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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC vs.
Revision 1.120 by root, Sun Feb 26 11:12:54 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
		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 port 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
		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
124		185
125	use AE ();	186	use AE ();
126		187
127	use base "Exporter";	188	use base "Exporter";
128		189
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	190	our $VERSION = '1.30';
130		191
131	our @EXPORT = qw(	192	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	193	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	194	configure
134	snd rcv mon kil reg psub spawn	195	snd rcv mon mon_guard kil psub peval spawn cal
135	port	196	port
136	);	197	);
137		198
138	our $SELF;	199	our $SELF;
139		200
…		…
143	kil $SELF, die => $msg;	204	kil $SELF, die => $msg;
144	}	205	}
145		206
146	=item $thisnode = NODE / $NODE	207	=item $thisnode = NODE / $NODE
147		208
148	The C<NODE> function returns, and the C<$NODE> variable contains	209	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	210	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	211	a call to C<configure>.
151	identifiers become invalid.
152		212
153	=item $noderef = node_of $port	213	=item $nodeid = node_of $port
154		214
155	Extracts and returns the noderef from a portid or a noderef.	215	Extracts and returns the node ID from a port ID or a node ID.
156		216
157	=item initialise_node $noderef, $seednode, $seednode...	217	=item configure $profile, key => value...
158		218
159	=item initialise_node "slave/", $master, $master...	219	=item configure key => value...
160		220
161	Before a node can talk to other nodes on the network it has to initialise	221	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	222	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	223	to know is its own name, and optionally it should know the addresses of
		224	some other nodes in the network to discover other nodes.
164		225
		226	The key/value pairs are basically the same ones as documented for the
		227	F<aemp> command line utility (sans the set/del prefix).
		228
165	This function initialises a node - it must be called exactly once (or	229	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	230	never) before calling other AnyEvent::MP functions.
167		231
168	All arguments are noderefs, which can be either resolved or unresolved.
169
170	There are two types of networked nodes, public nodes and slave nodes:
171
172	=over 4	232	=over 4
173		233
174	=item public nodes	234	=item step 1, gathering configuration from profiles
175		235
176	For public nodes, C<$noderef> must either be a (possibly unresolved)	236	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	237	L<aemp> commandline utility). The profile name can be specified via the
178	which case the noderef will be guessed.	238	named C<profile> parameter or can simply be the first parameter). If it is
		239	missing, then the nodename (F<uname -n>) will be used as profile name.
179		240
180	Afterwards, the node will bind itself on all endpoints and try to connect	241	The profile data is then gathered as follows:
181	to all additional C<$seednodes> that are specified. Seednodes are optional
182	and can be used to quickly bootstrap the node into an existing network.
183		242
184	=item slave nodes	243	First, all remaining key => value pairs (all of which are conveniently
		244	undocumented at the moment) will be interpreted as configuration
		245	data. Then they will be overwritten by any values specified in the global
		246	default configuration (see the F<aemp> utility), then the chain of
		247	profiles chosen by the profile name (and any C<parent> attributes).
185		248
186	When the C<$noderef> is the special string C<slave/>, then the node will	249	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	250	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.	251	and can only be used to specify defaults.
189		252
190	At least one additional noderef is required: The node will try to connect	253	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	254	this process. If not, then the profile name will be used as node ID. The
192	successfully connect to.	255	special node ID of C<anon/> will be replaced by a random node ID.
		256
		257	=item step 2, bind listener sockets
		258
		259	The next step is to look up the binds in the profile, followed by binding
		260	aemp protocol listeners on all binds specified (it is possible and valid
		261	to have no binds, meaning that the node cannot be contacted form the
		262	outside. This means the node cannot talk to other nodes that also have no
		263	binds, but it can still talk to all "normal" nodes).
		264
		265	If the profile does not specify a binds list, then a default of C<*> is
		266	used, meaning the node will bind on a dynamically-assigned port on every
		267	local IP address it finds.
		268
		269	=item step 3, connect to seed nodes
		270
		271	As the last step, the seed ID list from the profile is passed to the
		272	L<AnyEvent::MP::Global> module, which will then use it to keep
		273	connectivity with at least one node at any point in time.
193		274
194	=back	275	=back
195		276
196	This function will block until all nodes have been resolved and, for slave	277	Example: become a distributed node using the local node name as profile.
197	nodes, until it has successfully established a connection to a master	278	This should be the most common form of invocation for "daemon"-type nodes.
198	server.
199		279
200	Example: become a public node listening on the default node.	280	configure
201		281
202	initialise_node;	282	Example: become an anonymous node. This form is often used for commandline
		283	clients.
203		284
204	Example: become a public node, and try to contact some well-known master	285	configure nodeid => "anon/";
205	servers to become part of the network.
206		286
207	initialise_node undef, "master1", "master2";	287	Example: configure a node using a profile called seed, which is suitable
		288	for a seed node as it binds on all local addresses on a fixed port (4040,
		289	customary for aemp).
208		290
209	Example: become a public node listening on port C<4041>.	291	# use the aemp commandline utility
		292	# aemp profile seed nodeid anon/ binds '*:4040'
210		293
211	initialise_node 4041;	294	# then use it
		295	configure profile => "seed";
212		296
213	Example: become a public node, only visible on localhost port 4044.	297	# or simply use aemp from the shell again:
		298	# aemp run profile seed
214		299
215	initialise_node "locahost:4044";	300	# or provide a nicer-to-remember nodeid
216		301	# 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		302
250	=item $SELF	303	=item $SELF
251		304
252	Contains the current port id while executing C<rcv> callbacks or C<psub>	305	Contains the current port id while executing C<rcv> callbacks or C<psub>
253	blocks.	306	blocks.
254		307
255	=item SELF, %SELF, @SELF...	308	=item *SELF, SELF, %SELF, @SELF...
256		309
257	Due to some quirks in how perl exports variables, it is impossible to	310	Due to some quirks in how perl exports variables, it is impossible to
258	just export C<$SELF>, all the symbols called C<SELF> are exported by this	311	just export C<$SELF>, all the symbols named C<SELF> are exported by this
259	module, but only C<$SELF> is currently used.	312	module, but only C<$SELF> is currently used.
260		313
261	=item snd $port, type => @data	314	=item snd $port, type => @data
262		315
263	=item snd $port, @msg	316	=item snd $port, @msg
264		317
265	Send the given message to the given port ID, which can identify either	318	Send the given message to the given port, which can identify either a
266	a local or a remote port, and can be either a string or soemthignt hat	319	local or a remote port, and must be a port ID.
267	stringifies a sa port ID (such as a port object :).
268		320
269	While the message can be about anything, it is highly recommended to use a	321	While the message can be almost anything, it is highly recommended to
270	string as first element (a portid, or some word that indicates a request	322	use a string as first element (a port ID, or some word that indicates a
271	type etc.).	323	request type etc.) and to consist if only simple perl values (scalars,
		324	arrays, hashes) - if you think you need to pass an object, think again.
272		325
273	The message data effectively becomes read-only after a call to this	326	The message data logically becomes read-only after a call to this
274	function: modifying any argument is not allowed and can cause many	327	function: modifying any argument (or values referenced by them) is
275	problems.	328	forbidden, as there can be considerable time between the call to C<snd>
		329	and the time the message is actually being serialised - in fact, it might
		330	never be copied as within the same process it is simply handed to the
		331	receiving port.
276		332
277	The type of data you can transfer depends on the transport protocol: when	333	The type of data you can transfer depends on the transport protocol: when
278	JSON is used, then only strings, numbers and arrays and hashes consisting	334	JSON is used, then only strings, numbers and arrays and hashes consisting
279	of those are allowed (no objects). When Storable is used, then anything	335	of those are allowed (no objects). When Storable is used, then anything
280	that Storable can serialise and deserialise is allowed, and for the local	336	that Storable can serialise and deserialise is allowed, and for the local
281	node, anything can be passed.	337	node, anything can be passed. Best rely only on the common denominator of
		338	these.
282		339
283	=item $local_port = port	340	=item $local_port = port
284		341
285	Create a new local port object that can be used either as a pattern	342	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"),	343	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		344
289	=item $port = port { my @msg = @_; $finished }	345	=item $local_port = port { my @msg = @_ }
290		346
291	Creates a "miniport", that is, a very lightweight port without any pattern	347	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.	348	creating a port and calling C<rcv $port, $callback> on it.
294		349
295	The block will be called for every message received on the port. When the	350	The block will be called for every message received on the port, with the
296	callback returns a true value its job is considered "done" and the port	351	global variable C<$SELF> set to the port ID. Runtime errors will cause the
297	will be destroyed. Otherwise it will stay alive.	352	port to be C<kil>ed. The message will be passed as-is, no extra argument
		353	(i.e. no port ID) will be passed to the callback.
298		354
299	The message will be passed as-is, no extra argument (i.e. no port id) will	355	If you want to stop/destroy the port, simply C<kil> it:
300	be passed to the callback.
301		356
302	If you need the local port id in the callback, this works nicely:	357	my $port = port {
303		358	my @msg = @_;
304	my $port; $port = port {	359	...
305	snd $otherport, reply => $port;	360	kil $SELF;
306	};	361	};
307		362
308	=cut	363	=cut
309		364
310	sub rcv($@);	365	sub rcv($@);
		366
		367	sub _kilme {
		368	die "received message on port without callback";
		369	}
311		370
312	sub port(;&) {	371	sub port(;&) {
313	my $id = "$UNIQ." . $ID++;	372	my $id = "$UNIQ." . $ID++;
314	my $port = "$NODE#$id";	373	my $port = "$NODE#$id";
315		374
316	if (@_) {	375	rcv $port, shift \|\| \&_kilme;
317	rcv $port, shift;
318	} else {
319	$PORT{$id} = sub { }; # nop
320	}
321		376
322	$port	377	$port
323	}	378	}
324		379
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)	380	=item rcv $local_port, $callback->(@msg)
345		381
346	Replaces the callback on the specified miniport (after converting it to	382	Replaces the default callback on the specified port. There is no way to
347	one if required).	383	remove the default callback: use C<sub { }> to disable it, or better
348		384	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...] => $callback->(@msg), ...
354
355	Register callbacks to be called on matching messages on the given full
356	port (after converting it to one if required) and return the port.
357
358	The callback has to return a true value when its work is done, after
359	which is will be removed, or a false value in which case it will stay
360	registered.
361		385
362	The global C<$SELF> (exported by this module) contains C<$port> while	386	The global C<$SELF> (exported by this module) contains C<$port> while
363	executing the callback.	387	executing the callback. Runtime errors during callback execution will
		388	result in the port being C<kil>ed.
364		389
365	Runtime errors during callback execution will result in the port being	390	The default callback received all messages not matched by a more specific
366	C<kil>ed.	391	C<tag> match.
367		392
368	If the match is an array reference, then it will be matched against the	393	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
369	first elements of the message, otherwise only the first element is being
370	matched.
371		394
372	Any element in the match that is specified as C<_any_> (a function	395	Register (or replace) callbacks to be called on messages starting with the
373	exported by this module) matches any single element of the message.	396	given tag on the given port (and return the port), or unregister it (when
		397	C<$callback> is C<$undef> or missing). There can only be one callback
		398	registered for each tag.
374		399
375	While not required, it is highly recommended that the first matching	400	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	401	element (the tag) has been removed. The callback will use the same
377	also the most efficient match (by far).	402	environment as the default callback (see above).
378		403
379	Example: create a port and bind receivers on it in one go.	404	Example: create a port and bind receivers on it in one go.
380		405
381	my $port = rcv port,	406	my $port = rcv port,
382	msg1 => sub { ...; 0 },	407	msg1 => sub { ... },
383	msg2 => sub { ...; 0 },	408	msg2 => sub { ... },
384	;	409	;
385		410
386	Example: create a port, bind receivers and send it in a message elsewhere	411	Example: create a port, bind receivers and send it in a message elsewhere
387	in one go:	412	in one go:
388		413
389	snd $otherport, reply =>	414	snd $otherport, reply =>
390	rcv port,	415	rcv port,
391	msg1 => sub { ...; 0 },	416	msg1 => sub { ... },
392	...	417	...
393	;	418	;
394		419
		420	Example: temporarily register a rcv callback for a tag matching some port
		421	(e.g. for an rpc reply) and unregister it after a message was received.
		422
		423	rcv $port, $otherport => sub {
		424	my @reply = @_;
		425
		426	rcv $SELF, $otherport;
		427	};
		428
395	=cut	429	=cut
396		430
397	sub rcv($@) {	431	sub rcv($@) {
398	my $port = shift;	432	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	433	my ($nodeid, $portid) = split /#/, $port, 2;
400		434
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	435	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	436	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		437
404	if (@_ == 1) {	438	while (@_) {
		439	if (ref $_[0]) {
		440	if (my $self = $PORT_DATA{$portid}) {
		441	"AnyEvent::MP::Port" eq ref $self
		442	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		443
		444	$self->[0] = shift;
		445	} else {
405	my $cb = shift;	446	my $cb = shift;
406	delete $PORT_DATA{$portid};
407	$PORT{$portid} = sub {	447	$PORT{$portid} = sub {
408	local $SELF = $port;	448	local $SELF = $port;
409	eval {	449	eval { &$cb }; _self_die if $@;
410	&$cb	450	};
411	and kil $port;
412	};	451	}
413	_self_die if $@;	452	} elsif (defined $_[0]) {
414	};
415	} else {
416	my $self = $PORT_DATA{$portid} \|\|= do {	453	my $self = $PORT_DATA{$portid} \|\|= do {
417	my $self = bless {	454	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
418	id => $port,
419	}, "AnyEvent::MP::Port";
420		455
421	$PORT{$portid} = sub {	456	$PORT{$portid} = sub {
422	local $SELF = $port;	457	local $SELF = $port;
423		458
424	eval {
425	for (@{ $self->{rc0}{$_[0]} }) {	459	if (my $cb = $self->[1]{$_[0]}) {
426	$_ && &{$_->[0]}	460	shift;
427	&& undef $_;	461	eval { &$cb }; _self_die if $@;
428	}	462	} else {
429
430	for (@{ $self->{rcv}{$_[0]} }) {
431	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
432	&& &{$_->[0]}	463	&{ $self->[0] };
433	&& undef $_;
434	}
435
436	for (@{ $self->{any} }) {
437	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
438	&& &{$_->[0]}
439	&& undef $_;
440	}	464	}
441	};	465	};
442	_self_die if $@;	466
		467	$self
443	};	468	};
444		469
445	$self
446	};
447
448	"AnyEvent::MP::Port" eq ref $self	470	"AnyEvent::MP::Port" eq ref $self
449	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	471	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
450		472
451	while (@_) {
452	my ($match, $cb) = splice @_, 0, 2;	473	my ($tag, $cb) = splice @_, 0, 2;
453		474
454	if (!ref $match) {	475	if (defined $cb) {
455	push @{ $self->{rc0}{$match} }, [$cb];	476	$self->[1]{$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 {	477	} else {
462	push @{ $self->{any} }, [$cb, $match];	478	delete $self->[1]{$tag};
463	}	479	}
464	}	480	}
465	}	481	}
466		482
467	$port	483	$port
468	}	484	}
469		485
		486	=item peval $port, $coderef[, @args]
		487
		488	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		489	when the code throews an exception the C<$port> will be killed.
		490
		491	Any remaining args will be passed to the callback. Any return values will
		492	be returned to the caller.
		493
		494	This is useful when you temporarily want to execute code in the context of
		495	a port.
		496
		497	Example: create a port and run some initialisation code in it's context.
		498
		499	my $port = port { ... };
		500
		501	peval $port, sub {
		502	init
		503	or die "unable to init";
		504	};
		505
		506	=cut
		507
		508	sub peval($$) {
		509	local $SELF = shift;
		510	my $cb = shift;
		511
		512	if (wantarray) {
		513	my @res = eval { &$cb };
		514	_self_die if $@;
		515	@res
		516	} else {
		517	my $res = eval { &$cb };
		518	_self_die if $@;
		519	$res
		520	}
		521	}
		522
470	=item $closure = psub { BLOCK }	523	=item $closure = psub { BLOCK }
471		524
472	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	525	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
473	closure is executed, sets up the environment in the same way as in C<rcv>	526	closure is executed, sets up the environment in the same way as in C<rcv>
474	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	527	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		528
		529	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		530	BLOCK }, @_ } >>.
475		531
476	This is useful when you register callbacks from C<rcv> callbacks:	532	This is useful when you register callbacks from C<rcv> callbacks:
477		533
478	rcv delayed_reply => sub {	534	rcv delayed_reply => sub {
479	my ($delay, @reply) = @_;	535	my ($delay, @reply) = @_;
…		…
503	$res	559	$res
504	}	560	}
505	}	561	}
506	}	562	}
507		563
508	=item $guard = mon $port, $cb->(@reason)	564	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
509		565
510	=item $guard = mon $port, $rcvport	566	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
511		567
512	=item $guard = mon $port	568	=item $guard = mon $port # kill $SELF when $port dies
513		569
514	=item $guard = mon $port, $rcvport, @msg	570	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
515		571
516	Monitor the given port and do something when the port is killed or	572	Monitor the given port and do something when the port is killed or
517	messages to it were lost, and optionally return a guard that can be used	573	messages to it were lost, and optionally return a guard that can be used
518	to stop monitoring again.	574	to stop monitoring again.
519
520	C<mon> effectively guarantees that, in the absence of hardware failures,
521	that after starting the monitor, either all messages sent to the port
522	will arrive, or the monitoring action will be invoked after possible
523	message loss has been detected. No messages will be lost "in between"
524	(after the first lost message no further messages will be received by the
525	port). After the monitoring action was invoked, further messages might get
526	delivered again.
527		575
528	In the first form (callback), the callback is simply called with any	576	In the first form (callback), the callback is simply called with any
529	number of C<@reason> elements (no @reason means that the port was deleted	577	number of C<@reason> elements (no @reason means that the port was deleted
530	"normally"). Note also that I<< the callback B<must> never die >>, so use	578	"normally"). Note also that I<< the callback B<must> never die >>, so use
531	C<eval> if unsure.	579	C<eval> if unsure.
532		580
533	In the second form (another port given), the other port (C<$rcvport>)	581	In the second form (another port given), the other port (C<$rcvport>)
534	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	582	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
535	"normal" kils nothing happens, while under all other conditions, the other	583	"normal" kils nothing happens, while under all other conditions, the other
536	port is killed with the same reason.	584	port is killed with the same reason.
537		585
538	The third form (kill self) is the same as the second form, except that	586	The third form (kill self) is the same as the second form, except that
539	C<$rvport> defaults to C<$SELF>.	587	C<$rvport> defaults to C<$SELF>.
540		588
541	In the last form (message), a message of the form C<@msg, @reason> will be	589	In the last form (message), a message of the form C<@msg, @reason> will be
542	C<snd>.	590	C<snd>.
		591
		592	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		593	alert was raised), they are removed and will not trigger again.
543		594
544	As a rule of thumb, monitoring requests should always monitor a port from	595	As a rule of thumb, monitoring requests should always monitor a port from
545	a local port (or callback). The reason is that kill messages might get	596	a local port (or callback). The reason is that kill messages might get
546	lost, just like any other message. Another less obvious reason is that	597	lost, just like any other message. Another less obvious reason is that
547	even monitoring requests can get lost (for exmaple, when the connection	598	even monitoring requests can get lost (for example, when the connection
548	to the other node goes down permanently). When monitoring a port locally	599	to the other node goes down permanently). When monitoring a port locally
549	these problems do not exist.	600	these problems do not exist.
550		601
		602	C<mon> effectively guarantees that, in the absence of hardware failures,
		603	after starting the monitor, either all messages sent to the port will
		604	arrive, or the monitoring action will be invoked after possible message
		605	loss has been detected. No messages will be lost "in between" (after
		606	the first lost message no further messages will be received by the
		607	port). After the monitoring action was invoked, further messages might get
		608	delivered again.
		609
		610	Inter-host-connection timeouts and monitoring depend on the transport
		611	used. The only transport currently implemented is TCP, and AnyEvent::MP
		612	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		613	non-idle connection, and usually around two hours for idle connections).
		614
		615	This means that monitoring is good for program errors and cleaning up
		616	stuff eventually, but they are no replacement for a timeout when you need
		617	to ensure some maximum latency.
		618
551	Example: call a given callback when C<$port> is killed.	619	Example: call a given callback when C<$port> is killed.
552		620
553	mon $port, sub { warn "port died because of <@_>\n" };	621	mon $port, sub { warn "port died because of <@_>\n" };
554		622
555	Example: kill ourselves when C<$port> is killed abnormally.	623	Example: kill ourselves when C<$port> is killed abnormally.
…		…
561	mon $port, $self => "restart";	629	mon $port, $self => "restart";
562		630
563	=cut	631	=cut
564		632
565	sub mon {	633	sub mon {
566	my ($noderef, $port) = split /#/, shift, 2;	634	my ($nodeid, $port) = split /#/, shift, 2;
567		635
568	my $node = $NODE{$noderef} \|\| add_node $noderef;	636	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
569		637
570	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	638	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
571		639
572	unless (ref $cb) {	640	unless (ref $cb) {
573	if (@_) {	641	if (@_) {
…		…
582	}	650	}
583		651
584	$node->monitor ($port, $cb);	652	$node->monitor ($port, $cb);
585		653
586	defined wantarray	654	defined wantarray
587	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	655	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
588	}	656	}
589		657
590	=item $guard = mon_guard $port, $ref, $ref...	658	=item $guard = mon_guard $port, $ref, $ref...
591		659
592	Monitors the given C<$port> and keeps the passed references. When the port	660	Monitors the given C<$port> and keeps the passed references. When the port
593	is killed, the references will be freed.	661	is killed, the references will be freed.
594		662
595	Optionally returns a guard that will stop the monitoring.	663	Optionally returns a guard that will stop the monitoring.
596		664
597	This function is useful when you create e.g. timers or other watchers and	665	This function is useful when you create e.g. timers or other watchers and
598	want to free them when the port gets killed:	666	want to free them when the port gets killed (note the use of C<psub>):
599		667
600	$port->rcv (start => sub {	668	$port->rcv (start => sub {
601	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	669	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
602	undef $timer if 0.9 < rand;	670	undef $timer if 0.9 < rand;
603	});	671	});
604	});	672	});
605		673
606	=cut	674	=cut
…		…
615		683
616	=item kil $port[, @reason]	684	=item kil $port[, @reason]
617		685
618	Kill the specified port with the given C<@reason>.	686	Kill the specified port with the given C<@reason>.
619		687
620	If no C<@reason> is specified, then the port is killed "normally" (linked	688	If no C<@reason> is specified, then the port is killed "normally" -
621	ports will not be kileld, or even notified).	689	monitor callback will be invoked, but the kil will not cause linked ports
		690	(C<mon $mport, $lport> form) to get killed.
622		691
623	Otherwise, linked ports get killed with the same reason (second form of	692	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
624	C<mon>, see below).	693	form) get killed with the same reason.
625		694
626	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	695	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
627	will be reported as reason C<< die => $@ >>.	696	will be reported as reason C<< die => $@ >>.
628		697
629	Transport/communication errors are reported as C<< transport_error =>	698	Transport/communication errors are reported as C<< transport_error =>
…		…
634	=item $port = spawn $node, $initfunc[, @initdata]	703	=item $port = spawn $node, $initfunc[, @initdata]
635		704
636	Creates a port on the node C<$node> (which can also be a port ID, in which	705	Creates a port on the node C<$node> (which can also be a port ID, in which
637	case it's the node where that port resides).	706	case it's the node where that port resides).
638		707
639	The port ID of the newly created port is return immediately, and it is	708	The port ID of the newly created port is returned immediately, and it is
640	permissible to immediately start sending messages or monitor the port.	709	possible to immediately start sending messages or to monitor the port.
641		710
642	After the port has been created, the init function is	711	After the port has been created, the init function is called on the remote
643	called. This function must be a fully-qualified function name	712	node, in the same context as a C<rcv> callback. This function must be a
644	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	713	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
645	program, use C<::name>.	714	specify a function in the main program, use C<::name>.
646		715
647	If the function doesn't exist, then the node tries to C<require>	716	If the function doesn't exist, then the node tries to C<require>
648	the package, then the package above the package and so on (e.g.	717	the package, then the package above the package and so on (e.g.
649	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	718	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
650	exists or it runs out of package names.	719	exists or it runs out of package names.
651		720
652	The init function is then called with the newly-created port as context	721	The init function is then called with the newly-created port as context
653	object (C<$SELF>) and the C<@initdata> values as arguments.	722	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		723	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		724	the port might not get created.
654		725
655	A common idiom is to pass your own port, monitor the spawned port, and	726	A common idiom is to pass a local port, immediately monitor the spawned
656	in the init function, monitor the original port. This two-way monitoring	727	port, and in the remote init function, immediately monitor the passed
657	ensures that both ports get cleaned up when there is a problem.	728	local port. This two-way monitoring ensures that both ports get cleaned up
		729	when there is a problem.
		730
		731	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		732	caller before C<spawn> returns (by delaying invocation when spawn is
		733	called for the local node).
658		734
659	Example: spawn a chat server port on C<$othernode>.	735	Example: spawn a chat server port on C<$othernode>.
660		736
661	# this node, executed from within a port context:	737	# this node, executed from within a port context:
662	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	738	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
677		753
678	sub _spawn {	754	sub _spawn {
679	my $port = shift;	755	my $port = shift;
680	my $init = shift;	756	my $init = shift;
681		757
		758	# rcv will create the actual port
682	local $SELF = "$NODE#$port";	759	local $SELF = "$NODE#$port";
683	eval {	760	eval {
684	&{ load_func $init }	761	&{ load_func $init }
685	};	762	};
686	_self_die if $@;	763	_self_die if $@;
687	}	764	}
688		765
689	sub spawn(@) {	766	sub spawn(@) {
690	my ($noderef, undef) = split /#/, shift, 2;	767	my ($nodeid, undef) = split /#/, shift, 2;
691		768
692	my $id = "$RUNIQ." . $ID++;	769	my $id = "$RUNIQ." . $ID++;
693		770
694	$_[0] =~ /::/	771	$_[0] =~ /::/
695	or Carp::croak "spawn init function must be a fully-qualified name, caught";	772	or Carp::croak "spawn init function must be a fully-qualified name, caught";
696		773
697	($NODE{$noderef} \|\| add_node $noderef)	774	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
698	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
699		775
700	"$noderef#$id"	776	"$nodeid#$id"
701	}	777	}
702		778
703	=back	779	=item after $timeout, @msg
704		780
705	=head1 NODE MESSAGES	781	=item after $timeout, $callback
706		782
707	Nodes understand the following messages sent to them. Many of them take	783	Either sends the given message, or call the given callback, after the
708	arguments called C<@reply>, which will simply be used to compose a reply	784	specified number of seconds.
709	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
710	the remaining arguments are simply the message data.
711		785
712	While other messages exist, they are not public and subject to change.	786	This is simply a utility function that comes in handy at times - the
		787	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		788	so it may go away in the future.
713		789
714	=over 4
715
716	=cut	790	=cut
717		791
718	=item lookup => $name, @reply	792	sub after($@) {
		793	my ($timeout, @action) = @_;
719		794
720	Replies with the port ID of the specified well-known port, or C<undef>.	795	my $t; $t = AE::timer $timeout, 0, sub {
		796	undef $t;
		797	ref $action[0]
		798	? $action[0]()
		799	: snd @action;
		800	};
		801	}
721		802
722	=item devnull => ...	803	=item cal $port, @msg, $callback[, $timeout]
723		804
724	Generic data sink/CPU heat conversion.	805	A simple form of RPC - sends a message to the given C<$port> with the
		806	given contents (C<@msg>), but adds a reply port to the message.
725		807
726	=item relay => $port, @msg	808	The reply port is created temporarily just for the purpose of receiving
		809	the reply, and will be C<kil>ed when no longer needed.
727		810
728	Simply forwards the message to the given port.	811	A reply message sent to the port is passed to the C<$callback> as-is.
729		812
730	=item eval => $string[ @reply]	813	If an optional time-out (in seconds) is given and it is not C<undef>,
		814	then the callback will be called without any arguments after the time-out
		815	elapsed and the port is C<kil>ed.
731		816
732	Evaluates the given string. If C<@reply> is given, then a message of the	817	If no time-out is given (or it is C<undef>), then the local port will
733	form C<@reply, $@, @evalres> is sent.	818	monitor the remote port instead, so it eventually gets cleaned-up.
734		819
735	Example: crash another node.	820	Currently this function returns the temporary port, but this "feature"
		821	might go in future versions unless you can make a convincing case that
		822	this is indeed useful for something.
736		823
737	snd $othernode, eval => "exit";	824	=cut
738		825
739	=item time => @reply	826	sub cal(@) {
		827	my $timeout = ref $_[-1] ? undef : pop;
		828	my $cb = pop;
740		829
741	Replies the the current node time to C<@reply>.	830	my $port = port {
		831	undef $timeout;
		832	kil $SELF;
		833	&$cb;
		834	};
742		835
743	Example: tell the current node to send the current time to C<$myport> in a	836	if (defined $timeout) {
744	C<timereply> message.	837	$timeout = AE::timer $timeout, 0, sub {
		838	undef $timeout;
		839	kil $port;
		840	$cb->();
		841	};
		842	} else {
		843	mon $_[0], sub {
		844	kil $port;
		845	$cb->();
		846	};
		847	}
745		848
746	snd $NODE, time => $myport, timereply => 1, 2;	849	push @_, $port;
747	# => snd $myport, timereply => 1, 2, <time>	850	&snd;
		851
		852	$port
		853	}
748		854
749	=back	855	=back
750		856
751	=head1 AnyEvent::MP vs. Distributed Erlang	857	=head1 AnyEvent::MP vs. Distributed Erlang
752		858
753	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	859	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
754	== aemp node, Erlang process == aemp port), so many of the documents and	860	== aemp node, Erlang process == aemp port), so many of the documents and
755	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	861	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
756	sample:	862	sample:
757		863
758	http://www.Erlang.se/doc/programming_rules.shtml	864	http://www.erlang.se/doc/programming_rules.shtml
759	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	865	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
760	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	866	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
761	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	867	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
762		868
763	Despite the similarities, there are also some important differences:	869	Despite the similarities, there are also some important differences:
764		870
765	=over 4	871	=over 4
766		872
767	=item * Node references contain the recipe on how to contact them.	873	=item * Node IDs are arbitrary strings in AEMP.
768		874
769	Erlang relies on special naming and DNS to work everywhere in the	875	Erlang relies on special naming and DNS to work everywhere in the same
770	same way. AEMP relies on each node knowing it's own address(es), with	876	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
771	convenience functionality.	877	configuration or DNS), and possibly the addresses of some seed nodes, but
		878	will otherwise discover other nodes (and their IDs) itself.
772		879
773	This means that AEMP requires a less tightly controlled environment at the	880	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
774	cost of longer node references and a slightly higher management overhead.	881	uses "local ports are like remote ports".
		882
		883	The failure modes for local ports are quite different (runtime errors
		884	only) then for remote ports - when a local port dies, you I<know> it dies,
		885	when a connection to another node dies, you know nothing about the other
		886	port.
		887
		888	Erlang pretends remote ports are as reliable as local ports, even when
		889	they are not.
		890
		891	AEMP encourages a "treat remote ports differently" philosophy, with local
		892	ports being the special case/exception, where transport errors cannot
		893	occur.
775		894
776	=item * Erlang uses processes and a mailbox, AEMP does not queue.	895	=item * Erlang uses processes and a mailbox, AEMP does not queue.
777		896
778	Erlang uses processes that selctively receive messages, and therefore	897	Erlang uses processes that selectively receive messages out of order, and
779	needs a queue. AEMP is event based, queuing messages would serve no useful	898	therefore needs a queue. AEMP is event based, queuing messages would serve
780	purpose.	899	no useful purpose. For the same reason the pattern-matching abilities
		900	of AnyEvent::MP are more limited, as there is little need to be able to
		901	filter messages without dequeuing them.
781		902
782	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	903	This is not a philosophical difference, but simply stems from AnyEvent::MP
		904	being event-based, while Erlang is process-based.
		905
		906	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		907	top of AEMP and Coro threads.
783		908
784	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	909	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
785		910
786	Sending messages in Erlang is synchronous and blocks the process. AEMP	911	Sending messages in Erlang is synchronous and blocks the process until
787	sends are immediate, connection establishment is handled in the	912	a conenction has been established and the message sent (and so does not
788	background.	913	need a queue that can overflow). AEMP sends return immediately, connection
		914	establishment is handled in the background.
789		915
790	=item * Erlang can silently lose messages, AEMP cannot.	916	=item * Erlang suffers from silent message loss, AEMP does not.
791		917
792	Erlang makes few guarantees on messages delivery - messages can get lost	918	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,	919	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).	920	b, and c, and the other side only receives messages a and c).
795		921
796	AEMP guarantees correct ordering, and the guarantee that there are no	922	AEMP guarantees (modulo hardware errors) correct ordering, and the
		923	guarantee that after one message is lost, all following ones sent to the
		924	same port are lost as well, until monitoring raises an error, so there are
797	holes in the message sequence.	925	no silent "holes" in the message sequence.
798		926
799	=item * In Erlang, processes can be declared dead and later be found to be	927	If you want your software to be very reliable, you have to cope with
800	alive.	928	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
801		929	simply tries to work better in common error cases, such as when a network
802	In Erlang it can happen that a monitored process is declared dead and	930	link goes down.
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		931
810	=item * Erlang can send messages to the wrong port, AEMP does not.	932	=item * Erlang can send messages to the wrong port, AEMP does not.
811		933
812	In Erlang it is quite possible that a node that restarts reuses a process	934	In Erlang it is quite likely that a node that restarts reuses an Erlang
813	ID known to other nodes for a completely different process, causing	935	process ID known to other nodes for a completely different process,
814	messages destined for that process to end up in an unrelated process.	936	causing messages destined for that process to end up in an unrelated
		937	process.
815		938
816	AEMP never reuses port IDs, so old messages or old port IDs floating	939	AEMP does not reuse port IDs, so old messages or old port IDs floating
817	around in the network will not be sent to an unrelated port.	940	around in the network will not be sent to an unrelated port.
818		941
819	=item * Erlang uses unprotected connections, AEMP uses secure	942	=item * Erlang uses unprotected connections, AEMP uses secure
820	authentication and can use TLS.	943	authentication and can use TLS.
821		944
822	AEMP can use a proven protocol - SSL/TLS - to protect connections and	945	AEMP can use a proven protocol - TLS - to protect connections and
823	securely authenticate nodes.	946	securely authenticate nodes.
824		947
825	=item * The AEMP protocol is optimised for both text-based and binary	948	=item * The AEMP protocol is optimised for both text-based and binary
826	communications.	949	communications.
827		950
828	The AEMP protocol, unlike the Erlang protocol, supports both	951	The AEMP protocol, unlike the Erlang protocol, supports both programming
829	language-independent text-only protocols (good for debugging) and binary,	952	language independent text-only protocols (good for debugging), and binary,
830	language-specific serialisers (e.g. Storable).	953	language-specific serialisers (e.g. Storable). By default, unless TLS is
		954	used, the protocol is actually completely text-based.
831		955
832	It has also been carefully designed to be implementable in other languages	956	It has also been carefully designed to be implementable in other languages
833	with a minimum of work while gracefully degrading fucntionality to make the	957	with a minimum of work while gracefully degrading functionality to make the
834	protocol simple.	958	protocol simple.
835		959
836	=item * AEMP has more flexible monitoring options than Erlang.	960	=item * AEMP has more flexible monitoring options than Erlang.
837		961
838	In Erlang, you can chose to receive I<all> exit signals as messages	962	In Erlang, you can chose to receive I<all> exit signals as messages or
839	or I<none>, there is no in-between, so monitoring single processes is	963	I<none>, there is no in-between, so monitoring single Erlang processes is
840	difficult to implement. Monitoring in AEMP is more flexible than in	964	difficult to implement.
841	Erlang, as one can choose between automatic kill, exit message or callback	965
842	on a per-process basis.	966	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		967	between automatic kill, exit message or callback on a per-port basis.
843		968
844	=item * Erlang tries to hide remote/local connections, AEMP does not.	969	=item * Erlang tries to hide remote/local connections, AEMP does not.
845		970
846	Monitoring in Erlang is not an indicator of process death/crashes,	971	Monitoring in Erlang is not an indicator of process death/crashes, in the
847	as linking is (except linking is unreliable in Erlang).	972	same way as linking is (except linking is unreliable in Erlang).
848		973
849	In AEMP, you don't "look up" registered port names or send to named ports	974	In AEMP, you don't "look up" registered port names or send to named ports
850	that might or might not be persistent. Instead, you normally spawn a port	975	that might or might not be persistent. Instead, you normally spawn a port
851	on the remote node. The init function monitors the you, and you monitor	976	on the remote node. The init function monitors you, and you monitor the
852	the remote port. Since both monitors are local to the node, they are much	977	remote port. Since both monitors are local to the node, they are much more
853	more reliable.	978	reliable (no need for C<spawn_link>).
854		979
855	This also saves round-trips and avoids sending messages to the wrong port	980	This also saves round-trips and avoids sending messages to the wrong port
856	(hard to do in Erlang).	981	(hard to do in Erlang).
857		982
858	=back	983	=back
859		984
860	=head1 RATIONALE	985	=head1 RATIONALE
861		986
862	=over 4	987	=over 4
863		988
864	=item Why strings for ports and noderefs, why not objects?	989	=item Why strings for port and node IDs, why not objects?
865		990
866	We considered "objects", but found that the actual number of methods	991	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	992	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	993	the network frequently, the serialising/deserialising would add lots of
869	overhead, as well as having to keep a proxy object.	994	overhead, as well as having to keep a proxy object everywhere.
870		995
871	Strings can easily be printed, easily serialised etc. and need no special	996	Strings can easily be printed, easily serialised etc. and need no special
872	procedures to be "valid".	997	procedures to be "valid".
873		998
874	And a a miniport consists of a single closure stored in a global hash - it	999	And as a result, a port with just a default receiver consists of a single
875	can't become much cheaper.	1000	code reference stored in a global hash - it can't become much cheaper.
876		1001
877	=item Why favour JSON, why not real serialising format such as Storable?	1002	=item Why favour JSON, why not a real serialising format such as Storable?
878		1003
879	In fact, any AnyEvent::MP node will happily accept Storable as framing	1004	In fact, any AnyEvent::MP node will happily accept Storable as framing
880	format, but currently there is no way to make a node use Storable by	1005	format, but currently there is no way to make a node use Storable by
881	default.	1006	default (although all nodes will accept it).
882		1007
883	The default framing protocol is JSON because a) JSON::XS is many times	1008	The default framing protocol is JSON because a) JSON::XS is many times
884	faster for small messages and b) most importantly, after years of	1009	faster for small messages and b) most importantly, after years of
885	experience we found that object serialisation is causing more problems	1010	experience we found that object serialisation is causing more problems
886	than it gains: Just like function calls, objects simply do not travel	1011	than it solves: Just like function calls, objects simply do not travel
887	easily over the network, mostly because they will always be a copy, so you	1012	easily over the network, mostly because they will always be a copy, so you
888	always have to re-think your design.	1013	always have to re-think your design.
889		1014
890	Keeping your messages simple, concentrating on data structures rather than	1015	Keeping your messages simple, concentrating on data structures rather than
891	objects, will keep your messages clean, tidy and efficient.	1016	objects, will keep your messages clean, tidy and efficient.
892		1017
893	=back	1018	=back
894		1019
895	=head1 SEE ALSO	1020	=head1 SEE ALSO
896		1021
		1022	L<AnyEvent::MP::Intro> - a gentle introduction.
		1023
		1024	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1025
		1026	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1027	your applications.
		1028
		1029	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1030
		1031	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1032	all nodes.
		1033
897	L<AnyEvent>.	1034	L<AnyEvent>.
898		1035
899	=head1 AUTHOR	1036	=head1 AUTHOR
900		1037
901	Marc Lehmann <schmorp@schmorp.de>	1038	Marc Lehmann <schmorp@schmorp.de>

Diff Legend

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

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC vs. Revision 1.120 by root, Sun Feb 26 11:12:54 2012 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC vs.
Revision 1.120 by root, Sun Feb 26 11:12:54 2012 UTC