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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.70 by root, Sun Aug 30 19:49:47 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	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, key => value...	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 first 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). the profile is calculated as follows:	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.
182		275
		276	The profile data is then gathered as follows:
		277
183	First, all remaining key => value pairs (all of which are conviniently	278	First, all remaining key => value pairs (all of which are conveniently
184	undocumented at the moment) will be used. Then they will be overwritten by	279	undocumented at the moment) will be interpreted as configuration
185	any values specified in the global default configuration (see the F<aemp>	280	data. Then they will be overwritten by any values specified in the global
186	utility), then the chain of profiles selected, if any. That means that	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
187	the values specified in the profile have highest priority and the values	284	That means that the values specified in the profile have highest priority
188	specified via C<initialise_node> have lowest priority.	285	and the values specified directly via C<configure> have lowest priority,
		286	and can only be used to specify defaults.
189		287
190	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
191	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
192	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
193		299
194	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
195	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
196	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
197	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
198	binds, but it can still talk to all "normal" nodes).	304	binds, but it can still talk to all "normal" nodes).
199		305
200	If the profile does not specify a binds list, then a default of C<*> is	306	If the profile does not specify a binds list, then a default of C<*> is
201	used.	307	used, meaning the node will bind on a dynamically-assigned port on every
		308	local IP address it finds.
202		309
		310	=item step 3, connect to seed nodes
		311
203	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
204	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
205	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.
206		315
207	Example: become a distributed node listening on the guessed noderef, or	316	=back
208	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.
209	most common form of invocation for "daemon"-type nodes.	319	This should be the most common form of invocation for "daemon"-type nodes.
210		320
211	initialise_node;	321	configure
212		322
213	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
214	clients.	324	commandline clients.
215		325
216	initialise_node "anon/";	326	configure nodeid => "myscript/%n/%u";
217		327
218	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
219	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,
220	on the resulting addresses.	330	customary for aemp).
221		331
222	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)"
223		343
224	=item $SELF	344	=item $SELF
225		345
226	Contains the current port id while executing C<rcv> callbacks or C<psub>	346	Contains the current port id while executing C<rcv> callbacks or C<psub>
227	blocks.	347	blocks.
…		…
283		403
284	=cut	404	=cut
285		405
286	sub rcv($@);	406	sub rcv($@);
287		407
288	sub _kilme {	408	my $KILME = sub {
289	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
290	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
291		412
292	sub port(;&) {	413	sub port(;&) {
293	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
294	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
295		416
296	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
297		418
298	$port	419	$port
299	}	420	}
300		421
301	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
306		427
307	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
308	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
309	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
310		431
311	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
312	C<tag> match.	433	C<tag> match.
313		434
314	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
315		436
316	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
…		…
337	msg1 => sub { ... },	458	msg1 => sub { ... },
338	...	459	...
339	;	460	;
340		461
341	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
342	(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.
343		464
344	rcv $port, $otherport => sub {	465	rcv $port, $otherport => sub {
345	my @reply = @_;	466	my @reply = @_;
346		467
347	rcv $SELF, $otherport;	468	rcv $SELF, $otherport;
…		…
349		470
350	=cut	471	=cut
351		472
352	sub rcv($@) {	473	sub rcv($@) {
353	my $port = shift;	474	my $port = shift;
354	my ($noderef, $portid) = split /#/, $port, 2;	475	my ($nodeid, $portid) = split /#/, $port, 2;
355		476
356	$NODE{$noderef} == $NODE{""}	477	$NODE{$nodeid} == $NODE{""}
357	or Carp::croak "$port: rcv can only be called on local ports, caught";	478	or Carp::croak "$port: rcv can only be called on local ports, caught";
358		479
359	while (@_) {	480	while (@_) {
360	if (ref $_[0]) {	481	if (ref $_[0]) {
361	if (my $self = $PORT_DATA{$portid}) {	482	if (my $self = $PORT_DATA{$portid}) {
362	"AnyEvent::MP::Port" eq ref $self	483	"AnyEvent::MP::Port" eq ref $self
363	or Carp::croak "$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";
364		485
365	$self->[2] = shift;	486	$self->[0] = shift;
366	} else {	487	} else {
367	my $cb = shift;	488	my $cb = shift;
368	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
369	local $SELF = $port;	490	local $SELF = $port;
370	eval { &$cb }; _self_die if $@;	491	eval { &$cb }; _self_die if $@;
371	};	492	};
372	}	493	}
373	} elsif (defined $_[0]) {	494	} elsif (defined $_[0]) {
374	my $self = $PORT_DATA{$portid} \|\|= do {	495	my $self = $PORT_DATA{$portid} \|\|= do {
375	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	496	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
376		497
377	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
378	local $SELF = $port;	499	local $SELF = $port;
379		500
380	if (my $cb = $self->[1]{$_[0]}) {	501	if (my $cb = $self->[1]{$_[0]}) {
…		…
402	}	523	}
403		524
404	$port	525	$port
405	}	526	}
406		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
407	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
408		566
409	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
410	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>
411	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 }, @_ } >>.
412		573
413	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
414		575
415	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
416	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
452		613
453	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
454	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
455	to stop monitoring again.	616	to stop monitoring again.
456		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
457	C<mon> effectively guarantees that, in the absence of hardware failures,	644	C<mon> effectively guarantees that, in the absence of hardware failures,
458	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
459	arrive, or the monitoring action will be invoked after possible message	646	arrive, or the monitoring action will be invoked after possible message
460	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
461	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
462	port). After the monitoring action was invoked, further messages might get	649	port). After the monitoring action was invoked, further messages might get
463	delivered again.	650	delivered again.
464		651
465	Note that monitoring-actions are one-shot: once messages are lost (and a	652	Inter-host-connection timeouts and monitoring depend on the transport
466	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).
467		656
468	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
469	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
470	"normally"). Note also that I<< the callback B<must> never die >>, so use	659	to ensure some maximum latency.
471	C<eval> if unsure.
472
473	In the second form (another port given), the other port (C<$rcvport>)
474	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
475	"normal" kils nothing happens, while under all other conditions, the other
476	port is killed with the same reason.
477
478	The third form (kill self) is the same as the second form, except that
479	C<$rvport> defaults to C<$SELF>.
480
481	In the last form (message), a message of the form C<@msg, @reason> will be
482	C<snd>.
483
484	As a rule of thumb, monitoring requests should always monitor a port from
485	a local port (or callback). The reason is that kill messages might get
486	lost, just like any other message. Another less obvious reason is that
487	even monitoring requests can get lost (for exmaple, when the connection
488	to the other node goes down permanently). When monitoring a port locally
489	these problems do not exist.
490		660
491	Example: call a given callback when C<$port> is killed.	661	Example: call a given callback when C<$port> is killed.
492		662
493	mon $port, sub { warn "port died because of <@_>\n" };	663	mon $port, sub { warn "port died because of <@_>\n" };
494		664
…		…
501	mon $port, $self => "restart";	671	mon $port, $self => "restart";
502		672
503	=cut	673	=cut
504		674
505	sub mon {	675	sub mon {
506	my ($noderef, $port) = split /#/, shift, 2;	676	my ($nodeid, $port) = split /#/, shift, 2;
507		677
508	my $node = $NODE{$noderef} \|\| add_node $noderef;	678	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
509		679
510	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,';
511		681
512	unless (ref $cb) {	682	unless (ref $cb) {
513	if (@_) {	683	if (@_) {
…		…
522	}	692	}
523		693
524	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
525		695
526	defined wantarray	696	defined wantarray
527	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
528	}	698	}
529		699
530	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
531		701
532	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
…		…
555		725
556	=item kil $port[, @reason]	726	=item kil $port[, @reason]
557		727
558	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
559		729
560	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" -
561	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
562	"normally").	732	(C<mon $mport, $lport> form) to get killed.
563		733
564	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>
565	C<mon>, see above).	735	form) get killed with the same reason.
566		736
567	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
568	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
569		739
570	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
571	$message >>.	741	$message >>.
572		742
573	=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: $!";
574		754
575	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
576		756
577	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
578	case it's the node where that port resides).	758	case it's the node where that port resides).
…		…
589	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.
590	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
591	exists or it runs out of package names.	771	exists or it runs out of package names.
592		772
593	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
594	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.
595		777
596	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
597	port, and in the remote init function, immediately monitor the passed	779	port, and in the remote init function, immediately monitor the passed
598	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
599	when there is a problem.	781	when there is a problem.
600		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
601	Example: spawn a chat server port on C<$othernode>.	787	Example: spawn a chat server port on C<$othernode>.
602		788
603	# this node, executed from within a port context:	789	# this node, executed from within a port context:
604	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	790	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
605	mon $server;	791	mon $server;
…		…
619		805
620	sub _spawn {	806	sub _spawn {
621	my $port = shift;	807	my $port = shift;
622	my $init = shift;	808	my $init = shift;
623		809
		810	# rcv will create the actual port
624	local $SELF = "$NODE#$port";	811	local $SELF = "$NODE#$port";
625	eval {	812	eval {
626	&{ load_func $init }	813	&{ load_func $init }
627	};	814	};
628	_self_die if $@;	815	_self_die if $@;
629	}	816	}
630		817
631	sub spawn(@) {	818	sub spawn(@) {
632	my ($noderef, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
633		820
634	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
635		822
636	$_[0] =~ /::/	823	$_[0] =~ /::/
637	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";
638		825
639	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
640		827
641	"$noderef#$id"	828	"$nodeid#$id"
642	}	829	}
		830
643		831
644	=item after $timeout, @msg	832	=item after $timeout, @msg
645		833
646	=item after $timeout, $callback	834	=item after $timeout, $callback
647		835
…		…
663	? $action[0]()	851	? $action[0]()
664	: snd @action;	852	: snd @action;
665	};	853	};
666	}	854	}
667		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
668	=back	1092	=back
669		1093
670	=head1 AnyEvent::MP vs. Distributed Erlang	1094	=head1 AnyEvent::MP vs. Distributed Erlang
671		1095
672	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
673	== 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
674	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
675	sample:	1099	sample:
676		1100
677	http://www.Erlang.se/doc/programming_rules.shtml	1101	http://www.erlang.se/doc/programming_rules.shtml
678	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
679	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
680	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
681		1105
682	Despite the similarities, there are also some important differences:	1106	Despite the similarities, there are also some important differences:
683		1107
684	=over 4	1108	=over 4
685		1109
686	=item * Node IDs are arbitrary strings in AEMP.	1110	=item * Node IDs are arbitrary strings in AEMP.
687		1111
688	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
689	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
690	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.
691		1116
692	=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
693	uses "local ports are like remote ports".	1118	uses "local ports are like remote ports".
694		1119
695	The failure modes for local ports are quite different (runtime errors	1120	The failure modes for local ports are quite different (runtime errors
…		…
704	ports being the special case/exception, where transport errors cannot	1129	ports being the special case/exception, where transport errors cannot
705	occur.	1130	occur.
706		1131
707	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1132	=item * Erlang uses processes and a mailbox, AEMP does not queue.
708		1133
709	Erlang uses processes that selectively receive messages, and therefore	1134	Erlang uses processes that selectively receive messages out of order, and
710	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
711	useful purpose. For the same reason the pattern-matching abilities of	1136	no useful purpose. For the same reason the pattern-matching abilities
712	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
713	filter messages without dequeing them.	1138	filter messages without dequeuing them.
714		1139
715	(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.
716		1145
717	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1146	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
718		1147
719	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
720	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
721	connection establishment is handled in the background.	1151	establishment is handled in the background.
722		1152
723	=item * Erlang suffers from silent message loss, AEMP does not.	1153	=item * Erlang suffers from silent message loss, AEMP does not.
724		1154
725	Erlang makes few guarantees on messages delivery - messages can get lost	1155	Erlang implements few guarantees on messages delivery - messages can get
726	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,
727	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).
728		1158
729	AEMP guarantees correct ordering, and the guarantee that after one message	1159	AEMP guarantees (modulo hardware errors) correct ordering, and the
730	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
731	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
732	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.
733		1168
734	=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.
735		1170
736	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
737	known to other nodes for a completely different process, causing messages	1172	process ID known to other nodes for a completely different process,
738	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.
739		1175
740	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
741	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.
742		1178
743	=item * Erlang uses unprotected connections, AEMP uses secure	1179	=item * Erlang uses unprotected connections, AEMP uses secure
744	authentication and can use TLS.	1180	authentication and can use TLS.
745		1181
…		…
748		1184
749	=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
750	communications.	1186	communications.
751		1187
752	The AEMP protocol, unlike the Erlang protocol, supports both programming	1188	The AEMP protocol, unlike the Erlang protocol, supports both programming
753	language independent text-only protocols (good for debugging) and binary,	1189	language independent text-only protocols (good for debugging), and binary,
754	language-specific serialisers (e.g. Storable). By default, unless TLS is	1190	language-specific serialisers (e.g. Storable). By default, unless TLS is
755	used, the protocol is actually completely text-based.	1191	used, the protocol is actually completely text-based.
756		1192
757	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
758	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
759	protocol simple.	1195	protocol simple.
760		1196
761	=item * AEMP has more flexible monitoring options than Erlang.	1197	=item * AEMP has more flexible monitoring options than Erlang.
762		1198
763	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
764	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
765	difficult to implement. Monitoring in AEMP is more flexible than in	1201	difficult to implement.
766	Erlang, as one can choose between automatic kill, exit message or callback	1202
767	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.
768		1205
769	=item * Erlang tries to hide remote/local connections, AEMP does not.	1206	=item * Erlang tries to hide remote/local connections, AEMP does not.
770		1207
771	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
772	same way as linking is (except linking is unreliable in Erlang).	1209	same way as linking is (except linking is unreliable in Erlang).
…		…
794	overhead, as well as having to keep a proxy object everywhere.	1231	overhead, as well as having to keep a proxy object everywhere.
795		1232
796	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
797	procedures to be "valid".	1234	procedures to be "valid".
798		1235
799	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
800	global hash - it can't become much cheaper.	1237	code reference stored in a global hash - it can't become much cheaper.
801		1238
802	=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?
803		1240
804	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
805	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
…		…
815	Keeping your messages simple, concentrating on data structures rather than	1252	Keeping your messages simple, concentrating on data structures rather than
816	objects, will keep your messages clean, tidy and efficient.	1253	objects, will keep your messages clean, tidy and efficient.
817		1254
818	=back	1255	=back
819		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
820	=head1 SEE ALSO	1338	=head1 SEE ALSO
821		1339
822	L<AnyEvent::MP::Intro> - a gentle introduction.	1340	L<AnyEvent::MP::Intro> - a gentle introduction.
823		1341
824	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1342	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
825		1343
826	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1344	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
827	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.
828		1351
829	L<AnyEvent>.	1352	L<AnyEvent>.
830		1353
831	=head1 AUTHOR	1354	=head1 AUTHOR
832		1355

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Revision 1.137 by root, Wed Mar 21 23:48:39 2012 UTC