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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.74 by root, Mon Aug 31 11:11:27 2009 UTC vs.
Revision 1.128 by root, Sun Mar 4 14:28:44 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	configure;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
31	rcv $port, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
36	# monitoring	39	# monitoring
37	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $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
43	bin/aemp - stable.	54	bin/aemp - stable.
44	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
45	AnyEvent::MP::Intro - uptodate, but incomplete.	56	AnyEvent::MP::Intro - explains most concepts.
46	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
47	AnyEvent::MP::Global - stable API, protocol not yet final.	58	AnyEvent::MP::Global - stable API.
48
49	stay tuned.
50		59
51	=head1 DESCRIPTION	60	=head1 DESCRIPTION
52		61
53	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
54		63
…		…
56	on the same or other hosts, and you can supervise entities remotely.	65	on the same or other hosts, and you can supervise entities remotely.
57		66
58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
59	manual page and the examples under F<eg/>.	68	manual page and the examples under F<eg/>.
60		69
61	At the moment, this module family is a bit underdocumented.
62
63	=head1 CONCEPTS	70	=head1 CONCEPTS
64		71
65	=over 4	72	=over 4
66		73
67	=item port	74	=item port
68		75
69	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
70		78
71	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
72	some messages. Messages send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
73	anything was listening for them or not.	81	anything was listening for them or not.
74		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
75	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
76		86
77	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
78	separator, and a port name (a printable string of unspecified format).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
79		90
80	=item node	91	=item node
81		92
82	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
83	which enables nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
84	ports.	95	ports.
85		96
86	Nodes are either public (have one or more listening ports) or private	97	Nodes are either public (have one or more listening ports) or private
87	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
88	currently.	99	currently, but all nodes can talk to public nodes.
89		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
90	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
91		104
92	A node ID is a string that uniquely identifies the node within a	105	A node ID is a string that uniquely identifies the node within a
93	network. Depending on the configuration used, node IDs can look like a	106	network. Depending on the configuration used, node IDs can look like a
94	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
95	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
96		109
97	=item binds - C<ip:port>	110	=item binds - C<ip:port>
98		111
99	Nodes can only talk to each other by creating some kind of connection to	112	Nodes can only talk to each other by creating some kind of connection to
100	each other. To do this, nodes should listen on one or more local transport	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
101	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
102	be used, which specify TCP ports to listen on.	117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
103		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
104	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
105		150
106	When a node starts, it knows nothing about the network. To teach the node	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
107	about the network it first has to contact some other node within the	152	TCP port) of nodes that should be used as seed nodes.
108	network. This node is called a seed.
109		153
110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
111	are expected to be long-running, and at least one of those should always
112	be available. When nodes run out of connections (e.g. due to a network
113	error), they try to re-establish connections to some seednodes again to
114	join the network.
115		155
116	Apart from being sued for seeding, seednodes are not special in any way -	156	An AEMP network needs a discovery service - nodes need to know how to
117	every public node can be a seednode.	157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
118		170
119	=back	171	=back
120		172
121	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
122		174
…		…
124		176
125	=cut	177	=cut
126		178
127	package AnyEvent::MP;	179	package AnyEvent::MP;
128		180
		181	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130		184
131	use common::sense;	185	use common::sense;
132		186
133	use Carp ();	187	use Carp ();
134		188
135	use AE ();	189	use AE ();
		190	use Guard ();
136		191
137	use base "Exporter";	192	use base "Exporter";
138		193
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
140		195
141	our @EXPORT = qw(	196	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
143	configure	198	configure
144	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
145	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
146	);	203	);
147		204
148	our $SELF;	205	our $SELF;
149		206
150	sub _self_die() {	207	sub _self_die() {
…		…
161		218
162	=item $nodeid = node_of $port	219	=item $nodeid = node_of $port
163		220
164	Extracts and returns the node ID from a port ID or a node ID.	221	Extracts and returns the node ID from a port ID or a node ID.
165		222
		223	=item configure $profile, key => value...
		224
166	=item configure key => value...	225	=item configure key => value...
167		226
168	Before a node can talk to other nodes on the network (i.e. enter	227	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to configure itself - the minimum a node needs	228	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	229	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
172		231
173	This function configures a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
175		234
		235	The key/value pairs are basically the same ones as documented for the
		236	F<aemp> command line utility (sans the set/del prefix), with these additions:
		237
		238	=over 4
		239
		240	=item norc => $boolean (default false)
		241
		242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		243	be consulted - all configuraiton options must be specified in the
		244	C<configure> call.
		245
		246	=item force => $boolean (default false)
		247
		248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
		251
		252	=item secure => $pass->($nodeid)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every remote execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	See F<semp setsecure> for more info.
		259
		260	=back
		261
176	=over 4	262	=over 4
177		263
178	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
179		265
180	The function first looks up a profile in the aemp configuration (see the	266	The function first looks up a profile in the aemp configuration (see the
181	L<aemp> commandline utility). The profile name can be specified via the	267	L<aemp> commandline utility). The profile name can be specified via the
182	named C<profile> parameter. If it is missing, then the nodename (F<uname	268	named C<profile> parameter or can simply be the first parameter). If it is
183	-n>) will be used as profile name.	269	missing, then the nodename (F<uname -n>) will be used as profile name.
184		270
185	The profile data is then gathered as follows:	271	The profile data is then gathered as follows:
186		272
187	First, all remaining key => value pairs (all of which are conviniently	273	First, all remaining key => value pairs (all of which are conveniently
188	undocumented at the moment) will be interpreted as configuration	274	undocumented at the moment) will be interpreted as configuration
189	data. Then they will be overwritten by any values specified in the global	275	data. Then they will be overwritten by any values specified in the global
190	default configuration (see the F<aemp> utility), then the chain of	276	default configuration (see the F<aemp> utility), then the chain of
191	profiles chosen by the profile name (and any C<parent> attributes).	277	profiles chosen by the profile name (and any C<parent> attributes).
192		278
193	That means that the values specified in the profile have highest priority	279	That means that the values specified in the profile have highest priority
194	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	281	and can only be used to specify defaults.
196		282
197	If the profile specifies a node ID, then this will become the node ID of	283	If the profile specifies a node ID, then this will become the node ID of
198	this process. If not, then the profile name will be used as node ID. The	284	this process. If not, then the profile name will be used as node ID, with
199	special node ID of C<anon/> will be replaced by a random node ID.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
200		292
201	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
202		294
203	The next step is to look up the binds in the profile, followed by binding	295	The next step is to look up the binds in the profile, followed by binding
204	aemp protocol listeners on all binds specified (it is possible and valid	296	aemp protocol listeners on all binds specified (it is possible and valid
…		…
210	used, meaning the node will bind on a dynamically-assigned port on every	302	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	303	local IP address it finds.
212		304
213	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
214		306
215	As the last step, the seeds list from the profile is passed to the	307	As the last step, the seed ID list from the profile is passed to the
216	L<AnyEvent::MP::Global> module, which will then use it to keep	308	L<AnyEvent::MP::Global> module, which will then use it to keep
217	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
218		310
219	=back	311	=back
220		312
221	Example: become a distributed node using the locla node name as profile.	313	Example: become a distributed node using the local node name as profile.
222	This should be the most common form of invocation for "daemon"-type nodes.	314	This should be the most common form of invocation for "daemon"-type nodes.
223		315
224	configure	316	configure
225		317
226	Example: become an anonymous node. This form is often used for commandline	318	Example: become a semi-anonymous node. This form is often used for
227	clients.	319	commandline clients.
228		320
229	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
230		322
231	Example: configure a node using a profile called seed, which si suitable	323	Example: configure a node using a profile called seed, which is suitable
232	for a seed node as it binds on all local addresses on a fixed port (4040,	324	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	325	customary for aemp).
234		326
235	# use the aemp commandline utility	327	# use the aemp commandline utility
236	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
237		329
238	# then use it	330	# then use it
239	configure profile => "seed";	331	configure profile => "seed";
240		332
241	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
311	sub _kilme {	403	sub _kilme {
312	die "received message on port without callback";	404	die "received message on port without callback";
313	}	405	}
314		406
315	sub port(;&) {	407	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
318		410
319	rcv $port, shift \|\| \&_kilme;	411	rcv $port, shift \|\| \&_kilme;
320		412
321	$port	413	$port
…		…
360	msg1 => sub { ... },	452	msg1 => sub { ... },
361	...	453	...
362	;	454	;
363		455
364	Example: temporarily register a rcv callback for a tag matching some port	456	Example: temporarily register a rcv callback for a tag matching some port
365	(e.g. for a rpc reply) and unregister it after a message was received.	457	(e.g. for an rpc reply) and unregister it after a message was received.
366		458
367	rcv $port, $otherport => sub {	459	rcv $port, $otherport => sub {
368	my @reply = @_;	460	my @reply = @_;
369		461
370	rcv $SELF, $otherport;	462	rcv $SELF, $otherport;
…		…
372		464
373	=cut	465	=cut
374		466
375	sub rcv($@) {	467	sub rcv($@) {
376	my $port = shift;	468	my $port = shift;
377	my ($noderef, $portid) = split /#/, $port, 2;	469	my ($nodeid, $portid) = split /#/, $port, 2;
378		470
379	$NODE{$noderef} == $NODE{""}	471	$NODE{$nodeid} == $NODE{""}
380	or Carp::croak "$port: rcv can only be called on local ports, caught";	472	or Carp::croak "$port: rcv can only be called on local ports, caught";
381		473
382	while (@_) {	474	while (@_) {
383	if (ref $_[0]) {	475	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	476	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	477	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	478	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387		479
388	$self->[2] = shift;	480	$self->[0] = shift;
389	} else {	481	} else {
390	my $cb = shift;	482	my $cb = shift;
391	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
392	local $SELF = $port;	484	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	485	eval { &$cb }; _self_die if $@;
394	};	486	};
395	}	487	}
396	} elsif (defined $_[0]) {	488	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	489	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	490	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		491
400	$PORT{$portid} = sub {	492	$PORT{$portid} = sub {
401	local $SELF = $port;	493	local $SELF = $port;
402		494
403	if (my $cb = $self->[1]{$_[0]}) {	495	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	517	}
426		518
427	$port	519	$port
428	}	520	}
429		521
		522	=item peval $port, $coderef[, @args]
		523
		524	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		525	when the code throews an exception the C<$port> will be killed.
		526
		527	Any remaining args will be passed to the callback. Any return values will
		528	be returned to the caller.
		529
		530	This is useful when you temporarily want to execute code in the context of
		531	a port.
		532
		533	Example: create a port and run some initialisation code in it's context.
		534
		535	my $port = port { ... };
		536
		537	peval $port, sub {
		538	init
		539	or die "unable to init";
		540	};
		541
		542	=cut
		543
		544	sub peval($$) {
		545	local $SELF = shift;
		546	my $cb = shift;
		547
		548	if (wantarray) {
		549	my @res = eval { &$cb };
		550	_self_die if $@;
		551	@res
		552	} else {
		553	my $res = eval { &$cb };
		554	_self_die if $@;
		555	$res
		556	}
		557	}
		558
430	=item $closure = psub { BLOCK }	559	=item $closure = psub { BLOCK }
431		560
432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	561	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
433	closure is executed, sets up the environment in the same way as in C<rcv>	562	closure is executed, sets up the environment in the same way as in C<rcv>
434	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	563	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		564
		565	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		566	BLOCK }, @_ } >>.
435		567
436	This is useful when you register callbacks from C<rcv> callbacks:	568	This is useful when you register callbacks from C<rcv> callbacks:
437		569
438	rcv delayed_reply => sub {	570	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	571	my ($delay, @reply) = @_;
…		…
475		607
476	Monitor the given port and do something when the port is killed or	608	Monitor the given port and do something when the port is killed or
477	messages to it were lost, and optionally return a guard that can be used	609	messages to it were lost, and optionally return a guard that can be used
478	to stop monitoring again.	610	to stop monitoring again.
479		611
		612	In the first form (callback), the callback is simply called with any
		613	number of C<@reason> elements (no @reason means that the port was deleted
		614	"normally"). Note also that I<< the callback B<must> never die >>, so use
		615	C<eval> if unsure.
		616
		617	In the second form (another port given), the other port (C<$rcvport>)
		618	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		619	"normal" kils nothing happens, while under all other conditions, the other
		620	port is killed with the same reason.
		621
		622	The third form (kill self) is the same as the second form, except that
		623	C<$rvport> defaults to C<$SELF>.
		624
		625	In the last form (message), a message of the form C<@msg, @reason> will be
		626	C<snd>.
		627
		628	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		629	alert was raised), they are removed and will not trigger again.
		630
		631	As a rule of thumb, monitoring requests should always monitor a port from
		632	a local port (or callback). The reason is that kill messages might get
		633	lost, just like any other message. Another less obvious reason is that
		634	even monitoring requests can get lost (for example, when the connection
		635	to the other node goes down permanently). When monitoring a port locally
		636	these problems do not exist.
		637
480	C<mon> effectively guarantees that, in the absence of hardware failures,	638	C<mon> effectively guarantees that, in the absence of hardware failures,
481	after starting the monitor, either all messages sent to the port will	639	after starting the monitor, either all messages sent to the port will
482	arrive, or the monitoring action will be invoked after possible message	640	arrive, or the monitoring action will be invoked after possible message
483	loss has been detected. No messages will be lost "in between" (after	641	loss has been detected. No messages will be lost "in between" (after
484	the first lost message no further messages will be received by the	642	the first lost message no further messages will be received by the
485	port). After the monitoring action was invoked, further messages might get	643	port). After the monitoring action was invoked, further messages might get
486	delivered again.	644	delivered again.
487		645
488	Note that monitoring-actions are one-shot: once messages are lost (and a	646	Inter-host-connection timeouts and monitoring depend on the transport
489	monitoring alert was raised), they are removed and will not trigger again.	647	used. The only transport currently implemented is TCP, and AnyEvent::MP
		648	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		649	non-idle connection, and usually around two hours for idle connections).
490		650
491	In the first form (callback), the callback is simply called with any	651	This means that monitoring is good for program errors and cleaning up
492	number of C<@reason> elements (no @reason means that the port was deleted	652	stuff eventually, but they are no replacement for a timeout when you need
493	"normally"). Note also that I<< the callback B<must> never die >>, so use	653	to ensure some maximum latency.
494	C<eval> if unsure.
495
496	In the second form (another port given), the other port (C<$rcvport>)
497	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
498	"normal" kils nothing happens, while under all other conditions, the other
499	port is killed with the same reason.
500
501	The third form (kill self) is the same as the second form, except that
502	C<$rvport> defaults to C<$SELF>.
503
504	In the last form (message), a message of the form C<@msg, @reason> will be
505	C<snd>.
506
507	As a rule of thumb, monitoring requests should always monitor a port from
508	a local port (or callback). The reason is that kill messages might get
509	lost, just like any other message. Another less obvious reason is that
510	even monitoring requests can get lost (for exmaple, when the connection
511	to the other node goes down permanently). When monitoring a port locally
512	these problems do not exist.
513		654
514	Example: call a given callback when C<$port> is killed.	655	Example: call a given callback when C<$port> is killed.
515		656
516	mon $port, sub { warn "port died because of <@_>\n" };	657	mon $port, sub { warn "port died because of <@_>\n" };
517		658
…		…
524	mon $port, $self => "restart";	665	mon $port, $self => "restart";
525		666
526	=cut	667	=cut
527		668
528	sub mon {	669	sub mon {
529	my ($noderef, $port) = split /#/, shift, 2;	670	my ($nodeid, $port) = split /#/, shift, 2;
530		671
531	my $node = $NODE{$noderef} \|\| add_node $noderef;	672	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
532		673
533	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	674	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
534		675
535	unless (ref $cb) {	676	unless (ref $cb) {
536	if (@_) {	677	if (@_) {
…		…
545	}	686	}
546		687
547	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
548		689
549	defined wantarray	690	defined wantarray
550	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
551	}	692	}
552		693
553	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
554		695
555	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
…		…
578		719
579	=item kil $port[, @reason]	720	=item kil $port[, @reason]
580		721
581	Kill the specified port with the given C<@reason>.	722	Kill the specified port with the given C<@reason>.
582		723
583	If no C<@reason> is specified, then the port is killed "normally" (ports	724	If no C<@reason> is specified, then the port is killed "normally" -
584	monitoring other ports will not necessarily die because a port dies	725	monitor callback will be invoked, but the kil will not cause linked ports
585	"normally").	726	(C<mon $mport, $lport> form) to get killed.
586		727
587	Otherwise, linked ports get killed with the same reason (second form of	728	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
588	C<mon>, see above).	729	form) get killed with the same reason.
589		730
590	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	731	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
591	will be reported as reason C<< die => $@ >>.	732	will be reported as reason C<< die => $@ >>.
592		733
593	Transport/communication errors are reported as C<< transport_error =>	734	Transport/communication errors are reported as C<< transport_error =>
…		…
612	the package, then the package above the package and so on (e.g.	753	the package, then the package above the package and so on (e.g.
613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	754	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
614	exists or it runs out of package names.	755	exists or it runs out of package names.
615		756
616	The init function is then called with the newly-created port as context	757	The init function is then called with the newly-created port as context
617	object (C<$SELF>) and the C<@initdata> values as arguments.	758	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		759	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		760	the port might not get created.
618		761
619	A common idiom is to pass a local port, immediately monitor the spawned	762	A common idiom is to pass a local port, immediately monitor the spawned
620	port, and in the remote init function, immediately monitor the passed	763	port, and in the remote init function, immediately monitor the passed
621	local port. This two-way monitoring ensures that both ports get cleaned up	764	local port. This two-way monitoring ensures that both ports get cleaned up
622	when there is a problem.	765	when there is a problem.
623		766
		767	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		768	caller before C<spawn> returns (by delaying invocation when spawn is
		769	called for the local node).
		770
624	Example: spawn a chat server port on C<$othernode>.	771	Example: spawn a chat server port on C<$othernode>.
625		772
626	# this node, executed from within a port context:	773	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	774	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
628	mon $server;	775	mon $server;
…		…
642		789
643	sub _spawn {	790	sub _spawn {
644	my $port = shift;	791	my $port = shift;
645	my $init = shift;	792	my $init = shift;
646		793
		794	# rcv will create the actual port
647	local $SELF = "$NODE#$port";	795	local $SELF = "$NODE#$port";
648	eval {	796	eval {
649	&{ load_func $init }	797	&{ load_func $init }
650	};	798	};
651	_self_die if $@;	799	_self_die if $@;
652	}	800	}
653		801
654	sub spawn(@) {	802	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
656		804
657	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
658		806
659	$_[0] =~ /::/	807	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	808	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		809
662	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663		811
664	"$noderef#$id"	812	"$nodeid#$id"
665	}	813	}
		814
666		815
667	=item after $timeout, @msg	816	=item after $timeout, @msg
668		817
669	=item after $timeout, $callback	818	=item after $timeout, $callback
670		819
…		…
686	? $action[0]()	835	? $action[0]()
687	: snd @action;	836	: snd @action;
688	};	837	};
689	}	838	}
690		839
		840	=item cal $port, @msg, $callback[, $timeout]
		841
		842	A simple form of RPC - sends a message to the given C<$port> with the
		843	given contents (C<@msg>), but adds a reply port to the message.
		844
		845	The reply port is created temporarily just for the purpose of receiving
		846	the reply, and will be C<kil>ed when no longer needed.
		847
		848	A reply message sent to the port is passed to the C<$callback> as-is.
		849
		850	If an optional time-out (in seconds) is given and it is not C<undef>,
		851	then the callback will be called without any arguments after the time-out
		852	elapsed and the port is C<kil>ed.
		853
		854	If no time-out is given (or it is C<undef>), then the local port will
		855	monitor the remote port instead, so it eventually gets cleaned-up.
		856
		857	Currently this function returns the temporary port, but this "feature"
		858	might go in future versions unless you can make a convincing case that
		859	this is indeed useful for something.
		860
		861	=cut
		862
		863	sub cal(@) {
		864	my $timeout = ref $_[-1] ? undef : pop;
		865	my $cb = pop;
		866
		867	my $port = port {
		868	undef $timeout;
		869	kil $SELF;
		870	&$cb;
		871	};
		872
		873	if (defined $timeout) {
		874	$timeout = AE::timer $timeout, 0, sub {
		875	undef $timeout;
		876	kil $port;
		877	$cb->();
		878	};
		879	} else {
		880	mon $_[0], sub {
		881	kil $port;
		882	$cb->();
		883	};
		884	}
		885
		886	push @_, $port;
		887	&snd;
		888
		889	$port
		890	}
		891
		892	=back
		893
		894	=head1 DISTRIBUTED DATABASE
		895
		896	AnyEvent::MP comes with a simple distributed database. The database will
		897	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		898	the global nodes for their needs.
		899
		900	The database consists of a two-level hash - a hash contains a hash which
		901	contains values.
		902
		903	The top level hash key is called "family", and the second-level hash key
		904	is called "subkey" or simply "key".
		905
		906	The family must be alphanumeric, i.e. start with a letter and consist
		907	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		908	pretty much like Perl module names.
		909
		910	As the family namespace is global, it is recommended to prefix family names
		911	with the name of the application or module using it.
		912
		913	The subkeys must be non-empty strings, with no further restrictions.
		914
		915	The values should preferably be strings, but other perl scalars should
		916	work as well (such as undef, arrays and hashes).
		917
		918	Every database entry is owned by one node - adding the same family/subkey
		919	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		920	but the result might be nondeterministic, i.e. the key might have
		921	different values on different nodes.
		922
		923	Different subkeys in the same family can be owned by different nodes
		924	without problems, and in fact, this is the common method to create worker
		925	pools. For example, a worker port for image scaling might do this:
		926
		927	db_set my_image_scalers => $port;
		928
		929	And clients looking for an image scaler will want to get the
		930	C<my_image_scalers> keys:
		931
		932	db_keys "my_image_scalers" => 60 => sub {
		933	#d##TODO#
		934
		935	=over
		936
		937	=item db_set $family => $subkey [=> $value]
		938
		939	Sets (or replaces) a key to the database - if C<$value> is omitted,
		940	C<undef> is used instead.
		941
		942	=item db_del $family => $subkey
		943
		944	Deletes a key from the database.
		945
		946	=item $guard = db_reg $family => $subkey [=> $value]
		947
		948	Sets the key on the database and returns a guard. When the guard is
		949	destroyed, the key is deleted from the database. If C<$value> is missing,
		950	then C<undef> is used.
		951
		952	=item $guard = db_mon $family => $cb->($familyhash, \@subkeys...)
		953
		954	Creates a monitor on the given database family. Each time a key is set or
		955	or is deleted the callback is called with a hash containing the database
		956	family and an arrayref with subkeys that have changed.
		957
		958	Specifically, if one of the passed subkeys exists in the $familyhash, then
		959	it is currently set to the value in the $familyhash. Otherwise, it has
		960	been deleted.
		961
		962	The first call will be with the current contents of the family and all
		963	keys, as if they were just added.
		964
		965	It is possible that the callback is called with a change event even though
		966	the subkey is already present and the value has not changed.
		967
		968	The monitoring stops when the guard object is destroyed.
		969
		970	Example: on every change to the family "mygroup", print out all keys.
		971
		972	my $guard = db_mon mygroup => sub {
		973	my ($family, $keys) = @_;
		974	print "mygroup members: ", (join " ", keys %$family), "\n";
		975	};
		976
		977	Exmaple: wait until the family "My::Module::workers" is non-empty.
		978
		979	my $guard; $guard = db_mon My::Module::workers => sub {
		980	my ($family, $keys) = @_;
		981	return unless %$family;
		982	undef $guard;
		983	print "My::Module::workers now nonempty\n";
		984	};
		985
		986	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		987
		988	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		989	my ($family, $keys) = @_;
		990
		991	for (@$keys) {
		992	print "$_: ",
		993	(exists $family->{$_}
		994	? $family->{$_}
		995	: "(deleted)"),
		996	"\n";
		997	}
		998	};
		999
		1000	=cut
		1001
691	=back	1002	=back
692		1003
693	=head1 AnyEvent::MP vs. Distributed Erlang	1004	=head1 AnyEvent::MP vs. Distributed Erlang
694		1005
695	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1006	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
696	== aemp node, Erlang process == aemp port), so many of the documents and	1007	== aemp node, Erlang process == aemp port), so many of the documents and
697	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1008	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
698	sample:	1009	sample:
699		1010
700	http://www.Erlang.se/doc/programming_rules.shtml	1011	http://www.erlang.se/doc/programming_rules.shtml
701	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1012	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
702	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1013	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
703	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1014	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
704		1015
705	Despite the similarities, there are also some important differences:	1016	Despite the similarities, there are also some important differences:
706		1017
707	=over 4	1018	=over 4
708		1019
709	=item * Node IDs are arbitrary strings in AEMP.	1020	=item * Node IDs are arbitrary strings in AEMP.
710		1021
711	Erlang relies on special naming and DNS to work everywhere in the same	1022	Erlang relies on special naming and DNS to work everywhere in the same
712	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1023	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
713	configuraiton or DNS), but will otherwise discover other odes itself.	1024	configuration or DNS), and possibly the addresses of some seed nodes, but
		1025	will otherwise discover other nodes (and their IDs) itself.
714		1026
715	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1027	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
716	uses "local ports are like remote ports".	1028	uses "local ports are like remote ports".
717		1029
718	The failure modes for local ports are quite different (runtime errors	1030	The failure modes for local ports are quite different (runtime errors
…		…
727	ports being the special case/exception, where transport errors cannot	1039	ports being the special case/exception, where transport errors cannot
728	occur.	1040	occur.
729		1041
730	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1042	=item * Erlang uses processes and a mailbox, AEMP does not queue.
731		1043
732	Erlang uses processes that selectively receive messages, and therefore	1044	Erlang uses processes that selectively receive messages out of order, and
733	needs a queue. AEMP is event based, queuing messages would serve no	1045	therefore needs a queue. AEMP is event based, queuing messages would serve
734	useful purpose. For the same reason the pattern-matching abilities of	1046	no useful purpose. For the same reason the pattern-matching abilities
735	AnyEvent::MP are more limited, as there is little need to be able to	1047	of AnyEvent::MP are more limited, as there is little need to be able to
736	filter messages without dequeing them.	1048	filter messages without dequeuing them.
737		1049
738	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1050	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1051	being event-based, while Erlang is process-based.
		1052
		1053	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1054	top of AEMP and Coro threads.
739		1055
740	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1056	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
741		1057
742	Sending messages in Erlang is synchronous and blocks the process (and	1058	Sending messages in Erlang is synchronous and blocks the process until
		1059	a conenction has been established and the message sent (and so does not
743	so does not need a queue that can overflow). AEMP sends are immediate,	1060	need a queue that can overflow). AEMP sends return immediately, connection
744	connection establishment is handled in the background.	1061	establishment is handled in the background.
745		1062
746	=item * Erlang suffers from silent message loss, AEMP does not.	1063	=item * Erlang suffers from silent message loss, AEMP does not.
747		1064
748	Erlang makes few guarantees on messages delivery - messages can get lost	1065	Erlang implements few guarantees on messages delivery - messages can get
749	without any of the processes realising it (i.e. you send messages a, b,	1066	lost without any of the processes realising it (i.e. you send messages a,
750	and c, and the other side only receives messages a and c).	1067	b, and c, and the other side only receives messages a and c).
751		1068
752	AEMP guarantees correct ordering, and the guarantee that after one message	1069	AEMP guarantees (modulo hardware errors) correct ordering, and the
753	is lost, all following ones sent to the same port are lost as well, until	1070	guarantee that after one message is lost, all following ones sent to the
754	monitoring raises an error, so there are no silent "holes" in the message	1071	same port are lost as well, until monitoring raises an error, so there are
755	sequence.	1072	no silent "holes" in the message sequence.
		1073
		1074	If you want your software to be very reliable, you have to cope with
		1075	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1076	simply tries to work better in common error cases, such as when a network
		1077	link goes down.
756		1078
757	=item * Erlang can send messages to the wrong port, AEMP does not.	1079	=item * Erlang can send messages to the wrong port, AEMP does not.
758		1080
759	In Erlang it is quite likely that a node that restarts reuses a process ID	1081	In Erlang it is quite likely that a node that restarts reuses an Erlang
760	known to other nodes for a completely different process, causing messages	1082	process ID known to other nodes for a completely different process,
761	destined for that process to end up in an unrelated process.	1083	causing messages destined for that process to end up in an unrelated
		1084	process.
762		1085
763	AEMP never reuses port IDs, so old messages or old port IDs floating	1086	AEMP does not reuse port IDs, so old messages or old port IDs floating
764	around in the network will not be sent to an unrelated port.	1087	around in the network will not be sent to an unrelated port.
765		1088
766	=item * Erlang uses unprotected connections, AEMP uses secure	1089	=item * Erlang uses unprotected connections, AEMP uses secure
767	authentication and can use TLS.	1090	authentication and can use TLS.
768		1091
…		…
771		1094
772	=item * The AEMP protocol is optimised for both text-based and binary	1095	=item * The AEMP protocol is optimised for both text-based and binary
773	communications.	1096	communications.
774		1097
775	The AEMP protocol, unlike the Erlang protocol, supports both programming	1098	The AEMP protocol, unlike the Erlang protocol, supports both programming
776	language independent text-only protocols (good for debugging) and binary,	1099	language independent text-only protocols (good for debugging), and binary,
777	language-specific serialisers (e.g. Storable). By default, unless TLS is	1100	language-specific serialisers (e.g. Storable). By default, unless TLS is
778	used, the protocol is actually completely text-based.	1101	used, the protocol is actually completely text-based.
779		1102
780	It has also been carefully designed to be implementable in other languages	1103	It has also been carefully designed to be implementable in other languages
781	with a minimum of work while gracefully degrading functionality to make the	1104	with a minimum of work while gracefully degrading functionality to make the
782	protocol simple.	1105	protocol simple.
783		1106
784	=item * AEMP has more flexible monitoring options than Erlang.	1107	=item * AEMP has more flexible monitoring options than Erlang.
785		1108
786	In Erlang, you can chose to receive I<all> exit signals as messages	1109	In Erlang, you can chose to receive I<all> exit signals as messages or
787	or I<none>, there is no in-between, so monitoring single processes is	1110	I<none>, there is no in-between, so monitoring single Erlang processes is
788	difficult to implement. Monitoring in AEMP is more flexible than in	1111	difficult to implement.
789	Erlang, as one can choose between automatic kill, exit message or callback	1112
790	on a per-process basis.	1113	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1114	between automatic kill, exit message or callback on a per-port basis.
791		1115
792	=item * Erlang tries to hide remote/local connections, AEMP does not.	1116	=item * Erlang tries to hide remote/local connections, AEMP does not.
793		1117
794	Monitoring in Erlang is not an indicator of process death/crashes, in the	1118	Monitoring in Erlang is not an indicator of process death/crashes, in the
795	same way as linking is (except linking is unreliable in Erlang).	1119	same way as linking is (except linking is unreliable in Erlang).
…		…
817	overhead, as well as having to keep a proxy object everywhere.	1141	overhead, as well as having to keep a proxy object everywhere.
818		1142
819	Strings can easily be printed, easily serialised etc. and need no special	1143	Strings can easily be printed, easily serialised etc. and need no special
820	procedures to be "valid".	1144	procedures to be "valid".
821		1145
822	And as a result, a miniport consists of a single closure stored in a	1146	And as a result, a port with just a default receiver consists of a single
823	global hash - it can't become much cheaper.	1147	code reference stored in a global hash - it can't become much cheaper.
824		1148
825	=item Why favour JSON, why not a real serialising format such as Storable?	1149	=item Why favour JSON, why not a real serialising format such as Storable?
826		1150
827	In fact, any AnyEvent::MP node will happily accept Storable as framing	1151	In fact, any AnyEvent::MP node will happily accept Storable as framing
828	format, but currently there is no way to make a node use Storable by	1152	format, but currently there is no way to make a node use Storable by
…		…
844		1168
845	L<AnyEvent::MP::Intro> - a gentle introduction.	1169	L<AnyEvent::MP::Intro> - a gentle introduction.
846		1170
847	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1171	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
848		1172
849	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1173	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
850	your applications.	1174	your applications.
		1175
		1176	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1177
		1178	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1179	all nodes.
851		1180
852	L<AnyEvent>.	1181	L<AnyEvent>.
853		1182
854	=head1 AUTHOR	1183	=head1 AUTHOR
855		1184

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.74 by root, Mon Aug 31 11:11:27 2009 UTC vs. Revision 1.128 by root, Sun Mar 4 14:28:44 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.74 by root, Mon Aug 31 11:11:27 2009 UTC vs.
Revision 1.128 by root, Sun Mar 4 14:28:44 2012 UTC