[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 1.126 by root, Sat Mar 3 19:43:41 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 $localport, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
39	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
40		51
41	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
42		53
		54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - mostly stable	58	AnyEvent::MP::Global - stable API.
47	AnyEvent::MP::Node - mostly stable, but internal anyways
48	AnyEvent::MP::Transport - mostly stable, but internal anyways
49
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
57	on the same or other hosts, and you can supervise entities remotely.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page and the examples under F<eg/>.	68	manual page and the examples under F<eg/>.
61		69
62	At the moment, this module family is a bit underdocumented.
63
64	=head1 CONCEPTS	70	=head1 CONCEPTS
65		71
66	=over 4	72	=over 4
67		73
68	=item port	74	=item port
69		75
70	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
71		78
72	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	81	anything was listening for them or not.
75		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
76	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
77		86
78	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
79	separator, and a port name (a printable string of unspecified format).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
80		90
81	=item node	91	=item node
82		92
83	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
84	which enables nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
85	ports.	95	ports.
86		96
87	Nodes are either public (have one or more listening ports) or private	97	Nodes are either public (have one or more listening ports) or private
88	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
89	currently.	99	currently, but all nodes can talk to public nodes.
90		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
91	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
92		104
93	A node ID is a string that uniquely identifies the node within a	105	A node ID is a string that uniquely identifies the node within a
94	network. Depending on the configuration used, node IDs can look like a	106	network. Depending on the configuration used, node IDs can look like a
95	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
96	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
97		109
98	=item binds - C<ip:port>	110	=item binds - C<ip:port>
99		111
100	Nodes can only talk to each other by creating some kind of connection to	112	Nodes can only talk to each other by creating some kind of connection to
101	each other. To do this, nodes should listen on one or more local transport	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
102	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
103	be used, which specify TCP ports to listen on.	117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
104		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
105	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
106		150
107	When a node starts, it knows nothing about the network. To teach the node	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
108	about the network it first has to contact some other node within the	152	TCP port) of nodes that should be used as seed nodes.
109	network. This node is called a seed.
110		153
111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
112	are expected to be long-running, and at least one of those should always
113	be available. When nodes run out of connections (e.g. due to a network
114	error), they try to re-establish connections to some seednodes again to
115	join the network.
116		155
117	Apart from being sued for seeding, seednodes are not special in any way -	156	An AEMP network needs a discovery service - nodes need to know how to
118	every public node can be a seednode.	157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
119		170
120	=back	171	=back
121		172
122	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
123		174
…		…
125		176
126	=cut	177	=cut
127		178
128	package AnyEvent::MP;	179	package AnyEvent::MP;
129		180
		181	use AnyEvent::MP::Config ();
130	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
131		184
132	use common::sense;	185	use common::sense;
133		186
134	use Carp ();	187	use Carp ();
135		188
136	use AE ();	189	use AE ();
		190	use Guard ();
137		191
138	use base "Exporter";	192	use base "Exporter";
139		193
140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
141		195
142	our @EXPORT = qw(	196	our @EXPORT = qw(
143	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
144	initialise_node	198	configure
145	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
146	port	200	port
		201	db_set db_del db_reg
147	);	202	);
148		203
149	our $SELF;	204	our $SELF;
150		205
151	sub _self_die() {	206	sub _self_die() {
…		…
156		211
157	=item $thisnode = NODE / $NODE	212	=item $thisnode = NODE / $NODE
158		213
159	The C<NODE> function returns, and the C<$NODE> variable contains, the node	214	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	215	ID of the node running in the current process. This value is initialised by
161	a call to C<initialise_node>.	216	a call to C<configure>.
162		217
163	=item $nodeid = node_of $port	218	=item $nodeid = node_of $port
164		219
165	Extracts and returns the node ID from a port ID or a node ID.	220	Extracts and returns the node ID from a port ID or a node ID.
166		221
167	=item initialise_node $profile_name	222	=item configure $profile, key => value...
		223
		224	=item configure key => value...
168		225
169	Before a node can talk to other nodes on the network (i.e. enter	226	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	227	"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	228	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.	229	some other nodes in the network to discover other nodes.
173		230
174	This function initialises a node - it must be called exactly once (or	231	This function configures a node - it must be called exactly once (or
175	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
176		233
177	The first argument is a profile name. If it is C<undef> or missing, then	234	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>).	235	F<aemp> command line utility (sans the set/del prefix), with two additions:
179		236
		237	=over 4
		238
		239	=item norc => $boolean (default false)
		240
		241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		242	be consulted - all configuraiton options must be specified in the
		243	C<configure> call.
		244
		245	=item force => $boolean (default false)
		246
		247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
		250
		251	=back
		252
		253	=over 4
		254
		255	=item step 1, gathering configuration from profiles
		256
180	The function then looks up the profile in the aemp configuration (see the	257	The function first looks up a profile in the aemp configuration (see the
181	L<aemp> commandline utility).	258	L<aemp> commandline utility). The profile name can be specified via the
		259	named C<profile> parameter or can simply be the first parameter). If it is
		260	missing, then the nodename (F<uname -n>) will be used as profile name.
		261
		262	The profile data is then gathered as follows:
		263
		264	First, all remaining key => value pairs (all of which are conveniently
		265	undocumented at the moment) will be interpreted as configuration
		266	data. Then they will be overwritten by any values specified in the global
		267	default configuration (see the F<aemp> utility), then the chain of
		268	profiles chosen by the profile name (and any C<parent> attributes).
		269
		270	That means that the values specified in the profile have highest priority
		271	and the values specified directly via C<configure> have lowest priority,
		272	and can only be used to specify defaults.
182		273
183	If the profile specifies a node ID, then this will become the node ID of	274	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	275	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.	276	a unique randoms tring (C</%u>) appended.
		277
		278	The node ID can contain some C<%> sequences that are expanded: C<%n>
		279	is expanded to the local nodename, C<%u> is replaced by a random
		280	strign to make the node unique. For example, the F<aemp> commandline
		281	utility uses C<aemp/%n/%u> as nodename, which might expand to
		282	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		283
		284	=item step 2, bind listener sockets
186		285
187	The next step is to look up the binds in the profile, followed by binding	286	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	287	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	288	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	289	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).	290	binds, but it can still talk to all "normal" nodes).
192		291
193	If the profile does not specify a binds list, then the node ID will be	292	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	293	used, meaning the node will bind on a dynamically-assigned port on every
195	used as binds list.	294	local IP address it finds.
196		295
		296	=item step 3, connect to seed nodes
		297
197	Lastly, the seeds list from the profile is passed to the	298	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	299	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.	300	connectivity with at least one node at any point in time.
200		301
201	Example: become a distributed node listening on the guessed noderef, or	302	=back
202	the one specified via C<aemp> for the current node. This should be the	303
		304	Example: become a distributed node using the local node name as profile.
203	most common form of invocation for "daemon"-type nodes.	305	This should be the most common form of invocation for "daemon"-type nodes.
204		306
205	initialise_node;	307	configure
206		308
207	Example: become an anonymous node. This form is often used for commandline	309	Example: become a semi-anonymous node. This form is often used for
208	clients.	310	commandline clients.
209		311
210	initialise_node "anon/";	312	configure nodeid => "myscript/%n/%u";
211		313
212	Example: become a distributed node. If there is no profile of the given	314	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	315	for a seed node as it binds on all local addresses on a fixed port (4040,
214	on the resulting addresses.	316	customary for aemp).
215		317
216	initialise_node "localhost:4044";	318	# use the aemp commandline utility
		319	# aemp profile seed binds '*:4040'
		320
		321	# then use it
		322	configure profile => "seed";
		323
		324	# or simply use aemp from the shell again:
		325	# aemp run profile seed
		326
		327	# or provide a nicer-to-remember nodeid
		328	# aemp run profile seed nodeid "$(hostname)"
217		329
218	=item $SELF	330	=item $SELF
219		331
220	Contains the current port id while executing C<rcv> callbacks or C<psub>	332	Contains the current port id while executing C<rcv> callbacks or C<psub>
221	blocks.	333	blocks.
…		…
282	sub _kilme {	394	sub _kilme {
283	die "received message on port without callback";	395	die "received message on port without callback";
284	}	396	}
285		397
286	sub port(;&) {	398	sub port(;&) {
287	my $id = "$UNIQ." . $ID++;	399	my $id = $UNIQ . ++$ID;
288	my $port = "$NODE#$id";	400	my $port = "$NODE#$id";
289		401
290	rcv $port, shift \|\| \&_kilme;	402	rcv $port, shift \|\| \&_kilme;
291		403
292	$port	404	$port
…		…
331	msg1 => sub { ... },	443	msg1 => sub { ... },
332	...	444	...
333	;	445	;
334		446
335	Example: temporarily register a rcv callback for a tag matching some port	447	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.	448	(e.g. for an rpc reply) and unregister it after a message was received.
337		449
338	rcv $port, $otherport => sub {	450	rcv $port, $otherport => sub {
339	my @reply = @_;	451	my @reply = @_;
340		452
341	rcv $SELF, $otherport;	453	rcv $SELF, $otherport;
…		…
343		455
344	=cut	456	=cut
345		457
346	sub rcv($@) {	458	sub rcv($@) {
347	my $port = shift;	459	my $port = shift;
348	my ($noderef, $portid) = split /#/, $port, 2;	460	my ($nodeid, $portid) = split /#/, $port, 2;
349		461
350	$NODE{$noderef} == $NODE{""}	462	$NODE{$nodeid} == $NODE{""}
351	or Carp::croak "$port: rcv can only be called on local ports, caught";	463	or Carp::croak "$port: rcv can only be called on local ports, caught";
352		464
353	while (@_) {	465	while (@_) {
354	if (ref $_[0]) {	466	if (ref $_[0]) {
355	if (my $self = $PORT_DATA{$portid}) {	467	if (my $self = $PORT_DATA{$portid}) {
356	"AnyEvent::MP::Port" eq ref $self	468	"AnyEvent::MP::Port" eq ref $self
357	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	469	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
358		470
359	$self->[2] = shift;	471	$self->[0] = shift;
360	} else {	472	} else {
361	my $cb = shift;	473	my $cb = shift;
362	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
363	local $SELF = $port;	475	local $SELF = $port;
364	eval { &$cb }; _self_die if $@;	476	eval { &$cb }; _self_die if $@;
365	};	477	};
366	}	478	}
367	} elsif (defined $_[0]) {	479	} elsif (defined $_[0]) {
368	my $self = $PORT_DATA{$portid} \|\|= do {	480	my $self = $PORT_DATA{$portid} \|\|= do {
369	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	481	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
370		482
371	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
372	local $SELF = $port;	484	local $SELF = $port;
373		485
374	if (my $cb = $self->[1]{$_[0]}) {	486	if (my $cb = $self->[1]{$_[0]}) {
…		…
396	}	508	}
397		509
398	$port	510	$port
399	}	511	}
400		512
		513	=item peval $port, $coderef[, @args]
		514
		515	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		516	when the code throews an exception the C<$port> will be killed.
		517
		518	Any remaining args will be passed to the callback. Any return values will
		519	be returned to the caller.
		520
		521	This is useful when you temporarily want to execute code in the context of
		522	a port.
		523
		524	Example: create a port and run some initialisation code in it's context.
		525
		526	my $port = port { ... };
		527
		528	peval $port, sub {
		529	init
		530	or die "unable to init";
		531	};
		532
		533	=cut
		534
		535	sub peval($$) {
		536	local $SELF = shift;
		537	my $cb = shift;
		538
		539	if (wantarray) {
		540	my @res = eval { &$cb };
		541	_self_die if $@;
		542	@res
		543	} else {
		544	my $res = eval { &$cb };
		545	_self_die if $@;
		546	$res
		547	}
		548	}
		549
401	=item $closure = psub { BLOCK }	550	=item $closure = psub { BLOCK }
402		551
403	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	552	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>	553	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.	554	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		555
		556	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		557	BLOCK }, @_ } >>.
406		558
407	This is useful when you register callbacks from C<rcv> callbacks:	559	This is useful when you register callbacks from C<rcv> callbacks:
408		560
409	rcv delayed_reply => sub {	561	rcv delayed_reply => sub {
410	my ($delay, @reply) = @_;	562	my ($delay, @reply) = @_;
…		…
446		598
447	Monitor the given port and do something when the port is killed or	599	Monitor the given port and do something when the port is killed or
448	messages to it were lost, and optionally return a guard that can be used	600	messages to it were lost, and optionally return a guard that can be used
449	to stop monitoring again.	601	to stop monitoring again.
450		602
		603	In the first form (callback), the callback is simply called with any
		604	number of C<@reason> elements (no @reason means that the port was deleted
		605	"normally"). Note also that I<< the callback B<must> never die >>, so use
		606	C<eval> if unsure.
		607
		608	In the second form (another port given), the other port (C<$rcvport>)
		609	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		610	"normal" kils nothing happens, while under all other conditions, the other
		611	port is killed with the same reason.
		612
		613	The third form (kill self) is the same as the second form, except that
		614	C<$rvport> defaults to C<$SELF>.
		615
		616	In the last form (message), a message of the form C<@msg, @reason> will be
		617	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.
		621
		622	As a rule of thumb, monitoring requests should always monitor a port from
		623	a local port (or callback). The reason is that kill messages might get
		624	lost, just like any other message. Another less obvious reason is that
		625	even monitoring requests can get lost (for example, when the connection
		626	to the other node goes down permanently). When monitoring a port locally
		627	these problems do not exist.
		628
451	C<mon> effectively guarantees that, in the absence of hardware failures,	629	C<mon> effectively guarantees that, in the absence of hardware failures,
452	after starting the monitor, either all messages sent to the port will	630	after starting the monitor, either all messages sent to the port will
453	arrive, or the monitoring action will be invoked after possible message	631	arrive, or the monitoring action will be invoked after possible message
454	loss has been detected. No messages will be lost "in between" (after	632	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	633	the first lost message no further messages will be received by the
456	port). After the monitoring action was invoked, further messages might get	634	port). After the monitoring action was invoked, further messages might get
457	delivered again.	635	delivered again.
458		636
459	Note that monitoring-actions are one-shot: once messages are lost (and a	637	Inter-host-connection timeouts and monitoring depend on the transport
460	monitoring alert was raised), they are removed and will not trigger again.	638	used. The only transport currently implemented is TCP, and AnyEvent::MP
		639	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		640	non-idle connection, and usually around two hours for idle connections).
461		641
462	In the first form (callback), the callback is simply called with any	642	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	643	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	644	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<$SELF>.
474
475	In the last form (message), a message of the form C<@msg, @reason> will be
476	C<snd>.
477
478	As a rule of thumb, monitoring requests should always monitor a port from
479	a local port (or callback). The reason is that kill messages might get
480	lost, just like any other message. Another less obvious reason is that
481	even monitoring requests can get lost (for exmaple, when the connection
482	to the other node goes down permanently). When monitoring a port locally
483	these problems do not exist.
484		645
485	Example: call a given callback when C<$port> is killed.	646	Example: call a given callback when C<$port> is killed.
486		647
487	mon $port, sub { warn "port died because of <@_>\n" };	648	mon $port, sub { warn "port died because of <@_>\n" };
488		649
…		…
495	mon $port, $self => "restart";	656	mon $port, $self => "restart";
496		657
497	=cut	658	=cut
498		659
499	sub mon {	660	sub mon {
500	my ($noderef, $port) = split /#/, shift, 2;	661	my ($nodeid, $port) = split /#/, shift, 2;
501		662
502	my $node = $NODE{$noderef} \|\| add_node $noderef;	663	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
503		664
504	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	665	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
505		666
506	unless (ref $cb) {	667	unless (ref $cb) {
507	if (@_) {	668	if (@_) {
…		…
516	}	677	}
517		678
518	$node->monitor ($port, $cb);	679	$node->monitor ($port, $cb);
519		680
520	defined wantarray	681	defined wantarray
521	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	682	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
522	}	683	}
523		684
524	=item $guard = mon_guard $port, $ref, $ref...	685	=item $guard = mon_guard $port, $ref, $ref...
525		686
526	Monitors the given C<$port> and keeps the passed references. When the port	687	Monitors the given C<$port> and keeps the passed references. When the port
…		…
549		710
550	=item kil $port[, @reason]	711	=item kil $port[, @reason]
551		712
552	Kill the specified port with the given C<@reason>.	713	Kill the specified port with the given C<@reason>.
553		714
554	If no C<@reason> is specified, then the port is killed "normally" (ports	715	If no C<@reason> is specified, then the port is killed "normally" -
555	monitoring other ports will not necessarily die because a port dies	716	monitor callback will be invoked, but the kil will not cause linked ports
556	"normally").	717	(C<mon $mport, $lport> form) to get killed.
557		718
558	Otherwise, linked ports get killed with the same reason (second form of	719	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
559	C<mon>, see above).	720	form) get killed with the same reason.
560		721
561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	722	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
562	will be reported as reason C<< die => $@ >>.	723	will be reported as reason C<< die => $@ >>.
563		724
564	Transport/communication errors are reported as C<< transport_error =>	725	Transport/communication errors are reported as C<< transport_error =>
…		…
583	the package, then the package above the package and so on (e.g.	744	the package, then the package above the package and so on (e.g.
584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	745	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
585	exists or it runs out of package names.	746	exists or it runs out of package names.
586		747
587	The init function is then called with the newly-created port as context	748	The init function is then called with the newly-created port as context
588	object (C<$SELF>) and the C<@initdata> values as arguments.	749	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		750	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		751	the port might not get created.
589		752
590	A common idiom is to pass a local port, immediately monitor the spawned	753	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	754	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	755	local port. This two-way monitoring ensures that both ports get cleaned up
593	when there is a problem.	756	when there is a problem.
594		757
		758	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		759	caller before C<spawn> returns (by delaying invocation when spawn is
		760	called for the local node).
		761
595	Example: spawn a chat server port on C<$othernode>.	762	Example: spawn a chat server port on C<$othernode>.
596		763
597	# this node, executed from within a port context:	764	# this node, executed from within a port context:
598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	765	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
599	mon $server;	766	mon $server;
…		…
613		780
614	sub _spawn {	781	sub _spawn {
615	my $port = shift;	782	my $port = shift;
616	my $init = shift;	783	my $init = shift;
617		784
		785	# rcv will create the actual port
618	local $SELF = "$NODE#$port";	786	local $SELF = "$NODE#$port";
619	eval {	787	eval {
620	&{ load_func $init }	788	&{ load_func $init }
621	};	789	};
622	_self_die if $@;	790	_self_die if $@;
623	}	791	}
624		792
625	sub spawn(@) {	793	sub spawn(@) {
626	my ($noderef, undef) = split /#/, shift, 2;	794	my ($nodeid, undef) = split /#/, shift, 2;
627		795
628	my $id = "$RUNIQ." . $ID++;	796	my $id = $RUNIQ . ++$ID;
629		797
630	$_[0] =~ /::/	798	$_[0] =~ /::/
631	or Carp::croak "spawn init function must be a fully-qualified name, caught";	799	or Carp::croak "spawn init function must be a fully-qualified name, caught";
632		800
633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	801	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
634		802
635	"$noderef#$id"	803	"$nodeid#$id"
636	}	804	}
		805
637		806
638	=item after $timeout, @msg	807	=item after $timeout, @msg
639		808
640	=item after $timeout, $callback	809	=item after $timeout, $callback
641		810
…		…
657	? $action[0]()	826	? $action[0]()
658	: snd @action;	827	: snd @action;
659	};	828	};
660	}	829	}
661		830
		831	=item cal $port, @msg, $callback[, $timeout]
		832
		833	A simple form of RPC - sends a message to the given C<$port> with the
		834	given contents (C<@msg>), but adds a reply port to the message.
		835
		836	The reply port is created temporarily just for the purpose of receiving
		837	the reply, and will be C<kil>ed when no longer needed.
		838
		839	A reply message sent to the port is passed to the C<$callback> as-is.
		840
		841	If an optional time-out (in seconds) is given and it is not C<undef>,
		842	then the callback will be called without any arguments after the time-out
		843	elapsed and the port is C<kil>ed.
		844
		845	If no time-out is given (or it is C<undef>), then the local port will
		846	monitor the remote port instead, so it eventually gets cleaned-up.
		847
		848	Currently this function returns the temporary port, but this "feature"
		849	might go in future versions unless you can make a convincing case that
		850	this is indeed useful for something.
		851
		852	=cut
		853
		854	sub cal(@) {
		855	my $timeout = ref $_[-1] ? undef : pop;
		856	my $cb = pop;
		857
		858	my $port = port {
		859	undef $timeout;
		860	kil $SELF;
		861	&$cb;
		862	};
		863
		864	if (defined $timeout) {
		865	$timeout = AE::timer $timeout, 0, sub {
		866	undef $timeout;
		867	kil $port;
		868	$cb->();
		869	};
		870	} else {
		871	mon $_[0], sub {
		872	kil $port;
		873	$cb->();
		874	};
		875	}
		876
		877	push @_, $port;
		878	&snd;
		879
		880	$port
		881	}
		882
		883	=back
		884
		885	=head1 DISTRIBUTED DATABASE
		886
		887	AnyEvent::MP comes with a simple distributed database. The database will
		888	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		889	the global nodes for their needs.
		890
		891	The database consists of a two-level hash - a hash contains a hash which
		892	contains values.
		893
		894	The top level hash key is called "family", and the second-level hash key
		895	is called "subkey" or simply "key".
		896
		897	The family must be alphanumeric, i.e. start with a letter and consist
		898	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		899	pretty much like Perl module names.
		900
		901	As the family namespace is global, it is recommended to prefix family names
		902	with the name of the application or module using it.
		903
		904	The subkeys must be non-empty strings, with no further restrictions.
		905
		906	The values should preferably be strings, but other perl scalars should
		907	work as well (such as undef, arrays and hashes).
		908
		909	Every database entry is owned by one node - adding the same family/subkey
		910	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		911	but the result might be nondeterministic, i.e. the key might have
		912	different values on different nodes.
		913
		914	Different subkeys in the same family can be owned by different nodes
		915	without problems, and in fact, this is the common method to create worker
		916	pools. For example, a worker port for image scaling might do this:
		917
		918	db_set my_image_scalers => $port;
		919
		920	And clients looking for an image scaler will want to get the
		921	C<my_image_scalers> keys:
		922
		923	db_keys "my_image_scalers" => 60 => sub {
		924	#d##TODO#
		925
		926	=over
		927
		928	=item db_set $family => $subkey [=> $value]
		929
		930	Sets (or replaces) a key to the database - if C<$value> is omitted,
		931	C<undef> is used instead.
		932
		933	=item db_del $family => $subkey
		934
		935	Deletes a key from the database.
		936
		937	=item $guard = db_reg $family => $subkey [=> $value]
		938
		939	Sets the key on the database and returns a guard. When the guard is
		940	destroyed, the key is deleted from the database. If C<$value> is missing,
		941	then C<undef> is used.
		942
		943	=cut
		944
662	=back	945	=back
663		946
664	=head1 AnyEvent::MP vs. Distributed Erlang	947	=head1 AnyEvent::MP vs. Distributed Erlang
665		948
666	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	949	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	950	== 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	951	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
669	sample:	952	sample:
670		953
671	http://www.Erlang.se/doc/programming_rules.shtml	954	http://www.erlang.se/doc/programming_rules.shtml
672	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	955	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	956	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	957	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
675		958
676	Despite the similarities, there are also some important differences:	959	Despite the similarities, there are also some important differences:
677		960
678	=over 4	961	=over 4
679		962
680	=item * Node IDs are arbitrary strings in AEMP.	963	=item * Node IDs are arbitrary strings in AEMP.
681		964
682	Erlang relies on special naming and DNS to work everywhere in the same	965	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	966	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.	967	configuration or DNS), and possibly the addresses of some seed nodes, but
		968	will otherwise discover other nodes (and their IDs) itself.
685		969
686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	970	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
687	uses "local ports are like remote ports".	971	uses "local ports are like remote ports".
688		972
689	The failure modes for local ports are quite different (runtime errors	973	The failure modes for local ports are quite different (runtime errors
…		…
698	ports being the special case/exception, where transport errors cannot	982	ports being the special case/exception, where transport errors cannot
699	occur.	983	occur.
700		984
701	=item * Erlang uses processes and a mailbox, AEMP does not queue.	985	=item * Erlang uses processes and a mailbox, AEMP does not queue.
702		986
703	Erlang uses processes that selectively receive messages, and therefore	987	Erlang uses processes that selectively receive messages out of order, and
704	needs a queue. AEMP is event based, queuing messages would serve no	988	therefore needs a queue. AEMP is event based, queuing messages would serve
705	useful purpose. For the same reason the pattern-matching abilities of	989	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	990	of AnyEvent::MP are more limited, as there is little need to be able to
707	filter messages without dequeing them.	991	filter messages without dequeuing them.
708		992
709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	993	This is not a philosophical difference, but simply stems from AnyEvent::MP
		994	being event-based, while Erlang is process-based.
		995
		996	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		997	top of AEMP and Coro threads.
710		998
711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	999	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
712		1000
713	Sending messages in Erlang is synchronous and blocks the process (and	1001	Sending messages in Erlang is synchronous and blocks the process until
		1002	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,	1003	need a queue that can overflow). AEMP sends return immediately, connection
715	connection establishment is handled in the background.	1004	establishment is handled in the background.
716		1005
717	=item * Erlang suffers from silent message loss, AEMP does not.	1006	=item * Erlang suffers from silent message loss, AEMP does not.
718		1007
719	Erlang makes few guarantees on messages delivery - messages can get lost	1008	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,	1009	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).	1010	b, and c, and the other side only receives messages a and c).
722		1011
723	AEMP guarantees correct ordering, and the guarantee that after one message	1012	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	1013	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	1014	same port are lost as well, until monitoring raises an error, so there are
726	sequence.	1015	no silent "holes" in the message sequence.
		1016
		1017	If you want your software to be very reliable, you have to cope with
		1018	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1019	simply tries to work better in common error cases, such as when a network
		1020	link goes down.
727		1021
728	=item * Erlang can send messages to the wrong port, AEMP does not.	1022	=item * Erlang can send messages to the wrong port, AEMP does not.
729		1023
730	In Erlang it is quite likely that a node that restarts reuses a process ID	1024	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	1025	process ID known to other nodes for a completely different process,
732	destined for that process to end up in an unrelated process.	1026	causing messages destined for that process to end up in an unrelated
		1027	process.
733		1028
734	AEMP never reuses port IDs, so old messages or old port IDs floating	1029	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.	1030	around in the network will not be sent to an unrelated port.
736		1031
737	=item * Erlang uses unprotected connections, AEMP uses secure	1032	=item * Erlang uses unprotected connections, AEMP uses secure
738	authentication and can use TLS.	1033	authentication and can use TLS.
739		1034
…		…
742		1037
743	=item * The AEMP protocol is optimised for both text-based and binary	1038	=item * The AEMP protocol is optimised for both text-based and binary
744	communications.	1039	communications.
745		1040
746	The AEMP protocol, unlike the Erlang protocol, supports both programming	1041	The AEMP protocol, unlike the Erlang protocol, supports both programming
747	language independent text-only protocols (good for debugging) and binary,	1042	language independent text-only protocols (good for debugging), and binary,
748	language-specific serialisers (e.g. Storable). By default, unless TLS is	1043	language-specific serialisers (e.g. Storable). By default, unless TLS is
749	used, the protocol is actually completely text-based.	1044	used, the protocol is actually completely text-based.
750		1045
751	It has also been carefully designed to be implementable in other languages	1046	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	1047	with a minimum of work while gracefully degrading functionality to make the
753	protocol simple.	1048	protocol simple.
754		1049
755	=item * AEMP has more flexible monitoring options than Erlang.	1050	=item * AEMP has more flexible monitoring options than Erlang.
756		1051
757	In Erlang, you can chose to receive I<all> exit signals as messages	1052	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	1053	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	1054	difficult to implement.
760	Erlang, as one can choose between automatic kill, exit message or callback	1055
761	on a per-process basis.	1056	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1057	between automatic kill, exit message or callback on a per-port basis.
762		1058
763	=item * Erlang tries to hide remote/local connections, AEMP does not.	1059	=item * Erlang tries to hide remote/local connections, AEMP does not.
764		1060
765	Monitoring in Erlang is not an indicator of process death/crashes, in the	1061	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).	1062	same way as linking is (except linking is unreliable in Erlang).
…		…
788	overhead, as well as having to keep a proxy object everywhere.	1084	overhead, as well as having to keep a proxy object everywhere.
789		1085
790	Strings can easily be printed, easily serialised etc. and need no special	1086	Strings can easily be printed, easily serialised etc. and need no special
791	procedures to be "valid".	1087	procedures to be "valid".
792		1088
793	And as a result, a miniport consists of a single closure stored in a	1089	And as a result, a port with just a default receiver consists of a single
794	global hash - it can't become much cheaper.	1090	code reference stored in a global hash - it can't become much cheaper.
795		1091
796	=item Why favour JSON, why not a real serialising format such as Storable?	1092	=item Why favour JSON, why not a real serialising format such as Storable?
797		1093
798	In fact, any AnyEvent::MP node will happily accept Storable as framing	1094	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	1095	format, but currently there is no way to make a node use Storable by
…		…
815		1111
816	L<AnyEvent::MP::Intro> - a gentle introduction.	1112	L<AnyEvent::MP::Intro> - a gentle introduction.
817		1113
818	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1114	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
819		1115
820	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1116	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
821	your applications.	1117	your applications.
		1118
		1119	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1120
		1121	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1122	all nodes.
822		1123
823	L<AnyEvent>.	1124	L<AnyEvent>.
824		1125
825	=head1 AUTHOR	1126	=head1 AUTHOR
826		1127

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.68 by root, Fri Aug 28 23:06:33 2009 UTC vs. Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.68 by root, Fri Aug 28 23:06:33 2009 UTC vs.
Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC