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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC vs.
Revision 1.130 by root, Fri Mar 9 17:05:26 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $somple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, type matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
73		78
74	Some ports allow you to register C<rcv> handlers that can match specific	79	Ports allow you to register C<rcv> handlers that can match all or just
75	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	81	anything was listening for them or not.
77		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
78	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
79		86
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
81	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
82	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
83	reference.
84		90
85	=item node	91	=item node
86		92
87	A node is a single process containing at least one port - the node	93	A node is a single process containing at least one port - the node port,
88	port. You can send messages to node ports to find existing ports or to	94	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	95	ports.
90		96
91	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	98	(no listening ports). Private nodes cannot talk to other private nodes
		99	currently, but all nodes can talk to public nodes.
93		100
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
95		102
96	A node reference is a string that either simply identifies the node (for	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
97	private and slave nodes), or contains a recipe on how to reach a given
98	node (for public nodes).
99		104
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	A node ID is a string that uniquely identifies the node within a
101	TCP/IP, other protocols might look different).	106	network. Depending on the configuration used, node IDs can look like a
		107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
102		109
103	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
104	addresses) or unresolved (where hostnames are used instead of addresses).
105		111
106	Before using an unresolved node reference in a message you first have to	112	Nodes can only talk to each other by creating some kind of connection to
107	resolve it.	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
108		170
109	=back	171	=back
110		172
111	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
112		174
114		176
115	=cut	177	=cut
116		178
117	package AnyEvent::MP;	179	package AnyEvent::MP;
118		180
		181	use AnyEvent::MP::Config ();
119	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
120		184
121	use common::sense;	185	use common::sense;
122		186
123	use Carp ();	187	use Carp ();
124		188
125	use AE ();	189	use AE ();
		190	use Guard ();
126		191
127	use base "Exporter";	192	use base "Exporter";
128		193
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
130		195
131	our @EXPORT = qw(	196	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	198	configure
134	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
135	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
136	);	203	);
137		204
138	our $SELF;	205	our $SELF;
139		206
140	sub _self_die() {	207	sub _self_die() {
…		…
143	kil $SELF, die => $msg;	210	kil $SELF, die => $msg;
144	}	211	}
145		212
146	=item $thisnode = NODE / $NODE	213	=item $thisnode = NODE / $NODE
147		214
148	The C<NODE> function returns, and the C<$NODE> variable contains	215	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	216	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	217	a call to C<configure>.
151	identifiers become invalid.
152		218
153	=item $noderef = node_of $port	219	=item $nodeid = node_of $port
154		220
155	Extracts and returns the noderef from a portid or a noderef.	221	Extracts and returns the node ID from a port ID or a node ID.
156		222
157	=item initialise_node $noderef, $seednode, $seednode...	223	=item configure $profile, key => value...
158		224
159	=item initialise_node "slave/", $master, $master...	225	=item configure key => value...
160		226
161	Before a node can talk to other nodes on the network it has to initialise	227	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	228	"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.	229	to know is its own name, and optionally it should know the addresses of
		230	some other nodes in the network to discover other nodes.
164		231
165	This function initialises a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
167		234
168	All arguments (optionally except for the first) are noderefs, which can be	235	The key/value pairs are basically the same ones as documented for the
169	either resolved or unresolved.	236	F<aemp> command line utility (sans the set/del prefix), with these additions:
170
171	The first argument will be looked up in the configuration database first
172	(if it is C<undef> then the current nodename will be used instead) to find
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176
177	There are two types of networked nodes, public nodes and slave nodes:
178		237
179	=over 4	238	=over 4
180		239
181	=item public nodes	240	=item norc => $boolean (default false)
182		241
183	For public nodes, C<$noderef> (supplied either directly to	242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	243	be consulted - all configuraiton options must be specified in the
185	noderef (possibly unresolved, in which case it will be resolved).	244	C<configure> call.
186		245
187	After resolving, the node will bind itself on all endpoints and try to	246	=item force => $boolean (default false)
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191		247
192	=item slave nodes	248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
193		251
194	When the C<$noderef> (either as given or overriden by the config file)	252	=item secure => $pass->($nodeid)
195	is the special string C<slave/>, then the node will become a slave
196	node. Slave nodes cannot be contacted from outside and will route most of
197	their traffic to the master node that they attach to.
198		253
199	At least one additional noderef is required (either by specifying it	254	In addition to specifying a boolean, you can specify a code reference that
200	directly or because it is part of the configuration profile): The node	255	is called for every remote execution attempt - the execution request is
201	will try to connect to all of them and will become a slave attached to the	256	granted iff the callback returns a true value.
202	first node it can successfully connect to.	257
		258	See F<semp setsecure> for more info.
203		259
204	=back	260	=back
205		261
206	This function will block until all nodes have been resolved and, for slave
207	nodes, until it has successfully established a connection to a master
208	server.
209
210	Example: become a public node listening on the guessed noderef, or the one
211	specified via C<aemp> for the current node. This should be the most common
212	form of invocation for "daemon"-type nodes.
213
214	initialise_node;
215
216	Example: become a slave node to any of the the seednodes specified via
217	C<aemp>. This form is often used for commandline clients.
218
219	initialise_node "slave/";
220
221	Example: become a slave node to any of the specified master servers. This
222	form is also often used for commandline clients.
223
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	Example: become a public node, and try to contact some well-known master
227	servers to become part of the network.
228
229	initialise_node undef, "master1", "master2";
230
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236
237	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4	262	=over 4
249		263
250	=item the empty string	264	=item step 1, gathering configuration from profiles
251		265
252	An empty-string component gets resolved as if the default port (4040) was	266	The function first looks up a profile in the aemp configuration (see the
253	specified.	267	L<aemp> commandline utility). The profile name can be specified via the
		268	named C<profile> parameter or can simply be the first parameter). If it is
		269	missing, then the nodename (F<uname -n>) will be used as profile name.
254		270
255	=item naked port numbers (e.g. C<1234>)	271	The profile data is then gathered as follows:
256		272
257	These are resolved by prepending the local nodename and a colon, to be	273	First, all remaining key => value pairs (all of which are conveniently
258	further resolved.	274	undocumented at the moment) will be interpreted as configuration
		275	data. Then they will be overwritten by any values specified in the global
		276	default configuration (see the F<aemp> utility), then the chain of
		277	profiles chosen by the profile name (and any C<parent> attributes).
259		278
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	279	That means that the values specified in the profile have highest priority
		280	and the values specified directly via C<configure> have lowest priority,
		281	and can only be used to specify defaults.
261		282
262	These are resolved by using AnyEvent::DNS to resolve them, optionally	283	If the profile specifies a node ID, then this will become the node ID of
263	looking up SRV records for the C<aemp=4040> port, if no port was	284	this process. If not, then the profile name will be used as node ID, with
264	specified.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		292
		293	=item step 2, bind listener sockets
		294
		295	The next step is to look up the binds in the profile, followed by binding
		296	aemp protocol listeners on all binds specified (it is possible and valid
		297	to have no binds, meaning that the node cannot be contacted form the
		298	outside. This means the node cannot talk to other nodes that also have no
		299	binds, but it can still talk to all "normal" nodes).
		300
		301	If the profile does not specify a binds list, then a default of C<*> is
		302	used, meaning the node will bind on a dynamically-assigned port on every
		303	local IP address it finds.
		304
		305	=item step 3, connect to seed nodes
		306
		307	As the last step, the seed ID list from the profile is passed to the
		308	L<AnyEvent::MP::Global> module, which will then use it to keep
		309	connectivity with at least one node at any point in time.
265		310
266	=back	311	=back
		312
		313	Example: become a distributed node using the local node name as profile.
		314	This should be the most common form of invocation for "daemon"-type nodes.
		315
		316	configure
		317
		318	Example: become a semi-anonymous node. This form is often used for
		319	commandline clients.
		320
		321	configure nodeid => "myscript/%n/%u";
		322
		323	Example: configure a node using a profile called seed, which is suitable
		324	for a seed node as it binds on all local addresses on a fixed port (4040,
		325	customary for aemp).
		326
		327	# use the aemp commandline utility
		328	# aemp profile seed binds '*:4040'
		329
		330	# then use it
		331	configure profile => "seed";
		332
		333	# or simply use aemp from the shell again:
		334	# aemp run profile seed
		335
		336	# or provide a nicer-to-remember nodeid
		337	# aemp run profile seed nodeid "$(hostname)"
267		338
268	=item $SELF	339	=item $SELF
269		340
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	341	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	342	blocks.
272		343
273	=item SELF, %SELF, @SELF...	344	=item *SELF, SELF, %SELF, @SELF...
274		345
275	Due to some quirks in how perl exports variables, it is impossible to	346	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	347	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	348	module, but only C<$SELF> is currently used.
278		349
279	=item snd $port, type => @data	350	=item snd $port, type => @data
280		351
281	=item snd $port, @msg	352	=item snd $port, @msg
282		353
283	Send the given message to the given port ID, which can identify either	354	Send the given message to the given port, which can identify either a
284	a local or a remote port, and can be either a string or soemthignt hat	355	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		356
287	While the message can be about anything, it is highly recommended to use a	357	While the message can be almost anything, it is highly recommended to
288	string as first element (a portid, or some word that indicates a request	358	use a string as first element (a port ID, or some word that indicates a
289	type etc.).	359	request type etc.) and to consist if only simple perl values (scalars,
		360	arrays, hashes) - if you think you need to pass an object, think again.
290		361
291	The message data effectively becomes read-only after a call to this	362	The message data logically becomes read-only after a call to this
292	function: modifying any argument is not allowed and can cause many	363	function: modifying any argument (or values referenced by them) is
293	problems.	364	forbidden, as there can be considerable time between the call to C<snd>
		365	and the time the message is actually being serialised - in fact, it might
		366	never be copied as within the same process it is simply handed to the
		367	receiving port.
294		368
295	The type of data you can transfer depends on the transport protocol: when	369	The type of data you can transfer depends on the transport protocol: when
296	JSON is used, then only strings, numbers and arrays and hashes consisting	370	JSON is used, then only strings, numbers and arrays and hashes consisting
297	of those are allowed (no objects). When Storable is used, then anything	371	of those are allowed (no objects). When Storable is used, then anything
298	that Storable can serialise and deserialise is allowed, and for the local	372	that Storable can serialise and deserialise is allowed, and for the local
299	node, anything can be passed.	373	node, anything can be passed. Best rely only on the common denominator of
		374	these.
300		375
301	=item $local_port = port	376	=item $local_port = port
302		377
303	Create a new local port object and returns its port ID. Initially it has	378	Create a new local port object and returns its port ID. Initially it has
304	no callbacks set and will throw an error when it receives messages.	379	no callbacks set and will throw an error when it receives messages.
…		…
328	sub _kilme {	403	sub _kilme {
329	die "received message on port without callback";	404	die "received message on port without callback";
330	}	405	}
331		406
332	sub port(;&) {	407	sub port(;&) {
333	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
334	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
335		410
336	rcv $port, shift \|\| \&_kilme;	411	rcv $port, shift \|\| \&_kilme;
337		412
338	$port	413	$port
…		…
351	The default callback received all messages not matched by a more specific	426	The default callback received all messages not matched by a more specific
352	C<tag> match.	427	C<tag> match.
353		428
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	429	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		430
356	Register callbacks to be called on messages starting with the given tag on	431	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	432	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	433	C<$callback> is C<$undef> or missing). There can only be one callback
		434	registered for each tag.
359		435
360	The original message will be passed to the callback, after the first	436	The original message will be passed to the callback, after the first
361	element (the tag) has been removed. The callback will use the same	437	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	438	environment as the default callback (see above).
363		439
…		…
375	rcv port,	451	rcv port,
376	msg1 => sub { ... },	452	msg1 => sub { ... },
377	...	453	...
378	;	454	;
379		455
		456	Example: temporarily register a rcv callback for a tag matching some port
		457	(e.g. for an rpc reply) and unregister it after a message was received.
		458
		459	rcv $port, $otherport => sub {
		460	my @reply = @_;
		461
		462	rcv $SELF, $otherport;
		463	};
		464
380	=cut	465	=cut
381		466
382	sub rcv($@) {	467	sub rcv($@) {
383	my $port = shift;	468	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	469	my ($nodeid, $portid) = split /#/, $port, 2;
385		470
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	471	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	472	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		473
389	while (@_) {	474	while (@_) {
390	if (ref $_[0]) {	475	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	476	if (my $self = $PORT_DATA{$portid}) {
392	"AnyEvent::MP::Port" eq ref $self	477	"AnyEvent::MP::Port" eq ref $self
393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	478	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
394		479
395	$self->[2] = shift;	480	$self->[0] = shift;
396	} else {	481	} else {
397	my $cb = shift;	482	my $cb = shift;
398	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
399	local $SELF = $port;	484	local $SELF = $port;
400	eval { &$cb }; _self_die if $@;	485	eval { &$cb }; _self_die if $@;
401	};	486	};
402	}	487	}
403	} elsif (defined $_[0]) {	488	} elsif (defined $_[0]) {
404	my $self = $PORT_DATA{$portid} \|\|= do {	489	my $self = $PORT_DATA{$portid} \|\|= do {
405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	490	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
406		491
407	$PORT{$portid} = sub {	492	$PORT{$portid} = sub {
408	local $SELF = $port;	493	local $SELF = $port;
409		494
410	if (my $cb = $self->[1]{$_[0]}) {	495	if (my $cb = $self->[1]{$_[0]}) {
…		…
432	}	517	}
433		518
434	$port	519	$port
435	}	520	}
436		521
		522	=item peval $port, $coderef[, @args]
		523
		524	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		525	when the code throews an exception the C<$port> will be killed.
		526
		527	Any remaining args will be passed to the callback. Any return values will
		528	be returned to the caller.
		529
		530	This is useful when you temporarily want to execute code in the context of
		531	a port.
		532
		533	Example: create a port and run some initialisation code in it's context.
		534
		535	my $port = port { ... };
		536
		537	peval $port, sub {
		538	init
		539	or die "unable to init";
		540	};
		541
		542	=cut
		543
		544	sub peval($$) {
		545	local $SELF = shift;
		546	my $cb = shift;
		547
		548	if (wantarray) {
		549	my @res = eval { &$cb };
		550	_self_die if $@;
		551	@res
		552	} else {
		553	my $res = eval { &$cb };
		554	_self_die if $@;
		555	$res
		556	}
		557	}
		558
437	=item $closure = psub { BLOCK }	559	=item $closure = psub { BLOCK }
438		560
439	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	561	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
440	closure is executed, sets up the environment in the same way as in C<rcv>	562	closure is executed, sets up the environment in the same way as in C<rcv>
441	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	563	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		564
		565	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		566	BLOCK }, @_ } >>.
442		567
443	This is useful when you register callbacks from C<rcv> callbacks:	568	This is useful when you register callbacks from C<rcv> callbacks:
444		569
445	rcv delayed_reply => sub {	570	rcv delayed_reply => sub {
446	my ($delay, @reply) = @_;	571	my ($delay, @reply) = @_;
…		…
470	$res	595	$res
471	}	596	}
472	}	597	}
473	}	598	}
474		599
475	=item $guard = mon $port, $cb->(@reason)	600	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		601
477	=item $guard = mon $port, $rcvport	602	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		603
479	=item $guard = mon $port	604	=item $guard = mon $port # kill $SELF when $port dies
480		605
481	=item $guard = mon $port, $rcvport, @msg	606	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		607
483	Monitor the given port and do something when the port is killed or	608	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	609	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	610	to stop monitoring again.
486
487	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port
489	will arrive, or the monitoring action will be invoked after possible
490	message loss has been detected. No messages will be lost "in between"
491	(after the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get
493	delivered again.
494		611
495	In the first form (callback), the callback is simply called with any	612	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	613	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	614	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	615	C<eval> if unsure.
499		616
500	In the second form (another port given), the other port (C<$rcvport>)	617	In the second form (another port given), the other port (C<$rcvport>)
501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	618	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
502	"normal" kils nothing happens, while under all other conditions, the other	619	"normal" kils nothing happens, while under all other conditions, the other
503	port is killed with the same reason.	620	port is killed with the same reason.
504		621
505	The third form (kill self) is the same as the second form, except that	622	The third form (kill self) is the same as the second form, except that
506	C<$rvport> defaults to C<$SELF>.	623	C<$rvport> defaults to C<$SELF>.
507		624
508	In the last form (message), a message of the form C<@msg, @reason> will be	625	In the last form (message), a message of the form C<@msg, @reason> will be
509	C<snd>.	626	C<snd>.
		627
		628	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		629	alert was raised), they are removed and will not trigger again.
510		630
511	As a rule of thumb, monitoring requests should always monitor a port from	631	As a rule of thumb, monitoring requests should always monitor a port from
512	a local port (or callback). The reason is that kill messages might get	632	a local port (or callback). The reason is that kill messages might get
513	lost, just like any other message. Another less obvious reason is that	633	lost, just like any other message. Another less obvious reason is that
514	even monitoring requests can get lost (for exmaple, when the connection	634	even monitoring requests can get lost (for example, when the connection
515	to the other node goes down permanently). When monitoring a port locally	635	to the other node goes down permanently). When monitoring a port locally
516	these problems do not exist.	636	these problems do not exist.
517		637
		638	C<mon> effectively guarantees that, in the absence of hardware failures,
		639	after starting the monitor, either all messages sent to the port will
		640	arrive, or the monitoring action will be invoked after possible message
		641	loss has been detected. No messages will be lost "in between" (after
		642	the first lost message no further messages will be received by the
		643	port). After the monitoring action was invoked, further messages might get
		644	delivered again.
		645
		646	Inter-host-connection timeouts and monitoring depend on the transport
		647	used. The only transport currently implemented is TCP, and AnyEvent::MP
		648	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		649	non-idle connection, and usually around two hours for idle connections).
		650
		651	This means that monitoring is good for program errors and cleaning up
		652	stuff eventually, but they are no replacement for a timeout when you need
		653	to ensure some maximum latency.
		654
518	Example: call a given callback when C<$port> is killed.	655	Example: call a given callback when C<$port> is killed.
519		656
520	mon $port, sub { warn "port died because of <@_>\n" };	657	mon $port, sub { warn "port died because of <@_>\n" };
521		658
522	Example: kill ourselves when C<$port> is killed abnormally.	659	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	665	mon $port, $self => "restart";
529		666
530	=cut	667	=cut
531		668
532	sub mon {	669	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	670	my ($nodeid, $port) = split /#/, shift, 2;
534		671
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	672	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		673
537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	674	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		675
539	unless (ref $cb) {	676	unless (ref $cb) {
540	if (@_) {	677	if (@_) {
…		…
549	}	686	}
550		687
551	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
552		689
553	defined wantarray	690	defined wantarray
554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
555	}	692	}
556		693
557	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
558		695
559	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
560	is killed, the references will be freed.	697	is killed, the references will be freed.
561		698
562	Optionally returns a guard that will stop the monitoring.	699	Optionally returns a guard that will stop the monitoring.
563		700
564	This function is useful when you create e.g. timers or other watchers and	701	This function is useful when you create e.g. timers or other watchers and
565	want to free them when the port gets killed:	702	want to free them when the port gets killed (note the use of C<psub>):
566		703
567	$port->rcv (start => sub {	704	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	705	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	706	undef $timer if 0.9 < rand;
570	});	707	});
571	});	708	});
572		709
573	=cut	710	=cut
…		…
582		719
583	=item kil $port[, @reason]	720	=item kil $port[, @reason]
584		721
585	Kill the specified port with the given C<@reason>.	722	Kill the specified port with the given C<@reason>.
586		723
587	If no C<@reason> is specified, then the port is killed "normally" (linked	724	If no C<@reason> is specified, then the port is killed "normally" -
588	ports will not be kileld, or even notified).	725	monitor callback will be invoked, but the kil will not cause linked ports
		726	(C<mon $mport, $lport> form) to get killed.
589		727
590	Otherwise, linked ports get killed with the same reason (second form of	728	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
591	C<mon>, see below).	729	form) get killed with the same reason.
592		730
593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	731	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
594	will be reported as reason C<< die => $@ >>.	732	will be reported as reason C<< die => $@ >>.
595		733
596	Transport/communication errors are reported as C<< transport_error =>	734	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	739	=item $port = spawn $node, $initfunc[, @initdata]
602		740
603	Creates a port on the node C<$node> (which can also be a port ID, in which	741	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	742	case it's the node where that port resides).
605		743
606	The port ID of the newly created port is return immediately, and it is	744	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	745	possible to immediately start sending messages or to monitor the port.
608		746
609	After the port has been created, the init function is	747	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	748	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	749	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	750	specify a function in the main program, use C<::name>.
613		751
614	If the function doesn't exist, then the node tries to C<require>	752	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	753	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	754	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	755	exists or it runs out of package names.
618		756
619	The init function is then called with the newly-created port as context	757	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	758	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		759	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		760	the port might not get created.
621		761
622	A common idiom is to pass your own port, monitor the spawned port, and	762	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	763	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	764	local port. This two-way monitoring ensures that both ports get cleaned up
		765	when there is a problem.
		766
		767	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		768	caller before C<spawn> returns (by delaying invocation when spawn is
		769	called for the local node).
625		770
626	Example: spawn a chat server port on C<$othernode>.	771	Example: spawn a chat server port on C<$othernode>.
627		772
628	# this node, executed from within a port context:	773	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	774	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
644		789
645	sub _spawn {	790	sub _spawn {
646	my $port = shift;	791	my $port = shift;
647	my $init = shift;	792	my $init = shift;
648		793
		794	# rcv will create the actual port
649	local $SELF = "$NODE#$port";	795	local $SELF = "$NODE#$port";
650	eval {	796	eval {
651	&{ load_func $init }	797	&{ load_func $init }
652	};	798	};
653	_self_die if $@;	799	_self_die if $@;
654	}	800	}
655		801
656	sub spawn(@) {	802	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
658		804
659	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
660		806
661	$_[0] =~ /::/	807	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	808	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		809
664	($NODE{$noderef} \|\| add_node $noderef)	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		811
667	"$noderef#$id"	812	"$nodeid#$id"
668	}	813	}
669		814
		815
		816	=item after $timeout, @msg
		817
		818	=item after $timeout, $callback
		819
		820	Either sends the given message, or call the given callback, after the
		821	specified number of seconds.
		822
		823	This is simply a utility function that comes in handy at times - the
		824	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		825	so it may go away in the future.
		826
		827	=cut
		828
		829	sub after($@) {
		830	my ($timeout, @action) = @_;
		831
		832	my $t; $t = AE::timer $timeout, 0, sub {
		833	undef $t;
		834	ref $action[0]
		835	? $action[0]()
		836	: snd @action;
		837	};
		838	}
		839
		840	#=item $cb2 = timeout $seconds, $cb[, @args]
		841
		842	=item cal $port, @msg, $callback[, $timeout]
		843
		844	A simple form of RPC - sends a message to the given C<$port> with the
		845	given contents (C<@msg>), but adds a reply port to the message.
		846
		847	The reply port is created temporarily just for the purpose of receiving
		848	the reply, and will be C<kil>ed when no longer needed.
		849
		850	A reply message sent to the port is passed to the C<$callback> as-is.
		851
		852	If an optional time-out (in seconds) is given and it is not C<undef>,
		853	then the callback will be called without any arguments after the time-out
		854	elapsed and the port is C<kil>ed.
		855
		856	If no time-out is given (or it is C<undef>), then the local port will
		857	monitor the remote port instead, so it eventually gets cleaned-up.
		858
		859	Currently this function returns the temporary port, but this "feature"
		860	might go in future versions unless you can make a convincing case that
		861	this is indeed useful for something.
		862
		863	=cut
		864
		865	sub cal(@) {
		866	my $timeout = ref $_[-1] ? undef : pop;
		867	my $cb = pop;
		868
		869	my $port = port {
		870	undef $timeout;
		871	kil $SELF;
		872	&$cb;
		873	};
		874
		875	if (defined $timeout) {
		876	$timeout = AE::timer $timeout, 0, sub {
		877	undef $timeout;
		878	kil $port;
		879	$cb->();
		880	};
		881	} else {
		882	mon $_[0], sub {
		883	kil $port;
		884	$cb->();
		885	};
		886	}
		887
		888	push @_, $port;
		889	&snd;
		890
		891	$port
		892	}
		893
670	=back	894	=back
671		895
672	=head1 NODE MESSAGES	896	=head1 DISTRIBUTED DATABASE
673		897
674	Nodes understand the following messages sent to them. Many of them take	898	AnyEvent::MP comes with a simple distributed database. The database will
675	arguments called C<@reply>, which will simply be used to compose a reply	899	be mirrored asynchronously at all global nodes. Other nodes bind to one of
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	900	the global nodes for their needs.
677	the remaining arguments are simply the message data.
678		901
679	While other messages exist, they are not public and subject to change.	902	The database consists of a two-level hash - a hash contains a hash which
		903	contains values.
680		904
		905	The top level hash key is called "family", and the second-level hash key
		906	is called "subkey" or simply "key".
		907
		908	The family must be alphanumeric, i.e. start with a letter and consist
		909	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		910	pretty much like Perl module names.
		911
		912	As the family namespace is global, it is recommended to prefix family names
		913	with the name of the application or module using it.
		914
		915	The subkeys must be non-empty strings, with no further restrictions.
		916
		917	The values should preferably be strings, but other perl scalars should
		918	work as well (such as undef, arrays and hashes).
		919
		920	Every database entry is owned by one node - adding the same family/subkey
		921	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		922	but the result might be nondeterministic, i.e. the key might have
		923	different values on different nodes.
		924
		925	Different subkeys in the same family can be owned by different nodes
		926	without problems, and in fact, this is the common method to create worker
		927	pools. For example, a worker port for image scaling might do this:
		928
		929	db_set my_image_scalers => $port;
		930
		931	And clients looking for an image scaler will want to get the
		932	C<my_image_scalers> keys from time to time:
		933
		934	db_keys my_image_scalers => sub {
		935	@ports = @{ $_[0] };
		936	};
		937
		938	Or better yet, they want to monitor the database family, so they always
		939	have a reasonable up-to-date copy:
		940
		941	db_mon my_image_scalers => sub {
		942	@ports = keys %{ $_[0] };
		943	};
		944
		945	In general, you can set or delete single subkeys, but query and monitor
		946	whole families only.
		947
		948	If you feel the need to monitor or query a single subkey, try giving it
		949	it's own family.
		950
681	=over 4	951	=over
		952
		953	=item db_set $family => $subkey [=> $value]
		954
		955	Sets (or replaces) a key to the database - if C<$value> is omitted,
		956	C<undef> is used instead.
		957
		958	=item db_del $family => $subkey...
		959
		960	Deletes one or more subkeys from the database family.
		961
		962	=item $guard = db_reg $family => $subkey [=> $value]
		963
		964	Sets the key on the database and returns a guard. When the guard is
		965	destroyed, the key is deleted from the database. If C<$value> is missing,
		966	then C<undef> is used.
		967
		968	=item db_family $family => $cb->(\%familyhash)
		969
		970	Queries the named database C<$family> and call the callback with the
		971	family represented as a hash. You can keep and freely modify the hash.
		972
		973	=item db_keys $family => $cb->(\@keys)
		974
		975	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		976	them as array reference to the callback.
		977
		978	=item db_values $family => $cb->(\@values)
		979
		980	Same as C<db_family>, except it only queries the family I<values> and passes them
		981	as array reference to the callback.
		982
		983	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		984
		985	Creates a monitor on the given database family. Each time a key is set
		986	or or is deleted the callback is called with a hash containing the
		987	database family and three lists of added, changed and deleted subkeys,
		988	respectively. If no keys have changed then the array reference might be
		989	C<undef> or even missing.
		990
		991	The family hash reference and the key arrays belong to AnyEvent::MP and
		992	B<must not be modified or stored> by the callback. When in doubt, make a
		993	copy.
		994
		995	As soon as possible after the monitoring starts, the callback will be
		996	called with the intiial contents of the family, even if it is empty,
		997	i.e. there will always be a timely call to the callback with the current
		998	contents.
		999
		1000	It is possible that the callback is called with a change event even though
		1001	the subkey is already present and the value has not changed.
		1002
		1003	The monitoring stops when the guard object is destroyed.
		1004
		1005	Example: on every change to the family "mygroup", print out all keys.
		1006
		1007	my $guard = db_mon mygroup => sub {
		1008	my ($family, $a, $c, $d) = @_;
		1009	print "mygroup members: ", (join " ", keys %$family), "\n";
		1010	};
		1011
		1012	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1013
		1014	my $guard; $guard = db_mon My::Module::workers => sub {
		1015	my ($family, $a, $c, $d) = @_;
		1016	return unless %$family;
		1017	undef $guard;
		1018	print "My::Module::workers now nonempty\n";
		1019	};
		1020
		1021	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1022
		1023	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1024	my ($family, $a, $c, $d) = @_;
		1025
		1026	print "+$_=$family->{$_}\n" for @$a;
		1027	print "*$_=$family->{$_}\n" for @$c;
		1028	print "-$_=$family->{$_}\n" for @$d;
		1029	};
682		1030
683	=cut	1031	=cut
684
685	=item lookup => $name, @reply
686
687	Replies with the port ID of the specified well-known port, or C<undef>.
688
689	=item devnull => ...
690
691	Generic data sink/CPU heat conversion.
692
693	=item relay => $port, @msg
694
695	Simply forwards the message to the given port.
696
697	=item eval => $string[ @reply]
698
699	Evaluates the given string. If C<@reply> is given, then a message of the
700	form C<@reply, $@, @evalres> is sent.
701
702	Example: crash another node.
703
704	snd $othernode, eval => "exit";
705
706	=item time => @reply
707
708	Replies the the current node time to C<@reply>.
709
710	Example: tell the current node to send the current time to C<$myport> in a
711	C<timereply> message.
712
713	snd $NODE, time => $myport, timereply => 1, 2;
714	# => snd $myport, timereply => 1, 2, <time>
715		1032
716	=back	1033	=back
717		1034
718	=head1 AnyEvent::MP vs. Distributed Erlang	1035	=head1 AnyEvent::MP vs. Distributed Erlang
719		1036
720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1037	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
721	== aemp node, Erlang process == aemp port), so many of the documents and	1038	== aemp node, Erlang process == aemp port), so many of the documents and
722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1039	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
723	sample:	1040	sample:
724		1041
725	http://www.Erlang.se/doc/programming_rules.shtml	1042	http://www.erlang.se/doc/programming_rules.shtml
726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1043	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1044	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1045	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
729		1046
730	Despite the similarities, there are also some important differences:	1047	Despite the similarities, there are also some important differences:
731		1048
732	=over 4	1049	=over 4
733		1050
734	=item * Node references contain the recipe on how to contact them.	1051	=item * Node IDs are arbitrary strings in AEMP.
735		1052
736	Erlang relies on special naming and DNS to work everywhere in the	1053	Erlang relies on special naming and DNS to work everywhere in the same
737	same way. AEMP relies on each node knowing it's own address(es), with	1054	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
738	convenience functionality.	1055	configuration or DNS), and possibly the addresses of some seed nodes, but
		1056	will otherwise discover other nodes (and their IDs) itself.
739		1057
740	This means that AEMP requires a less tightly controlled environment at the
741	cost of longer node references and a slightly higher management overhead.
742
743	=item Erlang has a "remote ports are like local ports" philosophy, AEMP	1058	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
744	uses "local ports are like remote ports".	1059	uses "local ports are like remote ports".
745		1060
746	The failure modes for local ports are quite different (runtime errors	1061	The failure modes for local ports are quite different (runtime errors
747	only) then for remote ports - when a local port dies, you I<know> it dies,	1062	only) then for remote ports - when a local port dies, you I<know> it dies,
748	when a connection to another node dies, you know nothing about the other	1063	when a connection to another node dies, you know nothing about the other
…		…
755	ports being the special case/exception, where transport errors cannot	1070	ports being the special case/exception, where transport errors cannot
756	occur.	1071	occur.
757		1072
758	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1073	=item * Erlang uses processes and a mailbox, AEMP does not queue.
759		1074
760	Erlang uses processes that selectively receive messages, and therefore	1075	Erlang uses processes that selectively receive messages out of order, and
761	needs a queue. AEMP is event based, queuing messages would serve no	1076	therefore needs a queue. AEMP is event based, queuing messages would serve
762	useful purpose. For the same reason the pattern-matching abilities of	1077	no useful purpose. For the same reason the pattern-matching abilities
763	AnyEvent::MP are more limited, as there is little need to be able to	1078	of AnyEvent::MP are more limited, as there is little need to be able to
764	filter messages without dequeing them.	1079	filter messages without dequeuing them.
765		1080
766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1081	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1082	being event-based, while Erlang is process-based.
		1083
		1084	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1085	top of AEMP and Coro threads.
767		1086
768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1087	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
769		1088
770	Sending messages in Erlang is synchronous and blocks the process (and	1089	Sending messages in Erlang is synchronous and blocks the process until
		1090	a conenction has been established and the message sent (and so does not
771	so does not need a queue that can overflow). AEMP sends are immediate,	1091	need a queue that can overflow). AEMP sends return immediately, connection
772	connection establishment is handled in the background.	1092	establishment is handled in the background.
773		1093
774	=item * Erlang suffers from silent message loss, AEMP does not.	1094	=item * Erlang suffers from silent message loss, AEMP does not.
775		1095
776	Erlang makes few guarantees on messages delivery - messages can get lost	1096	Erlang implements few guarantees on messages delivery - messages can get
777	without any of the processes realising it (i.e. you send messages a, b,	1097	lost without any of the processes realising it (i.e. you send messages a,
778	and c, and the other side only receives messages a and c).	1098	b, and c, and the other side only receives messages a and c).
779		1099
780	AEMP guarantees correct ordering, and the guarantee that there are no	1100	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1101	guarantee that after one message is lost, all following ones sent to the
		1102	same port are lost as well, until monitoring raises an error, so there are
781	holes in the message sequence.	1103	no silent "holes" in the message sequence.
782		1104
783	=item * In Erlang, processes can be declared dead and later be found to be	1105	If you want your software to be very reliable, you have to cope with
784	alive.	1106	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
785		1107	simply tries to work better in common error cases, such as when a network
786	In Erlang it can happen that a monitored process is declared dead and	1108	link goes down.
787	linked processes get killed, but later it turns out that the process is
788	still alive - and can receive messages.
789
790	In AEMP, when port monitoring detects a port as dead, then that port will
791	eventually be killed - it cannot happen that a node detects a port as dead
792	and then later sends messages to it, finding it is still alive.
793		1109
794	=item * Erlang can send messages to the wrong port, AEMP does not.	1110	=item * Erlang can send messages to the wrong port, AEMP does not.
795		1111
796	In Erlang it is quite likely that a node that restarts reuses a process ID	1112	In Erlang it is quite likely that a node that restarts reuses an Erlang
797	known to other nodes for a completely different process, causing messages	1113	process ID known to other nodes for a completely different process,
798	destined for that process to end up in an unrelated process.	1114	causing messages destined for that process to end up in an unrelated
		1115	process.
799		1116
800	AEMP never reuses port IDs, so old messages or old port IDs floating	1117	AEMP does not reuse port IDs, so old messages or old port IDs floating
801	around in the network will not be sent to an unrelated port.	1118	around in the network will not be sent to an unrelated port.
802		1119
803	=item * Erlang uses unprotected connections, AEMP uses secure	1120	=item * Erlang uses unprotected connections, AEMP uses secure
804	authentication and can use TLS.	1121	authentication and can use TLS.
805		1122
806	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1123	AEMP can use a proven protocol - TLS - to protect connections and
807	securely authenticate nodes.	1124	securely authenticate nodes.
808		1125
809	=item * The AEMP protocol is optimised for both text-based and binary	1126	=item * The AEMP protocol is optimised for both text-based and binary
810	communications.	1127	communications.
811		1128
812	The AEMP protocol, unlike the Erlang protocol, supports both	1129	The AEMP protocol, unlike the Erlang protocol, supports both programming
813	language-independent text-only protocols (good for debugging) and binary,	1130	language independent text-only protocols (good for debugging), and binary,
814	language-specific serialisers (e.g. Storable).	1131	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1132	used, the protocol is actually completely text-based.
815		1133
816	It has also been carefully designed to be implementable in other languages	1134	It has also been carefully designed to be implementable in other languages
817	with a minimum of work while gracefully degrading fucntionality to make the	1135	with a minimum of work while gracefully degrading functionality to make the
818	protocol simple.	1136	protocol simple.
819		1137
820	=item * AEMP has more flexible monitoring options than Erlang.	1138	=item * AEMP has more flexible monitoring options than Erlang.
821		1139
822	In Erlang, you can chose to receive I<all> exit signals as messages	1140	In Erlang, you can chose to receive I<all> exit signals as messages or
823	or I<none>, there is no in-between, so monitoring single processes is	1141	I<none>, there is no in-between, so monitoring single Erlang processes is
824	difficult to implement. Monitoring in AEMP is more flexible than in	1142	difficult to implement.
825	Erlang, as one can choose between automatic kill, exit message or callback	1143
826	on a per-process basis.	1144	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1145	between automatic kill, exit message or callback on a per-port basis.
827		1146
828	=item * Erlang tries to hide remote/local connections, AEMP does not.	1147	=item * Erlang tries to hide remote/local connections, AEMP does not.
829		1148
830	Monitoring in Erlang is not an indicator of process death/crashes,	1149	Monitoring in Erlang is not an indicator of process death/crashes, in the
831	as linking is (except linking is unreliable in Erlang).	1150	same way as linking is (except linking is unreliable in Erlang).
832		1151
833	In AEMP, you don't "look up" registered port names or send to named ports	1152	In AEMP, you don't "look up" registered port names or send to named ports
834	that might or might not be persistent. Instead, you normally spawn a port	1153	that might or might not be persistent. Instead, you normally spawn a port
835	on the remote node. The init function monitors the you, and you monitor	1154	on the remote node. The init function monitors you, and you monitor the
836	the remote port. Since both monitors are local to the node, they are much	1155	remote port. Since both monitors are local to the node, they are much more
837	more reliable.	1156	reliable (no need for C<spawn_link>).
838		1157
839	This also saves round-trips and avoids sending messages to the wrong port	1158	This also saves round-trips and avoids sending messages to the wrong port
840	(hard to do in Erlang).	1159	(hard to do in Erlang).
841		1160
842	=back	1161	=back
843		1162
844	=head1 RATIONALE	1163	=head1 RATIONALE
845		1164
846	=over 4	1165	=over 4
847		1166
848	=item Why strings for ports and noderefs, why not objects?	1167	=item Why strings for port and node IDs, why not objects?
849		1168
850	We considered "objects", but found that the actual number of methods	1169	We considered "objects", but found that the actual number of methods
851	thatc an be called are very low. Since port IDs and noderefs travel over	1170	that can be called are quite low. Since port and node IDs travel over
852	the network frequently, the serialising/deserialising would add lots of	1171	the network frequently, the serialising/deserialising would add lots of
853	overhead, as well as having to keep a proxy object.	1172	overhead, as well as having to keep a proxy object everywhere.
854		1173
855	Strings can easily be printed, easily serialised etc. and need no special	1174	Strings can easily be printed, easily serialised etc. and need no special
856	procedures to be "valid".	1175	procedures to be "valid".
857		1176
858	And a a miniport consists of a single closure stored in a global hash - it	1177	And as a result, a port with just a default receiver consists of a single
859	can't become much cheaper.	1178	code reference stored in a global hash - it can't become much cheaper.
860		1179
861	=item Why favour JSON, why not real serialising format such as Storable?	1180	=item Why favour JSON, why not a real serialising format such as Storable?
862		1181
863	In fact, any AnyEvent::MP node will happily accept Storable as framing	1182	In fact, any AnyEvent::MP node will happily accept Storable as framing
864	format, but currently there is no way to make a node use Storable by	1183	format, but currently there is no way to make a node use Storable by
865	default.	1184	default (although all nodes will accept it).
866		1185
867	The default framing protocol is JSON because a) JSON::XS is many times	1186	The default framing protocol is JSON because a) JSON::XS is many times
868	faster for small messages and b) most importantly, after years of	1187	faster for small messages and b) most importantly, after years of
869	experience we found that object serialisation is causing more problems	1188	experience we found that object serialisation is causing more problems
870	than it gains: Just like function calls, objects simply do not travel	1189	than it solves: Just like function calls, objects simply do not travel
871	easily over the network, mostly because they will always be a copy, so you	1190	easily over the network, mostly because they will always be a copy, so you
872	always have to re-think your design.	1191	always have to re-think your design.
873		1192
874	Keeping your messages simple, concentrating on data structures rather than	1193	Keeping your messages simple, concentrating on data structures rather than
875	objects, will keep your messages clean, tidy and efficient.	1194	objects, will keep your messages clean, tidy and efficient.
876		1195
877	=back	1196	=back
878		1197
879	=head1 SEE ALSO	1198	=head1 SEE ALSO
880		1199
		1200	L<AnyEvent::MP::Intro> - a gentle introduction.
		1201
		1202	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1203
		1204	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1205	your applications.
		1206
		1207	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1208
		1209	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1210	all nodes.
		1211
881	L<AnyEvent>.	1212	L<AnyEvent>.
882		1213
883	=head1 AUTHOR	1214	=head1 AUTHOR
884		1215
885	Marc Lehmann <schmorp@schmorp.de>	1216	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC vs.
Revision 1.130 by root, Fri Mar 9 17:05:26 2012 UTC