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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.40 by root, Sat Aug 8 00:22:16 2009 UTC vs.
Revision 1.118 by root, Thu Jun 30 09:31:58 2011 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
15	# ports are message endpoints	17	# ports are message destinations
16		18
17	# sending messages	19	# sending messages
18	snd $port, type => data...;	20	snd $port, type => data...;
19	snd $port, @msg;	21	snd $port, @msg;
20	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
21		23
22	# miniports	24	# creating/using ports, the simple way
23	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
24		26
25	# full ports	27	# creating/using ports, tagged message matching
26	my $port = port;	28	my $port = port;
27	rcv $port, smartmatch => $cb->(@msg);
28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
29	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
30		31
31	# remote ports	32	# create a port on another node
32	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
33		34
34	# more, smarter, matches (_any_ is exported by this module)	35	# destroy a port again
35	rcv $port, [child_died => $pid] => sub { ...	36	kil $port; # "normal" kill
36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37	kil $port, my_error => "everything is broken"; # error kill
37		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
		51
		52	=head1 CURRENT STATUS
		53
		54	bin/aemp - stable.
		55	AnyEvent::MP - stable API, should work.
		56	AnyEvent::MP::Intro - explains most concepts.
		57	AnyEvent::MP::Kernel - mostly stable API.
		58	AnyEvent::MP::Global - stable API.
42		59
43	=head1 DESCRIPTION	60	=head1 DESCRIPTION
44		61
45	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
46		63
47	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
48	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
49		66
50	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
51	manual page.	68	manual page and the examples under F<eg/>.
52
53	At the moment, this module family is severly broken and underdocumented,
54	so do not use. This was uploaded mainly to reserve the CPAN namespace -
55	stay tuned! The basic API should be finished, however.
56		69
57	=head1 CONCEPTS	70	=head1 CONCEPTS
58		71
59	=over 4	72	=over 4
60		73
61	=item port	74	=item port
62		75
63	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
64		78
65	Some ports allow you to register C<rcv> handlers that can match specific	79	Ports allow you to register C<rcv> handlers that can match all or just
66	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
67	will not be queued.	81	anything was listening for them or not.
68		82
69	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
70		84
71	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	85	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
72	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
73	exception is the the node port, whose ID is identical to its node
74	reference.
75		87
76	=item node	88	=item node
77		89
78	A node is a single process containing at least one port - the node	90	A node is a single process containing at least one port - the node port,
79	port. You can send messages to node ports to find existing ports or to	91	which enables nodes to manage each other remotely, and to create new
80	create new ports, among other things.	92	ports.
81		93
82	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
83	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
84		97
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Za-z0-9_\-.:]*>
86		99
87	A node reference is a string that either simply identifies the node (for	100	A node ID is a string that uniquely identifies the node within a
88	private and slave nodes), or contains a recipe on how to reach a given	101	network. Depending on the configuration used, node IDs can look like a
89	node (for public nodes).	102	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		103	doesn't interpret node IDs in any way.
90		104
91	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
92	TCP/IP, other protocols might look different).
93		106
94	Node references come in two flavours: resolved (containing only numerical	107	Nodes can only talk to each other by creating some kind of connection to
95	addresses) or unresolved (where hostnames are used instead of addresses).	108	each other. To do this, nodes should listen on one or more local transport
		109	endpoints - binds. Currently, only standard C<ip:port> specifications can
		110	be used, which specify TCP ports to listen on.
96		111
97	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
98	resolve it.	113
		114	When a node starts, it knows nothing about the network. To teach the node
		115	about the network it first has to contact some other node within the
		116	network. This node is called a seed.
		117
		118	Apart from the fact that other nodes know them as seed nodes and they have
		119	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		120	any node can function as a seed node for others.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network and to connect nodes that otherwise would have
		124	trouble connecting. They form the backbone of an AnyEvent::MP network.
		125
		126	Seed nodes are expected to be long-running, and at least one seed node
		127	should always be available. They should also be relatively responsive - a
		128	seed node that blocks for long periods will slow down everybody else.
		129
		130	=item seeds - C<host:port>
		131
		132	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		133	TCP port) of nodes that should be used as seed nodes.
		134
		135	The nodes listening on those endpoints are expected to be long-running,
		136	and at least one of those should always be available. When nodes run out
		137	of connections (e.g. due to a network error), they try to re-establish
		138	connections to some seednodes again to join the network.
99		139
100	=back	140	=back
101		141
102	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
103		143
105		145
106	=cut	146	=cut
107		147
108	package AnyEvent::MP;	148	package AnyEvent::MP;
109		149
110	use AnyEvent::MP::Base;	150	use AnyEvent::MP::Kernel;
111		151
112	use common::sense;	152	use common::sense;
113		153
114	use Carp ();	154	use Carp ();
115		155
116	use AE ();	156	use AE ();
117		157
118	use base "Exporter";	158	use base "Exporter";
119		159
120	our $VERSION = '0.1';	160	our $VERSION = '1.30';
		161
121	our @EXPORT = qw(	162	our @EXPORT = qw(
122	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
123	resolve_node initialise_node	164	configure
124	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
125	port	166	port
126	);	167	);
127		168
128	our $SELF;	169	our $SELF;
129		170
…		…
133	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
134	}	175	}
135		176
136	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
137		178
138	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
139	the noderef of the local node. The value is initialised by a call	180	ID of the node running in the current process. This value is initialised by
140	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
141	identifiers become invalid.
142		182
143	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
144		184
145	Extracts and returns the noderef from a portid or a noderef.	185	Extracts and returns the node ID from a port ID or a node ID.
146		186
147	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
148		188
149	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
150		190
151	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
152	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
153	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
154		195
		196	The key/value pairs are basically the same ones as documented for the
		197	F<aemp> command line utility (sans the set/del prefix).
		198
155	This function initialises a node - it must be called exactly once (or	199	This function configures a node - it must be called exactly once (or
156	never) before calling other AnyEvent::MP functions.	200	never) before calling other AnyEvent::MP functions.
157		201
158	All arguments are noderefs, which can be either resolved or unresolved.
159
160	There are two types of networked nodes, public nodes and slave nodes:
161
162	=over 4	202	=over 4
163		203
164	=item public nodes	204	=item step 1, gathering configuration from profiles
165		205
166	For public nodes, C<$noderef> must either be a (possibly unresolved)	206	The function first looks up a profile in the aemp configuration (see the
167	noderef, in which case it will be resolved, or C<undef> (or missing), in	207	L<aemp> commandline utility). The profile name can be specified via the
168	which case the noderef will be guessed.	208	named C<profile> parameter or can simply be the first parameter). If it is
		209	missing, then the nodename (F<uname -n>) will be used as profile name.
169		210
170	Afterwards, the node will bind itself on all endpoints and try to connect	211	The profile data is then gathered as follows:
171	to all additional C<$seednodes> that are specified. Seednodes are optional
172	and can be used to quickly bootstrap the node into an existing network.
173		212
174	=item slave nodes	213	First, all remaining key => value pairs (all of which are conveniently
		214	undocumented at the moment) will be interpreted as configuration
		215	data. Then they will be overwritten by any values specified in the global
		216	default configuration (see the F<aemp> utility), then the chain of
		217	profiles chosen by the profile name (and any C<parent> attributes).
175		218
176	When the C<$noderef> is the special string C<slave/>, then the node will	219	That means that the values specified in the profile have highest priority
177	become a slave node. Slave nodes cannot be contacted from outside and will	220	and the values specified directly via C<configure> have lowest priority,
178	route most of their traffic to the master node that they attach to.	221	and can only be used to specify defaults.
179		222
180	At least one additional noderef is required: The node will try to connect	223	If the profile specifies a node ID, then this will become the node ID of
181	to all of them and will become a slave attached to the first node it can	224	this process. If not, then the profile name will be used as node ID. The
182	successfully connect to.	225	special node ID of C<anon/> will be replaced by a random node ID.
		226
		227	=item step 2, bind listener sockets
		228
		229	The next step is to look up the binds in the profile, followed by binding
		230	aemp protocol listeners on all binds specified (it is possible and valid
		231	to have no binds, meaning that the node cannot be contacted form the
		232	outside. This means the node cannot talk to other nodes that also have no
		233	binds, but it can still talk to all "normal" nodes).
		234
		235	If the profile does not specify a binds list, then a default of C<*> is
		236	used, meaning the node will bind on a dynamically-assigned port on every
		237	local IP address it finds.
		238
		239	=item step 3, connect to seed nodes
		240
		241	As the last step, the seeds list from the profile is passed to the
		242	L<AnyEvent::MP::Global> module, which will then use it to keep
		243	connectivity with at least one node at any point in time.
183		244
184	=back	245	=back
185		246
186	This function will block until all nodes have been resolved and, for slave	247	Example: become a distributed node using the local node name as profile.
187	nodes, until it has successfully established a connection to a master	248	This should be the most common form of invocation for "daemon"-type nodes.
188	server.
189		249
190	Example: become a public node listening on the default node.	250	configure
191		251
192	initialise_node;	252	Example: become an anonymous node. This form is often used for commandline
		253	clients.
193		254
194	Example: become a public node, and try to contact some well-known master	255	configure nodeid => "anon/";
195	servers to become part of the network.
196		256
197	initialise_node undef, "master1", "master2";	257	Example: configure a node using a profile called seed, which si suitable
		258	for a seed node as it binds on all local addresses on a fixed port (4040,
		259	customary for aemp).
198		260
199	Example: become a public node listening on port C<4041>.	261	# use the aemp commandline utility
		262	# aemp profile seed nodeid anon/ binds '*:4040'
200		263
201	initialise_node 4041;	264	# then use it
		265	configure profile => "seed";
202		266
203	Example: become a public node, only visible on localhost port 4044.	267	# or simply use aemp from the shell again:
		268	# aemp run profile seed
204		269
205	initialise_node "locahost:4044";	270	# or provide a nicer-to-remember nodeid
206		271	# aemp run profile seed nodeid "$(hostname)"
207	Example: become a slave node to any of the specified master servers.
208
209	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
210
211	=item $cv = resolve_node $noderef
212
213	Takes an unresolved node reference that may contain hostnames and
214	abbreviated IDs, resolves all of them and returns a resolved node
215	reference.
216
217	In addition to C<address:port> pairs allowed in resolved noderefs, the
218	following forms are supported:
219
220	=over 4
221
222	=item the empty string
223
224	An empty-string component gets resolved as if the default port (4040) was
225	specified.
226
227	=item naked port numbers (e.g. C<1234>)
228
229	These are resolved by prepending the local nodename and a colon, to be
230	further resolved.
231
232	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
233
234	These are resolved by using AnyEvent::DNS to resolve them, optionally
235	looking up SRV records for the C<aemp=4040> port, if no port was
236	specified.
237
238	=back
239		272
240	=item $SELF	273	=item $SELF
241		274
242	Contains the current port id while executing C<rcv> callbacks or C<psub>	275	Contains the current port id while executing C<rcv> callbacks or C<psub>
243	blocks.	276	blocks.
244		277
245	=item SELF, %SELF, @SELF...	278	=item *SELF, SELF, %SELF, @SELF...
246		279
247	Due to some quirks in how perl exports variables, it is impossible to	280	Due to some quirks in how perl exports variables, it is impossible to
248	just export C<$SELF>, all the symbols called C<SELF> are exported by this	281	just export C<$SELF>, all the symbols named C<SELF> are exported by this
249	module, but only C<$SELF> is currently used.	282	module, but only C<$SELF> is currently used.
250		283
251	=item snd $port, type => @data	284	=item snd $port, type => @data
252		285
253	=item snd $port, @msg	286	=item snd $port, @msg
254		287
255	Send the given message to the given port ID, which can identify either	288	Send the given message to the given port, which can identify either a
256	a local or a remote port, and can be either a string or soemthignt hat	289	local or a remote port, and must be a port ID.
257	stringifies a sa port ID (such as a port object :).
258		290
259	While the message can be about anything, it is highly recommended to use a	291	While the message can be almost anything, it is highly recommended to
260	string as first element (a portid, or some word that indicates a request	292	use a string as first element (a port ID, or some word that indicates a
261	type etc.).	293	request type etc.) and to consist if only simple perl values (scalars,
		294	arrays, hashes) - if you think you need to pass an object, think again.
262		295
263	The message data effectively becomes read-only after a call to this	296	The message data logically becomes read-only after a call to this
264	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument (or values referenced by them) is
265	problems.	298	forbidden, as there can be considerable time between the call to C<snd>
		299	and the time the message is actually being serialised - in fact, it might
		300	never be copied as within the same process it is simply handed to the
		301	receiving port.
266		302
267	The type of data you can transfer depends on the transport protocol: when	303	The type of data you can transfer depends on the transport protocol: when
268	JSON is used, then only strings, numbers and arrays and hashes consisting	304	JSON is used, then only strings, numbers and arrays and hashes consisting
269	of those are allowed (no objects). When Storable is used, then anything	305	of those are allowed (no objects). When Storable is used, then anything
270	that Storable can serialise and deserialise is allowed, and for the local	306	that Storable can serialise and deserialise is allowed, and for the local
271	node, anything can be passed.	307	node, anything can be passed. Best rely only on the common denominator of
		308	these.
272		309
273	=item $local_port = port	310	=item $local_port = port
274		311
275	Create a new local port object that can be used either as a pattern	312	Create a new local port object and returns its port ID. Initially it has
276	matching port ("full port") or a single-callback port ("miniport"),	313	no callbacks set and will throw an error when it receives messages.
277	depending on how C<rcv> callbacks are bound to the object.
278		314
279	=item $port = port { my @msg = @_; $finished }	315	=item $local_port = port { my @msg = @_ }
280		316
281	Creates a "miniport", that is, a very lightweight port without any pattern	317	Creates a new local port, and returns its ID. Semantically the same as
282	matching behind it, and returns its ID. Semantically the same as creating
283	a port and calling C<rcv $port, $callback> on it.	318	creating a port and calling C<rcv $port, $callback> on it.
284		319
285	The block will be called for every message received on the port. When the	320	The block will be called for every message received on the port, with the
286	callback returns a true value its job is considered "done" and the port	321	global variable C<$SELF> set to the port ID. Runtime errors will cause the
287	will be destroyed. Otherwise it will stay alive.	322	port to be C<kil>ed. The message will be passed as-is, no extra argument
		323	(i.e. no port ID) will be passed to the callback.
288		324
289	The message will be passed as-is, no extra argument (i.e. no port id) will	325	If you want to stop/destroy the port, simply C<kil> it:
290	be passed to the callback.
291		326
292	If you need the local port id in the callback, this works nicely:	327	my $port = port {
293		328	my @msg = @_;
294	my $port; $port = port {	329	...
295	snd $otherport, reply => $port;	330	kil $SELF;
296	};	331	};
297		332
298	=cut	333	=cut
299		334
300	sub rcv($@);	335	sub rcv($@);
		336
		337	sub _kilme {
		338	die "received message on port without callback";
		339	}
301		340
302	sub port(;&) {	341	sub port(;&) {
303	my $id = "$UNIQ." . $ID++;	342	my $id = "$UNIQ." . $ID++;
304	my $port = "$NODE#$id";	343	my $port = "$NODE#$id";
305		344
306	if (@_) {	345	rcv $port, shift \|\| \&_kilme;
307	rcv $port, shift;
308	} else {
309	$PORT{$id} = sub { }; # nop
310	}
311		346
312	$port	347	$port
313	}	348	}
314		349
315	=item reg $port, $name
316
317	=item reg $name
318
319	Registers the given port (or C<$SELF><<< if missing) under the name
320	C<$name>. If the name already exists it is replaced.
321
322	A port can only be registered under one well known name.
323
324	A port automatically becomes unregistered when it is killed.
325
326	=cut
327
328	sub reg(@) {
329	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
330
331	$REG{$_[0]} = $port;
332	}
333
334	=item rcv $port, $callback->(@msg)	350	=item rcv $local_port, $callback->(@msg)
335		351
336	Replaces the callback on the specified miniport (after converting it to	352	Replaces the default callback on the specified port. There is no way to
337	one if required).	353	remove the default callback: use C<sub { }> to disable it, or better
338		354	C<kil> the port when it is no longer needed.
339	=item rcv $port, tagstring => $callback->(@msg), ...
340
341	=item rcv $port, $smartmatch => $callback->(@msg), ...
342
343	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
344
345	Register callbacks to be called on matching messages on the given full
346	port (after converting it to one if required) and return the port.
347
348	The callback has to return a true value when its work is done, after
349	which is will be removed, or a false value in which case it will stay
350	registered.
351		355
352	The global C<$SELF> (exported by this module) contains C<$port> while	356	The global C<$SELF> (exported by this module) contains C<$port> while
353	executing the callback.	357	executing the callback. Runtime errors during callback execution will
		358	result in the port being C<kil>ed.
354		359
355	Runtime errors during callback execution will result in the port being	360	The default callback received all messages not matched by a more specific
356	C<kil>ed.	361	C<tag> match.
357		362
358	If the match is an array reference, then it will be matched against the	363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
359	first elements of the message, otherwise only the first element is being
360	matched.
361		364
362	Any element in the match that is specified as C<_any_> (a function	365	Register (or replace) callbacks to be called on messages starting with the
363	exported by this module) matches any single element of the message.	366	given tag on the given port (and return the port), or unregister it (when
		367	C<$callback> is C<$undef> or missing). There can only be one callback
		368	registered for each tag.
364		369
365	While not required, it is highly recommended that the first matching	370	The original message will be passed to the callback, after the first
366	element is a string identifying the message. The one-string-only match is	371	element (the tag) has been removed. The callback will use the same
367	also the most efficient match (by far).	372	environment as the default callback (see above).
368		373
369	Example: create a port and bind receivers on it in one go.	374	Example: create a port and bind receivers on it in one go.
370		375
371	my $port = rcv port,	376	my $port = rcv port,
372	msg1 => sub { ...; 0 },	377	msg1 => sub { ... },
373	msg2 => sub { ...; 0 },	378	msg2 => sub { ... },
374	;	379	;
375		380
376	Example: create a port, bind receivers and send it in a message elsewhere	381	Example: create a port, bind receivers and send it in a message elsewhere
377	in one go:	382	in one go:
378		383
379	snd $otherport, reply =>	384	snd $otherport, reply =>
380	rcv port,	385	rcv port,
381	msg1 => sub { ...; 0 },	386	msg1 => sub { ... },
382	...	387	...
383	;	388	;
384		389
		390	Example: temporarily register a rcv callback for a tag matching some port
		391	(e.g. for an rpc reply) and unregister it after a message was received.
		392
		393	rcv $port, $otherport => sub {
		394	my @reply = @_;
		395
		396	rcv $SELF, $otherport;
		397	};
		398
385	=cut	399	=cut
386		400
387	sub rcv($@) {	401	sub rcv($@) {
388	my $port = shift;	402	my $port = shift;
389	my ($noderef, $portid) = split /#/, $port, 2;	403	my ($nodeid, $portid) = split /#/, $port, 2;
390		404
391	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	405	$NODE{$nodeid} == $NODE{""}
392	or Carp::croak "$port: rcv can only be called on local ports, caught";	406	or Carp::croak "$port: rcv can only be called on local ports, caught";
393		407
394	if (@_ == 1) {	408	while (@_) {
		409	if (ref $_[0]) {
		410	if (my $self = $PORT_DATA{$portid}) {
		411	"AnyEvent::MP::Port" eq ref $self
		412	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		413
		414	$self->[0] = shift;
		415	} else {
395	my $cb = shift;	416	my $cb = shift;
396	delete $PORT_DATA{$portid};
397	$PORT{$portid} = sub {	417	$PORT{$portid} = sub {
398	local $SELF = $port;	418	local $SELF = $port;
399	eval {	419	eval { &$cb }; _self_die if $@;
400	&$cb	420	};
401	and kil $port;
402	};	421	}
403	_self_die if $@;	422	} elsif (defined $_[0]) {
404	};
405	} else {
406	my $self = $PORT_DATA{$portid} \|\|= do {	423	my $self = $PORT_DATA{$portid} \|\|= do {
407	my $self = bless {	424	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
408	id => $port,
409	}, "AnyEvent::MP::Port";
410		425
411	$PORT{$portid} = sub {	426	$PORT{$portid} = sub {
412	local $SELF = $port;	427	local $SELF = $port;
413		428
414	eval {
415	for (@{ $self->{rc0}{$_[0]} }) {	429	if (my $cb = $self->[1]{$_[0]}) {
416	$_ && &{$_->[0]}	430	shift;
417	&& undef $_;	431	eval { &$cb }; _self_die if $@;
418	}	432	} else {
419
420	for (@{ $self->{rcv}{$_[0]} }) {
421	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
422	&& &{$_->[0]}	433	&{ $self->[0] };
423	&& undef $_;
424	}
425
426	for (@{ $self->{any} }) {
427	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
428	&& &{$_->[0]}
429	&& undef $_;
430	}	434	}
431	};	435	};
432	_self_die if $@;	436
		437	$self
433	};	438	};
434		439
435	$self
436	};
437
438	"AnyEvent::MP::Port" eq ref $self	440	"AnyEvent::MP::Port" eq ref $self
439	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	441	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
440		442
441	while (@_) {
442	my ($match, $cb) = splice @_, 0, 2;	443	my ($tag, $cb) = splice @_, 0, 2;
443		444
444	if (!ref $match) {	445	if (defined $cb) {
445	push @{ $self->{rc0}{$match} }, [$cb];	446	$self->[1]{$tag} = $cb;
446	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
447	my ($type, @match) = @$match;
448	@match
449	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
450	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
451	} else {	447	} else {
452	push @{ $self->{any} }, [$cb, $match];	448	delete $self->[1]{$tag};
453	}	449	}
454	}	450	}
455	}	451	}
456		452
457	$port	453	$port
458	}	454	}
459		455
		456	=item peval $port, $coderef[, @args]
		457
		458	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		459	when the code throews an exception the C<$port> will be killed.
		460
		461	Any remaining args will be passed to the callback. Any return values will
		462	be returned to the caller.
		463
		464	This is useful when you temporarily want to execute code in the context of
		465	a port.
		466
		467	Example: create a port and run some initialisation code in it's context.
		468
		469	my $port = port { ... };
		470
		471	peval $port, sub {
		472	init
		473	or die "unable to init";
		474	};
		475
		476	=cut
		477
		478	sub peval($$) {
		479	local $SELF = shift;
		480	my $cb = shift;
		481
		482	if (wantarray) {
		483	my @res = eval { &$cb };
		484	_self_die if $@;
		485	@res
		486	} else {
		487	my $res = eval { &$cb };
		488	_self_die if $@;
		489	$res
		490	}
		491	}
		492
460	=item $closure = psub { BLOCK }	493	=item $closure = psub { BLOCK }
461		494
462	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	495	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
463	closure is executed, sets up the environment in the same way as in C<rcv>	496	closure is executed, sets up the environment in the same way as in C<rcv>
464	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	497	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		498
		499	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		500	BLOCK }, @_ } >>.
465		501
466	This is useful when you register callbacks from C<rcv> callbacks:	502	This is useful when you register callbacks from C<rcv> callbacks:
467		503
468	rcv delayed_reply => sub {	504	rcv delayed_reply => sub {
469	my ($delay, @reply) = @_;	505	my ($delay, @reply) = @_;
…		…
493	$res	529	$res
494	}	530	}
495	}	531	}
496	}	532	}
497		533
498	=item $guard = mon $port, $cb->(@reason)	534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
499		535
500	=item $guard = mon $port, $rcvport	536	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
501		537
502	=item $guard = mon $port	538	=item $guard = mon $port # kill $SELF when $port dies
503		539
504	=item $guard = mon $port, $rcvport, @msg	540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
505		541
506	Monitor the given port and do something when the port is killed, and	542	Monitor the given port and do something when the port is killed or
507	optionally return a guard that can be used to stop monitoring again.	543	messages to it were lost, and optionally return a guard that can be used
		544	to stop monitoring again.
508		545
509	In the first form (callback), the callback is simply called with any	546	In the first form (callback), the callback is simply called with any
510	number of C<@reason> elements (no @reason means that the port was deleted	547	number of C<@reason> elements (no @reason means that the port was deleted
511	"normally"). Note also that I<< the callback B<must> never die >>, so use	548	"normally"). Note also that I<< the callback B<must> never die >>, so use
512	C<eval> if unsure.	549	C<eval> if unsure.
513		550
514	In the second form (another port given), the other port (C<$rcvport)	551	In the second form (another port given), the other port (C<$rcvport>)
515	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	552	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
516	"normal" kils nothing happens, while under all other conditions, the other	553	"normal" kils nothing happens, while under all other conditions, the other
517	port is killed with the same reason.	554	port is killed with the same reason.
518		555
519	The third form (kill self) is the same as the second form, except that	556	The third form (kill self) is the same as the second form, except that
520	C<$rvport> defaults to C<$SELF>.	557	C<$rvport> defaults to C<$SELF>.
521		558
522	In the last form (message), a message of the form C<@msg, @reason> will be	559	In the last form (message), a message of the form C<@msg, @reason> will be
523	C<snd>.	560	C<snd>.
		561
		562	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		563	alert was raised), they are removed and will not trigger again.
524		564
525	As a rule of thumb, monitoring requests should always monitor a port from	565	As a rule of thumb, monitoring requests should always monitor a port from
526	a local port (or callback). The reason is that kill messages might get	566	a local port (or callback). The reason is that kill messages might get
527	lost, just like any other message. Another less obvious reason is that	567	lost, just like any other message. Another less obvious reason is that
528	even monitoring requests can get lost (for exmaple, when the connection	568	even monitoring requests can get lost (for example, when the connection
529	to the other node goes down permanently). When monitoring a port locally	569	to the other node goes down permanently). When monitoring a port locally
530	these problems do not exist.	570	these problems do not exist.
531		571
		572	C<mon> effectively guarantees that, in the absence of hardware failures,
		573	after starting the monitor, either all messages sent to the port will
		574	arrive, or the monitoring action will be invoked after possible message
		575	loss has been detected. No messages will be lost "in between" (after
		576	the first lost message no further messages will be received by the
		577	port). After the monitoring action was invoked, further messages might get
		578	delivered again.
		579
		580	Inter-host-connection timeouts and monitoring depend on the transport
		581	used. The only transport currently implemented is TCP, and AnyEvent::MP
		582	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		583	non-idle connection, and usually around two hours for idle connections).
		584
		585	This means that monitoring is good for program errors and cleaning up
		586	stuff eventually, but they are no replacement for a timeout when you need
		587	to ensure some maximum latency.
		588
532	Example: call a given callback when C<$port> is killed.	589	Example: call a given callback when C<$port> is killed.
533		590
534	mon $port, sub { warn "port died because of <@_>\n" };	591	mon $port, sub { warn "port died because of <@_>\n" };
535		592
536	Example: kill ourselves when C<$port> is killed abnormally.	593	Example: kill ourselves when C<$port> is killed abnormally.
…		…
542	mon $port, $self => "restart";	599	mon $port, $self => "restart";
543		600
544	=cut	601	=cut
545		602
546	sub mon {	603	sub mon {
547	my ($noderef, $port) = split /#/, shift, 2;	604	my ($nodeid, $port) = split /#/, shift, 2;
548		605
549	my $node = $NODE{$noderef} \|\| add_node $noderef;	606	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
550		607
551	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	608	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
552		609
553	unless (ref $cb) {	610	unless (ref $cb) {
554	if (@_) {	611	if (@_) {
555	# send a kill info message	612	# send a kill info message
556	my (@msg) = @_;	613	my (@msg) = ($cb, @_);
557	$cb = sub { snd @msg, @_ };	614	$cb = sub { snd @msg, @_ };
558	} else {	615	} else {
559	# simply kill other port	616	# simply kill other port
560	my $port = $cb;	617	my $port = $cb;
561	$cb = sub { kil $port, @_ if @_ };	618	$cb = sub { kil $port, @_ if @_ };
…		…
563	}	620	}
564		621
565	$node->monitor ($port, $cb);	622	$node->monitor ($port, $cb);
566		623
567	defined wantarray	624	defined wantarray
568	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
569	}	626	}
570		627
571	=item $guard = mon_guard $port, $ref, $ref...	628	=item $guard = mon_guard $port, $ref, $ref...
572		629
573	Monitors the given C<$port> and keeps the passed references. When the port	630	Monitors the given C<$port> and keeps the passed references. When the port
574	is killed, the references will be freed.	631	is killed, the references will be freed.
575		632
576	Optionally returns a guard that will stop the monitoring.	633	Optionally returns a guard that will stop the monitoring.
577		634
578	This function is useful when you create e.g. timers or other watchers and	635	This function is useful when you create e.g. timers or other watchers and
579	want to free them when the port gets killed:	636	want to free them when the port gets killed (note the use of C<psub>):
580		637
581	$port->rcv (start => sub {	638	$port->rcv (start => sub {
582	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	639	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
583	undef $timer if 0.9 < rand;	640	undef $timer if 0.9 < rand;
584	});	641	});
585	});	642	});
586		643
587	=cut	644	=cut
…		…
596		653
597	=item kil $port[, @reason]	654	=item kil $port[, @reason]
598		655
599	Kill the specified port with the given C<@reason>.	656	Kill the specified port with the given C<@reason>.
600		657
601	If no C<@reason> is specified, then the port is killed "normally" (linked	658	If no C<@reason> is specified, then the port is killed "normally" -
602	ports will not be kileld, or even notified).	659	monitor callback will be invoked, but the kil will not cause linked ports
		660	(C<mon $mport, $lport> form) to get killed.
603		661
604	Otherwise, linked ports get killed with the same reason (second form of	662	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
605	C<mon>, see below).	663	form) get killed with the same reason.
606		664
607	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	665	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
608	will be reported as reason C<< die => $@ >>.	666	will be reported as reason C<< die => $@ >>.
609		667
610	Transport/communication errors are reported as C<< transport_error =>	668	Transport/communication errors are reported as C<< transport_error =>
…		…
615	=item $port = spawn $node, $initfunc[, @initdata]	673	=item $port = spawn $node, $initfunc[, @initdata]
616		674
617	Creates a port on the node C<$node> (which can also be a port ID, in which	675	Creates a port on the node C<$node> (which can also be a port ID, in which
618	case it's the node where that port resides).	676	case it's the node where that port resides).
619		677
620	The port ID of the newly created port is return immediately, and it is	678	The port ID of the newly created port is returned immediately, and it is
621	permissible to immediately start sending messages or monitor the port.	679	possible to immediately start sending messages or to monitor the port.
622		680
623	After the port has been created, the init function is	681	After the port has been created, the init function is called on the remote
624	called. This function must be a fully-qualified function name	682	node, in the same context as a C<rcv> callback. This function must be a
625	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	683	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
626	program, use C<::name>.	684	specify a function in the main program, use C<::name>.
627		685
628	If the function doesn't exist, then the node tries to C<require>	686	If the function doesn't exist, then the node tries to C<require>
629	the package, then the package above the package and so on (e.g.	687	the package, then the package above the package and so on (e.g.
630	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	688	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
631	exists or it runs out of package names.	689	exists or it runs out of package names.
632		690
633	The init function is then called with the newly-created port as context	691	The init function is then called with the newly-created port as context
634	object (C<$SELF>) and the C<@initdata> values as arguments.	692	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		693	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		694	the port might not get created.
635		695
636	A common idiom is to pass your own port, monitor the spawned port, and	696	A common idiom is to pass a local port, immediately monitor the spawned
637	in the init function, monitor the original port. This two-way monitoring	697	port, and in the remote init function, immediately monitor the passed
638	ensures that both ports get cleaned up when there is a problem.	698	local port. This two-way monitoring ensures that both ports get cleaned up
		699	when there is a problem.
		700
		701	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		702	caller before C<spawn> returns (by delaying invocation when spawn is
		703	called for the local node).
639		704
640	Example: spawn a chat server port on C<$othernode>.	705	Example: spawn a chat server port on C<$othernode>.
641		706
642	# this node, executed from within a port context:	707	# this node, executed from within a port context:
643	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	708	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
658		723
659	sub _spawn {	724	sub _spawn {
660	my $port = shift;	725	my $port = shift;
661	my $init = shift;	726	my $init = shift;
662		727
		728	# rcv will create the actual port
663	local $SELF = "$NODE#$port";	729	local $SELF = "$NODE#$port";
664	eval {	730	eval {
665	&{ load_func $init }	731	&{ load_func $init }
666	};	732	};
667	_self_die if $@;	733	_self_die if $@;
668	}	734	}
669		735
670	sub spawn(@) {	736	sub spawn(@) {
671	my ($noderef, undef) = split /#/, shift, 2;	737	my ($nodeid, undef) = split /#/, shift, 2;
672		738
673	my $id = "$RUNIQ." . $ID++;	739	my $id = "$RUNIQ." . $ID++;
674		740
675	$_[0] =~ /::/	741	$_[0] =~ /::/
676	or Carp::croak "spawn init function must be a fully-qualified name, caught";	742	or Carp::croak "spawn init function must be a fully-qualified name, caught";
677		743
678	($NODE{$noderef} \|\| add_node $noderef)	744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
680		745
681	"$noderef#$id"	746	"$nodeid#$id"
682	}	747	}
683		748
684	=back	749	=item after $timeout, @msg
685		750
686	=head1 NODE MESSAGES	751	=item after $timeout, $callback
687		752
688	Nodes understand the following messages sent to them. Many of them take	753	Either sends the given message, or call the given callback, after the
689	arguments called C<@reply>, which will simply be used to compose a reply	754	specified number of seconds.
690	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
691	the remaining arguments are simply the message data.
692		755
693	While other messages exist, they are not public and subject to change.	756	This is simply a utility function that comes in handy at times - the
		757	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		758	so it may go away in the future.
694		759
695	=over 4
696
697	=cut	760	=cut
698		761
699	=item lookup => $name, @reply	762	sub after($@) {
		763	my ($timeout, @action) = @_;
700		764
701	Replies with the port ID of the specified well-known port, or C<undef>.	765	my $t; $t = AE::timer $timeout, 0, sub {
		766	undef $t;
		767	ref $action[0]
		768	? $action[0]()
		769	: snd @action;
		770	};
		771	}
702		772
703	=item devnull => ...	773	=item cal $port, @msg, $callback[, $timeout]
704		774
705	Generic data sink/CPU heat conversion.	775	A simple form of RPC - sends a message to the given C<$port> with the
		776	given contents (C<@msg>), but adds a reply port to the message.
706		777
707	=item relay => $port, @msg	778	The reply port is created temporarily just for the purpose of receiving
		779	the reply, and will be C<kil>ed when no longer needed.
708		780
709	Simply forwards the message to the given port.	781	A reply message sent to the port is passed to the C<$callback> as-is.
710		782
711	=item eval => $string[ @reply]	783	If an optional time-out (in seconds) is given and it is not C<undef>,
		784	then the callback will be called without any arguments after the time-out
		785	elapsed and the port is C<kil>ed.
712		786
713	Evaluates the given string. If C<@reply> is given, then a message of the	787	If no time-out is given (or it is C<undef>), then the local port will
714	form C<@reply, $@, @evalres> is sent.	788	monitor the remote port instead, so it eventually gets cleaned-up.
715		789
716	Example: crash another node.	790	Currently this function returns the temporary port, but this "feature"
		791	might go in future versions unless you can make a convincing case that
		792	this is indeed useful for something.
717		793
718	snd $othernode, eval => "exit";	794	=cut
719		795
720	=item time => @reply	796	sub cal(@) {
		797	my $timeout = ref $_[-1] ? undef : pop;
		798	my $cb = pop;
721		799
722	Replies the the current node time to C<@reply>.	800	my $port = port {
		801	undef $timeout;
		802	kil $SELF;
		803	&$cb;
		804	};
723		805
724	Example: tell the current node to send the current time to C<$myport> in a	806	if (defined $timeout) {
725	C<timereply> message.	807	$timeout = AE::timer $timeout, 0, sub {
		808	undef $timeout;
		809	kil $port;
		810	$cb->();
		811	};
		812	} else {
		813	mon $_[0], sub {
		814	kil $port;
		815	$cb->();
		816	};
		817	}
726		818
727	snd $NODE, time => $myport, timereply => 1, 2;	819	push @_, $port;
728	# => snd $myport, timereply => 1, 2, <time>	820	&snd;
		821
		822	$port
		823	}
729		824
730	=back	825	=back
731		826
732	=head1 AnyEvent::MP vs. Distributed Erlang	827	=head1 AnyEvent::MP vs. Distributed Erlang
733		828
734	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	829	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
735	== aemp node, Erlang process == aemp port), so many of the documents and	830	== aemp node, Erlang process == aemp port), so many of the documents and
736	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	831	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
737	sample:	832	sample:
738		833
739	http://www.Erlang.se/doc/programming_rules.shtml	834	http://www.erlang.se/doc/programming_rules.shtml
740	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	835	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
741	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	836	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
742	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	837	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
743		838
744	Despite the similarities, there are also some important differences:	839	Despite the similarities, there are also some important differences:
745		840
746	=over 4	841	=over 4
747		842
748	=item * Node references contain the recipe on how to contact them.	843	=item * Node IDs are arbitrary strings in AEMP.
749		844
750	Erlang relies on special naming and DNS to work everywhere in the	845	Erlang relies on special naming and DNS to work everywhere in the same
751	same way. AEMP relies on each node knowing it's own address(es), with	846	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
752	convenience functionality.	847	configuration or DNS), and possibly the addresses of some seed nodes, but
		848	will otherwise discover other nodes (and their IDs) itself.
753		849
754	This means that AEMP requires a less tightly controlled environment at the	850	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
755	cost of longer node references and a slightly higher management overhead.	851	uses "local ports are like remote ports".
		852
		853	The failure modes for local ports are quite different (runtime errors
		854	only) then for remote ports - when a local port dies, you I<know> it dies,
		855	when a connection to another node dies, you know nothing about the other
		856	port.
		857
		858	Erlang pretends remote ports are as reliable as local ports, even when
		859	they are not.
		860
		861	AEMP encourages a "treat remote ports differently" philosophy, with local
		862	ports being the special case/exception, where transport errors cannot
		863	occur.
756		864
757	=item * Erlang uses processes and a mailbox, AEMP does not queue.	865	=item * Erlang uses processes and a mailbox, AEMP does not queue.
758		866
759	Erlang uses processes that selctively receive messages, and therefore	867	Erlang uses processes that selectively receive messages, and therefore
760	needs a queue. AEMP is event based, queuing messages would serve no useful	868	needs a queue. AEMP is event based, queuing messages would serve no
761	purpose.	869	useful purpose. For the same reason the pattern-matching abilities of
		870	AnyEvent::MP are more limited, as there is little need to be able to
		871	filter messages without dequeuing them.
762		872
763	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	873	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
764		874
765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
766		876
767	Sending messages in Erlang is synchronous and blocks the process. AEMP	877	Sending messages in Erlang is synchronous and blocks the process (and
768	sends are immediate, connection establishment is handled in the	878	so does not need a queue that can overflow). AEMP sends are immediate,
769	background.	879	connection establishment is handled in the background.
770		880
771	=item * Erlang can silently lose messages, AEMP cannot.	881	=item * Erlang suffers from silent message loss, AEMP does not.
772		882
773	Erlang makes few guarantees on messages delivery - messages can get lost	883	Erlang implements few guarantees on messages delivery - messages can get
774	without any of the processes realising it (i.e. you send messages a, b,	884	lost without any of the processes realising it (i.e. you send messages a,
775	and c, and the other side only receives messages a and c).	885	b, and c, and the other side only receives messages a and c).
776		886
777	AEMP guarantees correct ordering, and the guarantee that there are no	887	AEMP guarantees (modulo hardware errors) correct ordering, and the
		888	guarantee that after one message is lost, all following ones sent to the
		889	same port are lost as well, until monitoring raises an error, so there are
778	holes in the message sequence.	890	no silent "holes" in the message sequence.
779
780	=item * In Erlang, processes can be declared dead and later be found to be
781	alive.
782
783	In Erlang it can happen that a monitored process is declared dead and
784	linked processes get killed, but later it turns out that the process is
785	still alive - and can receive messages.
786
787	In AEMP, when port monitoring detects a port as dead, then that port will
788	eventually be killed - it cannot happen that a node detects a port as dead
789	and then later sends messages to it, finding it is still alive.
790		891
791	=item * Erlang can send messages to the wrong port, AEMP does not.	892	=item * Erlang can send messages to the wrong port, AEMP does not.
792		893
793	In Erlang it is quite possible that a node that restarts reuses a process	894	In Erlang it is quite likely that a node that restarts reuses a process ID
794	ID known to other nodes for a completely different process, causing	895	known to other nodes for a completely different process, causing messages
795	messages destined for that process to end up in an unrelated process.	896	destined for that process to end up in an unrelated process.
796		897
797	AEMP never reuses port IDs, so old messages or old port IDs floating	898	AEMP never reuses port IDs, so old messages or old port IDs floating
798	around in the network will not be sent to an unrelated port.	899	around in the network will not be sent to an unrelated port.
799		900
800	=item * Erlang uses unprotected connections, AEMP uses secure	901	=item * Erlang uses unprotected connections, AEMP uses secure
801	authentication and can use TLS.	902	authentication and can use TLS.
802		903
803	AEMP can use a proven protocol - SSL/TLS - to protect connections and	904	AEMP can use a proven protocol - TLS - to protect connections and
804	securely authenticate nodes.	905	securely authenticate nodes.
805		906
806	=item * The AEMP protocol is optimised for both text-based and binary	907	=item * The AEMP protocol is optimised for both text-based and binary
807	communications.	908	communications.
808		909
809	The AEMP protocol, unlike the Erlang protocol, supports both	910	The AEMP protocol, unlike the Erlang protocol, supports both programming
810	language-independent text-only protocols (good for debugging) and binary,	911	language independent text-only protocols (good for debugging) and binary,
811	language-specific serialisers (e.g. Storable).	912	language-specific serialisers (e.g. Storable). By default, unless TLS is
		913	used, the protocol is actually completely text-based.
812		914
813	It has also been carefully designed to be implementable in other languages	915	It has also been carefully designed to be implementable in other languages
814	with a minimum of work while gracefully degrading fucntionality to make the	916	with a minimum of work while gracefully degrading functionality to make the
815	protocol simple.	917	protocol simple.
816		918
817	=item * AEMP has more flexible monitoring options than Erlang.	919	=item * AEMP has more flexible monitoring options than Erlang.
818		920
819	In Erlang, you can chose to receive I<all> exit signals as messages	921	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
822	Erlang, as one can choose between automatic kill, exit message or callback	924	Erlang, as one can choose between automatic kill, exit message or callback
823	on a per-process basis.	925	on a per-process basis.
824		926
825	=item * Erlang tries to hide remote/local connections, AEMP does not.	927	=item * Erlang tries to hide remote/local connections, AEMP does not.
826		928
827	Monitoring in Erlang is not an indicator of process death/crashes,	929	Monitoring in Erlang is not an indicator of process death/crashes, in the
828	as linking is (except linking is unreliable in Erlang).	930	same way as linking is (except linking is unreliable in Erlang).
829		931
830	In AEMP, you don't "look up" registered port names or send to named ports	932	In AEMP, you don't "look up" registered port names or send to named ports
831	that might or might not be persistent. Instead, you normally spawn a port	933	that might or might not be persistent. Instead, you normally spawn a port
832	on the remote node. The init function monitors the you, and you monitor	934	on the remote node. The init function monitors you, and you monitor the
833	the remote port. Since both monitors are local to the node, they are much	935	remote port. Since both monitors are local to the node, they are much more
834	more reliable.	936	reliable (no need for C<spawn_link>).
835		937
836	This also saves round-trips and avoids sending messages to the wrong port	938	This also saves round-trips and avoids sending messages to the wrong port
837	(hard to do in Erlang).	939	(hard to do in Erlang).
838		940
839	=back	941	=back
840		942
		943	=head1 RATIONALE
		944
		945	=over 4
		946
		947	=item Why strings for port and node IDs, why not objects?
		948
		949	We considered "objects", but found that the actual number of methods
		950	that can be called are quite low. Since port and node IDs travel over
		951	the network frequently, the serialising/deserialising would add lots of
		952	overhead, as well as having to keep a proxy object everywhere.
		953
		954	Strings can easily be printed, easily serialised etc. and need no special
		955	procedures to be "valid".
		956
		957	And as a result, a port with just a default receiver consists of a single
		958	code reference stored in a global hash - it can't become much cheaper.
		959
		960	=item Why favour JSON, why not a real serialising format such as Storable?
		961
		962	In fact, any AnyEvent::MP node will happily accept Storable as framing
		963	format, but currently there is no way to make a node use Storable by
		964	default (although all nodes will accept it).
		965
		966	The default framing protocol is JSON because a) JSON::XS is many times
		967	faster for small messages and b) most importantly, after years of
		968	experience we found that object serialisation is causing more problems
		969	than it solves: Just like function calls, objects simply do not travel
		970	easily over the network, mostly because they will always be a copy, so you
		971	always have to re-think your design.
		972
		973	Keeping your messages simple, concentrating on data structures rather than
		974	objects, will keep your messages clean, tidy and efficient.
		975
		976	=back
		977
841	=head1 SEE ALSO	978	=head1 SEE ALSO
		979
		980	L<AnyEvent::MP::Intro> - a gentle introduction.
		981
		982	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		983
		984	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		985	your applications.
		986
		987	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		988
		989	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		990	all nodes.
842		991
843	L<AnyEvent>.	992	L<AnyEvent>.
844		993
845	=head1 AUTHOR	994	=head1 AUTHOR
846		995

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Revision 1.118 by root, Thu Jun 30 09:31:58 2011 UTC