[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 1.134 by root, Mon Mar 12 14:47:23 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 => $pass->($nodeid)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every remote execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	See F<semp setsecure> for more info.
		259
		260	=back
		261
199	=over 4	262	=over 4
200		263
201	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
202		265
203	The function first looks up a profile in the aemp configuration (see the	266	The function first looks up a profile in the aemp configuration (see the
…		…
216	That means that the values specified in the profile have highest priority	279	That means that the values specified in the profile have highest priority
217	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
218	and can only be used to specify defaults.	281	and can only be used to specify defaults.
219		282
220	If the profile specifies a node ID, then this will become the node ID of	283	If the profile specifies a node ID, then this will become the node ID of
221	this process. If not, then the profile name will be used as node ID. The	284	this process. If not, then the profile name will be used as node ID, with
222	special node ID of C<anon/> will be replaced by a random node ID.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
223		292
224	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
225		294
226	The next step is to look up the binds in the profile, followed by binding	295	The next step is to look up the binds in the profile, followed by binding
227	aemp protocol listeners on all binds specified (it is possible and valid	296	aemp protocol listeners on all binds specified (it is possible and valid
…		…
233	used, meaning the node will bind on a dynamically-assigned port on every	302	used, meaning the node will bind on a dynamically-assigned port on every
234	local IP address it finds.	303	local IP address it finds.
235		304
236	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
237		306
238	As the last step, the seeds list from the profile is passed to the	307	As the last step, the seed ID list from the profile is passed to the
239	L<AnyEvent::MP::Global> module, which will then use it to keep	308	L<AnyEvent::MP::Global> module, which will then use it to keep
240	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
241		310
242	=back	311	=back
243		312
244	Example: become a distributed node using the local node name as profile.	313	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.	314	This should be the most common form of invocation for "daemon"-type nodes.
246		315
247	configure	316	configure
248		317
249	Example: become an anonymous node. This form is often used for commandline	318	Example: become a semi-anonymous node. This form is often used for
250	clients.	319	commandline clients.
251		320
252	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
253		322
254	Example: configure a node using a profile called seed, which si suitable	323	Example: configure a node using a profile called seed, which is suitable
255	for a seed node as it binds on all local addresses on a fixed port (4040,	324	for a seed node as it binds on all local addresses on a fixed port (4040,
256	customary for aemp).	325	customary for aemp).
257		326
258	# use the aemp commandline utility	327	# use the aemp commandline utility
259	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
260		329
261	# then use it	330	# then use it
262	configure profile => "seed";	331	configure profile => "seed";
263		332
264	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
329		398
330	=cut	399	=cut
331		400
332	sub rcv($@);	401	sub rcv($@);
333		402
334	sub _kilme {	403	my $KILME = sub {
335	die "received message on port without callback";	404	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
336	}	405	kil $SELF, unhandled_message => "missing (tag or fallback) callback for message '$tag'";
		406	};
337		407
338	sub port(;&) {	408	sub port(;&) {
339	my $id = "$UNIQ." . $ID++;	409	my $id = $UNIQ . ++$ID;
340	my $port = "$NODE#$id";	410	my $port = "$NODE#$id";
341		411
342	rcv $port, shift \|\| \&_kilme;	412	rcv $port, shift \|\| $KILME;
343		413
344	$port	414	$port
345	}	415	}
346		416
347	=item rcv $local_port, $callback->(@msg)	417	=item rcv $local_port, $callback->(@msg)
…		…
352		422
353	The global C<$SELF> (exported by this module) contains C<$port> while	423	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback. Runtime errors during callback execution will	424	executing the callback. Runtime errors during callback execution will
355	result in the port being C<kil>ed.	425	result in the port being C<kil>ed.
356		426
357	The default callback received all messages not matched by a more specific	427	The default callback receives all messages not matched by a more specific
358	C<tag> match.	428	C<tag> match.
359		429
360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	430	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
361		431
362	Register (or replace) callbacks to be called on messages starting with the	432	Register (or replace) callbacks to be called on messages starting with the
…		…
406	if (ref $_[0]) {	476	if (ref $_[0]) {
407	if (my $self = $PORT_DATA{$portid}) {	477	if (my $self = $PORT_DATA{$portid}) {
408	"AnyEvent::MP::Port" eq ref $self	478	"AnyEvent::MP::Port" eq ref $self
409	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	479	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
410		480
411	$self->[2] = shift;	481	$self->[0] = shift;
412	} else {	482	} else {
413	my $cb = shift;	483	my $cb = shift;
414	$PORT{$portid} = sub {	484	$PORT{$portid} = sub {
415	local $SELF = $port;	485	local $SELF = $port;
416	eval { &$cb }; _self_die if $@;	486	eval { &$cb }; _self_die if $@;
417	};	487	};
418	}	488	}
419	} elsif (defined $_[0]) {	489	} elsif (defined $_[0]) {
420	my $self = $PORT_DATA{$portid} \|\|= do {	490	my $self = $PORT_DATA{$portid} \|\|= do {
421	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	491	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
422		492
423	$PORT{$portid} = sub {	493	$PORT{$portid} = sub {
424	local $SELF = $port;	494	local $SELF = $port;
425		495
426	if (my $cb = $self->[1]{$_[0]}) {	496	if (my $cb = $self->[1]{$_[0]}) {
…		…
492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	562	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
493	closure is executed, sets up the environment in the same way as in C<rcv>	563	closure is executed, sets up the environment in the same way as in C<rcv>
494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	564	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
495		565
496	The effect is basically as if it returned C<< sub { peval $SELF, sub {	566	The effect is basically as if it returned C<< sub { peval $SELF, sub {
497	BLOCK } } >>.	567	BLOCK }, @_ } >>.
498		568
499	This is useful when you register callbacks from C<rcv> callbacks:	569	This is useful when you register callbacks from C<rcv> callbacks:
500		570
501	rcv delayed_reply => sub {	571	rcv delayed_reply => sub {
502	my ($delay, @reply) = @_;	572	my ($delay, @reply) = @_;
…		…
617	}	687	}
618		688
619	$node->monitor ($port, $cb);	689	$node->monitor ($port, $cb);
620		690
621	defined wantarray	691	defined wantarray
622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })	692	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
623	}	693	}
624		694
625	=item $guard = mon_guard $port, $ref, $ref...	695	=item $guard = mon_guard $port, $ref, $ref...
626		696
627	Monitors the given C<$port> and keeps the passed references. When the port	697	Monitors the given C<$port> and keeps the passed references. When the port
…		…
650		720
651	=item kil $port[, @reason]	721	=item kil $port[, @reason]
652		722
653	Kill the specified port with the given C<@reason>.	723	Kill the specified port with the given C<@reason>.
654		724
655	If no C<@reason> is specified, then the port is killed "normally" (ports	725	If no C<@reason> is specified, then the port is killed "normally" -
656	monitoring other ports will not necessarily die because a port dies	726	monitor callback will be invoked, but the kil will not cause linked ports
657	"normally").	727	(C<mon $mport, $lport> form) to get killed.
658		728
659	Otherwise, linked ports get killed with the same reason (second form of	729	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
660	C<mon>, see above).	730	form) get killed with the same reason.
661		731
662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	732	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
663	will be reported as reason C<< die => $@ >>.	733	will be reported as reason C<< die => $@ >>.
664		734
665	Transport/communication errors are reported as C<< transport_error =>	735	Transport/communication errors are reported as C<< transport_error =>
666	$message >>.	736	$message >>.
667		737
668	=cut	738	Common idioms:
		739
		740	# silently remove yourself, do not kill linked ports
		741	kil $SELF;
		742
		743	# report a failure in some detail
		744	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		745
		746	# do not waste much time with killing, just die when something goes wrong
		747	open my $fh, "<file"
		748	or die "file: $!";
669		749
670	=item $port = spawn $node, $initfunc[, @initdata]	750	=item $port = spawn $node, $initfunc[, @initdata]
671		751
672	Creates a port on the node C<$node> (which can also be a port ID, in which	752	Creates a port on the node C<$node> (which can also be a port ID, in which
673	case it's the node where that port resides).	753	case it's the node where that port resides).
…		…
731	}	811	}
732		812
733	sub spawn(@) {	813	sub spawn(@) {
734	my ($nodeid, undef) = split /#/, shift, 2;	814	my ($nodeid, undef) = split /#/, shift, 2;
735		815
736	my $id = "$RUNIQ." . $ID++;	816	my $id = $RUNIQ . ++$ID;
737		817
738	$_[0] =~ /::/	818	$_[0] =~ /::/
739	or Carp::croak "spawn init function must be a fully-qualified name, caught";	819	or Carp::croak "spawn init function must be a fully-qualified name, caught";
740		820
741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	821	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
742		822
743	"$nodeid#$id"	823	"$nodeid#$id"
744	}	824	}
		825
745		826
746	=item after $timeout, @msg	827	=item after $timeout, @msg
747		828
748	=item after $timeout, $callback	829	=item after $timeout, $callback
749		830
…		…
764	ref $action[0]	845	ref $action[0]
765	? $action[0]()	846	? $action[0]()
766	: snd @action;	847	: snd @action;
767	};	848	};
768	}	849	}
		850
		851	#=item $cb2 = timeout $seconds, $cb[, @args]
769		852
770	=item cal $port, @msg, $callback[, $timeout]	853	=item cal $port, @msg, $callback[, $timeout]
771		854
772	A simple form of RPC - sends a message to the given C<$port> with the	855	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.	856	given contents (C<@msg>), but adds a reply port to the message.
…		…
819	$port	902	$port
820	}	903	}
821		904
822	=back	905	=back
823		906
		907	=head1 DISTRIBUTED DATABASE
		908
		909	AnyEvent::MP comes with a simple distributed database. The database will
		910	be mirrored asynchronously on all global nodes. Other nodes bind to one
		911	of the global nodes for their needs. Every node has a "local database"
		912	which contains all the values that are set locally. All local databases
		913	are merged together to form the global database, which can be queried.
		914
		915	The database structure is that of a two-level hash - the database hash
		916	contains hashes which contain values, similarly to a perl hash of hashes,
		917	i.e.:
		918
		919	$DATABASE{$family}{$subkey} = $value
		920
		921	The top level hash key is called "family", and the second-level hash key
		922	is called "subkey" or simply "key".
		923
		924	The family must be alphanumeric, i.e. start with a letter and consist
		925	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		926	pretty much like Perl module names.
		927
		928	As the family namespace is global, it is recommended to prefix family names
		929	with the name of the application or module using it.
		930
		931	The subkeys must be non-empty strings, with no further restrictions.
		932
		933	The values should preferably be strings, but other perl scalars should
		934	work as well (such as C<undef>, arrays and hashes).
		935
		936	Every database entry is owned by one node - adding the same family/subkey
		937	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		938	but the result might be nondeterministic, i.e. the key might have
		939	different values on different nodes.
		940
		941	Different subkeys in the same family can be owned by different nodes
		942	without problems, and in fact, this is the common method to create worker
		943	pools. For example, a worker port for image scaling might do this:
		944
		945	db_set my_image_scalers => $port;
		946
		947	And clients looking for an image scaler will want to get the
		948	C<my_image_scalers> keys from time to time:
		949
		950	db_keys my_image_scalers => sub {
		951	@ports = @{ $_[0] };
		952	};
		953
		954	Or better yet, they want to monitor the database family, so they always
		955	have a reasonable up-to-date copy:
		956
		957	db_mon my_image_scalers => sub {
		958	@ports = keys %{ $_[0] };
		959	};
		960
		961	In general, you can set or delete single subkeys, but query and monitor
		962	whole families only.
		963
		964	If you feel the need to monitor or query a single subkey, try giving it
		965	it's own family.
		966
		967	=over
		968
		969	=item db_set $family => $subkey [=> $value]
		970
		971	Sets (or replaces) a key to the database - if C<$value> is omitted,
		972	C<undef> is used instead.
		973
		974	=item db_del $family => $subkey...
		975
		976	Deletes one or more subkeys from the database family.
		977
		978	=item $guard = db_reg $family => $subkey [=> $value]
		979
		980	Sets the key on the database and returns a guard. When the guard is
		981	destroyed, the key is deleted from the database. If C<$value> is missing,
		982	then C<undef> is used.
		983
		984	=item db_family $family => $cb->(\%familyhash)
		985
		986	Queries the named database C<$family> and call the callback with the
		987	family represented as a hash. You can keep and freely modify the hash.
		988
		989	=item db_keys $family => $cb->(\@keys)
		990
		991	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		992	them as array reference to the callback.
		993
		994	=item db_values $family => $cb->(\@values)
		995
		996	Same as C<db_family>, except it only queries the family I<values> and passes them
		997	as array reference to the callback.
		998
		999	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1000
		1001	Creates a monitor on the given database family. Each time a key is set
		1002	or or is deleted the callback is called with a hash containing the
		1003	database family and three lists of added, changed and deleted subkeys,
		1004	respectively. If no keys have changed then the array reference might be
		1005	C<undef> or even missing.
		1006
		1007	If not called in void context, a guard object is returned that, when
		1008	destroyed, stops the monitor.
		1009
		1010	The family hash reference and the key arrays belong to AnyEvent::MP and
		1011	B<must not be modified or stored> by the callback. When in doubt, make a
		1012	copy.
		1013
		1014	As soon as possible after the monitoring starts, the callback will be
		1015	called with the intiial contents of the family, even if it is empty,
		1016	i.e. there will always be a timely call to the callback with the current
		1017	contents.
		1018
		1019	It is possible that the callback is called with a change event even though
		1020	the subkey is already present and the value has not changed.
		1021
		1022	The monitoring stops when the guard object is destroyed.
		1023
		1024	Example: on every change to the family "mygroup", print out all keys.
		1025
		1026	my $guard = db_mon mygroup => sub {
		1027	my ($family, $a, $c, $d) = @_;
		1028	print "mygroup members: ", (join " ", keys %$family), "\n";
		1029	};
		1030
		1031	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1032
		1033	my $guard; $guard = db_mon My::Module::workers => sub {
		1034	my ($family, $a, $c, $d) = @_;
		1035	return unless %$family;
		1036	undef $guard;
		1037	print "My::Module::workers now nonempty\n";
		1038	};
		1039
		1040	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1041
		1042	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1043	my ($family, $a, $c, $d) = @_;
		1044
		1045	print "+$_=$family->{$_}\n" for @$a;
		1046	print "*$_=$family->{$_}\n" for @$c;
		1047	print "-$_=$family->{$_}\n" for @$d;
		1048	};
		1049
		1050	=cut
		1051
		1052	=back
		1053
824	=head1 AnyEvent::MP vs. Distributed Erlang	1054	=head1 AnyEvent::MP vs. Distributed Erlang
825		1055
826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1056	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
827	== aemp node, Erlang process == aemp port), so many of the documents and	1057	== aemp node, Erlang process == aemp port), so many of the documents and
828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1058	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
…		…
859	ports being the special case/exception, where transport errors cannot	1089	ports being the special case/exception, where transport errors cannot
860	occur.	1090	occur.
861		1091
862	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1092	=item * Erlang uses processes and a mailbox, AEMP does not queue.
863		1093
864	Erlang uses processes that selectively receive messages, and therefore	1094	Erlang uses processes that selectively receive messages out of order, and
865	needs a queue. AEMP is event based, queuing messages would serve no	1095	therefore needs a queue. AEMP is event based, queuing messages would serve
866	useful purpose. For the same reason the pattern-matching abilities of	1096	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	1097	of AnyEvent::MP are more limited, as there is little need to be able to
868	filter messages without dequeuing them.	1098	filter messages without dequeuing them.
869		1099
870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1100	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1101	being event-based, while Erlang is process-based.
		1102
		1103	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1104	top of AEMP and Coro threads.
871		1105
872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1106	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
873		1107
874	Sending messages in Erlang is synchronous and blocks the process (and	1108	Sending messages in Erlang is synchronous and blocks the process until
		1109	a conenction has been established and the message sent (and so does not
875	so does not need a queue that can overflow). AEMP sends are immediate,	1110	need a queue that can overflow). AEMP sends return immediately, connection
876	connection establishment is handled in the background.	1111	establishment is handled in the background.
877		1112
878	=item * Erlang suffers from silent message loss, AEMP does not.	1113	=item * Erlang suffers from silent message loss, AEMP does not.
879		1114
880	Erlang implements few guarantees on messages delivery - messages can get	1115	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,	1116	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).	1117	b, and c, and the other side only receives messages a and c).
883		1118
884	AEMP guarantees correct ordering, and the guarantee that after one message	1119	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	1120	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	1121	same port are lost as well, until monitoring raises an error, so there are
887	sequence.	1122	no silent "holes" in the message sequence.
		1123
		1124	If you want your software to be very reliable, you have to cope with
		1125	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1126	simply tries to work better in common error cases, such as when a network
		1127	link goes down.
888		1128
889	=item * Erlang can send messages to the wrong port, AEMP does not.	1129	=item * Erlang can send messages to the wrong port, AEMP does not.
890		1130
891	In Erlang it is quite likely that a node that restarts reuses a process ID	1131	In Erlang it is quite likely that a node that restarts reuses an Erlang
892	known to other nodes for a completely different process, causing messages	1132	process ID known to other nodes for a completely different process,
893	destined for that process to end up in an unrelated process.	1133	causing messages destined for that process to end up in an unrelated
		1134	process.
894		1135
895	AEMP never reuses port IDs, so old messages or old port IDs floating	1136	AEMP does not reuse port IDs, so old messages or old port IDs floating
896	around in the network will not be sent to an unrelated port.	1137	around in the network will not be sent to an unrelated port.
897		1138
898	=item * Erlang uses unprotected connections, AEMP uses secure	1139	=item * Erlang uses unprotected connections, AEMP uses secure
899	authentication and can use TLS.	1140	authentication and can use TLS.
900		1141
…		…
903		1144
904	=item * The AEMP protocol is optimised for both text-based and binary	1145	=item * The AEMP protocol is optimised for both text-based and binary
905	communications.	1146	communications.
906		1147
907	The AEMP protocol, unlike the Erlang protocol, supports both programming	1148	The AEMP protocol, unlike the Erlang protocol, supports both programming
908	language independent text-only protocols (good for debugging) and binary,	1149	language independent text-only protocols (good for debugging), and binary,
909	language-specific serialisers (e.g. Storable). By default, unless TLS is	1150	language-specific serialisers (e.g. Storable). By default, unless TLS is
910	used, the protocol is actually completely text-based.	1151	used, the protocol is actually completely text-based.
911		1152
912	It has also been carefully designed to be implementable in other languages	1153	It has also been carefully designed to be implementable in other languages
913	with a minimum of work while gracefully degrading functionality to make the	1154	with a minimum of work while gracefully degrading functionality to make the
914	protocol simple.	1155	protocol simple.
915		1156
916	=item * AEMP has more flexible monitoring options than Erlang.	1157	=item * AEMP has more flexible monitoring options than Erlang.
917		1158
918	In Erlang, you can chose to receive I<all> exit signals as messages	1159	In Erlang, you can chose to receive I<all> exit signals as messages or
919	or I<none>, there is no in-between, so monitoring single processes is	1160	I<none>, there is no in-between, so monitoring single Erlang processes is
920	difficult to implement. Monitoring in AEMP is more flexible than in	1161	difficult to implement.
921	Erlang, as one can choose between automatic kill, exit message or callback	1162
922	on a per-process basis.	1163	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1164	between automatic kill, exit message or callback on a per-port basis.
923		1165
924	=item * Erlang tries to hide remote/local connections, AEMP does not.	1166	=item * Erlang tries to hide remote/local connections, AEMP does not.
925		1167
926	Monitoring in Erlang is not an indicator of process death/crashes, in the	1168	Monitoring in Erlang is not an indicator of process death/crashes, in the
927	same way as linking is (except linking is unreliable in Erlang).	1169	same way as linking is (except linking is unreliable in Erlang).
…		…
949	overhead, as well as having to keep a proxy object everywhere.	1191	overhead, as well as having to keep a proxy object everywhere.
950		1192
951	Strings can easily be printed, easily serialised etc. and need no special	1193	Strings can easily be printed, easily serialised etc. and need no special
952	procedures to be "valid".	1194	procedures to be "valid".
953		1195
954	And as a result, a miniport consists of a single closure stored in a	1196	And as a result, a port with just a default receiver consists of a single
955	global hash - it can't become much cheaper.	1197	code reference stored in a global hash - it can't become much cheaper.
956		1198
957	=item Why favour JSON, why not a real serialising format such as Storable?	1199	=item Why favour JSON, why not a real serialising format such as Storable?
958		1200
959	In fact, any AnyEvent::MP node will happily accept Storable as framing	1201	In fact, any AnyEvent::MP node will happily accept Storable as framing
960	format, but currently there is no way to make a node use Storable by	1202	format, but currently there is no way to make a node use Storable by
…		…
976		1218
977	L<AnyEvent::MP::Intro> - a gentle introduction.	1219	L<AnyEvent::MP::Intro> - a gentle introduction.
978		1220
979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1221	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
980		1222
981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1223	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
982	your applications.	1224	your applications.
		1225
		1226	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
983		1227
984	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1228	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
985	all nodes.	1229	all nodes.
986		1230
987	L<AnyEvent>.	1231	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 1.134 by root, Mon Mar 12 14:47:23 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 1.134 by root, Mon Mar 12 14:47:23 2012 UTC