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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.112 by root, Thu Apr 1 19:24:22 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
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 $somple_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 prot 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	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
75	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	81	anything was listening for them or not.
77		82
78	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
79		84
80	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
81	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
82	exception is the the node port, whose ID is identical to its node
83	reference.
84		87
85	=item node	88	=item node
86		89
87	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,
88	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
89	create new ports, among other things.	92	ports.
90		93
91	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
93		97
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
95		99
96	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
97	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
98	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.
99		104
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		106
103	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
104	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.
105		111
106	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
107	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.
108		139
109	=back	140	=back
110		141
111	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
112		143
124		155
125	use AE ();	156	use AE ();
126		157
127	use base "Exporter";	158	use base "Exporter";
128		159
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	160	our $VERSION = 1.28;
130		161
131	our @EXPORT = qw(	162	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	164	configure
134	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
135	port	166	port
136	);	167	);
137		168
138	our $SELF;	169	our $SELF;
139		170
…		…
143	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
144	}	175	}
145		176
146	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
147		178
148	The C<NODE> function returns, and the C<$NODE> variable contains the	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	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
150	C<initialise_node>.	181	a call to C<configure>.
151		182
152	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
153		184
154	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.
155		186
156	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
157		188
158	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
159		190
160	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
161	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
162	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
163		195
		196	The key/value pairs are basically the same ones as documented for the
		197	F<aemp> command line utility (sans the set/del prefix).
		198
164	This function initialises a node - it must be called exactly once (or	199	This function configures a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	200	never) before calling other AnyEvent::MP functions.
166		201
167	All arguments (optionally except for the first) are noderefs, which can be
168	either resolved or unresolved.
169
170	The first argument will be looked up in the configuration database first
171	(if it is C<undef> then the current nodename will be used instead) to find
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175
176	There are two types of networked nodes, public nodes and slave nodes:
177
178	=over 4	202	=over 4
179		203
180	=item public nodes	204	=item step 1, gathering configuration from profiles
181		205
182	For public nodes, C<$noderef> (supplied either directly to	206	The function first looks up a profile in the aemp configuration (see the
183	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
184	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.
185		210
186	After resolving, the node will bind itself on all endpoints and try to	211	The profile data is then gathered as follows:
187	connect to all additional C<$seednodes> that are specified. Seednodes are
188	optional and can be used to quickly bootstrap the node into an existing
189	network.
190		212
191	=item slave nodes	213	First, all remaining key => value pairs (all of which are conveniently
		214	undocumented at the moment) will be interpreted as configuration
		215	data. Then they will be overwritten by any values specified in the global
		216	default configuration (see the F<aemp> utility), then the chain of
		217	profiles chosen by the profile name (and any C<parent> attributes).
192		218
193	When the C<$noderef> (either as given or overriden by the config file)	219	That means that the values specified in the profile have highest priority
194	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,
195	node. Slave nodes cannot be contacted from outside and will route most of	221	and can only be used to specify defaults.
196	their traffic to the master node that they attach to.
197		222
198	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
199	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
200	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.
201	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.
202		244
203	=back	245	=back
204		246
205	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.
206	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.
207	server.
208		249
209	Example: become a public node listening on the guessed noderef, or the one	250	configure
210	specified via C<aemp> for the current node. This should be the most common
211	form of invocation for "daemon"-type nodes.
212		251
213	initialise_node;	252	Example: become an anonymous node. This form is often used for commandline
		253	clients.
214		254
215	Example: become a slave node to any of the the seednodes specified via	255	configure nodeid => "anon/";
216	C<aemp>. This form is often used for commandline clients.
217		256
218	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).
219		260
220	Example: become a slave node to any of the specified master servers. This	261	# use the aemp commandline utility
221	form is also often used for commandline clients.	262	# aemp profile seed nodeid anon/ binds '*:4040'
222		263
223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	264	# then use it
		265	configure profile => "seed";
224		266
225	Example: become a public node, and try to contact some well-known master	267	# or simply use aemp from the shell again:
226	servers to become part of the network.	268	# aemp run profile seed
227		269
228	initialise_node undef, "master1", "master2";	270	# or provide a nicer-to-remember nodeid
229		271	# aemp run profile seed nodeid "$(hostname)"
230	Example: become a public node listening on port C<4041>.
231
232	initialise_node 4041;
233
234	Example: become a public node, only visible on localhost port 4044.
235
236	initialise_node "localhost:4044";
237
238	=item $cv = resolve_node $noderef
239
240	Takes an unresolved node reference that may contain hostnames and
241	abbreviated IDs, resolves all of them and returns a resolved node
242	reference.
243
244	In addition to C<address:port> pairs allowed in resolved noderefs, the
245	following forms are supported:
246
247	=over 4
248
249	=item the empty string
250
251	An empty-string component gets resolved as if the default port (4040) was
252	specified.
253
254	=item naked port numbers (e.g. C<1234>)
255
256	These are resolved by prepending the local nodename and a colon, to be
257	further resolved.
258
259	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
260
261	These are resolved by using AnyEvent::DNS to resolve them, optionally
262	looking up SRV records for the C<aemp=4040> port, if no port was
263	specified.
264
265	=back
266		272
267	=item $SELF	273	=item $SELF
268		274
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	275	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	276	blocks.
271		277
272	=item SELF, %SELF, @SELF...	278	=item *SELF, SELF, %SELF, @SELF...
273		279
274	Due to some quirks in how perl exports variables, it is impossible to	280	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	281	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	282	module, but only C<$SELF> is currently used.
277		283
278	=item snd $port, type => @data	284	=item snd $port, type => @data
279		285
280	=item snd $port, @msg	286	=item snd $port, @msg
281		287
282	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
283	a local or a remote port, and must be a port ID.	289	local or a remote port, and must be a port ID.
284		290
285	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
286	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
287	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.
288		295
289	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
290	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument (or values referenced by them) is
291	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.
292		302
293	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
294	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
295	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
296	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
297	node, anything can be passed.	307	node, anything can be passed. Best rely only on the common denominator of
		308	these.
298		309
299	=item $local_port = port	310	=item $local_port = port
300		311
301	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
302	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.
…		…
349	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
350	C<tag> match.	361	C<tag> match.
351		362
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		364
354	Register callbacks to be called on messages starting with the given tag on	365	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	366	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	367	C<$callback> is C<$undef> or missing). There can only be one callback
		368	registered for each tag.
357		369
358	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
359	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
360	environment as the default callback (see above).	372	environment as the default callback (see above).
361		373
…		…
373	rcv port,	385	rcv port,
374	msg1 => sub { ... },	386	msg1 => sub { ... },
375	...	387	...
376	;	388	;
377		389
		390	Example: temporarily register a rcv callback for a tag matching some port
		391	(e.g. for an rpc reply) and unregister it after a message was received.
		392
		393	rcv $port, $otherport => sub {
		394	my @reply = @_;
		395
		396	rcv $SELF, $otherport;
		397	};
		398
378	=cut	399	=cut
379		400
380	sub rcv($@) {	401	sub rcv($@) {
381	my $port = shift;	402	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	403	my ($nodeid, $portid) = split /#/, $port, 2;
383		404
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	405	$NODE{$nodeid} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	406	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		407
387	while (@_) {	408	while (@_) {
388	if (ref $_[0]) {	409	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	410	if (my $self = $PORT_DATA{$portid}) {
390	"AnyEvent::MP::Port" eq ref $self	411	"AnyEvent::MP::Port" eq ref $self
391	or Carp::croak "$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";
392		413
393	$self->[2] = shift;	414	$self->[0] = shift;
394	} else {	415	} else {
395	my $cb = shift;	416	my $cb = shift;
396	$PORT{$portid} = sub {	417	$PORT{$portid} = sub {
397	local $SELF = $port;	418	local $SELF = $port;
398	eval { &$cb }; _self_die if $@;	419	eval { &$cb }; _self_die if $@;
399	};	420	};
400	}	421	}
401	} elsif (defined $_[0]) {	422	} elsif (defined $_[0]) {
402	my $self = $PORT_DATA{$portid} \|\|= do {	423	my $self = $PORT_DATA{$portid} \|\|= do {
403	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	424	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
404		425
405	$PORT{$portid} = sub {	426	$PORT{$portid} = sub {
406	local $SELF = $port;	427	local $SELF = $port;
407		428
408	if (my $cb = $self->[1]{$_[0]}) {	429	if (my $cb = $self->[1]{$_[0]}) {
…		…
430	}	451	}
431		452
432	$port	453	$port
433	}	454	}
434		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
435	=item $closure = psub { BLOCK }	493	=item $closure = psub { BLOCK }
436		494
437	Remembers C<$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
438	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>
439	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 $SELF, sub {
		500	BLOCK } } >>.
440		501
441	This is useful when you register callbacks from C<rcv> callbacks:	502	This is useful when you register callbacks from C<rcv> callbacks:
442		503
443	rcv delayed_reply => sub {	504	rcv delayed_reply => sub {
444	my ($delay, @reply) = @_;	505	my ($delay, @reply) = @_;
…		…
468	$res	529	$res
469	}	530	}
470	}	531	}
471	}	532	}
472		533
473	=item $guard = mon $port, $cb->(@reason)	534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474		535
475	=item $guard = mon $port, $rcvport	536	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476		537
477	=item $guard = mon $port	538	=item $guard = mon $port # kill $SELF when $port dies
478		539
479	=item $guard = mon $port, $rcvport, @msg	540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		541
481	Monitor the given port and do something when the port is killed or	542	Monitor the given port and do something when the port is killed or
482	messages to it were lost, and optionally return a guard that can be used	543	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	544	to stop monitoring again.
484
485	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port
487	will arrive, or the monitoring action will be invoked after possible
488	message loss has been detected. No messages will be lost "in between"
489	(after the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get
491	delivered again.
492		545
493	In the first form (callback), the callback is simply called with any	546	In the first form (callback), the callback is simply called with any
494	number of C<@reason> elements (no @reason means that the port was deleted	547	number of C<@reason> elements (no @reason means that the port was deleted
495	"normally"). Note also that I<< the callback B<must> never die >>, so use	548	"normally"). Note also that I<< the callback B<must> never die >>, so use
496	C<eval> if unsure.	549	C<eval> if unsure.
497		550
498	In the second form (another port given), the other port (C<$rcvport>)	551	In the second form (another port given), the other port (C<$rcvport>)
499	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	552	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
500	"normal" kils nothing happens, while under all other conditions, the other	553	"normal" kils nothing happens, while under all other conditions, the other
501	port is killed with the same reason.	554	port is killed with the same reason.
502		555
503	The third form (kill self) is the same as the second form, except that	556	The third form (kill self) is the same as the second form, except that
504	C<$rvport> defaults to C<$SELF>.	557	C<$rvport> defaults to C<$SELF>.
505		558
506	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
507	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.
508		564
509	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
510	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
511	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
512	even monitoring requests can get lost (for exmaple, when the connection	568	even monitoring requests can get lost (for example, when the connection
513	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
514	these problems do not exist.	570	these problems do not exist.
515		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
516	Example: call a given callback when C<$port> is killed.	589	Example: call a given callback when C<$port> is killed.
517		590
518	mon $port, sub { warn "port died because of <@_>\n" };	591	mon $port, sub { warn "port died because of <@_>\n" };
519		592
520	Example: kill ourselves when C<$port> is killed abnormally.	593	Example: kill ourselves when C<$port> is killed abnormally.
…		…
526	mon $port, $self => "restart";	599	mon $port, $self => "restart";
527		600
528	=cut	601	=cut
529		602
530	sub mon {	603	sub mon {
531	my ($noderef, $port) = split /#/, shift, 2;	604	my ($nodeid, $port) = split /#/, shift, 2;
532		605
533	my $node = $NODE{$noderef} \|\| add_node $noderef;	606	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
534		607
535	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,';
536		609
537	unless (ref $cb) {	610	unless (ref $cb) {
538	if (@_) {	611	if (@_) {
…		…
547	}	620	}
548		621
549	$node->monitor ($port, $cb);	622	$node->monitor ($port, $cb);
550		623
551	defined wantarray	624	defined wantarray
552	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
553	}	626	}
554		627
555	=item $guard = mon_guard $port, $ref, $ref...	628	=item $guard = mon_guard $port, $ref, $ref...
556		629
557	Monitors the given C<$port> and keeps the passed references. When the port	630	Monitors the given C<$port> and keeps the passed references. When the port
558	is killed, the references will be freed.	631	is killed, the references will be freed.
559		632
560	Optionally returns a guard that will stop the monitoring.	633	Optionally returns a guard that will stop the monitoring.
561		634
562	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
563	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>):
564		637
565	$port->rcv (start => sub {	638	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	639	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	640	undef $timer if 0.9 < rand;
568	});	641	});
569	});	642	});
570		643
571	=cut	644	=cut
…		…
580		653
581	=item kil $port[, @reason]	654	=item kil $port[, @reason]
582		655
583	Kill the specified port with the given C<@reason>.	656	Kill the specified port with the given C<@reason>.
584		657
585	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" -
586	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.
587		661
588	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>
589	C<mon>, see below).	663	form) get killed with the same reason.
590		664
591	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
592	will be reported as reason C<< die => $@ >>.	666	will be reported as reason C<< die => $@ >>.
593		667
594	Transport/communication errors are reported as C<< transport_error =>	668	Transport/communication errors are reported as C<< transport_error =>
…		…
599	=item $port = spawn $node, $initfunc[, @initdata]	673	=item $port = spawn $node, $initfunc[, @initdata]
600		674
601	Creates a port on the node C<$node> (which can also be a port ID, in which	675	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	676	case it's the node where that port resides).
603		677
604	The port ID of the newly created port is return immediately, and it is	678	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	679	possible to immediately start sending messages or to monitor the port.
606		680
607	After the port has been created, the init function is	681	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	682	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	683	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	684	specify a function in the main program, use C<::name>.
611		685
612	If the function doesn't exist, then the node tries to C<require>	686	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	687	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	688	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	689	exists or it runs out of package names.
616		690
617	The init function is then called with the newly-created port as context	691	The init function is then called with the newly-created port as context
618	object (C<$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.
619		695
620	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
621	in the init function, monitor the original port. This two-way monitoring	697	port, and in the remote init function, immediately monitor the passed
622	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<$initfunc> has no visible effects on the
		702	caller before C<spawn> returns (by delaying invocation when spawn is
		703	called for the local node).
623		704
624	Example: spawn a chat server port on C<$othernode>.	705	Example: spawn a chat server port on C<$othernode>.
625		706
626	# this node, executed from within a port context:	707	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	708	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
642		723
643	sub _spawn {	724	sub _spawn {
644	my $port = shift;	725	my $port = shift;
645	my $init = shift;	726	my $init = shift;
646		727
		728	# rcv will create the actual port
647	local $SELF = "$NODE#$port";	729	local $SELF = "$NODE#$port";
648	eval {	730	eval {
649	&{ load_func $init }	731	&{ load_func $init }
650	};	732	};
651	_self_die if $@;	733	_self_die if $@;
652	}	734	}
653		735
654	sub spawn(@) {	736	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	737	my ($nodeid, undef) = split /#/, shift, 2;
656		738
657	my $id = "$RUNIQ." . $ID++;	739	my $id = "$RUNIQ." . $ID++;
658		740
659	$_[0] =~ /::/	741	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	742	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		743
662	($NODE{$noderef} \|\| add_node $noderef)	744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		745
665	"$noderef#$id"	746	"$nodeid#$id"
666	}	747	}
667		748
668	=back	749	=item after $timeout, @msg
669		750
670	=head1 NODE MESSAGES	751	=item after $timeout, $callback
671		752
672	Nodes understand the following messages sent to them. Many of them take	753	Either sends the given message, or call the given callback, after the
673	arguments called C<@reply>, which will simply be used to compose a reply	754	specified number of seconds.
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
675	the remaining arguments are simply the message data.
676		755
677	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.
678		759
679	=over 4
680
681	=cut	760	=cut
682		761
683	=item lookup => $name, @reply	762	sub after($@) {
		763	my ($timeout, @action) = @_;
684		764
685	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	}
686		772
687	=item devnull => ...	773	=item cal $port, @msg, $callback[, $timeout]
688		774
689	Generic data sink/CPU heat conversion.	775	A simple form of RPC - sends a message to the given C<$port> with the
		776	given contents (C<@msg>), but adds a reply port to the message.
690		777
691	=item relay => $port, @msg	778	The reply port is created temporarily just for the purpose of receiving
		779	the reply, and will be C<kil>ed when no longer needed.
692		780
693	Simply forwards the message to the given port.	781	A reply message sent to the port is passed to the C<$callback> as-is.
694		782
695	=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.
696		786
697	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
698	form C<@reply, $@, @evalres> is sent.	788	monitor the remote port instead, so it eventually gets cleaned-up.
699		789
700	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.
701		793
702	snd $othernode, eval => "exit";	794	=cut
703		795
704	=item time => @reply	796	sub cal(@) {
		797	my $timeout = ref $_[-1] ? undef : pop;
		798	my $cb = pop;
705		799
706	Replies the the current node time to C<@reply>.	800	my $port = port {
		801	undef $timeout;
		802	kil $SELF;
		803	&$cb;
		804	};
707		805
708	Example: tell the current node to send the current time to C<$myport> in a	806	if (defined $timeout) {
709	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	}
710		818
711	snd $NODE, time => $myport, timereply => 1, 2;	819	push @_, $port;
712	# => snd $myport, timereply => 1, 2, <time>	820	&snd;
		821
		822	$port
		823	}
713		824
714	=back	825	=back
715		826
716	=head1 AnyEvent::MP vs. Distributed Erlang	827	=head1 AnyEvent::MP vs. Distributed Erlang
717		828
718	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
719	== 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
720	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
721	sample:	832	sample:
722		833
723	http://www.Erlang.se/doc/programming_rules.shtml	834	http://www.erlang.se/doc/programming_rules.shtml
724	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
725	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
726	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
727		838
728	Despite the similarities, there are also some important differences:	839	Despite the similarities, there are also some important differences:
729		840
730	=over 4	841	=over 4
731		842
732	=item * Node references contain the recipe on how to contact them.	843	=item * Node IDs are arbitrary strings in AEMP.
733		844
734	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
735	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
736	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.
737		849
738	This means that AEMP requires a less tightly controlled environment at the
739	cost of longer node references and a slightly higher management overhead.
740
741	=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
742	uses "local ports are like remote ports".	851	uses "local ports are like remote ports".
743		852
744	The failure modes for local ports are quite different (runtime errors	853	The failure modes for local ports are quite different (runtime errors
745	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,
746	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
…		…
757		866
758	Erlang uses processes that selectively receive messages, and therefore	867	Erlang uses processes that selectively receive messages, and therefore
759	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
760	useful purpose. For the same reason the pattern-matching abilities of	869	useful purpose. For the same reason the pattern-matching abilities of
761	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
762	filter messages without dequeing them.	871	filter messages without dequeuing them.
763		872
764	(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).
765		874
766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
767		876
…		…
769	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,
770	connection establishment is handled in the background.	879	connection establishment is handled in the background.
771		880
772	=item * Erlang suffers from silent message loss, AEMP does not.	881	=item * Erlang suffers from silent message loss, AEMP does not.
773		882
774	Erlang makes few guarantees on messages delivery - messages can get lost	883	Erlang implements few guarantees on messages delivery - messages can get
775	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,
776	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).
777		886
778	AEMP guarantees correct ordering, and the guarantee that there are no	887	AEMP guarantees correct ordering, and the guarantee that after one message
779	holes in the message sequence.	888	is lost, all following ones sent to the same port are lost as well, until
780		889	monitoring raises an error, so there are no silent "holes" in the message
781	=item * In Erlang, processes can be declared dead and later be found to be	890	sequence.
782	alive.
783
784	In Erlang it can happen that a monitored process is declared dead and
785	linked processes get killed, but later it turns out that the process is
786	still alive - and can receive messages.
787
788	In AEMP, when port monitoring detects a port as dead, then that port will
789	eventually be killed - it cannot happen that a node detects a port as dead
790	and then later sends messages to it, finding it is still alive.
791		891
792	=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.
793		893
794	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
795	known to other nodes for a completely different process, causing messages	895	known to other nodes for a completely different process, causing messages
…		…
799	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.
800		900
801	=item * Erlang uses unprotected connections, AEMP uses secure	901	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	902	authentication and can use TLS.
803		903
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	904	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	905	securely authenticate nodes.
806		906
807	=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
808	communications.	908	communications.
809		909
810	The AEMP protocol, unlike the Erlang protocol, supports both	910	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	911	language independent text-only protocols (good for debugging) and binary,
812	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.
813		914
814	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
815	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
816	protocol simple.	917	protocol simple.
817		918
818	=item * AEMP has more flexible monitoring options than Erlang.	919	=item * AEMP has more flexible monitoring options than Erlang.
819		920
820	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
…		…
823	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
824	on a per-process basis.	925	on a per-process basis.
825		926
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	927	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		928
828	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
829	as linking is (except linking is unreliable in Erlang).	930	same way as linking is (except linking is unreliable in Erlang).
830		931
831	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
832	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
833	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
834	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
835	more reliable.	936	reliable (no need for C<spawn_link>).
836		937
837	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
838	(hard to do in Erlang).	939	(hard to do in Erlang).
839		940
840	=back	941	=back
841		942
842	=head1 RATIONALE	943	=head1 RATIONALE
843		944
844	=over 4	945	=over 4
845		946
846	=item Why strings for ports and noderefs, why not objects?	947	=item Why strings for port and node IDs, why not objects?
847		948
848	We considered "objects", but found that the actual number of methods	949	We considered "objects", but found that the actual number of methods
849	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
850	the network frequently, the serialising/deserialising would add lots of	951	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	952	overhead, as well as having to keep a proxy object everywhere.
852		953
853	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
854	procedures to be "valid".	955	procedures to be "valid".
855		956
856	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
857	can't become much cheaper.	958	closure stored in a global hash - it can't become much cheaper.
858		959
859	=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?
860		961
861	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
862	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
863	default.	964	default (although all nodes will accept it).
864		965
865	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
866	faster for small messages and b) most importantly, after years of	967	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	968	experience we found that object serialisation is causing more problems
868	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
869	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
870	always have to re-think your design.	971	always have to re-think your design.
871		972
872	Keeping your messages simple, concentrating on data structures rather than	973	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	974	objects, will keep your messages clean, tidy and efficient.
874		975
875	=back	976	=back
876		977
877	=head1 SEE ALSO	978	=head1 SEE ALSO
878		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 maintainance 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
879	L<AnyEvent>.	992	L<AnyEvent>.
880		993
881	=head1 AUTHOR	994	=head1 AUTHOR
882		995
883	Marc Lehmann <schmorp@schmorp.de>	996	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.112 by root, Thu Apr 1 19:24:22 2010 UTC