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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.56 by root, Sat Aug 15 04:12:38 2009 UTC vs.
Revision 1.120 by root, Sun Feb 26 11:12:54 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; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
73		78
74	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
76		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
77	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
78		86
79	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
80	separator, and a port name (a printable string of unspecified format). An	88	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		89
84	=item node	90	=item node
85		91
86	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,
87	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
88	ports.	94	ports.
89		95
90	Nodes are either private (single-process only), slaves (connected to a	96	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	97	(no listening ports). Private nodes cannot talk to other private nodes
		98	currently, but all nodes can talk to public nodes.
92		99
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	100	Nodes is represented by (printable) strings called "node IDs".
94		101
95	A node reference is a string that either simply identifies the node (for	102	=item node ID - C<[A-Za-z0-9_\-.:]*>
96	private and slave nodes), or contains a recipe on how to reach a given
97	node (for public nodes).
98		103
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	104	A node ID is a string that uniquely identifies the node within a
100	TCP/IP, other protocols might look different).	105	network. Depending on the configuration used, node IDs can look like a
		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.
101		108
102	Node references come in two flavours: resolved (containing only numerical	109	=item binds - C<ip:port>
103	addresses) or unresolved (where hostnames are used instead of addresses).
104		110
105	Before using an unresolved node reference in a message you first have to	111	Nodes can only talk to each other by creating some kind of connection to
106	resolve it.	112	each other. To do this, nodes should listen on one or more local transport
		113	endpoints - binds.
		114
		115	Currently, only standard C<ip:port> specifications can be used, which
		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).
107		169
108	=back	170	=back
109		171
110	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
111		173
123		185
124	use AE ();	186	use AE ();
125		187
126	use base "Exporter";	188	use base "Exporter";
127		189
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	190	our $VERSION = '1.30';
129		191
130	our @EXPORT = qw(	192	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	193	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	194	configure
133	snd rcv mon kil reg psub spawn	195	snd rcv mon mon_guard kil psub peval spawn cal
134	port	196	port
135	);	197	);
136		198
137	our $SELF;	199	our $SELF;
138		200
…		…
142	kil $SELF, die => $msg;	204	kil $SELF, die => $msg;
143	}	205	}
144		206
145	=item $thisnode = NODE / $NODE	207	=item $thisnode = NODE / $NODE
146		208
147	The C<NODE> function returns, and the C<$NODE> variable contains the	209	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef 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
149	C<initialise_node>.	211	a call to C<configure>.
150		212
151	=item $noderef = node_of $port	213	=item $nodeid = node_of $port
152		214
153	Extracts and returns the noderef from a port ID or a noderef.	215	Extracts and returns the node ID from a port ID or a node ID.
154		216
155	=item initialise_node $noderef, $seednode, $seednode...	217	=item configure $profile, key => value...
156		218
157	=item initialise_node "slave/", $master, $master...	219	=item configure key => value...
158		220
159	Before a node can talk to other nodes on the network it has to initialise	221	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	222	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	223	to know is its own name, and optionally it should know the addresses of
		224	some other nodes in the network to discover other nodes.
162		225
		226	The key/value pairs are basically the same ones as documented for the
		227	F<aemp> command line utility (sans the set/del prefix).
		228
163	This function initialises a node - it must be called exactly once (or	229	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	230	never) before calling other AnyEvent::MP functions.
165		231
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	232	=over 4
178		233
179	=item public nodes	234	=item step 1, gathering configuration from profiles
180		235
181	For public nodes, C<$noderef> (supplied either directly to	236	The function first looks up a profile in the aemp configuration (see the
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	237	L<aemp> commandline utility). The profile name can be specified via the
183	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.
184		240
185	After resolving, the node will bind itself on all endpoints and try to	241	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		242
190	=item slave nodes	243	First, all remaining key => value pairs (all of which are conveniently
		244	undocumented at the moment) will be interpreted as configuration
		245	data. Then they will be overwritten by any values specified in the global
		246	default configuration (see the F<aemp> utility), then the chain of
		247	profiles chosen by the profile name (and any C<parent> attributes).
191		248
192	When the C<$noderef> (either as given or overriden by the config file)	249	That means that the values specified in the profile have highest priority
193	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,
194	node. Slave nodes cannot be contacted from outside and will route most of	251	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		252
197	At least one additional noderef is required (either by specifying it	253	If the profile specifies a node ID, then this will become the node ID of
198	directly or because it is part of the configuration profile): The node	254	this process. If not, then the profile name will be used as node ID. The
199	will try to connect to all of them and will become a slave attached to the	255	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.
201		256
202	Note that slave nodes cannot change their name, and consequently, their	257	=item step 2, bind listener sockets
203	master, so if the master goes down, the slave node will not function well	258
204	anymore until it can re-establish conenciton to its master. This makes	259	The next step is to look up the binds in the profile, followed by binding
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.	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.
206		274
207	=back	275	=back
208		276
209	This function will block until all nodes have been resolved and, for slave	277	Example: become a distributed node using the local node name as profile.
210	nodes, until it has successfully established a connection to a master	278	This should be the most common form of invocation for "daemon"-type nodes.
211	server.
212		279
213	All the seednodes will also be specially marked to automatically retry	280	configure
214	connecting to them infinitely.
215		281
216	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
217	specified via C<aemp> for the current node. This should be the most common	283	clients.
218	form of invocation for "daemon"-type nodes.
219		284
220	initialise_node;	285	configure nodeid => "anon/";
221		286
222	Example: become a slave node to any of the the seednodes specified via	287	Example: configure a node using a profile called seed, which is suitable
223	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).
224		290
225	initialise_node "slave/";	291	# use the aemp commandline utility
		292	# aemp profile seed nodeid anon/ binds '*:4040'
226		293
227	Example: become a slave node to any of the specified master servers. This	294	# then use it
228	form is also often used for commandline clients.	295	configure profile => "seed";
229		296
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	297	# or simply use aemp from the shell again:
		298	# aemp run profile seed
231		299
232	Example: become a public node, and try to contact some well-known master	300	# or provide a nicer-to-remember nodeid
233	servers to become part of the network.	301	# aemp run profile seed nodeid "$(hostname)"
234
235	initialise_node undef, "master1", "master2";
236
237	Example: become a public node listening on port C<4041>.
238
239	initialise_node 4041;
240
241	Example: become a public node, only visible on localhost port 4044.
242
243	initialise_node "localhost:4044";
244
245	=item $cv = resolve_node $noderef
246
247	Takes an unresolved node reference that may contain hostnames and
248	abbreviated IDs, resolves all of them and returns a resolved node
249	reference.
250
251	In addition to C<address:port> pairs allowed in resolved noderefs, the
252	following forms are supported:
253
254	=over 4
255
256	=item the empty string
257
258	An empty-string component gets resolved as if the default port (4040) was
259	specified.
260
261	=item naked port numbers (e.g. C<1234>)
262
263	These are resolved by prepending the local nodename and a colon, to be
264	further resolved.
265
266	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
267
268	These are resolved by using AnyEvent::DNS to resolve them, optionally
269	looking up SRV records for the C<aemp=4040> port, if no port was
270	specified.
271
272	=back
273		302
274	=item $SELF	303	=item $SELF
275		304
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	305	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	306	blocks.
278		307
279	=item SELF, %SELF, @SELF...	308	=item *SELF, SELF, %SELF, @SELF...
280		309
281	Due to some quirks in how perl exports variables, it is impossible to	310	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	311	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	312	module, but only C<$SELF> is currently used.
284		313
285	=item snd $port, type => @data	314	=item snd $port, type => @data
286		315
287	=item snd $port, @msg	316	=item snd $port, @msg
288		317
289	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
290	a local or a remote port, and must be a port ID.	319	local or a remote port, and must be a port ID.
291		320
292	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
293	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
294	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.
295		325
296	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
297	function: modifying any argument is not allowed and can cause many	327	function: modifying any argument (or values referenced by them) is
298	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.
299		332
300	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
301	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
302	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
303	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
304	node, anything can be passed.	337	node, anything can be passed. Best rely only on the common denominator of
		338	these.
305		339
306	=item $local_port = port	340	=item $local_port = port
307		341
308	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
309	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.
…		…
382	msg1 => sub { ... },	416	msg1 => sub { ... },
383	...	417	...
384	;	418	;
385		419
386	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
387	(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.
388		422
389	rcv $port, $otherport => sub {	423	rcv $port, $otherport => sub {
390	my @reply = @_;	424	my @reply = @_;
391		425
392	rcv $SELF, $otherport;	426	rcv $SELF, $otherport;
…		…
394		428
395	=cut	429	=cut
396		430
397	sub rcv($@) {	431	sub rcv($@) {
398	my $port = shift;	432	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	433	my ($nodeid, $portid) = split /#/, $port, 2;
400		434
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	435	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	436	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		437
404	while (@_) {	438	while (@_) {
405	if (ref $_[0]) {	439	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	440	if (my $self = $PORT_DATA{$portid}) {
407	"AnyEvent::MP::Port" eq ref $self	441	"AnyEvent::MP::Port" eq ref $self
408	or Carp::croak "$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";
409		443
410	$self->[2] = shift;	444	$self->[0] = shift;
411	} else {	445	} else {
412	my $cb = shift;	446	my $cb = shift;
413	$PORT{$portid} = sub {	447	$PORT{$portid} = sub {
414	local $SELF = $port;	448	local $SELF = $port;
415	eval { &$cb }; _self_die if $@;	449	eval { &$cb }; _self_die if $@;
416	};	450	};
417	}	451	}
418	} elsif (defined $_[0]) {	452	} elsif (defined $_[0]) {
419	my $self = $PORT_DATA{$portid} \|\|= do {	453	my $self = $PORT_DATA{$portid} \|\|= do {
420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	454	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
421		455
422	$PORT{$portid} = sub {	456	$PORT{$portid} = sub {
423	local $SELF = $port;	457	local $SELF = $port;
424		458
425	if (my $cb = $self->[1]{$_[0]}) {	459	if (my $cb = $self->[1]{$_[0]}) {
…		…
447	}	481	}
448		482
449	$port	483	$port
450	}	484	}
451		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
452	=item $closure = psub { BLOCK }	523	=item $closure = psub { BLOCK }
453		524
454	Remembers C<$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
455	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>
456	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 $SELF, sub {
		530	BLOCK }, @_ } >>.
457		531
458	This is useful when you register callbacks from C<rcv> callbacks:	532	This is useful when you register callbacks from C<rcv> callbacks:
459		533
460	rcv delayed_reply => sub {	534	rcv delayed_reply => sub {
461	my ($delay, @reply) = @_;	535	my ($delay, @reply) = @_;
…		…
485	$res	559	$res
486	}	560	}
487	}	561	}
488	}	562	}
489		563
490	=item $guard = mon $port, $cb->(@reason)	564	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
491		565
492	=item $guard = mon $port, $rcvport	566	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
493		567
494	=item $guard = mon $port	568	=item $guard = mon $port # kill $SELF when $port dies
495		569
496	=item $guard = mon $port, $rcvport, @msg	570	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		571
498	Monitor the given port and do something when the port is killed or	572	Monitor the given port and do something when the port is killed or
499	messages to it were lost, and optionally return a guard that can be used	573	messages to it were lost, and optionally return a guard that can be used
500	to stop monitoring again.	574	to stop monitoring again.
501
502	C<mon> effectively guarantees that, in the absence of hardware failures,
503	that after starting the monitor, either all messages sent to the port
504	will arrive, or the monitoring action will be invoked after possible
505	message loss has been detected. No messages will be lost "in between"
506	(after the first lost message no further messages will be received by the
507	port). After the monitoring action was invoked, further messages might get
508	delivered again.
509		575
510	In the first form (callback), the callback is simply called with any	576	In the first form (callback), the callback is simply called with any
511	number of C<@reason> elements (no @reason means that the port was deleted	577	number of C<@reason> elements (no @reason means that the port was deleted
512	"normally"). Note also that I<< the callback B<must> never die >>, so use	578	"normally"). Note also that I<< the callback B<must> never die >>, so use
513	C<eval> if unsure.	579	C<eval> if unsure.
514		580
515	In the second form (another port given), the other port (C<$rcvport>)	581	In the second form (another port given), the other port (C<$rcvport>)
516	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	582	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
517	"normal" kils nothing happens, while under all other conditions, the other	583	"normal" kils nothing happens, while under all other conditions, the other
518	port is killed with the same reason.	584	port is killed with the same reason.
519		585
520	The third form (kill self) is the same as the second form, except that	586	The third form (kill self) is the same as the second form, except that
521	C<$rvport> defaults to C<$SELF>.	587	C<$rvport> defaults to C<$SELF>.
522		588
523	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
524	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.
525		594
526	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
527	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
528	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
529	even monitoring requests can get lost (for exmaple, when the connection	598	even monitoring requests can get lost (for example, when the connection
530	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
531	these problems do not exist.	600	these problems do not exist.
532		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
533	Example: call a given callback when C<$port> is killed.	619	Example: call a given callback when C<$port> is killed.
534		620
535	mon $port, sub { warn "port died because of <@_>\n" };	621	mon $port, sub { warn "port died because of <@_>\n" };
536		622
537	Example: kill ourselves when C<$port> is killed abnormally.	623	Example: kill ourselves when C<$port> is killed abnormally.
…		…
543	mon $port, $self => "restart";	629	mon $port, $self => "restart";
544		630
545	=cut	631	=cut
546		632
547	sub mon {	633	sub mon {
548	my ($noderef, $port) = split /#/, shift, 2;	634	my ($nodeid, $port) = split /#/, shift, 2;
549		635
550	my $node = $NODE{$noderef} \|\| add_node $noderef;	636	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
551		637
552	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,';
553		639
554	unless (ref $cb) {	640	unless (ref $cb) {
555	if (@_) {	641	if (@_) {
…		…
564	}	650	}
565		651
566	$node->monitor ($port, $cb);	652	$node->monitor ($port, $cb);
567		653
568	defined wantarray	654	defined wantarray
569	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	655	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
570	}	656	}
571		657
572	=item $guard = mon_guard $port, $ref, $ref...	658	=item $guard = mon_guard $port, $ref, $ref...
573		659
574	Monitors the given C<$port> and keeps the passed references. When the port	660	Monitors the given C<$port> and keeps the passed references. When the port
575	is killed, the references will be freed.	661	is killed, the references will be freed.
576		662
577	Optionally returns a guard that will stop the monitoring.	663	Optionally returns a guard that will stop the monitoring.
578		664
579	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
580	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>):
581		667
582	$port->rcv (start => sub {	668	$port->rcv (start => sub {
583	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	669	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
584	undef $timer if 0.9 < rand;	670	undef $timer if 0.9 < rand;
585	});	671	});
586	});	672	});
587		673
588	=cut	674	=cut
…		…
597		683
598	=item kil $port[, @reason]	684	=item kil $port[, @reason]
599		685
600	Kill the specified port with the given C<@reason>.	686	Kill the specified port with the given C<@reason>.
601		687
602	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" -
603	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.
604		691
605	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>
606	C<mon>, see below).	693	form) get killed with the same reason.
607		694
608	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
609	will be reported as reason C<< die => $@ >>.	696	will be reported as reason C<< die => $@ >>.
610		697
611	Transport/communication errors are reported as C<< transport_error =>	698	Transport/communication errors are reported as C<< transport_error =>
…		…
616	=item $port = spawn $node, $initfunc[, @initdata]	703	=item $port = spawn $node, $initfunc[, @initdata]
617		704
618	Creates a port on the node C<$node> (which can also be a port ID, in which	705	Creates a port on the node C<$node> (which can also be a port ID, in which
619	case it's the node where that port resides).	706	case it's the node where that port resides).
620		707
621	The port ID of the newly created port is return immediately, and it is	708	The port ID of the newly created port is returned immediately, and it is
622	permissible to immediately start sending messages or monitor the port.	709	possible to immediately start sending messages or to monitor the port.
623		710
624	After the port has been created, the init function is	711	After the port has been created, the init function is called on the remote
625	called. This function must be a fully-qualified function name	712	node, in the same context as a C<rcv> callback. This function must be a
626	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	713	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
627	program, use C<::name>.	714	specify a function in the main program, use C<::name>.
628		715
629	If the function doesn't exist, then the node tries to C<require>	716	If the function doesn't exist, then the node tries to C<require>
630	the package, then the package above the package and so on (e.g.	717	the package, then the package above the package and so on (e.g.
631	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	718	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
632	exists or it runs out of package names.	719	exists or it runs out of package names.
633		720
634	The init function is then called with the newly-created port as context	721	The init function is then called with the newly-created port as context
635	object (C<$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.
636		725
637	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
638	in the init function, monitor the original port. This two-way monitoring	727	port, and in the remote init function, immediately monitor the passed
639	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<$initfunc> has no visible effects on the
		732	caller before C<spawn> returns (by delaying invocation when spawn is
		733	called for the local node).
640		734
641	Example: spawn a chat server port on C<$othernode>.	735	Example: spawn a chat server port on C<$othernode>.
642		736
643	# this node, executed from within a port context:	737	# this node, executed from within a port context:
644	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	738	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
659		753
660	sub _spawn {	754	sub _spawn {
661	my $port = shift;	755	my $port = shift;
662	my $init = shift;	756	my $init = shift;
663		757
		758	# rcv will create the actual port
664	local $SELF = "$NODE#$port";	759	local $SELF = "$NODE#$port";
665	eval {	760	eval {
666	&{ load_func $init }	761	&{ load_func $init }
667	};	762	};
668	_self_die if $@;	763	_self_die if $@;
669	}	764	}
670		765
671	sub spawn(@) {	766	sub spawn(@) {
672	my ($noderef, undef) = split /#/, shift, 2;	767	my ($nodeid, undef) = split /#/, shift, 2;
673		768
674	my $id = "$RUNIQ." . $ID++;	769	my $id = "$RUNIQ." . $ID++;
675		770
676	$_[0] =~ /::/	771	$_[0] =~ /::/
677	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";
678		773
679	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	774	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
680		775
681	"$noderef#$id"	776	"$nodeid#$id"
682	}	777	}
683		778
684	=back	779	=item after $timeout, @msg
685		780
686	=head1 NODE MESSAGES	781	=item after $timeout, $callback
687		782
688	Nodes understand the following messages sent to them. Many of them take	783	Either sends the given message, or call the given callback, after the
689	arguments called C<@reply>, which will simply be used to compose a reply	784	specified number of seconds.
690	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
691	the remaining arguments are simply the message data.
692		785
693	While other messages exist, they are not public and subject to change.	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.
694		789
695	=over 4
696
697	=cut	790	=cut
698		791
699	=item lookup => $name, @reply	792	sub after($@) {
		793	my ($timeout, @action) = @_;
700		794
701	Replies with the port ID of the specified well-known port, or C<undef>.	795	my $t; $t = AE::timer $timeout, 0, sub {
		796	undef $t;
		797	ref $action[0]
		798	? $action[0]()
		799	: snd @action;
		800	};
		801	}
702		802
703	=item devnull => ...	803	=item cal $port, @msg, $callback[, $timeout]
704		804
705	Generic data sink/CPU heat conversion.	805	A simple form of RPC - sends a message to the given C<$port> with the
		806	given contents (C<@msg>), but adds a reply port to the message.
706		807
707	=item relay => $port, @msg	808	The reply port is created temporarily just for the purpose of receiving
		809	the reply, and will be C<kil>ed when no longer needed.
708		810
709	Simply forwards the message to the given port.	811	A reply message sent to the port is passed to the C<$callback> as-is.
710		812
711	=item eval => $string[ @reply]	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.
712		816
713	Evaluates the given string. If C<@reply> is given, then a message of the	817	If no time-out is given (or it is C<undef>), then the local port will
714	form C<@reply, $@, @evalres> is sent.	818	monitor the remote port instead, so it eventually gets cleaned-up.
715		819
716	Example: crash another node.	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.
717		823
718	snd $othernode, eval => "exit";	824	=cut
719		825
720	=item time => @reply	826	sub cal(@) {
		827	my $timeout = ref $_[-1] ? undef : pop;
		828	my $cb = pop;
721		829
722	Replies the the current node time to C<@reply>.	830	my $port = port {
		831	undef $timeout;
		832	kil $SELF;
		833	&$cb;
		834	};
723		835
724	Example: tell the current node to send the current time to C<$myport> in a	836	if (defined $timeout) {
725	C<timereply> message.	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	}
726		848
727	snd $NODE, time => $myport, timereply => 1, 2;	849	push @_, $port;
728	# => snd $myport, timereply => 1, 2, <time>	850	&snd;
		851
		852	$port
		853	}
729		854
730	=back	855	=back
731		856
732	=head1 AnyEvent::MP vs. Distributed Erlang	857	=head1 AnyEvent::MP vs. Distributed Erlang
733		858
734	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
735	== 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
736	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
737	sample:	862	sample:
738		863
739	http://www.Erlang.se/doc/programming_rules.shtml	864	http://www.erlang.se/doc/programming_rules.shtml
740	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
741	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
742	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
743		868
744	Despite the similarities, there are also some important differences:	869	Despite the similarities, there are also some important differences:
745		870
746	=over 4	871	=over 4
747		872
748	=item * Node references contain the recipe on how to contact them.	873	=item * Node IDs are arbitrary strings in AEMP.
749		874
750	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
751	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
752	convenience functionality.	877	configuration or DNS), and possibly the addresses of some seed nodes, but
753		878	will otherwise discover other nodes (and their IDs) itself.
754	This means that AEMP requires a less tightly controlled environment at the
755	cost of longer node references and a slightly higher management overhead.
756		879
757	=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
758	uses "local ports are like remote ports".	881	uses "local ports are like remote ports".
759		882
760	The failure modes for local ports are quite different (runtime errors	883	The failure modes for local ports are quite different (runtime errors
…		…
769	ports being the special case/exception, where transport errors cannot	892	ports being the special case/exception, where transport errors cannot
770	occur.	893	occur.
771		894
772	=item * Erlang uses processes and a mailbox, AEMP does not queue.	895	=item * Erlang uses processes and a mailbox, AEMP does not queue.
773		896
774	Erlang uses processes that selectively receive messages, and therefore	897	Erlang uses processes that selectively receive messages out of order, and
775	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
776	useful purpose. For the same reason the pattern-matching abilities of	899	no useful purpose. For the same reason the pattern-matching abilities
777	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
778	filter messages without dequeing them.	901	filter messages without dequeuing them.
779		902
780	(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.
781		908
782	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	909	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
783		910
784	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
785	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
786	connection establishment is handled in the background.	914	establishment is handled in the background.
787		915
788	=item * Erlang suffers from silent message loss, AEMP does not.	916	=item * Erlang suffers from silent message loss, AEMP does not.
789		917
790	Erlang makes few guarantees on messages delivery - messages can get lost	918	Erlang implements few guarantees on messages delivery - messages can get
791	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,
792	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).
793		921
794	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
795	holes in the message sequence.	925	no silent "holes" in the message sequence.
796		926
797	=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
798	alive.	928	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
799		929	simply tries to work better in common error cases, such as when a network
800	In Erlang it can happen that a monitored process is declared dead and	930	link goes down.
801	linked processes get killed, but later it turns out that the process is
802	still alive - and can receive messages.
803
804	In AEMP, when port monitoring detects a port as dead, then that port will
805	eventually be killed - it cannot happen that a node detects a port as dead
806	and then later sends messages to it, finding it is still alive.
807		931
808	=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.
809		933
810	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
811	known to other nodes for a completely different process, causing messages	935	process ID known to other nodes for a completely different process,
812	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.
813		938
814	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
815	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.
816		941
817	=item * Erlang uses unprotected connections, AEMP uses secure	942	=item * Erlang uses unprotected connections, AEMP uses secure
818	authentication and can use TLS.	943	authentication and can use TLS.
819		944
820	AEMP can use a proven protocol - SSL/TLS - to protect connections and	945	AEMP can use a proven protocol - TLS - to protect connections and
821	securely authenticate nodes.	946	securely authenticate nodes.
822		947
823	=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
824	communications.	949	communications.
825		950
826	The AEMP protocol, unlike the Erlang protocol, supports both	951	The AEMP protocol, unlike the Erlang protocol, supports both programming
827	language-independent text-only protocols (good for debugging) and binary,	952	language independent text-only protocols (good for debugging), and binary,
828	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.
829		955
830	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
831	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
832	protocol simple.	958	protocol simple.
833		959
834	=item * AEMP has more flexible monitoring options than Erlang.	960	=item * AEMP has more flexible monitoring options than Erlang.
835		961
836	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
837	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
838	difficult to implement. Monitoring in AEMP is more flexible than in	964	difficult to implement.
839	Erlang, as one can choose between automatic kill, exit message or callback	965
840	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.
841		968
842	=item * Erlang tries to hide remote/local connections, AEMP does not.	969	=item * Erlang tries to hide remote/local connections, AEMP does not.
843		970
844	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
845	as linking is (except linking is unreliable in Erlang).	972	same way as linking is (except linking is unreliable in Erlang).
846		973
847	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
848	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
849	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
850	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
851	more reliable.	978	reliable (no need for C<spawn_link>).
852		979
853	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
854	(hard to do in Erlang).	981	(hard to do in Erlang).
855		982
856	=back	983	=back
857		984
858	=head1 RATIONALE	985	=head1 RATIONALE
859		986
860	=over 4	987	=over 4
861		988
862	=item Why strings for ports and noderefs, why not objects?	989	=item Why strings for port and node IDs, why not objects?
863		990
864	We considered "objects", but found that the actual number of methods	991	We considered "objects", but found that the actual number of methods
865	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
866	the network frequently, the serialising/deserialising would add lots of	993	the network frequently, the serialising/deserialising would add lots of
867	overhead, as well as having to keep a proxy object.	994	overhead, as well as having to keep a proxy object everywhere.
868		995
869	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
870	procedures to be "valid".	997	procedures to be "valid".
871		998
872	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
873	can't become much cheaper.	1000	code reference stored in a global hash - it can't become much cheaper.
874		1001
875	=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?
876		1003
877	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
878	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
879	default.	1006	default (although all nodes will accept it).
880		1007
881	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
882	faster for small messages and b) most importantly, after years of	1009	faster for small messages and b) most importantly, after years of
883	experience we found that object serialisation is causing more problems	1010	experience we found that object serialisation is causing more problems
884	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
885	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
886	always have to re-think your design.	1013	always have to re-think your design.
887		1014
888	Keeping your messages simple, concentrating on data structures rather than	1015	Keeping your messages simple, concentrating on data structures rather than
889	objects, will keep your messages clean, tidy and efficient.	1016	objects, will keep your messages clean, tidy and efficient.
890		1017
891	=back	1018	=back
892		1019
893	=head1 SEE ALSO	1020	=head1 SEE ALSO
894		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
895	L<AnyEvent>.	1034	L<AnyEvent>.
896		1035
897	=head1 AUTHOR	1036	=head1 AUTHOR
898		1037
899	Marc Lehmann <schmorp@schmorp.de>	1038	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.56 by root, Sat Aug 15 04:12:38 2009 UTC vs.
Revision 1.120 by root, Sun Feb 26 11:12:54 2012 UTC