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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC vs.
Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC

…		…
39		39
40	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
41		41
42	bin/aemp - stable.	42	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work.	43	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - uptodate, but incomplete.	44	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable.	45	AnyEvent::MP::Kernel - mostly stable.
46	AnyEvent::MP::Global - stable API, protocol not yet final.	46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
47		47
48	stay tuned.	48	stay tuned.
49		49
50	=head1 DESCRIPTION	50	=head1 DESCRIPTION
51		51
52	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
53		53
…		…
55	on the same or other hosts, and you can supervise entities remotely.	55	on the same or other hosts, and you can supervise entities remotely.
56		56
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page and the examples under F<eg/>.	58	manual page and the examples under F<eg/>.
59		59
60	At the moment, this module family is a bit underdocumented.
61
62	=head1 CONCEPTS	60	=head1 CONCEPTS
63		61
64	=over 4	62	=over 4
65		63
66	=item port	64	=item port
67		65
68	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
69		68
70	Ports allow you to register C<rcv> handlers that can match all or just	69	Ports allow you to register C<rcv> handlers that can match all or just
71	some messages. Messages send to ports will not be queued, regardless of	70	some messages. Messages send to ports will not be queued, regardless of
72	anything was listening for them or not.	71	anything was listening for them or not.
73		72
…		…
84		83
85	Nodes are either public (have one or more listening ports) or private	84	Nodes are either public (have one or more listening ports) or private
86	(no listening ports). Private nodes cannot talk to other private nodes	85	(no listening ports). Private nodes cannot talk to other private nodes
87	currently.	86	currently.
88		87
89	=item node ID - C<[a-za-Z0-9_\-.:]+>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
90		89
91	A node ID is a string that uniquely identifies the node within a	90	A node ID is a string that uniquely identifies the node within a
92	network. Depending on the configuration used, node IDs can look like a	91	network. Depending on the configuration used, node IDs can look like a
93	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
94	doesn't interpret node IDs in any way.	93	doesn't interpret node IDs in any way.
…		…
98	Nodes can only talk to each other by creating some kind of connection to	97	Nodes can only talk to each other by creating some kind of connection to
99	each other. To do this, nodes should listen on one or more local transport	98	each other. To do this, nodes should listen on one or more local transport
100	endpoints - binds. Currently, only standard C<ip:port> specifications can	99	endpoints - binds. Currently, only standard C<ip:port> specifications can
101	be used, which specify TCP ports to listen on.	100	be used, which specify TCP ports to listen on.
102		101
103	=item seeds - C<host:port>	102	=item seed nodes
104		103
105	When a node starts, it knows nothing about the network. To teach the node	104	When a node starts, it knows nothing about the network. To teach the node
106	about the network it first has to contact some other node within the	105	about the network it first has to contact some other node within the
107	network. This node is called a seed.	106	network. This node is called a seed.
108		107
109	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of an AnyEvent::MP network.
		115
110	are expected to be long-running, and at least one of those should always	116	Seed nodes are expected to be long-running, and at least one seed node
111	be available. When nodes run out of connections (e.g. due to a network	117	should always be available. They should also be relatively responsive - a
112	error), they try to re-establish connections to some seednodes again to	118	seed node that blocks for long periods will slow down everybody else.
113	join the network.
114		119
115	Apart from being sued for seeding, seednodes are not special in any way -	120	=item seeds - C<host:port>
116	every public node can be a seednode.	121
		122	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		123	TCP port) of nodes thta should be used as seed nodes.
		124
		125	The nodes listening on those endpoints are expected to be long-running,
		126	and at least one of those should always be available. When nodes run out
		127	of connections (e.g. due to a network error), they try to re-establish
		128	connections to some seednodes again to join the network.
117		129
118	=back	130	=back
119		131
120	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
121		133
…		…
138	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
139		151
140	our @EXPORT = qw(	152	our @EXPORT = qw(
141	NODE $NODE *SELF node_of after	153	NODE $NODE *SELF node_of after
142	configure	154	configure
143	snd rcv mon mon_guard kil reg psub spawn	155	snd rcv mon mon_guard kil reg psub spawn cal
144	port	156	port
145	);	157	);
146		158
147	our $SELF;	159	our $SELF;
148		160
…		…
160		172
161	=item $nodeid = node_of $port	173	=item $nodeid = node_of $port
162		174
163	Extracts and returns the node ID from a port ID or a node ID.	175	Extracts and returns the node ID from a port ID or a node ID.
164		176
		177	=item configure $profile, key => value...
		178
165	=item configure key => value...	179	=item configure key => value...
166		180
167	Before a node can talk to other nodes on the network (i.e. enter	181	Before a node can talk to other nodes on the network (i.e. enter
168	"distributed mode") it has to configure itself - the minimum a node needs	182	"distributed mode") it has to configure itself - the minimum a node needs
169	to know is its own name, and optionally it should know the addresses of	183	to know is its own name, and optionally it should know the addresses of
…		…
176		190
177	=item step 1, gathering configuration from profiles	191	=item step 1, gathering configuration from profiles
178		192
179	The function first looks up a profile in the aemp configuration (see the	193	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility). The profile name can be specified via the	194	L<aemp> commandline utility). The profile name can be specified via the
181	named C<profile> parameter. If it is missing, then the nodename (F<uname	195	named C<profile> parameter or can simply be the first parameter). If it is
182	-n>) will be used as profile name.	196	missing, then the nodename (F<uname -n>) will be used as profile name.
183		197
184	The profile data is then gathered as follows:	198	The profile data is then gathered as follows:
185		199
186	First, all remaining key => value pairs (all of which are conviniently	200	First, all remaining key => value pairs (all of which are conveniently
187	undocumented at the moment) will be interpreted as configuration	201	undocumented at the moment) will be interpreted as configuration
188	data. Then they will be overwritten by any values specified in the global	202	data. Then they will be overwritten by any values specified in the global
189	default configuration (see the F<aemp> utility), then the chain of	203	default configuration (see the F<aemp> utility), then the chain of
190	profiles chosen by the profile name (and any C<parent> attributes).	204	profiles chosen by the profile name (and any C<parent> attributes).
191		205
…		…
215	L<AnyEvent::MP::Global> module, which will then use it to keep	229	L<AnyEvent::MP::Global> module, which will then use it to keep
216	connectivity with at least one node at any point in time.	230	connectivity with at least one node at any point in time.
217		231
218	=back	232	=back
219		233
220	Example: become a distributed node using the locla node name as profile.	234	Example: become a distributed node using the local node name as profile.
221	This should be the most common form of invocation for "daemon"-type nodes.	235	This should be the most common form of invocation for "daemon"-type nodes.
222		236
223	configure	237	configure
224		238
225	Example: become an anonymous node. This form is often used for commandline	239	Example: become an anonymous node. This form is often used for commandline
…		…
474		488
475	Monitor the given port and do something when the port is killed or	489	Monitor the given port and do something when the port is killed or
476	messages to it were lost, and optionally return a guard that can be used	490	messages to it were lost, and optionally return a guard that can be used
477	to stop monitoring again.	491	to stop monitoring again.
478		492
		493	In the first form (callback), the callback is simply called with any
		494	number of C<@reason> elements (no @reason means that the port was deleted
		495	"normally"). Note also that I<< the callback B<must> never die >>, so use
		496	C<eval> if unsure.
		497
		498	In the second form (another port given), the other port (C<$rcvport>)
		499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		500	"normal" kils nothing happens, while under all other conditions, the other
		501	port is killed with the same reason.
		502
		503	The third form (kill self) is the same as the second form, except that
		504	C<$rvport> defaults to C<$SELF>.
		505
		506	In the last form (message), a message of the form C<@msg, @reason> will be
		507	C<snd>.
		508
		509	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		510	alert was raised), they are removed and will not trigger again.
		511
		512	As a rule of thumb, monitoring requests should always monitor a port from
		513	a local port (or callback). The reason is that kill messages might get
		514	lost, just like any other message. Another less obvious reason is that
		515	even monitoring requests can get lost (for example, when the connection
		516	to the other node goes down permanently). When monitoring a port locally
		517	these problems do not exist.
		518
479	C<mon> effectively guarantees that, in the absence of hardware failures,	519	C<mon> effectively guarantees that, in the absence of hardware failures,
480	after starting the monitor, either all messages sent to the port will	520	after starting the monitor, either all messages sent to the port will
481	arrive, or the monitoring action will be invoked after possible message	521	arrive, or the monitoring action will be invoked after possible message
482	loss has been detected. No messages will be lost "in between" (after	522	loss has been detected. No messages will be lost "in between" (after
483	the first lost message no further messages will be received by the	523	the first lost message no further messages will be received by the
484	port). After the monitoring action was invoked, further messages might get	524	port). After the monitoring action was invoked, further messages might get
485	delivered again.	525	delivered again.
486		526
487	Note that monitoring-actions are one-shot: once messages are lost (and a	527	Inter-host-connection timeouts and monitoring depend on the transport
488	monitoring alert was raised), they are removed and will not trigger again.	528	used. The only transport currently implemented is TCP, and AnyEvent::MP
		529	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		530	non-idle connection, and usually around two hours for idle conenctions).
489		531
490	In the first form (callback), the callback is simply called with any	532	This means that monitoring is good for program errors and cleaning up
491	number of C<@reason> elements (no @reason means that the port was deleted	533	stuff eventually, but they are no replacement for a timeout when you need
492	"normally"). Note also that I<< the callback B<must> never die >>, so use	534	to ensure some maximum latency.
493	C<eval> if unsure.
494
495	In the second form (another port given), the other port (C<$rcvport>)
496	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
497	"normal" kils nothing happens, while under all other conditions, the other
498	port is killed with the same reason.
499
500	The third form (kill self) is the same as the second form, except that
501	C<$rvport> defaults to C<$SELF>.
502
503	In the last form (message), a message of the form C<@msg, @reason> will be
504	C<snd>.
505
506	As a rule of thumb, monitoring requests should always monitor a port from
507	a local port (or callback). The reason is that kill messages might get
508	lost, just like any other message. Another less obvious reason is that
509	even monitoring requests can get lost (for exmaple, when the connection
510	to the other node goes down permanently). When monitoring a port locally
511	these problems do not exist.
512		535
513	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
514		537
515	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
516		539
…		…
611	the package, then the package above the package and so on (e.g.	634	the package, then the package above the package and so on (e.g.
612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
613	exists or it runs out of package names.	636	exists or it runs out of package names.
614		637
615	The init function is then called with the newly-created port as context	638	The init function is then called with the newly-created port as context
616	object (C<$SELF>) and the C<@initdata> values as arguments.	639	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		640	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		641	the port might not get created.
617		642
618	A common idiom is to pass a local port, immediately monitor the spawned	643	A common idiom is to pass a local port, immediately monitor the spawned
619	port, and in the remote init function, immediately monitor the passed	644	port, and in the remote init function, immediately monitor the passed
620	local port. This two-way monitoring ensures that both ports get cleaned up	645	local port. This two-way monitoring ensures that both ports get cleaned up
621	when there is a problem.	646	when there is a problem.
622		647
		648	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
		651
623	Example: spawn a chat server port on C<$othernode>.	652	Example: spawn a chat server port on C<$othernode>.
624		653
625	# this node, executed from within a port context:	654	# this node, executed from within a port context:
626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
627	mon $server;	656	mon $server;
…		…
641		670
642	sub _spawn {	671	sub _spawn {
643	my $port = shift;	672	my $port = shift;
644	my $init = shift;	673	my $init = shift;
645		674
		675	# rcv will create the actual port
646	local $SELF = "$NODE#$port";	676	local $SELF = "$NODE#$port";
647	eval {	677	eval {
648	&{ load_func $init }	678	&{ load_func $init }
649	};	679	};
650	_self_die if $@;	680	_self_die if $@;
…		…
685	? $action[0]()	715	? $action[0]()
686	: snd @action;	716	: snd @action;
687	};	717	};
688	}	718	}
689		719
		720	=item cal $port, @msg, $callback[, $timeout]
		721
		722	A simple form of RPC - sends a message to the given C<$port> with the
		723	given contents (C<@msg>), but adds a reply port to the message.
		724
		725	The reply port is created temporarily just for the purpose of receiving
		726	the reply, and will be C<kil>ed when no longer needed.
		727
		728	A reply message sent to the port is passed to the C<$callback> as-is.
		729
		730	If an optional time-out (in seconds) is given and it is not C<undef>,
		731	then the callback will be called without any arguments after the time-out
		732	elapsed and the port is C<kil>ed.
		733
		734	If no time-out is given, then the local port will monitor the remote port
		735	instead, so it eventually gets cleaned-up.
		736
		737	Currently this function returns the temporary port, but this "feature"
		738	might go in future versions unless you can make a convincing case that
		739	this is indeed useful for something.
		740
		741	=cut
		742
		743	sub cal(@) {
		744	my $timeout = ref $_[-1] ? undef : pop;
		745	my $cb = pop;
		746
		747	my $port = port {
		748	undef $timeout;
		749	kil $SELF;
		750	&$cb;
		751	};
		752
		753	if (defined $timeout) {
		754	$timeout = AE::timer $timeout, 0, sub {
		755	undef $timeout;
		756	kil $port;
		757	$cb->();
		758	};
		759	} else {
		760	mon $_[0], sub {
		761	kil $port;
		762	$cb->();
		763	};
		764	}
		765
		766	push @_, $port;
		767	&snd;
		768
		769	$port
		770	}
		771
690	=back	772	=back
691		773
692	=head1 AnyEvent::MP vs. Distributed Erlang	774	=head1 AnyEvent::MP vs. Distributed Erlang
693		775
694	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	776	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
…		…
707		789
708	=item * Node IDs are arbitrary strings in AEMP.	790	=item * Node IDs are arbitrary strings in AEMP.
709		791
710	Erlang relies on special naming and DNS to work everywhere in the same	792	Erlang relies on special naming and DNS to work everywhere in the same
711	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	793	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
712	configuraiton or DNS), but will otherwise discover other odes itself.	794	configuration or DNS), but will otherwise discover other odes itself.
713		795
714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	796	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
715	uses "local ports are like remote ports".	797	uses "local ports are like remote ports".
716		798
717	The failure modes for local ports are quite different (runtime errors	799	The failure modes for local ports are quite different (runtime errors
…		…
730		812
731	Erlang uses processes that selectively receive messages, and therefore	813	Erlang uses processes that selectively receive messages, and therefore
732	needs a queue. AEMP is event based, queuing messages would serve no	814	needs a queue. AEMP is event based, queuing messages would serve no
733	useful purpose. For the same reason the pattern-matching abilities of	815	useful purpose. For the same reason the pattern-matching abilities of
734	AnyEvent::MP are more limited, as there is little need to be able to	816	AnyEvent::MP are more limited, as there is little need to be able to
735	filter messages without dequeing them.	817	filter messages without dequeuing them.
736		818
737	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	819	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
738		820
739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	821	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
740		822
…		…
846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	928	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
847		929
848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	930	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
849	your applications.	931	your applications.
850		932
		933	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		934	all nodes.
		935
851	L<AnyEvent>.	936	L<AnyEvent>.
852		937
853	=head1 AUTHOR	938	=head1 AUTHOR
854		939
855	Marc Lehmann <schmorp@schmorp.de>	940	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC vs. Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC vs.
Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC