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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.123 by root, Thu Mar 1 19:37:59 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $somple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, type matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a 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	Some ports allow you to register C<rcv> handlers that can match specific	79	Ports allow you to register C<rcv> handlers that can match all or just
75	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	81	anything was listening for them or not.
77		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
78	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
79		86
80	A port id is normaly 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<#>)
81	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
82	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
83	reference.
84		90
85	=item node	91	=item node
86		92
87	A node is a single process containing at least one port - the node	93	A node is a single process containing at least one port - the node port,
88	port. You can send messages to node ports to find existing ports or to	94	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	95	ports.
90		96
91	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	98	(no listening ports). Private nodes cannot talk to other private nodes
		99	currently, but all nodes can talk to public nodes.
93		100
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
95		102
96	A node reference is a string that either simply identifies the node (for	103	=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		104
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	A node ID is a string that uniquely identifies the node within a
101	TCP/IP, other protocols might look different).	106	network. Depending on the configuration used, node IDs can look like a
		107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
102		109
103	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
104	addresses) or unresolved (where hostnames are used instead of addresses).
105		111
106	Before using an unresolved node reference in a message you first have to	112	Nodes can only talk to each other by creating some kind of connection to
107	resolve it.	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
108		170
109	=back	171	=back
110		172
111	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
112		174
114		176
115	=cut	177	=cut
116		178
117	package AnyEvent::MP;	179	package AnyEvent::MP;
118		180
		181	use AnyEvent::MP::Config ();
119	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
120		184
121	use common::sense;	185	use common::sense;
122		186
123	use Carp ();	187	use Carp ();
124		188
125	use AE ();	189	use AE ();
126		190
127	use base "Exporter";	191	use base "Exporter";
128		192
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	193	our $VERSION = $AnyEvent::MP::Config::VERSION;
130		194
131	our @EXPORT = qw(	195	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	196	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	197	configure
134	snd rcv mon kil reg psub spawn	198	snd rcv mon mon_guard kil psub peval spawn cal
135	port	199	port
136	);	200	);
137		201
138	our $SELF;	202	our $SELF;
139		203
…		…
143	kil $SELF, die => $msg;	207	kil $SELF, die => $msg;
144	}	208	}
145		209
146	=item $thisnode = NODE / $NODE	210	=item $thisnode = NODE / $NODE
147		211
148	The C<NODE> function returns, and the C<$NODE> variable contains	212	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	the noderef of the local node. The value is initialised by a call	213	ID of the node running in the current process. This value is initialised by
150	to C<become_public> or C<become_slave>, after which all local port	214	a call to C<configure>.
151	identifiers become invalid.
152		215
153	=item $noderef = node_of $port	216	=item $nodeid = node_of $port
154		217
155	Extracts and returns the noderef from a portid or a noderef.	218	Extracts and returns the node ID from a port ID or a node ID.
156		219
157	=item initialise_node $noderef, $seednode, $seednode...	220	=item configure $profile, key => value...
158		221
159	=item initialise_node "slave/", $master, $master...	222	=item configure key => value...
160		223
161	Before a node can talk to other nodes on the network it has to initialise	224	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	225	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	226	to know is its own name, and optionally it should know the addresses of
		227	some other nodes in the network to discover other nodes.
164		228
165	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
166	never) before calling other AnyEvent::MP functions.	230	never) before calling other AnyEvent::MP functions.
167		231
168	All arguments (optionally except for the first) are noderefs, which can be	232	The key/value pairs are basically the same ones as documented for the
169	either resolved or unresolved.	233	F<aemp> command line utility (sans the set/del prefix), with two additions:
170
171	The first argument will be looked up in the configuration database first
172	(if it is C<undef> then the current nodename will be used instead) to find
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176
177	There are two types of networked nodes, public nodes and slave nodes:
178		234
179	=over 4	235	=over 4
180		236
181	=item public nodes	237	=item norc => $boolean (default false)
182		238
183	For public nodes, C<$noderef> (supplied either directly to	239	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	240	be consulted - all configuraiton options must be specified in the
185	noderef (possibly unresolved, in which case it will be resolved).	241	C<configure> call.
186		242
187	After resolving, the node will bind itself on all endpoints and try to	243	=item force => $boolean (default false)
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191		244
192	=item slave nodes	245	IF true, then the values specified in the C<configure> will take
193		246	precedence over any values configured via the rc file. The default is for
194	When the C<$noderef> (either as given or overriden by the config file)	247	the rc file to override any options specified in the program.
195	is the special string C<slave/>, then the node will become a slave
196	node. Slave nodes cannot be contacted from outside and will route most of
197	their traffic to the master node that they attach to.
198
199	At least one additional noderef is required (either by specifying it
200	directly or because it is part of the configuration profile): The node
201	will try to connect to all of them and will become a slave attached to the
202	first node it can successfully connect to.
203		248
204	=back	249	=back
205		250
206	This function will block until all nodes have been resolved and, for slave
207	nodes, until it has successfully established a connection to a master
208	server.
209
210	Example: become a public node listening on the guessed noderef, or the one
211	specified via C<aemp> for the current node. This should be the most common
212	form of invocation for "daemon"-type nodes.
213
214	initialise_node;
215
216	Example: become a slave node to any of the the seednodes specified via
217	C<aemp>. This form is often used for commandline clients.
218
219	initialise_node "slave/";
220
221	Example: become a slave node to any of the specified master servers. This
222	form is also often used for commandline clients.
223
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	Example: become a public node, and try to contact some well-known master
227	servers to become part of the network.
228
229	initialise_node undef, "master1", "master2";
230
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236
237	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4	251	=over 4
249		252
250	=item the empty string	253	=item step 1, gathering configuration from profiles
251		254
252	An empty-string component gets resolved as if the default port (4040) was	255	The function first looks up a profile in the aemp configuration (see the
253	specified.	256	L<aemp> commandline utility). The profile name can be specified via the
		257	named C<profile> parameter or can simply be the first parameter). If it is
		258	missing, then the nodename (F<uname -n>) will be used as profile name.
254		259
255	=item naked port numbers (e.g. C<1234>)	260	The profile data is then gathered as follows:
256		261
257	These are resolved by prepending the local nodename and a colon, to be	262	First, all remaining key => value pairs (all of which are conveniently
258	further resolved.	263	undocumented at the moment) will be interpreted as configuration
		264	data. Then they will be overwritten by any values specified in the global
		265	default configuration (see the F<aemp> utility), then the chain of
		266	profiles chosen by the profile name (and any C<parent> attributes).
259		267
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	268	That means that the values specified in the profile have highest priority
		269	and the values specified directly via C<configure> have lowest priority,
		270	and can only be used to specify defaults.
261		271
262	These are resolved by using AnyEvent::DNS to resolve them, optionally	272	If the profile specifies a node ID, then this will become the node ID of
263	looking up SRV records for the C<aemp=4040> port, if no port was	273	this process. If not, then the profile name will be used as node ID, with
264	specified.	274	a slash (C</>) attached.
		275
		276	If the node ID (or profile name) ends with a slash (C</>), then a random
		277	string is appended to make it unique.
		278
		279	=item step 2, bind listener sockets
		280
		281	The next step is to look up the binds in the profile, followed by binding
		282	aemp protocol listeners on all binds specified (it is possible and valid
		283	to have no binds, meaning that the node cannot be contacted form the
		284	outside. This means the node cannot talk to other nodes that also have no
		285	binds, but it can still talk to all "normal" nodes).
		286
		287	If the profile does not specify a binds list, then a default of C<*> is
		288	used, meaning the node will bind on a dynamically-assigned port on every
		289	local IP address it finds.
		290
		291	=item step 3, connect to seed nodes
		292
		293	As the last step, the seed ID list from the profile is passed to the
		294	L<AnyEvent::MP::Global> module, which will then use it to keep
		295	connectivity with at least one node at any point in time.
265		296
266	=back	297	=back
		298
		299	Example: become a distributed node using the local node name as profile.
		300	This should be the most common form of invocation for "daemon"-type nodes.
		301
		302	configure
		303
		304	Example: become an anonymous node. This form is often used for commandline
		305	clients.
		306
		307	configure nodeid => "anon/";
		308
		309	Example: configure a node using a profile called seed, which is suitable
		310	for a seed node as it binds on all local addresses on a fixed port (4040,
		311	customary for aemp).
		312
		313	# use the aemp commandline utility
		314	# aemp profile seed binds '*:4040'
		315
		316	# then use it
		317	configure profile => "seed";
		318
		319	# or simply use aemp from the shell again:
		320	# aemp run profile seed
		321
		322	# or provide a nicer-to-remember nodeid
		323	# aemp run profile seed nodeid "$(hostname)"
267		324
268	=item $SELF	325	=item $SELF
269		326
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	327	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	328	blocks.
272		329
273	=item SELF, %SELF, @SELF...	330	=item *SELF, SELF, %SELF, @SELF...
274		331
275	Due to some quirks in how perl exports variables, it is impossible to	332	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	333	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	334	module, but only C<$SELF> is currently used.
278		335
279	=item snd $port, type => @data	336	=item snd $port, type => @data
280		337
281	=item snd $port, @msg	338	=item snd $port, @msg
282		339
283	Send the given message to the given port ID, which can identify either	340	Send the given message to the given port, which can identify either a
284	a local or a remote port, and can be either a string or soemthignt hat	341	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		342
287	While the message can be about anything, it is highly recommended to use a	343	While the message can be almost anything, it is highly recommended to
288	string as first element (a portid, or some word that indicates a request	344	use a string as first element (a port ID, or some word that indicates a
289	type etc.).	345	request type etc.) and to consist if only simple perl values (scalars,
		346	arrays, hashes) - if you think you need to pass an object, think again.
290		347
291	The message data effectively becomes read-only after a call to this	348	The message data logically becomes read-only after a call to this
292	function: modifying any argument is not allowed and can cause many	349	function: modifying any argument (or values referenced by them) is
293	problems.	350	forbidden, as there can be considerable time between the call to C<snd>
		351	and the time the message is actually being serialised - in fact, it might
		352	never be copied as within the same process it is simply handed to the
		353	receiving port.
294		354
295	The type of data you can transfer depends on the transport protocol: when	355	The type of data you can transfer depends on the transport protocol: when
296	JSON is used, then only strings, numbers and arrays and hashes consisting	356	JSON is used, then only strings, numbers and arrays and hashes consisting
297	of those are allowed (no objects). When Storable is used, then anything	357	of those are allowed (no objects). When Storable is used, then anything
298	that Storable can serialise and deserialise is allowed, and for the local	358	that Storable can serialise and deserialise is allowed, and for the local
299	node, anything can be passed.	359	node, anything can be passed. Best rely only on the common denominator of
		360	these.
300		361
301	=item $local_port = port	362	=item $local_port = port
302		363
303	Create a new local port object and returns its port ID. Initially it has	364	Create a new local port object and returns its port ID. Initially it has
304	no callbacks set and will throw an error when it receives messages.	365	no callbacks set and will throw an error when it receives messages.
…		…
328	sub _kilme {	389	sub _kilme {
329	die "received message on port without callback";	390	die "received message on port without callback";
330	}	391	}
331		392
332	sub port(;&) {	393	sub port(;&) {
333	my $id = "$UNIQ." . $ID++;	394	my $id = $UNIQ . ++$ID;
334	my $port = "$NODE#$id";	395	my $port = "$NODE#$id";
335		396
336	rcv $port, shift \|\| \&_kilme;	397	rcv $port, shift \|\| \&_kilme;
337		398
338	$port	399	$port
…		…
351	The default callback received all messages not matched by a more specific	412	The default callback received all messages not matched by a more specific
352	C<tag> match.	413	C<tag> match.
353		414
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	415	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		416
356	Register callbacks to be called on messages starting with the given tag on	417	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	418	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	419	C<$callback> is C<$undef> or missing). There can only be one callback
		420	registered for each tag.
359		421
360	The original message will be passed to the callback, after the first	422	The original message will be passed to the callback, after the first
361	element (the tag) has been removed. The callback will use the same	423	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	424	environment as the default callback (see above).
363		425
…		…
375	rcv port,	437	rcv port,
376	msg1 => sub { ... },	438	msg1 => sub { ... },
377	...	439	...
378	;	440	;
379		441
		442	Example: temporarily register a rcv callback for a tag matching some port
		443	(e.g. for an rpc reply) and unregister it after a message was received.
		444
		445	rcv $port, $otherport => sub {
		446	my @reply = @_;
		447
		448	rcv $SELF, $otherport;
		449	};
		450
380	=cut	451	=cut
381		452
382	sub rcv($@) {	453	sub rcv($@) {
383	my $port = shift;	454	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	455	my ($nodeid, $portid) = split /#/, $port, 2;
385		456
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	457	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	458	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		459
389	while (@_) {	460	while (@_) {
390	if (ref $_[0]) {	461	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	462	if (my $self = $PORT_DATA{$portid}) {
392	"AnyEvent::MP::Port" eq ref $self	463	"AnyEvent::MP::Port" eq ref $self
393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	464	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
394		465
395	$self->[2] = shift;	466	$self->[0] = shift;
396	} else {	467	} else {
397	my $cb = shift;	468	my $cb = shift;
398	$PORT{$portid} = sub {	469	$PORT{$portid} = sub {
399	local $SELF = $port;	470	local $SELF = $port;
400	eval { &$cb }; _self_die if $@;	471	eval { &$cb }; _self_die if $@;
401	};	472	};
402	}	473	}
403	} elsif (defined $_[0]) {	474	} elsif (defined $_[0]) {
404	my $self = $PORT_DATA{$portid} \|\|= do {	475	my $self = $PORT_DATA{$portid} \|\|= do {
405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	476	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
406		477
407	$PORT{$portid} = sub {	478	$PORT{$portid} = sub {
408	local $SELF = $port;	479	local $SELF = $port;
409		480
410	if (my $cb = $self->[1]{$_[0]}) {	481	if (my $cb = $self->[1]{$_[0]}) {
…		…
432	}	503	}
433		504
434	$port	505	$port
435	}	506	}
436		507
		508	=item peval $port, $coderef[, @args]
		509
		510	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		511	when the code throews an exception the C<$port> will be killed.
		512
		513	Any remaining args will be passed to the callback. Any return values will
		514	be returned to the caller.
		515
		516	This is useful when you temporarily want to execute code in the context of
		517	a port.
		518
		519	Example: create a port and run some initialisation code in it's context.
		520
		521	my $port = port { ... };
		522
		523	peval $port, sub {
		524	init
		525	or die "unable to init";
		526	};
		527
		528	=cut
		529
		530	sub peval($$) {
		531	local $SELF = shift;
		532	my $cb = shift;
		533
		534	if (wantarray) {
		535	my @res = eval { &$cb };
		536	_self_die if $@;
		537	@res
		538	} else {
		539	my $res = eval { &$cb };
		540	_self_die if $@;
		541	$res
		542	}
		543	}
		544
437	=item $closure = psub { BLOCK }	545	=item $closure = psub { BLOCK }
438		546
439	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	547	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
440	closure is executed, sets up the environment in the same way as in C<rcv>	548	closure is executed, sets up the environment in the same way as in C<rcv>
441	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	549	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		550
		551	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		552	BLOCK }, @_ } >>.
442		553
443	This is useful when you register callbacks from C<rcv> callbacks:	554	This is useful when you register callbacks from C<rcv> callbacks:
444		555
445	rcv delayed_reply => sub {	556	rcv delayed_reply => sub {
446	my ($delay, @reply) = @_;	557	my ($delay, @reply) = @_;
…		…
470	$res	581	$res
471	}	582	}
472	}	583	}
473	}	584	}
474		585
475	=item $guard = mon $port, $cb->(@reason)	586	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		587
477	=item $guard = mon $port, $rcvport	588	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		589
479	=item $guard = mon $port	590	=item $guard = mon $port # kill $SELF when $port dies
480		591
481	=item $guard = mon $port, $rcvport, @msg	592	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		593
483	Monitor the given port and do something when the port is killed or	594	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	595	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	596	to stop monitoring again.
486
487	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port
489	will arrive, or the monitoring action will be invoked after possible
490	message loss has been detected. No messages will be lost "in between"
491	(after the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get
493	delivered again.
494		597
495	In the first form (callback), the callback is simply called with any	598	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	599	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	600	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	601	C<eval> if unsure.
499		602
500	In the second form (another port given), the other port (C<$rcvport>)	603	In the second form (another port given), the other port (C<$rcvport>)
501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	604	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
502	"normal" kils nothing happens, while under all other conditions, the other	605	"normal" kils nothing happens, while under all other conditions, the other
503	port is killed with the same reason.	606	port is killed with the same reason.
504		607
505	The third form (kill self) is the same as the second form, except that	608	The third form (kill self) is the same as the second form, except that
506	C<$rvport> defaults to C<$SELF>.	609	C<$rvport> defaults to C<$SELF>.
507		610
508	In the last form (message), a message of the form C<@msg, @reason> will be	611	In the last form (message), a message of the form C<@msg, @reason> will be
509	C<snd>.	612	C<snd>.
		613
		614	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		615	alert was raised), they are removed and will not trigger again.
510		616
511	As a rule of thumb, monitoring requests should always monitor a port from	617	As a rule of thumb, monitoring requests should always monitor a port from
512	a local port (or callback). The reason is that kill messages might get	618	a local port (or callback). The reason is that kill messages might get
513	lost, just like any other message. Another less obvious reason is that	619	lost, just like any other message. Another less obvious reason is that
514	even monitoring requests can get lost (for exmaple, when the connection	620	even monitoring requests can get lost (for example, when the connection
515	to the other node goes down permanently). When monitoring a port locally	621	to the other node goes down permanently). When monitoring a port locally
516	these problems do not exist.	622	these problems do not exist.
517		623
		624	C<mon> effectively guarantees that, in the absence of hardware failures,
		625	after starting the monitor, either all messages sent to the port will
		626	arrive, or the monitoring action will be invoked after possible message
		627	loss has been detected. No messages will be lost "in between" (after
		628	the first lost message no further messages will be received by the
		629	port). After the monitoring action was invoked, further messages might get
		630	delivered again.
		631
		632	Inter-host-connection timeouts and monitoring depend on the transport
		633	used. The only transport currently implemented is TCP, and AnyEvent::MP
		634	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		635	non-idle connection, and usually around two hours for idle connections).
		636
		637	This means that monitoring is good for program errors and cleaning up
		638	stuff eventually, but they are no replacement for a timeout when you need
		639	to ensure some maximum latency.
		640
518	Example: call a given callback when C<$port> is killed.	641	Example: call a given callback when C<$port> is killed.
519		642
520	mon $port, sub { warn "port died because of <@_>\n" };	643	mon $port, sub { warn "port died because of <@_>\n" };
521		644
522	Example: kill ourselves when C<$port> is killed abnormally.	645	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	651	mon $port, $self => "restart";
529		652
530	=cut	653	=cut
531		654
532	sub mon {	655	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	656	my ($nodeid, $port) = split /#/, shift, 2;
534		657
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	658	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		659
537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	660	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		661
539	unless (ref $cb) {	662	unless (ref $cb) {
540	if (@_) {	663	if (@_) {
…		…
549	}	672	}
550		673
551	$node->monitor ($port, $cb);	674	$node->monitor ($port, $cb);
552		675
553	defined wantarray	676	defined wantarray
554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	677	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
555	}	678	}
556		679
557	=item $guard = mon_guard $port, $ref, $ref...	680	=item $guard = mon_guard $port, $ref, $ref...
558		681
559	Monitors the given C<$port> and keeps the passed references. When the port	682	Monitors the given C<$port> and keeps the passed references. When the port
560	is killed, the references will be freed.	683	is killed, the references will be freed.
561		684
562	Optionally returns a guard that will stop the monitoring.	685	Optionally returns a guard that will stop the monitoring.
563		686
564	This function is useful when you create e.g. timers or other watchers and	687	This function is useful when you create e.g. timers or other watchers and
565	want to free them when the port gets killed:	688	want to free them when the port gets killed (note the use of C<psub>):
566		689
567	$port->rcv (start => sub {	690	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	691	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	692	undef $timer if 0.9 < rand;
570	});	693	});
571	});	694	});
572		695
573	=cut	696	=cut
…		…
582		705
583	=item kil $port[, @reason]	706	=item kil $port[, @reason]
584		707
585	Kill the specified port with the given C<@reason>.	708	Kill the specified port with the given C<@reason>.
586		709
587	If no C<@reason> is specified, then the port is killed "normally" (linked	710	If no C<@reason> is specified, then the port is killed "normally" -
588	ports will not be kileld, or even notified).	711	monitor callback will be invoked, but the kil will not cause linked ports
		712	(C<mon $mport, $lport> form) to get killed.
589		713
590	Otherwise, linked ports get killed with the same reason (second form of	714	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
591	C<mon>, see below).	715	form) get killed with the same reason.
592		716
593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	717	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
594	will be reported as reason C<< die => $@ >>.	718	will be reported as reason C<< die => $@ >>.
595		719
596	Transport/communication errors are reported as C<< transport_error =>	720	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	725	=item $port = spawn $node, $initfunc[, @initdata]
602		726
603	Creates a port on the node C<$node> (which can also be a port ID, in which	727	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	728	case it's the node where that port resides).
605		729
606	The port ID of the newly created port is return immediately, and it is	730	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	731	possible to immediately start sending messages or to monitor the port.
608		732
609	After the port has been created, the init function is	733	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	734	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	735	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	736	specify a function in the main program, use C<::name>.
613		737
614	If the function doesn't exist, then the node tries to C<require>	738	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	739	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	740	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	741	exists or it runs out of package names.
618		742
619	The init function is then called with the newly-created port as context	743	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	744	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		745	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		746	the port might not get created.
621		747
622	A common idiom is to pass your own port, monitor the spawned port, and	748	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	749	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	750	local port. This two-way monitoring ensures that both ports get cleaned up
		751	when there is a problem.
		752
		753	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		754	caller before C<spawn> returns (by delaying invocation when spawn is
		755	called for the local node).
625		756
626	Example: spawn a chat server port on C<$othernode>.	757	Example: spawn a chat server port on C<$othernode>.
627		758
628	# this node, executed from within a port context:	759	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	760	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
644		775
645	sub _spawn {	776	sub _spawn {
646	my $port = shift;	777	my $port = shift;
647	my $init = shift;	778	my $init = shift;
648		779
		780	# rcv will create the actual port
649	local $SELF = "$NODE#$port";	781	local $SELF = "$NODE#$port";
650	eval {	782	eval {
651	&{ load_func $init }	783	&{ load_func $init }
652	};	784	};
653	_self_die if $@;	785	_self_die if $@;
654	}	786	}
655		787
656	sub spawn(@) {	788	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	789	my ($nodeid, undef) = split /#/, shift, 2;
658		790
659	my $id = "$RUNIQ." . $ID++;	791	my $id = $RUNIQ . ++$ID;
660		792
661	$_[0] =~ /::/	793	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	794	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		795
664	($NODE{$noderef} \|\| add_node $noderef)	796	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		797
667	"$noderef#$id"	798	"$nodeid#$id"
668	}	799	}
669		800
670	=back
671		801
672	=head1 NODE MESSAGES	802	=item after $timeout, @msg
673		803
674	Nodes understand the following messages sent to them. Many of them take	804	=item after $timeout, $callback
675	arguments called C<@reply>, which will simply be used to compose a reply
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
677	the remaining arguments are simply the message data.
678		805
679	While other messages exist, they are not public and subject to change.	806	Either sends the given message, or call the given callback, after the
		807	specified number of seconds.
680		808
681	=over 4	809	This is simply a utility function that comes in handy at times - the
		810	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		811	so it may go away in the future.
682		812
683	=cut	813	=cut
684		814
685	=item lookup => $name, @reply	815	sub after($@) {
		816	my ($timeout, @action) = @_;
686		817
687	Replies with the port ID of the specified well-known port, or C<undef>.	818	my $t; $t = AE::timer $timeout, 0, sub {
		819	undef $t;
		820	ref $action[0]
		821	? $action[0]()
		822	: snd @action;
		823	};
		824	}
688		825
689	=item devnull => ...	826	=item cal $port, @msg, $callback[, $timeout]
690		827
691	Generic data sink/CPU heat conversion.	828	A simple form of RPC - sends a message to the given C<$port> with the
		829	given contents (C<@msg>), but adds a reply port to the message.
692		830
693	=item relay => $port, @msg	831	The reply port is created temporarily just for the purpose of receiving
		832	the reply, and will be C<kil>ed when no longer needed.
694		833
695	Simply forwards the message to the given port.	834	A reply message sent to the port is passed to the C<$callback> as-is.
696		835
697	=item eval => $string[ @reply]	836	If an optional time-out (in seconds) is given and it is not C<undef>,
		837	then the callback will be called without any arguments after the time-out
		838	elapsed and the port is C<kil>ed.
698		839
699	Evaluates the given string. If C<@reply> is given, then a message of the	840	If no time-out is given (or it is C<undef>), then the local port will
700	form C<@reply, $@, @evalres> is sent.	841	monitor the remote port instead, so it eventually gets cleaned-up.
701		842
702	Example: crash another node.	843	Currently this function returns the temporary port, but this "feature"
		844	might go in future versions unless you can make a convincing case that
		845	this is indeed useful for something.
703		846
704	snd $othernode, eval => "exit";	847	=cut
705		848
706	=item time => @reply	849	sub cal(@) {
		850	my $timeout = ref $_[-1] ? undef : pop;
		851	my $cb = pop;
707		852
708	Replies the the current node time to C<@reply>.	853	my $port = port {
		854	undef $timeout;
		855	kil $SELF;
		856	&$cb;
		857	};
709		858
710	Example: tell the current node to send the current time to C<$myport> in a	859	if (defined $timeout) {
711	C<timereply> message.	860	$timeout = AE::timer $timeout, 0, sub {
		861	undef $timeout;
		862	kil $port;
		863	$cb->();
		864	};
		865	} else {
		866	mon $_[0], sub {
		867	kil $port;
		868	$cb->();
		869	};
		870	}
712		871
713	snd $NODE, time => $myport, timereply => 1, 2;	872	push @_, $port;
714	# => snd $myport, timereply => 1, 2, <time>	873	&snd;
		874
		875	$port
		876	}
715		877
716	=back	878	=back
717		879
718	=head1 AnyEvent::MP vs. Distributed Erlang	880	=head1 AnyEvent::MP vs. Distributed Erlang
719		881
720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	882	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
721	== aemp node, Erlang process == aemp port), so many of the documents and	883	== aemp node, Erlang process == aemp port), so many of the documents and
722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	884	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
723	sample:	885	sample:
724		886
725	http://www.Erlang.se/doc/programming_rules.shtml	887	http://www.erlang.se/doc/programming_rules.shtml
726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	888	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	889	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	890	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
729		891
730	Despite the similarities, there are also some important differences:	892	Despite the similarities, there are also some important differences:
731		893
732	=over 4	894	=over 4
733		895
734	=item * Node references contain the recipe on how to contact them.	896	=item * Node IDs are arbitrary strings in AEMP.
735		897
736	Erlang relies on special naming and DNS to work everywhere in the	898	Erlang relies on special naming and DNS to work everywhere in the same
737	same way. AEMP relies on each node knowing it's own address(es), with	899	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
738	convenience functionality.	900	configuration or DNS), and possibly the addresses of some seed nodes, but
		901	will otherwise discover other nodes (and their IDs) itself.
739		902
740	This means that AEMP requires a less tightly controlled environment at the	903	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	904	uses "local ports are like remote ports".
		905
		906	The failure modes for local ports are quite different (runtime errors
		907	only) then for remote ports - when a local port dies, you I<know> it dies,
		908	when a connection to another node dies, you know nothing about the other
		909	port.
		910
		911	Erlang pretends remote ports are as reliable as local ports, even when
		912	they are not.
		913
		914	AEMP encourages a "treat remote ports differently" philosophy, with local
		915	ports being the special case/exception, where transport errors cannot
		916	occur.
742		917
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	918	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		919
745	Erlang uses processes that selctively receive messages, and therefore	920	Erlang uses processes that selectively receive messages out of order, and
746	needs a queue. AEMP is event based, queuing messages would serve no useful	921	therefore needs a queue. AEMP is event based, queuing messages would serve
747	purpose.	922	no useful purpose. For the same reason the pattern-matching abilities
		923	of AnyEvent::MP are more limited, as there is little need to be able to
		924	filter messages without dequeuing them.
748		925
749	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	926	This is not a philosophical difference, but simply stems from AnyEvent::MP
		927	being event-based, while Erlang is process-based.
		928
		929	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		930	top of AEMP and Coro threads.
750		931
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	932	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		933
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	934	Sending messages in Erlang is synchronous and blocks the process until
754	sends are immediate, connection establishment is handled in the	935	a conenction has been established and the message sent (and so does not
755	background.	936	need a queue that can overflow). AEMP sends return immediately, connection
		937	establishment is handled in the background.
756		938
757	=item * Erlang can silently lose messages, AEMP cannot.	939	=item * Erlang suffers from silent message loss, AEMP does not.
758		940
759	Erlang makes few guarantees on messages delivery - messages can get lost	941	Erlang implements few guarantees on messages delivery - messages can get
760	without any of the processes realising it (i.e. you send messages a, b,	942	lost without any of the processes realising it (i.e. you send messages a,
761	and c, and the other side only receives messages a and c).	943	b, and c, and the other side only receives messages a and c).
762		944
763	AEMP guarantees correct ordering, and the guarantee that there are no	945	AEMP guarantees (modulo hardware errors) correct ordering, and the
		946	guarantee that after one message is lost, all following ones sent to the
		947	same port are lost as well, until monitoring raises an error, so there are
764	holes in the message sequence.	948	no silent "holes" in the message sequence.
765		949
766	=item * In Erlang, processes can be declared dead and later be found to be	950	If you want your software to be very reliable, you have to cope with
767	alive.	951	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
768		952	simply tries to work better in common error cases, such as when a network
769	In Erlang it can happen that a monitored process is declared dead and	953	link goes down.
770	linked processes get killed, but later it turns out that the process is
771	still alive - and can receive messages.
772
773	In AEMP, when port monitoring detects a port as dead, then that port will
774	eventually be killed - it cannot happen that a node detects a port as dead
775	and then later sends messages to it, finding it is still alive.
776		954
777	=item * Erlang can send messages to the wrong port, AEMP does not.	955	=item * Erlang can send messages to the wrong port, AEMP does not.
778		956
779	In Erlang it is quite possible that a node that restarts reuses a process	957	In Erlang it is quite likely that a node that restarts reuses an Erlang
780	ID known to other nodes for a completely different process, causing	958	process ID known to other nodes for a completely different process,
781	messages destined for that process to end up in an unrelated process.	959	causing messages destined for that process to end up in an unrelated
		960	process.
782		961
783	AEMP never reuses port IDs, so old messages or old port IDs floating	962	AEMP does not reuse port IDs, so old messages or old port IDs floating
784	around in the network will not be sent to an unrelated port.	963	around in the network will not be sent to an unrelated port.
785		964
786	=item * Erlang uses unprotected connections, AEMP uses secure	965	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	966	authentication and can use TLS.
788		967
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	968	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	969	securely authenticate nodes.
791		970
792	=item * The AEMP protocol is optimised for both text-based and binary	971	=item * The AEMP protocol is optimised for both text-based and binary
793	communications.	972	communications.
794		973
795	The AEMP protocol, unlike the Erlang protocol, supports both	974	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	975	language independent text-only protocols (good for debugging), and binary,
797	language-specific serialisers (e.g. Storable).	976	language-specific serialisers (e.g. Storable). By default, unless TLS is
		977	used, the protocol is actually completely text-based.
798		978
799	It has also been carefully designed to be implementable in other languages	979	It has also been carefully designed to be implementable in other languages
800	with a minimum of work while gracefully degrading fucntionality to make the	980	with a minimum of work while gracefully degrading functionality to make the
801	protocol simple.	981	protocol simple.
802		982
803	=item * AEMP has more flexible monitoring options than Erlang.	983	=item * AEMP has more flexible monitoring options than Erlang.
804		984
805	In Erlang, you can chose to receive I<all> exit signals as messages	985	In Erlang, you can chose to receive I<all> exit signals as messages or
806	or I<none>, there is no in-between, so monitoring single processes is	986	I<none>, there is no in-between, so monitoring single Erlang processes is
807	difficult to implement. Monitoring in AEMP is more flexible than in	987	difficult to implement.
808	Erlang, as one can choose between automatic kill, exit message or callback	988
809	on a per-process basis.	989	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		990	between automatic kill, exit message or callback on a per-port basis.
810		991
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	992	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		993
813	Monitoring in Erlang is not an indicator of process death/crashes,	994	Monitoring in Erlang is not an indicator of process death/crashes, in the
814	as linking is (except linking is unreliable in Erlang).	995	same way as linking is (except linking is unreliable in Erlang).
815		996
816	In AEMP, you don't "look up" registered port names or send to named ports	997	In AEMP, you don't "look up" registered port names or send to named ports
817	that might or might not be persistent. Instead, you normally spawn a port	998	that might or might not be persistent. Instead, you normally spawn a port
818	on the remote node. The init function monitors the you, and you monitor	999	on the remote node. The init function monitors you, and you monitor the
819	the remote port. Since both monitors are local to the node, they are much	1000	remote port. Since both monitors are local to the node, they are much more
820	more reliable.	1001	reliable (no need for C<spawn_link>).
821		1002
822	This also saves round-trips and avoids sending messages to the wrong port	1003	This also saves round-trips and avoids sending messages to the wrong port
823	(hard to do in Erlang).	1004	(hard to do in Erlang).
824		1005
825	=back	1006	=back
826		1007
827	=head1 RATIONALE	1008	=head1 RATIONALE
828		1009
829	=over 4	1010	=over 4
830		1011
831	=item Why strings for ports and noderefs, why not objects?	1012	=item Why strings for port and node IDs, why not objects?
832		1013
833	We considered "objects", but found that the actual number of methods	1014	We considered "objects", but found that the actual number of methods
834	thatc an be called are very low. Since port IDs and noderefs travel over	1015	that can be called are quite low. Since port and node IDs travel over
835	the network frequently, the serialising/deserialising would add lots of	1016	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	1017	overhead, as well as having to keep a proxy object everywhere.
837		1018
838	Strings can easily be printed, easily serialised etc. and need no special	1019	Strings can easily be printed, easily serialised etc. and need no special
839	procedures to be "valid".	1020	procedures to be "valid".
840		1021
841	And a a miniport consists of a single closure stored in a global hash - it	1022	And as a result, a port with just a default receiver consists of a single
842	can't become much cheaper.	1023	code reference stored in a global hash - it can't become much cheaper.
843		1024
844	=item Why favour JSON, why not real serialising format such as Storable?	1025	=item Why favour JSON, why not a real serialising format such as Storable?
845		1026
846	In fact, any AnyEvent::MP node will happily accept Storable as framing	1027	In fact, any AnyEvent::MP node will happily accept Storable as framing
847	format, but currently there is no way to make a node use Storable by	1028	format, but currently there is no way to make a node use Storable by
848	default.	1029	default (although all nodes will accept it).
849		1030
850	The default framing protocol is JSON because a) JSON::XS is many times	1031	The default framing protocol is JSON because a) JSON::XS is many times
851	faster for small messages and b) most importantly, after years of	1032	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	1033	experience we found that object serialisation is causing more problems
853	than it gains: Just like function calls, objects simply do not travel	1034	than it solves: Just like function calls, objects simply do not travel
854	easily over the network, mostly because they will always be a copy, so you	1035	easily over the network, mostly because they will always be a copy, so you
855	always have to re-think your design.	1036	always have to re-think your design.
856		1037
857	Keeping your messages simple, concentrating on data structures rather than	1038	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	1039	objects, will keep your messages clean, tidy and efficient.
859		1040
860	=back	1041	=back
861		1042
862	=head1 SEE ALSO	1043	=head1 SEE ALSO
863		1044
		1045	L<AnyEvent::MP::Intro> - a gentle introduction.
		1046
		1047	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1048
		1049	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1050	your applications.
		1051
		1052	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1053
		1054	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1055	all nodes.
		1056
864	L<AnyEvent>.	1057	L<AnyEvent>.
865		1058
866	=head1 AUTHOR	1059	=head1 AUTHOR
867		1060
868	Marc Lehmann <schmorp@schmorp.de>	1061	Marc Lehmann <schmorp@schmorp.de>

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