[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 1.122 by root, Wed Feb 29 18:44:59 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<#>) 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-Z_][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
102	=item seed nodes	119	=item seed nodes
103		120
104	When a node starts, it knows nothing about the network. To teach the node	121	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	122	needs to connect to at least one other node that is already in the
106	network. This node is called a seed.	123	network. These other nodes are called "seed nodes".
107		124
108	Apart from the fact that other nodes know them as seed nodes and they have	125	Seed nodes themselves are not special - they are seed nodes only because
109	to have fixed listening addresses, seed nodes are perfectly normal nodes -	126	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.	127	node for other nodes, and eahc node cna use a different set of seed nodes.
111		128
112	In addition to discovering the network, seed nodes are also used to	129	In addition to discovering the network, seed nodes are also used to
113	maintain the network and to connect nodes that otherwise would have	130	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.	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.
115		134
116	Seed nodes are expected to be long-running, and at least one seed node	135	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	136	should always be available. They should also be relatively responsive - a
118	seed node that blocks for long periods will slow down everybody else.	137	seed node that blocks for long periods will slow down everybody else.
119		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
120	=item seeds - C<host:port>	148	=item seed IDs - C<host:port>
121		149
122	Seeds are transport endpoint(s) (usually a hostname/IP address and a	150	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.	151	TCP port) of nodes that should be used as seed nodes.
124		152
125	The nodes listening on those endpoints are expected to be long-running,	153	=item global nodes
126	and at least one of those should always be available. When nodes run out	154
127	of connections (e.g. due to a network error), they try to re-establish	155	An AEMP network needs a discovery service - nodes need to know how to
128	connections to some seednodes again to join the network.	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).
129		169
130	=back	170	=back
131		171
132	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
133		173
…		…
135		175
136	=cut	176	=cut
137		177
138	package AnyEvent::MP;	178	package AnyEvent::MP;
139		179
		180	use AnyEvent::MP::Config ();
140	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
141		183
142	use common::sense;	184	use common::sense;
143		185
144	use Carp ();	186	use Carp ();
145		187
146	use AE ();	188	use AE ();
147		189
148	use base "Exporter";	190	use base "Exporter";
149		191
150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
151		193
152	our @EXPORT = qw(	194	our @EXPORT = qw(
153	NODE $NODE *SELF node_of after	195	NODE $NODE *SELF node_of after
154	configure	196	configure
155	snd rcv mon mon_guard kil reg psub spawn cal	197	snd rcv mon mon_guard kil psub peval spawn cal
156	port	198	port
157	);	199	);
158		200
159	our $SELF;	201	our $SELF;
160		202
…		…
183	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
184	some other nodes in the network to discover other nodes.	226	some other nodes in the network to discover other nodes.
185		227
186	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
187	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
188		249
189	=over 4	250	=over 4
190		251
191	=item step 1, gathering configuration from profiles	252	=item step 1, gathering configuration from profiles
192		253
…		…
206	That means that the values specified in the profile have highest priority	267	That means that the values specified in the profile have highest priority
207	and the values specified directly via C<configure> have lowest priority,	268	and the values specified directly via C<configure> have lowest priority,
208	and can only be used to specify defaults.	269	and can only be used to specify defaults.
209		270
210	If the profile specifies a node ID, then this will become the node ID of	271	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	272	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.	273	a slash (C</>) attached.
		274
		275	If the node ID (or profile name) ends with a slash (C</>), then a random
		276	string is appended to make it unique.
213		277
214	=item step 2, bind listener sockets	278	=item step 2, bind listener sockets
215		279
216	The next step is to look up the binds in the profile, followed by binding	280	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	281	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	287	used, meaning the node will bind on a dynamically-assigned port on every
224	local IP address it finds.	288	local IP address it finds.
225		289
226	=item step 3, connect to seed nodes	290	=item step 3, connect to seed nodes
227		291
228	As the last step, the seeds list from the profile is passed to the	292	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	293	L<AnyEvent::MP::Global> module, which will then use it to keep
230	connectivity with at least one node at any point in time.	294	connectivity with at least one node at any point in time.
231		295
232	=back	296	=back
233		297
…		…
239	Example: become an anonymous node. This form is often used for commandline	303	Example: become an anonymous node. This form is often used for commandline
240	clients.	304	clients.
241		305
242	configure nodeid => "anon/";	306	configure nodeid => "anon/";
243		307
244	Example: configure a node using a profile called seed, which si suitable	308	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,	309	for a seed node as it binds on all local addresses on a fixed port (4040,
246	customary for aemp).	310	customary for aemp).
247		311
248	# use the aemp commandline utility	312	# use the aemp commandline utility
249	# aemp profile seed nodeid anon/ binds '*:4040'	313	# aemp profile seed binds '*:4040'
250		314
251	# then use it	315	# then use it
252	configure profile => "seed";	316	configure profile => "seed";
253		317
254	# or simply use aemp from the shell again:	318	# or simply use aemp from the shell again:
…		…
324	sub _kilme {	388	sub _kilme {
325	die "received message on port without callback";	389	die "received message on port without callback";
326	}	390	}
327		391
328	sub port(;&) {	392	sub port(;&) {
329	my $id = "$UNIQ." . $ID++;	393	my $id = "$UNIQ." . ++$ID;
330	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
331		395
332	rcv $port, shift \|\| \&_kilme;	396	rcv $port, shift \|\| \&_kilme;
333		397
334	$port	398	$port
…		…
373	msg1 => sub { ... },	437	msg1 => sub { ... },
374	...	438	...
375	;	439	;
376		440
377	Example: temporarily register a rcv callback for a tag matching some port	441	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.	442	(e.g. for an rpc reply) and unregister it after a message was received.
379		443
380	rcv $port, $otherport => sub {	444	rcv $port, $otherport => sub {
381	my @reply = @_;	445	my @reply = @_;
382		446
383	rcv $SELF, $otherport;	447	rcv $SELF, $otherport;
…		…
396	if (ref $_[0]) {	460	if (ref $_[0]) {
397	if (my $self = $PORT_DATA{$portid}) {	461	if (my $self = $PORT_DATA{$portid}) {
398	"AnyEvent::MP::Port" eq ref $self	462	"AnyEvent::MP::Port" eq ref $self
399	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	463	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
400		464
401	$self->[2] = shift;	465	$self->[0] = shift;
402	} else {	466	} else {
403	my $cb = shift;	467	my $cb = shift;
404	$PORT{$portid} = sub {	468	$PORT{$portid} = sub {
405	local $SELF = $port;	469	local $SELF = $port;
406	eval { &$cb }; _self_die if $@;	470	eval { &$cb }; _self_die if $@;
407	};	471	};
408	}	472	}
409	} elsif (defined $_[0]) {	473	} elsif (defined $_[0]) {
410	my $self = $PORT_DATA{$portid} \|\|= do {	474	my $self = $PORT_DATA{$portid} \|\|= do {
411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	475	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
412		476
413	$PORT{$portid} = sub {	477	$PORT{$portid} = sub {
414	local $SELF = $port;	478	local $SELF = $port;
415		479
416	if (my $cb = $self->[1]{$_[0]}) {	480	if (my $cb = $self->[1]{$_[0]}) {
…		…
438	}	502	}
439		503
440	$port	504	$port
441	}	505	}
442		506
		507	=item peval $port, $coderef[, @args]
		508
		509	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		510	when the code throews an exception the C<$port> will be killed.
		511
		512	Any remaining args will be passed to the callback. Any return values will
		513	be returned to the caller.
		514
		515	This is useful when you temporarily want to execute code in the context of
		516	a port.
		517
		518	Example: create a port and run some initialisation code in it's context.
		519
		520	my $port = port { ... };
		521
		522	peval $port, sub {
		523	init
		524	or die "unable to init";
		525	};
		526
		527	=cut
		528
		529	sub peval($$) {
		530	local $SELF = shift;
		531	my $cb = shift;
		532
		533	if (wantarray) {
		534	my @res = eval { &$cb };
		535	_self_die if $@;
		536	@res
		537	} else {
		538	my $res = eval { &$cb };
		539	_self_die if $@;
		540	$res
		541	}
		542	}
		543
443	=item $closure = psub { BLOCK }	544	=item $closure = psub { BLOCK }
444		545
445	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	546	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>	547	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.	548	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		549
		550	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		551	BLOCK }, @_ } >>.
448		552
449	This is useful when you register callbacks from C<rcv> callbacks:	553	This is useful when you register callbacks from C<rcv> callbacks:
450		554
451	rcv delayed_reply => sub {	555	rcv delayed_reply => sub {
452	my ($delay, @reply) = @_;	556	my ($delay, @reply) = @_;
…		…
525	delivered again.	629	delivered again.
526		630
527	Inter-host-connection timeouts and monitoring depend on the transport	631	Inter-host-connection timeouts and monitoring depend on the transport
528	used. The only transport currently implemented is TCP, and AnyEvent::MP	632	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	633	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).	634	non-idle connection, and usually around two hours for idle connections).
531		635
532	This means that monitoring is good for program errors and cleaning up	636	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	637	stuff eventually, but they are no replacement for a timeout when you need
534	to ensure some maximum latency.	638	to ensure some maximum latency.
535		639
…		…
567	}	671	}
568		672
569	$node->monitor ($port, $cb);	673	$node->monitor ($port, $cb);
570		674
571	defined wantarray	675	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	676	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
573	}	677	}
574		678
575	=item $guard = mon_guard $port, $ref, $ref...	679	=item $guard = mon_guard $port, $ref, $ref...
576		680
577	Monitors the given C<$port> and keeps the passed references. When the port	681	Monitors the given C<$port> and keeps the passed references. When the port
…		…
600		704
601	=item kil $port[, @reason]	705	=item kil $port[, @reason]
602		706
603	Kill the specified port with the given C<@reason>.	707	Kill the specified port with the given C<@reason>.
604		708
605	If no C<@reason> is specified, then the port is killed "normally" (ports	709	If no C<@reason> is specified, then the port is killed "normally" -
606	monitoring other ports will not necessarily die because a port dies	710	monitor callback will be invoked, but the kil will not cause linked ports
607	"normally").	711	(C<mon $mport, $lport> form) to get killed.
608		712
609	Otherwise, linked ports get killed with the same reason (second form of	713	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
610	C<mon>, see above).	714	form) get killed with the same reason.
611		715
612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	716	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
613	will be reported as reason C<< die => $@ >>.	717	will be reported as reason C<< die => $@ >>.
614		718
615	Transport/communication errors are reported as C<< transport_error =>	719	Transport/communication errors are reported as C<< transport_error =>
…		…
681	}	785	}
682		786
683	sub spawn(@) {	787	sub spawn(@) {
684	my ($nodeid, undef) = split /#/, shift, 2;	788	my ($nodeid, undef) = split /#/, shift, 2;
685		789
686	my $id = "$RUNIQ." . $ID++;	790	my $id = "$RUNIQ." . ++$ID;
687		791
688	$_[0] =~ /::/	792	$_[0] =~ /::/
689	or Carp::croak "spawn init function must be a fully-qualified name, caught";	793	or Carp::croak "spawn init function must be a fully-qualified name, caught";
690		794
691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	795	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
692		796
693	"$nodeid#$id"	797	"$nodeid#$id"
694	}	798	}
		799
695		800
696	=item after $timeout, @msg	801	=item after $timeout, @msg
697		802
698	=item after $timeout, $callback	803	=item after $timeout, $callback
699		804
…		…
729		834
730	If an optional time-out (in seconds) is given and it is not C<undef>,	835	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	836	then the callback will be called without any arguments after the time-out
732	elapsed and the port is C<kil>ed.	837	elapsed and the port is C<kil>ed.
733		838
734	If no time-out is given, then the local port will monitor the remote port	839	If no time-out is given (or it is C<undef>), then the local port will
735	instead, so it eventually gets cleaned-up.	840	monitor the remote port instead, so it eventually gets cleaned-up.
736		841
737	Currently this function returns the temporary port, but this "feature"	842	Currently this function returns the temporary port, but this "feature"
738	might go in future versions unless you can make a convincing case that	843	might go in future versions unless you can make a convincing case that
739	this is indeed useful for something.	844	this is indeed useful for something.
740		845
…		…
776	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	881	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	882	== 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	883	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
779	sample:	884	sample:
780		885
781	http://www.Erlang.se/doc/programming_rules.shtml	886	http://www.erlang.se/doc/programming_rules.shtml
782	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	887	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	888	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	889	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
785		890
786	Despite the similarities, there are also some important differences:	891	Despite the similarities, there are also some important differences:
787		892
788	=over 4	893	=over 4
789		894
790	=item * Node IDs are arbitrary strings in AEMP.	895	=item * Node IDs are arbitrary strings in AEMP.
791		896
792	Erlang relies on special naming and DNS to work everywhere in the same	897	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	898	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.	899	configuration or DNS), and possibly the addresses of some seed nodes, but
		900	will otherwise discover other nodes (and their IDs) itself.
795		901
796	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	902	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
797	uses "local ports are like remote ports".	903	uses "local ports are like remote ports".
798		904
799	The failure modes for local ports are quite different (runtime errors	905	The failure modes for local ports are quite different (runtime errors
…		…
808	ports being the special case/exception, where transport errors cannot	914	ports being the special case/exception, where transport errors cannot
809	occur.	915	occur.
810		916
811	=item * Erlang uses processes and a mailbox, AEMP does not queue.	917	=item * Erlang uses processes and a mailbox, AEMP does not queue.
812		918
813	Erlang uses processes that selectively receive messages, and therefore	919	Erlang uses processes that selectively receive messages out of order, and
814	needs a queue. AEMP is event based, queuing messages would serve no	920	therefore needs a queue. AEMP is event based, queuing messages would serve
815	useful purpose. For the same reason the pattern-matching abilities of	921	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	922	of AnyEvent::MP are more limited, as there is little need to be able to
817	filter messages without dequeuing them.	923	filter messages without dequeuing them.
818		924
819	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	925	This is not a philosophical difference, but simply stems from AnyEvent::MP
		926	being event-based, while Erlang is process-based.
		927
		928	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		929	top of AEMP and Coro threads.
820		930
821	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	931	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
822		932
823	Sending messages in Erlang is synchronous and blocks the process (and	933	Sending messages in Erlang is synchronous and blocks the process until
		934	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,	935	need a queue that can overflow). AEMP sends return immediately, connection
825	connection establishment is handled in the background.	936	establishment is handled in the background.
826		937
827	=item * Erlang suffers from silent message loss, AEMP does not.	938	=item * Erlang suffers from silent message loss, AEMP does not.
828		939
829	Erlang makes few guarantees on messages delivery - messages can get lost	940	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,	941	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).	942	b, and c, and the other side only receives messages a and c).
832		943
833	AEMP guarantees correct ordering, and the guarantee that after one message	944	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	945	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	946	same port are lost as well, until monitoring raises an error, so there are
836	sequence.	947	no silent "holes" in the message sequence.
		948
		949	If you want your software to be very reliable, you have to cope with
		950	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		951	simply tries to work better in common error cases, such as when a network
		952	link goes down.
837		953
838	=item * Erlang can send messages to the wrong port, AEMP does not.	954	=item * Erlang can send messages to the wrong port, AEMP does not.
839		955
840	In Erlang it is quite likely that a node that restarts reuses a process ID	956	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	957	process ID known to other nodes for a completely different process,
842	destined for that process to end up in an unrelated process.	958	causing messages destined for that process to end up in an unrelated
		959	process.
843		960
844	AEMP never reuses port IDs, so old messages or old port IDs floating	961	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.	962	around in the network will not be sent to an unrelated port.
846		963
847	=item * Erlang uses unprotected connections, AEMP uses secure	964	=item * Erlang uses unprotected connections, AEMP uses secure
848	authentication and can use TLS.	965	authentication and can use TLS.
849		966
…		…
852		969
853	=item * The AEMP protocol is optimised for both text-based and binary	970	=item * The AEMP protocol is optimised for both text-based and binary
854	communications.	971	communications.
855		972
856	The AEMP protocol, unlike the Erlang protocol, supports both programming	973	The AEMP protocol, unlike the Erlang protocol, supports both programming
857	language independent text-only protocols (good for debugging) and binary,	974	language independent text-only protocols (good for debugging), and binary,
858	language-specific serialisers (e.g. Storable). By default, unless TLS is	975	language-specific serialisers (e.g. Storable). By default, unless TLS is
859	used, the protocol is actually completely text-based.	976	used, the protocol is actually completely text-based.
860		977
861	It has also been carefully designed to be implementable in other languages	978	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	979	with a minimum of work while gracefully degrading functionality to make the
863	protocol simple.	980	protocol simple.
864		981
865	=item * AEMP has more flexible monitoring options than Erlang.	982	=item * AEMP has more flexible monitoring options than Erlang.
866		983
867	In Erlang, you can chose to receive I<all> exit signals as messages	984	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	985	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	986	difficult to implement.
870	Erlang, as one can choose between automatic kill, exit message or callback	987
871	on a per-process basis.	988	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		989	between automatic kill, exit message or callback on a per-port basis.
872		990
873	=item * Erlang tries to hide remote/local connections, AEMP does not.	991	=item * Erlang tries to hide remote/local connections, AEMP does not.
874		992
875	Monitoring in Erlang is not an indicator of process death/crashes, in the	993	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).	994	same way as linking is (except linking is unreliable in Erlang).
…		…
898	overhead, as well as having to keep a proxy object everywhere.	1016	overhead, as well as having to keep a proxy object everywhere.
899		1017
900	Strings can easily be printed, easily serialised etc. and need no special	1018	Strings can easily be printed, easily serialised etc. and need no special
901	procedures to be "valid".	1019	procedures to be "valid".
902		1020
903	And as a result, a miniport consists of a single closure stored in a	1021	And as a result, a port with just a default receiver consists of a single
904	global hash - it can't become much cheaper.	1022	code reference stored in a global hash - it can't become much cheaper.
905		1023
906	=item Why favour JSON, why not a real serialising format such as Storable?	1024	=item Why favour JSON, why not a real serialising format such as Storable?
907		1025
908	In fact, any AnyEvent::MP node will happily accept Storable as framing	1026	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	1027	format, but currently there is no way to make a node use Storable by
…		…
925		1043
926	L<AnyEvent::MP::Intro> - a gentle introduction.	1044	L<AnyEvent::MP::Intro> - a gentle introduction.
927		1045
928	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1046	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
929		1047
930	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1048	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
931	your applications.	1049	your applications.
		1050
		1051	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
932		1052
933	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1053	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
934	all nodes.	1054	all nodes.
935		1055
936	L<AnyEvent>.	1056	L<AnyEvent>.

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Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC vs.
Revision 1.122 by root, Wed Feb 29 18:44:59 2012 UTC