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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs.
Revision 1.103 by root, Sat Oct 17 01:42:39 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
		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	34
		35	# destroy a prot again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
		39	# monitoring
		40	mon $localport, $cb->(@msg) # callback is invoked on death
		41	mon $localport, $otherport # kill otherport on abnormal 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.
27		59
28	=head1 DESCRIPTION	60	=head1 DESCRIPTION
29		61
30	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
31		63
32	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
33	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
34		66
35	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>
36	manual page.	68	manual page and the examples under F<eg/>.
37
38	At the moment, this module family is severly broken and underdocumented,
39	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.
41		69
42	=head1 CONCEPTS	70	=head1 CONCEPTS
43		71
44	=over 4	72	=over 4
45		73
46	=item port	74	=item port
47		75
48	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).
49		78
50	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
51	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
52	will not be queued.	81	anything was listening for them or not.
53		82
54	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
55		84
56	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
57	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
58	exception is the the node port, whose ID is identical to its node
59	reference.
60		87
61	=item node	88	=item node
62		89
63	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,
64	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
65	create new ports, among other things.	92	ports.
66		93
67	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
68	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
69		97
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
71		99
72	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
73	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
74	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.
75		104
76	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
77	TCP/IP, other protocols might look different).
78		106
79	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
80	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.
81		111
82	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
83	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.
84		139
85	=back	140	=back
86		141
87	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
88		143
90		145
91	=cut	146	=cut
92		147
93	package AnyEvent::MP;	148	package AnyEvent::MP;
94		149
95	use AnyEvent::MP::Base;	150	use AnyEvent::MP::Kernel;
96		151
97	use common::sense;	152	use common::sense;
98		153
99	use Carp ();	154	use Carp ();
100		155
101	use AE ();	156	use AE ();
102		157
103	use base "Exporter";	158	use base "Exporter";
104		159
105	our $VERSION = '0.1';	160	our $VERSION = 1.22;
		161
106	our @EXPORT = qw(	162	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
108	resolve_node initialise_node	164	configure
109	snd rcv mon kil reg psub	165	snd rcv mon mon_guard kil psub peval spawn cal
110	port	166	port
111	);	167	);
112		168
113	our $SELF;	169	our $SELF;
114		170
…		…
118	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
119	}	175	}
120		176
121	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
122		178
123	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
124	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
125	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
126	identifiers become invalid.
127		182
128	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
129		184
130	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.
131		186
132	=item $cv = resolve_node $noderef	187	=item configure $profile, key => value...
133		188
134	Takes an unresolved node reference that may contain hostnames and	189	=item configure key => value...
135	abbreviated IDs, resolves all of them and returns a resolved node
136	reference.
137		190
138	In addition to C<address:port> pairs allowed in resolved noderefs, the	191	Before a node can talk to other nodes on the network (i.e. enter
139	following forms are supported:	192	"distributed mode") it has to configure itself - the minimum a node needs
		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.
		195
		196	This function configures a node - it must be called exactly once (or
		197	never) before calling other AnyEvent::MP functions.
140		198
141	=over 4	199	=over 4
142		200
143	=item the empty string	201	=item step 1, gathering configuration from profiles
144		202
145	An empty-string component gets resolved as if the default port (4040) was	203	The function first looks up a profile in the aemp configuration (see the
146	specified.	204	L<aemp> commandline utility). The profile name can be specified via the
		205	named C<profile> parameter or can simply be the first parameter). If it is
		206	missing, then the nodename (F<uname -n>) will be used as profile name.
147		207
148	=item naked port numbers (e.g. C<1234>)	208	The profile data is then gathered as follows:
149		209
150	These are resolved by prepending the local nodename and a colon, to be	210	First, all remaining key => value pairs (all of which are conveniently
151	further resolved.	211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
152		215
153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	216	That means that the values specified in the profile have highest priority
		217	and the values specified directly via C<configure> have lowest priority,
		218	and can only be used to specify defaults.
154		219
155	These are resolved by using AnyEvent::DNS to resolve them, optionally	220	If the profile specifies a node ID, then this will become the node ID of
156	looking up SRV records for the C<aemp=4040> port, if no port was	221	this process. If not, then the profile name will be used as node ID. The
157	specified.	222	special node ID of C<anon/> will be replaced by a random node ID.
		223
		224	=item step 2, bind listener sockets
		225
		226	The next step is to look up the binds in the profile, followed by binding
		227	aemp protocol listeners on all binds specified (it is possible and valid
		228	to have no binds, meaning that the node cannot be contacted form the
		229	outside. This means the node cannot talk to other nodes that also have no
		230	binds, but it can still talk to all "normal" nodes).
		231
		232	If the profile does not specify a binds list, then a default of C<*> is
		233	used, meaning the node will bind on a dynamically-assigned port on every
		234	local IP address it finds.
		235
		236	=item step 3, connect to seed nodes
		237
		238	As the last step, the seeds list from the profile is passed to the
		239	L<AnyEvent::MP::Global> module, which will then use it to keep
		240	connectivity with at least one node at any point in time.
158		241
159	=back	242	=back
		243
		244	Example: become a distributed node using the local node name as profile.
		245	This should be the most common form of invocation for "daemon"-type nodes.
		246
		247	configure
		248
		249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
		251
		252	configure nodeid => "anon/";
		253
		254	Example: configure a node using a profile called seed, which si suitable
		255	for a seed node as it binds on all local addresses on a fixed port (4040,
		256	customary for aemp).
		257
		258	# use the aemp commandline utility
		259	# aemp profile seed nodeid anon/ binds '*:4040'
		260
		261	# then use it
		262	configure profile => "seed";
		263
		264	# or simply use aemp from the shell again:
		265	# aemp run profile seed
		266
		267	# or provide a nicer-to-remember nodeid
		268	# aemp run profile seed nodeid "$(hostname)"
160		269
161	=item $SELF	270	=item $SELF
162		271
163	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
164	blocks.	273	blocks.
165		274
166	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
167		276
168	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
171		280
172	=item snd $port, type => @data	281	=item snd $port, type => @data
173		282
174	=item snd $port, @msg	283	=item snd $port, @msg
175		284
176	Send the given message to the given port ID, which can identify either	285	Send the given message to the given port, which can identify either a
177	a local or a remote port, and can be either a string or soemthignt hat	286	local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		287
180	While the message can be about anything, it is highly recommended to use a	288	While the message can be almost anything, it is highly recommended to
181	string as first element (a portid, or some word that indicates a request	289	use a string as first element (a port ID, or some word that indicates a
182	type etc.).	290	request type etc.) and to consist if only simple perl values (scalars,
		291	arrays, hashes) - if you think you need to pass an object, think again.
183		292
184	The message data effectively becomes read-only after a call to this	293	The message data logically becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
186	problems.	295	forbidden, as there can be considerable time between the call to C<snd>
		296	and the time the message is actually being serialised - in fact, it might
		297	never be copied as within the same process it is simply handed to the
		298	receiving port.
187		299
188	The type of data you can transfer depends on the transport protocol: when	300	The type of data you can transfer depends on the transport protocol: when
189	JSON is used, then only strings, numbers and arrays and hashes consisting	301	JSON is used, then only strings, numbers and arrays and hashes consisting
190	of those are allowed (no objects). When Storable is used, then anything	302	of those are allowed (no objects). When Storable is used, then anything
191	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
193		306
194	=item $local_port = port	307	=item $local_port = port
195		308
196	Create a new local port object that can be used either as a pattern	309	Create a new local port object and returns its port ID. Initially it has
197	matching port ("full port") or a single-callback port ("miniport"),	310	no callbacks set and will throw an error when it receives messages.
198	depending on how C<rcv> callbacks are bound to the object.
199		311
200	=item $port = port { my @msg = @_; $finished }	312	=item $local_port = port { my @msg = @_ }
201		313
202	Creates a "miniport", that is, a very lightweight port without any pattern	314	Creates a new local port, and returns its ID. Semantically the same as
203	matching behind it, and returns its ID. Semantically the same as creating
204	a port and calling C<rcv $port, $callback> on it.	315	creating a port and calling C<rcv $port, $callback> on it.
205		316
206	The block will be called for every message received on the port. When the	317	The block will be called for every message received on the port, with the
207	callback returns a true value its job is considered "done" and the port	318	global variable C<$SELF> set to the port ID. Runtime errors will cause the
208	will be destroyed. Otherwise it will stay alive.	319	port to be C<kil>ed. The message will be passed as-is, no extra argument
		320	(i.e. no port ID) will be passed to the callback.
209		321
210	The message will be passed as-is, no extra argument (i.e. no port id) will	322	If you want to stop/destroy the port, simply C<kil> it:
211	be passed to the callback.
212		323
213	If you need the local port id in the callback, this works nicely:	324	my $port = port {
214		325	my @msg = @_;
215	my $port; $port = port {	326	...
216	snd $otherport, reply => $port;	327	kil $SELF;
217	};	328	};
218		329
219	=cut	330	=cut
220		331
221	sub rcv($@);	332	sub rcv($@);
		333
		334	sub _kilme {
		335	die "received message on port without callback";
		336	}
222		337
223	sub port(;&) {	338	sub port(;&) {
224	my $id = "$UNIQ." . $ID++;	339	my $id = "$UNIQ." . $ID++;
225	my $port = "$NODE#$id";	340	my $port = "$NODE#$id";
226		341
227	if (@_) {	342	rcv $port, shift \|\| \&_kilme;
228	rcv $port, shift;
229	} else {
230	$PORT{$id} = sub { }; # nop
231	}
232		343
233	$port	344	$port
234	}	345	}
235		346
236	=item reg $port, $name
237
238	Registers the given port under the name C<$name>. If the name already
239	exists it is replaced.
240
241	A port can only be registered under one well known name.
242
243	A port automatically becomes unregistered when it is killed.
244
245	=cut
246
247	sub reg(@) {
248	my ($port, $name) = @_;
249
250	$REG{$name} = $port;
251	}
252
253	=item rcv $port, $callback->(@msg)	347	=item rcv $local_port, $callback->(@msg)
254		348
255	Replaces the callback on the specified miniport (after converting it to	349	Replaces the default callback on the specified port. There is no way to
256	one if required).	350	remove the default callback: use C<sub { }> to disable it, or better
257		351	C<kil> the port when it is no longer needed.
258	=item rcv $port, tagstring => $callback->(@msg), ...
259
260	=item rcv $port, $smartmatch => $callback->(@msg), ...
261
262	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
263
264	Register callbacks to be called on matching messages on the given full
265	port (after converting it to one if required).
266
267	The callback has to return a true value when its work is done, after
268	which is will be removed, or a false value in which case it will stay
269	registered.
270		352
271	The global C<$SELF> (exported by this module) contains C<$port> while	353	The global C<$SELF> (exported by this module) contains C<$port> while
272	executing the callback.	354	executing the callback. Runtime errors during callback execution will
		355	result in the port being C<kil>ed.
273		356
274	Runtime errors wdurign callback execution will result in the port being	357	The default callback received all messages not matched by a more specific
275	C<kil>ed.	358	C<tag> match.
276		359
277	If the match is an array reference, then it will be matched against the	360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
278	first elements of the message, otherwise only the first element is being
279	matched.
280		361
281	Any element in the match that is specified as C<_any_> (a function	362	Register (or replace) callbacks to be called on messages starting with the
282	exported by this module) matches any single element of the message.	363	given tag on the given port (and return the port), or unregister it (when
		364	C<$callback> is C<$undef> or missing). There can only be one callback
		365	registered for each tag.
283		366
284	While not required, it is highly recommended that the first matching	367	The original message will be passed to the callback, after the first
285	element is a string identifying the message. The one-string-only match is	368	element (the tag) has been removed. The callback will use the same
286	also the most efficient match (by far).	369	environment as the default callback (see above).
		370
		371	Example: create a port and bind receivers on it in one go.
		372
		373	my $port = rcv port,
		374	msg1 => sub { ... },
		375	msg2 => sub { ... },
		376	;
		377
		378	Example: create a port, bind receivers and send it in a message elsewhere
		379	in one go:
		380
		381	snd $otherport, reply =>
		382	rcv port,
		383	msg1 => sub { ... },
		384	...
		385	;
		386
		387	Example: temporarily register a rcv callback for a tag matching some port
		388	(e.g. for an rpc reply) and unregister it after a message was received.
		389
		390	rcv $port, $otherport => sub {
		391	my @reply = @_;
		392
		393	rcv $SELF, $otherport;
		394	};
287		395
288	=cut	396	=cut
289		397
290	sub rcv($@) {	398	sub rcv($@) {
291	my $port = shift;	399	my $port = shift;
292	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
293		401
294	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
295	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
296		404
297	if (@_ == 1) {	405	while (@_) {
		406	if (ref $_[0]) {
		407	if (my $self = $PORT_DATA{$portid}) {
		408	"AnyEvent::MP::Port" eq ref $self
		409	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		410
		411	$self->[0] = shift;
		412	} else {
298	my $cb = shift;	413	my $cb = shift;
299	delete $PORT_DATA{$portid};
300	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
301	local $SELF = $port;	415	local $SELF = $port;
302	eval {	416	eval { &$cb }; _self_die if $@;
303	&$cb	417	};
304	and kil $port;
305	};	418	}
306	_self_die if $@;	419	} elsif (defined $_[0]) {
307	};
308	} else {
309	my $self = $PORT_DATA{$portid} \|\|= do {	420	my $self = $PORT_DATA{$portid} \|\|= do {
310	my $self = bless {	421	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
311	id => $port,
312	}, "AnyEvent::MP::Port";
313		422
314	$PORT{$portid} = sub {	423	$PORT{$portid} = sub {
315	local $SELF = $port;	424	local $SELF = $port;
316		425
317	eval {
318	for (@{ $self->{rc0}{$_[0]} }) {	426	if (my $cb = $self->[1]{$_[0]}) {
319	$_ && &{$_->[0]}	427	shift;
320	&& undef $_;	428	eval { &$cb }; _self_die if $@;
321	}	429	} else {
322
323	for (@{ $self->{rcv}{$_[0]} }) {
324	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
325	&& &{$_->[0]}	430	&{ $self->[0] };
326	&& undef $_;
327	}
328
329	for (@{ $self->{any} }) {
330	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
331	&& &{$_->[0]}
332	&& undef $_;
333	}	431	}
334	};	432	};
335	_self_die if $@;	433
		434	$self
336	};	435	};
337		436
338	$self
339	};
340
341	"AnyEvent::MP::Port" eq ref $self	437	"AnyEvent::MP::Port" eq ref $self
342	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	438	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
343		439
344	while (@_) {
345	my ($match, $cb) = splice @_, 0, 2;	440	my ($tag, $cb) = splice @_, 0, 2;
346		441
347	if (!ref $match) {	442	if (defined $cb) {
348	push @{ $self->{rc0}{$match} }, [$cb];	443	$self->[1]{$tag} = $cb;
349	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
350	my ($type, @match) = @$match;
351	@match
352	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
353	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
354	} else {	444	} else {
355	push @{ $self->{any} }, [$cb, $match];	445	delete $self->[1]{$tag};
356	}	446	}
357	}	447	}
358	}	448	}
359		449
360	$port	450	$port
361	}	451	}
362		452
		453	=item peval $port, $coderef[, @args]
		454
		455	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		456	when the code throews an exception the C<$port> will be killed.
		457
		458	Any remaining args will be passed to the callback. Any return values will
		459	be returned to the caller.
		460
		461	This is useful when you temporarily want to execute code in the context of
		462	a port.
		463
		464	Example: create a port and run some initialisation code in it's context.
		465
		466	my $port = port { ... };
		467
		468	peval $port, sub {
		469	init
		470	or die "unable to init";
		471	};
		472
		473	=cut
		474
		475	sub peval($$) {
		476	local $SELF = shift;
		477	my $cb = shift;
		478
		479	if (wantarray) {
		480	my @res = eval { &$cb };
		481	_self_die if $@;
		482	@res
		483	} else {
		484	my $res = eval { &$cb };
		485	_self_die if $@;
		486	$res
		487	}
		488	}
		489
363	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
364		491
365	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
366	closure is executed, sets up the environment in the same way as in C<rcv>	493	closure is executed, sets up the environment in the same way as in C<rcv>
367	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		495
		496	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		497	BLOCK } } >>.
368		498
369	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
370		500
371	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
372	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
396	$res	526	$res
397	}	527	}
398	}	528	}
399	}	529	}
400		530
401	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
402		532
403	=item $guard = mon $port, $otherport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
404		534
405	=item $guard = mon $port, $otherport, @msg	535	=item $guard = mon $port # kill $SELF when $port dies
406		536
		537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		538
407	Monitor the given port and do something when the port is killed.	539	Monitor the given port and do something when the port is killed or
		540	messages to it were lost, and optionally return a guard that can be used
		541	to stop monitoring again.
408		542
409	In the first form, the callback is simply called with any number	543	In the first form (callback), the callback is simply called with any
410	of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
411	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
412	C<eval> if unsure.	546	C<eval> if unsure.
413		547
414	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	548	In the second form (another port given), the other port (C<$rcvport>)
415	a @reason was specified, i.e. on "normal" kils nothing happens, while	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
416	under all other conditions, the other port is killed with the same reason.	550	"normal" kils nothing happens, while under all other conditions, the other
		551	port is killed with the same reason.
417		552
		553	The third form (kill self) is the same as the second form, except that
		554	C<$rvport> defaults to C<$SELF>.
		555
418	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	556	In the last form (message), a message of the form C<@msg, @reason> will be
		557	C<snd>.
		558
		559	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		560	alert was raised), they are removed and will not trigger again.
		561
		562	As a rule of thumb, monitoring requests should always monitor a port from
		563	a local port (or callback). The reason is that kill messages might get
		564	lost, just like any other message. Another less obvious reason is that
		565	even monitoring requests can get lost (for example, when the connection
		566	to the other node goes down permanently). When monitoring a port locally
		567	these problems do not exist.
		568
		569	C<mon> effectively guarantees that, in the absence of hardware failures,
		570	after starting the monitor, either all messages sent to the port will
		571	arrive, or the monitoring action will be invoked after possible message
		572	loss has been detected. No messages will be lost "in between" (after
		573	the first lost message no further messages will be received by the
		574	port). After the monitoring action was invoked, further messages might get
		575	delivered again.
		576
		577	Inter-host-connection timeouts and monitoring depend on the transport
		578	used. The only transport currently implemented is TCP, and AnyEvent::MP
		579	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		580	non-idle connection, and usually around two hours for idle connections).
		581
		582	This means that monitoring is good for program errors and cleaning up
		583	stuff eventually, but they are no replacement for a timeout when you need
		584	to ensure some maximum latency.
419		585
420	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
421		587
422	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
423		589
424	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
425		591
426	mon $port, $self;	592	mon $port;
427		593
428	Example: send us a restart message another C<$port> is killed.	594	Example: send us a restart message when another C<$port> is killed.
429		595
430	mon $port, $self => "restart";	596	mon $port, $self => "restart";
431		597
432	=cut	598	=cut
433		599
434	sub mon {	600	sub mon {
435	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
436		602
437	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
438		604
439	my $cb = shift;	605	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
440		606
441	unless (ref $cb) {	607	unless (ref $cb) {
442	if (@_) {	608	if (@_) {
443	# send a kill info message	609	# send a kill info message
444	my (@msg) = ($cb, @_);	610	my (@msg) = ($cb, @_);
…		…
451	}	617	}
452		618
453	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
454		620
455	defined wantarray	621	defined wantarray
456	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
457	}	623	}
458		624
459	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
460		626
461	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
462	is killed, the references will be freed.	628	is killed, the references will be freed.
463		629
464	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
465		631
466	This function is useful when you create e.g. timers or other watchers and	632	This function is useful when you create e.g. timers or other watchers and
467	want to free them when the port gets killed:	633	want to free them when the port gets killed (note the use of C<psub>):
468		634
469	$port->rcv (start => sub {	635	$port->rcv (start => sub {
470	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
471	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
472	});	638	});
473	});	639	});
474		640
475	=cut	641	=cut
476		642
477	sub mon_guard {	643	sub mon_guard {
478	my ($port, @refs) = @_;	644	my ($port, @refs) = @_;
479		645
		646	#TODO: mon-less form?
		647
480	mon $port, sub { 0 && @refs }	648	mon $port, sub { 0 && @refs }
481	}	649	}
482		650
483	=item lnk $port1, $port2
484
485	Link two ports. This is simply a shorthand for:
486
487	mon $port1, $port2;
488	mon $port2, $port1;
489
490	It means that if either one is killed abnormally, the other one gets
491	killed as well.
492
493	=item kil $port[, @reason]	651	=item kil $port[, @reason]
494		652
495	Kill the specified port with the given C<@reason>.	653	Kill the specified port with the given C<@reason>.
496		654
497	If no C<@reason> is specified, then the port is killed "normally" (linked	655	If no C<@reason> is specified, then the port is killed "normally" (ports
498	ports will not be kileld, or even notified).	656	monitoring other ports will not necessarily die because a port dies
		657	"normally").
499		658
500	Otherwise, linked ports get killed with the same reason (second form of	659	Otherwise, linked ports get killed with the same reason (second form of
501	C<mon>, see below).	660	C<mon>, see above).
502		661
503	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
504	will be reported as reason C<< die => $@ >>.	663	will be reported as reason C<< die => $@ >>.
505		664
506	Transport/communication errors are reported as C<< transport_error =>	665	Transport/communication errors are reported as C<< transport_error =>
507	$message >>.	666	$message >>.
508		667
		668	=cut
		669
		670	=item $port = spawn $node, $initfunc[, @initdata]
		671
		672	Creates a port on the node C<$node> (which can also be a port ID, in which
		673	case it's the node where that port resides).
		674
		675	The port ID of the newly created port is returned immediately, and it is
		676	possible to immediately start sending messages or to monitor the port.
		677
		678	After the port has been created, the init function is called on the remote
		679	node, in the same context as a C<rcv> callback. This function must be a
		680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		681	specify a function in the main program, use C<::name>.
		682
		683	If the function doesn't exist, then the node tries to C<require>
		684	the package, then the package above the package and so on (e.g.
		685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		686	exists or it runs out of package names.
		687
		688	The init function is then called with the newly-created port as context
		689	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		690	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		691	the port might not get created.
		692
		693	A common idiom is to pass a local port, immediately monitor the spawned
		694	port, and in the remote init function, immediately monitor the passed
		695	local port. This two-way monitoring ensures that both ports get cleaned up
		696	when there is a problem.
		697
		698	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
		701
		702	Example: spawn a chat server port on C<$othernode>.
		703
		704	# this node, executed from within a port context:
		705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		706	mon $server;
		707
		708	# init function on C<$othernode>
		709	sub connect {
		710	my ($srcport) = @_;
		711
		712	mon $srcport;
		713
		714	rcv $SELF, sub {
		715	...
		716	};
		717	}
		718
		719	=cut
		720
		721	sub _spawn {
		722	my $port = shift;
		723	my $init = shift;
		724
		725	# rcv will create the actual port
		726	local $SELF = "$NODE#$port";
		727	eval {
		728	&{ load_func $init }
		729	};
		730	_self_die if $@;
		731	}
		732
		733	sub spawn(@) {
		734	my ($nodeid, undef) = split /#/, shift, 2;
		735
		736	my $id = "$RUNIQ." . $ID++;
		737
		738	$_[0] =~ /::/
		739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		740
		741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		742
		743	"$nodeid#$id"
		744	}
		745
		746	=item after $timeout, @msg
		747
		748	=item after $timeout, $callback
		749
		750	Either sends the given message, or call the given callback, after the
		751	specified number of seconds.
		752
		753	This is simply a utility function that comes in handy at times - the
		754	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		755	so it may go away in the future.
		756
		757	=cut
		758
		759	sub after($@) {
		760	my ($timeout, @action) = @_;
		761
		762	my $t; $t = AE::timer $timeout, 0, sub {
		763	undef $t;
		764	ref $action[0]
		765	? $action[0]()
		766	: snd @action;
		767	};
		768	}
		769
		770	=item cal $port, @msg, $callback[, $timeout]
		771
		772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
		774
		775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
		777
		778	A reply message sent to the port is passed to the C<$callback> as-is.
		779
		780	If an optional time-out (in seconds) is given and it is not C<undef>,
		781	then the callback will be called without any arguments after the time-out
		782	elapsed and the port is C<kil>ed.
		783
		784	If no time-out is given (or it is C<undef>), then the local port will
		785	monitor the remote port instead, so it eventually gets cleaned-up.
		786
		787	Currently this function returns the temporary port, but this "feature"
		788	might go in future versions unless you can make a convincing case that
		789	this is indeed useful for something.
		790
		791	=cut
		792
		793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
		796
		797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
		802
		803	if (defined $timeout) {
		804	$timeout = AE::timer $timeout, 0, sub {
		805	undef $timeout;
		806	kil $port;
		807	$cb->();
		808	};
		809	} else {
		810	mon $_[0], sub {
		811	kil $port;
		812	$cb->();
		813	};
		814	}
		815
		816	push @_, $port;
		817	&snd;
		818
		819	$port
		820	}
		821
509	=back	822	=back
510		823
511	=head1 FUNCTIONS FOR NODES
512
513	=over 4
514
515	=item initialise_node $noderef, $seednode, $seednode...
516
517	=item initialise_node "slave/", $master, $master...
518
519	Initialises a node - must be called exactly once before calling other
520	AnyEvent::MP functions when talking to other nodes is required.
521
522	All arguments are noderefs, which can be either resolved or unresolved.
523
524	There are two types of networked nodes, public nodes and slave nodes:
525
526	=over 4
527
528	=item public nodes
529
530	For public nodes, C<$noderef> must either be a (possibly unresolved)
531	noderef, in which case it will be resolved, or C<undef> (or missing), in
532	which case the noderef will be guessed.
533
534	Afterwards, the node will bind itself on all endpoints and try to connect
535	to all additional C<$seednodes> that are specified. Seednodes are optional
536	and can be used to quickly bootstrap the node into an existing network.
537
538	=item slave nodes
539
540	When the C<$noderef> is the special string C<slave/>, then the node will
541	become a slave node. Slave nodes cannot be contacted from outside and will
542	route most of their traffic to the master node that they attach to.
543
544	At least one additional noderef is required: The node will try to connect
545	to all of them and will become a slave attached to the first node it can
546	successfully connect to.
547
548	=back
549
550	This function will block until all nodes have been resolved and, for slave
551	nodes, until it has successfully established a connection to a master
552	server.
553
554	Example: become a public node listening on the default node.
555
556	initialise_node;
557
558	Example: become a public node, and try to contact some well-known master
559	servers to become part of the network.
560
561	initialise_node undef, "master1", "master2";
562
563	Example: become a public node listening on port C<4041>.
564
565	initialise_node 4041;
566
567	Example: become a public node, only visible on localhost port 4044.
568
569	initialise_node "locahost:4044";
570
571	Example: become a slave node to any of the specified master servers.
572
573	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
574
575	=cut
576
577	=back
578
579	=head1 NODE MESSAGES
580
581	Nodes understand the following messages sent to them. Many of them take
582	arguments called C<@reply>, which will simply be used to compose a reply
583	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
584	the remaining arguments are simply the message data.
585
586	While other messages exist, they are not public and subject to change.
587
588	=over 4
589
590	=cut
591
592	=item lookup => $name, @reply
593
594	Replies with the port ID of the specified well-known port, or C<undef>.
595
596	=item devnull => ...
597
598	Generic data sink/CPU heat conversion.
599
600	=item relay => $port, @msg
601
602	Simply forwards the message to the given port.
603
604	=item eval => $string[ @reply]
605
606	Evaluates the given string. If C<@reply> is given, then a message of the
607	form C<@reply, $@, @evalres> is sent.
608
609	Example: crash another node.
610
611	snd $othernode, eval => "exit";
612
613	=item time => @reply
614
615	Replies the the current node time to C<@reply>.
616
617	Example: tell the current node to send the current time to C<$myport> in a
618	C<timereply> message.
619
620	snd $NODE, time => $myport, timereply => 1, 2;
621	# => snd $myport, timereply => 1, 2, <time>
622
623	=back
624
625	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
626		825
627	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
628	== aemp node, erlang process == aemp port), so many of the documents and	827	== aemp node, Erlang process == aemp port), so many of the documents and
629	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
630	sample:	829	sample:
631		830
632	http://www.erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
633	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	832	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
634	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	833	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
…		…
636		835
637	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
638		837
639	=over 4	838	=over 4
640		839
641	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
642		841
643	Erlang relies on special naming and DNS to work everywhere in the	842	Erlang relies on special naming and DNS to work everywhere in the same
644	same way. AEMP relies on each node knowing it's own address(es), with	843	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
645	convenience functionality.	844	configuration or DNS), and possibly the addresses of some seed nodes, but
		845	will otherwise discover other nodes (and their IDs) itself.
646		846
647	This means that AEMP requires a less tightly controlled environment at the	847	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
648	cost of longer node references and a slightly higher management overhead.	848	uses "local ports are like remote ports".
		849
		850	The failure modes for local ports are quite different (runtime errors
		851	only) then for remote ports - when a local port dies, you I<know> it dies,
		852	when a connection to another node dies, you know nothing about the other
		853	port.
		854
		855	Erlang pretends remote ports are as reliable as local ports, even when
		856	they are not.
		857
		858	AEMP encourages a "treat remote ports differently" philosophy, with local
		859	ports being the special case/exception, where transport errors cannot
		860	occur.
649		861
650	=item * Erlang uses processes and a mailbox, AEMP does not queue.	862	=item * Erlang uses processes and a mailbox, AEMP does not queue.
651		863
652	Erlang uses processes that selctively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
653	needs a queue. AEMP is event based, queuing messages would serve no useful	865	needs a queue. AEMP is event based, queuing messages would serve no
654	purpose.	866	useful purpose. For the same reason the pattern-matching abilities of
		867	AnyEvent::MP are more limited, as there is little need to be able to
		868	filter messages without dequeuing them.
655		869
656	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
657		871
658	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
659		873
660	Sending messages in erlang is synchronous and blocks the process. AEMP	874	Sending messages in Erlang is synchronous and blocks the process (and
661	sends are immediate, connection establishment is handled in the	875	so does not need a queue that can overflow). AEMP sends are immediate,
662	background.	876	connection establishment is handled in the background.
663		877
664	=item * Erlang can silently lose messages, AEMP cannot.	878	=item * Erlang suffers from silent message loss, AEMP does not.
665		879
666	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
667	without any of the processes realising it (i.e. you send messages a, b,	881	lost without any of the processes realising it (i.e. you send messages a,
668	and c, and the other side only receives messages a and c).	882	b, and c, and the other side only receives messages a and c).
669		883
670	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
671	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
672		886	monitoring raises an error, so there are no silent "holes" in the message
673	=item * In erlang, processes can be declared dead and later be found to be	887	sequence.
674	alive.
675
676	In erlang it can happen that a monitored process is declared dead and
677	linked processes get killed, but later it turns out that the process is
678	still alive - and can receive messages.
679
680	In AEMP, when port monitoring detects a port as dead, then that port will
681	eventually be killed - it cannot happen that a node detects a port as dead
682	and then later sends messages to it, finding it is still alive.
683		888
684	=item * Erlang can send messages to the wrong port, AEMP does not.	889	=item * Erlang can send messages to the wrong port, AEMP does not.
685		890
686	In erlang it is quite possible that a node that restarts reuses a process	891	In Erlang it is quite likely that a node that restarts reuses a process ID
687	ID known to other nodes for a completely different process, causing	892	known to other nodes for a completely different process, causing messages
688	messages destined for that process to end up in an unrelated process.	893	destined for that process to end up in an unrelated process.
689		894
690	AEMP never reuses port IDs, so old messages or old port IDs floating	895	AEMP never reuses port IDs, so old messages or old port IDs floating
691	around in the network will not be sent to an unrelated port.	896	around in the network will not be sent to an unrelated port.
692		897
693	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
694	authentication and can use TLS.	899	authentication and can use TLS.
695		900
696	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
697	securely authenticate nodes.	902	securely authenticate nodes.
698		903
699	=item * The AEMP protocol is optimised for both text-based and binary	904	=item * The AEMP protocol is optimised for both text-based and binary
700	communications.	905	communications.
701		906
702	The AEMP protocol, unlike the erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
703	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
704	language-specific serialisers (e.g. Storable).	909	language-specific serialisers (e.g. Storable). By default, unless TLS is
		910	used, the protocol is actually completely text-based.
705		911
706	It has also been carefully designed to be implementable in other languages	912	It has also been carefully designed to be implementable in other languages
707	with a minimum of work while gracefully degrading fucntionality to make the	913	with a minimum of work while gracefully degrading functionality to make the
708	protocol simple.	914	protocol simple.
709		915
		916	=item * AEMP has more flexible monitoring options than Erlang.
		917
		918	In Erlang, you can chose to receive I<all> exit signals as messages
		919	or I<none>, there is no in-between, so monitoring single processes is
		920	difficult to implement. Monitoring in AEMP is more flexible than in
		921	Erlang, as one can choose between automatic kill, exit message or callback
		922	on a per-process basis.
		923
		924	=item * Erlang tries to hide remote/local connections, AEMP does not.
		925
		926	Monitoring in Erlang is not an indicator of process death/crashes, in the
		927	same way as linking is (except linking is unreliable in Erlang).
		928
		929	In AEMP, you don't "look up" registered port names or send to named ports
		930	that might or might not be persistent. Instead, you normally spawn a port
		931	on the remote node. The init function monitors you, and you monitor the
		932	remote port. Since both monitors are local to the node, they are much more
		933	reliable (no need for C<spawn_link>).
		934
		935	This also saves round-trips and avoids sending messages to the wrong port
		936	(hard to do in Erlang).
		937
710	=back	938	=back
711		939
		940	=head1 RATIONALE
		941
		942	=over 4
		943
		944	=item Why strings for port and node IDs, why not objects?
		945
		946	We considered "objects", but found that the actual number of methods
		947	that can be called are quite low. Since port and node IDs travel over
		948	the network frequently, the serialising/deserialising would add lots of
		949	overhead, as well as having to keep a proxy object everywhere.
		950
		951	Strings can easily be printed, easily serialised etc. and need no special
		952	procedures to be "valid".
		953
		954	And as a result, a miniport consists of a single closure stored in a
		955	global hash - it can't become much cheaper.
		956
		957	=item Why favour JSON, why not a real serialising format such as Storable?
		958
		959	In fact, any AnyEvent::MP node will happily accept Storable as framing
		960	format, but currently there is no way to make a node use Storable by
		961	default (although all nodes will accept it).
		962
		963	The default framing protocol is JSON because a) JSON::XS is many times
		964	faster for small messages and b) most importantly, after years of
		965	experience we found that object serialisation is causing more problems
		966	than it solves: Just like function calls, objects simply do not travel
		967	easily over the network, mostly because they will always be a copy, so you
		968	always have to re-think your design.
		969
		970	Keeping your messages simple, concentrating on data structures rather than
		971	objects, will keep your messages clean, tidy and efficient.
		972
		973	=back
		974
712	=head1 SEE ALSO	975	=head1 SEE ALSO
		976
		977	L<AnyEvent::MP::Intro> - a gentle introduction.
		978
		979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		980
		981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		982	your applications.
		983
		984	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		985	all nodes.
713		986
714	L<AnyEvent>.	987	L<AnyEvent>.
715		988
716	=head1 AUTHOR	989	=head1 AUTHOR
717		990

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Revision 1.103 by root, Sat Oct 17 01:42:39 2009 UTC