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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.64 by root, Fri Aug 28 00:58:44 2009 UTC vs.
Revision 1.123 by root, Thu Mar 1 19:37:59 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 send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	81	anything was listening for them or not.
75		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
76	=item port ID - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
77		86
78	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<#>)
79	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
80	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
81	reference.
82		90
83	=item node	91	=item node
84		92
85	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
86	which provides nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
87	ports.	95	ports.
88		96
89	Nodes are either private (single-process only), slaves (can only talk to	97	Nodes are either public (have one or more listening ports) or private
90	public nodes, but do not need an open port) or public nodes (connectable	98	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	99	currently, but all nodes can talk to public nodes.
92		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
94		104
95	A node ID is a string that uniquely identifies the node within a	105	A node ID is a string that uniquely identifies the node within a
96	network. Depending on the configuration used, node IDs can look like a	106	network. Depending on the configuration used, node IDs can look like a
97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
98	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
99		109
100	=item binds - C<ip:port>	110	=item binds - C<ip:port>
101		111
102	Nodes can only talk to each other by creating some kind of connection to	112	Nodes can only talk to each other by creating some kind of connection to
103	each other. To do this, nodes should listen on one or more local transport	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
104	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
105	be used, which specify TCP ports to listen on.	117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
106		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
107	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
108		150
109	When a node starts, it knows nothing about the network. To teach the node	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
110	about the network it first has to contact some other node within the	152	TCP port) of nodes that should be used as seed nodes.
111	network. This node is called a seed.
112		153
113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
114	are expected to be long-running, and at least one of those should always	155
115	be available. When nodes run out of connections (e.g. due to a network	156	An AEMP network needs a discovery service - nodes need to know how to
116	error), they try to re-establish connections to some seednodes again to	157	connect to other nodes they only know by name. In addition, AEMP offers a
117	join the network.	158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
118		170
119	=back	171	=back
120		172
121	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
122		174
124		176
125	=cut	177	=cut
126		178
127	package AnyEvent::MP;	179	package AnyEvent::MP;
128		180
		181	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130		184
131	use common::sense;	185	use common::sense;
132		186
133	use Carp ();	187	use Carp ();
134		188
135	use AE ();	189	use AE ();
136		190
137	use base "Exporter";	191	use base "Exporter";
138		192
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	193	our $VERSION = $AnyEvent::MP::Config::VERSION;
140		194
141	our @EXPORT = qw(	195	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	196	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	197	configure
144	snd rcv mon mon_guard kil reg psub spawn	198	snd rcv mon mon_guard kil psub peval spawn cal
145	port	199	port
146	);	200	);
147		201
148	our $SELF;	202	our $SELF;
149		203
…		…
153	kil $SELF, die => $msg;	207	kil $SELF, die => $msg;
154	}	208	}
155		209
156	=item $thisnode = NODE / $NODE	210	=item $thisnode = NODE / $NODE
157		211
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	212	The C<NODE> function returns, and the C<$NODE> variable contains, the node
159	ID of the node running in the current process. This value is initialised by	213	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	214	a call to C<configure>.
161		215
162	=item $nodeid = node_of $port	216	=item $nodeid = node_of $port
163		217
164	Extracts and returns the node ID part from a port ID or a node ID.	218	Extracts and returns the node ID from a port ID or a node ID.
165		219
166	=item initialise_node $profile_name	220	=item configure $profile, key => value...
		221
		222	=item configure key => value...
167		223
168	Before a node can talk to other nodes on the network (i.e. enter	224	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to initialise itself - the minimum a node needs	225	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	226	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	227	some other nodes in the network to discover other nodes.
172		228
173	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
174	never) before calling other AnyEvent::MP functions.	230	never) before calling other AnyEvent::MP functions.
175		231
176	The first argument is a profile name. If it is C<undef> or missing, then	232	The key/value pairs are basically the same ones as documented for the
177	the current nodename will be used instead (i.e. F<uname -n>).	233	F<aemp> command line utility (sans the set/del prefix), with two additions:
178		234
		235	=over 4
		236
		237	=item norc => $boolean (default false)
		238
		239	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		240	be consulted - all configuraiton options must be specified in the
		241	C<configure> call.
		242
		243	=item force => $boolean (default false)
		244
		245	IF true, then the values specified in the C<configure> will take
		246	precedence over any values configured via the rc file. The default is for
		247	the rc file to override any options specified in the program.
		248
		249	=back
		250
		251	=over 4
		252
		253	=item step 1, gathering configuration from profiles
		254
179	The function then looks up the profile in the aemp configuration (see the	255	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	256	L<aemp> commandline utility). The profile name can be specified via the
		257	named C<profile> parameter or can simply be the first parameter). If it is
		258	missing, then the nodename (F<uname -n>) will be used as profile name.
		259
		260	The profile data is then gathered as follows:
		261
		262	First, all remaining key => value pairs (all of which are conveniently
		263	undocumented at the moment) will be interpreted as configuration
		264	data. Then they will be overwritten by any values specified in the global
		265	default configuration (see the F<aemp> utility), then the chain of
		266	profiles chosen by the profile name (and any C<parent> attributes).
		267
		268	That means that the values specified in the profile have highest priority
		269	and the values specified directly via C<configure> have lowest priority,
		270	and can only be used to specify defaults.
181		271
182	If the profile specifies a node ID, then this will become the node ID of	272	If the profile specifies a node ID, then this will become the node ID of
183	this process. If not, then the profile name will be used as node ID. The	273	this process. If not, then the profile name will be used as node ID, with
184	special node ID of C<anon/> will be replaced by a random node ID.	274	a slash (C</>) attached.
		275
		276	If the node ID (or profile name) ends with a slash (C</>), then a random
		277	string is appended to make it unique.
		278
		279	=item step 2, bind listener sockets
185		280
186	The next step is to look up the binds in the profile, followed by binding	281	The next step is to look up the binds in the profile, followed by binding
187	aemp protocol listeners on all binds specified (it is possible and valid	282	aemp protocol listeners on all binds specified (it is possible and valid
188	to have no binds, meaning that the node cannot be contacted form the	283	to have no binds, meaning that the node cannot be contacted form the
189	outside. This means the node cannot talk to other nodes that also have no	284	outside. This means the node cannot talk to other nodes that also have no
190	binds, but it can still talk to all "normal" nodes).	285	binds, but it can still talk to all "normal" nodes).
191		286
192	If the profile does not specify a binds list, then the node ID will be	287	If the profile does not specify a binds list, then a default of C<*> is
193	treated as if it were of the form C<host:port>, which will be resolved and	288	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	289	local IP address it finds.
195		290
		291	=item step 3, connect to seed nodes
		292
196	Lastly, the seeds list from the profile is passed to the	293	As the last step, the seed ID list from the profile is passed to the
197	L<AnyEvent::MP::Global> module, which will then use it to keep	294	L<AnyEvent::MP::Global> module, which will then use it to keep
198	connectivity with at least on of those seed nodes at any point in time.	295	connectivity with at least one node at any point in time.
199		296
200	Example: become a distributed node listening on the guessed noderef, or	297	=back
201	the one specified via C<aemp> for the current node. This should be the	298
		299	Example: become a distributed node using the local node name as profile.
202	most common form of invocation for "daemon"-type nodes.	300	This should be the most common form of invocation for "daemon"-type nodes.
203		301
204	initialise_node;	302	configure
205		303
206	Example: become an anonymous node. This form is often used for commandline	304	Example: become an anonymous node. This form is often used for commandline
207	clients.	305	clients.
208		306
209	initialise_node "anon/";	307	configure nodeid => "anon/";
210		308
211	Example: become a distributed node. If there is no profile of the given	309	Example: configure a node using a profile called seed, which is suitable
212	name, or no binds list was specified, resolve C<localhost:4044> and bind	310	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	311	customary for aemp).
214		312
215	initialise_node "localhost:4044";	313	# use the aemp commandline utility
		314	# aemp profile seed binds '*:4040'
		315
		316	# then use it
		317	configure profile => "seed";
		318
		319	# or simply use aemp from the shell again:
		320	# aemp run profile seed
		321
		322	# or provide a nicer-to-remember nodeid
		323	# aemp run profile seed nodeid "$(hostname)"
216		324
217	=item $SELF	325	=item $SELF
218		326
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	327	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	328	blocks.
221		329
222	=item SELF, %SELF, @SELF...	330	=item *SELF, SELF, %SELF, @SELF...
223		331
224	Due to some quirks in how perl exports variables, it is impossible to	332	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	333	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	334	module, but only C<$SELF> is currently used.
227		335
228	=item snd $port, type => @data	336	=item snd $port, type => @data
229		337
230	=item snd $port, @msg	338	=item snd $port, @msg
231		339
232	Send the given message to the given port ID, which can identify either	340	Send the given message to the given port, which can identify either a
233	a local or a remote port, and must be a port ID.	341	local or a remote port, and must be a port ID.
234		342
235	While the message can be about anything, it is highly recommended to use a	343	While the message can be almost anything, it is highly recommended to
236	string as first element (a port ID, or some word that indicates a request	344	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	345	request type etc.) and to consist if only simple perl values (scalars,
		346	arrays, hashes) - if you think you need to pass an object, think again.
238		347
239	The message data effectively becomes read-only after a call to this	348	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	349	function: modifying any argument (or values referenced by them) is
241	problems.	350	forbidden, as there can be considerable time between the call to C<snd>
		351	and the time the message is actually being serialised - in fact, it might
		352	never be copied as within the same process it is simply handed to the
		353	receiving port.
242		354
243	The type of data you can transfer depends on the transport protocol: when	355	The type of data you can transfer depends on the transport protocol: when
244	JSON is used, then only strings, numbers and arrays and hashes consisting	356	JSON is used, then only strings, numbers and arrays and hashes consisting
245	of those are allowed (no objects). When Storable is used, then anything	357	of those are allowed (no objects). When Storable is used, then anything
246	that Storable can serialise and deserialise is allowed, and for the local	358	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	359	node, anything can be passed. Best rely only on the common denominator of
		360	these.
248		361
249	=item $local_port = port	362	=item $local_port = port
250		363
251	Create a new local port object and returns its port ID. Initially it has	364	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	365	no callbacks set and will throw an error when it receives messages.
…		…
276	sub _kilme {	389	sub _kilme {
277	die "received message on port without callback";	390	die "received message on port without callback";
278	}	391	}
279		392
280	sub port(;&) {	393	sub port(;&) {
281	my $id = "$UNIQ." . $ID++;	394	my $id = $UNIQ . ++$ID;
282	my $port = "$NODE#$id";	395	my $port = "$NODE#$id";
283		396
284	rcv $port, shift \|\| \&_kilme;	397	rcv $port, shift \|\| \&_kilme;
285		398
286	$port	399	$port
…		…
325	msg1 => sub { ... },	438	msg1 => sub { ... },
326	...	439	...
327	;	440	;
328		441
329	Example: temporarily register a rcv callback for a tag matching some port	442	Example: temporarily register a rcv callback for a tag matching some port
330	(e.g. for a rpc reply) and unregister it after a message was received.	443	(e.g. for an rpc reply) and unregister it after a message was received.
331		444
332	rcv $port, $otherport => sub {	445	rcv $port, $otherport => sub {
333	my @reply = @_;	446	my @reply = @_;
334		447
335	rcv $SELF, $otherport;	448	rcv $SELF, $otherport;
…		…
337		450
338	=cut	451	=cut
339		452
340	sub rcv($@) {	453	sub rcv($@) {
341	my $port = shift;	454	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	455	my ($nodeid, $portid) = split /#/, $port, 2;
343		456
344	$NODE{$noderef} == $NODE{""}	457	$NODE{$nodeid} == $NODE{""}
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	458	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		459
347	while (@_) {	460	while (@_) {
348	if (ref $_[0]) {	461	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	462	if (my $self = $PORT_DATA{$portid}) {
350	"AnyEvent::MP::Port" eq ref $self	463	"AnyEvent::MP::Port" eq ref $self
351	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	464	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
352		465
353	$self->[2] = shift;	466	$self->[0] = shift;
354	} else {	467	} else {
355	my $cb = shift;	468	my $cb = shift;
356	$PORT{$portid} = sub {	469	$PORT{$portid} = sub {
357	local $SELF = $port;	470	local $SELF = $port;
358	eval { &$cb }; _self_die if $@;	471	eval { &$cb }; _self_die if $@;
359	};	472	};
360	}	473	}
361	} elsif (defined $_[0]) {	474	} elsif (defined $_[0]) {
362	my $self = $PORT_DATA{$portid} \|\|= do {	475	my $self = $PORT_DATA{$portid} \|\|= do {
363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	476	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
364		477
365	$PORT{$portid} = sub {	478	$PORT{$portid} = sub {
366	local $SELF = $port;	479	local $SELF = $port;
367		480
368	if (my $cb = $self->[1]{$_[0]}) {	481	if (my $cb = $self->[1]{$_[0]}) {
…		…
390	}	503	}
391		504
392	$port	505	$port
393	}	506	}
394		507
		508	=item peval $port, $coderef[, @args]
		509
		510	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		511	when the code throews an exception the C<$port> will be killed.
		512
		513	Any remaining args will be passed to the callback. Any return values will
		514	be returned to the caller.
		515
		516	This is useful when you temporarily want to execute code in the context of
		517	a port.
		518
		519	Example: create a port and run some initialisation code in it's context.
		520
		521	my $port = port { ... };
		522
		523	peval $port, sub {
		524	init
		525	or die "unable to init";
		526	};
		527
		528	=cut
		529
		530	sub peval($$) {
		531	local $SELF = shift;
		532	my $cb = shift;
		533
		534	if (wantarray) {
		535	my @res = eval { &$cb };
		536	_self_die if $@;
		537	@res
		538	} else {
		539	my $res = eval { &$cb };
		540	_self_die if $@;
		541	$res
		542	}
		543	}
		544
395	=item $closure = psub { BLOCK }	545	=item $closure = psub { BLOCK }
396		546
397	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	547	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
398	closure is executed, sets up the environment in the same way as in C<rcv>	548	closure is executed, sets up the environment in the same way as in C<rcv>
399	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	549	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		550
		551	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		552	BLOCK }, @_ } >>.
400		553
401	This is useful when you register callbacks from C<rcv> callbacks:	554	This is useful when you register callbacks from C<rcv> callbacks:
402		555
403	rcv delayed_reply => sub {	556	rcv delayed_reply => sub {
404	my ($delay, @reply) = @_;	557	my ($delay, @reply) = @_;
…		…
428	$res	581	$res
429	}	582	}
430	}	583	}
431	}	584	}
432		585
433	=item $guard = mon $port, $cb->(@reason)	586	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
434		587
435	=item $guard = mon $port, $rcvport	588	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
436		589
437	=item $guard = mon $port	590	=item $guard = mon $port # kill $SELF when $port dies
438		591
439	=item $guard = mon $port, $rcvport, @msg	592	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		593
441	Monitor the given port and do something when the port is killed or	594	Monitor the given port and do something when the port is killed or
442	messages to it were lost, and optionally return a guard that can be used	595	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	596	to stop monitoring again.
444
445	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port
447	will arrive, or the monitoring action will be invoked after possible
448	message loss has been detected. No messages will be lost "in between"
449	(after the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get
451	delivered again.
452
453	Note that monitoring-actions are one-shot: once released, they are removed
454	and will not trigger again.
455		597
456	In the first form (callback), the callback is simply called with any	598	In the first form (callback), the callback is simply called with any
457	number of C<@reason> elements (no @reason means that the port was deleted	599	number of C<@reason> elements (no @reason means that the port was deleted
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	600	"normally"). Note also that I<< the callback B<must> never die >>, so use
459	C<eval> if unsure.	601	C<eval> if unsure.
460		602
461	In the second form (another port given), the other port (C<$rcvport>)	603	In the second form (another port given), the other port (C<$rcvport>)
462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	604	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
463	"normal" kils nothing happens, while under all other conditions, the other	605	"normal" kils nothing happens, while under all other conditions, the other
464	port is killed with the same reason.	606	port is killed with the same reason.
465		607
466	The third form (kill self) is the same as the second form, except that	608	The third form (kill self) is the same as the second form, except that
467	C<$rvport> defaults to C<$SELF>.	609	C<$rvport> defaults to C<$SELF>.
468		610
469	In the last form (message), a message of the form C<@msg, @reason> will be	611	In the last form (message), a message of the form C<@msg, @reason> will be
470	C<snd>.	612	C<snd>.
		613
		614	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		615	alert was raised), they are removed and will not trigger again.
471		616
472	As a rule of thumb, monitoring requests should always monitor a port from	617	As a rule of thumb, monitoring requests should always monitor a port from
473	a local port (or callback). The reason is that kill messages might get	618	a local port (or callback). The reason is that kill messages might get
474	lost, just like any other message. Another less obvious reason is that	619	lost, just like any other message. Another less obvious reason is that
475	even monitoring requests can get lost (for exmaple, when the connection	620	even monitoring requests can get lost (for example, when the connection
476	to the other node goes down permanently). When monitoring a port locally	621	to the other node goes down permanently). When monitoring a port locally
477	these problems do not exist.	622	these problems do not exist.
478		623
		624	C<mon> effectively guarantees that, in the absence of hardware failures,
		625	after starting the monitor, either all messages sent to the port will
		626	arrive, or the monitoring action will be invoked after possible message
		627	loss has been detected. No messages will be lost "in between" (after
		628	the first lost message no further messages will be received by the
		629	port). After the monitoring action was invoked, further messages might get
		630	delivered again.
		631
		632	Inter-host-connection timeouts and monitoring depend on the transport
		633	used. The only transport currently implemented is TCP, and AnyEvent::MP
		634	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		635	non-idle connection, and usually around two hours for idle connections).
		636
		637	This means that monitoring is good for program errors and cleaning up
		638	stuff eventually, but they are no replacement for a timeout when you need
		639	to ensure some maximum latency.
		640
479	Example: call a given callback when C<$port> is killed.	641	Example: call a given callback when C<$port> is killed.
480		642
481	mon $port, sub { warn "port died because of <@_>\n" };	643	mon $port, sub { warn "port died because of <@_>\n" };
482		644
483	Example: kill ourselves when C<$port> is killed abnormally.	645	Example: kill ourselves when C<$port> is killed abnormally.
…		…
489	mon $port, $self => "restart";	651	mon $port, $self => "restart";
490		652
491	=cut	653	=cut
492		654
493	sub mon {	655	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	656	my ($nodeid, $port) = split /#/, shift, 2;
495		657
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	658	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		659
498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	660	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
499		661
500	unless (ref $cb) {	662	unless (ref $cb) {
501	if (@_) {	663	if (@_) {
…		…
510	}	672	}
511		673
512	$node->monitor ($port, $cb);	674	$node->monitor ($port, $cb);
513		675
514	defined wantarray	676	defined wantarray
515	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	677	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
516	}	678	}
517		679
518	=item $guard = mon_guard $port, $ref, $ref...	680	=item $guard = mon_guard $port, $ref, $ref...
519		681
520	Monitors the given C<$port> and keeps the passed references. When the port	682	Monitors the given C<$port> and keeps the passed references. When the port
521	is killed, the references will be freed.	683	is killed, the references will be freed.
522		684
523	Optionally returns a guard that will stop the monitoring.	685	Optionally returns a guard that will stop the monitoring.
524		686
525	This function is useful when you create e.g. timers or other watchers and	687	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	688	want to free them when the port gets killed (note the use of C<psub>):
527		689
528	$port->rcv (start => sub {	690	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	691	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	692	undef $timer if 0.9 < rand;
531	});	693	});
532	});	694	});
533		695
534	=cut	696	=cut
…		…
543		705
544	=item kil $port[, @reason]	706	=item kil $port[, @reason]
545		707
546	Kill the specified port with the given C<@reason>.	708	Kill the specified port with the given C<@reason>.
547		709
548	If no C<@reason> is specified, then the port is killed "normally" (linked	710	If no C<@reason> is specified, then the port is killed "normally" -
549	ports will not be kileld, or even notified).	711	monitor callback will be invoked, but the kil will not cause linked ports
		712	(C<mon $mport, $lport> form) to get killed.
550		713
551	Otherwise, linked ports get killed with the same reason (second form of	714	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
552	C<mon>, see below).	715	form) get killed with the same reason.
553		716
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	717	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	718	will be reported as reason C<< die => $@ >>.
556		719
557	Transport/communication errors are reported as C<< transport_error =>	720	Transport/communication errors are reported as C<< transport_error =>
…		…
562	=item $port = spawn $node, $initfunc[, @initdata]	725	=item $port = spawn $node, $initfunc[, @initdata]
563		726
564	Creates a port on the node C<$node> (which can also be a port ID, in which	727	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	728	case it's the node where that port resides).
566		729
567	The port ID of the newly created port is return immediately, and it is	730	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	731	possible to immediately start sending messages or to monitor the port.
569		732
570	After the port has been created, the init function is	733	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	734	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	735	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	736	specify a function in the main program, use C<::name>.
574		737
575	If the function doesn't exist, then the node tries to C<require>	738	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	739	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	740	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	741	exists or it runs out of package names.
579		742
580	The init function is then called with the newly-created port as context	743	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	744	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		745	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		746	the port might not get created.
582		747
583	A common idiom is to pass your own port, monitor the spawned port, and	748	A common idiom is to pass a local port, immediately monitor the spawned
584	in the init function, monitor the original port. This two-way monitoring	749	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	750	local port. This two-way monitoring ensures that both ports get cleaned up
		751	when there is a problem.
		752
		753	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		754	caller before C<spawn> returns (by delaying invocation when spawn is
		755	called for the local node).
586		756
587	Example: spawn a chat server port on C<$othernode>.	757	Example: spawn a chat server port on C<$othernode>.
588		758
589	# this node, executed from within a port context:	759	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	760	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
605		775
606	sub _spawn {	776	sub _spawn {
607	my $port = shift;	777	my $port = shift;
608	my $init = shift;	778	my $init = shift;
609		779
		780	# rcv will create the actual port
610	local $SELF = "$NODE#$port";	781	local $SELF = "$NODE#$port";
611	eval {	782	eval {
612	&{ load_func $init }	783	&{ load_func $init }
613	};	784	};
614	_self_die if $@;	785	_self_die if $@;
615	}	786	}
616		787
617	sub spawn(@) {	788	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	789	my ($nodeid, undef) = split /#/, shift, 2;
619		790
620	my $id = "$RUNIQ." . $ID++;	791	my $id = $RUNIQ . ++$ID;
621		792
622	$_[0] =~ /::/	793	$_[0] =~ /::/
623	or Carp::croak "spawn init function must be a fully-qualified name, caught";	794	or Carp::croak "spawn init function must be a fully-qualified name, caught";
624		795
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	796	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		797
627	"$noderef#$id"	798	"$nodeid#$id"
628	}	799	}
		800
629		801
630	=item after $timeout, @msg	802	=item after $timeout, @msg
631		803
632	=item after $timeout, $callback	804	=item after $timeout, $callback
633		805
634	Either sends the given message, or call the given callback, after the	806	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	807	specified number of seconds.
636		808
637	This is simply a utility function that come sin handy at times.	809	This is simply a utility function that comes in handy at times - the
		810	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		811	so it may go away in the future.
638		812
639	=cut	813	=cut
640		814
641	sub after($@) {	815	sub after($@) {
642	my ($timeout, @action) = @_;	816	my ($timeout, @action) = @_;
…		…
647	? $action[0]()	821	? $action[0]()
648	: snd @action;	822	: snd @action;
649	};	823	};
650	}	824	}
651		825
		826	=item cal $port, @msg, $callback[, $timeout]
		827
		828	A simple form of RPC - sends a message to the given C<$port> with the
		829	given contents (C<@msg>), but adds a reply port to the message.
		830
		831	The reply port is created temporarily just for the purpose of receiving
		832	the reply, and will be C<kil>ed when no longer needed.
		833
		834	A reply message sent to the port is passed to the C<$callback> as-is.
		835
		836	If an optional time-out (in seconds) is given and it is not C<undef>,
		837	then the callback will be called without any arguments after the time-out
		838	elapsed and the port is C<kil>ed.
		839
		840	If no time-out is given (or it is C<undef>), then the local port will
		841	monitor the remote port instead, so it eventually gets cleaned-up.
		842
		843	Currently this function returns the temporary port, but this "feature"
		844	might go in future versions unless you can make a convincing case that
		845	this is indeed useful for something.
		846
		847	=cut
		848
		849	sub cal(@) {
		850	my $timeout = ref $_[-1] ? undef : pop;
		851	my $cb = pop;
		852
		853	my $port = port {
		854	undef $timeout;
		855	kil $SELF;
		856	&$cb;
		857	};
		858
		859	if (defined $timeout) {
		860	$timeout = AE::timer $timeout, 0, sub {
		861	undef $timeout;
		862	kil $port;
		863	$cb->();
		864	};
		865	} else {
		866	mon $_[0], sub {
		867	kil $port;
		868	$cb->();
		869	};
		870	}
		871
		872	push @_, $port;
		873	&snd;
		874
		875	$port
		876	}
		877
652	=back	878	=back
653		879
654	=head1 AnyEvent::MP vs. Distributed Erlang	880	=head1 AnyEvent::MP vs. Distributed Erlang
655		881
656	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	882	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
657	== aemp node, Erlang process == aemp port), so many of the documents and	883	== aemp node, Erlang process == aemp port), so many of the documents and
658	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	884	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
659	sample:	885	sample:
660		886
661	http://www.Erlang.se/doc/programming_rules.shtml	887	http://www.erlang.se/doc/programming_rules.shtml
662	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	888	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
663	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	889	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
664	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	890	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
665		891
666	Despite the similarities, there are also some important differences:	892	Despite the similarities, there are also some important differences:
667		893
668	=over 4	894	=over 4
669		895
670	=item * Node references contain the recipe on how to contact them.	896	=item * Node IDs are arbitrary strings in AEMP.
671		897
672	Erlang relies on special naming and DNS to work everywhere in the	898	Erlang relies on special naming and DNS to work everywhere in the same
673	same way. AEMP relies on each node knowing it's own address(es), with	899	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	convenience functionality.	900	configuration or DNS), and possibly the addresses of some seed nodes, but
675		901	will otherwise discover other nodes (and their IDs) itself.
676	This means that AEMP requires a less tightly controlled environment at the
677	cost of longer node references and a slightly higher management overhead.
678		902
679	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	903	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
680	uses "local ports are like remote ports".	904	uses "local ports are like remote ports".
681		905
682	The failure modes for local ports are quite different (runtime errors	906	The failure modes for local ports are quite different (runtime errors
…		…
691	ports being the special case/exception, where transport errors cannot	915	ports being the special case/exception, where transport errors cannot
692	occur.	916	occur.
693		917
694	=item * Erlang uses processes and a mailbox, AEMP does not queue.	918	=item * Erlang uses processes and a mailbox, AEMP does not queue.
695		919
696	Erlang uses processes that selectively receive messages, and therefore	920	Erlang uses processes that selectively receive messages out of order, and
697	needs a queue. AEMP is event based, queuing messages would serve no	921	therefore needs a queue. AEMP is event based, queuing messages would serve
698	useful purpose. For the same reason the pattern-matching abilities of	922	no useful purpose. For the same reason the pattern-matching abilities
699	AnyEvent::MP are more limited, as there is little need to be able to	923	of AnyEvent::MP are more limited, as there is little need to be able to
700	filter messages without dequeing them.	924	filter messages without dequeuing them.
701		925
702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	926	This is not a philosophical difference, but simply stems from AnyEvent::MP
		927	being event-based, while Erlang is process-based.
		928
		929	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		930	top of AEMP and Coro threads.
703		931
704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	932	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
705		933
706	Sending messages in Erlang is synchronous and blocks the process (and	934	Sending messages in Erlang is synchronous and blocks the process until
		935	a conenction has been established and the message sent (and so does not
707	so does not need a queue that can overflow). AEMP sends are immediate,	936	need a queue that can overflow). AEMP sends return immediately, connection
708	connection establishment is handled in the background.	937	establishment is handled in the background.
709		938
710	=item * Erlang suffers from silent message loss, AEMP does not.	939	=item * Erlang suffers from silent message loss, AEMP does not.
711		940
712	Erlang makes few guarantees on messages delivery - messages can get lost	941	Erlang implements few guarantees on messages delivery - messages can get
713	without any of the processes realising it (i.e. you send messages a, b,	942	lost without any of the processes realising it (i.e. you send messages a,
714	and c, and the other side only receives messages a and c).	943	b, and c, and the other side only receives messages a and c).
715		944
716	AEMP guarantees correct ordering, and the guarantee that there are no	945	AEMP guarantees (modulo hardware errors) correct ordering, and the
		946	guarantee that after one message is lost, all following ones sent to the
		947	same port are lost as well, until monitoring raises an error, so there are
717	holes in the message sequence.	948	no silent "holes" in the message sequence.
718		949
719	=item * In Erlang, processes can be declared dead and later be found to be	950	If you want your software to be very reliable, you have to cope with
720	alive.	951	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
721		952	simply tries to work better in common error cases, such as when a network
722	In Erlang it can happen that a monitored process is declared dead and	953	link goes down.
723	linked processes get killed, but later it turns out that the process is
724	still alive - and can receive messages.
725
726	In AEMP, when port monitoring detects a port as dead, then that port will
727	eventually be killed - it cannot happen that a node detects a port as dead
728	and then later sends messages to it, finding it is still alive.
729		954
730	=item * Erlang can send messages to the wrong port, AEMP does not.	955	=item * Erlang can send messages to the wrong port, AEMP does not.
731		956
732	In Erlang it is quite likely that a node that restarts reuses a process ID	957	In Erlang it is quite likely that a node that restarts reuses an Erlang
733	known to other nodes for a completely different process, causing messages	958	process ID known to other nodes for a completely different process,
734	destined for that process to end up in an unrelated process.	959	causing messages destined for that process to end up in an unrelated
		960	process.
735		961
736	AEMP never reuses port IDs, so old messages or old port IDs floating	962	AEMP does not reuse port IDs, so old messages or old port IDs floating
737	around in the network will not be sent to an unrelated port.	963	around in the network will not be sent to an unrelated port.
738		964
739	=item * Erlang uses unprotected connections, AEMP uses secure	965	=item * Erlang uses unprotected connections, AEMP uses secure
740	authentication and can use TLS.	966	authentication and can use TLS.
741		967
742	AEMP can use a proven protocol - SSL/TLS - to protect connections and	968	AEMP can use a proven protocol - TLS - to protect connections and
743	securely authenticate nodes.	969	securely authenticate nodes.
744		970
745	=item * The AEMP protocol is optimised for both text-based and binary	971	=item * The AEMP protocol is optimised for both text-based and binary
746	communications.	972	communications.
747		973
748	The AEMP protocol, unlike the Erlang protocol, supports both	974	The AEMP protocol, unlike the Erlang protocol, supports both programming
749	language-independent text-only protocols (good for debugging) and binary,	975	language independent text-only protocols (good for debugging), and binary,
750	language-specific serialisers (e.g. Storable).	976	language-specific serialisers (e.g. Storable). By default, unless TLS is
		977	used, the protocol is actually completely text-based.
751		978
752	It has also been carefully designed to be implementable in other languages	979	It has also been carefully designed to be implementable in other languages
753	with a minimum of work while gracefully degrading fucntionality to make the	980	with a minimum of work while gracefully degrading functionality to make the
754	protocol simple.	981	protocol simple.
755		982
756	=item * AEMP has more flexible monitoring options than Erlang.	983	=item * AEMP has more flexible monitoring options than Erlang.
757		984
758	In Erlang, you can chose to receive I<all> exit signals as messages	985	In Erlang, you can chose to receive I<all> exit signals as messages or
759	or I<none>, there is no in-between, so monitoring single processes is	986	I<none>, there is no in-between, so monitoring single Erlang processes is
760	difficult to implement. Monitoring in AEMP is more flexible than in	987	difficult to implement.
761	Erlang, as one can choose between automatic kill, exit message or callback	988
762	on a per-process basis.	989	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		990	between automatic kill, exit message or callback on a per-port basis.
763		991
764	=item * Erlang tries to hide remote/local connections, AEMP does not.	992	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		993
766	Monitoring in Erlang is not an indicator of process death/crashes,	994	Monitoring in Erlang is not an indicator of process death/crashes, in the
767	as linking is (except linking is unreliable in Erlang).	995	same way as linking is (except linking is unreliable in Erlang).
768		996
769	In AEMP, you don't "look up" registered port names or send to named ports	997	In AEMP, you don't "look up" registered port names or send to named ports
770	that might or might not be persistent. Instead, you normally spawn a port	998	that might or might not be persistent. Instead, you normally spawn a port
771	on the remote node. The init function monitors the you, and you monitor	999	on the remote node. The init function monitors you, and you monitor the
772	the remote port. Since both monitors are local to the node, they are much	1000	remote port. Since both monitors are local to the node, they are much more
773	more reliable.	1001	reliable (no need for C<spawn_link>).
774		1002
775	This also saves round-trips and avoids sending messages to the wrong port	1003	This also saves round-trips and avoids sending messages to the wrong port
776	(hard to do in Erlang).	1004	(hard to do in Erlang).
777		1005
778	=back	1006	=back
779		1007
780	=head1 RATIONALE	1008	=head1 RATIONALE
781		1009
782	=over 4	1010	=over 4
783		1011
784	=item Why strings for ports and noderefs, why not objects?	1012	=item Why strings for port and node IDs, why not objects?
785		1013
786	We considered "objects", but found that the actual number of methods	1014	We considered "objects", but found that the actual number of methods
787	thatc an be called are very low. Since port IDs and noderefs travel over	1015	that can be called are quite low. Since port and node IDs travel over
788	the network frequently, the serialising/deserialising would add lots of	1016	the network frequently, the serialising/deserialising would add lots of
789	overhead, as well as having to keep a proxy object.	1017	overhead, as well as having to keep a proxy object everywhere.
790		1018
791	Strings can easily be printed, easily serialised etc. and need no special	1019	Strings can easily be printed, easily serialised etc. and need no special
792	procedures to be "valid".	1020	procedures to be "valid".
793		1021
794	And a a miniport consists of a single closure stored in a global hash - it	1022	And as a result, a port with just a default receiver consists of a single
795	can't become much cheaper.	1023	code reference stored in a global hash - it can't become much cheaper.
796		1024
797	=item Why favour JSON, why not real serialising format such as Storable?	1025	=item Why favour JSON, why not a real serialising format such as Storable?
798		1026
799	In fact, any AnyEvent::MP node will happily accept Storable as framing	1027	In fact, any AnyEvent::MP node will happily accept Storable as framing
800	format, but currently there is no way to make a node use Storable by	1028	format, but currently there is no way to make a node use Storable by
801	default.	1029	default (although all nodes will accept it).
802		1030
803	The default framing protocol is JSON because a) JSON::XS is many times	1031	The default framing protocol is JSON because a) JSON::XS is many times
804	faster for small messages and b) most importantly, after years of	1032	faster for small messages and b) most importantly, after years of
805	experience we found that object serialisation is causing more problems	1033	experience we found that object serialisation is causing more problems
806	than it gains: Just like function calls, objects simply do not travel	1034	than it solves: Just like function calls, objects simply do not travel
807	easily over the network, mostly because they will always be a copy, so you	1035	easily over the network, mostly because they will always be a copy, so you
808	always have to re-think your design.	1036	always have to re-think your design.
809		1037
810	Keeping your messages simple, concentrating on data structures rather than	1038	Keeping your messages simple, concentrating on data structures rather than
811	objects, will keep your messages clean, tidy and efficient.	1039	objects, will keep your messages clean, tidy and efficient.
812		1040
813	=back	1041	=back
814		1042
815	=head1 SEE ALSO	1043	=head1 SEE ALSO
816		1044
		1045	L<AnyEvent::MP::Intro> - a gentle introduction.
		1046
		1047	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1048
		1049	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1050	your applications.
		1051
		1052	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1053
		1054	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1055	all nodes.
		1056
817	L<AnyEvent>.	1057	L<AnyEvent>.
818		1058
819	=head1 AUTHOR	1059	=head1 AUTHOR
820		1060
821	Marc Lehmann <schmorp@schmorp.de>	1061	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.123 by root, Thu Mar 1 19:37:59 2012 UTC