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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.46 by root, Thu Aug 13 01:46:10 2009 UTC vs.
Revision 1.99 by root, Fri Oct 2 14:12:16 2009 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	rcv $port, [child_died => $pid] => sub { ...
36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
37
38	# monitoring	35	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	36	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $localport, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable API.
49		46	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		47
52	=head1 DESCRIPTION	48	=head1 DESCRIPTION
53		49
54	This module (-family) implements a simple message passing framework.	50	This module (-family) implements a simple message passing framework.
55		51
56	Despite its simplicity, you can securely message other processes running	52	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	53	on the same or other hosts, and you can supervise entities remotely.
58		54
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	55	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	56	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		57
66	=head1 CONCEPTS	58	=head1 CONCEPTS
67		59
68	=over 4	60	=over 4
69		61
70	=item port	62	=item port
71		63
72	A port is something you can send messages to (with the C<snd> function).	64	Not to be confused with a TCP port, a "port" is something you can send
		65	messages to (with the C<snd> function).
73		66
74	Some ports allow you to register C<rcv> handlers that can match specific	67	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	68	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	69	anything was listening for them or not.
77		70
78	=item port id - C<noderef#portname>	71	=item port ID - C<nodeid#portname>
79		72
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	73	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	74	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		75
85	=item node	76	=item node
86		77
87	A node is a single process containing at least one port - the node	78	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	79	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	80	ports.
90		81
91	Nodes are either private (single-process only), slaves (connected to a	82	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	83	(no listening ports). Private nodes cannot talk to other private nodes
		84	currently.
93		85
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
95		87
96	A node reference is a string that either simply identifies the node (for	88	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	89	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	90	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		91	doesn't interpret node IDs in any way.
99		92
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	93	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		94
103	Node references come in two flavours: resolved (containing only numerical	95	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).	96	each other. To do this, nodes should listen on one or more local transport
		97	endpoints - binds. Currently, only standard C<ip:port> specifications can
		98	be used, which specify TCP ports to listen on.
105		99
106	Before using an unresolved node reference in a message you first have to	100	=item seed nodes
107	resolve it.	101
		102	When a node starts, it knows nothing about the network. To teach the node
		103	about the network it first has to contact some other node within the
		104	network. This node is called a seed.
		105
		106	Apart from the fact that other nodes know them as seed nodes and they have
		107	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		108	any node can function as a seed node for others.
		109
		110	In addition to discovering the network, seed nodes are also used to
		111	maintain the network and to connect nodes that otherwise would have
		112	trouble connecting. They form the backbone of an AnyEvent::MP network.
		113
		114	Seed nodes are expected to be long-running, and at least one seed node
		115	should always be available. They should also be relatively responsive - a
		116	seed node that blocks for long periods will slow down everybody else.
		117
		118	=item seeds - C<host:port>
		119
		120	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		121	TCP port) of nodes that should be used as seed nodes.
		122
		123	The nodes listening on those endpoints are expected to be long-running,
		124	and at least one of those should always be available. When nodes run out
		125	of connections (e.g. due to a network error), they try to re-establish
		126	connections to some seednodes again to join the network.
108		127
109	=back	128	=back
110		129
111	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
112		131
124		143
125	use AE ();	144	use AE ();
126		145
127	use base "Exporter";	146	use base "Exporter";
128		147
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	148	our $VERSION = 1.2;
130		149
131	our @EXPORT = qw(	150	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	152	configure
134	snd rcv mon kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
135	port	154	port
136	);	155	);
137		156
138	our $SELF;	157	our $SELF;
139		158
…		…
143	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
144	}	163	}
145		164
146	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
147		166
148	The C<NODE> function returns, and the C<$NODE> variable contains	167	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	168	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	169	a call to C<configure>.
151	identifiers become invalid.
152		170
153	=item $noderef = node_of $port	171	=item $nodeid = node_of $port
154		172
155	Extracts and returns the noderef from a portid or a noderef.	173	Extracts and returns the node ID from a port ID or a node ID.
156		174
157	=item initialise_node $noderef, $seednode, $seednode...	175	=item configure $profile, key => value...
158		176
159	=item initialise_node "slave/", $master, $master...	177	=item configure key => value...
160		178
161	Before a node can talk to other nodes on the network it has to initialise	179	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	180	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
164		183
165	This function initialises a node - it must be called exactly once (or	184	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	185	never) before calling other AnyEvent::MP functions.
167		186
168	All arguments are noderefs, which can be either resolved or unresolved.
169
170	There are two types of networked nodes, public nodes and slave nodes:
171
172	=over 4	187	=over 4
173		188
174	=item public nodes	189	=item step 1, gathering configuration from profiles
175		190
176	For public nodes, C<$noderef> must either be a (possibly unresolved)	191	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	192	L<aemp> commandline utility). The profile name can be specified via the
178	which case the noderef will be guessed.	193	named C<profile> parameter or can simply be the first parameter). If it is
		194	missing, then the nodename (F<uname -n>) will be used as profile name.
179		195
180	Afterwards, the node will bind itself on all endpoints and try to connect	196	The profile data is then gathered as follows:
181	to all additional C<$seednodes> that are specified. Seednodes are optional
182	and can be used to quickly bootstrap the node into an existing network.
183		197
184	=item slave nodes	198	First, all remaining key => value pairs (all of which are conveniently
		199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
185		203
186	When the C<$noderef> is the special string C<slave/>, then the node will	204	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	205	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.	206	and can only be used to specify defaults.
189		207
190	At least one additional noderef is required: The node will try to connect	208	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	209	this process. If not, then the profile name will be used as node ID. The
192	successfully connect to.	210	special node ID of C<anon/> will be replaced by a random node ID.
		211
		212	=item step 2, bind listener sockets
		213
		214	The next step is to look up the binds in the profile, followed by binding
		215	aemp protocol listeners on all binds specified (it is possible and valid
		216	to have no binds, meaning that the node cannot be contacted form the
		217	outside. This means the node cannot talk to other nodes that also have no
		218	binds, but it can still talk to all "normal" nodes).
		219
		220	If the profile does not specify a binds list, then a default of C<*> is
		221	used, meaning the node will bind on a dynamically-assigned port on every
		222	local IP address it finds.
		223
		224	=item step 3, connect to seed nodes
		225
		226	As the last step, the seeds list from the profile is passed to the
		227	L<AnyEvent::MP::Global> module, which will then use it to keep
		228	connectivity with at least one node at any point in time.
193		229
194	=back	230	=back
195		231
196	This function will block until all nodes have been resolved and, for slave	232	Example: become a distributed node using the local node name as profile.
197	nodes, until it has successfully established a connection to a master	233	This should be the most common form of invocation for "daemon"-type nodes.
198	server.
199		234
200	Example: become a public node listening on the default node.	235	configure
201		236
202	initialise_node;	237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
203		239
204	Example: become a public node, and try to contact some well-known master	240	configure nodeid => "anon/";
205	servers to become part of the network.
206		241
207	initialise_node undef, "master1", "master2";	242	Example: configure a node using a profile called seed, which si suitable
		243	for a seed node as it binds on all local addresses on a fixed port (4040,
		244	customary for aemp).
208		245
209	Example: become a public node listening on port C<4041>.	246	# use the aemp commandline utility
		247	# aemp profile seed nodeid anon/ binds '*:4040'
210		248
211	initialise_node 4041;	249	# then use it
		250	configure profile => "seed";
212		251
213	Example: become a public node, only visible on localhost port 4044.	252	# or simply use aemp from the shell again:
		253	# aemp run profile seed
214		254
215	initialise_node "locahost:4044";	255	# or provide a nicer-to-remember nodeid
216		256	# 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		257
250	=item $SELF	258	=item $SELF
251		259
252	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
253	blocks.	261	blocks.
254		262
255	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
256		264
257	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
258	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
259	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
260		268
261	=item snd $port, type => @data	269	=item snd $port, type => @data
262		270
263	=item snd $port, @msg	271	=item snd $port, @msg
264		272
265	Send the given message to the given port ID, which can identify either	273	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	274	local or a remote port, and must be a port ID.
267	stringifies a sa port ID (such as a port object :).
268		275
269	While the message can be about anything, it is highly recommended to use a	276	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	277	use a string as first element (a port ID, or some word that indicates a
271	type etc.).	278	request type etc.) and to consist if only simple perl values (scalars,
		279	arrays, hashes) - if you think you need to pass an object, think again.
272		280
273	The message data effectively becomes read-only after a call to this	281	The message data logically becomes read-only after a call to this
274	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
275	problems.	283	forbidden, as there can be considerable time between the call to C<snd>
		284	and the time the message is actually being serialised - in fact, it might
		285	never be copied as within the same process it is simply handed to the
		286	receiving port.
276		287
277	The type of data you can transfer depends on the transport protocol: when	288	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	289	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	290	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	291	that Storable can serialise and deserialise is allowed, and for the local
281	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
282		294
283	=item $local_port = port	295	=item $local_port = port
284		296
285	Create a new local port object that can be used either as a pattern	297	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"),	298	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		299
289	=item $port = port { my @msg = @_; $finished }	300	=item $local_port = port { my @msg = @_ }
290		301
291	Creates a "miniport", that is, a very lightweight port without any pattern	302	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.	303	creating a port and calling C<rcv $port, $callback> on it.
294		304
295	The block will be called for every message received on the port. When the	305	The block will be called for every message received on the port, with the
296	callback returns a true value its job is considered "done" and the port	306	global variable C<$SELF> set to the port ID. Runtime errors will cause the
297	will be destroyed. Otherwise it will stay alive.	307	port to be C<kil>ed. The message will be passed as-is, no extra argument
		308	(i.e. no port ID) will be passed to the callback.
298		309
299	The message will be passed as-is, no extra argument (i.e. no port id) will	310	If you want to stop/destroy the port, simply C<kil> it:
300	be passed to the callback.
301		311
302	If you need the local port id in the callback, this works nicely:	312	my $port = port {
303		313	my @msg = @_;
304	my $port; $port = port {	314	...
305	snd $otherport, reply => $port;	315	kil $SELF;
306	};	316	};
307		317
308	=cut	318	=cut
309		319
310	sub rcv($@);	320	sub rcv($@);
		321
		322	sub _kilme {
		323	die "received message on port without callback";
		324	}
311		325
312	sub port(;&) {	326	sub port(;&) {
313	my $id = "$UNIQ." . $ID++;	327	my $id = "$UNIQ." . $ID++;
314	my $port = "$NODE#$id";	328	my $port = "$NODE#$id";
315		329
316	if (@_) {	330	rcv $port, shift \|\| \&_kilme;
317	rcv $port, shift;
318	} else {
319	$PORT{$id} = sub { }; # nop
320	}
321		331
322	$port	332	$port
323	}	333	}
324		334
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)	335	=item rcv $local_port, $callback->(@msg)
345		336
346	Replaces the callback on the specified miniport (after converting it to	337	Replaces the default callback on the specified port. There is no way to
347	one if required).	338	remove the default callback: use C<sub { }> to disable it, or better
348		339	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...] => $callback->(@msg), ...
354
355	Register callbacks to be called on matching messages on the given full
356	port (after converting it to one if required) and return the port.
357
358	The callback has to return a true value when its work is done, after
359	which is will be removed, or a false value in which case it will stay
360	registered.
361		340
362	The global C<$SELF> (exported by this module) contains C<$port> while	341	The global C<$SELF> (exported by this module) contains C<$port> while
363	executing the callback.	342	executing the callback. Runtime errors during callback execution will
		343	result in the port being C<kil>ed.
364		344
365	Runtime errors during callback execution will result in the port being	345	The default callback received all messages not matched by a more specific
366	C<kil>ed.	346	C<tag> match.
367		347
368	If the match is an array reference, then it will be matched against the	348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
369	first elements of the message, otherwise only the first element is being
370	matched.
371		349
372	Any element in the match that is specified as C<_any_> (a function	350	Register (or replace) callbacks to be called on messages starting with the
373	exported by this module) matches any single element of the message.	351	given tag on the given port (and return the port), or unregister it (when
		352	C<$callback> is C<$undef> or missing). There can only be one callback
		353	registered for each tag.
374		354
375	While not required, it is highly recommended that the first matching	355	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	356	element (the tag) has been removed. The callback will use the same
377	also the most efficient match (by far).	357	environment as the default callback (see above).
378		358
379	Example: create a port and bind receivers on it in one go.	359	Example: create a port and bind receivers on it in one go.
380		360
381	my $port = rcv port,	361	my $port = rcv port,
382	msg1 => sub { ...; 0 },	362	msg1 => sub { ... },
383	msg2 => sub { ...; 0 },	363	msg2 => sub { ... },
384	;	364	;
385		365
386	Example: create a port, bind receivers and send it in a message elsewhere	366	Example: create a port, bind receivers and send it in a message elsewhere
387	in one go:	367	in one go:
388		368
389	snd $otherport, reply =>	369	snd $otherport, reply =>
390	rcv port,	370	rcv port,
391	msg1 => sub { ...; 0 },	371	msg1 => sub { ... },
392	...	372	...
393	;	373	;
394		374
		375	Example: temporarily register a rcv callback for a tag matching some port
		376	(e.g. for a rpc reply) and unregister it after a message was received.
		377
		378	rcv $port, $otherport => sub {
		379	my @reply = @_;
		380
		381	rcv $SELF, $otherport;
		382	};
		383
395	=cut	384	=cut
396		385
397	sub rcv($@) {	386	sub rcv($@) {
398	my $port = shift;	387	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	388	my ($nodeid, $portid) = split /#/, $port, 2;
400		389
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	390	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	391	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		392
404	if (@_ == 1) {	393	while (@_) {
		394	if (ref $_[0]) {
		395	if (my $self = $PORT_DATA{$portid}) {
		396	"AnyEvent::MP::Port" eq ref $self
		397	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		398
		399	$self->[2] = shift;
		400	} else {
405	my $cb = shift;	401	my $cb = shift;
406	delete $PORT_DATA{$portid};
407	$PORT{$portid} = sub {	402	$PORT{$portid} = sub {
408	local $SELF = $port;	403	local $SELF = $port;
409	eval {	404	eval { &$cb }; _self_die if $@;
410	&$cb	405	};
411	and kil $port;
412	};	406	}
413	_self_die if $@;	407	} elsif (defined $_[0]) {
414	};
415	} else {
416	my $self = $PORT_DATA{$portid} \|\|= do {	408	my $self = $PORT_DATA{$portid} \|\|= do {
417	my $self = bless {	409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
418	id => $port,
419	}, "AnyEvent::MP::Port";
420		410
421	$PORT{$portid} = sub {	411	$PORT{$portid} = sub {
422	local $SELF = $port;	412	local $SELF = $port;
423		413
424	eval {
425	for (@{ $self->{rc0}{$_[0]} }) {	414	if (my $cb = $self->[1]{$_[0]}) {
426	$_ && &{$_->[0]}	415	shift;
427	&& undef $_;	416	eval { &$cb }; _self_die if $@;
428	}	417	} else {
429
430	for (@{ $self->{rcv}{$_[0]} }) {
431	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
432	&& &{$_->[0]}	418	&{ $self->[0] };
433	&& undef $_;
434	}
435
436	for (@{ $self->{any} }) {
437	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
438	&& &{$_->[0]}
439	&& undef $_;
440	}	419	}
441	};	420	};
442	_self_die if $@;	421
		422	$self
443	};	423	};
444		424
445	$self
446	};
447
448	"AnyEvent::MP::Port" eq ref $self	425	"AnyEvent::MP::Port" eq ref $self
449	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	426	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
450		427
451	while (@_) {
452	my ($match, $cb) = splice @_, 0, 2;	428	my ($tag, $cb) = splice @_, 0, 2;
453		429
454	if (!ref $match) {	430	if (defined $cb) {
455	push @{ $self->{rc0}{$match} }, [$cb];	431	$self->[1]{$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 {	432	} else {
462	push @{ $self->{any} }, [$cb, $match];	433	delete $self->[1]{$tag};
463	}	434	}
464	}	435	}
465	}	436	}
466		437
467	$port	438	$port
…		…
503	$res	474	$res
504	}	475	}
505	}	476	}
506	}	477	}
507		478
508	=item $guard = mon $port, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
509		480
510	=item $guard = mon $port, $rcvport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
511		482
512	=item $guard = mon $port	483	=item $guard = mon $port # kill $SELF when $port dies
513		484
514	=item $guard = mon $port, $rcvport, @msg	485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
515		486
516	Monitor the given port and do something when the port is killed or	487	Monitor the given port and do something when the port is killed or
517	messages to it were lost, and optionally return a guard that can be used	488	messages to it were lost, and optionally return a guard that can be used
518	to stop monitoring again.	489	to stop monitoring again.
519
520	C<mon> effectively guarantees that, in the absence of hardware failures,
521	that after starting the monitor, either all messages sent to the port
522	will arrive, or the monitoring action will be invoked after possible
523	message loss has been detected. No messages will be lost "in between"
524	(after the first lost message no further messages will be received by the
525	port). After the monitoring action was invoked, further messages might get
526	delivered again.
527		490
528	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
529	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
530	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
531	C<eval> if unsure.	494	C<eval> if unsure.
532		495
533	In the second form (another port given), the other port (C<$rcvport>)	496	In the second form (another port given), the other port (C<$rcvport>)
534	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
535	"normal" kils nothing happens, while under all other conditions, the other	498	"normal" kils nothing happens, while under all other conditions, the other
536	port is killed with the same reason.	499	port is killed with the same reason.
537		500
538	The third form (kill self) is the same as the second form, except that	501	The third form (kill self) is the same as the second form, except that
539	C<$rvport> defaults to C<$SELF>.	502	C<$rvport> defaults to C<$SELF>.
540		503
541	In the last form (message), a message of the form C<@msg, @reason> will be	504	In the last form (message), a message of the form C<@msg, @reason> will be
542	C<snd>.	505	C<snd>.
		506
		507	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		508	alert was raised), they are removed and will not trigger again.
543		509
544	As a rule of thumb, monitoring requests should always monitor a port from	510	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	511	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	512	lost, just like any other message. Another less obvious reason is that
547	even monitoring requests can get lost (for exmaple, when the connection	513	even monitoring requests can get lost (for example, when the connection
548	to the other node goes down permanently). When monitoring a port locally	514	to the other node goes down permanently). When monitoring a port locally
549	these problems do not exist.	515	these problems do not exist.
550		516
		517	C<mon> effectively guarantees that, in the absence of hardware failures,
		518	after starting the monitor, either all messages sent to the port will
		519	arrive, or the monitoring action will be invoked after possible message
		520	loss has been detected. No messages will be lost "in between" (after
		521	the first lost message no further messages will be received by the
		522	port). After the monitoring action was invoked, further messages might get
		523	delivered again.
		524
		525	Inter-host-connection timeouts and monitoring depend on the transport
		526	used. The only transport currently implemented is TCP, and AnyEvent::MP
		527	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		528	non-idle connection, and usually around two hours for idle connections).
		529
		530	This means that monitoring is good for program errors and cleaning up
		531	stuff eventually, but they are no replacement for a timeout when you need
		532	to ensure some maximum latency.
		533
551	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
552		535
553	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
554		537
555	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
…		…
561	mon $port, $self => "restart";	544	mon $port, $self => "restart";
562		545
563	=cut	546	=cut
564		547
565	sub mon {	548	sub mon {
566	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
567		550
568	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
569		552
570	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	553	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
571		554
572	unless (ref $cb) {	555	unless (ref $cb) {
573	if (@_) {	556	if (@_) {
…		…
582	}	565	}
583		566
584	$node->monitor ($port, $cb);	567	$node->monitor ($port, $cb);
585		568
586	defined wantarray	569	defined wantarray
587	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	570	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
588	}	571	}
589		572
590	=item $guard = mon_guard $port, $ref, $ref...	573	=item $guard = mon_guard $port, $ref, $ref...
591		574
592	Monitors the given C<$port> and keeps the passed references. When the port	575	Monitors the given C<$port> and keeps the passed references. When the port
593	is killed, the references will be freed.	576	is killed, the references will be freed.
594		577
595	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
596		579
597	This function is useful when you create e.g. timers or other watchers and	580	This function is useful when you create e.g. timers or other watchers and
598	want to free them when the port gets killed:	581	want to free them when the port gets killed (note the use of C<psub>):
599		582
600	$port->rcv (start => sub {	583	$port->rcv (start => sub {
601	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
602	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
603	});	586	});
604	});	587	});
605		588
606	=cut	589	=cut
…		…
615		598
616	=item kil $port[, @reason]	599	=item kil $port[, @reason]
617		600
618	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
619		602
620	If no C<@reason> is specified, then the port is killed "normally" (linked	603	If no C<@reason> is specified, then the port is killed "normally" (ports
621	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
622		606
623	Otherwise, linked ports get killed with the same reason (second form of	607	Otherwise, linked ports get killed with the same reason (second form of
624	C<mon>, see below).	608	C<mon>, see above).
625		609
626	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	610	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
627	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
628		612
629	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
…		…
634	=item $port = spawn $node, $initfunc[, @initdata]	618	=item $port = spawn $node, $initfunc[, @initdata]
635		619
636	Creates a port on the node C<$node> (which can also be a port ID, in which	620	Creates a port on the node C<$node> (which can also be a port ID, in which
637	case it's the node where that port resides).	621	case it's the node where that port resides).
638		622
639	The port ID of the newly created port is return immediately, and it is	623	The port ID of the newly created port is returned immediately, and it is
640	permissible to immediately start sending messages or monitor the port.	624	possible to immediately start sending messages or to monitor the port.
641		625
642	After the port has been created, the init function is	626	After the port has been created, the init function is called on the remote
643	called. This function must be a fully-qualified function name	627	node, in the same context as a C<rcv> callback. This function must be a
644	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
645	program, use C<::name>.	629	specify a function in the main program, use C<::name>.
646		630
647	If the function doesn't exist, then the node tries to C<require>	631	If the function doesn't exist, then the node tries to C<require>
648	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
649	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
650	exists or it runs out of package names.	634	exists or it runs out of package names.
651		635
652	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
653	object (C<$SELF>) and the C<@initdata> values as arguments.	637	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		638	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		639	the port might not get created.
654		640
655	A common idiom is to pass your own port, monitor the spawned port, and	641	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	642	port, and in the remote init function, immediately monitor the passed
657	ensures that both ports get cleaned up when there is a problem.	643	local port. This two-way monitoring ensures that both ports get cleaned up
		644	when there is a problem.
		645
		646	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
658		649
659	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
660		651
661	# this node, executed from within a port context:	652	# this node, executed from within a port context:
662	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
677		668
678	sub _spawn {	669	sub _spawn {
679	my $port = shift;	670	my $port = shift;
680	my $init = shift;	671	my $init = shift;
681		672
		673	# rcv will create the actual port
682	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
683	eval {	675	eval {
684	&{ load_func $init }	676	&{ load_func $init }
685	};	677	};
686	_self_die if $@;	678	_self_die if $@;
687	}	679	}
688		680
689	sub spawn(@) {	681	sub spawn(@) {
690	my ($noderef, undef) = split /#/, shift, 2;	682	my ($nodeid, undef) = split /#/, shift, 2;
691		683
692	my $id = "$RUNIQ." . $ID++;	684	my $id = "$RUNIQ." . $ID++;
693		685
694	$_[0] =~ /::/	686	$_[0] =~ /::/
695	or Carp::croak "spawn init function must be a fully-qualified name, caught";	687	or Carp::croak "spawn init function must be a fully-qualified name, caught";
696		688
697	($NODE{$noderef} \|\| add_node $noderef)	689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
698	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
699		690
700	"$noderef#$id"	691	"$nodeid#$id"
701	}	692	}
702		693
703	=back	694	=item after $timeout, @msg
704		695
705	=head1 NODE MESSAGES	696	=item after $timeout, $callback
706		697
707	Nodes understand the following messages sent to them. Many of them take	698	Either sends the given message, or call the given callback, after the
708	arguments called C<@reply>, which will simply be used to compose a reply	699	specified number of seconds.
709	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
710	the remaining arguments are simply the message data.
711		700
712	While other messages exist, they are not public and subject to change.	701	This is simply a utility function that comes in handy at times - the
		702	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		703	so it may go away in the future.
713		704
714	=over 4
715
716	=cut	705	=cut
717		706
718	=item lookup => $name, @reply	707	sub after($@) {
		708	my ($timeout, @action) = @_;
719		709
720	Replies with the port ID of the specified well-known port, or C<undef>.	710	my $t; $t = AE::timer $timeout, 0, sub {
		711	undef $t;
		712	ref $action[0]
		713	? $action[0]()
		714	: snd @action;
		715	};
		716	}
721		717
722	=item devnull => ...	718	=item cal $port, @msg, $callback[, $timeout]
723		719
724	Generic data sink/CPU heat conversion.	720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
725		722
726	=item relay => $port, @msg	723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
727		725
728	Simply forwards the message to the given port.	726	A reply message sent to the port is passed to the C<$callback> as-is.
729		727
730	=item eval => $string[ @reply]	728	If an optional time-out (in seconds) is given and it is not C<undef>,
		729	then the callback will be called without any arguments after the time-out
		730	elapsed and the port is C<kil>ed.
731		731
732	Evaluates the given string. If C<@reply> is given, then a message of the	732	If no time-out is given (or it is C<undef>), then the local port will
733	form C<@reply, $@, @evalres> is sent.	733	monitor the remote port instead, so it eventually gets cleaned-up.
734		734
735	Example: crash another node.	735	Currently this function returns the temporary port, but this "feature"
		736	might go in future versions unless you can make a convincing case that
		737	this is indeed useful for something.
736		738
737	snd $othernode, eval => "exit";	739	=cut
738		740
739	=item time => @reply	741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
740		744
741	Replies the the current node time to C<@reply>.	745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
742		750
743	Example: tell the current node to send the current time to C<$myport> in a	751	if (defined $timeout) {
744	C<timereply> message.	752	$timeout = AE::timer $timeout, 0, sub {
		753	undef $timeout;
		754	kil $port;
		755	$cb->();
		756	};
		757	} else {
		758	mon $_[0], sub {
		759	kil $port;
		760	$cb->();
		761	};
		762	}
745		763
746	snd $NODE, time => $myport, timereply => 1, 2;	764	push @_, $port;
747	# => snd $myport, timereply => 1, 2, <time>	765	&snd;
		766
		767	$port
		768	}
748		769
749	=back	770	=back
750		771
751	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
752		773
753	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	774	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	775	== 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	776	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
756	sample:	777	sample:
757		778
758	http://www.Erlang.se/doc/programming_rules.shtml	779	http://www.erlang.se/doc/programming_rules.shtml
759	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	780	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	781	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	782	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
762		783
763	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
764		785
765	=over 4	786	=over 4
766		787
767	=item * Node references contain the recipe on how to contact them.	788	=item * Node IDs are arbitrary strings in AEMP.
768		789
769	Erlang relies on special naming and DNS to work everywhere in the	790	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	791	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
771	convenience functionality.	792	configuration or DNS), and possibly the addresses of some seed nodes, but
		793	will otherwise discover other nodes (and their IDs) itself.
772		794
773	This means that AEMP requires a less tightly controlled environment at the	795	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
774	cost of longer node references and a slightly higher management overhead.	796	uses "local ports are like remote ports".
		797
		798	The failure modes for local ports are quite different (runtime errors
		799	only) then for remote ports - when a local port dies, you I<know> it dies,
		800	when a connection to another node dies, you know nothing about the other
		801	port.
		802
		803	Erlang pretends remote ports are as reliable as local ports, even when
		804	they are not.
		805
		806	AEMP encourages a "treat remote ports differently" philosophy, with local
		807	ports being the special case/exception, where transport errors cannot
		808	occur.
775		809
776	=item * Erlang uses processes and a mailbox, AEMP does not queue.	810	=item * Erlang uses processes and a mailbox, AEMP does not queue.
777		811
778	Erlang uses processes that selctively receive messages, and therefore	812	Erlang uses processes that selectively receive messages, and therefore
779	needs a queue. AEMP is event based, queuing messages would serve no useful	813	needs a queue. AEMP is event based, queuing messages would serve no
780	purpose.	814	useful purpose. For the same reason the pattern-matching abilities of
		815	AnyEvent::MP are more limited, as there is little need to be able to
		816	filter messages without dequeuing them.
781		817
782	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	818	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
783		819
784	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	820	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
785		821
786	Sending messages in Erlang is synchronous and blocks the process. AEMP	822	Sending messages in Erlang is synchronous and blocks the process (and
787	sends are immediate, connection establishment is handled in the	823	so does not need a queue that can overflow). AEMP sends are immediate,
788	background.	824	connection establishment is handled in the background.
789		825
790	=item * Erlang can silently lose messages, AEMP cannot.	826	=item * Erlang suffers from silent message loss, AEMP does not.
791		827
792	Erlang makes few guarantees on messages delivery - messages can get lost	828	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,	829	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).	830	b, and c, and the other side only receives messages a and c).
795		831
796	AEMP guarantees correct ordering, and the guarantee that there are no	832	AEMP guarantees correct ordering, and the guarantee that after one message
797	holes in the message sequence.	833	is lost, all following ones sent to the same port are lost as well, until
798		834	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	835	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		836
810	=item * Erlang can send messages to the wrong port, AEMP does not.	837	=item * Erlang can send messages to the wrong port, AEMP does not.
811		838
812	In Erlang it is quite possible that a node that restarts reuses a process	839	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	840	known to other nodes for a completely different process, causing messages
814	messages destined for that process to end up in an unrelated process.	841	destined for that process to end up in an unrelated process.
815		842
816	AEMP never reuses port IDs, so old messages or old port IDs floating	843	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.	844	around in the network will not be sent to an unrelated port.
818		845
819	=item * Erlang uses unprotected connections, AEMP uses secure	846	=item * Erlang uses unprotected connections, AEMP uses secure
820	authentication and can use TLS.	847	authentication and can use TLS.
821		848
822	AEMP can use a proven protocol - SSL/TLS - to protect connections and	849	AEMP can use a proven protocol - TLS - to protect connections and
823	securely authenticate nodes.	850	securely authenticate nodes.
824		851
825	=item * The AEMP protocol is optimised for both text-based and binary	852	=item * The AEMP protocol is optimised for both text-based and binary
826	communications.	853	communications.
827		854
828	The AEMP protocol, unlike the Erlang protocol, supports both	855	The AEMP protocol, unlike the Erlang protocol, supports both programming
829	language-independent text-only protocols (good for debugging) and binary,	856	language independent text-only protocols (good for debugging) and binary,
830	language-specific serialisers (e.g. Storable).	857	language-specific serialisers (e.g. Storable). By default, unless TLS is
		858	used, the protocol is actually completely text-based.
831		859
832	It has also been carefully designed to be implementable in other languages	860	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	861	with a minimum of work while gracefully degrading functionality to make the
834	protocol simple.	862	protocol simple.
835		863
836	=item * AEMP has more flexible monitoring options than Erlang.	864	=item * AEMP has more flexible monitoring options than Erlang.
837		865
838	In Erlang, you can chose to receive I<all> exit signals as messages	866	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	869	Erlang, as one can choose between automatic kill, exit message or callback
842	on a per-process basis.	870	on a per-process basis.
843		871
844	=item * Erlang tries to hide remote/local connections, AEMP does not.	872	=item * Erlang tries to hide remote/local connections, AEMP does not.
845		873
846	Monitoring in Erlang is not an indicator of process death/crashes,	874	Monitoring in Erlang is not an indicator of process death/crashes, in the
847	as linking is (except linking is unreliable in Erlang).	875	same way as linking is (except linking is unreliable in Erlang).
848		876
849	In AEMP, you don't "look up" registered port names or send to named ports	877	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	878	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	879	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	880	remote port. Since both monitors are local to the node, they are much more
853	more reliable.	881	reliable (no need for C<spawn_link>).
854		882
855	This also saves round-trips and avoids sending messages to the wrong port	883	This also saves round-trips and avoids sending messages to the wrong port
856	(hard to do in Erlang).	884	(hard to do in Erlang).
857		885
858	=back	886	=back
859		887
860	=head1 RATIONALE	888	=head1 RATIONALE
861		889
862	=over 4	890	=over 4
863		891
864	=item Why strings for ports and noderefs, why not objects?	892	=item Why strings for port and node IDs, why not objects?
865		893
866	We considered "objects", but found that the actual number of methods	894	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	895	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	896	the network frequently, the serialising/deserialising would add lots of
869	overhead, as well as having to keep a proxy object.	897	overhead, as well as having to keep a proxy object everywhere.
870		898
871	Strings can easily be printed, easily serialised etc. and need no special	899	Strings can easily be printed, easily serialised etc. and need no special
872	procedures to be "valid".	900	procedures to be "valid".
873		901
		902	And as a result, a miniport consists of a single closure stored in a
		903	global hash - it can't become much cheaper.
		904
874	=item Why favour JSON, why not real serialising format such as Storable?	905	=item Why favour JSON, why not a real serialising format such as Storable?
875		906
876	In fact, any AnyEvent::MP node will happily accept Storable as framing	907	In fact, any AnyEvent::MP node will happily accept Storable as framing
877	format, but currently there is no way to make a node use Storable by	908	format, but currently there is no way to make a node use Storable by
878	default.	909	default (although all nodes will accept it).
879		910
880	The default framing protocol is JSON because a) JSON::XS is many times	911	The default framing protocol is JSON because a) JSON::XS is many times
881	faster for small messages and b) most importantly, after years of	912	faster for small messages and b) most importantly, after years of
882	experience we found that object serialisation is causing more problems	913	experience we found that object serialisation is causing more problems
883	than it gains: Just like function calls, objects simply do not travel	914	than it solves: Just like function calls, objects simply do not travel
884	easily over the network, mostly because they will always be a copy, so you	915	easily over the network, mostly because they will always be a copy, so you
885	always have to re-think your design.	916	always have to re-think your design.
886		917
887	Keeping your messages simple, concentrating on data structures rather than	918	Keeping your messages simple, concentrating on data structures rather than
888	objects, will keep your messages clean, tidy and efficient.	919	objects, will keep your messages clean, tidy and efficient.
889		920
890	=back	921	=back
891		922
892	=head1 SEE ALSO	923	=head1 SEE ALSO
893		924
		925	L<AnyEvent::MP::Intro> - a gentle introduction.
		926
		927	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		928
		929	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		930	your applications.
		931
		932	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		933	all nodes.
		934
894	L<AnyEvent>.	935	L<AnyEvent>.
895		936
896	=head1 AUTHOR	937	=head1 AUTHOR
897		938
898	Marc Lehmann <schmorp@schmorp.de>	939	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.99 by root, Fri Oct 2 14:12:16 2009 UTC