[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 1.84 by root, Tue Sep 8 01:42:14 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 the 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.
112	error), they try to re-establish connections to some seednodes again to
113	join the network.
114		118
115	Apart from being sued for seeding, seednodes are not special in any way -	119	=item seeds - C<host:port>
116	every public node can be a seednode.	120
		121	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		122	TCP port) of nodes thta should be used as seed nodes.
		123
		124	The nodes listening on those endpoints are expected to be long-running,
		125	and at least one of those should always be available. When nodes run out
		126	of connections (e.g. due to a network error), they try to re-establish
		127	connections to some seednodes again to join the network.
117		128
118	=back	129	=back
119		130
120	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
121		132
…		…
160		171
161	=item $nodeid = node_of $port	172	=item $nodeid = node_of $port
162		173
163	Extracts and returns the node ID from a port ID or a node ID.	174	Extracts and returns the node ID from a port ID or a node ID.
164		175
		176	=item configure $profile, key => value...
		177
165	=item configure key => value...	178	=item configure key => value...
166		179
167	Before a node can talk to other nodes on the network (i.e. enter	180	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	181	"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	182	to know is its own name, and optionally it should know the addresses of
…		…
176		189
177	=item step 1, gathering configuration from profiles	190	=item step 1, gathering configuration from profiles
178		191
179	The function first looks up a profile in the aemp configuration (see the	192	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	193	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	194	named C<profile> parameter or can simply be the first parameter). If it is
182	-n>) will be used as profile name.	195	missing, then the nodename (F<uname -n>) will be used as profile name.
183		196
184	The profile data is then gathered as follows:	197	The profile data is then gathered as follows:
185		198
186	First, all remaining key => value pairs (all of which are conviniently	199	First, all remaining key => value pairs (all of which are conveniently
187	undocumented at the moment) will be interpreted as configuration	200	undocumented at the moment) will be interpreted as configuration
188	data. Then they will be overwritten by any values specified in the global	201	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	202	default configuration (see the F<aemp> utility), then the chain of
190	profiles chosen by the profile name (and any C<parent> attributes).	203	profiles chosen by the profile name (and any C<parent> attributes).
191		204
…		…
474		487
475	Monitor the given port and do something when the port is killed or	488	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	489	messages to it were lost, and optionally return a guard that can be used
477	to stop monitoring again.	490	to stop monitoring again.
478		491
		492	In the first form (callback), the callback is simply called with any
		493	number of C<@reason> elements (no @reason means that the port was deleted
		494	"normally"). Note also that I<< the callback B<must> never die >>, so use
		495	C<eval> if unsure.
		496
		497	In the second form (another port given), the other port (C<$rcvport>)
		498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		499	"normal" kils nothing happens, while under all other conditions, the other
		500	port is killed with the same reason.
		501
		502	The third form (kill self) is the same as the second form, except that
		503	C<$rvport> defaults to C<$SELF>.
		504
		505	In the last form (message), a message of the form C<@msg, @reason> will be
		506	C<snd>.
		507
		508	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		509	alert was raised), they are removed and will not trigger again.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for example, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
		517
479	C<mon> effectively guarantees that, in the absence of hardware failures,	518	C<mon> effectively guarantees that, in the absence of hardware failures,
480	after starting the monitor, either all messages sent to the port will	519	after starting the monitor, either all messages sent to the port will
481	arrive, or the monitoring action will be invoked after possible message	520	arrive, or the monitoring action will be invoked after possible message
482	loss has been detected. No messages will be lost "in between" (after	521	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	522	the first lost message no further messages will be received by the
484	port). After the monitoring action was invoked, further messages might get	523	port). After the monitoring action was invoked, further messages might get
485	delivered again.	524	delivered again.
486		525
487	Note that monitoring-actions are one-shot: once messages are lost (and a	526	Inter-host-connection timeouts and monitoring depend on the transport
488	monitoring alert was raised), they are removed and will not trigger again.	527	used. The only transport currently implemented is TCP, and AnyEvent::MP
		528	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		529	non-idle connection, and usually around two hours for idle conenctions).
489		530
490	In the first form (callback), the callback is simply called with any	531	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	532	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	533	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<$SELF>.
502
503	In the last form (message), a message of the form C<@msg, @reason> will be
504	C<snd>.
505
506	As a rule of thumb, monitoring requests should always monitor a port from
507	a local port (or callback). The reason is that kill messages might get
508	lost, just like any other message. Another less obvious reason is that
509	even monitoring requests can get lost (for exmaple, when the connection
510	to the other node goes down permanently). When monitoring a port locally
511	these problems do not exist.
512		534
513	Example: call a given callback when C<$port> is killed.	535	Example: call a given callback when C<$port> is killed.
514		536
515	mon $port, sub { warn "port died because of <@_>\n" };	537	mon $port, sub { warn "port died because of <@_>\n" };
516		538
…		…
611	the package, then the package above the package and so on (e.g.	633	the package, then the package above the package and so on (e.g.
612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
613	exists or it runs out of package names.	635	exists or it runs out of package names.
614		636
615	The init function is then called with the newly-created port as context	637	The init function is then called with the newly-created port as context
616	object (C<$SELF>) and the C<@initdata> values as arguments.	638	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		639	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		640	the port might not get created.
617		641
618	A common idiom is to pass a local port, immediately monitor the spawned	642	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	643	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	644	local port. This two-way monitoring ensures that both ports get cleaned up
621	when there is a problem.	645	when there is a problem.
622		646
		647	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
		650
623	Example: spawn a chat server port on C<$othernode>.	651	Example: spawn a chat server port on C<$othernode>.
624		652
625	# this node, executed from within a port context:	653	# this node, executed from within a port context:
626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
627	mon $server;	655	mon $server;
…		…
641		669
642	sub _spawn {	670	sub _spawn {
643	my $port = shift;	671	my $port = shift;
644	my $init = shift;	672	my $init = shift;
645		673
		674	# rcv will create the actual port
646	local $SELF = "$NODE#$port";	675	local $SELF = "$NODE#$port";
647	eval {	676	eval {
648	&{ load_func $init }	677	&{ load_func $init }
649	};	678	};
650	_self_die if $@;	679	_self_die if $@;
…		…
707		736
708	=item * Node IDs are arbitrary strings in AEMP.	737	=item * Node IDs are arbitrary strings in AEMP.
709		738
710	Erlang relies on special naming and DNS to work everywhere in the same	739	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	740	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.	741	configuration or DNS), but will otherwise discover other odes itself.
713		742
714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
715	uses "local ports are like remote ports".	744	uses "local ports are like remote ports".
716		745
717	The failure modes for local ports are quite different (runtime errors	746	The failure modes for local ports are quite different (runtime errors
…		…
730		759
731	Erlang uses processes that selectively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
732	needs a queue. AEMP is event based, queuing messages would serve no	761	needs a queue. AEMP is event based, queuing messages would serve no
733	useful purpose. For the same reason the pattern-matching abilities of	762	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	763	AnyEvent::MP are more limited, as there is little need to be able to
735	filter messages without dequeing them.	764	filter messages without dequeuing them.
736		765
737	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
738		767
739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
740		769
…		…
846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
847		876
848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
849	your applications.	878	your applications.
850		879
		880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		881	all nodes.
		882
851	L<AnyEvent>.	883	L<AnyEvent>.
852		884
853	=head1 AUTHOR	885	=head1 AUTHOR
854		886
855	Marc Lehmann <schmorp@schmorp.de>	887	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 1.84 by root, Tue Sep 8 01:42:14 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 1.84 by root, Tue Sep 8 01:42:14 2009 UTC