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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC vs.
Revision 1.134 by root, Mon Mar 12 14:47:23 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
30	rcv $port, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
31		31
32	# create a port on another node	32	# create a port on another node
33	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
34		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
35	# monitoring	39	# monitoring
36	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
38	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
39		51
40	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
41		53
42	bin/aemp - stable.	54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - explains most concepts.	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - stable API, protocol not yet final.	58	AnyEvent::MP::Global - stable API.
47
48	stay tuned.
49		59
50	=head1 DESCRIPTION	60	=head1 DESCRIPTION
51		61
52	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
53		63
…		…
61		71
62	=over 4	72	=over 4
63		73
64	=item port	74	=item port
65		75
66	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).
67		78
68	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
69	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
70	anything was listening for them or not.	81	anything was listening for them or not.
71		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
72	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
73		86
74	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<#>)
75	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).
76		90
77	=item node	91	=item node
78		92
79	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,
80	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
81	ports.	95	ports.
82		96
83	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
84	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
85	currently.	99	currently, but all nodes can talk to public nodes.
86		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
87	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
88		104
89	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
90	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
91	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
92	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
93		109
94	=item binds - C<ip:port>	110	=item binds - C<ip:port>
95		111
96	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
97	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
98	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
99	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.
100		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
101	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
102		150
103	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
104	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.
105	network. This node is called a seed.
106		153
107	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=item global nodes
108	are expected to be long-running, and at least one of those should always
109	be available. When nodes run out of connections (e.g. due to a network
110	error), they try to re-establish connections to some seednodes again to
111	join the network.
112		155
113	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
114	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).
115		170
116	=back	171	=back
117		172
118	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
119		174
…		…
121		176
122	=cut	177	=cut
123		178
124	package AnyEvent::MP;	179	package AnyEvent::MP;
125		180
		181	use AnyEvent::MP::Config ();
126	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
127		184
128	use common::sense;	185	use common::sense;
129		186
130	use Carp ();	187	use Carp ();
131		188
132	use AE ();	189	use AE ();
		190	use Guard ();
133		191
134	use base "Exporter";	192	use base "Exporter";
135		193
136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
137		195
138	our @EXPORT = qw(	196	our @EXPORT = qw(
139	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
140	configure	198	configure
141	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
142	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
143	);	203	);
144		204
145	our $SELF;	205	our $SELF;
146		206
147	sub _self_die() {	207	sub _self_die() {
…		…
158		218
159	=item $nodeid = node_of $port	219	=item $nodeid = node_of $port
160		220
161	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.
162		222
		223	=item configure $profile, key => value...
		224
163	=item configure key => value...	225	=item configure key => value...
164		226
165	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
166	"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
167	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
168	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
169		231
170	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
171	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
172		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
173	=over 4	262	=over 4
174		263
175	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
176		265
177	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
178	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
179	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
180	-n>) will be used as profile name.	269	missing, then the nodename (F<uname -n>) will be used as profile name.
181		270
182	The profile data is then gathered as follows:	271	The profile data is then gathered as follows:
183		272
184	First, all remaining key => value pairs (all of which are conveniently	273	First, all remaining key => value pairs (all of which are conveniently
185	undocumented at the moment) will be interpreted as configuration	274	undocumented at the moment) will be interpreted as configuration
…		…
190	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
191	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
192	and can only be used to specify defaults.	281	and can only be used to specify defaults.
193		282
194	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
195	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
196	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>.
197		292
198	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
199		294
200	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
201	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
…		…
207	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
208	local IP address it finds.	303	local IP address it finds.
209		304
210	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
211		306
212	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
213	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
214	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
215		310
216	=back	311	=back
217		312
218	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.
219	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.
220		315
221	configure	316	configure
222		317
223	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
224	clients.	319	commandline clients.
225		320
226	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
227		322
228	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
229	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,
230	customary for aemp).	325	customary for aemp).
231		326
232	# use the aemp commandline utility	327	# use the aemp commandline utility
233	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
234		329
235	# then use it	330	# then use it
236	configure profile => "seed";	331	configure profile => "seed";
237		332
238	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
303		398
304	=cut	399	=cut
305		400
306	sub rcv($@);	401	sub rcv($@);
307		402
308	sub _kilme {	403	my $KILME = sub {
309	die "received message on port without callback";	404	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
310	}	405	kil $SELF, unhandled_message => "missing (tag or fallback) callback for message '$tag'";
		406	};
311		407
312	sub port(;&) {	408	sub port(;&) {
313	my $id = "$UNIQ." . $ID++;	409	my $id = $UNIQ . ++$ID;
314	my $port = "$NODE#$id";	410	my $port = "$NODE#$id";
315		411
316	rcv $port, shift \|\| \&_kilme;	412	rcv $port, shift \|\| $KILME;
317		413
318	$port	414	$port
319	}	415	}
320		416
321	=item rcv $local_port, $callback->(@msg)	417	=item rcv $local_port, $callback->(@msg)
…		…
326		422
327	The global C<$SELF> (exported by this module) contains C<$port> while	423	The global C<$SELF> (exported by this module) contains C<$port> while
328	executing the callback. Runtime errors during callback execution will	424	executing the callback. Runtime errors during callback execution will
329	result in the port being C<kil>ed.	425	result in the port being C<kil>ed.
330		426
331	The default callback received all messages not matched by a more specific	427	The default callback receives all messages not matched by a more specific
332	C<tag> match.	428	C<tag> match.
333		429
334	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	430	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
335		431
336	Register (or replace) callbacks to be called on messages starting with the	432	Register (or replace) callbacks to be called on messages starting with the
…		…
357	msg1 => sub { ... },	453	msg1 => sub { ... },
358	...	454	...
359	;	455	;
360		456
361	Example: temporarily register a rcv callback for a tag matching some port	457	Example: temporarily register a rcv callback for a tag matching some port
362	(e.g. for a rpc reply) and unregister it after a message was received.	458	(e.g. for an rpc reply) and unregister it after a message was received.
363		459
364	rcv $port, $otherport => sub {	460	rcv $port, $otherport => sub {
365	my @reply = @_;	461	my @reply = @_;
366		462
367	rcv $SELF, $otherport;	463	rcv $SELF, $otherport;
…		…
380	if (ref $_[0]) {	476	if (ref $_[0]) {
381	if (my $self = $PORT_DATA{$portid}) {	477	if (my $self = $PORT_DATA{$portid}) {
382	"AnyEvent::MP::Port" eq ref $self	478	"AnyEvent::MP::Port" eq ref $self
383	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	479	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
384		480
385	$self->[2] = shift;	481	$self->[0] = shift;
386	} else {	482	} else {
387	my $cb = shift;	483	my $cb = shift;
388	$PORT{$portid} = sub {	484	$PORT{$portid} = sub {
389	local $SELF = $port;	485	local $SELF = $port;
390	eval { &$cb }; _self_die if $@;	486	eval { &$cb }; _self_die if $@;
391	};	487	};
392	}	488	}
393	} elsif (defined $_[0]) {	489	} elsif (defined $_[0]) {
394	my $self = $PORT_DATA{$portid} \|\|= do {	490	my $self = $PORT_DATA{$portid} \|\|= do {
395	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	491	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
396		492
397	$PORT{$portid} = sub {	493	$PORT{$portid} = sub {
398	local $SELF = $port;	494	local $SELF = $port;
399		495
400	if (my $cb = $self->[1]{$_[0]}) {	496	if (my $cb = $self->[1]{$_[0]}) {
…		…
422	}	518	}
423		519
424	$port	520	$port
425	}	521	}
426		522
		523	=item peval $port, $coderef[, @args]
		524
		525	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		526	when the code throews an exception the C<$port> will be killed.
		527
		528	Any remaining args will be passed to the callback. Any return values will
		529	be returned to the caller.
		530
		531	This is useful when you temporarily want to execute code in the context of
		532	a port.
		533
		534	Example: create a port and run some initialisation code in it's context.
		535
		536	my $port = port { ... };
		537
		538	peval $port, sub {
		539	init
		540	or die "unable to init";
		541	};
		542
		543	=cut
		544
		545	sub peval($$) {
		546	local $SELF = shift;
		547	my $cb = shift;
		548
		549	if (wantarray) {
		550	my @res = eval { &$cb };
		551	_self_die if $@;
		552	@res
		553	} else {
		554	my $res = eval { &$cb };
		555	_self_die if $@;
		556	$res
		557	}
		558	}
		559
427	=item $closure = psub { BLOCK }	560	=item $closure = psub { BLOCK }
428		561
429	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	562	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
430	closure is executed, sets up the environment in the same way as in C<rcv>	563	closure is executed, sets up the environment in the same way as in C<rcv>
431	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	564	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		565
		566	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		567	BLOCK }, @_ } >>.
432		568
433	This is useful when you register callbacks from C<rcv> callbacks:	569	This is useful when you register callbacks from C<rcv> callbacks:
434		570
435	rcv delayed_reply => sub {	571	rcv delayed_reply => sub {
436	my ($delay, @reply) = @_;	572	my ($delay, @reply) = @_;
…		…
472		608
473	Monitor the given port and do something when the port is killed or	609	Monitor the given port and do something when the port is killed or
474	messages to it were lost, and optionally return a guard that can be used	610	messages to it were lost, and optionally return a guard that can be used
475	to stop monitoring again.	611	to stop monitoring again.
476		612
		613	In the first form (callback), the callback is simply called with any
		614	number of C<@reason> elements (no @reason means that the port was deleted
		615	"normally"). Note also that I<< the callback B<must> never die >>, so use
		616	C<eval> if unsure.
		617
		618	In the second form (another port given), the other port (C<$rcvport>)
		619	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		620	"normal" kils nothing happens, while under all other conditions, the other
		621	port is killed with the same reason.
		622
		623	The third form (kill self) is the same as the second form, except that
		624	C<$rvport> defaults to C<$SELF>.
		625
		626	In the last form (message), a message of the form C<@msg, @reason> will be
		627	C<snd>.
		628
		629	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		630	alert was raised), they are removed and will not trigger again.
		631
		632	As a rule of thumb, monitoring requests should always monitor a port from
		633	a local port (or callback). The reason is that kill messages might get
		634	lost, just like any other message. Another less obvious reason is that
		635	even monitoring requests can get lost (for example, when the connection
		636	to the other node goes down permanently). When monitoring a port locally
		637	these problems do not exist.
		638
477	C<mon> effectively guarantees that, in the absence of hardware failures,	639	C<mon> effectively guarantees that, in the absence of hardware failures,
478	after starting the monitor, either all messages sent to the port will	640	after starting the monitor, either all messages sent to the port will
479	arrive, or the monitoring action will be invoked after possible message	641	arrive, or the monitoring action will be invoked after possible message
480	loss has been detected. No messages will be lost "in between" (after	642	loss has been detected. No messages will be lost "in between" (after
481	the first lost message no further messages will be received by the	643	the first lost message no further messages will be received by the
482	port). After the monitoring action was invoked, further messages might get	644	port). After the monitoring action was invoked, further messages might get
483	delivered again.	645	delivered again.
484		646
485	Note that monitoring-actions are one-shot: once messages are lost (and a	647	Inter-host-connection timeouts and monitoring depend on the transport
486	monitoring alert was raised), they are removed and will not trigger again.	648	used. The only transport currently implemented is TCP, and AnyEvent::MP
		649	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		650	non-idle connection, and usually around two hours for idle connections).
487		651
488	In the first form (callback), the callback is simply called with any	652	This means that monitoring is good for program errors and cleaning up
489	number of C<@reason> elements (no @reason means that the port was deleted	653	stuff eventually, but they are no replacement for a timeout when you need
490	"normally"). Note also that I<< the callback B<must> never die >>, so use	654	to ensure some maximum latency.
491	C<eval> if unsure.
492
493	In the second form (another port given), the other port (C<$rcvport>)
494	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
495	"normal" kils nothing happens, while under all other conditions, the other
496	port is killed with the same reason.
497
498	The third form (kill self) is the same as the second form, except that
499	C<$rvport> defaults to C<$SELF>.
500
501	In the last form (message), a message of the form C<@msg, @reason> will be
502	C<snd>.
503
504	As a rule of thumb, monitoring requests should always monitor a port from
505	a local port (or callback). The reason is that kill messages might get
506	lost, just like any other message. Another less obvious reason is that
507	even monitoring requests can get lost (for example, when the connection
508	to the other node goes down permanently). When monitoring a port locally
509	these problems do not exist.
510		655
511	Example: call a given callback when C<$port> is killed.	656	Example: call a given callback when C<$port> is killed.
512		657
513	mon $port, sub { warn "port died because of <@_>\n" };	658	mon $port, sub { warn "port died because of <@_>\n" };
514		659
…		…
542	}	687	}
543		688
544	$node->monitor ($port, $cb);	689	$node->monitor ($port, $cb);
545		690
546	defined wantarray	691	defined wantarray
547	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	692	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
548	}	693	}
549		694
550	=item $guard = mon_guard $port, $ref, $ref...	695	=item $guard = mon_guard $port, $ref, $ref...
551		696
552	Monitors the given C<$port> and keeps the passed references. When the port	697	Monitors the given C<$port> and keeps the passed references. When the port
…		…
575		720
576	=item kil $port[, @reason]	721	=item kil $port[, @reason]
577		722
578	Kill the specified port with the given C<@reason>.	723	Kill the specified port with the given C<@reason>.
579		724
580	If no C<@reason> is specified, then the port is killed "normally" (ports	725	If no C<@reason> is specified, then the port is killed "normally" -
581	monitoring other ports will not necessarily die because a port dies	726	monitor callback will be invoked, but the kil will not cause linked ports
582	"normally").	727	(C<mon $mport, $lport> form) to get killed.
583		728
584	Otherwise, linked ports get killed with the same reason (second form of	729	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
585	C<mon>, see above).	730	form) get killed with the same reason.
586		731
587	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	732	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
588	will be reported as reason C<< die => $@ >>.	733	will be reported as reason C<< die => $@ >>.
589		734
590	Transport/communication errors are reported as C<< transport_error =>	735	Transport/communication errors are reported as C<< transport_error =>
591	$message >>.	736	$message >>.
592		737
593	=cut	738	Common idioms:
		739
		740	# silently remove yourself, do not kill linked ports
		741	kil $SELF;
		742
		743	# report a failure in some detail
		744	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		745
		746	# do not waste much time with killing, just die when something goes wrong
		747	open my $fh, "<file"
		748	or die "file: $!";
594		749
595	=item $port = spawn $node, $initfunc[, @initdata]	750	=item $port = spawn $node, $initfunc[, @initdata]
596		751
597	Creates a port on the node C<$node> (which can also be a port ID, in which	752	Creates a port on the node C<$node> (which can also be a port ID, in which
598	case it's the node where that port resides).	753	case it's the node where that port resides).
…		…
609	the package, then the package above the package and so on (e.g.	764	the package, then the package above the package and so on (e.g.
610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	765	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
611	exists or it runs out of package names.	766	exists or it runs out of package names.
612		767
613	The init function is then called with the newly-created port as context	768	The init function is then called with the newly-created port as context
614	object (C<$SELF>) and the C<@initdata> values as arguments.	769	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		770	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		771	the port might not get created.
615		772
616	A common idiom is to pass a local port, immediately monitor the spawned	773	A common idiom is to pass a local port, immediately monitor the spawned
617	port, and in the remote init function, immediately monitor the passed	774	port, and in the remote init function, immediately monitor the passed
618	local port. This two-way monitoring ensures that both ports get cleaned up	775	local port. This two-way monitoring ensures that both ports get cleaned up
619	when there is a problem.	776	when there is a problem.
620		777
		778	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		779	caller before C<spawn> returns (by delaying invocation when spawn is
		780	called for the local node).
		781
621	Example: spawn a chat server port on C<$othernode>.	782	Example: spawn a chat server port on C<$othernode>.
622		783
623	# this node, executed from within a port context:	784	# this node, executed from within a port context:
624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	785	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
625	mon $server;	786	mon $server;
…		…
639		800
640	sub _spawn {	801	sub _spawn {
641	my $port = shift;	802	my $port = shift;
642	my $init = shift;	803	my $init = shift;
643		804
		805	# rcv will create the actual port
644	local $SELF = "$NODE#$port";	806	local $SELF = "$NODE#$port";
645	eval {	807	eval {
646	&{ load_func $init }	808	&{ load_func $init }
647	};	809	};
648	_self_die if $@;	810	_self_die if $@;
649	}	811	}
650		812
651	sub spawn(@) {	813	sub spawn(@) {
652	my ($nodeid, undef) = split /#/, shift, 2;	814	my ($nodeid, undef) = split /#/, shift, 2;
653		815
654	my $id = "$RUNIQ." . $ID++;	816	my $id = $RUNIQ . ++$ID;
655		817
656	$_[0] =~ /::/	818	$_[0] =~ /::/
657	or Carp::croak "spawn init function must be a fully-qualified name, caught";	819	or Carp::croak "spawn init function must be a fully-qualified name, caught";
658		820
659	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	821	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
660		822
661	"$nodeid#$id"	823	"$nodeid#$id"
662	}	824	}
		825
663		826
664	=item after $timeout, @msg	827	=item after $timeout, @msg
665		828
666	=item after $timeout, $callback	829	=item after $timeout, $callback
667		830
…		…
683	? $action[0]()	846	? $action[0]()
684	: snd @action;	847	: snd @action;
685	};	848	};
686	}	849	}
687		850
		851	#=item $cb2 = timeout $seconds, $cb[, @args]
		852
		853	=item cal $port, @msg, $callback[, $timeout]
		854
		855	A simple form of RPC - sends a message to the given C<$port> with the
		856	given contents (C<@msg>), but adds a reply port to the message.
		857
		858	The reply port is created temporarily just for the purpose of receiving
		859	the reply, and will be C<kil>ed when no longer needed.
		860
		861	A reply message sent to the port is passed to the C<$callback> as-is.
		862
		863	If an optional time-out (in seconds) is given and it is not C<undef>,
		864	then the callback will be called without any arguments after the time-out
		865	elapsed and the port is C<kil>ed.
		866
		867	If no time-out is given (or it is C<undef>), then the local port will
		868	monitor the remote port instead, so it eventually gets cleaned-up.
		869
		870	Currently this function returns the temporary port, but this "feature"
		871	might go in future versions unless you can make a convincing case that
		872	this is indeed useful for something.
		873
		874	=cut
		875
		876	sub cal(@) {
		877	my $timeout = ref $_[-1] ? undef : pop;
		878	my $cb = pop;
		879
		880	my $port = port {
		881	undef $timeout;
		882	kil $SELF;
		883	&$cb;
		884	};
		885
		886	if (defined $timeout) {
		887	$timeout = AE::timer $timeout, 0, sub {
		888	undef $timeout;
		889	kil $port;
		890	$cb->();
		891	};
		892	} else {
		893	mon $_[0], sub {
		894	kil $port;
		895	$cb->();
		896	};
		897	}
		898
		899	push @_, $port;
		900	&snd;
		901
		902	$port
		903	}
		904
		905	=back
		906
		907	=head1 DISTRIBUTED DATABASE
		908
		909	AnyEvent::MP comes with a simple distributed database. The database will
		910	be mirrored asynchronously on all global nodes. Other nodes bind to one
		911	of the global nodes for their needs. Every node has a "local database"
		912	which contains all the values that are set locally. All local databases
		913	are merged together to form the global database, which can be queried.
		914
		915	The database structure is that of a two-level hash - the database hash
		916	contains hashes which contain values, similarly to a perl hash of hashes,
		917	i.e.:
		918
		919	$DATABASE{$family}{$subkey} = $value
		920
		921	The top level hash key is called "family", and the second-level hash key
		922	is called "subkey" or simply "key".
		923
		924	The family must be alphanumeric, i.e. start with a letter and consist
		925	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		926	pretty much like Perl module names.
		927
		928	As the family namespace is global, it is recommended to prefix family names
		929	with the name of the application or module using it.
		930
		931	The subkeys must be non-empty strings, with no further restrictions.
		932
		933	The values should preferably be strings, but other perl scalars should
		934	work as well (such as C<undef>, arrays and hashes).
		935
		936	Every database entry is owned by one node - adding the same family/subkey
		937	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		938	but the result might be nondeterministic, i.e. the key might have
		939	different values on different nodes.
		940
		941	Different subkeys in the same family can be owned by different nodes
		942	without problems, and in fact, this is the common method to create worker
		943	pools. For example, a worker port for image scaling might do this:
		944
		945	db_set my_image_scalers => $port;
		946
		947	And clients looking for an image scaler will want to get the
		948	C<my_image_scalers> keys from time to time:
		949
		950	db_keys my_image_scalers => sub {
		951	@ports = @{ $_[0] };
		952	};
		953
		954	Or better yet, they want to monitor the database family, so they always
		955	have a reasonable up-to-date copy:
		956
		957	db_mon my_image_scalers => sub {
		958	@ports = keys %{ $_[0] };
		959	};
		960
		961	In general, you can set or delete single subkeys, but query and monitor
		962	whole families only.
		963
		964	If you feel the need to monitor or query a single subkey, try giving it
		965	it's own family.
		966
		967	=over
		968
		969	=item db_set $family => $subkey [=> $value]
		970
		971	Sets (or replaces) a key to the database - if C<$value> is omitted,
		972	C<undef> is used instead.
		973
		974	=item db_del $family => $subkey...
		975
		976	Deletes one or more subkeys from the database family.
		977
		978	=item $guard = db_reg $family => $subkey [=> $value]
		979
		980	Sets the key on the database and returns a guard. When the guard is
		981	destroyed, the key is deleted from the database. If C<$value> is missing,
		982	then C<undef> is used.
		983
		984	=item db_family $family => $cb->(\%familyhash)
		985
		986	Queries the named database C<$family> and call the callback with the
		987	family represented as a hash. You can keep and freely modify the hash.
		988
		989	=item db_keys $family => $cb->(\@keys)
		990
		991	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		992	them as array reference to the callback.
		993
		994	=item db_values $family => $cb->(\@values)
		995
		996	Same as C<db_family>, except it only queries the family I<values> and passes them
		997	as array reference to the callback.
		998
		999	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1000
		1001	Creates a monitor on the given database family. Each time a key is set
		1002	or or is deleted the callback is called with a hash containing the
		1003	database family and three lists of added, changed and deleted subkeys,
		1004	respectively. If no keys have changed then the array reference might be
		1005	C<undef> or even missing.
		1006
		1007	If not called in void context, a guard object is returned that, when
		1008	destroyed, stops the monitor.
		1009
		1010	The family hash reference and the key arrays belong to AnyEvent::MP and
		1011	B<must not be modified or stored> by the callback. When in doubt, make a
		1012	copy.
		1013
		1014	As soon as possible after the monitoring starts, the callback will be
		1015	called with the intiial contents of the family, even if it is empty,
		1016	i.e. there will always be a timely call to the callback with the current
		1017	contents.
		1018
		1019	It is possible that the callback is called with a change event even though
		1020	the subkey is already present and the value has not changed.
		1021
		1022	The monitoring stops when the guard object is destroyed.
		1023
		1024	Example: on every change to the family "mygroup", print out all keys.
		1025
		1026	my $guard = db_mon mygroup => sub {
		1027	my ($family, $a, $c, $d) = @_;
		1028	print "mygroup members: ", (join " ", keys %$family), "\n";
		1029	};
		1030
		1031	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1032
		1033	my $guard; $guard = db_mon My::Module::workers => sub {
		1034	my ($family, $a, $c, $d) = @_;
		1035	return unless %$family;
		1036	undef $guard;
		1037	print "My::Module::workers now nonempty\n";
		1038	};
		1039
		1040	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1041
		1042	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1043	my ($family, $a, $c, $d) = @_;
		1044
		1045	print "+$_=$family->{$_}\n" for @$a;
		1046	print "*$_=$family->{$_}\n" for @$c;
		1047	print "-$_=$family->{$_}\n" for @$d;
		1048	};
		1049
		1050	=cut
		1051
688	=back	1052	=back
689		1053
690	=head1 AnyEvent::MP vs. Distributed Erlang	1054	=head1 AnyEvent::MP vs. Distributed Erlang
691		1055
692	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1056	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
693	== aemp node, Erlang process == aemp port), so many of the documents and	1057	== aemp node, Erlang process == aemp port), so many of the documents and
694	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1058	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
695	sample:	1059	sample:
696		1060
697	http://www.Erlang.se/doc/programming_rules.shtml	1061	http://www.erlang.se/doc/programming_rules.shtml
698	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1062	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
699	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1063	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
700	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1064	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
701		1065
702	Despite the similarities, there are also some important differences:	1066	Despite the similarities, there are also some important differences:
703		1067
704	=over 4	1068	=over 4
705		1069
706	=item * Node IDs are arbitrary strings in AEMP.	1070	=item * Node IDs are arbitrary strings in AEMP.
707		1071
708	Erlang relies on special naming and DNS to work everywhere in the same	1072	Erlang relies on special naming and DNS to work everywhere in the same
709	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1073	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
710	configuration or DNS), but will otherwise discover other odes itself.	1074	configuration or DNS), and possibly the addresses of some seed nodes, but
		1075	will otherwise discover other nodes (and their IDs) itself.
711		1076
712	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1077	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
713	uses "local ports are like remote ports".	1078	uses "local ports are like remote ports".
714		1079
715	The failure modes for local ports are quite different (runtime errors	1080	The failure modes for local ports are quite different (runtime errors
…		…
724	ports being the special case/exception, where transport errors cannot	1089	ports being the special case/exception, where transport errors cannot
725	occur.	1090	occur.
726		1091
727	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1092	=item * Erlang uses processes and a mailbox, AEMP does not queue.
728		1093
729	Erlang uses processes that selectively receive messages, and therefore	1094	Erlang uses processes that selectively receive messages out of order, and
730	needs a queue. AEMP is event based, queuing messages would serve no	1095	therefore needs a queue. AEMP is event based, queuing messages would serve
731	useful purpose. For the same reason the pattern-matching abilities of	1096	no useful purpose. For the same reason the pattern-matching abilities
732	AnyEvent::MP are more limited, as there is little need to be able to	1097	of AnyEvent::MP are more limited, as there is little need to be able to
733	filter messages without dequeuing them.	1098	filter messages without dequeuing them.
734		1099
735	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1100	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1101	being event-based, while Erlang is process-based.
		1102
		1103	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1104	top of AEMP and Coro threads.
736		1105
737	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1106	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
738		1107
739	Sending messages in Erlang is synchronous and blocks the process (and	1108	Sending messages in Erlang is synchronous and blocks the process until
		1109	a conenction has been established and the message sent (and so does not
740	so does not need a queue that can overflow). AEMP sends are immediate,	1110	need a queue that can overflow). AEMP sends return immediately, connection
741	connection establishment is handled in the background.	1111	establishment is handled in the background.
742		1112
743	=item * Erlang suffers from silent message loss, AEMP does not.	1113	=item * Erlang suffers from silent message loss, AEMP does not.
744		1114
745	Erlang makes few guarantees on messages delivery - messages can get lost	1115	Erlang implements few guarantees on messages delivery - messages can get
746	without any of the processes realising it (i.e. you send messages a, b,	1116	lost without any of the processes realising it (i.e. you send messages a,
747	and c, and the other side only receives messages a and c).	1117	b, and c, and the other side only receives messages a and c).
748		1118
749	AEMP guarantees correct ordering, and the guarantee that after one message	1119	AEMP guarantees (modulo hardware errors) correct ordering, and the
750	is lost, all following ones sent to the same port are lost as well, until	1120	guarantee that after one message is lost, all following ones sent to the
751	monitoring raises an error, so there are no silent "holes" in the message	1121	same port are lost as well, until monitoring raises an error, so there are
752	sequence.	1122	no silent "holes" in the message sequence.
		1123
		1124	If you want your software to be very reliable, you have to cope with
		1125	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1126	simply tries to work better in common error cases, such as when a network
		1127	link goes down.
753		1128
754	=item * Erlang can send messages to the wrong port, AEMP does not.	1129	=item * Erlang can send messages to the wrong port, AEMP does not.
755		1130
756	In Erlang it is quite likely that a node that restarts reuses a process ID	1131	In Erlang it is quite likely that a node that restarts reuses an Erlang
757	known to other nodes for a completely different process, causing messages	1132	process ID known to other nodes for a completely different process,
758	destined for that process to end up in an unrelated process.	1133	causing messages destined for that process to end up in an unrelated
		1134	process.
759		1135
760	AEMP never reuses port IDs, so old messages or old port IDs floating	1136	AEMP does not reuse port IDs, so old messages or old port IDs floating
761	around in the network will not be sent to an unrelated port.	1137	around in the network will not be sent to an unrelated port.
762		1138
763	=item * Erlang uses unprotected connections, AEMP uses secure	1139	=item * Erlang uses unprotected connections, AEMP uses secure
764	authentication and can use TLS.	1140	authentication and can use TLS.
765		1141
…		…
768		1144
769	=item * The AEMP protocol is optimised for both text-based and binary	1145	=item * The AEMP protocol is optimised for both text-based and binary
770	communications.	1146	communications.
771		1147
772	The AEMP protocol, unlike the Erlang protocol, supports both programming	1148	The AEMP protocol, unlike the Erlang protocol, supports both programming
773	language independent text-only protocols (good for debugging) and binary,	1149	language independent text-only protocols (good for debugging), and binary,
774	language-specific serialisers (e.g. Storable). By default, unless TLS is	1150	language-specific serialisers (e.g. Storable). By default, unless TLS is
775	used, the protocol is actually completely text-based.	1151	used, the protocol is actually completely text-based.
776		1152
777	It has also been carefully designed to be implementable in other languages	1153	It has also been carefully designed to be implementable in other languages
778	with a minimum of work while gracefully degrading functionality to make the	1154	with a minimum of work while gracefully degrading functionality to make the
779	protocol simple.	1155	protocol simple.
780		1156
781	=item * AEMP has more flexible monitoring options than Erlang.	1157	=item * AEMP has more flexible monitoring options than Erlang.
782		1158
783	In Erlang, you can chose to receive I<all> exit signals as messages	1159	In Erlang, you can chose to receive I<all> exit signals as messages or
784	or I<none>, there is no in-between, so monitoring single processes is	1160	I<none>, there is no in-between, so monitoring single Erlang processes is
785	difficult to implement. Monitoring in AEMP is more flexible than in	1161	difficult to implement.
786	Erlang, as one can choose between automatic kill, exit message or callback	1162
787	on a per-process basis.	1163	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1164	between automatic kill, exit message or callback on a per-port basis.
788		1165
789	=item * Erlang tries to hide remote/local connections, AEMP does not.	1166	=item * Erlang tries to hide remote/local connections, AEMP does not.
790		1167
791	Monitoring in Erlang is not an indicator of process death/crashes, in the	1168	Monitoring in Erlang is not an indicator of process death/crashes, in the
792	same way as linking is (except linking is unreliable in Erlang).	1169	same way as linking is (except linking is unreliable in Erlang).
…		…
814	overhead, as well as having to keep a proxy object everywhere.	1191	overhead, as well as having to keep a proxy object everywhere.
815		1192
816	Strings can easily be printed, easily serialised etc. and need no special	1193	Strings can easily be printed, easily serialised etc. and need no special
817	procedures to be "valid".	1194	procedures to be "valid".
818		1195
819	And as a result, a miniport consists of a single closure stored in a	1196	And as a result, a port with just a default receiver consists of a single
820	global hash - it can't become much cheaper.	1197	code reference stored in a global hash - it can't become much cheaper.
821		1198
822	=item Why favour JSON, why not a real serialising format such as Storable?	1199	=item Why favour JSON, why not a real serialising format such as Storable?
823		1200
824	In fact, any AnyEvent::MP node will happily accept Storable as framing	1201	In fact, any AnyEvent::MP node will happily accept Storable as framing
825	format, but currently there is no way to make a node use Storable by	1202	format, but currently there is no way to make a node use Storable by
…		…
841		1218
842	L<AnyEvent::MP::Intro> - a gentle introduction.	1219	L<AnyEvent::MP::Intro> - a gentle introduction.
843		1220
844	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1221	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
845		1222
846	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1223	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
847	your applications.	1224	your applications.
		1225
		1226	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1227
		1228	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1229	all nodes.
848		1230
849	L<AnyEvent>.	1231	L<AnyEvent>.
850		1232
851	=head1 AUTHOR	1233	=head1 AUTHOR
852		1234

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC vs. Revision 1.134 by root, Mon Mar 12 14:47:23 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC vs.
Revision 1.134 by root, Mon Mar 12 14:47:23 2012 UTC