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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.76 by root, Mon Aug 31 18:45:05 2009 UTC vs.
Revision 1.86 by root, Wed Sep 9 01:47:01 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 - epxlains most concepts.	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
…		…
61		61
62	=over 4	62	=over 4
63		63
64	=item port	64	=item port
65		65
66	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).
67		68
68	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
69	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
70	anything was listening for them or not.	71	anything was listening for them or not.
71		72
…		…
82		83
83	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
84	(no listening ports). Private nodes cannot talk to other private nodes	85	(no listening ports). Private nodes cannot talk to other private nodes
85	currently.	86	currently.
86		87
87	=item node ID - C<[a-za-Z0-9_\-.:]+>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
88		89
89	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
90	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
91	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
92	doesn't interpret node IDs in any way.	93	doesn't interpret node IDs in any way.
…		…
96	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
97	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
98	endpoints - binds. Currently, only standard C<ip:port> specifications can	99	endpoints - binds. Currently, only standard C<ip:port> specifications can
99	be used, which specify TCP ports to listen on.	100	be used, which specify TCP ports to listen on.
100		101
101	=item seeds - C<host:port>	102	=item seed nodes
102		103
103	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
104	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
105	network. This node is called a seed.	106	network. This node is called a seed.
106		107
107	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
108	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
109	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
110	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.
111	join the network.
112		119
113	Apart from being sued for seeding, seednodes are not special in any way -	120	=item seeds - C<host:port>
114	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.
115		129
116	=back	130	=back
117		131
118	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
119		133
…		…
158		172
159	=item $nodeid = node_of $port	173	=item $nodeid = node_of $port
160		174
161	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.
162		176
		177	=item configure $profile, key => value...
		178
163	=item configure key => value...	179	=item configure key => value...
164		180
165	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
166	"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
167	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
…		…
174		190
175	=item step 1, gathering configuration from profiles	191	=item step 1, gathering configuration from profiles
176		192
177	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
178	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
179	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
180	-n>) will be used as profile name.	196	missing, then the nodename (F<uname -n>) will be used as profile name.
181		197
182	The profile data is then gathered as follows:	198	The profile data is then gathered as follows:
183		199
184	First, all remaining key => value pairs (all of which are conviniently	200	First, all remaining key => value pairs (all of which are conveniently
185	undocumented at the moment) will be interpreted as configuration	201	undocumented at the moment) will be interpreted as configuration
186	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
187	default configuration (see the F<aemp> utility), then the chain of	203	default configuration (see the F<aemp> utility), then the chain of
188	profiles chosen by the profile name (and any C<parent> attributes).	204	profiles chosen by the profile name (and any C<parent> attributes).
189		205
…		…
472		488
473	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
474	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
475	to stop monitoring again.	491	to stop monitoring again.
476		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
477	C<mon> effectively guarantees that, in the absence of hardware failures,	519	C<mon> effectively guarantees that, in the absence of hardware failures,
478	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
479	arrive, or the monitoring action will be invoked after possible message	521	arrive, or the monitoring action will be invoked after possible message
480	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
481	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
482	port). After the monitoring action was invoked, further messages might get	524	port). After the monitoring action was invoked, further messages might get
483	delivered again.	525	delivered again.
484		526
485	Note that monitoring-actions are one-shot: once messages are lost (and a	527	Inter-host-connection timeouts and monitoring depend on the transport
486	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).
487		531
488	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
489	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
490	"normally"). Note also that I<< the callback B<must> never die >>, so use	534	to ensure some maximum latency.
491	C<eval> if unsure.
492
493	In the second form (another port given), the other port (C<$rcvport>)
494	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
495	"normal" kils nothing happens, while under all other conditions, the other
496	port is killed with the same reason.
497
498	The third form (kill self) is the same as the second form, except that
499	C<$rvport> defaults to C<$SELF>.
500
501	In the last form (message), a message of the form C<@msg, @reason> will be
502	C<snd>.
503
504	As a rule of thumb, monitoring requests should always monitor a port from
505	a local port (or callback). The reason is that kill messages might get
506	lost, just like any other message. Another less obvious reason is that
507	even monitoring requests can get lost (for exmaple, when the connection
508	to the other node goes down permanently). When monitoring a port locally
509	these problems do not exist.
510		535
511	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
512		537
513	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
514		539
…		…
609	the package, then the package above the package and so on (e.g.	634	the package, then the package above the package and so on (e.g.
610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
611	exists or it runs out of package names.	636	exists or it runs out of package names.
612		637
613	The init function is then called with the newly-created port as context	638	The init function is then called with the newly-created port as context
614	object (C<$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.
615		642
616	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
617	port, and in the remote init function, immediately monitor the passed	644	port, and in the remote init function, immediately monitor the passed
618	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
619	when there is a problem.	646	when there is a problem.
620		647
		648	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
		651
621	Example: spawn a chat server port on C<$othernode>.	652	Example: spawn a chat server port on C<$othernode>.
622		653
623	# this node, executed from within a port context:	654	# this node, executed from within a port context:
624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
625	mon $server;	656	mon $server;
…		…
639		670
640	sub _spawn {	671	sub _spawn {
641	my $port = shift;	672	my $port = shift;
642	my $init = shift;	673	my $init = shift;
643		674
		675	# rcv will create the actual port
644	local $SELF = "$NODE#$port";	676	local $SELF = "$NODE#$port";
645	eval {	677	eval {
646	&{ load_func $init }	678	&{ load_func $init }
647	};	679	};
648	_self_die if $@;	680	_self_die if $@;
…		…
705		737
706	=item * Node IDs are arbitrary strings in AEMP.	738	=item * Node IDs are arbitrary strings in AEMP.
707		739
708	Erlang relies on special naming and DNS to work everywhere in the same	740	Erlang relies on special naming and DNS to work everywhere in the same
709	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	741	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
710	configuraiton or DNS), but will otherwise discover other odes itself.	742	configuration or DNS), but will otherwise discover other odes itself.
711		743
712	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
713	uses "local ports are like remote ports".	745	uses "local ports are like remote ports".
714		746
715	The failure modes for local ports are quite different (runtime errors	747	The failure modes for local ports are quite different (runtime errors
…		…
728		760
729	Erlang uses processes that selectively receive messages, and therefore	761	Erlang uses processes that selectively receive messages, and therefore
730	needs a queue. AEMP is event based, queuing messages would serve no	762	needs a queue. AEMP is event based, queuing messages would serve no
731	useful purpose. For the same reason the pattern-matching abilities of	763	useful purpose. For the same reason the pattern-matching abilities of
732	AnyEvent::MP are more limited, as there is little need to be able to	764	AnyEvent::MP are more limited, as there is little need to be able to
733	filter messages without dequeing them.	765	filter messages without dequeuing them.
734		766
735	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	767	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
736		768
737	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
738		770
…		…
844	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	876	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
845		877
846	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	878	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
847	your applications.	879	your applications.
848		880
		881	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		882	all nodes.
		883
849	L<AnyEvent>.	884	L<AnyEvent>.
850		885
851	=head1 AUTHOR	886	=head1 AUTHOR
852		887
853	Marc Lehmann <schmorp@schmorp.de>	888	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.76 by root, Mon Aug 31 18:45:05 2009 UTC vs. Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.76 by root, Mon Aug 31 18:45:05 2009 UTC vs.
Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC