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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.64 by root, Fri Aug 28 00:58:44 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;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
13	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
14		24
15	$SELF # receiving/own port id in rcv callbacks	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_; 0 };
16		27
17	rcv $port, smartmatch => $cb->($port, @msg);	28	# creating/using ports, tagged message matching
18		29	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		32
24	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	35
		36	# monitoring
		37	mon $port, $cb->(@msg) # callback is invoked on death
		38	mon $port, $otherport # kill otherport on abnormal death
		39	mon $port, $otherport, @msg # send message on death
		40
		41	=head1 CURRENT STATUS
		42
		43	AnyEvent::MP - stable API, should work
		44	AnyEvent::MP::Intro - outdated
		45	AnyEvent::MP::Kernel - WIP
		46	AnyEvent::MP::Transport - mostly stable
		47
		48	stay tuned.
27		49
28	=head1 DESCRIPTION	50	=head1 DESCRIPTION
29		51
30	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
31		53
…		…
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	58	manual page.
37		59
38	At the moment, this module family is severly broken and underdocumented,	60	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 -	61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.	62	stay tuned!
41		63
42	=head1 CONCEPTS	64	=head1 CONCEPTS
43		65
44	=over 4	66	=over 4
45		67
46	=item port	68	=item port
47		69
48	A port is something you can send messages to (with the C<snd> function).	70	A port is something you can send messages to (with the C<snd> function).
49		71
50	Some ports allow you to register C<rcv> handlers that can match specific	72	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	73	some messages. Messages send to ports will not be queued, regardless of
52	will not be queued.	74	anything was listening for them or not.
53		75
54	=item port id - C<noderef#portname>	76	=item port ID - C<noderef#portname>
55		77
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	78	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	79	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	80	exception is the the node port, whose ID is identical to its node
59	reference.	81	reference.
60		82
61	=item node	83	=item node
62		84
63	A node is a single process containing at least one port - the node	85	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	86	which provides nodes to manage each other remotely, and to create new
65	create new ports, among other things.	87	ports.
66		88
67	Nodes are either private (single-process only), slaves (connected to a	89	Nodes are either private (single-process only), slaves (can only talk to
68	master node only) or public nodes (connectable from unrelated nodes).	90	public nodes, but do not need an open port) or public nodes (connectable
		91	from any other node).
69		92
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item node ID - C<[a-za-Z0-9_\-.:]+>
71		94
72	A node reference is a string that either simply identifies the node (for	95	A node ID is a string that uniquely identifies the node within a
73	private and slave nodes), or contains a recipe on how to reach a given	96	network. Depending on the configuration used, node IDs can look like a
74	node (for public nodes).	97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		98	doesn't interpret node IDs in any way.
75		99
76	This recipe is simply a comma-separated list of C<address:port> pairs (for	100	=item binds - C<ip:port>
77	TCP/IP, other protocols might look different).
78		101
79	Node references come in two flavours: resolved (containing only numerical	102	Nodes can only talk to each other by creating some kind of connection to
80	addresses) or unresolved (where hostnames are used instead of addresses).	103	each other. To do this, nodes should listen on one or more local transport
		104	endpoints - binds. Currently, only standard C<ip:port> specifications can
		105	be used, which specify TCP ports to listen on.
81		106
82	Before using an unresolved node reference in a message you first have to	107	=item seeds - C<host:port>
83	resolve it.	108
		109	When a node starts, it knows nothing about the network. To teach the node
		110	about the network it first has to contact some other node within the
		111	network. This node is called a seed.
		112
		113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		114	are expected to be long-running, and at least one of those should always
		115	be available. When nodes run out of connections (e.g. due to a network
		116	error), they try to re-establish connections to some seednodes again to
		117	join the network.
84		118
85	=back	119	=back
86		120
87	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
88		122
…		…
90		124
91	=cut	125	=cut
92		126
93	package AnyEvent::MP;	127	package AnyEvent::MP;
94		128
95	use AnyEvent::MP::Base;	129	use AnyEvent::MP::Kernel;
96		130
97	use common::sense;	131	use common::sense;
98		132
99	use Carp ();	133	use Carp ();
100		134
101	use AE ();	135	use AE ();
102		136
103	use base "Exporter";	137	use base "Exporter";
104		138
105	our $VERSION = '0.1';	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		140
106	our @EXPORT = qw(	141	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	142	NODE $NODE *SELF node_of after
108	resolve_node initialise_node	143	resolve_node initialise_node
109	snd rcv mon kil reg psub	144	snd rcv mon mon_guard kil reg psub spawn
110	port	145	port
111	);	146	);
112		147
113	our $SELF;	148	our $SELF;
114		149
…		…
118	kil $SELF, die => $msg;	153	kil $SELF, die => $msg;
119	}	154	}
120		155
121	=item $thisnode = NODE / $NODE	156	=item $thisnode = NODE / $NODE
122		157
123	The C<NODE> function returns, and the C<$NODE> variable contains	158	The C<NODE> function returns, and the C<$NODE> variable contains the node
124	the noderef of the local node. The value is initialised by a call	159	ID of the node running in the current process. This value is initialised by
125	to C<become_public> or C<become_slave>, after which all local port	160	a call to C<initialise_node>.
126	identifiers become invalid.
127		161
128	=item $noderef = node_of $portid	162	=item $nodeid = node_of $port
129		163
130	Extracts and returns the noderef from a portid or a noderef.	164	Extracts and returns the node ID part from a port ID or a node ID.
131		165
132	=item $cv = resolve_node $noderef	166	=item initialise_node $profile_name
133		167
134	Takes an unresolved node reference that may contain hostnames and	168	Before a node can talk to other nodes on the network (i.e. enter
135	abbreviated IDs, resolves all of them and returns a resolved node	169	"distributed mode") it has to initialise itself - the minimum a node needs
136	reference.	170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
137		172
138	In addition to C<address:port> pairs allowed in resolved noderefs, the	173	This function initialises a node - it must be called exactly once (or
139	following forms are supported:	174	never) before calling other AnyEvent::MP functions.
140		175
141	=over 4	176	The first argument is a profile name. If it is C<undef> or missing, then
		177	the current nodename will be used instead (i.e. F<uname -n>).
142		178
143	=item the empty string	179	The function then looks up the profile in the aemp configuration (see the
		180	L<aemp> commandline utility).
144		181
145	An empty-string component gets resolved as if the default port (4040) was	182	If the profile specifies a node ID, then this will become the node ID of
146	specified.	183	this process. If not, then the profile name will be used as node ID. The
		184	special node ID of C<anon/> will be replaced by a random node ID.
147		185
148	=item naked port numbers (e.g. C<1234>)	186	The next step is to look up the binds in the profile, followed by binding
		187	aemp protocol listeners on all binds specified (it is possible and valid
		188	to have no binds, meaning that the node cannot be contacted form the
		189	outside. This means the node cannot talk to other nodes that also have no
		190	binds, but it can still talk to all "normal" nodes).
149		191
150	These are resolved by prepending the local nodename and a colon, to be	192	If the profile does not specify a binds list, then the node ID will be
151	further resolved.	193	treated as if it were of the form C<host:port>, which will be resolved and
		194	used as binds list.
152		195
153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	196	Lastly, the seeds list from the profile is passed to the
		197	L<AnyEvent::MP::Global> module, which will then use it to keep
		198	connectivity with at least on of those seed nodes at any point in time.
154		199
155	These are resolved by using AnyEvent::DNS to resolve them, optionally	200	Example: become a distributed node listening on the guessed noderef, or
156	looking up SRV records for the C<aemp=4040> port, if no port was	201	the one specified via C<aemp> for the current node. This should be the
157	specified.	202	most common form of invocation for "daemon"-type nodes.
158		203
159	=back	204	initialise_node;
		205
		206	Example: become an anonymous node. This form is often used for commandline
		207	clients.
		208
		209	initialise_node "anon/";
		210
		211	Example: become a distributed node. If there is no profile of the given
		212	name, or no binds list was specified, resolve C<localhost:4044> and bind
		213	on the resulting addresses.
		214
		215	initialise_node "localhost:4044";
160		216
161	=item $SELF	217	=item $SELF
162		218
163	Contains the current port id while executing C<rcv> callbacks or C<psub>	219	Contains the current port id while executing C<rcv> callbacks or C<psub>
164	blocks.	220	blocks.
…		…
167		223
168	Due to some quirks in how perl exports variables, it is impossible to	224	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	225	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	226	module, but only C<$SELF> is currently used.
171		227
172	=item snd $portid, type => @data	228	=item snd $port, type => @data
173		229
174	=item snd $portid, @msg	230	=item snd $port, @msg
175		231
176	Send the given message to the given port ID, which can identify either	232	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	233	a local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		234
180	While the message can be about anything, it is highly recommended to use a	235	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	236	string as first element (a port ID, or some word that indicates a request
182	type etc.).	237	type etc.).
183		238
184	The message data effectively becomes read-only after a call to this	239	The message data effectively becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	240	function: modifying any argument is not allowed and can cause many
186	problems.	241	problems.
…		…
191	that Storable can serialise and deserialise is allowed, and for the local	246	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	247	node, anything can be passed.
193		248
194	=item $local_port = port	249	=item $local_port = port
195		250
196	Create a new local port object that can be used either as a pattern	251	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"),	252	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		253
200	=item $portid = port { my @msg = @_; $finished }	254	=item $local_port = port { my @msg = @_ }
201		255
202	Creates a "mini port", that is, a very lightweight port without any	256	Creates a new local port, and returns its ID. Semantically the same as
203	pattern matching behind it, and returns its ID.	257	creating a port and calling C<rcv $port, $callback> on it.
204		258
205	The block will be called for every message received on the port. When the	259	The block will be called for every message received on the port, with the
206	callback returns a true value its job is considered "done" and the port	260	global variable C<$SELF> set to the port ID. Runtime errors will cause the
207	will be destroyed. Otherwise it will stay alive.	261	port to be C<kil>ed. The message will be passed as-is, no extra argument
		262	(i.e. no port ID) will be passed to the callback.
208		263
209	The message will be passed as-is, no extra argument (i.e. no port id) will	264	If you want to stop/destroy the port, simply C<kil> it:
210	be passed to the callback.
211		265
212	If you need the local port id in the callback, this works nicely:	266	my $port = port {
213		267	my @msg = @_;
214	my $port; $port = port {	268	...
215	snd $otherport, reply => $port;	269	kil $SELF;
216	};	270	};
217		271
218	=cut	272	=cut
		273
		274	sub rcv($@);
		275
		276	sub _kilme {
		277	die "received message on port without callback";
		278	}
219		279
220	sub port(;&) {	280	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	281	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	282	my $port = "$NODE#$id";
223		283
		284	rcv $port, shift \|\| \&_kilme;
		285
		286	$port
		287	}
		288
		289	=item rcv $local_port, $callback->(@msg)
		290
		291	Replaces the default callback on the specified port. There is no way to
		292	remove the default callback: use C<sub { }> to disable it, or better
		293	C<kil> the port when it is no longer needed.
		294
		295	The global C<$SELF> (exported by this module) contains C<$port> while
		296	executing the callback. Runtime errors during callback execution will
		297	result in the port being C<kil>ed.
		298
		299	The default callback received all messages not matched by a more specific
		300	C<tag> match.
		301
		302	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		303
		304	Register (or replace) callbacks to be called on messages starting with the
		305	given tag on the given port (and return the port), or unregister it (when
		306	C<$callback> is C<$undef> or missing). There can only be one callback
		307	registered for each tag.
		308
		309	The original message will be passed to the callback, after the first
		310	element (the tag) has been removed. The callback will use the same
		311	environment as the default callback (see above).
		312
		313	Example: create a port and bind receivers on it in one go.
		314
		315	my $port = rcv port,
		316	msg1 => sub { ... },
		317	msg2 => sub { ... },
		318	;
		319
		320	Example: create a port, bind receivers and send it in a message elsewhere
		321	in one go:
		322
		323	snd $otherport, reply =>
		324	rcv port,
		325	msg1 => sub { ... },
		326	...
		327	;
		328
		329	Example: temporarily register a rcv callback for a tag matching some port
		330	(e.g. for a rpc reply) and unregister it after a message was received.
		331
		332	rcv $port, $otherport => sub {
		333	my @reply = @_;
		334
		335	rcv $SELF, $otherport;
		336	};
		337
		338	=cut
		339
		340	sub rcv($@) {
		341	my $port = shift;
		342	my ($noderef, $portid) = split /#/, $port, 2;
		343
		344	$NODE{$noderef} == $NODE{""}
		345	or Carp::croak "$port: rcv can only be called on local ports, caught";
		346
224	if (@_) {	347	while (@_) {
		348	if (ref $_[0]) {
		349	if (my $self = $PORT_DATA{$portid}) {
		350	"AnyEvent::MP::Port" eq ref $self
		351	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		352
		353	$self->[2] = shift;
		354	} else {
225	my $cb = shift;	355	my $cb = shift;
226	$PORT{$id} = sub {	356	$PORT{$portid} = sub {
227	local $SELF = $port;	357	local $SELF = $port;
228	eval {	358	eval { &$cb }; _self_die if $@;
229	&$cb	359	};
230	and kil $id;	360	}
		361	} elsif (defined $_[0]) {
		362	my $self = $PORT_DATA{$portid} \|\|= do {
		363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		364
		365	$PORT{$portid} = sub {
		366	local $SELF = $port;
		367
		368	if (my $cb = $self->[1]{$_[0]}) {
		369	shift;
		370	eval { &$cb }; _self_die if $@;
		371	} else {
		372	&{ $self->[0] };
		373	}
		374	};
		375
		376	$self
231	};	377	};
232	_self_die if $@;	378
233	};
234	} else {
235	my $self = bless {
236	id => "$NODE#$id",
237	}, "AnyEvent::MP::Port";	379	"AnyEvent::MP::Port" eq ref $self
		380	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
238		381
239	$PORT_DATA{$id} = $self;	382	my ($tag, $cb) = splice @_, 0, 2;
240	$PORT{$id} = sub {
241	local $SELF = $port;
242		383
		384	if (defined $cb) {
		385	$self->[1]{$tag} = $cb;
243	eval {	386	} else {
244	for (@{ $self->{rc0}{$_[0]} }) {	387	delete $self->[1]{$tag};
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	};	388	}
261	_self_die if $@;
262	};
263	}
264
265	$port
266	}
267
268	=item reg $portid, $name
269
270	Registers the given port under the name C<$name>. If the name already
271	exists it is replaced.
272
273	A port can only be registered under one well known name.
274
275	A port automatically becomes unregistered when it is killed.
276
277	=cut
278
279	sub reg(@) {
280	my ($portid, $name) = @_;
281
282	$REG{$name} = $portid;
283	}
284
285	=item rcv $portid, $callback->(@msg)
286
287	Replaces the callback on the specified miniport (or newly created port
288	object, see C<port>). Full ports are configured with the following calls:
289
290	=item rcv $portid, tagstring => $callback->(@msg), ...
291
292	=item rcv $portid, $smartmatch => $callback->(@msg), ...
293
294	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
295
296	Register callbacks to be called on matching messages on the given full
297	port (or newly created port).
298
299	The callback has to return a true value when its work is done, after
300	which is will be removed, or a false value in which case it will stay
301	registered.
302
303	The global C<$SELF> (exported by this module) contains C<$portid> while
304	executing the callback.
305
306	Runtime errors wdurign callback execution will result in the port being
307	C<kil>ed.
308
309	If the match is an array reference, then it will be matched against the
310	first elements of the message, otherwise only the first element is being
311	matched.
312
313	Any element in the match that is specified as C<_any_> (a function
314	exported by this module) matches any single element of the message.
315
316	While not required, it is highly recommended that the first matching
317	element is a string identifying the message. The one-string-only match is
318	also the most efficient match (by far).
319
320	=cut
321
322	sub rcv($@) {
323	my $portid = shift;
324	my ($noderef, $port) = split /#/, $port, 2;
325
326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
328
329	my $self = $PORT_DATA{$port}
330	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
331
332	"AnyEvent::MP::Port" eq ref $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
334
335	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;
337
338	if (!ref $match) {
339	push @{ $self->{rc0}{$match} }, [$cb];
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
341	my ($type, @match) = @$match;
342	@match
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {
346	push @{ $self->{any} }, [$cb, $match];
347	}	389	}
348	}	390	}
349		391
350	$portid	392	$port
351	}	393	}
352		394
353	=item $closure = psub { BLOCK }	395	=item $closure = psub { BLOCK }
354		396
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	397	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	428	$res
387	}	429	}
388	}	430	}
389	}	431	}
390		432
391	=item $guard = mon $portid, $cb->(@reason)	433	=item $guard = mon $port, $cb->(@reason)
392		434
393	=item $guard = mon $portid, $otherport	435	=item $guard = mon $port, $rcvport
394		436
		437	=item $guard = mon $port
		438
395	=item $guard = mon $portid, $otherport, @msg	439	=item $guard = mon $port, $rcvport, @msg
396		440
397	Monitor the given port and do something when the port is killed.	441	Monitor the given port and do something when the port is killed or
		442	messages to it were lost, and optionally return a guard that can be used
		443	to stop monitoring again.
398		444
		445	C<mon> effectively guarantees that, in the absence of hardware failures,
		446	that after starting the monitor, either all messages sent to the port
		447	will arrive, or the monitoring action will be invoked after possible
		448	message loss has been detected. No messages will be lost "in between"
		449	(after the first lost message no further messages will be received by the
		450	port). After the monitoring action was invoked, further messages might get
		451	delivered again.
		452
		453	Note that monitoring-actions are one-shot: once released, they are removed
		454	and will not trigger again.
		455
399	In the first form, the callback is simply called with any number	456	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	457	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	458	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	459	C<eval> if unsure.
403		460
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	461	In the second form (another port given), the other port (C<$rcvport>)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	462	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.	463	"normal" kils nothing happens, while under all other conditions, the other
		464	port is killed with the same reason.
407		465
		466	The third form (kill self) is the same as the second form, except that
		467	C<$rvport> defaults to C<$SELF>.
		468
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	469	In the last form (message), a message of the form C<@msg, @reason> will be
		470	C<snd>.
		471
		472	As a rule of thumb, monitoring requests should always monitor a port from
		473	a local port (or callback). The reason is that kill messages might get
		474	lost, just like any other message. Another less obvious reason is that
		475	even monitoring requests can get lost (for exmaple, when the connection
		476	to the other node goes down permanently). When monitoring a port locally
		477	these problems do not exist.
409		478
410	Example: call a given callback when C<$port> is killed.	479	Example: call a given callback when C<$port> is killed.
411		480
412	mon $port, sub { warn "port died because of <@_>\n" };	481	mon $port, sub { warn "port died because of <@_>\n" };
413		482
414	Example: kill ourselves when C<$port> is killed abnormally.	483	Example: kill ourselves when C<$port> is killed abnormally.
415		484
416	mon $port, $self;	485	mon $port;
417		486
418	Example: send us a restart message another C<$port> is killed.	487	Example: send us a restart message when another C<$port> is killed.
419		488
420	mon $port, $self => "restart";	489	mon $port, $self => "restart";
421		490
422	=cut	491	=cut
423		492
424	sub mon {	493	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	494	my ($noderef, $port) = split /#/, shift, 2;
426		495
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	496	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		497
429	my $cb = shift;	498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		499
431	unless (ref $cb) {	500	unless (ref $cb) {
432	if (@_) {	501	if (@_) {
433	# send a kill info message	502	# send a kill info message
434	my (@msg) = ($cb, @_);	503	my (@msg) = ($cb, @_);
…		…
465	=cut	534	=cut
466		535
467	sub mon_guard {	536	sub mon_guard {
468	my ($port, @refs) = @_;	537	my ($port, @refs) = @_;
469		538
		539	#TODO: mon-less form?
		540
470	mon $port, sub { 0 && @refs }	541	mon $port, sub { 0 && @refs }
471	}	542	}
472		543
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]	544	=item kil $port[, @reason]
484		545
485	Kill the specified port with the given C<@reason>.	546	Kill the specified port with the given C<@reason>.
486		547
487	If no C<@reason> is specified, then the port is killed "normally" (linked	548	If no C<@reason> is specified, then the port is killed "normally" (linked
488	ports will not be kileld, or even notified).	549	ports will not be kileld, or even notified).
…		…
494	will be reported as reason C<< die => $@ >>.	555	will be reported as reason C<< die => $@ >>.
495		556
496	Transport/communication errors are reported as C<< transport_error =>	557	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	558	$message >>.
498		559
		560	=cut
		561
		562	=item $port = spawn $node, $initfunc[, @initdata]
		563
		564	Creates a port on the node C<$node> (which can also be a port ID, in which
		565	case it's the node where that port resides).
		566
		567	The port ID of the newly created port is return immediately, and it is
		568	permissible to immediately start sending messages or monitor the port.
		569
		570	After the port has been created, the init function is
		571	called. This function must be a fully-qualified function name
		572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		573	program, use C<::name>.
		574
		575	If the function doesn't exist, then the node tries to C<require>
		576	the package, then the package above the package and so on (e.g.
		577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		578	exists or it runs out of package names.
		579
		580	The init function is then called with the newly-created port as context
		581	object (C<$SELF>) and the C<@initdata> values as arguments.
		582
		583	A common idiom is to pass your own port, monitor the spawned port, and
		584	in the init function, monitor the original port. This two-way monitoring
		585	ensures that both ports get cleaned up when there is a problem.
		586
		587	Example: spawn a chat server port on C<$othernode>.
		588
		589	# this node, executed from within a port context:
		590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		591	mon $server;
		592
		593	# init function on C<$othernode>
		594	sub connect {
		595	my ($srcport) = @_;
		596
		597	mon $srcport;
		598
		599	rcv $SELF, sub {
		600	...
		601	};
		602	}
		603
		604	=cut
		605
		606	sub _spawn {
		607	my $port = shift;
		608	my $init = shift;
		609
		610	local $SELF = "$NODE#$port";
		611	eval {
		612	&{ load_func $init }
		613	};
		614	_self_die if $@;
		615	}
		616
		617	sub spawn(@) {
		618	my ($noderef, undef) = split /#/, shift, 2;
		619
		620	my $id = "$RUNIQ." . $ID++;
		621
		622	$_[0] =~ /::/
		623	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		624
		625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		626
		627	"$noderef#$id"
		628	}
		629
		630	=item after $timeout, @msg
		631
		632	=item after $timeout, $callback
		633
		634	Either sends the given message, or call the given callback, after the
		635	specified number of seconds.
		636
		637	This is simply a utility function that come sin handy at times.
		638
		639	=cut
		640
		641	sub after($@) {
		642	my ($timeout, @action) = @_;
		643
		644	my $t; $t = AE::timer $timeout, 0, sub {
		645	undef $t;
		646	ref $action[0]
		647	? $action[0]()
		648	: snd @action;
		649	};
		650	}
		651
499	=back	652	=back
500		653
501	=head1 FUNCTIONS FOR NODES
502
503	=over 4
504
505	=item become_public $noderef
506
507	Tells the node to become a public node, i.e. reachable from other nodes.
508
509	The first argument is the (unresolved) node reference of the local node
510	(if missing then the empty string is used).
511
512	It is quite common to not specify anything, in which case the local node
513	tries to listen on the default port, or to only specify a port number, in
514	which case AnyEvent::MP tries to guess the local addresses.
515
516	=cut
517
518	=back
519
520	=head1 NODE MESSAGES
521
522	Nodes understand the following messages sent to them. Many of them take
523	arguments called C<@reply>, which will simply be used to compose a reply
524	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
525	the remaining arguments are simply the message data.
526
527	While other messages exist, they are not public and subject to change.
528
529	=over 4
530
531	=cut
532
533	=item lookup => $name, @reply
534
535	Replies with the port ID of the specified well-known port, or C<undef>.
536
537	=item devnull => ...
538
539	Generic data sink/CPU heat conversion.
540
541	=item relay => $port, @msg
542
543	Simply forwards the message to the given port.
544
545	=item eval => $string[ @reply]
546
547	Evaluates the given string. If C<@reply> is given, then a message of the
548	form C<@reply, $@, @evalres> is sent.
549
550	Example: crash another node.
551
552	snd $othernode, eval => "exit";
553
554	=item time => @reply
555
556	Replies the the current node time to C<@reply>.
557
558	Example: tell the current node to send the current time to C<$myport> in a
559	C<timereply> message.
560
561	snd $NODE, time => $myport, timereply => 1, 2;
562	# => snd $myport, timereply => 1, 2, <time>
563
564	=back
565
566	=head1 AnyEvent::MP vs. Distributed Erlang	654	=head1 AnyEvent::MP vs. Distributed Erlang
567		655
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	656	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	657	== 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	658	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
571	sample:	659	sample:
572		660
573	http://www.erlang.se/doc/programming_rules.shtml	661	http://www.Erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	662	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	663	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	664	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577		665
578	Despite the similarities, there are also some important differences:	666	Despite the similarities, there are also some important differences:
579		667
580	=over 4	668	=over 4
581		669
…		…
586	convenience functionality.	674	convenience functionality.
587		675
588	This means that AEMP requires a less tightly controlled environment at the	676	This means that AEMP requires a less tightly controlled environment at the
589	cost of longer node references and a slightly higher management overhead.	677	cost of longer node references and a slightly higher management overhead.
590		678
		679	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		680	uses "local ports are like remote ports".
		681
		682	The failure modes for local ports are quite different (runtime errors
		683	only) then for remote ports - when a local port dies, you I<know> it dies,
		684	when a connection to another node dies, you know nothing about the other
		685	port.
		686
		687	Erlang pretends remote ports are as reliable as local ports, even when
		688	they are not.
		689
		690	AEMP encourages a "treat remote ports differently" philosophy, with local
		691	ports being the special case/exception, where transport errors cannot
		692	occur.
		693
591	=item * Erlang uses processes and a mailbox, AEMP does not queue.	694	=item * Erlang uses processes and a mailbox, AEMP does not queue.
592		695
593	Erlang uses processes that selctively receive messages, and therefore	696	Erlang uses processes that selectively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	697	needs a queue. AEMP is event based, queuing messages would serve no
595	purpose.	698	useful purpose. For the same reason the pattern-matching abilities of
		699	AnyEvent::MP are more limited, as there is little need to be able to
		700	filter messages without dequeing them.
596		701
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		703
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		705
601	Sending messages in erlang is synchronous and blocks the process. AEMP	706	Sending messages in Erlang is synchronous and blocks the process (and
602	sends are immediate, connection establishment is handled in the	707	so does not need a queue that can overflow). AEMP sends are immediate,
603	background.	708	connection establishment is handled in the background.
604		709
605	=item * Erlang can silently lose messages, AEMP cannot.	710	=item * Erlang suffers from silent message loss, AEMP does not.
606		711
607	Erlang makes few guarantees on messages delivery - messages can get lost	712	Erlang makes few guarantees on messages delivery - messages can get lost
608	without any of the processes realising it (i.e. you send messages a, b,	713	without any of the processes realising it (i.e. you send messages a, b,
609	and c, and the other side only receives messages a and c).	714	and c, and the other side only receives messages a and c).
610		715
611	AEMP guarantees correct ordering, and the guarantee that there are no	716	AEMP guarantees correct ordering, and the guarantee that there are no
612	holes in the message sequence.	717	holes in the message sequence.
613		718
614	=item * In erlang, processes can be declared dead and later be found to be	719	=item * In Erlang, processes can be declared dead and later be found to be
615	alive.	720	alive.
616		721
617	In erlang it can happen that a monitored process is declared dead and	722	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	723	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.	724	still alive - and can receive messages.
620		725
621	In AEMP, when port monitoring detects a port as dead, then that port will	726	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	727	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.	728	and then later sends messages to it, finding it is still alive.
624		729
625	=item * Erlang can send messages to the wrong port, AEMP does not.	730	=item * Erlang can send messages to the wrong port, AEMP does not.
626		731
627	In erlang it is quite possible that a node that restarts reuses a process	732	In Erlang it is quite likely that a node that restarts reuses a process ID
628	ID known to other nodes for a completely different process, causing	733	known to other nodes for a completely different process, causing messages
629	messages destined for that process to end up in an unrelated process.	734	destined for that process to end up in an unrelated process.
630		735
631	AEMP never reuses port IDs, so old messages or old port IDs floating	736	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.	737	around in the network will not be sent to an unrelated port.
633		738
634	=item * Erlang uses unprotected connections, AEMP uses secure	739	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
638	securely authenticate nodes.	743	securely authenticate nodes.
639		744
640	=item * The AEMP protocol is optimised for both text-based and binary	745	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	746	communications.
642		747
643	The AEMP protocol, unlike the erlang protocol, supports both	748	The AEMP protocol, unlike the Erlang protocol, supports both
644	language-independent text-only protocols (good for debugging) and binary,	749	language-independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	750	language-specific serialisers (e.g. Storable).
646		751
647	It has also been carefully designed to be implementable in other languages	752	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	753	with a minimum of work while gracefully degrading fucntionality to make the
649	protocol simple.	754	protocol simple.
650		755
		756	=item * AEMP has more flexible monitoring options than Erlang.
		757
		758	In Erlang, you can chose to receive I<all> exit signals as messages
		759	or I<none>, there is no in-between, so monitoring single processes is
		760	difficult to implement. Monitoring in AEMP is more flexible than in
		761	Erlang, as one can choose between automatic kill, exit message or callback
		762	on a per-process basis.
		763
		764	=item * Erlang tries to hide remote/local connections, AEMP does not.
		765
		766	Monitoring in Erlang is not an indicator of process death/crashes,
		767	as linking is (except linking is unreliable in Erlang).
		768
		769	In AEMP, you don't "look up" registered port names or send to named ports
		770	that might or might not be persistent. Instead, you normally spawn a port
		771	on the remote node. The init function monitors the you, and you monitor
		772	the remote port. Since both monitors are local to the node, they are much
		773	more reliable.
		774
		775	This also saves round-trips and avoids sending messages to the wrong port
		776	(hard to do in Erlang).
		777
		778	=back
		779
		780	=head1 RATIONALE
		781
		782	=over 4
		783
		784	=item Why strings for ports and noderefs, why not objects?
		785
		786	We considered "objects", but found that the actual number of methods
		787	thatc an be called are very low. Since port IDs and noderefs travel over
		788	the network frequently, the serialising/deserialising would add lots of
		789	overhead, as well as having to keep a proxy object.
		790
		791	Strings can easily be printed, easily serialised etc. and need no special
		792	procedures to be "valid".
		793
		794	And a a miniport consists of a single closure stored in a global hash - it
		795	can't become much cheaper.
		796
		797	=item Why favour JSON, why not real serialising format such as Storable?
		798
		799	In fact, any AnyEvent::MP node will happily accept Storable as framing
		800	format, but currently there is no way to make a node use Storable by
		801	default.
		802
		803	The default framing protocol is JSON because a) JSON::XS is many times
		804	faster for small messages and b) most importantly, after years of
		805	experience we found that object serialisation is causing more problems
		806	than it gains: Just like function calls, objects simply do not travel
		807	easily over the network, mostly because they will always be a copy, so you
		808	always have to re-think your design.
		809
		810	Keeping your messages simple, concentrating on data structures rather than
		811	objects, will keep your messages clean, tidy and efficient.
		812
651	=back	813	=back
652		814
653	=head1 SEE ALSO	815	=head1 SEE ALSO
654		816
655	L<AnyEvent>.	817	L<AnyEvent>.

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