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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.61 by root, Mon Aug 24 08:06:49 2009 UTC vs.
Revision 1.125 by root, Sat Mar 3 13:07:19 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 $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
73		78
74	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
76		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
77	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
78		86
79	A port ID is 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<#>)
80	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
81	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
82	reference.
83		90
84	=item node	91	=item node
85		92
86	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
88	ports.	95	ports.
89		96
90	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
91	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.
92		100
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
94		102
95	A node reference is a string that either simply identifies the node (for	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
96	private and slave nodes), or contains a recipe on how to reach a given
97	node (for public nodes).
98		104
99	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
100	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.
101		109
102	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
103	addresses) or unresolved (where hostnames are used instead of addresses).
104		111
105	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
106	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).
107		170
108	=back	171	=back
109		172
110	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
111		174
113		176
114	=cut	177	=cut
115		178
116	package AnyEvent::MP;	179	package AnyEvent::MP;
117		180
		181	use AnyEvent::MP::Config ();
118	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
119		184
120	use common::sense;	185	use common::sense;
121		186
122	use Carp ();	187	use Carp ();
123		188
124	use AE ();	189	use AE ();
		190	use Guard ();
125		191
126	use base "Exporter";	192	use base "Exporter";
127		193
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
129		195
130	our @EXPORT = qw(	196	our @EXPORT = qw(
131	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	198	configure
133	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
134	port	200	port
		201	db_set db_del db_reg
135	);	202	);
136		203
137	our $SELF;	204	our $SELF;
138		205
139	sub _self_die() {	206	sub _self_die() {
…		…
142	kil $SELF, die => $msg;	209	kil $SELF, die => $msg;
143	}	210	}
144		211
145	=item $thisnode = NODE / $NODE	212	=item $thisnode = NODE / $NODE
146		213
147	The C<NODE> function returns, and the C<$NODE> variable contains the	214	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef of the local node. The value is initialised by a call to	215	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	216	a call to C<configure>.
150		217
151	=item $noderef = node_of $port	218	=item $nodeid = node_of $port
152		219
153	Extracts and returns the noderef from a port ID or a noderef.	220	Extracts and returns the node ID from a port ID or a node ID.
154		221
155	=item initialise_node $noderef, $seednode, $seednode...	222	=item configure $profile, key => value...
156		223
157	=item initialise_node "slave/", $master, $master...	224	=item configure key => value...
158		225
159	Before a node can talk to other nodes on the network it has to initialise	226	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	227	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	228	to know is its own name, and optionally it should know the addresses of
		229	some other nodes in the network to discover other nodes.
162		230
163	This function initialises a node - it must be called exactly once (or	231	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
165		233
166	All arguments (optionally except for the first) are noderefs, which can be	234	The key/value pairs are basically the same ones as documented for the
167	either resolved or unresolved.	235	F<aemp> command line utility (sans the set/del prefix), with two additions:
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176		236
177	=over 4	237	=over 4
178		238
179	=item public nodes	239	=item norc => $boolean (default false)
180		240
181	For public nodes, C<$noderef> (supplied either directly to	241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	242	be consulted - all configuraiton options must be specified in the
183	noderef (possibly unresolved, in which case it will be resolved).	243	C<configure> call.
184		244
185	After resolving, the node will bind itself on all endpoints and try to	245	=item force => $boolean (default false)
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		246
190	=item slave nodes	247	IF true, then the values specified in the C<configure> will take
191		248	precedence over any values configured via the rc file. The default is for
192	When the C<$noderef> (either as given or overriden by the config file)	249	the rc file to override any options specified in the program.
193	is the special string C<slave/>, then the node will become a slave
194	node. Slave nodes cannot be contacted from outside and will route most of
195	their traffic to the master node that they attach to.
196
197	At least one additional noderef is required (either by specifying it
198	directly or because it is part of the configuration profile): The node
199	will try to connect to all of them and will become a slave attached to the
200	first node it can successfully connect to.
201
202	Note that slave nodes cannot change their name, and consequently, their
203	master, so if the master goes down, the slave node will not function well
204	anymore until it can re-establish conenciton to its master. This makes
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.
206		250
207	=back	251	=back
208		252
209	This function will block until all nodes have been resolved and, for slave
210	nodes, until it has successfully established a connection to a master
211	server.
212
213	All the seednodes will also be specially marked to automatically retry
214	connecting to them infinitely.
215
216	Example: become a public node listening on the guessed noderef, or the one
217	specified via C<aemp> for the current node. This should be the most common
218	form of invocation for "daemon"-type nodes.
219
220	initialise_node;
221
222	Example: become a slave node to any of the the seednodes specified via
223	C<aemp>. This form is often used for commandline clients.
224
225	initialise_node "slave/";
226
227	Example: become a slave node to any of the specified master servers. This
228	form is also often used for commandline clients.
229
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
231
232	Example: become a public node, and try to contact some well-known master
233	servers to become part of the network.
234
235	initialise_node undef, "master1", "master2";
236
237	Example: become a public node listening on port C<4041>.
238
239	initialise_node 4041;
240
241	Example: become a public node, only visible on localhost port 4044.
242
243	initialise_node "localhost:4044";
244
245	=item $cv = resolve_node $noderef
246
247	Takes an unresolved node reference that may contain hostnames and
248	abbreviated IDs, resolves all of them and returns a resolved node
249	reference.
250
251	In addition to C<address:port> pairs allowed in resolved noderefs, the
252	following forms are supported:
253
254	=over 4	253	=over 4
255		254
256	=item the empty string	255	=item step 1, gathering configuration from profiles
257		256
258	An empty-string component gets resolved as if the default port (4040) was	257	The function first looks up a profile in the aemp configuration (see the
259	specified.	258	L<aemp> commandline utility). The profile name can be specified via the
		259	named C<profile> parameter or can simply be the first parameter). If it is
		260	missing, then the nodename (F<uname -n>) will be used as profile name.
260		261
261	=item naked port numbers (e.g. C<1234>)	262	The profile data is then gathered as follows:
262		263
263	These are resolved by prepending the local nodename and a colon, to be	264	First, all remaining key => value pairs (all of which are conveniently
264	further resolved.	265	undocumented at the moment) will be interpreted as configuration
		266	data. Then they will be overwritten by any values specified in the global
		267	default configuration (see the F<aemp> utility), then the chain of
		268	profiles chosen by the profile name (and any C<parent> attributes).
265		269
266	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	270	That means that the values specified in the profile have highest priority
		271	and the values specified directly via C<configure> have lowest priority,
		272	and can only be used to specify defaults.
267		273
268	These are resolved by using AnyEvent::DNS to resolve them, optionally	274	If the profile specifies a node ID, then this will become the node ID of
269	looking up SRV records for the C<aemp=4040> port, if no port was	275	this process. If not, then the profile name will be used as node ID, with
270	specified.	276	a slash (C</>) attached.
		277
		278	If the node ID (or profile name) ends with a slash (C</>), then a random
		279	string is appended to make it unique.
		280
		281	=item step 2, bind listener sockets
		282
		283	The next step is to look up the binds in the profile, followed by binding
		284	aemp protocol listeners on all binds specified (it is possible and valid
		285	to have no binds, meaning that the node cannot be contacted form the
		286	outside. This means the node cannot talk to other nodes that also have no
		287	binds, but it can still talk to all "normal" nodes).
		288
		289	If the profile does not specify a binds list, then a default of C<*> is
		290	used, meaning the node will bind on a dynamically-assigned port on every
		291	local IP address it finds.
		292
		293	=item step 3, connect to seed nodes
		294
		295	As the last step, the seed ID list from the profile is passed to the
		296	L<AnyEvent::MP::Global> module, which will then use it to keep
		297	connectivity with at least one node at any point in time.
271		298
272	=back	299	=back
		300
		301	Example: become a distributed node using the local node name as profile.
		302	This should be the most common form of invocation for "daemon"-type nodes.
		303
		304	configure
		305
		306	Example: become an anonymous node. This form is often used for commandline
		307	clients.
		308
		309	configure nodeid => "anon/";
		310
		311	Example: configure a node using a profile called seed, which is suitable
		312	for a seed node as it binds on all local addresses on a fixed port (4040,
		313	customary for aemp).
		314
		315	# use the aemp commandline utility
		316	# aemp profile seed binds '*:4040'
		317
		318	# then use it
		319	configure profile => "seed";
		320
		321	# or simply use aemp from the shell again:
		322	# aemp run profile seed
		323
		324	# or provide a nicer-to-remember nodeid
		325	# aemp run profile seed nodeid "$(hostname)"
273		326
274	=item $SELF	327	=item $SELF
275		328
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	329	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	330	blocks.
278		331
279	=item SELF, %SELF, @SELF...	332	=item *SELF, SELF, %SELF, @SELF...
280		333
281	Due to some quirks in how perl exports variables, it is impossible to	334	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	335	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	336	module, but only C<$SELF> is currently used.
284		337
285	=item snd $port, type => @data	338	=item snd $port, type => @data
286		339
287	=item snd $port, @msg	340	=item snd $port, @msg
288		341
289	Send the given message to the given port ID, which can identify either	342	Send the given message to the given port, which can identify either a
290	a local or a remote port, and must be a port ID.	343	local or a remote port, and must be a port ID.
291		344
292	While the message can be about anything, it is highly recommended to use a	345	While the message can be almost anything, it is highly recommended to
293	string as first element (a port ID, or some word that indicates a request	346	use a string as first element (a port ID, or some word that indicates a
294	type etc.).	347	request type etc.) and to consist if only simple perl values (scalars,
		348	arrays, hashes) - if you think you need to pass an object, think again.
295		349
296	The message data effectively becomes read-only after a call to this	350	The message data logically becomes read-only after a call to this
297	function: modifying any argument is not allowed and can cause many	351	function: modifying any argument (or values referenced by them) is
298	problems.	352	forbidden, as there can be considerable time between the call to C<snd>
		353	and the time the message is actually being serialised - in fact, it might
		354	never be copied as within the same process it is simply handed to the
		355	receiving port.
299		356
300	The type of data you can transfer depends on the transport protocol: when	357	The type of data you can transfer depends on the transport protocol: when
301	JSON is used, then only strings, numbers and arrays and hashes consisting	358	JSON is used, then only strings, numbers and arrays and hashes consisting
302	of those are allowed (no objects). When Storable is used, then anything	359	of those are allowed (no objects). When Storable is used, then anything
303	that Storable can serialise and deserialise is allowed, and for the local	360	that Storable can serialise and deserialise is allowed, and for the local
304	node, anything can be passed.	361	node, anything can be passed. Best rely only on the common denominator of
		362	these.
305		363
306	=item $local_port = port	364	=item $local_port = port
307		365
308	Create a new local port object and returns its port ID. Initially it has	366	Create a new local port object and returns its port ID. Initially it has
309	no callbacks set and will throw an error when it receives messages.	367	no callbacks set and will throw an error when it receives messages.
…		…
333	sub _kilme {	391	sub _kilme {
334	die "received message on port without callback";	392	die "received message on port without callback";
335	}	393	}
336		394
337	sub port(;&) {	395	sub port(;&) {
338	my $id = "$UNIQ." . $ID++;	396	my $id = $UNIQ . ++$ID;
339	my $port = "$NODE#$id";	397	my $port = "$NODE#$id";
340		398
341	rcv $port, shift \|\| \&_kilme;	399	rcv $port, shift \|\| \&_kilme;
342		400
343	$port	401	$port
…		…
382	msg1 => sub { ... },	440	msg1 => sub { ... },
383	...	441	...
384	;	442	;
385		443
386	Example: temporarily register a rcv callback for a tag matching some port	444	Example: temporarily register a rcv callback for a tag matching some port
387	(e.g. for a rpc reply) and unregister it after a message was received.	445	(e.g. for an rpc reply) and unregister it after a message was received.
388		446
389	rcv $port, $otherport => sub {	447	rcv $port, $otherport => sub {
390	my @reply = @_;	448	my @reply = @_;
391		449
392	rcv $SELF, $otherport;	450	rcv $SELF, $otherport;
…		…
394		452
395	=cut	453	=cut
396		454
397	sub rcv($@) {	455	sub rcv($@) {
398	my $port = shift;	456	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	457	my ($nodeid, $portid) = split /#/, $port, 2;
400		458
401	$NODE{$noderef} == $NODE{""}	459	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	460	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		461
404	while (@_) {	462	while (@_) {
405	if (ref $_[0]) {	463	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	464	if (my $self = $PORT_DATA{$portid}) {
407	"AnyEvent::MP::Port" eq ref $self	465	"AnyEvent::MP::Port" eq ref $self
408	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	466	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
409		467
410	$self->[2] = shift;	468	$self->[0] = shift;
411	} else {	469	} else {
412	my $cb = shift;	470	my $cb = shift;
413	$PORT{$portid} = sub {	471	$PORT{$portid} = sub {
414	local $SELF = $port;	472	local $SELF = $port;
415	eval { &$cb }; _self_die if $@;	473	eval { &$cb }; _self_die if $@;
416	};	474	};
417	}	475	}
418	} elsif (defined $_[0]) {	476	} elsif (defined $_[0]) {
419	my $self = $PORT_DATA{$portid} \|\|= do {	477	my $self = $PORT_DATA{$portid} \|\|= do {
420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	478	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
421		479
422	$PORT{$portid} = sub {	480	$PORT{$portid} = sub {
423	local $SELF = $port;	481	local $SELF = $port;
424		482
425	if (my $cb = $self->[1]{$_[0]}) {	483	if (my $cb = $self->[1]{$_[0]}) {
…		…
447	}	505	}
448		506
449	$port	507	$port
450	}	508	}
451		509
		510	=item peval $port, $coderef[, @args]
		511
		512	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		513	when the code throews an exception the C<$port> will be killed.
		514
		515	Any remaining args will be passed to the callback. Any return values will
		516	be returned to the caller.
		517
		518	This is useful when you temporarily want to execute code in the context of
		519	a port.
		520
		521	Example: create a port and run some initialisation code in it's context.
		522
		523	my $port = port { ... };
		524
		525	peval $port, sub {
		526	init
		527	or die "unable to init";
		528	};
		529
		530	=cut
		531
		532	sub peval($$) {
		533	local $SELF = shift;
		534	my $cb = shift;
		535
		536	if (wantarray) {
		537	my @res = eval { &$cb };
		538	_self_die if $@;
		539	@res
		540	} else {
		541	my $res = eval { &$cb };
		542	_self_die if $@;
		543	$res
		544	}
		545	}
		546
452	=item $closure = psub { BLOCK }	547	=item $closure = psub { BLOCK }
453		548
454	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	549	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
455	closure is executed, sets up the environment in the same way as in C<rcv>	550	closure is executed, sets up the environment in the same way as in C<rcv>
456	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	551	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		552
		553	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		554	BLOCK }, @_ } >>.
457		555
458	This is useful when you register callbacks from C<rcv> callbacks:	556	This is useful when you register callbacks from C<rcv> callbacks:
459		557
460	rcv delayed_reply => sub {	558	rcv delayed_reply => sub {
461	my ($delay, @reply) = @_;	559	my ($delay, @reply) = @_;
…		…
485	$res	583	$res
486	}	584	}
487	}	585	}
488	}	586	}
489		587
490	=item $guard = mon $port, $cb->(@reason)	588	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
491		589
492	=item $guard = mon $port, $rcvport	590	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
493		591
494	=item $guard = mon $port	592	=item $guard = mon $port # kill $SELF when $port dies
495		593
496	=item $guard = mon $port, $rcvport, @msg	594	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		595
498	Monitor the given port and do something when the port is killed or	596	Monitor the given port and do something when the port is killed or
499	messages to it were lost, and optionally return a guard that can be used	597	messages to it were lost, and optionally return a guard that can be used
500	to stop monitoring again.	598	to stop monitoring again.
501
502	C<mon> effectively guarantees that, in the absence of hardware failures,
503	that after starting the monitor, either all messages sent to the port
504	will arrive, or the monitoring action will be invoked after possible
505	message loss has been detected. No messages will be lost "in between"
506	(after the first lost message no further messages will be received by the
507	port). After the monitoring action was invoked, further messages might get
508	delivered again.
509
510	Note that monitoring-actions are one-shot: once released, they are removed
511	and will not trigger again.
512		599
513	In the first form (callback), the callback is simply called with any	600	In the first form (callback), the callback is simply called with any
514	number of C<@reason> elements (no @reason means that the port was deleted	601	number of C<@reason> elements (no @reason means that the port was deleted
515	"normally"). Note also that I<< the callback B<must> never die >>, so use	602	"normally"). Note also that I<< the callback B<must> never die >>, so use
516	C<eval> if unsure.	603	C<eval> if unsure.
517		604
518	In the second form (another port given), the other port (C<$rcvport>)	605	In the second form (another port given), the other port (C<$rcvport>)
519	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	606	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
520	"normal" kils nothing happens, while under all other conditions, the other	607	"normal" kils nothing happens, while under all other conditions, the other
521	port is killed with the same reason.	608	port is killed with the same reason.
522		609
523	The third form (kill self) is the same as the second form, except that	610	The third form (kill self) is the same as the second form, except that
524	C<$rvport> defaults to C<$SELF>.	611	C<$rvport> defaults to C<$SELF>.
525		612
526	In the last form (message), a message of the form C<@msg, @reason> will be	613	In the last form (message), a message of the form C<@msg, @reason> will be
527	C<snd>.	614	C<snd>.
		615
		616	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		617	alert was raised), they are removed and will not trigger again.
528		618
529	As a rule of thumb, monitoring requests should always monitor a port from	619	As a rule of thumb, monitoring requests should always monitor a port from
530	a local port (or callback). The reason is that kill messages might get	620	a local port (or callback). The reason is that kill messages might get
531	lost, just like any other message. Another less obvious reason is that	621	lost, just like any other message. Another less obvious reason is that
532	even monitoring requests can get lost (for exmaple, when the connection	622	even monitoring requests can get lost (for example, when the connection
533	to the other node goes down permanently). When monitoring a port locally	623	to the other node goes down permanently). When monitoring a port locally
534	these problems do not exist.	624	these problems do not exist.
535		625
		626	C<mon> effectively guarantees that, in the absence of hardware failures,
		627	after starting the monitor, either all messages sent to the port will
		628	arrive, or the monitoring action will be invoked after possible message
		629	loss has been detected. No messages will be lost "in between" (after
		630	the first lost message no further messages will be received by the
		631	port). After the monitoring action was invoked, further messages might get
		632	delivered again.
		633
		634	Inter-host-connection timeouts and monitoring depend on the transport
		635	used. The only transport currently implemented is TCP, and AnyEvent::MP
		636	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		637	non-idle connection, and usually around two hours for idle connections).
		638
		639	This means that monitoring is good for program errors and cleaning up
		640	stuff eventually, but they are no replacement for a timeout when you need
		641	to ensure some maximum latency.
		642
536	Example: call a given callback when C<$port> is killed.	643	Example: call a given callback when C<$port> is killed.
537		644
538	mon $port, sub { warn "port died because of <@_>\n" };	645	mon $port, sub { warn "port died because of <@_>\n" };
539		646
540	Example: kill ourselves when C<$port> is killed abnormally.	647	Example: kill ourselves when C<$port> is killed abnormally.
…		…
546	mon $port, $self => "restart";	653	mon $port, $self => "restart";
547		654
548	=cut	655	=cut
549		656
550	sub mon {	657	sub mon {
551	my ($noderef, $port) = split /#/, shift, 2;	658	my ($nodeid, $port) = split /#/, shift, 2;
552		659
553	my $node = $NODE{$noderef} \|\| add_node $noderef;	660	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
554		661
555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	662	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
556		663
557	unless (ref $cb) {	664	unless (ref $cb) {
558	if (@_) {	665	if (@_) {
…		…
567	}	674	}
568		675
569	$node->monitor ($port, $cb);	676	$node->monitor ($port, $cb);
570		677
571	defined wantarray	678	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	679	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
573	}	680	}
574		681
575	=item $guard = mon_guard $port, $ref, $ref...	682	=item $guard = mon_guard $port, $ref, $ref...
576		683
577	Monitors the given C<$port> and keeps the passed references. When the port	684	Monitors the given C<$port> and keeps the passed references. When the port
578	is killed, the references will be freed.	685	is killed, the references will be freed.
579		686
580	Optionally returns a guard that will stop the monitoring.	687	Optionally returns a guard that will stop the monitoring.
581		688
582	This function is useful when you create e.g. timers or other watchers and	689	This function is useful when you create e.g. timers or other watchers and
583	want to free them when the port gets killed:	690	want to free them when the port gets killed (note the use of C<psub>):
584		691
585	$port->rcv (start => sub {	692	$port->rcv (start => sub {
586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	693	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
587	undef $timer if 0.9 < rand;	694	undef $timer if 0.9 < rand;
588	});	695	});
589	});	696	});
590		697
591	=cut	698	=cut
…		…
600		707
601	=item kil $port[, @reason]	708	=item kil $port[, @reason]
602		709
603	Kill the specified port with the given C<@reason>.	710	Kill the specified port with the given C<@reason>.
604		711
605	If no C<@reason> is specified, then the port is killed "normally" (linked	712	If no C<@reason> is specified, then the port is killed "normally" -
606	ports will not be kileld, or even notified).	713	monitor callback will be invoked, but the kil will not cause linked ports
		714	(C<mon $mport, $lport> form) to get killed.
607		715
608	Otherwise, linked ports get killed with the same reason (second form of	716	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
609	C<mon>, see below).	717	form) get killed with the same reason.
610		718
611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	719	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
612	will be reported as reason C<< die => $@ >>.	720	will be reported as reason C<< die => $@ >>.
613		721
614	Transport/communication errors are reported as C<< transport_error =>	722	Transport/communication errors are reported as C<< transport_error =>
…		…
619	=item $port = spawn $node, $initfunc[, @initdata]	727	=item $port = spawn $node, $initfunc[, @initdata]
620		728
621	Creates a port on the node C<$node> (which can also be a port ID, in which	729	Creates a port on the node C<$node> (which can also be a port ID, in which
622	case it's the node where that port resides).	730	case it's the node where that port resides).
623		731
624	The port ID of the newly created port is return immediately, and it is	732	The port ID of the newly created port is returned immediately, and it is
625	permissible to immediately start sending messages or monitor the port.	733	possible to immediately start sending messages or to monitor the port.
626		734
627	After the port has been created, the init function is	735	After the port has been created, the init function is called on the remote
628	called. This function must be a fully-qualified function name	736	node, in the same context as a C<rcv> callback. This function must be a
629	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	737	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
630	program, use C<::name>.	738	specify a function in the main program, use C<::name>.
631		739
632	If the function doesn't exist, then the node tries to C<require>	740	If the function doesn't exist, then the node tries to C<require>
633	the package, then the package above the package and so on (e.g.	741	the package, then the package above the package and so on (e.g.
634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	742	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
635	exists or it runs out of package names.	743	exists or it runs out of package names.
636		744
637	The init function is then called with the newly-created port as context	745	The init function is then called with the newly-created port as context
638	object (C<$SELF>) and the C<@initdata> values as arguments.	746	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		747	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		748	the port might not get created.
639		749
640	A common idiom is to pass your own port, monitor the spawned port, and	750	A common idiom is to pass a local port, immediately monitor the spawned
641	in the init function, monitor the original port. This two-way monitoring	751	port, and in the remote init function, immediately monitor the passed
642	ensures that both ports get cleaned up when there is a problem.	752	local port. This two-way monitoring ensures that both ports get cleaned up
		753	when there is a problem.
		754
		755	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		756	caller before C<spawn> returns (by delaying invocation when spawn is
		757	called for the local node).
643		758
644	Example: spawn a chat server port on C<$othernode>.	759	Example: spawn a chat server port on C<$othernode>.
645		760
646	# this node, executed from within a port context:	761	# this node, executed from within a port context:
647	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	762	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
662		777
663	sub _spawn {	778	sub _spawn {
664	my $port = shift;	779	my $port = shift;
665	my $init = shift;	780	my $init = shift;
666		781
		782	# rcv will create the actual port
667	local $SELF = "$NODE#$port";	783	local $SELF = "$NODE#$port";
668	eval {	784	eval {
669	&{ load_func $init }	785	&{ load_func $init }
670	};	786	};
671	_self_die if $@;	787	_self_die if $@;
672	}	788	}
673		789
674	sub spawn(@) {	790	sub spawn(@) {
675	my ($noderef, undef) = split /#/, shift, 2;	791	my ($nodeid, undef) = split /#/, shift, 2;
676		792
677	my $id = "$RUNIQ." . $ID++;	793	my $id = $RUNIQ . ++$ID;
678		794
679	$_[0] =~ /::/	795	$_[0] =~ /::/
680	or Carp::croak "spawn init function must be a fully-qualified name, caught";	796	or Carp::croak "spawn init function must be a fully-qualified name, caught";
681		797
682	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	798	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
683		799
684	"$noderef#$id"	800	"$nodeid#$id"
685	}	801	}
		802
686		803
687	=item after $timeout, @msg	804	=item after $timeout, @msg
688		805
689	=item after $timeout, $callback	806	=item after $timeout, $callback
690		807
691	Either sends the given message, or call the given callback, after the	808	Either sends the given message, or call the given callback, after the
692	specified number of seconds.	809	specified number of seconds.
693		810
694	This is simply a utility function that come sin handy at times.	811	This is simply a utility function that comes in handy at times - the
		812	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		813	so it may go away in the future.
695		814
696	=cut	815	=cut
697		816
698	sub after($@) {	817	sub after($@) {
699	my ($timeout, @action) = @_;	818	my ($timeout, @action) = @_;
…		…
704	? $action[0]()	823	? $action[0]()
705	: snd @action;	824	: snd @action;
706	};	825	};
707	}	826	}
708		827
		828	=item cal $port, @msg, $callback[, $timeout]
		829
		830	A simple form of RPC - sends a message to the given C<$port> with the
		831	given contents (C<@msg>), but adds a reply port to the message.
		832
		833	The reply port is created temporarily just for the purpose of receiving
		834	the reply, and will be C<kil>ed when no longer needed.
		835
		836	A reply message sent to the port is passed to the C<$callback> as-is.
		837
		838	If an optional time-out (in seconds) is given and it is not C<undef>,
		839	then the callback will be called without any arguments after the time-out
		840	elapsed and the port is C<kil>ed.
		841
		842	If no time-out is given (or it is C<undef>), then the local port will
		843	monitor the remote port instead, so it eventually gets cleaned-up.
		844
		845	Currently this function returns the temporary port, but this "feature"
		846	might go in future versions unless you can make a convincing case that
		847	this is indeed useful for something.
		848
		849	=cut
		850
		851	sub cal(@) {
		852	my $timeout = ref $_[-1] ? undef : pop;
		853	my $cb = pop;
		854
		855	my $port = port {
		856	undef $timeout;
		857	kil $SELF;
		858	&$cb;
		859	};
		860
		861	if (defined $timeout) {
		862	$timeout = AE::timer $timeout, 0, sub {
		863	undef $timeout;
		864	kil $port;
		865	$cb->();
		866	};
		867	} else {
		868	mon $_[0], sub {
		869	kil $port;
		870	$cb->();
		871	};
		872	}
		873
		874	push @_, $port;
		875	&snd;
		876
		877	$port
		878	}
		879
		880	=back
		881
		882	=head1 DISTRIBUTED DATABASE
		883
		884	AnyEvent::MP comes with a simple distributed database. The database will
		885	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		886	the global nodes for their needs.
		887
		888	The database consists of a two-level hash - a hash contains a hash which
		889	contains values.
		890
		891	The top level hash key is called "family", and the second-level hash key
		892	is simply called "key".
		893
		894	The family must be alphanumeric, i.e. start with a letter and consist
		895	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		896	pretty much like Perl module names.
		897
		898	As the family namespace is global, it is recommended to prefix family names
		899	with the name of the application or module using it.
		900
		901	The keys must be strings, with no other limitations.
		902
		903	The values should preferably be strings, but other perl scalars should
		904	work as well (such as undef, arrays and hashes).
		905
		906	Every database entry is owned by one node - adding the same family/key
		907	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		908	but the result might be nondeterministic, i.e. the key might have
		909	different values on different nodes.
		910
		911	=item db_set $family => $key => $value
		912
		913	Sets (or replaces) a key to the database.
		914
		915	=item db_del $family => $key
		916
		917	Deletes a key from the database.
		918
		919	=item $guard = db_reg $family => $key [=> $value]
		920
		921	Sets the key on the database and returns a guard. When the guard is
		922	destroyed, the key is deleted from the database. If C<$value> is missing,
		923	then C<undef> is used.
		924
		925	=cut
		926
709	=back	927	=back
710		928
711	=head1 AnyEvent::MP vs. Distributed Erlang	929	=head1 AnyEvent::MP vs. Distributed Erlang
712		930
713	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	931	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
714	== aemp node, Erlang process == aemp port), so many of the documents and	932	== aemp node, Erlang process == aemp port), so many of the documents and
715	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	933	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
716	sample:	934	sample:
717		935
718	http://www.Erlang.se/doc/programming_rules.shtml	936	http://www.erlang.se/doc/programming_rules.shtml
719	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	937	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
720	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	938	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
721	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	939	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
722		940
723	Despite the similarities, there are also some important differences:	941	Despite the similarities, there are also some important differences:
724		942
725	=over 4	943	=over 4
726		944
727	=item * Node references contain the recipe on how to contact them.	945	=item * Node IDs are arbitrary strings in AEMP.
728		946
729	Erlang relies on special naming and DNS to work everywhere in the	947	Erlang relies on special naming and DNS to work everywhere in the same
730	same way. AEMP relies on each node knowing it's own address(es), with	948	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
731	convenience functionality.	949	configuration or DNS), and possibly the addresses of some seed nodes, but
732		950	will otherwise discover other nodes (and their IDs) itself.
733	This means that AEMP requires a less tightly controlled environment at the
734	cost of longer node references and a slightly higher management overhead.
735		951
736	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	952	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
737	uses "local ports are like remote ports".	953	uses "local ports are like remote ports".
738		954
739	The failure modes for local ports are quite different (runtime errors	955	The failure modes for local ports are quite different (runtime errors
…		…
748	ports being the special case/exception, where transport errors cannot	964	ports being the special case/exception, where transport errors cannot
749	occur.	965	occur.
750		966
751	=item * Erlang uses processes and a mailbox, AEMP does not queue.	967	=item * Erlang uses processes and a mailbox, AEMP does not queue.
752		968
753	Erlang uses processes that selectively receive messages, and therefore	969	Erlang uses processes that selectively receive messages out of order, and
754	needs a queue. AEMP is event based, queuing messages would serve no	970	therefore needs a queue. AEMP is event based, queuing messages would serve
755	useful purpose. For the same reason the pattern-matching abilities of	971	no useful purpose. For the same reason the pattern-matching abilities
756	AnyEvent::MP are more limited, as there is little need to be able to	972	of AnyEvent::MP are more limited, as there is little need to be able to
757	filter messages without dequeing them.	973	filter messages without dequeuing them.
758		974
759	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	975	This is not a philosophical difference, but simply stems from AnyEvent::MP
		976	being event-based, while Erlang is process-based.
		977
		978	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		979	top of AEMP and Coro threads.
760		980
761	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	981	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
762		982
763	Sending messages in Erlang is synchronous and blocks the process (and	983	Sending messages in Erlang is synchronous and blocks the process until
		984	a conenction has been established and the message sent (and so does not
764	so does not need a queue that can overflow). AEMP sends are immediate,	985	need a queue that can overflow). AEMP sends return immediately, connection
765	connection establishment is handled in the background.	986	establishment is handled in the background.
766		987
767	=item * Erlang suffers from silent message loss, AEMP does not.	988	=item * Erlang suffers from silent message loss, AEMP does not.
768		989
769	Erlang makes few guarantees on messages delivery - messages can get lost	990	Erlang implements few guarantees on messages delivery - messages can get
770	without any of the processes realising it (i.e. you send messages a, b,	991	lost without any of the processes realising it (i.e. you send messages a,
771	and c, and the other side only receives messages a and c).	992	b, and c, and the other side only receives messages a and c).
772		993
773	AEMP guarantees correct ordering, and the guarantee that there are no	994	AEMP guarantees (modulo hardware errors) correct ordering, and the
		995	guarantee that after one message is lost, all following ones sent to the
		996	same port are lost as well, until monitoring raises an error, so there are
774	holes in the message sequence.	997	no silent "holes" in the message sequence.
775		998
776	=item * In Erlang, processes can be declared dead and later be found to be	999	If you want your software to be very reliable, you have to cope with
777	alive.	1000	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
778		1001	simply tries to work better in common error cases, such as when a network
779	In Erlang it can happen that a monitored process is declared dead and	1002	link goes down.
780	linked processes get killed, but later it turns out that the process is
781	still alive - and can receive messages.
782
783	In AEMP, when port monitoring detects a port as dead, then that port will
784	eventually be killed - it cannot happen that a node detects a port as dead
785	and then later sends messages to it, finding it is still alive.
786		1003
787	=item * Erlang can send messages to the wrong port, AEMP does not.	1004	=item * Erlang can send messages to the wrong port, AEMP does not.
788		1005
789	In Erlang it is quite likely that a node that restarts reuses a process ID	1006	In Erlang it is quite likely that a node that restarts reuses an Erlang
790	known to other nodes for a completely different process, causing messages	1007	process ID known to other nodes for a completely different process,
791	destined for that process to end up in an unrelated process.	1008	causing messages destined for that process to end up in an unrelated
		1009	process.
792		1010
793	AEMP never reuses port IDs, so old messages or old port IDs floating	1011	AEMP does not reuse port IDs, so old messages or old port IDs floating
794	around in the network will not be sent to an unrelated port.	1012	around in the network will not be sent to an unrelated port.
795		1013
796	=item * Erlang uses unprotected connections, AEMP uses secure	1014	=item * Erlang uses unprotected connections, AEMP uses secure
797	authentication and can use TLS.	1015	authentication and can use TLS.
798		1016
799	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1017	AEMP can use a proven protocol - TLS - to protect connections and
800	securely authenticate nodes.	1018	securely authenticate nodes.
801		1019
802	=item * The AEMP protocol is optimised for both text-based and binary	1020	=item * The AEMP protocol is optimised for both text-based and binary
803	communications.	1021	communications.
804		1022
805	The AEMP protocol, unlike the Erlang protocol, supports both	1023	The AEMP protocol, unlike the Erlang protocol, supports both programming
806	language-independent text-only protocols (good for debugging) and binary,	1024	language independent text-only protocols (good for debugging), and binary,
807	language-specific serialisers (e.g. Storable).	1025	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1026	used, the protocol is actually completely text-based.
808		1027
809	It has also been carefully designed to be implementable in other languages	1028	It has also been carefully designed to be implementable in other languages
810	with a minimum of work while gracefully degrading fucntionality to make the	1029	with a minimum of work while gracefully degrading functionality to make the
811	protocol simple.	1030	protocol simple.
812		1031
813	=item * AEMP has more flexible monitoring options than Erlang.	1032	=item * AEMP has more flexible monitoring options than Erlang.
814		1033
815	In Erlang, you can chose to receive I<all> exit signals as messages	1034	In Erlang, you can chose to receive I<all> exit signals as messages or
816	or I<none>, there is no in-between, so monitoring single processes is	1035	I<none>, there is no in-between, so monitoring single Erlang processes is
817	difficult to implement. Monitoring in AEMP is more flexible than in	1036	difficult to implement.
818	Erlang, as one can choose between automatic kill, exit message or callback	1037
819	on a per-process basis.	1038	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1039	between automatic kill, exit message or callback on a per-port basis.
820		1040
821	=item * Erlang tries to hide remote/local connections, AEMP does not.	1041	=item * Erlang tries to hide remote/local connections, AEMP does not.
822		1042
823	Monitoring in Erlang is not an indicator of process death/crashes,	1043	Monitoring in Erlang is not an indicator of process death/crashes, in the
824	as linking is (except linking is unreliable in Erlang).	1044	same way as linking is (except linking is unreliable in Erlang).
825		1045
826	In AEMP, you don't "look up" registered port names or send to named ports	1046	In AEMP, you don't "look up" registered port names or send to named ports
827	that might or might not be persistent. Instead, you normally spawn a port	1047	that might or might not be persistent. Instead, you normally spawn a port
828	on the remote node. The init function monitors the you, and you monitor	1048	on the remote node. The init function monitors you, and you monitor the
829	the remote port. Since both monitors are local to the node, they are much	1049	remote port. Since both monitors are local to the node, they are much more
830	more reliable.	1050	reliable (no need for C<spawn_link>).
831		1051
832	This also saves round-trips and avoids sending messages to the wrong port	1052	This also saves round-trips and avoids sending messages to the wrong port
833	(hard to do in Erlang).	1053	(hard to do in Erlang).
834		1054
835	=back	1055	=back
836		1056
837	=head1 RATIONALE	1057	=head1 RATIONALE
838		1058
839	=over 4	1059	=over 4
840		1060
841	=item Why strings for ports and noderefs, why not objects?	1061	=item Why strings for port and node IDs, why not objects?
842		1062
843	We considered "objects", but found that the actual number of methods	1063	We considered "objects", but found that the actual number of methods
844	thatc an be called are very low. Since port IDs and noderefs travel over	1064	that can be called are quite low. Since port and node IDs travel over
845	the network frequently, the serialising/deserialising would add lots of	1065	the network frequently, the serialising/deserialising would add lots of
846	overhead, as well as having to keep a proxy object.	1066	overhead, as well as having to keep a proxy object everywhere.
847		1067
848	Strings can easily be printed, easily serialised etc. and need no special	1068	Strings can easily be printed, easily serialised etc. and need no special
849	procedures to be "valid".	1069	procedures to be "valid".
850		1070
851	And a a miniport consists of a single closure stored in a global hash - it	1071	And as a result, a port with just a default receiver consists of a single
852	can't become much cheaper.	1072	code reference stored in a global hash - it can't become much cheaper.
853		1073
854	=item Why favour JSON, why not real serialising format such as Storable?	1074	=item Why favour JSON, why not a real serialising format such as Storable?
855		1075
856	In fact, any AnyEvent::MP node will happily accept Storable as framing	1076	In fact, any AnyEvent::MP node will happily accept Storable as framing
857	format, but currently there is no way to make a node use Storable by	1077	format, but currently there is no way to make a node use Storable by
858	default.	1078	default (although all nodes will accept it).
859		1079
860	The default framing protocol is JSON because a) JSON::XS is many times	1080	The default framing protocol is JSON because a) JSON::XS is many times
861	faster for small messages and b) most importantly, after years of	1081	faster for small messages and b) most importantly, after years of
862	experience we found that object serialisation is causing more problems	1082	experience we found that object serialisation is causing more problems
863	than it gains: Just like function calls, objects simply do not travel	1083	than it solves: Just like function calls, objects simply do not travel
864	easily over the network, mostly because they will always be a copy, so you	1084	easily over the network, mostly because they will always be a copy, so you
865	always have to re-think your design.	1085	always have to re-think your design.
866		1086
867	Keeping your messages simple, concentrating on data structures rather than	1087	Keeping your messages simple, concentrating on data structures rather than
868	objects, will keep your messages clean, tidy and efficient.	1088	objects, will keep your messages clean, tidy and efficient.
869		1089
870	=back	1090	=back
871		1091
872	=head1 SEE ALSO	1092	=head1 SEE ALSO
873		1093
		1094	L<AnyEvent::MP::Intro> - a gentle introduction.
		1095
		1096	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1097
		1098	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1099	your applications.
		1100
		1101	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1102
		1103	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1104	all nodes.
		1105
874	L<AnyEvent>.	1106	L<AnyEvent>.
875		1107
876	=head1 AUTHOR	1108	=head1 AUTHOR
877		1109
878	Marc Lehmann <schmorp@schmorp.de>	1110	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.61 by root, Mon Aug 24 08:06:49 2009 UTC vs.
Revision 1.125 by root, Sat Mar 3 13:07:19 2012 UTC