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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC vs.
Revision 1.112 by root, Thu Apr 1 19:24:22 2010 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 prot 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	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	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>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	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).
73		78
74	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
75	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	81	anything was listening for them or not.
77		82
78	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
79		84
80	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
81	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
82	exception is the the node port, whose ID is identical to its node
83	reference.
84		87
85	=item node	88	=item node
86		89
87	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,
88	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
89	create new ports, among other things.	92	ports.
90		93
91	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
93		97
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
95		99
96	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
97	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
98	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.
99		104
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		106
103	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
104	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.
105		111
106	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
107	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.
108		139
109	=back	140	=back
110		141
111	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
112		143
124		155
125	use AE ();	156	use AE ();
126		157
127	use base "Exporter";	158	use base "Exporter";
128		159
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	160	our $VERSION = 1.28;
130		161
131	our @EXPORT = qw(	162	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	164	configure
134	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
135	port	166	port
136	);	167	);
137		168
138	our $SELF;	169	our $SELF;
139		170
…		…
143	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
144	}	175	}
145		176
146	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
147		178
148	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	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
150	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
151	identifiers become invalid.
152		182
153	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
154		184
155	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.
156		186
157	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
158		188
159	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
160		190
161	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
164		195
		196	The key/value pairs are basically the same ones as documented for the
		197	F<aemp> command line utility (sans the set/del prefix).
		198
165	This function initialises a node - it must be called exactly once (or	199	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	200	never) before calling other AnyEvent::MP functions.
167		201
168	All arguments are noderefs, which can be either resolved or unresolved.
169
170	There are two types of networked nodes, public nodes and slave nodes:
171
172	=over 4	202	=over 4
173		203
174	=item public nodes	204	=item step 1, gathering configuration from profiles
175		205
176	For public nodes, C<$noderef> must either be a (possibly unresolved)	206	The function first looks up a profile in the aemp configuration (see the
177	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
178	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.
179		210
180	Afterwards, the node will bind itself on all endpoints and try to connect	211	The profile data is then gathered as follows:
181	to all additional C<$seednodes> that are specified. Seednodes are optional
182	and can be used to quickly bootstrap the node into an existing network.
183		212
184	=item slave nodes	213	First, all remaining key => value pairs (all of which are conveniently
		214	undocumented at the moment) will be interpreted as configuration
		215	data. Then they will be overwritten by any values specified in the global
		216	default configuration (see the F<aemp> utility), then the chain of
		217	profiles chosen by the profile name (and any C<parent> attributes).
185		218
186	When the C<$noderef> is the special string C<slave/>, then the node will	219	That means that the values specified in the profile have highest priority
187	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,
188	route most of their traffic to the master node that they attach to.	221	and can only be used to specify defaults.
189		222
190	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
191	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
192	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.
193		244
194	=back	245	=back
195		246
196	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.
197	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.
198	server.
199		249
200	Example: become a public node listening on the default node.	250	configure
201		251
202	initialise_node;	252	Example: become an anonymous node. This form is often used for commandline
		253	clients.
203		254
204	Example: become a public node, and try to contact some well-known master	255	configure nodeid => "anon/";
205	servers to become part of the network.
206		256
207	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).
208		260
209	Example: become a public node listening on port C<4041>.	261	# use the aemp commandline utility
		262	# aemp profile seed nodeid anon/ binds '*:4040'
210		263
211	initialise_node 4041;	264	# then use it
		265	configure profile => "seed";
212		266
213	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
214		269
215	initialise_node "locahost:4044";	270	# or provide a nicer-to-remember nodeid
216		271	# aemp run profile seed nodeid "$(hostname)"
217	Example: become a slave node to any of the specified master servers.
218
219	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
220
221	=item $cv = resolve_node $noderef
222
223	Takes an unresolved node reference that may contain hostnames and
224	abbreviated IDs, resolves all of them and returns a resolved node
225	reference.
226
227	In addition to C<address:port> pairs allowed in resolved noderefs, the
228	following forms are supported:
229
230	=over 4
231
232	=item the empty string
233
234	An empty-string component gets resolved as if the default port (4040) was
235	specified.
236
237	=item naked port numbers (e.g. C<1234>)
238
239	These are resolved by prepending the local nodename and a colon, to be
240	further resolved.
241
242	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
243
244	These are resolved by using AnyEvent::DNS to resolve them, optionally
245	looking up SRV records for the C<aemp=4040> port, if no port was
246	specified.
247
248	=back
249		272
250	=item $SELF	273	=item $SELF
251		274
252	Contains the current port id while executing C<rcv> callbacks or C<psub>	275	Contains the current port id while executing C<rcv> callbacks or C<psub>
253	blocks.	276	blocks.
254		277
255	=item SELF, %SELF, @SELF...	278	=item *SELF, SELF, %SELF, @SELF...
256		279
257	Due to some quirks in how perl exports variables, it is impossible to	280	Due to some quirks in how perl exports variables, it is impossible to
258	just export C<$SELF>, all the symbols called C<SELF> are exported by this	281	just export C<$SELF>, all the symbols named C<SELF> are exported by this
259	module, but only C<$SELF> is currently used.	282	module, but only C<$SELF> is currently used.
260		283
261	=item snd $port, type => @data	284	=item snd $port, type => @data
262		285
263	=item snd $port, @msg	286	=item snd $port, @msg
264		287
265	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
266	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.
267	stringifies a sa port ID (such as a port object :).
268		290
269	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
270	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
271	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.
272		295
273	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
274	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument (or values referenced by them) is
275	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.
276		302
277	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
278	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
279	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
280	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
281	node, anything can be passed.	307	node, anything can be passed. Best rely only on the common denominator of
		308	these.
282		309
283	=item $local_port = port	310	=item $local_port = port
284		311
285	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
286	matching port ("full port") or a single-callback port ("miniport"),	313	no callbacks set and will throw an error when it receives messages.
287	depending on how C<rcv> callbacks are bound to the object.
288		314
289	=item $port = port { my @msg = @_; $finished }	315	=item $local_port = port { my @msg = @_ }
290		316
291	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
292	matching behind it, and returns its ID. Semantically the same as creating
293	a port and calling C<rcv $port, $callback> on it.	318	creating a port and calling C<rcv $port, $callback> on it.
294		319
295	The block will be called for every message received on the port. When the	320	The block will be called for every message received on the port, with the
296	callback returns a true value its job is considered "done" and the port	321	global variable C<$SELF> set to the port ID. Runtime errors will cause the
297	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.
298		324
299	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:
300	be passed to the callback.
301		326
302	If you need the local port id in the callback, this works nicely:	327	my $port = port {
303		328	my @msg = @_;
304	my $port; $port = port {	329	...
305	snd $otherport, reply => $port;	330	kil $SELF;
306	};	331	};
307		332
308	=cut	333	=cut
309		334
310	sub rcv($@);	335	sub rcv($@);
		336
		337	sub _kilme {
		338	die "received message on port without callback";
		339	}
311		340
312	sub port(;&) {	341	sub port(;&) {
313	my $id = "$UNIQ." . $ID++;	342	my $id = "$UNIQ." . $ID++;
314	my $port = "$NODE#$id";	343	my $port = "$NODE#$id";
315		344
316	if (@_) {	345	rcv $port, shift \|\| \&_kilme;
317	rcv $port, shift;
318	} else {
319	$PORT{$id} = sub { }; # nop
320	}
321		346
322	$port	347	$port
323	}	348	}
324		349
325	=item reg $port, $name
326
327	=item reg $name
328
329	Registers the given port (or C<$SELF><<< if missing) under the name
330	C<$name>. If the name already exists it is replaced.
331
332	A port can only be registered under one well known name.
333
334	A port automatically becomes unregistered when it is killed.
335
336	=cut
337
338	sub reg(@) {
339	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
340
341	$REG{$_[0]} = $port;
342	}
343
344	=item rcv $port, $callback->(@msg)	350	=item rcv $local_port, $callback->(@msg)
345		351
346	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
347	one if required).	353	remove the default callback: use C<sub { }> to disable it, or better
348		354	C<kil> the port when it is no longer needed.
349	=item rcv $port, tagstring => $callback->(@msg), ...
350
351	=item rcv $port, $smartmatch => $callback->(@msg), ...
352
353	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
354
355	Register callbacks to be called on matching messages on the given full
356	port (after converting it to one if required) and return the port.
357
358	The callback has to return a true value when its work is done, after
359	which is will be removed, or a false value in which case it will stay
360	registered.
361		355
362	The global C<$SELF> (exported by this module) contains C<$port> while	356	The global C<$SELF> (exported by this module) contains C<$port> while
363	executing the callback.	357	executing the callback. Runtime errors during callback execution will
		358	result in the port being C<kil>ed.
364		359
365	Runtime errors during callback execution will result in the port being	360	The default callback received all messages not matched by a more specific
366	C<kil>ed.	361	C<tag> match.
367		362
368	If the match is an array reference, then it will be matched against the	363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
369	first elements of the message, otherwise only the first element is being
370	matched.
371		364
372	Any element in the match that is specified as C<_any_> (a function	365	Register (or replace) callbacks to be called on messages starting with the
373	exported by this module) matches any single element of the message.	366	given tag on the given port (and return the port), or unregister it (when
		367	C<$callback> is C<$undef> or missing). There can only be one callback
		368	registered for each tag.
374		369
375	While not required, it is highly recommended that the first matching	370	The original message will be passed to the callback, after the first
376	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
377	also the most efficient match (by far).	372	environment as the default callback (see above).
378		373
379	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.
380		375
381	my $port = rcv port,	376	my $port = rcv port,
382	msg1 => sub { ...; 0 },	377	msg1 => sub { ... },
383	msg2 => sub { ...; 0 },	378	msg2 => sub { ... },
384	;	379	;
385		380
386	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
387	in one go:	382	in one go:
388		383
389	snd $otherport, reply =>	384	snd $otherport, reply =>
390	rcv port,	385	rcv port,
391	msg1 => sub { ...; 0 },	386	msg1 => sub { ... },
392	...	387	...
393	;	388	;
394		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, $otherport;
		397	};
		398
395	=cut	399	=cut
396		400
397	sub rcv($@) {	401	sub rcv($@) {
398	my $port = shift;	402	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	403	my ($nodeid, $portid) = split /#/, $port, 2;
400		404
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	405	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	406	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		407
404	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 {
405	my $cb = shift;	416	my $cb = shift;
406	delete $PORT_DATA{$portid};
407	$PORT{$portid} = sub {	417	$PORT{$portid} = sub {
408	local $SELF = $port;	418	local $SELF = $port;
409	eval {	419	eval { &$cb }; _self_die if $@;
410	&$cb	420	};
411	and kil $port;
412	};	421	}
413	_self_die if $@;	422	} elsif (defined $_[0]) {
414	};
415	} else {
416	my $self = $PORT_DATA{$portid} \|\|= do {	423	my $self = $PORT_DATA{$portid} \|\|= do {
417	my $self = bless {	424	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
418	id => $port,
419	}, "AnyEvent::MP::Port";
420		425
421	$PORT{$portid} = sub {	426	$PORT{$portid} = sub {
422	local $SELF = $port;	427	local $SELF = $port;
423		428
424	eval {
425	for (@{ $self->{rc0}{$_[0]} }) {	429	if (my $cb = $self->[1]{$_[0]}) {
426	$_ && &{$_->[0]}	430	shift;
427	&& undef $_;	431	eval { &$cb }; _self_die if $@;
428	}	432	} else {
429
430	for (@{ $self->{rcv}{$_[0]} }) {
431	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
432	&& &{$_->[0]}	433	&{ $self->[0] };
433	&& undef $_;
434	}
435
436	for (@{ $self->{any} }) {
437	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
438	&& &{$_->[0]}
439	&& undef $_;
440	}	434	}
441	};	435	};
442	_self_die if $@;	436
		437	$self
443	};	438	};
444		439
445	$self
446	};
447
448	"AnyEvent::MP::Port" eq ref $self	440	"AnyEvent::MP::Port" eq ref $self
449	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	441	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
450		442
451	while (@_) {
452	my ($match, $cb) = splice @_, 0, 2;	443	my ($tag, $cb) = splice @_, 0, 2;
453		444
454	if (!ref $match) {	445	if (defined $cb) {
455	push @{ $self->{rc0}{$match} }, [$cb];	446	$self->[1]{$tag} = $cb;
456	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
457	my ($type, @match) = @$match;
458	@match
459	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
460	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
461	} else {	447	} else {
462	push @{ $self->{any} }, [$cb, $match];	448	delete $self->[1]{$tag};
463	}	449	}
464	}	450	}
465	}	451	}
466		452
467	$port	453	$port
468	}	454	}
469		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
470	=item $closure = psub { BLOCK }	493	=item $closure = psub { BLOCK }
471		494
472	Remembers C<$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
473	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>
474	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 $SELF, sub {
		500	BLOCK } } >>.
475		501
476	This is useful when you register callbacks from C<rcv> callbacks:	502	This is useful when you register callbacks from C<rcv> callbacks:
477		503
478	rcv delayed_reply => sub {	504	rcv delayed_reply => sub {
479	my ($delay, @reply) = @_;	505	my ($delay, @reply) = @_;
…		…
503	$res	529	$res
504	}	530	}
505	}	531	}
506	}	532	}
507		533
508	=item $guard = mon $port, $cb->(@reason)	534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
509		535
510	=item $guard = mon $port, $rcvport	536	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
511		537
512	=item $guard = mon $port	538	=item $guard = mon $port # kill $SELF when $port dies
513		539
514	=item $guard = mon $port, $rcvport, @msg	540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
515		541
516	Monitor the given port and do something when the port is killed or	542	Monitor the given port and do something when the port is killed or
517	messages to it were lost, and optionally return a guard that can be used	543	messages to it were lost, and optionally return a guard that can be used
518	to stop monitoring again.	544	to stop monitoring again.
519
520	C<mon> effectively guarantees that, in the absence of hardware failures,
521	that after starting the monitor, either all messages sent to the port
522	will arrive, or the monitoring action will be invoked after possible
523	message loss has been detected. No messages will be lost "in between"
524	(after the first lost message no further messages will be received by the
525	port). After the monitoring action was invoked, further messages might get
526	delivered again.
527		545
528	In the first form (callback), the callback is simply called with any	546	In the first form (callback), the callback is simply called with any
529	number of C<@reason> elements (no @reason means that the port was deleted	547	number of C<@reason> elements (no @reason means that the port was deleted
530	"normally"). Note also that I<< the callback B<must> never die >>, so use	548	"normally"). Note also that I<< the callback B<must> never die >>, so use
531	C<eval> if unsure.	549	C<eval> if unsure.
532		550
533	In the second form (another port given), the other port (C<$rcvport>)	551	In the second form (another port given), the other port (C<$rcvport>)
534	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	552	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
535	"normal" kils nothing happens, while under all other conditions, the other	553	"normal" kils nothing happens, while under all other conditions, the other
536	port is killed with the same reason.	554	port is killed with the same reason.
537		555
538	The third form (kill self) is the same as the second form, except that	556	The third form (kill self) is the same as the second form, except that
539	C<$rvport> defaults to C<$SELF>.	557	C<$rvport> defaults to C<$SELF>.
540		558
541	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
542	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.
543		564
544	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
545	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
546	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
547	even monitoring requests can get lost (for exmaple, when the connection	568	even monitoring requests can get lost (for example, when the connection
548	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
549	these problems do not exist.	570	these problems do not exist.
550		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
551	Example: call a given callback when C<$port> is killed.	589	Example: call a given callback when C<$port> is killed.
552		590
553	mon $port, sub { warn "port died because of <@_>\n" };	591	mon $port, sub { warn "port died because of <@_>\n" };
554		592
555	Example: kill ourselves when C<$port> is killed abnormally.	593	Example: kill ourselves when C<$port> is killed abnormally.
…		…
561	mon $port, $self => "restart";	599	mon $port, $self => "restart";
562		600
563	=cut	601	=cut
564		602
565	sub mon {	603	sub mon {
566	my ($noderef, $port) = split /#/, shift, 2;	604	my ($nodeid, $port) = split /#/, shift, 2;
567		605
568	my $node = $NODE{$noderef} \|\| add_node $noderef;	606	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
569		607
570	my $cb = @_ ? shift : $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,';
571		609
572	unless (ref $cb) {	610	unless (ref $cb) {
573	if (@_) {	611	if (@_) {
…		…
582	}	620	}
583		621
584	$node->monitor ($port, $cb);	622	$node->monitor ($port, $cb);
585		623
586	defined wantarray	624	defined wantarray
587	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
588	}	626	}
589		627
590	=item $guard = mon_guard $port, $ref, $ref...	628	=item $guard = mon_guard $port, $ref, $ref...
591		629
592	Monitors the given C<$port> and keeps the passed references. When the port	630	Monitors the given C<$port> and keeps the passed references. When the port
593	is killed, the references will be freed.	631	is killed, the references will be freed.
594		632
595	Optionally returns a guard that will stop the monitoring.	633	Optionally returns a guard that will stop the monitoring.
596		634
597	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
598	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>):
599		637
600	$port->rcv (start => sub {	638	$port->rcv (start => sub {
601	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	639	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
602	undef $timer if 0.9 < rand;	640	undef $timer if 0.9 < rand;
603	});	641	});
604	});	642	});
605		643
606	=cut	644	=cut
…		…
615		653
616	=item kil $port[, @reason]	654	=item kil $port[, @reason]
617		655
618	Kill the specified port with the given C<@reason>.	656	Kill the specified port with the given C<@reason>.
619		657
620	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" -
621	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.
622		661
623	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>
624	C<mon>, see below).	663	form) get killed with the same reason.
625		664
626	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
627	will be reported as reason C<< die => $@ >>.	666	will be reported as reason C<< die => $@ >>.
628		667
629	Transport/communication errors are reported as C<< transport_error =>	668	Transport/communication errors are reported as C<< transport_error =>
…		…
634	=item $port = spawn $node, $initfunc[, @initdata]	673	=item $port = spawn $node, $initfunc[, @initdata]
635		674
636	Creates a port on the node C<$node> (which can also be a port ID, in which	675	Creates a port on the node C<$node> (which can also be a port ID, in which
637	case it's the node where that port resides).	676	case it's the node where that port resides).
638		677
639	The port ID of the newly created port is return immediately, and it is	678	The port ID of the newly created port is returned immediately, and it is
640	permissible to immediately start sending messages or monitor the port.	679	possible to immediately start sending messages or to monitor the port.
641		680
642	After the port has been created, the init function is	681	After the port has been created, the init function is called on the remote
643	called. This function must be a fully-qualified function name	682	node, in the same context as a C<rcv> callback. This function must be a
644	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	683	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
645	program, use C<::name>.	684	specify a function in the main program, use C<::name>.
646		685
647	If the function doesn't exist, then the node tries to C<require>	686	If the function doesn't exist, then the node tries to C<require>
648	the package, then the package above the package and so on (e.g.	687	the package, then the package above the package and so on (e.g.
649	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	688	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
650	exists or it runs out of package names.	689	exists or it runs out of package names.
651		690
652	The init function is then called with the newly-created port as context	691	The init function is then called with the newly-created port as context
653	object (C<$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.
654		695
655	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
656	in the init function, monitor the original port. This two-way monitoring	697	port, and in the remote init function, immediately monitor the passed
657	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<$initfunc> has no visible effects on the
		702	caller before C<spawn> returns (by delaying invocation when spawn is
		703	called for the local node).
658		704
659	Example: spawn a chat server port on C<$othernode>.	705	Example: spawn a chat server port on C<$othernode>.
660		706
661	# this node, executed from within a port context:	707	# this node, executed from within a port context:
662	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	708	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
677		723
678	sub _spawn {	724	sub _spawn {
679	my $port = shift;	725	my $port = shift;
680	my $init = shift;	726	my $init = shift;
681		727
		728	# rcv will create the actual port
682	local $SELF = "$NODE#$port";	729	local $SELF = "$NODE#$port";
683	eval {	730	eval {
684	&{ load_func $init }	731	&{ load_func $init }
685	};	732	};
686	_self_die if $@;	733	_self_die if $@;
687	}	734	}
688		735
689	sub spawn(@) {	736	sub spawn(@) {
690	my ($noderef, undef) = split /#/, shift, 2;	737	my ($nodeid, undef) = split /#/, shift, 2;
691		738
692	my $id = "$RUNIQ." . $ID++;	739	my $id = "$RUNIQ." . $ID++;
693		740
694	$_[0] =~ /::/	741	$_[0] =~ /::/
695	or Carp::croak "spawn init function must be a fully-qualified name, caught";	742	or Carp::croak "spawn init function must be a fully-qualified name, caught";
696		743
697	($NODE{$noderef} \|\| add_node $noderef)	744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
698	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
699		745
700	"$noderef#$id"	746	"$nodeid#$id"
701	}	747	}
702		748
703	=back	749	=item after $timeout, @msg
704		750
705	=head1 NODE MESSAGES	751	=item after $timeout, $callback
706		752
707	Nodes understand the following messages sent to them. Many of them take	753	Either sends the given message, or call the given callback, after the
708	arguments called C<@reply>, which will simply be used to compose a reply	754	specified number of seconds.
709	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
710	the remaining arguments are simply the message data.
711		755
712	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.
713		759
714	=over 4
715
716	=cut	760	=cut
717		761
718	=item lookup => $name, @reply	762	sub after($@) {
		763	my ($timeout, @action) = @_;
719		764
720	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	}
721		772
722	=item devnull => ...	773	=item cal $port, @msg, $callback[, $timeout]
723		774
724	Generic data sink/CPU heat conversion.	775	A simple form of RPC - sends a message to the given C<$port> with the
		776	given contents (C<@msg>), but adds a reply port to the message.
725		777
726	=item relay => $port, @msg	778	The reply port is created temporarily just for the purpose of receiving
		779	the reply, and will be C<kil>ed when no longer needed.
727		780
728	Simply forwards the message to the given port.	781	A reply message sent to the port is passed to the C<$callback> as-is.
729		782
730	=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.
731		786
732	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
733	form C<@reply, $@, @evalres> is sent.	788	monitor the remote port instead, so it eventually gets cleaned-up.
734		789
735	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.
736		793
737	snd $othernode, eval => "exit";	794	=cut
738		795
739	=item time => @reply	796	sub cal(@) {
		797	my $timeout = ref $_[-1] ? undef : pop;
		798	my $cb = pop;
740		799
741	Replies the the current node time to C<@reply>.	800	my $port = port {
		801	undef $timeout;
		802	kil $SELF;
		803	&$cb;
		804	};
742		805
743	Example: tell the current node to send the current time to C<$myport> in a	806	if (defined $timeout) {
744	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	}
745		818
746	snd $NODE, time => $myport, timereply => 1, 2;	819	push @_, $port;
747	# => snd $myport, timereply => 1, 2, <time>	820	&snd;
		821
		822	$port
		823	}
748		824
749	=back	825	=back
750		826
751	=head1 AnyEvent::MP vs. Distributed Erlang	827	=head1 AnyEvent::MP vs. Distributed Erlang
752		828
753	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
754	== 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
755	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
756	sample:	832	sample:
757		833
758	http://www.Erlang.se/doc/programming_rules.shtml	834	http://www.erlang.se/doc/programming_rules.shtml
759	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
760	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
761	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
762		838
763	Despite the similarities, there are also some important differences:	839	Despite the similarities, there are also some important differences:
764		840
765	=over 4	841	=over 4
766		842
767	=item * Node references contain the recipe on how to contact them.	843	=item * Node IDs are arbitrary strings in AEMP.
768		844
769	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
770	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
771	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.
772		849
773	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
774	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.
775		864
776	=item * Erlang uses processes and a mailbox, AEMP does not queue.	865	=item * Erlang uses processes and a mailbox, AEMP does not queue.
777		866
778	Erlang uses processes that selctively receive messages, and therefore	867	Erlang uses processes that selectively receive messages, and therefore
779	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
780	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.
781		872
782	(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).
783		874
784	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
785		876
786	Sending messages in Erlang is synchronous and blocks the process. AEMP	877	Sending messages in Erlang is synchronous and blocks the process (and
787	sends are immediate, connection establishment is handled in the	878	so does not need a queue that can overflow). AEMP sends are immediate,
788	background.	879	connection establishment is handled in the background.
789		880
790	=item * Erlang can silently lose messages, AEMP cannot.	881	=item * Erlang suffers from silent message loss, AEMP does not.
791		882
792	Erlang makes few guarantees on messages delivery - messages can get lost	883	Erlang implements few guarantees on messages delivery - messages can get
793	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,
794	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).
795		886
796	AEMP guarantees correct ordering, and the guarantee that there are no	887	AEMP guarantees correct ordering, and the guarantee that after one message
797	holes in the message sequence.	888	is lost, all following ones sent to the same port are lost as well, until
798		889	monitoring raises an error, so there are no silent "holes" in the message
799	=item * In Erlang, processes can be declared dead and later be found to be	890	sequence.
800	alive.
801
802	In Erlang it can happen that a monitored process is declared dead and
803	linked processes get killed, but later it turns out that the process is
804	still alive - and can receive messages.
805
806	In AEMP, when port monitoring detects a port as dead, then that port will
807	eventually be killed - it cannot happen that a node detects a port as dead
808	and then later sends messages to it, finding it is still alive.
809		891
810	=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.
811		893
812	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
813	ID known to other nodes for a completely different process, causing	895	known to other nodes for a completely different process, causing messages
814	messages destined for that process to end up in an unrelated process.	896	destined for that process to end up in an unrelated process.
815		897
816	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
817	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.
818		900
819	=item * Erlang uses unprotected connections, AEMP uses secure	901	=item * Erlang uses unprotected connections, AEMP uses secure
820	authentication and can use TLS.	902	authentication and can use TLS.
821		903
822	AEMP can use a proven protocol - SSL/TLS - to protect connections and	904	AEMP can use a proven protocol - TLS - to protect connections and
823	securely authenticate nodes.	905	securely authenticate nodes.
824		906
825	=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
826	communications.	908	communications.
827		909
828	The AEMP protocol, unlike the Erlang protocol, supports both	910	The AEMP protocol, unlike the Erlang protocol, supports both programming
829	language-independent text-only protocols (good for debugging) and binary,	911	language independent text-only protocols (good for debugging) and binary,
830	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.
831		914
832	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
833	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
834	protocol simple.	917	protocol simple.
835		918
836	=item * AEMP has more flexible monitoring options than Erlang.	919	=item * AEMP has more flexible monitoring options than Erlang.
837		920
838	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
…		…
841	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
842	on a per-process basis.	925	on a per-process basis.
843		926
844	=item * Erlang tries to hide remote/local connections, AEMP does not.	927	=item * Erlang tries to hide remote/local connections, AEMP does not.
845		928
846	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
847	as linking is (except linking is unreliable in Erlang).	930	same way as linking is (except linking is unreliable in Erlang).
848		931
849	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
850	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
851	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
852	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
853	more reliable.	936	reliable (no need for C<spawn_link>).
854		937
855	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
856	(hard to do in Erlang).	939	(hard to do in Erlang).
857		940
858	=back	941	=back
859		942
860	=head1 RATIONALE	943	=head1 RATIONALE
861		944
862	=over 4	945	=over 4
863		946
864	=item Why strings for ports and noderefs, why not objects?	947	=item Why strings for port and node IDs, why not objects?
865		948
866	We considered "objects", but found that the actual number of methods	949	We considered "objects", but found that the actual number of methods
867	thatc an be called are very low. Since port IDs and noderefs travel over	950	that can be called are quite low. Since port and node IDs travel over
868	the network frequently, the serialising/deserialising would add lots of	951	the network frequently, the serialising/deserialising would add lots of
869	overhead, as well as having to keep a proxy object.	952	overhead, as well as having to keep a proxy object everywhere.
870		953
871	Strings can easily be printed, easily serialised etc. and need no special	954	Strings can easily be printed, easily serialised etc. and need no special
872	procedures to be "valid".	955	procedures to be "valid".
873		956
874	And a a miniport consists of a single closure stored in a global hash - it	957	And as a result, a port with just a default receiver consists of a single
875	can't become much cheaper.	958	closure stored in a global hash - it can't become much cheaper.
876		959
877	=item Why favour JSON, why not real serialising format such as Storable?	960	=item Why favour JSON, why not a real serialising format such as Storable?
878		961
879	In fact, any AnyEvent::MP node will happily accept Storable as framing	962	In fact, any AnyEvent::MP node will happily accept Storable as framing
880	format, but currently there is no way to make a node use Storable by	963	format, but currently there is no way to make a node use Storable by
881	default.	964	default (although all nodes will accept it).
882		965
883	The default framing protocol is JSON because a) JSON::XS is many times	966	The default framing protocol is JSON because a) JSON::XS is many times
884	faster for small messages and b) most importantly, after years of	967	faster for small messages and b) most importantly, after years of
885	experience we found that object serialisation is causing more problems	968	experience we found that object serialisation is causing more problems
886	than it gains: Just like function calls, objects simply do not travel	969	than it solves: Just like function calls, objects simply do not travel
887	easily over the network, mostly because they will always be a copy, so you	970	easily over the network, mostly because they will always be a copy, so you
888	always have to re-think your design.	971	always have to re-think your design.
889		972
890	Keeping your messages simple, concentrating on data structures rather than	973	Keeping your messages simple, concentrating on data structures rather than
891	objects, will keep your messages clean, tidy and efficient.	974	objects, will keep your messages clean, tidy and efficient.
892		975
893	=back	976	=back
894		977
895	=head1 SEE ALSO	978	=head1 SEE ALSO
896		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 maintainance 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.
		991
897	L<AnyEvent>.	992	L<AnyEvent>.
898		993
899	=head1 AUTHOR	994	=head1 AUTHOR
900		995
901	Marc Lehmann <schmorp@schmorp.de>	996	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.112 by root, Thu Apr 1 19:24:22 2010 UTC