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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC vs.
Revision 1.123 by root, Thu Mar 1 19:37:59 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<#>)
76	separator, and a port name (a printable string of unspecified format).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
77		90
78	=item node	91	=item node
79		92
80	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
81	which enables nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
82	ports.	95	ports.
83		96
84	Nodes are either public (have one or more listening ports) or private	97	Nodes are either public (have one or more listening ports) or private
85	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
86	currently.	99	currently, but all nodes can talk to public nodes.
87		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
89		104
90	A node ID is a string that uniquely identifies the node within a	105	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	106	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	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
93	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
94		109
95	=item binds - C<ip:port>	110	=item binds - C<ip:port>
96		111
97	Nodes can only talk to each other by creating some kind of connection to	112	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	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
99	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
100	be used, which specify TCP ports to listen on.	117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
101		119
102	=item seed nodes	120	=item seed nodes
103		121
104	When a node starts, it knows nothing about the network. To teach the node	122	When a node starts, it knows nothing about the network it is in - it
105	about the network it first has to contact some other node within the	123	needs to connect to at least one other node that is already in the
106	network. This node is called a seed.	124	network. These other nodes are called "seed nodes".
107		125
108	Apart from the fact that other nodes know them as seed nodes and they have	126	Seed nodes themselves are not special - they are seed nodes only because
109	to have fixed listening addresses, seed nodes are perfectly normal nodes -	127	some other node I<uses> them as such, but any node can be used as seed
110	any node can function as a seed node for others.	128	node for other nodes, and eahc node cna use a different set of seed nodes.
111		129
112	In addition to discovering the network, seed nodes are also used to	130	In addition to discovering the network, seed nodes are also used to
113	maintain the network and to connect nodes that otherwise would have	131	maintain the network - all nodes using the same seed node form are part of
114	trouble connecting. They form the backbone of an AnyEvent::MP network.	132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
115		135
116	Seed nodes are expected to be long-running, and at least one seed node	136	Seed nodes are expected to be long-running, and at least one seed node
117	should always be available. They should also be relatively responsive - a	137	should always be available. They should also be relatively responsive - a
118	seed node that blocks for long periods will slow down everybody else.	138	seed node that blocks for long periods will slow down everybody else.
119		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
120	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
121		150
122	Seeds are transport endpoint(s) (usually a hostname/IP address and a	151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
123	TCP port) of nodes thta should be used as seed nodes.	152	TCP port) of nodes that should be used as seed nodes.
124		153
125	The nodes listening on those endpoints are expected to be long-running,	154	=item global nodes
126	and at least one of those should always be available. When nodes run out	155
127	of connections (e.g. due to a network error), they try to re-establish	156	An AEMP network needs a discovery service - nodes need to know how to
128	connections to some seednodes again to join the network.	157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
129		170
130	=back	171	=back
131		172
132	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
133		174
…		…
135		176
136	=cut	177	=cut
137		178
138	package AnyEvent::MP;	179	package AnyEvent::MP;
139		180
		181	use AnyEvent::MP::Config ();
140	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
141		184
142	use common::sense;	185	use common::sense;
143		186
144	use Carp ();	187	use Carp ();
145		188
146	use AE ();	189	use AE ();
147		190
148	use base "Exporter";	191	use base "Exporter";
149		192
150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	193	our $VERSION = $AnyEvent::MP::Config::VERSION;
151		194
152	our @EXPORT = qw(	195	our @EXPORT = qw(
153	NODE $NODE *SELF node_of after	196	NODE $NODE *SELF node_of after
154	configure	197	configure
155	snd rcv mon mon_guard kil reg psub spawn cal	198	snd rcv mon mon_guard kil psub peval spawn cal
156	port	199	port
157	);	200	);
158		201
159	our $SELF;	202	our $SELF;
160		203
…		…
183	to know is its own name, and optionally it should know the addresses of	226	to know is its own name, and optionally it should know the addresses of
184	some other nodes in the network to discover other nodes.	227	some other nodes in the network to discover other nodes.
185		228
186	This function configures a node - it must be called exactly once (or	229	This function configures a node - it must be called exactly once (or
187	never) before calling other AnyEvent::MP functions.	230	never) before calling other AnyEvent::MP functions.
		231
		232	The key/value pairs are basically the same ones as documented for the
		233	F<aemp> command line utility (sans the set/del prefix), with two additions:
		234
		235	=over 4
		236
		237	=item norc => $boolean (default false)
		238
		239	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		240	be consulted - all configuraiton options must be specified in the
		241	C<configure> call.
		242
		243	=item force => $boolean (default false)
		244
		245	IF true, then the values specified in the C<configure> will take
		246	precedence over any values configured via the rc file. The default is for
		247	the rc file to override any options specified in the program.
		248
		249	=back
188		250
189	=over 4	251	=over 4
190		252
191	=item step 1, gathering configuration from profiles	253	=item step 1, gathering configuration from profiles
192		254
…		…
206	That means that the values specified in the profile have highest priority	268	That means that the values specified in the profile have highest priority
207	and the values specified directly via C<configure> have lowest priority,	269	and the values specified directly via C<configure> have lowest priority,
208	and can only be used to specify defaults.	270	and can only be used to specify defaults.
209		271
210	If the profile specifies a node ID, then this will become the node ID of	272	If the profile specifies a node ID, then this will become the node ID of
211	this process. If not, then the profile name will be used as node ID. The	273	this process. If not, then the profile name will be used as node ID, with
212	special node ID of C<anon/> will be replaced by a random node ID.	274	a slash (C</>) attached.
		275
		276	If the node ID (or profile name) ends with a slash (C</>), then a random
		277	string is appended to make it unique.
213		278
214	=item step 2, bind listener sockets	279	=item step 2, bind listener sockets
215		280
216	The next step is to look up the binds in the profile, followed by binding	281	The next step is to look up the binds in the profile, followed by binding
217	aemp protocol listeners on all binds specified (it is possible and valid	282	aemp protocol listeners on all binds specified (it is possible and valid
…		…
223	used, meaning the node will bind on a dynamically-assigned port on every	288	used, meaning the node will bind on a dynamically-assigned port on every
224	local IP address it finds.	289	local IP address it finds.
225		290
226	=item step 3, connect to seed nodes	291	=item step 3, connect to seed nodes
227		292
228	As the last step, the seeds list from the profile is passed to the	293	As the last step, the seed ID list from the profile is passed to the
229	L<AnyEvent::MP::Global> module, which will then use it to keep	294	L<AnyEvent::MP::Global> module, which will then use it to keep
230	connectivity with at least one node at any point in time.	295	connectivity with at least one node at any point in time.
231		296
232	=back	297	=back
233		298
…		…
239	Example: become an anonymous node. This form is often used for commandline	304	Example: become an anonymous node. This form is often used for commandline
240	clients.	305	clients.
241		306
242	configure nodeid => "anon/";	307	configure nodeid => "anon/";
243		308
244	Example: configure a node using a profile called seed, which si suitable	309	Example: configure a node using a profile called seed, which is suitable
245	for a seed node as it binds on all local addresses on a fixed port (4040,	310	for a seed node as it binds on all local addresses on a fixed port (4040,
246	customary for aemp).	311	customary for aemp).
247		312
248	# use the aemp commandline utility	313	# use the aemp commandline utility
249	# aemp profile seed nodeid anon/ binds '*:4040'	314	# aemp profile seed binds '*:4040'
250		315
251	# then use it	316	# then use it
252	configure profile => "seed";	317	configure profile => "seed";
253		318
254	# or simply use aemp from the shell again:	319	# or simply use aemp from the shell again:
…		…
324	sub _kilme {	389	sub _kilme {
325	die "received message on port without callback";	390	die "received message on port without callback";
326	}	391	}
327		392
328	sub port(;&) {	393	sub port(;&) {
329	my $id = "$UNIQ." . $ID++;	394	my $id = $UNIQ . ++$ID;
330	my $port = "$NODE#$id";	395	my $port = "$NODE#$id";
331		396
332	rcv $port, shift \|\| \&_kilme;	397	rcv $port, shift \|\| \&_kilme;
333		398
334	$port	399	$port
…		…
373	msg1 => sub { ... },	438	msg1 => sub { ... },
374	...	439	...
375	;	440	;
376		441
377	Example: temporarily register a rcv callback for a tag matching some port	442	Example: temporarily register a rcv callback for a tag matching some port
378	(e.g. for a rpc reply) and unregister it after a message was received.	443	(e.g. for an rpc reply) and unregister it after a message was received.
379		444
380	rcv $port, $otherport => sub {	445	rcv $port, $otherport => sub {
381	my @reply = @_;	446	my @reply = @_;
382		447
383	rcv $SELF, $otherport;	448	rcv $SELF, $otherport;
…		…
396	if (ref $_[0]) {	461	if (ref $_[0]) {
397	if (my $self = $PORT_DATA{$portid}) {	462	if (my $self = $PORT_DATA{$portid}) {
398	"AnyEvent::MP::Port" eq ref $self	463	"AnyEvent::MP::Port" eq ref $self
399	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	464	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
400		465
401	$self->[2] = shift;	466	$self->[0] = shift;
402	} else {	467	} else {
403	my $cb = shift;	468	my $cb = shift;
404	$PORT{$portid} = sub {	469	$PORT{$portid} = sub {
405	local $SELF = $port;	470	local $SELF = $port;
406	eval { &$cb }; _self_die if $@;	471	eval { &$cb }; _self_die if $@;
407	};	472	};
408	}	473	}
409	} elsif (defined $_[0]) {	474	} elsif (defined $_[0]) {
410	my $self = $PORT_DATA{$portid} \|\|= do {	475	my $self = $PORT_DATA{$portid} \|\|= do {
411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	476	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
412		477
413	$PORT{$portid} = sub {	478	$PORT{$portid} = sub {
414	local $SELF = $port;	479	local $SELF = $port;
415		480
416	if (my $cb = $self->[1]{$_[0]}) {	481	if (my $cb = $self->[1]{$_[0]}) {
…		…
438	}	503	}
439		504
440	$port	505	$port
441	}	506	}
442		507
		508	=item peval $port, $coderef[, @args]
		509
		510	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		511	when the code throews an exception the C<$port> will be killed.
		512
		513	Any remaining args will be passed to the callback. Any return values will
		514	be returned to the caller.
		515
		516	This is useful when you temporarily want to execute code in the context of
		517	a port.
		518
		519	Example: create a port and run some initialisation code in it's context.
		520
		521	my $port = port { ... };
		522
		523	peval $port, sub {
		524	init
		525	or die "unable to init";
		526	};
		527
		528	=cut
		529
		530	sub peval($$) {
		531	local $SELF = shift;
		532	my $cb = shift;
		533
		534	if (wantarray) {
		535	my @res = eval { &$cb };
		536	_self_die if $@;
		537	@res
		538	} else {
		539	my $res = eval { &$cb };
		540	_self_die if $@;
		541	$res
		542	}
		543	}
		544
443	=item $closure = psub { BLOCK }	545	=item $closure = psub { BLOCK }
444		546
445	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	547	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
446	closure is executed, sets up the environment in the same way as in C<rcv>	548	closure is executed, sets up the environment in the same way as in C<rcv>
447	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	549	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		550
		551	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		552	BLOCK }, @_ } >>.
448		553
449	This is useful when you register callbacks from C<rcv> callbacks:	554	This is useful when you register callbacks from C<rcv> callbacks:
450		555
451	rcv delayed_reply => sub {	556	rcv delayed_reply => sub {
452	my ($delay, @reply) = @_;	557	my ($delay, @reply) = @_;
…		…
525	delivered again.	630	delivered again.
526		631
527	Inter-host-connection timeouts and monitoring depend on the transport	632	Inter-host-connection timeouts and monitoring depend on the transport
528	used. The only transport currently implemented is TCP, and AnyEvent::MP	633	used. The only transport currently implemented is TCP, and AnyEvent::MP
529	relies on TCP to detect node-downs (this can take 10-15 minutes on a	634	relies on TCP to detect node-downs (this can take 10-15 minutes on a
530	non-idle connection, and usually around two hours for idle conenctions).	635	non-idle connection, and usually around two hours for idle connections).
531		636
532	This means that monitoring is good for program errors and cleaning up	637	This means that monitoring is good for program errors and cleaning up
533	stuff eventually, but they are no replacement for a timeout when you need	638	stuff eventually, but they are no replacement for a timeout when you need
534	to ensure some maximum latency.	639	to ensure some maximum latency.
535		640
…		…
567	}	672	}
568		673
569	$node->monitor ($port, $cb);	674	$node->monitor ($port, $cb);
570		675
571	defined wantarray	676	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	677	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
573	}	678	}
574		679
575	=item $guard = mon_guard $port, $ref, $ref...	680	=item $guard = mon_guard $port, $ref, $ref...
576		681
577	Monitors the given C<$port> and keeps the passed references. When the port	682	Monitors the given C<$port> and keeps the passed references. When the port
…		…
600		705
601	=item kil $port[, @reason]	706	=item kil $port[, @reason]
602		707
603	Kill the specified port with the given C<@reason>.	708	Kill the specified port with the given C<@reason>.
604		709
605	If no C<@reason> is specified, then the port is killed "normally" (ports	710	If no C<@reason> is specified, then the port is killed "normally" -
606	monitoring other ports will not necessarily die because a port dies	711	monitor callback will be invoked, but the kil will not cause linked ports
607	"normally").	712	(C<mon $mport, $lport> form) to get killed.
608		713
609	Otherwise, linked ports get killed with the same reason (second form of	714	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
610	C<mon>, see above).	715	form) get killed with the same reason.
611		716
612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	717	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
613	will be reported as reason C<< die => $@ >>.	718	will be reported as reason C<< die => $@ >>.
614		719
615	Transport/communication errors are reported as C<< transport_error =>	720	Transport/communication errors are reported as C<< transport_error =>
…		…
681	}	786	}
682		787
683	sub spawn(@) {	788	sub spawn(@) {
684	my ($nodeid, undef) = split /#/, shift, 2;	789	my ($nodeid, undef) = split /#/, shift, 2;
685		790
686	my $id = "$RUNIQ." . $ID++;	791	my $id = $RUNIQ . ++$ID;
687		792
688	$_[0] =~ /::/	793	$_[0] =~ /::/
689	or Carp::croak "spawn init function must be a fully-qualified name, caught";	794	or Carp::croak "spawn init function must be a fully-qualified name, caught";
690		795
691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	796	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
692		797
693	"$nodeid#$id"	798	"$nodeid#$id"
694	}	799	}
		800
695		801
696	=item after $timeout, @msg	802	=item after $timeout, @msg
697		803
698	=item after $timeout, $callback	804	=item after $timeout, $callback
699		805
…		…
729		835
730	If an optional time-out (in seconds) is given and it is not C<undef>,	836	If an optional time-out (in seconds) is given and it is not C<undef>,
731	then the callback will be called without any arguments after the time-out	837	then the callback will be called without any arguments after the time-out
732	elapsed and the port is C<kil>ed.	838	elapsed and the port is C<kil>ed.
733		839
734	If no time-out is given, then the local port will monitor the remote port	840	If no time-out is given (or it is C<undef>), then the local port will
735	instead, so it eventually gets cleaned-up.	841	monitor the remote port instead, so it eventually gets cleaned-up.
736		842
737	Currently this function returns the temporary port, but this "feature"	843	Currently this function returns the temporary port, but this "feature"
738	might go in future versions unless you can make a convincing case that	844	might go in future versions unless you can make a convincing case that
739	this is indeed useful for something.	845	this is indeed useful for something.
740		846
…		…
776	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	882	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
777	== aemp node, Erlang process == aemp port), so many of the documents and	883	== aemp node, Erlang process == aemp port), so many of the documents and
778	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	884	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
779	sample:	885	sample:
780		886
781	http://www.Erlang.se/doc/programming_rules.shtml	887	http://www.erlang.se/doc/programming_rules.shtml
782	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	888	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
783	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	889	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
784	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	890	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
785		891
786	Despite the similarities, there are also some important differences:	892	Despite the similarities, there are also some important differences:
787		893
788	=over 4	894	=over 4
789		895
790	=item * Node IDs are arbitrary strings in AEMP.	896	=item * Node IDs are arbitrary strings in AEMP.
791		897
792	Erlang relies on special naming and DNS to work everywhere in the same	898	Erlang relies on special naming and DNS to work everywhere in the same
793	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	899	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
794	configuration or DNS), but will otherwise discover other odes itself.	900	configuration or DNS), and possibly the addresses of some seed nodes, but
		901	will otherwise discover other nodes (and their IDs) itself.
795		902
796	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	903	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
797	uses "local ports are like remote ports".	904	uses "local ports are like remote ports".
798		905
799	The failure modes for local ports are quite different (runtime errors	906	The failure modes for local ports are quite different (runtime errors
…		…
808	ports being the special case/exception, where transport errors cannot	915	ports being the special case/exception, where transport errors cannot
809	occur.	916	occur.
810		917
811	=item * Erlang uses processes and a mailbox, AEMP does not queue.	918	=item * Erlang uses processes and a mailbox, AEMP does not queue.
812		919
813	Erlang uses processes that selectively receive messages, and therefore	920	Erlang uses processes that selectively receive messages out of order, and
814	needs a queue. AEMP is event based, queuing messages would serve no	921	therefore needs a queue. AEMP is event based, queuing messages would serve
815	useful purpose. For the same reason the pattern-matching abilities of	922	no useful purpose. For the same reason the pattern-matching abilities
816	AnyEvent::MP are more limited, as there is little need to be able to	923	of AnyEvent::MP are more limited, as there is little need to be able to
817	filter messages without dequeuing them.	924	filter messages without dequeuing them.
818		925
819	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	926	This is not a philosophical difference, but simply stems from AnyEvent::MP
		927	being event-based, while Erlang is process-based.
		928
		929	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		930	top of AEMP and Coro threads.
820		931
821	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	932	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
822		933
823	Sending messages in Erlang is synchronous and blocks the process (and	934	Sending messages in Erlang is synchronous and blocks the process until
		935	a conenction has been established and the message sent (and so does not
824	so does not need a queue that can overflow). AEMP sends are immediate,	936	need a queue that can overflow). AEMP sends return immediately, connection
825	connection establishment is handled in the background.	937	establishment is handled in the background.
826		938
827	=item * Erlang suffers from silent message loss, AEMP does not.	939	=item * Erlang suffers from silent message loss, AEMP does not.
828		940
829	Erlang makes few guarantees on messages delivery - messages can get lost	941	Erlang implements few guarantees on messages delivery - messages can get
830	without any of the processes realising it (i.e. you send messages a, b,	942	lost without any of the processes realising it (i.e. you send messages a,
831	and c, and the other side only receives messages a and c).	943	b, and c, and the other side only receives messages a and c).
832		944
833	AEMP guarantees correct ordering, and the guarantee that after one message	945	AEMP guarantees (modulo hardware errors) correct ordering, and the
834	is lost, all following ones sent to the same port are lost as well, until	946	guarantee that after one message is lost, all following ones sent to the
835	monitoring raises an error, so there are no silent "holes" in the message	947	same port are lost as well, until monitoring raises an error, so there are
836	sequence.	948	no silent "holes" in the message sequence.
		949
		950	If you want your software to be very reliable, you have to cope with
		951	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		952	simply tries to work better in common error cases, such as when a network
		953	link goes down.
837		954
838	=item * Erlang can send messages to the wrong port, AEMP does not.	955	=item * Erlang can send messages to the wrong port, AEMP does not.
839		956
840	In Erlang it is quite likely that a node that restarts reuses a process ID	957	In Erlang it is quite likely that a node that restarts reuses an Erlang
841	known to other nodes for a completely different process, causing messages	958	process ID known to other nodes for a completely different process,
842	destined for that process to end up in an unrelated process.	959	causing messages destined for that process to end up in an unrelated
		960	process.
843		961
844	AEMP never reuses port IDs, so old messages or old port IDs floating	962	AEMP does not reuse port IDs, so old messages or old port IDs floating
845	around in the network will not be sent to an unrelated port.	963	around in the network will not be sent to an unrelated port.
846		964
847	=item * Erlang uses unprotected connections, AEMP uses secure	965	=item * Erlang uses unprotected connections, AEMP uses secure
848	authentication and can use TLS.	966	authentication and can use TLS.
849		967
…		…
852		970
853	=item * The AEMP protocol is optimised for both text-based and binary	971	=item * The AEMP protocol is optimised for both text-based and binary
854	communications.	972	communications.
855		973
856	The AEMP protocol, unlike the Erlang protocol, supports both programming	974	The AEMP protocol, unlike the Erlang protocol, supports both programming
857	language independent text-only protocols (good for debugging) and binary,	975	language independent text-only protocols (good for debugging), and binary,
858	language-specific serialisers (e.g. Storable). By default, unless TLS is	976	language-specific serialisers (e.g. Storable). By default, unless TLS is
859	used, the protocol is actually completely text-based.	977	used, the protocol is actually completely text-based.
860		978
861	It has also been carefully designed to be implementable in other languages	979	It has also been carefully designed to be implementable in other languages
862	with a minimum of work while gracefully degrading functionality to make the	980	with a minimum of work while gracefully degrading functionality to make the
863	protocol simple.	981	protocol simple.
864		982
865	=item * AEMP has more flexible monitoring options than Erlang.	983	=item * AEMP has more flexible monitoring options than Erlang.
866		984
867	In Erlang, you can chose to receive I<all> exit signals as messages	985	In Erlang, you can chose to receive I<all> exit signals as messages or
868	or I<none>, there is no in-between, so monitoring single processes is	986	I<none>, there is no in-between, so monitoring single Erlang processes is
869	difficult to implement. Monitoring in AEMP is more flexible than in	987	difficult to implement.
870	Erlang, as one can choose between automatic kill, exit message or callback	988
871	on a per-process basis.	989	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		990	between automatic kill, exit message or callback on a per-port basis.
872		991
873	=item * Erlang tries to hide remote/local connections, AEMP does not.	992	=item * Erlang tries to hide remote/local connections, AEMP does not.
874		993
875	Monitoring in Erlang is not an indicator of process death/crashes, in the	994	Monitoring in Erlang is not an indicator of process death/crashes, in the
876	same way as linking is (except linking is unreliable in Erlang).	995	same way as linking is (except linking is unreliable in Erlang).
…		…
898	overhead, as well as having to keep a proxy object everywhere.	1017	overhead, as well as having to keep a proxy object everywhere.
899		1018
900	Strings can easily be printed, easily serialised etc. and need no special	1019	Strings can easily be printed, easily serialised etc. and need no special
901	procedures to be "valid".	1020	procedures to be "valid".
902		1021
903	And as a result, a miniport consists of a single closure stored in a	1022	And as a result, a port with just a default receiver consists of a single
904	global hash - it can't become much cheaper.	1023	code reference stored in a global hash - it can't become much cheaper.
905		1024
906	=item Why favour JSON, why not a real serialising format such as Storable?	1025	=item Why favour JSON, why not a real serialising format such as Storable?
907		1026
908	In fact, any AnyEvent::MP node will happily accept Storable as framing	1027	In fact, any AnyEvent::MP node will happily accept Storable as framing
909	format, but currently there is no way to make a node use Storable by	1028	format, but currently there is no way to make a node use Storable by
…		…
925		1044
926	L<AnyEvent::MP::Intro> - a gentle introduction.	1045	L<AnyEvent::MP::Intro> - a gentle introduction.
927		1046
928	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1047	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
929		1048
930	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1049	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
931	your applications.	1050	your applications.
		1051
		1052	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
932		1053
933	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1054	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
934	all nodes.	1055	all nodes.
935		1056
936	L<AnyEvent>.	1057	L<AnyEvent>.

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Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC vs.
Revision 1.123 by root, Thu Mar 1 19:37:59 2012 UTC