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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.124 by root, Sat Mar 3 11:38:43 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;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
36	# monitoring	39	# monitoring
37	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
39	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	};
40		51
41	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
42		53
		54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - WIP
46	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
47		58	AnyEvent::MP::Global - stable API.
48	stay tuned.
49		59
50	=head1 DESCRIPTION	60	=head1 DESCRIPTION
51		61
52	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
53		63
54	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
56		66
57	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>
58	manual page.	68	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		69
64	=head1 CONCEPTS	70	=head1 CONCEPTS
65		71
66	=over 4	72	=over 4
67		73
68	=item port	74	=item port
69		75
70	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).
71		78
72	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
73	some messages. Messages send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	81	anything was listening for them or not.
75		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
76	=item port ID - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
77		86
78	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<#>)
79	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
80	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
81	reference.
82		90
83	=item node	91	=item node
84		92
85	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,
86	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
87	ports.	95	ports.
88		96
89	Nodes are either private (single-process only), slaves (can only talk to	97	Nodes are either public (have one or more listening ports) or private
90	public nodes, but do not need an open port) or public nodes (connectable	98	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	99	currently, but all nodes can talk to public nodes.
92		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
94		104
95	A node ID is a string that uniquely identifies the node within a	105	A node ID is a string that uniquely identifies the node within a
96	network. Depending on the configuration used, node IDs can look like a	106	network. Depending on the configuration used, node IDs can look like a
97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
98	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
99		109
100	=item binds - C<ip:port>	110	=item binds - C<ip:port>
101		111
102	Nodes can only talk to each other by creating some kind of connection to	112	Nodes can only talk to each other by creating some kind of connection to
103	each other. To do this, nodes should listen on one or more local transport	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
104	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
105	be used, which specify TCP ports to listen on.	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.
106		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
107	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
108		150
109	When a node starts, it knows nothing about the network. To teach the node	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
110	about the network it first has to contact some other node within the	152	TCP port) of nodes that should be used as seed nodes.
111	network. This node is called a seed.
112		153
113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
114	are expected to be long-running, and at least one of those should always	155
115	be available. When nodes run out of connections (e.g. due to a network	156	An AEMP network needs a discovery service - nodes need to know how to
116	error), they try to re-establish connections to some seednodes again to	157	connect to other nodes they only know by name. In addition, AEMP offers a
117	join the network.	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).
118		170
119	=back	171	=back
120		172
121	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
122		174
124		176
125	=cut	177	=cut
126		178
127	package AnyEvent::MP;	179	package AnyEvent::MP;
128		180
		181	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130		184
131	use common::sense;	185	use common::sense;
132		186
133	use Carp ();	187	use Carp ();
134		188
135	use AE ();	189	use AE ();
		190	use Guard ();
136		191
137	use base "Exporter";	192	use base "Exporter";
138		193
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
140		195
141	our @EXPORT = qw(	196	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	198	configure
144	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
145	port	200	port
		201	db_set db_del db_reg
146	);	202	);
147		203
148	our $SELF;	204	our $SELF;
149		205
150	sub _self_die() {	206	sub _self_die() {
…		…
153	kil $SELF, die => $msg;	209	kil $SELF, die => $msg;
154	}	210	}
155		211
156	=item $thisnode = NODE / $NODE	212	=item $thisnode = NODE / $NODE
157		213
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	214	The C<NODE> function returns, and the C<$NODE> variable contains, the node
159	ID of the node running in the current process. This value is initialised by	215	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	216	a call to C<configure>.
161		217
162	=item $nodeid = node_of $port	218	=item $nodeid = node_of $port
163		219
164	Extracts and returns the node ID part from a port ID or a node ID.	220	Extracts and returns the node ID from a port ID or a node ID.
165		221
166	=item initialise_node $profile_name	222	=item configure $profile, key => value...
		223
		224	=item configure key => value...
167		225
168	Before a node can talk to other nodes on the network (i.e. enter	226	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to initialise itself - the minimum a node needs	227	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	228	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	229	some other nodes in the network to discover other nodes.
172		230
173	This function initialises a node - it must be called exactly once (or	231	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
175		233
176	The first argument is a profile name. If it is C<undef> or missing, then	234	The key/value pairs are basically the same ones as documented for the
177	the current nodename will be used instead (i.e. F<uname -n>).	235	F<aemp> command line utility (sans the set/del prefix), with two additions:
178		236
		237	=over 4
		238
		239	=item norc => $boolean (default false)
		240
		241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		242	be consulted - all configuraiton options must be specified in the
		243	C<configure> call.
		244
		245	=item force => $boolean (default false)
		246
		247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
		250
		251	=back
		252
		253	=over 4
		254
		255	=item step 1, gathering configuration from profiles
		256
179	The function then looks up the profile in the aemp configuration (see the	257	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	258	L<aemp> commandline utility). The profile name can be specified via the
		259	named C<profile> parameter or can simply be the first parameter). If it is
		260	missing, then the nodename (F<uname -n>) will be used as profile name.
		261
		262	The profile data is then gathered as follows:
		263
		264	First, all remaining key => value pairs (all of which are conveniently
		265	undocumented at the moment) will be interpreted as configuration
		266	data. Then they will be overwritten by any values specified in the global
		267	default configuration (see the F<aemp> utility), then the chain of
		268	profiles chosen by the profile name (and any C<parent> attributes).
		269
		270	That means that the values specified in the profile have highest priority
		271	and the values specified directly via C<configure> have lowest priority,
		272	and can only be used to specify defaults.
181		273
182	If the profile specifies a node ID, then this will become the node ID of	274	If the profile specifies a node ID, then this will become the node ID of
183	this process. If not, then the profile name will be used as node ID. The	275	this process. If not, then the profile name will be used as node ID, with
184	special node ID of C<anon/> will be replaced by a random node ID.	276	a slash (C</>) attached.
		277
		278	If the node ID (or profile name) ends with a slash (C</>), then a random
		279	string is appended to make it unique.
		280
		281	=item step 2, bind listener sockets
185		282
186	The next step is to look up the binds in the profile, followed by binding	283	The next step is to look up the binds in the profile, followed by binding
187	aemp protocol listeners on all binds specified (it is possible and valid	284	aemp protocol listeners on all binds specified (it is possible and valid
188	to have no binds, meaning that the node cannot be contacted form the	285	to have no binds, meaning that the node cannot be contacted form the
189	outside. This means the node cannot talk to other nodes that also have no	286	outside. This means the node cannot talk to other nodes that also have no
190	binds, but it can still talk to all "normal" nodes).	287	binds, but it can still talk to all "normal" nodes).
191		288
192	If the profile does not specify a binds list, then the node ID will be	289	If the profile does not specify a binds list, then a default of C<*> is
193	treated as if it were of the form C<host:port>, which will be resolved and	290	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	291	local IP address it finds.
195		292
		293	=item step 3, connect to seed nodes
		294
196	Lastly, the seeds list from the profile is passed to the	295	As the last step, the seed ID list from the profile is passed to the
197	L<AnyEvent::MP::Global> module, which will then use it to keep	296	L<AnyEvent::MP::Global> module, which will then use it to keep
198	connectivity with at least on of those seed nodes at any point in time.	297	connectivity with at least one node at any point in time.
199		298
200	Example: become a distributed node listening on the guessed noderef, or	299	=back
201	the one specified via C<aemp> for the current node. This should be the	300
		301	Example: become a distributed node using the local node name as profile.
202	most common form of invocation for "daemon"-type nodes.	302	This should be the most common form of invocation for "daemon"-type nodes.
203		303
204	initialise_node;	304	configure
205		305
206	Example: become an anonymous node. This form is often used for commandline	306	Example: become an anonymous node. This form is often used for commandline
207	clients.	307	clients.
208		308
209	initialise_node "anon/";	309	configure nodeid => "anon/";
210		310
211	Example: become a distributed node. If there is no profile of the given	311	Example: configure a node using a profile called seed, which is suitable
212	name, or no binds list was specified, resolve C<localhost:4044> and bind	312	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	313	customary for aemp).
214		314
215	initialise_node "localhost:4044";	315	# use the aemp commandline utility
		316	# aemp profile seed binds '*:4040'
		317
		318	# then use it
		319	configure profile => "seed";
		320
		321	# or simply use aemp from the shell again:
		322	# aemp run profile seed
		323
		324	# or provide a nicer-to-remember nodeid
		325	# aemp run profile seed nodeid "$(hostname)"
216		326
217	=item $SELF	327	=item $SELF
218		328
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	329	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	330	blocks.
221		331
222	=item SELF, %SELF, @SELF...	332	=item *SELF, SELF, %SELF, @SELF...
223		333
224	Due to some quirks in how perl exports variables, it is impossible to	334	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	335	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	336	module, but only C<$SELF> is currently used.
227		337
228	=item snd $port, type => @data	338	=item snd $port, type => @data
229		339
230	=item snd $port, @msg	340	=item snd $port, @msg
231		341
232	Send the given message to the given port ID, which can identify either	342	Send the given message to the given port, which can identify either a
233	a local or a remote port, and must be a port ID.	343	local or a remote port, and must be a port ID.
234		344
235	While the message can be about anything, it is highly recommended to use a	345	While the message can be almost anything, it is highly recommended to
236	string as first element (a port ID, or some word that indicates a request	346	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	347	request type etc.) and to consist if only simple perl values (scalars,
		348	arrays, hashes) - if you think you need to pass an object, think again.
238		349
239	The message data effectively becomes read-only after a call to this	350	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	351	function: modifying any argument (or values referenced by them) is
241	problems.	352	forbidden, as there can be considerable time between the call to C<snd>
		353	and the time the message is actually being serialised - in fact, it might
		354	never be copied as within the same process it is simply handed to the
		355	receiving port.
242		356
243	The type of data you can transfer depends on the transport protocol: when	357	The type of data you can transfer depends on the transport protocol: when
244	JSON is used, then only strings, numbers and arrays and hashes consisting	358	JSON is used, then only strings, numbers and arrays and hashes consisting
245	of those are allowed (no objects). When Storable is used, then anything	359	of those are allowed (no objects). When Storable is used, then anything
246	that Storable can serialise and deserialise is allowed, and for the local	360	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	361	node, anything can be passed. Best rely only on the common denominator of
		362	these.
248		363
249	=item $local_port = port	364	=item $local_port = port
250		365
251	Create a new local port object and returns its port ID. Initially it has	366	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	367	no callbacks set and will throw an error when it receives messages.
…		…
276	sub _kilme {	391	sub _kilme {
277	die "received message on port without callback";	392	die "received message on port without callback";
278	}	393	}
279		394
280	sub port(;&) {	395	sub port(;&) {
281	my $id = "$UNIQ." . $ID++;	396	my $id = $UNIQ . ++$ID;
282	my $port = "$NODE#$id";	397	my $port = "$NODE#$id";
283		398
284	rcv $port, shift \|\| \&_kilme;	399	rcv $port, shift \|\| \&_kilme;
285		400
286	$port	401	$port
…		…
325	msg1 => sub { ... },	440	msg1 => sub { ... },
326	...	441	...
327	;	442	;
328		443
329	Example: temporarily register a rcv callback for a tag matching some port	444	Example: temporarily register a rcv callback for a tag matching some port
330	(e.g. for a rpc reply) and unregister it after a message was received.	445	(e.g. for an rpc reply) and unregister it after a message was received.
331		446
332	rcv $port, $otherport => sub {	447	rcv $port, $otherport => sub {
333	my @reply = @_;	448	my @reply = @_;
334		449
335	rcv $SELF, $otherport;	450	rcv $SELF, $otherport;
…		…
337		452
338	=cut	453	=cut
339		454
340	sub rcv($@) {	455	sub rcv($@) {
341	my $port = shift;	456	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	457	my ($nodeid, $portid) = split /#/, $port, 2;
343		458
344	$NODE{$noderef} == $NODE{""}	459	$NODE{$nodeid} == $NODE{""}
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	460	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		461
347	while (@_) {	462	while (@_) {
348	if (ref $_[0]) {	463	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	464	if (my $self = $PORT_DATA{$portid}) {
350	"AnyEvent::MP::Port" eq ref $self	465	"AnyEvent::MP::Port" eq ref $self
351	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	466	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
352		467
353	$self->[2] = shift;	468	$self->[0] = shift;
354	} else {	469	} else {
355	my $cb = shift;	470	my $cb = shift;
356	$PORT{$portid} = sub {	471	$PORT{$portid} = sub {
357	local $SELF = $port;	472	local $SELF = $port;
358	eval { &$cb }; _self_die if $@;	473	eval { &$cb }; _self_die if $@;
359	};	474	};
360	}	475	}
361	} elsif (defined $_[0]) {	476	} elsif (defined $_[0]) {
362	my $self = $PORT_DATA{$portid} \|\|= do {	477	my $self = $PORT_DATA{$portid} \|\|= do {
363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	478	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
364		479
365	$PORT{$portid} = sub {	480	$PORT{$portid} = sub {
366	local $SELF = $port;	481	local $SELF = $port;
367		482
368	if (my $cb = $self->[1]{$_[0]}) {	483	if (my $cb = $self->[1]{$_[0]}) {
…		…
390	}	505	}
391		506
392	$port	507	$port
393	}	508	}
394		509
		510	=item peval $port, $coderef[, @args]
		511
		512	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		513	when the code throews an exception the C<$port> will be killed.
		514
		515	Any remaining args will be passed to the callback. Any return values will
		516	be returned to the caller.
		517
		518	This is useful when you temporarily want to execute code in the context of
		519	a port.
		520
		521	Example: create a port and run some initialisation code in it's context.
		522
		523	my $port = port { ... };
		524
		525	peval $port, sub {
		526	init
		527	or die "unable to init";
		528	};
		529
		530	=cut
		531
		532	sub peval($$) {
		533	local $SELF = shift;
		534	my $cb = shift;
		535
		536	if (wantarray) {
		537	my @res = eval { &$cb };
		538	_self_die if $@;
		539	@res
		540	} else {
		541	my $res = eval { &$cb };
		542	_self_die if $@;
		543	$res
		544	}
		545	}
		546
395	=item $closure = psub { BLOCK }	547	=item $closure = psub { BLOCK }
396		548
397	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	549	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
398	closure is executed, sets up the environment in the same way as in C<rcv>	550	closure is executed, sets up the environment in the same way as in C<rcv>
399	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	551	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		552
		553	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		554	BLOCK }, @_ } >>.
400		555
401	This is useful when you register callbacks from C<rcv> callbacks:	556	This is useful when you register callbacks from C<rcv> callbacks:
402		557
403	rcv delayed_reply => sub {	558	rcv delayed_reply => sub {
404	my ($delay, @reply) = @_;	559	my ($delay, @reply) = @_;
…		…
428	$res	583	$res
429	}	584	}
430	}	585	}
431	}	586	}
432		587
433	=item $guard = mon $port, $cb->(@reason)	588	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
434		589
435	=item $guard = mon $port, $rcvport	590	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
436		591
437	=item $guard = mon $port	592	=item $guard = mon $port # kill $SELF when $port dies
438		593
439	=item $guard = mon $port, $rcvport, @msg	594	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		595
441	Monitor the given port and do something when the port is killed or	596	Monitor the given port and do something when the port is killed or
442	messages to it were lost, and optionally return a guard that can be used	597	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	598	to stop monitoring again.
444
445	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port
447	will arrive, or the monitoring action will be invoked after possible
448	message loss has been detected. No messages will be lost "in between"
449	(after the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get
451	delivered again.
452
453	Note that monitoring-actions are one-shot: once released, they are removed
454	and will not trigger again.
455		599
456	In the first form (callback), the callback is simply called with any	600	In the first form (callback), the callback is simply called with any
457	number of C<@reason> elements (no @reason means that the port was deleted	601	number of C<@reason> elements (no @reason means that the port was deleted
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	602	"normally"). Note also that I<< the callback B<must> never die >>, so use
459	C<eval> if unsure.	603	C<eval> if unsure.
460		604
461	In the second form (another port given), the other port (C<$rcvport>)	605	In the second form (another port given), the other port (C<$rcvport>)
462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	606	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
463	"normal" kils nothing happens, while under all other conditions, the other	607	"normal" kils nothing happens, while under all other conditions, the other
464	port is killed with the same reason.	608	port is killed with the same reason.
465		609
466	The third form (kill self) is the same as the second form, except that	610	The third form (kill self) is the same as the second form, except that
467	C<$rvport> defaults to C<$SELF>.	611	C<$rvport> defaults to C<$SELF>.
468		612
469	In the last form (message), a message of the form C<@msg, @reason> will be	613	In the last form (message), a message of the form C<@msg, @reason> will be
470	C<snd>.	614	C<snd>.
		615
		616	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		617	alert was raised), they are removed and will not trigger again.
471		618
472	As a rule of thumb, monitoring requests should always monitor a port from	619	As a rule of thumb, monitoring requests should always monitor a port from
473	a local port (or callback). The reason is that kill messages might get	620	a local port (or callback). The reason is that kill messages might get
474	lost, just like any other message. Another less obvious reason is that	621	lost, just like any other message. Another less obvious reason is that
475	even monitoring requests can get lost (for exmaple, when the connection	622	even monitoring requests can get lost (for example, when the connection
476	to the other node goes down permanently). When monitoring a port locally	623	to the other node goes down permanently). When monitoring a port locally
477	these problems do not exist.	624	these problems do not exist.
478		625
		626	C<mon> effectively guarantees that, in the absence of hardware failures,
		627	after starting the monitor, either all messages sent to the port will
		628	arrive, or the monitoring action will be invoked after possible message
		629	loss has been detected. No messages will be lost "in between" (after
		630	the first lost message no further messages will be received by the
		631	port). After the monitoring action was invoked, further messages might get
		632	delivered again.
		633
		634	Inter-host-connection timeouts and monitoring depend on the transport
		635	used. The only transport currently implemented is TCP, and AnyEvent::MP
		636	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		637	non-idle connection, and usually around two hours for idle connections).
		638
		639	This means that monitoring is good for program errors and cleaning up
		640	stuff eventually, but they are no replacement for a timeout when you need
		641	to ensure some maximum latency.
		642
479	Example: call a given callback when C<$port> is killed.	643	Example: call a given callback when C<$port> is killed.
480		644
481	mon $port, sub { warn "port died because of <@_>\n" };	645	mon $port, sub { warn "port died because of <@_>\n" };
482		646
483	Example: kill ourselves when C<$port> is killed abnormally.	647	Example: kill ourselves when C<$port> is killed abnormally.
…		…
489	mon $port, $self => "restart";	653	mon $port, $self => "restart";
490		654
491	=cut	655	=cut
492		656
493	sub mon {	657	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	658	my ($nodeid, $port) = split /#/, shift, 2;
495		659
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	660	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		661
498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	662	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
499		663
500	unless (ref $cb) {	664	unless (ref $cb) {
501	if (@_) {	665	if (@_) {
…		…
510	}	674	}
511		675
512	$node->monitor ($port, $cb);	676	$node->monitor ($port, $cb);
513		677
514	defined wantarray	678	defined wantarray
515	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	679	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
516	}	680	}
517		681
518	=item $guard = mon_guard $port, $ref, $ref...	682	=item $guard = mon_guard $port, $ref, $ref...
519		683
520	Monitors the given C<$port> and keeps the passed references. When the port	684	Monitors the given C<$port> and keeps the passed references. When the port
521	is killed, the references will be freed.	685	is killed, the references will be freed.
522		686
523	Optionally returns a guard that will stop the monitoring.	687	Optionally returns a guard that will stop the monitoring.
524		688
525	This function is useful when you create e.g. timers or other watchers and	689	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	690	want to free them when the port gets killed (note the use of C<psub>):
527		691
528	$port->rcv (start => sub {	692	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	693	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	694	undef $timer if 0.9 < rand;
531	});	695	});
532	});	696	});
533		697
534	=cut	698	=cut
…		…
543		707
544	=item kil $port[, @reason]	708	=item kil $port[, @reason]
545		709
546	Kill the specified port with the given C<@reason>.	710	Kill the specified port with the given C<@reason>.
547		711
548	If no C<@reason> is specified, then the port is killed "normally" (linked	712	If no C<@reason> is specified, then the port is killed "normally" -
549	ports will not be kileld, or even notified).	713	monitor callback will be invoked, but the kil will not cause linked ports
		714	(C<mon $mport, $lport> form) to get killed.
550		715
551	Otherwise, linked ports get killed with the same reason (second form of	716	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
552	C<mon>, see below).	717	form) get killed with the same reason.
553		718
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	719	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	720	will be reported as reason C<< die => $@ >>.
556		721
557	Transport/communication errors are reported as C<< transport_error =>	722	Transport/communication errors are reported as C<< transport_error =>
…		…
562	=item $port = spawn $node, $initfunc[, @initdata]	727	=item $port = spawn $node, $initfunc[, @initdata]
563		728
564	Creates a port on the node C<$node> (which can also be a port ID, in which	729	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	730	case it's the node where that port resides).
566		731
567	The port ID of the newly created port is return immediately, and it is	732	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	733	possible to immediately start sending messages or to monitor the port.
569		734
570	After the port has been created, the init function is	735	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	736	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	737	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	738	specify a function in the main program, use C<::name>.
574		739
575	If the function doesn't exist, then the node tries to C<require>	740	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	741	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	742	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	743	exists or it runs out of package names.
579		744
580	The init function is then called with the newly-created port as context	745	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	746	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		747	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		748	the port might not get created.
582		749
583	A common idiom is to pass your own port, monitor the spawned port, and	750	A common idiom is to pass a local port, immediately monitor the spawned
584	in the init function, monitor the original port. This two-way monitoring	751	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	752	local port. This two-way monitoring ensures that both ports get cleaned up
		753	when there is a problem.
		754
		755	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		756	caller before C<spawn> returns (by delaying invocation when spawn is
		757	called for the local node).
586		758
587	Example: spawn a chat server port on C<$othernode>.	759	Example: spawn a chat server port on C<$othernode>.
588		760
589	# this node, executed from within a port context:	761	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	762	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
605		777
606	sub _spawn {	778	sub _spawn {
607	my $port = shift;	779	my $port = shift;
608	my $init = shift;	780	my $init = shift;
609		781
		782	# rcv will create the actual port
610	local $SELF = "$NODE#$port";	783	local $SELF = "$NODE#$port";
611	eval {	784	eval {
612	&{ load_func $init }	785	&{ load_func $init }
613	};	786	};
614	_self_die if $@;	787	_self_die if $@;
615	}	788	}
616		789
617	sub spawn(@) {	790	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	791	my ($nodeid, undef) = split /#/, shift, 2;
619		792
620	my $id = "$RUNIQ." . $ID++;	793	my $id = $RUNIQ . ++$ID;
621		794
622	$_[0] =~ /::/	795	$_[0] =~ /::/
623	or Carp::croak "spawn init function must be a fully-qualified name, caught";	796	or Carp::croak "spawn init function must be a fully-qualified name, caught";
624		797
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	798	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		799
627	"$noderef#$id"	800	"$nodeid#$id"
628	}	801	}
		802
629		803
630	=item after $timeout, @msg	804	=item after $timeout, @msg
631		805
632	=item after $timeout, $callback	806	=item after $timeout, $callback
633		807
634	Either sends the given message, or call the given callback, after the	808	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	809	specified number of seconds.
636		810
637	This is simply a utility function that come sin handy at times.	811	This is simply a utility function that comes in handy at times - the
		812	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		813	so it may go away in the future.
638		814
639	=cut	815	=cut
640		816
641	sub after($@) {	817	sub after($@) {
642	my ($timeout, @action) = @_;	818	my ($timeout, @action) = @_;
…		…
647	? $action[0]()	823	? $action[0]()
648	: snd @action;	824	: snd @action;
649	};	825	};
650	}	826	}
651		827
		828	=item cal $port, @msg, $callback[, $timeout]
		829
		830	A simple form of RPC - sends a message to the given C<$port> with the
		831	given contents (C<@msg>), but adds a reply port to the message.
		832
		833	The reply port is created temporarily just for the purpose of receiving
		834	the reply, and will be C<kil>ed when no longer needed.
		835
		836	A reply message sent to the port is passed to the C<$callback> as-is.
		837
		838	If an optional time-out (in seconds) is given and it is not C<undef>,
		839	then the callback will be called without any arguments after the time-out
		840	elapsed and the port is C<kil>ed.
		841
		842	If no time-out is given (or it is C<undef>), then the local port will
		843	monitor the remote port instead, so it eventually gets cleaned-up.
		844
		845	Currently this function returns the temporary port, but this "feature"
		846	might go in future versions unless you can make a convincing case that
		847	this is indeed useful for something.
		848
		849	=cut
		850
		851	sub cal(@) {
		852	my $timeout = ref $_[-1] ? undef : pop;
		853	my $cb = pop;
		854
		855	my $port = port {
		856	undef $timeout;
		857	kil $SELF;
		858	&$cb;
		859	};
		860
		861	if (defined $timeout) {
		862	$timeout = AE::timer $timeout, 0, sub {
		863	undef $timeout;
		864	kil $port;
		865	$cb->();
		866	};
		867	} else {
		868	mon $_[0], sub {
		869	kil $port;
		870	$cb->();
		871	};
		872	}
		873
		874	push @_, $port;
		875	&snd;
		876
		877	$port
		878	}
		879
		880	=back
		881
		882	=head1 DISTRIBUTED DATABASE
		883
		884	AnyEvent::MP comes with a simple distributed database. The database will
		885	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		886	the global nodes for their needs.
		887
		888	The database consists of a two-level hash - a hash contains a hash which
		889	contains values.
		890
		891	The top level hash key is called "family", and the second-level hash key
		892	is simply called "key".
		893
		894	The family and key must be alphanumeric ASCII strings, i.e. start
		895	with a letter and consist of letters, digits, underscores and colons
		896	(C<[A-Za-z][A-Za-z0-9_:]*>, pretty much like Perl module names.
		897
		898	As the family namespaceis global, it is recommended to prefix family names
		899	with the name of the application or module using it.
		900
		901	The values should preferably be strings, but other perl scalars should
		902	work as well (such as arrays and hashes).
		903
		904	Every database entry is owned by one node - adding the same family/key
		905	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		906	but the result might be nondeterministic, i.e. the key might have
		907	different values on different nodes.
		908
		909	=item db_set $family => $key => $value
		910
		911	Sets (or replaces) a key to the database.
		912
		913	=item db_del $family => $key
		914
		915	Deletes a key from the database.
		916
		917	=item $guard = db_reg $family => $key [=> $value]
		918
		919	Sets the key on the database and returns a guard. When the guard is
		920	destroyed, the key is deleted from the database. If C<$value> is missing,
		921	then C<undef> is used.
		922
		923	=cut
		924
652	=back	925	=back
653		926
654	=head1 AnyEvent::MP vs. Distributed Erlang	927	=head1 AnyEvent::MP vs. Distributed Erlang
655		928
656	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	929	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
657	== aemp node, Erlang process == aemp port), so many of the documents and	930	== aemp node, Erlang process == aemp port), so many of the documents and
658	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	931	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
659	sample:	932	sample:
660		933
661	http://www.Erlang.se/doc/programming_rules.shtml	934	http://www.erlang.se/doc/programming_rules.shtml
662	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	935	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
663	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	936	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
664	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	937	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
665		938
666	Despite the similarities, there are also some important differences:	939	Despite the similarities, there are also some important differences:
667		940
668	=over 4	941	=over 4
669		942
670	=item * Node IDs are arbitrary strings in AEMP.	943	=item * Node IDs are arbitrary strings in AEMP.
671		944
672	Erlang relies on special naming and DNS to work everywhere in the same	945	Erlang relies on special naming and DNS to work everywhere in the same
673	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	946	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	configuraiton or DNS), but will otherwise discover other odes itself.	947	configuration or DNS), and possibly the addresses of some seed nodes, but
		948	will otherwise discover other nodes (and their IDs) itself.
675		949
676	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	950	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
677	uses "local ports are like remote ports".	951	uses "local ports are like remote ports".
678		952
679	The failure modes for local ports are quite different (runtime errors	953	The failure modes for local ports are quite different (runtime errors
…		…
688	ports being the special case/exception, where transport errors cannot	962	ports being the special case/exception, where transport errors cannot
689	occur.	963	occur.
690		964
691	=item * Erlang uses processes and a mailbox, AEMP does not queue.	965	=item * Erlang uses processes and a mailbox, AEMP does not queue.
692		966
693	Erlang uses processes that selectively receive messages, and therefore	967	Erlang uses processes that selectively receive messages out of order, and
694	needs a queue. AEMP is event based, queuing messages would serve no	968	therefore needs a queue. AEMP is event based, queuing messages would serve
695	useful purpose. For the same reason the pattern-matching abilities of	969	no useful purpose. For the same reason the pattern-matching abilities
696	AnyEvent::MP are more limited, as there is little need to be able to	970	of AnyEvent::MP are more limited, as there is little need to be able to
697	filter messages without dequeing them.	971	filter messages without dequeuing them.
698		972
699	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	973	This is not a philosophical difference, but simply stems from AnyEvent::MP
		974	being event-based, while Erlang is process-based.
		975
		976	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		977	top of AEMP and Coro threads.
700		978
701	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	979	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
702		980
703	Sending messages in Erlang is synchronous and blocks the process (and	981	Sending messages in Erlang is synchronous and blocks the process until
		982	a conenction has been established and the message sent (and so does not
704	so does not need a queue that can overflow). AEMP sends are immediate,	983	need a queue that can overflow). AEMP sends return immediately, connection
705	connection establishment is handled in the background.	984	establishment is handled in the background.
706		985
707	=item * Erlang suffers from silent message loss, AEMP does not.	986	=item * Erlang suffers from silent message loss, AEMP does not.
708		987
709	Erlang makes few guarantees on messages delivery - messages can get lost	988	Erlang implements few guarantees on messages delivery - messages can get
710	without any of the processes realising it (i.e. you send messages a, b,	989	lost without any of the processes realising it (i.e. you send messages a,
711	and c, and the other side only receives messages a and c).	990	b, and c, and the other side only receives messages a and c).
712		991
713	AEMP guarantees correct ordering, and the guarantee that there are no	992	AEMP guarantees (modulo hardware errors) correct ordering, and the
		993	guarantee that after one message is lost, all following ones sent to the
		994	same port are lost as well, until monitoring raises an error, so there are
714	holes in the message sequence.	995	no silent "holes" in the message sequence.
715		996
716	=item * In Erlang, processes can be declared dead and later be found to be	997	If you want your software to be very reliable, you have to cope with
717	alive.	998	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
718		999	simply tries to work better in common error cases, such as when a network
719	In Erlang it can happen that a monitored process is declared dead and	1000	link goes down.
720	linked processes get killed, but later it turns out that the process is
721	still alive - and can receive messages.
722
723	In AEMP, when port monitoring detects a port as dead, then that port will
724	eventually be killed - it cannot happen that a node detects a port as dead
725	and then later sends messages to it, finding it is still alive.
726		1001
727	=item * Erlang can send messages to the wrong port, AEMP does not.	1002	=item * Erlang can send messages to the wrong port, AEMP does not.
728		1003
729	In Erlang it is quite likely that a node that restarts reuses a process ID	1004	In Erlang it is quite likely that a node that restarts reuses an Erlang
730	known to other nodes for a completely different process, causing messages	1005	process ID known to other nodes for a completely different process,
731	destined for that process to end up in an unrelated process.	1006	causing messages destined for that process to end up in an unrelated
		1007	process.
732		1008
733	AEMP never reuses port IDs, so old messages or old port IDs floating	1009	AEMP does not reuse port IDs, so old messages or old port IDs floating
734	around in the network will not be sent to an unrelated port.	1010	around in the network will not be sent to an unrelated port.
735		1011
736	=item * Erlang uses unprotected connections, AEMP uses secure	1012	=item * Erlang uses unprotected connections, AEMP uses secure
737	authentication and can use TLS.	1013	authentication and can use TLS.
738		1014
739	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1015	AEMP can use a proven protocol - TLS - to protect connections and
740	securely authenticate nodes.	1016	securely authenticate nodes.
741		1017
742	=item * The AEMP protocol is optimised for both text-based and binary	1018	=item * The AEMP protocol is optimised for both text-based and binary
743	communications.	1019	communications.
744		1020
745	The AEMP protocol, unlike the Erlang protocol, supports both	1021	The AEMP protocol, unlike the Erlang protocol, supports both programming
746	language-independent text-only protocols (good for debugging) and binary,	1022	language independent text-only protocols (good for debugging), and binary,
747	language-specific serialisers (e.g. Storable).	1023	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1024	used, the protocol is actually completely text-based.
748		1025
749	It has also been carefully designed to be implementable in other languages	1026	It has also been carefully designed to be implementable in other languages
750	with a minimum of work while gracefully degrading fucntionality to make the	1027	with a minimum of work while gracefully degrading functionality to make the
751	protocol simple.	1028	protocol simple.
752		1029
753	=item * AEMP has more flexible monitoring options than Erlang.	1030	=item * AEMP has more flexible monitoring options than Erlang.
754		1031
755	In Erlang, you can chose to receive I<all> exit signals as messages	1032	In Erlang, you can chose to receive I<all> exit signals as messages or
756	or I<none>, there is no in-between, so monitoring single processes is	1033	I<none>, there is no in-between, so monitoring single Erlang processes is
757	difficult to implement. Monitoring in AEMP is more flexible than in	1034	difficult to implement.
758	Erlang, as one can choose between automatic kill, exit message or callback	1035
759	on a per-process basis.	1036	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1037	between automatic kill, exit message or callback on a per-port basis.
760		1038
761	=item * Erlang tries to hide remote/local connections, AEMP does not.	1039	=item * Erlang tries to hide remote/local connections, AEMP does not.
762		1040
763	Monitoring in Erlang is not an indicator of process death/crashes,	1041	Monitoring in Erlang is not an indicator of process death/crashes, in the
764	as linking is (except linking is unreliable in Erlang).	1042	same way as linking is (except linking is unreliable in Erlang).
765		1043
766	In AEMP, you don't "look up" registered port names or send to named ports	1044	In AEMP, you don't "look up" registered port names or send to named ports
767	that might or might not be persistent. Instead, you normally spawn a port	1045	that might or might not be persistent. Instead, you normally spawn a port
768	on the remote node. The init function monitors the you, and you monitor	1046	on the remote node. The init function monitors you, and you monitor the
769	the remote port. Since both monitors are local to the node, they are much	1047	remote port. Since both monitors are local to the node, they are much more
770	more reliable.	1048	reliable (no need for C<spawn_link>).
771		1049
772	This also saves round-trips and avoids sending messages to the wrong port	1050	This also saves round-trips and avoids sending messages to the wrong port
773	(hard to do in Erlang).	1051	(hard to do in Erlang).
774		1052
775	=back	1053	=back
776		1054
777	=head1 RATIONALE	1055	=head1 RATIONALE
778		1056
779	=over 4	1057	=over 4
780		1058
781	=item Why strings for ports and noderefs, why not objects?	1059	=item Why strings for port and node IDs, why not objects?
782		1060
783	We considered "objects", but found that the actual number of methods	1061	We considered "objects", but found that the actual number of methods
784	thatc an be called are very low. Since port IDs and noderefs travel over	1062	that can be called are quite low. Since port and node IDs travel over
785	the network frequently, the serialising/deserialising would add lots of	1063	the network frequently, the serialising/deserialising would add lots of
786	overhead, as well as having to keep a proxy object.	1064	overhead, as well as having to keep a proxy object everywhere.
787		1065
788	Strings can easily be printed, easily serialised etc. and need no special	1066	Strings can easily be printed, easily serialised etc. and need no special
789	procedures to be "valid".	1067	procedures to be "valid".
790		1068
791	And a a miniport consists of a single closure stored in a global hash - it	1069	And as a result, a port with just a default receiver consists of a single
792	can't become much cheaper.	1070	code reference stored in a global hash - it can't become much cheaper.
793		1071
794	=item Why favour JSON, why not real serialising format such as Storable?	1072	=item Why favour JSON, why not a real serialising format such as Storable?
795		1073
796	In fact, any AnyEvent::MP node will happily accept Storable as framing	1074	In fact, any AnyEvent::MP node will happily accept Storable as framing
797	format, but currently there is no way to make a node use Storable by	1075	format, but currently there is no way to make a node use Storable by
798	default.	1076	default (although all nodes will accept it).
799		1077
800	The default framing protocol is JSON because a) JSON::XS is many times	1078	The default framing protocol is JSON because a) JSON::XS is many times
801	faster for small messages and b) most importantly, after years of	1079	faster for small messages and b) most importantly, after years of
802	experience we found that object serialisation is causing more problems	1080	experience we found that object serialisation is causing more problems
803	than it gains: Just like function calls, objects simply do not travel	1081	than it solves: Just like function calls, objects simply do not travel
804	easily over the network, mostly because they will always be a copy, so you	1082	easily over the network, mostly because they will always be a copy, so you
805	always have to re-think your design.	1083	always have to re-think your design.
806		1084
807	Keeping your messages simple, concentrating on data structures rather than	1085	Keeping your messages simple, concentrating on data structures rather than
808	objects, will keep your messages clean, tidy and efficient.	1086	objects, will keep your messages clean, tidy and efficient.
809		1087
810	=back	1088	=back
811		1089
812	=head1 SEE ALSO	1090	=head1 SEE ALSO
813		1091
		1092	L<AnyEvent::MP::Intro> - a gentle introduction.
		1093
		1094	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1095
		1096	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1097	your applications.
		1098
		1099	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1100
		1101	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1102	all nodes.
		1103
814	L<AnyEvent>.	1104	L<AnyEvent>.
815		1105
816	=head1 AUTHOR	1106	=head1 AUTHOR
817		1107
818	Marc Lehmann <schmorp@schmorp.de>	1108	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.124 by root, Sat Mar 3 11:38:43 2012 UTC