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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.60 by root, Mon Aug 24 08:04:52 2009 UTC vs.
Revision 1.123 by root, Thu Mar 1 19:37:59 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<#>)
80	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
81	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
82	reference.
83		90
84	=item node	91	=item node
85		92
86	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
88	ports.	95	ports.
89		96
90	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	98	(no listening ports). Private nodes cannot talk to other private nodes
		99	currently, but all nodes can talk to public nodes.
92		100
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
94		102
95	A node reference is a string that either simply identifies the node (for	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
96	private and slave nodes), or contains a recipe on how to reach a given
97	node (for public nodes).
98		104
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	A node ID is a string that uniquely identifies the node within a
100	TCP/IP, other protocols might look different).	106	network. Depending on the configuration used, node IDs can look like a
		107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
101		109
102	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
103	addresses) or unresolved (where hostnames are used instead of addresses).
104		111
105	Before using an unresolved node reference in a message you first have to	112	Nodes can only talk to each other by creating some kind of connection to
106	resolve it.	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
107		170
108	=back	171	=back
109		172
110	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
111		174
113		176
114	=cut	177	=cut
115		178
116	package AnyEvent::MP;	179	package AnyEvent::MP;
117		180
		181	use AnyEvent::MP::Config ();
118	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
119		184
120	use common::sense;	185	use common::sense;
121		186
122	use Carp ();	187	use Carp ();
123		188
124	use AE ();	189	use AE ();
125		190
126	use base "Exporter";	191	use base "Exporter";
127		192
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	193	our $VERSION = $AnyEvent::MP::Config::VERSION;
129		194
130	our @EXPORT = qw(	195	our @EXPORT = qw(
131	NODE $NODE *SELF node_of after	196	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	197	configure
133	snd rcv mon mob_guard kil reg psub spawn	198	snd rcv mon mon_guard kil psub peval spawn cal
134	port	199	port
135	);	200	);
136		201
137	our $SELF;	202	our $SELF;
138		203
…		…
142	kil $SELF, die => $msg;	207	kil $SELF, die => $msg;
143	}	208	}
144		209
145	=item $thisnode = NODE / $NODE	210	=item $thisnode = NODE / $NODE
146		211
147	The C<NODE> function returns, and the C<$NODE> variable contains the	212	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	213	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	214	a call to C<configure>.
150		215
151	=item $noderef = node_of $port	216	=item $nodeid = node_of $port
152		217
153	Extracts and returns the noderef from a port ID or a noderef.	218	Extracts and returns the node ID from a port ID or a node ID.
154		219
155	=item initialise_node $noderef, $seednode, $seednode...	220	=item configure $profile, key => value...
156		221
157	=item initialise_node "slave/", $master, $master...	222	=item configure key => value...
158		223
159	Before a node can talk to other nodes on the network it has to initialise	224	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	225	"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.	226	to know is its own name, and optionally it should know the addresses of
		227	some other nodes in the network to discover other nodes.
162		228
163	This function initialises a node - it must be called exactly once (or	229	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	230	never) before calling other AnyEvent::MP functions.
165		231
166	All arguments (optionally except for the first) are noderefs, which can be	232	The key/value pairs are basically the same ones as documented for the
167	either resolved or unresolved.	233	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		234
177	=over 4	235	=over 4
178		236
179	=item public nodes	237	=item norc => $boolean (default false)
180		238
181	For public nodes, C<$noderef> (supplied either directly to	239	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	240	be consulted - all configuraiton options must be specified in the
183	noderef (possibly unresolved, in which case it will be resolved).	241	C<configure> call.
184		242
185	After resolving, the node will bind itself on all endpoints and try to	243	=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		244
190	=item slave nodes	245	IF true, then the values specified in the C<configure> will take
191		246	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)	247	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		248
207	=back	249	=back
208		250
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	251	=over 4
255		252
256	=item the empty string	253	=item step 1, gathering configuration from profiles
257		254
258	An empty-string component gets resolved as if the default port (4040) was	255	The function first looks up a profile in the aemp configuration (see the
259	specified.	256	L<aemp> commandline utility). The profile name can be specified via the
		257	named C<profile> parameter or can simply be the first parameter). If it is
		258	missing, then the nodename (F<uname -n>) will be used as profile name.
260		259
261	=item naked port numbers (e.g. C<1234>)	260	The profile data is then gathered as follows:
262		261
263	These are resolved by prepending the local nodename and a colon, to be	262	First, all remaining key => value pairs (all of which are conveniently
264	further resolved.	263	undocumented at the moment) will be interpreted as configuration
		264	data. Then they will be overwritten by any values specified in the global
		265	default configuration (see the F<aemp> utility), then the chain of
		266	profiles chosen by the profile name (and any C<parent> attributes).
265		267
266	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	268	That means that the values specified in the profile have highest priority
		269	and the values specified directly via C<configure> have lowest priority,
		270	and can only be used to specify defaults.
267		271
268	These are resolved by using AnyEvent::DNS to resolve them, optionally	272	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	273	this process. If not, then the profile name will be used as node ID, with
270	specified.	274	a slash (C</>) attached.
		275
		276	If the node ID (or profile name) ends with a slash (C</>), then a random
		277	string is appended to make it unique.
		278
		279	=item step 2, bind listener sockets
		280
		281	The next step is to look up the binds in the profile, followed by binding
		282	aemp protocol listeners on all binds specified (it is possible and valid
		283	to have no binds, meaning that the node cannot be contacted form the
		284	outside. This means the node cannot talk to other nodes that also have no
		285	binds, but it can still talk to all "normal" nodes).
		286
		287	If the profile does not specify a binds list, then a default of C<*> is
		288	used, meaning the node will bind on a dynamically-assigned port on every
		289	local IP address it finds.
		290
		291	=item step 3, connect to seed nodes
		292
		293	As the last step, the seed ID list from the profile is passed to the
		294	L<AnyEvent::MP::Global> module, which will then use it to keep
		295	connectivity with at least one node at any point in time.
271		296
272	=back	297	=back
		298
		299	Example: become a distributed node using the local node name as profile.
		300	This should be the most common form of invocation for "daemon"-type nodes.
		301
		302	configure
		303
		304	Example: become an anonymous node. This form is often used for commandline
		305	clients.
		306
		307	configure nodeid => "anon/";
		308
		309	Example: configure a node using a profile called seed, which is suitable
		310	for a seed node as it binds on all local addresses on a fixed port (4040,
		311	customary for aemp).
		312
		313	# use the aemp commandline utility
		314	# aemp profile seed binds '*:4040'
		315
		316	# then use it
		317	configure profile => "seed";
		318
		319	# or simply use aemp from the shell again:
		320	# aemp run profile seed
		321
		322	# or provide a nicer-to-remember nodeid
		323	# aemp run profile seed nodeid "$(hostname)"
273		324
274	=item $SELF	325	=item $SELF
275		326
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	327	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	328	blocks.
278		329
279	=item SELF, %SELF, @SELF...	330	=item *SELF, SELF, %SELF, @SELF...
280		331
281	Due to some quirks in how perl exports variables, it is impossible to	332	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	333	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	334	module, but only C<$SELF> is currently used.
284		335
285	=item snd $port, type => @data	336	=item snd $port, type => @data
286		337
287	=item snd $port, @msg	338	=item snd $port, @msg
288		339
289	Send the given message to the given port ID, which can identify either	340	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.	341	local or a remote port, and must be a port ID.
291		342
292	While the message can be about anything, it is highly recommended to use a	343	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	344	use a string as first element (a port ID, or some word that indicates a
294	type etc.).	345	request type etc.) and to consist if only simple perl values (scalars,
		346	arrays, hashes) - if you think you need to pass an object, think again.
295		347
296	The message data effectively becomes read-only after a call to this	348	The message data logically becomes read-only after a call to this
297	function: modifying any argument is not allowed and can cause many	349	function: modifying any argument (or values referenced by them) is
298	problems.	350	forbidden, as there can be considerable time between the call to C<snd>
		351	and the time the message is actually being serialised - in fact, it might
		352	never be copied as within the same process it is simply handed to the
		353	receiving port.
299		354
300	The type of data you can transfer depends on the transport protocol: when	355	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	356	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	357	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	358	that Storable can serialise and deserialise is allowed, and for the local
304	node, anything can be passed.	359	node, anything can be passed. Best rely only on the common denominator of
		360	these.
305		361
306	=item $local_port = port	362	=item $local_port = port
307		363
308	Create a new local port object and returns its port ID. Initially it has	364	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.	365	no callbacks set and will throw an error when it receives messages.
…		…
333	sub _kilme {	389	sub _kilme {
334	die "received message on port without callback";	390	die "received message on port without callback";
335	}	391	}
336		392
337	sub port(;&) {	393	sub port(;&) {
338	my $id = "$UNIQ." . $ID++;	394	my $id = $UNIQ . ++$ID;
339	my $port = "$NODE#$id";	395	my $port = "$NODE#$id";
340		396
341	rcv $port, shift \|\| \&_kilme;	397	rcv $port, shift \|\| \&_kilme;
342		398
343	$port	399	$port
…		…
382	msg1 => sub { ... },	438	msg1 => sub { ... },
383	...	439	...
384	;	440	;
385		441
386	Example: temporarily register a rcv callback for a tag matching some port	442	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.	443	(e.g. for an rpc reply) and unregister it after a message was received.
388		444
389	rcv $port, $otherport => sub {	445	rcv $port, $otherport => sub {
390	my @reply = @_;	446	my @reply = @_;
391		447
392	rcv $SELF, $otherport;	448	rcv $SELF, $otherport;
…		…
394		450
395	=cut	451	=cut
396		452
397	sub rcv($@) {	453	sub rcv($@) {
398	my $port = shift;	454	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	455	my ($nodeid, $portid) = split /#/, $port, 2;
400		456
401	$NODE{$noderef} == $NODE{""}	457	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	458	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		459
404	while (@_) {	460	while (@_) {
405	if (ref $_[0]) {	461	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	462	if (my $self = $PORT_DATA{$portid}) {
407	"AnyEvent::MP::Port" eq ref $self	463	"AnyEvent::MP::Port" eq ref $self
408	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	464	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
409		465
410	$self->[2] = shift;	466	$self->[0] = shift;
411	} else {	467	} else {
412	my $cb = shift;	468	my $cb = shift;
413	$PORT{$portid} = sub {	469	$PORT{$portid} = sub {
414	local $SELF = $port;	470	local $SELF = $port;
415	eval { &$cb }; _self_die if $@;	471	eval { &$cb }; _self_die if $@;
416	};	472	};
417	}	473	}
418	} elsif (defined $_[0]) {	474	} elsif (defined $_[0]) {
419	my $self = $PORT_DATA{$portid} \|\|= do {	475	my $self = $PORT_DATA{$portid} \|\|= do {
420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	476	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
421		477
422	$PORT{$portid} = sub {	478	$PORT{$portid} = sub {
423	local $SELF = $port;	479	local $SELF = $port;
424		480
425	if (my $cb = $self->[1]{$_[0]}) {	481	if (my $cb = $self->[1]{$_[0]}) {
…		…
447	}	503	}
448		504
449	$port	505	$port
450	}	506	}
451		507
		508	=item peval $port, $coderef[, @args]
		509
		510	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		511	when the code throews an exception the C<$port> will be killed.
		512
		513	Any remaining args will be passed to the callback. Any return values will
		514	be returned to the caller.
		515
		516	This is useful when you temporarily want to execute code in the context of
		517	a port.
		518
		519	Example: create a port and run some initialisation code in it's context.
		520
		521	my $port = port { ... };
		522
		523	peval $port, sub {
		524	init
		525	or die "unable to init";
		526	};
		527
		528	=cut
		529
		530	sub peval($$) {
		531	local $SELF = shift;
		532	my $cb = shift;
		533
		534	if (wantarray) {
		535	my @res = eval { &$cb };
		536	_self_die if $@;
		537	@res
		538	} else {
		539	my $res = eval { &$cb };
		540	_self_die if $@;
		541	$res
		542	}
		543	}
		544
452	=item $closure = psub { BLOCK }	545	=item $closure = psub { BLOCK }
453		546
454	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	547	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>	548	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.	549	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		550
		551	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		552	BLOCK }, @_ } >>.
457		553
458	This is useful when you register callbacks from C<rcv> callbacks:	554	This is useful when you register callbacks from C<rcv> callbacks:
459		555
460	rcv delayed_reply => sub {	556	rcv delayed_reply => sub {
461	my ($delay, @reply) = @_;	557	my ($delay, @reply) = @_;
…		…
485	$res	581	$res
486	}	582	}
487	}	583	}
488	}	584	}
489		585
490	=item $guard = mon $port, $cb->(@reason)	586	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
491		587
492	=item $guard = mon $port, $rcvport	588	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
493		589
494	=item $guard = mon $port	590	=item $guard = mon $port # kill $SELF when $port dies
495		591
496	=item $guard = mon $port, $rcvport, @msg	592	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		593
498	Monitor the given port and do something when the port is killed or	594	Monitor the given port and do something when the port is killed or
499	messages to it were lost, and optionally return a guard that can be used	595	messages to it were lost, and optionally return a guard that can be used
500	to stop monitoring again.	596	to stop monitoring again.
501
502	C<mon> effectively guarantees that, in the absence of hardware failures,
503	that after starting the monitor, either all messages sent to the port
504	will arrive, or the monitoring action will be invoked after possible
505	message loss has been detected. No messages will be lost "in between"
506	(after the first lost message no further messages will be received by the
507	port). After the monitoring action was invoked, further messages might get
508	delivered again.
509
510	Note that monitoring-actions are one-shot: once released, they are removed
511	and will not trigger again.
512		597
513	In the first form (callback), the callback is simply called with any	598	In the first form (callback), the callback is simply called with any
514	number of C<@reason> elements (no @reason means that the port was deleted	599	number of C<@reason> elements (no @reason means that the port was deleted
515	"normally"). Note also that I<< the callback B<must> never die >>, so use	600	"normally"). Note also that I<< the callback B<must> never die >>, so use
516	C<eval> if unsure.	601	C<eval> if unsure.
517		602
518	In the second form (another port given), the other port (C<$rcvport>)	603	In the second form (another port given), the other port (C<$rcvport>)
519	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	604	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
520	"normal" kils nothing happens, while under all other conditions, the other	605	"normal" kils nothing happens, while under all other conditions, the other
521	port is killed with the same reason.	606	port is killed with the same reason.
522		607
523	The third form (kill self) is the same as the second form, except that	608	The third form (kill self) is the same as the second form, except that
524	C<$rvport> defaults to C<$SELF>.	609	C<$rvport> defaults to C<$SELF>.
525		610
526	In the last form (message), a message of the form C<@msg, @reason> will be	611	In the last form (message), a message of the form C<@msg, @reason> will be
527	C<snd>.	612	C<snd>.
		613
		614	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		615	alert was raised), they are removed and will not trigger again.
528		616
529	As a rule of thumb, monitoring requests should always monitor a port from	617	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	618	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	619	lost, just like any other message. Another less obvious reason is that
532	even monitoring requests can get lost (for exmaple, when the connection	620	even monitoring requests can get lost (for example, when the connection
533	to the other node goes down permanently). When monitoring a port locally	621	to the other node goes down permanently). When monitoring a port locally
534	these problems do not exist.	622	these problems do not exist.
535		623
		624	C<mon> effectively guarantees that, in the absence of hardware failures,
		625	after starting the monitor, either all messages sent to the port will
		626	arrive, or the monitoring action will be invoked after possible message
		627	loss has been detected. No messages will be lost "in between" (after
		628	the first lost message no further messages will be received by the
		629	port). After the monitoring action was invoked, further messages might get
		630	delivered again.
		631
		632	Inter-host-connection timeouts and monitoring depend on the transport
		633	used. The only transport currently implemented is TCP, and AnyEvent::MP
		634	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		635	non-idle connection, and usually around two hours for idle connections).
		636
		637	This means that monitoring is good for program errors and cleaning up
		638	stuff eventually, but they are no replacement for a timeout when you need
		639	to ensure some maximum latency.
		640
536	Example: call a given callback when C<$port> is killed.	641	Example: call a given callback when C<$port> is killed.
537		642
538	mon $port, sub { warn "port died because of <@_>\n" };	643	mon $port, sub { warn "port died because of <@_>\n" };
539		644
540	Example: kill ourselves when C<$port> is killed abnormally.	645	Example: kill ourselves when C<$port> is killed abnormally.
…		…
546	mon $port, $self => "restart";	651	mon $port, $self => "restart";
547		652
548	=cut	653	=cut
549		654
550	sub mon {	655	sub mon {
551	my ($noderef, $port) = split /#/, shift, 2;	656	my ($nodeid, $port) = split /#/, shift, 2;
552		657
553	my $node = $NODE{$noderef} \|\| add_node $noderef;	658	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
554		659
555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	660	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
556		661
557	unless (ref $cb) {	662	unless (ref $cb) {
558	if (@_) {	663	if (@_) {
…		…
567	}	672	}
568		673
569	$node->monitor ($port, $cb);	674	$node->monitor ($port, $cb);
570		675
571	defined wantarray	676	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	677	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
573	}	678	}
574		679
575	=item $guard = mon_guard $port, $ref, $ref...	680	=item $guard = mon_guard $port, $ref, $ref...
576		681
577	Monitors the given C<$port> and keeps the passed references. When the port	682	Monitors the given C<$port> and keeps the passed references. When the port
578	is killed, the references will be freed.	683	is killed, the references will be freed.
579		684
580	Optionally returns a guard that will stop the monitoring.	685	Optionally returns a guard that will stop the monitoring.
581		686
582	This function is useful when you create e.g. timers or other watchers and	687	This function is useful when you create e.g. timers or other watchers and
583	want to free them when the port gets killed:	688	want to free them when the port gets killed (note the use of C<psub>):
584		689
585	$port->rcv (start => sub {	690	$port->rcv (start => sub {
586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	691	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
587	undef $timer if 0.9 < rand;	692	undef $timer if 0.9 < rand;
588	});	693	});
589	});	694	});
590		695
591	=cut	696	=cut
…		…
600		705
601	=item kil $port[, @reason]	706	=item kil $port[, @reason]
602		707
603	Kill the specified port with the given C<@reason>.	708	Kill the specified port with the given C<@reason>.
604		709
605	If no C<@reason> is specified, then the port is killed "normally" (linked	710	If no C<@reason> is specified, then the port is killed "normally" -
606	ports will not be kileld, or even notified).	711	monitor callback will be invoked, but the kil will not cause linked ports
		712	(C<mon $mport, $lport> form) to get killed.
607		713
608	Otherwise, linked ports get killed with the same reason (second form of	714	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
609	C<mon>, see below).	715	form) get killed with the same reason.
610		716
611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	717	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
612	will be reported as reason C<< die => $@ >>.	718	will be reported as reason C<< die => $@ >>.
613		719
614	Transport/communication errors are reported as C<< transport_error =>	720	Transport/communication errors are reported as C<< transport_error =>
…		…
619	=item $port = spawn $node, $initfunc[, @initdata]	725	=item $port = spawn $node, $initfunc[, @initdata]
620		726
621	Creates a port on the node C<$node> (which can also be a port ID, in which	727	Creates a port on the node C<$node> (which can also be a port ID, in which
622	case it's the node where that port resides).	728	case it's the node where that port resides).
623		729
624	The port ID of the newly created port is return immediately, and it is	730	The port ID of the newly created port is returned immediately, and it is
625	permissible to immediately start sending messages or monitor the port.	731	possible to immediately start sending messages or to monitor the port.
626		732
627	After the port has been created, the init function is	733	After the port has been created, the init function is called on the remote
628	called. This function must be a fully-qualified function name	734	node, in the same context as a C<rcv> callback. This function must be a
629	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	735	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
630	program, use C<::name>.	736	specify a function in the main program, use C<::name>.
631		737
632	If the function doesn't exist, then the node tries to C<require>	738	If the function doesn't exist, then the node tries to C<require>
633	the package, then the package above the package and so on (e.g.	739	the package, then the package above the package and so on (e.g.
634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	740	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
635	exists or it runs out of package names.	741	exists or it runs out of package names.
636		742
637	The init function is then called with the newly-created port as context	743	The init function is then called with the newly-created port as context
638	object (C<$SELF>) and the C<@initdata> values as arguments.	744	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		745	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		746	the port might not get created.
639		747
640	A common idiom is to pass your own port, monitor the spawned port, and	748	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	749	port, and in the remote init function, immediately monitor the passed
642	ensures that both ports get cleaned up when there is a problem.	750	local port. This two-way monitoring ensures that both ports get cleaned up
		751	when there is a problem.
		752
		753	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		754	caller before C<spawn> returns (by delaying invocation when spawn is
		755	called for the local node).
643		756
644	Example: spawn a chat server port on C<$othernode>.	757	Example: spawn a chat server port on C<$othernode>.
645		758
646	# this node, executed from within a port context:	759	# this node, executed from within a port context:
647	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	760	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
662		775
663	sub _spawn {	776	sub _spawn {
664	my $port = shift;	777	my $port = shift;
665	my $init = shift;	778	my $init = shift;
666		779
		780	# rcv will create the actual port
667	local $SELF = "$NODE#$port";	781	local $SELF = "$NODE#$port";
668	eval {	782	eval {
669	&{ load_func $init }	783	&{ load_func $init }
670	};	784	};
671	_self_die if $@;	785	_self_die if $@;
672	}	786	}
673		787
674	sub spawn(@) {	788	sub spawn(@) {
675	my ($noderef, undef) = split /#/, shift, 2;	789	my ($nodeid, undef) = split /#/, shift, 2;
676		790
677	my $id = "$RUNIQ." . $ID++;	791	my $id = $RUNIQ . ++$ID;
678		792
679	$_[0] =~ /::/	793	$_[0] =~ /::/
680	or Carp::croak "spawn init function must be a fully-qualified name, caught";	794	or Carp::croak "spawn init function must be a fully-qualified name, caught";
681		795
682	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	796	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
683		797
684	"$noderef#$id"	798	"$nodeid#$id"
685	}	799	}
		800
686		801
687	=item after $timeout, @msg	802	=item after $timeout, @msg
688		803
689	=item after $timeout, $callback	804	=item after $timeout, $callback
690		805
691	Either sends the given message, or call the given callback, after the	806	Either sends the given message, or call the given callback, after the
692	specified number of seconds.	807	specified number of seconds.
693		808
694	This is simply a utility function that come sin handy at times.	809	This is simply a utility function that comes in handy at times - the
		810	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		811	so it may go away in the future.
695		812
696	=cut	813	=cut
697		814
698	sub after($@) {	815	sub after($@) {
699	my ($timeout, @action) = @_;	816	my ($timeout, @action) = @_;
…		…
704	? $action[0]()	821	? $action[0]()
705	: snd @action;	822	: snd @action;
706	};	823	};
707	}	824	}
708		825
		826	=item cal $port, @msg, $callback[, $timeout]
		827
		828	A simple form of RPC - sends a message to the given C<$port> with the
		829	given contents (C<@msg>), but adds a reply port to the message.
		830
		831	The reply port is created temporarily just for the purpose of receiving
		832	the reply, and will be C<kil>ed when no longer needed.
		833
		834	A reply message sent to the port is passed to the C<$callback> as-is.
		835
		836	If an optional time-out (in seconds) is given and it is not C<undef>,
		837	then the callback will be called without any arguments after the time-out
		838	elapsed and the port is C<kil>ed.
		839
		840	If no time-out is given (or it is C<undef>), then the local port will
		841	monitor the remote port instead, so it eventually gets cleaned-up.
		842
		843	Currently this function returns the temporary port, but this "feature"
		844	might go in future versions unless you can make a convincing case that
		845	this is indeed useful for something.
		846
		847	=cut
		848
		849	sub cal(@) {
		850	my $timeout = ref $_[-1] ? undef : pop;
		851	my $cb = pop;
		852
		853	my $port = port {
		854	undef $timeout;
		855	kil $SELF;
		856	&$cb;
		857	};
		858
		859	if (defined $timeout) {
		860	$timeout = AE::timer $timeout, 0, sub {
		861	undef $timeout;
		862	kil $port;
		863	$cb->();
		864	};
		865	} else {
		866	mon $_[0], sub {
		867	kil $port;
		868	$cb->();
		869	};
		870	}
		871
		872	push @_, $port;
		873	&snd;
		874
		875	$port
		876	}
		877
709	=back	878	=back
710		879
711	=head1 AnyEvent::MP vs. Distributed Erlang	880	=head1 AnyEvent::MP vs. Distributed Erlang
712		881
713	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	882	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
714	== aemp node, Erlang process == aemp port), so many of the documents and	883	== aemp node, Erlang process == aemp port), so many of the documents and
715	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	884	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
716	sample:	885	sample:
717		886
718	http://www.Erlang.se/doc/programming_rules.shtml	887	http://www.erlang.se/doc/programming_rules.shtml
719	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	888	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
720	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	889	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
721	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	890	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
722		891
723	Despite the similarities, there are also some important differences:	892	Despite the similarities, there are also some important differences:
724		893
725	=over 4	894	=over 4
726		895
727	=item * Node references contain the recipe on how to contact them.	896	=item * Node IDs are arbitrary strings in AEMP.
728		897
729	Erlang relies on special naming and DNS to work everywhere in the	898	Erlang relies on special naming and DNS to work everywhere in the same
730	same way. AEMP relies on each node knowing it's own address(es), with	899	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
731	convenience functionality.	900	configuration or DNS), and possibly the addresses of some seed nodes, but
732		901	will otherwise discover other nodes (and their IDs) itself.
733	This means that AEMP requires a less tightly controlled environment at the
734	cost of longer node references and a slightly higher management overhead.
735		902
736	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	903	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
737	uses "local ports are like remote ports".	904	uses "local ports are like remote ports".
738		905
739	The failure modes for local ports are quite different (runtime errors	906	The failure modes for local ports are quite different (runtime errors
…		…
748	ports being the special case/exception, where transport errors cannot	915	ports being the special case/exception, where transport errors cannot
749	occur.	916	occur.
750		917
751	=item * Erlang uses processes and a mailbox, AEMP does not queue.	918	=item * Erlang uses processes and a mailbox, AEMP does not queue.
752		919
753	Erlang uses processes that selectively receive messages, and therefore	920	Erlang uses processes that selectively receive messages out of order, and
754	needs a queue. AEMP is event based, queuing messages would serve no	921	therefore needs a queue. AEMP is event based, queuing messages would serve
755	useful purpose. For the same reason the pattern-matching abilities of	922	no useful purpose. For the same reason the pattern-matching abilities
756	AnyEvent::MP are more limited, as there is little need to be able to	923	of AnyEvent::MP are more limited, as there is little need to be able to
757	filter messages without dequeing them.	924	filter messages without dequeuing them.
758		925
759	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	926	This is not a philosophical difference, but simply stems from AnyEvent::MP
		927	being event-based, while Erlang is process-based.
		928
		929	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		930	top of AEMP and Coro threads.
760		931
761	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	932	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
762		933
763	Sending messages in Erlang is synchronous and blocks the process (and	934	Sending messages in Erlang is synchronous and blocks the process until
		935	a conenction has been established and the message sent (and so does not
764	so does not need a queue that can overflow). AEMP sends are immediate,	936	need a queue that can overflow). AEMP sends return immediately, connection
765	connection establishment is handled in the background.	937	establishment is handled in the background.
766		938
767	=item * Erlang suffers from silent message loss, AEMP does not.	939	=item * Erlang suffers from silent message loss, AEMP does not.
768		940
769	Erlang makes few guarantees on messages delivery - messages can get lost	941	Erlang implements few guarantees on messages delivery - messages can get
770	without any of the processes realising it (i.e. you send messages a, b,	942	lost without any of the processes realising it (i.e. you send messages a,
771	and c, and the other side only receives messages a and c).	943	b, and c, and the other side only receives messages a and c).
772		944
773	AEMP guarantees correct ordering, and the guarantee that there are no	945	AEMP guarantees (modulo hardware errors) correct ordering, and the
		946	guarantee that after one message is lost, all following ones sent to the
		947	same port are lost as well, until monitoring raises an error, so there are
774	holes in the message sequence.	948	no silent "holes" in the message sequence.
775		949
776	=item * In Erlang, processes can be declared dead and later be found to be	950	If you want your software to be very reliable, you have to cope with
777	alive.	951	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
778		952	simply tries to work better in common error cases, such as when a network
779	In Erlang it can happen that a monitored process is declared dead and	953	link goes down.
780	linked processes get killed, but later it turns out that the process is
781	still alive - and can receive messages.
782
783	In AEMP, when port monitoring detects a port as dead, then that port will
784	eventually be killed - it cannot happen that a node detects a port as dead
785	and then later sends messages to it, finding it is still alive.
786		954
787	=item * Erlang can send messages to the wrong port, AEMP does not.	955	=item * Erlang can send messages to the wrong port, AEMP does not.
788		956
789	In Erlang it is quite likely that a node that restarts reuses a process ID	957	In Erlang it is quite likely that a node that restarts reuses an Erlang
790	known to other nodes for a completely different process, causing messages	958	process ID known to other nodes for a completely different process,
791	destined for that process to end up in an unrelated process.	959	causing messages destined for that process to end up in an unrelated
		960	process.
792		961
793	AEMP never reuses port IDs, so old messages or old port IDs floating	962	AEMP does not reuse port IDs, so old messages or old port IDs floating
794	around in the network will not be sent to an unrelated port.	963	around in the network will not be sent to an unrelated port.
795		964
796	=item * Erlang uses unprotected connections, AEMP uses secure	965	=item * Erlang uses unprotected connections, AEMP uses secure
797	authentication and can use TLS.	966	authentication and can use TLS.
798		967
799	AEMP can use a proven protocol - SSL/TLS - to protect connections and	968	AEMP can use a proven protocol - TLS - to protect connections and
800	securely authenticate nodes.	969	securely authenticate nodes.
801		970
802	=item * The AEMP protocol is optimised for both text-based and binary	971	=item * The AEMP protocol is optimised for both text-based and binary
803	communications.	972	communications.
804		973
805	The AEMP protocol, unlike the Erlang protocol, supports both	974	The AEMP protocol, unlike the Erlang protocol, supports both programming
806	language-independent text-only protocols (good for debugging) and binary,	975	language independent text-only protocols (good for debugging), and binary,
807	language-specific serialisers (e.g. Storable).	976	language-specific serialisers (e.g. Storable). By default, unless TLS is
		977	used, the protocol is actually completely text-based.
808		978
809	It has also been carefully designed to be implementable in other languages	979	It has also been carefully designed to be implementable in other languages
810	with a minimum of work while gracefully degrading fucntionality to make the	980	with a minimum of work while gracefully degrading functionality to make the
811	protocol simple.	981	protocol simple.
812		982
813	=item * AEMP has more flexible monitoring options than Erlang.	983	=item * AEMP has more flexible monitoring options than Erlang.
814		984
815	In Erlang, you can chose to receive I<all> exit signals as messages	985	In Erlang, you can chose to receive I<all> exit signals as messages or
816	or I<none>, there is no in-between, so monitoring single processes is	986	I<none>, there is no in-between, so monitoring single Erlang processes is
817	difficult to implement. Monitoring in AEMP is more flexible than in	987	difficult to implement.
818	Erlang, as one can choose between automatic kill, exit message or callback	988
819	on a per-process basis.	989	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		990	between automatic kill, exit message or callback on a per-port basis.
820		991
821	=item * Erlang tries to hide remote/local connections, AEMP does not.	992	=item * Erlang tries to hide remote/local connections, AEMP does not.
822		993
823	Monitoring in Erlang is not an indicator of process death/crashes,	994	Monitoring in Erlang is not an indicator of process death/crashes, in the
824	as linking is (except linking is unreliable in Erlang).	995	same way as linking is (except linking is unreliable in Erlang).
825		996
826	In AEMP, you don't "look up" registered port names or send to named ports	997	In AEMP, you don't "look up" registered port names or send to named ports
827	that might or might not be persistent. Instead, you normally spawn a port	998	that might or might not be persistent. Instead, you normally spawn a port
828	on the remote node. The init function monitors the you, and you monitor	999	on the remote node. The init function monitors you, and you monitor the
829	the remote port. Since both monitors are local to the node, they are much	1000	remote port. Since both monitors are local to the node, they are much more
830	more reliable.	1001	reliable (no need for C<spawn_link>).
831		1002
832	This also saves round-trips and avoids sending messages to the wrong port	1003	This also saves round-trips and avoids sending messages to the wrong port
833	(hard to do in Erlang).	1004	(hard to do in Erlang).
834		1005
835	=back	1006	=back
836		1007
837	=head1 RATIONALE	1008	=head1 RATIONALE
838		1009
839	=over 4	1010	=over 4
840		1011
841	=item Why strings for ports and noderefs, why not objects?	1012	=item Why strings for port and node IDs, why not objects?
842		1013
843	We considered "objects", but found that the actual number of methods	1014	We considered "objects", but found that the actual number of methods
844	thatc an be called are very low. Since port IDs and noderefs travel over	1015	that can be called are quite low. Since port and node IDs travel over
845	the network frequently, the serialising/deserialising would add lots of	1016	the network frequently, the serialising/deserialising would add lots of
846	overhead, as well as having to keep a proxy object.	1017	overhead, as well as having to keep a proxy object everywhere.
847		1018
848	Strings can easily be printed, easily serialised etc. and need no special	1019	Strings can easily be printed, easily serialised etc. and need no special
849	procedures to be "valid".	1020	procedures to be "valid".
850		1021
851	And a a miniport consists of a single closure stored in a global hash - it	1022	And as a result, a port with just a default receiver consists of a single
852	can't become much cheaper.	1023	code reference stored in a global hash - it can't become much cheaper.
853		1024
854	=item Why favour JSON, why not real serialising format such as Storable?	1025	=item Why favour JSON, why not a real serialising format such as Storable?
855		1026
856	In fact, any AnyEvent::MP node will happily accept Storable as framing	1027	In fact, any AnyEvent::MP node will happily accept Storable as framing
857	format, but currently there is no way to make a node use Storable by	1028	format, but currently there is no way to make a node use Storable by
858	default.	1029	default (although all nodes will accept it).
859		1030
860	The default framing protocol is JSON because a) JSON::XS is many times	1031	The default framing protocol is JSON because a) JSON::XS is many times
861	faster for small messages and b) most importantly, after years of	1032	faster for small messages and b) most importantly, after years of
862	experience we found that object serialisation is causing more problems	1033	experience we found that object serialisation is causing more problems
863	than it gains: Just like function calls, objects simply do not travel	1034	than it solves: Just like function calls, objects simply do not travel
864	easily over the network, mostly because they will always be a copy, so you	1035	easily over the network, mostly because they will always be a copy, so you
865	always have to re-think your design.	1036	always have to re-think your design.
866		1037
867	Keeping your messages simple, concentrating on data structures rather than	1038	Keeping your messages simple, concentrating on data structures rather than
868	objects, will keep your messages clean, tidy and efficient.	1039	objects, will keep your messages clean, tidy and efficient.
869		1040
870	=back	1041	=back
871		1042
872	=head1 SEE ALSO	1043	=head1 SEE ALSO
873		1044
		1045	L<AnyEvent::MP::Intro> - a gentle introduction.
		1046
		1047	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1048
		1049	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1050	your applications.
		1051
		1052	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1053
		1054	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1055	all nodes.
		1056
874	L<AnyEvent>.	1057	L<AnyEvent>.
875		1058
876	=head1 AUTHOR	1059	=head1 AUTHOR
877		1060
878	Marc Lehmann <schmorp@schmorp.de>	1061	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.123 by root, Thu Mar 1 19:37:59 2012 UTC