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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 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 $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<#>) as
81	separator, and a port name (a printable string of unspecified format). An	88	separator, and a port name (a printable string of unspecified format).
82	exception is the the node port, whose ID is identical to its node
83	reference.
84		89
85	=item node	90	=item node
86		91
87	A node is a single process containing at least one port - the node	92	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	93	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	94	ports.
90		95
91	Nodes are either private (single-process only), slaves (connected to a	96	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	97	(no listening ports). Private nodes cannot talk to other private nodes
		98	currently, but all nodes can talk to public nodes.
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 _any_	195	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	196	configure
134	snd rcv mon 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	211	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	212	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	213	a call to C<configure>.
151	identifiers become invalid.
152		214
153	=item $noderef = node_of $port	215	=item $nodeid = node_of $port
154		216
155	Extracts and returns the noderef from a portid or a noderef.	217	Extracts and returns the node ID from a port ID or a node ID.
156		218
157	=item initialise_node $noderef, $seednode, $seednode...	219	=item configure $profile, key => value...
158		220
159	=item initialise_node "slave/", $master, $master...	221	=item configure key => value...
160		222
161	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
162	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
163	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.
164		227
165	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
166	never) before calling other AnyEvent::MP functions.	229	never) before calling other AnyEvent::MP functions.
167		230
168	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
169	either resolved or unresolved.	232	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		233
179	=over 4	234	=over 4
180		235
181	=item public nodes	236	=item norc => $boolean (default false)
182		237
183	For public nodes, C<$noderef> (supplied either directly to	238	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
184	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
185	noderef (possibly unresolved, in which case it will be resolved).	240	C<configure> call.
186		241
187	After resolving, the node will bind itself on all endpoints and try to	242	=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		243
192	=item slave nodes	244	IF true, then the values specified in the C<configure> will take
193		245	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)	246	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		247
204	=back	248	=back
205		249
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	250	=over 4
249		251
250	=item the empty string	252	=item step 1, gathering configuration from profiles
251		253
252	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
253	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.
254		258
255	=item naked port numbers (e.g. C<1234>)	259	The profile data is then gathered as follows:
256		260
257	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
258	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).
259		266
260	=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.
261		270
262	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
263	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
264	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.
265		292
266	=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)"
267		320
268	=item $SELF	321	=item $SELF
269		322
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	323	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	324	blocks.
272		325
273	=item SELF, %SELF, @SELF...	326	=item *SELF, SELF, %SELF, @SELF...
274		327
275	Due to some quirks in how perl exports variables, it is impossible to	328	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	329	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	330	module, but only C<$SELF> is currently used.
278		331
279	=item snd $port, type => @data	332	=item snd $port, type => @data
280		333
281	=item snd $port, @msg	334	=item snd $port, @msg
282		335
283	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
284	a local or a remote port, and can be either a string or soemthignt hat	337	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		338
287	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
288	string as first element (a portid, or some word that indicates a request	340	use a string as first element (a port ID, or some word that indicates a
289	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.
290		343
291	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
292	function: modifying any argument is not allowed and can cause many	345	function: modifying any argument (or values referenced by them) is
293	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.
294		350
295	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
296	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
297	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
298	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
299	node, anything can be passed.	355	node, anything can be passed. Best rely only on the common denominator of
		356	these.
300		357
301	=item $local_port = port	358	=item $local_port = port
302		359
303	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
304	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.
…		…
328	sub _kilme {	385	sub _kilme {
329	die "received message on port without callback";	386	die "received message on port without callback";
330	}	387	}
331		388
332	sub port(;&) {	389	sub port(;&) {
333	my $id = "$UNIQ." . $ID++;	390	my $id = "$UNIQ." . ++$ID;
334	my $port = "$NODE#$id";	391	my $port = "$NODE#$id";
335		392
336	rcv $port, shift \|\| \&_kilme;	393	rcv $port, shift \|\| \&_kilme;
337		394
338	$port	395	$port
…		…
351	The default callback received all messages not matched by a more specific	408	The default callback received all messages not matched by a more specific
352	C<tag> match.	409	C<tag> match.
353		410
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	411	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		412
356	Register callbacks to be called on messages starting with the given tag on	413	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	414	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	415	C<$callback> is C<$undef> or missing). There can only be one callback
		416	registered for each tag.
359		417
360	The original message will be passed to the callback, after the first	418	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	419	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	420	environment as the default callback (see above).
363		421
…		…
375	rcv port,	433	rcv port,
376	msg1 => sub { ... },	434	msg1 => sub { ... },
377	...	435	...
378	;	436	;
379		437
		438	Example: temporarily register a rcv callback for a tag matching some port
		439	(e.g. for an rpc reply) and unregister it after a message was received.
		440
		441	rcv $port, $otherport => sub {
		442	my @reply = @_;
		443
		444	rcv $SELF, $otherport;
		445	};
		446
380	=cut	447	=cut
381		448
382	sub rcv($@) {	449	sub rcv($@) {
383	my $port = shift;	450	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	451	my ($nodeid, $portid) = split /#/, $port, 2;
385		452
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	453	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	454	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		455
389	while (@_) {	456	while (@_) {
390	if (ref $_[0]) {	457	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	458	if (my $self = $PORT_DATA{$portid}) {
392	"AnyEvent::MP::Port" eq ref $self	459	"AnyEvent::MP::Port" eq ref $self
393	or Carp::croak "$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";
394		461
395	$self->[2] = shift;	462	$self->[0] = shift;
396	} else {	463	} else {
397	my $cb = shift;	464	my $cb = shift;
398	$PORT{$portid} = sub {	465	$PORT{$portid} = sub {
399	local $SELF = $port;	466	local $SELF = $port;
400	eval { &$cb }; _self_die if $@;	467	eval { &$cb }; _self_die if $@;
401	};	468	};
402	}	469	}
403	} elsif (defined $_[0]) {	470	} elsif (defined $_[0]) {
404	my $self = $PORT_DATA{$portid} \|\|= do {	471	my $self = $PORT_DATA{$portid} \|\|= do {
405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	472	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
406		473
407	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
408	local $SELF = $port;	475	local $SELF = $port;
409		476
410	if (my $cb = $self->[1]{$_[0]}) {	477	if (my $cb = $self->[1]{$_[0]}) {
…		…
432	}	499	}
433		500
434	$port	501	$port
435	}	502	}
436		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
437	=item $closure = psub { BLOCK }	541	=item $closure = psub { BLOCK }
438		542
439	Remembers C<$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
440	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>
441	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 $SELF, sub {
		548	BLOCK }, @_ } >>.
442		549
443	This is useful when you register callbacks from C<rcv> callbacks:	550	This is useful when you register callbacks from C<rcv> callbacks:
444		551
445	rcv delayed_reply => sub {	552	rcv delayed_reply => sub {
446	my ($delay, @reply) = @_;	553	my ($delay, @reply) = @_;
…		…
470	$res	577	$res
471	}	578	}
472	}	579	}
473	}	580	}
474		581
475	=item $guard = mon $port, $cb->(@reason)	582	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		583
477	=item $guard = mon $port, $rcvport	584	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		585
479	=item $guard = mon $port	586	=item $guard = mon $port # kill $SELF when $port dies
480		587
481	=item $guard = mon $port, $rcvport, @msg	588	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		589
483	Monitor the given port and do something when the port is killed or	590	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	591	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	592	to stop monitoring again.
486
487	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port
489	will arrive, or the monitoring action will be invoked after possible
490	message loss has been detected. No messages will be lost "in between"
491	(after the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get
493	delivered again.
494		593
495	In the first form (callback), the callback is simply called with any	594	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	595	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	596	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	597	C<eval> if unsure.
499		598
500	In the second form (another port given), the other port (C<$rcvport>)	599	In the second form (another port given), the other port (C<$rcvport>)
501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	600	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
502	"normal" kils nothing happens, while under all other conditions, the other	601	"normal" kils nothing happens, while under all other conditions, the other
503	port is killed with the same reason.	602	port is killed with the same reason.
504		603
505	The third form (kill self) is the same as the second form, except that	604	The third form (kill self) is the same as the second form, except that
506	C<$rvport> defaults to C<$SELF>.	605	C<$rvport> defaults to C<$SELF>.
507		606
508	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
509	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.
510		612
511	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
512	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
513	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
514	even monitoring requests can get lost (for exmaple, when the connection	616	even monitoring requests can get lost (for example, when the connection
515	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
516	these problems do not exist.	618	these problems do not exist.
517		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
518	Example: call a given callback when C<$port> is killed.	637	Example: call a given callback when C<$port> is killed.
519		638
520	mon $port, sub { warn "port died because of <@_>\n" };	639	mon $port, sub { warn "port died because of <@_>\n" };
521		640
522	Example: kill ourselves when C<$port> is killed abnormally.	641	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	647	mon $port, $self => "restart";
529		648
530	=cut	649	=cut
531		650
532	sub mon {	651	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	652	my ($nodeid, $port) = split /#/, shift, 2;
534		653
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	654	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		655
537	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,';
538		657
539	unless (ref $cb) {	658	unless (ref $cb) {
540	if (@_) {	659	if (@_) {
…		…
549	}	668	}
550		669
551	$node->monitor ($port, $cb);	670	$node->monitor ($port, $cb);
552		671
553	defined wantarray	672	defined wantarray
554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	673	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
555	}	674	}
556		675
557	=item $guard = mon_guard $port, $ref, $ref...	676	=item $guard = mon_guard $port, $ref, $ref...
558		677
559	Monitors the given C<$port> and keeps the passed references. When the port	678	Monitors the given C<$port> and keeps the passed references. When the port
560	is killed, the references will be freed.	679	is killed, the references will be freed.
561		680
562	Optionally returns a guard that will stop the monitoring.	681	Optionally returns a guard that will stop the monitoring.
563		682
564	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
565	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>):
566		685
567	$port->rcv (start => sub {	686	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	687	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	688	undef $timer if 0.9 < rand;
570	});	689	});
571	});	690	});
572		691
573	=cut	692	=cut
…		…
582		701
583	=item kil $port[, @reason]	702	=item kil $port[, @reason]
584		703
585	Kill the specified port with the given C<@reason>.	704	Kill the specified port with the given C<@reason>.
586		705
587	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" -
588	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.
589		709
590	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>
591	C<mon>, see below).	711	form) get killed with the same reason.
592		712
593	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
594	will be reported as reason C<< die => $@ >>.	714	will be reported as reason C<< die => $@ >>.
595		715
596	Transport/communication errors are reported as C<< transport_error =>	716	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	721	=item $port = spawn $node, $initfunc[, @initdata]
602		722
603	Creates a port on the node C<$node> (which can also be a port ID, in which	723	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	724	case it's the node where that port resides).
605		725
606	The port ID of the newly created port is return immediately, and it is	726	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	727	possible to immediately start sending messages or to monitor the port.
608		728
609	After the port has been created, the init function is	729	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	730	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	731	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	732	specify a function in the main program, use C<::name>.
613		733
614	If the function doesn't exist, then the node tries to C<require>	734	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	735	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	736	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	737	exists or it runs out of package names.
618		738
619	The init function is then called with the newly-created port as context	739	The init function is then called with the newly-created port as context
620	object (C<$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.
621		743
622	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
623	in the init function, monitor the original port. This two-way monitoring	745	port, and in the remote init function, immediately monitor the passed
624	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<$initfunc> has no visible effects on the
		750	caller before C<spawn> returns (by delaying invocation when spawn is
		751	called for the local node).
625		752
626	Example: spawn a chat server port on C<$othernode>.	753	Example: spawn a chat server port on C<$othernode>.
627		754
628	# this node, executed from within a port context:	755	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	756	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
644		771
645	sub _spawn {	772	sub _spawn {
646	my $port = shift;	773	my $port = shift;
647	my $init = shift;	774	my $init = shift;
648		775
		776	# rcv will create the actual port
649	local $SELF = "$NODE#$port";	777	local $SELF = "$NODE#$port";
650	eval {	778	eval {
651	&{ load_func $init }	779	&{ load_func $init }
652	};	780	};
653	_self_die if $@;	781	_self_die if $@;
654	}	782	}
655		783
656	sub spawn(@) {	784	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	785	my ($nodeid, undef) = split /#/, shift, 2;
658		786
659	my $id = "$RUNIQ." . $ID++;	787	my $id = "$RUNIQ." . ++$ID;
660		788
661	$_[0] =~ /::/	789	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	790	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		791
664	($NODE{$noderef} \|\| add_node $noderef)	792	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		793
667	"$noderef#$id"	794	"$nodeid#$id"
668	}	795	}
669		796
670	=back
671		797
672	=head1 NODE MESSAGES	798	=item after $timeout, @msg
673		799
674	Nodes understand the following messages sent to them. Many of them take	800	=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		801
679	While other messages exist, they are not public and subject to change.	802	Either sends the given message, or call the given callback, after the
		803	specified number of seconds.
680		804
681	=over 4	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.
682		808
683	=cut	809	=cut
684		810
685	=item lookup => $name, @reply	811	sub after($@) {
		812	my ($timeout, @action) = @_;
686		813
687	Replies with the port ID of the specified well-known port, or C<undef>.	814	my $t; $t = AE::timer $timeout, 0, sub {
		815	undef $t;
		816	ref $action[0]
		817	? $action[0]()
		818	: snd @action;
		819	};
		820	}
688		821
689	=item devnull => ...	822	=item cal $port, @msg, $callback[, $timeout]
690		823
691	Generic data sink/CPU heat conversion.	824	A simple form of RPC - sends a message to the given C<$port> with the
		825	given contents (C<@msg>), but adds a reply port to the message.
692		826
693	=item relay => $port, @msg	827	The reply port is created temporarily just for the purpose of receiving
		828	the reply, and will be C<kil>ed when no longer needed.
694		829
695	Simply forwards the message to the given port.	830	A reply message sent to the port is passed to the C<$callback> as-is.
696		831
697	=item eval => $string[ @reply]	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.
698		835
699	Evaluates the given string. If C<@reply> is given, then a message of the	836	If no time-out is given (or it is C<undef>), then the local port will
700	form C<@reply, $@, @evalres> is sent.	837	monitor the remote port instead, so it eventually gets cleaned-up.
701		838
702	Example: crash another node.	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.
703		842
704	snd $othernode, eval => "exit";	843	=cut
705		844
706	=item time => @reply	845	sub cal(@) {
		846	my $timeout = ref $_[-1] ? undef : pop;
		847	my $cb = pop;
707		848
708	Replies the the current node time to C<@reply>.	849	my $port = port {
		850	undef $timeout;
		851	kil $SELF;
		852	&$cb;
		853	};
709		854
710	Example: tell the current node to send the current time to C<$myport> in a	855	if (defined $timeout) {
711	C<timereply> message.	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	}
712		867
713	snd $NODE, time => $myport, timereply => 1, 2;	868	push @_, $port;
714	# => snd $myport, timereply => 1, 2, <time>	869	&snd;
		870
		871	$port
		872	}
715		873
716	=back	874	=back
717		875
718	=head1 AnyEvent::MP vs. Distributed Erlang	876	=head1 AnyEvent::MP vs. Distributed Erlang
719		877
720	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
721	== 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
722	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
723	sample:	881	sample:
724		882
725	http://www.Erlang.se/doc/programming_rules.shtml	883	http://www.erlang.se/doc/programming_rules.shtml
726	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
727	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
728	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
729		887
730	Despite the similarities, there are also some important differences:	888	Despite the similarities, there are also some important differences:
731		889
732	=over 4	890	=over 4
733		891
734	=item * Node references contain the recipe on how to contact them.	892	=item * Node IDs are arbitrary strings in AEMP.
735		893
736	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
737	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
738	convenience functionality.	896	configuration or DNS), and possibly the addresses of some seed nodes, but
		897	will otherwise discover other nodes (and their IDs) itself.
739		898
740	This means that AEMP requires a less tightly controlled environment at the	899	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	900	uses "local ports are like remote ports".
		901
		902	The failure modes for local ports are quite different (runtime errors
		903	only) then for remote ports - when a local port dies, you I<know> it dies,
		904	when a connection to another node dies, you know nothing about the other
		905	port.
		906
		907	Erlang pretends remote ports are as reliable as local ports, even when
		908	they are not.
		909
		910	AEMP encourages a "treat remote ports differently" philosophy, with local
		911	ports being the special case/exception, where transport errors cannot
		912	occur.
742		913
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	914	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		915
745	Erlang uses processes that selctively receive messages, and therefore	916	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	917	therefore needs a queue. AEMP is event based, queuing messages would serve
747	purpose.	918	no useful purpose. For the same reason the pattern-matching abilities
		919	of AnyEvent::MP are more limited, as there is little need to be able to
		920	filter messages without dequeuing them.
748		921
749	(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.
750		927
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	928	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		929
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	930	Sending messages in Erlang is synchronous and blocks the process until
754	sends are immediate, connection establishment is handled in the	931	a conenction has been established and the message sent (and so does not
755	background.	932	need a queue that can overflow). AEMP sends return immediately, connection
		933	establishment is handled in the background.
756		934
757	=item * Erlang can silently lose messages, AEMP cannot.	935	=item * Erlang suffers from silent message loss, AEMP does not.
758		936
759	Erlang makes few guarantees on messages delivery - messages can get lost	937	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,	938	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).	939	b, and c, and the other side only receives messages a and c).
762		940
763	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
764	holes in the message sequence.	944	no silent "holes" in the message sequence.
765		945
766	=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
767	alive.	947	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
768		948	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	949	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		950
777	=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.
778		952
779	In Erlang it is quite possible that a node that restarts reuses a process	953	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	954	process ID known to other nodes for a completely different process,
781	messages 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.
782		957
783	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
784	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.
785		960
786	=item * Erlang uses unprotected connections, AEMP uses secure	961	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	962	authentication and can use TLS.
788		963
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	964	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	965	securely authenticate nodes.
791		966
792	=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
793	communications.	968	communications.
794		969
795	The AEMP protocol, unlike the Erlang protocol, supports both	970	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	971	language independent text-only protocols (good for debugging), and binary,
797	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.
798		974
799	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
800	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
801	protocol simple.	977	protocol simple.
802		978
803	=item * AEMP has more flexible monitoring options than Erlang.	979	=item * AEMP has more flexible monitoring options than Erlang.
804		980
805	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
806	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
807	difficult to implement. Monitoring in AEMP is more flexible than in	983	difficult to implement.
808	Erlang, as one can choose between automatic kill, exit message or callback	984
809	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.
810		987
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	988	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		989
813	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
814	as linking is (except linking is unreliable in Erlang).	991	same way as linking is (except linking is unreliable in Erlang).
815		992
816	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
817	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
818	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
819	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
820	more reliable.	997	reliable (no need for C<spawn_link>).
821		998
822	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
823	(hard to do in Erlang).	1000	(hard to do in Erlang).
824		1001
825	=back	1002	=back
826		1003
827	=head1 RATIONALE	1004	=head1 RATIONALE
828		1005
829	=over 4	1006	=over 4
830		1007
831	=item Why strings for ports and noderefs, why not objects?	1008	=item Why strings for port and node IDs, why not objects?
832		1009
833	We considered "objects", but found that the actual number of methods	1010	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	1011	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	1012	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	1013	overhead, as well as having to keep a proxy object everywhere.
837		1014
838	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
839	procedures to be "valid".	1016	procedures to be "valid".
840		1017
841	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
842	can't become much cheaper.	1019	code reference stored in a global hash - it can't become much cheaper.
843		1020
844	=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?
845		1022
846	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
847	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
848	default.	1025	default (although all nodes will accept it).
849		1026
850	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
851	faster for small messages and b) most importantly, after years of	1028	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	1029	experience we found that object serialisation is causing more problems
853	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
854	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
855	always have to re-think your design.	1032	always have to re-think your design.
856		1033
857	Keeping your messages simple, concentrating on data structures rather than	1034	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	1035	objects, will keep your messages clean, tidy and efficient.
859		1036
860	=back	1037	=back
861		1038
862	=head1 SEE ALSO	1039	=head1 SEE ALSO
863		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
864	L<AnyEvent>.	1053	L<AnyEvent>.
865		1054
866	=head1 AUTHOR	1055	=head1 AUTHOR
867		1056
868	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