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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.118 by root, Thu Jun 30 09:31:58 2011 UTC vs.
Revision 1.142 by root, Fri Mar 23 13:44:01 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
48	my $timer = AE::timer 1, 0, psub {	48	my $timer = AE::timer 1, 0, psub {
49	die "kill the port, delayed";	49	die "kill the port, delayed";
50	};	50	};
51		51
52	=head1 CURRENT STATUS
53
54	bin/aemp - stable.
55	AnyEvent::MP - stable API, should work.
56	AnyEvent::MP::Intro - explains most concepts.
57	AnyEvent::MP::Kernel - mostly stable API.
58	AnyEvent::MP::Global - stable API.
59
60	=head1 DESCRIPTION	52	=head1 DESCRIPTION
61		53
62	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
63		55
64	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
…		…
78		70
79	Ports allow you to register C<rcv> handlers that can match all or just	71	Ports allow you to register C<rcv> handlers that can match all or just
80	some messages. Messages send to ports will not be queued, regardless of	72	some messages. Messages send to ports will not be queued, regardless of
81	anything was listening for them or not.	73	anything was listening for them or not.
82		74
		75	Ports are represented by (printable) strings called "port IDs".
		76
83	=item port ID - C<nodeid#portname>	77	=item port ID - C<nodeid#portname>
84		78
85	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	79	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
86	separator, and a port name (a printable string of unspecified format).	80	as separator, and a port name (a printable string of unspecified
		81	format created by AnyEvent::MP).
87		82
88	=item node	83	=item node
89		84
90	A node is a single process containing at least one port - the node port,	85	A node is a single process containing at least one port - the node port,
91	which enables nodes to manage each other remotely, and to create new	86	which enables nodes to manage each other remotely, and to create new
92	ports.	87	ports.
93		88
94	Nodes are either public (have one or more listening ports) or private	89	Nodes are either public (have one or more listening ports) or private
95	(no listening ports). Private nodes cannot talk to other private nodes	90	(no listening ports). Private nodes cannot talk to other private nodes
96	currently.	91	currently, but all nodes can talk to public nodes.
		92
		93	Nodes is represented by (printable) strings called "node IDs".
97		94
98	=item node ID - C<[A-Za-z0-9_\-.:]*>	95	=item node ID - C<[A-Za-z0-9_\-.:]*>
99		96
100	A node ID is a string that uniquely identifies the node within a	97	A node ID is a string that uniquely identifies the node within a
101	network. Depending on the configuration used, node IDs can look like a	98	network. Depending on the configuration used, node IDs can look like a
102	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	99	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
103	doesn't interpret node IDs in any way.	100	doesn't interpret node IDs in any way except to uniquely identify a node.
104		101
105	=item binds - C<ip:port>	102	=item binds - C<ip:port>
106		103
107	Nodes can only talk to each other by creating some kind of connection to	104	Nodes can only talk to each other by creating some kind of connection to
108	each other. To do this, nodes should listen on one or more local transport	105	each other. To do this, nodes should listen on one or more local transport
		106	endpoints - binds.
		107
109	endpoints - binds. Currently, only standard C<ip:port> specifications can	108	Currently, only standard C<ip:port> specifications can be used, which
110	be used, which specify TCP ports to listen on.	109	specify TCP ports to listen on. So a bind is basically just a tcp socket
		110	in listening mode thta accepts conenctions form other nodes.
111		111
112	=item seed nodes	112	=item seed nodes
113		113
114	When a node starts, it knows nothing about the network. To teach the node	114	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	115	needs to connect to at least one other node that is already in the
116	network. This node is called a seed.	116	network. These other nodes are called "seed nodes".
117		117
118	Apart from the fact that other nodes know them as seed nodes and they have	118	Seed nodes themselves are not special - they are seed nodes only because
119	to have fixed listening addresses, seed nodes are perfectly normal nodes -	119	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.	120	node for other nodes, and eahc node cna use a different set of seed nodes.
121		121
122	In addition to discovering the network, seed nodes are also used to	122	In addition to discovering the network, seed nodes are also used to
123	maintain the network and to connect nodes that otherwise would have	123	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.	124	the same network. If a network is split into multiple subnets because e.g.
		125	the network link between the parts goes down, then using the same seed
		126	nodes for all nodes ensures that eventually the subnets get merged again.
125		127
126	Seed nodes are expected to be long-running, and at least one seed node	128	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	129	should always be available. They should also be relatively responsive - a
128	seed node that blocks for long periods will slow down everybody else.	130	seed node that blocks for long periods will slow down everybody else.
129		131
		132	For small networks, it's best if every node uses the same set of seed
		133	nodes. For large networks, it can be useful to specify "regional" seed
		134	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		135	each other. What's important is that all seed nodes connections form a
		136	complete graph, so that the network cannot split into separate subnets
		137	forever.
		138
		139	Seed nodes are represented by seed IDs.
		140
130	=item seeds - C<host:port>	141	=item seed IDs - C<host:port>
131		142
132	Seeds are transport endpoint(s) (usually a hostname/IP address and a	143	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.	144	TCP port) of nodes that should be used as seed nodes.
134		145
135	The nodes listening on those endpoints are expected to be long-running,	146	=item global nodes
136	and at least one of those should always be available. When nodes run out	147
137	of connections (e.g. due to a network error), they try to re-establish	148	An AEMP network needs a discovery service - nodes need to know how to
138	connections to some seednodes again to join the network.	149	connect to other nodes they only know by name. In addition, AEMP offers a
		150	distributed "group database", which maps group names to a list of strings
		151	- for example, to register worker ports.
		152
		153	A network needs at least one global node to work, and allows every node to
		154	be a global node.
		155
		156	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		157	node and tries to keep connections to all other nodes. So while it can
		158	make sense to make every node "global" in small networks, it usually makes
		159	sense to only make seed nodes into global nodes in large networks (nodes
		160	keep connections to seed nodes and global nodes, so makign them the same
		161	reduces overhead).
139		162
140	=back	163	=back
141		164
142	=head1 VARIABLES/FUNCTIONS	165	=head1 VARIABLES/FUNCTIONS
143		166
…		…
145		168
146	=cut	169	=cut
147		170
148	package AnyEvent::MP;	171	package AnyEvent::MP;
149		172
		173	use AnyEvent::MP::Config ();
150	use AnyEvent::MP::Kernel;	174	use AnyEvent::MP::Kernel;
		175	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
151		176
152	use common::sense;	177	use common::sense;
153		178
154	use Carp ();	179	use Carp ();
155		180
156	use AE ();	181	use AnyEvent ();
		182	use Guard ();
157		183
158	use base "Exporter";	184	use base "Exporter";
159		185
160	our $VERSION = '1.30';	186	our $VERSION = $AnyEvent::MP::Config::VERSION;
161		187
162	our @EXPORT = qw(	188	our @EXPORT = qw(
163	NODE $NODE *SELF node_of after	189	NODE $NODE *SELF node_of after
164	configure	190	configure
165	snd rcv mon mon_guard kil psub peval spawn cal	191	snd rcv mon mon_guard kil psub peval spawn cal
166	port	192	port
		193	db_set db_del db_reg
		194	db_mon db_family db_keys db_values
167	);	195	);
168		196
169	our $SELF;	197	our $SELF;
170		198
171	sub _self_die() {	199	sub _self_die() {
…		…
191	Before a node can talk to other nodes on the network (i.e. enter	219	Before a node can talk to other nodes on the network (i.e. enter
192	"distributed mode") it has to configure itself - the minimum a node needs	220	"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	221	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.	222	some other nodes in the network to discover other nodes.
195		223
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	224	This function configures a node - it must be called exactly once (or
200	never) before calling other AnyEvent::MP functions.	225	never) before calling other AnyEvent::MP functions.
		226
		227	The key/value pairs are basically the same ones as documented for the
		228	F<aemp> command line utility (sans the set/del prefix), with these additions:
		229
		230	=over 4
		231
		232	=item norc => $boolean (default false)
		233
		234	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		235	be consulted - all configuraiton options must be specified in the
		236	C<configure> call.
		237
		238	=item force => $boolean (default false)
		239
		240	IF true, then the values specified in the C<configure> will take
		241	precedence over any values configured via the rc file. The default is for
		242	the rc file to override any options specified in the program.
		243
		244	=back
201		245
202	=over 4	246	=over 4
203		247
204	=item step 1, gathering configuration from profiles	248	=item step 1, gathering configuration from profiles
205		249
…		…
219	That means that the values specified in the profile have highest priority	263	That means that the values specified in the profile have highest priority
220	and the values specified directly via C<configure> have lowest priority,	264	and the values specified directly via C<configure> have lowest priority,
221	and can only be used to specify defaults.	265	and can only be used to specify defaults.
222		266
223	If the profile specifies a node ID, then this will become the node ID of	267	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	268	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.	269	a unique randoms tring (C</%u>) appended.
		270
		271	The node ID can contain some C<%> sequences that are expanded: C<%n>
		272	is expanded to the local nodename, C<%u> is replaced by a random
		273	strign to make the node unique. For example, the F<aemp> commandline
		274	utility uses C<aemp/%n/%u> as nodename, which might expand to
		275	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
226		276
227	=item step 2, bind listener sockets	277	=item step 2, bind listener sockets
228		278
229	The next step is to look up the binds in the profile, followed by binding	279	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	280	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	286	used, meaning the node will bind on a dynamically-assigned port on every
237	local IP address it finds.	287	local IP address it finds.
238		288
239	=item step 3, connect to seed nodes	289	=item step 3, connect to seed nodes
240		290
241	As the last step, the seeds list from the profile is passed to the	291	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	292	L<AnyEvent::MP::Global> module, which will then use it to keep
243	connectivity with at least one node at any point in time.	293	connectivity with at least one node at any point in time.
244		294
245	=back	295	=back
246		296
247	Example: become a distributed node using the local node name as profile.	297	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.	298	This should be the most common form of invocation for "daemon"-type nodes.
249		299
250	configure	300	configure
251		301
252	Example: become an anonymous node. This form is often used for commandline	302	Example: become a semi-anonymous node. This form is often used for
253	clients.	303	commandline clients.
254		304
255	configure nodeid => "anon/";	305	configure nodeid => "myscript/%n/%u";
256		306
257	Example: configure a node using a profile called seed, which si suitable	307	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,	308	for a seed node as it binds on all local addresses on a fixed port (4040,
259	customary for aemp).	309	customary for aemp).
260		310
261	# use the aemp commandline utility	311	# use the aemp commandline utility
262	# aemp profile seed nodeid anon/ binds '*:4040'	312	# aemp profile seed binds '*:4040'
263		313
264	# then use it	314	# then use it
265	configure profile => "seed";	315	configure profile => "seed";
266		316
267	# or simply use aemp from the shell again:	317	# or simply use aemp from the shell again:
…		…
332		382
333	=cut	383	=cut
334		384
335	sub rcv($@);	385	sub rcv($@);
336		386
337	sub _kilme {	387	my $KILME = sub {
338	die "received message on port without callback";	388	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
339	}	389	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		390	};
340		391
341	sub port(;&) {	392	sub port(;&) {
342	my $id = "$UNIQ." . $ID++;	393	my $id = $UNIQ . ++$ID;
343	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
344		395
345	rcv $port, shift \|\| \&_kilme;	396	rcv $port, shift \|\| $KILME;
346		397
347	$port	398	$port
348	}	399	}
349		400
350	=item rcv $local_port, $callback->(@msg)	401	=item rcv $local_port, $callback->(@msg)
…		…
355		406
356	The global C<$SELF> (exported by this module) contains C<$port> while	407	The global C<$SELF> (exported by this module) contains C<$port> while
357	executing the callback. Runtime errors during callback execution will	408	executing the callback. Runtime errors during callback execution will
358	result in the port being C<kil>ed.	409	result in the port being C<kil>ed.
359		410
360	The default callback received all messages not matched by a more specific	411	The default callback receives all messages not matched by a more specific
361	C<tag> match.	412	C<tag> match.
362		413
363	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	414	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
364		415
365	Register (or replace) callbacks to be called on messages starting with the	416	Register (or replace) callbacks to be called on messages starting with the
…		…
529	$res	580	$res
530	}	581	}
531	}	582	}
532	}	583	}
533		584
		585	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		586
		587	=item $guard = mon $port # kill $SELF when $port dies
		588
534	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	589	=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		590
540	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	591	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
541		592
542	Monitor the given port and do something when the port is killed or	593	Monitor the given port and do something when the port is killed or
543	messages to it were lost, and optionally return a guard that can be used	594	messages to it were lost, and optionally return a guard that can be used
544	to stop monitoring again.	595	to stop monitoring again.
545		596
		597	The first two forms distinguish between "normal" and "abnormal" kil's:
		598
		599	In the first form (another port given), if the C<$port> is C<kil>'ed with
		600	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		601	same reason. That is, on "normal" kil's nothing happens, while under all
		602	other conditions, the other port is killed with the same reason.
		603
		604	The second form (kill self) is the same as the first form, except that
		605	C<$rvport> defaults to C<$SELF>.
		606
		607	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		608	- it's up to the callback or receiver to check whether the C<@reason> is
		609	empty and act accordingly.
		610
546	In the first form (callback), the callback is simply called with any	611	In the third form (callback), the callback is simply called with any
547	number of C<@reason> elements (no @reason means that the port was deleted	612	number of C<@reason> elements (empty @reason means that the port was deleted
548	"normally"). Note also that I<< the callback B<must> never die >>, so use	613	"normally"). Note also that I<< the callback B<must> never die >>, so use
549	C<eval> if unsure.	614	C<eval> if unsure.
550		615
551	In the second form (another port given), the other port (C<$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	616	In the last form (message), a message of the form C<$rcvport, @msg,
560	C<snd>.	617	@reason> will be C<snd>.
561		618
562	Monitoring-actions are one-shot: once messages are lost (and a monitoring	619	Monitoring-actions are one-shot: once messages are lost (and a monitoring
563	alert was raised), they are removed and will not trigger again.	620	alert was raised), they are removed and will not trigger again, even if it
		621	turns out that the port is still alive.
564		622
565	As a rule of thumb, monitoring requests should always monitor a port from	623	As a rule of thumb, monitoring requests should always monitor a remote
566	a local port (or callback). The reason is that kill messages might get	624	port locally (using a local C<$rcvport> or a callback). The reason is that
567	lost, just like any other message. Another less obvious reason is that	625	kill messages might get lost, just like any other message. Another less
568	even monitoring requests can get lost (for example, when the connection	626	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	627	when the connection to the other node goes down permanently). When
570	these problems do not exist.	628	monitoring a port locally these problems do not exist.
571		629
572	C<mon> effectively guarantees that, in the absence of hardware failures,	630	C<mon> effectively guarantees that, in the absence of hardware failures,
573	after starting the monitor, either all messages sent to the port will	631	after starting the monitor, either all messages sent to the port will
574	arrive, or the monitoring action will be invoked after possible message	632	arrive, or the monitoring action will be invoked after possible message
575	loss has been detected. No messages will be lost "in between" (after	633	loss has been detected. No messages will be lost "in between" (after
…		…
620	}	678	}
621		679
622	$node->monitor ($port, $cb);	680	$node->monitor ($port, $cb);
623		681
624	defined wantarray	682	defined wantarray
625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })	683	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
626	}	684	}
627		685
628	=item $guard = mon_guard $port, $ref, $ref...	686	=item $guard = mon_guard $port, $ref, $ref...
629		687
630	Monitors the given C<$port> and keeps the passed references. When the port	688	Monitors the given C<$port> and keeps the passed references. When the port
…		…
666	will be reported as reason C<< die => $@ >>.	724	will be reported as reason C<< die => $@ >>.
667		725
668	Transport/communication errors are reported as C<< transport_error =>	726	Transport/communication errors are reported as C<< transport_error =>
669	$message >>.	727	$message >>.
670		728
671	=cut	729	Common idioms:
		730
		731	# silently remove yourself, do not kill linked ports
		732	kil $SELF;
		733
		734	# report a failure in some detail
		735	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		736
		737	# do not waste much time with killing, just die when something goes wrong
		738	open my $fh, "<file"
		739	or die "file: $!";
672		740
673	=item $port = spawn $node, $initfunc[, @initdata]	741	=item $port = spawn $node, $initfunc[, @initdata]
674		742
675	Creates a port on the node C<$node> (which can also be a port ID, in which	743	Creates a port on the node C<$node> (which can also be a port ID, in which
676	case it's the node where that port resides).	744	case it's the node where that port resides).
…		…
734	}	802	}
735		803
736	sub spawn(@) {	804	sub spawn(@) {
737	my ($nodeid, undef) = split /#/, shift, 2;	805	my ($nodeid, undef) = split /#/, shift, 2;
738		806
739	my $id = "$RUNIQ." . $ID++;	807	my $id = $RUNIQ . ++$ID;
740		808
741	$_[0] =~ /::/	809	$_[0] =~ /::/
742	or Carp::croak "spawn init function must be a fully-qualified name, caught";	810	or Carp::croak "spawn init function must be a fully-qualified name, caught";
743		811
744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	812	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
745		813
746	"$nodeid#$id"	814	"$nodeid#$id"
747	}	815	}
		816
748		817
749	=item after $timeout, @msg	818	=item after $timeout, @msg
750		819
751	=item after $timeout, $callback	820	=item after $timeout, $callback
752		821
…		…
767	ref $action[0]	836	ref $action[0]
768	? $action[0]()	837	? $action[0]()
769	: snd @action;	838	: snd @action;
770	};	839	};
771	}	840	}
		841
		842	#=item $cb2 = timeout $seconds, $cb[, @args]
772		843
773	=item cal $port, @msg, $callback[, $timeout]	844	=item cal $port, @msg, $callback[, $timeout]
774		845
775	A simple form of RPC - sends a message to the given C<$port> with the	846	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.	847	given contents (C<@msg>), but adds a reply port to the message.
…		…
822	$port	893	$port
823	}	894	}
824		895
825	=back	896	=back
826		897
		898	=head1 DISTRIBUTED DATABASE
		899
		900	AnyEvent::MP comes with a simple distributed database. The database will
		901	be mirrored asynchronously on all global nodes. Other nodes bind to one
		902	of the global nodes for their needs. Every node has a "local database"
		903	which contains all the values that are set locally. All local databases
		904	are merged together to form the global database, which can be queried.
		905
		906	The database structure is that of a two-level hash - the database hash
		907	contains hashes which contain values, similarly to a perl hash of hashes,
		908	i.e.:
		909
		910	$DATABASE{$family}{$subkey} = $value
		911
		912	The top level hash key is called "family", and the second-level hash key
		913	is called "subkey" or simply "key".
		914
		915	The family must be alphanumeric, i.e. start with a letter and consist
		916	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		917	pretty much like Perl module names.
		918
		919	As the family namespace is global, it is recommended to prefix family names
		920	with the name of the application or module using it.
		921
		922	The subkeys must be non-empty strings, with no further restrictions.
		923
		924	The values should preferably be strings, but other perl scalars should
		925	work as well (such as C<undef>, arrays and hashes).
		926
		927	Every database entry is owned by one node - adding the same family/subkey
		928	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		929	but the result might be nondeterministic, i.e. the key might have
		930	different values on different nodes.
		931
		932	Different subkeys in the same family can be owned by different nodes
		933	without problems, and in fact, this is the common method to create worker
		934	pools. For example, a worker port for image scaling might do this:
		935
		936	db_set my_image_scalers => $port;
		937
		938	And clients looking for an image scaler will want to get the
		939	C<my_image_scalers> keys from time to time:
		940
		941	db_keys my_image_scalers => sub {
		942	@ports = @{ $_[0] };
		943	};
		944
		945	Or better yet, they want to monitor the database family, so they always
		946	have a reasonable up-to-date copy:
		947
		948	db_mon my_image_scalers => sub {
		949	@ports = keys %{ $_[0] };
		950	};
		951
		952	In general, you can set or delete single subkeys, but query and monitor
		953	whole families only.
		954
		955	If you feel the need to monitor or query a single subkey, try giving it
		956	it's own family.
		957
		958	=over
		959
		960	=item $guard = db_set $family => $subkey [=> $value]
		961
		962	Sets (or replaces) a key to the database - if C<$value> is omitted,
		963	C<undef> is used instead.
		964
		965	When called in non-void context, C<db_set> returns a guard that
		966	automatically calls C<db_del> when it is destroyed.
		967
		968	=item db_del $family => $subkey...
		969
		970	Deletes one or more subkeys from the database family.
		971
		972	=item $guard = db_reg $family => $port => $value
		973
		974	=item $guard = db_reg $family => $port
		975
		976	=item $guard = db_reg $family
		977
		978	Registers a port in the given family and optionally returns a guard to
		979	remove it.
		980
		981	This function basically does the same as:
		982
		983	db_set $family => $port => $value
		984
		985	Except that the port is monitored and automatically removed from the
		986	database family when it is kil'ed.
		987
		988	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		989	C<$SELF> is used.
		990
		991	This function is most useful to register a port in some port group (which
		992	is just another name for a database family), and have it removed when the
		993	port is gone. This works best when the port is a local port.
		994
		995	=cut
		996
		997	sub db_reg($$;$) {
		998	my $family = shift;
		999	my $port = @_ ? shift : $SELF;
		1000
		1001	my $clr = sub { db_del $family => $port };
		1002	mon $port, $clr;
		1003
		1004	db_set $family => $port => $_[0];
		1005
		1006	defined wantarray
		1007	and &Guard::guard ($clr)
		1008	}
		1009
		1010	=item db_family $family => $cb->(\%familyhash)
		1011
		1012	Queries the named database C<$family> and call the callback with the
		1013	family represented as a hash. You can keep and freely modify the hash.
		1014
		1015	=item db_keys $family => $cb->(\@keys)
		1016
		1017	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1018	them as array reference to the callback.
		1019
		1020	=item db_values $family => $cb->(\@values)
		1021
		1022	Same as C<db_family>, except it only queries the family I<values> and passes them
		1023	as array reference to the callback.
		1024
		1025	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1026
		1027	Creates a monitor on the given database family. Each time a key is set
		1028	or or is deleted the callback is called with a hash containing the
		1029	database family and three lists of added, changed and deleted subkeys,
		1030	respectively. If no keys have changed then the array reference might be
		1031	C<undef> or even missing.
		1032
		1033	If not called in void context, a guard object is returned that, when
		1034	destroyed, stops the monitor.
		1035
		1036	The family hash reference and the key arrays belong to AnyEvent::MP and
		1037	B<must not be modified or stored> by the callback. When in doubt, make a
		1038	copy.
		1039
		1040	As soon as possible after the monitoring starts, the callback will be
		1041	called with the intiial contents of the family, even if it is empty,
		1042	i.e. there will always be a timely call to the callback with the current
		1043	contents.
		1044
		1045	It is possible that the callback is called with a change event even though
		1046	the subkey is already present and the value has not changed.
		1047
		1048	The monitoring stops when the guard object is destroyed.
		1049
		1050	Example: on every change to the family "mygroup", print out all keys.
		1051
		1052	my $guard = db_mon mygroup => sub {
		1053	my ($family, $a, $c, $d) = @_;
		1054	print "mygroup members: ", (join " ", keys %$family), "\n";
		1055	};
		1056
		1057	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1058
		1059	my $guard; $guard = db_mon My::Module::workers => sub {
		1060	my ($family, $a, $c, $d) = @_;
		1061	return unless %$family;
		1062	undef $guard;
		1063	print "My::Module::workers now nonempty\n";
		1064	};
		1065
		1066	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1067
		1068	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1069	my ($family, $a, $c, $d) = @_;
		1070
		1071	print "+$_=$family->{$_}\n" for @$a;
		1072	print "*$_=$family->{$_}\n" for @$c;
		1073	print "-$_=$family->{$_}\n" for @$d;
		1074	};
		1075
		1076	=cut
		1077
		1078	=back
		1079
827	=head1 AnyEvent::MP vs. Distributed Erlang	1080	=head1 AnyEvent::MP vs. Distributed Erlang
828		1081
829	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1082	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	1083	== 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	1084	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
…		…
862	ports being the special case/exception, where transport errors cannot	1115	ports being the special case/exception, where transport errors cannot
863	occur.	1116	occur.
864		1117
865	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1118	=item * Erlang uses processes and a mailbox, AEMP does not queue.
866		1119
867	Erlang uses processes that selectively receive messages, and therefore	1120	Erlang uses processes that selectively receive messages out of order, and
868	needs a queue. AEMP is event based, queuing messages would serve no	1121	therefore needs a queue. AEMP is event based, queuing messages would serve
869	useful purpose. For the same reason the pattern-matching abilities of	1122	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	1123	of AnyEvent::MP are more limited, as there is little need to be able to
871	filter messages without dequeuing them.	1124	filter messages without dequeuing them.
872		1125
873	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1126	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1127	being event-based, while Erlang is process-based.
		1128
		1129	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1130	top of AEMP and Coro threads.
874		1131
875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1132	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
876		1133
877	Sending messages in Erlang is synchronous and blocks the process (and	1134	Sending messages in Erlang is synchronous and blocks the process until
		1135	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,	1136	need a queue that can overflow). AEMP sends return immediately, connection
879	connection establishment is handled in the background.	1137	establishment is handled in the background.
880		1138
881	=item * Erlang suffers from silent message loss, AEMP does not.	1139	=item * Erlang suffers from silent message loss, AEMP does not.
882		1140
883	Erlang implements few guarantees on messages delivery - messages can get	1141	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,	1142	lost without any of the processes realising it (i.e. you send messages a,
…		…
887	AEMP guarantees (modulo hardware errors) correct ordering, and the	1145	AEMP guarantees (modulo hardware errors) correct ordering, and the
888	guarantee that after one message is lost, all following ones sent to the	1146	guarantee that after one message is lost, all following ones sent to the
889	same port are lost as well, until monitoring raises an error, so there are	1147	same port are lost as well, until monitoring raises an error, so there are
890	no silent "holes" in the message sequence.	1148	no silent "holes" in the message sequence.
891		1149
		1150	If you want your software to be very reliable, you have to cope with
		1151	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1152	simply tries to work better in common error cases, such as when a network
		1153	link goes down.
		1154
892	=item * Erlang can send messages to the wrong port, AEMP does not.	1155	=item * Erlang can send messages to the wrong port, AEMP does not.
893		1156
894	In Erlang it is quite likely that a node that restarts reuses a process ID	1157	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	1158	process ID known to other nodes for a completely different process,
896	destined for that process to end up in an unrelated process.	1159	causing messages destined for that process to end up in an unrelated
		1160	process.
897		1161
898	AEMP never reuses port IDs, so old messages or old port IDs floating	1162	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.	1163	around in the network will not be sent to an unrelated port.
900		1164
901	=item * Erlang uses unprotected connections, AEMP uses secure	1165	=item * Erlang uses unprotected connections, AEMP uses secure
902	authentication and can use TLS.	1166	authentication and can use TLS.
903		1167
…		…
906		1170
907	=item * The AEMP protocol is optimised for both text-based and binary	1171	=item * The AEMP protocol is optimised for both text-based and binary
908	communications.	1172	communications.
909		1173
910	The AEMP protocol, unlike the Erlang protocol, supports both programming	1174	The AEMP protocol, unlike the Erlang protocol, supports both programming
911	language independent text-only protocols (good for debugging) and binary,	1175	language independent text-only protocols (good for debugging), and binary,
912	language-specific serialisers (e.g. Storable). By default, unless TLS is	1176	language-specific serialisers (e.g. Storable). By default, unless TLS is
913	used, the protocol is actually completely text-based.	1177	used, the protocol is actually completely text-based.
914		1178
915	It has also been carefully designed to be implementable in other languages	1179	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	1180	with a minimum of work while gracefully degrading functionality to make the
917	protocol simple.	1181	protocol simple.
918		1182
919	=item * AEMP has more flexible monitoring options than Erlang.	1183	=item * AEMP has more flexible monitoring options than Erlang.
920		1184
921	In Erlang, you can chose to receive I<all> exit signals as messages	1185	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	1186	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	1187	difficult to implement.
924	Erlang, as one can choose between automatic kill, exit message or callback	1188
925	on a per-process basis.	1189	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1190	between automatic kill, exit message or callback on a per-port basis.
926		1191
927	=item * Erlang tries to hide remote/local connections, AEMP does not.	1192	=item * Erlang tries to hide remote/local connections, AEMP does not.
928		1193
929	Monitoring in Erlang is not an indicator of process death/crashes, in the	1194	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).	1195	same way as linking is (except linking is unreliable in Erlang).
…		…
973	Keeping your messages simple, concentrating on data structures rather than	1238	Keeping your messages simple, concentrating on data structures rather than
974	objects, will keep your messages clean, tidy and efficient.	1239	objects, will keep your messages clean, tidy and efficient.
975		1240
976	=back	1241	=back
977		1242
		1243	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1244
		1245	AEMP version 2 has a few major incompatible changes compared to version 1:
		1246
		1247	=over 4
		1248
		1249	=item AnyEvent::MP::Global no longer has group management functions.
		1250
		1251	At least not officially - the grp_* functions are still exported and might
		1252	work, but they will be removed in some later release.
		1253
		1254	AnyEvent::MP now comes with a distributed database that is more
		1255	powerful. Its database families map closely to port groups, but the API
		1256	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1257	a rough porting guide:
		1258
		1259	grp_reg $group, $port # old
		1260	db_reg $group, $port # new
		1261
		1262	$list = grp_get $group # old
		1263	db_keys $group, sub { my $list = shift } # new
		1264
		1265	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1266	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1267
		1268	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1269	no longer instant, because the local node might not have a copy of the
		1270	group. You can either modify your code to allow for a callback, or use
		1271	C<db_mon> to keep an updated copy of the group:
		1272
		1273	my $local_group_copy;
		1274	db_mon $group => sub { $local_group_copy = $_[0] };
		1275
		1276	# now "keys %$local_group_copy" always returns the most up-to-date
		1277	# list of ports in the group.
		1278
		1279	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1280	passes a hash as first argument, and an extra C<$chg> argument that can be
		1281	ignored:
		1282
		1283	db_mon $group => sub {
		1284	my ($ports, $add, $chg, $lde) = @_;
		1285	$ports = [keys %$ports];
		1286
		1287	# now $ports, $add and $del are the same as
		1288	# were originally passed by grp_mon.
		1289	...
		1290	};
		1291
		1292	=item Nodes not longer connect to all other nodes.
		1293
		1294	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1295	module, which in turn would create connections to all other nodes in the
		1296	network (helped by the seed nodes).
		1297
		1298	In version 2.x, global nodes still connect to all other global nodes, but
		1299	other nodes don't - now every node either is a global node itself, or
		1300	attaches itself to another global node.
		1301
		1302	If a node isn't a global node itself, then it attaches itself to one
		1303	of its seed nodes. If that seed node isn't a global node yet, it will
		1304	automatically be upgraded to a global node.
		1305
		1306	So in many cases, nothing needs to be changed - one just has to make sure
		1307	that all seed nodes are meshed together with the other seed nodes (as with
		1308	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1309	achieved by specifying the same set of seed nodes for all nodes in the
		1310	network.
		1311
		1312	Not opening a connection to every other node is usually an advantage,
		1313	except when you need the lower latency of an already established
		1314	connection. To ensure a node establishes a connection to another node,
		1315	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1316	create the connection (and notify you when the connection fails).
		1317
		1318	=item Listener-less nodes (nodes without binds) are gone.
		1319
		1320	And are not coming back, at least not in their old form. If no C<binds>
		1321	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1322
		1323	There are vague plans to implement some form of routing domains, which
		1324	might or might not bring back listener-less nodes, but don't count on it.
		1325
		1326	The fact that most connections are now optional somewhat mitigates this,
		1327	as a node can be effectively unreachable from the outside without any
		1328	problems, as long as it isn't a global node and only reaches out to other
		1329	nodes (as opposed to being contacted from other nodes).
		1330
		1331	=item $AnyEvent::MP::Kernel::WARN has gone.
		1332
		1333	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1334	uses this, and so should your programs.
		1335
		1336	Every module now documents what kinds of messages it generates, with
		1337	AnyEvent::MP acting as a catch all.
		1338
		1339	On the positive side, this means that instead of setting
		1340	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1341	much less to type.
		1342
		1343	=back
		1344
		1345	=head1 LOGGING
		1346
		1347	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1348	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1349	all log messages by submodules.
		1350
978	=head1 SEE ALSO	1351	=head1 SEE ALSO
979		1352
980	L<AnyEvent::MP::Intro> - a gentle introduction.	1353	L<AnyEvent::MP::Intro> - a gentle introduction.
981		1354
982	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1355	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.118 by root, Thu Jun 30 09:31:58 2011 UTC vs. Revision 1.142 by root, Fri Mar 23 13:44:01 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.118 by root, Thu Jun 30 09:31:58 2011 UTC vs.
Revision 1.142 by root, Fri Mar 23 13:44:01 2012 UTC