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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs.
Revision 1.121 by root, Tue Feb 28 18:37:24 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $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<#>) as
80	separator, and a port name (a printable string of unspecified format). An	88	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		89
84	=item node	90	=item node
85		91
86	A node is a single process containing at least one port - the node port,	92	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	93	which enables nodes to manage each other remotely, and to create new
88	ports.	94	ports.
89		95
90	Nodes are either private (single-process only), slaves (connected to a	96	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	97	(no listening ports). Private nodes cannot talk to other private nodes
		98	currently, but all nodes can talk to public nodes.
92		99
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	100	Nodes is represented by (printable) strings called "node IDs".
94		101
95	A node reference is a string that either simply identifies the node (for	102	=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		103
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	104	A node ID is a string that uniquely identifies the node within a
100	TCP/IP, other protocols might look different).	105	network. Depending on the configuration used, node IDs can look like a
		106	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		107	doesn't interpret node IDs in any way except to uniquely identify a node.
101		108
102	Node references come in two flavours: resolved (containing only numerical	109	=item binds - C<ip:port>
103	addresses) or unresolved (where hostnames are used instead of addresses).
104		110
105	Before using an unresolved node reference in a message you first have to	111	Nodes can only talk to each other by creating some kind of connection to
106	resolve it.	112	each other. To do this, nodes should listen on one or more local transport
		113	endpoints - binds.
		114
		115	Currently, only standard C<ip:port> specifications can be used, which
		116	specify TCP ports to listen on. So a bind is basically just a tcp socket
		117	in listening mode thta accepts conenctions form other nodes.
		118
		119	=item seed nodes
		120
		121	When a node starts, it knows nothing about the network it is in - it
		122	needs to connect to at least one other node that is already in the
		123	network. These other nodes are called "seed nodes".
		124
		125	Seed nodes themselves are not special - they are seed nodes only because
		126	some other node I<uses> them as such, but any node can be used as seed
		127	node for other nodes, and eahc node cna use a different set of seed nodes.
		128
		129	In addition to discovering the network, seed nodes are also used to
		130	maintain the network - all nodes using the same seed node form are part of
		131	the same network. If a network is split into multiple subnets because e.g.
		132	the network link between the parts goes down, then using the same seed
		133	nodes for all nodes ensures that eventually the subnets get merged again.
		134
		135	Seed nodes are expected to be long-running, and at least one seed node
		136	should always be available. They should also be relatively responsive - a
		137	seed node that blocks for long periods will slow down everybody else.
		138
		139	For small networks, it's best if every node uses the same set of seed
		140	nodes. For large networks, it can be useful to specify "regional" seed
		141	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		142	each other. What's important is that all seed nodes connections form a
		143	complete graph, so that the network cannot split into separate subnets
		144	forever.
		145
		146	Seed nodes are represented by seed IDs.
		147
		148	=item seed IDs - C<host:port>
		149
		150	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		151	TCP port) of nodes that should be used as seed nodes.
		152
		153	=item global nodes
		154
		155	An AEMP network needs a discovery service - nodes need to know how to
		156	connect to other nodes they only know by name. In addition, AEMP offers a
		157	distributed "group database", which maps group names to a list of strings
		158	- for example, to register worker ports.
		159
		160	A network needs at least one global node to work, and allows every node to
		161	be a global node.
		162
		163	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		164	node and tries to keep connections to all other nodes. So while it can
		165	make sense to make every node "global" in small networks, it usually makes
		166	sense to only make seed nodes into global nodes in large networks (nodes
		167	keep connections to seed nodes and global nodes, so makign them the same
		168	reduces overhead).
107		169
108	=back	170	=back
109		171
110	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
111		173
113		175
114	=cut	176	=cut
115		177
116	package AnyEvent::MP;	178	package AnyEvent::MP;
117		179
		180	use AnyEvent::MP::Config ();
118	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
119		183
120	use common::sense;	184	use common::sense;
121		185
122	use Carp ();	186	use Carp ();
123		187
124	use AE ();	188	use AE ();
125		189
126	use base "Exporter";	190	use base "Exporter";
127		191
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
129		193
130	our @EXPORT = qw(	194	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	195	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	196	configure
133	snd rcv mon kil reg psub spawn	197	snd rcv mon mon_guard kil psub peval spawn cal
134	port	198	port
135	);	199	);
136		200
137	our $SELF;	201	our $SELF;
138		202
…		…
142	kil $SELF, die => $msg;	206	kil $SELF, die => $msg;
143	}	207	}
144		208
145	=item $thisnode = NODE / $NODE	209	=item $thisnode = NODE / $NODE
146		210
147	The C<NODE> function returns, and the C<$NODE> variable contains the	211	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	212	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	213	a call to C<configure>.
150		214
151	=item $noderef = node_of $port	215	=item $nodeid = node_of $port
152		216
153	Extracts and returns the noderef from a port ID or a noderef.	217	Extracts and returns the node ID from a port ID or a node ID.
154		218
155	=item initialise_node $noderef, $seednode, $seednode...	219	=item configure $profile, key => value...
156		220
157	=item initialise_node "slave/", $master, $master...	221	=item configure key => value...
158		222
159	Before a node can talk to other nodes on the network it has to initialise	223	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	224	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	225	to know is its own name, and optionally it should know the addresses of
		226	some other nodes in the network to discover other nodes.
162		227
163	This function initialises a node - it must be called exactly once (or	228	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	229	never) before calling other AnyEvent::MP functions.
165		230
166	All arguments (optionally except for the first) are noderefs, which can be	231	The key/value pairs are basically the same ones as documented for the
167	either resolved or unresolved.	232	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		233
177	=over 4	234	=over 4
178		235
179	=item public nodes	236	=item norc => $boolean (default false)
180		237
181	For public nodes, C<$noderef> (supplied either directly to	238	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	239	be consulted - all configuraiton options must be specified in the
183	noderef (possibly unresolved, in which case it will be resolved).	240	C<configure> call.
184		241
185	After resolving, the node will bind itself on all endpoints and try to	242	=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		243
190	=item slave nodes	244	IF true, then the values specified in the C<configure> will take
191		245	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)	246	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		247
202	=back	248	=back
203		249
204	This function will block until all nodes have been resolved and, for slave
205	nodes, until it has successfully established a connection to a master
206	server.
207
208	Example: become a public node listening on the guessed noderef, or the one
209	specified via C<aemp> for the current node. This should be the most common
210	form of invocation for "daemon"-type nodes.
211
212	initialise_node;
213
214	Example: become a slave node to any of the the seednodes specified via
215	C<aemp>. This form is often used for commandline clients.
216
217	initialise_node "slave/";
218
219	Example: become a slave node to any of the specified master servers. This
220	form is also often used for commandline clients.
221
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
223
224	Example: become a public node, and try to contact some well-known master
225	servers to become part of the network.
226
227	initialise_node undef, "master1", "master2";
228
229	Example: become a public node listening on port C<4041>.
230
231	initialise_node 4041;
232
233	Example: become a public node, only visible on localhost port 4044.
234
235	initialise_node "localhost:4044";
236
237	=item $cv = resolve_node $noderef
238
239	Takes an unresolved node reference that may contain hostnames and
240	abbreviated IDs, resolves all of them and returns a resolved node
241	reference.
242
243	In addition to C<address:port> pairs allowed in resolved noderefs, the
244	following forms are supported:
245
246	=over 4	250	=over 4
247		251
248	=item the empty string	252	=item step 1, gathering configuration from profiles
249		253
250	An empty-string component gets resolved as if the default port (4040) was	254	The function first looks up a profile in the aemp configuration (see the
251	specified.	255	L<aemp> commandline utility). The profile name can be specified via the
		256	named C<profile> parameter or can simply be the first parameter). If it is
		257	missing, then the nodename (F<uname -n>) will be used as profile name.
252		258
253	=item naked port numbers (e.g. C<1234>)	259	The profile data is then gathered as follows:
254		260
255	These are resolved by prepending the local nodename and a colon, to be	261	First, all remaining key => value pairs (all of which are conveniently
256	further resolved.	262	undocumented at the moment) will be interpreted as configuration
		263	data. Then they will be overwritten by any values specified in the global
		264	default configuration (see the F<aemp> utility), then the chain of
		265	profiles chosen by the profile name (and any C<parent> attributes).
257		266
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	267	That means that the values specified in the profile have highest priority
		268	and the values specified directly via C<configure> have lowest priority,
		269	and can only be used to specify defaults.
259		270
260	These are resolved by using AnyEvent::DNS to resolve them, optionally	271	If the profile specifies a node ID, then this will become the node ID of
261	looking up SRV records for the C<aemp=4040> port, if no port was	272	this process. If not, then the profile name will be used as node ID. The
262	specified.	273	special node ID of C<anon/> will be replaced by a random node ID.
		274
		275	=item step 2, bind listener sockets
		276
		277	The next step is to look up the binds in the profile, followed by binding
		278	aemp protocol listeners on all binds specified (it is possible and valid
		279	to have no binds, meaning that the node cannot be contacted form the
		280	outside. This means the node cannot talk to other nodes that also have no
		281	binds, but it can still talk to all "normal" nodes).
		282
		283	If the profile does not specify a binds list, then a default of C<*> is
		284	used, meaning the node will bind on a dynamically-assigned port on every
		285	local IP address it finds.
		286
		287	=item step 3, connect to seed nodes
		288
		289	As the last step, the seed ID list from the profile is passed to the
		290	L<AnyEvent::MP::Global> module, which will then use it to keep
		291	connectivity with at least one node at any point in time.
263		292
264	=back	293	=back
		294
		295	Example: become a distributed node using the local node name as profile.
		296	This should be the most common form of invocation for "daemon"-type nodes.
		297
		298	configure
		299
		300	Example: become an anonymous node. This form is often used for commandline
		301	clients.
		302
		303	configure nodeid => "anon/";
		304
		305	Example: configure a node using a profile called seed, which is suitable
		306	for a seed node as it binds on all local addresses on a fixed port (4040,
		307	customary for aemp).
		308
		309	# use the aemp commandline utility
		310	# aemp profile seed nodeid anon/ binds '*:4040'
		311
		312	# then use it
		313	configure profile => "seed";
		314
		315	# or simply use aemp from the shell again:
		316	# aemp run profile seed
		317
		318	# or provide a nicer-to-remember nodeid
		319	# aemp run profile seed nodeid "$(hostname)"
265		320
266	=item $SELF	321	=item $SELF
267		322
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	323	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	324	blocks.
270		325
271	=item SELF, %SELF, @SELF...	326	=item *SELF, SELF, %SELF, @SELF...
272		327
273	Due to some quirks in how perl exports variables, it is impossible to	328	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	329	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	330	module, but only C<$SELF> is currently used.
276		331
277	=item snd $port, type => @data	332	=item snd $port, type => @data
278		333
279	=item snd $port, @msg	334	=item snd $port, @msg
280		335
281	Send the given message to the given port ID, which can identify either	336	Send the given message to the given port, which can identify either a
282	a local or a remote port, and must be a port ID.	337	local or a remote port, and must be a port ID.
283		338
284	While the message can be about anything, it is highly recommended to use a	339	While the message can be almost anything, it is highly recommended to
285	string as first element (a port ID, or some word that indicates a request	340	use a string as first element (a port ID, or some word that indicates a
286	type etc.).	341	request type etc.) and to consist if only simple perl values (scalars,
		342	arrays, hashes) - if you think you need to pass an object, think again.
287		343
288	The message data effectively becomes read-only after a call to this	344	The message data logically becomes read-only after a call to this
289	function: modifying any argument is not allowed and can cause many	345	function: modifying any argument (or values referenced by them) is
290	problems.	346	forbidden, as there can be considerable time between the call to C<snd>
		347	and the time the message is actually being serialised - in fact, it might
		348	never be copied as within the same process it is simply handed to the
		349	receiving port.
291		350
292	The type of data you can transfer depends on the transport protocol: when	351	The type of data you can transfer depends on the transport protocol: when
293	JSON is used, then only strings, numbers and arrays and hashes consisting	352	JSON is used, then only strings, numbers and arrays and hashes consisting
294	of those are allowed (no objects). When Storable is used, then anything	353	of those are allowed (no objects). When Storable is used, then anything
295	that Storable can serialise and deserialise is allowed, and for the local	354	that Storable can serialise and deserialise is allowed, and for the local
296	node, anything can be passed.	355	node, anything can be passed. Best rely only on the common denominator of
		356	these.
297		357
298	=item $local_port = port	358	=item $local_port = port
299		359
300	Create a new local port object and returns its port ID. Initially it has	360	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	361	no callbacks set and will throw an error when it receives messages.
…		…
325	sub _kilme {	385	sub _kilme {
326	die "received message on port without callback";	386	die "received message on port without callback";
327	}	387	}
328		388
329	sub port(;&) {	389	sub port(;&) {
330	my $id = "$UNIQ." . $ID++;	390	my $id = "$UNIQ." . ++$ID;
331	my $port = "$NODE#$id";	391	my $port = "$NODE#$id";
332		392
333	rcv $port, shift \|\| \&_kilme;	393	rcv $port, shift \|\| \&_kilme;
334		394
335	$port	395	$port
…		…
374	msg1 => sub { ... },	434	msg1 => sub { ... },
375	...	435	...
376	;	436	;
377		437
378	Example: temporarily register a rcv callback for a tag matching some port	438	Example: temporarily register a rcv callback for a tag matching some port
379	(e.g. for a rpc reply) and unregister it after a message was received.	439	(e.g. for an rpc reply) and unregister it after a message was received.
380		440
381	rcv $port, $otherport => sub {	441	rcv $port, $otherport => sub {
382	my @reply = @_;	442	my @reply = @_;
383		443
384	rcv $SELF, $otherport;	444	rcv $SELF, $otherport;
…		…
386		446
387	=cut	447	=cut
388		448
389	sub rcv($@) {	449	sub rcv($@) {
390	my $port = shift;	450	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	451	my ($nodeid, $portid) = split /#/, $port, 2;
392		452
393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	453	$NODE{$nodeid} == $NODE{""}
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	454	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		455
396	while (@_) {	456	while (@_) {
397	if (ref $_[0]) {	457	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	458	if (my $self = $PORT_DATA{$portid}) {
399	"AnyEvent::MP::Port" eq ref $self	459	"AnyEvent::MP::Port" eq ref $self
400	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	460	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
401		461
402	$self->[2] = shift;	462	$self->[0] = shift;
403	} else {	463	} else {
404	my $cb = shift;	464	my $cb = shift;
405	$PORT{$portid} = sub {	465	$PORT{$portid} = sub {
406	local $SELF = $port;	466	local $SELF = $port;
407	eval { &$cb }; _self_die if $@;	467	eval { &$cb }; _self_die if $@;
408	};	468	};
409	}	469	}
410	} elsif (defined $_[0]) {	470	} elsif (defined $_[0]) {
411	my $self = $PORT_DATA{$portid} \|\|= do {	471	my $self = $PORT_DATA{$portid} \|\|= do {
412	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	472	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
413		473
414	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
415	local $SELF = $port;	475	local $SELF = $port;
416		476
417	if (my $cb = $self->[1]{$_[0]}) {	477	if (my $cb = $self->[1]{$_[0]}) {
…		…
439	}	499	}
440		500
441	$port	501	$port
442	}	502	}
443		503
		504	=item peval $port, $coderef[, @args]
		505
		506	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		507	when the code throews an exception the C<$port> will be killed.
		508
		509	Any remaining args will be passed to the callback. Any return values will
		510	be returned to the caller.
		511
		512	This is useful when you temporarily want to execute code in the context of
		513	a port.
		514
		515	Example: create a port and run some initialisation code in it's context.
		516
		517	my $port = port { ... };
		518
		519	peval $port, sub {
		520	init
		521	or die "unable to init";
		522	};
		523
		524	=cut
		525
		526	sub peval($$) {
		527	local $SELF = shift;
		528	my $cb = shift;
		529
		530	if (wantarray) {
		531	my @res = eval { &$cb };
		532	_self_die if $@;
		533	@res
		534	} else {
		535	my $res = eval { &$cb };
		536	_self_die if $@;
		537	$res
		538	}
		539	}
		540
444	=item $closure = psub { BLOCK }	541	=item $closure = psub { BLOCK }
445		542
446	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	543	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
447	closure is executed, sets up the environment in the same way as in C<rcv>	544	closure is executed, sets up the environment in the same way as in C<rcv>
448	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	545	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		546
		547	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		548	BLOCK }, @_ } >>.
449		549
450	This is useful when you register callbacks from C<rcv> callbacks:	550	This is useful when you register callbacks from C<rcv> callbacks:
451		551
452	rcv delayed_reply => sub {	552	rcv delayed_reply => sub {
453	my ($delay, @reply) = @_;	553	my ($delay, @reply) = @_;
…		…
477	$res	577	$res
478	}	578	}
479	}	579	}
480	}	580	}
481		581
482	=item $guard = mon $port, $cb->(@reason)	582	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483		583
484	=item $guard = mon $port, $rcvport	584	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485		585
486	=item $guard = mon $port	586	=item $guard = mon $port # kill $SELF when $port dies
487		587
488	=item $guard = mon $port, $rcvport, @msg	588	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		589
490	Monitor the given port and do something when the port is killed or	590	Monitor the given port and do something when the port is killed or
491	messages to it were lost, and optionally return a guard that can be used	591	messages to it were lost, and optionally return a guard that can be used
492	to stop monitoring again.	592	to stop monitoring again.
493
494	C<mon> effectively guarantees that, in the absence of hardware failures,
495	that after starting the monitor, either all messages sent to the port
496	will arrive, or the monitoring action will be invoked after possible
497	message loss has been detected. No messages will be lost "in between"
498	(after the first lost message no further messages will be received by the
499	port). After the monitoring action was invoked, further messages might get
500	delivered again.
501		593
502	In the first form (callback), the callback is simply called with any	594	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	595	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	596	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	597	C<eval> if unsure.
506		598
507	In the second form (another port given), the other port (C<$rcvport>)	599	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	600	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	601	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	602	port is killed with the same reason.
511		603
512	The third form (kill self) is the same as the second form, except that	604	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	605	C<$rvport> defaults to C<$SELF>.
514		606
515	In the last form (message), a message of the form C<@msg, @reason> will be	607	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	608	C<snd>.
		609
		610	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		611	alert was raised), they are removed and will not trigger again.
517		612
518	As a rule of thumb, monitoring requests should always monitor a port from	613	As a rule of thumb, monitoring requests should always monitor a port from
519	a local port (or callback). The reason is that kill messages might get	614	a local port (or callback). The reason is that kill messages might get
520	lost, just like any other message. Another less obvious reason is that	615	lost, just like any other message. Another less obvious reason is that
521	even monitoring requests can get lost (for exmaple, when the connection	616	even monitoring requests can get lost (for example, when the connection
522	to the other node goes down permanently). When monitoring a port locally	617	to the other node goes down permanently). When monitoring a port locally
523	these problems do not exist.	618	these problems do not exist.
524		619
		620	C<mon> effectively guarantees that, in the absence of hardware failures,
		621	after starting the monitor, either all messages sent to the port will
		622	arrive, or the monitoring action will be invoked after possible message
		623	loss has been detected. No messages will be lost "in between" (after
		624	the first lost message no further messages will be received by the
		625	port). After the monitoring action was invoked, further messages might get
		626	delivered again.
		627
		628	Inter-host-connection timeouts and monitoring depend on the transport
		629	used. The only transport currently implemented is TCP, and AnyEvent::MP
		630	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		631	non-idle connection, and usually around two hours for idle connections).
		632
		633	This means that monitoring is good for program errors and cleaning up
		634	stuff eventually, but they are no replacement for a timeout when you need
		635	to ensure some maximum latency.
		636
525	Example: call a given callback when C<$port> is killed.	637	Example: call a given callback when C<$port> is killed.
526		638
527	mon $port, sub { warn "port died because of <@_>\n" };	639	mon $port, sub { warn "port died because of <@_>\n" };
528		640
529	Example: kill ourselves when C<$port> is killed abnormally.	641	Example: kill ourselves when C<$port> is killed abnormally.
…		…
535	mon $port, $self => "restart";	647	mon $port, $self => "restart";
536		648
537	=cut	649	=cut
538		650
539	sub mon {	651	sub mon {
540	my ($noderef, $port) = split /#/, shift, 2;	652	my ($nodeid, $port) = split /#/, shift, 2;
541		653
542	my $node = $NODE{$noderef} \|\| add_node $noderef;	654	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
543		655
544	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	656	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
545		657
546	unless (ref $cb) {	658	unless (ref $cb) {
547	if (@_) {	659	if (@_) {
…		…
556	}	668	}
557		669
558	$node->monitor ($port, $cb);	670	$node->monitor ($port, $cb);
559		671
560	defined wantarray	672	defined wantarray
561	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	673	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
562	}	674	}
563		675
564	=item $guard = mon_guard $port, $ref, $ref...	676	=item $guard = mon_guard $port, $ref, $ref...
565		677
566	Monitors the given C<$port> and keeps the passed references. When the port	678	Monitors the given C<$port> and keeps the passed references. When the port
567	is killed, the references will be freed.	679	is killed, the references will be freed.
568		680
569	Optionally returns a guard that will stop the monitoring.	681	Optionally returns a guard that will stop the monitoring.
570		682
571	This function is useful when you create e.g. timers or other watchers and	683	This function is useful when you create e.g. timers or other watchers and
572	want to free them when the port gets killed:	684	want to free them when the port gets killed (note the use of C<psub>):
573		685
574	$port->rcv (start => sub {	686	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	687	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	688	undef $timer if 0.9 < rand;
577	});	689	});
578	});	690	});
579		691
580	=cut	692	=cut
…		…
589		701
590	=item kil $port[, @reason]	702	=item kil $port[, @reason]
591		703
592	Kill the specified port with the given C<@reason>.	704	Kill the specified port with the given C<@reason>.
593		705
594	If no C<@reason> is specified, then the port is killed "normally" (linked	706	If no C<@reason> is specified, then the port is killed "normally" -
595	ports will not be kileld, or even notified).	707	monitor callback will be invoked, but the kil will not cause linked ports
		708	(C<mon $mport, $lport> form) to get killed.
596		709
597	Otherwise, linked ports get killed with the same reason (second form of	710	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
598	C<mon>, see below).	711	form) get killed with the same reason.
599		712
600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	713	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
601	will be reported as reason C<< die => $@ >>.	714	will be reported as reason C<< die => $@ >>.
602		715
603	Transport/communication errors are reported as C<< transport_error =>	716	Transport/communication errors are reported as C<< transport_error =>
…		…
608	=item $port = spawn $node, $initfunc[, @initdata]	721	=item $port = spawn $node, $initfunc[, @initdata]
609		722
610	Creates a port on the node C<$node> (which can also be a port ID, in which	723	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	724	case it's the node where that port resides).
612		725
613	The port ID of the newly created port is return immediately, and it is	726	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	727	possible to immediately start sending messages or to monitor the port.
615		728
616	After the port has been created, the init function is	729	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	730	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	731	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	732	specify a function in the main program, use C<::name>.
620		733
621	If the function doesn't exist, then the node tries to C<require>	734	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	735	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	736	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	737	exists or it runs out of package names.
625		738
626	The init function is then called with the newly-created port as context	739	The init function is then called with the newly-created port as context
627	object (C<$SELF>) and the C<@initdata> values as arguments.	740	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		741	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		742	the port might not get created.
628		743
629	A common idiom is to pass your own port, monitor the spawned port, and	744	A common idiom is to pass a local port, immediately monitor the spawned
630	in the init function, monitor the original port. This two-way monitoring	745	port, and in the remote init function, immediately monitor the passed
631	ensures that both ports get cleaned up when there is a problem.	746	local port. This two-way monitoring ensures that both ports get cleaned up
		747	when there is a problem.
		748
		749	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		750	caller before C<spawn> returns (by delaying invocation when spawn is
		751	called for the local node).
632		752
633	Example: spawn a chat server port on C<$othernode>.	753	Example: spawn a chat server port on C<$othernode>.
634		754
635	# this node, executed from within a port context:	755	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	756	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
651		771
652	sub _spawn {	772	sub _spawn {
653	my $port = shift;	773	my $port = shift;
654	my $init = shift;	774	my $init = shift;
655		775
		776	# rcv will create the actual port
656	local $SELF = "$NODE#$port";	777	local $SELF = "$NODE#$port";
657	eval {	778	eval {
658	&{ load_func $init }	779	&{ load_func $init }
659	};	780	};
660	_self_die if $@;	781	_self_die if $@;
661	}	782	}
662		783
663	sub spawn(@) {	784	sub spawn(@) {
664	my ($noderef, undef) = split /#/, shift, 2;	785	my ($nodeid, undef) = split /#/, shift, 2;
665		786
666	my $id = "$RUNIQ." . $ID++;	787	my $id = "$RUNIQ." . ++$ID;
667		788
668	$_[0] =~ /::/	789	$_[0] =~ /::/
669	or Carp::croak "spawn init function must be a fully-qualified name, caught";	790	or Carp::croak "spawn init function must be a fully-qualified name, caught";
670		791
671	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	792	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672		793
673	"$noderef#$id"	794	"$nodeid#$id"
674	}	795	}
675		796
676	=back
677		797
678	=head1 NODE MESSAGES	798	=item after $timeout, @msg
679		799
680	Nodes understand the following messages sent to them. Many of them take	800	=item after $timeout, $callback
681	arguments called C<@reply>, which will simply be used to compose a reply
682	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
683	the remaining arguments are simply the message data.
684		801
685	While other messages exist, they are not public and subject to change.	802	Either sends the given message, or call the given callback, after the
		803	specified number of seconds.
686		804
687	=over 4	805	This is simply a utility function that comes in handy at times - the
		806	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		807	so it may go away in the future.
688		808
689	=cut	809	=cut
690		810
691	=item lookup => $name, @reply	811	sub after($@) {
		812	my ($timeout, @action) = @_;
692		813
693	Replies with the port ID of the specified well-known port, or C<undef>.	814	my $t; $t = AE::timer $timeout, 0, sub {
		815	undef $t;
		816	ref $action[0]
		817	? $action[0]()
		818	: snd @action;
		819	};
		820	}
694		821
695	=item devnull => ...	822	=item cal $port, @msg, $callback[, $timeout]
696		823
697	Generic data sink/CPU heat conversion.	824	A simple form of RPC - sends a message to the given C<$port> with the
		825	given contents (C<@msg>), but adds a reply port to the message.
698		826
699	=item relay => $port, @msg	827	The reply port is created temporarily just for the purpose of receiving
		828	the reply, and will be C<kil>ed when no longer needed.
700		829
701	Simply forwards the message to the given port.	830	A reply message sent to the port is passed to the C<$callback> as-is.
702		831
703	=item eval => $string[ @reply]	832	If an optional time-out (in seconds) is given and it is not C<undef>,
		833	then the callback will be called without any arguments after the time-out
		834	elapsed and the port is C<kil>ed.
704		835
705	Evaluates the given string. If C<@reply> is given, then a message of the	836	If no time-out is given (or it is C<undef>), then the local port will
706	form C<@reply, $@, @evalres> is sent.	837	monitor the remote port instead, so it eventually gets cleaned-up.
707		838
708	Example: crash another node.	839	Currently this function returns the temporary port, but this "feature"
		840	might go in future versions unless you can make a convincing case that
		841	this is indeed useful for something.
709		842
710	snd $othernode, eval => "exit";	843	=cut
711		844
712	=item time => @reply	845	sub cal(@) {
		846	my $timeout = ref $_[-1] ? undef : pop;
		847	my $cb = pop;
713		848
714	Replies the the current node time to C<@reply>.	849	my $port = port {
		850	undef $timeout;
		851	kil $SELF;
		852	&$cb;
		853	};
715		854
716	Example: tell the current node to send the current time to C<$myport> in a	855	if (defined $timeout) {
717	C<timereply> message.	856	$timeout = AE::timer $timeout, 0, sub {
		857	undef $timeout;
		858	kil $port;
		859	$cb->();
		860	};
		861	} else {
		862	mon $_[0], sub {
		863	kil $port;
		864	$cb->();
		865	};
		866	}
718		867
719	snd $NODE, time => $myport, timereply => 1, 2;	868	push @_, $port;
720	# => snd $myport, timereply => 1, 2, <time>	869	&snd;
		870
		871	$port
		872	}
721		873
722	=back	874	=back
723		875
724	=head1 AnyEvent::MP vs. Distributed Erlang	876	=head1 AnyEvent::MP vs. Distributed Erlang
725		877
726	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	878	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
727	== aemp node, Erlang process == aemp port), so many of the documents and	879	== aemp node, Erlang process == aemp port), so many of the documents and
728	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	880	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
729	sample:	881	sample:
730		882
731	http://www.Erlang.se/doc/programming_rules.shtml	883	http://www.erlang.se/doc/programming_rules.shtml
732	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	884	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
733	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	885	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
734	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	886	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
735		887
736	Despite the similarities, there are also some important differences:	888	Despite the similarities, there are also some important differences:
737		889
738	=over 4	890	=over 4
739		891
740	=item * Node references contain the recipe on how to contact them.	892	=item * Node IDs are arbitrary strings in AEMP.
741		893
742	Erlang relies on special naming and DNS to work everywhere in the	894	Erlang relies on special naming and DNS to work everywhere in the same
743	same way. AEMP relies on each node knowing it's own address(es), with	895	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
744	convenience functionality.	896	configuration or DNS), and possibly the addresses of some seed nodes, but
745		897	will otherwise discover other nodes (and their IDs) itself.
746	This means that AEMP requires a less tightly controlled environment at the
747	cost of longer node references and a slightly higher management overhead.
748		898
749	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	899	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
750	uses "local ports are like remote ports".	900	uses "local ports are like remote ports".
751		901
752	The failure modes for local ports are quite different (runtime errors	902	The failure modes for local ports are quite different (runtime errors
…		…
761	ports being the special case/exception, where transport errors cannot	911	ports being the special case/exception, where transport errors cannot
762	occur.	912	occur.
763		913
764	=item * Erlang uses processes and a mailbox, AEMP does not queue.	914	=item * Erlang uses processes and a mailbox, AEMP does not queue.
765		915
766	Erlang uses processes that selectively receive messages, and therefore	916	Erlang uses processes that selectively receive messages out of order, and
767	needs a queue. AEMP is event based, queuing messages would serve no	917	therefore needs a queue. AEMP is event based, queuing messages would serve
768	useful purpose. For the same reason the pattern-matching abilities of	918	no useful purpose. For the same reason the pattern-matching abilities
769	AnyEvent::MP are more limited, as there is little need to be able to	919	of AnyEvent::MP are more limited, as there is little need to be able to
770	filter messages without dequeing them.	920	filter messages without dequeuing them.
771		921
772	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	922	This is not a philosophical difference, but simply stems from AnyEvent::MP
		923	being event-based, while Erlang is process-based.
		924
		925	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		926	top of AEMP and Coro threads.
773		927
774	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	928	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
775		929
776	Sending messages in Erlang is synchronous and blocks the process (and	930	Sending messages in Erlang is synchronous and blocks the process until
		931	a conenction has been established and the message sent (and so does not
777	so does not need a queue that can overflow). AEMP sends are immediate,	932	need a queue that can overflow). AEMP sends return immediately, connection
778	connection establishment is handled in the background.	933	establishment is handled in the background.
779		934
780	=item * Erlang suffers from silent message loss, AEMP does not.	935	=item * Erlang suffers from silent message loss, AEMP does not.
781		936
782	Erlang makes few guarantees on messages delivery - messages can get lost	937	Erlang implements few guarantees on messages delivery - messages can get
783	without any of the processes realising it (i.e. you send messages a, b,	938	lost without any of the processes realising it (i.e. you send messages a,
784	and c, and the other side only receives messages a and c).	939	b, and c, and the other side only receives messages a and c).
785		940
786	AEMP guarantees correct ordering, and the guarantee that there are no	941	AEMP guarantees (modulo hardware errors) correct ordering, and the
		942	guarantee that after one message is lost, all following ones sent to the
		943	same port are lost as well, until monitoring raises an error, so there are
787	holes in the message sequence.	944	no silent "holes" in the message sequence.
788		945
789	=item * In Erlang, processes can be declared dead and later be found to be	946	If you want your software to be very reliable, you have to cope with
790	alive.	947	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
791		948	simply tries to work better in common error cases, such as when a network
792	In Erlang it can happen that a monitored process is declared dead and	949	link goes down.
793	linked processes get killed, but later it turns out that the process is
794	still alive - and can receive messages.
795
796	In AEMP, when port monitoring detects a port as dead, then that port will
797	eventually be killed - it cannot happen that a node detects a port as dead
798	and then later sends messages to it, finding it is still alive.
799		950
800	=item * Erlang can send messages to the wrong port, AEMP does not.	951	=item * Erlang can send messages to the wrong port, AEMP does not.
801		952
802	In Erlang it is quite likely that a node that restarts reuses a process ID	953	In Erlang it is quite likely that a node that restarts reuses an Erlang
803	known to other nodes for a completely different process, causing messages	954	process ID known to other nodes for a completely different process,
804	destined for that process to end up in an unrelated process.	955	causing messages destined for that process to end up in an unrelated
		956	process.
805		957
806	AEMP never reuses port IDs, so old messages or old port IDs floating	958	AEMP does not reuse port IDs, so old messages or old port IDs floating
807	around in the network will not be sent to an unrelated port.	959	around in the network will not be sent to an unrelated port.
808		960
809	=item * Erlang uses unprotected connections, AEMP uses secure	961	=item * Erlang uses unprotected connections, AEMP uses secure
810	authentication and can use TLS.	962	authentication and can use TLS.
811		963
812	AEMP can use a proven protocol - SSL/TLS - to protect connections and	964	AEMP can use a proven protocol - TLS - to protect connections and
813	securely authenticate nodes.	965	securely authenticate nodes.
814		966
815	=item * The AEMP protocol is optimised for both text-based and binary	967	=item * The AEMP protocol is optimised for both text-based and binary
816	communications.	968	communications.
817		969
818	The AEMP protocol, unlike the Erlang protocol, supports both	970	The AEMP protocol, unlike the Erlang protocol, supports both programming
819	language-independent text-only protocols (good for debugging) and binary,	971	language independent text-only protocols (good for debugging), and binary,
820	language-specific serialisers (e.g. Storable).	972	language-specific serialisers (e.g. Storable). By default, unless TLS is
		973	used, the protocol is actually completely text-based.
821		974
822	It has also been carefully designed to be implementable in other languages	975	It has also been carefully designed to be implementable in other languages
823	with a minimum of work while gracefully degrading fucntionality to make the	976	with a minimum of work while gracefully degrading functionality to make the
824	protocol simple.	977	protocol simple.
825		978
826	=item * AEMP has more flexible monitoring options than Erlang.	979	=item * AEMP has more flexible monitoring options than Erlang.
827		980
828	In Erlang, you can chose to receive I<all> exit signals as messages	981	In Erlang, you can chose to receive I<all> exit signals as messages or
829	or I<none>, there is no in-between, so monitoring single processes is	982	I<none>, there is no in-between, so monitoring single Erlang processes is
830	difficult to implement. Monitoring in AEMP is more flexible than in	983	difficult to implement.
831	Erlang, as one can choose between automatic kill, exit message or callback	984
832	on a per-process basis.	985	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		986	between automatic kill, exit message or callback on a per-port basis.
833		987
834	=item * Erlang tries to hide remote/local connections, AEMP does not.	988	=item * Erlang tries to hide remote/local connections, AEMP does not.
835		989
836	Monitoring in Erlang is not an indicator of process death/crashes,	990	Monitoring in Erlang is not an indicator of process death/crashes, in the
837	as linking is (except linking is unreliable in Erlang).	991	same way as linking is (except linking is unreliable in Erlang).
838		992
839	In AEMP, you don't "look up" registered port names or send to named ports	993	In AEMP, you don't "look up" registered port names or send to named ports
840	that might or might not be persistent. Instead, you normally spawn a port	994	that might or might not be persistent. Instead, you normally spawn a port
841	on the remote node. The init function monitors the you, and you monitor	995	on the remote node. The init function monitors you, and you monitor the
842	the remote port. Since both monitors are local to the node, they are much	996	remote port. Since both monitors are local to the node, they are much more
843	more reliable.	997	reliable (no need for C<spawn_link>).
844		998
845	This also saves round-trips and avoids sending messages to the wrong port	999	This also saves round-trips and avoids sending messages to the wrong port
846	(hard to do in Erlang).	1000	(hard to do in Erlang).
847		1001
848	=back	1002	=back
849		1003
850	=head1 RATIONALE	1004	=head1 RATIONALE
851		1005
852	=over 4	1006	=over 4
853		1007
854	=item Why strings for ports and noderefs, why not objects?	1008	=item Why strings for port and node IDs, why not objects?
855		1009
856	We considered "objects", but found that the actual number of methods	1010	We considered "objects", but found that the actual number of methods
857	thatc an be called are very low. Since port IDs and noderefs travel over	1011	that can be called are quite low. Since port and node IDs travel over
858	the network frequently, the serialising/deserialising would add lots of	1012	the network frequently, the serialising/deserialising would add lots of
859	overhead, as well as having to keep a proxy object.	1013	overhead, as well as having to keep a proxy object everywhere.
860		1014
861	Strings can easily be printed, easily serialised etc. and need no special	1015	Strings can easily be printed, easily serialised etc. and need no special
862	procedures to be "valid".	1016	procedures to be "valid".
863		1017
864	And a a miniport consists of a single closure stored in a global hash - it	1018	And as a result, a port with just a default receiver consists of a single
865	can't become much cheaper.	1019	code reference stored in a global hash - it can't become much cheaper.
866		1020
867	=item Why favour JSON, why not real serialising format such as Storable?	1021	=item Why favour JSON, why not a real serialising format such as Storable?
868		1022
869	In fact, any AnyEvent::MP node will happily accept Storable as framing	1023	In fact, any AnyEvent::MP node will happily accept Storable as framing
870	format, but currently there is no way to make a node use Storable by	1024	format, but currently there is no way to make a node use Storable by
871	default.	1025	default (although all nodes will accept it).
872		1026
873	The default framing protocol is JSON because a) JSON::XS is many times	1027	The default framing protocol is JSON because a) JSON::XS is many times
874	faster for small messages and b) most importantly, after years of	1028	faster for small messages and b) most importantly, after years of
875	experience we found that object serialisation is causing more problems	1029	experience we found that object serialisation is causing more problems
876	than it gains: Just like function calls, objects simply do not travel	1030	than it solves: Just like function calls, objects simply do not travel
877	easily over the network, mostly because they will always be a copy, so you	1031	easily over the network, mostly because they will always be a copy, so you
878	always have to re-think your design.	1032	always have to re-think your design.
879		1033
880	Keeping your messages simple, concentrating on data structures rather than	1034	Keeping your messages simple, concentrating on data structures rather than
881	objects, will keep your messages clean, tidy and efficient.	1035	objects, will keep your messages clean, tidy and efficient.
882		1036
883	=back	1037	=back
884		1038
885	=head1 SEE ALSO	1039	=head1 SEE ALSO
886		1040
		1041	L<AnyEvent::MP::Intro> - a gentle introduction.
		1042
		1043	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1044
		1045	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1046	your applications.
		1047
		1048	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1049
		1050	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1051	all nodes.
		1052
887	L<AnyEvent>.	1053	L<AnyEvent>.
888		1054
889	=head1 AUTHOR	1055	=head1 AUTHOR
890		1056
891	Marc Lehmann <schmorp@schmorp.de>	1057	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.121 by root, Tue Feb 28 18:37:24 2012 UTC