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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.46 by root, Thu Aug 13 01:46:10 2009 UTC vs.
Revision 1.106 by root, Wed Dec 9 14:00:49 2009 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
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
15	# ports are message endpoints	17	# ports are message destinations
16		18
17	# sending messages	19	# sending messages
18	snd $port, type => data...;	20	snd $port, type => data...;
19	snd $port, @msg;	21	snd $port, @msg;
20	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
21		23
22	# miniports	24	# creating/using ports, the simple way
23	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
24		26
25	# full ports	27	# creating/using ports, tagged message matching
26	my $port = port;	28	my $port = port;
27	rcv $port, smartmatch => $cb->(@msg);
28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
29	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
30		31
31	# remote ports	32	# create a port on another node
32	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
33		34
34	# more, smarter, matches (_any_ is exported by this module)	35	# destroy a prot again
35	rcv $port, [child_died => $pid] => sub { ...	36	kil $port; # "normal" kill
36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37	kil $port, my_error => "everything is broken"; # error kill
37		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
78	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
79		84
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	85	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	86	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		87
85	=item node	88	=item node
86		89
87	A node is a single process containing at least one port - the node	90	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	91	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	92	ports.
90		93
91	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
93		97
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
95		99
96	A node reference is a string that either simply identifies the node (for	100	A node ID is a string that uniquely identifies the node within a
97	private and slave nodes), or contains a recipe on how to reach a given	101	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	102	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		103	doesn't interpret node IDs in any way.
99		104
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		106
103	Node references come in two flavours: resolved (containing only numerical	107	Nodes can only talk to each other by creating some kind of connection to
104	addresses) or unresolved (where hostnames are used instead of addresses).	108	each other. To do this, nodes should listen on one or more local transport
		109	endpoints - binds. Currently, only standard C<ip:port> specifications can
		110	be used, which specify TCP ports to listen on.
105		111
106	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
107	resolve it.	113
		114	When a node starts, it knows nothing about the network. To teach the node
		115	about the network it first has to contact some other node within the
		116	network. This node is called a seed.
		117
		118	Apart from the fact that other nodes know them as seed nodes and they have
		119	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		120	any node can function as a seed node for others.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network and to connect nodes that otherwise would have
		124	trouble connecting. They form the backbone of an AnyEvent::MP network.
		125
		126	Seed nodes are expected to be long-running, and at least one seed node
		127	should always be available. They should also be relatively responsive - a
		128	seed node that blocks for long periods will slow down everybody else.
		129
		130	=item seeds - C<host:port>
		131
		132	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		133	TCP port) of nodes that should be used as seed nodes.
		134
		135	The nodes listening on those endpoints are expected to be long-running,
		136	and at least one of those should always be available. When nodes run out
		137	of connections (e.g. due to a network error), they try to re-establish
		138	connections to some seednodes again to join the network.
108		139
109	=back	140	=back
110		141
111	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
112		143
124		155
125	use AE ();	156	use AE ();
126		157
127	use base "Exporter";	158	use base "Exporter";
128		159
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	160	our $VERSION = 1.24;
130		161
131	our @EXPORT = qw(	162	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	164	configure
134	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
135	port	166	port
136	);	167	);
137		168
138	our $SELF;	169	our $SELF;
139		170
…		…
143	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
144	}	175	}
145		176
146	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
147		178
148	The C<NODE> function returns, and the C<$NODE> variable contains	179	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	180	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	181	a call to C<configure>.
151	identifiers become invalid.
152		182
153	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
154		184
155	Extracts and returns the noderef from a portid or a noderef.	185	Extracts and returns the node ID from a port ID or a node ID.
156		186
157	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
158		188
159	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
160		190
161	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
164		195
165	This function initialises a node - it must be called exactly once (or	196	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	197	never) before calling other AnyEvent::MP functions.
167		198
168	All arguments are noderefs, which can be either resolved or unresolved.
169
170	There are two types of networked nodes, public nodes and slave nodes:
171
172	=over 4	199	=over 4
173		200
174	=item public nodes	201	=item step 1, gathering configuration from profiles
175		202
176	For public nodes, C<$noderef> must either be a (possibly unresolved)	203	The function first looks up a profile in the aemp configuration (see the
177	noderef, in which case it will be resolved, or C<undef> (or missing), in	204	L<aemp> commandline utility). The profile name can be specified via the
178	which case the noderef will be guessed.	205	named C<profile> parameter or can simply be the first parameter). If it is
		206	missing, then the nodename (F<uname -n>) will be used as profile name.
179		207
180	Afterwards, the node will bind itself on all endpoints and try to connect	208	The profile data is then gathered as follows:
181	to all additional C<$seednodes> that are specified. Seednodes are optional
182	and can be used to quickly bootstrap the node into an existing network.
183		209
184	=item slave nodes	210	First, all remaining key => value pairs (all of which are conveniently
		211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
185		215
186	When the C<$noderef> is the special string C<slave/>, then the node will	216	That means that the values specified in the profile have highest priority
187	become a slave node. Slave nodes cannot be contacted from outside and will	217	and the values specified directly via C<configure> have lowest priority,
188	route most of their traffic to the master node that they attach to.	218	and can only be used to specify defaults.
189		219
190	At least one additional noderef is required: The node will try to connect	220	If the profile specifies a node ID, then this will become the node ID of
191	to all of them and will become a slave attached to the first node it can	221	this process. If not, then the profile name will be used as node ID. The
192	successfully connect to.	222	special node ID of C<anon/> will be replaced by a random node ID.
		223
		224	=item step 2, bind listener sockets
		225
		226	The next step is to look up the binds in the profile, followed by binding
		227	aemp protocol listeners on all binds specified (it is possible and valid
		228	to have no binds, meaning that the node cannot be contacted form the
		229	outside. This means the node cannot talk to other nodes that also have no
		230	binds, but it can still talk to all "normal" nodes).
		231
		232	If the profile does not specify a binds list, then a default of C<*> is
		233	used, meaning the node will bind on a dynamically-assigned port on every
		234	local IP address it finds.
		235
		236	=item step 3, connect to seed nodes
		237
		238	As the last step, the seeds list from the profile is passed to the
		239	L<AnyEvent::MP::Global> module, which will then use it to keep
		240	connectivity with at least one node at any point in time.
193		241
194	=back	242	=back
195		243
196	This function will block until all nodes have been resolved and, for slave	244	Example: become a distributed node using the local node name as profile.
197	nodes, until it has successfully established a connection to a master	245	This should be the most common form of invocation for "daemon"-type nodes.
198	server.
199		246
200	Example: become a public node listening on the default node.	247	configure
201		248
202	initialise_node;	249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
203		251
204	Example: become a public node, and try to contact some well-known master	252	configure nodeid => "anon/";
205	servers to become part of the network.
206		253
207	initialise_node undef, "master1", "master2";	254	Example: configure a node using a profile called seed, which si suitable
		255	for a seed node as it binds on all local addresses on a fixed port (4040,
		256	customary for aemp).
208		257
209	Example: become a public node listening on port C<4041>.	258	# use the aemp commandline utility
		259	# aemp profile seed nodeid anon/ binds '*:4040'
210		260
211	initialise_node 4041;	261	# then use it
		262	configure profile => "seed";
212		263
213	Example: become a public node, only visible on localhost port 4044.	264	# or simply use aemp from the shell again:
		265	# aemp run profile seed
214		266
215	initialise_node "locahost:4044";	267	# or provide a nicer-to-remember nodeid
216		268	# aemp run profile seed nodeid "$(hostname)"
217	Example: become a slave node to any of the specified master servers.
218
219	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
220
221	=item $cv = resolve_node $noderef
222
223	Takes an unresolved node reference that may contain hostnames and
224	abbreviated IDs, resolves all of them and returns a resolved node
225	reference.
226
227	In addition to C<address:port> pairs allowed in resolved noderefs, the
228	following forms are supported:
229
230	=over 4
231
232	=item the empty string
233
234	An empty-string component gets resolved as if the default port (4040) was
235	specified.
236
237	=item naked port numbers (e.g. C<1234>)
238
239	These are resolved by prepending the local nodename and a colon, to be
240	further resolved.
241
242	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
243
244	These are resolved by using AnyEvent::DNS to resolve them, optionally
245	looking up SRV records for the C<aemp=4040> port, if no port was
246	specified.
247
248	=back
249		269
250	=item $SELF	270	=item $SELF
251		271
252	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
253	blocks.	273	blocks.
254		274
255	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
256		276
257	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
258	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
259	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
260		280
261	=item snd $port, type => @data	281	=item snd $port, type => @data
262		282
263	=item snd $port, @msg	283	=item snd $port, @msg
264		284
265	Send the given message to the given port ID, which can identify either	285	Send the given message to the given port, which can identify either a
266	a local or a remote port, and can be either a string or soemthignt hat	286	local or a remote port, and must be a port ID.
267	stringifies a sa port ID (such as a port object :).
268		287
269	While the message can be about anything, it is highly recommended to use a	288	While the message can be almost anything, it is highly recommended to
270	string as first element (a portid, or some word that indicates a request	289	use a string as first element (a port ID, or some word that indicates a
271	type etc.).	290	request type etc.) and to consist if only simple perl values (scalars,
		291	arrays, hashes) - if you think you need to pass an object, think again.
272		292
273	The message data effectively becomes read-only after a call to this	293	The message data logically becomes read-only after a call to this
274	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
275	problems.	295	forbidden, as there can be considerable time between the call to C<snd>
		296	and the time the message is actually being serialised - in fact, it might
		297	never be copied as within the same process it is simply handed to the
		298	receiving port.
276		299
277	The type of data you can transfer depends on the transport protocol: when	300	The type of data you can transfer depends on the transport protocol: when
278	JSON is used, then only strings, numbers and arrays and hashes consisting	301	JSON is used, then only strings, numbers and arrays and hashes consisting
279	of those are allowed (no objects). When Storable is used, then anything	302	of those are allowed (no objects). When Storable is used, then anything
280	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
281	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
282		306
283	=item $local_port = port	307	=item $local_port = port
284		308
285	Create a new local port object that can be used either as a pattern	309	Create a new local port object and returns its port ID. Initially it has
286	matching port ("full port") or a single-callback port ("miniport"),	310	no callbacks set and will throw an error when it receives messages.
287	depending on how C<rcv> callbacks are bound to the object.
288		311
289	=item $port = port { my @msg = @_; $finished }	312	=item $local_port = port { my @msg = @_ }
290		313
291	Creates a "miniport", that is, a very lightweight port without any pattern	314	Creates a new local port, and returns its ID. Semantically the same as
292	matching behind it, and returns its ID. Semantically the same as creating
293	a port and calling C<rcv $port, $callback> on it.	315	creating a port and calling C<rcv $port, $callback> on it.
294		316
295	The block will be called for every message received on the port. When the	317	The block will be called for every message received on the port, with the
296	callback returns a true value its job is considered "done" and the port	318	global variable C<$SELF> set to the port ID. Runtime errors will cause the
297	will be destroyed. Otherwise it will stay alive.	319	port to be C<kil>ed. The message will be passed as-is, no extra argument
		320	(i.e. no port ID) will be passed to the callback.
298		321
299	The message will be passed as-is, no extra argument (i.e. no port id) will	322	If you want to stop/destroy the port, simply C<kil> it:
300	be passed to the callback.
301		323
302	If you need the local port id in the callback, this works nicely:	324	my $port = port {
303		325	my @msg = @_;
304	my $port; $port = port {	326	...
305	snd $otherport, reply => $port;	327	kil $SELF;
306	};	328	};
307		329
308	=cut	330	=cut
309		331
310	sub rcv($@);	332	sub rcv($@);
		333
		334	sub _kilme {
		335	die "received message on port without callback";
		336	}
311		337
312	sub port(;&) {	338	sub port(;&) {
313	my $id = "$UNIQ." . $ID++;	339	my $id = "$UNIQ." . $ID++;
314	my $port = "$NODE#$id";	340	my $port = "$NODE#$id";
315		341
316	if (@_) {	342	rcv $port, shift \|\| \&_kilme;
317	rcv $port, shift;
318	} else {
319	$PORT{$id} = sub { }; # nop
320	}
321		343
322	$port	344	$port
323	}	345	}
324		346
325	=item reg $port, $name
326
327	=item reg $name
328
329	Registers the given port (or C<$SELF><<< if missing) under the name
330	C<$name>. If the name already exists it is replaced.
331
332	A port can only be registered under one well known name.
333
334	A port automatically becomes unregistered when it is killed.
335
336	=cut
337
338	sub reg(@) {
339	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
340
341	$REG{$_[0]} = $port;
342	}
343
344	=item rcv $port, $callback->(@msg)	347	=item rcv $local_port, $callback->(@msg)
345		348
346	Replaces the callback on the specified miniport (after converting it to	349	Replaces the default callback on the specified port. There is no way to
347	one if required).	350	remove the default callback: use C<sub { }> to disable it, or better
348		351	C<kil> the port when it is no longer needed.
349	=item rcv $port, tagstring => $callback->(@msg), ...
350
351	=item rcv $port, $smartmatch => $callback->(@msg), ...
352
353	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
354
355	Register callbacks to be called on matching messages on the given full
356	port (after converting it to one if required) and return the port.
357
358	The callback has to return a true value when its work is done, after
359	which is will be removed, or a false value in which case it will stay
360	registered.
361		352
362	The global C<$SELF> (exported by this module) contains C<$port> while	353	The global C<$SELF> (exported by this module) contains C<$port> while
363	executing the callback.	354	executing the callback. Runtime errors during callback execution will
		355	result in the port being C<kil>ed.
364		356
365	Runtime errors during callback execution will result in the port being	357	The default callback received all messages not matched by a more specific
366	C<kil>ed.	358	C<tag> match.
367		359
368	If the match is an array reference, then it will be matched against the	360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
369	first elements of the message, otherwise only the first element is being
370	matched.
371		361
372	Any element in the match that is specified as C<_any_> (a function	362	Register (or replace) callbacks to be called on messages starting with the
373	exported by this module) matches any single element of the message.	363	given tag on the given port (and return the port), or unregister it (when
		364	C<$callback> is C<$undef> or missing). There can only be one callback
		365	registered for each tag.
374		366
375	While not required, it is highly recommended that the first matching	367	The original message will be passed to the callback, after the first
376	element is a string identifying the message. The one-string-only match is	368	element (the tag) has been removed. The callback will use the same
377	also the most efficient match (by far).	369	environment as the default callback (see above).
378		370
379	Example: create a port and bind receivers on it in one go.	371	Example: create a port and bind receivers on it in one go.
380		372
381	my $port = rcv port,	373	my $port = rcv port,
382	msg1 => sub { ...; 0 },	374	msg1 => sub { ... },
383	msg2 => sub { ...; 0 },	375	msg2 => sub { ... },
384	;	376	;
385		377
386	Example: create a port, bind receivers and send it in a message elsewhere	378	Example: create a port, bind receivers and send it in a message elsewhere
387	in one go:	379	in one go:
388		380
389	snd $otherport, reply =>	381	snd $otherport, reply =>
390	rcv port,	382	rcv port,
391	msg1 => sub { ...; 0 },	383	msg1 => sub { ... },
392	...	384	...
393	;	385	;
394		386
		387	Example: temporarily register a rcv callback for a tag matching some port
		388	(e.g. for an rpc reply) and unregister it after a message was received.
		389
		390	rcv $port, $otherport => sub {
		391	my @reply = @_;
		392
		393	rcv $SELF, $otherport;
		394	};
		395
395	=cut	396	=cut
396		397
397	sub rcv($@) {	398	sub rcv($@) {
398	my $port = shift;	399	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
400		401
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		404
404	if (@_ == 1) {	405	while (@_) {
		406	if (ref $_[0]) {
		407	if (my $self = $PORT_DATA{$portid}) {
		408	"AnyEvent::MP::Port" eq ref $self
		409	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		410
		411	$self->[0] = shift;
		412	} else {
405	my $cb = shift;	413	my $cb = shift;
406	delete $PORT_DATA{$portid};
407	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
408	local $SELF = $port;	415	local $SELF = $port;
409	eval {	416	eval { &$cb }; _self_die if $@;
410	&$cb	417	};
411	and kil $port;
412	};	418	}
413	_self_die if $@;	419	} elsif (defined $_[0]) {
414	};
415	} else {
416	my $self = $PORT_DATA{$portid} \|\|= do {	420	my $self = $PORT_DATA{$portid} \|\|= do {
417	my $self = bless {	421	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
418	id => $port,
419	}, "AnyEvent::MP::Port";
420		422
421	$PORT{$portid} = sub {	423	$PORT{$portid} = sub {
422	local $SELF = $port;	424	local $SELF = $port;
423		425
424	eval {
425	for (@{ $self->{rc0}{$_[0]} }) {	426	if (my $cb = $self->[1]{$_[0]}) {
426	$_ && &{$_->[0]}	427	shift;
427	&& undef $_;	428	eval { &$cb }; _self_die if $@;
428	}	429	} else {
429
430	for (@{ $self->{rcv}{$_[0]} }) {
431	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
432	&& &{$_->[0]}	430	&{ $self->[0] };
433	&& undef $_;
434	}
435
436	for (@{ $self->{any} }) {
437	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
438	&& &{$_->[0]}
439	&& undef $_;
440	}	431	}
441	};	432	};
442	_self_die if $@;	433
		434	$self
443	};	435	};
444		436
445	$self
446	};
447
448	"AnyEvent::MP::Port" eq ref $self	437	"AnyEvent::MP::Port" eq ref $self
449	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	438	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
450		439
451	while (@_) {
452	my ($match, $cb) = splice @_, 0, 2;	440	my ($tag, $cb) = splice @_, 0, 2;
453		441
454	if (!ref $match) {	442	if (defined $cb) {
455	push @{ $self->{rc0}{$match} }, [$cb];	443	$self->[1]{$tag} = $cb;
456	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
457	my ($type, @match) = @$match;
458	@match
459	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
460	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
461	} else {	444	} else {
462	push @{ $self->{any} }, [$cb, $match];	445	delete $self->[1]{$tag};
463	}	446	}
464	}	447	}
465	}	448	}
466		449
467	$port	450	$port
468	}	451	}
469		452
		453	=item peval $port, $coderef[, @args]
		454
		455	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		456	when the code throews an exception the C<$port> will be killed.
		457
		458	Any remaining args will be passed to the callback. Any return values will
		459	be returned to the caller.
		460
		461	This is useful when you temporarily want to execute code in the context of
		462	a port.
		463
		464	Example: create a port and run some initialisation code in it's context.
		465
		466	my $port = port { ... };
		467
		468	peval $port, sub {
		469	init
		470	or die "unable to init";
		471	};
		472
		473	=cut
		474
		475	sub peval($$) {
		476	local $SELF = shift;
		477	my $cb = shift;
		478
		479	if (wantarray) {
		480	my @res = eval { &$cb };
		481	_self_die if $@;
		482	@res
		483	} else {
		484	my $res = eval { &$cb };
		485	_self_die if $@;
		486	$res
		487	}
		488	}
		489
470	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
471		491
472	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
473	closure is executed, sets up the environment in the same way as in C<rcv>	493	closure is executed, sets up the environment in the same way as in C<rcv>
474	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		495
		496	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		497	BLOCK } } >>.
475		498
476	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
477		500
478	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
479	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
503	$res	526	$res
504	}	527	}
505	}	528	}
506	}	529	}
507		530
508	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
509		532
510	=item $guard = mon $port, $rcvport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
511		534
512	=item $guard = mon $port	535	=item $guard = mon $port # kill $SELF when $port dies
513		536
514	=item $guard = mon $port, $rcvport, @msg	537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
515		538
516	Monitor the given port and do something when the port is killed or	539	Monitor the given port and do something when the port is killed or
517	messages to it were lost, and optionally return a guard that can be used	540	messages to it were lost, and optionally return a guard that can be used
518	to stop monitoring again.	541	to stop monitoring again.
519
520	C<mon> effectively guarantees that, in the absence of hardware failures,
521	that after starting the monitor, either all messages sent to the port
522	will arrive, or the monitoring action will be invoked after possible
523	message loss has been detected. No messages will be lost "in between"
524	(after the first lost message no further messages will be received by the
525	port). After the monitoring action was invoked, further messages might get
526	delivered again.
527		542
528	In the first form (callback), the callback is simply called with any	543	In the first form (callback), the callback is simply called with any
529	number of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
530	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
531	C<eval> if unsure.	546	C<eval> if unsure.
532		547
533	In the second form (another port given), the other port (C<$rcvport>)	548	In the second form (another port given), the other port (C<$rcvport>)
534	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
535	"normal" kils nothing happens, while under all other conditions, the other	550	"normal" kils nothing happens, while under all other conditions, the other
536	port is killed with the same reason.	551	port is killed with the same reason.
537		552
538	The third form (kill self) is the same as the second form, except that	553	The third form (kill self) is the same as the second form, except that
539	C<$rvport> defaults to C<$SELF>.	554	C<$rvport> defaults to C<$SELF>.
540		555
541	In the last form (message), a message of the form C<@msg, @reason> will be	556	In the last form (message), a message of the form C<@msg, @reason> will be
542	C<snd>.	557	C<snd>.
		558
		559	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		560	alert was raised), they are removed and will not trigger again.
543		561
544	As a rule of thumb, monitoring requests should always monitor a port from	562	As a rule of thumb, monitoring requests should always monitor a port from
545	a local port (or callback). The reason is that kill messages might get	563	a local port (or callback). The reason is that kill messages might get
546	lost, just like any other message. Another less obvious reason is that	564	lost, just like any other message. Another less obvious reason is that
547	even monitoring requests can get lost (for exmaple, when the connection	565	even monitoring requests can get lost (for example, when the connection
548	to the other node goes down permanently). When monitoring a port locally	566	to the other node goes down permanently). When monitoring a port locally
549	these problems do not exist.	567	these problems do not exist.
550		568
		569	C<mon> effectively guarantees that, in the absence of hardware failures,
		570	after starting the monitor, either all messages sent to the port will
		571	arrive, or the monitoring action will be invoked after possible message
		572	loss has been detected. No messages will be lost "in between" (after
		573	the first lost message no further messages will be received by the
		574	port). After the monitoring action was invoked, further messages might get
		575	delivered again.
		576
		577	Inter-host-connection timeouts and monitoring depend on the transport
		578	used. The only transport currently implemented is TCP, and AnyEvent::MP
		579	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		580	non-idle connection, and usually around two hours for idle connections).
		581
		582	This means that monitoring is good for program errors and cleaning up
		583	stuff eventually, but they are no replacement for a timeout when you need
		584	to ensure some maximum latency.
		585
551	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
552		587
553	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
554		589
555	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
…		…
561	mon $port, $self => "restart";	596	mon $port, $self => "restart";
562		597
563	=cut	598	=cut
564		599
565	sub mon {	600	sub mon {
566	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
567		602
568	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
569		604
570	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	605	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
571		606
572	unless (ref $cb) {	607	unless (ref $cb) {
573	if (@_) {	608	if (@_) {
…		…
582	}	617	}
583		618
584	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
585		620
586	defined wantarray	621	defined wantarray
587	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
588	}	623	}
589		624
590	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
591		626
592	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
593	is killed, the references will be freed.	628	is killed, the references will be freed.
594		629
595	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
596		631
597	This function is useful when you create e.g. timers or other watchers and	632	This function is useful when you create e.g. timers or other watchers and
598	want to free them when the port gets killed:	633	want to free them when the port gets killed (note the use of C<psub>):
599		634
600	$port->rcv (start => sub {	635	$port->rcv (start => sub {
601	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
602	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
603	});	638	});
604	});	639	});
605		640
606	=cut	641	=cut
…		…
615		650
616	=item kil $port[, @reason]	651	=item kil $port[, @reason]
617		652
618	Kill the specified port with the given C<@reason>.	653	Kill the specified port with the given C<@reason>.
619		654
620	If no C<@reason> is specified, then the port is killed "normally" (linked	655	If no C<@reason> is specified, then the port is killed "normally" (ports
621	ports will not be kileld, or even notified).	656	monitoring other ports will not necessarily die because a port dies
		657	"normally").
622		658
623	Otherwise, linked ports get killed with the same reason (second form of	659	Otherwise, linked ports get killed with the same reason (second form of
624	C<mon>, see below).	660	C<mon>, see above).
625		661
626	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
627	will be reported as reason C<< die => $@ >>.	663	will be reported as reason C<< die => $@ >>.
628		664
629	Transport/communication errors are reported as C<< transport_error =>	665	Transport/communication errors are reported as C<< transport_error =>
…		…
634	=item $port = spawn $node, $initfunc[, @initdata]	670	=item $port = spawn $node, $initfunc[, @initdata]
635		671
636	Creates a port on the node C<$node> (which can also be a port ID, in which	672	Creates a port on the node C<$node> (which can also be a port ID, in which
637	case it's the node where that port resides).	673	case it's the node where that port resides).
638		674
639	The port ID of the newly created port is return immediately, and it is	675	The port ID of the newly created port is returned immediately, and it is
640	permissible to immediately start sending messages or monitor the port.	676	possible to immediately start sending messages or to monitor the port.
641		677
642	After the port has been created, the init function is	678	After the port has been created, the init function is called on the remote
643	called. This function must be a fully-qualified function name	679	node, in the same context as a C<rcv> callback. This function must be a
644	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
645	program, use C<::name>.	681	specify a function in the main program, use C<::name>.
646		682
647	If the function doesn't exist, then the node tries to C<require>	683	If the function doesn't exist, then the node tries to C<require>
648	the package, then the package above the package and so on (e.g.	684	the package, then the package above the package and so on (e.g.
649	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
650	exists or it runs out of package names.	686	exists or it runs out of package names.
651		687
652	The init function is then called with the newly-created port as context	688	The init function is then called with the newly-created port as context
653	object (C<$SELF>) and the C<@initdata> values as arguments.	689	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		690	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		691	the port might not get created.
654		692
655	A common idiom is to pass your own port, monitor the spawned port, and	693	A common idiom is to pass a local port, immediately monitor the spawned
656	in the init function, monitor the original port. This two-way monitoring	694	port, and in the remote init function, immediately monitor the passed
657	ensures that both ports get cleaned up when there is a problem.	695	local port. This two-way monitoring ensures that both ports get cleaned up
		696	when there is a problem.
		697
		698	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
658		701
659	Example: spawn a chat server port on C<$othernode>.	702	Example: spawn a chat server port on C<$othernode>.
660		703
661	# this node, executed from within a port context:	704	# this node, executed from within a port context:
662	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
677		720
678	sub _spawn {	721	sub _spawn {
679	my $port = shift;	722	my $port = shift;
680	my $init = shift;	723	my $init = shift;
681		724
		725	# rcv will create the actual port
682	local $SELF = "$NODE#$port";	726	local $SELF = "$NODE#$port";
683	eval {	727	eval {
684	&{ load_func $init }	728	&{ load_func $init }
685	};	729	};
686	_self_die if $@;	730	_self_die if $@;
687	}	731	}
688		732
689	sub spawn(@) {	733	sub spawn(@) {
690	my ($noderef, undef) = split /#/, shift, 2;	734	my ($nodeid, undef) = split /#/, shift, 2;
691		735
692	my $id = "$RUNIQ." . $ID++;	736	my $id = "$RUNIQ." . $ID++;
693		737
694	$_[0] =~ /::/	738	$_[0] =~ /::/
695	or Carp::croak "spawn init function must be a fully-qualified name, caught";	739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
696		740
697	($NODE{$noderef} \|\| add_node $noderef)	741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
698	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
699		742
700	"$noderef#$id"	743	"$nodeid#$id"
701	}	744	}
702		745
703	=back	746	=item after $timeout, @msg
704		747
705	=head1 NODE MESSAGES	748	=item after $timeout, $callback
706		749
707	Nodes understand the following messages sent to them. Many of them take	750	Either sends the given message, or call the given callback, after the
708	arguments called C<@reply>, which will simply be used to compose a reply	751	specified number of seconds.
709	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
710	the remaining arguments are simply the message data.
711		752
712	While other messages exist, they are not public and subject to change.	753	This is simply a utility function that comes in handy at times - the
		754	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		755	so it may go away in the future.
713		756
714	=over 4
715
716	=cut	757	=cut
717		758
718	=item lookup => $name, @reply	759	sub after($@) {
		760	my ($timeout, @action) = @_;
719		761
720	Replies with the port ID of the specified well-known port, or C<undef>.	762	my $t; $t = AE::timer $timeout, 0, sub {
		763	undef $t;
		764	ref $action[0]
		765	? $action[0]()
		766	: snd @action;
		767	};
		768	}
721		769
722	=item devnull => ...	770	=item cal $port, @msg, $callback[, $timeout]
723		771
724	Generic data sink/CPU heat conversion.	772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
725		774
726	=item relay => $port, @msg	775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
727		777
728	Simply forwards the message to the given port.	778	A reply message sent to the port is passed to the C<$callback> as-is.
729		779
730	=item eval => $string[ @reply]	780	If an optional time-out (in seconds) is given and it is not C<undef>,
		781	then the callback will be called without any arguments after the time-out
		782	elapsed and the port is C<kil>ed.
731		783
732	Evaluates the given string. If C<@reply> is given, then a message of the	784	If no time-out is given (or it is C<undef>), then the local port will
733	form C<@reply, $@, @evalres> is sent.	785	monitor the remote port instead, so it eventually gets cleaned-up.
734		786
735	Example: crash another node.	787	Currently this function returns the temporary port, but this "feature"
		788	might go in future versions unless you can make a convincing case that
		789	this is indeed useful for something.
736		790
737	snd $othernode, eval => "exit";	791	=cut
738		792
739	=item time => @reply	793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
740		796
741	Replies the the current node time to C<@reply>.	797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
742		802
743	Example: tell the current node to send the current time to C<$myport> in a	803	if (defined $timeout) {
744	C<timereply> message.	804	$timeout = AE::timer $timeout, 0, sub {
		805	undef $timeout;
		806	kil $port;
		807	$cb->();
		808	};
		809	} else {
		810	mon $_[0], sub {
		811	kil $port;
		812	$cb->();
		813	};
		814	}
745		815
746	snd $NODE, time => $myport, timereply => 1, 2;	816	push @_, $port;
747	# => snd $myport, timereply => 1, 2, <time>	817	&snd;
		818
		819	$port
		820	}
748		821
749	=back	822	=back
750		823
751	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
752		825
753	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
754	== aemp node, Erlang process == aemp port), so many of the documents and	827	== aemp node, Erlang process == aemp port), so many of the documents and
755	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
756	sample:	829	sample:
757		830
758	http://www.Erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
759	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	832	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
760	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	833	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
761	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	834	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
762		835
763	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
764		837
765	=over 4	838	=over 4
766		839
767	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
768		841
769	Erlang relies on special naming and DNS to work everywhere in the	842	Erlang relies on special naming and DNS to work everywhere in the same
770	same way. AEMP relies on each node knowing it's own address(es), with	843	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
771	convenience functionality.	844	configuration or DNS), and possibly the addresses of some seed nodes, but
		845	will otherwise discover other nodes (and their IDs) itself.
772		846
773	This means that AEMP requires a less tightly controlled environment at the	847	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
774	cost of longer node references and a slightly higher management overhead.	848	uses "local ports are like remote ports".
		849
		850	The failure modes for local ports are quite different (runtime errors
		851	only) then for remote ports - when a local port dies, you I<know> it dies,
		852	when a connection to another node dies, you know nothing about the other
		853	port.
		854
		855	Erlang pretends remote ports are as reliable as local ports, even when
		856	they are not.
		857
		858	AEMP encourages a "treat remote ports differently" philosophy, with local
		859	ports being the special case/exception, where transport errors cannot
		860	occur.
775		861
776	=item * Erlang uses processes and a mailbox, AEMP does not queue.	862	=item * Erlang uses processes and a mailbox, AEMP does not queue.
777		863
778	Erlang uses processes that selctively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
779	needs a queue. AEMP is event based, queuing messages would serve no useful	865	needs a queue. AEMP is event based, queuing messages would serve no
780	purpose.	866	useful purpose. For the same reason the pattern-matching abilities of
		867	AnyEvent::MP are more limited, as there is little need to be able to
		868	filter messages without dequeuing them.
781		869
782	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
783		871
784	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
785		873
786	Sending messages in Erlang is synchronous and blocks the process. AEMP	874	Sending messages in Erlang is synchronous and blocks the process (and
787	sends are immediate, connection establishment is handled in the	875	so does not need a queue that can overflow). AEMP sends are immediate,
788	background.	876	connection establishment is handled in the background.
789		877
790	=item * Erlang can silently lose messages, AEMP cannot.	878	=item * Erlang suffers from silent message loss, AEMP does not.
791		879
792	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
793	without any of the processes realising it (i.e. you send messages a, b,	881	lost without any of the processes realising it (i.e. you send messages a,
794	and c, and the other side only receives messages a and c).	882	b, and c, and the other side only receives messages a and c).
795		883
796	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
797	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
798		886	monitoring raises an error, so there are no silent "holes" in the message
799	=item * In Erlang, processes can be declared dead and later be found to be	887	sequence.
800	alive.
801
802	In Erlang it can happen that a monitored process is declared dead and
803	linked processes get killed, but later it turns out that the process is
804	still alive - and can receive messages.
805
806	In AEMP, when port monitoring detects a port as dead, then that port will
807	eventually be killed - it cannot happen that a node detects a port as dead
808	and then later sends messages to it, finding it is still alive.
809		888
810	=item * Erlang can send messages to the wrong port, AEMP does not.	889	=item * Erlang can send messages to the wrong port, AEMP does not.
811		890
812	In Erlang it is quite possible that a node that restarts reuses a process	891	In Erlang it is quite likely that a node that restarts reuses a process ID
813	ID known to other nodes for a completely different process, causing	892	known to other nodes for a completely different process, causing messages
814	messages destined for that process to end up in an unrelated process.	893	destined for that process to end up in an unrelated process.
815		894
816	AEMP never reuses port IDs, so old messages or old port IDs floating	895	AEMP never reuses port IDs, so old messages or old port IDs floating
817	around in the network will not be sent to an unrelated port.	896	around in the network will not be sent to an unrelated port.
818		897
819	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
820	authentication and can use TLS.	899	authentication and can use TLS.
821		900
822	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
823	securely authenticate nodes.	902	securely authenticate nodes.
824		903
825	=item * The AEMP protocol is optimised for both text-based and binary	904	=item * The AEMP protocol is optimised for both text-based and binary
826	communications.	905	communications.
827		906
828	The AEMP protocol, unlike the Erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
829	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
830	language-specific serialisers (e.g. Storable).	909	language-specific serialisers (e.g. Storable). By default, unless TLS is
		910	used, the protocol is actually completely text-based.
831		911
832	It has also been carefully designed to be implementable in other languages	912	It has also been carefully designed to be implementable in other languages
833	with a minimum of work while gracefully degrading fucntionality to make the	913	with a minimum of work while gracefully degrading functionality to make the
834	protocol simple.	914	protocol simple.
835		915
836	=item * AEMP has more flexible monitoring options than Erlang.	916	=item * AEMP has more flexible monitoring options than Erlang.
837		917
838	In Erlang, you can chose to receive I<all> exit signals as messages	918	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
841	Erlang, as one can choose between automatic kill, exit message or callback	921	Erlang, as one can choose between automatic kill, exit message or callback
842	on a per-process basis.	922	on a per-process basis.
843		923
844	=item * Erlang tries to hide remote/local connections, AEMP does not.	924	=item * Erlang tries to hide remote/local connections, AEMP does not.
845		925
846	Monitoring in Erlang is not an indicator of process death/crashes,	926	Monitoring in Erlang is not an indicator of process death/crashes, in the
847	as linking is (except linking is unreliable in Erlang).	927	same way as linking is (except linking is unreliable in Erlang).
848		928
849	In AEMP, you don't "look up" registered port names or send to named ports	929	In AEMP, you don't "look up" registered port names or send to named ports
850	that might or might not be persistent. Instead, you normally spawn a port	930	that might or might not be persistent. Instead, you normally spawn a port
851	on the remote node. The init function monitors the you, and you monitor	931	on the remote node. The init function monitors you, and you monitor the
852	the remote port. Since both monitors are local to the node, they are much	932	remote port. Since both monitors are local to the node, they are much more
853	more reliable.	933	reliable (no need for C<spawn_link>).
854		934
855	This also saves round-trips and avoids sending messages to the wrong port	935	This also saves round-trips and avoids sending messages to the wrong port
856	(hard to do in Erlang).	936	(hard to do in Erlang).
857		937
858	=back	938	=back
859		939
860	=head1 RATIONALE	940	=head1 RATIONALE
861		941
862	=over 4	942	=over 4
863		943
864	=item Why strings for ports and noderefs, why not objects?	944	=item Why strings for port and node IDs, why not objects?
865		945
866	We considered "objects", but found that the actual number of methods	946	We considered "objects", but found that the actual number of methods
867	thatc an be called are very low. Since port IDs and noderefs travel over	947	that can be called are quite low. Since port and node IDs travel over
868	the network frequently, the serialising/deserialising would add lots of	948	the network frequently, the serialising/deserialising would add lots of
869	overhead, as well as having to keep a proxy object.	949	overhead, as well as having to keep a proxy object everywhere.
870		950
871	Strings can easily be printed, easily serialised etc. and need no special	951	Strings can easily be printed, easily serialised etc. and need no special
872	procedures to be "valid".	952	procedures to be "valid".
873		953
		954	And as a result, a miniport consists of a single closure stored in a
		955	global hash - it can't become much cheaper.
		956
874	=item Why favour JSON, why not real serialising format such as Storable?	957	=item Why favour JSON, why not a real serialising format such as Storable?
875		958
876	In fact, any AnyEvent::MP node will happily accept Storable as framing	959	In fact, any AnyEvent::MP node will happily accept Storable as framing
877	format, but currently there is no way to make a node use Storable by	960	format, but currently there is no way to make a node use Storable by
878	default.	961	default (although all nodes will accept it).
879		962
880	The default framing protocol is JSON because a) JSON::XS is many times	963	The default framing protocol is JSON because a) JSON::XS is many times
881	faster for small messages and b) most importantly, after years of	964	faster for small messages and b) most importantly, after years of
882	experience we found that object serialisation is causing more problems	965	experience we found that object serialisation is causing more problems
883	than it gains: Just like function calls, objects simply do not travel	966	than it solves: Just like function calls, objects simply do not travel
884	easily over the network, mostly because they will always be a copy, so you	967	easily over the network, mostly because they will always be a copy, so you
885	always have to re-think your design.	968	always have to re-think your design.
886		969
887	Keeping your messages simple, concentrating on data structures rather than	970	Keeping your messages simple, concentrating on data structures rather than
888	objects, will keep your messages clean, tidy and efficient.	971	objects, will keep your messages clean, tidy and efficient.
889		972
890	=back	973	=back
891		974
892	=head1 SEE ALSO	975	=head1 SEE ALSO
893		976
		977	L<AnyEvent::MP::Intro> - a gentle introduction.
		978
		979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		980
		981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		982	your applications.
		983
		984	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		985
		986	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		987	all nodes.
		988
894	L<AnyEvent>.	989	L<AnyEvent>.
895		990
896	=head1 AUTHOR	991	=head1 AUTHOR
897		992
898	Marc Lehmann <schmorp@schmorp.de>	993	Marc Lehmann <schmorp@schmorp.de>

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.46 by root, Thu Aug 13 01:46:10 2009 UTC vs. Revision 1.106 by root, Wed Dec 9 14:00:49 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.46 by root, Thu Aug 13 01:46:10 2009 UTC vs.
Revision 1.106 by root, Wed Dec 9 14:00:49 2009 UTC