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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.93 by root, Tue Sep 22 14:14:29 2009 UTC vs.
Revision 1.125 by root, Sat Mar 3 13:07:19 2012 UTC

…		…
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 $localport, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
37	mon $localport, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
38	mon $localport, $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.
…		…
66		78
67	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
68	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
69	anything was listening for them or not.	81	anything was listening for them or not.
70		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
71	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
72		86
73	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<#>)
74	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).
75		90
76	=item node	91	=item node
77		92
78	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,
79	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
80	ports.	95	ports.
81		96
82	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
83	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
84	currently.	99	currently, but all nodes can talk to public nodes.
85		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
87		104
88	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
89	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
90	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
91	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
92		109
93	=item binds - C<ip:port>	110	=item binds - C<ip:port>
94		111
95	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
96	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
97	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
98	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.
99		119
100	=item seed nodes	120	=item seed nodes
101		121
102	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
103	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
104	network. This node is called a seed.	124	network. These other nodes are called "seed nodes".
105		125
106	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
107	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
108	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.
109		129
110	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
111	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
112	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.
113		135
114	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
115	should always be available. They should also be relatively responsive - a	137	should always be available. They should also be relatively responsive - a
116	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.
117		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
118	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
119		150
120	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
121	TCP port) of nodes thta should be used as seed nodes.	152	TCP port) of nodes that should be used as seed nodes.
122		153
123	The nodes listening on those endpoints are expected to be long-running,	154	=item global nodes
124	and at least one of those should always be available. When nodes run out	155
125	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
126	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).
127		170
128	=back	171	=back
129		172
130	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
131		174
…		…
133		176
134	=cut	177	=cut
135		178
136	package AnyEvent::MP;	179	package AnyEvent::MP;
137		180
		181	use AnyEvent::MP::Config ();
138	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
139		184
140	use common::sense;	185	use common::sense;
141		186
142	use Carp ();	187	use Carp ();
143		188
144	use AE ();	189	use AE ();
		190	use Guard ();
145		191
146	use base "Exporter";	192	use base "Exporter";
147		193
148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
149		195
150	our @EXPORT = qw(	196	our @EXPORT = qw(
151	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
152	configure	198	configure
153	snd rcv mon mon_guard kil psub spawn cal	199	snd rcv mon mon_guard kil psub peval spawn cal
154	port	200	port
		201	db_set db_del db_reg
155	);	202	);
156		203
157	our $SELF;	204	our $SELF;
158		205
159	sub _self_die() {	206	sub _self_die() {
…		…
182	some other nodes in the network to discover other nodes.	229	some other nodes in the network to discover other nodes.
183		230
184	This function configures a node - it must be called exactly once (or	231	This function configures a node - it must be called exactly once (or
185	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
186		233
		234	The key/value pairs are basically the same ones as documented for the
		235	F<aemp> command line utility (sans the set/del prefix), with two additions:
		236
		237	=over 4
		238
		239	=item norc => $boolean (default false)
		240
		241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		242	be consulted - all configuraiton options must be specified in the
		243	C<configure> call.
		244
		245	=item force => $boolean (default false)
		246
		247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
		250
		251	=back
		252
187	=over 4	253	=over 4
188		254
189	=item step 1, gathering configuration from profiles	255	=item step 1, gathering configuration from profiles
190		256
191	The function first looks up a profile in the aemp configuration (see the	257	The function first looks up a profile in the aemp configuration (see the
…		…
204	That means that the values specified in the profile have highest priority	270	That means that the values specified in the profile have highest priority
205	and the values specified directly via C<configure> have lowest priority,	271	and the values specified directly via C<configure> have lowest priority,
206	and can only be used to specify defaults.	272	and can only be used to specify defaults.
207		273
208	If the profile specifies a node ID, then this will become the node ID of	274	If the profile specifies a node ID, then this will become the node ID of
209	this process. If not, then the profile name will be used as node ID. The	275	this process. If not, then the profile name will be used as node ID, with
210	special node ID of C<anon/> will be replaced by a random node ID.	276	a slash (C</>) attached.
		277
		278	If the node ID (or profile name) ends with a slash (C</>), then a random
		279	string is appended to make it unique.
211		280
212	=item step 2, bind listener sockets	281	=item step 2, bind listener sockets
213		282
214	The next step is to look up the binds in the profile, followed by binding	283	The next step is to look up the binds in the profile, followed by binding
215	aemp protocol listeners on all binds specified (it is possible and valid	284	aemp protocol listeners on all binds specified (it is possible and valid
…		…
221	used, meaning the node will bind on a dynamically-assigned port on every	290	used, meaning the node will bind on a dynamically-assigned port on every
222	local IP address it finds.	291	local IP address it finds.
223		292
224	=item step 3, connect to seed nodes	293	=item step 3, connect to seed nodes
225		294
226	As the last step, the seeds list from the profile is passed to the	295	As the last step, the seed ID list from the profile is passed to the
227	L<AnyEvent::MP::Global> module, which will then use it to keep	296	L<AnyEvent::MP::Global> module, which will then use it to keep
228	connectivity with at least one node at any point in time.	297	connectivity with at least one node at any point in time.
229		298
230	=back	299	=back
231		300
…		…
237	Example: become an anonymous node. This form is often used for commandline	306	Example: become an anonymous node. This form is often used for commandline
238	clients.	307	clients.
239		308
240	configure nodeid => "anon/";	309	configure nodeid => "anon/";
241		310
242	Example: configure a node using a profile called seed, which si suitable	311	Example: configure a node using a profile called seed, which is suitable
243	for a seed node as it binds on all local addresses on a fixed port (4040,	312	for a seed node as it binds on all local addresses on a fixed port (4040,
244	customary for aemp).	313	customary for aemp).
245		314
246	# use the aemp commandline utility	315	# use the aemp commandline utility
247	# aemp profile seed nodeid anon/ binds '*:4040'	316	# aemp profile seed binds '*:4040'
248		317
249	# then use it	318	# then use it
250	configure profile => "seed";	319	configure profile => "seed";
251		320
252	# or simply use aemp from the shell again:	321	# or simply use aemp from the shell again:
…		…
322	sub _kilme {	391	sub _kilme {
323	die "received message on port without callback";	392	die "received message on port without callback";
324	}	393	}
325		394
326	sub port(;&) {	395	sub port(;&) {
327	my $id = "$UNIQ." . $ID++;	396	my $id = $UNIQ . ++$ID;
328	my $port = "$NODE#$id";	397	my $port = "$NODE#$id";
329		398
330	rcv $port, shift \|\| \&_kilme;	399	rcv $port, shift \|\| \&_kilme;
331		400
332	$port	401	$port
…		…
371	msg1 => sub { ... },	440	msg1 => sub { ... },
372	...	441	...
373	;	442	;
374		443
375	Example: temporarily register a rcv callback for a tag matching some port	444	Example: temporarily register a rcv callback for a tag matching some port
376	(e.g. for a rpc reply) and unregister it after a message was received.	445	(e.g. for an rpc reply) and unregister it after a message was received.
377		446
378	rcv $port, $otherport => sub {	447	rcv $port, $otherport => sub {
379	my @reply = @_;	448	my @reply = @_;
380		449
381	rcv $SELF, $otherport;	450	rcv $SELF, $otherport;
…		…
394	if (ref $_[0]) {	463	if (ref $_[0]) {
395	if (my $self = $PORT_DATA{$portid}) {	464	if (my $self = $PORT_DATA{$portid}) {
396	"AnyEvent::MP::Port" eq ref $self	465	"AnyEvent::MP::Port" eq ref $self
397	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	466	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
398		467
399	$self->[2] = shift;	468	$self->[0] = shift;
400	} else {	469	} else {
401	my $cb = shift;	470	my $cb = shift;
402	$PORT{$portid} = sub {	471	$PORT{$portid} = sub {
403	local $SELF = $port;	472	local $SELF = $port;
404	eval { &$cb }; _self_die if $@;	473	eval { &$cb }; _self_die if $@;
405	};	474	};
406	}	475	}
407	} elsif (defined $_[0]) {	476	} elsif (defined $_[0]) {
408	my $self = $PORT_DATA{$portid} \|\|= do {	477	my $self = $PORT_DATA{$portid} \|\|= do {
409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	478	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
410		479
411	$PORT{$portid} = sub {	480	$PORT{$portid} = sub {
412	local $SELF = $port;	481	local $SELF = $port;
413		482
414	if (my $cb = $self->[1]{$_[0]}) {	483	if (my $cb = $self->[1]{$_[0]}) {
…		…
436	}	505	}
437		506
438	$port	507	$port
439	}	508	}
440		509
		510	=item peval $port, $coderef[, @args]
		511
		512	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		513	when the code throews an exception the C<$port> will be killed.
		514
		515	Any remaining args will be passed to the callback. Any return values will
		516	be returned to the caller.
		517
		518	This is useful when you temporarily want to execute code in the context of
		519	a port.
		520
		521	Example: create a port and run some initialisation code in it's context.
		522
		523	my $port = port { ... };
		524
		525	peval $port, sub {
		526	init
		527	or die "unable to init";
		528	};
		529
		530	=cut
		531
		532	sub peval($$) {
		533	local $SELF = shift;
		534	my $cb = shift;
		535
		536	if (wantarray) {
		537	my @res = eval { &$cb };
		538	_self_die if $@;
		539	@res
		540	} else {
		541	my $res = eval { &$cb };
		542	_self_die if $@;
		543	$res
		544	}
		545	}
		546
441	=item $closure = psub { BLOCK }	547	=item $closure = psub { BLOCK }
442		548
443	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	549	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
444	closure is executed, sets up the environment in the same way as in C<rcv>	550	closure is executed, sets up the environment in the same way as in C<rcv>
445	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	551	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		552
		553	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		554	BLOCK }, @_ } >>.
446		555
447	This is useful when you register callbacks from C<rcv> callbacks:	556	This is useful when you register callbacks from C<rcv> callbacks:
448		557
449	rcv delayed_reply => sub {	558	rcv delayed_reply => sub {
450	my ($delay, @reply) = @_;	559	my ($delay, @reply) = @_;
…		…
523	delivered again.	632	delivered again.
524		633
525	Inter-host-connection timeouts and monitoring depend on the transport	634	Inter-host-connection timeouts and monitoring depend on the transport
526	used. The only transport currently implemented is TCP, and AnyEvent::MP	635	used. The only transport currently implemented is TCP, and AnyEvent::MP
527	relies on TCP to detect node-downs (this can take 10-15 minutes on a	636	relies on TCP to detect node-downs (this can take 10-15 minutes on a
528	non-idle connection, and usually around two hours for idle conenctions).	637	non-idle connection, and usually around two hours for idle connections).
529		638
530	This means that monitoring is good for program errors and cleaning up	639	This means that monitoring is good for program errors and cleaning up
531	stuff eventually, but they are no replacement for a timeout when you need	640	stuff eventually, but they are no replacement for a timeout when you need
532	to ensure some maximum latency.	641	to ensure some maximum latency.
533		642
…		…
565	}	674	}
566		675
567	$node->monitor ($port, $cb);	676	$node->monitor ($port, $cb);
568		677
569	defined wantarray	678	defined wantarray
570	and $cb += 0
571	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	679	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
572	}	680	}
573		681
574	=item $guard = mon_guard $port, $ref, $ref...	682	=item $guard = mon_guard $port, $ref, $ref...
575		683
576	Monitors the given C<$port> and keeps the passed references. When the port	684	Monitors the given C<$port> and keeps the passed references. When the port
…		…
599		707
600	=item kil $port[, @reason]	708	=item kil $port[, @reason]
601		709
602	Kill the specified port with the given C<@reason>.	710	Kill the specified port with the given C<@reason>.
603		711
604	If no C<@reason> is specified, then the port is killed "normally" (ports	712	If no C<@reason> is specified, then the port is killed "normally" -
605	monitoring other ports will not necessarily die because a port dies	713	monitor callback will be invoked, but the kil will not cause linked ports
606	"normally").	714	(C<mon $mport, $lport> form) to get killed.
607		715
608	Otherwise, linked ports get killed with the same reason (second form of	716	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
609	C<mon>, see above).	717	form) get killed with the same reason.
610		718
611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	719	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
612	will be reported as reason C<< die => $@ >>.	720	will be reported as reason C<< die => $@ >>.
613		721
614	Transport/communication errors are reported as C<< transport_error =>	722	Transport/communication errors are reported as C<< transport_error =>
…		…
680	}	788	}
681		789
682	sub spawn(@) {	790	sub spawn(@) {
683	my ($nodeid, undef) = split /#/, shift, 2;	791	my ($nodeid, undef) = split /#/, shift, 2;
684		792
685	my $id = "$RUNIQ." . $ID++;	793	my $id = $RUNIQ . ++$ID;
686		794
687	$_[0] =~ /::/	795	$_[0] =~ /::/
688	or Carp::croak "spawn init function must be a fully-qualified name, caught";	796	or Carp::croak "spawn init function must be a fully-qualified name, caught";
689		797
690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	798	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
691		799
692	"$nodeid#$id"	800	"$nodeid#$id"
693	}	801	}
		802
694		803
695	=item after $timeout, @msg	804	=item after $timeout, @msg
696		805
697	=item after $timeout, $callback	806	=item after $timeout, $callback
698		807
…		…
728		837
729	If an optional time-out (in seconds) is given and it is not C<undef>,	838	If an optional time-out (in seconds) is given and it is not C<undef>,
730	then the callback will be called without any arguments after the time-out	839	then the callback will be called without any arguments after the time-out
731	elapsed and the port is C<kil>ed.	840	elapsed and the port is C<kil>ed.
732		841
733	If no time-out is given, then the local port will monitor the remote port	842	If no time-out is given (or it is C<undef>), then the local port will
734	instead, so it eventually gets cleaned-up.	843	monitor the remote port instead, so it eventually gets cleaned-up.
735		844
736	Currently this function returns the temporary port, but this "feature"	845	Currently this function returns the temporary port, but this "feature"
737	might go in future versions unless you can make a convincing case that	846	might go in future versions unless you can make a convincing case that
738	this is indeed useful for something.	847	this is indeed useful for something.
739		848
…		…
768	$port	877	$port
769	}	878	}
770		879
771	=back	880	=back
772		881
		882	=head1 DISTRIBUTED DATABASE
		883
		884	AnyEvent::MP comes with a simple distributed database. The database will
		885	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		886	the global nodes for their needs.
		887
		888	The database consists of a two-level hash - a hash contains a hash which
		889	contains values.
		890
		891	The top level hash key is called "family", and the second-level hash key
		892	is simply called "key".
		893
		894	The family must be alphanumeric, i.e. start with a letter and consist
		895	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		896	pretty much like Perl module names.
		897
		898	As the family namespace is global, it is recommended to prefix family names
		899	with the name of the application or module using it.
		900
		901	The keys must be strings, with no other limitations.
		902
		903	The values should preferably be strings, but other perl scalars should
		904	work as well (such as undef, arrays and hashes).
		905
		906	Every database entry is owned by one node - adding the same family/key
		907	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		908	but the result might be nondeterministic, i.e. the key might have
		909	different values on different nodes.
		910
		911	=item db_set $family => $key => $value
		912
		913	Sets (or replaces) a key to the database.
		914
		915	=item db_del $family => $key
		916
		917	Deletes a key from the database.
		918
		919	=item $guard = db_reg $family => $key [=> $value]
		920
		921	Sets the key on the database and returns a guard. When the guard is
		922	destroyed, the key is deleted from the database. If C<$value> is missing,
		923	then C<undef> is used.
		924
		925	=cut
		926
		927	=back
		928
773	=head1 AnyEvent::MP vs. Distributed Erlang	929	=head1 AnyEvent::MP vs. Distributed Erlang
774		930
775	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	931	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
776	== aemp node, Erlang process == aemp port), so many of the documents and	932	== aemp node, Erlang process == aemp port), so many of the documents and
777	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	933	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
778	sample:	934	sample:
779		935
780	http://www.Erlang.se/doc/programming_rules.shtml	936	http://www.erlang.se/doc/programming_rules.shtml
781	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	937	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
782	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	938	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
783	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	939	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
784		940
785	Despite the similarities, there are also some important differences:	941	Despite the similarities, there are also some important differences:
786		942
787	=over 4	943	=over 4
788		944
789	=item * Node IDs are arbitrary strings in AEMP.	945	=item * Node IDs are arbitrary strings in AEMP.
790		946
791	Erlang relies on special naming and DNS to work everywhere in the same	947	Erlang relies on special naming and DNS to work everywhere in the same
792	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	948	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
793	configuration or DNS), but will otherwise discover other odes itself.	949	configuration or DNS), and possibly the addresses of some seed nodes, but
		950	will otherwise discover other nodes (and their IDs) itself.
794		951
795	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	952	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
796	uses "local ports are like remote ports".	953	uses "local ports are like remote ports".
797		954
798	The failure modes for local ports are quite different (runtime errors	955	The failure modes for local ports are quite different (runtime errors
…		…
807	ports being the special case/exception, where transport errors cannot	964	ports being the special case/exception, where transport errors cannot
808	occur.	965	occur.
809		966
810	=item * Erlang uses processes and a mailbox, AEMP does not queue.	967	=item * Erlang uses processes and a mailbox, AEMP does not queue.
811		968
812	Erlang uses processes that selectively receive messages, and therefore	969	Erlang uses processes that selectively receive messages out of order, and
813	needs a queue. AEMP is event based, queuing messages would serve no	970	therefore needs a queue. AEMP is event based, queuing messages would serve
814	useful purpose. For the same reason the pattern-matching abilities of	971	no useful purpose. For the same reason the pattern-matching abilities
815	AnyEvent::MP are more limited, as there is little need to be able to	972	of AnyEvent::MP are more limited, as there is little need to be able to
816	filter messages without dequeuing them.	973	filter messages without dequeuing them.
817		974
818	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	975	This is not a philosophical difference, but simply stems from AnyEvent::MP
		976	being event-based, while Erlang is process-based.
		977
		978	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		979	top of AEMP and Coro threads.
819		980
820	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	981	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
821		982
822	Sending messages in Erlang is synchronous and blocks the process (and	983	Sending messages in Erlang is synchronous and blocks the process until
		984	a conenction has been established and the message sent (and so does not
823	so does not need a queue that can overflow). AEMP sends are immediate,	985	need a queue that can overflow). AEMP sends return immediately, connection
824	connection establishment is handled in the background.	986	establishment is handled in the background.
825		987
826	=item * Erlang suffers from silent message loss, AEMP does not.	988	=item * Erlang suffers from silent message loss, AEMP does not.
827		989
828	Erlang makes few guarantees on messages delivery - messages can get lost	990	Erlang implements few guarantees on messages delivery - messages can get
829	without any of the processes realising it (i.e. you send messages a, b,	991	lost without any of the processes realising it (i.e. you send messages a,
830	and c, and the other side only receives messages a and c).	992	b, and c, and the other side only receives messages a and c).
831		993
832	AEMP guarantees correct ordering, and the guarantee that after one message	994	AEMP guarantees (modulo hardware errors) correct ordering, and the
833	is lost, all following ones sent to the same port are lost as well, until	995	guarantee that after one message is lost, all following ones sent to the
834	monitoring raises an error, so there are no silent "holes" in the message	996	same port are lost as well, until monitoring raises an error, so there are
835	sequence.	997	no silent "holes" in the message sequence.
		998
		999	If you want your software to be very reliable, you have to cope with
		1000	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1001	simply tries to work better in common error cases, such as when a network
		1002	link goes down.
836		1003
837	=item * Erlang can send messages to the wrong port, AEMP does not.	1004	=item * Erlang can send messages to the wrong port, AEMP does not.
838		1005
839	In Erlang it is quite likely that a node that restarts reuses a process ID	1006	In Erlang it is quite likely that a node that restarts reuses an Erlang
840	known to other nodes for a completely different process, causing messages	1007	process ID known to other nodes for a completely different process,
841	destined for that process to end up in an unrelated process.	1008	causing messages destined for that process to end up in an unrelated
		1009	process.
842		1010
843	AEMP never reuses port IDs, so old messages or old port IDs floating	1011	AEMP does not reuse port IDs, so old messages or old port IDs floating
844	around in the network will not be sent to an unrelated port.	1012	around in the network will not be sent to an unrelated port.
845		1013
846	=item * Erlang uses unprotected connections, AEMP uses secure	1014	=item * Erlang uses unprotected connections, AEMP uses secure
847	authentication and can use TLS.	1015	authentication and can use TLS.
848		1016
…		…
851		1019
852	=item * The AEMP protocol is optimised for both text-based and binary	1020	=item * The AEMP protocol is optimised for both text-based and binary
853	communications.	1021	communications.
854		1022
855	The AEMP protocol, unlike the Erlang protocol, supports both programming	1023	The AEMP protocol, unlike the Erlang protocol, supports both programming
856	language independent text-only protocols (good for debugging) and binary,	1024	language independent text-only protocols (good for debugging), and binary,
857	language-specific serialisers (e.g. Storable). By default, unless TLS is	1025	language-specific serialisers (e.g. Storable). By default, unless TLS is
858	used, the protocol is actually completely text-based.	1026	used, the protocol is actually completely text-based.
859		1027
860	It has also been carefully designed to be implementable in other languages	1028	It has also been carefully designed to be implementable in other languages
861	with a minimum of work while gracefully degrading functionality to make the	1029	with a minimum of work while gracefully degrading functionality to make the
862	protocol simple.	1030	protocol simple.
863		1031
864	=item * AEMP has more flexible monitoring options than Erlang.	1032	=item * AEMP has more flexible monitoring options than Erlang.
865		1033
866	In Erlang, you can chose to receive I<all> exit signals as messages	1034	In Erlang, you can chose to receive I<all> exit signals as messages or
867	or I<none>, there is no in-between, so monitoring single processes is	1035	I<none>, there is no in-between, so monitoring single Erlang processes is
868	difficult to implement. Monitoring in AEMP is more flexible than in	1036	difficult to implement.
869	Erlang, as one can choose between automatic kill, exit message or callback	1037
870	on a per-process basis.	1038	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1039	between automatic kill, exit message or callback on a per-port basis.
871		1040
872	=item * Erlang tries to hide remote/local connections, AEMP does not.	1041	=item * Erlang tries to hide remote/local connections, AEMP does not.
873		1042
874	Monitoring in Erlang is not an indicator of process death/crashes, in the	1043	Monitoring in Erlang is not an indicator of process death/crashes, in the
875	same way as linking is (except linking is unreliable in Erlang).	1044	same way as linking is (except linking is unreliable in Erlang).
…		…
897	overhead, as well as having to keep a proxy object everywhere.	1066	overhead, as well as having to keep a proxy object everywhere.
898		1067
899	Strings can easily be printed, easily serialised etc. and need no special	1068	Strings can easily be printed, easily serialised etc. and need no special
900	procedures to be "valid".	1069	procedures to be "valid".
901		1070
902	And as a result, a miniport consists of a single closure stored in a	1071	And as a result, a port with just a default receiver consists of a single
903	global hash - it can't become much cheaper.	1072	code reference stored in a global hash - it can't become much cheaper.
904		1073
905	=item Why favour JSON, why not a real serialising format such as Storable?	1074	=item Why favour JSON, why not a real serialising format such as Storable?
906		1075
907	In fact, any AnyEvent::MP node will happily accept Storable as framing	1076	In fact, any AnyEvent::MP node will happily accept Storable as framing
908	format, but currently there is no way to make a node use Storable by	1077	format, but currently there is no way to make a node use Storable by
…		…
924		1093
925	L<AnyEvent::MP::Intro> - a gentle introduction.	1094	L<AnyEvent::MP::Intro> - a gentle introduction.
926		1095
927	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1096	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
928		1097
929	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1098	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
930	your applications.	1099	your applications.
		1100
		1101	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
931		1102
932	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1103	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
933	all nodes.	1104	all nodes.
934		1105
935	L<AnyEvent>.	1106	L<AnyEvent>.

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Revision 1.93 by root, Tue Sep 22 14:14:29 2009 UTC vs.
Revision 1.125 by root, Sat Mar 3 13:07:19 2012 UTC