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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs.
Revision 1.116 by root, Mon Jun 21 15:09:34 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
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
13	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
14		23
15	$SELF # receiving/own port id in rcv callbacks	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
16		26
17	rcv $port, smartmatch => $cb->($port, @msg);	27	# creating/using ports, tagged message matching
18		28	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
21	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
22	snd $port2, ping => $port1;
23		31
24	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
27		34
28	# linking two ports, so they both crash together	35	# destroy a port again
29	lnk $port1, $port2;	36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
30		38
31	# monitoring	39	# monitoring
32	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
33	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
34	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
		51
		52	=head1 CURRENT STATUS
		53
		54	bin/aemp - stable.
		55	AnyEvent::MP - stable API, should work.
		56	AnyEvent::MP::Intro - explains most concepts.
		57	AnyEvent::MP::Kernel - mostly stable API.
		58	AnyEvent::MP::Global - stable API.
35		59
36	=head1 DESCRIPTION	60	=head1 DESCRIPTION
37		61
38	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
39		63
40	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
41	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
42		66
43	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>
44	manual page.	68	manual page and the examples under F<eg/>.
45
46	At the moment, this module family is severly broken and underdocumented,
47	so do not use. This was uploaded mainly to reserve the CPAN namespace -
48	stay tuned! The basic API should be finished, however.
49		69
50	=head1 CONCEPTS	70	=head1 CONCEPTS
51		71
52	=over 4	72	=over 4
53		73
54	=item port	74	=item port
55		75
56	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).
57		78
58	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
59	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
60	will not be queued.	81	anything was listening for them or not.
61		82
62	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
63		84
64	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
65	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
66	exception is the the node port, whose ID is identical to its node
67	reference.
68		87
69	=item node	88	=item node
70		89
71	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,
72	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
73	create new ports, among other things.	92	ports.
74		93
75	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
76	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
77		97
78	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
79		99
80	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
81	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
82	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.
83		104
84	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
85	TCP/IP, other protocols might look different).
86		106
87	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
88	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.
89		111
90	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
91	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.
92		139
93	=back	140	=back
94		141
95	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
96		143
98		145
99	=cut	146	=cut
100		147
101	package AnyEvent::MP;	148	package AnyEvent::MP;
102		149
103	use AnyEvent::MP::Base;	150	use AnyEvent::MP::Kernel;
104		151
105	use common::sense;	152	use common::sense;
106		153
107	use Carp ();	154	use Carp ();
108		155
109	use AE ();	156	use AE ();
110		157
111	use base "Exporter";	158	use base "Exporter";
112		159
113	our $VERSION = '0.1';	160	our $VERSION = 1.29;
		161
114	our @EXPORT = qw(	162	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
116	resolve_node initialise_node	164	configure
117	snd rcv mon kil reg psub	165	snd rcv mon mon_guard kil psub peval spawn cal
118	port	166	port
119	);	167	);
120		168
121	our $SELF;	169	our $SELF;
122		170
…		…
126	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
127	}	175	}
128		176
129	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
130		178
131	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
132	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
133	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
134	identifiers become invalid.
135		182
136	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
137		184
138	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.
139		186
140	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
141		188
142	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
143		190
144	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
145	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
146	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
147		195
		196	The key/value pairs are basically the same ones as documented for the
		197	F<aemp> command line utility (sans the set/del prefix).
		198
148	This function initialises a node - it must be called exactly once (or	199	This function configures a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	200	never) before calling other AnyEvent::MP functions.
150		201
151	All arguments are noderefs, which can be either resolved or unresolved.
152
153	There are two types of networked nodes, public nodes and slave nodes:
154
155	=over 4	202	=over 4
156		203
157	=item public nodes	204	=item step 1, gathering configuration from profiles
158		205
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	206	The function first looks up a profile in the aemp configuration (see the
160	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
161	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.
162		210
163	Afterwards, the node will bind itself on all endpoints and try to connect	211	The profile data is then gathered as follows:
164	to all additional C<$seednodes> that are specified. Seednodes are optional
165	and can be used to quickly bootstrap the node into an existing network.
166		212
167	=item slave nodes	213	First, all remaining key => value pairs (all of which are conveniently
		214	undocumented at the moment) will be interpreted as configuration
		215	data. Then they will be overwritten by any values specified in the global
		216	default configuration (see the F<aemp> utility), then the chain of
		217	profiles chosen by the profile name (and any C<parent> attributes).
168		218
169	When the C<$noderef> is the special string C<slave/>, then the node will	219	That means that the values specified in the profile have highest priority
170	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,
171	route most of their traffic to the master node that they attach to.	221	and can only be used to specify defaults.
172		222
173	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
174	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
175	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.
176		244
177	=back	245	=back
178		246
179	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.
180	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.
181	server.
182		249
183	Example: become a public node listening on the default node.	250	configure
184		251
185	initialise_node;	252	Example: become an anonymous node. This form is often used for commandline
		253	clients.
186		254
187	Example: become a public node, and try to contact some well-known master	255	configure nodeid => "anon/";
188	servers to become part of the network.
189		256
190	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).
191		260
192	Example: become a public node listening on port C<4041>.	261	# use the aemp commandline utility
		262	# aemp profile seed nodeid anon/ binds '*:4040'
193		263
194	initialise_node 4041;	264	# then use it
		265	configure profile => "seed";
195		266
196	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
197		269
198	initialise_node "locahost:4044";	270	# or provide a nicer-to-remember nodeid
199		271	# aemp run profile seed nodeid "$(hostname)"
200	Example: become a slave node to any of the specified master servers.
201
202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
203
204	=item $cv = resolve_node $noderef
205
206	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node
208	reference.
209
210	In addition to C<address:port> pairs allowed in resolved noderefs, the
211	following forms are supported:
212
213	=over 4
214
215	=item the empty string
216
217	An empty-string component gets resolved as if the default port (4040) was
218	specified.
219
220	=item naked port numbers (e.g. C<1234>)
221
222	These are resolved by prepending the local nodename and a colon, to be
223	further resolved.
224
225	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
226
227	These are resolved by using AnyEvent::DNS to resolve them, optionally
228	looking up SRV records for the C<aemp=4040> port, if no port was
229	specified.
230
231	=back
232		272
233	=item $SELF	273	=item $SELF
234		274
235	Contains the current port id while executing C<rcv> callbacks or C<psub>	275	Contains the current port id while executing C<rcv> callbacks or C<psub>
236	blocks.	276	blocks.
237		277
238	=item SELF, %SELF, @SELF...	278	=item *SELF, SELF, %SELF, @SELF...
239		279
240	Due to some quirks in how perl exports variables, it is impossible to	280	Due to some quirks in how perl exports variables, it is impossible to
241	just export C<$SELF>, all the symbols called C<SELF> are exported by this	281	just export C<$SELF>, all the symbols named C<SELF> are exported by this
242	module, but only C<$SELF> is currently used.	282	module, but only C<$SELF> is currently used.
243		283
244	=item snd $port, type => @data	284	=item snd $port, type => @data
245		285
246	=item snd $port, @msg	286	=item snd $port, @msg
247		287
248	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
249	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.
250	stringifies a sa port ID (such as a port object :).
251		290
252	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
253	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
254	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.
255		295
256	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
257	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument (or values referenced by them) is
258	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.
259		302
260	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
261	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
262	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
263	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
264	node, anything can be passed.	307	node, anything can be passed. Best rely only on the common denominator of
		308	these.
265		309
266	=item $local_port = port	310	=item $local_port = port
267		311
268	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
269	matching port ("full port") or a single-callback port ("miniport"),	313	no callbacks set and will throw an error when it receives messages.
270	depending on how C<rcv> callbacks are bound to the object.
271		314
272	=item $port = port { my @msg = @_; $finished }	315	=item $local_port = port { my @msg = @_ }
273		316
274	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
275	matching behind it, and returns its ID. Semantically the same as creating
276	a port and calling C<rcv $port, $callback> on it.	318	creating a port and calling C<rcv $port, $callback> on it.
277		319
278	The block will be called for every message received on the port. When the	320	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	321	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	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.
281		324
282	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:
283	be passed to the callback.
284		326
285	If you need the local port id in the callback, this works nicely:	327	my $port = port {
286		328	my @msg = @_;
287	my $port; $port = port {	329	...
288	snd $otherport, reply => $port;	330	kil $SELF;
289	};	331	};
290		332
291	=cut	333	=cut
292		334
293	sub rcv($@);	335	sub rcv($@);
		336
		337	sub _kilme {
		338	die "received message on port without callback";
		339	}
294		340
295	sub port(;&) {	341	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	342	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	343	my $port = "$NODE#$id";
298		344
299	if (@_) {	345	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		346
305	$port	347	$port
306	}	348	}
307		349
308	=item reg $port, $name
309
310	=item reg $name
311
312	Registers the given port (or C<$SELF><<< if missing) under the name
313	C<$name>. If the name already exists it is replaced.
314
315	A port can only be registered under one well known name.
316
317	A port automatically becomes unregistered when it is killed.
318
319	=cut
320
321	sub reg(@) {
322	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
323
324	$REG{$_[0]} = $port;
325	}
326
327	=item rcv $port, $callback->(@msg)	350	=item rcv $local_port, $callback->(@msg)
328		351
329	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
330	one if required).	353	remove the default callback: use C<sub { }> to disable it, or better
331		354	C<kil> the port when it is no longer needed.
332	=item rcv $port, tagstring => $callback->(@msg), ...
333
334	=item rcv $port, $smartmatch => $callback->(@msg), ...
335
336	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
337
338	Register callbacks to be called on matching messages on the given full
339	port (after converting it to one if required) and return the port.
340
341	The callback has to return a true value when its work is done, after
342	which is will be removed, or a false value in which case it will stay
343	registered.
344		355
345	The global C<$SELF> (exported by this module) contains C<$port> while	356	The global C<$SELF> (exported by this module) contains C<$port> while
346	executing the callback.	357	executing the callback. Runtime errors during callback execution will
		358	result in the port being C<kil>ed.
347		359
348	Runtime errors wdurign callback execution will result in the port being	360	The default callback received all messages not matched by a more specific
349	C<kil>ed.	361	C<tag> match.
350		362
351	If the match is an array reference, then it will be matched against the	363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352	first elements of the message, otherwise only the first element is being
353	matched.
354		364
355	Any element in the match that is specified as C<_any_> (a function	365	Register (or replace) callbacks to be called on messages starting with the
356	exported by this module) matches any single element of the message.	366	given tag on the given port (and return the port), or unregister it (when
		367	C<$callback> is C<$undef> or missing). There can only be one callback
		368	registered for each tag.
357		369
358	While not required, it is highly recommended that the first matching	370	The original message will be passed to the callback, after the first
359	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
360	also the most efficient match (by far).	372	environment as the default callback (see above).
361		373
362	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.
363		375
364	my $port = rcv port,	376	my $port = rcv port,
365	msg1 => sub { ...; 0 },	377	msg1 => sub { ... },
366	msg2 => sub { ...; 0 },	378	msg2 => sub { ... },
367	;	379	;
368		380
369	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
370	in one go:	382	in one go:
371		383
372	snd $otherport, reply =>	384	snd $otherport, reply =>
373	rcv port,	385	rcv port,
374	msg1 => sub { ...; 0 },	386	msg1 => sub { ... },
375	...	387	...
376	;	388	;
377		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, $otherport;
		397	};
		398
378	=cut	399	=cut
379		400
380	sub rcv($@) {	401	sub rcv($@) {
381	my $port = shift;	402	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	403	my ($nodeid, $portid) = split /#/, $port, 2;
383		404
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	405	$NODE{$nodeid} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	406	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		407
387	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 {
388	my $cb = shift;	416	my $cb = shift;
389	delete $PORT_DATA{$portid};
390	$PORT{$portid} = sub {	417	$PORT{$portid} = sub {
391	local $SELF = $port;	418	local $SELF = $port;
392	eval {	419	eval { &$cb }; _self_die if $@;
393	&$cb	420	};
394	and kil $port;
395	};	421	}
396	_self_die if $@;	422	} elsif (defined $_[0]) {
397	};
398	} else {
399	my $self = $PORT_DATA{$portid} \|\|= do {	423	my $self = $PORT_DATA{$portid} \|\|= do {
400	my $self = bless {	424	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
401	id => $port,
402	}, "AnyEvent::MP::Port";
403		425
404	$PORT{$portid} = sub {	426	$PORT{$portid} = sub {
405	local $SELF = $port;	427	local $SELF = $port;
406		428
407	eval {
408	for (@{ $self->{rc0}{$_[0]} }) {	429	if (my $cb = $self->[1]{$_[0]}) {
409	$_ && &{$_->[0]}	430	shift;
410	&& undef $_;	431	eval { &$cb }; _self_die if $@;
411	}	432	} else {
412
413	for (@{ $self->{rcv}{$_[0]} }) {
414	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
415	&& &{$_->[0]}	433	&{ $self->[0] };
416	&& undef $_;
417	}
418
419	for (@{ $self->{any} }) {
420	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
421	&& &{$_->[0]}
422	&& undef $_;
423	}	434	}
424	};	435	};
425	_self_die if $@;	436
		437	$self
426	};	438	};
427		439
428	$self
429	};
430
431	"AnyEvent::MP::Port" eq ref $self	440	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	441	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
433		442
434	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;	443	my ($tag, $cb) = splice @_, 0, 2;
436		444
437	if (!ref $match) {	445	if (defined $cb) {
438	push @{ $self->{rc0}{$match} }, [$cb];	446	$self->[1]{$tag} = $cb;
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440	my ($type, @match) = @$match;
441	@match
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	447	} else {
445	push @{ $self->{any} }, [$cb, $match];	448	delete $self->[1]{$tag};
446	}	449	}
447	}	450	}
448	}	451	}
449		452
450	$port	453	$port
451	}	454	}
452		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
453	=item $closure = psub { BLOCK }	493	=item $closure = psub { BLOCK }
454		494
455	Remembers C<$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
456	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>
457	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 $SELF, sub {
		500	BLOCK }, @_ } >>.
458		501
459	This is useful when you register callbacks from C<rcv> callbacks:	502	This is useful when you register callbacks from C<rcv> callbacks:
460		503
461	rcv delayed_reply => sub {	504	rcv delayed_reply => sub {
462	my ($delay, @reply) = @_;	505	my ($delay, @reply) = @_;
…		…
486	$res	529	$res
487	}	530	}
488	}	531	}
489	}	532	}
490		533
491	=item $guard = mon $port, $cb->(@reason)	534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
492		535
493	=item $guard = mon $port, $rcvport	536	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
494		537
495	=item $guard = mon $port	538	=item $guard = mon $port # kill $SELF when $port dies
496		539
497	=item $guard = mon $port, $rcvport, @msg	540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
498		541
499	Monitor the given port and do something when the port is killed, and	542	Monitor the given port and do something when the port is killed or
500	optionally return a guard that can be used to stop monitoring again.	543	messages to it were lost, and optionally return a guard that can be used
		544	to stop monitoring again.
501		545
502	In the first form (callback), the callback is simply called with any	546	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	547	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	548	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	549	C<eval> if unsure.
506		550
507	In the second form (another port given), the other port (C<$rcvport)	551	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	552	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	553	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	554	port is killed with the same reason.
511		555
512	The third form (kill self) is the same as the second form, except that	556	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	557	C<$rvport> defaults to C<$SELF>.
514		558
515	In the last form (message), a message of the form C<@msg, @reason> will be	559	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	560	C<snd>.
517		561
		562	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		563	alert was raised), they are removed and will not trigger again.
		564
		565	As a rule of thumb, monitoring requests should always monitor a port from
		566	a local port (or callback). The reason is that kill messages might get
		567	lost, just like any other message. Another less obvious reason is that
		568	even monitoring requests can get lost (for example, when the connection
		569	to the other node goes down permanently). When monitoring a port locally
		570	these problems do not exist.
		571
		572	C<mon> effectively guarantees that, in the absence of hardware failures,
		573	after starting the monitor, either all messages sent to the port will
		574	arrive, or the monitoring action will be invoked after possible message
		575	loss has been detected. No messages will be lost "in between" (after
		576	the first lost message no further messages will be received by the
		577	port). After the monitoring action was invoked, further messages might get
		578	delivered again.
		579
		580	Inter-host-connection timeouts and monitoring depend on the transport
		581	used. The only transport currently implemented is TCP, and AnyEvent::MP
		582	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		583	non-idle connection, and usually around two hours for idle connections).
		584
		585	This means that monitoring is good for program errors and cleaning up
		586	stuff eventually, but they are no replacement for a timeout when you need
		587	to ensure some maximum latency.
		588
518	Example: call a given callback when C<$port> is killed.	589	Example: call a given callback when C<$port> is killed.
519		590
520	mon $port, sub { warn "port died because of <@_>\n" };	591	mon $port, sub { warn "port died because of <@_>\n" };
521		592
522	Example: kill ourselves when C<$port> is killed abnormally.	593	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	599	mon $port, $self => "restart";
529		600
530	=cut	601	=cut
531		602
532	sub mon {	603	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	604	my ($nodeid, $port) = split /#/, shift, 2;
534		605
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	606	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		607
537	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	608	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		609
539	unless (ref $cb) {	610	unless (ref $cb) {
540	if (@_) {	611	if (@_) {
541	# send a kill info message	612	# send a kill info message
542	my (@msg) = @_;	613	my (@msg) = ($cb, @_);
543	$cb = sub { snd @msg, @_ };	614	$cb = sub { snd @msg, @_ };
544	} else {	615	} else {
545	# simply kill other port	616	# simply kill other port
546	my $port = $cb;	617	my $port = $cb;
547	$cb = sub { kil $port, @_ if @_ };	618	$cb = sub { kil $port, @_ if @_ };
…		…
549	}	620	}
550		621
551	$node->monitor ($port, $cb);	622	$node->monitor ($port, $cb);
552		623
553	defined wantarray	624	defined wantarray
554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
555	}	626	}
556		627
557	=item $guard = mon_guard $port, $ref, $ref...	628	=item $guard = mon_guard $port, $ref, $ref...
558		629
559	Monitors the given C<$port> and keeps the passed references. When the port	630	Monitors the given C<$port> and keeps the passed references. When the port
560	is killed, the references will be freed.	631	is killed, the references will be freed.
561		632
562	Optionally returns a guard that will stop the monitoring.	633	Optionally returns a guard that will stop the monitoring.
563		634
564	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
565	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>):
566		637
567	$port->rcv (start => sub {	638	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	639	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	640	undef $timer if 0.9 < rand;
570	});	641	});
571	});	642	});
572		643
573	=cut	644	=cut
…		…
578	#TODO: mon-less form?	649	#TODO: mon-less form?
579		650
580	mon $port, sub { 0 && @refs }	651	mon $port, sub { 0 && @refs }
581	}	652	}
582		653
583	=item lnk $port1, $port2
584
585	=item lnk $otherport
586
587	Link two ports. This is simply a shorthand for:
588
589	mon $port1, $port2;
590	mon $port2, $port1;
591
592	It means that if either one is killed abnormally, the other one gets
593	killed as well.
594
595	The one-argument form assumes that one port is C<$SELF>.
596
597	=cut
598
599	sub lnk {
600	my $port1 = shift;
601	my $port2 = @_ ? shift : $SELF \|\| Carp::croak 'lnk: called with one argument only, but $SELF not set,';
602
603	mon $port1, $port2;
604	mon $port2, $port1;
605	}
606
607	=item kil $port[, @reason]	654	=item kil $port[, @reason]
608		655
609	Kill the specified port with the given C<@reason>.	656	Kill the specified port with the given C<@reason>.
610		657
611	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" -
612	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.
613		661
614	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>
615	C<mon>, see below).	663	form) get killed with the same reason.
616		664
617	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
618	will be reported as reason C<< die => $@ >>.	666	will be reported as reason C<< die => $@ >>.
619		667
620	Transport/communication errors are reported as C<< transport_error =>	668	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	669	$message >>.
622		670
623	=back
624
625	=head1 NODE MESSAGES
626
627	Nodes understand the following messages sent to them. Many of them take
628	arguments called C<@reply>, which will simply be used to compose a reply
629	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
630	the remaining arguments are simply the message data.
631
632	While other messages exist, they are not public and subject to change.
633
634	=over 4
635
636	=cut	671	=cut
637		672
638	=item lookup => $name, @reply	673	=item $port = spawn $node, $initfunc[, @initdata]
639		674
640	Replies with the port ID of the specified well-known port, or C<undef>.	675	Creates a port on the node C<$node> (which can also be a port ID, in which
		676	case it's the node where that port resides).
641		677
642	=item devnull => ...	678	The port ID of the newly created port is returned immediately, and it is
		679	possible to immediately start sending messages or to monitor the port.
643		680
644	Generic data sink/CPU heat conversion.	681	After the port has been created, the init function is called on the remote
		682	node, in the same context as a C<rcv> callback. This function must be a
		683	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		684	specify a function in the main program, use C<::name>.
645		685
646	=item relay => $port, @msg	686	If the function doesn't exist, then the node tries to C<require>
		687	the package, then the package above the package and so on (e.g.
		688	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		689	exists or it runs out of package names.
647		690
648	Simply forwards the message to the given port.	691	The init function is then called with the newly-created port as context
		692	object (C<$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.
649		695
650	=item eval => $string[ @reply]	696	A common idiom is to pass a local port, immediately monitor the spawned
		697	port, and in the remote init function, immediately monitor the passed
		698	local port. This two-way monitoring ensures that both ports get cleaned up
		699	when there is a problem.
651		700
652	Evaluates the given string. If C<@reply> is given, then a message of the	701	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
653	form C<@reply, $@, @evalres> is sent.	702	caller before C<spawn> returns (by delaying invocation when spawn is
		703	called for the local node).
654		704
655	Example: crash another node.	705	Example: spawn a chat server port on C<$othernode>.
656		706
657	snd $othernode, eval => "exit";	707	# this node, executed from within a port context:
		708	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		709	mon $server;
658		710
659	=item time => @reply	711	# init function on C<$othernode>
		712	sub connect {
		713	my ($srcport) = @_;
660		714
661	Replies the the current node time to C<@reply>.	715	mon $srcport;
662		716
663	Example: tell the current node to send the current time to C<$myport> in a	717	rcv $SELF, sub {
664	C<timereply> message.	718	...
		719	};
		720	}
665		721
666	snd $NODE, time => $myport, timereply => 1, 2;	722	=cut
667	# => snd $myport, timereply => 1, 2, <time>	723
		724	sub _spawn {
		725	my $port = shift;
		726	my $init = shift;
		727
		728	# rcv will create the actual port
		729	local $SELF = "$NODE#$port";
		730	eval {
		731	&{ load_func $init }
		732	};
		733	_self_die if $@;
		734	}
		735
		736	sub spawn(@) {
		737	my ($nodeid, undef) = split /#/, shift, 2;
		738
		739	my $id = "$RUNIQ." . $ID++;
		740
		741	$_[0] =~ /::/
		742	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		743
		744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		745
		746	"$nodeid#$id"
		747	}
		748
		749	=item after $timeout, @msg
		750
		751	=item after $timeout, $callback
		752
		753	Either sends the given message, or call the given callback, after the
		754	specified number of seconds.
		755
		756	This is simply a utility function that comes in handy at times - the
		757	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		758	so it may go away in the future.
		759
		760	=cut
		761
		762	sub after($@) {
		763	my ($timeout, @action) = @_;
		764
		765	my $t; $t = AE::timer $timeout, 0, sub {
		766	undef $t;
		767	ref $action[0]
		768	? $action[0]()
		769	: snd @action;
		770	};
		771	}
		772
		773	=item cal $port, @msg, $callback[, $timeout]
		774
		775	A simple form of RPC - sends a message to the given C<$port> with the
		776	given contents (C<@msg>), but adds a reply port to the message.
		777
		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.
		780
		781	A reply message sent to the port is passed to the C<$callback> as-is.
		782
		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.
		786
		787	If no time-out is given (or it is C<undef>), then the local port will
		788	monitor the remote port instead, so it eventually gets cleaned-up.
		789
		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.
		793
		794	=cut
		795
		796	sub cal(@) {
		797	my $timeout = ref $_[-1] ? undef : pop;
		798	my $cb = pop;
		799
		800	my $port = port {
		801	undef $timeout;
		802	kil $SELF;
		803	&$cb;
		804	};
		805
		806	if (defined $timeout) {
		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	}
		818
		819	push @_, $port;
		820	&snd;
		821
		822	$port
		823	}
668		824
669	=back	825	=back
670		826
671	=head1 AnyEvent::MP vs. Distributed Erlang	827	=head1 AnyEvent::MP vs. Distributed Erlang
672		828
673	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
674	== 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
675	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
676	sample:	832	sample:
677		833
678	http://www.Erlang.se/doc/programming_rules.shtml	834	http://www.erlang.se/doc/programming_rules.shtml
679	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
680	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
681	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
682		838
683	Despite the similarities, there are also some important differences:	839	Despite the similarities, there are also some important differences:
684		840
685	=over 4	841	=over 4
686		842
687	=item * Node references contain the recipe on how to contact them.	843	=item * Node IDs are arbitrary strings in AEMP.
688		844
689	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
690	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
691	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.
692		849
693	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
694	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.
695		864
696	=item * Erlang uses processes and a mailbox, AEMP does not queue.	865	=item * Erlang uses processes and a mailbox, AEMP does not queue.
697		866
698	Erlang uses processes that selctively receive messages, and therefore	867	Erlang uses processes that selectively receive messages, and therefore
699	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
700	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.
701		872
702	(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).
703		874
704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
705		876
706	Sending messages in Erlang is synchronous and blocks the process. AEMP	877	Sending messages in Erlang is synchronous and blocks the process (and
707	sends are immediate, connection establishment is handled in the	878	so does not need a queue that can overflow). AEMP sends are immediate,
708	background.	879	connection establishment is handled in the background.
709		880
710	=item * Erlang can silently lose messages, AEMP cannot.	881	=item * Erlang suffers from silent message loss, AEMP does not.
711		882
712	Erlang makes few guarantees on messages delivery - messages can get lost	883	Erlang implements few guarantees on messages delivery - messages can get
713	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,
714	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).
715		886
716	AEMP guarantees correct ordering, and the guarantee that there are no	887	AEMP guarantees correct ordering, and the guarantee that after one message
717	holes in the message sequence.	888	is lost, all following ones sent to the same port are lost as well, until
718		889	monitoring raises an error, so there are no silent "holes" in the message
719	=item * In Erlang, processes can be declared dead and later be found to be	890	sequence.
720	alive.
721
722	In Erlang it can happen that a monitored process is declared dead and
723	linked processes get killed, but later it turns out that the process is
724	still alive - and can receive messages.
725
726	In AEMP, when port monitoring detects a port as dead, then that port will
727	eventually be killed - it cannot happen that a node detects a port as dead
728	and then later sends messages to it, finding it is still alive.
729		891
730	=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.
731		893
732	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
733	ID known to other nodes for a completely different process, causing	895	known to other nodes for a completely different process, causing messages
734	messages destined for that process to end up in an unrelated process.	896	destined for that process to end up in an unrelated process.
735		897
736	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
737	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.
738		900
739	=item * Erlang uses unprotected connections, AEMP uses secure	901	=item * Erlang uses unprotected connections, AEMP uses secure
740	authentication and can use TLS.	902	authentication and can use TLS.
741		903
742	AEMP can use a proven protocol - SSL/TLS - to protect connections and	904	AEMP can use a proven protocol - TLS - to protect connections and
743	securely authenticate nodes.	905	securely authenticate nodes.
744		906
745	=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
746	communications.	908	communications.
747		909
748	The AEMP protocol, unlike the Erlang protocol, supports both	910	The AEMP protocol, unlike the Erlang protocol, supports both programming
749	language-independent text-only protocols (good for debugging) and binary,	911	language independent text-only protocols (good for debugging) and binary,
750	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.
751		914
752	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
753	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
754	protocol simple.	917	protocol simple.
755		918
756	=item * AEMP has more flexible monitoring options than Erlang.	919	=item * AEMP has more flexible monitoring options than Erlang.
757		920
758	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
759	or I<none>, there is no in-between, so monitoring single processes is	922	or I<none>, there is no in-between, so monitoring single processes is
760	difficult to implement. Monitoring in AEMP is more flexible than in	923	difficult to implement. Monitoring in AEMP is more flexible than in
761	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
762	on a per-process basis.	925	on a per-process basis.
763		926
764	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	927	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		928
766	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
767	as linking is (except linking is unreliable in Erlang). In AEMP, the	930	same way as linking is (except linking is unreliable in Erlang).
768	semantics of monitoring and linking are identical, linking is simply	931
769	two-way monitoring with automatic kill.	932	In AEMP, you don't "look up" registered port names or send to named ports
		933	that might or might not be persistent. Instead, you normally spawn a port
		934	on the remote node. The init function monitors you, and you monitor the
		935	remote port. Since both monitors are local to the node, they are much more
		936	reliable (no need for C<spawn_link>).
		937
		938	This also saves round-trips and avoids sending messages to the wrong port
		939	(hard to do in Erlang).
770		940
771	=back	941	=back
772		942
		943	=head1 RATIONALE
		944
		945	=over 4
		946
		947	=item Why strings for port and node IDs, why not objects?
		948
		949	We considered "objects", but found that the actual number of methods
		950	that can be called are quite low. Since port and node IDs travel over
		951	the network frequently, the serialising/deserialising would add lots of
		952	overhead, as well as having to keep a proxy object everywhere.
		953
		954	Strings can easily be printed, easily serialised etc. and need no special
		955	procedures to be "valid".
		956
		957	And as a result, a port with just a default receiver consists of a single
		958	closure stored in a global hash - it can't become much cheaper.
		959
		960	=item Why favour JSON, why not a real serialising format such as Storable?
		961
		962	In fact, any AnyEvent::MP node will happily accept Storable as framing
		963	format, but currently there is no way to make a node use Storable by
		964	default (although all nodes will accept it).
		965
		966	The default framing protocol is JSON because a) JSON::XS is many times
		967	faster for small messages and b) most importantly, after years of
		968	experience we found that object serialisation is causing more problems
		969	than it solves: Just like function calls, objects simply do not travel
		970	easily over the network, mostly because they will always be a copy, so you
		971	always have to re-think your design.
		972
		973	Keeping your messages simple, concentrating on data structures rather than
		974	objects, will keep your messages clean, tidy and efficient.
		975
		976	=back
		977
773	=head1 SEE ALSO	978	=head1 SEE ALSO
		979
		980	L<AnyEvent::MP::Intro> - a gentle introduction.
		981
		982	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		983
		984	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		985	your applications.
		986
		987	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		988
		989	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		990	all nodes.
774		991
775	L<AnyEvent>.	992	L<AnyEvent>.
776		993
777	=head1 AUTHOR	994	=head1 AUTHOR
778		995

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Revision 1.116 by root, Mon Jun 21 15:09:34 2010 UTC