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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.68 by root, Fri Aug 28 23:06:33 2009 UTC vs.
Revision 1.142 by root, Fri Mar 23 13:44:01 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
40		43
41	=head1 CURRENT STATUS	44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
42		46
43	AnyEvent::MP - stable API, should work	47	# execute callbacks in $SELF port context
44	AnyEvent::MP::Intro - outdated	48	my $timer = AE::timer 1, 0, psub {
45	AnyEvent::MP::Kernel - mostly stable	49	die "kill the port, delayed";
46	AnyEvent::MP::Global - mostly stable	50	};
47	AnyEvent::MP::Node - mostly stable, but internal anyways
48	AnyEvent::MP::Transport - mostly stable, but internal anyways
49
50	stay tuned.
51		51
52	=head1 DESCRIPTION	52	=head1 DESCRIPTION
53		53
54	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
55		55
57	on the same or other hosts, and you can supervise entities remotely.	57	on the same or other hosts, and you can supervise entities remotely.
58		58
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page and the examples under F<eg/>.	60	manual page and the examples under F<eg/>.
61		61
62	At the moment, this module family is a bit underdocumented.
63
64	=head1 CONCEPTS	62	=head1 CONCEPTS
65		63
66	=over 4	64	=over 4
67		65
68	=item port	66	=item port
69		67
70	A port is something you can send messages to (with the C<snd> function).	68	Not to be confused with a TCP port, a "port" is something you can send
		69	messages to (with the C<snd> function).
71		70
72	Ports allow you to register C<rcv> handlers that can match all or just	71	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	72	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	73	anything was listening for them or not.
75		74
		75	Ports are represented by (printable) strings called "port IDs".
		76
76	=item port ID - C<nodeid#portname>	77	=item port ID - C<nodeid#portname>
77		78
78	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	79	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).	80	as separator, and a port name (a printable string of unspecified
		81	format created by AnyEvent::MP).
80		82
81	=item node	83	=item node
82		84
83	A node is a single process containing at least one port - the node port,	85	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	86	which enables nodes to manage each other remotely, and to create new
85	ports.	87	ports.
86		88
87	Nodes are either public (have one or more listening ports) or private	89	Nodes are either public (have one or more listening ports) or private
88	(no listening ports). Private nodes cannot talk to other private nodes	90	(no listening ports). Private nodes cannot talk to other private nodes
89	currently.	91	currently, but all nodes can talk to public nodes.
90		92
		93	Nodes is represented by (printable) strings called "node IDs".
		94
91	=item node ID - C<[a-za-Z0-9_\-.:]+>	95	=item node ID - C<[A-Za-z0-9_\-.:]*>
92		96
93	A node ID is a string that uniquely identifies the node within a	97	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	98	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	99	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
96	doesn't interpret node IDs in any way.	100	doesn't interpret node IDs in any way except to uniquely identify a node.
97		101
98	=item binds - C<ip:port>	102	=item binds - C<ip:port>
99		103
100	Nodes can only talk to each other by creating some kind of connection to	104	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	105	each other. To do this, nodes should listen on one or more local transport
		106	endpoints - binds.
		107
102	endpoints - binds. Currently, only standard C<ip:port> specifications can	108	Currently, only standard C<ip:port> specifications can be used, which
103	be used, which specify TCP ports to listen on.	109	specify TCP ports to listen on. So a bind is basically just a tcp socket
		110	in listening mode thta accepts conenctions form other nodes.
104		111
		112	=item seed nodes
		113
		114	When a node starts, it knows nothing about the network it is in - it
		115	needs to connect to at least one other node that is already in the
		116	network. These other nodes are called "seed nodes".
		117
		118	Seed nodes themselves are not special - they are seed nodes only because
		119	some other node I<uses> them as such, but any node can be used as seed
		120	node for other nodes, and eahc node cna use a different set of seed nodes.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network - all nodes using the same seed node form are part of
		124	the same network. If a network is split into multiple subnets because e.g.
		125	the network link between the parts goes down, then using the same seed
		126	nodes for all nodes ensures that eventually the subnets get merged again.
		127
		128	Seed nodes are expected to be long-running, and at least one seed node
		129	should always be available. They should also be relatively responsive - a
		130	seed node that blocks for long periods will slow down everybody else.
		131
		132	For small networks, it's best if every node uses the same set of seed
		133	nodes. For large networks, it can be useful to specify "regional" seed
		134	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		135	each other. What's important is that all seed nodes connections form a
		136	complete graph, so that the network cannot split into separate subnets
		137	forever.
		138
		139	Seed nodes are represented by seed IDs.
		140
105	=item seeds - C<host:port>	141	=item seed IDs - C<host:port>
106		142
107	When a node starts, it knows nothing about the network. To teach the node	143	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	144	TCP port) of nodes that should be used as seed nodes.
109	network. This node is called a seed.
110		145
111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	146	=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		147
117	Apart from being sued for seeding, seednodes are not special in any way -	148	An AEMP network needs a discovery service - nodes need to know how to
118	every public node can be a seednode.	149	connect to other nodes they only know by name. In addition, AEMP offers a
		150	distributed "group database", which maps group names to a list of strings
		151	- for example, to register worker ports.
		152
		153	A network needs at least one global node to work, and allows every node to
		154	be a global node.
		155
		156	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		157	node and tries to keep connections to all other nodes. So while it can
		158	make sense to make every node "global" in small networks, it usually makes
		159	sense to only make seed nodes into global nodes in large networks (nodes
		160	keep connections to seed nodes and global nodes, so makign them the same
		161	reduces overhead).
119		162
120	=back	163	=back
121		164
122	=head1 VARIABLES/FUNCTIONS	165	=head1 VARIABLES/FUNCTIONS
123		166
…		…
125		168
126	=cut	169	=cut
127		170
128	package AnyEvent::MP;	171	package AnyEvent::MP;
129		172
		173	use AnyEvent::MP::Config ();
130	use AnyEvent::MP::Kernel;	174	use AnyEvent::MP::Kernel;
		175	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
131		176
132	use common::sense;	177	use common::sense;
133		178
134	use Carp ();	179	use Carp ();
135		180
136	use AE ();	181	use AnyEvent ();
		182	use Guard ();
137		183
138	use base "Exporter";	184	use base "Exporter";
139		185
140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	186	our $VERSION = $AnyEvent::MP::Config::VERSION;
141		187
142	our @EXPORT = qw(	188	our @EXPORT = qw(
143	NODE $NODE *SELF node_of after	189	NODE $NODE *SELF node_of after
144	initialise_node	190	configure
145	snd rcv mon mon_guard kil reg psub spawn	191	snd rcv mon mon_guard kil psub peval spawn cal
146	port	192	port
		193	db_set db_del db_reg
		194	db_mon db_family db_keys db_values
147	);	195	);
148		196
149	our $SELF;	197	our $SELF;
150		198
151	sub _self_die() {	199	sub _self_die() {
…		…
156		204
157	=item $thisnode = NODE / $NODE	205	=item $thisnode = NODE / $NODE
158		206
159	The C<NODE> function returns, and the C<$NODE> variable contains, the node	207	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	208	ID of the node running in the current process. This value is initialised by
161	a call to C<initialise_node>.	209	a call to C<configure>.
162		210
163	=item $nodeid = node_of $port	211	=item $nodeid = node_of $port
164		212
165	Extracts and returns the node ID from a port ID or a node ID.	213	Extracts and returns the node ID from a port ID or a node ID.
166		214
167	=item initialise_node $profile_name	215	=item configure $profile, key => value...
		216
		217	=item configure key => value...
168		218
169	Before a node can talk to other nodes on the network (i.e. enter	219	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	220	"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	221	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.	222	some other nodes in the network to discover other nodes.
173		223
174	This function initialises a node - it must be called exactly once (or	224	This function configures a node - it must be called exactly once (or
175	never) before calling other AnyEvent::MP functions.	225	never) before calling other AnyEvent::MP functions.
176		226
177	The first argument is a profile name. If it is C<undef> or missing, then	227	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>).	228	F<aemp> command line utility (sans the set/del prefix), with these additions:
179		229
		230	=over 4
		231
		232	=item norc => $boolean (default false)
		233
		234	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		235	be consulted - all configuraiton options must be specified in the
		236	C<configure> call.
		237
		238	=item force => $boolean (default false)
		239
		240	IF true, then the values specified in the C<configure> will take
		241	precedence over any values configured via the rc file. The default is for
		242	the rc file to override any options specified in the program.
		243
		244	=back
		245
		246	=over 4
		247
		248	=item step 1, gathering configuration from profiles
		249
180	The function then looks up the profile in the aemp configuration (see the	250	The function first looks up a profile in the aemp configuration (see the
181	L<aemp> commandline utility).	251	L<aemp> commandline utility). The profile name can be specified via the
		252	named C<profile> parameter or can simply be the first parameter). If it is
		253	missing, then the nodename (F<uname -n>) will be used as profile name.
		254
		255	The profile data is then gathered as follows:
		256
		257	First, all remaining key => value pairs (all of which are conveniently
		258	undocumented at the moment) will be interpreted as configuration
		259	data. Then they will be overwritten by any values specified in the global
		260	default configuration (see the F<aemp> utility), then the chain of
		261	profiles chosen by the profile name (and any C<parent> attributes).
		262
		263	That means that the values specified in the profile have highest priority
		264	and the values specified directly via C<configure> have lowest priority,
		265	and can only be used to specify defaults.
182		266
183	If the profile specifies a node ID, then this will become the node ID of	267	If the profile specifies a node ID, then this will become the node ID of
184	this process. If not, then the profile name will be used as node ID. The	268	this process. If not, then the profile name will be used as node ID, with
185	special node ID of C<anon/> will be replaced by a random node ID.	269	a unique randoms tring (C</%u>) appended.
		270
		271	The node ID can contain some C<%> sequences that are expanded: C<%n>
		272	is expanded to the local nodename, C<%u> is replaced by a random
		273	strign to make the node unique. For example, the F<aemp> commandline
		274	utility uses C<aemp/%n/%u> as nodename, which might expand to
		275	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		276
		277	=item step 2, bind listener sockets
186		278
187	The next step is to look up the binds in the profile, followed by binding	279	The next step is to look up the binds in the profile, followed by binding
188	aemp protocol listeners on all binds specified (it is possible and valid	280	aemp protocol listeners on all binds specified (it is possible and valid
189	to have no binds, meaning that the node cannot be contacted form the	281	to have no binds, meaning that the node cannot be contacted form the
190	outside. This means the node cannot talk to other nodes that also have no	282	outside. This means the node cannot talk to other nodes that also have no
191	binds, but it can still talk to all "normal" nodes).	283	binds, but it can still talk to all "normal" nodes).
192		284
193	If the profile does not specify a binds list, then the node ID will be	285	If the profile does not specify a binds list, then a default of C<*> is
194	treated as if it were of the form C<host:port>, which will be resolved and	286	used, meaning the node will bind on a dynamically-assigned port on every
195	used as binds list.	287	local IP address it finds.
196		288
		289	=item step 3, connect to seed nodes
		290
197	Lastly, the seeds list from the profile is passed to the	291	As the last step, the seed ID list from the profile is passed to the
198	L<AnyEvent::MP::Global> module, which will then use it to keep	292	L<AnyEvent::MP::Global> module, which will then use it to keep
199	connectivity with at least on of those seed nodes at any point in time.	293	connectivity with at least one node at any point in time.
200		294
201	Example: become a distributed node listening on the guessed noderef, or	295	=back
202	the one specified via C<aemp> for the current node. This should be the	296
		297	Example: become a distributed node using the local node name as profile.
203	most common form of invocation for "daemon"-type nodes.	298	This should be the most common form of invocation for "daemon"-type nodes.
204		299
205	initialise_node;	300	configure
206		301
207	Example: become an anonymous node. This form is often used for commandline	302	Example: become a semi-anonymous node. This form is often used for
208	clients.	303	commandline clients.
209		304
210	initialise_node "anon/";	305	configure nodeid => "myscript/%n/%u";
211		306
212	Example: become a distributed node. If there is no profile of the given	307	Example: configure a node using a profile called seed, which is suitable
213	name, or no binds list was specified, resolve C<localhost:4044> and bind	308	for a seed node as it binds on all local addresses on a fixed port (4040,
214	on the resulting addresses.	309	customary for aemp).
215		310
216	initialise_node "localhost:4044";	311	# use the aemp commandline utility
		312	# aemp profile seed binds '*:4040'
		313
		314	# then use it
		315	configure profile => "seed";
		316
		317	# or simply use aemp from the shell again:
		318	# aemp run profile seed
		319
		320	# or provide a nicer-to-remember nodeid
		321	# aemp run profile seed nodeid "$(hostname)"
217		322
218	=item $SELF	323	=item $SELF
219		324
220	Contains the current port id while executing C<rcv> callbacks or C<psub>	325	Contains the current port id while executing C<rcv> callbacks or C<psub>
221	blocks.	326	blocks.
…		…
277		382
278	=cut	383	=cut
279		384
280	sub rcv($@);	385	sub rcv($@);
281		386
282	sub _kilme {	387	my $KILME = sub {
283	die "received message on port without callback";	388	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
284	}	389	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		390	};
285		391
286	sub port(;&) {	392	sub port(;&) {
287	my $id = "$UNIQ." . $ID++;	393	my $id = $UNIQ . ++$ID;
288	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
289		395
290	rcv $port, shift \|\| \&_kilme;	396	rcv $port, shift \|\| $KILME;
291		397
292	$port	398	$port
293	}	399	}
294		400
295	=item rcv $local_port, $callback->(@msg)	401	=item rcv $local_port, $callback->(@msg)
…		…
300		406
301	The global C<$SELF> (exported by this module) contains C<$port> while	407	The global C<$SELF> (exported by this module) contains C<$port> while
302	executing the callback. Runtime errors during callback execution will	408	executing the callback. Runtime errors during callback execution will
303	result in the port being C<kil>ed.	409	result in the port being C<kil>ed.
304		410
305	The default callback received all messages not matched by a more specific	411	The default callback receives all messages not matched by a more specific
306	C<tag> match.	412	C<tag> match.
307		413
308	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	414	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
309		415
310	Register (or replace) callbacks to be called on messages starting with the	416	Register (or replace) callbacks to be called on messages starting with the
…		…
331	msg1 => sub { ... },	437	msg1 => sub { ... },
332	...	438	...
333	;	439	;
334		440
335	Example: temporarily register a rcv callback for a tag matching some port	441	Example: temporarily register a rcv callback for a tag matching some port
336	(e.g. for a rpc reply) and unregister it after a message was received.	442	(e.g. for an rpc reply) and unregister it after a message was received.
337		443
338	rcv $port, $otherport => sub {	444	rcv $port, $otherport => sub {
339	my @reply = @_;	445	my @reply = @_;
340		446
341	rcv $SELF, $otherport;	447	rcv $SELF, $otherport;
…		…
343		449
344	=cut	450	=cut
345		451
346	sub rcv($@) {	452	sub rcv($@) {
347	my $port = shift;	453	my $port = shift;
348	my ($noderef, $portid) = split /#/, $port, 2;	454	my ($nodeid, $portid) = split /#/, $port, 2;
349		455
350	$NODE{$noderef} == $NODE{""}	456	$NODE{$nodeid} == $NODE{""}
351	or Carp::croak "$port: rcv can only be called on local ports, caught";	457	or Carp::croak "$port: rcv can only be called on local ports, caught";
352		458
353	while (@_) {	459	while (@_) {
354	if (ref $_[0]) {	460	if (ref $_[0]) {
355	if (my $self = $PORT_DATA{$portid}) {	461	if (my $self = $PORT_DATA{$portid}) {
356	"AnyEvent::MP::Port" eq ref $self	462	"AnyEvent::MP::Port" eq ref $self
357	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	463	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
358		464
359	$self->[2] = shift;	465	$self->[0] = shift;
360	} else {	466	} else {
361	my $cb = shift;	467	my $cb = shift;
362	$PORT{$portid} = sub {	468	$PORT{$portid} = sub {
363	local $SELF = $port;	469	local $SELF = $port;
364	eval { &$cb }; _self_die if $@;	470	eval { &$cb }; _self_die if $@;
365	};	471	};
366	}	472	}
367	} elsif (defined $_[0]) {	473	} elsif (defined $_[0]) {
368	my $self = $PORT_DATA{$portid} \|\|= do {	474	my $self = $PORT_DATA{$portid} \|\|= do {
369	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	475	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
370		476
371	$PORT{$portid} = sub {	477	$PORT{$portid} = sub {
372	local $SELF = $port;	478	local $SELF = $port;
373		479
374	if (my $cb = $self->[1]{$_[0]}) {	480	if (my $cb = $self->[1]{$_[0]}) {
…		…
396	}	502	}
397		503
398	$port	504	$port
399	}	505	}
400		506
		507	=item peval $port, $coderef[, @args]
		508
		509	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		510	when the code throews an exception the C<$port> will be killed.
		511
		512	Any remaining args will be passed to the callback. Any return values will
		513	be returned to the caller.
		514
		515	This is useful when you temporarily want to execute code in the context of
		516	a port.
		517
		518	Example: create a port and run some initialisation code in it's context.
		519
		520	my $port = port { ... };
		521
		522	peval $port, sub {
		523	init
		524	or die "unable to init";
		525	};
		526
		527	=cut
		528
		529	sub peval($$) {
		530	local $SELF = shift;
		531	my $cb = shift;
		532
		533	if (wantarray) {
		534	my @res = eval { &$cb };
		535	_self_die if $@;
		536	@res
		537	} else {
		538	my $res = eval { &$cb };
		539	_self_die if $@;
		540	$res
		541	}
		542	}
		543
401	=item $closure = psub { BLOCK }	544	=item $closure = psub { BLOCK }
402		545
403	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	546	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
404	closure is executed, sets up the environment in the same way as in C<rcv>	547	closure is executed, sets up the environment in the same way as in C<rcv>
405	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	548	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		549
		550	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		551	BLOCK }, @_ } >>.
406		552
407	This is useful when you register callbacks from C<rcv> callbacks:	553	This is useful when you register callbacks from C<rcv> callbacks:
408		554
409	rcv delayed_reply => sub {	555	rcv delayed_reply => sub {
410	my ($delay, @reply) = @_;	556	my ($delay, @reply) = @_;
…		…
434	$res	580	$res
435	}	581	}
436	}	582	}
437	}	583	}
438		584
		585	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		586
		587	=item $guard = mon $port # kill $SELF when $port dies
		588
439	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	589	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
440
441	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
442
443	=item $guard = mon $port # kill $SELF when $port dies
444		590
445	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	591	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
446		592
447	Monitor the given port and do something when the port is killed or	593	Monitor the given port and do something when the port is killed or
448	messages to it were lost, and optionally return a guard that can be used	594	messages to it were lost, and optionally return a guard that can be used
449	to stop monitoring again.	595	to stop monitoring again.
		596
		597	The first two forms distinguish between "normal" and "abnormal" kil's:
		598
		599	In the first form (another port given), if the C<$port> is C<kil>'ed with
		600	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		601	same reason. That is, on "normal" kil's nothing happens, while under all
		602	other conditions, the other port is killed with the same reason.
		603
		604	The second form (kill self) is the same as the first form, except that
		605	C<$rvport> defaults to C<$SELF>.
		606
		607	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		608	- it's up to the callback or receiver to check whether the C<@reason> is
		609	empty and act accordingly.
		610
		611	In the third form (callback), the callback is simply called with any
		612	number of C<@reason> elements (empty @reason means that the port was deleted
		613	"normally"). Note also that I<< the callback B<must> never die >>, so use
		614	C<eval> if unsure.
		615
		616	In the last form (message), a message of the form C<$rcvport, @msg,
		617	@reason> will be C<snd>.
		618
		619	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		620	alert was raised), they are removed and will not trigger again, even if it
		621	turns out that the port is still alive.
		622
		623	As a rule of thumb, monitoring requests should always monitor a remote
		624	port locally (using a local C<$rcvport> or a callback). The reason is that
		625	kill messages might get lost, just like any other message. Another less
		626	obvious reason is that even monitoring requests can get lost (for example,
		627	when the connection to the other node goes down permanently). When
		628	monitoring a port locally these problems do not exist.
450		629
451	C<mon> effectively guarantees that, in the absence of hardware failures,	630	C<mon> effectively guarantees that, in the absence of hardware failures,
452	after starting the monitor, either all messages sent to the port will	631	after starting the monitor, either all messages sent to the port will
453	arrive, or the monitoring action will be invoked after possible message	632	arrive, or the monitoring action will be invoked after possible message
454	loss has been detected. No messages will be lost "in between" (after	633	loss has been detected. No messages will be lost "in between" (after
455	the first lost message no further messages will be received by the	634	the first lost message no further messages will be received by the
456	port). After the monitoring action was invoked, further messages might get	635	port). After the monitoring action was invoked, further messages might get
457	delivered again.	636	delivered again.
458		637
459	Note that monitoring-actions are one-shot: once messages are lost (and a	638	Inter-host-connection timeouts and monitoring depend on the transport
460	monitoring alert was raised), they are removed and will not trigger again.	639	used. The only transport currently implemented is TCP, and AnyEvent::MP
		640	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		641	non-idle connection, and usually around two hours for idle connections).
461		642
462	In the first form (callback), the callback is simply called with any	643	This means that monitoring is good for program errors and cleaning up
463	number of C<@reason> elements (no @reason means that the port was deleted	644	stuff eventually, but they are no replacement for a timeout when you need
464	"normally"). Note also that I<< the callback B<must> never die >>, so use	645	to ensure some maximum latency.
465	C<eval> if unsure.
466
467	In the second form (another port given), the other port (C<$rcvport>)
468	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
469	"normal" kils nothing happens, while under all other conditions, the other
470	port is killed with the same reason.
471
472	The third form (kill self) is the same as the second form, except that
473	C<$rvport> defaults to C<$SELF>.
474
475	In the last form (message), a message of the form C<@msg, @reason> will be
476	C<snd>.
477
478	As a rule of thumb, monitoring requests should always monitor a port from
479	a local port (or callback). The reason is that kill messages might get
480	lost, just like any other message. Another less obvious reason is that
481	even monitoring requests can get lost (for exmaple, when the connection
482	to the other node goes down permanently). When monitoring a port locally
483	these problems do not exist.
484		646
485	Example: call a given callback when C<$port> is killed.	647	Example: call a given callback when C<$port> is killed.
486		648
487	mon $port, sub { warn "port died because of <@_>\n" };	649	mon $port, sub { warn "port died because of <@_>\n" };
488		650
…		…
495	mon $port, $self => "restart";	657	mon $port, $self => "restart";
496		658
497	=cut	659	=cut
498		660
499	sub mon {	661	sub mon {
500	my ($noderef, $port) = split /#/, shift, 2;	662	my ($nodeid, $port) = split /#/, shift, 2;
501		663
502	my $node = $NODE{$noderef} \|\| add_node $noderef;	664	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
503		665
504	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	666	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
505		667
506	unless (ref $cb) {	668	unless (ref $cb) {
507	if (@_) {	669	if (@_) {
…		…
516	}	678	}
517		679
518	$node->monitor ($port, $cb);	680	$node->monitor ($port, $cb);
519		681
520	defined wantarray	682	defined wantarray
521	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	683	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
522	}	684	}
523		685
524	=item $guard = mon_guard $port, $ref, $ref...	686	=item $guard = mon_guard $port, $ref, $ref...
525		687
526	Monitors the given C<$port> and keeps the passed references. When the port	688	Monitors the given C<$port> and keeps the passed references. When the port
…		…
549		711
550	=item kil $port[, @reason]	712	=item kil $port[, @reason]
551		713
552	Kill the specified port with the given C<@reason>.	714	Kill the specified port with the given C<@reason>.
553		715
554	If no C<@reason> is specified, then the port is killed "normally" (ports	716	If no C<@reason> is specified, then the port is killed "normally" -
555	monitoring other ports will not necessarily die because a port dies	717	monitor callback will be invoked, but the kil will not cause linked ports
556	"normally").	718	(C<mon $mport, $lport> form) to get killed.
557		719
558	Otherwise, linked ports get killed with the same reason (second form of	720	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
559	C<mon>, see above).	721	form) get killed with the same reason.
560		722
561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	723	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
562	will be reported as reason C<< die => $@ >>.	724	will be reported as reason C<< die => $@ >>.
563		725
564	Transport/communication errors are reported as C<< transport_error =>	726	Transport/communication errors are reported as C<< transport_error =>
565	$message >>.	727	$message >>.
566		728
567	=cut	729	Common idioms:
		730
		731	# silently remove yourself, do not kill linked ports
		732	kil $SELF;
		733
		734	# report a failure in some detail
		735	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		736
		737	# do not waste much time with killing, just die when something goes wrong
		738	open my $fh, "<file"
		739	or die "file: $!";
568		740
569	=item $port = spawn $node, $initfunc[, @initdata]	741	=item $port = spawn $node, $initfunc[, @initdata]
570		742
571	Creates a port on the node C<$node> (which can also be a port ID, in which	743	Creates a port on the node C<$node> (which can also be a port ID, in which
572	case it's the node where that port resides).	744	case it's the node where that port resides).
…		…
583	the package, then the package above the package and so on (e.g.	755	the package, then the package above the package and so on (e.g.
584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	756	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
585	exists or it runs out of package names.	757	exists or it runs out of package names.
586		758
587	The init function is then called with the newly-created port as context	759	The init function is then called with the newly-created port as context
588	object (C<$SELF>) and the C<@initdata> values as arguments.	760	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		761	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		762	the port might not get created.
589		763
590	A common idiom is to pass a local port, immediately monitor the spawned	764	A common idiom is to pass a local port, immediately monitor the spawned
591	port, and in the remote init function, immediately monitor the passed	765	port, and in the remote init function, immediately monitor the passed
592	local port. This two-way monitoring ensures that both ports get cleaned up	766	local port. This two-way monitoring ensures that both ports get cleaned up
593	when there is a problem.	767	when there is a problem.
594		768
		769	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		770	caller before C<spawn> returns (by delaying invocation when spawn is
		771	called for the local node).
		772
595	Example: spawn a chat server port on C<$othernode>.	773	Example: spawn a chat server port on C<$othernode>.
596		774
597	# this node, executed from within a port context:	775	# this node, executed from within a port context:
598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	776	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
599	mon $server;	777	mon $server;
…		…
613		791
614	sub _spawn {	792	sub _spawn {
615	my $port = shift;	793	my $port = shift;
616	my $init = shift;	794	my $init = shift;
617		795
		796	# rcv will create the actual port
618	local $SELF = "$NODE#$port";	797	local $SELF = "$NODE#$port";
619	eval {	798	eval {
620	&{ load_func $init }	799	&{ load_func $init }
621	};	800	};
622	_self_die if $@;	801	_self_die if $@;
623	}	802	}
624		803
625	sub spawn(@) {	804	sub spawn(@) {
626	my ($noderef, undef) = split /#/, shift, 2;	805	my ($nodeid, undef) = split /#/, shift, 2;
627		806
628	my $id = "$RUNIQ." . $ID++;	807	my $id = $RUNIQ . ++$ID;
629		808
630	$_[0] =~ /::/	809	$_[0] =~ /::/
631	or Carp::croak "spawn init function must be a fully-qualified name, caught";	810	or Carp::croak "spawn init function must be a fully-qualified name, caught";
632		811
633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	812	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
634		813
635	"$noderef#$id"	814	"$nodeid#$id"
636	}	815	}
		816
637		817
638	=item after $timeout, @msg	818	=item after $timeout, @msg
639		819
640	=item after $timeout, $callback	820	=item after $timeout, $callback
641		821
…		…
657	? $action[0]()	837	? $action[0]()
658	: snd @action;	838	: snd @action;
659	};	839	};
660	}	840	}
661		841
		842	#=item $cb2 = timeout $seconds, $cb[, @args]
		843
		844	=item cal $port, @msg, $callback[, $timeout]
		845
		846	A simple form of RPC - sends a message to the given C<$port> with the
		847	given contents (C<@msg>), but adds a reply port to the message.
		848
		849	The reply port is created temporarily just for the purpose of receiving
		850	the reply, and will be C<kil>ed when no longer needed.
		851
		852	A reply message sent to the port is passed to the C<$callback> as-is.
		853
		854	If an optional time-out (in seconds) is given and it is not C<undef>,
		855	then the callback will be called without any arguments after the time-out
		856	elapsed and the port is C<kil>ed.
		857
		858	If no time-out is given (or it is C<undef>), then the local port will
		859	monitor the remote port instead, so it eventually gets cleaned-up.
		860
		861	Currently this function returns the temporary port, but this "feature"
		862	might go in future versions unless you can make a convincing case that
		863	this is indeed useful for something.
		864
		865	=cut
		866
		867	sub cal(@) {
		868	my $timeout = ref $_[-1] ? undef : pop;
		869	my $cb = pop;
		870
		871	my $port = port {
		872	undef $timeout;
		873	kil $SELF;
		874	&$cb;
		875	};
		876
		877	if (defined $timeout) {
		878	$timeout = AE::timer $timeout, 0, sub {
		879	undef $timeout;
		880	kil $port;
		881	$cb->();
		882	};
		883	} else {
		884	mon $_[0], sub {
		885	kil $port;
		886	$cb->();
		887	};
		888	}
		889
		890	push @_, $port;
		891	&snd;
		892
		893	$port
		894	}
		895
		896	=back
		897
		898	=head1 DISTRIBUTED DATABASE
		899
		900	AnyEvent::MP comes with a simple distributed database. The database will
		901	be mirrored asynchronously on all global nodes. Other nodes bind to one
		902	of the global nodes for their needs. Every node has a "local database"
		903	which contains all the values that are set locally. All local databases
		904	are merged together to form the global database, which can be queried.
		905
		906	The database structure is that of a two-level hash - the database hash
		907	contains hashes which contain values, similarly to a perl hash of hashes,
		908	i.e.:
		909
		910	$DATABASE{$family}{$subkey} = $value
		911
		912	The top level hash key is called "family", and the second-level hash key
		913	is called "subkey" or simply "key".
		914
		915	The family must be alphanumeric, i.e. start with a letter and consist
		916	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		917	pretty much like Perl module names.
		918
		919	As the family namespace is global, it is recommended to prefix family names
		920	with the name of the application or module using it.
		921
		922	The subkeys must be non-empty strings, with no further restrictions.
		923
		924	The values should preferably be strings, but other perl scalars should
		925	work as well (such as C<undef>, arrays and hashes).
		926
		927	Every database entry is owned by one node - adding the same family/subkey
		928	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		929	but the result might be nondeterministic, i.e. the key might have
		930	different values on different nodes.
		931
		932	Different subkeys in the same family can be owned by different nodes
		933	without problems, and in fact, this is the common method to create worker
		934	pools. For example, a worker port for image scaling might do this:
		935
		936	db_set my_image_scalers => $port;
		937
		938	And clients looking for an image scaler will want to get the
		939	C<my_image_scalers> keys from time to time:
		940
		941	db_keys my_image_scalers => sub {
		942	@ports = @{ $_[0] };
		943	};
		944
		945	Or better yet, they want to monitor the database family, so they always
		946	have a reasonable up-to-date copy:
		947
		948	db_mon my_image_scalers => sub {
		949	@ports = keys %{ $_[0] };
		950	};
		951
		952	In general, you can set or delete single subkeys, but query and monitor
		953	whole families only.
		954
		955	If you feel the need to monitor or query a single subkey, try giving it
		956	it's own family.
		957
		958	=over
		959
		960	=item $guard = db_set $family => $subkey [=> $value]
		961
		962	Sets (or replaces) a key to the database - if C<$value> is omitted,
		963	C<undef> is used instead.
		964
		965	When called in non-void context, C<db_set> returns a guard that
		966	automatically calls C<db_del> when it is destroyed.
		967
		968	=item db_del $family => $subkey...
		969
		970	Deletes one or more subkeys from the database family.
		971
		972	=item $guard = db_reg $family => $port => $value
		973
		974	=item $guard = db_reg $family => $port
		975
		976	=item $guard = db_reg $family
		977
		978	Registers a port in the given family and optionally returns a guard to
		979	remove it.
		980
		981	This function basically does the same as:
		982
		983	db_set $family => $port => $value
		984
		985	Except that the port is monitored and automatically removed from the
		986	database family when it is kil'ed.
		987
		988	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		989	C<$SELF> is used.
		990
		991	This function is most useful to register a port in some port group (which
		992	is just another name for a database family), and have it removed when the
		993	port is gone. This works best when the port is a local port.
		994
		995	=cut
		996
		997	sub db_reg($$;$) {
		998	my $family = shift;
		999	my $port = @_ ? shift : $SELF;
		1000
		1001	my $clr = sub { db_del $family => $port };
		1002	mon $port, $clr;
		1003
		1004	db_set $family => $port => $_[0];
		1005
		1006	defined wantarray
		1007	and &Guard::guard ($clr)
		1008	}
		1009
		1010	=item db_family $family => $cb->(\%familyhash)
		1011
		1012	Queries the named database C<$family> and call the callback with the
		1013	family represented as a hash. You can keep and freely modify the hash.
		1014
		1015	=item db_keys $family => $cb->(\@keys)
		1016
		1017	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1018	them as array reference to the callback.
		1019
		1020	=item db_values $family => $cb->(\@values)
		1021
		1022	Same as C<db_family>, except it only queries the family I<values> and passes them
		1023	as array reference to the callback.
		1024
		1025	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1026
		1027	Creates a monitor on the given database family. Each time a key is set
		1028	or or is deleted the callback is called with a hash containing the
		1029	database family and three lists of added, changed and deleted subkeys,
		1030	respectively. If no keys have changed then the array reference might be
		1031	C<undef> or even missing.
		1032
		1033	If not called in void context, a guard object is returned that, when
		1034	destroyed, stops the monitor.
		1035
		1036	The family hash reference and the key arrays belong to AnyEvent::MP and
		1037	B<must not be modified or stored> by the callback. When in doubt, make a
		1038	copy.
		1039
		1040	As soon as possible after the monitoring starts, the callback will be
		1041	called with the intiial contents of the family, even if it is empty,
		1042	i.e. there will always be a timely call to the callback with the current
		1043	contents.
		1044
		1045	It is possible that the callback is called with a change event even though
		1046	the subkey is already present and the value has not changed.
		1047
		1048	The monitoring stops when the guard object is destroyed.
		1049
		1050	Example: on every change to the family "mygroup", print out all keys.
		1051
		1052	my $guard = db_mon mygroup => sub {
		1053	my ($family, $a, $c, $d) = @_;
		1054	print "mygroup members: ", (join " ", keys %$family), "\n";
		1055	};
		1056
		1057	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1058
		1059	my $guard; $guard = db_mon My::Module::workers => sub {
		1060	my ($family, $a, $c, $d) = @_;
		1061	return unless %$family;
		1062	undef $guard;
		1063	print "My::Module::workers now nonempty\n";
		1064	};
		1065
		1066	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1067
		1068	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1069	my ($family, $a, $c, $d) = @_;
		1070
		1071	print "+$_=$family->{$_}\n" for @$a;
		1072	print "*$_=$family->{$_}\n" for @$c;
		1073	print "-$_=$family->{$_}\n" for @$d;
		1074	};
		1075
		1076	=cut
		1077
662	=back	1078	=back
663		1079
664	=head1 AnyEvent::MP vs. Distributed Erlang	1080	=head1 AnyEvent::MP vs. Distributed Erlang
665		1081
666	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1082	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
667	== aemp node, Erlang process == aemp port), so many of the documents and	1083	== aemp node, Erlang process == aemp port), so many of the documents and
668	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1084	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
669	sample:	1085	sample:
670		1086
671	http://www.Erlang.se/doc/programming_rules.shtml	1087	http://www.erlang.se/doc/programming_rules.shtml
672	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1088	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
673	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1089	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
674	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1090	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
675		1091
676	Despite the similarities, there are also some important differences:	1092	Despite the similarities, there are also some important differences:
677		1093
678	=over 4	1094	=over 4
679		1095
680	=item * Node IDs are arbitrary strings in AEMP.	1096	=item * Node IDs are arbitrary strings in AEMP.
681		1097
682	Erlang relies on special naming and DNS to work everywhere in the same	1098	Erlang relies on special naming and DNS to work everywhere in the same
683	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1099	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
684	configuraiton or DNS), but will otherwise discover other odes itself.	1100	configuration or DNS), and possibly the addresses of some seed nodes, but
		1101	will otherwise discover other nodes (and their IDs) itself.
685		1102
686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1103	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
687	uses "local ports are like remote ports".	1104	uses "local ports are like remote ports".
688		1105
689	The failure modes for local ports are quite different (runtime errors	1106	The failure modes for local ports are quite different (runtime errors
…		…
698	ports being the special case/exception, where transport errors cannot	1115	ports being the special case/exception, where transport errors cannot
699	occur.	1116	occur.
700		1117
701	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1118	=item * Erlang uses processes and a mailbox, AEMP does not queue.
702		1119
703	Erlang uses processes that selectively receive messages, and therefore	1120	Erlang uses processes that selectively receive messages out of order, and
704	needs a queue. AEMP is event based, queuing messages would serve no	1121	therefore needs a queue. AEMP is event based, queuing messages would serve
705	useful purpose. For the same reason the pattern-matching abilities of	1122	no useful purpose. For the same reason the pattern-matching abilities
706	AnyEvent::MP are more limited, as there is little need to be able to	1123	of AnyEvent::MP are more limited, as there is little need to be able to
707	filter messages without dequeing them.	1124	filter messages without dequeuing them.
708		1125
709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1126	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1127	being event-based, while Erlang is process-based.
		1128
		1129	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1130	top of AEMP and Coro threads.
710		1131
711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1132	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
712		1133
713	Sending messages in Erlang is synchronous and blocks the process (and	1134	Sending messages in Erlang is synchronous and blocks the process until
		1135	a conenction has been established and the message sent (and so does not
714	so does not need a queue that can overflow). AEMP sends are immediate,	1136	need a queue that can overflow). AEMP sends return immediately, connection
715	connection establishment is handled in the background.	1137	establishment is handled in the background.
716		1138
717	=item * Erlang suffers from silent message loss, AEMP does not.	1139	=item * Erlang suffers from silent message loss, AEMP does not.
718		1140
719	Erlang makes few guarantees on messages delivery - messages can get lost	1141	Erlang implements few guarantees on messages delivery - messages can get
720	without any of the processes realising it (i.e. you send messages a, b,	1142	lost without any of the processes realising it (i.e. you send messages a,
721	and c, and the other side only receives messages a and c).	1143	b, and c, and the other side only receives messages a and c).
722		1144
723	AEMP guarantees correct ordering, and the guarantee that after one message	1145	AEMP guarantees (modulo hardware errors) correct ordering, and the
724	is lost, all following ones sent to the same port are lost as well, until	1146	guarantee that after one message is lost, all following ones sent to the
725	monitoring raises an error, so there are no silent "holes" in the message	1147	same port are lost as well, until monitoring raises an error, so there are
726	sequence.	1148	no silent "holes" in the message sequence.
		1149
		1150	If you want your software to be very reliable, you have to cope with
		1151	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1152	simply tries to work better in common error cases, such as when a network
		1153	link goes down.
727		1154
728	=item * Erlang can send messages to the wrong port, AEMP does not.	1155	=item * Erlang can send messages to the wrong port, AEMP does not.
729		1156
730	In Erlang it is quite likely that a node that restarts reuses a process ID	1157	In Erlang it is quite likely that a node that restarts reuses an Erlang
731	known to other nodes for a completely different process, causing messages	1158	process ID known to other nodes for a completely different process,
732	destined for that process to end up in an unrelated process.	1159	causing messages destined for that process to end up in an unrelated
		1160	process.
733		1161
734	AEMP never reuses port IDs, so old messages or old port IDs floating	1162	AEMP does not reuse port IDs, so old messages or old port IDs floating
735	around in the network will not be sent to an unrelated port.	1163	around in the network will not be sent to an unrelated port.
736		1164
737	=item * Erlang uses unprotected connections, AEMP uses secure	1165	=item * Erlang uses unprotected connections, AEMP uses secure
738	authentication and can use TLS.	1166	authentication and can use TLS.
739		1167
…		…
742		1170
743	=item * The AEMP protocol is optimised for both text-based and binary	1171	=item * The AEMP protocol is optimised for both text-based and binary
744	communications.	1172	communications.
745		1173
746	The AEMP protocol, unlike the Erlang protocol, supports both programming	1174	The AEMP protocol, unlike the Erlang protocol, supports both programming
747	language independent text-only protocols (good for debugging) and binary,	1175	language independent text-only protocols (good for debugging), and binary,
748	language-specific serialisers (e.g. Storable). By default, unless TLS is	1176	language-specific serialisers (e.g. Storable). By default, unless TLS is
749	used, the protocol is actually completely text-based.	1177	used, the protocol is actually completely text-based.
750		1178
751	It has also been carefully designed to be implementable in other languages	1179	It has also been carefully designed to be implementable in other languages
752	with a minimum of work while gracefully degrading functionality to make the	1180	with a minimum of work while gracefully degrading functionality to make the
753	protocol simple.	1181	protocol simple.
754		1182
755	=item * AEMP has more flexible monitoring options than Erlang.	1183	=item * AEMP has more flexible monitoring options than Erlang.
756		1184
757	In Erlang, you can chose to receive I<all> exit signals as messages	1185	In Erlang, you can chose to receive I<all> exit signals as messages or
758	or I<none>, there is no in-between, so monitoring single processes is	1186	I<none>, there is no in-between, so monitoring single Erlang processes is
759	difficult to implement. Monitoring in AEMP is more flexible than in	1187	difficult to implement.
760	Erlang, as one can choose between automatic kill, exit message or callback	1188
761	on a per-process basis.	1189	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1190	between automatic kill, exit message or callback on a per-port basis.
762		1191
763	=item * Erlang tries to hide remote/local connections, AEMP does not.	1192	=item * Erlang tries to hide remote/local connections, AEMP does not.
764		1193
765	Monitoring in Erlang is not an indicator of process death/crashes, in the	1194	Monitoring in Erlang is not an indicator of process death/crashes, in the
766	same way as linking is (except linking is unreliable in Erlang).	1195	same way as linking is (except linking is unreliable in Erlang).
…		…
788	overhead, as well as having to keep a proxy object everywhere.	1217	overhead, as well as having to keep a proxy object everywhere.
789		1218
790	Strings can easily be printed, easily serialised etc. and need no special	1219	Strings can easily be printed, easily serialised etc. and need no special
791	procedures to be "valid".	1220	procedures to be "valid".
792		1221
793	And as a result, a miniport consists of a single closure stored in a	1222	And as a result, a port with just a default receiver consists of a single
794	global hash - it can't become much cheaper.	1223	code reference stored in a global hash - it can't become much cheaper.
795		1224
796	=item Why favour JSON, why not a real serialising format such as Storable?	1225	=item Why favour JSON, why not a real serialising format such as Storable?
797		1226
798	In fact, any AnyEvent::MP node will happily accept Storable as framing	1227	In fact, any AnyEvent::MP node will happily accept Storable as framing
799	format, but currently there is no way to make a node use Storable by	1228	format, but currently there is no way to make a node use Storable by
…		…
809	Keeping your messages simple, concentrating on data structures rather than	1238	Keeping your messages simple, concentrating on data structures rather than
810	objects, will keep your messages clean, tidy and efficient.	1239	objects, will keep your messages clean, tidy and efficient.
811		1240
812	=back	1241	=back
813		1242
		1243	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1244
		1245	AEMP version 2 has a few major incompatible changes compared to version 1:
		1246
		1247	=over 4
		1248
		1249	=item AnyEvent::MP::Global no longer has group management functions.
		1250
		1251	At least not officially - the grp_* functions are still exported and might
		1252	work, but they will be removed in some later release.
		1253
		1254	AnyEvent::MP now comes with a distributed database that is more
		1255	powerful. Its database families map closely to port groups, but the API
		1256	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1257	a rough porting guide:
		1258
		1259	grp_reg $group, $port # old
		1260	db_reg $group, $port # new
		1261
		1262	$list = grp_get $group # old
		1263	db_keys $group, sub { my $list = shift } # new
		1264
		1265	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1266	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1267
		1268	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1269	no longer instant, because the local node might not have a copy of the
		1270	group. You can either modify your code to allow for a callback, or use
		1271	C<db_mon> to keep an updated copy of the group:
		1272
		1273	my $local_group_copy;
		1274	db_mon $group => sub { $local_group_copy = $_[0] };
		1275
		1276	# now "keys %$local_group_copy" always returns the most up-to-date
		1277	# list of ports in the group.
		1278
		1279	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1280	passes a hash as first argument, and an extra C<$chg> argument that can be
		1281	ignored:
		1282
		1283	db_mon $group => sub {
		1284	my ($ports, $add, $chg, $lde) = @_;
		1285	$ports = [keys %$ports];
		1286
		1287	# now $ports, $add and $del are the same as
		1288	# were originally passed by grp_mon.
		1289	...
		1290	};
		1291
		1292	=item Nodes not longer connect to all other nodes.
		1293
		1294	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1295	module, which in turn would create connections to all other nodes in the
		1296	network (helped by the seed nodes).
		1297
		1298	In version 2.x, global nodes still connect to all other global nodes, but
		1299	other nodes don't - now every node either is a global node itself, or
		1300	attaches itself to another global node.
		1301
		1302	If a node isn't a global node itself, then it attaches itself to one
		1303	of its seed nodes. If that seed node isn't a global node yet, it will
		1304	automatically be upgraded to a global node.
		1305
		1306	So in many cases, nothing needs to be changed - one just has to make sure
		1307	that all seed nodes are meshed together with the other seed nodes (as with
		1308	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1309	achieved by specifying the same set of seed nodes for all nodes in the
		1310	network.
		1311
		1312	Not opening a connection to every other node is usually an advantage,
		1313	except when you need the lower latency of an already established
		1314	connection. To ensure a node establishes a connection to another node,
		1315	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1316	create the connection (and notify you when the connection fails).
		1317
		1318	=item Listener-less nodes (nodes without binds) are gone.
		1319
		1320	And are not coming back, at least not in their old form. If no C<binds>
		1321	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1322
		1323	There are vague plans to implement some form of routing domains, which
		1324	might or might not bring back listener-less nodes, but don't count on it.
		1325
		1326	The fact that most connections are now optional somewhat mitigates this,
		1327	as a node can be effectively unreachable from the outside without any
		1328	problems, as long as it isn't a global node and only reaches out to other
		1329	nodes (as opposed to being contacted from other nodes).
		1330
		1331	=item $AnyEvent::MP::Kernel::WARN has gone.
		1332
		1333	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1334	uses this, and so should your programs.
		1335
		1336	Every module now documents what kinds of messages it generates, with
		1337	AnyEvent::MP acting as a catch all.
		1338
		1339	On the positive side, this means that instead of setting
		1340	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1341	much less to type.
		1342
		1343	=back
		1344
		1345	=head1 LOGGING
		1346
		1347	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1348	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1349	all log messages by submodules.
		1350
814	=head1 SEE ALSO	1351	=head1 SEE ALSO
815		1352
816	L<AnyEvent::MP::Intro> - a gentle introduction.	1353	L<AnyEvent::MP::Intro> - a gentle introduction.
817		1354
818	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1355	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
819		1356
820	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1357	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
821	your applications.	1358	your applications.
		1359
		1360	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1361
		1362	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1363	all nodes.
822		1364
823	L<AnyEvent>.	1365	L<AnyEvent>.
824		1366
825	=head1 AUTHOR	1367	=head1 AUTHOR
826		1368

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Revision 1.142 by root, Fri Mar 23 13:44:01 2012 UTC