $port, type => @data
132		280
133	=item snd $portid, @msg	281	=item snd $port, @msg
134		282
135	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
136	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
137	stringifies a sa port ID (such as a port object :).	285	stringifies a sa port ID (such as a port object :).
138		286
…		…
148	JSON is used, then only strings, numbers and arrays and hashes consisting	296	JSON is used, then only strings, numbers and arrays and hashes consisting
149	of those are allowed (no objects). When Storable is used, then anything	297	of those are allowed (no objects). When Storable is used, then anything
150	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
151	node, anything can be passed.	299	node, anything can be passed.
152		300
153	=item kil $portid[, @reason]	301	=item $local_port = port
154		302
155	Kill the specified port with the given C<@reason>.	303	Create a new local port object and returns its port ID. Initially it has
		304	no callbacks set and will throw an error when it receives messages.
156		305
157	If no C<@reason> is specified, then the port is killed "normally" (linked	306	=item $local_port = port { my @msg = @_ }
158	ports will not be kileld, or even notified).
159		307
160	Otherwise, linked ports get killed with the same reason (second form of	308	Creates a new local port, and returns its ID. Semantically the same as
161	C<mon>, see below).	309	creating a port and calling C<rcv $port, $callback> on it.
162		310
163	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	311	The block will be called for every message received on the port, with the
164	will be reported as reason C<< die => $@ >>.	312	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		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.
165		315
166	Transport/communication errors are reported as C<< transport_error =>	316	If you want to stop/destroy the port, simply C<kil> it:
167	$message >>.
168		317
169	=item $guard = mon $portid, $cb->(@reason)	318	my $port = port {
170
171	=item $guard = mon $portid, $otherport
172
173	=item $guard = mon $portid, $otherport, @msg
174
175	Monitor the given port and do something when the port is killed.
176
177	In the first form, the callback is simply called with any number
178	of C<@reason> elements (no @reason means that the port was deleted
179	"normally"). Note also that I<< the callback B<must> never die >>, so use
180	C<eval> if unsure.
181
182	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
183	a @reason was specified, i.e. on "normal" kils nothing happens, while
184	under all other conditions, the other port is killed with the same reason.
185
186	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
187
188	Example: call a given callback when C<$port> is killed.
189
190	mon $port, sub { warn "port died because of <@_>\n" };
191
192	Example: kill ourselves when C<$port> is killed abnormally.
193
194	mon $port, $self;
195
196	Example: send us a restart message another C<$port> is killed.
197
198	mon $port, $self => "restart";
199
200	=cut
201
202	sub mon {
203	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);
204
205	my $node = $NODE{$noderef} \|\| add_node $noderef;
206
207	#TODO: ports must not be references
208	if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {
209	if (@_) {
210	# send a kill info message
211	my (@msg) = ($cb, @_);	319	my @msg = @_;
212	$cb = sub { snd @msg, @_ };
213	} else {
214	# simply kill other port
215	my $port = $cb;
216	$cb = sub { kil $port, @_ if @_ };
217	}	320	...
		321	kil $SELF;
218	}	322	};
219		323
220	$node->monitor ($port, $cb);	324	=cut
221		325
222	defined wantarray	326	sub rcv($@);
223	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	327
		328	sub _kilme {
		329	die "received message on port without callback";
224	}	330	}
225
226	=item $guard = mon_guard $port, $ref, $ref...
227
228	Monitors the given C<$port> and keeps the passed references. When the port
229	is killed, the references will be freed.
230
231	Optionally returns a guard that will stop the monitoring.
232
233	This function is useful when you create e.g. timers or other watchers and
234	want to free them when the port gets killed:
235
236	$port->rcv (start => sub {
237	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
238	undef $timer if 0.9 < rand;
239	});
240	});
241
242	=cut
243
244	sub mon_guard {
245	my ($port, @refs) = @_;
246
247	mon $port, sub { 0 && @refs }
248	}
249
250	=item lnk $port1, $port2
251
252	Link two ports. This is simply a shorthand for:
253
254	mon $port1, $port2;
255	mon $port2, $port1;
256
257	It means that if either one is killed abnormally, the other one gets
258	killed as well.
259
260	=item $local_port = port
261
262	Create a new local port object that supports message matching.
263
264	=item $portid = port { my @msg = @_; $finished }
265
266	Creates a "mini port", that is, a very lightweight port without any
267	pattern matching behind it, and returns its ID.
268
269	The block will be called for every message received on the port. When the
270	callback returns a true value its job is considered "done" and the port
271	will be destroyed. Otherwise it will stay alive.
272
273	The message will be passed as-is, no extra argument (i.e. no port id) will
274	be passed to the callback.
275
276	If you need the local port id in the callback, this works nicely:
277
278	my $port; $port = miniport {
279	snd $otherport, reply => $port;
280	};
281
282	=cut
283		331
284	sub port(;&) {	332	sub port(;&) {
285	my $id = "$UNIQ." . $ID++;	333	my $id = "$UNIQ." . $ID++;
286	my $port = "$NODE#$id";	334	my $port = "$NODE#$id";
287		335
288	if (@_) {	336	rcv $port, shift \|\| \&_kilme;
289	my $cb = shift;
290	$PORT{$id} = sub {
291	local $SELF = $port;
292	eval {
293	&$cb
294	and kil $id;
295	};
296	_self_die if $@;
297	};
298	} else {
299	my $self = bless {
300	id => "$NODE#$id",
301	}, "AnyEvent::MP::Port";
302
303	$PORT_DATA{$id} = $self;
304	$PORT{$id} = sub {
305	local $SELF = $port;
306
307	eval {
308	for (@{ $self->{rc0}{$_[0]} }) {
309	$_ && &{$_->[0]}
310	&& undef $_;
311	}
312
313	for (@{ $self->{rcv}{$_[0]} }) {
314	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
315	&& &{$_->[0]}
316	&& undef $_;
317	}
318
319	for (@{ $self->{any} }) {
320	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
321	&& &{$_->[0]}
322	&& undef $_;
323	}
324	};
325	_self_die if $@;
326	};
327	}
328		337
329	$port	338	$port
330	}	339	}
331		340
332	=item reg $portid, $name	341	=item rcv $local_port, $callback->(@msg)
333		342
334	Registers the given port under the name C<$name>. If the name already	343	Replaces the default callback on the specified port. There is no way to
335	exists it is replaced.	344	remove the default callback: use C<sub { }> to disable it, or better
		345	C<kil> the port when it is no longer needed.
336		346
337	A port can only be registered under one well known name.
338
339	A port automatically becomes unregistered when it is killed.
340
341	=cut
342
343	sub reg(@) {
344	my ($portid, $name) = @_;
345
346	$REG{$name} = $portid;
347	}
348
349	=item rcv $portid, tagstring => $callback->(@msg), ...
350
351	=item rcv $portid, $smartmatch => $callback->(@msg), ...
352
353	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
354
355	Register callbacks to be called on matching messages on the given port.
356
357	The callback has to return a true value when its work is done, after
358	which is will be removed, or a false value in which case it will stay
359	registered.
360
361	The global C<$SELF> (exported by this module) contains C<$portid> while	347	The global C<$SELF> (exported by this module) contains C<$port> while
362	executing the callback.	348	executing the callback. Runtime errors during callback execution will
		349	result in the port being C<kil>ed.
363		350
364	Runtime errors wdurign callback execution will result in the port being	351	The default callback received all messages not matched by a more specific
365	C<kil>ed.	352	C<tag> match.
366		353
367	If the match is an array reference, then it will be matched against the	354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
368	first elements of the message, otherwise only the first element is being
369	matched.
370		355
371	Any element in the match that is specified as C<_any_> (a function	356	Register callbacks to be called on messages starting with the given tag on
372	exported by this module) matches any single element of the message.	357	the given port (and return the port), or unregister it (when C<$callback>
		358	is C<$undef>).
373		359
374	While not required, it is highly recommended that the first matching	360	The original message will be passed to the callback, after the first
375	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
376	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 $otherport, reply =>
		375	rcv port,
		376	msg1 => sub { ... },
		377	...
		378	;
377		379
378	=cut	380	=cut
379		381
380	sub rcv($@) {	382	sub rcv($@) {
		383	my $port = shift;
381	my ($noderef, $port) = split /#/, shift, 2;	384	my ($noderef, $portid) = split /#/, $port, 2;
382		385
383	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
384	or Carp::croak "$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";
385
386	my $self = $PORT_DATA{$port}
387	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
388
389	"AnyEvent::MP::Port" eq ref $self
390	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
391		388
392	while (@_) {	389	while (@_) {
393	my ($match, $cb) = splice @_, 0, 2;
394
395	if (!ref $match) {	390	if (ref $_[0]) {
396	push @{ $self->{rc0}{$match} }, [$cb];	391	if (my $self = $PORT_DATA{$portid}) {
397	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	392	"AnyEvent::MP::Port" eq ref $self
398	my ($type, @match) = @$match;	393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
399	@match	394
400	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	395	$self->[2] = shift;
401	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
402	} else {	396	} else {
403	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	}
404	}	431	}
405	}	432	}
		433
		434	$port
406	}	435	}
407		436
408	=item $closure = psub { BLOCK }	437	=item $closure = psub { BLOCK }
409		438
410	Remembers C<$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
…		…
441	$res	470	$res
442	}	471	}
443	}	472	}
444	}	473	}
445		474
446	=back	475	=item $guard = mon $port, $cb->(@reason)
447		476
448	=head1 FUNCTIONS FOR NODES	477	=item $guard = mon $port, $rcvport
449		478
450	=over 4	479	=item $guard = mon $port
451		480
452	=item become_public endpoint...	481	=item $guard = mon $port, $rcvport, @msg
453		482
454	Tells the node to become a public node, i.e. reachable from other nodes.	483	Monitor the given port and do something when the port is killed or
		484	messages to it were lost, and optionally return a guard that can be used
		485	to stop monitoring again.
455		486
456	If no arguments are given, or the first argument is C<undef>, then	487	C<mon> effectively guarantees that, in the absence of hardware failures,
457	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	488	that after starting the monitor, either all messages sent to the port
458	local nodename resolves to.	489	will arrive, or the monitoring action will be invoked after possible
		490	message loss has been detected. No messages will be lost "in between"
		491	(after the first lost message no further messages will be received by the
		492	port). After the monitoring action was invoked, further messages might get
		493	delivered again.
459		494
460	Otherwise the first argument must be an array-reference with transport	495	In the first form (callback), the callback is simply called with any
461	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	496	number of C<@reason> elements (no @reason means that the port was deleted
462	local nodename is used as hostname). The endpoints are all resolved and	497	"normally"). Note also that I<< the callback B<must> never die >>, so use
463	will become the node reference.	498	C<eval> if unsure.
464		499
		500	In the second form (another port given), the other port (C<$rcvport>)
		501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		502	"normal" kils nothing happens, while under all other conditions, the other
		503	port is killed with the same reason.
		504
		505	The third form (kill self) is the same as the second form, except that
		506	C<$rvport> defaults to C<$SELF>.
		507
		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.
		517
		518	Example: call a given callback when C<$port> is killed.
		519
		520	mon $port, sub { warn "port died because of <@_>\n" };
		521
		522	Example: kill ourselves when C<$port> is killed abnormally.
		523
		524	mon $port;
		525
		526	Example: send us a restart message when another C<$port> is killed.
		527
		528	mon $port, $self => "restart";
		529
465	=cut	530	=cut
		531
		532	sub mon {
		533	my ($noderef, $port) = split /#/, shift, 2;
		534
		535	my $node = $NODE{$noderef} \|\| add_node $noderef;
		536
		537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		538
		539	unless (ref $cb) {
		540	if (@_) {
		541	# send a kill info message
		542	my (@msg) = ($cb, @_);
		543	$cb = sub { snd @msg, @_ };
		544	} else {
		545	# simply kill other port
		546	my $port = $cb;
		547	$cb = sub { kil $port, @_ if @_ };
		548	}
		549	}
		550
		551	$node->monitor ($port, $cb);
		552
		553	defined wantarray
		554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		555	}
		556
		557	=item $guard = mon_guard $port, $ref, $ref...
		558
		559	Monitors the given C<$port> and keeps the passed references. When the port
		560	is killed, the references will be freed.
		561
		562	Optionally returns a guard that will stop the monitoring.
		563
		564	This function is useful when you create e.g. timers or other watchers and
		565	want to free them when the port gets killed:
		566
		567	$port->rcv (start => sub {
		568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		569	undef $timer if 0.9 < rand;
		570	});
		571	});
		572
		573	=cut
		574
		575	sub mon_guard {
		576	my ($port, @refs) = @_;
		577
		578	#TODO: mon-less form?
		579
		580	mon $port, sub { 0 && @refs }
		581	}
		582
		583	=item kil $port[, @reason]
		584
		585	Kill the specified port with the given C<@reason>.
		586
		587	If no C<@reason> is specified, then the port is killed "normally" (linked
		588	ports will not be kileld, or even notified).
		589
		590	Otherwise, linked ports get killed with the same reason (second form of
		591	C<mon>, see below).
		592
		593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		594	will be reported as reason C<< die => $@ >>.
		595
		596	Transport/communication errors are reported as C<< transport_error =>
		597	$message >>.
		598
		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#$id"
		668	}
466		669
467	=back	670	=back
468		671
469	=head1 NODE MESSAGES	672	=head1 NODE MESSAGES
470		673
471	Nodes understand the following messages sent to them. Many of them take	674	Nodes understand the following messages sent to them. Many of them take
472	arguments called C<@reply>, which will simply be used to compose a reply	675	arguments called C<@reply>, which will simply be used to compose a reply
473	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
474	the remaining arguments are simply the message data.	677	the remaining arguments are simply the message data.
475		678
		679	While other messages exist, they are not public and subject to change.
		680
476	=over 4	681	=over 4
477		682
478	=cut	683	=cut
479		684
480	=item lookup => $name, @reply	685	=item lookup => $name, @reply
…		…
510		715
511	=back	716	=back
512		717
513	=head1 AnyEvent::MP vs. Distributed Erlang	718	=head1 AnyEvent::MP vs. Distributed Erlang
514		719
515	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
516	== 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
517	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
518	sample:	723	sample:
519		724
520	http://www.erlang.se/doc/programming_rules.shtml	725	http://www.Erlang.se/doc/programming_rules.shtml
521	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
522	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
523	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
524		729
525	Despite the similarities, there are also some important differences:	730	Despite the similarities, there are also some important differences:
526		731
527	=over 4	732	=over 4
528		733
…		…
533	convenience functionality.	738	convenience functionality.
534		739
535	This means that AEMP requires a less tightly controlled environment at the	740	This means that AEMP requires a less tightly controlled environment at the
536	cost of longer node references and a slightly higher management overhead.	741	cost of longer node references and a slightly higher management overhead.
537		742
		743	=item Erlang has a "remote ports are like local ports" philosophy, AEMP
		744	uses "local ports are like remote ports".
		745
		746	The failure modes for local ports are quite different (runtime errors
		747	only) then for remote ports - when a local port dies, you I<know> it dies,
		748	when a connection to another node dies, you know nothing about the other
		749	port.
		750
		751	Erlang pretends remote ports are as reliable as local ports, even when
		752	they are not.
		753
		754	AEMP encourages a "treat remote ports differently" philosophy, with local
		755	ports being the special case/exception, where transport errors cannot
		756	occur.
		757
538	=item * Erlang uses processes and a mailbox, AEMP does not queue.	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
539		759
540	Erlang uses processes that selctively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
541	needs a queue. AEMP is event based, queuing messages would serve no useful	761	needs a queue. AEMP is event based, queuing messages would serve no
542	purpose.	762	useful purpose. For the same reason the pattern-matching abilities of
		763	AnyEvent::MP are more limited, as there is little need to be able to
		764	filter messages without dequeing them.
543		765
544	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
545		767
546	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
547		769
548	Sending messages in erlang is synchronous and blocks the process. AEMP	770	Sending messages in Erlang is synchronous and blocks the process (and
549	sends are immediate, connection establishment is handled in the	771	so does not need a queue that can overflow). AEMP sends are immediate,
550	background.	772	connection establishment is handled in the background.
551		773
552	=item * Erlang can silently lose messages, AEMP cannot.	774	=item * Erlang suffers from silent message loss, AEMP does not.
553		775
554	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
555	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
556	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
557		779
558	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that there are no
559	holes in the message sequence.	781	holes in the message sequence.
560		782
561	=item * In erlang, processes can be declared dead and later be found to be	783	=item * In Erlang, processes can be declared dead and later be found to be
562	alive.	784	alive.
563		785
564	In erlang it can happen that a monitored process is declared dead and	786	In Erlang it can happen that a monitored process is declared dead and
565	linked processes get killed, but later it turns out that the process is	787	linked processes get killed, but later it turns out that the process is
566	still alive - and can receive messages.	788	still alive - and can receive messages.
567		789
568	In AEMP, when port monitoring detects a port as dead, then that port will	790	In AEMP, when port monitoring detects a port as dead, then that port will
569	eventually be killed - it cannot happen that a node detects a port as dead	791	eventually be killed - it cannot happen that a node detects a port as dead
570	and then later sends messages to it, finding it is still alive.	792	and then later sends messages to it, finding it is still alive.
571		793
572	=item * Erlang can send messages to the wrong port, AEMP does not.	794	=item * Erlang can send messages to the wrong port, AEMP does not.
573		795
574	In erlang it is quite possible that a node that restarts reuses a process	796	In Erlang it is quite likely that a node that restarts reuses a process ID
575	ID known to other nodes for a completely different process, causing	797	known to other nodes for a completely different process, causing messages
576	messages destined for that process to end up in an unrelated process.	798	destined for that process to end up in an unrelated process.
577		799
578	AEMP never reuses port IDs, so old messages or old port IDs floating	800	AEMP never reuses port IDs, so old messages or old port IDs floating
579	around in the network will not be sent to an unrelated port.	801	around in the network will not be sent to an unrelated port.
580		802
581	=item * Erlang uses unprotected connections, AEMP uses secure	803	=item * Erlang uses unprotected connections, AEMP uses secure
582	authentication and can use TLS.	804	authentication and can use TLS.
583		805
584	AEMP can use a proven protocol - SSL/TLS - to protect connections and	806	AEMP can use a proven protocol - SSL/TLS - to protect connections and
585	securely authenticate nodes.	807	securely authenticate nodes.
586		808
		809	=item * The AEMP protocol is optimised for both text-based and binary
		810	communications.
		811
		812	The AEMP protocol, unlike the Erlang protocol, supports both
		813	language-independent text-only protocols (good for debugging) and binary,
		814	language-specific serialisers (e.g. Storable).
		815
		816	It has also been carefully designed to be implementable in other languages
		817	with a minimum of work while gracefully degrading fucntionality to make the
		818	protocol simple.
		819
		820	=item * AEMP has more flexible monitoring options than Erlang.
		821
		822	In Erlang, you can chose to receive I<all> exit signals as messages
		823	or I<none>, there is no in-between, so monitoring single processes is
		824	difficult to implement. Monitoring in AEMP is more flexible than in
		825	Erlang, as one can choose between automatic kill, exit message or callback
		826	on a per-process basis.
		827
		828	=item * Erlang tries to hide remote/local connections, AEMP does not.
		829
		830	Monitoring in Erlang is not an indicator of process death/crashes,
		831	as linking is (except linking is unreliable in Erlang).
		832
		833	In AEMP, you don't "look up" registered port names or send to named ports
		834	that might or might not be persistent. Instead, you normally spawn a port
		835	on the remote node. The init function monitors the you, and you monitor
		836	the remote port. Since both monitors are local to the node, they are much
		837	more reliable.
		838
		839	This also saves round-trips and avoids sending messages to the wrong port
		840	(hard to do in Erlang).
		841
		842	=back
		843
		844	=head1 RATIONALE
		845
		846	=over 4
		847
		848	=item Why strings for ports and noderefs, why not objects?
		849
		850	We considered "objects", but found that the actual number of methods
		851	thatc an be called are very low. Since port IDs and noderefs travel over
		852	the network frequently, the serialising/deserialising would add lots of
		853	overhead, as well as having to keep a proxy object.
		854
		855	Strings can easily be printed, easily serialised etc. and need no special
		856	procedures to be "valid".
		857
		858	And a a miniport consists of a single closure stored in a global hash - it
		859	can't become much cheaper.
		860
		861	=item Why favour JSON, why not real serialising format such as Storable?
		862
		863	In fact, any AnyEvent::MP node will happily accept Storable as framing
		864	format, but currently there is no way to make a node use Storable by
		865	default.
		866
		867	The default framing protocol is JSON because a) JSON::XS is many times
		868	faster for small messages and b) most importantly, after years of
		869	experience we found that object serialisation is causing more problems
		870	than it gains: Just like function calls, objects simply do not travel
		871	easily over the network, mostly because they will always be a copy, so you
		872	always have to re-think your design.
		873
		874	Keeping your messages simple, concentrating on data structures rather than
		875	objects, will keep your messages clean, tidy and efficient.
		876
587	=back	877	=back
588		878
589	=head1 SEE ALSO	879	=head1 SEE ALSO
590		880
591	L<AnyEvent>.	881	L<AnyEvent>.

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Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC