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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.62 by root, Thu Aug 27 07:12:48 2009 UTC vs.
Revision 1.121 by root, Tue Feb 28 18:37:24 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 (can only talk to	96	Nodes are either public (have one or more listening ports) or private
91	public nodes, but do not need an open port) or public nodes (connectable	97	(no listening ports). Private nodes cannot talk to other private nodes
92	from any other node).	98	currently, but all nodes can talk to public nodes.
93		99
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	100	Nodes is represented by (printable) strings called "node IDs".
95		101
96	A node reference is a string that either simply identifies the node (for	102	=item node ID - C<[A-Za-z0-9_\-.:]*>
97	private and slave nodes), or contains a recipe on how to reach a given
98	node (for public nodes).
99		103
100	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
101	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.
102		108
103	Node references come in two flavours: resolved (containing only numerical	109	=item binds - C<ip:port>
104	addresses) or unresolved (where hostnames are used instead of addresses).
105		110
106	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
107	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).
108		169
109	=back	170	=back
110		171
111	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
112		173
114		175
115	=cut	176	=cut
116		177
117	package AnyEvent::MP;	178	package AnyEvent::MP;
118		179
		180	use AnyEvent::MP::Config ();
119	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
120		183
121	use common::sense;	184	use common::sense;
122		185
123	use Carp ();	186	use Carp ();
124		187
125	use AE ();	188	use AE ();
126		189
127	use base "Exporter";	190	use base "Exporter";
128		191
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
130		193
131	our @EXPORT = qw(	194	our @EXPORT = qw(
132	NODE $NODE *SELF node_of after	195	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	196	configure
134	snd rcv mon mon_guard kil reg psub spawn	197	snd rcv mon mon_guard kil psub peval spawn cal
135	port	198	port
136	);	199	);
137		200
138	our $SELF;	201	our $SELF;
139		202
…		…
143	kil $SELF, die => $msg;	206	kil $SELF, die => $msg;
144	}	207	}
145		208
146	=item $thisnode = NODE / $NODE	209	=item $thisnode = NODE / $NODE
147		210
148	The C<NODE> function returns, and the C<$NODE> variable contains the	211	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	noderef of the local node. The value is initialised by a call to	212	ID of the node running in the current process. This value is initialised by
150	C<initialise_node>.	213	a call to C<configure>.
151		214
152	=item $noderef = node_of $port	215	=item $nodeid = node_of $port
153		216
154	Extracts and returns the noderef from a port ID or a noderef.	217	Extracts and returns the node ID from a port ID or a node ID.
155		218
156	=item initialise_node $noderef, $seednode, $seednode...	219	=item configure $profile, key => value...
157		220
158	=item initialise_node "slave/", $master, $master...	221	=item configure key => value...
159		222
160	Before a node can talk to other nodes on the network it has to initialise	223	Before a node can talk to other nodes on the network (i.e. enter
161	itself - the minimum a node needs to know is it's own name, and optionally	224	"distributed mode") it has to configure itself - the minimum a node needs
162	it should know the noderefs of some other nodes in the network.	225	to know is its own name, and optionally it should know the addresses of
		226	some other nodes in the network to discover other nodes.
163		227
164	This function initialises a node - it must be called exactly once (or	228	This function configures a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	229	never) before calling other AnyEvent::MP functions.
166		230
167	All arguments (optionally except for the first) are noderefs, which can be	231	The key/value pairs are basically the same ones as documented for the
168	either resolved or unresolved.	232	F<aemp> command line utility (sans the set/del prefix), with two additions:
169
170	The first argument will be looked up in the configuration database first
171	(if it is C<undef> then the current nodename will be used instead) to find
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175
176	There are two types of networked nodes, public nodes and slave nodes:
177		233
178	=over 4	234	=over 4
179		235
180	=item public nodes	236	=item norc => $boolean (default false)
181		237
182	For public nodes, C<$noderef> (supplied either directly to	238	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
183	C<initialise_node> or indirectly via a profile or the nodename) must be a	239	be consulted - all configuraiton options must be specified in the
184	noderef (possibly unresolved, in which case it will be resolved).	240	C<configure> call.
185		241
186	After resolving, the node will bind itself on all endpoints.	242	=item force => $boolean (default false)
187		243
188	=item slave nodes	244	IF true, then the values specified in the C<configure> will take
189		245	precedence over any values configured via the rc file. The default is for
190	When the C<$noderef> (either as given or overriden by the config file)	246	the rc file to override any options specified in the program.
191	is the special string C<slave/>, then the node will become a slave
192	node. Slave nodes cannot be contacted from outside, and cannot talk to
193	each other (at least in this version of AnyEvent::MP).
194
195	Slave nodes work by creating connections to all public nodes, using the
196	L<AnyEvent::MP::Global> service.
197		247
198	=back	248	=back
199		249
200	After initialising itself, the node will connect to all additional
201	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
202	optional and can be used to quickly bootstrap the node into an existing
203	network.
204
205	All the seednodes will also be specially marked to automatically retry
206	connecting to them indefinitely, so make sure that seednodes are really
207	reliable and up (this might also change in the future).
208
209	Example: become a public node listening on the guessed noderef, or the one
210	specified via C<aemp> for the current node. This should be the most common
211	form of invocation for "daemon"-type nodes.
212
213	initialise_node;
214
215	Example: become a slave node to any of the the seednodes specified via
216	C<aemp>. This form is often used for commandline clients.
217
218	initialise_node "slave/";
219
220	Example: become a public node, and try to contact some well-known master
221	servers to become part of the network.
222
223	initialise_node undef, "master1", "master2";
224
225	Example: become a public node listening on port C<4041>.
226
227	initialise_node 4041;
228
229	Example: become a public node, only visible on localhost port 4044.
230
231	initialise_node "localhost:4044";
232
233	=item $cv = resolve_node $noderef
234
235	Takes an unresolved node reference that may contain hostnames and
236	abbreviated IDs, resolves all of them and returns a resolved node
237	reference.
238
239	In addition to C<address:port> pairs allowed in resolved noderefs, the
240	following forms are supported:
241
242	=over 4	250	=over 4
243		251
244	=item the empty string	252	=item step 1, gathering configuration from profiles
245		253
246	An empty-string component gets resolved as if the default port (4040) was	254	The function first looks up a profile in the aemp configuration (see the
247	specified.	255	L<aemp> commandline utility). The profile name can be specified via the
		256	named C<profile> parameter or can simply be the first parameter). If it is
		257	missing, then the nodename (F<uname -n>) will be used as profile name.
248		258
249	=item naked port numbers (e.g. C<1234>)	259	The profile data is then gathered as follows:
250		260
251	These are resolved by prepending the local nodename and a colon, to be	261	First, all remaining key => value pairs (all of which are conveniently
252	further resolved.	262	undocumented at the moment) will be interpreted as configuration
		263	data. Then they will be overwritten by any values specified in the global
		264	default configuration (see the F<aemp> utility), then the chain of
		265	profiles chosen by the profile name (and any C<parent> attributes).
253		266
254	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	267	That means that the values specified in the profile have highest priority
		268	and the values specified directly via C<configure> have lowest priority,
		269	and can only be used to specify defaults.
255		270
256	These are resolved by using AnyEvent::DNS to resolve them, optionally	271	If the profile specifies a node ID, then this will become the node ID of
257	looking up SRV records for the C<aemp=4040> port, if no port was	272	this process. If not, then the profile name will be used as node ID. The
258	specified.	273	special node ID of C<anon/> will be replaced by a random node ID.
		274
		275	=item step 2, bind listener sockets
		276
		277	The next step is to look up the binds in the profile, followed by binding
		278	aemp protocol listeners on all binds specified (it is possible and valid
		279	to have no binds, meaning that the node cannot be contacted form the
		280	outside. This means the node cannot talk to other nodes that also have no
		281	binds, but it can still talk to all "normal" nodes).
		282
		283	If the profile does not specify a binds list, then a default of C<*> is
		284	used, meaning the node will bind on a dynamically-assigned port on every
		285	local IP address it finds.
		286
		287	=item step 3, connect to seed nodes
		288
		289	As the last step, the seed ID list from the profile is passed to the
		290	L<AnyEvent::MP::Global> module, which will then use it to keep
		291	connectivity with at least one node at any point in time.
259		292
260	=back	293	=back
		294
		295	Example: become a distributed node using the local node name as profile.
		296	This should be the most common form of invocation for "daemon"-type nodes.
		297
		298	configure
		299
		300	Example: become an anonymous node. This form is often used for commandline
		301	clients.
		302
		303	configure nodeid => "anon/";
		304
		305	Example: configure a node using a profile called seed, which is suitable
		306	for a seed node as it binds on all local addresses on a fixed port (4040,
		307	customary for aemp).
		308
		309	# use the aemp commandline utility
		310	# aemp profile seed nodeid anon/ binds '*:4040'
		311
		312	# then use it
		313	configure profile => "seed";
		314
		315	# or simply use aemp from the shell again:
		316	# aemp run profile seed
		317
		318	# or provide a nicer-to-remember nodeid
		319	# aemp run profile seed nodeid "$(hostname)"
261		320
262	=item $SELF	321	=item $SELF
263		322
264	Contains the current port id while executing C<rcv> callbacks or C<psub>	323	Contains the current port id while executing C<rcv> callbacks or C<psub>
265	blocks.	324	blocks.
266		325
267	=item SELF, %SELF, @SELF...	326	=item *SELF, SELF, %SELF, @SELF...
268		327
269	Due to some quirks in how perl exports variables, it is impossible to	328	Due to some quirks in how perl exports variables, it is impossible to
270	just export C<$SELF>, all the symbols called C<SELF> are exported by this	329	just export C<$SELF>, all the symbols named C<SELF> are exported by this
271	module, but only C<$SELF> is currently used.	330	module, but only C<$SELF> is currently used.
272		331
273	=item snd $port, type => @data	332	=item snd $port, type => @data
274		333
275	=item snd $port, @msg	334	=item snd $port, @msg
276		335
277	Send the given message to the given port ID, which can identify either	336	Send the given message to the given port, which can identify either a
278	a local or a remote port, and must be a port ID.	337	local or a remote port, and must be a port ID.
279		338
280	While the message can be about anything, it is highly recommended to use a	339	While the message can be almost anything, it is highly recommended to
281	string as first element (a port ID, or some word that indicates a request	340	use a string as first element (a port ID, or some word that indicates a
282	type etc.).	341	request type etc.) and to consist if only simple perl values (scalars,
		342	arrays, hashes) - if you think you need to pass an object, think again.
283		343
284	The message data effectively becomes read-only after a call to this	344	The message data logically becomes read-only after a call to this
285	function: modifying any argument is not allowed and can cause many	345	function: modifying any argument (or values referenced by them) is
286	problems.	346	forbidden, as there can be considerable time between the call to C<snd>
		347	and the time the message is actually being serialised - in fact, it might
		348	never be copied as within the same process it is simply handed to the
		349	receiving port.
287		350
288	The type of data you can transfer depends on the transport protocol: when	351	The type of data you can transfer depends on the transport protocol: when
289	JSON is used, then only strings, numbers and arrays and hashes consisting	352	JSON is used, then only strings, numbers and arrays and hashes consisting
290	of those are allowed (no objects). When Storable is used, then anything	353	of those are allowed (no objects). When Storable is used, then anything
291	that Storable can serialise and deserialise is allowed, and for the local	354	that Storable can serialise and deserialise is allowed, and for the local
292	node, anything can be passed.	355	node, anything can be passed. Best rely only on the common denominator of
		356	these.
293		357
294	=item $local_port = port	358	=item $local_port = port
295		359
296	Create a new local port object and returns its port ID. Initially it has	360	Create a new local port object and returns its port ID. Initially it has
297	no callbacks set and will throw an error when it receives messages.	361	no callbacks set and will throw an error when it receives messages.
…		…
321	sub _kilme {	385	sub _kilme {
322	die "received message on port without callback";	386	die "received message on port without callback";
323	}	387	}
324		388
325	sub port(;&) {	389	sub port(;&) {
326	my $id = "$UNIQ." . $ID++;	390	my $id = "$UNIQ." . ++$ID;
327	my $port = "$NODE#$id";	391	my $port = "$NODE#$id";
328		392
329	rcv $port, shift \|\| \&_kilme;	393	rcv $port, shift \|\| \&_kilme;
330		394
331	$port	395	$port
…		…
370	msg1 => sub { ... },	434	msg1 => sub { ... },
371	...	435	...
372	;	436	;
373		437
374	Example: temporarily register a rcv callback for a tag matching some port	438	Example: temporarily register a rcv callback for a tag matching some port
375	(e.g. for a rpc reply) and unregister it after a message was received.	439	(e.g. for an rpc reply) and unregister it after a message was received.
376		440
377	rcv $port, $otherport => sub {	441	rcv $port, $otherport => sub {
378	my @reply = @_;	442	my @reply = @_;
379		443
380	rcv $SELF, $otherport;	444	rcv $SELF, $otherport;
…		…
382		446
383	=cut	447	=cut
384		448
385	sub rcv($@) {	449	sub rcv($@) {
386	my $port = shift;	450	my $port = shift;
387	my ($noderef, $portid) = split /#/, $port, 2;	451	my ($nodeid, $portid) = split /#/, $port, 2;
388		452
389	$NODE{$noderef} == $NODE{""}	453	$NODE{$nodeid} == $NODE{""}
390	or Carp::croak "$port: rcv can only be called on local ports, caught";	454	or Carp::croak "$port: rcv can only be called on local ports, caught";
391		455
392	while (@_) {	456	while (@_) {
393	if (ref $_[0]) {	457	if (ref $_[0]) {
394	if (my $self = $PORT_DATA{$portid}) {	458	if (my $self = $PORT_DATA{$portid}) {
395	"AnyEvent::MP::Port" eq ref $self	459	"AnyEvent::MP::Port" eq ref $self
396	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	460	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
397		461
398	$self->[2] = shift;	462	$self->[0] = shift;
399	} else {	463	} else {
400	my $cb = shift;	464	my $cb = shift;
401	$PORT{$portid} = sub {	465	$PORT{$portid} = sub {
402	local $SELF = $port;	466	local $SELF = $port;
403	eval { &$cb }; _self_die if $@;	467	eval { &$cb }; _self_die if $@;
404	};	468	};
405	}	469	}
406	} elsif (defined $_[0]) {	470	} elsif (defined $_[0]) {
407	my $self = $PORT_DATA{$portid} \|\|= do {	471	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	472	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409		473
410	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
411	local $SELF = $port;	475	local $SELF = $port;
412		476
413	if (my $cb = $self->[1]{$_[0]}) {	477	if (my $cb = $self->[1]{$_[0]}) {
…		…
435	}	499	}
436		500
437	$port	501	$port
438	}	502	}
439		503
		504	=item peval $port, $coderef[, @args]
		505
		506	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		507	when the code throews an exception the C<$port> will be killed.
		508
		509	Any remaining args will be passed to the callback. Any return values will
		510	be returned to the caller.
		511
		512	This is useful when you temporarily want to execute code in the context of
		513	a port.
		514
		515	Example: create a port and run some initialisation code in it's context.
		516
		517	my $port = port { ... };
		518
		519	peval $port, sub {
		520	init
		521	or die "unable to init";
		522	};
		523
		524	=cut
		525
		526	sub peval($$) {
		527	local $SELF = shift;
		528	my $cb = shift;
		529
		530	if (wantarray) {
		531	my @res = eval { &$cb };
		532	_self_die if $@;
		533	@res
		534	} else {
		535	my $res = eval { &$cb };
		536	_self_die if $@;
		537	$res
		538	}
		539	}
		540
440	=item $closure = psub { BLOCK }	541	=item $closure = psub { BLOCK }
441		542
442	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	543	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
443	closure is executed, sets up the environment in the same way as in C<rcv>	544	closure is executed, sets up the environment in the same way as in C<rcv>
444	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	545	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		546
		547	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		548	BLOCK }, @_ } >>.
445		549
446	This is useful when you register callbacks from C<rcv> callbacks:	550	This is useful when you register callbacks from C<rcv> callbacks:
447		551
448	rcv delayed_reply => sub {	552	rcv delayed_reply => sub {
449	my ($delay, @reply) = @_;	553	my ($delay, @reply) = @_;
…		…
473	$res	577	$res
474	}	578	}
475	}	579	}
476	}	580	}
477		581
478	=item $guard = mon $port, $cb->(@reason)	582	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
479		583
480	=item $guard = mon $port, $rcvport	584	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
481		585
482	=item $guard = mon $port	586	=item $guard = mon $port # kill $SELF when $port dies
483		587
484	=item $guard = mon $port, $rcvport, @msg	588	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
485		589
486	Monitor the given port and do something when the port is killed or	590	Monitor the given port and do something when the port is killed or
487	messages to it were lost, and optionally return a guard that can be used	591	messages to it were lost, and optionally return a guard that can be used
488	to stop monitoring again.	592	to stop monitoring again.
489
490	C<mon> effectively guarantees that, in the absence of hardware failures,
491	that after starting the monitor, either all messages sent to the port
492	will arrive, or the monitoring action will be invoked after possible
493	message loss has been detected. No messages will be lost "in between"
494	(after the first lost message no further messages will be received by the
495	port). After the monitoring action was invoked, further messages might get
496	delivered again.
497
498	Note that monitoring-actions are one-shot: once released, they are removed
499	and will not trigger again.
500		593
501	In the first form (callback), the callback is simply called with any	594	In the first form (callback), the callback is simply called with any
502	number of C<@reason> elements (no @reason means that the port was deleted	595	number of C<@reason> elements (no @reason means that the port was deleted
503	"normally"). Note also that I<< the callback B<must> never die >>, so use	596	"normally"). Note also that I<< the callback B<must> never die >>, so use
504	C<eval> if unsure.	597	C<eval> if unsure.
505		598
506	In the second form (another port given), the other port (C<$rcvport>)	599	In the second form (another port given), the other port (C<$rcvport>)
507	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	600	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
508	"normal" kils nothing happens, while under all other conditions, the other	601	"normal" kils nothing happens, while under all other conditions, the other
509	port is killed with the same reason.	602	port is killed with the same reason.
510		603
511	The third form (kill self) is the same as the second form, except that	604	The third form (kill self) is the same as the second form, except that
512	C<$rvport> defaults to C<$SELF>.	605	C<$rvport> defaults to C<$SELF>.
513		606
514	In the last form (message), a message of the form C<@msg, @reason> will be	607	In the last form (message), a message of the form C<@msg, @reason> will be
515	C<snd>.	608	C<snd>.
		609
		610	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		611	alert was raised), they are removed and will not trigger again.
516		612
517	As a rule of thumb, monitoring requests should always monitor a port from	613	As a rule of thumb, monitoring requests should always monitor a port from
518	a local port (or callback). The reason is that kill messages might get	614	a local port (or callback). The reason is that kill messages might get
519	lost, just like any other message. Another less obvious reason is that	615	lost, just like any other message. Another less obvious reason is that
520	even monitoring requests can get lost (for exmaple, when the connection	616	even monitoring requests can get lost (for example, when the connection
521	to the other node goes down permanently). When monitoring a port locally	617	to the other node goes down permanently). When monitoring a port locally
522	these problems do not exist.	618	these problems do not exist.
523		619
		620	C<mon> effectively guarantees that, in the absence of hardware failures,
		621	after starting the monitor, either all messages sent to the port will
		622	arrive, or the monitoring action will be invoked after possible message
		623	loss has been detected. No messages will be lost "in between" (after
		624	the first lost message no further messages will be received by the
		625	port). After the monitoring action was invoked, further messages might get
		626	delivered again.
		627
		628	Inter-host-connection timeouts and monitoring depend on the transport
		629	used. The only transport currently implemented is TCP, and AnyEvent::MP
		630	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		631	non-idle connection, and usually around two hours for idle connections).
		632
		633	This means that monitoring is good for program errors and cleaning up
		634	stuff eventually, but they are no replacement for a timeout when you need
		635	to ensure some maximum latency.
		636
524	Example: call a given callback when C<$port> is killed.	637	Example: call a given callback when C<$port> is killed.
525		638
526	mon $port, sub { warn "port died because of <@_>\n" };	639	mon $port, sub { warn "port died because of <@_>\n" };
527		640
528	Example: kill ourselves when C<$port> is killed abnormally.	641	Example: kill ourselves when C<$port> is killed abnormally.
…		…
534	mon $port, $self => "restart";	647	mon $port, $self => "restart";
535		648
536	=cut	649	=cut
537		650
538	sub mon {	651	sub mon {
539	my ($noderef, $port) = split /#/, shift, 2;	652	my ($nodeid, $port) = split /#/, shift, 2;
540		653
541	my $node = $NODE{$noderef} \|\| add_node $noderef;	654	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
542		655
543	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	656	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
544		657
545	unless (ref $cb) {	658	unless (ref $cb) {
546	if (@_) {	659	if (@_) {
…		…
555	}	668	}
556		669
557	$node->monitor ($port, $cb);	670	$node->monitor ($port, $cb);
558		671
559	defined wantarray	672	defined wantarray
560	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	673	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
561	}	674	}
562		675
563	=item $guard = mon_guard $port, $ref, $ref...	676	=item $guard = mon_guard $port, $ref, $ref...
564		677
565	Monitors the given C<$port> and keeps the passed references. When the port	678	Monitors the given C<$port> and keeps the passed references. When the port
566	is killed, the references will be freed.	679	is killed, the references will be freed.
567		680
568	Optionally returns a guard that will stop the monitoring.	681	Optionally returns a guard that will stop the monitoring.
569		682
570	This function is useful when you create e.g. timers or other watchers and	683	This function is useful when you create e.g. timers or other watchers and
571	want to free them when the port gets killed:	684	want to free them when the port gets killed (note the use of C<psub>):
572		685
573	$port->rcv (start => sub {	686	$port->rcv (start => sub {
574	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	687	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
575	undef $timer if 0.9 < rand;	688	undef $timer if 0.9 < rand;
576	});	689	});
577	});	690	});
578		691
579	=cut	692	=cut
…		…
588		701
589	=item kil $port[, @reason]	702	=item kil $port[, @reason]
590		703
591	Kill the specified port with the given C<@reason>.	704	Kill the specified port with the given C<@reason>.
592		705
593	If no C<@reason> is specified, then the port is killed "normally" (linked	706	If no C<@reason> is specified, then the port is killed "normally" -
594	ports will not be kileld, or even notified).	707	monitor callback will be invoked, but the kil will not cause linked ports
		708	(C<mon $mport, $lport> form) to get killed.
595		709
596	Otherwise, linked ports get killed with the same reason (second form of	710	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
597	C<mon>, see below).	711	form) get killed with the same reason.
598		712
599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	713	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
600	will be reported as reason C<< die => $@ >>.	714	will be reported as reason C<< die => $@ >>.
601		715
602	Transport/communication errors are reported as C<< transport_error =>	716	Transport/communication errors are reported as C<< transport_error =>
…		…
607	=item $port = spawn $node, $initfunc[, @initdata]	721	=item $port = spawn $node, $initfunc[, @initdata]
608		722
609	Creates a port on the node C<$node> (which can also be a port ID, in which	723	Creates a port on the node C<$node> (which can also be a port ID, in which
610	case it's the node where that port resides).	724	case it's the node where that port resides).
611		725
612	The port ID of the newly created port is return immediately, and it is	726	The port ID of the newly created port is returned immediately, and it is
613	permissible to immediately start sending messages or monitor the port.	727	possible to immediately start sending messages or to monitor the port.
614		728
615	After the port has been created, the init function is	729	After the port has been created, the init function is called on the remote
616	called. This function must be a fully-qualified function name	730	node, in the same context as a C<rcv> callback. This function must be a
617	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	731	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
618	program, use C<::name>.	732	specify a function in the main program, use C<::name>.
619		733
620	If the function doesn't exist, then the node tries to C<require>	734	If the function doesn't exist, then the node tries to C<require>
621	the package, then the package above the package and so on (e.g.	735	the package, then the package above the package and so on (e.g.
622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	736	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
623	exists or it runs out of package names.	737	exists or it runs out of package names.
624		738
625	The init function is then called with the newly-created port as context	739	The init function is then called with the newly-created port as context
626	object (C<$SELF>) and the C<@initdata> values as arguments.	740	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		741	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		742	the port might not get created.
627		743
628	A common idiom is to pass your own port, monitor the spawned port, and	744	A common idiom is to pass a local port, immediately monitor the spawned
629	in the init function, monitor the original port. This two-way monitoring	745	port, and in the remote init function, immediately monitor the passed
630	ensures that both ports get cleaned up when there is a problem.	746	local port. This two-way monitoring ensures that both ports get cleaned up
		747	when there is a problem.
		748
		749	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		750	caller before C<spawn> returns (by delaying invocation when spawn is
		751	called for the local node).
631		752
632	Example: spawn a chat server port on C<$othernode>.	753	Example: spawn a chat server port on C<$othernode>.
633		754
634	# this node, executed from within a port context:	755	# this node, executed from within a port context:
635	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	756	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
650		771
651	sub _spawn {	772	sub _spawn {
652	my $port = shift;	773	my $port = shift;
653	my $init = shift;	774	my $init = shift;
654		775
		776	# rcv will create the actual port
655	local $SELF = "$NODE#$port";	777	local $SELF = "$NODE#$port";
656	eval {	778	eval {
657	&{ load_func $init }	779	&{ load_func $init }
658	};	780	};
659	_self_die if $@;	781	_self_die if $@;
660	}	782	}
661		783
662	sub spawn(@) {	784	sub spawn(@) {
663	my ($noderef, undef) = split /#/, shift, 2;	785	my ($nodeid, undef) = split /#/, shift, 2;
664		786
665	my $id = "$RUNIQ." . $ID++;	787	my $id = "$RUNIQ." . ++$ID;
666		788
667	$_[0] =~ /::/	789	$_[0] =~ /::/
668	or Carp::croak "spawn init function must be a fully-qualified name, caught";	790	or Carp::croak "spawn init function must be a fully-qualified name, caught";
669		791
670	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	792	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
671		793
672	"$noderef#$id"	794	"$nodeid#$id"
673	}	795	}
		796
674		797
675	=item after $timeout, @msg	798	=item after $timeout, @msg
676		799
677	=item after $timeout, $callback	800	=item after $timeout, $callback
678		801
679	Either sends the given message, or call the given callback, after the	802	Either sends the given message, or call the given callback, after the
680	specified number of seconds.	803	specified number of seconds.
681		804
682	This is simply a utility function that come sin handy at times.	805	This is simply a utility function that comes in handy at times - the
		806	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		807	so it may go away in the future.
683		808
684	=cut	809	=cut
685		810
686	sub after($@) {	811	sub after($@) {
687	my ($timeout, @action) = @_;	812	my ($timeout, @action) = @_;
…		…
692	? $action[0]()	817	? $action[0]()
693	: snd @action;	818	: snd @action;
694	};	819	};
695	}	820	}
696		821
		822	=item cal $port, @msg, $callback[, $timeout]
		823
		824	A simple form of RPC - sends a message to the given C<$port> with the
		825	given contents (C<@msg>), but adds a reply port to the message.
		826
		827	The reply port is created temporarily just for the purpose of receiving
		828	the reply, and will be C<kil>ed when no longer needed.
		829
		830	A reply message sent to the port is passed to the C<$callback> as-is.
		831
		832	If an optional time-out (in seconds) is given and it is not C<undef>,
		833	then the callback will be called without any arguments after the time-out
		834	elapsed and the port is C<kil>ed.
		835
		836	If no time-out is given (or it is C<undef>), then the local port will
		837	monitor the remote port instead, so it eventually gets cleaned-up.
		838
		839	Currently this function returns the temporary port, but this "feature"
		840	might go in future versions unless you can make a convincing case that
		841	this is indeed useful for something.
		842
		843	=cut
		844
		845	sub cal(@) {
		846	my $timeout = ref $_[-1] ? undef : pop;
		847	my $cb = pop;
		848
		849	my $port = port {
		850	undef $timeout;
		851	kil $SELF;
		852	&$cb;
		853	};
		854
		855	if (defined $timeout) {
		856	$timeout = AE::timer $timeout, 0, sub {
		857	undef $timeout;
		858	kil $port;
		859	$cb->();
		860	};
		861	} else {
		862	mon $_[0], sub {
		863	kil $port;
		864	$cb->();
		865	};
		866	}
		867
		868	push @_, $port;
		869	&snd;
		870
		871	$port
		872	}
		873
697	=back	874	=back
698		875
699	=head1 AnyEvent::MP vs. Distributed Erlang	876	=head1 AnyEvent::MP vs. Distributed Erlang
700		877
701	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	878	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
702	== aemp node, Erlang process == aemp port), so many of the documents and	879	== aemp node, Erlang process == aemp port), so many of the documents and
703	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	880	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
704	sample:	881	sample:
705		882
706	http://www.Erlang.se/doc/programming_rules.shtml	883	http://www.erlang.se/doc/programming_rules.shtml
707	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	884	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
708	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	885	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
709	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	886	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
710		887
711	Despite the similarities, there are also some important differences:	888	Despite the similarities, there are also some important differences:
712		889
713	=over 4	890	=over 4
714		891
715	=item * Node references contain the recipe on how to contact them.	892	=item * Node IDs are arbitrary strings in AEMP.
716		893
717	Erlang relies on special naming and DNS to work everywhere in the	894	Erlang relies on special naming and DNS to work everywhere in the same
718	same way. AEMP relies on each node knowing it's own address(es), with	895	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
719	convenience functionality.	896	configuration or DNS), and possibly the addresses of some seed nodes, but
720		897	will otherwise discover other nodes (and their IDs) itself.
721	This means that AEMP requires a less tightly controlled environment at the
722	cost of longer node references and a slightly higher management overhead.
723		898
724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	899	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
725	uses "local ports are like remote ports".	900	uses "local ports are like remote ports".
726		901
727	The failure modes for local ports are quite different (runtime errors	902	The failure modes for local ports are quite different (runtime errors
…		…
736	ports being the special case/exception, where transport errors cannot	911	ports being the special case/exception, where transport errors cannot
737	occur.	912	occur.
738		913
739	=item * Erlang uses processes and a mailbox, AEMP does not queue.	914	=item * Erlang uses processes and a mailbox, AEMP does not queue.
740		915
741	Erlang uses processes that selectively receive messages, and therefore	916	Erlang uses processes that selectively receive messages out of order, and
742	needs a queue. AEMP is event based, queuing messages would serve no	917	therefore needs a queue. AEMP is event based, queuing messages would serve
743	useful purpose. For the same reason the pattern-matching abilities of	918	no useful purpose. For the same reason the pattern-matching abilities
744	AnyEvent::MP are more limited, as there is little need to be able to	919	of AnyEvent::MP are more limited, as there is little need to be able to
745	filter messages without dequeing them.	920	filter messages without dequeuing them.
746		921
747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	922	This is not a philosophical difference, but simply stems from AnyEvent::MP
		923	being event-based, while Erlang is process-based.
		924
		925	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		926	top of AEMP and Coro threads.
748		927
749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	928	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
750		929
751	Sending messages in Erlang is synchronous and blocks the process (and	930	Sending messages in Erlang is synchronous and blocks the process until
		931	a conenction has been established and the message sent (and so does not
752	so does not need a queue that can overflow). AEMP sends are immediate,	932	need a queue that can overflow). AEMP sends return immediately, connection
753	connection establishment is handled in the background.	933	establishment is handled in the background.
754		934
755	=item * Erlang suffers from silent message loss, AEMP does not.	935	=item * Erlang suffers from silent message loss, AEMP does not.
756		936
757	Erlang makes few guarantees on messages delivery - messages can get lost	937	Erlang implements few guarantees on messages delivery - messages can get
758	without any of the processes realising it (i.e. you send messages a, b,	938	lost without any of the processes realising it (i.e. you send messages a,
759	and c, and the other side only receives messages a and c).	939	b, and c, and the other side only receives messages a and c).
760		940
761	AEMP guarantees correct ordering, and the guarantee that there are no	941	AEMP guarantees (modulo hardware errors) correct ordering, and the
		942	guarantee that after one message is lost, all following ones sent to the
		943	same port are lost as well, until monitoring raises an error, so there are
762	holes in the message sequence.	944	no silent "holes" in the message sequence.
763		945
764	=item * In Erlang, processes can be declared dead and later be found to be	946	If you want your software to be very reliable, you have to cope with
765	alive.	947	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
766		948	simply tries to work better in common error cases, such as when a network
767	In Erlang it can happen that a monitored process is declared dead and	949	link goes down.
768	linked processes get killed, but later it turns out that the process is
769	still alive - and can receive messages.
770
771	In AEMP, when port monitoring detects a port as dead, then that port will
772	eventually be killed - it cannot happen that a node detects a port as dead
773	and then later sends messages to it, finding it is still alive.
774		950
775	=item * Erlang can send messages to the wrong port, AEMP does not.	951	=item * Erlang can send messages to the wrong port, AEMP does not.
776		952
777	In Erlang it is quite likely that a node that restarts reuses a process ID	953	In Erlang it is quite likely that a node that restarts reuses an Erlang
778	known to other nodes for a completely different process, causing messages	954	process ID known to other nodes for a completely different process,
779	destined for that process to end up in an unrelated process.	955	causing messages destined for that process to end up in an unrelated
		956	process.
780		957
781	AEMP never reuses port IDs, so old messages or old port IDs floating	958	AEMP does not reuse port IDs, so old messages or old port IDs floating
782	around in the network will not be sent to an unrelated port.	959	around in the network will not be sent to an unrelated port.
783		960
784	=item * Erlang uses unprotected connections, AEMP uses secure	961	=item * Erlang uses unprotected connections, AEMP uses secure
785	authentication and can use TLS.	962	authentication and can use TLS.
786		963
787	AEMP can use a proven protocol - SSL/TLS - to protect connections and	964	AEMP can use a proven protocol - TLS - to protect connections and
788	securely authenticate nodes.	965	securely authenticate nodes.
789		966
790	=item * The AEMP protocol is optimised for both text-based and binary	967	=item * The AEMP protocol is optimised for both text-based and binary
791	communications.	968	communications.
792		969
793	The AEMP protocol, unlike the Erlang protocol, supports both	970	The AEMP protocol, unlike the Erlang protocol, supports both programming
794	language-independent text-only protocols (good for debugging) and binary,	971	language independent text-only protocols (good for debugging), and binary,
795	language-specific serialisers (e.g. Storable).	972	language-specific serialisers (e.g. Storable). By default, unless TLS is
		973	used, the protocol is actually completely text-based.
796		974
797	It has also been carefully designed to be implementable in other languages	975	It has also been carefully designed to be implementable in other languages
798	with a minimum of work while gracefully degrading fucntionality to make the	976	with a minimum of work while gracefully degrading functionality to make the
799	protocol simple.	977	protocol simple.
800		978
801	=item * AEMP has more flexible monitoring options than Erlang.	979	=item * AEMP has more flexible monitoring options than Erlang.
802		980
803	In Erlang, you can chose to receive I<all> exit signals as messages	981	In Erlang, you can chose to receive I<all> exit signals as messages or
804	or I<none>, there is no in-between, so monitoring single processes is	982	I<none>, there is no in-between, so monitoring single Erlang processes is
805	difficult to implement. Monitoring in AEMP is more flexible than in	983	difficult to implement.
806	Erlang, as one can choose between automatic kill, exit message or callback	984
807	on a per-process basis.	985	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		986	between automatic kill, exit message or callback on a per-port basis.
808		987
809	=item * Erlang tries to hide remote/local connections, AEMP does not.	988	=item * Erlang tries to hide remote/local connections, AEMP does not.
810		989
811	Monitoring in Erlang is not an indicator of process death/crashes,	990	Monitoring in Erlang is not an indicator of process death/crashes, in the
812	as linking is (except linking is unreliable in Erlang).	991	same way as linking is (except linking is unreliable in Erlang).
813		992
814	In AEMP, you don't "look up" registered port names or send to named ports	993	In AEMP, you don't "look up" registered port names or send to named ports
815	that might or might not be persistent. Instead, you normally spawn a port	994	that might or might not be persistent. Instead, you normally spawn a port
816	on the remote node. The init function monitors the you, and you monitor	995	on the remote node. The init function monitors you, and you monitor the
817	the remote port. Since both monitors are local to the node, they are much	996	remote port. Since both monitors are local to the node, they are much more
818	more reliable.	997	reliable (no need for C<spawn_link>).
819		998
820	This also saves round-trips and avoids sending messages to the wrong port	999	This also saves round-trips and avoids sending messages to the wrong port
821	(hard to do in Erlang).	1000	(hard to do in Erlang).
822		1001
823	=back	1002	=back
824		1003
825	=head1 RATIONALE	1004	=head1 RATIONALE
826		1005
827	=over 4	1006	=over 4
828		1007
829	=item Why strings for ports and noderefs, why not objects?	1008	=item Why strings for port and node IDs, why not objects?
830		1009
831	We considered "objects", but found that the actual number of methods	1010	We considered "objects", but found that the actual number of methods
832	thatc an be called are very low. Since port IDs and noderefs travel over	1011	that can be called are quite low. Since port and node IDs travel over
833	the network frequently, the serialising/deserialising would add lots of	1012	the network frequently, the serialising/deserialising would add lots of
834	overhead, as well as having to keep a proxy object.	1013	overhead, as well as having to keep a proxy object everywhere.
835		1014
836	Strings can easily be printed, easily serialised etc. and need no special	1015	Strings can easily be printed, easily serialised etc. and need no special
837	procedures to be "valid".	1016	procedures to be "valid".
838		1017
839	And a a miniport consists of a single closure stored in a global hash - it	1018	And as a result, a port with just a default receiver consists of a single
840	can't become much cheaper.	1019	code reference stored in a global hash - it can't become much cheaper.
841		1020
842	=item Why favour JSON, why not real serialising format such as Storable?	1021	=item Why favour JSON, why not a real serialising format such as Storable?
843		1022
844	In fact, any AnyEvent::MP node will happily accept Storable as framing	1023	In fact, any AnyEvent::MP node will happily accept Storable as framing
845	format, but currently there is no way to make a node use Storable by	1024	format, but currently there is no way to make a node use Storable by
846	default.	1025	default (although all nodes will accept it).
847		1026
848	The default framing protocol is JSON because a) JSON::XS is many times	1027	The default framing protocol is JSON because a) JSON::XS is many times
849	faster for small messages and b) most importantly, after years of	1028	faster for small messages and b) most importantly, after years of
850	experience we found that object serialisation is causing more problems	1029	experience we found that object serialisation is causing more problems
851	than it gains: Just like function calls, objects simply do not travel	1030	than it solves: Just like function calls, objects simply do not travel
852	easily over the network, mostly because they will always be a copy, so you	1031	easily over the network, mostly because they will always be a copy, so you
853	always have to re-think your design.	1032	always have to re-think your design.
854		1033
855	Keeping your messages simple, concentrating on data structures rather than	1034	Keeping your messages simple, concentrating on data structures rather than
856	objects, will keep your messages clean, tidy and efficient.	1035	objects, will keep your messages clean, tidy and efficient.
857		1036
858	=back	1037	=back
859		1038
860	=head1 SEE ALSO	1039	=head1 SEE ALSO
861		1040
		1041	L<AnyEvent::MP::Intro> - a gentle introduction.
		1042
		1043	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1044
		1045	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1046	your applications.
		1047
		1048	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1049
		1050	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1051	all nodes.
		1052
862	L<AnyEvent>.	1053	L<AnyEvent>.
863		1054
864	=head1 AUTHOR	1055	=head1 AUTHOR
865		1056
866	Marc Lehmann <schmorp@schmorp.de>	1057	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.121 by root, Tue Feb 28 18:37:24 2012 UTC