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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.62 by root, Thu Aug 27 07:12:48 2009 UTC vs.
Revision 1.122 by root, Wed Feb 29 18:44:59 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 (can only talk to	96	Nodes are either public (have one or more listening ports) or private
91	public nodes, but do not need an open port) or public nodes (connectable	97	(no listening ports). Private nodes cannot talk to other private nodes
92	from any other node).	98	currently, but all nodes can talk to public nodes.
93		99
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	100	Nodes is represented by (printable) strings called "node IDs".
95		101
96	A node reference is a string that either simply identifies the node (for	102	=item node ID - C<[A-Za-z0-9_\-.:]*>
97	private and slave nodes), or contains a recipe on how to reach a given
98	node (for public nodes).
99		103
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	104	A node ID is a string that uniquely identifies the node within a
101	TCP/IP, other protocols might look different).	105	network. Depending on the configuration used, node IDs can look like a
		106	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		107	doesn't interpret node IDs in any way except to uniquely identify a node.
102		108
103	Node references come in two flavours: resolved (containing only numerical	109	=item binds - C<ip:port>
104	addresses) or unresolved (where hostnames are used instead of addresses).
105		110
106	Before using an unresolved node reference in a message you first have to	111	Nodes can only talk to each other by creating some kind of connection to
107	resolve it.	112	each other. To do this, nodes should listen on one or more local transport
		113	endpoints - binds.
		114
		115	Currently, only standard C<ip:port> specifications can be used, which
		116	specify TCP ports to listen on. So a bind is basically just a tcp socket
		117	in listening mode thta accepts conenctions form other nodes.
		118
		119	=item seed nodes
		120
		121	When a node starts, it knows nothing about the network it is in - it
		122	needs to connect to at least one other node that is already in the
		123	network. These other nodes are called "seed nodes".
		124
		125	Seed nodes themselves are not special - they are seed nodes only because
		126	some other node I<uses> them as such, but any node can be used as seed
		127	node for other nodes, and eahc node cna use a different set of seed nodes.
		128
		129	In addition to discovering the network, seed nodes are also used to
		130	maintain the network - all nodes using the same seed node form are part of
		131	the same network. If a network is split into multiple subnets because e.g.
		132	the network link between the parts goes down, then using the same seed
		133	nodes for all nodes ensures that eventually the subnets get merged again.
		134
		135	Seed nodes are expected to be long-running, and at least one seed node
		136	should always be available. They should also be relatively responsive - a
		137	seed node that blocks for long periods will slow down everybody else.
		138
		139	For small networks, it's best if every node uses the same set of seed
		140	nodes. For large networks, it can be useful to specify "regional" seed
		141	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		142	each other. What's important is that all seed nodes connections form a
		143	complete graph, so that the network cannot split into separate subnets
		144	forever.
		145
		146	Seed nodes are represented by seed IDs.
		147
		148	=item seed IDs - C<host:port>
		149
		150	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		151	TCP port) of nodes that should be used as seed nodes.
		152
		153	=item global nodes
		154
		155	An AEMP network needs a discovery service - nodes need to know how to
		156	connect to other nodes they only know by name. In addition, AEMP offers a
		157	distributed "group database", which maps group names to a list of strings
		158	- for example, to register worker ports.
		159
		160	A network needs at least one global node to work, and allows every node to
		161	be a global node.
		162
		163	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		164	node and tries to keep connections to all other nodes. So while it can
		165	make sense to make every node "global" in small networks, it usually makes
		166	sense to only make seed nodes into global nodes in large networks (nodes
		167	keep connections to seed nodes and global nodes, so makign them the same
		168	reduces overhead).
108		169
109	=back	170	=back
110		171
111	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
112		173
114		175
115	=cut	176	=cut
116		177
117	package AnyEvent::MP;	178	package AnyEvent::MP;
118		179
		180	use AnyEvent::MP::Config ();
119	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
120		183
121	use common::sense;	184	use common::sense;
122		185
123	use Carp ();	186	use Carp ();
124		187
125	use AE ();	188	use AE ();
126		189
127	use base "Exporter";	190	use base "Exporter";
128		191
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
130		193
131	our @EXPORT = qw(	194	our @EXPORT = qw(
132	NODE $NODE *SELF node_of after	195	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	196	configure
134	snd rcv mon mon_guard kil reg psub spawn	197	snd rcv mon mon_guard kil psub peval spawn cal
135	port	198	port
136	);	199	);
137		200
138	our $SELF;	201	our $SELF;
139		202
…		…
143	kil $SELF, die => $msg;	206	kil $SELF, die => $msg;
144	}	207	}
145		208
146	=item $thisnode = NODE / $NODE	209	=item $thisnode = NODE / $NODE
147		210
148	The C<NODE> function returns, and the C<$NODE> variable contains the	211	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	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
150	C<initialise_node>.	213	a call to C<configure>.
151		214
152	=item $noderef = node_of $port	215	=item $nodeid = node_of $port
153		216
154	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.
155		218
156	=item initialise_node $noderef, $seednode, $seednode...	219	=item configure $profile, key => value...
157		220
158	=item initialise_node "slave/", $master, $master...	221	=item configure key => value...
159		222
160	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
161	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
162	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.
163		227
164	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
165	never) before calling other AnyEvent::MP functions.	229	never) before calling other AnyEvent::MP functions.
166		230
167	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
168	either resolved or unresolved.	232	F<aemp> command line utility (sans the set/del prefix), with two additions:
169
170	The first argument will be looked up in the configuration database first
171	(if it is C<undef> then the current nodename will be used instead) to find
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175
176	There are two types of networked nodes, public nodes and slave nodes:
177		233
178	=over 4	234	=over 4
179		235
180	=item public nodes	236	=item norc => $boolean (default false)
181		237
182	For public nodes, C<$noderef> (supplied either directly to	238	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
183	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
184	noderef (possibly unresolved, in which case it will be resolved).	240	C<configure> call.
185		241
186	After resolving, the node will bind itself on all endpoints.	242	=item force => $boolean (default false)
187		243
188	=item slave nodes	244	IF true, then the values specified in the C<configure> will take
189		245	precedence over any values configured via the rc file. The default is for
190	When the C<$noderef> (either as given or overriden by the config file)	246	the rc file to override any options specified in the program.
191	is the special string C<slave/>, then the node will become a slave
192	node. Slave nodes cannot be contacted from outside, and cannot talk to
193	each other (at least in this version of AnyEvent::MP).
194
195	Slave nodes work by creating connections to all public nodes, using the
196	L<AnyEvent::MP::Global> service.
197		247
198	=back	248	=back
199		249
200	After initialising itself, the node will connect to all additional
201	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
202	optional and can be used to quickly bootstrap the node into an existing
203	network.
204
205	All the seednodes will also be specially marked to automatically retry
206	connecting to them indefinitely, so make sure that seednodes are really
207	reliable and up (this might also change in the future).
208
209	Example: become a public node listening on the guessed noderef, or the one
210	specified via C<aemp> for the current node. This should be the most common
211	form of invocation for "daemon"-type nodes.
212
213	initialise_node;
214
215	Example: become a slave node to any of the the seednodes specified via
216	C<aemp>. This form is often used for commandline clients.
217
218	initialise_node "slave/";
219
220	Example: become a public node, and try to contact some well-known master
221	servers to become part of the network.
222
223	initialise_node undef, "master1", "master2";
224
225	Example: become a public node listening on port C<4041>.
226
227	initialise_node 4041;
228
229	Example: become a public node, only visible on localhost port 4044.
230
231	initialise_node "localhost:4044";
232
233	=item $cv = resolve_node $noderef
234
235	Takes an unresolved node reference that may contain hostnames and
236	abbreviated IDs, resolves all of them and returns a resolved node
237	reference.
238
239	In addition to C<address:port> pairs allowed in resolved noderefs, the
240	following forms are supported:
241
242	=over 4	250	=over 4
243		251
244	=item the empty string	252	=item step 1, gathering configuration from profiles
245		253
246	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
247	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.
248		258
249	=item naked port numbers (e.g. C<1234>)	259	The profile data is then gathered as follows:
250		260
251	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
252	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).
253		266
254	=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.
255		270
256	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
257	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, with
258	specified.	273	a slash (C</>) attached.
		274
		275	If the node ID (or profile name) ends with a slash (C</>), then a random
		276	string is appended to make it unique.
		277
		278	=item step 2, bind listener sockets
		279
		280	The next step is to look up the binds in the profile, followed by binding
		281	aemp protocol listeners on all binds specified (it is possible and valid
		282	to have no binds, meaning that the node cannot be contacted form the
		283	outside. This means the node cannot talk to other nodes that also have no
		284	binds, but it can still talk to all "normal" nodes).
		285
		286	If the profile does not specify a binds list, then a default of C<*> is
		287	used, meaning the node will bind on a dynamically-assigned port on every
		288	local IP address it finds.
		289
		290	=item step 3, connect to seed nodes
		291
		292	As the last step, the seed ID list from the profile is passed to the
		293	L<AnyEvent::MP::Global> module, which will then use it to keep
		294	connectivity with at least one node at any point in time.
259		295
260	=back	296	=back
		297
		298	Example: become a distributed node using the local node name as profile.
		299	This should be the most common form of invocation for "daemon"-type nodes.
		300
		301	configure
		302
		303	Example: become an anonymous node. This form is often used for commandline
		304	clients.
		305
		306	configure nodeid => "anon/";
		307
		308	Example: configure a node using a profile called seed, which is suitable
		309	for a seed node as it binds on all local addresses on a fixed port (4040,
		310	customary for aemp).
		311
		312	# use the aemp commandline utility
		313	# aemp profile seed binds '*:4040'
		314
		315	# then use it
		316	configure profile => "seed";
		317
		318	# or simply use aemp from the shell again:
		319	# aemp run profile seed
		320
		321	# or provide a nicer-to-remember nodeid
		322	# aemp run profile seed nodeid "$(hostname)"
261		323
262	=item $SELF	324	=item $SELF
263		325
264	Contains the current port id while executing C<rcv> callbacks or C<psub>	326	Contains the current port id while executing C<rcv> callbacks or C<psub>
265	blocks.	327	blocks.
266		328
267	=item SELF, %SELF, @SELF...	329	=item *SELF, SELF, %SELF, @SELF...
268		330
269	Due to some quirks in how perl exports variables, it is impossible to	331	Due to some quirks in how perl exports variables, it is impossible to
270	just export C<$SELF>, all the symbols called C<SELF> are exported by this	332	just export C<$SELF>, all the symbols named C<SELF> are exported by this
271	module, but only C<$SELF> is currently used.	333	module, but only C<$SELF> is currently used.
272		334
273	=item snd $port, type => @data	335	=item snd $port, type => @data
274		336
275	=item snd $port, @msg	337	=item snd $port, @msg
276		338
277	Send the given message to the given port ID, which can identify either	339	Send the given message to the given port, which can identify either a
278	a local or a remote port, and must be a port ID.	340	local or a remote port, and must be a port ID.
279		341
280	While the message can be about anything, it is highly recommended to use a	342	While the message can be almost anything, it is highly recommended to
281	string as first element (a port ID, or some word that indicates a request	343	use a string as first element (a port ID, or some word that indicates a
282	type etc.).	344	request type etc.) and to consist if only simple perl values (scalars,
		345	arrays, hashes) - if you think you need to pass an object, think again.
283		346
284	The message data effectively becomes read-only after a call to this	347	The message data logically becomes read-only after a call to this
285	function: modifying any argument is not allowed and can cause many	348	function: modifying any argument (or values referenced by them) is
286	problems.	349	forbidden, as there can be considerable time between the call to C<snd>
		350	and the time the message is actually being serialised - in fact, it might
		351	never be copied as within the same process it is simply handed to the
		352	receiving port.
287		353
288	The type of data you can transfer depends on the transport protocol: when	354	The type of data you can transfer depends on the transport protocol: when
289	JSON is used, then only strings, numbers and arrays and hashes consisting	355	JSON is used, then only strings, numbers and arrays and hashes consisting
290	of those are allowed (no objects). When Storable is used, then anything	356	of those are allowed (no objects). When Storable is used, then anything
291	that Storable can serialise and deserialise is allowed, and for the local	357	that Storable can serialise and deserialise is allowed, and for the local
292	node, anything can be passed.	358	node, anything can be passed. Best rely only on the common denominator of
		359	these.
293		360
294	=item $local_port = port	361	=item $local_port = port
295		362
296	Create a new local port object and returns its port ID. Initially it has	363	Create a new local port object and returns its port ID. Initially it has
297	no callbacks set and will throw an error when it receives messages.	364	no callbacks set and will throw an error when it receives messages.
…		…
321	sub _kilme {	388	sub _kilme {
322	die "received message on port without callback";	389	die "received message on port without callback";
323	}	390	}
324		391
325	sub port(;&) {	392	sub port(;&) {
326	my $id = "$UNIQ." . $ID++;	393	my $id = "$UNIQ." . ++$ID;
327	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
328		395
329	rcv $port, shift \|\| \&_kilme;	396	rcv $port, shift \|\| \&_kilme;
330		397
331	$port	398	$port
…		…
370	msg1 => sub { ... },	437	msg1 => sub { ... },
371	...	438	...
372	;	439	;
373		440
374	Example: temporarily register a rcv callback for a tag matching some port	441	Example: temporarily register a rcv callback for a tag matching some port
375	(e.g. for a rpc reply) and unregister it after a message was received.	442	(e.g. for an rpc reply) and unregister it after a message was received.
376		443
377	rcv $port, $otherport => sub {	444	rcv $port, $otherport => sub {
378	my @reply = @_;	445	my @reply = @_;
379		446
380	rcv $SELF, $otherport;	447	rcv $SELF, $otherport;
…		…
382		449
383	=cut	450	=cut
384		451
385	sub rcv($@) {	452	sub rcv($@) {
386	my $port = shift;	453	my $port = shift;
387	my ($noderef, $portid) = split /#/, $port, 2;	454	my ($nodeid, $portid) = split /#/, $port, 2;
388		455
389	$NODE{$noderef} == $NODE{""}	456	$NODE{$nodeid} == $NODE{""}
390	or Carp::croak "$port: rcv can only be called on local ports, caught";	457	or Carp::croak "$port: rcv can only be called on local ports, caught";
391		458
392	while (@_) {	459	while (@_) {
393	if (ref $_[0]) {	460	if (ref $_[0]) {
394	if (my $self = $PORT_DATA{$portid}) {	461	if (my $self = $PORT_DATA{$portid}) {
395	"AnyEvent::MP::Port" eq ref $self	462	"AnyEvent::MP::Port" eq ref $self
396	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	463	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
397		464
398	$self->[2] = shift;	465	$self->[0] = shift;
399	} else {	466	} else {
400	my $cb = shift;	467	my $cb = shift;
401	$PORT{$portid} = sub {	468	$PORT{$portid} = sub {
402	local $SELF = $port;	469	local $SELF = $port;
403	eval { &$cb }; _self_die if $@;	470	eval { &$cb }; _self_die if $@;
404	};	471	};
405	}	472	}
406	} elsif (defined $_[0]) {	473	} elsif (defined $_[0]) {
407	my $self = $PORT_DATA{$portid} \|\|= do {	474	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	475	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409		476
410	$PORT{$portid} = sub {	477	$PORT{$portid} = sub {
411	local $SELF = $port;	478	local $SELF = $port;
412		479
413	if (my $cb = $self->[1]{$_[0]}) {	480	if (my $cb = $self->[1]{$_[0]}) {
…		…
435	}	502	}
436		503
437	$port	504	$port
438	}	505	}
439		506
		507	=item peval $port, $coderef[, @args]
		508
		509	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		510	when the code throews an exception the C<$port> will be killed.
		511
		512	Any remaining args will be passed to the callback. Any return values will
		513	be returned to the caller.
		514
		515	This is useful when you temporarily want to execute code in the context of
		516	a port.
		517
		518	Example: create a port and run some initialisation code in it's context.
		519
		520	my $port = port { ... };
		521
		522	peval $port, sub {
		523	init
		524	or die "unable to init";
		525	};
		526
		527	=cut
		528
		529	sub peval($$) {
		530	local $SELF = shift;
		531	my $cb = shift;
		532
		533	if (wantarray) {
		534	my @res = eval { &$cb };
		535	_self_die if $@;
		536	@res
		537	} else {
		538	my $res = eval { &$cb };
		539	_self_die if $@;
		540	$res
		541	}
		542	}
		543
440	=item $closure = psub { BLOCK }	544	=item $closure = psub { BLOCK }
441		545
442	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	546	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
443	closure is executed, sets up the environment in the same way as in C<rcv>	547	closure is executed, sets up the environment in the same way as in C<rcv>
444	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	548	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		549
		550	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		551	BLOCK }, @_ } >>.
445		552
446	This is useful when you register callbacks from C<rcv> callbacks:	553	This is useful when you register callbacks from C<rcv> callbacks:
447		554
448	rcv delayed_reply => sub {	555	rcv delayed_reply => sub {
449	my ($delay, @reply) = @_;	556	my ($delay, @reply) = @_;
…		…
473	$res	580	$res
474	}	581	}
475	}	582	}
476	}	583	}
477		584
478	=item $guard = mon $port, $cb->(@reason)	585	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
479		586
480	=item $guard = mon $port, $rcvport	587	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
481		588
482	=item $guard = mon $port	589	=item $guard = mon $port # kill $SELF when $port dies
483		590
484	=item $guard = mon $port, $rcvport, @msg	591	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
485		592
486	Monitor the given port and do something when the port is killed or	593	Monitor the given port and do something when the port is killed or
487	messages to it were lost, and optionally return a guard that can be used	594	messages to it were lost, and optionally return a guard that can be used
488	to stop monitoring again.	595	to stop monitoring again.
489
490	C<mon> effectively guarantees that, in the absence of hardware failures,
491	that after starting the monitor, either all messages sent to the port
492	will arrive, or the monitoring action will be invoked after possible
493	message loss has been detected. No messages will be lost "in between"
494	(after the first lost message no further messages will be received by the
495	port). After the monitoring action was invoked, further messages might get
496	delivered again.
497
498	Note that monitoring-actions are one-shot: once released, they are removed
499	and will not trigger again.
500		596
501	In the first form (callback), the callback is simply called with any	597	In the first form (callback), the callback is simply called with any
502	number of C<@reason> elements (no @reason means that the port was deleted	598	number of C<@reason> elements (no @reason means that the port was deleted
503	"normally"). Note also that I<< the callback B<must> never die >>, so use	599	"normally"). Note also that I<< the callback B<must> never die >>, so use
504	C<eval> if unsure.	600	C<eval> if unsure.
505		601
506	In the second form (another port given), the other port (C<$rcvport>)	602	In the second form (another port given), the other port (C<$rcvport>)
507	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	603	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
508	"normal" kils nothing happens, while under all other conditions, the other	604	"normal" kils nothing happens, while under all other conditions, the other
509	port is killed with the same reason.	605	port is killed with the same reason.
510		606
511	The third form (kill self) is the same as the second form, except that	607	The third form (kill self) is the same as the second form, except that
512	C<$rvport> defaults to C<$SELF>.	608	C<$rvport> defaults to C<$SELF>.
513		609
514	In the last form (message), a message of the form C<@msg, @reason> will be	610	In the last form (message), a message of the form C<@msg, @reason> will be
515	C<snd>.	611	C<snd>.
		612
		613	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		614	alert was raised), they are removed and will not trigger again.
516		615
517	As a rule of thumb, monitoring requests should always monitor a port from	616	As a rule of thumb, monitoring requests should always monitor a port from
518	a local port (or callback). The reason is that kill messages might get	617	a local port (or callback). The reason is that kill messages might get
519	lost, just like any other message. Another less obvious reason is that	618	lost, just like any other message. Another less obvious reason is that
520	even monitoring requests can get lost (for exmaple, when the connection	619	even monitoring requests can get lost (for example, when the connection
521	to the other node goes down permanently). When monitoring a port locally	620	to the other node goes down permanently). When monitoring a port locally
522	these problems do not exist.	621	these problems do not exist.
523		622
		623	C<mon> effectively guarantees that, in the absence of hardware failures,
		624	after starting the monitor, either all messages sent to the port will
		625	arrive, or the monitoring action will be invoked after possible message
		626	loss has been detected. No messages will be lost "in between" (after
		627	the first lost message no further messages will be received by the
		628	port). After the monitoring action was invoked, further messages might get
		629	delivered again.
		630
		631	Inter-host-connection timeouts and monitoring depend on the transport
		632	used. The only transport currently implemented is TCP, and AnyEvent::MP
		633	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		634	non-idle connection, and usually around two hours for idle connections).
		635
		636	This means that monitoring is good for program errors and cleaning up
		637	stuff eventually, but they are no replacement for a timeout when you need
		638	to ensure some maximum latency.
		639
524	Example: call a given callback when C<$port> is killed.	640	Example: call a given callback when C<$port> is killed.
525		641
526	mon $port, sub { warn "port died because of <@_>\n" };	642	mon $port, sub { warn "port died because of <@_>\n" };
527		643
528	Example: kill ourselves when C<$port> is killed abnormally.	644	Example: kill ourselves when C<$port> is killed abnormally.
…		…
534	mon $port, $self => "restart";	650	mon $port, $self => "restart";
535		651
536	=cut	652	=cut
537		653
538	sub mon {	654	sub mon {
539	my ($noderef, $port) = split /#/, shift, 2;	655	my ($nodeid, $port) = split /#/, shift, 2;
540		656
541	my $node = $NODE{$noderef} \|\| add_node $noderef;	657	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
542		658
543	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	659	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
544		660
545	unless (ref $cb) {	661	unless (ref $cb) {
546	if (@_) {	662	if (@_) {
…		…
555	}	671	}
556		672
557	$node->monitor ($port, $cb);	673	$node->monitor ($port, $cb);
558		674
559	defined wantarray	675	defined wantarray
560	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	676	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
561	}	677	}
562		678
563	=item $guard = mon_guard $port, $ref, $ref...	679	=item $guard = mon_guard $port, $ref, $ref...
564		680
565	Monitors the given C<$port> and keeps the passed references. When the port	681	Monitors the given C<$port> and keeps the passed references. When the port
566	is killed, the references will be freed.	682	is killed, the references will be freed.
567		683
568	Optionally returns a guard that will stop the monitoring.	684	Optionally returns a guard that will stop the monitoring.
569		685
570	This function is useful when you create e.g. timers or other watchers and	686	This function is useful when you create e.g. timers or other watchers and
571	want to free them when the port gets killed:	687	want to free them when the port gets killed (note the use of C<psub>):
572		688
573	$port->rcv (start => sub {	689	$port->rcv (start => sub {
574	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	690	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
575	undef $timer if 0.9 < rand;	691	undef $timer if 0.9 < rand;
576	});	692	});
577	});	693	});
578		694
579	=cut	695	=cut
…		…
588		704
589	=item kil $port[, @reason]	705	=item kil $port[, @reason]
590		706
591	Kill the specified port with the given C<@reason>.	707	Kill the specified port with the given C<@reason>.
592		708
593	If no C<@reason> is specified, then the port is killed "normally" (linked	709	If no C<@reason> is specified, then the port is killed "normally" -
594	ports will not be kileld, or even notified).	710	monitor callback will be invoked, but the kil will not cause linked ports
		711	(C<mon $mport, $lport> form) to get killed.
595		712
596	Otherwise, linked ports get killed with the same reason (second form of	713	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
597	C<mon>, see below).	714	form) get killed with the same reason.
598		715
599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	716	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
600	will be reported as reason C<< die => $@ >>.	717	will be reported as reason C<< die => $@ >>.
601		718
602	Transport/communication errors are reported as C<< transport_error =>	719	Transport/communication errors are reported as C<< transport_error =>
…		…
607	=item $port = spawn $node, $initfunc[, @initdata]	724	=item $port = spawn $node, $initfunc[, @initdata]
608		725
609	Creates a port on the node C<$node> (which can also be a port ID, in which	726	Creates a port on the node C<$node> (which can also be a port ID, in which
610	case it's the node where that port resides).	727	case it's the node where that port resides).
611		728
612	The port ID of the newly created port is return immediately, and it is	729	The port ID of the newly created port is returned immediately, and it is
613	permissible to immediately start sending messages or monitor the port.	730	possible to immediately start sending messages or to monitor the port.
614		731
615	After the port has been created, the init function is	732	After the port has been created, the init function is called on the remote
616	called. This function must be a fully-qualified function name	733	node, in the same context as a C<rcv> callback. This function must be a
617	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	734	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
618	program, use C<::name>.	735	specify a function in the main program, use C<::name>.
619		736
620	If the function doesn't exist, then the node tries to C<require>	737	If the function doesn't exist, then the node tries to C<require>
621	the package, then the package above the package and so on (e.g.	738	the package, then the package above the package and so on (e.g.
622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	739	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
623	exists or it runs out of package names.	740	exists or it runs out of package names.
624		741
625	The init function is then called with the newly-created port as context	742	The init function is then called with the newly-created port as context
626	object (C<$SELF>) and the C<@initdata> values as arguments.	743	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		744	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		745	the port might not get created.
627		746
628	A common idiom is to pass your own port, monitor the spawned port, and	747	A common idiom is to pass a local port, immediately monitor the spawned
629	in the init function, monitor the original port. This two-way monitoring	748	port, and in the remote init function, immediately monitor the passed
630	ensures that both ports get cleaned up when there is a problem.	749	local port. This two-way monitoring ensures that both ports get cleaned up
		750	when there is a problem.
		751
		752	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		753	caller before C<spawn> returns (by delaying invocation when spawn is
		754	called for the local node).
631		755
632	Example: spawn a chat server port on C<$othernode>.	756	Example: spawn a chat server port on C<$othernode>.
633		757
634	# this node, executed from within a port context:	758	# this node, executed from within a port context:
635	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	759	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
650		774
651	sub _spawn {	775	sub _spawn {
652	my $port = shift;	776	my $port = shift;
653	my $init = shift;	777	my $init = shift;
654		778
		779	# rcv will create the actual port
655	local $SELF = "$NODE#$port";	780	local $SELF = "$NODE#$port";
656	eval {	781	eval {
657	&{ load_func $init }	782	&{ load_func $init }
658	};	783	};
659	_self_die if $@;	784	_self_die if $@;
660	}	785	}
661		786
662	sub spawn(@) {	787	sub spawn(@) {
663	my ($noderef, undef) = split /#/, shift, 2;	788	my ($nodeid, undef) = split /#/, shift, 2;
664		789
665	my $id = "$RUNIQ." . $ID++;	790	my $id = "$RUNIQ." . ++$ID;
666		791
667	$_[0] =~ /::/	792	$_[0] =~ /::/
668	or Carp::croak "spawn init function must be a fully-qualified name, caught";	793	or Carp::croak "spawn init function must be a fully-qualified name, caught";
669		794
670	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	795	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
671		796
672	"$noderef#$id"	797	"$nodeid#$id"
673	}	798	}
		799
674		800
675	=item after $timeout, @msg	801	=item after $timeout, @msg
676		802
677	=item after $timeout, $callback	803	=item after $timeout, $callback
678		804
679	Either sends the given message, or call the given callback, after the	805	Either sends the given message, or call the given callback, after the
680	specified number of seconds.	806	specified number of seconds.
681		807
682	This is simply a utility function that come sin handy at times.	808	This is simply a utility function that comes in handy at times - the
		809	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		810	so it may go away in the future.
683		811
684	=cut	812	=cut
685		813
686	sub after($@) {	814	sub after($@) {
687	my ($timeout, @action) = @_;	815	my ($timeout, @action) = @_;
…		…
692	? $action[0]()	820	? $action[0]()
693	: snd @action;	821	: snd @action;
694	};	822	};
695	}	823	}
696		824
		825	=item cal $port, @msg, $callback[, $timeout]
		826
		827	A simple form of RPC - sends a message to the given C<$port> with the
		828	given contents (C<@msg>), but adds a reply port to the message.
		829
		830	The reply port is created temporarily just for the purpose of receiving
		831	the reply, and will be C<kil>ed when no longer needed.
		832
		833	A reply message sent to the port is passed to the C<$callback> as-is.
		834
		835	If an optional time-out (in seconds) is given and it is not C<undef>,
		836	then the callback will be called without any arguments after the time-out
		837	elapsed and the port is C<kil>ed.
		838
		839	If no time-out is given (or it is C<undef>), then the local port will
		840	monitor the remote port instead, so it eventually gets cleaned-up.
		841
		842	Currently this function returns the temporary port, but this "feature"
		843	might go in future versions unless you can make a convincing case that
		844	this is indeed useful for something.
		845
		846	=cut
		847
		848	sub cal(@) {
		849	my $timeout = ref $_[-1] ? undef : pop;
		850	my $cb = pop;
		851
		852	my $port = port {
		853	undef $timeout;
		854	kil $SELF;
		855	&$cb;
		856	};
		857
		858	if (defined $timeout) {
		859	$timeout = AE::timer $timeout, 0, sub {
		860	undef $timeout;
		861	kil $port;
		862	$cb->();
		863	};
		864	} else {
		865	mon $_[0], sub {
		866	kil $port;
		867	$cb->();
		868	};
		869	}
		870
		871	push @_, $port;
		872	&snd;
		873
		874	$port
		875	}
		876
697	=back	877	=back
698		878
699	=head1 AnyEvent::MP vs. Distributed Erlang	879	=head1 AnyEvent::MP vs. Distributed Erlang
700		880
701	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	881	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
702	== aemp node, Erlang process == aemp port), so many of the documents and	882	== aemp node, Erlang process == aemp port), so many of the documents and
703	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	883	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
704	sample:	884	sample:
705		885
706	http://www.Erlang.se/doc/programming_rules.shtml	886	http://www.erlang.se/doc/programming_rules.shtml
707	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	887	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
708	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	888	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
709	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	889	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
710		890
711	Despite the similarities, there are also some important differences:	891	Despite the similarities, there are also some important differences:
712		892
713	=over 4	893	=over 4
714		894
715	=item * Node references contain the recipe on how to contact them.	895	=item * Node IDs are arbitrary strings in AEMP.
716		896
717	Erlang relies on special naming and DNS to work everywhere in the	897	Erlang relies on special naming and DNS to work everywhere in the same
718	same way. AEMP relies on each node knowing it's own address(es), with	898	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
719	convenience functionality.	899	configuration or DNS), and possibly the addresses of some seed nodes, but
720		900	will otherwise discover other nodes (and their IDs) itself.
721	This means that AEMP requires a less tightly controlled environment at the
722	cost of longer node references and a slightly higher management overhead.
723		901
724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	902	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
725	uses "local ports are like remote ports".	903	uses "local ports are like remote ports".
726		904
727	The failure modes for local ports are quite different (runtime errors	905	The failure modes for local ports are quite different (runtime errors
…		…
736	ports being the special case/exception, where transport errors cannot	914	ports being the special case/exception, where transport errors cannot
737	occur.	915	occur.
738		916
739	=item * Erlang uses processes and a mailbox, AEMP does not queue.	917	=item * Erlang uses processes and a mailbox, AEMP does not queue.
740		918
741	Erlang uses processes that selectively receive messages, and therefore	919	Erlang uses processes that selectively receive messages out of order, and
742	needs a queue. AEMP is event based, queuing messages would serve no	920	therefore needs a queue. AEMP is event based, queuing messages would serve
743	useful purpose. For the same reason the pattern-matching abilities of	921	no useful purpose. For the same reason the pattern-matching abilities
744	AnyEvent::MP are more limited, as there is little need to be able to	922	of AnyEvent::MP are more limited, as there is little need to be able to
745	filter messages without dequeing them.	923	filter messages without dequeuing them.
746		924
747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	925	This is not a philosophical difference, but simply stems from AnyEvent::MP
		926	being event-based, while Erlang is process-based.
		927
		928	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		929	top of AEMP and Coro threads.
748		930
749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	931	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
750		932
751	Sending messages in Erlang is synchronous and blocks the process (and	933	Sending messages in Erlang is synchronous and blocks the process until
		934	a conenction has been established and the message sent (and so does not
752	so does not need a queue that can overflow). AEMP sends are immediate,	935	need a queue that can overflow). AEMP sends return immediately, connection
753	connection establishment is handled in the background.	936	establishment is handled in the background.
754		937
755	=item * Erlang suffers from silent message loss, AEMP does not.	938	=item * Erlang suffers from silent message loss, AEMP does not.
756		939
757	Erlang makes few guarantees on messages delivery - messages can get lost	940	Erlang implements few guarantees on messages delivery - messages can get
758	without any of the processes realising it (i.e. you send messages a, b,	941	lost without any of the processes realising it (i.e. you send messages a,
759	and c, and the other side only receives messages a and c).	942	b, and c, and the other side only receives messages a and c).
760		943
761	AEMP guarantees correct ordering, and the guarantee that there are no	944	AEMP guarantees (modulo hardware errors) correct ordering, and the
		945	guarantee that after one message is lost, all following ones sent to the
		946	same port are lost as well, until monitoring raises an error, so there are
762	holes in the message sequence.	947	no silent "holes" in the message sequence.
763		948
764	=item * In Erlang, processes can be declared dead and later be found to be	949	If you want your software to be very reliable, you have to cope with
765	alive.	950	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
766		951	simply tries to work better in common error cases, such as when a network
767	In Erlang it can happen that a monitored process is declared dead and	952	link goes down.
768	linked processes get killed, but later it turns out that the process is
769	still alive - and can receive messages.
770
771	In AEMP, when port monitoring detects a port as dead, then that port will
772	eventually be killed - it cannot happen that a node detects a port as dead
773	and then later sends messages to it, finding it is still alive.
774		953
775	=item * Erlang can send messages to the wrong port, AEMP does not.	954	=item * Erlang can send messages to the wrong port, AEMP does not.
776		955
777	In Erlang it is quite likely that a node that restarts reuses a process ID	956	In Erlang it is quite likely that a node that restarts reuses an Erlang
778	known to other nodes for a completely different process, causing messages	957	process ID known to other nodes for a completely different process,
779	destined for that process to end up in an unrelated process.	958	causing messages destined for that process to end up in an unrelated
		959	process.
780		960
781	AEMP never reuses port IDs, so old messages or old port IDs floating	961	AEMP does not reuse port IDs, so old messages or old port IDs floating
782	around in the network will not be sent to an unrelated port.	962	around in the network will not be sent to an unrelated port.
783		963
784	=item * Erlang uses unprotected connections, AEMP uses secure	964	=item * Erlang uses unprotected connections, AEMP uses secure
785	authentication and can use TLS.	965	authentication and can use TLS.
786		966
787	AEMP can use a proven protocol - SSL/TLS - to protect connections and	967	AEMP can use a proven protocol - TLS - to protect connections and
788	securely authenticate nodes.	968	securely authenticate nodes.
789		969
790	=item * The AEMP protocol is optimised for both text-based and binary	970	=item * The AEMP protocol is optimised for both text-based and binary
791	communications.	971	communications.
792		972
793	The AEMP protocol, unlike the Erlang protocol, supports both	973	The AEMP protocol, unlike the Erlang protocol, supports both programming
794	language-independent text-only protocols (good for debugging) and binary,	974	language independent text-only protocols (good for debugging), and binary,
795	language-specific serialisers (e.g. Storable).	975	language-specific serialisers (e.g. Storable). By default, unless TLS is
		976	used, the protocol is actually completely text-based.
796		977
797	It has also been carefully designed to be implementable in other languages	978	It has also been carefully designed to be implementable in other languages
798	with a minimum of work while gracefully degrading fucntionality to make the	979	with a minimum of work while gracefully degrading functionality to make the
799	protocol simple.	980	protocol simple.
800		981
801	=item * AEMP has more flexible monitoring options than Erlang.	982	=item * AEMP has more flexible monitoring options than Erlang.
802		983
803	In Erlang, you can chose to receive I<all> exit signals as messages	984	In Erlang, you can chose to receive I<all> exit signals as messages or
804	or I<none>, there is no in-between, so monitoring single processes is	985	I<none>, there is no in-between, so monitoring single Erlang processes is
805	difficult to implement. Monitoring in AEMP is more flexible than in	986	difficult to implement.
806	Erlang, as one can choose between automatic kill, exit message or callback	987
807	on a per-process basis.	988	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		989	between automatic kill, exit message or callback on a per-port basis.
808		990
809	=item * Erlang tries to hide remote/local connections, AEMP does not.	991	=item * Erlang tries to hide remote/local connections, AEMP does not.
810		992
811	Monitoring in Erlang is not an indicator of process death/crashes,	993	Monitoring in Erlang is not an indicator of process death/crashes, in the
812	as linking is (except linking is unreliable in Erlang).	994	same way as linking is (except linking is unreliable in Erlang).
813		995
814	In AEMP, you don't "look up" registered port names or send to named ports	996	In AEMP, you don't "look up" registered port names or send to named ports
815	that might or might not be persistent. Instead, you normally spawn a port	997	that might or might not be persistent. Instead, you normally spawn a port
816	on the remote node. The init function monitors the you, and you monitor	998	on the remote node. The init function monitors you, and you monitor the
817	the remote port. Since both monitors are local to the node, they are much	999	remote port. Since both monitors are local to the node, they are much more
818	more reliable.	1000	reliable (no need for C<spawn_link>).
819		1001
820	This also saves round-trips and avoids sending messages to the wrong port	1002	This also saves round-trips and avoids sending messages to the wrong port
821	(hard to do in Erlang).	1003	(hard to do in Erlang).
822		1004
823	=back	1005	=back
824		1006
825	=head1 RATIONALE	1007	=head1 RATIONALE
826		1008
827	=over 4	1009	=over 4
828		1010
829	=item Why strings for ports and noderefs, why not objects?	1011	=item Why strings for port and node IDs, why not objects?
830		1012
831	We considered "objects", but found that the actual number of methods	1013	We considered "objects", but found that the actual number of methods
832	thatc an be called are very low. Since port IDs and noderefs travel over	1014	that can be called are quite low. Since port and node IDs travel over
833	the network frequently, the serialising/deserialising would add lots of	1015	the network frequently, the serialising/deserialising would add lots of
834	overhead, as well as having to keep a proxy object.	1016	overhead, as well as having to keep a proxy object everywhere.
835		1017
836	Strings can easily be printed, easily serialised etc. and need no special	1018	Strings can easily be printed, easily serialised etc. and need no special
837	procedures to be "valid".	1019	procedures to be "valid".
838		1020
839	And a a miniport consists of a single closure stored in a global hash - it	1021	And as a result, a port with just a default receiver consists of a single
840	can't become much cheaper.	1022	code reference stored in a global hash - it can't become much cheaper.
841		1023
842	=item Why favour JSON, why not real serialising format such as Storable?	1024	=item Why favour JSON, why not a real serialising format such as Storable?
843		1025
844	In fact, any AnyEvent::MP node will happily accept Storable as framing	1026	In fact, any AnyEvent::MP node will happily accept Storable as framing
845	format, but currently there is no way to make a node use Storable by	1027	format, but currently there is no way to make a node use Storable by
846	default.	1028	default (although all nodes will accept it).
847		1029
848	The default framing protocol is JSON because a) JSON::XS is many times	1030	The default framing protocol is JSON because a) JSON::XS is many times
849	faster for small messages and b) most importantly, after years of	1031	faster for small messages and b) most importantly, after years of
850	experience we found that object serialisation is causing more problems	1032	experience we found that object serialisation is causing more problems
851	than it gains: Just like function calls, objects simply do not travel	1033	than it solves: Just like function calls, objects simply do not travel
852	easily over the network, mostly because they will always be a copy, so you	1034	easily over the network, mostly because they will always be a copy, so you
853	always have to re-think your design.	1035	always have to re-think your design.
854		1036
855	Keeping your messages simple, concentrating on data structures rather than	1037	Keeping your messages simple, concentrating on data structures rather than
856	objects, will keep your messages clean, tidy and efficient.	1038	objects, will keep your messages clean, tidy and efficient.
857		1039
858	=back	1040	=back
859		1041
860	=head1 SEE ALSO	1042	=head1 SEE ALSO
861		1043
		1044	L<AnyEvent::MP::Intro> - a gentle introduction.
		1045
		1046	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1047
		1048	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1049	your applications.
		1050
		1051	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1052
		1053	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1054	all nodes.
		1055
862	L<AnyEvent>.	1056	L<AnyEvent>.
863		1057
864	=head1 AUTHOR	1058	=head1 AUTHOR
865		1059
866	Marc Lehmann <schmorp@schmorp.de>	1060	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.122 by root, Wed Feb 29 18:44:59 2012 UTC