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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.79 by root, Fri Sep 4 21:52:09 2009 UTC vs.
Revision 1.121 by root, Tue Feb 28 18:37:24 2012 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
30	rcv $port, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
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	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
35	# monitoring	39	# monitoring
36	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
38	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
39		51
40	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
41		53
42	bin/aemp - stable.	54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - explains most concepts.	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.	58	AnyEvent::MP::Global - stable API.
47
48	stay tuned.
49		59
50	=head1 DESCRIPTION	60	=head1 DESCRIPTION
51		61
52	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
53		63
…		…
68		78
69	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
70	some messages. Messages send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
71	anything was listening for them or not.	81	anything was listening for them or not.
72		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
73	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
74		86
75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
76	separator, and a port name (a printable string of unspecified format).	88	separator, and a port name (a printable string of unspecified format).
77		89
…		…
81	which enables nodes to manage each other remotely, and to create new	93	which enables nodes to manage each other remotely, and to create new
82	ports.	94	ports.
83		95
84	Nodes are either public (have one or more listening ports) or private	96	Nodes are either public (have one or more listening ports) or private
85	(no listening ports). Private nodes cannot talk to other private nodes	97	(no listening ports). Private nodes cannot talk to other private nodes
86	currently.	98	currently, but all nodes can talk to public nodes.
87		99
		100	Nodes is represented by (printable) strings called "node IDs".
		101
88	=item node ID - C<[a-za-Z0-9_\-.:]+>	102	=item node ID - C<[A-Za-z0-9_\-.:]*>
89		103
90	A node ID is a string that uniquely identifies the node within a	104	A node ID is a string that uniquely identifies the node within a
91	network. Depending on the configuration used, node IDs can look like a	105	network. Depending on the configuration used, node IDs can look like a
92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	106	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
93	doesn't interpret node IDs in any way.	107	doesn't interpret node IDs in any way except to uniquely identify a node.
94		108
95	=item binds - C<ip:port>	109	=item binds - C<ip:port>
96		110
97	Nodes can only talk to each other by creating some kind of connection to	111	Nodes can only talk to each other by creating some kind of connection to
98	each other. To do this, nodes should listen on one or more local transport	112	each other. To do this, nodes should listen on one or more local transport
		113	endpoints - binds.
		114
99	endpoints - binds. Currently, only standard C<ip:port> specifications can	115	Currently, only standard C<ip:port> specifications can be used, which
100	be used, which specify TCP ports to listen on.	116	specify TCP ports to listen on. So a bind is basically just a tcp socket
		117	in listening mode thta accepts conenctions form other nodes.
101		118
		119	=item seed nodes
		120
		121	When a node starts, it knows nothing about the network it is in - it
		122	needs to connect to at least one other node that is already in the
		123	network. These other nodes are called "seed nodes".
		124
		125	Seed nodes themselves are not special - they are seed nodes only because
		126	some other node I<uses> them as such, but any node can be used as seed
		127	node for other nodes, and eahc node cna use a different set of seed nodes.
		128
		129	In addition to discovering the network, seed nodes are also used to
		130	maintain the network - all nodes using the same seed node form are part of
		131	the same network. If a network is split into multiple subnets because e.g.
		132	the network link between the parts goes down, then using the same seed
		133	nodes for all nodes ensures that eventually the subnets get merged again.
		134
		135	Seed nodes are expected to be long-running, and at least one seed node
		136	should always be available. They should also be relatively responsive - a
		137	seed node that blocks for long periods will slow down everybody else.
		138
		139	For small networks, it's best if every node uses the same set of seed
		140	nodes. For large networks, it can be useful to specify "regional" seed
		141	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		142	each other. What's important is that all seed nodes connections form a
		143	complete graph, so that the network cannot split into separate subnets
		144	forever.
		145
		146	Seed nodes are represented by seed IDs.
		147
102	=item seeds - C<host:port>	148	=item seed IDs - C<host:port>
103		149
104	When a node starts, it knows nothing about the network. To teach the node	150	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
105	about the network it first has to contact some other node within the	151	TCP port) of nodes that should be used as seed nodes.
106	network. This node is called a seed.
107		152
108	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	153	=item global nodes
109	are expected to be long-running, and at least one of those should always
110	be available. When nodes run out of connections (e.g. due to a network
111	error), they try to re-establish connections to some seednodes again to
112	join the network.
113		154
114	Apart from being sued for seeding, seednodes are not special in any way -	155	An AEMP network needs a discovery service - nodes need to know how to
115	every public node can be a seednode.	156	connect to other nodes they only know by name. In addition, AEMP offers a
		157	distributed "group database", which maps group names to a list of strings
		158	- for example, to register worker ports.
		159
		160	A network needs at least one global node to work, and allows every node to
		161	be a global node.
		162
		163	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		164	node and tries to keep connections to all other nodes. So while it can
		165	make sense to make every node "global" in small networks, it usually makes
		166	sense to only make seed nodes into global nodes in large networks (nodes
		167	keep connections to seed nodes and global nodes, so makign them the same
		168	reduces overhead).
116		169
117	=back	170	=back
118		171
119	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
120		173
…		…
122		175
123	=cut	176	=cut
124		177
125	package AnyEvent::MP;	178	package AnyEvent::MP;
126		179
		180	use AnyEvent::MP::Config ();
127	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
128		183
129	use common::sense;	184	use common::sense;
130		185
131	use Carp ();	186	use Carp ();
132		187
133	use AE ();	188	use AE ();
134		189
135	use base "Exporter";	190	use base "Exporter";
136		191
137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
138		193
139	our @EXPORT = qw(	194	our @EXPORT = qw(
140	NODE $NODE *SELF node_of after	195	NODE $NODE *SELF node_of after
141	configure	196	configure
142	snd rcv mon mon_guard kil reg psub spawn	197	snd rcv mon mon_guard kil psub peval spawn cal
143	port	198	port
144	);	199	);
145		200
146	our $SELF;	201	our $SELF;
147		202
…		…
170	to know is its own name, and optionally it should know the addresses of	225	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	226	some other nodes in the network to discover other nodes.
172		227
173	This function configures a node - it must be called exactly once (or	228	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	229	never) before calling other AnyEvent::MP functions.
		230
		231	The key/value pairs are basically the same ones as documented for the
		232	F<aemp> command line utility (sans the set/del prefix), with two additions:
		233
		234	=over 4
		235
		236	=item norc => $boolean (default false)
		237
		238	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		239	be consulted - all configuraiton options must be specified in the
		240	C<configure> call.
		241
		242	=item force => $boolean (default false)
		243
		244	IF true, then the values specified in the C<configure> will take
		245	precedence over any values configured via the rc file. The default is for
		246	the rc file to override any options specified in the program.
		247
		248	=back
175		249
176	=over 4	250	=over 4
177		251
178	=item step 1, gathering configuration from profiles	252	=item step 1, gathering configuration from profiles
179		253
…		…
210	used, meaning the node will bind on a dynamically-assigned port on every	284	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	285	local IP address it finds.
212		286
213	=item step 3, connect to seed nodes	287	=item step 3, connect to seed nodes
214		288
215	As the last step, the seeds list from the profile is passed to the	289	As the last step, the seed ID list from the profile is passed to the
216	L<AnyEvent::MP::Global> module, which will then use it to keep	290	L<AnyEvent::MP::Global> module, which will then use it to keep
217	connectivity with at least one node at any point in time.	291	connectivity with at least one node at any point in time.
218		292
219	=back	293	=back
220		294
221	Example: become a distributed node using the locla node name as profile.	295	Example: become a distributed node using the local node name as profile.
222	This should be the most common form of invocation for "daemon"-type nodes.	296	This should be the most common form of invocation for "daemon"-type nodes.
223		297
224	configure	298	configure
225		299
226	Example: become an anonymous node. This form is often used for commandline	300	Example: become an anonymous node. This form is often used for commandline
227	clients.	301	clients.
228		302
229	configure nodeid => "anon/";	303	configure nodeid => "anon/";
230		304
231	Example: configure a node using a profile called seed, which si suitable	305	Example: configure a node using a profile called seed, which is suitable
232	for a seed node as it binds on all local addresses on a fixed port (4040,	306	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	307	customary for aemp).
234		308
235	# use the aemp commandline utility	309	# use the aemp commandline utility
236	# aemp profile seed nodeid anon/ binds '*:4040'	310	# aemp profile seed nodeid anon/ binds '*:4040'
…		…
311	sub _kilme {	385	sub _kilme {
312	die "received message on port without callback";	386	die "received message on port without callback";
313	}	387	}
314		388
315	sub port(;&) {	389	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	390	my $id = "$UNIQ." . ++$ID;
317	my $port = "$NODE#$id";	391	my $port = "$NODE#$id";
318		392
319	rcv $port, shift \|\| \&_kilme;	393	rcv $port, shift \|\| \&_kilme;
320		394
321	$port	395	$port
…		…
360	msg1 => sub { ... },	434	msg1 => sub { ... },
361	...	435	...
362	;	436	;
363		437
364	Example: temporarily register a rcv callback for a tag matching some port	438	Example: temporarily register a rcv callback for a tag matching some port
365	(e.g. for a rpc reply) and unregister it after a message was received.	439	(e.g. for an rpc reply) and unregister it after a message was received.
366		440
367	rcv $port, $otherport => sub {	441	rcv $port, $otherport => sub {
368	my @reply = @_;	442	my @reply = @_;
369		443
370	rcv $SELF, $otherport;	444	rcv $SELF, $otherport;
…		…
383	if (ref $_[0]) {	457	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	458	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	459	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	460	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387		461
388	$self->[2] = shift;	462	$self->[0] = shift;
389	} else {	463	} else {
390	my $cb = shift;	464	my $cb = shift;
391	$PORT{$portid} = sub {	465	$PORT{$portid} = sub {
392	local $SELF = $port;	466	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	467	eval { &$cb }; _self_die if $@;
394	};	468	};
395	}	469	}
396	} elsif (defined $_[0]) {	470	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	471	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	472	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		473
400	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
401	local $SELF = $port;	475	local $SELF = $port;
402		476
403	if (my $cb = $self->[1]{$_[0]}) {	477	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	499	}
426		500
427	$port	501	$port
428	}	502	}
429		503
		504	=item peval $port, $coderef[, @args]
		505
		506	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		507	when the code throews an exception the C<$port> will be killed.
		508
		509	Any remaining args will be passed to the callback. Any return values will
		510	be returned to the caller.
		511
		512	This is useful when you temporarily want to execute code in the context of
		513	a port.
		514
		515	Example: create a port and run some initialisation code in it's context.
		516
		517	my $port = port { ... };
		518
		519	peval $port, sub {
		520	init
		521	or die "unable to init";
		522	};
		523
		524	=cut
		525
		526	sub peval($$) {
		527	local $SELF = shift;
		528	my $cb = shift;
		529
		530	if (wantarray) {
		531	my @res = eval { &$cb };
		532	_self_die if $@;
		533	@res
		534	} else {
		535	my $res = eval { &$cb };
		536	_self_die if $@;
		537	$res
		538	}
		539	}
		540
430	=item $closure = psub { BLOCK }	541	=item $closure = psub { BLOCK }
431		542
432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	543	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
433	closure is executed, sets up the environment in the same way as in C<rcv>	544	closure is executed, sets up the environment in the same way as in C<rcv>
434	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	545	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		546
		547	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		548	BLOCK }, @_ } >>.
435		549
436	This is useful when you register callbacks from C<rcv> callbacks:	550	This is useful when you register callbacks from C<rcv> callbacks:
437		551
438	rcv delayed_reply => sub {	552	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	553	my ($delay, @reply) = @_;
…		…
512	delivered again.	626	delivered again.
513		627
514	Inter-host-connection timeouts and monitoring depend on the transport	628	Inter-host-connection timeouts and monitoring depend on the transport
515	used. The only transport currently implemented is TCP, and AnyEvent::MP	629	used. The only transport currently implemented is TCP, and AnyEvent::MP
516	relies on TCP to detect node-downs (this can take 10-15 minutes on a	630	relies on TCP to detect node-downs (this can take 10-15 minutes on a
517	non-idle connection, and usually around two hours for idle conenctions).	631	non-idle connection, and usually around two hours for idle connections).
518		632
519	This means that monitoring is good for program errors and cleaning up	633	This means that monitoring is good for program errors and cleaning up
520	stuff eventually, but they are no replacement for a timeout when you need	634	stuff eventually, but they are no replacement for a timeout when you need
521	to ensure some maximum latency.	635	to ensure some maximum latency.
522		636
…		…
554	}	668	}
555		669
556	$node->monitor ($port, $cb);	670	$node->monitor ($port, $cb);
557		671
558	defined wantarray	672	defined wantarray
559	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	673	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
560	}	674	}
561		675
562	=item $guard = mon_guard $port, $ref, $ref...	676	=item $guard = mon_guard $port, $ref, $ref...
563		677
564	Monitors the given C<$port> and keeps the passed references. When the port	678	Monitors the given C<$port> and keeps the passed references. When the port
…		…
587		701
588	=item kil $port[, @reason]	702	=item kil $port[, @reason]
589		703
590	Kill the specified port with the given C<@reason>.	704	Kill the specified port with the given C<@reason>.
591		705
592	If no C<@reason> is specified, then the port is killed "normally" (ports	706	If no C<@reason> is specified, then the port is killed "normally" -
593	monitoring other ports will not necessarily die because a port dies	707	monitor callback will be invoked, but the kil will not cause linked ports
594	"normally").	708	(C<mon $mport, $lport> form) to get killed.
595		709
596	Otherwise, linked ports get killed with the same reason (second form of	710	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
597	C<mon>, see above).	711	form) get killed with the same reason.
598		712
599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	713	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
600	will be reported as reason C<< die => $@ >>.	714	will be reported as reason C<< die => $@ >>.
601		715
602	Transport/communication errors are reported as C<< transport_error =>	716	Transport/communication errors are reported as C<< transport_error =>
…		…
621	the package, then the package above the package and so on (e.g.	735	the package, then the package above the package and so on (e.g.
622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	736	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
623	exists or it runs out of package names.	737	exists or it runs out of package names.
624		738
625	The init function is then called with the newly-created port as context	739	The init function is then called with the newly-created port as context
626	object (C<$SELF>) and the C<@initdata> values as arguments.	740	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		741	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		742	the port might not get created.
627		743
628	A common idiom is to pass a local port, immediately monitor the spawned	744	A common idiom is to pass a local port, immediately monitor the spawned
629	port, and in the remote init function, immediately monitor the passed	745	port, and in the remote init function, immediately monitor the passed
630	local port. This two-way monitoring ensures that both ports get cleaned up	746	local port. This two-way monitoring ensures that both ports get cleaned up
631	when there is a problem.	747	when there is a problem.
632		748
		749	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		750	caller before C<spawn> returns (by delaying invocation when spawn is
		751	called for the local node).
		752
633	Example: spawn a chat server port on C<$othernode>.	753	Example: spawn a chat server port on C<$othernode>.
634		754
635	# this node, executed from within a port context:	755	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	756	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
637	mon $server;	757	mon $server;
…		…
651		771
652	sub _spawn {	772	sub _spawn {
653	my $port = shift;	773	my $port = shift;
654	my $init = shift;	774	my $init = shift;
655		775
		776	# rcv will create the actual port
656	local $SELF = "$NODE#$port";	777	local $SELF = "$NODE#$port";
657	eval {	778	eval {
658	&{ load_func $init }	779	&{ load_func $init }
659	};	780	};
660	_self_die if $@;	781	_self_die if $@;
661	}	782	}
662		783
663	sub spawn(@) {	784	sub spawn(@) {
664	my ($nodeid, undef) = split /#/, shift, 2;	785	my ($nodeid, undef) = split /#/, shift, 2;
665		786
666	my $id = "$RUNIQ." . $ID++;	787	my $id = "$RUNIQ." . ++$ID;
667		788
668	$_[0] =~ /::/	789	$_[0] =~ /::/
669	or Carp::croak "spawn init function must be a fully-qualified name, caught";	790	or Carp::croak "spawn init function must be a fully-qualified name, caught";
670		791
671	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	792	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672		793
673	"$nodeid#$id"	794	"$nodeid#$id"
674	}	795	}
		796
675		797
676	=item after $timeout, @msg	798	=item after $timeout, @msg
677		799
678	=item after $timeout, $callback	800	=item after $timeout, $callback
679		801
…		…
695	? $action[0]()	817	? $action[0]()
696	: snd @action;	818	: snd @action;
697	};	819	};
698	}	820	}
699		821
		822	=item cal $port, @msg, $callback[, $timeout]
		823
		824	A simple form of RPC - sends a message to the given C<$port> with the
		825	given contents (C<@msg>), but adds a reply port to the message.
		826
		827	The reply port is created temporarily just for the purpose of receiving
		828	the reply, and will be C<kil>ed when no longer needed.
		829
		830	A reply message sent to the port is passed to the C<$callback> as-is.
		831
		832	If an optional time-out (in seconds) is given and it is not C<undef>,
		833	then the callback will be called without any arguments after the time-out
		834	elapsed and the port is C<kil>ed.
		835
		836	If no time-out is given (or it is C<undef>), then the local port will
		837	monitor the remote port instead, so it eventually gets cleaned-up.
		838
		839	Currently this function returns the temporary port, but this "feature"
		840	might go in future versions unless you can make a convincing case that
		841	this is indeed useful for something.
		842
		843	=cut
		844
		845	sub cal(@) {
		846	my $timeout = ref $_[-1] ? undef : pop;
		847	my $cb = pop;
		848
		849	my $port = port {
		850	undef $timeout;
		851	kil $SELF;
		852	&$cb;
		853	};
		854
		855	if (defined $timeout) {
		856	$timeout = AE::timer $timeout, 0, sub {
		857	undef $timeout;
		858	kil $port;
		859	$cb->();
		860	};
		861	} else {
		862	mon $_[0], sub {
		863	kil $port;
		864	$cb->();
		865	};
		866	}
		867
		868	push @_, $port;
		869	&snd;
		870
		871	$port
		872	}
		873
700	=back	874	=back
701		875
702	=head1 AnyEvent::MP vs. Distributed Erlang	876	=head1 AnyEvent::MP vs. Distributed Erlang
703		877
704	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	878	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
705	== aemp node, Erlang process == aemp port), so many of the documents and	879	== aemp node, Erlang process == aemp port), so many of the documents and
706	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	880	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
707	sample:	881	sample:
708		882
709	http://www.Erlang.se/doc/programming_rules.shtml	883	http://www.erlang.se/doc/programming_rules.shtml
710	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	884	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
711	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	885	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
712	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	886	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
713		887
714	Despite the similarities, there are also some important differences:	888	Despite the similarities, there are also some important differences:
715		889
716	=over 4	890	=over 4
717		891
718	=item * Node IDs are arbitrary strings in AEMP.	892	=item * Node IDs are arbitrary strings in AEMP.
719		893
720	Erlang relies on special naming and DNS to work everywhere in the same	894	Erlang relies on special naming and DNS to work everywhere in the same
721	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	895	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
722	configuration or DNS), but will otherwise discover other odes itself.	896	configuration or DNS), and possibly the addresses of some seed nodes, but
		897	will otherwise discover other nodes (and their IDs) itself.
723		898
724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	899	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
725	uses "local ports are like remote ports".	900	uses "local ports are like remote ports".
726		901
727	The failure modes for local ports are quite different (runtime errors	902	The failure modes for local ports are quite different (runtime errors
…		…
736	ports being the special case/exception, where transport errors cannot	911	ports being the special case/exception, where transport errors cannot
737	occur.	912	occur.
738		913
739	=item * Erlang uses processes and a mailbox, AEMP does not queue.	914	=item * Erlang uses processes and a mailbox, AEMP does not queue.
740		915
741	Erlang uses processes that selectively receive messages, and therefore	916	Erlang uses processes that selectively receive messages out of order, and
742	needs a queue. AEMP is event based, queuing messages would serve no	917	therefore needs a queue. AEMP is event based, queuing messages would serve
743	useful purpose. For the same reason the pattern-matching abilities of	918	no useful purpose. For the same reason the pattern-matching abilities
744	AnyEvent::MP are more limited, as there is little need to be able to	919	of AnyEvent::MP are more limited, as there is little need to be able to
745	filter messages without dequeuing them.	920	filter messages without dequeuing them.
746		921
747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	922	This is not a philosophical difference, but simply stems from AnyEvent::MP
		923	being event-based, while Erlang is process-based.
		924
		925	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		926	top of AEMP and Coro threads.
748		927
749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	928	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
750		929
751	Sending messages in Erlang is synchronous and blocks the process (and	930	Sending messages in Erlang is synchronous and blocks the process until
		931	a conenction has been established and the message sent (and so does not
752	so does not need a queue that can overflow). AEMP sends are immediate,	932	need a queue that can overflow). AEMP sends return immediately, connection
753	connection establishment is handled in the background.	933	establishment is handled in the background.
754		934
755	=item * Erlang suffers from silent message loss, AEMP does not.	935	=item * Erlang suffers from silent message loss, AEMP does not.
756		936
757	Erlang makes few guarantees on messages delivery - messages can get lost	937	Erlang implements few guarantees on messages delivery - messages can get
758	without any of the processes realising it (i.e. you send messages a, b,	938	lost without any of the processes realising it (i.e. you send messages a,
759	and c, and the other side only receives messages a and c).	939	b, and c, and the other side only receives messages a and c).
760		940
761	AEMP guarantees correct ordering, and the guarantee that after one message	941	AEMP guarantees (modulo hardware errors) correct ordering, and the
762	is lost, all following ones sent to the same port are lost as well, until	942	guarantee that after one message is lost, all following ones sent to the
763	monitoring raises an error, so there are no silent "holes" in the message	943	same port are lost as well, until monitoring raises an error, so there are
764	sequence.	944	no silent "holes" in the message sequence.
		945
		946	If you want your software to be very reliable, you have to cope with
		947	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		948	simply tries to work better in common error cases, such as when a network
		949	link goes down.
765		950
766	=item * Erlang can send messages to the wrong port, AEMP does not.	951	=item * Erlang can send messages to the wrong port, AEMP does not.
767		952
768	In Erlang it is quite likely that a node that restarts reuses a process ID	953	In Erlang it is quite likely that a node that restarts reuses an Erlang
769	known to other nodes for a completely different process, causing messages	954	process ID known to other nodes for a completely different process,
770	destined for that process to end up in an unrelated process.	955	causing messages destined for that process to end up in an unrelated
		956	process.
771		957
772	AEMP never reuses port IDs, so old messages or old port IDs floating	958	AEMP does not reuse port IDs, so old messages or old port IDs floating
773	around in the network will not be sent to an unrelated port.	959	around in the network will not be sent to an unrelated port.
774		960
775	=item * Erlang uses unprotected connections, AEMP uses secure	961	=item * Erlang uses unprotected connections, AEMP uses secure
776	authentication and can use TLS.	962	authentication and can use TLS.
777		963
…		…
780		966
781	=item * The AEMP protocol is optimised for both text-based and binary	967	=item * The AEMP protocol is optimised for both text-based and binary
782	communications.	968	communications.
783		969
784	The AEMP protocol, unlike the Erlang protocol, supports both programming	970	The AEMP protocol, unlike the Erlang protocol, supports both programming
785	language independent text-only protocols (good for debugging) and binary,	971	language independent text-only protocols (good for debugging), and binary,
786	language-specific serialisers (e.g. Storable). By default, unless TLS is	972	language-specific serialisers (e.g. Storable). By default, unless TLS is
787	used, the protocol is actually completely text-based.	973	used, the protocol is actually completely text-based.
788		974
789	It has also been carefully designed to be implementable in other languages	975	It has also been carefully designed to be implementable in other languages
790	with a minimum of work while gracefully degrading functionality to make the	976	with a minimum of work while gracefully degrading functionality to make the
791	protocol simple.	977	protocol simple.
792		978
793	=item * AEMP has more flexible monitoring options than Erlang.	979	=item * AEMP has more flexible monitoring options than Erlang.
794		980
795	In Erlang, you can chose to receive I<all> exit signals as messages	981	In Erlang, you can chose to receive I<all> exit signals as messages or
796	or I<none>, there is no in-between, so monitoring single processes is	982	I<none>, there is no in-between, so monitoring single Erlang processes is
797	difficult to implement. Monitoring in AEMP is more flexible than in	983	difficult to implement.
798	Erlang, as one can choose between automatic kill, exit message or callback	984
799	on a per-process basis.	985	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		986	between automatic kill, exit message or callback on a per-port basis.
800		987
801	=item * Erlang tries to hide remote/local connections, AEMP does not.	988	=item * Erlang tries to hide remote/local connections, AEMP does not.
802		989
803	Monitoring in Erlang is not an indicator of process death/crashes, in the	990	Monitoring in Erlang is not an indicator of process death/crashes, in the
804	same way as linking is (except linking is unreliable in Erlang).	991	same way as linking is (except linking is unreliable in Erlang).
…		…
826	overhead, as well as having to keep a proxy object everywhere.	1013	overhead, as well as having to keep a proxy object everywhere.
827		1014
828	Strings can easily be printed, easily serialised etc. and need no special	1015	Strings can easily be printed, easily serialised etc. and need no special
829	procedures to be "valid".	1016	procedures to be "valid".
830		1017
831	And as a result, a miniport consists of a single closure stored in a	1018	And as a result, a port with just a default receiver consists of a single
832	global hash - it can't become much cheaper.	1019	code reference stored in a global hash - it can't become much cheaper.
833		1020
834	=item Why favour JSON, why not a real serialising format such as Storable?	1021	=item Why favour JSON, why not a real serialising format such as Storable?
835		1022
836	In fact, any AnyEvent::MP node will happily accept Storable as framing	1023	In fact, any AnyEvent::MP node will happily accept Storable as framing
837	format, but currently there is no way to make a node use Storable by	1024	format, but currently there is no way to make a node use Storable by
…		…
853		1040
854	L<AnyEvent::MP::Intro> - a gentle introduction.	1041	L<AnyEvent::MP::Intro> - a gentle introduction.
855		1042
856	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1043	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
857		1044
858	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1045	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
859	your applications.	1046	your applications.
		1047
		1048	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1049
		1050	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1051	all nodes.
860		1052
861	L<AnyEvent>.	1053	L<AnyEvent>.
862		1054
863	=head1 AUTHOR	1055	=head1 AUTHOR
864		1056

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.79 by root, Fri Sep 4 21:52:09 2009 UTC vs.
Revision 1.121 by root, Tue Feb 28 18:37:24 2012 UTC