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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.37 by root, Fri Aug 7 16:47:23 2009 UTC vs.
Revision 1.113 by root, Sat Apr 3 15:32:18 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	34
		35	# destroy a prot again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
27		38
28	# monitoring	39	# monitoring
29	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
30	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
31	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.
32		59
33	=head1 DESCRIPTION	60	=head1 DESCRIPTION
34		61
35	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
36		63
37	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
38	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
39		66
40	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>
41	manual page.	68	manual page and the examples under F<eg/>.
42
43	At the moment, this module family is severly broken and underdocumented,
44	so do not use. This was uploaded mainly to reserve the CPAN namespace -
45	stay tuned! The basic API should be finished, however.
46		69
47	=head1 CONCEPTS	70	=head1 CONCEPTS
48		71
49	=over 4	72	=over 4
50		73
51	=item port	74	=item port
52		75
53	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).
54		78
55	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
56	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
57	will not be queued.	81	anything was listening for them or not.
58		82
59	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
60		84
61	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
62	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
63	exception is the the node port, whose ID is identical to its node
64	reference.
65		87
66	=item node	88	=item node
67		89
68	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,
69	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
70	create new ports, among other things.	92	ports.
71		93
72	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
73	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
74		97
75	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
76		99
77	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
78	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
79	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.
80		104
81	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
82	TCP/IP, other protocols might look different).
83		106
84	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
85	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.
86		111
87	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
88	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.
89		139
90	=back	140	=back
91		141
92	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
93		143
95		145
96	=cut	146	=cut
97		147
98	package AnyEvent::MP;	148	package AnyEvent::MP;
99		149
100	use AnyEvent::MP::Base;	150	use AnyEvent::MP::Kernel;
101		151
102	use common::sense;	152	use common::sense;
103		153
104	use Carp ();	154	use Carp ();
105		155
106	use AE ();	156	use AE ();
107		157
108	use base "Exporter";	158	use base "Exporter";
109		159
110	our $VERSION = '0.1';	160	our $VERSION = 1.28;
		161
111	our @EXPORT = qw(	162	our @EXPORT = qw(
112	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
113	resolve_node initialise_node	164	configure
114	snd rcv mon kil reg psub	165	snd rcv mon mon_guard kil psub peval spawn cal
115	port	166	port
116	);	167	);
117		168
118	our $SELF;	169	our $SELF;
119		170
…		…
123	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
124	}	175	}
125		176
126	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
127		178
128	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
129	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
130	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
131	identifiers become invalid.
132		182
133	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
134		184
135	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.
136		186
137	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
138		188
139	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
140		190
141	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
142	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
143	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
144		195
		196	The key/value pairs are basically the same ones as documented for the
		197	F<aemp> command line utility (sans the set/del prefix).
		198
145	This function initialises a node - it must be called exactly once (or	199	This function configures a node - it must be called exactly once (or
146	never) before calling other AnyEvent::MP functions.	200	never) before calling other AnyEvent::MP functions.
147		201
148	All arguments are noderefs, which can be either resolved or unresolved.
149
150	There are two types of networked nodes, public nodes and slave nodes:
151
152	=over 4	202	=over 4
153		203
154	=item public nodes	204	=item step 1, gathering configuration from profiles
155		205
156	For public nodes, C<$noderef> must either be a (possibly unresolved)	206	The function first looks up a profile in the aemp configuration (see the
157	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
158	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.
159		210
160	Afterwards, the node will bind itself on all endpoints and try to connect	211	The profile data is then gathered as follows:
161	to all additional C<$seednodes> that are specified. Seednodes are optional
162	and can be used to quickly bootstrap the node into an existing network.
163		212
164	=item slave nodes	213	First, all remaining key => value pairs (all of which are conveniently
		214	undocumented at the moment) will be interpreted as configuration
		215	data. Then they will be overwritten by any values specified in the global
		216	default configuration (see the F<aemp> utility), then the chain of
		217	profiles chosen by the profile name (and any C<parent> attributes).
165		218
166	When the C<$noderef> is the special string C<slave/>, then the node will	219	That means that the values specified in the profile have highest priority
167	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,
168	route most of their traffic to the master node that they attach to.	221	and can only be used to specify defaults.
169		222
170	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
171	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
172	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.
173		244
174	=back	245	=back
175		246
176	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.
177	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.
178	server.
179		249
180	Example: become a public node listening on the default node.	250	configure
181		251
182	initialise_node;	252	Example: become an anonymous node. This form is often used for commandline
		253	clients.
183		254
184	Example: become a public node, and try to contact some well-known master	255	configure nodeid => "anon/";
185	servers to become part of the network.
186		256
187	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).
188		260
189	Example: become a public node listening on port C<4041>.	261	# use the aemp commandline utility
		262	# aemp profile seed nodeid anon/ binds '*:4040'
190		263
191	initialise_node 4041;	264	# then use it
		265	configure profile => "seed";
192		266
193	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
194		269
195	initialise_node "locahost:4044";	270	# or provide a nicer-to-remember nodeid
196		271	# aemp run profile seed nodeid "$(hostname)"
197	Example: become a slave node to any of the specified master servers.
198
199	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
200
201	=item $cv = resolve_node $noderef
202
203	Takes an unresolved node reference that may contain hostnames and
204	abbreviated IDs, resolves all of them and returns a resolved node
205	reference.
206
207	In addition to C<address:port> pairs allowed in resolved noderefs, the
208	following forms are supported:
209
210	=over 4
211
212	=item the empty string
213
214	An empty-string component gets resolved as if the default port (4040) was
215	specified.
216
217	=item naked port numbers (e.g. C<1234>)
218
219	These are resolved by prepending the local nodename and a colon, to be
220	further resolved.
221
222	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
223
224	These are resolved by using AnyEvent::DNS to resolve them, optionally
225	looking up SRV records for the C<aemp=4040> port, if no port was
226	specified.
227
228	=back
229		272
230	=item $SELF	273	=item $SELF
231		274
232	Contains the current port id while executing C<rcv> callbacks or C<psub>	275	Contains the current port id while executing C<rcv> callbacks or C<psub>
233	blocks.	276	blocks.
234		277
235	=item SELF, %SELF, @SELF...	278	=item *SELF, SELF, %SELF, @SELF...
236		279
237	Due to some quirks in how perl exports variables, it is impossible to	280	Due to some quirks in how perl exports variables, it is impossible to
238	just export C<$SELF>, all the symbols called C<SELF> are exported by this	281	just export C<$SELF>, all the symbols named C<SELF> are exported by this
239	module, but only C<$SELF> is currently used.	282	module, but only C<$SELF> is currently used.
240		283
241	=item snd $port, type => @data	284	=item snd $port, type => @data
242		285
243	=item snd $port, @msg	286	=item snd $port, @msg
244		287
245	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
246	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.
247	stringifies a sa port ID (such as a port object :).
248		290
249	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
250	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
251	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.
252		295
253	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
254	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument (or values referenced by them) is
255	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.
256		302
257	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
258	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
259	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
260	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
261	node, anything can be passed.	307	node, anything can be passed. Best rely only on the common denominator of
		308	these.
262		309
263	=item $local_port = port	310	=item $local_port = port
264		311
265	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
266	matching port ("full port") or a single-callback port ("miniport"),	313	no callbacks set and will throw an error when it receives messages.
267	depending on how C<rcv> callbacks are bound to the object.
268		314
269	=item $port = port { my @msg = @_; $finished }	315	=item $local_port = port { my @msg = @_ }
270		316
271	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
272	matching behind it, and returns its ID. Semantically the same as creating
273	a port and calling C<rcv $port, $callback> on it.	318	creating a port and calling C<rcv $port, $callback> on it.
274		319
275	The block will be called for every message received on the port. When the	320	The block will be called for every message received on the port, with the
276	callback returns a true value its job is considered "done" and the port	321	global variable C<$SELF> set to the port ID. Runtime errors will cause the
277	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.
278		324
279	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:
280	be passed to the callback.
281		326
282	If you need the local port id in the callback, this works nicely:	327	my $port = port {
283		328	my @msg = @_;
284	my $port; $port = port {	329	...
285	snd $otherport, reply => $port;	330	kil $SELF;
286	};	331	};
287		332
288	=cut	333	=cut
289		334
290	sub rcv($@);	335	sub rcv($@);
		336
		337	sub _kilme {
		338	die "received message on port without callback";
		339	}
291		340
292	sub port(;&) {	341	sub port(;&) {
293	my $id = "$UNIQ." . $ID++;	342	my $id = "$UNIQ." . $ID++;
294	my $port = "$NODE#$id";	343	my $port = "$NODE#$id";
295		344
296	if (@_) {	345	rcv $port, shift \|\| \&_kilme;
297	rcv $port, shift;
298	} else {
299	$PORT{$id} = sub { }; # nop
300	}
301		346
302	$port	347	$port
303	}	348	}
304		349
305	=item reg $port, $name
306
307	=item reg $name
308
309	Registers the given port (or C<$SELF><<< if missing) under the name
310	C<$name>. If the name already exists it is replaced.
311
312	A port can only be registered under one well known name.
313
314	A port automatically becomes unregistered when it is killed.
315
316	=cut
317
318	sub reg(@) {
319	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
320
321	$REG{$_[0]} = $port;
322	}
323
324	=item rcv $port, $callback->(@msg)	350	=item rcv $local_port, $callback->(@msg)
325		351
326	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
327	one if required).	353	remove the default callback: use C<sub { }> to disable it, or better
328		354	C<kil> the port when it is no longer needed.
329	=item rcv $port, tagstring => $callback->(@msg), ...
330
331	=item rcv $port, $smartmatch => $callback->(@msg), ...
332
333	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
334
335	Register callbacks to be called on matching messages on the given full
336	port (after converting it to one if required) and return the port.
337
338	The callback has to return a true value when its work is done, after
339	which is will be removed, or a false value in which case it will stay
340	registered.
341		355
342	The global C<$SELF> (exported by this module) contains C<$port> while	356	The global C<$SELF> (exported by this module) contains C<$port> while
343	executing the callback.	357	executing the callback. Runtime errors during callback execution will
		358	result in the port being C<kil>ed.
344		359
345	Runtime errors wdurign callback execution will result in the port being	360	The default callback received all messages not matched by a more specific
346	C<kil>ed.	361	C<tag> match.
347		362
348	If the match is an array reference, then it will be matched against the	363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
349	first elements of the message, otherwise only the first element is being
350	matched.
351		364
352	Any element in the match that is specified as C<_any_> (a function	365	Register (or replace) callbacks to be called on messages starting with the
353	exported by this module) matches any single element of the message.	366	given tag on the given port (and return the port), or unregister it (when
		367	C<$callback> is C<$undef> or missing). There can only be one callback
		368	registered for each tag.
354		369
355	While not required, it is highly recommended that the first matching	370	The original message will be passed to the callback, after the first
356	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
357	also the most efficient match (by far).	372	environment as the default callback (see above).
358		373
359	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.
360		375
361	my $port = rcv port,	376	my $port = rcv port,
362	msg1 => sub { ...; 0 },	377	msg1 => sub { ... },
363	msg2 => sub { ...; 0 },	378	msg2 => sub { ... },
364	;	379	;
365		380
366	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
367	in one go:	382	in one go:
368		383
369	snd $otherport, reply =>	384	snd $otherport, reply =>
370	rcv port,	385	rcv port,
371	msg1 => sub { ...; 0 },	386	msg1 => sub { ... },
372	...	387	...
373	;	388	;
374		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, $otherport;
		397	};
		398
375	=cut	399	=cut
376		400
377	sub rcv($@) {	401	sub rcv($@) {
378	my $port = shift;	402	my $port = shift;
379	my ($noderef, $portid) = split /#/, $port, 2;	403	my ($nodeid, $portid) = split /#/, $port, 2;
380		404
381	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	405	$NODE{$nodeid} == $NODE{""}
382	or Carp::croak "$port: rcv can only be called on local ports, caught";	406	or Carp::croak "$port: rcv can only be called on local ports, caught";
383		407
384	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 {
385	my $cb = shift;	416	my $cb = shift;
386	delete $PORT_DATA{$portid};
387	$PORT{$portid} = sub {	417	$PORT{$portid} = sub {
388	local $SELF = $port;	418	local $SELF = $port;
389	eval {	419	eval { &$cb }; _self_die if $@;
390	&$cb	420	};
391	and kil $port;
392	};	421	}
393	_self_die if $@;	422	} elsif (defined $_[0]) {
394	};
395	} else {
396	my $self = $PORT_DATA{$portid} \|\|= do {	423	my $self = $PORT_DATA{$portid} \|\|= do {
397	my $self = bless {	424	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
398	id => $port,
399	}, "AnyEvent::MP::Port";
400		425
401	$PORT{$portid} = sub {	426	$PORT{$portid} = sub {
402	local $SELF = $port;	427	local $SELF = $port;
403		428
404	eval {
405	for (@{ $self->{rc0}{$_[0]} }) {	429	if (my $cb = $self->[1]{$_[0]}) {
406	$_ && &{$_->[0]}	430	shift;
407	&& undef $_;	431	eval { &$cb }; _self_die if $@;
408	}	432	} else {
409
410	for (@{ $self->{rcv}{$_[0]} }) {
411	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
412	&& &{$_->[0]}	433	&{ $self->[0] };
413	&& undef $_;
414	}
415
416	for (@{ $self->{any} }) {
417	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
418	&& &{$_->[0]}
419	&& undef $_;
420	}	434	}
421	};	435	};
422	_self_die if $@;	436
		437	$self
423	};	438	};
424		439
425	$self
426	};
427
428	"AnyEvent::MP::Port" eq ref $self	440	"AnyEvent::MP::Port" eq ref $self
429	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	441	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
430		442
431	while (@_) {
432	my ($match, $cb) = splice @_, 0, 2;	443	my ($tag, $cb) = splice @_, 0, 2;
433		444
434	if (!ref $match) {	445	if (defined $cb) {
435	push @{ $self->{rc0}{$match} }, [$cb];	446	$self->[1]{$tag} = $cb;
436	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
437	my ($type, @match) = @$match;
438	@match
439	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
440	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
441	} else {	447	} else {
442	push @{ $self->{any} }, [$cb, $match];	448	delete $self->[1]{$tag};
443	}	449	}
444	}	450	}
445	}	451	}
446		452
447	$port	453	$port
448	}	454	}
449		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
450	=item $closure = psub { BLOCK }	493	=item $closure = psub { BLOCK }
451		494
452	Remembers C<$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
453	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>
454	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 $SELF, sub {
		500	BLOCK } } >>.
455		501
456	This is useful when you register callbacks from C<rcv> callbacks:	502	This is useful when you register callbacks from C<rcv> callbacks:
457		503
458	rcv delayed_reply => sub {	504	rcv delayed_reply => sub {
459	my ($delay, @reply) = @_;	505	my ($delay, @reply) = @_;
…		…
483	$res	529	$res
484	}	530	}
485	}	531	}
486	}	532	}
487		533
488	=item $guard = mon $port, $cb->(@reason)	534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
489		535
490	=item $guard = mon $port, $rcvport	536	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
491		537
492	=item $guard = mon $port	538	=item $guard = mon $port # kill $SELF when $port dies
493		539
494	=item $guard = mon $port, $rcvport, @msg	540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
495		541
496	Monitor the given port and do something when the port is killed, and	542	Monitor the given port and do something when the port is killed or
497	optionally return a guard that can be used to stop monitoring again.	543	messages to it were lost, and optionally return a guard that can be used
		544	to stop monitoring again.
498		545
499	In the first form (callback), the callback is simply called with any	546	In the first form (callback), the callback is simply called with any
500	number of C<@reason> elements (no @reason means that the port was deleted	547	number of C<@reason> elements (no @reason means that the port was deleted
501	"normally"). Note also that I<< the callback B<must> never die >>, so use	548	"normally"). Note also that I<< the callback B<must> never die >>, so use
502	C<eval> if unsure.	549	C<eval> if unsure.
503		550
504	In the second form (another port given), the other port (C<$rcvport)	551	In the second form (another port given), the other port (C<$rcvport>)
505	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	552	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
506	"normal" kils nothing happens, while under all other conditions, the other	553	"normal" kils nothing happens, while under all other conditions, the other
507	port is killed with the same reason.	554	port is killed with the same reason.
508		555
509	The third form (kill self) is the same as the second form, except that	556	The third form (kill self) is the same as the second form, except that
510	C<$rvport> defaults to C<$SELF>.	557	C<$rvport> defaults to C<$SELF>.
511		558
512	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
513	C<snd>.	560	C<snd>.
		561
		562	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		563	alert was raised), they are removed and will not trigger again.
514		564
515	As a rule of thumb, monitoring requests should always monitor a port from	565	As a rule of thumb, monitoring requests should always monitor a port from
516	a local port (or callback). The reason is that kill messages might get	566	a local port (or callback). The reason is that kill messages might get
517	lost, just like any other message. Another less obvious reason is that	567	lost, just like any other message. Another less obvious reason is that
518	even monitoring requests can get lost (for exmaple, when the connection	568	even monitoring requests can get lost (for example, when the connection
519	to the other node goes down permanently). When monitoring a port locally	569	to the other node goes down permanently). When monitoring a port locally
520	these problems do not exist.	570	these problems do not exist.
521		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
522	Example: call a given callback when C<$port> is killed.	589	Example: call a given callback when C<$port> is killed.
523		590
524	mon $port, sub { warn "port died because of <@_>\n" };	591	mon $port, sub { warn "port died because of <@_>\n" };
525		592
526	Example: kill ourselves when C<$port> is killed abnormally.	593	Example: kill ourselves when C<$port> is killed abnormally.
…		…
532	mon $port, $self => "restart";	599	mon $port, $self => "restart";
533		600
534	=cut	601	=cut
535		602
536	sub mon {	603	sub mon {
537	my ($noderef, $port) = split /#/, shift, 2;	604	my ($nodeid, $port) = split /#/, shift, 2;
538		605
539	my $node = $NODE{$noderef} \|\| add_node $noderef;	606	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
540		607
541	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,';
542		609
543	unless (ref $cb) {	610	unless (ref $cb) {
544	if (@_) {	611	if (@_) {
545	# send a kill info message	612	# send a kill info message
546	my (@msg) = @_;	613	my (@msg) = ($cb, @_);
547	$cb = sub { snd @msg, @_ };	614	$cb = sub { snd @msg, @_ };
548	} else {	615	} else {
549	# simply kill other port	616	# simply kill other port
550	my $port = $cb;	617	my $port = $cb;
551	$cb = sub { kil $port, @_ if @_ };	618	$cb = sub { kil $port, @_ if @_ };
…		…
553	}	620	}
554		621
555	$node->monitor ($port, $cb);	622	$node->monitor ($port, $cb);
556		623
557	defined wantarray	624	defined wantarray
558	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
559	}	626	}
560		627
561	=item $guard = mon_guard $port, $ref, $ref...	628	=item $guard = mon_guard $port, $ref, $ref...
562		629
563	Monitors the given C<$port> and keeps the passed references. When the port	630	Monitors the given C<$port> and keeps the passed references. When the port
564	is killed, the references will be freed.	631	is killed, the references will be freed.
565		632
566	Optionally returns a guard that will stop the monitoring.	633	Optionally returns a guard that will stop the monitoring.
567		634
568	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
569	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>):
570		637
571	$port->rcv (start => sub {	638	$port->rcv (start => sub {
572	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	639	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
573	undef $timer if 0.9 < rand;	640	undef $timer if 0.9 < rand;
574	});	641	});
575	});	642	});
576		643
577	=cut	644	=cut
…		…
586		653
587	=item kil $port[, @reason]	654	=item kil $port[, @reason]
588		655
589	Kill the specified port with the given C<@reason>.	656	Kill the specified port with the given C<@reason>.
590		657
591	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" -
592	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.
593		661
594	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>
595	C<mon>, see below).	663	form) get killed with the same reason.
596		664
597	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
598	will be reported as reason C<< die => $@ >>.	666	will be reported as reason C<< die => $@ >>.
599		667
600	Transport/communication errors are reported as C<< transport_error =>	668	Transport/communication errors are reported as C<< transport_error =>
601	$message >>.	669	$message >>.
602		670
603	=back
604
605	=head1 NODE MESSAGES
606
607	Nodes understand the following messages sent to them. Many of them take
608	arguments called C<@reply>, which will simply be used to compose a reply
609	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
610	the remaining arguments are simply the message data.
611
612	While other messages exist, they are not public and subject to change.
613
614	=over 4
615
616	=cut	671	=cut
617		672
618	=item lookup => $name, @reply	673	=item $port = spawn $node, $initfunc[, @initdata]
619		674
620	Replies with the port ID of the specified well-known port, or C<undef>.	675	Creates a port on the node C<$node> (which can also be a port ID, in which
		676	case it's the node where that port resides).
621		677
622	=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.
623		680
624	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>.
625		685
626	=item relay => $port, @msg	686	If the function doesn't exist, then the node tries to C<require>
		687	the package, then the package above the package and so on (e.g.
		688	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		689	exists or it runs out of package names.
627		690
628	Simply forwards the message to the given port.	691	The init function is then called with the newly-created port as context
		692	object (C<$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.
629		695
630	=item eval => $string[ @reply]	696	A common idiom is to pass a local port, immediately monitor the spawned
		697	port, and in the remote init function, immediately monitor the passed
		698	local port. This two-way monitoring ensures that both ports get cleaned up
		699	when there is a problem.
631		700
632	Evaluates the given string. If C<@reply> is given, then a message of the	701	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
633	form C<@reply, $@, @evalres> is sent.	702	caller before C<spawn> returns (by delaying invocation when spawn is
		703	called for the local node).
634		704
635	Example: crash another node.	705	Example: spawn a chat server port on C<$othernode>.
636		706
637	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 $server;
638		710
639	=item time => @reply	711	# init function on C<$othernode>
		712	sub connect {
		713	my ($srcport) = @_;
640		714
641	Replies the the current node time to C<@reply>.	715	mon $srcport;
642		716
643	Example: tell the current node to send the current time to C<$myport> in a	717	rcv $SELF, sub {
644	C<timereply> message.	718	...
		719	};
		720	}
645		721
646	snd $NODE, time => $myport, timereply => 1, 2;	722	=cut
647	# => 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	}
648		824
649	=back	825	=back
650		826
651	=head1 AnyEvent::MP vs. Distributed Erlang	827	=head1 AnyEvent::MP vs. Distributed Erlang
652		828
653	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
654	== 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
655	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
656	sample:	832	sample:
657		833
658	http://www.Erlang.se/doc/programming_rules.shtml	834	http://www.erlang.se/doc/programming_rules.shtml
659	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
660	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
661	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
662		838
663	Despite the similarities, there are also some important differences:	839	Despite the similarities, there are also some important differences:
664		840
665	=over 4	841	=over 4
666		842
667	=item * Node references contain the recipe on how to contact them.	843	=item * Node IDs are arbitrary strings in AEMP.
668		844
669	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
670	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
671	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.
672		849
673	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
674	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.
675		864
676	=item * Erlang uses processes and a mailbox, AEMP does not queue.	865	=item * Erlang uses processes and a mailbox, AEMP does not queue.
677		866
678	Erlang uses processes that selctively receive messages, and therefore	867	Erlang uses processes that selectively receive messages, and therefore
679	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
680	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.
681		872
682	(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).
683		874
684	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
685		876
686	Sending messages in Erlang is synchronous and blocks the process. AEMP	877	Sending messages in Erlang is synchronous and blocks the process (and
687	sends are immediate, connection establishment is handled in the	878	so does not need a queue that can overflow). AEMP sends are immediate,
688	background.	879	connection establishment is handled in the background.
689		880
690	=item * Erlang can silently lose messages, AEMP cannot.	881	=item * Erlang suffers from silent message loss, AEMP does not.
691		882
692	Erlang makes few guarantees on messages delivery - messages can get lost	883	Erlang implements few guarantees on messages delivery - messages can get
693	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,
694	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).
695		886
696	AEMP guarantees correct ordering, and the guarantee that there are no	887	AEMP guarantees correct ordering, and the guarantee that after one message
697	holes in the message sequence.	888	is lost, all following ones sent to the same port are lost as well, until
698		889	monitoring raises an error, so there are no silent "holes" in the message
699	=item * In Erlang, processes can be declared dead and later be found to be	890	sequence.
700	alive.
701
702	In Erlang it can happen that a monitored process is declared dead and
703	linked processes get killed, but later it turns out that the process is
704	still alive - and can receive messages.
705
706	In AEMP, when port monitoring detects a port as dead, then that port will
707	eventually be killed - it cannot happen that a node detects a port as dead
708	and then later sends messages to it, finding it is still alive.
709		891
710	=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.
711		893
712	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
713	ID known to other nodes for a completely different process, causing	895	known to other nodes for a completely different process, causing messages
714	messages destined for that process to end up in an unrelated process.	896	destined for that process to end up in an unrelated process.
715		897
716	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
717	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.
718		900
719	=item * Erlang uses unprotected connections, AEMP uses secure	901	=item * Erlang uses unprotected connections, AEMP uses secure
720	authentication and can use TLS.	902	authentication and can use TLS.
721		903
722	AEMP can use a proven protocol - SSL/TLS - to protect connections and	904	AEMP can use a proven protocol - TLS - to protect connections and
723	securely authenticate nodes.	905	securely authenticate nodes.
724		906
725	=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
726	communications.	908	communications.
727		909
728	The AEMP protocol, unlike the Erlang protocol, supports both	910	The AEMP protocol, unlike the Erlang protocol, supports both programming
729	language-independent text-only protocols (good for debugging) and binary,	911	language independent text-only protocols (good for debugging) and binary,
730	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.
731		914
732	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
733	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
734	protocol simple.	917	protocol simple.
735		918
736	=item * AEMP has more flexible monitoring options than Erlang.	919	=item * AEMP has more flexible monitoring options than Erlang.
737		920
738	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
…		…
741	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
742	on a per-process basis.	925	on a per-process basis.
743		926
744	=item * Erlang tries to hide remote/local connections, AEMP does not.	927	=item * Erlang tries to hide remote/local connections, AEMP does not.
745		928
746	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
747	as linking is (except linking is unreliable in Erlang).	930	same way as linking is (except linking is unreliable in Erlang).
748		931
749	In AEMP, you don't "look up" registered port names or send to named ports	932	In AEMP, you don't "look up" registered port names or send to named ports
750	that might or might not be persistent. Instead, you normally spawn a port	933	that might or might not be persistent. Instead, you normally spawn a port
751	on the remote node. The init function monitors the you, and you monitor	934	on the remote node. The init function monitors you, and you monitor the
752	the remote port. Since both monitors are local to the node, they are much	935	remote port. Since both monitors are local to the node, they are much more
753	more reliable.	936	reliable (no need for C<spawn_link>).
754		937
755	This also saves round-trips and avoids sending messages to the wrong port	938	This also saves round-trips and avoids sending messages to the wrong port
756	(hard to do in Erlang).	939	(hard to do in Erlang).
757		940
758	=back	941	=back
759		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
760	=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.
761		991
762	L<AnyEvent>.	992	L<AnyEvent>.
763		993
764	=head1 AUTHOR	994	=head1 AUTHOR
765		995

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Revision 1.113 by root, Sat Apr 3 15:32:18 2010 UTC