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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC vs.
Revision 1.137 by root, Wed Mar 21 23:48:39 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	configure;	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;
31	rcv $port, pong => sub { warn "pong received\n" };	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
43	bin/aemp - stable.	54	bin/aemp - stable.
44	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
45	AnyEvent::MP::Intro - uptodate, but incomplete.	56	AnyEvent::MP::Intro - explains most concepts.
46	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
47	AnyEvent::MP::Global - stable API, protocol not yet final.	58	AnyEvent::MP::Global - stable API.
48
49	stay tuned.
50		59
51	=head1 DESCRIPTION	60	=head1 DESCRIPTION
52		61
53	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
54		63
…		…
56	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.
57		66
58	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>
59	manual page and the examples under F<eg/>.	68	manual page and the examples under F<eg/>.
60		69
61	At the moment, this module family is a bit underdocumented.
62
63	=head1 CONCEPTS	70	=head1 CONCEPTS
64		71
65	=over 4	72	=over 4
66		73
67	=item port	74	=item port
68		75
69	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).
70		78
71	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
72	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
73	anything was listening for them or not.	81	anything was listening for them or not.
74		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
75	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
76		86
77	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<#>)
78	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).
79		90
80	=item node	91	=item node
81		92
82	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,
83	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
84	ports.	95	ports.
85		96
86	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
87	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
88	currently.	99	currently, but all nodes can talk to public nodes.
89		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
90	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
91		104
92	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
93	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
94	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
95	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
96		109
97	=item binds - C<ip:port>	110	=item binds - C<ip:port>
98		111
99	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
100	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
101	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
102	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.
103		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
104	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
105		150
106	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
107	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.
108	network. This node is called a seed.
109		153
110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
111	are expected to be long-running, and at least one of those should always
112	be available. When nodes run out of connections (e.g. due to a network
113	error), they try to re-establish connections to some seednodes again to
114	join the network.
115		155
116	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
117	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).
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	configure	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
		202	db_mon db_family db_keys db_values
146	);	203	);
147		204
148	our $SELF;	205	our $SELF;
149		206
150	sub _self_die() {	207	sub _self_die() {
…		…
161		218
162	=item $nodeid = node_of $port	219	=item $nodeid = node_of $port
163		220
164	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.
165		222
		223	=item configure $profile, key => value...
		224
166	=item configure key => value...	225	=item configure key => value...
167		226
168	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
169	"distributed mode") it has to configure itself - the minimum a node needs	228	"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	229	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.	230	some other nodes in the network to discover other nodes.
172		231
173	This function configures a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
175		234
		235	The key/value pairs are basically the same ones as documented for the
		236	F<aemp> command line utility (sans the set/del prefix), with these additions:
		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
176	=over 4	267	=over 4
177		268
178	=item step 1, gathering configuration from profiles	269	=item step 1, gathering configuration from profiles
179		270
180	The function first looks up a 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). The profile name can be specified via the	272	L<aemp> commandline utility). The profile name can be specified via the
182	named C<profile> parameter. If it is missing, then the nodename (F<uname	273	named C<profile> parameter or can simply be the first parameter). If it is
183	-n>) will be used as profile name.	274	missing, then the nodename (F<uname -n>) will be used as profile name.
184		275
185	The profile data is then gathered as follows:	276	The profile data is then gathered as follows:
186		277
187	First, all remaining key => value pairs (all of which are conviniently	278	First, all remaining key => value pairs (all of which are conveniently
188	undocumented at the moment) will be interpreted as configuration	279	undocumented at the moment) will be interpreted as configuration
189	data. Then they will be overwritten by any values specified in the global	280	data. Then they will be overwritten by any values specified in the global
190	default configuration (see the F<aemp> utility), then the chain of	281	default configuration (see the F<aemp> utility), then the chain of
191	profiles chosen by the profile name (and any C<parent> attributes).	282	profiles chosen by the profile name (and any C<parent> attributes).
192		283
193	That means that the values specified in the profile have highest priority	284	That means that the values specified in the profile have highest priority
194	and the values specified directly via C<configure> have lowest priority,	285	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	286	and can only be used to specify defaults.
196		287
197	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
198	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
199	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>.
200		297
201	=item step 2, bind listener sockets	298	=item step 2, bind listener sockets
202		299
203	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
204	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
…		…
210	used, meaning the node will bind on a dynamically-assigned port on every	307	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	308	local IP address it finds.
212		309
213	=item step 3, connect to seed nodes	310	=item step 3, connect to seed nodes
214		311
215	As the last step, 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
216	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
217	connectivity with at least one node at any point in time.	314	connectivity with at least one node at any point in time.
218		315
219	=back	316	=back
220		317
221	Example: become a distributed node using the locla node name as profile.	318	Example: become a distributed node using the local node name as profile.
222	This should be the most common form of invocation for "daemon"-type nodes.	319	This should be the most common form of invocation for "daemon"-type nodes.
223		320
224	configure	321	configure
225		322
226	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
227	clients.	324	commandline clients.
228		325
229	configure nodeid => "anon/";	326	configure nodeid => "myscript/%n/%u";
230		327
231	Example: configure a node using a profile called seed, which si suitable	328	Example: configure a node using a profile called seed, which is suitable
232	for a seed node as it binds on all local addresses on a fixed port (4040,	329	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	330	customary for aemp).
234		331
235	# use the aemp commandline utility	332	# use the aemp commandline utility
236	# aemp profile seed setnodeid anon/ setbinds '*:4040'	333	# aemp profile seed binds '*:4040'
237		334
238	# then use it	335	# then use it
239	configure profile => "seed";	336	configure profile => "seed";
240		337
241	# or simply use aemp from the shell again:	338	# or simply use aemp from the shell again:
…		…
306		403
307	=cut	404	=cut
308		405
309	sub rcv($@);	406	sub rcv($@);
310		407
311	sub _kilme {	408	my $KILME = sub {
312	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
313	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
314		412
315	sub port(;&) {	413	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
318		416
319	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
320		418
321	$port	419	$port
322	}	420	}
323		421
324	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
329		427
330	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
331	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
332	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
333		431
334	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
335	C<tag> match.	433	C<tag> match.
336		434
337	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
338		436
339	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
…		…
360	msg1 => sub { ... },	458	msg1 => sub { ... },
361	...	459	...
362	;	460	;
363		461
364	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
365	(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.
366		464
367	rcv $port, $otherport => sub {	465	rcv $port, $otherport => sub {
368	my @reply = @_;	466	my @reply = @_;
369		467
370	rcv $SELF, $otherport;	468	rcv $SELF, $otherport;
…		…
372		470
373	=cut	471	=cut
374		472
375	sub rcv($@) {	473	sub rcv($@) {
376	my $port = shift;	474	my $port = shift;
377	my ($noderef, $portid) = split /#/, $port, 2;	475	my ($nodeid, $portid) = split /#/, $port, 2;
378		476
379	$NODE{$noderef} == $NODE{""}	477	$NODE{$nodeid} == $NODE{""}
380	or Carp::croak "$port: rcv can only be called on local ports, caught";	478	or Carp::croak "$port: rcv can only be called on local ports, caught";
381		479
382	while (@_) {	480	while (@_) {
383	if (ref $_[0]) {	481	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	482	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	483	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$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";
387		485
388	$self->[2] = shift;	486	$self->[0] = shift;
389	} else {	487	} else {
390	my $cb = shift;	488	my $cb = shift;
391	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
392	local $SELF = $port;	490	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	491	eval { &$cb }; _self_die if $@;
394	};	492	};
395	}	493	}
396	} elsif (defined $_[0]) {	494	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	495	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	496	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		497
400	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
401	local $SELF = $port;	499	local $SELF = $port;
402		500
403	if (my $cb = $self->[1]{$_[0]}) {	501	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	523	}
426		524
427	$port	525	$port
428	}	526	}
429		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
430	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
431		566
432	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
433	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>
434	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 }, @_ } >>.
435		573
436	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
437		575
438	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
475		613
476	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
477	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
478	to stop monitoring again.	616	to stop monitoring again.
479		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
480	C<mon> effectively guarantees that, in the absence of hardware failures,	644	C<mon> effectively guarantees that, in the absence of hardware failures,
481	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
482	arrive, or the monitoring action will be invoked after possible message	646	arrive, or the monitoring action will be invoked after possible message
483	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
484	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
485	port). After the monitoring action was invoked, further messages might get	649	port). After the monitoring action was invoked, further messages might get
486	delivered again.	650	delivered again.
487		651
488	Note that monitoring-actions are one-shot: once messages are lost (and a	652	Inter-host-connection timeouts and monitoring depend on the transport
489	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).
490		656
491	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
492	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
493	"normally"). Note also that I<< the callback B<must> never die >>, so use	659	to ensure some maximum latency.
494	C<eval> if unsure.
495
496	In the second form (another port given), the other port (C<$rcvport>)
497	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
498	"normal" kils nothing happens, while under all other conditions, the other
499	port is killed with the same reason.
500
501	The third form (kill self) is the same as the second form, except that
502	C<$rvport> defaults to C<$SELF>.
503
504	In the last form (message), a message of the form C<@msg, @reason> will be
505	C<snd>.
506
507	As a rule of thumb, monitoring requests should always monitor a port from
508	a local port (or callback). The reason is that kill messages might get
509	lost, just like any other message. Another less obvious reason is that
510	even monitoring requests can get lost (for exmaple, when the connection
511	to the other node goes down permanently). When monitoring a port locally
512	these problems do not exist.
513		660
514	Example: call a given callback when C<$port> is killed.	661	Example: call a given callback when C<$port> is killed.
515		662
516	mon $port, sub { warn "port died because of <@_>\n" };	663	mon $port, sub { warn "port died because of <@_>\n" };
517		664
…		…
524	mon $port, $self => "restart";	671	mon $port, $self => "restart";
525		672
526	=cut	673	=cut
527		674
528	sub mon {	675	sub mon {
529	my ($noderef, $port) = split /#/, shift, 2;	676	my ($nodeid, $port) = split /#/, shift, 2;
530		677
531	my $node = $NODE{$noderef} \|\| add_node $noderef;	678	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
532		679
533	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,';
534		681
535	unless (ref $cb) {	682	unless (ref $cb) {
536	if (@_) {	683	if (@_) {
…		…
545	}	692	}
546		693
547	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
548		695
549	defined wantarray	696	defined wantarray
550	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
551	}	698	}
552		699
553	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
554		701
555	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
…		…
578		725
579	=item kil $port[, @reason]	726	=item kil $port[, @reason]
580		727
581	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
582		729
583	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" -
584	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
585	"normally").	732	(C<mon $mport, $lport> form) to get killed.
586		733
587	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>
588	C<mon>, see above).	735	form) get killed with the same reason.
589		736
590	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
591	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
592		739
593	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
594	$message >>.	741	$message >>.
595		742
596	=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: $!";
597		754
598	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
599		756
600	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
601	case it's the node where that port resides).	758	case it's the node where that port resides).
…		…
612	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.
613	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
614	exists or it runs out of package names.	771	exists or it runs out of package names.
615		772
616	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
617	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.
618		777
619	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
620	port, and in the remote init function, immediately monitor the passed	779	port, and in the remote init function, immediately monitor the passed
621	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
622	when there is a problem.	781	when there is a problem.
623		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
624	Example: spawn a chat server port on C<$othernode>.	787	Example: spawn a chat server port on C<$othernode>.
625		788
626	# this node, executed from within a port context:	789	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	790	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
628	mon $server;	791	mon $server;
…		…
642		805
643	sub _spawn {	806	sub _spawn {
644	my $port = shift;	807	my $port = shift;
645	my $init = shift;	808	my $init = shift;
646		809
		810	# rcv will create the actual port
647	local $SELF = "$NODE#$port";	811	local $SELF = "$NODE#$port";
648	eval {	812	eval {
649	&{ load_func $init }	813	&{ load_func $init }
650	};	814	};
651	_self_die if $@;	815	_self_die if $@;
652	}	816	}
653		817
654	sub spawn(@) {	818	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
656		820
657	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
658		822
659	$_[0] =~ /::/	823	$_[0] =~ /::/
660	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";
661		825
662	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663		827
664	"$noderef#$id"	828	"$nodeid#$id"
665	}	829	}
		830
666		831
667	=item after $timeout, @msg	832	=item after $timeout, @msg
668		833
669	=item after $timeout, $callback	834	=item after $timeout, $callback
670		835
…		…
686	? $action[0]()	851	? $action[0]()
687	: snd @action;	852	: snd @action;
688	};	853	};
689	}	854	}
690		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 $guard = 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	When called in non-void context, C<db_set> returns a guard that
		980	automatically calls C<db_del> when it is destroyed.
		981
		982	=item db_del $family => $subkey...
		983
		984	Deletes one or more subkeys from the database family.
		985
		986	=item $guard = db_reg $family => $port => $value
		987
		988	=item $guard = db_reg $family => $port
		989
		990	=item $guard = db_reg $family
		991
		992	Registers a port in the given family and optionally returns a guard to
		993	remove it.
		994
		995	This function basically does the same as:
		996
		997	db_set $family => $port => $value
		998
		999	Except that the port is monitored and automatically removed from the
		1000	database family when it is kil'ed.
		1001
		1002	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1003	C<$SELF> is used.
		1004
		1005	This function is most useful to register a port in some port group (which
		1006	is just another name for a database family), and have it removed when the
		1007	port is gone. This works best when the port is a local port.
		1008
		1009	=cut
		1010
		1011	sub db_reg($$;$) {
		1012	my $family = shift;
		1013	my $port = @_ ? shift : $SELF;
		1014
		1015	my $clr = sub { db_del $family => $port };
		1016	mon $port, $clr;
		1017
		1018	db_set $family => $port => $_[0];
		1019
		1020	defined wantarray
		1021	and &Guard::guard ($clr)
		1022	}
		1023
		1024	=item db_family $family => $cb->(\%familyhash)
		1025
		1026	Queries the named database C<$family> and call the callback with the
		1027	family represented as a hash. You can keep and freely modify the hash.
		1028
		1029	=item db_keys $family => $cb->(\@keys)
		1030
		1031	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1032	them as array reference to the callback.
		1033
		1034	=item db_values $family => $cb->(\@values)
		1035
		1036	Same as C<db_family>, except it only queries the family I<values> and passes them
		1037	as array reference to the callback.
		1038
		1039	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1040
		1041	Creates a monitor on the given database family. Each time a key is set
		1042	or or is deleted the callback is called with a hash containing the
		1043	database family and three lists of added, changed and deleted subkeys,
		1044	respectively. If no keys have changed then the array reference might be
		1045	C<undef> or even missing.
		1046
		1047	If not called in void context, a guard object is returned that, when
		1048	destroyed, stops the monitor.
		1049
		1050	The family hash reference and the key arrays belong to AnyEvent::MP and
		1051	B<must not be modified or stored> by the callback. When in doubt, make a
		1052	copy.
		1053
		1054	As soon as possible after the monitoring starts, the callback will be
		1055	called with the intiial contents of the family, even if it is empty,
		1056	i.e. there will always be a timely call to the callback with the current
		1057	contents.
		1058
		1059	It is possible that the callback is called with a change event even though
		1060	the subkey is already present and the value has not changed.
		1061
		1062	The monitoring stops when the guard object is destroyed.
		1063
		1064	Example: on every change to the family "mygroup", print out all keys.
		1065
		1066	my $guard = db_mon mygroup => sub {
		1067	my ($family, $a, $c, $d) = @_;
		1068	print "mygroup members: ", (join " ", keys %$family), "\n";
		1069	};
		1070
		1071	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1072
		1073	my $guard; $guard = db_mon My::Module::workers => sub {
		1074	my ($family, $a, $c, $d) = @_;
		1075	return unless %$family;
		1076	undef $guard;
		1077	print "My::Module::workers now nonempty\n";
		1078	};
		1079
		1080	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1081
		1082	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1083	my ($family, $a, $c, $d) = @_;
		1084
		1085	print "+$_=$family->{$_}\n" for @$a;
		1086	print "*$_=$family->{$_}\n" for @$c;
		1087	print "-$_=$family->{$_}\n" for @$d;
		1088	};
		1089
		1090	=cut
		1091
691	=back	1092	=back
692		1093
693	=head1 AnyEvent::MP vs. Distributed Erlang	1094	=head1 AnyEvent::MP vs. Distributed Erlang
694		1095
695	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1096	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
696	== aemp node, Erlang process == aemp port), so many of the documents and	1097	== aemp node, Erlang process == aemp port), so many of the documents and
697	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1098	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
698	sample:	1099	sample:
699		1100
700	http://www.Erlang.se/doc/programming_rules.shtml	1101	http://www.erlang.se/doc/programming_rules.shtml
701	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1102	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
702	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1103	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
703	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1104	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
704		1105
705	Despite the similarities, there are also some important differences:	1106	Despite the similarities, there are also some important differences:
706		1107
707	=over 4	1108	=over 4
708		1109
709	=item * Node IDs are arbitrary strings in AEMP.	1110	=item * Node IDs are arbitrary strings in AEMP.
710		1111
711	Erlang relies on special naming and DNS to work everywhere in the same	1112	Erlang relies on special naming and DNS to work everywhere in the same
712	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1113	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
713	configuraiton or DNS), but will otherwise discover other odes itself.	1114	configuration or DNS), and possibly the addresses of some seed nodes, but
		1115	will otherwise discover other nodes (and their IDs) itself.
714		1116
715	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1117	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
716	uses "local ports are like remote ports".	1118	uses "local ports are like remote ports".
717		1119
718	The failure modes for local ports are quite different (runtime errors	1120	The failure modes for local ports are quite different (runtime errors
…		…
727	ports being the special case/exception, where transport errors cannot	1129	ports being the special case/exception, where transport errors cannot
728	occur.	1130	occur.
729		1131
730	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1132	=item * Erlang uses processes and a mailbox, AEMP does not queue.
731		1133
732	Erlang uses processes that selectively receive messages, and therefore	1134	Erlang uses processes that selectively receive messages out of order, and
733	needs a queue. AEMP is event based, queuing messages would serve no	1135	therefore needs a queue. AEMP is event based, queuing messages would serve
734	useful purpose. For the same reason the pattern-matching abilities of	1136	no useful purpose. For the same reason the pattern-matching abilities
735	AnyEvent::MP are more limited, as there is little need to be able to	1137	of AnyEvent::MP are more limited, as there is little need to be able to
736	filter messages without dequeing them.	1138	filter messages without dequeuing them.
737		1139
738	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1140	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1141	being event-based, while Erlang is process-based.
		1142
		1143	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1144	top of AEMP and Coro threads.
739		1145
740	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1146	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
741		1147
742	Sending messages in Erlang is synchronous and blocks the process (and	1148	Sending messages in Erlang is synchronous and blocks the process until
		1149	a conenction has been established and the message sent (and so does not
743	so does not need a queue that can overflow). AEMP sends are immediate,	1150	need a queue that can overflow). AEMP sends return immediately, connection
744	connection establishment is handled in the background.	1151	establishment is handled in the background.
745		1152
746	=item * Erlang suffers from silent message loss, AEMP does not.	1153	=item * Erlang suffers from silent message loss, AEMP does not.
747		1154
748	Erlang makes few guarantees on messages delivery - messages can get lost	1155	Erlang implements few guarantees on messages delivery - messages can get
749	without any of the processes realising it (i.e. you send messages a, b,	1156	lost without any of the processes realising it (i.e. you send messages a,
750	and c, and the other side only receives messages a and c).	1157	b, and c, and the other side only receives messages a and c).
751		1158
752	AEMP guarantees correct ordering, and the guarantee that after one message	1159	AEMP guarantees (modulo hardware errors) correct ordering, and the
753	is lost, all following ones sent to the same port are lost as well, until	1160	guarantee that after one message is lost, all following ones sent to the
754	monitoring raises an error, so there are no silent "holes" in the message	1161	same port are lost as well, until monitoring raises an error, so there are
755	sequence.	1162	no silent "holes" in the message sequence.
		1163
		1164	If you want your software to be very reliable, you have to cope with
		1165	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1166	simply tries to work better in common error cases, such as when a network
		1167	link goes down.
756		1168
757	=item * Erlang can send messages to the wrong port, AEMP does not.	1169	=item * Erlang can send messages to the wrong port, AEMP does not.
758		1170
759	In Erlang it is quite likely that a node that restarts reuses a process ID	1171	In Erlang it is quite likely that a node that restarts reuses an Erlang
760	known to other nodes for a completely different process, causing messages	1172	process ID known to other nodes for a completely different process,
761	destined for that process to end up in an unrelated process.	1173	causing messages destined for that process to end up in an unrelated
		1174	process.
762		1175
763	AEMP never reuses port IDs, so old messages or old port IDs floating	1176	AEMP does not reuse port IDs, so old messages or old port IDs floating
764	around in the network will not be sent to an unrelated port.	1177	around in the network will not be sent to an unrelated port.
765		1178
766	=item * Erlang uses unprotected connections, AEMP uses secure	1179	=item * Erlang uses unprotected connections, AEMP uses secure
767	authentication and can use TLS.	1180	authentication and can use TLS.
768		1181
…		…
771		1184
772	=item * The AEMP protocol is optimised for both text-based and binary	1185	=item * The AEMP protocol is optimised for both text-based and binary
773	communications.	1186	communications.
774		1187
775	The AEMP protocol, unlike the Erlang protocol, supports both programming	1188	The AEMP protocol, unlike the Erlang protocol, supports both programming
776	language independent text-only protocols (good for debugging) and binary,	1189	language independent text-only protocols (good for debugging), and binary,
777	language-specific serialisers (e.g. Storable). By default, unless TLS is	1190	language-specific serialisers (e.g. Storable). By default, unless TLS is
778	used, the protocol is actually completely text-based.	1191	used, the protocol is actually completely text-based.
779		1192
780	It has also been carefully designed to be implementable in other languages	1193	It has also been carefully designed to be implementable in other languages
781	with a minimum of work while gracefully degrading functionality to make the	1194	with a minimum of work while gracefully degrading functionality to make the
782	protocol simple.	1195	protocol simple.
783		1196
784	=item * AEMP has more flexible monitoring options than Erlang.	1197	=item * AEMP has more flexible monitoring options than Erlang.
785		1198
786	In Erlang, you can chose to receive I<all> exit signals as messages	1199	In Erlang, you can chose to receive I<all> exit signals as messages or
787	or I<none>, there is no in-between, so monitoring single processes is	1200	I<none>, there is no in-between, so monitoring single Erlang processes is
788	difficult to implement. Monitoring in AEMP is more flexible than in	1201	difficult to implement.
789	Erlang, as one can choose between automatic kill, exit message or callback	1202
790	on a per-process basis.	1203	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1204	between automatic kill, exit message or callback on a per-port basis.
791		1205
792	=item * Erlang tries to hide remote/local connections, AEMP does not.	1206	=item * Erlang tries to hide remote/local connections, AEMP does not.
793		1207
794	Monitoring in Erlang is not an indicator of process death/crashes, in the	1208	Monitoring in Erlang is not an indicator of process death/crashes, in the
795	same way as linking is (except linking is unreliable in Erlang).	1209	same way as linking is (except linking is unreliable in Erlang).
…		…
817	overhead, as well as having to keep a proxy object everywhere.	1231	overhead, as well as having to keep a proxy object everywhere.
818		1232
819	Strings can easily be printed, easily serialised etc. and need no special	1233	Strings can easily be printed, easily serialised etc. and need no special
820	procedures to be "valid".	1234	procedures to be "valid".
821		1235
822	And as a result, a miniport consists of a single closure stored in a	1236	And as a result, a port with just a default receiver consists of a single
823	global hash - it can't become much cheaper.	1237	code reference stored in a global hash - it can't become much cheaper.
824		1238
825	=item Why favour JSON, why not a real serialising format such as Storable?	1239	=item Why favour JSON, why not a real serialising format such as Storable?
826		1240
827	In fact, any AnyEvent::MP node will happily accept Storable as framing	1241	In fact, any AnyEvent::MP node will happily accept Storable as framing
828	format, but currently there is no way to make a node use Storable by	1242	format, but currently there is no way to make a node use Storable by
…		…
838	Keeping your messages simple, concentrating on data structures rather than	1252	Keeping your messages simple, concentrating on data structures rather than
839	objects, will keep your messages clean, tidy and efficient.	1253	objects, will keep your messages clean, tidy and efficient.
840		1254
841	=back	1255	=back
842		1256
		1257	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1258
		1259	AEMP version 2 has three major incompatible changes compared to version 1:
		1260
		1261	=over 4
		1262
		1263	=item AnyEvent::MP::Global no longer has group management functions.
		1264
		1265	AnyEvent::MP now comes with a distributed database that is more
		1266	powerful. It's database families map closely to ports, but the API has
		1267	minor differences:
		1268
		1269	grp_reg $group, $port # old
		1270	db_reg $group, $port # new
		1271
		1272	$list = grp_get $group # old
		1273	db_keys $group, sub { my $list = shift } # new
		1274
		1275	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1276	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1277
		1278	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get>
		1279	is no longer instant, because the local node might not have a copy of
		1280	the group. This can be partially remedied by using C<db_mon> to keep an
		1281	updated copy of the group:
		1282
		1283	my $local_group_copy;
		1284	db_mon $group => sub { $local_group_copy = shift };
		1285
		1286	# no keys %$local_group_copy always returns the most up-to-date
		1287	# list of ports in the group.
		1288
		1289	C<grp_mon> can almost be replaced by C<db_mon>:
		1290
		1291	db_mon $group => sub {
		1292	my ($ports, $add, $chg, $lde) = @_;
		1293	$ports = [keys %$ports];
		1294
		1295	# now $ports, $add and $del are the same as
		1296	# were originally passed by grp_mon.
		1297	...
		1298	};
		1299
		1300	=item Nodes not longer connect to all other nodes.
		1301
		1302	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1303	module, which in turn would create connections to all other nodes in the
		1304	network (helped by the seed nodes).
		1305
		1306	In version 2.x, global nodes still connect to all other global nodes, but
		1307	other nodes don't - now every node either is a global node itself, or
		1308	attaches itself to another global node.
		1309
		1310	If a node isn't a global node itself, then it attaches itself to one
		1311	of its seed nodes. If that seed node isn't a global node yet, it will
		1312	automatically be upgraded to a global node.
		1313
		1314	So in many cases, nothing needs to be changed - one just has to make sure
		1315	that all seed nodes are meshed together with the other seed nodes (as with
		1316	AEMP 1.x), and other nodes specify them as seed nodes.
		1317
		1318	Not opening a connection to every other node is usually an advantage,
		1319	except when you need the lower latency of an already established
		1320	connection. To ensure a node establishes a connection to another node,
		1321	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1322	create the connection (And notify you when the connection fails).
		1323
		1324	=item Listener-less nodes are gone.
		1325
		1326	And are not coming back, at least not in their old form.
		1327
		1328	There are vague plans to implement some form of routing domains, which
		1329	might or might not bring back listener-less nodes, but don't count on it.
		1330
		1331	The fact that most connections are now optional somewhat mitigates this,
		1332	as a node can be effectively unreachable from the outside without any
		1333	problems, as long as it isn't a global node and only reaches out to other
		1334	nodes (as opposed to being contacted from other nodes).
		1335
		1336	=back
		1337
843	=head1 SEE ALSO	1338	=head1 SEE ALSO
844		1339
845	L<AnyEvent::MP::Intro> - a gentle introduction.	1340	L<AnyEvent::MP::Intro> - a gentle introduction.
846		1341
847	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1342	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
848		1343
849	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1344	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
850	your applications.	1345	your applications.
		1346
		1347	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1348
		1349	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1350	all nodes.
851		1351
852	L<AnyEvent>.	1352	L<AnyEvent>.
853		1353
854	=head1 AUTHOR	1354	=head1 AUTHOR
855		1355

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC vs. Revision 1.137 by root, Wed Mar 21 23:48:39 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC vs.
Revision 1.137 by root, Wed Mar 21 23:48:39 2012 UTC