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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.105 by root, Sun Nov 8 23:58:02 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
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, type 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 = 1.23;
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	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	the noderef of the local node. The value is initialised by a call	180	ID of the node running in the current process. This value is initialised by
150	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
151	identifiers become invalid.
152		182
153	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
154		184
155	Extracts and returns the noderef from a portid or a noderef.	185	Extracts and returns the node ID from a port ID or a node ID.
156		186
157	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
158		188
159	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
160		190
161	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
164		195
165	This function initialises a node - it must be called exactly once (or	196	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	197	never) before calling other AnyEvent::MP functions.
167		198
168	All arguments (optionally except for the first) are noderefs, which can be
169	either resolved or unresolved.
170
171	The first argument will be looked up in the configuration database first
172	(if it is C<undef> then the current nodename will be used instead) to find
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176
177	There are two types of networked nodes, public nodes and slave nodes:
178
179	=over 4	199	=over 4
180		200
181	=item public nodes	201	=item step 1, gathering configuration from profiles
182		202
183	For public nodes, C<$noderef> (supplied either directly to	203	The function first looks up a profile in the aemp configuration (see the
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	204	L<aemp> commandline utility). The profile name can be specified via the
185	noderef (possibly unresolved, in which case it will be resolved).	205	named C<profile> parameter or can simply be the first parameter). If it is
		206	missing, then the nodename (F<uname -n>) will be used as profile name.
186		207
187	After resolving, the node will bind itself on all endpoints and try to	208	The profile data is then gathered as follows:
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191		209
192	=item slave nodes	210	First, all remaining key => value pairs (all of which are conveniently
		211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
193		215
194	When the C<$noderef> (either as given or overriden by the config file)	216	That means that the values specified in the profile have highest priority
195	is the special string C<slave/>, then the node will become a slave	217	and the values specified directly via C<configure> have lowest priority,
196	node. Slave nodes cannot be contacted from outside and will route most of	218	and can only be used to specify defaults.
197	their traffic to the master node that they attach to.
198		219
199	At least one additional noderef is required (either by specifying it	220	If the profile specifies a node ID, then this will become the node ID of
200	directly or because it is part of the configuration profile): The node	221	this process. If not, then the profile name will be used as node ID. The
201	will try to connect to all of them and will become a slave attached to the	222	special node ID of C<anon/> will be replaced by a random node ID.
202	first node it can successfully connect to.	223
		224	=item step 2, bind listener sockets
		225
		226	The next step is to look up the binds in the profile, followed by binding
		227	aemp protocol listeners on all binds specified (it is possible and valid
		228	to have no binds, meaning that the node cannot be contacted form the
		229	outside. This means the node cannot talk to other nodes that also have no
		230	binds, but it can still talk to all "normal" nodes).
		231
		232	If the profile does not specify a binds list, then a default of C<*> is
		233	used, meaning the node will bind on a dynamically-assigned port on every
		234	local IP address it finds.
		235
		236	=item step 3, connect to seed nodes
		237
		238	As the last step, the seeds list from the profile is passed to the
		239	L<AnyEvent::MP::Global> module, which will then use it to keep
		240	connectivity with at least one node at any point in time.
203		241
204	=back	242	=back
205		243
206	This function will block until all nodes have been resolved and, for slave	244	Example: become a distributed node using the local node name as profile.
207	nodes, until it has successfully established a connection to a master	245	This should be the most common form of invocation for "daemon"-type nodes.
208	server.
209		246
210	Example: become a public node listening on the guessed noderef, or the one	247	configure
211	specified via C<aemp> for the current node. This should be the most common
212	form of invocation for "daemon"-type nodes.
213		248
214	initialise_node;	249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
215		251
216	Example: become a slave node to any of the the seednodes specified via	252	configure nodeid => "anon/";
217	C<aemp>. This form is often used for commandline clients.
218		253
219	initialise_node "slave/";	254	Example: configure a node using a profile called seed, which si suitable
		255	for a seed node as it binds on all local addresses on a fixed port (4040,
		256	customary for aemp).
220		257
221	Example: become a slave node to any of the specified master servers. This	258	# use the aemp commandline utility
222	form is also often used for commandline clients.	259	# aemp profile seed nodeid anon/ binds '*:4040'
223		260
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	261	# then use it
		262	configure profile => "seed";
225		263
226	Example: become a public node, and try to contact some well-known master	264	# or simply use aemp from the shell again:
227	servers to become part of the network.	265	# aemp run profile seed
228		266
229	initialise_node undef, "master1", "master2";	267	# or provide a nicer-to-remember nodeid
230		268	# aemp run profile seed nodeid "$(hostname)"
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236
237	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4
249
250	=item the empty string
251
252	An empty-string component gets resolved as if the default port (4040) was
253	specified.
254
255	=item naked port numbers (e.g. C<1234>)
256
257	These are resolved by prepending the local nodename and a colon, to be
258	further resolved.
259
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
261
262	These are resolved by using AnyEvent::DNS to resolve them, optionally
263	looking up SRV records for the C<aemp=4040> port, if no port was
264	specified.
265
266	=back
267		269
268	=item $SELF	270	=item $SELF
269		271
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	273	blocks.
272		274
273	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
274		276
275	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
278		280
279	=item snd $port, type => @data	281	=item snd $port, type => @data
280		282
281	=item snd $port, @msg	283	=item snd $port, @msg
282		284
283	Send the given message to the given port ID, which can identify either	285	Send the given message to the given port, which can identify either a
284	a local or a remote port, and can be either a string or soemthignt hat	286	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		287
287	While the message can be about anything, it is highly recommended to use a	288	While the message can be almost anything, it is highly recommended to
288	string as first element (a portid, or some word that indicates a request	289	use a string as first element (a port ID, or some word that indicates a
289	type etc.).	290	request type etc.) and to consist if only simple perl values (scalars,
		291	arrays, hashes) - if you think you need to pass an object, think again.
290		292
291	The message data effectively becomes read-only after a call to this	293	The message data logically becomes read-only after a call to this
292	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
293	problems.	295	forbidden, as there can be considerable time between the call to C<snd>
		296	and the time the message is actually being serialised - in fact, it might
		297	never be copied as within the same process it is simply handed to the
		298	receiving port.
294		299
295	The type of data you can transfer depends on the transport protocol: when	300	The type of data you can transfer depends on the transport protocol: when
296	JSON is used, then only strings, numbers and arrays and hashes consisting	301	JSON is used, then only strings, numbers and arrays and hashes consisting
297	of those are allowed (no objects). When Storable is used, then anything	302	of those are allowed (no objects). When Storable is used, then anything
298	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
299	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
300		306
301	=item $local_port = port	307	=item $local_port = port
302		308
303	Create a new local port object and returns its port ID. Initially it has	309	Create a new local port object and returns its port ID. Initially it has
304	no callbacks set and will throw an error when it receives messages.	310	no callbacks set and will throw an error when it receives messages.
…		…
351	The default callback received all messages not matched by a more specific	357	The default callback received all messages not matched by a more specific
352	C<tag> match.	358	C<tag> match.
353		359
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		361
356	Register callbacks to be called on messages starting with the given tag on	362	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	363	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	364	C<$callback> is C<$undef> or missing). There can only be one callback
		365	registered for each tag.
359		366
360	The original message will be passed to the callback, after the first	367	The original message will be passed to the callback, after the first
361	element (the tag) has been removed. The callback will use the same	368	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	369	environment as the default callback (see above).
363		370
…		…
375	rcv port,	382	rcv port,
376	msg1 => sub { ... },	383	msg1 => sub { ... },
377	...	384	...
378	;	385	;
379		386
		387	Example: temporarily register a rcv callback for a tag matching some port
		388	(e.g. for an rpc reply) and unregister it after a message was received.
		389
		390	rcv $port, $otherport => sub {
		391	my @reply = @_;
		392
		393	rcv $SELF, $otherport;
		394	};
		395
380	=cut	396	=cut
381		397
382	sub rcv($@) {	398	sub rcv($@) {
383	my $port = shift;	399	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
385		401
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		404
389	while (@_) {	405	while (@_) {
390	if (ref $_[0]) {	406	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	407	if (my $self = $PORT_DATA{$portid}) {
392	"AnyEvent::MP::Port" eq ref $self	408	"AnyEvent::MP::Port" eq ref $self
393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	409	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
394		410
395	$self->[2] = shift;	411	$self->[0] = shift;
396	} else {	412	} else {
397	my $cb = shift;	413	my $cb = shift;
398	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
399	local $SELF = $port;	415	local $SELF = $port;
400	eval { &$cb }; _self_die if $@;	416	eval { &$cb }; _self_die if $@;
401	};	417	};
402	}	418	}
403	} elsif (defined $_[0]) {	419	} elsif (defined $_[0]) {
404	my $self = $PORT_DATA{$portid} \|\|= do {	420	my $self = $PORT_DATA{$portid} \|\|= do {
405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	421	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
406		422
407	$PORT{$portid} = sub {	423	$PORT{$portid} = sub {
408	local $SELF = $port;	424	local $SELF = $port;
409		425
410	if (my $cb = $self->[1]{$_[0]}) {	426	if (my $cb = $self->[1]{$_[0]}) {
…		…
432	}	448	}
433		449
434	$port	450	$port
435	}	451	}
436		452
		453	=item peval $port, $coderef[, @args]
		454
		455	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		456	when the code throews an exception the C<$port> will be killed.
		457
		458	Any remaining args will be passed to the callback. Any return values will
		459	be returned to the caller.
		460
		461	This is useful when you temporarily want to execute code in the context of
		462	a port.
		463
		464	Example: create a port and run some initialisation code in it's context.
		465
		466	my $port = port { ... };
		467
		468	peval $port, sub {
		469	init
		470	or die "unable to init";
		471	};
		472
		473	=cut
		474
		475	sub peval($$) {
		476	local $SELF = shift;
		477	my $cb = shift;
		478
		479	if (wantarray) {
		480	my @res = eval { &$cb };
		481	_self_die if $@;
		482	@res
		483	} else {
		484	my $res = eval { &$cb };
		485	_self_die if $@;
		486	$res
		487	}
		488	}
		489
437	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
438		491
439	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
440	closure is executed, sets up the environment in the same way as in C<rcv>	493	closure is executed, sets up the environment in the same way as in C<rcv>
441	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		495
		496	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		497	BLOCK } } >>.
442		498
443	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
444		500
445	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
446	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
470	$res	526	$res
471	}	527	}
472	}	528	}
473	}	529	}
474		530
475	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		532
477	=item $guard = mon $port, $rcvport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		534
479	=item $guard = mon $port	535	=item $guard = mon $port # kill $SELF when $port dies
480		536
481	=item $guard = mon $port, $rcvport, @msg	537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		538
483	Monitor the given port and do something when the port is killed or	539	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	540	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	541	to stop monitoring again.
486
487	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port
489	will arrive, or the monitoring action will be invoked after possible
490	message loss has been detected. No messages will be lost "in between"
491	(after the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get
493	delivered again.
494		542
495	In the first form (callback), the callback is simply called with any	543	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	546	C<eval> if unsure.
499		547
500	In the second form (another port given), the other port (C<$rcvport>)	548	In the second form (another port given), the other port (C<$rcvport>)
501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
502	"normal" kils nothing happens, while under all other conditions, the other	550	"normal" kils nothing happens, while under all other conditions, the other
503	port is killed with the same reason.	551	port is killed with the same reason.
504		552
505	The third form (kill self) is the same as the second form, except that	553	The third form (kill self) is the same as the second form, except that
506	C<$rvport> defaults to C<$SELF>.	554	C<$rvport> defaults to C<$SELF>.
507		555
508	In the last form (message), a message of the form C<@msg, @reason> will be	556	In the last form (message), a message of the form C<@msg, @reason> will be
509	C<snd>.	557	C<snd>.
		558
		559	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		560	alert was raised), they are removed and will not trigger again.
510		561
511	As a rule of thumb, monitoring requests should always monitor a port from	562	As a rule of thumb, monitoring requests should always monitor a port from
512	a local port (or callback). The reason is that kill messages might get	563	a local port (or callback). The reason is that kill messages might get
513	lost, just like any other message. Another less obvious reason is that	564	lost, just like any other message. Another less obvious reason is that
514	even monitoring requests can get lost (for exmaple, when the connection	565	even monitoring requests can get lost (for example, when the connection
515	to the other node goes down permanently). When monitoring a port locally	566	to the other node goes down permanently). When monitoring a port locally
516	these problems do not exist.	567	these problems do not exist.
517		568
		569	C<mon> effectively guarantees that, in the absence of hardware failures,
		570	after starting the monitor, either all messages sent to the port will
		571	arrive, or the monitoring action will be invoked after possible message
		572	loss has been detected. No messages will be lost "in between" (after
		573	the first lost message no further messages will be received by the
		574	port). After the monitoring action was invoked, further messages might get
		575	delivered again.
		576
		577	Inter-host-connection timeouts and monitoring depend on the transport
		578	used. The only transport currently implemented is TCP, and AnyEvent::MP
		579	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		580	non-idle connection, and usually around two hours for idle connections).
		581
		582	This means that monitoring is good for program errors and cleaning up
		583	stuff eventually, but they are no replacement for a timeout when you need
		584	to ensure some maximum latency.
		585
518	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
519		587
520	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
521		589
522	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	596	mon $port, $self => "restart";
529		597
530	=cut	598	=cut
531		599
532	sub mon {	600	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
534		602
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		604
537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	605	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		606
539	unless (ref $cb) {	607	unless (ref $cb) {
540	if (@_) {	608	if (@_) {
…		…
549	}	617	}
550		618
551	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
552		620
553	defined wantarray	621	defined wantarray
554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
555	}	623	}
556		624
557	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
558		626
559	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
560	is killed, the references will be freed.	628	is killed, the references will be freed.
561		629
562	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
563		631
564	This function is useful when you create e.g. timers or other watchers and	632	This function is useful when you create e.g. timers or other watchers and
565	want to free them when the port gets killed:	633	want to free them when the port gets killed (note the use of C<psub>):
566		634
567	$port->rcv (start => sub {	635	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
570	});	638	});
571	});	639	});
572		640
573	=cut	641	=cut
…		…
582		650
583	=item kil $port[, @reason]	651	=item kil $port[, @reason]
584		652
585	Kill the specified port with the given C<@reason>.	653	Kill the specified port with the given C<@reason>.
586		654
587	If no C<@reason> is specified, then the port is killed "normally" (linked	655	If no C<@reason> is specified, then the port is killed "normally" (ports
588	ports will not be kileld, or even notified).	656	monitoring other ports will not necessarily die because a port dies
		657	"normally").
589		658
590	Otherwise, linked ports get killed with the same reason (second form of	659	Otherwise, linked ports get killed with the same reason (second form of
591	C<mon>, see below).	660	C<mon>, see above).
592		661
593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
594	will be reported as reason C<< die => $@ >>.	663	will be reported as reason C<< die => $@ >>.
595		664
596	Transport/communication errors are reported as C<< transport_error =>	665	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	670	=item $port = spawn $node, $initfunc[, @initdata]
602		671
603	Creates a port on the node C<$node> (which can also be a port ID, in which	672	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	673	case it's the node where that port resides).
605		674
606	The port ID of the newly created port is return immediately, and it is	675	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	676	possible to immediately start sending messages or to monitor the port.
608		677
609	After the port has been created, the init function is	678	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	679	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	681	specify a function in the main program, use C<::name>.
613		682
614	If the function doesn't exist, then the node tries to C<require>	683	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	684	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	686	exists or it runs out of package names.
618		687
619	The init function is then called with the newly-created port as context	688	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	689	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		690	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		691	the port might not get created.
621		692
622	A common idiom is to pass your own port, monitor the spawned port, and	693	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	694	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	695	local port. This two-way monitoring ensures that both ports get cleaned up
		696	when there is a problem.
		697
		698	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
625		701
626	Example: spawn a chat server port on C<$othernode>.	702	Example: spawn a chat server port on C<$othernode>.
627		703
628	# this node, executed from within a port context:	704	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
644		720
645	sub _spawn {	721	sub _spawn {
646	my $port = shift;	722	my $port = shift;
647	my $init = shift;	723	my $init = shift;
648		724
		725	# rcv will create the actual port
649	local $SELF = "$NODE#$port";	726	local $SELF = "$NODE#$port";
650	eval {	727	eval {
651	&{ load_func $init }	728	&{ load_func $init }
652	};	729	};
653	_self_die if $@;	730	_self_die if $@;
654	}	731	}
655		732
656	sub spawn(@) {	733	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	734	my ($nodeid, undef) = split /#/, shift, 2;
658		735
659	my $id = "$RUNIQ." . $ID++;	736	my $id = "$RUNIQ." . $ID++;
660		737
661	$_[0] =~ /::/	738	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		740
664	($NODE{$noderef} \|\| add_node $noderef)	741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		742
667	"$noderef#$id"	743	"$nodeid#$id"
668	}	744	}
669		745
670	=back	746	=item after $timeout, @msg
671		747
672	=head1 NODE MESSAGES	748	=item after $timeout, $callback
673		749
674	Nodes understand the following messages sent to them. Many of them take	750	Either sends the given message, or call the given callback, after the
675	arguments called C<@reply>, which will simply be used to compose a reply	751	specified number of seconds.
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
677	the remaining arguments are simply the message data.
678		752
679	While other messages exist, they are not public and subject to change.	753	This is simply a utility function that comes in handy at times - the
		754	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		755	so it may go away in the future.
680		756
681	=over 4
682
683	=cut	757	=cut
684		758
685	=item lookup => $name, @reply	759	sub after($@) {
		760	my ($timeout, @action) = @_;
686		761
687	Replies with the port ID of the specified well-known port, or C<undef>.	762	my $t; $t = AE::timer $timeout, 0, sub {
		763	undef $t;
		764	ref $action[0]
		765	? $action[0]()
		766	: snd @action;
		767	};
		768	}
688		769
689	=item devnull => ...	770	=item cal $port, @msg, $callback[, $timeout]
690		771
691	Generic data sink/CPU heat conversion.	772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
692		774
693	=item relay => $port, @msg	775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
694		777
695	Simply forwards the message to the given port.	778	A reply message sent to the port is passed to the C<$callback> as-is.
696		779
697	=item eval => $string[ @reply]	780	If an optional time-out (in seconds) is given and it is not C<undef>,
		781	then the callback will be called without any arguments after the time-out
		782	elapsed and the port is C<kil>ed.
698		783
699	Evaluates the given string. If C<@reply> is given, then a message of the	784	If no time-out is given (or it is C<undef>), then the local port will
700	form C<@reply, $@, @evalres> is sent.	785	monitor the remote port instead, so it eventually gets cleaned-up.
701		786
702	Example: crash another node.	787	Currently this function returns the temporary port, but this "feature"
		788	might go in future versions unless you can make a convincing case that
		789	this is indeed useful for something.
703		790
704	snd $othernode, eval => "exit";	791	=cut
705		792
706	=item time => @reply	793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
707		796
708	Replies the the current node time to C<@reply>.	797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
709		802
710	Example: tell the current node to send the current time to C<$myport> in a	803	if (defined $timeout) {
711	C<timereply> message.	804	$timeout = AE::timer $timeout, 0, sub {
		805	undef $timeout;
		806	kil $port;
		807	$cb->();
		808	};
		809	} else {
		810	mon $_[0], sub {
		811	kil $port;
		812	$cb->();
		813	};
		814	}
712		815
713	snd $NODE, time => $myport, timereply => 1, 2;	816	push @_, $port;
714	# => snd $myport, timereply => 1, 2, <time>	817	&snd;
		818
		819	$port
		820	}
715		821
716	=back	822	=back
717		823
718	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
719		825
720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
721	== aemp node, Erlang process == aemp port), so many of the documents and	827	== aemp node, Erlang process == aemp port), so many of the documents and
722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
723	sample:	829	sample:
724		830
725	http://www.Erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	832	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	833	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	834	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
729		835
730	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
731		837
732	=over 4	838	=over 4
733		839
734	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
735		841
736	Erlang relies on special naming and DNS to work everywhere in the	842	Erlang relies on special naming and DNS to work everywhere in the same
737	same way. AEMP relies on each node knowing it's own address(es), with	843	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
738	convenience functionality.	844	configuration or DNS), and possibly the addresses of some seed nodes, but
		845	will otherwise discover other nodes (and their IDs) itself.
739		846
740	This means that AEMP requires a less tightly controlled environment at the	847	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	848	uses "local ports are like remote ports".
		849
		850	The failure modes for local ports are quite different (runtime errors
		851	only) then for remote ports - when a local port dies, you I<know> it dies,
		852	when a connection to another node dies, you know nothing about the other
		853	port.
		854
		855	Erlang pretends remote ports are as reliable as local ports, even when
		856	they are not.
		857
		858	AEMP encourages a "treat remote ports differently" philosophy, with local
		859	ports being the special case/exception, where transport errors cannot
		860	occur.
742		861
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	862	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		863
745	Erlang uses processes that selctively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
746	needs a queue. AEMP is event based, queuing messages would serve no useful	865	needs a queue. AEMP is event based, queuing messages would serve no
747	purpose.	866	useful purpose. For the same reason the pattern-matching abilities of
		867	AnyEvent::MP are more limited, as there is little need to be able to
		868	filter messages without dequeuing them.
748		869
749	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
750		871
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		873
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	874	Sending messages in Erlang is synchronous and blocks the process (and
754	sends are immediate, connection establishment is handled in the	875	so does not need a queue that can overflow). AEMP sends are immediate,
755	background.	876	connection establishment is handled in the background.
756		877
757	=item * Erlang can silently lose messages, AEMP cannot.	878	=item * Erlang suffers from silent message loss, AEMP does not.
758		879
759	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
760	without any of the processes realising it (i.e. you send messages a, b,	881	lost without any of the processes realising it (i.e. you send messages a,
761	and c, and the other side only receives messages a and c).	882	b, and c, and the other side only receives messages a and c).
762		883
763	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
764	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
765		886	monitoring raises an error, so there are no silent "holes" in the message
766	=item * In Erlang, processes can be declared dead and later be found to be	887	sequence.
767	alive.
768
769	In Erlang it can happen that a monitored process is declared dead and
770	linked processes get killed, but later it turns out that the process is
771	still alive - and can receive messages.
772
773	In AEMP, when port monitoring detects a port as dead, then that port will
774	eventually be killed - it cannot happen that a node detects a port as dead
775	and then later sends messages to it, finding it is still alive.
776		888
777	=item * Erlang can send messages to the wrong port, AEMP does not.	889	=item * Erlang can send messages to the wrong port, AEMP does not.
778		890
779	In Erlang it is quite possible that a node that restarts reuses a process	891	In Erlang it is quite likely that a node that restarts reuses a process ID
780	ID known to other nodes for a completely different process, causing	892	known to other nodes for a completely different process, causing messages
781	messages destined for that process to end up in an unrelated process.	893	destined for that process to end up in an unrelated process.
782		894
783	AEMP never reuses port IDs, so old messages or old port IDs floating	895	AEMP never reuses port IDs, so old messages or old port IDs floating
784	around in the network will not be sent to an unrelated port.	896	around in the network will not be sent to an unrelated port.
785		897
786	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	899	authentication and can use TLS.
788		900
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	902	securely authenticate nodes.
791		903
792	=item * The AEMP protocol is optimised for both text-based and binary	904	=item * The AEMP protocol is optimised for both text-based and binary
793	communications.	905	communications.
794		906
795	The AEMP protocol, unlike the Erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
797	language-specific serialisers (e.g. Storable).	909	language-specific serialisers (e.g. Storable). By default, unless TLS is
		910	used, the protocol is actually completely text-based.
798		911
799	It has also been carefully designed to be implementable in other languages	912	It has also been carefully designed to be implementable in other languages
800	with a minimum of work while gracefully degrading fucntionality to make the	913	with a minimum of work while gracefully degrading functionality to make the
801	protocol simple.	914	protocol simple.
802		915
803	=item * AEMP has more flexible monitoring options than Erlang.	916	=item * AEMP has more flexible monitoring options than Erlang.
804		917
805	In Erlang, you can chose to receive I<all> exit signals as messages	918	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
808	Erlang, as one can choose between automatic kill, exit message or callback	921	Erlang, as one can choose between automatic kill, exit message or callback
809	on a per-process basis.	922	on a per-process basis.
810		923
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	924	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		925
813	Monitoring in Erlang is not an indicator of process death/crashes,	926	Monitoring in Erlang is not an indicator of process death/crashes, in the
814	as linking is (except linking is unreliable in Erlang).	927	same way as linking is (except linking is unreliable in Erlang).
815		928
816	In AEMP, you don't "look up" registered port names or send to named ports	929	In AEMP, you don't "look up" registered port names or send to named ports
817	that might or might not be persistent. Instead, you normally spawn a port	930	that might or might not be persistent. Instead, you normally spawn a port
818	on the remote node. The init function monitors the you, and you monitor	931	on the remote node. The init function monitors you, and you monitor the
819	the remote port. Since both monitors are local to the node, they are much	932	remote port. Since both monitors are local to the node, they are much more
820	more reliable.	933	reliable (no need for C<spawn_link>).
821		934
822	This also saves round-trips and avoids sending messages to the wrong port	935	This also saves round-trips and avoids sending messages to the wrong port
823	(hard to do in Erlang).	936	(hard to do in Erlang).
824		937
825	=back	938	=back
826		939
827	=head1 RATIONALE	940	=head1 RATIONALE
828		941
829	=over 4	942	=over 4
830		943
831	=item Why strings for ports and noderefs, why not objects?	944	=item Why strings for port and node IDs, why not objects?
832		945
833	We considered "objects", but found that the actual number of methods	946	We considered "objects", but found that the actual number of methods
834	thatc an be called are very low. Since port IDs and noderefs travel over	947	that can be called are quite low. Since port and node IDs travel over
835	the network frequently, the serialising/deserialising would add lots of	948	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	949	overhead, as well as having to keep a proxy object everywhere.
837		950
838	Strings can easily be printed, easily serialised etc. and need no special	951	Strings can easily be printed, easily serialised etc. and need no special
839	procedures to be "valid".	952	procedures to be "valid".
840		953
841	And a a miniport consists of a single closure stored in a global hash - it	954	And as a result, a miniport consists of a single closure stored in a
842	can't become much cheaper.	955	global hash - it can't become much cheaper.
843		956
844	=item Why favour JSON, why not real serialising format such as Storable?	957	=item Why favour JSON, why not a real serialising format such as Storable?
845		958
846	In fact, any AnyEvent::MP node will happily accept Storable as framing	959	In fact, any AnyEvent::MP node will happily accept Storable as framing
847	format, but currently there is no way to make a node use Storable by	960	format, but currently there is no way to make a node use Storable by
848	default.	961	default (although all nodes will accept it).
849		962
850	The default framing protocol is JSON because a) JSON::XS is many times	963	The default framing protocol is JSON because a) JSON::XS is many times
851	faster for small messages and b) most importantly, after years of	964	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	965	experience we found that object serialisation is causing more problems
853	than it gains: Just like function calls, objects simply do not travel	966	than it solves: Just like function calls, objects simply do not travel
854	easily over the network, mostly because they will always be a copy, so you	967	easily over the network, mostly because they will always be a copy, so you
855	always have to re-think your design.	968	always have to re-think your design.
856		969
857	Keeping your messages simple, concentrating on data structures rather than	970	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	971	objects, will keep your messages clean, tidy and efficient.
859		972
860	=back	973	=back
861		974
862	=head1 SEE ALSO	975	=head1 SEE ALSO
863		976
		977	L<AnyEvent::MP::Intro> - a gentle introduction.
		978
		979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		980
		981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		982	your applications.
		983
		984	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		985
		986	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		987	all nodes.
		988
864	L<AnyEvent>.	989	L<AnyEvent>.
865		990
866	=head1 AUTHOR	991	=head1 AUTHOR
867		992
868	Marc Lehmann <schmorp@schmorp.de>	993	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.105 by root, Sun Nov 8 23:58:02 2009 UTC