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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.102 by root, Tue Oct 6 13:37:52 2009 UTC vs.
Revision 1.136 by root, Wed Mar 21 15:22:16 2012 UTC

…		…
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 prot 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 = 1.21;	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() {
…		…
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	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
197	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
198		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
		266
199	=over 4	267	=over 4
200		268
201	=item step 1, gathering configuration from profiles	269	=item step 1, gathering configuration from profiles
202		270
203	The function first looks up a profile in the aemp configuration (see the	271	The function first looks up a profile in the aemp configuration (see the
…		…
216	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
217	and the values specified directly via C<configure> have lowest priority,	285	and the values specified directly via C<configure> have lowest priority,
218	and can only be used to specify defaults.	286	and can only be used to specify defaults.
219		287
220	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
221	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
222	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>.
223		297
224	=item step 2, bind listener sockets	298	=item step 2, bind listener sockets
225		299
226	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
227	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
…		…
233	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
234	local IP address it finds.	308	local IP address it finds.
235		309
236	=item step 3, connect to seed nodes	310	=item step 3, connect to seed nodes
237		311
238	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
239	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
240	connectivity with at least one node at any point in time.	314	connectivity with at least one node at any point in time.
241		315
242	=back	316	=back
243		317
244	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.
245	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.
246		320
247	configure	321	configure
248		322
249	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
250	clients.	324	commandline clients.
251		325
252	configure nodeid => "anon/";	326	configure nodeid => "myscript/%n/%u";
253		327
254	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
255	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,
256	customary for aemp).	330	customary for aemp).
257		331
258	# use the aemp commandline utility	332	# use the aemp commandline utility
259	# aemp profile seed nodeid anon/ binds '*:4040'	333	# aemp profile seed binds '*:4040'
260		334
261	# then use it	335	# then use it
262	configure profile => "seed";	336	configure profile => "seed";
263		337
264	# or simply use aemp from the shell again:	338	# or simply use aemp from the shell again:
…		…
329		403
330	=cut	404	=cut
331		405
332	sub rcv($@);	406	sub rcv($@);
333		407
334	sub _kilme {	408	my $KILME = sub {
335	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
336	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
337		412
338	sub port(;&) {	413	sub port(;&) {
339	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
340	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
341		416
342	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
343		418
344	$port	419	$port
345	}	420	}
346		421
347	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
352		427
353	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
355	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
356		431
357	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
358	C<tag> match.	433	C<tag> match.
359		434
360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
361		436
362	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
…		…
406	if (ref $_[0]) {	481	if (ref $_[0]) {
407	if (my $self = $PORT_DATA{$portid}) {	482	if (my $self = $PORT_DATA{$portid}) {
408	"AnyEvent::MP::Port" eq ref $self	483	"AnyEvent::MP::Port" eq ref $self
409	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	484	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
410		485
411	$self->[2] = shift;	486	$self->[0] = shift;
412	} else {	487	} else {
413	my $cb = shift;	488	my $cb = shift;
414	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
415	local $SELF = $port;	490	local $SELF = $port;
416	eval { &$cb }; _self_die if $@;	491	eval { &$cb }; _self_die if $@;
417	};	492	};
418	}	493	}
419	} elsif (defined $_[0]) {	494	} elsif (defined $_[0]) {
420	my $self = $PORT_DATA{$portid} \|\|= do {	495	my $self = $PORT_DATA{$portid} \|\|= do {
421	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	496	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
422		497
423	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
424	local $SELF = $port;	499	local $SELF = $port;
425		500
426	if (my $cb = $self->[1]{$_[0]}) {	501	if (my $cb = $self->[1]{$_[0]}) {
…		…
492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	567	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
493	closure is executed, sets up the environment in the same way as in C<rcv>	568	closure is executed, sets up the environment in the same way as in C<rcv>
494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	569	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
495		570
496	The effect is basically as if it returned C<< sub { peval $SELF, sub {	571	The effect is basically as if it returned C<< sub { peval $SELF, sub {
497	BLOCK } } >>.	572	BLOCK }, @_ } >>.
498		573
499	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
500		575
501	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
502	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
617	}	692	}
618		693
619	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
620		695
621	defined wantarray	696	defined wantarray
622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
623	}	698	}
624		699
625	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
626		701
627	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
…		…
650		725
651	=item kil $port[, @reason]	726	=item kil $port[, @reason]
652		727
653	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
654		729
655	If no C<@reason> is specified, then the port is killed "normally" (ports	730	If no C<@reason> is specified, then the port is killed "normally" -
656	monitoring other ports will not necessarily die because a port dies	731	monitor callback will be invoked, but the kil will not cause linked ports
657	"normally").	732	(C<mon $mport, $lport> form) to get killed.
658		733
659	Otherwise, linked ports get killed with the same reason (second form of	734	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
660	C<mon>, see above).	735	form) get killed with the same reason.
661		736
662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	737	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
663	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
664		739
665	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
666	$message >>.	741	$message >>.
667		742
668	=cut	743	Common idioms:
		744
		745	# silently remove yourself, do not kill linked ports
		746	kil $SELF;
		747
		748	# report a failure in some detail
		749	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		750
		751	# do not waste much time with killing, just die when something goes wrong
		752	open my $fh, "<file"
		753	or die "file: $!";
669		754
670	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
671		756
672	Creates a port on the node C<$node> (which can also be a port ID, in which	757	Creates a port on the node C<$node> (which can also be a port ID, in which
673	case it's the node where that port resides).	758	case it's the node where that port resides).
…		…
731	}	816	}
732		817
733	sub spawn(@) {	818	sub spawn(@) {
734	my ($nodeid, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
735		820
736	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
737		822
738	$_[0] =~ /::/	823	$_[0] =~ /::/
739	or Carp::croak "spawn init function must be a fully-qualified name, caught";	824	or Carp::croak "spawn init function must be a fully-qualified name, caught";
740		825
741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
742		827
743	"$nodeid#$id"	828	"$nodeid#$id"
744	}	829	}
		830
745		831
746	=item after $timeout, @msg	832	=item after $timeout, @msg
747		833
748	=item after $timeout, $callback	834	=item after $timeout, $callback
749		835
…		…
764	ref $action[0]	850	ref $action[0]
765	? $action[0]()	851	? $action[0]()
766	: snd @action;	852	: snd @action;
767	};	853	};
768	}	854	}
		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
769		857
770	=item cal $port, @msg, $callback[, $timeout]	858	=item cal $port, @msg, $callback[, $timeout]
771		859
772	A simple form of RPC - sends a message to the given C<$port> with the	860	A simple form of RPC - sends a message to the given C<$port> with the
773	given contents (C<@msg>), but adds a reply port to the message.	861	given contents (C<@msg>), but adds a reply port to the message.
…		…
819	$port	907	$port
820	}	908	}
821		909
822	=back	910	=back
823		911
		912	=head1 DISTRIBUTED DATABASE
		913
		914	AnyEvent::MP comes with a simple distributed database. The database will
		915	be mirrored asynchronously on all global nodes. Other nodes bind to one
		916	of the global nodes for their needs. Every node has a "local database"
		917	which contains all the values that are set locally. All local databases
		918	are merged together to form the global database, which can be queried.
		919
		920	The database structure is that of a two-level hash - the database hash
		921	contains hashes which contain values, similarly to a perl hash of hashes,
		922	i.e.:
		923
		924	$DATABASE{$family}{$subkey} = $value
		925
		926	The top level hash key is called "family", and the second-level hash key
		927	is called "subkey" or simply "key".
		928
		929	The family must be alphanumeric, i.e. start with a letter and consist
		930	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		931	pretty much like Perl module names.
		932
		933	As the family namespace is global, it is recommended to prefix family names
		934	with the name of the application or module using it.
		935
		936	The subkeys must be non-empty strings, with no further restrictions.
		937
		938	The values should preferably be strings, but other perl scalars should
		939	work as well (such as C<undef>, arrays and hashes).
		940
		941	Every database entry is owned by one node - adding the same family/subkey
		942	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		943	but the result might be nondeterministic, i.e. the key might have
		944	different values on different nodes.
		945
		946	Different subkeys in the same family can be owned by different nodes
		947	without problems, and in fact, this is the common method to create worker
		948	pools. For example, a worker port for image scaling might do this:
		949
		950	db_set my_image_scalers => $port;
		951
		952	And clients looking for an image scaler will want to get the
		953	C<my_image_scalers> keys from time to time:
		954
		955	db_keys my_image_scalers => sub {
		956	@ports = @{ $_[0] };
		957	};
		958
		959	Or better yet, they want to monitor the database family, so they always
		960	have a reasonable up-to-date copy:
		961
		962	db_mon my_image_scalers => sub {
		963	@ports = keys %{ $_[0] };
		964	};
		965
		966	In general, you can set or delete single subkeys, but query and monitor
		967	whole families only.
		968
		969	If you feel the need to monitor or query a single subkey, try giving it
		970	it's own family.
		971
		972	=over
		973
		974	=item db_set $family => $subkey [=> $value]
		975
		976	Sets (or replaces) a key to the database - if C<$value> is omitted,
		977	C<undef> is used instead.
		978
		979	=item db_del $family => $subkey...
		980
		981	Deletes one or more subkeys from the database family.
		982
		983	=item $guard = db_reg $family => $subkey [=> $value]
		984
		985	Sets the key on the database and returns a guard. When the guard is
		986	destroyed, the key is deleted from the database. If C<$value> is missing,
		987	then C<undef> is used.
		988
		989	=item db_family $family => $cb->(\%familyhash)
		990
		991	Queries the named database C<$family> and call the callback with the
		992	family represented as a hash. You can keep and freely modify the hash.
		993
		994	=item db_keys $family => $cb->(\@keys)
		995
		996	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		997	them as array reference to the callback.
		998
		999	=item db_values $family => $cb->(\@values)
		1000
		1001	Same as C<db_family>, except it only queries the family I<values> and passes them
		1002	as array reference to the callback.
		1003
		1004	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1005
		1006	Creates a monitor on the given database family. Each time a key is set
		1007	or or is deleted the callback is called with a hash containing the
		1008	database family and three lists of added, changed and deleted subkeys,
		1009	respectively. If no keys have changed then the array reference might be
		1010	C<undef> or even missing.
		1011
		1012	If not called in void context, a guard object is returned that, when
		1013	destroyed, stops the monitor.
		1014
		1015	The family hash reference and the key arrays belong to AnyEvent::MP and
		1016	B<must not be modified or stored> by the callback. When in doubt, make a
		1017	copy.
		1018
		1019	As soon as possible after the monitoring starts, the callback will be
		1020	called with the intiial contents of the family, even if it is empty,
		1021	i.e. there will always be a timely call to the callback with the current
		1022	contents.
		1023
		1024	It is possible that the callback is called with a change event even though
		1025	the subkey is already present and the value has not changed.
		1026
		1027	The monitoring stops when the guard object is destroyed.
		1028
		1029	Example: on every change to the family "mygroup", print out all keys.
		1030
		1031	my $guard = db_mon mygroup => sub {
		1032	my ($family, $a, $c, $d) = @_;
		1033	print "mygroup members: ", (join " ", keys %$family), "\n";
		1034	};
		1035
		1036	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1037
		1038	my $guard; $guard = db_mon My::Module::workers => sub {
		1039	my ($family, $a, $c, $d) = @_;
		1040	return unless %$family;
		1041	undef $guard;
		1042	print "My::Module::workers now nonempty\n";
		1043	};
		1044
		1045	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1046
		1047	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1048	my ($family, $a, $c, $d) = @_;
		1049
		1050	print "+$_=$family->{$_}\n" for @$a;
		1051	print "*$_=$family->{$_}\n" for @$c;
		1052	print "-$_=$family->{$_}\n" for @$d;
		1053	};
		1054
		1055	=cut
		1056
		1057	=back
		1058
824	=head1 AnyEvent::MP vs. Distributed Erlang	1059	=head1 AnyEvent::MP vs. Distributed Erlang
825		1060
826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1061	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
827	== aemp node, Erlang process == aemp port), so many of the documents and	1062	== aemp node, Erlang process == aemp port), so many of the documents and
828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1063	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
…		…
859	ports being the special case/exception, where transport errors cannot	1094	ports being the special case/exception, where transport errors cannot
860	occur.	1095	occur.
861		1096
862	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1097	=item * Erlang uses processes and a mailbox, AEMP does not queue.
863		1098
864	Erlang uses processes that selectively receive messages, and therefore	1099	Erlang uses processes that selectively receive messages out of order, and
865	needs a queue. AEMP is event based, queuing messages would serve no	1100	therefore needs a queue. AEMP is event based, queuing messages would serve
866	useful purpose. For the same reason the pattern-matching abilities of	1101	no useful purpose. For the same reason the pattern-matching abilities
867	AnyEvent::MP are more limited, as there is little need to be able to	1102	of AnyEvent::MP are more limited, as there is little need to be able to
868	filter messages without dequeuing them.	1103	filter messages without dequeuing them.
869		1104
870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1105	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1106	being event-based, while Erlang is process-based.
		1107
		1108	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1109	top of AEMP and Coro threads.
871		1110
872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1111	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
873		1112
874	Sending messages in Erlang is synchronous and blocks the process (and	1113	Sending messages in Erlang is synchronous and blocks the process until
		1114	a conenction has been established and the message sent (and so does not
875	so does not need a queue that can overflow). AEMP sends are immediate,	1115	need a queue that can overflow). AEMP sends return immediately, connection
876	connection establishment is handled in the background.	1116	establishment is handled in the background.
877		1117
878	=item * Erlang suffers from silent message loss, AEMP does not.	1118	=item * Erlang suffers from silent message loss, AEMP does not.
879		1119
880	Erlang implements few guarantees on messages delivery - messages can get	1120	Erlang implements few guarantees on messages delivery - messages can get
881	lost without any of the processes realising it (i.e. you send messages a,	1121	lost without any of the processes realising it (i.e. you send messages a,
882	b, and c, and the other side only receives messages a and c).	1122	b, and c, and the other side only receives messages a and c).
883		1123
884	AEMP guarantees correct ordering, and the guarantee that after one message	1124	AEMP guarantees (modulo hardware errors) correct ordering, and the
885	is lost, all following ones sent to the same port are lost as well, until	1125	guarantee that after one message is lost, all following ones sent to the
886	monitoring raises an error, so there are no silent "holes" in the message	1126	same port are lost as well, until monitoring raises an error, so there are
887	sequence.	1127	no silent "holes" in the message sequence.
		1128
		1129	If you want your software to be very reliable, you have to cope with
		1130	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1131	simply tries to work better in common error cases, such as when a network
		1132	link goes down.
888		1133
889	=item * Erlang can send messages to the wrong port, AEMP does not.	1134	=item * Erlang can send messages to the wrong port, AEMP does not.
890		1135
891	In Erlang it is quite likely that a node that restarts reuses a process ID	1136	In Erlang it is quite likely that a node that restarts reuses an Erlang
892	known to other nodes for a completely different process, causing messages	1137	process ID known to other nodes for a completely different process,
893	destined for that process to end up in an unrelated process.	1138	causing messages destined for that process to end up in an unrelated
		1139	process.
894		1140
895	AEMP never reuses port IDs, so old messages or old port IDs floating	1141	AEMP does not reuse port IDs, so old messages or old port IDs floating
896	around in the network will not be sent to an unrelated port.	1142	around in the network will not be sent to an unrelated port.
897		1143
898	=item * Erlang uses unprotected connections, AEMP uses secure	1144	=item * Erlang uses unprotected connections, AEMP uses secure
899	authentication and can use TLS.	1145	authentication and can use TLS.
900		1146
…		…
903		1149
904	=item * The AEMP protocol is optimised for both text-based and binary	1150	=item * The AEMP protocol is optimised for both text-based and binary
905	communications.	1151	communications.
906		1152
907	The AEMP protocol, unlike the Erlang protocol, supports both programming	1153	The AEMP protocol, unlike the Erlang protocol, supports both programming
908	language independent text-only protocols (good for debugging) and binary,	1154	language independent text-only protocols (good for debugging), and binary,
909	language-specific serialisers (e.g. Storable). By default, unless TLS is	1155	language-specific serialisers (e.g. Storable). By default, unless TLS is
910	used, the protocol is actually completely text-based.	1156	used, the protocol is actually completely text-based.
911		1157
912	It has also been carefully designed to be implementable in other languages	1158	It has also been carefully designed to be implementable in other languages
913	with a minimum of work while gracefully degrading functionality to make the	1159	with a minimum of work while gracefully degrading functionality to make the
914	protocol simple.	1160	protocol simple.
915		1161
916	=item * AEMP has more flexible monitoring options than Erlang.	1162	=item * AEMP has more flexible monitoring options than Erlang.
917		1163
918	In Erlang, you can chose to receive I<all> exit signals as messages	1164	In Erlang, you can chose to receive I<all> exit signals as messages or
919	or I<none>, there is no in-between, so monitoring single processes is	1165	I<none>, there is no in-between, so monitoring single Erlang processes is
920	difficult to implement. Monitoring in AEMP is more flexible than in	1166	difficult to implement.
921	Erlang, as one can choose between automatic kill, exit message or callback	1167
922	on a per-process basis.	1168	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1169	between automatic kill, exit message or callback on a per-port basis.
923		1170
924	=item * Erlang tries to hide remote/local connections, AEMP does not.	1171	=item * Erlang tries to hide remote/local connections, AEMP does not.
925		1172
926	Monitoring in Erlang is not an indicator of process death/crashes, in the	1173	Monitoring in Erlang is not an indicator of process death/crashes, in the
927	same way as linking is (except linking is unreliable in Erlang).	1174	same way as linking is (except linking is unreliable in Erlang).
…		…
949	overhead, as well as having to keep a proxy object everywhere.	1196	overhead, as well as having to keep a proxy object everywhere.
950		1197
951	Strings can easily be printed, easily serialised etc. and need no special	1198	Strings can easily be printed, easily serialised etc. and need no special
952	procedures to be "valid".	1199	procedures to be "valid".
953		1200
954	And as a result, a miniport consists of a single closure stored in a	1201	And as a result, a port with just a default receiver consists of a single
955	global hash - it can't become much cheaper.	1202	code reference stored in a global hash - it can't become much cheaper.
956		1203
957	=item Why favour JSON, why not a real serialising format such as Storable?	1204	=item Why favour JSON, why not a real serialising format such as Storable?
958		1205
959	In fact, any AnyEvent::MP node will happily accept Storable as framing	1206	In fact, any AnyEvent::MP node will happily accept Storable as framing
960	format, but currently there is no way to make a node use Storable by	1207	format, but currently there is no way to make a node use Storable by
…		…
976		1223
977	L<AnyEvent::MP::Intro> - a gentle introduction.	1224	L<AnyEvent::MP::Intro> - a gentle introduction.
978		1225
979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1226	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
980		1227
981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1228	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
982	your applications.	1229	your applications.
		1230
		1231	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
983		1232
984	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1233	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
985	all nodes.	1234	all nodes.
986		1235
987	L<AnyEvent>.	1236	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.102 by root, Tue Oct 6 13:37:52 2009 UTC vs. Revision 1.136 by root, Wed Mar 21 15:22:16 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.102 by root, Tue Oct 6 13:37:52 2009 UTC vs.
Revision 1.136 by root, Wed Mar 21 15:22:16 2012 UTC