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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.58 by root, Sun Aug 16 02:55:16 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 (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
202	Note that slave nodes cannot change their name, and consequently, their
203	master, so if the master goes down, the slave node will not function well
204	anymore until it can re-establish conenciton to its master. This makes
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.
206		247
207	=back	248	=back
208		249
209	This function will block until all nodes have been resolved and, for slave
210	nodes, until it has successfully established a connection to a master
211	server.
212
213	All the seednodes will also be specially marked to automatically retry
214	connecting to them infinitely.
215
216	Example: become a public node listening on the guessed noderef, or the one
217	specified via C<aemp> for the current node. This should be the most common
218	form of invocation for "daemon"-type nodes.
219
220	initialise_node;
221
222	Example: become a slave node to any of the the seednodes specified via
223	C<aemp>. This form is often used for commandline clients.
224
225	initialise_node "slave/";
226
227	Example: become a slave node to any of the specified master servers. This
228	form is also often used for commandline clients.
229
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
231
232	Example: become a public node, and try to contact some well-known master
233	servers to become part of the network.
234
235	initialise_node undef, "master1", "master2";
236
237	Example: become a public node listening on port C<4041>.
238
239	initialise_node 4041;
240
241	Example: become a public node, only visible on localhost port 4044.
242
243	initialise_node "localhost:4044";
244
245	=item $cv = resolve_node $noderef
246
247	Takes an unresolved node reference that may contain hostnames and
248	abbreviated IDs, resolves all of them and returns a resolved node
249	reference.
250
251	In addition to C<address:port> pairs allowed in resolved noderefs, the
252	following forms are supported:
253
254	=over 4	250	=over 4
255		251
256	=item the empty string	252	=item step 1, gathering configuration from profiles
257		253
258	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
259	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.
260		258
261	=item naked port numbers (e.g. C<1234>)	259	The profile data is then gathered as follows:
262		260
263	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
264	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).
265		266
266	=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.
267		270
268	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
269	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
270	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.
271		295
272	=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)"
273		323
274	=item $SELF	324	=item $SELF
275		325
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	326	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	327	blocks.
278		328
279	=item SELF, %SELF, @SELF...	329	=item *SELF, SELF, %SELF, @SELF...
280		330
281	Due to some quirks in how perl exports variables, it is impossible to	331	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	332	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	333	module, but only C<$SELF> is currently used.
284		334
285	=item snd $port, type => @data	335	=item snd $port, type => @data
286		336
287	=item snd $port, @msg	337	=item snd $port, @msg
288		338
289	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
290	a local or a remote port, and must be a port ID.	340	local or a remote port, and must be a port ID.
291		341
292	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
293	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
294	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.
295		346
296	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
297	function: modifying any argument is not allowed and can cause many	348	function: modifying any argument (or values referenced by them) is
298	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.
299		353
300	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
301	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
302	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
303	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
304	node, anything can be passed.	358	node, anything can be passed. Best rely only on the common denominator of
		359	these.
305		360
306	=item $local_port = port	361	=item $local_port = port
307		362
308	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
309	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.
…		…
333	sub _kilme {	388	sub _kilme {
334	die "received message on port without callback";	389	die "received message on port without callback";
335	}	390	}
336		391
337	sub port(;&) {	392	sub port(;&) {
338	my $id = "$UNIQ." . $ID++;	393	my $id = "$UNIQ." . ++$ID;
339	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
340		395
341	rcv $port, shift \|\| \&_kilme;	396	rcv $port, shift \|\| \&_kilme;
342		397
343	$port	398	$port
…		…
382	msg1 => sub { ... },	437	msg1 => sub { ... },
383	...	438	...
384	;	439	;
385		440
386	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
387	(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.
388		443
389	rcv $port, $otherport => sub {	444	rcv $port, $otherport => sub {
390	my @reply = @_;	445	my @reply = @_;
391		446
392	rcv $SELF, $otherport;	447	rcv $SELF, $otherport;
…		…
394		449
395	=cut	450	=cut
396		451
397	sub rcv($@) {	452	sub rcv($@) {
398	my $port = shift;	453	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	454	my ($nodeid, $portid) = split /#/, $port, 2;
400		455
401	$NODE{$noderef} == $NODE{""}	456	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	457	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		458
404	while (@_) {	459	while (@_) {
405	if (ref $_[0]) {	460	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	461	if (my $self = $PORT_DATA{$portid}) {
407	"AnyEvent::MP::Port" eq ref $self	462	"AnyEvent::MP::Port" eq ref $self
408	or Carp::croak "$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";
409		464
410	$self->[2] = shift;	465	$self->[0] = shift;
411	} else {	466	} else {
412	my $cb = shift;	467	my $cb = shift;
413	$PORT{$portid} = sub {	468	$PORT{$portid} = sub {
414	local $SELF = $port;	469	local $SELF = $port;
415	eval { &$cb }; _self_die if $@;	470	eval { &$cb }; _self_die if $@;
416	};	471	};
417	}	472	}
418	} elsif (defined $_[0]) {	473	} elsif (defined $_[0]) {
419	my $self = $PORT_DATA{$portid} \|\|= do {	474	my $self = $PORT_DATA{$portid} \|\|= do {
420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	475	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
421		476
422	$PORT{$portid} = sub {	477	$PORT{$portid} = sub {
423	local $SELF = $port;	478	local $SELF = $port;
424		479
425	if (my $cb = $self->[1]{$_[0]}) {	480	if (my $cb = $self->[1]{$_[0]}) {
…		…
447	}	502	}
448		503
449	$port	504	$port
450	}	505	}
451		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
452	=item $closure = psub { BLOCK }	544	=item $closure = psub { BLOCK }
453		545
454	Remembers C<$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
455	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>
456	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 $SELF, sub {
		551	BLOCK }, @_ } >>.
457		552
458	This is useful when you register callbacks from C<rcv> callbacks:	553	This is useful when you register callbacks from C<rcv> callbacks:
459		554
460	rcv delayed_reply => sub {	555	rcv delayed_reply => sub {
461	my ($delay, @reply) = @_;	556	my ($delay, @reply) = @_;
…		…
485	$res	580	$res
486	}	581	}
487	}	582	}
488	}	583	}
489		584
490	=item $guard = mon $port, $cb->(@reason)	585	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
491		586
492	=item $guard = mon $port, $rcvport	587	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
493		588
494	=item $guard = mon $port	589	=item $guard = mon $port # kill $SELF when $port dies
495		590
496	=item $guard = mon $port, $rcvport, @msg	591	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		592
498	Monitor the given port and do something when the port is killed or	593	Monitor the given port and do something when the port is killed or
499	messages to it were lost, and optionally return a guard that can be used	594	messages to it were lost, and optionally return a guard that can be used
500	to stop monitoring again.	595	to stop monitoring again.
501
502	C<mon> effectively guarantees that, in the absence of hardware failures,
503	that after starting the monitor, either all messages sent to the port
504	will arrive, or the monitoring action will be invoked after possible
505	message loss has been detected. No messages will be lost "in between"
506	(after the first lost message no further messages will be received by the
507	port). After the monitoring action was invoked, further messages might get
508	delivered again.
509
510	Note that monitoring-actions are one-shot: once released, they are removed
511	and will not trigger again.
512		596
513	In the first form (callback), the callback is simply called with any	597	In the first form (callback), the callback is simply called with any
514	number of C<@reason> elements (no @reason means that the port was deleted	598	number of C<@reason> elements (no @reason means that the port was deleted
515	"normally"). Note also that I<< the callback B<must> never die >>, so use	599	"normally"). Note also that I<< the callback B<must> never die >>, so use
516	C<eval> if unsure.	600	C<eval> if unsure.
517		601
518	In the second form (another port given), the other port (C<$rcvport>)	602	In the second form (another port given), the other port (C<$rcvport>)
519	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	603	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
520	"normal" kils nothing happens, while under all other conditions, the other	604	"normal" kils nothing happens, while under all other conditions, the other
521	port is killed with the same reason.	605	port is killed with the same reason.
522		606
523	The third form (kill self) is the same as the second form, except that	607	The third form (kill self) is the same as the second form, except that
524	C<$rvport> defaults to C<$SELF>.	608	C<$rvport> defaults to C<$SELF>.
525		609
526	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
527	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.
528		615
529	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
530	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
531	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
532	even monitoring requests can get lost (for exmaple, when the connection	619	even monitoring requests can get lost (for example, when the connection
533	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
534	these problems do not exist.	621	these problems do not exist.
535		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
536	Example: call a given callback when C<$port> is killed.	640	Example: call a given callback when C<$port> is killed.
537		641
538	mon $port, sub { warn "port died because of <@_>\n" };	642	mon $port, sub { warn "port died because of <@_>\n" };
539		643
540	Example: kill ourselves when C<$port> is killed abnormally.	644	Example: kill ourselves when C<$port> is killed abnormally.
…		…
546	mon $port, $self => "restart";	650	mon $port, $self => "restart";
547		651
548	=cut	652	=cut
549		653
550	sub mon {	654	sub mon {
551	my ($noderef, $port) = split /#/, shift, 2;	655	my ($nodeid, $port) = split /#/, shift, 2;
552		656
553	my $node = $NODE{$noderef} \|\| add_node $noderef;	657	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
554		658
555	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,';
556		660
557	unless (ref $cb) {	661	unless (ref $cb) {
558	if (@_) {	662	if (@_) {
…		…
567	}	671	}
568		672
569	$node->monitor ($port, $cb);	673	$node->monitor ($port, $cb);
570		674
571	defined wantarray	675	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	676	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
573	}	677	}
574		678
575	=item $guard = mon_guard $port, $ref, $ref...	679	=item $guard = mon_guard $port, $ref, $ref...
576		680
577	Monitors the given C<$port> and keeps the passed references. When the port	681	Monitors the given C<$port> and keeps the passed references. When the port
578	is killed, the references will be freed.	682	is killed, the references will be freed.
579		683
580	Optionally returns a guard that will stop the monitoring.	684	Optionally returns a guard that will stop the monitoring.
581		685
582	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
583	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>):
584		688
585	$port->rcv (start => sub {	689	$port->rcv (start => sub {
586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	690	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
587	undef $timer if 0.9 < rand;	691	undef $timer if 0.9 < rand;
588	});	692	});
589	});	693	});
590		694
591	=cut	695	=cut
…		…
600		704
601	=item kil $port[, @reason]	705	=item kil $port[, @reason]
602		706
603	Kill the specified port with the given C<@reason>.	707	Kill the specified port with the given C<@reason>.
604		708
605	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" -
606	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.
607		712
608	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>
609	C<mon>, see below).	714	form) get killed with the same reason.
610		715
611	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
612	will be reported as reason C<< die => $@ >>.	717	will be reported as reason C<< die => $@ >>.
613		718
614	Transport/communication errors are reported as C<< transport_error =>	719	Transport/communication errors are reported as C<< transport_error =>
…		…
619	=item $port = spawn $node, $initfunc[, @initdata]	724	=item $port = spawn $node, $initfunc[, @initdata]
620		725
621	Creates a port on the node C<$node> (which can also be a port ID, in which	726	Creates a port on the node C<$node> (which can also be a port ID, in which
622	case it's the node where that port resides).	727	case it's the node where that port resides).
623		728
624	The port ID of the newly created port is return immediately, and it is	729	The port ID of the newly created port is returned immediately, and it is
625	permissible to immediately start sending messages or monitor the port.	730	possible to immediately start sending messages or to monitor the port.
626		731
627	After the port has been created, the init function is	732	After the port has been created, the init function is called on the remote
628	called. This function must be a fully-qualified function name	733	node, in the same context as a C<rcv> callback. This function must be a
629	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	734	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
630	program, use C<::name>.	735	specify a function in the main program, use C<::name>.
631		736
632	If the function doesn't exist, then the node tries to C<require>	737	If the function doesn't exist, then the node tries to C<require>
633	the package, then the package above the package and so on (e.g.	738	the package, then the package above the package and so on (e.g.
634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	739	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
635	exists or it runs out of package names.	740	exists or it runs out of package names.
636		741
637	The init function is then called with the newly-created port as context	742	The init function is then called with the newly-created port as context
638	object (C<$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.
639		746
640	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
641	in the init function, monitor the original port. This two-way monitoring	748	port, and in the remote init function, immediately monitor the passed
642	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<$initfunc> has no visible effects on the
		753	caller before C<spawn> returns (by delaying invocation when spawn is
		754	called for the local node).
643		755
644	Example: spawn a chat server port on C<$othernode>.	756	Example: spawn a chat server port on C<$othernode>.
645		757
646	# this node, executed from within a port context:	758	# this node, executed from within a port context:
647	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	759	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
662		774
663	sub _spawn {	775	sub _spawn {
664	my $port = shift;	776	my $port = shift;
665	my $init = shift;	777	my $init = shift;
666		778
		779	# rcv will create the actual port
667	local $SELF = "$NODE#$port";	780	local $SELF = "$NODE#$port";
668	eval {	781	eval {
669	&{ load_func $init }	782	&{ load_func $init }
670	};	783	};
671	_self_die if $@;	784	_self_die if $@;
672	}	785	}
673		786
674	sub spawn(@) {	787	sub spawn(@) {
675	my ($noderef, undef) = split /#/, shift, 2;	788	my ($nodeid, undef) = split /#/, shift, 2;
676		789
677	my $id = "$RUNIQ." . $ID++;	790	my $id = "$RUNIQ." . ++$ID;
678		791
679	$_[0] =~ /::/	792	$_[0] =~ /::/
680	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";
681		794
682	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	795	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
683		796
684	"$noderef#$id"	797	"$nodeid#$id"
		798	}
		799
		800
		801	=item after $timeout, @msg
		802
		803	=item after $timeout, $callback
		804
		805	Either sends the given message, or call the given callback, after the
		806	specified number of seconds.
		807
		808	This is simply a utility function that comes in handy at times - the
		809	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		810	so it may go away in the future.
		811
		812	=cut
		813
		814	sub after($@) {
		815	my ($timeout, @action) = @_;
		816
		817	my $t; $t = AE::timer $timeout, 0, sub {
		818	undef $t;
		819	ref $action[0]
		820	? $action[0]()
		821	: snd @action;
		822	};
		823	}
		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
685	}	875	}
686		876
687	=back	877	=back
688		878
689	=head1 AnyEvent::MP vs. Distributed Erlang	879	=head1 AnyEvent::MP vs. Distributed Erlang
…		…
691	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
692	== 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
693	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
694	sample:	884	sample:
695		885
696	http://www.Erlang.se/doc/programming_rules.shtml	886	http://www.erlang.se/doc/programming_rules.shtml
697	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
698	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
699	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
700		890
701	Despite the similarities, there are also some important differences:	891	Despite the similarities, there are also some important differences:
702		892
703	=over 4	893	=over 4
704		894
705	=item * Node references contain the recipe on how to contact them.	895	=item * Node IDs are arbitrary strings in AEMP.
706		896
707	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
708	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
709	convenience functionality.	899	configuration or DNS), and possibly the addresses of some seed nodes, but
710		900	will otherwise discover other nodes (and their IDs) itself.
711	This means that AEMP requires a less tightly controlled environment at the
712	cost of longer node references and a slightly higher management overhead.
713		901
714	=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
715	uses "local ports are like remote ports".	903	uses "local ports are like remote ports".
716		904
717	The failure modes for local ports are quite different (runtime errors	905	The failure modes for local ports are quite different (runtime errors
…		…
726	ports being the special case/exception, where transport errors cannot	914	ports being the special case/exception, where transport errors cannot
727	occur.	915	occur.
728		916
729	=item * Erlang uses processes and a mailbox, AEMP does not queue.	917	=item * Erlang uses processes and a mailbox, AEMP does not queue.
730		918
731	Erlang uses processes that selectively receive messages, and therefore	919	Erlang uses processes that selectively receive messages out of order, and
732	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
733	useful purpose. For the same reason the pattern-matching abilities of	921	no useful purpose. For the same reason the pattern-matching abilities
734	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
735	filter messages without dequeing them.	923	filter messages without dequeuing them.
736		924
737	(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.
738		930
739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	931	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
740		932
741	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
742	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
743	connection establishment is handled in the background.	936	establishment is handled in the background.
744		937
745	=item * Erlang suffers from silent message loss, AEMP does not.	938	=item * Erlang suffers from silent message loss, AEMP does not.
746		939
747	Erlang makes few guarantees on messages delivery - messages can get lost	940	Erlang implements few guarantees on messages delivery - messages can get
748	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,
749	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).
750		943
751	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
752	holes in the message sequence.	947	no silent "holes" in the message sequence.
753		948
754	=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
755	alive.	950	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
756		951	simply tries to work better in common error cases, such as when a network
757	In Erlang it can happen that a monitored process is declared dead and	952	link goes down.
758	linked processes get killed, but later it turns out that the process is
759	still alive - and can receive messages.
760
761	In AEMP, when port monitoring detects a port as dead, then that port will
762	eventually be killed - it cannot happen that a node detects a port as dead
763	and then later sends messages to it, finding it is still alive.
764		953
765	=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.
766		955
767	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
768	known to other nodes for a completely different process, causing messages	957	process ID known to other nodes for a completely different process,
769	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.
770		960
771	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
772	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.
773		963
774	=item * Erlang uses unprotected connections, AEMP uses secure	964	=item * Erlang uses unprotected connections, AEMP uses secure
775	authentication and can use TLS.	965	authentication and can use TLS.
776		966
777	AEMP can use a proven protocol - SSL/TLS - to protect connections and	967	AEMP can use a proven protocol - TLS - to protect connections and
778	securely authenticate nodes.	968	securely authenticate nodes.
779		969
780	=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
781	communications.	971	communications.
782		972
783	The AEMP protocol, unlike the Erlang protocol, supports both	973	The AEMP protocol, unlike the Erlang protocol, supports both programming
784	language-independent text-only protocols (good for debugging) and binary,	974	language independent text-only protocols (good for debugging), and binary,
785	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.
786		977
787	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
788	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
789	protocol simple.	980	protocol simple.
790		981
791	=item * AEMP has more flexible monitoring options than Erlang.	982	=item * AEMP has more flexible monitoring options than Erlang.
792		983
793	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
794	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
795	difficult to implement. Monitoring in AEMP is more flexible than in	986	difficult to implement.
796	Erlang, as one can choose between automatic kill, exit message or callback	987
797	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.
798		990
799	=item * Erlang tries to hide remote/local connections, AEMP does not.	991	=item * Erlang tries to hide remote/local connections, AEMP does not.
800		992
801	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
802	as linking is (except linking is unreliable in Erlang).	994	same way as linking is (except linking is unreliable in Erlang).
803		995
804	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
805	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
806	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
807	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
808	more reliable.	1000	reliable (no need for C<spawn_link>).
809		1001
810	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
811	(hard to do in Erlang).	1003	(hard to do in Erlang).
812		1004
813	=back	1005	=back
814		1006
815	=head1 RATIONALE	1007	=head1 RATIONALE
816		1008
817	=over 4	1009	=over 4
818		1010
819	=item Why strings for ports and noderefs, why not objects?	1011	=item Why strings for port and node IDs, why not objects?
820		1012
821	We considered "objects", but found that the actual number of methods	1013	We considered "objects", but found that the actual number of methods
822	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
823	the network frequently, the serialising/deserialising would add lots of	1015	the network frequently, the serialising/deserialising would add lots of
824	overhead, as well as having to keep a proxy object.	1016	overhead, as well as having to keep a proxy object everywhere.
825		1017
826	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
827	procedures to be "valid".	1019	procedures to be "valid".
828		1020
829	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
830	can't become much cheaper.	1022	code reference stored in a global hash - it can't become much cheaper.
831		1023
832	=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?
833		1025
834	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
835	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
836	default.	1028	default (although all nodes will accept it).
837		1029
838	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
839	faster for small messages and b) most importantly, after years of	1031	faster for small messages and b) most importantly, after years of
840	experience we found that object serialisation is causing more problems	1032	experience we found that object serialisation is causing more problems
841	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
842	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
843	always have to re-think your design.	1035	always have to re-think your design.
844		1036
845	Keeping your messages simple, concentrating on data structures rather than	1037	Keeping your messages simple, concentrating on data structures rather than
846	objects, will keep your messages clean, tidy and efficient.	1038	objects, will keep your messages clean, tidy and efficient.
847		1039
848	=back	1040	=back
849		1041
850	=head1 SEE ALSO	1042	=head1 SEE ALSO
851		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
852	L<AnyEvent>.	1056	L<AnyEvent>.
853		1057
854	=head1 AUTHOR	1058	=head1 AUTHOR
855		1059
856	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