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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.53 by root, Fri Aug 14 15:31:21 2009 UTC vs.
Revision 1.118 by root, Thu Jun 30 09:31:58 2011 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
73		78
74	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
76		82
77	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
78		84
79	A port ID is 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
80	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		87
84	=item node	88	=item node
85		89
86	A node is a single process containing at least one port - the node port,	90	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	91	which enables nodes to manage each other remotely, and to create new
88	ports.	92	ports.
89		93
90	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
92		97
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Za-z0-9_\-.:]*>
94		99
95	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
96	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
97	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.
98		104
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		106
102	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
103	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.
104		111
105	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
106	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.
107		139
108	=back	140	=back
109		141
110	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
111		143
123		155
124	use AE ();	156	use AE ();
125		157
126	use base "Exporter";	158	use base "Exporter";
127		159
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	160	our $VERSION = '1.30';
129		161
130	our @EXPORT = qw(	162	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	164	configure
133	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
134	port	166	port
135	);	167	);
136		168
137	our $SELF;	169	our $SELF;
138		170
…		…
142	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
143	}	175	}
144		176
145	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
146		178
147	The C<NODE> function returns, and the C<$NODE> variable contains the	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef of the local node. The value is initialised by a call to	180	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	181	a call to C<configure>.
150		182
151	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
152		184
153	Extracts and returns the noderef from a port ID or a noderef.	185	Extracts and returns the node ID from a port ID or a node ID.
154		186
155	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
156		188
157	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
158		190
159	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
162		195
		196	The key/value pairs are basically the same ones as documented for the
		197	F<aemp> command line utility (sans the set/del prefix).
		198
163	This function initialises a node - it must be called exactly once (or	199	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	200	never) before calling other AnyEvent::MP functions.
165		201
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	202	=over 4
178		203
179	=item public nodes	204	=item step 1, gathering configuration from profiles
180		205
181	For public nodes, C<$noderef> (supplied either directly to	206	The function first looks up a profile in the aemp configuration (see the
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	207	L<aemp> commandline utility). The profile name can be specified via the
183	noderef (possibly unresolved, in which case it will be resolved).	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.
184		210
185	After resolving, the node will bind itself on all endpoints and try to	211	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		212
190	=item slave nodes	213	First, all remaining key => value pairs (all of which are conveniently
		214	undocumented at the moment) will be interpreted as configuration
		215	data. Then they will be overwritten by any values specified in the global
		216	default configuration (see the F<aemp> utility), then the chain of
		217	profiles chosen by the profile name (and any C<parent> attributes).
191		218
192	When the C<$noderef> (either as given or overriden by the config file)	219	That means that the values specified in the profile have highest priority
193	is the special string C<slave/>, then the node will become a slave	220	and the values specified directly via C<configure> have lowest priority,
194	node. Slave nodes cannot be contacted from outside and will route most of	221	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		222
197	At least one additional noderef is required (either by specifying it	223	If the profile specifies a node ID, then this will become the node ID of
198	directly or because it is part of the configuration profile): The node	224	this process. If not, then the profile name will be used as node ID. The
199	will try to connect to all of them and will become a slave attached to the	225	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.	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.
201		244
202	=back	245	=back
203		246
204	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.
205	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.
206	server.
207		249
208	Example: become a public node listening on the guessed noderef, or the one	250	configure
209	specified via C<aemp> for the current node. This should be the most common
210	form of invocation for "daemon"-type nodes.
211		251
212	initialise_node;	252	Example: become an anonymous node. This form is often used for commandline
		253	clients.
213		254
214	Example: become a slave node to any of the the seednodes specified via	255	configure nodeid => "anon/";
215	C<aemp>. This form is often used for commandline clients.
216		256
217	initialise_node "slave/";	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).
218		260
219	Example: become a slave node to any of the specified master servers. This	261	# use the aemp commandline utility
220	form is also often used for commandline clients.	262	# aemp profile seed nodeid anon/ binds '*:4040'
221		263
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	264	# then use it
		265	configure profile => "seed";
223		266
224	Example: become a public node, and try to contact some well-known master	267	# or simply use aemp from the shell again:
225	servers to become part of the network.	268	# aemp run profile seed
226		269
227	initialise_node undef, "master1", "master2";	270	# or provide a nicer-to-remember nodeid
228		271	# aemp run profile seed nodeid "$(hostname)"
229	Example: become a public node listening on port C<4041>.
230
231	initialise_node 4041;
232
233	Example: become a public node, only visible on localhost port 4044.
234
235	initialise_node "localhost:4044";
236
237	=item $cv = resolve_node $noderef
238
239	Takes an unresolved node reference that may contain hostnames and
240	abbreviated IDs, resolves all of them and returns a resolved node
241	reference.
242
243	In addition to C<address:port> pairs allowed in resolved noderefs, the
244	following forms are supported:
245
246	=over 4
247
248	=item the empty string
249
250	An empty-string component gets resolved as if the default port (4040) was
251	specified.
252
253	=item naked port numbers (e.g. C<1234>)
254
255	These are resolved by prepending the local nodename and a colon, to be
256	further resolved.
257
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
259
260	These are resolved by using AnyEvent::DNS to resolve them, optionally
261	looking up SRV records for the C<aemp=4040> port, if no port was
262	specified.
263
264	=back
265		272
266	=item $SELF	273	=item $SELF
267		274
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	275	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	276	blocks.
270		277
271	=item SELF, %SELF, @SELF...	278	=item *SELF, SELF, %SELF, @SELF...
272		279
273	Due to some quirks in how perl exports variables, it is impossible to	280	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	281	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	282	module, but only C<$SELF> is currently used.
276		283
277	=item snd $port, type => @data	284	=item snd $port, type => @data
278		285
279	=item snd $port, @msg	286	=item snd $port, @msg
280		287
281	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
282	a local or a remote port, and must be a port ID.	289	local or a remote port, and must be a port ID.
283		290
284	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
285	string as first element (a port ID, or some word that indicates a request	292	use a string as first element (a port ID, or some word that indicates a
286	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.
287		295
288	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
289	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument (or values referenced by them) is
290	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.
291		302
292	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
293	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
294	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
295	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
296	node, anything can be passed.	307	node, anything can be passed. Best rely only on the common denominator of
		308	these.
297		309
298	=item $local_port = port	310	=item $local_port = port
299		311
300	Create a new local port object and returns its port ID. Initially it has	312	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	313	no callbacks set and will throw an error when it receives messages.
…		…
348	The default callback received all messages not matched by a more specific	360	The default callback received all messages not matched by a more specific
349	C<tag> match.	361	C<tag> match.
350		362
351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352		364
353	Register callbacks to be called on messages starting with the given tag on	365	Register (or replace) callbacks to be called on messages starting with the
354	the given port (and return the port), or unregister it (when C<$callback>	366	given tag on the given port (and return the port), or unregister it (when
355	is C<$undef>).	367	C<$callback> is C<$undef> or missing). There can only be one callback
		368	registered for each tag.
356		369
357	The original message will be passed to the callback, after the first	370	The original message will be passed to the callback, after the first
358	element (the tag) has been removed. The callback will use the same	371	element (the tag) has been removed. The callback will use the same
359	environment as the default callback (see above).	372	environment as the default callback (see above).
360		373
…		…
372	rcv port,	385	rcv port,
373	msg1 => sub { ... },	386	msg1 => sub { ... },
374	...	387	...
375	;	388	;
376		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, $otherport;
		397	};
		398
377	=cut	399	=cut
378		400
379	sub rcv($@) {	401	sub rcv($@) {
380	my $port = shift;	402	my $port = shift;
381	my ($noderef, $portid) = split /#/, $port, 2;	403	my ($nodeid, $portid) = split /#/, $port, 2;
382		404
383	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	405	$NODE{$nodeid} == $NODE{""}
384	or Carp::croak "$port: rcv can only be called on local ports, caught";	406	or Carp::croak "$port: rcv can only be called on local ports, caught";
385		407
386	while (@_) {	408	while (@_) {
387	if (ref $_[0]) {	409	if (ref $_[0]) {
388	if (my $self = $PORT_DATA{$portid}) {	410	if (my $self = $PORT_DATA{$portid}) {
389	"AnyEvent::MP::Port" eq ref $self	411	"AnyEvent::MP::Port" eq ref $self
390	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	412	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
391		413
392	$self->[2] = shift;	414	$self->[0] = shift;
393	} else {	415	} else {
394	my $cb = shift;	416	my $cb = shift;
395	$PORT{$portid} = sub {	417	$PORT{$portid} = sub {
396	local $SELF = $port;	418	local $SELF = $port;
397	eval { &$cb }; _self_die if $@;	419	eval { &$cb }; _self_die if $@;
398	};	420	};
399	}	421	}
400	} elsif (defined $_[0]) {	422	} elsif (defined $_[0]) {
401	my $self = $PORT_DATA{$portid} \|\|= do {	423	my $self = $PORT_DATA{$portid} \|\|= do {
402	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	424	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
403		425
404	$PORT{$portid} = sub {	426	$PORT{$portid} = sub {
405	local $SELF = $port;	427	local $SELF = $port;
406		428
407	if (my $cb = $self->[1]{$_[0]}) {	429	if (my $cb = $self->[1]{$_[0]}) {
…		…
429	}	451	}
430		452
431	$port	453	$port
432	}	454	}
433		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
434	=item $closure = psub { BLOCK }	493	=item $closure = psub { BLOCK }
435		494
436	Remembers C<$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
437	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>
438	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 $SELF, sub {
		500	BLOCK }, @_ } >>.
439		501
440	This is useful when you register callbacks from C<rcv> callbacks:	502	This is useful when you register callbacks from C<rcv> callbacks:
441		503
442	rcv delayed_reply => sub {	504	rcv delayed_reply => sub {
443	my ($delay, @reply) = @_;	505	my ($delay, @reply) = @_;
…		…
467	$res	529	$res
468	}	530	}
469	}	531	}
470	}	532	}
471		533
472	=item $guard = mon $port, $cb->(@reason)	534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
473		535
474	=item $guard = mon $port, $rcvport	536	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
475		537
476	=item $guard = mon $port	538	=item $guard = mon $port # kill $SELF when $port dies
477		539
478	=item $guard = mon $port, $rcvport, @msg	540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
479		541
480	Monitor the given port and do something when the port is killed or	542	Monitor the given port and do something when the port is killed or
481	messages to it were lost, and optionally return a guard that can be used	543	messages to it were lost, and optionally return a guard that can be used
482	to stop monitoring again.	544	to stop monitoring again.
483
484	C<mon> effectively guarantees that, in the absence of hardware failures,
485	that after starting the monitor, either all messages sent to the port
486	will arrive, or the monitoring action will be invoked after possible
487	message loss has been detected. No messages will be lost "in between"
488	(after the first lost message no further messages will be received by the
489	port). After the monitoring action was invoked, further messages might get
490	delivered again.
491		545
492	In the first form (callback), the callback is simply called with any	546	In the first form (callback), the callback is simply called with any
493	number of C<@reason> elements (no @reason means that the port was deleted	547	number of C<@reason> elements (no @reason means that the port was deleted
494	"normally"). Note also that I<< the callback B<must> never die >>, so use	548	"normally"). Note also that I<< the callback B<must> never die >>, so use
495	C<eval> if unsure.	549	C<eval> if unsure.
496		550
497	In the second form (another port given), the other port (C<$rcvport>)	551	In the second form (another port given), the other port (C<$rcvport>)
498	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	552	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
499	"normal" kils nothing happens, while under all other conditions, the other	553	"normal" kils nothing happens, while under all other conditions, the other
500	port is killed with the same reason.	554	port is killed with the same reason.
501		555
502	The third form (kill self) is the same as the second form, except that	556	The third form (kill self) is the same as the second form, except that
503	C<$rvport> defaults to C<$SELF>.	557	C<$rvport> defaults to C<$SELF>.
504		558
505	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
506	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.
507		564
508	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
509	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
510	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
511	even monitoring requests can get lost (for exmaple, when the connection	568	even monitoring requests can get lost (for example, when the connection
512	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
513	these problems do not exist.	570	these problems do not exist.
514		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
515	Example: call a given callback when C<$port> is killed.	589	Example: call a given callback when C<$port> is killed.
516		590
517	mon $port, sub { warn "port died because of <@_>\n" };	591	mon $port, sub { warn "port died because of <@_>\n" };
518		592
519	Example: kill ourselves when C<$port> is killed abnormally.	593	Example: kill ourselves when C<$port> is killed abnormally.
…		…
525	mon $port, $self => "restart";	599	mon $port, $self => "restart";
526		600
527	=cut	601	=cut
528		602
529	sub mon {	603	sub mon {
530	my ($noderef, $port) = split /#/, shift, 2;	604	my ($nodeid, $port) = split /#/, shift, 2;
531		605
532	my $node = $NODE{$noderef} \|\| add_node $noderef;	606	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
533		607
534	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	608	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
535		609
536	unless (ref $cb) {	610	unless (ref $cb) {
537	if (@_) {	611	if (@_) {
…		…
546	}	620	}
547		621
548	$node->monitor ($port, $cb);	622	$node->monitor ($port, $cb);
549		623
550	defined wantarray	624	defined wantarray
551	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
552	}	626	}
553		627
554	=item $guard = mon_guard $port, $ref, $ref...	628	=item $guard = mon_guard $port, $ref, $ref...
555		629
556	Monitors the given C<$port> and keeps the passed references. When the port	630	Monitors the given C<$port> and keeps the passed references. When the port
557	is killed, the references will be freed.	631	is killed, the references will be freed.
558		632
559	Optionally returns a guard that will stop the monitoring.	633	Optionally returns a guard that will stop the monitoring.
560		634
561	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
562	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>):
563		637
564	$port->rcv (start => sub {	638	$port->rcv (start => sub {
565	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	639	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
566	undef $timer if 0.9 < rand;	640	undef $timer if 0.9 < rand;
567	});	641	});
568	});	642	});
569		643
570	=cut	644	=cut
…		…
579		653
580	=item kil $port[, @reason]	654	=item kil $port[, @reason]
581		655
582	Kill the specified port with the given C<@reason>.	656	Kill the specified port with the given C<@reason>.
583		657
584	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" -
585	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.
586		661
587	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>
588	C<mon>, see below).	663	form) get killed with the same reason.
589		664
590	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
591	will be reported as reason C<< die => $@ >>.	666	will be reported as reason C<< die => $@ >>.
592		667
593	Transport/communication errors are reported as C<< transport_error =>	668	Transport/communication errors are reported as C<< transport_error =>
…		…
598	=item $port = spawn $node, $initfunc[, @initdata]	673	=item $port = spawn $node, $initfunc[, @initdata]
599		674
600	Creates a port on the node C<$node> (which can also be a port ID, in which	675	Creates a port on the node C<$node> (which can also be a port ID, in which
601	case it's the node where that port resides).	676	case it's the node where that port resides).
602		677
603	The port ID of the newly created port is return immediately, and it is	678	The port ID of the newly created port is returned immediately, and it is
604	permissible to immediately start sending messages or monitor the port.	679	possible to immediately start sending messages or to monitor the port.
605		680
606	After the port has been created, the init function is	681	After the port has been created, the init function is called on the remote
607	called. This function must be a fully-qualified function name	682	node, in the same context as a C<rcv> callback. This function must be a
608	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	683	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
609	program, use C<::name>.	684	specify a function in the main program, use C<::name>.
610		685
611	If the function doesn't exist, then the node tries to C<require>	686	If the function doesn't exist, then the node tries to C<require>
612	the package, then the package above the package and so on (e.g.	687	the package, then the package above the package and so on (e.g.
613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	688	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
614	exists or it runs out of package names.	689	exists or it runs out of package names.
615		690
616	The init function is then called with the newly-created port as context	691	The init function is then called with the newly-created port as context
617	object (C<$SELF>) and the C<@initdata> values as arguments.	692	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		693	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		694	the port might not get created.
618		695
619	A common idiom is to pass your own port, monitor the spawned port, and	696	A common idiom is to pass a local port, immediately monitor the spawned
620	in the init function, monitor the original port. This two-way monitoring	697	port, and in the remote init function, immediately monitor the passed
621	ensures that both ports get cleaned up when there is a problem.	698	local port. This two-way monitoring ensures that both ports get cleaned up
		699	when there is a problem.
		700
		701	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		702	caller before C<spawn> returns (by delaying invocation when spawn is
		703	called for the local node).
622		704
623	Example: spawn a chat server port on C<$othernode>.	705	Example: spawn a chat server port on C<$othernode>.
624		706
625	# this node, executed from within a port context:	707	# this node, executed from within a port context:
626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	708	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
641		723
642	sub _spawn {	724	sub _spawn {
643	my $port = shift;	725	my $port = shift;
644	my $init = shift;	726	my $init = shift;
645		727
		728	# rcv will create the actual port
646	local $SELF = "$NODE#$port";	729	local $SELF = "$NODE#$port";
647	eval {	730	eval {
648	&{ load_func $init }	731	&{ load_func $init }
649	};	732	};
650	_self_die if $@;	733	_self_die if $@;
651	}	734	}
652		735
653	sub spawn(@) {	736	sub spawn(@) {
654	my ($noderef, undef) = split /#/, shift, 2;	737	my ($nodeid, undef) = split /#/, shift, 2;
655		738
656	my $id = "$RUNIQ." . $ID++;	739	my $id = "$RUNIQ." . $ID++;
657		740
658	$_[0] =~ /::/	741	$_[0] =~ /::/
659	or Carp::croak "spawn init function must be a fully-qualified name, caught";	742	or Carp::croak "spawn init function must be a fully-qualified name, caught";
660		743
661	($NODE{$noderef} \|\| add_node $noderef)	744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
662	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
663		745
664	"$noderef#$id"	746	"$nodeid#$id"
665	}	747	}
666		748
667	=back	749	=item after $timeout, @msg
668		750
669	=head1 NODE MESSAGES	751	=item after $timeout, $callback
670		752
671	Nodes understand the following messages sent to them. Many of them take	753	Either sends the given message, or call the given callback, after the
672	arguments called C<@reply>, which will simply be used to compose a reply	754	specified number of seconds.
673	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
674	the remaining arguments are simply the message data.
675		755
676	While other messages exist, they are not public and subject to change.	756	This is simply a utility function that comes in handy at times - the
		757	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		758	so it may go away in the future.
677		759
678	=over 4
679
680	=cut	760	=cut
681		761
682	=item lookup => $name, @reply	762	sub after($@) {
		763	my ($timeout, @action) = @_;
683		764
684	Replies with the port ID of the specified well-known port, or C<undef>.	765	my $t; $t = AE::timer $timeout, 0, sub {
		766	undef $t;
		767	ref $action[0]
		768	? $action[0]()
		769	: snd @action;
		770	};
		771	}
685		772
686	=item devnull => ...	773	=item cal $port, @msg, $callback[, $timeout]
687		774
688	Generic data sink/CPU heat conversion.	775	A simple form of RPC - sends a message to the given C<$port> with the
		776	given contents (C<@msg>), but adds a reply port to the message.
689		777
690	=item relay => $port, @msg	778	The reply port is created temporarily just for the purpose of receiving
		779	the reply, and will be C<kil>ed when no longer needed.
691		780
692	Simply forwards the message to the given port.	781	A reply message sent to the port is passed to the C<$callback> as-is.
693		782
694	=item eval => $string[ @reply]	783	If an optional time-out (in seconds) is given and it is not C<undef>,
		784	then the callback will be called without any arguments after the time-out
		785	elapsed and the port is C<kil>ed.
695		786
696	Evaluates the given string. If C<@reply> is given, then a message of the	787	If no time-out is given (or it is C<undef>), then the local port will
697	form C<@reply, $@, @evalres> is sent.	788	monitor the remote port instead, so it eventually gets cleaned-up.
698		789
699	Example: crash another node.	790	Currently this function returns the temporary port, but this "feature"
		791	might go in future versions unless you can make a convincing case that
		792	this is indeed useful for something.
700		793
701	snd $othernode, eval => "exit";	794	=cut
702		795
703	=item time => @reply	796	sub cal(@) {
		797	my $timeout = ref $_[-1] ? undef : pop;
		798	my $cb = pop;
704		799
705	Replies the the current node time to C<@reply>.	800	my $port = port {
		801	undef $timeout;
		802	kil $SELF;
		803	&$cb;
		804	};
706		805
707	Example: tell the current node to send the current time to C<$myport> in a	806	if (defined $timeout) {
708	C<timereply> message.	807	$timeout = AE::timer $timeout, 0, sub {
		808	undef $timeout;
		809	kil $port;
		810	$cb->();
		811	};
		812	} else {
		813	mon $_[0], sub {
		814	kil $port;
		815	$cb->();
		816	};
		817	}
709		818
710	snd $NODE, time => $myport, timereply => 1, 2;	819	push @_, $port;
711	# => snd $myport, timereply => 1, 2, <time>	820	&snd;
		821
		822	$port
		823	}
712		824
713	=back	825	=back
714		826
715	=head1 AnyEvent::MP vs. Distributed Erlang	827	=head1 AnyEvent::MP vs. Distributed Erlang
716		828
717	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
718	== 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
719	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
720	sample:	832	sample:
721		833
722	http://www.Erlang.se/doc/programming_rules.shtml	834	http://www.erlang.se/doc/programming_rules.shtml
723	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
724	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
725	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
726		838
727	Despite the similarities, there are also some important differences:	839	Despite the similarities, there are also some important differences:
728		840
729	=over 4	841	=over 4
730		842
731	=item * Node references contain the recipe on how to contact them.	843	=item * Node IDs are arbitrary strings in AEMP.
732		844
733	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
734	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
735	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.
736		849
737	This means that AEMP requires a less tightly controlled environment at the
738	cost of longer node references and a slightly higher management overhead.
739
740	=item Erlang has a "remote ports are like local ports" philosophy, AEMP	850	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	uses "local ports are like remote ports".	851	uses "local ports are like remote ports".
742		852
743	The failure modes for local ports are quite different (runtime errors	853	The failure modes for local ports are quite different (runtime errors
744	only) then for remote ports - when a local port dies, you I<know> it dies,	854	only) then for remote ports - when a local port dies, you I<know> it dies,
745	when a connection to another node dies, you know nothing about the other	855	when a connection to another node dies, you know nothing about the other
…		…
756		866
757	Erlang uses processes that selectively receive messages, and therefore	867	Erlang uses processes that selectively receive messages, and therefore
758	needs a queue. AEMP is event based, queuing messages would serve no	868	needs a queue. AEMP is event based, queuing messages would serve no
759	useful purpose. For the same reason the pattern-matching abilities of	869	useful purpose. For the same reason the pattern-matching abilities of
760	AnyEvent::MP are more limited, as there is little need to be able to	870	AnyEvent::MP are more limited, as there is little need to be able to
761	filter messages without dequeing them.	871	filter messages without dequeuing them.
762		872
763	(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).
764		874
765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
766		876
…		…
768	so does not need a queue that can overflow). AEMP sends are immediate,	878	so does not need a queue that can overflow). AEMP sends are immediate,
769	connection establishment is handled in the background.	879	connection establishment is handled in the background.
770		880
771	=item * Erlang suffers from silent message loss, AEMP does not.	881	=item * Erlang suffers from silent message loss, AEMP does not.
772		882
773	Erlang makes few guarantees on messages delivery - messages can get lost	883	Erlang implements few guarantees on messages delivery - messages can get
774	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,
775	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).
776		886
777	AEMP guarantees correct ordering, and the guarantee that there are no	887	AEMP guarantees (modulo hardware errors) correct ordering, and the
		888	guarantee that after one message is lost, all following ones sent to the
		889	same port are lost as well, until monitoring raises an error, so there are
778	holes in the message sequence.	890	no silent "holes" in the message sequence.
779
780	=item * In Erlang, processes can be declared dead and later be found to be
781	alive.
782
783	In Erlang it can happen that a monitored process is declared dead and
784	linked processes get killed, but later it turns out that the process is
785	still alive - and can receive messages.
786
787	In AEMP, when port monitoring detects a port as dead, then that port will
788	eventually be killed - it cannot happen that a node detects a port as dead
789	and then later sends messages to it, finding it is still alive.
790		891
791	=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.
792		893
793	In Erlang it is quite likely that a node that restarts reuses a process ID	894	In Erlang it is quite likely that a node that restarts reuses a process ID
794	known to other nodes for a completely different process, causing messages	895	known to other nodes for a completely different process, causing messages
…		…
798	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.
799		900
800	=item * Erlang uses unprotected connections, AEMP uses secure	901	=item * Erlang uses unprotected connections, AEMP uses secure
801	authentication and can use TLS.	902	authentication and can use TLS.
802		903
803	AEMP can use a proven protocol - SSL/TLS - to protect connections and	904	AEMP can use a proven protocol - TLS - to protect connections and
804	securely authenticate nodes.	905	securely authenticate nodes.
805		906
806	=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
807	communications.	908	communications.
808		909
809	The AEMP protocol, unlike the Erlang protocol, supports both	910	The AEMP protocol, unlike the Erlang protocol, supports both programming
810	language-independent text-only protocols (good for debugging) and binary,	911	language independent text-only protocols (good for debugging) and binary,
811	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.
812		914
813	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
814	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
815	protocol simple.	917	protocol simple.
816		918
817	=item * AEMP has more flexible monitoring options than Erlang.	919	=item * AEMP has more flexible monitoring options than Erlang.
818		920
819	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
…		…
822	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
823	on a per-process basis.	925	on a per-process basis.
824		926
825	=item * Erlang tries to hide remote/local connections, AEMP does not.	927	=item * Erlang tries to hide remote/local connections, AEMP does not.
826		928
827	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
828	as linking is (except linking is unreliable in Erlang).	930	same way as linking is (except linking is unreliable in Erlang).
829		931
830	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
831	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
832	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
833	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
834	more reliable.	936	reliable (no need for C<spawn_link>).
835		937
836	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
837	(hard to do in Erlang).	939	(hard to do in Erlang).
838		940
839	=back	941	=back
840		942
841	=head1 RATIONALE	943	=head1 RATIONALE
842		944
843	=over 4	945	=over 4
844		946
845	=item Why strings for ports and noderefs, why not objects?	947	=item Why strings for port and node IDs, why not objects?
846		948
847	We considered "objects", but found that the actual number of methods	949	We considered "objects", but found that the actual number of methods
848	thatc an be called are very low. Since port IDs and noderefs travel over	950	that can be called are quite low. Since port and node IDs travel over
849	the network frequently, the serialising/deserialising would add lots of	951	the network frequently, the serialising/deserialising would add lots of
850	overhead, as well as having to keep a proxy object.	952	overhead, as well as having to keep a proxy object everywhere.
851		953
852	Strings can easily be printed, easily serialised etc. and need no special	954	Strings can easily be printed, easily serialised etc. and need no special
853	procedures to be "valid".	955	procedures to be "valid".
854		956
855	And a a miniport consists of a single closure stored in a global hash - it	957	And as a result, a port with just a default receiver consists of a single
856	can't become much cheaper.	958	code reference stored in a global hash - it can't become much cheaper.
857		959
858	=item Why favour JSON, why not real serialising format such as Storable?	960	=item Why favour JSON, why not a real serialising format such as Storable?
859		961
860	In fact, any AnyEvent::MP node will happily accept Storable as framing	962	In fact, any AnyEvent::MP node will happily accept Storable as framing
861	format, but currently there is no way to make a node use Storable by	963	format, but currently there is no way to make a node use Storable by
862	default.	964	default (although all nodes will accept it).
863		965
864	The default framing protocol is JSON because a) JSON::XS is many times	966	The default framing protocol is JSON because a) JSON::XS is many times
865	faster for small messages and b) most importantly, after years of	967	faster for small messages and b) most importantly, after years of
866	experience we found that object serialisation is causing more problems	968	experience we found that object serialisation is causing more problems
867	than it gains: Just like function calls, objects simply do not travel	969	than it solves: Just like function calls, objects simply do not travel
868	easily over the network, mostly because they will always be a copy, so you	970	easily over the network, mostly because they will always be a copy, so you
869	always have to re-think your design.	971	always have to re-think your design.
870		972
871	Keeping your messages simple, concentrating on data structures rather than	973	Keeping your messages simple, concentrating on data structures rather than
872	objects, will keep your messages clean, tidy and efficient.	974	objects, will keep your messages clean, tidy and efficient.
873		975
874	=back	976	=back
875		977
876	=head1 SEE ALSO	978	=head1 SEE ALSO
877		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.
		991
878	L<AnyEvent>.	992	L<AnyEvent>.
879		993
880	=head1 AUTHOR	994	=head1 AUTHOR
881		995
882	Marc Lehmann <schmorp@schmorp.de>	996	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.53 by root, Fri Aug 14 15:31:21 2009 UTC vs.
Revision 1.118 by root, Thu Jun 30 09:31:58 2011 UTC