[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 1.91 by root, Tue Sep 22 09:54:42 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
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	# monitoring	35	# monitoring
36	mon $port, $cb->(@msg) # callback is invoked on death	36	mon $localport, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	37	mon $localport, $otherport # kill otherport on abnormal death
38	mon $port, $otherport, @msg # send message on death	38	mon $localport, $otherport, @msg # send message on death
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 API.
46	AnyEvent::MP::Global - stable API, protocol not yet final.	46	AnyEvent::MP::Global - stable API.
47
48	stay tuned.
49		47
50	=head1 DESCRIPTION	48	=head1 DESCRIPTION
51		49
52	This module (-family) implements a simple message passing framework.	50	This module (-family) implements a simple message passing framework.
53		51
…		…
55	on the same or other hosts, and you can supervise entities remotely.	53	on the same or other hosts, and you can supervise entities remotely.
56		54
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	55	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page and the examples under F<eg/>.	56	manual page and the examples under F<eg/>.
59		57
60	At the moment, this module family is a bit underdocumented.
61
62	=head1 CONCEPTS	58	=head1 CONCEPTS
63		59
64	=over 4	60	=over 4
65		61
66	=item port	62	=item port
67		63
68	A port is something you can send messages to (with the C<snd> function).	64	Not to be confused with a TCP port, a "port" is something you can send
		65	messages to (with the C<snd> function).
69		66
70	Ports allow you to register C<rcv> handlers that can match all or just	67	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	68	some messages. Messages send to ports will not be queued, regardless of
72	anything was listening for them or not.	69	anything was listening for them or not.
73		70
…		…
84		81
85	Nodes are either public (have one or more listening ports) or private	82	Nodes are either public (have one or more listening ports) or private
86	(no listening ports). Private nodes cannot talk to other private nodes	83	(no listening ports). Private nodes cannot talk to other private nodes
87	currently.	84	currently.
88		85
89	=item node ID - C<[a-za-Z0-9_\-.:]+>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
90		87
91	A node ID is a string that uniquely identifies the node within a	88	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	89	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	90	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
94	doesn't interpret node IDs in any way.	91	doesn't interpret node IDs in any way.
…		…
98	Nodes can only talk to each other by creating some kind of connection to	95	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	96	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	97	endpoints - binds. Currently, only standard C<ip:port> specifications can
101	be used, which specify TCP ports to listen on.	98	be used, which specify TCP ports to listen on.
102		99
103	=item seeds - C<host:port>	100	=item seed nodes
104		101
105	When a node starts, it knows nothing about the network. To teach the node	102	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	103	about the network it first has to contact some other node within the
107	network. This node is called a seed.	104	network. This node is called a seed.
108		105
109	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	106	Apart from the fact that other nodes know them as seed nodes and they have
		107	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		108	any node can function as a seed node for others.
		109
		110	In addition to discovering the network, seed nodes are also used to
		111	maintain the network and to connect nodes that otherwise would have
		112	trouble connecting. They form the backbone of an AnyEvent::MP network.
		113
110	are expected to be long-running, and at least one of those should always	114	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	115	should always be available. They should also be relatively responsive - a
112	error), they try to re-establish connections to some seednodes again to	116	seed node that blocks for long periods will slow down everybody else.
113	join the network.
114		117
115	Apart from being sued for seeding, seednodes are not special in any way -	118	=item seeds - C<host:port>
116	every public node can be a seednode.	119
		120	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		121	TCP port) of nodes thta should be used as seed nodes.
		122
		123	The nodes listening on those endpoints are expected to be long-running,
		124	and at least one of those should always be available. When nodes run out
		125	of connections (e.g. due to a network error), they try to re-establish
		126	connections to some seednodes again to join the network.
117		127
118	=back	128	=back
119		129
120	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
121		131
…		…
138	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
139		149
140	our @EXPORT = qw(	150	our @EXPORT = qw(
141	NODE $NODE *SELF node_of after	151	NODE $NODE *SELF node_of after
142	configure	152	configure
143	snd rcv mon mon_guard kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
144	port	154	port
145	);	155	);
146		156
147	our $SELF;	157	our $SELF;
148		158
…		…
160		170
161	=item $nodeid = node_of $port	171	=item $nodeid = node_of $port
162		172
163	Extracts and returns the node ID from a port ID or a node ID.	173	Extracts and returns the node ID from a port ID or a node ID.
164		174
		175	=item configure $profile, key => value...
		176
165	=item configure key => value...	177	=item configure key => value...
166		178
167	Before a node can talk to other nodes on the network (i.e. enter	179	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	180	"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	181	to know is its own name, and optionally it should know the addresses of
…		…
176		188
177	=item step 1, gathering configuration from profiles	189	=item step 1, gathering configuration from profiles
178		190
179	The function first looks up a profile in the aemp configuration (see the	191	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	192	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	193	named C<profile> parameter or can simply be the first parameter). If it is
182	-n>) will be used as profile name.	194	missing, then the nodename (F<uname -n>) will be used as profile name.
183		195
184	The profile data is then gathered as follows:	196	The profile data is then gathered as follows:
185		197
186	First, all remaining key => value pairs (all of which are conviniently	198	First, all remaining key => value pairs (all of which are conveniently
187	undocumented at the moment) will be interpreted as configuration	199	undocumented at the moment) will be interpreted as configuration
188	data. Then they will be overwritten by any values specified in the global	200	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	201	default configuration (see the F<aemp> utility), then the chain of
190	profiles chosen by the profile name (and any C<parent> attributes).	202	profiles chosen by the profile name (and any C<parent> attributes).
191		203
…		…
215	L<AnyEvent::MP::Global> module, which will then use it to keep	227	L<AnyEvent::MP::Global> module, which will then use it to keep
216	connectivity with at least one node at any point in time.	228	connectivity with at least one node at any point in time.
217		229
218	=back	230	=back
219		231
220	Example: become a distributed node using the locla node name as profile.	232	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.	233	This should be the most common form of invocation for "daemon"-type nodes.
222		234
223	configure	235	configure
224		236
225	Example: become an anonymous node. This form is often used for commandline	237	Example: become an anonymous node. This form is often used for commandline
…		…
474		486
475	Monitor the given port and do something when the port is killed or	487	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	488	messages to it were lost, and optionally return a guard that can be used
477	to stop monitoring again.	489	to stop monitoring again.
478		490
		491	In the first form (callback), the callback is simply called with any
		492	number of C<@reason> elements (no @reason means that the port was deleted
		493	"normally"). Note also that I<< the callback B<must> never die >>, so use
		494	C<eval> if unsure.
		495
		496	In the second form (another port given), the other port (C<$rcvport>)
		497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		498	"normal" kils nothing happens, while under all other conditions, the other
		499	port is killed with the same reason.
		500
		501	The third form (kill self) is the same as the second form, except that
		502	C<$rvport> defaults to C<$SELF>.
		503
		504	In the last form (message), a message of the form C<@msg, @reason> will be
		505	C<snd>.
		506
		507	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		508	alert was raised), they are removed and will not trigger again.
		509
		510	As a rule of thumb, monitoring requests should always monitor a port from
		511	a local port (or callback). The reason is that kill messages might get
		512	lost, just like any other message. Another less obvious reason is that
		513	even monitoring requests can get lost (for example, when the connection
		514	to the other node goes down permanently). When monitoring a port locally
		515	these problems do not exist.
		516
479	C<mon> effectively guarantees that, in the absence of hardware failures,	517	C<mon> effectively guarantees that, in the absence of hardware failures,
480	after starting the monitor, either all messages sent to the port will	518	after starting the monitor, either all messages sent to the port will
481	arrive, or the monitoring action will be invoked after possible message	519	arrive, or the monitoring action will be invoked after possible message
482	loss has been detected. No messages will be lost "in between" (after	520	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	521	the first lost message no further messages will be received by the
484	port). After the monitoring action was invoked, further messages might get	522	port). After the monitoring action was invoked, further messages might get
485	delivered again.	523	delivered again.
486		524
487	Note that monitoring-actions are one-shot: once messages are lost (and a	525	Inter-host-connection timeouts and monitoring depend on the transport
488	monitoring alert was raised), they are removed and will not trigger again.	526	used. The only transport currently implemented is TCP, and AnyEvent::MP
		527	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		528	non-idle connection, and usually around two hours for idle conenctions).
489		529
490	In the first form (callback), the callback is simply called with any	530	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	531	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	532	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<$SELF>.
502
503	In the last form (message), a message of the form C<@msg, @reason> will be
504	C<snd>.
505
506	As a rule of thumb, monitoring requests should always monitor a port from
507	a local port (or callback). The reason is that kill messages might get
508	lost, just like any other message. Another less obvious reason is that
509	even monitoring requests can get lost (for exmaple, when the connection
510	to the other node goes down permanently). When monitoring a port locally
511	these problems do not exist.
512		533
513	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
514		535
515	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
516		537
…		…
611	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
613	exists or it runs out of package names.	634	exists or it runs out of package names.
614		635
615	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
616	object (C<$SELF>) and the C<@initdata> values as arguments.	637	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		638	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		639	the port might not get created.
617		640
618	A common idiom is to pass a local port, immediately monitor the spawned	641	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	642	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	643	local port. This two-way monitoring ensures that both ports get cleaned up
621	when there is a problem.	644	when there is a problem.
622		645
		646	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
		649
623	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
624		651
625	# this node, executed from within a port context:	652	# this node, executed from within a port context:
626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
627	mon $server;	654	mon $server;
…		…
641		668
642	sub _spawn {	669	sub _spawn {
643	my $port = shift;	670	my $port = shift;
644	my $init = shift;	671	my $init = shift;
645		672
		673	# rcv will create the actual port
646	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
647	eval {	675	eval {
648	&{ load_func $init }	676	&{ load_func $init }
649	};	677	};
650	_self_die if $@;	678	_self_die if $@;
…		…
685	? $action[0]()	713	? $action[0]()
686	: snd @action;	714	: snd @action;
687	};	715	};
688	}	716	}
689		717
		718	=item cal $port, @msg, $callback[, $timeout]
		719
		720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
		722
		723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
		725
		726	A reply message sent to the port is passed to the C<$callback> as-is.
		727
		728	If an optional time-out (in seconds) is given and it is not C<undef>,
		729	then the callback will be called without any arguments after the time-out
		730	elapsed and the port is C<kil>ed.
		731
		732	If no time-out is given, then the local port will monitor the remote port
		733	instead, so it eventually gets cleaned-up.
		734
		735	Currently this function returns the temporary port, but this "feature"
		736	might go in future versions unless you can make a convincing case that
		737	this is indeed useful for something.
		738
		739	=cut
		740
		741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
		744
		745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
		750
		751	if (defined $timeout) {
		752	$timeout = AE::timer $timeout, 0, sub {
		753	undef $timeout;
		754	kil $port;
		755	$cb->();
		756	};
		757	} else {
		758	mon $_[0], sub {
		759	kil $port;
		760	$cb->();
		761	};
		762	}
		763
		764	push @_, $port;
		765	&snd;
		766
		767	$port
		768	}
		769
690	=back	770	=back
691		771
692	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
693		773
694	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	774	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
…		…
707		787
708	=item * Node IDs are arbitrary strings in AEMP.	788	=item * Node IDs are arbitrary strings in AEMP.
709		789
710	Erlang relies on special naming and DNS to work everywhere in the same	790	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	791	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.	792	configuration or DNS), but will otherwise discover other odes itself.
713		793
714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	794	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
715	uses "local ports are like remote ports".	795	uses "local ports are like remote ports".
716		796
717	The failure modes for local ports are quite different (runtime errors	797	The failure modes for local ports are quite different (runtime errors
…		…
730		810
731	Erlang uses processes that selectively receive messages, and therefore	811	Erlang uses processes that selectively receive messages, and therefore
732	needs a queue. AEMP is event based, queuing messages would serve no	812	needs a queue. AEMP is event based, queuing messages would serve no
733	useful purpose. For the same reason the pattern-matching abilities of	813	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	814	AnyEvent::MP are more limited, as there is little need to be able to
735	filter messages without dequeing them.	815	filter messages without dequeuing them.
736		816
737	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	817	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
738		818
739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	819	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
740		820
…		…
846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	926	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
847		927
848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	928	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
849	your applications.	929	your applications.
850		930
		931	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		932	all nodes.
		933
851	L<AnyEvent>.	934	L<AnyEvent>.
852		935
853	=head1 AUTHOR	936	=head1 AUTHOR
854		937
855	Marc Lehmann <schmorp@schmorp.de>	938	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 1.91 by root, Tue Sep 22 09:54:42 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 1.91 by root, Tue Sep 22 09:54:42 2009 UTC