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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC vs.
Revision 1.136 by root, Wed Mar 21 15:22:16 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 $port, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
39	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @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 - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - mostly stable	58	AnyEvent::MP::Global - stable API.
47	AnyEvent::MP::Node - mostly stable, but internal anyways
48	AnyEvent::MP::Transport - mostly stable, but internal anyways
49
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
57	on the same or other hosts, and you can supervise entities remotely.	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 and the examples under F<eg/>.	68	manual page and the examples under F<eg/>.
61		69
62	At the moment, this module family is a bit underdocumented.
63
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<nodeid#portname>	85	=item port ID - C<nodeid#portname>
77		86
78	A port ID is the concatenation of a node ID, 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).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
80		90
81	=item node	91	=item node
82		92
83	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,
84	which enables nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
85	ports.	95	ports.
86		96
87	Nodes are either public (have one or more listening ports) or private	97	Nodes are either public (have one or more listening ports) or private
88	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
89	currently.	99	currently, but all nodes can talk to public nodes.
90		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
91	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
92		104
93	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
94	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
95	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
96	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
97		109
98	=item binds - C<ip:port>	110	=item binds - C<ip:port>
99		111
100	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
101	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
102	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
103	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.
104		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
105	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
106		150
107	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
108	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.
109	network. This node is called a seed.
110		153
111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
112	are expected to be long-running, and at least one of those should always
113	be available. When nodes run out of connections (e.g. due to a network
114	error), they try to re-establish connections to some seednodes again to
115	join the network.
116		155
117	Apart from being sued for seeding, seednodes are not special in any way -	156	An AEMP network needs a discovery service - nodes need to know how to
118	every public node can be a seednode.	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).
119		170
120	=back	171	=back
121		172
122	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
123		174
…		…
125		176
126	=cut	177	=cut
127		178
128	package AnyEvent::MP;	179	package AnyEvent::MP;
129		180
		181	use AnyEvent::MP::Config ();
130	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
131		184
132	use common::sense;	185	use common::sense;
133		186
134	use Carp ();	187	use Carp ();
135		188
136	use AE ();	189	use AE ();
		190	use Guard ();
137		191
138	use base "Exporter";	192	use base "Exporter";
139		193
140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
141		195
142	our @EXPORT = qw(	196	our @EXPORT = qw(
143	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
144	initialise_node	198	configure
145	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
146	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
147	);	203	);
148		204
149	our $SELF;	205	our $SELF;
150		206
151	sub _self_die() {	207	sub _self_die() {
…		…
156		212
157	=item $thisnode = NODE / $NODE	213	=item $thisnode = NODE / $NODE
158		214
159	The C<NODE> function returns, and the C<$NODE> variable contains, the node	215	The C<NODE> function returns, and the C<$NODE> variable contains, the node
160	ID of the node running in the current process. This value is initialised by	216	ID of the node running in the current process. This value is initialised by
161	a call to C<initialise_node>.	217	a call to C<configure>.
162		218
163	=item $nodeid = node_of $port	219	=item $nodeid = node_of $port
164		220
165	Extracts and returns the node ID from a port ID or a node ID.	221	Extracts and returns the node ID from a port ID or a node ID.
166		222
167	=item initialise_node $profile_name	223	=item configure $profile, key => value...
		224
		225	=item configure key => value...
168		226
169	Before a node can talk to other nodes on the network (i.e. enter	227	Before a node can talk to other nodes on the network (i.e. enter
170	"distributed mode") it has to initialise itself - the minimum a node needs	228	"distributed mode") it has to configure itself - the minimum a node needs
171	to know is its own name, and optionally it should know the addresses of	229	to know is its own name, and optionally it should know the addresses of
172	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
173		231
174	This function initialises a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
175	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
176		234
177	The first argument is a profile name. If it is C<undef> or missing, then	235	The key/value pairs are basically the same ones as documented for the
178	the current nodename will be used instead (i.e. F<uname -n>).	236	F<aemp> command line utility (sans the set/del prefix), with these additions:
179		237
		238	=over 4
		239
		240	=item norc => $boolean (default false)
		241
		242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		243	be consulted - all configuraiton options must be specified in the
		244	C<configure> call.
		245
		246	=item force => $boolean (default false)
		247
		248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
		251
		252	=item secure => $pass->(@msg)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every code execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	Most of the time the callback should look only at
		259	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		260	actual message (which can be about anything, and is mostly provided for
		261	diagnostic purposes).
		262
		263	See F<semp setsecure> for more info.
		264
		265	=back
		266
		267	=over 4
		268
		269	=item step 1, gathering configuration from profiles
		270
180	The function then looks up the profile in the aemp configuration (see the	271	The function first looks up a profile in the aemp configuration (see the
181	L<aemp> commandline utility).	272	L<aemp> commandline utility). The profile name can be specified via the
		273	named C<profile> parameter or can simply be the first parameter). If it is
		274	missing, then the nodename (F<uname -n>) will be used as profile name.
		275
		276	The profile data is then gathered as follows:
		277
		278	First, all remaining key => value pairs (all of which are conveniently
		279	undocumented at the moment) will be interpreted as configuration
		280	data. Then they will be overwritten by any values specified in the global
		281	default configuration (see the F<aemp> utility), then the chain of
		282	profiles chosen by the profile name (and any C<parent> attributes).
		283
		284	That means that the values specified in the profile have highest priority
		285	and the values specified directly via C<configure> have lowest priority,
		286	and can only be used to specify defaults.
182		287
183	If the profile specifies a node ID, then this will become the node ID of	288	If the profile specifies a node ID, then this will become the node ID of
184	this process. If not, then the profile name will be used as node ID. The	289	this process. If not, then the profile name will be used as node ID, with
185	special node ID of C<anon/> will be replaced by a random node ID.	290	a unique randoms tring (C</%u>) appended.
		291
		292	The node ID can contain some C<%> sequences that are expanded: C<%n>
		293	is expanded to the local nodename, C<%u> is replaced by a random
		294	strign to make the node unique. For example, the F<aemp> commandline
		295	utility uses C<aemp/%n/%u> as nodename, which might expand to
		296	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		297
		298	=item step 2, bind listener sockets
186		299
187	The next step is to look up the binds in the profile, followed by binding	300	The next step is to look up the binds in the profile, followed by binding
188	aemp protocol listeners on all binds specified (it is possible and valid	301	aemp protocol listeners on all binds specified (it is possible and valid
189	to have no binds, meaning that the node cannot be contacted form the	302	to have no binds, meaning that the node cannot be contacted form the
190	outside. This means the node cannot talk to other nodes that also have no	303	outside. This means the node cannot talk to other nodes that also have no
191	binds, but it can still talk to all "normal" nodes).	304	binds, but it can still talk to all "normal" nodes).
192		305
193	If the profile does not specify a binds list, then the node ID will be	306	If the profile does not specify a binds list, then a default of C<*> is
194	treated as if it were of the form C<host:port>, which will be resolved and	307	used, meaning the node will bind on a dynamically-assigned port on every
195	used as binds list.	308	local IP address it finds.
196		309
		310	=item step 3, connect to seed nodes
		311
197	Lastly, the seeds list from the profile is passed to the	312	As the last step, the seed ID list from the profile is passed to the
198	L<AnyEvent::MP::Global> module, which will then use it to keep	313	L<AnyEvent::MP::Global> module, which will then use it to keep
199	connectivity with at least on of those seed nodes at any point in time.	314	connectivity with at least one node at any point in time.
200		315
201	Example: become a distributed node listening on the guessed noderef, or	316	=back
202	the one specified via C<aemp> for the current node. This should be the	317
		318	Example: become a distributed node using the local node name as profile.
203	most common form of invocation for "daemon"-type nodes.	319	This should be the most common form of invocation for "daemon"-type nodes.
204		320
205	initialise_node;	321	configure
206		322
207	Example: become an anonymous node. This form is often used for commandline	323	Example: become a semi-anonymous node. This form is often used for
208	clients.	324	commandline clients.
209		325
210	initialise_node "anon/";	326	configure nodeid => "myscript/%n/%u";
211		327
212	Example: become a distributed node. If there is no profile of the given	328	Example: configure a node using a profile called seed, which is suitable
213	name, or no binds list was specified, resolve C<localhost:4044> and bind	329	for a seed node as it binds on all local addresses on a fixed port (4040,
214	on the resulting addresses.	330	customary for aemp).
215		331
216	initialise_node "localhost:4044";	332	# use the aemp commandline utility
		333	# aemp profile seed binds '*:4040'
		334
		335	# then use it
		336	configure profile => "seed";
		337
		338	# or simply use aemp from the shell again:
		339	# aemp run profile seed
		340
		341	# or provide a nicer-to-remember nodeid
		342	# aemp run profile seed nodeid "$(hostname)"
217		343
218	=item $SELF	344	=item $SELF
219		345
220	Contains the current port id while executing C<rcv> callbacks or C<psub>	346	Contains the current port id while executing C<rcv> callbacks or C<psub>
221	blocks.	347	blocks.
…		…
277		403
278	=cut	404	=cut
279		405
280	sub rcv($@);	406	sub rcv($@);
281		407
282	sub _kilme {	408	my $KILME = sub {
283	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
284	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
285		412
286	sub port(;&) {	413	sub port(;&) {
287	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
288	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
289		416
290	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
291		418
292	$port	419	$port
293	}	420	}
294		421
295	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
300		427
301	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
302	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
303	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
304		431
305	The default callback received all messages not matched by a more specific	432	The default callback receives all messages not matched by a more specific
306	C<tag> match.	433	C<tag> match.
307		434
308	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
309		436
310	Register (or replace) callbacks to be called on messages starting with the	437	Register (or replace) callbacks to be called on messages starting with the
…		…
331	msg1 => sub { ... },	458	msg1 => sub { ... },
332	...	459	...
333	;	460	;
334		461
335	Example: temporarily register a rcv callback for a tag matching some port	462	Example: temporarily register a rcv callback for a tag matching some port
336	(e.g. for a rpc reply) and unregister it after a message was received.	463	(e.g. for an rpc reply) and unregister it after a message was received.
337		464
338	rcv $port, $otherport => sub {	465	rcv $port, $otherport => sub {
339	my @reply = @_;	466	my @reply = @_;
340		467
341	rcv $SELF, $otherport;	468	rcv $SELF, $otherport;
…		…
343		470
344	=cut	471	=cut
345		472
346	sub rcv($@) {	473	sub rcv($@) {
347	my $port = shift;	474	my $port = shift;
348	my ($noderef, $portid) = split /#/, $port, 2;	475	my ($nodeid, $portid) = split /#/, $port, 2;
349		476
350	$NODE{$noderef} == $NODE{""}	477	$NODE{$nodeid} == $NODE{""}
351	or Carp::croak "$port: rcv can only be called on local ports, caught";	478	or Carp::croak "$port: rcv can only be called on local ports, caught";
352		479
353	while (@_) {	480	while (@_) {
354	if (ref $_[0]) {	481	if (ref $_[0]) {
355	if (my $self = $PORT_DATA{$portid}) {	482	if (my $self = $PORT_DATA{$portid}) {
356	"AnyEvent::MP::Port" eq ref $self	483	"AnyEvent::MP::Port" eq ref $self
357	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	484	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
358		485
359	$self->[2] = shift;	486	$self->[0] = shift;
360	} else {	487	} else {
361	my $cb = shift;	488	my $cb = shift;
362	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
363	local $SELF = $port;	490	local $SELF = $port;
364	eval { &$cb }; _self_die if $@;	491	eval { &$cb }; _self_die if $@;
365	};	492	};
366	}	493	}
367	} elsif (defined $_[0]) {	494	} elsif (defined $_[0]) {
368	my $self = $PORT_DATA{$portid} \|\|= do {	495	my $self = $PORT_DATA{$portid} \|\|= do {
369	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	496	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
370		497
371	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
372	local $SELF = $port;	499	local $SELF = $port;
373		500
374	if (my $cb = $self->[1]{$_[0]}) {	501	if (my $cb = $self->[1]{$_[0]}) {
…		…
396	}	523	}
397		524
398	$port	525	$port
399	}	526	}
400		527
		528	=item peval $port, $coderef[, @args]
		529
		530	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		531	when the code throews an exception the C<$port> will be killed.
		532
		533	Any remaining args will be passed to the callback. Any return values will
		534	be returned to the caller.
		535
		536	This is useful when you temporarily want to execute code in the context of
		537	a port.
		538
		539	Example: create a port and run some initialisation code in it's context.
		540
		541	my $port = port { ... };
		542
		543	peval $port, sub {
		544	init
		545	or die "unable to init";
		546	};
		547
		548	=cut
		549
		550	sub peval($$) {
		551	local $SELF = shift;
		552	my $cb = shift;
		553
		554	if (wantarray) {
		555	my @res = eval { &$cb };
		556	_self_die if $@;
		557	@res
		558	} else {
		559	my $res = eval { &$cb };
		560	_self_die if $@;
		561	$res
		562	}
		563	}
		564
401	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
402		566
403	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	567	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
404	closure is executed, sets up the environment in the same way as in C<rcv>	568	closure is executed, sets up the environment in the same way as in C<rcv>
405	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	569	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		570
		571	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		572	BLOCK }, @_ } >>.
406		573
407	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
408		575
409	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
410	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
446		613
447	Monitor the given port and do something when the port is killed or	614	Monitor the given port and do something when the port is killed or
448	messages to it were lost, and optionally return a guard that can be used	615	messages to it were lost, and optionally return a guard that can be used
449	to stop monitoring again.	616	to stop monitoring again.
450		617
		618	In the first form (callback), the callback is simply called with any
		619	number of C<@reason> elements (no @reason means that the port was deleted
		620	"normally"). Note also that I<< the callback B<must> never die >>, so use
		621	C<eval> if unsure.
		622
		623	In the second form (another port given), the other port (C<$rcvport>)
		624	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		625	"normal" kils nothing happens, while under all other conditions, the other
		626	port is killed with the same reason.
		627
		628	The third form (kill self) is the same as the second form, except that
		629	C<$rvport> defaults to C<$SELF>.
		630
		631	In the last form (message), a message of the form C<@msg, @reason> will be
		632	C<snd>.
		633
		634	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		635	alert was raised), they are removed and will not trigger again.
		636
		637	As a rule of thumb, monitoring requests should always monitor a port from
		638	a local port (or callback). The reason is that kill messages might get
		639	lost, just like any other message. Another less obvious reason is that
		640	even monitoring requests can get lost (for example, when the connection
		641	to the other node goes down permanently). When monitoring a port locally
		642	these problems do not exist.
		643
451	C<mon> effectively guarantees that, in the absence of hardware failures,	644	C<mon> effectively guarantees that, in the absence of hardware failures,
452	after starting the monitor, either all messages sent to the port will	645	after starting the monitor, either all messages sent to the port will
453	arrive, or the monitoring action will be invoked after possible message	646	arrive, or the monitoring action will be invoked after possible message
454	loss has been detected. No messages will be lost "in between" (after	647	loss has been detected. No messages will be lost "in between" (after
455	the first lost message no further messages will be received by the	648	the first lost message no further messages will be received by the
456	port). After the monitoring action was invoked, further messages might get	649	port). After the monitoring action was invoked, further messages might get
457	delivered again.	650	delivered again.
458		651
459	Note that monitoring-actions are one-shot: once messages are lost (and a	652	Inter-host-connection timeouts and monitoring depend on the transport
460	monitoring alert was raised), they are removed and will not trigger again.	653	used. The only transport currently implemented is TCP, and AnyEvent::MP
		654	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		655	non-idle connection, and usually around two hours for idle connections).
461		656
462	In the first form (callback), the callback is simply called with any	657	This means that monitoring is good for program errors and cleaning up
463	number of C<@reason> elements (no @reason means that the port was deleted	658	stuff eventually, but they are no replacement for a timeout when you need
464	"normally"). Note also that I<< the callback B<must> never die >>, so use	659	to ensure some maximum latency.
465	C<eval> if unsure.
466
467	In the second form (another port given), the other port (C<$rcvport>)
468	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
469	"normal" kils nothing happens, while under all other conditions, the other
470	port is killed with the same reason.
471
472	The third form (kill self) is the same as the second form, except that
473	C<$rvport> defaults to C<$SELF>.
474
475	In the last form (message), a message of the form C<@msg, @reason> will be
476	C<snd>.
477
478	As a rule of thumb, monitoring requests should always monitor a port from
479	a local port (or callback). The reason is that kill messages might get
480	lost, just like any other message. Another less obvious reason is that
481	even monitoring requests can get lost (for exmaple, when the connection
482	to the other node goes down permanently). When monitoring a port locally
483	these problems do not exist.
484		660
485	Example: call a given callback when C<$port> is killed.	661	Example: call a given callback when C<$port> is killed.
486		662
487	mon $port, sub { warn "port died because of <@_>\n" };	663	mon $port, sub { warn "port died because of <@_>\n" };
488		664
…		…
495	mon $port, $self => "restart";	671	mon $port, $self => "restart";
496		672
497	=cut	673	=cut
498		674
499	sub mon {	675	sub mon {
500	my ($noderef, $port) = split /#/, shift, 2;	676	my ($nodeid, $port) = split /#/, shift, 2;
501		677
502	my $node = $NODE{$noderef} \|\| add_node $noderef;	678	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
503		679
504	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	680	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
505		681
506	unless (ref $cb) {	682	unless (ref $cb) {
507	if (@_) {	683	if (@_) {
…		…
516	}	692	}
517		693
518	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
519		695
520	defined wantarray	696	defined wantarray
521	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
522	}	698	}
523		699
524	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
525		701
526	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
…		…
549		725
550	=item kil $port[, @reason]	726	=item kil $port[, @reason]
551		727
552	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
553		729
554	If no C<@reason> is specified, then the port is killed "normally" (ports	730	If no C<@reason> is specified, then the port is killed "normally" -
555	monitoring other ports will not necessarily die because a port dies	731	monitor callback will be invoked, but the kil will not cause linked ports
556	"normally").	732	(C<mon $mport, $lport> form) to get killed.
557		733
558	Otherwise, linked ports get killed with the same reason (second form of	734	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
559	C<mon>, see above).	735	form) get killed with the same reason.
560		736
561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	737	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
562	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
563		739
564	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
565	$message >>.	741	$message >>.
566		742
567	=cut	743	Common idioms:
		744
		745	# silently remove yourself, do not kill linked ports
		746	kil $SELF;
		747
		748	# report a failure in some detail
		749	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		750
		751	# do not waste much time with killing, just die when something goes wrong
		752	open my $fh, "<file"
		753	or die "file: $!";
568		754
569	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
570		756
571	Creates a port on the node C<$node> (which can also be a port ID, in which	757	Creates a port on the node C<$node> (which can also be a port ID, in which
572	case it's the node where that port resides).	758	case it's the node where that port resides).
…		…
583	the package, then the package above the package and so on (e.g.	769	the package, then the package above the package and so on (e.g.
584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	770	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
585	exists or it runs out of package names.	771	exists or it runs out of package names.
586		772
587	The init function is then called with the newly-created port as context	773	The init function is then called with the newly-created port as context
588	object (C<$SELF>) and the C<@initdata> values as arguments.	774	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		775	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		776	the port might not get created.
589		777
590	A common idiom is to pass a local port, immediately monitor the spawned	778	A common idiom is to pass a local port, immediately monitor the spawned
591	port, and in the remote init function, immediately monitor the passed	779	port, and in the remote init function, immediately monitor the passed
592	local port. This two-way monitoring ensures that both ports get cleaned up	780	local port. This two-way monitoring ensures that both ports get cleaned up
593	when there is a problem.	781	when there is a problem.
594		782
		783	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		784	caller before C<spawn> returns (by delaying invocation when spawn is
		785	called for the local node).
		786
595	Example: spawn a chat server port on C<$othernode>.	787	Example: spawn a chat server port on C<$othernode>.
596		788
597	# this node, executed from within a port context:	789	# this node, executed from within a port context:
598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	790	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
599	mon $server;	791	mon $server;
…		…
613		805
614	sub _spawn {	806	sub _spawn {
615	my $port = shift;	807	my $port = shift;
616	my $init = shift;	808	my $init = shift;
617		809
		810	# rcv will create the actual port
618	local $SELF = "$NODE#$port";	811	local $SELF = "$NODE#$port";
619	eval {	812	eval {
620	&{ load_func $init }	813	&{ load_func $init }
621	};	814	};
622	_self_die if $@;	815	_self_die if $@;
623	}	816	}
624		817
625	sub spawn(@) {	818	sub spawn(@) {
626	my ($noderef, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
627		820
628	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
629		822
630	$_[0] =~ /::/	823	$_[0] =~ /::/
631	or Carp::croak "spawn init function must be a fully-qualified name, caught";	824	or Carp::croak "spawn init function must be a fully-qualified name, caught";
632		825
633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
634		827
635	"$noderef#$id"	828	"$nodeid#$id"
636	}	829	}
		830
637		831
638	=item after $timeout, @msg	832	=item after $timeout, @msg
639		833
640	=item after $timeout, $callback	834	=item after $timeout, $callback
641		835
…		…
657	? $action[0]()	851	? $action[0]()
658	: snd @action;	852	: snd @action;
659	};	853	};
660	}	854	}
661		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
		857
		858	=item cal $port, @msg, $callback[, $timeout]
		859
		860	A simple form of RPC - sends a message to the given C<$port> with the
		861	given contents (C<@msg>), but adds a reply port to the message.
		862
		863	The reply port is created temporarily just for the purpose of receiving
		864	the reply, and will be C<kil>ed when no longer needed.
		865
		866	A reply message sent to the port is passed to the C<$callback> as-is.
		867
		868	If an optional time-out (in seconds) is given and it is not C<undef>,
		869	then the callback will be called without any arguments after the time-out
		870	elapsed and the port is C<kil>ed.
		871
		872	If no time-out is given (or it is C<undef>), then the local port will
		873	monitor the remote port instead, so it eventually gets cleaned-up.
		874
		875	Currently this function returns the temporary port, but this "feature"
		876	might go in future versions unless you can make a convincing case that
		877	this is indeed useful for something.
		878
		879	=cut
		880
		881	sub cal(@) {
		882	my $timeout = ref $_[-1] ? undef : pop;
		883	my $cb = pop;
		884
		885	my $port = port {
		886	undef $timeout;
		887	kil $SELF;
		888	&$cb;
		889	};
		890
		891	if (defined $timeout) {
		892	$timeout = AE::timer $timeout, 0, sub {
		893	undef $timeout;
		894	kil $port;
		895	$cb->();
		896	};
		897	} else {
		898	mon $_[0], sub {
		899	kil $port;
		900	$cb->();
		901	};
		902	}
		903
		904	push @_, $port;
		905	&snd;
		906
		907	$port
		908	}
		909
		910	=back
		911
		912	=head1 DISTRIBUTED DATABASE
		913
		914	AnyEvent::MP comes with a simple distributed database. The database will
		915	be mirrored asynchronously on all global nodes. Other nodes bind to one
		916	of the global nodes for their needs. Every node has a "local database"
		917	which contains all the values that are set locally. All local databases
		918	are merged together to form the global database, which can be queried.
		919
		920	The database structure is that of a two-level hash - the database hash
		921	contains hashes which contain values, similarly to a perl hash of hashes,
		922	i.e.:
		923
		924	$DATABASE{$family}{$subkey} = $value
		925
		926	The top level hash key is called "family", and the second-level hash key
		927	is called "subkey" or simply "key".
		928
		929	The family must be alphanumeric, i.e. start with a letter and consist
		930	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		931	pretty much like Perl module names.
		932
		933	As the family namespace is global, it is recommended to prefix family names
		934	with the name of the application or module using it.
		935
		936	The subkeys must be non-empty strings, with no further restrictions.
		937
		938	The values should preferably be strings, but other perl scalars should
		939	work as well (such as C<undef>, arrays and hashes).
		940
		941	Every database entry is owned by one node - adding the same family/subkey
		942	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		943	but the result might be nondeterministic, i.e. the key might have
		944	different values on different nodes.
		945
		946	Different subkeys in the same family can be owned by different nodes
		947	without problems, and in fact, this is the common method to create worker
		948	pools. For example, a worker port for image scaling might do this:
		949
		950	db_set my_image_scalers => $port;
		951
		952	And clients looking for an image scaler will want to get the
		953	C<my_image_scalers> keys from time to time:
		954
		955	db_keys my_image_scalers => sub {
		956	@ports = @{ $_[0] };
		957	};
		958
		959	Or better yet, they want to monitor the database family, so they always
		960	have a reasonable up-to-date copy:
		961
		962	db_mon my_image_scalers => sub {
		963	@ports = keys %{ $_[0] };
		964	};
		965
		966	In general, you can set or delete single subkeys, but query and monitor
		967	whole families only.
		968
		969	If you feel the need to monitor or query a single subkey, try giving it
		970	it's own family.
		971
		972	=over
		973
		974	=item db_set $family => $subkey [=> $value]
		975
		976	Sets (or replaces) a key to the database - if C<$value> is omitted,
		977	C<undef> is used instead.
		978
		979	=item db_del $family => $subkey...
		980
		981	Deletes one or more subkeys from the database family.
		982
		983	=item $guard = db_reg $family => $subkey [=> $value]
		984
		985	Sets the key on the database and returns a guard. When the guard is
		986	destroyed, the key is deleted from the database. If C<$value> is missing,
		987	then C<undef> is used.
		988
		989	=item db_family $family => $cb->(\%familyhash)
		990
		991	Queries the named database C<$family> and call the callback with the
		992	family represented as a hash. You can keep and freely modify the hash.
		993
		994	=item db_keys $family => $cb->(\@keys)
		995
		996	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		997	them as array reference to the callback.
		998
		999	=item db_values $family => $cb->(\@values)
		1000
		1001	Same as C<db_family>, except it only queries the family I<values> and passes them
		1002	as array reference to the callback.
		1003
		1004	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1005
		1006	Creates a monitor on the given database family. Each time a key is set
		1007	or or is deleted the callback is called with a hash containing the
		1008	database family and three lists of added, changed and deleted subkeys,
		1009	respectively. If no keys have changed then the array reference might be
		1010	C<undef> or even missing.
		1011
		1012	If not called in void context, a guard object is returned that, when
		1013	destroyed, stops the monitor.
		1014
		1015	The family hash reference and the key arrays belong to AnyEvent::MP and
		1016	B<must not be modified or stored> by the callback. When in doubt, make a
		1017	copy.
		1018
		1019	As soon as possible after the monitoring starts, the callback will be
		1020	called with the intiial contents of the family, even if it is empty,
		1021	i.e. there will always be a timely call to the callback with the current
		1022	contents.
		1023
		1024	It is possible that the callback is called with a change event even though
		1025	the subkey is already present and the value has not changed.
		1026
		1027	The monitoring stops when the guard object is destroyed.
		1028
		1029	Example: on every change to the family "mygroup", print out all keys.
		1030
		1031	my $guard = db_mon mygroup => sub {
		1032	my ($family, $a, $c, $d) = @_;
		1033	print "mygroup members: ", (join " ", keys %$family), "\n";
		1034	};
		1035
		1036	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1037
		1038	my $guard; $guard = db_mon My::Module::workers => sub {
		1039	my ($family, $a, $c, $d) = @_;
		1040	return unless %$family;
		1041	undef $guard;
		1042	print "My::Module::workers now nonempty\n";
		1043	};
		1044
		1045	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1046
		1047	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1048	my ($family, $a, $c, $d) = @_;
		1049
		1050	print "+$_=$family->{$_}\n" for @$a;
		1051	print "*$_=$family->{$_}\n" for @$c;
		1052	print "-$_=$family->{$_}\n" for @$d;
		1053	};
		1054
		1055	=cut
		1056
662	=back	1057	=back
663		1058
664	=head1 AnyEvent::MP vs. Distributed Erlang	1059	=head1 AnyEvent::MP vs. Distributed Erlang
665		1060
666	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1061	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
667	== aemp node, Erlang process == aemp port), so many of the documents and	1062	== aemp node, Erlang process == aemp port), so many of the documents and
668	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1063	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
669	sample:	1064	sample:
670		1065
671	http://www.Erlang.se/doc/programming_rules.shtml	1066	http://www.erlang.se/doc/programming_rules.shtml
672	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1067	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
673	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1068	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
674	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1069	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
675		1070
676	Despite the similarities, there are also some important differences:	1071	Despite the similarities, there are also some important differences:
677		1072
678	=over 4	1073	=over 4
679		1074
680	=item * Node IDs are arbitrary strings in AEMP.	1075	=item * Node IDs are arbitrary strings in AEMP.
681		1076
682	Erlang relies on special naming and DNS to work everywhere in the same	1077	Erlang relies on special naming and DNS to work everywhere in the same
683	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1078	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
684	configuraiton or DNS), but will otherwise discover other odes itself.	1079	configuration or DNS), and possibly the addresses of some seed nodes, but
		1080	will otherwise discover other nodes (and their IDs) itself.
685		1081
686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1082	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
687	uses "local ports are like remote ports".	1083	uses "local ports are like remote ports".
688		1084
689	The failure modes for local ports are quite different (runtime errors	1085	The failure modes for local ports are quite different (runtime errors
…		…
698	ports being the special case/exception, where transport errors cannot	1094	ports being the special case/exception, where transport errors cannot
699	occur.	1095	occur.
700		1096
701	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1097	=item * Erlang uses processes and a mailbox, AEMP does not queue.
702		1098
703	Erlang uses processes that selectively receive messages, and therefore	1099	Erlang uses processes that selectively receive messages out of order, and
704	needs a queue. AEMP is event based, queuing messages would serve no	1100	therefore needs a queue. AEMP is event based, queuing messages would serve
705	useful purpose. For the same reason the pattern-matching abilities of	1101	no useful purpose. For the same reason the pattern-matching abilities
706	AnyEvent::MP are more limited, as there is little need to be able to	1102	of AnyEvent::MP are more limited, as there is little need to be able to
707	filter messages without dequeing them.	1103	filter messages without dequeuing them.
708		1104
709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1105	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1106	being event-based, while Erlang is process-based.
		1107
		1108	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1109	top of AEMP and Coro threads.
710		1110
711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1111	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
712		1112
713	Sending messages in Erlang is synchronous and blocks the process (and	1113	Sending messages in Erlang is synchronous and blocks the process until
		1114	a conenction has been established and the message sent (and so does not
714	so does not need a queue that can overflow). AEMP sends are immediate,	1115	need a queue that can overflow). AEMP sends return immediately, connection
715	connection establishment is handled in the background.	1116	establishment is handled in the background.
716		1117
717	=item * Erlang suffers from silent message loss, AEMP does not.	1118	=item * Erlang suffers from silent message loss, AEMP does not.
718		1119
719	Erlang makes few guarantees on messages delivery - messages can get lost	1120	Erlang implements few guarantees on messages delivery - messages can get
720	without any of the processes realising it (i.e. you send messages a, b,	1121	lost without any of the processes realising it (i.e. you send messages a,
721	and c, and the other side only receives messages a and c).	1122	b, and c, and the other side only receives messages a and c).
722		1123
723	AEMP guarantees correct ordering, and the guarantee that after one message	1124	AEMP guarantees (modulo hardware errors) correct ordering, and the
724	is lost, all following ones sent to the same port are lost as well, until	1125	guarantee that after one message is lost, all following ones sent to the
725	monitoring raises an error, so there are no silent "holes" in the message	1126	same port are lost as well, until monitoring raises an error, so there are
726	sequence.	1127	no silent "holes" in the message sequence.
		1128
		1129	If you want your software to be very reliable, you have to cope with
		1130	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1131	simply tries to work better in common error cases, such as when a network
		1132	link goes down.
727		1133
728	=item * Erlang can send messages to the wrong port, AEMP does not.	1134	=item * Erlang can send messages to the wrong port, AEMP does not.
729		1135
730	In Erlang it is quite likely that a node that restarts reuses a process ID	1136	In Erlang it is quite likely that a node that restarts reuses an Erlang
731	known to other nodes for a completely different process, causing messages	1137	process ID known to other nodes for a completely different process,
732	destined for that process to end up in an unrelated process.	1138	causing messages destined for that process to end up in an unrelated
		1139	process.
733		1140
734	AEMP never reuses port IDs, so old messages or old port IDs floating	1141	AEMP does not reuse port IDs, so old messages or old port IDs floating
735	around in the network will not be sent to an unrelated port.	1142	around in the network will not be sent to an unrelated port.
736		1143
737	=item * Erlang uses unprotected connections, AEMP uses secure	1144	=item * Erlang uses unprotected connections, AEMP uses secure
738	authentication and can use TLS.	1145	authentication and can use TLS.
739		1146
…		…
742		1149
743	=item * The AEMP protocol is optimised for both text-based and binary	1150	=item * The AEMP protocol is optimised for both text-based and binary
744	communications.	1151	communications.
745		1152
746	The AEMP protocol, unlike the Erlang protocol, supports both programming	1153	The AEMP protocol, unlike the Erlang protocol, supports both programming
747	language independent text-only protocols (good for debugging) and binary,	1154	language independent text-only protocols (good for debugging), and binary,
748	language-specific serialisers (e.g. Storable). By default, unless TLS is	1155	language-specific serialisers (e.g. Storable). By default, unless TLS is
749	used, the protocol is actually completely text-based.	1156	used, the protocol is actually completely text-based.
750		1157
751	It has also been carefully designed to be implementable in other languages	1158	It has also been carefully designed to be implementable in other languages
752	with a minimum of work while gracefully degrading functionality to make the	1159	with a minimum of work while gracefully degrading functionality to make the
753	protocol simple.	1160	protocol simple.
754		1161
755	=item * AEMP has more flexible monitoring options than Erlang.	1162	=item * AEMP has more flexible monitoring options than Erlang.
756		1163
757	In Erlang, you can chose to receive I<all> exit signals as messages	1164	In Erlang, you can chose to receive I<all> exit signals as messages or
758	or I<none>, there is no in-between, so monitoring single processes is	1165	I<none>, there is no in-between, so monitoring single Erlang processes is
759	difficult to implement. Monitoring in AEMP is more flexible than in	1166	difficult to implement.
760	Erlang, as one can choose between automatic kill, exit message or callback	1167
761	on a per-process basis.	1168	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1169	between automatic kill, exit message or callback on a per-port basis.
762		1170
763	=item * Erlang tries to hide remote/local connections, AEMP does not.	1171	=item * Erlang tries to hide remote/local connections, AEMP does not.
764		1172
765	Monitoring in Erlang is not an indicator of process death/crashes, in the	1173	Monitoring in Erlang is not an indicator of process death/crashes, in the
766	same way as linking is (except linking is unreliable in Erlang).	1174	same way as linking is (except linking is unreliable in Erlang).
…		…
788	overhead, as well as having to keep a proxy object everywhere.	1196	overhead, as well as having to keep a proxy object everywhere.
789		1197
790	Strings can easily be printed, easily serialised etc. and need no special	1198	Strings can easily be printed, easily serialised etc. and need no special
791	procedures to be "valid".	1199	procedures to be "valid".
792		1200
793	And as a result, a miniport consists of a single closure stored in a	1201	And as a result, a port with just a default receiver consists of a single
794	global hash - it can't become much cheaper.	1202	code reference stored in a global hash - it can't become much cheaper.
795		1203
796	=item Why favour JSON, why not a real serialising format such as Storable?	1204	=item Why favour JSON, why not a real serialising format such as Storable?
797		1205
798	In fact, any AnyEvent::MP node will happily accept Storable as framing	1206	In fact, any AnyEvent::MP node will happily accept Storable as framing
799	format, but currently there is no way to make a node use Storable by	1207	format, but currently there is no way to make a node use Storable by
…		…
811		1219
812	=back	1220	=back
813		1221
814	=head1 SEE ALSO	1222	=head1 SEE ALSO
815		1223
		1224	L<AnyEvent::MP::Intro> - a gentle introduction.
		1225
		1226	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1227
		1228	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1229	your applications.
		1230
		1231	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1232
		1233	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1234	all nodes.
		1235
816	L<AnyEvent>.	1236	L<AnyEvent>.
817		1237
818	=head1 AUTHOR	1238	=head1 AUTHOR
819		1239
820	Marc Lehmann <schmorp@schmorp.de>	1240	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.136 by root, Wed Mar 21 15:22:16 2012 UTC