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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.63 by root, Thu Aug 27 21:29:37 2009 UTC vs.
Revision 1.119 by root, Sun Feb 26 10:29:59 2012 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;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
36	# monitoring	39	# monitoring
37	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
39	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	};
40		51
41	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
42		53
		54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - WIP
46	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
47		58	AnyEvent::MP::Global - stable API.
48	stay tuned.
49		59
50	=head1 DESCRIPTION	60	=head1 DESCRIPTION
51		61
52	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
53		63
54	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
56		66
57	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>
58	manual page.	68	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		69
64	=head1 CONCEPTS	70	=head1 CONCEPTS
65		71
66	=over 4	72	=over 4
67		73
68	=item port	74	=item port
69		75
70	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).
71		78
72	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages will not be queued.	80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
74		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
75	=item port ID - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
76		86
77	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
78	separator, and a port name (a printable string of unspecified format). An	88	separator, and a port name (a printable string of unspecified format).
79	exception is the the node port, whose ID is identical to its node
80	reference.
81		89
82	=item node	90	=item node
83		91
84	A node is a single process containing at least one port - the node port,	92	A node is a single process containing at least one port - the node port,
85	which provides nodes to manage each other remotely, and to create new	93	which enables nodes to manage each other remotely, and to create new
86	ports.	94	ports.
87		95
88	Nodes are either private (single-process only), slaves (can only talk to	96	Nodes are either public (have one or more listening ports) or private
89	public nodes, but do not need an open port) or public nodes (connectable	97	(no listening ports). Private nodes cannot talk to other private nodes
90	from any other node).	98	currently, but all nodes can talk to public nodes.
91		99
		100	Nodes is represented by (printable) strings called "node IDs".
		101
92	=item node ID - C<[a-za-Z0-9_\-.:]+>	102	=item node ID - C<[A-Za-z0-9_\-.:]*>
93		103
94	A node ID is a string that either simply identifies the node (for	104	A node ID is a string that uniquely identifies the node within a
95	private and slave nodes), or contains a recipe on how to reach a given	105	network. Depending on the configuration used, node IDs can look like a
96	node (for public nodes).	106	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		107	doesn't interpret node IDs in any way except to uniquely identify a node.
97		108
98	This recipe is simply a comma-separated list of C<address:port> pairs (for	109	=item binds - C<ip:port>
99	TCP/IP, other protocols might look different).
100		110
101	Node references come in two flavours: resolved (containing only numerical	111	Nodes can only talk to each other by creating some kind of connection to
102	addresses) or unresolved (where hostnames are used instead of addresses).	112	each other. To do this, nodes should listen on one or more local transport
		113	endpoints - binds.
103		114
104	Before using an unresolved node reference in a message you first have to	115	Currently, only standard C<ip:port> specifications can be used, which
105	resolve it.	116	specify TCP ports to listen on. So a bind is basically just a tcp socket
		117	in listening mode thta accepts conenctions form other nodes.
		118
		119	=item seed nodes
		120
		121	When a node starts, it knows nothing about the network it is in - it
		122	needs to connect to at least one other node that is already in the
		123	network. These other nodes are called "seed nodes".
		124
		125	Seed nodes themselves are not special - they are seed nodes only because
		126	some other node I<uses> them as such, but any node can be used as seed
		127	node for other nodes, and eahc node cna use a different set of seed nodes.
		128
		129	In addition to discovering the network, seed nodes are also used to
		130	maintain the network - all nodes using the same seed node form are part of
		131	the same network. If a network is split into multiple subnets because e.g.
		132	the network link between the parts goes down, then using the same seed
		133	nodes for all nodes ensures that eventually the subnets get merged again.
		134
		135	Seed nodes are expected to be long-running, and at least one seed node
		136	should always be available. They should also be relatively responsive - a
		137	seed node that blocks for long periods will slow down everybody else.
		138
		139	For small networks, it's best if every node uses the same set of seed
		140	nodes. For large networks, it can be useful to specify "regional" seed
		141	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		142	each other. What's important is that all seed nodes connections form a
		143	complete graph, so that the network cannot split into separate subnets
		144	forever.
		145
		146	Seed nodes are represented by seed IDs.
		147
		148	=item seed IDs - C<host:port>
		149
		150	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		151	TCP port) of nodes that should be used as seed nodes.
		152
		153	=item global nodes
		154
		155	An AEMP network needs a discovery service - nodes need to know how to
		156	connect to other nodes they only know by name. In addition, AEMP offers a
		157	distributed "group database", which maps group names to a list of strings
		158	- for example, to register worker ports.
		159
		160	A network needs at least one global node to work, and allows every node to
		161	be a global node.
		162
		163	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		164	node and tries to keep connections to all other nodes. So while it can
		165	make sense to make every node "global" in small networks, it usually makes
		166	sense to only make seed nodes into global nodes in large networks (nodes
		167	keep connections to seed nodes and global nodes, so makign them the same
		168	reduces overhead).
106		169
107	=back	170	=back
108		171
109	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
110		173
122		185
123	use AE ();	186	use AE ();
124		187
125	use base "Exporter";	188	use base "Exporter";
126		189
127	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	190	our $VERSION = '1.30';
128		191
129	our @EXPORT = qw(	192	our @EXPORT = qw(
130	NODE $NODE *SELF node_of after	193	NODE $NODE *SELF node_of after
131	resolve_node initialise_node	194	configure
132	snd rcv mon mon_guard kil reg psub spawn	195	snd rcv mon mon_guard kil psub peval spawn cal
133	port	196	port
134	);	197	);
135		198
136	our $SELF;	199	our $SELF;
137		200
…		…
141	kil $SELF, die => $msg;	204	kil $SELF, die => $msg;
142	}	205	}
143		206
144	=item $thisnode = NODE / $NODE	207	=item $thisnode = NODE / $NODE
145		208
146	The C<NODE> function returns, and the C<$NODE> variable contains the	209	The C<NODE> function returns, and the C<$NODE> variable contains, the node
147	node id of the local node. The value is initialised by a call to	210	ID of the node running in the current process. This value is initialised by
148	C<initialise_node>.	211	a call to C<configure>.
149		212
150	=item $nodeid = node_of $port	213	=item $nodeid = node_of $port
151		214
152	Extracts and returns the noderef from a port ID or a node ID.	215	Extracts and returns the node ID from a port ID or a node ID.
153		216
154	=item initialise_node $profile_name	217	=item configure $profile, key => value...
155		218
		219	=item configure key => value...
		220
156	Before a node can talk to other nodes on the network it has to initialise	221	Before a node can talk to other nodes on the network (i.e. enter
157	itself - the minimum a node needs to know is it's own name, and optionally	222	"distributed mode") it has to configure itself - the minimum a node needs
158	it should know the noderefs of some other nodes in the network.	223	to know is its own name, and optionally it should know the addresses of
		224	some other nodes in the network to discover other nodes.
159		225
		226	The key/value pairs are basically the same ones as documented for the
		227	F<aemp> command line utility (sans the set/del prefix).
		228
160	This function initialises a node - it must be called exactly once (or	229	This function configures a node - it must be called exactly once (or
161	never) before calling other AnyEvent::MP functions.	230	never) before calling other AnyEvent::MP functions.
162		231
163	All arguments (optionally except for the first) are noderefs, which can be
164	either resolved or unresolved.
165
166	The first argument will be looked up in the configuration database first
167	(if it is C<undef> then the current nodename will be used instead) to find
168	the relevant configuration profile (see L<aemp>). If none is found then
169	the default configuration is used. The configuration supplies additional
170	seed/master nodes and can override the actual noderef.
171
172	There are two types of networked nodes, public nodes and slave nodes:
173
174	=over 4	232	=over 4
175		233
176	=item public nodes	234	=item step 1, gathering configuration from profiles
177		235
178	For public nodes, C<$noderef> (supplied either directly to	236	The function first looks up a profile in the aemp configuration (see the
179	C<initialise_node> or indirectly via a profile or the nodename) must be a	237	L<aemp> commandline utility). The profile name can be specified via the
180	noderef (possibly unresolved, in which case it will be resolved).	238	named C<profile> parameter or can simply be the first parameter). If it is
		239	missing, then the nodename (F<uname -n>) will be used as profile name.
181		240
182	After resolving, the node will bind itself on all endpoints.	241	The profile data is then gathered as follows:
183		242
184	=item slave nodes	243	First, all remaining key => value pairs (all of which are conveniently
		244	undocumented at the moment) will be interpreted as configuration
		245	data. Then they will be overwritten by any values specified in the global
		246	default configuration (see the F<aemp> utility), then the chain of
		247	profiles chosen by the profile name (and any C<parent> attributes).
185		248
186	When the C<$noderef> (either as given or overriden by the config file)	249	That means that the values specified in the profile have highest priority
187	is the special string C<slave/>, then the node will become a slave	250	and the values specified directly via C<configure> have lowest priority,
188	node. Slave nodes cannot be contacted from outside, and cannot talk to	251	and can only be used to specify defaults.
189	each other (at least in this version of AnyEvent::MP).
190		252
191	Slave nodes work by creating connections to all public nodes, using the	253	If the profile specifies a node ID, then this will become the node ID of
192	L<AnyEvent::MP::Global> service.	254	this process. If not, then the profile name will be used as node ID. The
		255	special node ID of C<anon/> will be replaced by a random node ID.
		256
		257	=item step 2, bind listener sockets
		258
		259	The next step is to look up the binds in the profile, followed by binding
		260	aemp protocol listeners on all binds specified (it is possible and valid
		261	to have no binds, meaning that the node cannot be contacted form the
		262	outside. This means the node cannot talk to other nodes that also have no
		263	binds, but it can still talk to all "normal" nodes).
		264
		265	If the profile does not specify a binds list, then a default of C<*> is
		266	used, meaning the node will bind on a dynamically-assigned port on every
		267	local IP address it finds.
		268
		269	=item step 3, connect to seed nodes
		270
		271	As the last step, the seed ID list from the profile is passed to the
		272	L<AnyEvent::MP::Global> module, which will then use it to keep
		273	connectivity with at least one node at any point in time.
193		274
194	=back	275	=back
195		276
196	After initialising itself, the node will connect to all additional	277	Example: become a distributed node using the local node name as profile.
197	C<$seednodes> that are specified diretcly or via a profile. Seednodes are	278	This should be the most common form of invocation for "daemon"-type nodes.
198	optional and can be used to quickly bootstrap the node into an existing
199	network.
200		279
201	All the seednodes will also be specially marked to automatically retry	280	configure
202	connecting to them indefinitely, so make sure that seednodes are really
203	reliable and up (this might also change in the future).
204		281
205	Example: become a public node listening on the guessed noderef, or the one	282	Example: become an anonymous node. This form is often used for commandline
206	specified via C<aemp> for the current node. This should be the most common	283	clients.
207	form of invocation for "daemon"-type nodes.
208		284
209	initialise_node;	285	configure nodeid => "anon/";
210		286
211	Example: become a slave node to any of the the seednodes specified via	287	Example: configure a node using a profile called seed, which si suitable
212	C<aemp>. This form is often used for commandline clients.	288	for a seed node as it binds on all local addresses on a fixed port (4040,
		289	customary for aemp).
213		290
214	initialise_node "slave/";	291	# use the aemp commandline utility
		292	# aemp profile seed nodeid anon/ binds '*:4040'
215		293
216	Example: become a public node, and try to contact some well-known master	294	# then use it
217	servers to become part of the network.	295	configure profile => "seed";
218		296
219	initialise_node undef, "master1", "master2";	297	# or simply use aemp from the shell again:
		298	# aemp run profile seed
220		299
221	Example: become a public node listening on port C<4041>.	300	# or provide a nicer-to-remember nodeid
222		301	# aemp run profile seed nodeid "$(hostname)"
223	initialise_node 4041;
224
225	Example: become a public node, only visible on localhost port 4044.
226
227	initialise_node "localhost:4044";
228
229	=item $cv = resolve_node $noderef
230
231	Takes an unresolved node reference that may contain hostnames and
232	abbreviated IDs, resolves all of them and returns a resolved node
233	reference.
234
235	In addition to C<address:port> pairs allowed in resolved noderefs, the
236	following forms are supported:
237
238	=over 4
239
240	=item the empty string
241
242	An empty-string component gets resolved as if the default port (4040) was
243	specified.
244
245	=item naked port numbers (e.g. C<1234>)
246
247	These are resolved by prepending the local nodename and a colon, to be
248	further resolved.
249
250	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
251
252	These are resolved by using AnyEvent::DNS to resolve them, optionally
253	looking up SRV records for the C<aemp=4040> port, if no port was
254	specified.
255
256	=back
257		302
258	=item $SELF	303	=item $SELF
259		304
260	Contains the current port id while executing C<rcv> callbacks or C<psub>	305	Contains the current port id while executing C<rcv> callbacks or C<psub>
261	blocks.	306	blocks.
262		307
263	=item SELF, %SELF, @SELF...	308	=item *SELF, SELF, %SELF, @SELF...
264		309
265	Due to some quirks in how perl exports variables, it is impossible to	310	Due to some quirks in how perl exports variables, it is impossible to
266	just export C<$SELF>, all the symbols called C<SELF> are exported by this	311	just export C<$SELF>, all the symbols named C<SELF> are exported by this
267	module, but only C<$SELF> is currently used.	312	module, but only C<$SELF> is currently used.
268		313
269	=item snd $port, type => @data	314	=item snd $port, type => @data
270		315
271	=item snd $port, @msg	316	=item snd $port, @msg
272		317
273	Send the given message to the given port ID, which can identify either	318	Send the given message to the given port, which can identify either a
274	a local or a remote port, and must be a port ID.	319	local or a remote port, and must be a port ID.
275		320
276	While the message can be about anything, it is highly recommended to use a	321	While the message can be almost anything, it is highly recommended to
277	string as first element (a port ID, or some word that indicates a request	322	use a string as first element (a port ID, or some word that indicates a
278	type etc.).	323	request type etc.) and to consist if only simple perl values (scalars,
		324	arrays, hashes) - if you think you need to pass an object, think again.
279		325
280	The message data effectively becomes read-only after a call to this	326	The message data logically becomes read-only after a call to this
281	function: modifying any argument is not allowed and can cause many	327	function: modifying any argument (or values referenced by them) is
282	problems.	328	forbidden, as there can be considerable time between the call to C<snd>
		329	and the time the message is actually being serialised - in fact, it might
		330	never be copied as within the same process it is simply handed to the
		331	receiving port.
283		332
284	The type of data you can transfer depends on the transport protocol: when	333	The type of data you can transfer depends on the transport protocol: when
285	JSON is used, then only strings, numbers and arrays and hashes consisting	334	JSON is used, then only strings, numbers and arrays and hashes consisting
286	of those are allowed (no objects). When Storable is used, then anything	335	of those are allowed (no objects). When Storable is used, then anything
287	that Storable can serialise and deserialise is allowed, and for the local	336	that Storable can serialise and deserialise is allowed, and for the local
288	node, anything can be passed.	337	node, anything can be passed. Best rely only on the common denominator of
		338	these.
289		339
290	=item $local_port = port	340	=item $local_port = port
291		341
292	Create a new local port object and returns its port ID. Initially it has	342	Create a new local port object and returns its port ID. Initially it has
293	no callbacks set and will throw an error when it receives messages.	343	no callbacks set and will throw an error when it receives messages.
…		…
366	msg1 => sub { ... },	416	msg1 => sub { ... },
367	...	417	...
368	;	418	;
369		419
370	Example: temporarily register a rcv callback for a tag matching some port	420	Example: temporarily register a rcv callback for a tag matching some port
371	(e.g. for a rpc reply) and unregister it after a message was received.	421	(e.g. for an rpc reply) and unregister it after a message was received.
372		422
373	rcv $port, $otherport => sub {	423	rcv $port, $otherport => sub {
374	my @reply = @_;	424	my @reply = @_;
375		425
376	rcv $SELF, $otherport;	426	rcv $SELF, $otherport;
…		…
378		428
379	=cut	429	=cut
380		430
381	sub rcv($@) {	431	sub rcv($@) {
382	my $port = shift;	432	my $port = shift;
383	my ($noderef, $portid) = split /#/, $port, 2;	433	my ($nodeid, $portid) = split /#/, $port, 2;
384		434
385	$NODE{$noderef} == $NODE{""}	435	$NODE{$nodeid} == $NODE{""}
386	or Carp::croak "$port: rcv can only be called on local ports, caught";	436	or Carp::croak "$port: rcv can only be called on local ports, caught";
387		437
388	while (@_) {	438	while (@_) {
389	if (ref $_[0]) {	439	if (ref $_[0]) {
390	if (my $self = $PORT_DATA{$portid}) {	440	if (my $self = $PORT_DATA{$portid}) {
391	"AnyEvent::MP::Port" eq ref $self	441	"AnyEvent::MP::Port" eq ref $self
392	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	442	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
393		443
394	$self->[2] = shift;	444	$self->[0] = shift;
395	} else {	445	} else {
396	my $cb = shift;	446	my $cb = shift;
397	$PORT{$portid} = sub {	447	$PORT{$portid} = sub {
398	local $SELF = $port;	448	local $SELF = $port;
399	eval { &$cb }; _self_die if $@;	449	eval { &$cb }; _self_die if $@;
400	};	450	};
401	}	451	}
402	} elsif (defined $_[0]) {	452	} elsif (defined $_[0]) {
403	my $self = $PORT_DATA{$portid} \|\|= do {	453	my $self = $PORT_DATA{$portid} \|\|= do {
404	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	454	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
405		455
406	$PORT{$portid} = sub {	456	$PORT{$portid} = sub {
407	local $SELF = $port;	457	local $SELF = $port;
408		458
409	if (my $cb = $self->[1]{$_[0]}) {	459	if (my $cb = $self->[1]{$_[0]}) {
…		…
431	}	481	}
432		482
433	$port	483	$port
434	}	484	}
435		485
		486	=item peval $port, $coderef[, @args]
		487
		488	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		489	when the code throews an exception the C<$port> will be killed.
		490
		491	Any remaining args will be passed to the callback. Any return values will
		492	be returned to the caller.
		493
		494	This is useful when you temporarily want to execute code in the context of
		495	a port.
		496
		497	Example: create a port and run some initialisation code in it's context.
		498
		499	my $port = port { ... };
		500
		501	peval $port, sub {
		502	init
		503	or die "unable to init";
		504	};
		505
		506	=cut
		507
		508	sub peval($$) {
		509	local $SELF = shift;
		510	my $cb = shift;
		511
		512	if (wantarray) {
		513	my @res = eval { &$cb };
		514	_self_die if $@;
		515	@res
		516	} else {
		517	my $res = eval { &$cb };
		518	_self_die if $@;
		519	$res
		520	}
		521	}
		522
436	=item $closure = psub { BLOCK }	523	=item $closure = psub { BLOCK }
437		524
438	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	525	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
439	closure is executed, sets up the environment in the same way as in C<rcv>	526	closure is executed, sets up the environment in the same way as in C<rcv>
440	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	527	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		528
		529	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		530	BLOCK }, @_ } >>.
441		531
442	This is useful when you register callbacks from C<rcv> callbacks:	532	This is useful when you register callbacks from C<rcv> callbacks:
443		533
444	rcv delayed_reply => sub {	534	rcv delayed_reply => sub {
445	my ($delay, @reply) = @_;	535	my ($delay, @reply) = @_;
…		…
469	$res	559	$res
470	}	560	}
471	}	561	}
472	}	562	}
473		563
474	=item $guard = mon $port, $cb->(@reason)	564	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
475		565
476	=item $guard = mon $port, $rcvport	566	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
477		567
478	=item $guard = mon $port	568	=item $guard = mon $port # kill $SELF when $port dies
479		569
480	=item $guard = mon $port, $rcvport, @msg	570	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
481		571
482	Monitor the given port and do something when the port is killed or	572	Monitor the given port and do something when the port is killed or
483	messages to it were lost, and optionally return a guard that can be used	573	messages to it were lost, and optionally return a guard that can be used
484	to stop monitoring again.	574	to stop monitoring again.
485
486	C<mon> effectively guarantees that, in the absence of hardware failures,
487	that after starting the monitor, either all messages sent to the port
488	will arrive, or the monitoring action will be invoked after possible
489	message loss has been detected. No messages will be lost "in between"
490	(after the first lost message no further messages will be received by the
491	port). After the monitoring action was invoked, further messages might get
492	delivered again.
493
494	Note that monitoring-actions are one-shot: once released, they are removed
495	and will not trigger again.
496		575
497	In the first form (callback), the callback is simply called with any	576	In the first form (callback), the callback is simply called with any
498	number of C<@reason> elements (no @reason means that the port was deleted	577	number of C<@reason> elements (no @reason means that the port was deleted
499	"normally"). Note also that I<< the callback B<must> never die >>, so use	578	"normally"). Note also that I<< the callback B<must> never die >>, so use
500	C<eval> if unsure.	579	C<eval> if unsure.
501		580
502	In the second form (another port given), the other port (C<$rcvport>)	581	In the second form (another port given), the other port (C<$rcvport>)
503	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	582	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
504	"normal" kils nothing happens, while under all other conditions, the other	583	"normal" kils nothing happens, while under all other conditions, the other
505	port is killed with the same reason.	584	port is killed with the same reason.
506		585
507	The third form (kill self) is the same as the second form, except that	586	The third form (kill self) is the same as the second form, except that
508	C<$rvport> defaults to C<$SELF>.	587	C<$rvport> defaults to C<$SELF>.
509		588
510	In the last form (message), a message of the form C<@msg, @reason> will be	589	In the last form (message), a message of the form C<@msg, @reason> will be
511	C<snd>.	590	C<snd>.
		591
		592	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		593	alert was raised), they are removed and will not trigger again.
512		594
513	As a rule of thumb, monitoring requests should always monitor a port from	595	As a rule of thumb, monitoring requests should always monitor a port from
514	a local port (or callback). The reason is that kill messages might get	596	a local port (or callback). The reason is that kill messages might get
515	lost, just like any other message. Another less obvious reason is that	597	lost, just like any other message. Another less obvious reason is that
516	even monitoring requests can get lost (for exmaple, when the connection	598	even monitoring requests can get lost (for example, when the connection
517	to the other node goes down permanently). When monitoring a port locally	599	to the other node goes down permanently). When monitoring a port locally
518	these problems do not exist.	600	these problems do not exist.
519		601
		602	C<mon> effectively guarantees that, in the absence of hardware failures,
		603	after starting the monitor, either all messages sent to the port will
		604	arrive, or the monitoring action will be invoked after possible message
		605	loss has been detected. No messages will be lost "in between" (after
		606	the first lost message no further messages will be received by the
		607	port). After the monitoring action was invoked, further messages might get
		608	delivered again.
		609
		610	Inter-host-connection timeouts and monitoring depend on the transport
		611	used. The only transport currently implemented is TCP, and AnyEvent::MP
		612	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		613	non-idle connection, and usually around two hours for idle connections).
		614
		615	This means that monitoring is good for program errors and cleaning up
		616	stuff eventually, but they are no replacement for a timeout when you need
		617	to ensure some maximum latency.
		618
520	Example: call a given callback when C<$port> is killed.	619	Example: call a given callback when C<$port> is killed.
521		620
522	mon $port, sub { warn "port died because of <@_>\n" };	621	mon $port, sub { warn "port died because of <@_>\n" };
523		622
524	Example: kill ourselves when C<$port> is killed abnormally.	623	Example: kill ourselves when C<$port> is killed abnormally.
…		…
530	mon $port, $self => "restart";	629	mon $port, $self => "restart";
531		630
532	=cut	631	=cut
533		632
534	sub mon {	633	sub mon {
535	my ($noderef, $port) = split /#/, shift, 2;	634	my ($nodeid, $port) = split /#/, shift, 2;
536		635
537	my $node = $NODE{$noderef} \|\| add_node $noderef;	636	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
538		637
539	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	638	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
540		639
541	unless (ref $cb) {	640	unless (ref $cb) {
542	if (@_) {	641	if (@_) {
…		…
551	}	650	}
552		651
553	$node->monitor ($port, $cb);	652	$node->monitor ($port, $cb);
554		653
555	defined wantarray	654	defined wantarray
556	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	655	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
557	}	656	}
558		657
559	=item $guard = mon_guard $port, $ref, $ref...	658	=item $guard = mon_guard $port, $ref, $ref...
560		659
561	Monitors the given C<$port> and keeps the passed references. When the port	660	Monitors the given C<$port> and keeps the passed references. When the port
562	is killed, the references will be freed.	661	is killed, the references will be freed.
563		662
564	Optionally returns a guard that will stop the monitoring.	663	Optionally returns a guard that will stop the monitoring.
565		664
566	This function is useful when you create e.g. timers or other watchers and	665	This function is useful when you create e.g. timers or other watchers and
567	want to free them when the port gets killed:	666	want to free them when the port gets killed (note the use of C<psub>):
568		667
569	$port->rcv (start => sub {	668	$port->rcv (start => sub {
570	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	669	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
571	undef $timer if 0.9 < rand;	670	undef $timer if 0.9 < rand;
572	});	671	});
573	});	672	});
574		673
575	=cut	674	=cut
…		…
584		683
585	=item kil $port[, @reason]	684	=item kil $port[, @reason]
586		685
587	Kill the specified port with the given C<@reason>.	686	Kill the specified port with the given C<@reason>.
588		687
589	If no C<@reason> is specified, then the port is killed "normally" (linked	688	If no C<@reason> is specified, then the port is killed "normally" -
590	ports will not be kileld, or even notified).	689	monitor callback will be invoked, but the kil will not cause linked ports
		690	(C<mon $mport, $lport> form) to get killed.
591		691
592	Otherwise, linked ports get killed with the same reason (second form of	692	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
593	C<mon>, see below).	693	form) get killed with the same reason.
594		694
595	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	695	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
596	will be reported as reason C<< die => $@ >>.	696	will be reported as reason C<< die => $@ >>.
597		697
598	Transport/communication errors are reported as C<< transport_error =>	698	Transport/communication errors are reported as C<< transport_error =>
…		…
603	=item $port = spawn $node, $initfunc[, @initdata]	703	=item $port = spawn $node, $initfunc[, @initdata]
604		704
605	Creates a port on the node C<$node> (which can also be a port ID, in which	705	Creates a port on the node C<$node> (which can also be a port ID, in which
606	case it's the node where that port resides).	706	case it's the node where that port resides).
607		707
608	The port ID of the newly created port is return immediately, and it is	708	The port ID of the newly created port is returned immediately, and it is
609	permissible to immediately start sending messages or monitor the port.	709	possible to immediately start sending messages or to monitor the port.
610		710
611	After the port has been created, the init function is	711	After the port has been created, the init function is called on the remote
612	called. This function must be a fully-qualified function name	712	node, in the same context as a C<rcv> callback. This function must be a
613	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	713	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
614	program, use C<::name>.	714	specify a function in the main program, use C<::name>.
615		715
616	If the function doesn't exist, then the node tries to C<require>	716	If the function doesn't exist, then the node tries to C<require>
617	the package, then the package above the package and so on (e.g.	717	the package, then the package above the package and so on (e.g.
618	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	718	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
619	exists or it runs out of package names.	719	exists or it runs out of package names.
620		720
621	The init function is then called with the newly-created port as context	721	The init function is then called with the newly-created port as context
622	object (C<$SELF>) and the C<@initdata> values as arguments.	722	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		723	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		724	the port might not get created.
623		725
624	A common idiom is to pass your own port, monitor the spawned port, and	726	A common idiom is to pass a local port, immediately monitor the spawned
625	in the init function, monitor the original port. This two-way monitoring	727	port, and in the remote init function, immediately monitor the passed
626	ensures that both ports get cleaned up when there is a problem.	728	local port. This two-way monitoring ensures that both ports get cleaned up
		729	when there is a problem.
		730
		731	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		732	caller before C<spawn> returns (by delaying invocation when spawn is
		733	called for the local node).
627		734
628	Example: spawn a chat server port on C<$othernode>.	735	Example: spawn a chat server port on C<$othernode>.
629		736
630	# this node, executed from within a port context:	737	# this node, executed from within a port context:
631	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	738	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
646		753
647	sub _spawn {	754	sub _spawn {
648	my $port = shift;	755	my $port = shift;
649	my $init = shift;	756	my $init = shift;
650		757
		758	# rcv will create the actual port
651	local $SELF = "$NODE#$port";	759	local $SELF = "$NODE#$port";
652	eval {	760	eval {
653	&{ load_func $init }	761	&{ load_func $init }
654	};	762	};
655	_self_die if $@;	763	_self_die if $@;
656	}	764	}
657		765
658	sub spawn(@) {	766	sub spawn(@) {
659	my ($noderef, undef) = split /#/, shift, 2;	767	my ($nodeid, undef) = split /#/, shift, 2;
660		768
661	my $id = "$RUNIQ." . $ID++;	769	my $id = "$RUNIQ." . $ID++;
662		770
663	$_[0] =~ /::/	771	$_[0] =~ /::/
664	or Carp::croak "spawn init function must be a fully-qualified name, caught";	772	or Carp::croak "spawn init function must be a fully-qualified name, caught";
665		773
666	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	774	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
667		775
668	"$noderef#$id"	776	"$nodeid#$id"
669	}	777	}
670		778
671	=item after $timeout, @msg	779	=item after $timeout, @msg
672		780
673	=item after $timeout, $callback	781	=item after $timeout, $callback
674		782
675	Either sends the given message, or call the given callback, after the	783	Either sends the given message, or call the given callback, after the
676	specified number of seconds.	784	specified number of seconds.
677		785
678	This is simply a utility function that come sin handy at times.	786	This is simply a utility function that comes in handy at times - the
		787	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		788	so it may go away in the future.
679		789
680	=cut	790	=cut
681		791
682	sub after($@) {	792	sub after($@) {
683	my ($timeout, @action) = @_;	793	my ($timeout, @action) = @_;
…		…
688	? $action[0]()	798	? $action[0]()
689	: snd @action;	799	: snd @action;
690	};	800	};
691	}	801	}
692		802
		803	=item cal $port, @msg, $callback[, $timeout]
		804
		805	A simple form of RPC - sends a message to the given C<$port> with the
		806	given contents (C<@msg>), but adds a reply port to the message.
		807
		808	The reply port is created temporarily just for the purpose of receiving
		809	the reply, and will be C<kil>ed when no longer needed.
		810
		811	A reply message sent to the port is passed to the C<$callback> as-is.
		812
		813	If an optional time-out (in seconds) is given and it is not C<undef>,
		814	then the callback will be called without any arguments after the time-out
		815	elapsed and the port is C<kil>ed.
		816
		817	If no time-out is given (or it is C<undef>), then the local port will
		818	monitor the remote port instead, so it eventually gets cleaned-up.
		819
		820	Currently this function returns the temporary port, but this "feature"
		821	might go in future versions unless you can make a convincing case that
		822	this is indeed useful for something.
		823
		824	=cut
		825
		826	sub cal(@) {
		827	my $timeout = ref $_[-1] ? undef : pop;
		828	my $cb = pop;
		829
		830	my $port = port {
		831	undef $timeout;
		832	kil $SELF;
		833	&$cb;
		834	};
		835
		836	if (defined $timeout) {
		837	$timeout = AE::timer $timeout, 0, sub {
		838	undef $timeout;
		839	kil $port;
		840	$cb->();
		841	};
		842	} else {
		843	mon $_[0], sub {
		844	kil $port;
		845	$cb->();
		846	};
		847	}
		848
		849	push @_, $port;
		850	&snd;
		851
		852	$port
		853	}
		854
693	=back	855	=back
694		856
695	=head1 AnyEvent::MP vs. Distributed Erlang	857	=head1 AnyEvent::MP vs. Distributed Erlang
696		858
697	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	859	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
698	== aemp node, Erlang process == aemp port), so many of the documents and	860	== aemp node, Erlang process == aemp port), so many of the documents and
699	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	861	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
700	sample:	862	sample:
701		863
702	http://www.Erlang.se/doc/programming_rules.shtml	864	http://www.erlang.se/doc/programming_rules.shtml
703	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	865	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
704	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	866	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
705	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	867	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
706		868
707	Despite the similarities, there are also some important differences:	869	Despite the similarities, there are also some important differences:
708		870
709	=over 4	871	=over 4
710		872
711	=item * Node references contain the recipe on how to contact them.	873	=item * Node IDs are arbitrary strings in AEMP.
712		874
713	Erlang relies on special naming and DNS to work everywhere in the	875	Erlang relies on special naming and DNS to work everywhere in the same
714	same way. AEMP relies on each node knowing it's own address(es), with	876	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
715	convenience functionality.	877	configuration or DNS), and possibly the addresses of some seed nodes, but
716		878	will otherwise discover other nodes (and their IDs) itself.
717	This means that AEMP requires a less tightly controlled environment at the
718	cost of longer node references and a slightly higher management overhead.
719		879
720	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	880	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
721	uses "local ports are like remote ports".	881	uses "local ports are like remote ports".
722		882
723	The failure modes for local ports are quite different (runtime errors	883	The failure modes for local ports are quite different (runtime errors
…		…
732	ports being the special case/exception, where transport errors cannot	892	ports being the special case/exception, where transport errors cannot
733	occur.	893	occur.
734		894
735	=item * Erlang uses processes and a mailbox, AEMP does not queue.	895	=item * Erlang uses processes and a mailbox, AEMP does not queue.
736		896
737	Erlang uses processes that selectively receive messages, and therefore	897	Erlang uses processes that selectively receive messages out of order, and
738	needs a queue. AEMP is event based, queuing messages would serve no	898	therefore needs a queue. AEMP is event based, queuing messages would serve
739	useful purpose. For the same reason the pattern-matching abilities of	899	no useful purpose. For the same reason the pattern-matching abilities
740	AnyEvent::MP are more limited, as there is little need to be able to	900	of AnyEvent::MP are more limited, as there is little need to be able to
741	filter messages without dequeing them.	901	filter messages without dequeuing them.
742		902
743	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	903	This is not a philosophical difference, but simply stems from AnyEvent::MP
		904	being event-based, while Erlang is process-based.
		905
		906	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		907	top of AEMP and Coro threads.
744		908
745	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	909	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
746		910
747	Sending messages in Erlang is synchronous and blocks the process (and	911	Sending messages in Erlang is synchronous and blocks the process until
		912	a conenction has been established and the message sent (and so does not
748	so does not need a queue that can overflow). AEMP sends are immediate,	913	need a queue that can overflow). AEMP sends return immediately, connection
749	connection establishment is handled in the background.	914	establishment is handled in the background.
750		915
751	=item * Erlang suffers from silent message loss, AEMP does not.	916	=item * Erlang suffers from silent message loss, AEMP does not.
752		917
753	Erlang makes few guarantees on messages delivery - messages can get lost	918	Erlang implements few guarantees on messages delivery - messages can get
754	without any of the processes realising it (i.e. you send messages a, b,	919	lost without any of the processes realising it (i.e. you send messages a,
755	and c, and the other side only receives messages a and c).	920	b, and c, and the other side only receives messages a and c).
756		921
757	AEMP guarantees correct ordering, and the guarantee that there are no	922	AEMP guarantees (modulo hardware errors) correct ordering, and the
		923	guarantee that after one message is lost, all following ones sent to the
		924	same port are lost as well, until monitoring raises an error, so there are
758	holes in the message sequence.	925	no silent "holes" in the message sequence.
759		926
760	=item * In Erlang, processes can be declared dead and later be found to be	927	If you want your software to be very reliable, you have to cope with
761	alive.	928	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
762		929	simply tries to work better in common error cases, such as when a network
763	In Erlang it can happen that a monitored process is declared dead and	930	link goes down.
764	linked processes get killed, but later it turns out that the process is
765	still alive - and can receive messages.
766
767	In AEMP, when port monitoring detects a port as dead, then that port will
768	eventually be killed - it cannot happen that a node detects a port as dead
769	and then later sends messages to it, finding it is still alive.
770		931
771	=item * Erlang can send messages to the wrong port, AEMP does not.	932	=item * Erlang can send messages to the wrong port, AEMP does not.
772		933
773	In Erlang it is quite likely that a node that restarts reuses a process ID	934	In Erlang it is quite likely that a node that restarts reuses an Erlang
774	known to other nodes for a completely different process, causing messages	935	process ID known to other nodes for a completely different process,
775	destined for that process to end up in an unrelated process.	936	causing messages destined for that process to end up in an unrelated
		937	process.
776		938
777	AEMP never reuses port IDs, so old messages or old port IDs floating	939	AEMP does not reuse port IDs, so old messages or old port IDs floating
778	around in the network will not be sent to an unrelated port.	940	around in the network will not be sent to an unrelated port.
779		941
780	=item * Erlang uses unprotected connections, AEMP uses secure	942	=item * Erlang uses unprotected connections, AEMP uses secure
781	authentication and can use TLS.	943	authentication and can use TLS.
782		944
783	AEMP can use a proven protocol - SSL/TLS - to protect connections and	945	AEMP can use a proven protocol - TLS - to protect connections and
784	securely authenticate nodes.	946	securely authenticate nodes.
785		947
786	=item * The AEMP protocol is optimised for both text-based and binary	948	=item * The AEMP protocol is optimised for both text-based and binary
787	communications.	949	communications.
788		950
789	The AEMP protocol, unlike the Erlang protocol, supports both	951	The AEMP protocol, unlike the Erlang protocol, supports both programming
790	language-independent text-only protocols (good for debugging) and binary,	952	language independent text-only protocols (good for debugging), and binary,
791	language-specific serialisers (e.g. Storable).	953	language-specific serialisers (e.g. Storable). By default, unless TLS is
		954	used, the protocol is actually completely text-based.
792		955
793	It has also been carefully designed to be implementable in other languages	956	It has also been carefully designed to be implementable in other languages
794	with a minimum of work while gracefully degrading fucntionality to make the	957	with a minimum of work while gracefully degrading functionality to make the
795	protocol simple.	958	protocol simple.
796		959
797	=item * AEMP has more flexible monitoring options than Erlang.	960	=item * AEMP has more flexible monitoring options than Erlang.
798		961
799	In Erlang, you can chose to receive I<all> exit signals as messages	962	In Erlang, you can chose to receive I<all> exit signals as messages or
800	or I<none>, there is no in-between, so monitoring single processes is	963	I<none>, there is no in-between, so monitoring single Erlang processes is
801	difficult to implement. Monitoring in AEMP is more flexible than in	964	difficult to implement.
802	Erlang, as one can choose between automatic kill, exit message or callback	965
803	on a per-process basis.	966	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		967	between automatic kill, exit message or callback on a per-port basis.
804		968
805	=item * Erlang tries to hide remote/local connections, AEMP does not.	969	=item * Erlang tries to hide remote/local connections, AEMP does not.
806		970
807	Monitoring in Erlang is not an indicator of process death/crashes,	971	Monitoring in Erlang is not an indicator of process death/crashes, in the
808	as linking is (except linking is unreliable in Erlang).	972	same way as linking is (except linking is unreliable in Erlang).
809		973
810	In AEMP, you don't "look up" registered port names or send to named ports	974	In AEMP, you don't "look up" registered port names or send to named ports
811	that might or might not be persistent. Instead, you normally spawn a port	975	that might or might not be persistent. Instead, you normally spawn a port
812	on the remote node. The init function monitors the you, and you monitor	976	on the remote node. The init function monitors you, and you monitor the
813	the remote port. Since both monitors are local to the node, they are much	977	remote port. Since both monitors are local to the node, they are much more
814	more reliable.	978	reliable (no need for C<spawn_link>).
815		979
816	This also saves round-trips and avoids sending messages to the wrong port	980	This also saves round-trips and avoids sending messages to the wrong port
817	(hard to do in Erlang).	981	(hard to do in Erlang).
818		982
819	=back	983	=back
820		984
821	=head1 RATIONALE	985	=head1 RATIONALE
822		986
823	=over 4	987	=over 4
824		988
825	=item Why strings for ports and noderefs, why not objects?	989	=item Why strings for port and node IDs, why not objects?
826		990
827	We considered "objects", but found that the actual number of methods	991	We considered "objects", but found that the actual number of methods
828	thatc an be called are very low. Since port IDs and noderefs travel over	992	that can be called are quite low. Since port and node IDs travel over
829	the network frequently, the serialising/deserialising would add lots of	993	the network frequently, the serialising/deserialising would add lots of
830	overhead, as well as having to keep a proxy object.	994	overhead, as well as having to keep a proxy object everywhere.
831		995
832	Strings can easily be printed, easily serialised etc. and need no special	996	Strings can easily be printed, easily serialised etc. and need no special
833	procedures to be "valid".	997	procedures to be "valid".
834		998
835	And a a miniport consists of a single closure stored in a global hash - it	999	And as a result, a port with just a default receiver consists of a single
836	can't become much cheaper.	1000	code reference stored in a global hash - it can't become much cheaper.
837		1001
838	=item Why favour JSON, why not real serialising format such as Storable?	1002	=item Why favour JSON, why not a real serialising format such as Storable?
839		1003
840	In fact, any AnyEvent::MP node will happily accept Storable as framing	1004	In fact, any AnyEvent::MP node will happily accept Storable as framing
841	format, but currently there is no way to make a node use Storable by	1005	format, but currently there is no way to make a node use Storable by
842	default.	1006	default (although all nodes will accept it).
843		1007
844	The default framing protocol is JSON because a) JSON::XS is many times	1008	The default framing protocol is JSON because a) JSON::XS is many times
845	faster for small messages and b) most importantly, after years of	1009	faster for small messages and b) most importantly, after years of
846	experience we found that object serialisation is causing more problems	1010	experience we found that object serialisation is causing more problems
847	than it gains: Just like function calls, objects simply do not travel	1011	than it solves: Just like function calls, objects simply do not travel
848	easily over the network, mostly because they will always be a copy, so you	1012	easily over the network, mostly because they will always be a copy, so you
849	always have to re-think your design.	1013	always have to re-think your design.
850		1014
851	Keeping your messages simple, concentrating on data structures rather than	1015	Keeping your messages simple, concentrating on data structures rather than
852	objects, will keep your messages clean, tidy and efficient.	1016	objects, will keep your messages clean, tidy and efficient.
853		1017
854	=back	1018	=back
855		1019
856	=head1 SEE ALSO	1020	=head1 SEE ALSO
857		1021
		1022	L<AnyEvent::MP::Intro> - a gentle introduction.
		1023
		1024	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1025
		1026	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1027	your applications.
		1028
		1029	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1030
		1031	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1032	all nodes.
		1033
858	L<AnyEvent>.	1034	L<AnyEvent>.
859		1035
860	=head1 AUTHOR	1036	=head1 AUTHOR
861		1037
862	Marc Lehmann <schmorp@schmorp.de>	1038	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.63 by root, Thu Aug 27 21:29:37 2009 UTC vs.
Revision 1.119 by root, Sun Feb 26 10:29:59 2012 UTC