[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 1.141 by root, Fri Mar 23 03:24:41 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	=item secure => $pass->(@msg)
		245
		246	In addition to specifying a boolean, you can specify a code reference that
		247	is called for every code execution attempt - the execution request is
		248	granted iff the callback returns a true value.
		249
		250	Most of the time the callback should look only at
		251	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		252	actual message (which can be about anything, and is mostly provided for
		253	diagnostic purposes).
		254
		255	See F<semp setsecure> for more info.
		256
		257	=back
		258
		259	=over 4
		260
		261	=item step 1, gathering configuration from profiles
		262
180	The function then looks up the profile in the aemp configuration (see the	263	The function first looks up a profile in the aemp configuration (see the
181	L<aemp> commandline utility).	264	L<aemp> commandline utility). The profile name can be specified via the
		265	named C<profile> parameter or can simply be the first parameter). If it is
		266	missing, then the nodename (F<uname -n>) will be used as profile name.
		267
		268	The profile data is then gathered as follows:
		269
		270	First, all remaining key => value pairs (all of which are conveniently
		271	undocumented at the moment) will be interpreted as configuration
		272	data. Then they will be overwritten by any values specified in the global
		273	default configuration (see the F<aemp> utility), then the chain of
		274	profiles chosen by the profile name (and any C<parent> attributes).
		275
		276	That means that the values specified in the profile have highest priority
		277	and the values specified directly via C<configure> have lowest priority,
		278	and can only be used to specify defaults.
182		279
183	If the profile specifies a node ID, then this will become the node ID of	280	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	281	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.	282	a unique randoms tring (C</%u>) appended.
		283
		284	The node ID can contain some C<%> sequences that are expanded: C<%n>
		285	is expanded to the local nodename, C<%u> is replaced by a random
		286	strign to make the node unique. For example, the F<aemp> commandline
		287	utility uses C<aemp/%n/%u> as nodename, which might expand to
		288	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		289
		290	=item step 2, bind listener sockets
186		291
187	The next step is to look up the binds in the profile, followed by binding	292	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	293	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	294	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	295	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).	296	binds, but it can still talk to all "normal" nodes).
192		297
193	If the profile does not specify a binds list, then the node ID will be	298	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	299	used, meaning the node will bind on a dynamically-assigned port on every
195	used as binds list.	300	local IP address it finds.
196		301
		302	=item step 3, connect to seed nodes
		303
197	Lastly, the seeds list from the profile is passed to the	304	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	305	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.	306	connectivity with at least one node at any point in time.
200		307
201	Example: become a distributed node listening on the guessed noderef, or	308	=back
202	the one specified via C<aemp> for the current node. This should be the	309
		310	Example: become a distributed node using the local node name as profile.
203	most common form of invocation for "daemon"-type nodes.	311	This should be the most common form of invocation for "daemon"-type nodes.
204		312
205	initialise_node;	313	configure
206		314
207	Example: become an anonymous node. This form is often used for commandline	315	Example: become a semi-anonymous node. This form is often used for
208	clients.	316	commandline clients.
209		317
210	initialise_node "anon/";	318	configure nodeid => "myscript/%n/%u";
211		319
212	Example: become a distributed node. If there is no profile of the given	320	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	321	for a seed node as it binds on all local addresses on a fixed port (4040,
214	on the resulting addresses.	322	customary for aemp).
215		323
216	initialise_node "localhost:4044";	324	# use the aemp commandline utility
		325	# aemp profile seed binds '*:4040'
		326
		327	# then use it
		328	configure profile => "seed";
		329
		330	# or simply use aemp from the shell again:
		331	# aemp run profile seed
		332
		333	# or provide a nicer-to-remember nodeid
		334	# aemp run profile seed nodeid "$(hostname)"
217		335
218	=item $SELF	336	=item $SELF
219		337
220	Contains the current port id while executing C<rcv> callbacks or C<psub>	338	Contains the current port id while executing C<rcv> callbacks or C<psub>
221	blocks.	339	blocks.
…		…
277		395
278	=cut	396	=cut
279		397
280	sub rcv($@);	398	sub rcv($@);
281		399
282	sub _kilme {	400	my $KILME = sub {
283	die "received message on port without callback";	401	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
284	}	402	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		403	};
285		404
286	sub port(;&) {	405	sub port(;&) {
287	my $id = "$UNIQ." . $ID++;	406	my $id = $UNIQ . ++$ID;
288	my $port = "$NODE#$id";	407	my $port = "$NODE#$id";
289		408
290	rcv $port, shift \|\| \&_kilme;	409	rcv $port, shift \|\| $KILME;
291		410
292	$port	411	$port
293	}	412	}
294		413
295	=item rcv $local_port, $callback->(@msg)	414	=item rcv $local_port, $callback->(@msg)
…		…
300		419
301	The global C<$SELF> (exported by this module) contains C<$port> while	420	The global C<$SELF> (exported by this module) contains C<$port> while
302	executing the callback. Runtime errors during callback execution will	421	executing the callback. Runtime errors during callback execution will
303	result in the port being C<kil>ed.	422	result in the port being C<kil>ed.
304		423
305	The default callback received all messages not matched by a more specific	424	The default callback receives all messages not matched by a more specific
306	C<tag> match.	425	C<tag> match.
307		426
308	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	427	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
309		428
310	Register (or replace) callbacks to be called on messages starting with the	429	Register (or replace) callbacks to be called on messages starting with the
…		…
331	msg1 => sub { ... },	450	msg1 => sub { ... },
332	...	451	...
333	;	452	;
334		453
335	Example: temporarily register a rcv callback for a tag matching some port	454	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.	455	(e.g. for an rpc reply) and unregister it after a message was received.
337		456
338	rcv $port, $otherport => sub {	457	rcv $port, $otherport => sub {
339	my @reply = @_;	458	my @reply = @_;
340		459
341	rcv $SELF, $otherport;	460	rcv $SELF, $otherport;
…		…
343		462
344	=cut	463	=cut
345		464
346	sub rcv($@) {	465	sub rcv($@) {
347	my $port = shift;	466	my $port = shift;
348	my ($noderef, $portid) = split /#/, $port, 2;	467	my ($nodeid, $portid) = split /#/, $port, 2;
349		468
350	$NODE{$noderef} == $NODE{""}	469	$NODE{$nodeid} == $NODE{""}
351	or Carp::croak "$port: rcv can only be called on local ports, caught";	470	or Carp::croak "$port: rcv can only be called on local ports, caught";
352		471
353	while (@_) {	472	while (@_) {
354	if (ref $_[0]) {	473	if (ref $_[0]) {
355	if (my $self = $PORT_DATA{$portid}) {	474	if (my $self = $PORT_DATA{$portid}) {
356	"AnyEvent::MP::Port" eq ref $self	475	"AnyEvent::MP::Port" eq ref $self
357	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	476	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
358		477
359	$self->[2] = shift;	478	$self->[0] = shift;
360	} else {	479	} else {
361	my $cb = shift;	480	my $cb = shift;
362	$PORT{$portid} = sub {	481	$PORT{$portid} = sub {
363	local $SELF = $port;	482	local $SELF = $port;
364	eval { &$cb }; _self_die if $@;	483	eval { &$cb }; _self_die if $@;
365	};	484	};
366	}	485	}
367	} elsif (defined $_[0]) {	486	} elsif (defined $_[0]) {
368	my $self = $PORT_DATA{$portid} \|\|= do {	487	my $self = $PORT_DATA{$portid} \|\|= do {
369	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	488	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
370		489
371	$PORT{$portid} = sub {	490	$PORT{$portid} = sub {
372	local $SELF = $port;	491	local $SELF = $port;
373		492
374	if (my $cb = $self->[1]{$_[0]}) {	493	if (my $cb = $self->[1]{$_[0]}) {
…		…
396	}	515	}
397		516
398	$port	517	$port
399	}	518	}
400		519
		520	=item peval $port, $coderef[, @args]
		521
		522	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		523	when the code throews an exception the C<$port> will be killed.
		524
		525	Any remaining args will be passed to the callback. Any return values will
		526	be returned to the caller.
		527
		528	This is useful when you temporarily want to execute code in the context of
		529	a port.
		530
		531	Example: create a port and run some initialisation code in it's context.
		532
		533	my $port = port { ... };
		534
		535	peval $port, sub {
		536	init
		537	or die "unable to init";
		538	};
		539
		540	=cut
		541
		542	sub peval($$) {
		543	local $SELF = shift;
		544	my $cb = shift;
		545
		546	if (wantarray) {
		547	my @res = eval { &$cb };
		548	_self_die if $@;
		549	@res
		550	} else {
		551	my $res = eval { &$cb };
		552	_self_die if $@;
		553	$res
		554	}
		555	}
		556
401	=item $closure = psub { BLOCK }	557	=item $closure = psub { BLOCK }
402		558
403	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	559	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>	560	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.	561	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		562
		563	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		564	BLOCK }, @_ } >>.
406		565
407	This is useful when you register callbacks from C<rcv> callbacks:	566	This is useful when you register callbacks from C<rcv> callbacks:
408		567
409	rcv delayed_reply => sub {	568	rcv delayed_reply => sub {
410	my ($delay, @reply) = @_;	569	my ($delay, @reply) = @_;
…		…
434	$res	593	$res
435	}	594	}
436	}	595	}
437	}	596	}
438		597
		598	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		599
		600	=item $guard = mon $port # kill $SELF when $port dies
		601
439	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	602	=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		603
445	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	604	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
446		605
447	Monitor the given port and do something when the port is killed or	606	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	607	messages to it were lost, and optionally return a guard that can be used
449	to stop monitoring again.	608	to stop monitoring again.
		609
		610	The first two forms distinguish between "normal" and "abnormal" kil's:
		611
		612	In the first form (another port given), if the C<$port> is C<kil>'ed with
		613	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		614	same reason. That is, on "normal" kil's nothing happens, while under all
		615	other conditions, the other port is killed with the same reason.
		616
		617	The second form (kill self) is the same as the first form, except that
		618	C<$rvport> defaults to C<$SELF>.
		619
		620	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		621	- it's up to the callback or receiver to check whether the C<@reason> is
		622	empty and act accordingly.
		623
		624	In the third form (callback), the callback is simply called with any
		625	number of C<@reason> elements (empty @reason means that the port was deleted
		626	"normally"). Note also that I<< the callback B<must> never die >>, so use
		627	C<eval> if unsure.
		628
		629	In the last form (message), a message of the form C<$rcvport, @msg,
		630	@reason> will be C<snd>.
		631
		632	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		633	alert was raised), they are removed and will not trigger again, even if it
		634	turns out that the port is still alive.
		635
		636	As a rule of thumb, monitoring requests should always monitor a remote
		637	port locally (using a local C<$rcvport> or a callback). The reason is that
		638	kill messages might get lost, just like any other message. Another less
		639	obvious reason is that even monitoring requests can get lost (for example,
		640	when the connection to the other node goes down permanently). When
		641	monitoring a port locally these problems do not exist.
450		642
451	C<mon> effectively guarantees that, in the absence of hardware failures,	643	C<mon> effectively guarantees that, in the absence of hardware failures,
452	after starting the monitor, either all messages sent to the port will	644	after starting the monitor, either all messages sent to the port will
453	arrive, or the monitoring action will be invoked after possible message	645	arrive, or the monitoring action will be invoked after possible message
454	loss has been detected. No messages will be lost "in between" (after	646	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	647	the first lost message no further messages will be received by the
456	port). After the monitoring action was invoked, further messages might get	648	port). After the monitoring action was invoked, further messages might get
457	delivered again.	649	delivered again.
458		650
459	Note that monitoring-actions are one-shot: once messages are lost (and a	651	Inter-host-connection timeouts and monitoring depend on the transport
460	monitoring alert was raised), they are removed and will not trigger again.	652	used. The only transport currently implemented is TCP, and AnyEvent::MP
		653	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		654	non-idle connection, and usually around two hours for idle connections).
461		655
462	In the first form (callback), the callback is simply called with any	656	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	657	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	658	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		659
485	Example: call a given callback when C<$port> is killed.	660	Example: call a given callback when C<$port> is killed.
486		661
487	mon $port, sub { warn "port died because of <@_>\n" };	662	mon $port, sub { warn "port died because of <@_>\n" };
488		663
…		…
495	mon $port, $self => "restart";	670	mon $port, $self => "restart";
496		671
497	=cut	672	=cut
498		673
499	sub mon {	674	sub mon {
500	my ($noderef, $port) = split /#/, shift, 2;	675	my ($nodeid, $port) = split /#/, shift, 2;
501		676
502	my $node = $NODE{$noderef} \|\| add_node $noderef;	677	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
503		678
504	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	679	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
505		680
506	unless (ref $cb) {	681	unless (ref $cb) {
507	if (@_) {	682	if (@_) {
…		…
516	}	691	}
517		692
518	$node->monitor ($port, $cb);	693	$node->monitor ($port, $cb);
519		694
520	defined wantarray	695	defined wantarray
521	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	696	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
522	}	697	}
523		698
524	=item $guard = mon_guard $port, $ref, $ref...	699	=item $guard = mon_guard $port, $ref, $ref...
525		700
526	Monitors the given C<$port> and keeps the passed references. When the port	701	Monitors the given C<$port> and keeps the passed references. When the port
…		…
549		724
550	=item kil $port[, @reason]	725	=item kil $port[, @reason]
551		726
552	Kill the specified port with the given C<@reason>.	727	Kill the specified port with the given C<@reason>.
553		728
554	If no C<@reason> is specified, then the port is killed "normally" (ports	729	If no C<@reason> is specified, then the port is killed "normally" -
555	monitoring other ports will not necessarily die because a port dies	730	monitor callback will be invoked, but the kil will not cause linked ports
556	"normally").	731	(C<mon $mport, $lport> form) to get killed.
557		732
558	Otherwise, linked ports get killed with the same reason (second form of	733	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
559	C<mon>, see above).	734	form) get killed with the same reason.
560		735
561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	736	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
562	will be reported as reason C<< die => $@ >>.	737	will be reported as reason C<< die => $@ >>.
563		738
564	Transport/communication errors are reported as C<< transport_error =>	739	Transport/communication errors are reported as C<< transport_error =>
565	$message >>.	740	$message >>.
566		741
567	=cut	742	Common idioms:
		743
		744	# silently remove yourself, do not kill linked ports
		745	kil $SELF;
		746
		747	# report a failure in some detail
		748	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		749
		750	# do not waste much time with killing, just die when something goes wrong
		751	open my $fh, "<file"
		752	or die "file: $!";
568		753
569	=item $port = spawn $node, $initfunc[, @initdata]	754	=item $port = spawn $node, $initfunc[, @initdata]
570		755
571	Creates a port on the node C<$node> (which can also be a port ID, in which	756	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).	757	case it's the node where that port resides).
…		…
583	the package, then the package above the package and so on (e.g.	768	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	769	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
585	exists or it runs out of package names.	770	exists or it runs out of package names.
586		771
587	The init function is then called with the newly-created port as context	772	The init function is then called with the newly-created port as context
588	object (C<$SELF>) and the C<@initdata> values as arguments.	773	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		774	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		775	the port might not get created.
589		776
590	A common idiom is to pass a local port, immediately monitor the spawned	777	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	778	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	779	local port. This two-way monitoring ensures that both ports get cleaned up
593	when there is a problem.	780	when there is a problem.
594		781
		782	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		783	caller before C<spawn> returns (by delaying invocation when spawn is
		784	called for the local node).
		785
595	Example: spawn a chat server port on C<$othernode>.	786	Example: spawn a chat server port on C<$othernode>.
596		787
597	# this node, executed from within a port context:	788	# this node, executed from within a port context:
598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	789	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
599	mon $server;	790	mon $server;
…		…
613		804
614	sub _spawn {	805	sub _spawn {
615	my $port = shift;	806	my $port = shift;
616	my $init = shift;	807	my $init = shift;
617		808
		809	# rcv will create the actual port
618	local $SELF = "$NODE#$port";	810	local $SELF = "$NODE#$port";
619	eval {	811	eval {
620	&{ load_func $init }	812	&{ load_func $init }
621	};	813	};
622	_self_die if $@;	814	_self_die if $@;
623	}	815	}
624		816
625	sub spawn(@) {	817	sub spawn(@) {
626	my ($noderef, undef) = split /#/, shift, 2;	818	my ($nodeid, undef) = split /#/, shift, 2;
627		819
628	my $id = "$RUNIQ." . $ID++;	820	my $id = $RUNIQ . ++$ID;
629		821
630	$_[0] =~ /::/	822	$_[0] =~ /::/
631	or Carp::croak "spawn init function must be a fully-qualified name, caught";	823	or Carp::croak "spawn init function must be a fully-qualified name, caught";
632		824
633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	825	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
634		826
635	"$noderef#$id"	827	"$nodeid#$id"
636	}	828	}
		829
637		830
638	=item after $timeout, @msg	831	=item after $timeout, @msg
639		832
640	=item after $timeout, $callback	833	=item after $timeout, $callback
641		834
…		…
657	? $action[0]()	850	? $action[0]()
658	: snd @action;	851	: snd @action;
659	};	852	};
660	}	853	}
661		854
		855	#=item $cb2 = timeout $seconds, $cb[, @args]
		856
		857	=item cal $port, @msg, $callback[, $timeout]
		858
		859	A simple form of RPC - sends a message to the given C<$port> with the
		860	given contents (C<@msg>), but adds a reply port to the message.
		861
		862	The reply port is created temporarily just for the purpose of receiving
		863	the reply, and will be C<kil>ed when no longer needed.
		864
		865	A reply message sent to the port is passed to the C<$callback> as-is.
		866
		867	If an optional time-out (in seconds) is given and it is not C<undef>,
		868	then the callback will be called without any arguments after the time-out
		869	elapsed and the port is C<kil>ed.
		870
		871	If no time-out is given (or it is C<undef>), then the local port will
		872	monitor the remote port instead, so it eventually gets cleaned-up.
		873
		874	Currently this function returns the temporary port, but this "feature"
		875	might go in future versions unless you can make a convincing case that
		876	this is indeed useful for something.
		877
		878	=cut
		879
		880	sub cal(@) {
		881	my $timeout = ref $_[-1] ? undef : pop;
		882	my $cb = pop;
		883
		884	my $port = port {
		885	undef $timeout;
		886	kil $SELF;
		887	&$cb;
		888	};
		889
		890	if (defined $timeout) {
		891	$timeout = AE::timer $timeout, 0, sub {
		892	undef $timeout;
		893	kil $port;
		894	$cb->();
		895	};
		896	} else {
		897	mon $_[0], sub {
		898	kil $port;
		899	$cb->();
		900	};
		901	}
		902
		903	push @_, $port;
		904	&snd;
		905
		906	$port
		907	}
		908
		909	=back
		910
		911	=head1 DISTRIBUTED DATABASE
		912
		913	AnyEvent::MP comes with a simple distributed database. The database will
		914	be mirrored asynchronously on all global nodes. Other nodes bind to one
		915	of the global nodes for their needs. Every node has a "local database"
		916	which contains all the values that are set locally. All local databases
		917	are merged together to form the global database, which can be queried.
		918
		919	The database structure is that of a two-level hash - the database hash
		920	contains hashes which contain values, similarly to a perl hash of hashes,
		921	i.e.:
		922
		923	$DATABASE{$family}{$subkey} = $value
		924
		925	The top level hash key is called "family", and the second-level hash key
		926	is called "subkey" or simply "key".
		927
		928	The family must be alphanumeric, i.e. start with a letter and consist
		929	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		930	pretty much like Perl module names.
		931
		932	As the family namespace is global, it is recommended to prefix family names
		933	with the name of the application or module using it.
		934
		935	The subkeys must be non-empty strings, with no further restrictions.
		936
		937	The values should preferably be strings, but other perl scalars should
		938	work as well (such as C<undef>, arrays and hashes).
		939
		940	Every database entry is owned by one node - adding the same family/subkey
		941	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		942	but the result might be nondeterministic, i.e. the key might have
		943	different values on different nodes.
		944
		945	Different subkeys in the same family can be owned by different nodes
		946	without problems, and in fact, this is the common method to create worker
		947	pools. For example, a worker port for image scaling might do this:
		948
		949	db_set my_image_scalers => $port;
		950
		951	And clients looking for an image scaler will want to get the
		952	C<my_image_scalers> keys from time to time:
		953
		954	db_keys my_image_scalers => sub {
		955	@ports = @{ $_[0] };
		956	};
		957
		958	Or better yet, they want to monitor the database family, so they always
		959	have a reasonable up-to-date copy:
		960
		961	db_mon my_image_scalers => sub {
		962	@ports = keys %{ $_[0] };
		963	};
		964
		965	In general, you can set or delete single subkeys, but query and monitor
		966	whole families only.
		967
		968	If you feel the need to monitor or query a single subkey, try giving it
		969	it's own family.
		970
		971	=over
		972
		973	=item $guard = db_set $family => $subkey [=> $value]
		974
		975	Sets (or replaces) a key to the database - if C<$value> is omitted,
		976	C<undef> is used instead.
		977
		978	When called in non-void context, C<db_set> returns a guard that
		979	automatically calls C<db_del> when it is destroyed.
		980
		981	=item db_del $family => $subkey...
		982
		983	Deletes one or more subkeys from the database family.
		984
		985	=item $guard = db_reg $family => $port => $value
		986
		987	=item $guard = db_reg $family => $port
		988
		989	=item $guard = db_reg $family
		990
		991	Registers a port in the given family and optionally returns a guard to
		992	remove it.
		993
		994	This function basically does the same as:
		995
		996	db_set $family => $port => $value
		997
		998	Except that the port is monitored and automatically removed from the
		999	database family when it is kil'ed.
		1000
		1001	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1002	C<$SELF> is used.
		1003
		1004	This function is most useful to register a port in some port group (which
		1005	is just another name for a database family), and have it removed when the
		1006	port is gone. This works best when the port is a local port.
		1007
		1008	=cut
		1009
		1010	sub db_reg($$;$) {
		1011	my $family = shift;
		1012	my $port = @_ ? shift : $SELF;
		1013
		1014	my $clr = sub { db_del $family => $port };
		1015	mon $port, $clr;
		1016
		1017	db_set $family => $port => $_[0];
		1018
		1019	defined wantarray
		1020	and &Guard::guard ($clr)
		1021	}
		1022
		1023	=item db_family $family => $cb->(\%familyhash)
		1024
		1025	Queries the named database C<$family> and call the callback with the
		1026	family represented as a hash. You can keep and freely modify the hash.
		1027
		1028	=item db_keys $family => $cb->(\@keys)
		1029
		1030	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1031	them as array reference to the callback.
		1032
		1033	=item db_values $family => $cb->(\@values)
		1034
		1035	Same as C<db_family>, except it only queries the family I<values> and passes them
		1036	as array reference to the callback.
		1037
		1038	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1039
		1040	Creates a monitor on the given database family. Each time a key is set
		1041	or or is deleted the callback is called with a hash containing the
		1042	database family and three lists of added, changed and deleted subkeys,
		1043	respectively. If no keys have changed then the array reference might be
		1044	C<undef> or even missing.
		1045
		1046	If not called in void context, a guard object is returned that, when
		1047	destroyed, stops the monitor.
		1048
		1049	The family hash reference and the key arrays belong to AnyEvent::MP and
		1050	B<must not be modified or stored> by the callback. When in doubt, make a
		1051	copy.
		1052
		1053	As soon as possible after the monitoring starts, the callback will be
		1054	called with the intiial contents of the family, even if it is empty,
		1055	i.e. there will always be a timely call to the callback with the current
		1056	contents.
		1057
		1058	It is possible that the callback is called with a change event even though
		1059	the subkey is already present and the value has not changed.
		1060
		1061	The monitoring stops when the guard object is destroyed.
		1062
		1063	Example: on every change to the family "mygroup", print out all keys.
		1064
		1065	my $guard = db_mon mygroup => sub {
		1066	my ($family, $a, $c, $d) = @_;
		1067	print "mygroup members: ", (join " ", keys %$family), "\n";
		1068	};
		1069
		1070	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1071
		1072	my $guard; $guard = db_mon My::Module::workers => sub {
		1073	my ($family, $a, $c, $d) = @_;
		1074	return unless %$family;
		1075	undef $guard;
		1076	print "My::Module::workers now nonempty\n";
		1077	};
		1078
		1079	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1080
		1081	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1082	my ($family, $a, $c, $d) = @_;
		1083
		1084	print "+$_=$family->{$_}\n" for @$a;
		1085	print "*$_=$family->{$_}\n" for @$c;
		1086	print "-$_=$family->{$_}\n" for @$d;
		1087	};
		1088
		1089	=cut
		1090
662	=back	1091	=back
663		1092
664	=head1 AnyEvent::MP vs. Distributed Erlang	1093	=head1 AnyEvent::MP vs. Distributed Erlang
665		1094
666	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1095	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	1096	== 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	1097	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
669	sample:	1098	sample:
670		1099
671	http://www.Erlang.se/doc/programming_rules.shtml	1100	http://www.erlang.se/doc/programming_rules.shtml
672	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1101	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	1102	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	1103	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
675		1104
676	Despite the similarities, there are also some important differences:	1105	Despite the similarities, there are also some important differences:
677		1106
678	=over 4	1107	=over 4
679		1108
680	=item * Node IDs are arbitrary strings in AEMP.	1109	=item * Node IDs are arbitrary strings in AEMP.
681		1110
682	Erlang relies on special naming and DNS to work everywhere in the same	1111	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	1112	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.	1113	configuration or DNS), and possibly the addresses of some seed nodes, but
		1114	will otherwise discover other nodes (and their IDs) itself.
685		1115
686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1116	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
687	uses "local ports are like remote ports".	1117	uses "local ports are like remote ports".
688		1118
689	The failure modes for local ports are quite different (runtime errors	1119	The failure modes for local ports are quite different (runtime errors
…		…
698	ports being the special case/exception, where transport errors cannot	1128	ports being the special case/exception, where transport errors cannot
699	occur.	1129	occur.
700		1130
701	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1131	=item * Erlang uses processes and a mailbox, AEMP does not queue.
702		1132
703	Erlang uses processes that selectively receive messages, and therefore	1133	Erlang uses processes that selectively receive messages out of order, and
704	needs a queue. AEMP is event based, queuing messages would serve no	1134	therefore needs a queue. AEMP is event based, queuing messages would serve
705	useful purpose. For the same reason the pattern-matching abilities of	1135	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	1136	of AnyEvent::MP are more limited, as there is little need to be able to
707	filter messages without dequeing them.	1137	filter messages without dequeuing them.
708		1138
709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1139	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1140	being event-based, while Erlang is process-based.
		1141
		1142	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1143	top of AEMP and Coro threads.
710		1144
711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1145	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
712		1146
713	Sending messages in Erlang is synchronous and blocks the process (and	1147	Sending messages in Erlang is synchronous and blocks the process until
		1148	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,	1149	need a queue that can overflow). AEMP sends return immediately, connection
715	connection establishment is handled in the background.	1150	establishment is handled in the background.
716		1151
717	=item * Erlang suffers from silent message loss, AEMP does not.	1152	=item * Erlang suffers from silent message loss, AEMP does not.
718		1153
719	Erlang makes few guarantees on messages delivery - messages can get lost	1154	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,	1155	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).	1156	b, and c, and the other side only receives messages a and c).
722		1157
723	AEMP guarantees correct ordering, and the guarantee that after one message	1158	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	1159	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	1160	same port are lost as well, until monitoring raises an error, so there are
726	sequence.	1161	no silent "holes" in the message sequence.
		1162
		1163	If you want your software to be very reliable, you have to cope with
		1164	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1165	simply tries to work better in common error cases, such as when a network
		1166	link goes down.
727		1167
728	=item * Erlang can send messages to the wrong port, AEMP does not.	1168	=item * Erlang can send messages to the wrong port, AEMP does not.
729		1169
730	In Erlang it is quite likely that a node that restarts reuses a process ID	1170	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	1171	process ID known to other nodes for a completely different process,
732	destined for that process to end up in an unrelated process.	1172	causing messages destined for that process to end up in an unrelated
		1173	process.
733		1174
734	AEMP never reuses port IDs, so old messages or old port IDs floating	1175	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.	1176	around in the network will not be sent to an unrelated port.
736		1177
737	=item * Erlang uses unprotected connections, AEMP uses secure	1178	=item * Erlang uses unprotected connections, AEMP uses secure
738	authentication and can use TLS.	1179	authentication and can use TLS.
739		1180
…		…
742		1183
743	=item * The AEMP protocol is optimised for both text-based and binary	1184	=item * The AEMP protocol is optimised for both text-based and binary
744	communications.	1185	communications.
745		1186
746	The AEMP protocol, unlike the Erlang protocol, supports both programming	1187	The AEMP protocol, unlike the Erlang protocol, supports both programming
747	language independent text-only protocols (good for debugging) and binary,	1188	language independent text-only protocols (good for debugging), and binary,
748	language-specific serialisers (e.g. Storable). By default, unless TLS is	1189	language-specific serialisers (e.g. Storable). By default, unless TLS is
749	used, the protocol is actually completely text-based.	1190	used, the protocol is actually completely text-based.
750		1191
751	It has also been carefully designed to be implementable in other languages	1192	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	1193	with a minimum of work while gracefully degrading functionality to make the
753	protocol simple.	1194	protocol simple.
754		1195
755	=item * AEMP has more flexible monitoring options than Erlang.	1196	=item * AEMP has more flexible monitoring options than Erlang.
756		1197
757	In Erlang, you can chose to receive I<all> exit signals as messages	1198	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	1199	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	1200	difficult to implement.
760	Erlang, as one can choose between automatic kill, exit message or callback	1201
761	on a per-process basis.	1202	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1203	between automatic kill, exit message or callback on a per-port basis.
762		1204
763	=item * Erlang tries to hide remote/local connections, AEMP does not.	1205	=item * Erlang tries to hide remote/local connections, AEMP does not.
764		1206
765	Monitoring in Erlang is not an indicator of process death/crashes, in the	1207	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).	1208	same way as linking is (except linking is unreliable in Erlang).
…		…
788	overhead, as well as having to keep a proxy object everywhere.	1230	overhead, as well as having to keep a proxy object everywhere.
789		1231
790	Strings can easily be printed, easily serialised etc. and need no special	1232	Strings can easily be printed, easily serialised etc. and need no special
791	procedures to be "valid".	1233	procedures to be "valid".
792		1234
793	And as a result, a miniport consists of a single closure stored in a	1235	And as a result, a port with just a default receiver consists of a single
794	global hash - it can't become much cheaper.	1236	code reference stored in a global hash - it can't become much cheaper.
795		1237
796	=item Why favour JSON, why not a real serialising format such as Storable?	1238	=item Why favour JSON, why not a real serialising format such as Storable?
797		1239
798	In fact, any AnyEvent::MP node will happily accept Storable as framing	1240	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	1241	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	1251	Keeping your messages simple, concentrating on data structures rather than
810	objects, will keep your messages clean, tidy and efficient.	1252	objects, will keep your messages clean, tidy and efficient.
811		1253
812	=back	1254	=back
813		1255
		1256	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1257
		1258	AEMP version 2 has a few major incompatible changes compared to version 1:
		1259
		1260	=over 4
		1261
		1262	=item AnyEvent::MP::Global no longer has group management functions.
		1263
		1264	At least not officially - the grp_* functions are still exported and might
		1265	work, but they will be removed in some later release.
		1266
		1267	AnyEvent::MP now comes with a distributed database that is more
		1268	powerful. Its database families map closely to port groups, but the API
		1269	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1270	a rough porting guide:
		1271
		1272	grp_reg $group, $port # old
		1273	db_reg $group, $port # new
		1274
		1275	$list = grp_get $group # old
		1276	db_keys $group, sub { my $list = shift } # new
		1277
		1278	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1279	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1280
		1281	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1282	no longer instant, because the local node might not have a copy of the
		1283	group. You can either modify your code to allow for a callback, or use
		1284	C<db_mon> to keep an updated copy of the group:
		1285
		1286	my $local_group_copy;
		1287	db_mon $group => sub { $local_group_copy = $_[0] };
		1288
		1289	# now "keys %$local_group_copy" always returns the most up-to-date
		1290	# list of ports in the group.
		1291
		1292	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1293	passes a hash as first argument, and an extra C<$chg> argument that can be
		1294	ignored:
		1295
		1296	db_mon $group => sub {
		1297	my ($ports, $add, $chg, $lde) = @_;
		1298	$ports = [keys %$ports];
		1299
		1300	# now $ports, $add and $del are the same as
		1301	# were originally passed by grp_mon.
		1302	...
		1303	};
		1304
		1305	=item Nodes not longer connect to all other nodes.
		1306
		1307	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1308	module, which in turn would create connections to all other nodes in the
		1309	network (helped by the seed nodes).
		1310
		1311	In version 2.x, global nodes still connect to all other global nodes, but
		1312	other nodes don't - now every node either is a global node itself, or
		1313	attaches itself to another global node.
		1314
		1315	If a node isn't a global node itself, then it attaches itself to one
		1316	of its seed nodes. If that seed node isn't a global node yet, it will
		1317	automatically be upgraded to a global node.
		1318
		1319	So in many cases, nothing needs to be changed - one just has to make sure
		1320	that all seed nodes are meshed together with the other seed nodes (as with
		1321	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1322	achieved by specifying the same set of seed nodes for all nodes in the
		1323	network.
		1324
		1325	Not opening a connection to every other node is usually an advantage,
		1326	except when you need the lower latency of an already established
		1327	connection. To ensure a node establishes a connection to another node,
		1328	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1329	create the connection (and notify you when the connection fails).
		1330
		1331	=item Listener-less nodes (nodes without binds) are gone.
		1332
		1333	And are not coming back, at least not in their old form. If no C<binds>
		1334	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1335
		1336	There are vague plans to implement some form of routing domains, which
		1337	might or might not bring back listener-less nodes, but don't count on it.
		1338
		1339	The fact that most connections are now optional somewhat mitigates this,
		1340	as a node can be effectively unreachable from the outside without any
		1341	problems, as long as it isn't a global node and only reaches out to other
		1342	nodes (as opposed to being contacted from other nodes).
		1343
		1344	=item $AnyEvent::MP::Kernel::WARN has gone.
		1345
		1346	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1347	uses this, and so should your programs.
		1348
		1349	Every module now documents what kinds of messages it generates, with
		1350	AnyEvent::MP acting as a catch all.
		1351
		1352	On the positive side, this means that instead of setting
		1353	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1354	much less to type.
		1355
		1356	=back
		1357
		1358	=head1 LOGGING
		1359
		1360	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1361	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1362	all log messages by submodules.
		1363
814	=head1 SEE ALSO	1364	=head1 SEE ALSO
815		1365
816	L<AnyEvent::MP::Intro> - a gentle introduction.	1366	L<AnyEvent::MP::Intro> - a gentle introduction.
817		1367
818	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1368	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
819		1369
820	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1370	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
821	your applications.	1371	your applications.
		1372
		1373	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1374
		1375	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1376	all nodes.
822		1377
823	L<AnyEvent>.	1378	L<AnyEvent>.
824		1379
825	=head1 AUTHOR	1380	=head1 AUTHOR
826		1381

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Revision 1.141 by root, Fri Mar 23 03:24:41 2012 UTC