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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC vs.
Revision 1.100 by root, Fri Oct 2 20:41:56 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 - explains most concepts.	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
…		…
61		59
62	=over 4	60	=over 4
63		61
64	=item port	62	=item port
65		63
66	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).
67		66
68	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
69	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
70	anything was listening for them or not.	69	anything was listening for them or not.
71		70
…		…
82		81
83	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
84	(no listening ports). Private nodes cannot talk to other private nodes	83	(no listening ports). Private nodes cannot talk to other private nodes
85	currently.	84	currently.
86		85
87	=item node ID - C<[a-za-Z0-9_\-.:]+>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
88		87
89	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
90	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
91	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
92	doesn't interpret node IDs in any way.	91	doesn't interpret node IDs in any way.
…		…
96	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
97	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
98	endpoints - binds. Currently, only standard C<ip:port> specifications can	97	endpoints - binds. Currently, only standard C<ip:port> specifications can
99	be used, which specify TCP ports to listen on.	98	be used, which specify TCP ports to listen on.
100		99
101	=item seeds - C<host:port>	100	=item seed nodes
102		101
103	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
104	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
105	network. This node is called a seed.	104	network. This node is called a seed.
106		105
107	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
108	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
109	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
110	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.
111	join the network.
112		117
113	Apart from being sued for seeding, seednodes are not special in any way -	118	=item seeds - C<host:port>
114	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 that 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.
115		127
116	=back	128	=back
117		129
118	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
119		131
…		…
131		143
132	use AE ();	144	use AE ();
133		145
134	use base "Exporter";	146	use base "Exporter";
135		147
136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	148	our $VERSION = 1.21;
137		149
138	our @EXPORT = qw(	150	our @EXPORT = qw(
139	NODE $NODE *SELF node_of after	151	NODE $NODE *SELF node_of after
140	configure	152	configure
141	snd rcv mon mon_guard kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
142	port	154	port
143	);	155	);
144		156
145	our $SELF;	157	our $SELF;
146		158
…		…
158		170
159	=item $nodeid = node_of $port	171	=item $nodeid = node_of $port
160		172
161	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.
162		174
		175	=item configure $profile, key => value...
		176
163	=item configure key => value...	177	=item configure key => value...
164		178
165	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
166	"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
167	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
…		…
174		188
175	=item step 1, gathering configuration from profiles	189	=item step 1, gathering configuration from profiles
176		190
177	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
178	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
179	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
180	-n>) will be used as profile name.	194	missing, then the nodename (F<uname -n>) will be used as profile name.
181		195
182	The profile data is then gathered as follows:	196	The profile data is then gathered as follows:
183		197
184	First, all remaining key => value pairs (all of which are conveniently	198	First, all remaining key => value pairs (all of which are conveniently
185	undocumented at the moment) will be interpreted as configuration	199	undocumented at the moment) will be interpreted as configuration
…		…
213	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
214	connectivity with at least one node at any point in time.	228	connectivity with at least one node at any point in time.
215		229
216	=back	230	=back
217		231
218	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.
219	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.
220		234
221	configure	235	configure
222		236
223	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
…		…
472		486
473	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
474	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
475	to stop monitoring again.	489	to stop monitoring again.
476		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
477	C<mon> effectively guarantees that, in the absence of hardware failures,	517	C<mon> effectively guarantees that, in the absence of hardware failures,
478	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
479	arrive, or the monitoring action will be invoked after possible message	519	arrive, or the monitoring action will be invoked after possible message
480	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
481	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
482	port). After the monitoring action was invoked, further messages might get	522	port). After the monitoring action was invoked, further messages might get
483	delivered again.	523	delivered again.
484		524
485	Note that monitoring-actions are one-shot: once messages are lost (and a	525	Inter-host-connection timeouts and monitoring depend on the transport
486	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 connections).
487		529
488	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
489	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
490	"normally"). Note also that I<< the callback B<must> never die >>, so use	532	to ensure some maximum latency.
491	C<eval> if unsure.
492
493	In the second form (another port given), the other port (C<$rcvport>)
494	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
495	"normal" kils nothing happens, while under all other conditions, the other
496	port is killed with the same reason.
497
498	The third form (kill self) is the same as the second form, except that
499	C<$rvport> defaults to C<$SELF>.
500
501	In the last form (message), a message of the form C<@msg, @reason> will be
502	C<snd>.
503
504	As a rule of thumb, monitoring requests should always monitor a port from
505	a local port (or callback). The reason is that kill messages might get
506	lost, just like any other message. Another less obvious reason is that
507	even monitoring requests can get lost (for example, when the connection
508	to the other node goes down permanently). When monitoring a port locally
509	these problems do not exist.
510		533
511	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
512		535
513	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
514		537
…		…
542	}	565	}
543		566
544	$node->monitor ($port, $cb);	567	$node->monitor ($port, $cb);
545		568
546	defined wantarray	569	defined wantarray
547	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	570	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
548	}	571	}
549		572
550	=item $guard = mon_guard $port, $ref, $ref...	573	=item $guard = mon_guard $port, $ref, $ref...
551		574
552	Monitors the given C<$port> and keeps the passed references. When the port	575	Monitors the given C<$port> and keeps the passed references. When the port
…		…
609	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
611	exists or it runs out of package names.	634	exists or it runs out of package names.
612		635
613	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
614	object (C<$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.
615		640
616	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
617	port, and in the remote init function, immediately monitor the passed	642	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	643	local port. This two-way monitoring ensures that both ports get cleaned up
619	when there is a problem.	644	when there is a problem.
620		645
		646	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
		649
621	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
622		651
623	# this node, executed from within a port context:	652	# this node, executed from within a port context:
624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
625	mon $server;	654	mon $server;
…		…
639		668
640	sub _spawn {	669	sub _spawn {
641	my $port = shift;	670	my $port = shift;
642	my $init = shift;	671	my $init = shift;
643		672
		673	# rcv will create the actual port
644	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
645	eval {	675	eval {
646	&{ load_func $init }	676	&{ load_func $init }
647	};	677	};
648	_self_die if $@;	678	_self_die if $@;
…		…
683	? $action[0]()	713	? $action[0]()
684	: snd @action;	714	: snd @action;
685	};	715	};
686	}	716	}
687		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 (or it is C<undef>), then the local port will
		733	monitor the remote port 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
688	=back	770	=back
689		771
690	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
691		773
692	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
693	== aemp node, Erlang process == aemp port), so many of the documents and	775	== aemp node, Erlang process == aemp port), so many of the documents and
694	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	776	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
695	sample:	777	sample:
696		778
697	http://www.Erlang.se/doc/programming_rules.shtml	779	http://www.erlang.se/doc/programming_rules.shtml
698	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	780	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
699	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	781	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
700	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	782	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
701		783
702	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
703		785
704	=over 4	786	=over 4
705		787
706	=item * Node IDs are arbitrary strings in AEMP.	788	=item * Node IDs are arbitrary strings in AEMP.
707		789
708	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
709	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
710	configuration or DNS), but will otherwise discover other odes itself.	792	configuration or DNS), and possibly the addresses of some seed nodes, but
		793	will otherwise discover other nodes (and their IDs) itself.
711		794
712	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	795	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
713	uses "local ports are like remote ports".	796	uses "local ports are like remote ports".
714		797
715	The failure modes for local ports are quite different (runtime errors	798	The failure modes for local ports are quite different (runtime errors
…		…
740	so does not need a queue that can overflow). AEMP sends are immediate,	823	so does not need a queue that can overflow). AEMP sends are immediate,
741	connection establishment is handled in the background.	824	connection establishment is handled in the background.
742		825
743	=item * Erlang suffers from silent message loss, AEMP does not.	826	=item * Erlang suffers from silent message loss, AEMP does not.
744		827
745	Erlang makes few guarantees on messages delivery - messages can get lost	828	Erlang implements few guarantees on messages delivery - messages can get
746	without any of the processes realising it (i.e. you send messages a, b,	829	lost without any of the processes realising it (i.e. you send messages a,
747	and c, and the other side only receives messages a and c).	830	b, and c, and the other side only receives messages a and c).
748		831
749	AEMP guarantees correct ordering, and the guarantee that after one message	832	AEMP guarantees correct ordering, and the guarantee that after one message
750	is lost, all following ones sent to the same port are lost as well, until	833	is lost, all following ones sent to the same port are lost as well, until
751	monitoring raises an error, so there are no silent "holes" in the message	834	monitoring raises an error, so there are no silent "holes" in the message
752	sequence.	835	sequence.
…		…
844	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	927	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
845		928
846	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	929	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
847	your applications.	930	your applications.
848		931
		932	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		933	all nodes.
		934
849	L<AnyEvent>.	935	L<AnyEvent>.
850		936
851	=head1 AUTHOR	937	=head1 AUTHOR
852		938
853	Marc Lehmann <schmorp@schmorp.de>	939	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC vs. Revision 1.100 by root, Fri Oct 2 20:41:56 2009 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC vs.
Revision 1.100 by root, Fri Oct 2 20:41:56 2009 UTC