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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.34 by root, Wed Aug 5 23:50:46 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		44	AnyEvent::MP::Intro - outdated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 $port	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 initialise_node $noderef, $seednode, $seednode...	166	=item initialise_node $profile_name
133		167
134	=item initialise_node "slave/", $master, $master...
135
136	Before a node can talk to other nodes on the network it has to initialise	168	Before a node can talk to other nodes on the network (i.e. enter
137	itself - the minimum a node needs to know is it's own name, and optionally	169	"distributed mode") it has to initialise itself - the minimum a node needs
138	it should know the noderefs of some other nodes in the network.	170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
139		172
140	This function initialises a node - it must be called exactly once (or	173	This function initialises a node - it must be called exactly once (or
141	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
142		175
143	All arguments are noderefs, which can be either resolved or unresolved.	176	The first argument is a profile name. If it is C<undef> or missing, then
		177	the current nodename will be used instead (i.e. F<uname -n>).
144		178
145	There are two types of networked nodes, public nodes and slave nodes:	179	The function then looks up the profile in the aemp configuration (see the
		180	L<aemp> commandline utility).
146		181
147	=over 4	182	If the profile specifies a node ID, then this will become the node ID of
		183	this process. If not, then the profile name will be used as node ID. The
		184	special node ID of C<anon/> will be replaced by a random node ID.
148		185
149	=item public nodes	186	The next step is to look up the binds in the profile, followed by binding
		187	aemp protocol listeners on all binds specified (it is possible and valid
		188	to have no binds, meaning that the node cannot be contacted form the
		189	outside. This means the node cannot talk to other nodes that also have no
		190	binds, but it can still talk to all "normal" nodes).
150		191
151	For public nodes, C<$noderef> must either be a (possibly unresolved)	192	If the profile does not specify a binds list, then the node ID will be
152	noderef, in which case it will be resolved, or C<undef> (or missing), in	193	treated as if it were of the form C<host:port>, which will be resolved and
153	which case the noderef will be guessed.	194	used as binds list.
154		195
155	Afterwards, the node will bind itself on all endpoints and try to connect	196	Lastly, the seeds list from the profile is passed to the
156	to all additional C<$seednodes> that are specified. Seednodes are optional	197	L<AnyEvent::MP::Global> module, which will then use it to keep
157	and can be used to quickly bootstrap the node into an existing network.	198	connectivity with at least on of those seed nodes at any point in time.
158		199
159	=item slave nodes	200	Example: become a distributed node listening on the guessed noderef, or
160		201	the one specified via C<aemp> for the current node. This should be the
161	When the C<$noderef> is the special string C<slave/>, then the node will	202	most common form of invocation for "daemon"-type nodes.
162	become a slave node. Slave nodes cannot be contacted from outside and will
163	route most of their traffic to the master node that they attach to.
164
165	At least one additional noderef is required: The node will try to connect
166	to all of them and will become a slave attached to the first node it can
167	successfully connect to.
168
169	=back
170
171	This function will block until all nodes have been resolved and, for slave
172	nodes, until it has successfully established a connection to a master
173	server.
174
175	Example: become a public node listening on the default node.
176		203
177	initialise_node;	204	initialise_node;
178		205
179	Example: become a public node, and try to contact some well-known master	206	Example: become an anonymous node. This form is often used for commandline
180	servers to become part of the network.	207	clients.
181		208
182	initialise_node undef, "master1", "master2";
183
184	Example: become a public node listening on port C<4041>.
185
186	initialise_node 4041;	209	initialise_node "anon/";
187		210
188	Example: become a public node, only visible on localhost port 4044.	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.
189		214
190	initialise_node "locahost:4044";	215	initialise_node "localhost:4044";
191
192	Example: become a slave node to any of the specified master servers.
193
194	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
195
196	=item $cv = resolve_node $noderef
197
198	Takes an unresolved node reference that may contain hostnames and
199	abbreviated IDs, resolves all of them and returns a resolved node
200	reference.
201
202	In addition to C<address:port> pairs allowed in resolved noderefs, the
203	following forms are supported:
204
205	=over 4
206
207	=item the empty string
208
209	An empty-string component gets resolved as if the default port (4040) was
210	specified.
211
212	=item naked port numbers (e.g. C<1234>)
213
214	These are resolved by prepending the local nodename and a colon, to be
215	further resolved.
216
217	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
218
219	These are resolved by using AnyEvent::DNS to resolve them, optionally
220	looking up SRV records for the C<aemp=4040> port, if no port was
221	specified.
222
223	=back
224		216
225	=item $SELF	217	=item $SELF
226		218
227	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>
228	blocks.	220	blocks.
…		…
236	=item snd $port, type => @data	228	=item snd $port, type => @data
237		229
238	=item snd $port, @msg	230	=item snd $port, @msg
239		231
240	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
241	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.
242	stringifies a sa port ID (such as a port object :).
243		234
244	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
245	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
246	type etc.).	237	type etc.).
247		238
248	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
249	function: modifying any argument is not allowed and can cause many	240	function: modifying any argument is not allowed and can cause many
250	problems.	241	problems.
…		…
255	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
256	node, anything can be passed.	247	node, anything can be passed.
257		248
258	=item $local_port = port	249	=item $local_port = port
259		250
260	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
261	matching port ("full port") or a single-callback port ("miniport"),	252	no callbacks set and will throw an error when it receives messages.
262	depending on how C<rcv> callbacks are bound to the object.
263		253
264	=item $port = port { my @msg = @_; $finished }	254	=item $local_port = port { my @msg = @_ }
265		255
266	Creates a "miniport", that is, a very lightweight port without any pattern	256	Creates a new local port, and returns its ID. Semantically the same as
267	matching behind it, and returns its ID. Semantically the same as creating
268	a port and calling C<rcv $port, $callback> on it.	257	creating a port and calling C<rcv $port, $callback> on it.
269		258
270	The block will be called for every message received on the port. When the	259	The block will be called for every message received on the port, with the
271	callback returns a true value its job is considered "done" and the port	260	global variable C<$SELF> set to the port ID. Runtime errors will cause the
272	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.
273		263
274	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:
275	be passed to the callback.
276		265
277	If you need the local port id in the callback, this works nicely:	266	my $port = port {
278		267	my @msg = @_;
279	my $port; $port = port {	268	...
280	snd $otherport, reply => $port;	269	kil $SELF;
281	};	270	};
282		271
283	=cut	272	=cut
284		273
285	sub rcv($@);	274	sub rcv($@);
		275
		276	sub _kilme {
		277	die "received message on port without callback";
		278	}
286		279
287	sub port(;&) {	280	sub port(;&) {
288	my $id = "$UNIQ." . $ID++;	281	my $id = "$UNIQ." . $ID++;
289	my $port = "$NODE#$id";	282	my $port = "$NODE#$id";
290		283
291	if (@_) {	284	rcv $port, shift \|\| \&_kilme;
292	rcv $port, shift;
293	} else {
294	$PORT{$id} = sub { }; # nop
295	}
296		285
297	$port	286	$port
298	}	287	}
299		288
300	=item reg $port, $name
301
302	Registers the given port under the name C<$name>. If the name already
303	exists it is replaced.
304
305	A port can only be registered under one well known name.
306
307	A port automatically becomes unregistered when it is killed.
308
309	=cut
310
311	sub reg(@) {
312	my ($port, $name) = @_;
313
314	$REG{$name} = $port;
315	}
316
317	=item rcv $port, $callback->(@msg)	289	=item rcv $local_port, $callback->(@msg)
318		290
319	Replaces the callback on the specified miniport (after converting it to	291	Replaces the default callback on the specified port. There is no way to
320	one if required).	292	remove the default callback: use C<sub { }> to disable it, or better
321		293	C<kil> the port when it is no longer needed.
322	=item rcv $port, tagstring => $callback->(@msg), ...
323
324	=item rcv $port, $smartmatch => $callback->(@msg), ...
325
326	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
327
328	Register callbacks to be called on matching messages on the given full
329	port (after converting it to one if required).
330
331	The callback has to return a true value when its work is done, after
332	which is will be removed, or a false value in which case it will stay
333	registered.
334		294
335	The global C<$SELF> (exported by this module) contains C<$port> while	295	The global C<$SELF> (exported by this module) contains C<$port> while
336	executing the callback.	296	executing the callback. Runtime errors during callback execution will
		297	result in the port being C<kil>ed.
337		298
338	Runtime errors wdurign callback execution will result in the port being	299	The default callback received all messages not matched by a more specific
339	C<kil>ed.	300	C<tag> match.
340		301
341	If the match is an array reference, then it will be matched against the	302	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
342	first elements of the message, otherwise only the first element is being
343	matched.
344		303
345	Any element in the match that is specified as C<_any_> (a function	304	Register (or replace) callbacks to be called on messages starting with the
346	exported by this module) matches any single element of the message.	305	given tag on the given port (and return the port), or unregister it (when
		306	C<$callback> is C<$undef> or missing). There can only be one callback
		307	registered for each tag.
347		308
348	While not required, it is highly recommended that the first matching	309	The original message will be passed to the callback, after the first
349	element is a string identifying the message. The one-string-only match is	310	element (the tag) has been removed. The callback will use the same
350	also the most efficient match (by far).	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, $otherport;
		336	};
351		337
352	=cut	338	=cut
353		339
354	sub rcv($@) {	340	sub rcv($@) {
355	my $port = shift;	341	my $port = shift;
356	my ($noderef, $portid) = split /#/, $port, 2;	342	my ($noderef, $portid) = split /#/, $port, 2;
357		343
358	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	344	$NODE{$noderef} == $NODE{""}
359	or Carp::croak "$port: rcv can only be called on local ports, caught";	345	or Carp::croak "$port: rcv can only be called on local ports, caught";
360		346
361	if (@_ == 1) {	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 {
362	my $cb = shift;	355	my $cb = shift;
363	delete $PORT_DATA{$portid};
364	$PORT{$portid} = sub {	356	$PORT{$portid} = sub {
365	local $SELF = $port;	357	local $SELF = $port;
366	eval {	358	eval { &$cb }; _self_die if $@;
367	&$cb	359	};
368	and kil $port;
369	};	360	}
370	_self_die if $@;	361	} elsif (defined $_[0]) {
371	};
372	} else {
373	my $self = $PORT_DATA{$portid} \|\|= do {	362	my $self = $PORT_DATA{$portid} \|\|= do {
374	my $self = bless {	363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
375	id => $port,
376	}, "AnyEvent::MP::Port";
377		364
378	$PORT{$portid} = sub {	365	$PORT{$portid} = sub {
379	local $SELF = $port;	366	local $SELF = $port;
380		367
381	eval {
382	for (@{ $self->{rc0}{$_[0]} }) {	368	if (my $cb = $self->[1]{$_[0]}) {
383	$_ && &{$_->[0]}	369	shift;
384	&& undef $_;	370	eval { &$cb }; _self_die if $@;
385	}	371	} else {
386
387	for (@{ $self->{rcv}{$_[0]} }) {
388	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
389	&& &{$_->[0]}	372	&{ $self->[0] };
390	&& undef $_;
391	}
392
393	for (@{ $self->{any} }) {
394	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
395	&& &{$_->[0]}
396	&& undef $_;
397	}	373	}
398	};	374	};
399	_self_die if $@;	375
		376	$self
400	};	377	};
401		378
402	$self
403	};
404
405	"AnyEvent::MP::Port" eq ref $self	379	"AnyEvent::MP::Port" eq ref $self
406	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	380	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
407		381
408	while (@_) {
409	my ($match, $cb) = splice @_, 0, 2;	382	my ($tag, $cb) = splice @_, 0, 2;
410		383
411	if (!ref $match) {	384	if (defined $cb) {
412	push @{ $self->{rc0}{$match} }, [$cb];	385	$self->[1]{$tag} = $cb;
413	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
414	my ($type, @match) = @$match;
415	@match
416	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
417	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
418	} else {	386	} else {
419	push @{ $self->{any} }, [$cb, $match];	387	delete $self->[1]{$tag};
420	}	388	}
421	}	389	}
422	}	390	}
423		391
424	$port	392	$port
…		…
462	}	430	}
463	}	431	}
464		432
465	=item $guard = mon $port, $cb->(@reason)	433	=item $guard = mon $port, $cb->(@reason)
466		434
467	=item $guard = mon $port, $otherport	435	=item $guard = mon $port, $rcvport
468		436
		437	=item $guard = mon $port
		438
469	=item $guard = mon $port, $otherport, @msg	439	=item $guard = mon $port, $rcvport, @msg
470		440
471	Monitor the given port and do something when the port is killed.	441	Monitor the given port and do something when the port is killed or
		442	messages to it were lost, and optionally return a guard that can be used
		443	to stop monitoring again.
472		444
		445	C<mon> effectively guarantees that, in the absence of hardware failures,
		446	that after starting the monitor, either all messages sent to the port
		447	will arrive, or the monitoring action will be invoked after possible
		448	message loss has been detected. No messages will be lost "in between"
		449	(after the first lost message no further messages will be received by the
		450	port). After the monitoring action was invoked, further messages might get
		451	delivered again.
		452
		453	Note that monitoring-actions are one-shot: once released, they are removed
		454	and will not trigger again.
		455
473	In the first form, the callback is simply called with any number	456	In the first form (callback), the callback is simply called with any
474	of C<@reason> elements (no @reason means that the port was deleted	457	number of C<@reason> elements (no @reason means that the port was deleted
475	"normally"). Note also that I<< the callback B<must> never die >>, so use	458	"normally"). Note also that I<< the callback B<must> never die >>, so use
476	C<eval> if unsure.	459	C<eval> if unsure.
477		460
478	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	461	In the second form (another port given), the other port (C<$rcvport>)
479	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
480	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.
481		465
		466	The third form (kill self) is the same as the second form, except that
		467	C<$rvport> defaults to C<$SELF>.
		468
482	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.
483		478
484	Example: call a given callback when C<$port> is killed.	479	Example: call a given callback when C<$port> is killed.
485		480
486	mon $port, sub { warn "port died because of <@_>\n" };	481	mon $port, sub { warn "port died because of <@_>\n" };
487		482
488	Example: kill ourselves when C<$port> is killed abnormally.	483	Example: kill ourselves when C<$port> is killed abnormally.
489		484
490	mon $port, $self;	485	mon $port;
491		486
492	Example: send us a restart message another C<$port> is killed.	487	Example: send us a restart message when another C<$port> is killed.
493		488
494	mon $port, $self => "restart";	489	mon $port, $self => "restart";
495		490
496	=cut	491	=cut
497		492
498	sub mon {	493	sub mon {
499	my ($noderef, $port) = split /#/, shift, 2;	494	my ($noderef, $port) = split /#/, shift, 2;
500		495
501	my $node = $NODE{$noderef} \|\| add_node $noderef;	496	my $node = $NODE{$noderef} \|\| add_node $noderef;
502		497
503	my $cb = shift;	498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
504		499
505	unless (ref $cb) {	500	unless (ref $cb) {
506	if (@_) {	501	if (@_) {
507	# send a kill info message	502	# send a kill info message
508	my (@msg) = ($cb, @_);	503	my (@msg) = ($cb, @_);
…		…
539	=cut	534	=cut
540		535
541	sub mon_guard {	536	sub mon_guard {
542	my ($port, @refs) = @_;	537	my ($port, @refs) = @_;
543		538
		539	#TODO: mon-less form?
		540
544	mon $port, sub { 0 && @refs }	541	mon $port, sub { 0 && @refs }
545	}	542	}
546
547	=item lnk $port1, $port2
548
549	Link two ports. This is simply a shorthand for:
550
551	mon $port1, $port2;
552	mon $port2, $port1;
553
554	It means that if either one is killed abnormally, the other one gets
555	killed as well.
556		543
557	=item kil $port[, @reason]	544	=item kil $port[, @reason]
558		545
559	Kill the specified port with the given C<@reason>.	546	Kill the specified port with the given C<@reason>.
560		547
…		…
568	will be reported as reason C<< die => $@ >>.	555	will be reported as reason C<< die => $@ >>.
569		556
570	Transport/communication errors are reported as C<< transport_error =>	557	Transport/communication errors are reported as C<< transport_error =>
571	$message >>.	558	$message >>.
572		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	? $action[0]()
		648	: snd @action;
		649	};
		650	}
		651
573	=back	652	=back
574		653
575	=head1 NODE MESSAGES
576
577	Nodes understand the following messages sent to them. Many of them take
578	arguments called C<@reply>, which will simply be used to compose a reply
579	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
580	the remaining arguments are simply the message data.
581
582	While other messages exist, they are not public and subject to change.
583
584	=over 4
585
586	=cut
587
588	=item lookup => $name, @reply
589
590	Replies with the port ID of the specified well-known port, or C<undef>.
591
592	=item devnull => ...
593
594	Generic data sink/CPU heat conversion.
595
596	=item relay => $port, @msg
597
598	Simply forwards the message to the given port.
599
600	=item eval => $string[ @reply]
601
602	Evaluates the given string. If C<@reply> is given, then a message of the
603	form C<@reply, $@, @evalres> is sent.
604
605	Example: crash another node.
606
607	snd $othernode, eval => "exit";
608
609	=item time => @reply
610
611	Replies the the current node time to C<@reply>.
612
613	Example: tell the current node to send the current time to C<$myport> in a
614	C<timereply> message.
615
616	snd $NODE, time => $myport, timereply => 1, 2;
617	# => snd $myport, timereply => 1, 2, <time>
618
619	=back
620
621	=head1 AnyEvent::MP vs. Distributed Erlang	654	=head1 AnyEvent::MP vs. Distributed Erlang
622		655
623	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
624	== 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
625	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
626	sample:	659	sample:
627		660
628	http://www.erlang.se/doc/programming_rules.shtml	661	http://www.Erlang.se/doc/programming_rules.shtml
629	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
630	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
631	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
632		665
633	Despite the similarities, there are also some important differences:	666	Despite the similarities, there are also some important differences:
634		667
635	=over 4	668	=over 4
636		669
…		…
641	convenience functionality.	674	convenience functionality.
642		675
643	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
644	cost of longer node references and a slightly higher management overhead.	677	cost of longer node references and a slightly higher management overhead.
645		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
646	=item * Erlang uses processes and a mailbox, AEMP does not queue.	694	=item * Erlang uses processes and a mailbox, AEMP does not queue.
647		695
648	Erlang uses processes that selctively receive messages, and therefore	696	Erlang uses processes that selectively receive messages, and therefore
649	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
650	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.
651		701
652	(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).
653		703
654	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
655		705
656	Sending messages in erlang is synchronous and blocks the process. AEMP	706	Sending messages in Erlang is synchronous and blocks the process (and
657	sends are immediate, connection establishment is handled in the	707	so does not need a queue that can overflow). AEMP sends are immediate,
658	background.	708	connection establishment is handled in the background.
659		709
660	=item * Erlang can silently lose messages, AEMP cannot.	710	=item * Erlang suffers from silent message loss, AEMP does not.
661		711
662	Erlang makes few guarantees on messages delivery - messages can get lost	712	Erlang makes few guarantees on messages delivery - messages can get lost
663	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,
664	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).
665		715
666	AEMP guarantees correct ordering, and the guarantee that there are no	716	AEMP guarantees correct ordering, and the guarantee that there are no
667	holes in the message sequence.	717	holes in the message sequence.
668		718
669	=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
670	alive.	720	alive.
671		721
672	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
673	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
674	still alive - and can receive messages.	724	still alive - and can receive messages.
675		725
676	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
677	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
678	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.
679		729
680	=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.
681		731
682	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
683	ID known to other nodes for a completely different process, causing	733	known to other nodes for a completely different process, causing messages
684	messages destined for that process to end up in an unrelated process.	734	destined for that process to end up in an unrelated process.
685		735
686	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
687	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.
688		738
689	=item * Erlang uses unprotected connections, AEMP uses secure	739	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
693	securely authenticate nodes.	743	securely authenticate nodes.
694		744
695	=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
696	communications.	746	communications.
697		747
698	The AEMP protocol, unlike the erlang protocol, supports both	748	The AEMP protocol, unlike the Erlang protocol, supports both
699	language-independent text-only protocols (good for debugging) and binary,	749	language-independent text-only protocols (good for debugging) and binary,
700	language-specific serialisers (e.g. Storable).	750	language-specific serialisers (e.g. Storable).
701		751
702	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
703	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
704	protocol simple.	754	protocol simple.
705		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
706	=back	813	=back
707		814
708	=head1 SEE ALSO	815	=head1 SEE ALSO
709		816
710	L<AnyEvent>.	817	L<AnyEvent>.

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Revision 1.64 by root, Fri Aug 28 00:58:44 2009 UTC