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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.116 by root, Mon Jun 21 15:09:34 2010 UTC vs.
Revision 1.139 by root, Thu Mar 22 20:07:31 2012 UTC

…		…
35	# destroy a port again	35	# destroy a port again
36	kil $port; # "normal" kill	36	kil $port; # "normal" kill
37	kil $port, my_error => "everything is broken"; # error kill	37	kil $port, my_error => "everything is broken"; # error kill
38		38
39	# monitoring	39	# monitoring
40	mon $localport, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
41	mon $localport, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
42	mon $localport, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
43		43
44	# temporarily execute code in port context	44	# temporarily execute code in port context
45	peval $port, sub { die "kill the port!" };	45	peval $port, sub { die "kill the port!" };
46		46
47	# execute callbacks in $SELF port context	47	# execute callbacks in $SELF port context
…		…
78		78
79	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
80	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
81	anything was listening for them or not.	81	anything was listening for them or not.
82		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
83	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
84		86
85	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<#>)
86	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).
87		90
88	=item node	91	=item node
89		92
90	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,
91	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
92	ports.	95	ports.
93		96
94	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
95	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
96	currently.	99	currently, but all nodes can talk to public nodes.
97		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
99		104
100	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
101	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
102	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
103	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
104		109
105	=item binds - C<ip:port>	110	=item binds - C<ip:port>
106		111
107	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
108	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
109	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
110	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.
111		119
112	=item seed nodes	120	=item seed nodes
113		121
114	When a node starts, it knows nothing about the network. To teach the node	122	When a node starts, it knows nothing about the network it is in - it
115	about the network it first has to contact some other node within the	123	needs to connect to at least one other node that is already in the
116	network. This node is called a seed.	124	network. These other nodes are called "seed nodes".
117		125
118	Apart from the fact that other nodes know them as seed nodes and they have	126	Seed nodes themselves are not special - they are seed nodes only because
119	to have fixed listening addresses, seed nodes are perfectly normal nodes -	127	some other node I<uses> them as such, but any node can be used as seed
120	any node can function as a seed node for others.	128	node for other nodes, and eahc node cna use a different set of seed nodes.
121		129
122	In addition to discovering the network, seed nodes are also used to	130	In addition to discovering the network, seed nodes are also used to
123	maintain the network and to connect nodes that otherwise would have	131	maintain the network - all nodes using the same seed node form are part of
124	trouble connecting. They form the backbone of an AnyEvent::MP network.	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.
125		135
126	Seed nodes are expected to be long-running, and at least one seed node	136	Seed nodes are expected to be long-running, and at least one seed node
127	should always be available. They should also be relatively responsive - a	137	should always be available. They should also be relatively responsive - a
128	seed node that blocks for long periods will slow down everybody else.	138	seed node that blocks for long periods will slow down everybody else.
129		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
130	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
131		150
132	Seeds are transport endpoint(s) (usually a hostname/IP address and a	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
133	TCP port) of nodes that should be used as seed nodes.	152	TCP port) of nodes that should be used as seed nodes.
134		153
135	The nodes listening on those endpoints are expected to be long-running,	154	=item global nodes
136	and at least one of those should always be available. When nodes run out	155
137	of connections (e.g. due to a network error), they try to re-establish	156	An AEMP network needs a discovery service - nodes need to know how to
138	connections to some seednodes again to join the network.	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).
139		170
140	=back	171	=back
141		172
142	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
143		174
…		…
145		176
146	=cut	177	=cut
147		178
148	package AnyEvent::MP;	179	package AnyEvent::MP;
149		180
		181	use AnyEvent::MP::Config ();
150	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
151		184
152	use common::sense;	185	use common::sense;
153		186
154	use Carp ();	187	use Carp ();
155		188
156	use AE ();	189	use AE ();
		190	use Guard ();
157		191
158	use base "Exporter";	192	use base "Exporter";
159		193
160	our $VERSION = 1.29;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
161		195
162	our @EXPORT = qw(	196	our @EXPORT = qw(
163	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
164	configure	198	configure
165	snd rcv mon mon_guard kil psub peval spawn cal	199	snd rcv mon mon_guard kil psub peval spawn cal
166	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
167	);	203	);
168		204
169	our $SELF;	205	our $SELF;
170		206
171	sub _self_die() {	207	sub _self_die() {
…		…
191	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
192	"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
193	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
194	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
195		231
196	The key/value pairs are basically the same ones as documented for the
197	F<aemp> command line utility (sans the set/del prefix).
198
199	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
200	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
		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 => $pass->(@msg)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every code execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	Most of the time the callback should look only at
		259	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		260	actual message (which can be about anything, and is mostly provided for
		261	diagnostic purposes).
		262
		263	See F<semp setsecure> for more info.
		264
		265	=back
201		266
202	=over 4	267	=over 4
203		268
204	=item step 1, gathering configuration from profiles	269	=item step 1, gathering configuration from profiles
205		270
…		…
219	That means that the values specified in the profile have highest priority	284	That means that the values specified in the profile have highest priority
220	and the values specified directly via C<configure> have lowest priority,	285	and the values specified directly via C<configure> have lowest priority,
221	and can only be used to specify defaults.	286	and can only be used to specify defaults.
222		287
223	If the profile specifies a node ID, then this will become the node ID of	288	If the profile specifies a node ID, then this will become the node ID of
224	this process. If not, then the profile name will be used as node ID. The	289	this process. If not, then the profile name will be used as node ID, with
225	special node ID of C<anon/> will be replaced by a random node ID.	290	a unique randoms tring (C</%u>) appended.
		291
		292	The node ID can contain some C<%> sequences that are expanded: C<%n>
		293	is expanded to the local nodename, C<%u> is replaced by a random
		294	strign to make the node unique. For example, the F<aemp> commandline
		295	utility uses C<aemp/%n/%u> as nodename, which might expand to
		296	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
226		297
227	=item step 2, bind listener sockets	298	=item step 2, bind listener sockets
228		299
229	The next step is to look up the binds in the profile, followed by binding	300	The next step is to look up the binds in the profile, followed by binding
230	aemp protocol listeners on all binds specified (it is possible and valid	301	aemp protocol listeners on all binds specified (it is possible and valid
…		…
236	used, meaning the node will bind on a dynamically-assigned port on every	307	used, meaning the node will bind on a dynamically-assigned port on every
237	local IP address it finds.	308	local IP address it finds.
238		309
239	=item step 3, connect to seed nodes	310	=item step 3, connect to seed nodes
240		311
241	As the last step, the seeds list from the profile is passed to the	312	As the last step, the seed ID list from the profile is passed to the
242	L<AnyEvent::MP::Global> module, which will then use it to keep	313	L<AnyEvent::MP::Global> module, which will then use it to keep
243	connectivity with at least one node at any point in time.	314	connectivity with at least one node at any point in time.
244		315
245	=back	316	=back
246		317
247	Example: become a distributed node using the local node name as profile.	318	Example: become a distributed node using the local node name as profile.
248	This should be the most common form of invocation for "daemon"-type nodes.	319	This should be the most common form of invocation for "daemon"-type nodes.
249		320
250	configure	321	configure
251		322
252	Example: become an anonymous node. This form is often used for commandline	323	Example: become a semi-anonymous node. This form is often used for
253	clients.	324	commandline clients.
254		325
255	configure nodeid => "anon/";	326	configure nodeid => "myscript/%n/%u";
256		327
257	Example: configure a node using a profile called seed, which si suitable	328	Example: configure a node using a profile called seed, which is suitable
258	for a seed node as it binds on all local addresses on a fixed port (4040,	329	for a seed node as it binds on all local addresses on a fixed port (4040,
259	customary for aemp).	330	customary for aemp).
260		331
261	# use the aemp commandline utility	332	# use the aemp commandline utility
262	# aemp profile seed nodeid anon/ binds '*:4040'	333	# aemp profile seed binds '*:4040'
263		334
264	# then use it	335	# then use it
265	configure profile => "seed";	336	configure profile => "seed";
266		337
267	# or simply use aemp from the shell again:	338	# or simply use aemp from the shell again:
…		…
332		403
333	=cut	404	=cut
334		405
335	sub rcv($@);	406	sub rcv($@);
336		407
337	sub _kilme {	408	my $KILME = sub {
338	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
339	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
340		412
341	sub port(;&) {	413	sub port(;&) {
342	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
343	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
344		416
345	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
346		418
347	$port	419	$port
348	}	420	}
349		421
350	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
355		427
356	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
357	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
358	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
359		431
360	The default callback received all messages not matched by a more specific	432	The default callback receives all messages not matched by a more specific
361	C<tag> match.	433	C<tag> match.
362		434
363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
364		436
365	Register (or replace) callbacks to be called on messages starting with the	437	Register (or replace) callbacks to be called on messages starting with the
…		…
529	$res	601	$res
530	}	602	}
531	}	603	}
532	}	604	}
533		605
		606	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		607
		608	=item $guard = mon $port # kill $SELF when $port dies
		609
534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	610	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
535
536	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
537
538	=item $guard = mon $port # kill $SELF when $port dies
539		611
540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	612	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
541		613
542	Monitor the given port and do something when the port is killed or	614	Monitor the given port and do something when the port is killed or
543	messages to it were lost, and optionally return a guard that can be used	615	messages to it were lost, and optionally return a guard that can be used
544	to stop monitoring again.	616	to stop monitoring again.
545		617
		618	The first two forms distinguish between "normal" and "abnormal" kil's:
		619
		620	In the first form (another port given), if the C<$port> is C<kil>'ed with
		621	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		622	same reason. That is, on "normal" kil's nothing happens, while under all
		623	other conditions, the other port is killed with the same reason.
		624
		625	The second form (kill self) is the same as the first form, except that
		626	C<$rvport> defaults to C<$SELF>.
		627
		628	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		629	- it's up to the callback or receiver to check whether the C<@reason> is
		630	empty and act accordingly.
		631
546	In the first form (callback), the callback is simply called with any	632	In the third form (callback), the callback is simply called with any
547	number of C<@reason> elements (no @reason means that the port was deleted	633	number of C<@reason> elements (empty @reason means that the port was deleted
548	"normally"). Note also that I<< the callback B<must> never die >>, so use	634	"normally"). Note also that I<< the callback B<must> never die >>, so use
549	C<eval> if unsure.	635	C<eval> if unsure.
550		636
551	In the second form (another port given), the other port (C<$rcvport>)
552	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
553	"normal" kils nothing happens, while under all other conditions, the other
554	port is killed with the same reason.
555
556	The third form (kill self) is the same as the second form, except that
557	C<$rvport> defaults to C<$SELF>.
558
559	In the last form (message), a message of the form C<@msg, @reason> will be	637	In the last form (message), a message of the form C<$rcvport, @msg,
560	C<snd>.	638	@reason> will be C<snd>.
561		639
562	Monitoring-actions are one-shot: once messages are lost (and a monitoring	640	Monitoring-actions are one-shot: once messages are lost (and a monitoring
563	alert was raised), they are removed and will not trigger again.	641	alert was raised), they are removed and will not trigger again, even if it
		642	turns out that the port is still alive.
564		643
565	As a rule of thumb, monitoring requests should always monitor a port from	644	As a rule of thumb, monitoring requests should always monitor a remote
566	a local port (or callback). The reason is that kill messages might get	645	port locally (using a local C<$rcvport> or a callback). The reason is that
567	lost, just like any other message. Another less obvious reason is that	646	kill messages might get lost, just like any other message. Another less
568	even monitoring requests can get lost (for example, when the connection	647	obvious reason is that even monitoring requests can get lost (for example,
569	to the other node goes down permanently). When monitoring a port locally	648	when the connection to the other node goes down permanently). When
570	these problems do not exist.	649	monitoring a port locally these problems do not exist.
571		650
572	C<mon> effectively guarantees that, in the absence of hardware failures,	651	C<mon> effectively guarantees that, in the absence of hardware failures,
573	after starting the monitor, either all messages sent to the port will	652	after starting the monitor, either all messages sent to the port will
574	arrive, or the monitoring action will be invoked after possible message	653	arrive, or the monitoring action will be invoked after possible message
575	loss has been detected. No messages will be lost "in between" (after	654	loss has been detected. No messages will be lost "in between" (after
…		…
620	}	699	}
621		700
622	$node->monitor ($port, $cb);	701	$node->monitor ($port, $cb);
623		702
624	defined wantarray	703	defined wantarray
625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })	704	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
626	}	705	}
627		706
628	=item $guard = mon_guard $port, $ref, $ref...	707	=item $guard = mon_guard $port, $ref, $ref...
629		708
630	Monitors the given C<$port> and keeps the passed references. When the port	709	Monitors the given C<$port> and keeps the passed references. When the port
…		…
666	will be reported as reason C<< die => $@ >>.	745	will be reported as reason C<< die => $@ >>.
667		746
668	Transport/communication errors are reported as C<< transport_error =>	747	Transport/communication errors are reported as C<< transport_error =>
669	$message >>.	748	$message >>.
670		749
671	=cut	750	Common idioms:
		751
		752	# silently remove yourself, do not kill linked ports
		753	kil $SELF;
		754
		755	# report a failure in some detail
		756	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		757
		758	# do not waste much time with killing, just die when something goes wrong
		759	open my $fh, "<file"
		760	or die "file: $!";
672		761
673	=item $port = spawn $node, $initfunc[, @initdata]	762	=item $port = spawn $node, $initfunc[, @initdata]
674		763
675	Creates a port on the node C<$node> (which can also be a port ID, in which	764	Creates a port on the node C<$node> (which can also be a port ID, in which
676	case it's the node where that port resides).	765	case it's the node where that port resides).
…		…
734	}	823	}
735		824
736	sub spawn(@) {	825	sub spawn(@) {
737	my ($nodeid, undef) = split /#/, shift, 2;	826	my ($nodeid, undef) = split /#/, shift, 2;
738		827
739	my $id = "$RUNIQ." . $ID++;	828	my $id = $RUNIQ . ++$ID;
740		829
741	$_[0] =~ /::/	830	$_[0] =~ /::/
742	or Carp::croak "spawn init function must be a fully-qualified name, caught";	831	or Carp::croak "spawn init function must be a fully-qualified name, caught";
743		832
744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	833	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
745		834
746	"$nodeid#$id"	835	"$nodeid#$id"
747	}	836	}
		837
748		838
749	=item after $timeout, @msg	839	=item after $timeout, @msg
750		840
751	=item after $timeout, $callback	841	=item after $timeout, $callback
752		842
…		…
767	ref $action[0]	857	ref $action[0]
768	? $action[0]()	858	? $action[0]()
769	: snd @action;	859	: snd @action;
770	};	860	};
771	}	861	}
		862
		863	#=item $cb2 = timeout $seconds, $cb[, @args]
772		864
773	=item cal $port, @msg, $callback[, $timeout]	865	=item cal $port, @msg, $callback[, $timeout]
774		866
775	A simple form of RPC - sends a message to the given C<$port> with the	867	A simple form of RPC - sends a message to the given C<$port> with the
776	given contents (C<@msg>), but adds a reply port to the message.	868	given contents (C<@msg>), but adds a reply port to the message.
…		…
822	$port	914	$port
823	}	915	}
824		916
825	=back	917	=back
826		918
		919	=head1 DISTRIBUTED DATABASE
		920
		921	AnyEvent::MP comes with a simple distributed database. The database will
		922	be mirrored asynchronously on all global nodes. Other nodes bind to one
		923	of the global nodes for their needs. Every node has a "local database"
		924	which contains all the values that are set locally. All local databases
		925	are merged together to form the global database, which can be queried.
		926
		927	The database structure is that of a two-level hash - the database hash
		928	contains hashes which contain values, similarly to a perl hash of hashes,
		929	i.e.:
		930
		931	$DATABASE{$family}{$subkey} = $value
		932
		933	The top level hash key is called "family", and the second-level hash key
		934	is called "subkey" or simply "key".
		935
		936	The family must be alphanumeric, i.e. start with a letter and consist
		937	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		938	pretty much like Perl module names.
		939
		940	As the family namespace is global, it is recommended to prefix family names
		941	with the name of the application or module using it.
		942
		943	The subkeys must be non-empty strings, with no further restrictions.
		944
		945	The values should preferably be strings, but other perl scalars should
		946	work as well (such as C<undef>, arrays and hashes).
		947
		948	Every database entry is owned by one node - adding the same family/subkey
		949	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		950	but the result might be nondeterministic, i.e. the key might have
		951	different values on different nodes.
		952
		953	Different subkeys in the same family can be owned by different nodes
		954	without problems, and in fact, this is the common method to create worker
		955	pools. For example, a worker port for image scaling might do this:
		956
		957	db_set my_image_scalers => $port;
		958
		959	And clients looking for an image scaler will want to get the
		960	C<my_image_scalers> keys from time to time:
		961
		962	db_keys my_image_scalers => sub {
		963	@ports = @{ $_[0] };
		964	};
		965
		966	Or better yet, they want to monitor the database family, so they always
		967	have a reasonable up-to-date copy:
		968
		969	db_mon my_image_scalers => sub {
		970	@ports = keys %{ $_[0] };
		971	};
		972
		973	In general, you can set or delete single subkeys, but query and monitor
		974	whole families only.
		975
		976	If you feel the need to monitor or query a single subkey, try giving it
		977	it's own family.
		978
		979	=over
		980
		981	=item $guard = db_set $family => $subkey [=> $value]
		982
		983	Sets (or replaces) a key to the database - if C<$value> is omitted,
		984	C<undef> is used instead.
		985
		986	When called in non-void context, C<db_set> returns a guard that
		987	automatically calls C<db_del> when it is destroyed.
		988
		989	=item db_del $family => $subkey...
		990
		991	Deletes one or more subkeys from the database family.
		992
		993	=item $guard = db_reg $family => $port => $value
		994
		995	=item $guard = db_reg $family => $port
		996
		997	=item $guard = db_reg $family
		998
		999	Registers a port in the given family and optionally returns a guard to
		1000	remove it.
		1001
		1002	This function basically does the same as:
		1003
		1004	db_set $family => $port => $value
		1005
		1006	Except that the port is monitored and automatically removed from the
		1007	database family when it is kil'ed.
		1008
		1009	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1010	C<$SELF> is used.
		1011
		1012	This function is most useful to register a port in some port group (which
		1013	is just another name for a database family), and have it removed when the
		1014	port is gone. This works best when the port is a local port.
		1015
		1016	=cut
		1017
		1018	sub db_reg($$;$) {
		1019	my $family = shift;
		1020	my $port = @_ ? shift : $SELF;
		1021
		1022	my $clr = sub { db_del $family => $port };
		1023	mon $port, $clr;
		1024
		1025	db_set $family => $port => $_[0];
		1026
		1027	defined wantarray
		1028	and &Guard::guard ($clr)
		1029	}
		1030
		1031	=item db_family $family => $cb->(\%familyhash)
		1032
		1033	Queries the named database C<$family> and call the callback with the
		1034	family represented as a hash. You can keep and freely modify the hash.
		1035
		1036	=item db_keys $family => $cb->(\@keys)
		1037
		1038	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1039	them as array reference to the callback.
		1040
		1041	=item db_values $family => $cb->(\@values)
		1042
		1043	Same as C<db_family>, except it only queries the family I<values> and passes them
		1044	as array reference to the callback.
		1045
		1046	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1047
		1048	Creates a monitor on the given database family. Each time a key is set
		1049	or or is deleted the callback is called with a hash containing the
		1050	database family and three lists of added, changed and deleted subkeys,
		1051	respectively. If no keys have changed then the array reference might be
		1052	C<undef> or even missing.
		1053
		1054	If not called in void context, a guard object is returned that, when
		1055	destroyed, stops the monitor.
		1056
		1057	The family hash reference and the key arrays belong to AnyEvent::MP and
		1058	B<must not be modified or stored> by the callback. When in doubt, make a
		1059	copy.
		1060
		1061	As soon as possible after the monitoring starts, the callback will be
		1062	called with the intiial contents of the family, even if it is empty,
		1063	i.e. there will always be a timely call to the callback with the current
		1064	contents.
		1065
		1066	It is possible that the callback is called with a change event even though
		1067	the subkey is already present and the value has not changed.
		1068
		1069	The monitoring stops when the guard object is destroyed.
		1070
		1071	Example: on every change to the family "mygroup", print out all keys.
		1072
		1073	my $guard = db_mon mygroup => sub {
		1074	my ($family, $a, $c, $d) = @_;
		1075	print "mygroup members: ", (join " ", keys %$family), "\n";
		1076	};
		1077
		1078	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1079
		1080	my $guard; $guard = db_mon My::Module::workers => sub {
		1081	my ($family, $a, $c, $d) = @_;
		1082	return unless %$family;
		1083	undef $guard;
		1084	print "My::Module::workers now nonempty\n";
		1085	};
		1086
		1087	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1088
		1089	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1090	my ($family, $a, $c, $d) = @_;
		1091
		1092	print "+$_=$family->{$_}\n" for @$a;
		1093	print "*$_=$family->{$_}\n" for @$c;
		1094	print "-$_=$family->{$_}\n" for @$d;
		1095	};
		1096
		1097	=cut
		1098
		1099	=back
		1100
827	=head1 AnyEvent::MP vs. Distributed Erlang	1101	=head1 AnyEvent::MP vs. Distributed Erlang
828		1102
829	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1103	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
830	== aemp node, Erlang process == aemp port), so many of the documents and	1104	== aemp node, Erlang process == aemp port), so many of the documents and
831	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1105	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
…		…
862	ports being the special case/exception, where transport errors cannot	1136	ports being the special case/exception, where transport errors cannot
863	occur.	1137	occur.
864		1138
865	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1139	=item * Erlang uses processes and a mailbox, AEMP does not queue.
866		1140
867	Erlang uses processes that selectively receive messages, and therefore	1141	Erlang uses processes that selectively receive messages out of order, and
868	needs a queue. AEMP is event based, queuing messages would serve no	1142	therefore needs a queue. AEMP is event based, queuing messages would serve
869	useful purpose. For the same reason the pattern-matching abilities of	1143	no useful purpose. For the same reason the pattern-matching abilities
870	AnyEvent::MP are more limited, as there is little need to be able to	1144	of AnyEvent::MP are more limited, as there is little need to be able to
871	filter messages without dequeuing them.	1145	filter messages without dequeuing them.
872		1146
873	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1147	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1148	being event-based, while Erlang is process-based.
		1149
		1150	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1151	top of AEMP and Coro threads.
874		1152
875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1153	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
876		1154
877	Sending messages in Erlang is synchronous and blocks the process (and	1155	Sending messages in Erlang is synchronous and blocks the process until
		1156	a conenction has been established and the message sent (and so does not
878	so does not need a queue that can overflow). AEMP sends are immediate,	1157	need a queue that can overflow). AEMP sends return immediately, connection
879	connection establishment is handled in the background.	1158	establishment is handled in the background.
880		1159
881	=item * Erlang suffers from silent message loss, AEMP does not.	1160	=item * Erlang suffers from silent message loss, AEMP does not.
882		1161
883	Erlang implements few guarantees on messages delivery - messages can get	1162	Erlang implements few guarantees on messages delivery - messages can get
884	lost without any of the processes realising it (i.e. you send messages a,	1163	lost without any of the processes realising it (i.e. you send messages a,
885	b, and c, and the other side only receives messages a and c).	1164	b, and c, and the other side only receives messages a and c).
886		1165
887	AEMP guarantees correct ordering, and the guarantee that after one message	1166	AEMP guarantees (modulo hardware errors) correct ordering, and the
888	is lost, all following ones sent to the same port are lost as well, until	1167	guarantee that after one message is lost, all following ones sent to the
889	monitoring raises an error, so there are no silent "holes" in the message	1168	same port are lost as well, until monitoring raises an error, so there are
890	sequence.	1169	no silent "holes" in the message sequence.
		1170
		1171	If you want your software to be very reliable, you have to cope with
		1172	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1173	simply tries to work better in common error cases, such as when a network
		1174	link goes down.
891		1175
892	=item * Erlang can send messages to the wrong port, AEMP does not.	1176	=item * Erlang can send messages to the wrong port, AEMP does not.
893		1177
894	In Erlang it is quite likely that a node that restarts reuses a process ID	1178	In Erlang it is quite likely that a node that restarts reuses an Erlang
895	known to other nodes for a completely different process, causing messages	1179	process ID known to other nodes for a completely different process,
896	destined for that process to end up in an unrelated process.	1180	causing messages destined for that process to end up in an unrelated
		1181	process.
897		1182
898	AEMP never reuses port IDs, so old messages or old port IDs floating	1183	AEMP does not reuse port IDs, so old messages or old port IDs floating
899	around in the network will not be sent to an unrelated port.	1184	around in the network will not be sent to an unrelated port.
900		1185
901	=item * Erlang uses unprotected connections, AEMP uses secure	1186	=item * Erlang uses unprotected connections, AEMP uses secure
902	authentication and can use TLS.	1187	authentication and can use TLS.
903		1188
…		…
906		1191
907	=item * The AEMP protocol is optimised for both text-based and binary	1192	=item * The AEMP protocol is optimised for both text-based and binary
908	communications.	1193	communications.
909		1194
910	The AEMP protocol, unlike the Erlang protocol, supports both programming	1195	The AEMP protocol, unlike the Erlang protocol, supports both programming
911	language independent text-only protocols (good for debugging) and binary,	1196	language independent text-only protocols (good for debugging), and binary,
912	language-specific serialisers (e.g. Storable). By default, unless TLS is	1197	language-specific serialisers (e.g. Storable). By default, unless TLS is
913	used, the protocol is actually completely text-based.	1198	used, the protocol is actually completely text-based.
914		1199
915	It has also been carefully designed to be implementable in other languages	1200	It has also been carefully designed to be implementable in other languages
916	with a minimum of work while gracefully degrading functionality to make the	1201	with a minimum of work while gracefully degrading functionality to make the
917	protocol simple.	1202	protocol simple.
918		1203
919	=item * AEMP has more flexible monitoring options than Erlang.	1204	=item * AEMP has more flexible monitoring options than Erlang.
920		1205
921	In Erlang, you can chose to receive I<all> exit signals as messages	1206	In Erlang, you can chose to receive I<all> exit signals as messages or
922	or I<none>, there is no in-between, so monitoring single processes is	1207	I<none>, there is no in-between, so monitoring single Erlang processes is
923	difficult to implement. Monitoring in AEMP is more flexible than in	1208	difficult to implement.
924	Erlang, as one can choose between automatic kill, exit message or callback	1209
925	on a per-process basis.	1210	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1211	between automatic kill, exit message or callback on a per-port basis.
926		1212
927	=item * Erlang tries to hide remote/local connections, AEMP does not.	1213	=item * Erlang tries to hide remote/local connections, AEMP does not.
928		1214
929	Monitoring in Erlang is not an indicator of process death/crashes, in the	1215	Monitoring in Erlang is not an indicator of process death/crashes, in the
930	same way as linking is (except linking is unreliable in Erlang).	1216	same way as linking is (except linking is unreliable in Erlang).
…		…
953		1239
954	Strings can easily be printed, easily serialised etc. and need no special	1240	Strings can easily be printed, easily serialised etc. and need no special
955	procedures to be "valid".	1241	procedures to be "valid".
956		1242
957	And as a result, a port with just a default receiver consists of a single	1243	And as a result, a port with just a default receiver consists of a single
958	closure stored in a global hash - it can't become much cheaper.	1244	code reference stored in a global hash - it can't become much cheaper.
959		1245
960	=item Why favour JSON, why not a real serialising format such as Storable?	1246	=item Why favour JSON, why not a real serialising format such as Storable?
961		1247
962	In fact, any AnyEvent::MP node will happily accept Storable as framing	1248	In fact, any AnyEvent::MP node will happily accept Storable as framing
963	format, but currently there is no way to make a node use Storable by	1249	format, but currently there is no way to make a node use Storable by
…		…
973	Keeping your messages simple, concentrating on data structures rather than	1259	Keeping your messages simple, concentrating on data structures rather than
974	objects, will keep your messages clean, tidy and efficient.	1260	objects, will keep your messages clean, tidy and efficient.
975		1261
976	=back	1262	=back
977		1263
		1264	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1265
		1266	AEMP version 2 has a few major incompatible changes compared to version 1:
		1267
		1268	=over 4
		1269
		1270	=item AnyEvent::MP::Global no longer has group management functions.
		1271
		1272	AnyEvent::MP now comes with a distributed database that is more
		1273	powerful. Its database families map closely to port groups, but the API
		1274	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1275	a rough porting guide:
		1276
		1277	grp_reg $group, $port # old
		1278	db_reg $group, $port # new
		1279
		1280	$list = grp_get $group # old
		1281	db_keys $group, sub { my $list = shift } # new
		1282
		1283	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1284	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1285
		1286	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1287	no longer instant, because the local node might not have a copy of the
		1288	group. You can either modify your code to allow for a callback, or use
		1289	C<db_mon> to keep an updated copy of the group:
		1290
		1291	my $local_group_copy;
		1292	db_mon $group => sub { $local_group_copy = $_[0] };
		1293
		1294	# now "keys %$local_group_copy" always returns the most up-to-date
		1295	# list of ports in the group.
		1296
		1297	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1298	passes a hash as first argument, and an extra C<$chg> argument that can be
		1299	ignored:
		1300
		1301	db_mon $group => sub {
		1302	my ($ports, $add, $chg, $lde) = @_;
		1303	$ports = [keys %$ports];
		1304
		1305	# now $ports, $add and $del are the same as
		1306	# were originally passed by grp_mon.
		1307	...
		1308	};
		1309
		1310	=item Nodes not longer connect to all other nodes.
		1311
		1312	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1313	module, which in turn would create connections to all other nodes in the
		1314	network (helped by the seed nodes).
		1315
		1316	In version 2.x, global nodes still connect to all other global nodes, but
		1317	other nodes don't - now every node either is a global node itself, or
		1318	attaches itself to another global node.
		1319
		1320	If a node isn't a global node itself, then it attaches itself to one
		1321	of its seed nodes. If that seed node isn't a global node yet, it will
		1322	automatically be upgraded to a global node.
		1323
		1324	So in many cases, nothing needs to be changed - one just has to make sure
		1325	that all seed nodes are meshed together with the other seed nodes (as with
		1326	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1327	achieved by specifying the same set of seed nodes for all nodes in the
		1328	network.
		1329
		1330	Not opening a connection to every other node is usually an advantage,
		1331	except when you need the lower latency of an already established
		1332	connection. To ensure a node establishes a connection to another node,
		1333	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1334	create the connection (and notify you when the connection fails).
		1335
		1336	=item Listener-less nodes (nodes without binds) are gone.
		1337
		1338	And are not coming back, at least not in their old form. If no C<binds>
		1339	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1340
		1341	There are vague plans to implement some form of routing domains, which
		1342	might or might not bring back listener-less nodes, but don't count on it.
		1343
		1344	The fact that most connections are now optional somewhat mitigates this,
		1345	as a node can be effectively unreachable from the outside without any
		1346	problems, as long as it isn't a global node and only reaches out to other
		1347	nodes (as opposed to being contacted from other nodes).
		1348
		1349	=item $AnyEvent::MP::Kernel::WARN has gone.
		1350
		1351	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1352	uses this, and so should your programs.
		1353
		1354	Every module now documents what kinds of messages it generates, with
		1355	AnyEvent::MP acting as a catch all.
		1356
		1357	On the positive side, this means that instead of setting
		1358	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1359	much less to type.
		1360
		1361	=back
		1362
		1363	=head1 LOGGING
		1364
		1365	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1366	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1367	all log messages by submodules.
		1368
978	=head1 SEE ALSO	1369	=head1 SEE ALSO
979		1370
980	L<AnyEvent::MP::Intro> - a gentle introduction.	1371	L<AnyEvent::MP::Intro> - a gentle introduction.
981		1372
982	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1373	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.116 by root, Mon Jun 21 15:09:34 2010 UTC vs. Revision 1.139 by root, Thu Mar 22 20:07:31 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.116 by root, Mon Jun 21 15:09:34 2010 UTC vs.
Revision 1.139 by root, Thu Mar 22 20:07:31 2012 UTC