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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.82 by root, Mon Sep 7 18:42:09 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-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
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		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.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		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
102	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
103		150
104	When a node starts, it knows nothing about the network. To teach the node	151	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	152	TCP port) of nodes that should be used as seed nodes.
106	network. This node is called a seed.
107		153
108	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=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		155
114	Apart from being sued for seeding, seednodes are not special in any way -	156	An AEMP network needs a discovery service - nodes need to know how to
115	every public node can be a seednode.	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).
116		170
117	=back	171	=back
118		172
119	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
120		174
…		…
122		176
123	=cut	177	=cut
124		178
125	package AnyEvent::MP;	179	package AnyEvent::MP;
126		180
		181	use AnyEvent::MP::Config ();
127	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
128		184
129	use common::sense;	185	use common::sense;
130		186
131	use Carp ();	187	use Carp ();
132		188
133	use AE ();	189	use AE ();
134		190
135	use base "Exporter";	191	use base "Exporter";
136		192
137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	193	our $VERSION = $AnyEvent::MP::Config::VERSION;
138		194
139	our @EXPORT = qw(	195	our @EXPORT = qw(
140	NODE $NODE *SELF node_of after	196	NODE $NODE *SELF node_of after
141	configure	197	configure
142	snd rcv mon mon_guard kil reg psub spawn	198	snd rcv mon mon_guard kil psub peval spawn cal
143	port	199	port
144	);	200	);
145		201
146	our $SELF;	202	our $SELF;
147		203
…		…
170	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
171	some other nodes in the network to discover other nodes.	227	some other nodes in the network to discover other nodes.
172		228
173	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
174	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
175		250
176	=over 4	251	=over 4
177		252
178	=item step 1, gathering configuration from profiles	253	=item step 1, gathering configuration from profiles
179		254
…		…
193	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
194	and the values specified directly via C<configure> have lowest priority,	269	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	270	and can only be used to specify defaults.
196		271
197	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
198	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
199	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.
200		278
201	=item step 2, bind listener sockets	279	=item step 2, bind listener sockets
202		280
203	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
204	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
…		…
210	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
211	local IP address it finds.	289	local IP address it finds.
212		290
213	=item step 3, connect to seed nodes	291	=item step 3, connect to seed nodes
214		292
215	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
216	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
217	connectivity with at least one node at any point in time.	295	connectivity with at least one node at any point in time.
218		296
219	=back	297	=back
220		298
221	Example: become a distributed node using the locla node name as profile.	299	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.	300	This should be the most common form of invocation for "daemon"-type nodes.
223		301
224	configure	302	configure
225		303
226	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
227	clients.	305	clients.
228		306
229	configure nodeid => "anon/";	307	configure nodeid => "anon/";
230		308
231	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
232	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,
233	customary for aemp).	311	customary for aemp).
234		312
235	# use the aemp commandline utility	313	# use the aemp commandline utility
236	# aemp profile seed nodeid anon/ binds '*:4040'	314	# aemp profile seed binds '*:4040'
237		315
238	# then use it	316	# then use it
239	configure profile => "seed";	317	configure profile => "seed";
240		318
241	# or simply use aemp from the shell again:	319	# or simply use aemp from the shell again:
…		…
311	sub _kilme {	389	sub _kilme {
312	die "received message on port without callback";	390	die "received message on port without callback";
313	}	391	}
314		392
315	sub port(;&) {	393	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	394	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	395	my $port = "$NODE#$id";
318		396
319	rcv $port, shift \|\| \&_kilme;	397	rcv $port, shift \|\| \&_kilme;
320		398
321	$port	399	$port
…		…
360	msg1 => sub { ... },	438	msg1 => sub { ... },
361	...	439	...
362	;	440	;
363		441
364	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
365	(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.
366		444
367	rcv $port, $otherport => sub {	445	rcv $port, $otherport => sub {
368	my @reply = @_;	446	my @reply = @_;
369		447
370	rcv $SELF, $otherport;	448	rcv $SELF, $otherport;
…		…
383	if (ref $_[0]) {	461	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	462	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	463	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$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";
387		465
388	$self->[2] = shift;	466	$self->[0] = shift;
389	} else {	467	} else {
390	my $cb = shift;	468	my $cb = shift;
391	$PORT{$portid} = sub {	469	$PORT{$portid} = sub {
392	local $SELF = $port;	470	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	471	eval { &$cb }; _self_die if $@;
394	};	472	};
395	}	473	}
396	} elsif (defined $_[0]) {	474	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	475	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	476	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		477
400	$PORT{$portid} = sub {	478	$PORT{$portid} = sub {
401	local $SELF = $port;	479	local $SELF = $port;
402		480
403	if (my $cb = $self->[1]{$_[0]}) {	481	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	503	}
426		504
427	$port	505	$port
428	}	506	}
429		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
430	=item $closure = psub { BLOCK }	545	=item $closure = psub { BLOCK }
431		546
432	Remembers C<$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
433	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>
434	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 $SELF, sub {
		552	BLOCK }, @_ } >>.
435		553
436	This is useful when you register callbacks from C<rcv> callbacks:	554	This is useful when you register callbacks from C<rcv> callbacks:
437		555
438	rcv delayed_reply => sub {	556	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	557	my ($delay, @reply) = @_;
…		…
512	delivered again.	630	delivered again.
513		631
514	Inter-host-connection timeouts and monitoring depend on the transport	632	Inter-host-connection timeouts and monitoring depend on the transport
515	used. The only transport currently implemented is TCP, and AnyEvent::MP	633	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	634	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).	635	non-idle connection, and usually around two hours for idle connections).
518		636
519	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
520	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
521	to ensure some maximum latency.	639	to ensure some maximum latency.
522		640
…		…
554	}	672	}
555		673
556	$node->monitor ($port, $cb);	674	$node->monitor ($port, $cb);
557		675
558	defined wantarray	676	defined wantarray
559	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	677	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
560	}	678	}
561		679
562	=item $guard = mon_guard $port, $ref, $ref...	680	=item $guard = mon_guard $port, $ref, $ref...
563		681
564	Monitors the given C<$port> and keeps the passed references. When the port	682	Monitors the given C<$port> and keeps the passed references. When the port
…		…
587		705
588	=item kil $port[, @reason]	706	=item kil $port[, @reason]
589		707
590	Kill the specified port with the given C<@reason>.	708	Kill the specified port with the given C<@reason>.
591		709
592	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" -
593	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
594	"normally").	712	(C<mon $mport, $lport> form) to get killed.
595		713
596	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>
597	C<mon>, see above).	715	form) get killed with the same reason.
598		716
599	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
600	will be reported as reason C<< die => $@ >>.	718	will be reported as reason C<< die => $@ >>.
601		719
602	Transport/communication errors are reported as C<< transport_error =>	720	Transport/communication errors are reported as C<< transport_error =>
…		…
668	}	786	}
669		787
670	sub spawn(@) {	788	sub spawn(@) {
671	my ($nodeid, undef) = split /#/, shift, 2;	789	my ($nodeid, undef) = split /#/, shift, 2;
672		790
673	my $id = "$RUNIQ." . $ID++;	791	my $id = $RUNIQ . ++$ID;
674		792
675	$_[0] =~ /::/	793	$_[0] =~ /::/
676	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";
677		795
678	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	796	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679		797
680	"$nodeid#$id"	798	"$nodeid#$id"
681	}	799	}
		800
682		801
683	=item after $timeout, @msg	802	=item after $timeout, @msg
684		803
685	=item after $timeout, $callback	804	=item after $timeout, $callback
686		805
…		…
702	? $action[0]()	821	? $action[0]()
703	: snd @action;	822	: snd @action;
704	};	823	};
705	}	824	}
706		825
		826	=item cal $port, @msg, $callback[, $timeout]
		827
		828	A simple form of RPC - sends a message to the given C<$port> with the
		829	given contents (C<@msg>), but adds a reply port to the message.
		830
		831	The reply port is created temporarily just for the purpose of receiving
		832	the reply, and will be C<kil>ed when no longer needed.
		833
		834	A reply message sent to the port is passed to the C<$callback> as-is.
		835
		836	If an optional time-out (in seconds) is given and it is not C<undef>,
		837	then the callback will be called without any arguments after the time-out
		838	elapsed and the port is C<kil>ed.
		839
		840	If no time-out is given (or it is C<undef>), then the local port will
		841	monitor the remote port instead, so it eventually gets cleaned-up.
		842
		843	Currently this function returns the temporary port, but this "feature"
		844	might go in future versions unless you can make a convincing case that
		845	this is indeed useful for something.
		846
		847	=cut
		848
		849	sub cal(@) {
		850	my $timeout = ref $_[-1] ? undef : pop;
		851	my $cb = pop;
		852
		853	my $port = port {
		854	undef $timeout;
		855	kil $SELF;
		856	&$cb;
		857	};
		858
		859	if (defined $timeout) {
		860	$timeout = AE::timer $timeout, 0, sub {
		861	undef $timeout;
		862	kil $port;
		863	$cb->();
		864	};
		865	} else {
		866	mon $_[0], sub {
		867	kil $port;
		868	$cb->();
		869	};
		870	}
		871
		872	push @_, $port;
		873	&snd;
		874
		875	$port
		876	}
		877
707	=back	878	=back
708		879
709	=head1 AnyEvent::MP vs. Distributed Erlang	880	=head1 AnyEvent::MP vs. Distributed Erlang
710		881
711	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
712	== 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
713	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
714	sample:	885	sample:
715		886
716	http://www.Erlang.se/doc/programming_rules.shtml	887	http://www.erlang.se/doc/programming_rules.shtml
717	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
718	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
719	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
720		891
721	Despite the similarities, there are also some important differences:	892	Despite the similarities, there are also some important differences:
722		893
723	=over 4	894	=over 4
724		895
725	=item * Node IDs are arbitrary strings in AEMP.	896	=item * Node IDs are arbitrary strings in AEMP.
726		897
727	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
728	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
729	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.
730		902
731	=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
732	uses "local ports are like remote ports".	904	uses "local ports are like remote ports".
733		905
734	The failure modes for local ports are quite different (runtime errors	906	The failure modes for local ports are quite different (runtime errors
…		…
743	ports being the special case/exception, where transport errors cannot	915	ports being the special case/exception, where transport errors cannot
744	occur.	916	occur.
745		917
746	=item * Erlang uses processes and a mailbox, AEMP does not queue.	918	=item * Erlang uses processes and a mailbox, AEMP does not queue.
747		919
748	Erlang uses processes that selectively receive messages, and therefore	920	Erlang uses processes that selectively receive messages out of order, and
749	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
750	useful purpose. For the same reason the pattern-matching abilities of	922	no useful purpose. For the same reason the pattern-matching abilities
751	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
752	filter messages without dequeuing them.	924	filter messages without dequeuing them.
753		925
754	(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.
755		931
756	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	932	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
757		933
758	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
759	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
760	connection establishment is handled in the background.	937	establishment is handled in the background.
761		938
762	=item * Erlang suffers from silent message loss, AEMP does not.	939	=item * Erlang suffers from silent message loss, AEMP does not.
763		940
764	Erlang makes few guarantees on messages delivery - messages can get lost	941	Erlang implements few guarantees on messages delivery - messages can get
765	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,
766	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).
767		944
768	AEMP guarantees correct ordering, and the guarantee that after one message	945	AEMP guarantees (modulo hardware errors) correct ordering, and the
769	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
770	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
771	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.
772		954
773	=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.
774		956
775	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
776	known to other nodes for a completely different process, causing messages	958	process ID known to other nodes for a completely different process,
777	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.
778		961
779	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
780	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.
781		964
782	=item * Erlang uses unprotected connections, AEMP uses secure	965	=item * Erlang uses unprotected connections, AEMP uses secure
783	authentication and can use TLS.	966	authentication and can use TLS.
784		967
…		…
787		970
788	=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
789	communications.	972	communications.
790		973
791	The AEMP protocol, unlike the Erlang protocol, supports both programming	974	The AEMP protocol, unlike the Erlang protocol, supports both programming
792	language independent text-only protocols (good for debugging) and binary,	975	language independent text-only protocols (good for debugging), and binary,
793	language-specific serialisers (e.g. Storable). By default, unless TLS is	976	language-specific serialisers (e.g. Storable). By default, unless TLS is
794	used, the protocol is actually completely text-based.	977	used, the protocol is actually completely text-based.
795		978
796	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
797	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
798	protocol simple.	981	protocol simple.
799		982
800	=item * AEMP has more flexible monitoring options than Erlang.	983	=item * AEMP has more flexible monitoring options than Erlang.
801		984
802	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
803	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
804	difficult to implement. Monitoring in AEMP is more flexible than in	987	difficult to implement.
805	Erlang, as one can choose between automatic kill, exit message or callback	988
806	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.
807		991
808	=item * Erlang tries to hide remote/local connections, AEMP does not.	992	=item * Erlang tries to hide remote/local connections, AEMP does not.
809		993
810	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
811	same way as linking is (except linking is unreliable in Erlang).	995	same way as linking is (except linking is unreliable in Erlang).
…		…
833	overhead, as well as having to keep a proxy object everywhere.	1017	overhead, as well as having to keep a proxy object everywhere.
834		1018
835	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
836	procedures to be "valid".	1020	procedures to be "valid".
837		1021
838	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
839	global hash - it can't become much cheaper.	1023	code reference stored in a global hash - it can't become much cheaper.
840		1024
841	=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?
842		1026
843	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
844	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
…		…
860		1044
861	L<AnyEvent::MP::Intro> - a gentle introduction.	1045	L<AnyEvent::MP::Intro> - a gentle introduction.
862		1046
863	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1047	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
864		1048
865	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1049	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
866	your applications.	1050	your applications.
		1051
		1052	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
867		1053
868	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1054	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
869	all nodes.	1055	all nodes.
870		1056
871	L<AnyEvent>.	1057	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC vs. Revision 1.123 by root, Thu Mar 1 19:37:59 2012 UTC

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Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC vs.
Revision 1.123 by root, Thu Mar 1 19:37:59 2012 UTC