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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.84 by root, Tue Sep 8 01:42:14 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 the 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.	136	should always be available. They should also be relatively responsive - a
		137	seed node that blocks for long periods will slow down everybody else.
118		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
119	=item seeds - C<host:port>	148	=item seed IDs - C<host:port>
120		149
121	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
122	TCP port) of nodes thta should be used as seed nodes.	151	TCP port) of nodes that should be used as seed nodes.
123		152
124	The nodes listening on those endpoints are expected to be long-running,	153	=item global nodes
125	and at least one of those should always be available. When nodes run out	154
126	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
127	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).
128		169
129	=back	170	=back
130		171
131	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
132		173
…		…
134		175
135	=cut	176	=cut
136		177
137	package AnyEvent::MP;	178	package AnyEvent::MP;
138		179
		180	use AnyEvent::MP::Config ();
139	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
140		183
141	use common::sense;	184	use common::sense;
142		185
143	use Carp ();	186	use Carp ();
144		187
145	use AE ();	188	use AE ();
146		189
147	use base "Exporter";	190	use base "Exporter";
148		191
149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
150		193
151	our @EXPORT = qw(	194	our @EXPORT = qw(
152	NODE $NODE *SELF node_of after	195	NODE $NODE *SELF node_of after
153	configure	196	configure
154	snd rcv mon mon_guard kil reg psub spawn	197	snd rcv mon mon_guard kil psub peval spawn cal
155	port	198	port
156	);	199	);
157		200
158	our $SELF;	201	our $SELF;
159		202
…		…
182	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
183	some other nodes in the network to discover other nodes.	226	some other nodes in the network to discover other nodes.
184		227
185	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
186	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
187		249
188	=over 4	250	=over 4
189		251
190	=item step 1, gathering configuration from profiles	252	=item step 1, gathering configuration from profiles
191		253
…		…
205	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
206	and the values specified directly via C<configure> have lowest priority,	268	and the values specified directly via C<configure> have lowest priority,
207	and can only be used to specify defaults.	269	and can only be used to specify defaults.
208		270
209	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
210	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
211	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.
212		277
213	=item step 2, bind listener sockets	278	=item step 2, bind listener sockets
214		279
215	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
216	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
…		…
222	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
223	local IP address it finds.	288	local IP address it finds.
224		289
225	=item step 3, connect to seed nodes	290	=item step 3, connect to seed nodes
226		291
227	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
228	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
229	connectivity with at least one node at any point in time.	294	connectivity with at least one node at any point in time.
230		295
231	=back	296	=back
232		297
233	Example: become a distributed node using the locla node name as profile.	298	Example: become a distributed node using the local node name as profile.
234	This should be the most common form of invocation for "daemon"-type nodes.	299	This should be the most common form of invocation for "daemon"-type nodes.
235		300
236	configure	301	configure
237		302
238	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
239	clients.	304	clients.
240		305
241	configure nodeid => "anon/";	306	configure nodeid => "anon/";
242		307
243	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
244	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,
245	customary for aemp).	310	customary for aemp).
246		311
247	# use the aemp commandline utility	312	# use the aemp commandline utility
248	# aemp profile seed nodeid anon/ binds '*:4040'	313	# aemp profile seed binds '*:4040'
249		314
250	# then use it	315	# then use it
251	configure profile => "seed";	316	configure profile => "seed";
252		317
253	# or simply use aemp from the shell again:	318	# or simply use aemp from the shell again:
…		…
323	sub _kilme {	388	sub _kilme {
324	die "received message on port without callback";	389	die "received message on port without callback";
325	}	390	}
326		391
327	sub port(;&) {	392	sub port(;&) {
328	my $id = "$UNIQ." . $ID++;	393	my $id = "$UNIQ." . ++$ID;
329	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
330		395
331	rcv $port, shift \|\| \&_kilme;	396	rcv $port, shift \|\| \&_kilme;
332		397
333	$port	398	$port
…		…
372	msg1 => sub { ... },	437	msg1 => sub { ... },
373	...	438	...
374	;	439	;
375		440
376	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
377	(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.
378		443
379	rcv $port, $otherport => sub {	444	rcv $port, $otherport => sub {
380	my @reply = @_;	445	my @reply = @_;
381		446
382	rcv $SELF, $otherport;	447	rcv $SELF, $otherport;
…		…
395	if (ref $_[0]) {	460	if (ref $_[0]) {
396	if (my $self = $PORT_DATA{$portid}) {	461	if (my $self = $PORT_DATA{$portid}) {
397	"AnyEvent::MP::Port" eq ref $self	462	"AnyEvent::MP::Port" eq ref $self
398	or Carp::croak "$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";
399		464
400	$self->[2] = shift;	465	$self->[0] = shift;
401	} else {	466	} else {
402	my $cb = shift;	467	my $cb = shift;
403	$PORT{$portid} = sub {	468	$PORT{$portid} = sub {
404	local $SELF = $port;	469	local $SELF = $port;
405	eval { &$cb }; _self_die if $@;	470	eval { &$cb }; _self_die if $@;
406	};	471	};
407	}	472	}
408	} elsif (defined $_[0]) {	473	} elsif (defined $_[0]) {
409	my $self = $PORT_DATA{$portid} \|\|= do {	474	my $self = $PORT_DATA{$portid} \|\|= do {
410	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	475	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
411		476
412	$PORT{$portid} = sub {	477	$PORT{$portid} = sub {
413	local $SELF = $port;	478	local $SELF = $port;
414		479
415	if (my $cb = $self->[1]{$_[0]}) {	480	if (my $cb = $self->[1]{$_[0]}) {
…		…
437	}	502	}
438		503
439	$port	504	$port
440	}	505	}
441		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
442	=item $closure = psub { BLOCK }	544	=item $closure = psub { BLOCK }
443		545
444	Remembers C<$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
445	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>
446	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 $SELF, sub {
		551	BLOCK }, @_ } >>.
447		552
448	This is useful when you register callbacks from C<rcv> callbacks:	553	This is useful when you register callbacks from C<rcv> callbacks:
449		554
450	rcv delayed_reply => sub {	555	rcv delayed_reply => sub {
451	my ($delay, @reply) = @_;	556	my ($delay, @reply) = @_;
…		…
524	delivered again.	629	delivered again.
525		630
526	Inter-host-connection timeouts and monitoring depend on the transport	631	Inter-host-connection timeouts and monitoring depend on the transport
527	used. The only transport currently implemented is TCP, and AnyEvent::MP	632	used. The only transport currently implemented is TCP, and AnyEvent::MP
528	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
529	non-idle connection, and usually around two hours for idle conenctions).	634	non-idle connection, and usually around two hours for idle connections).
530		635
531	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
532	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
533	to ensure some maximum latency.	638	to ensure some maximum latency.
534		639
…		…
566	}	671	}
567		672
568	$node->monitor ($port, $cb);	673	$node->monitor ($port, $cb);
569		674
570	defined wantarray	675	defined wantarray
571	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	676	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
572	}	677	}
573		678
574	=item $guard = mon_guard $port, $ref, $ref...	679	=item $guard = mon_guard $port, $ref, $ref...
575		680
576	Monitors the given C<$port> and keeps the passed references. When the port	681	Monitors the given C<$port> and keeps the passed references. When the port
…		…
599		704
600	=item kil $port[, @reason]	705	=item kil $port[, @reason]
601		706
602	Kill the specified port with the given C<@reason>.	707	Kill the specified port with the given C<@reason>.
603		708
604	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" -
605	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
606	"normally").	711	(C<mon $mport, $lport> form) to get killed.
607		712
608	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>
609	C<mon>, see above).	714	form) get killed with the same reason.
610		715
611	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
612	will be reported as reason C<< die => $@ >>.	717	will be reported as reason C<< die => $@ >>.
613		718
614	Transport/communication errors are reported as C<< transport_error =>	719	Transport/communication errors are reported as C<< transport_error =>
…		…
680	}	785	}
681		786
682	sub spawn(@) {	787	sub spawn(@) {
683	my ($nodeid, undef) = split /#/, shift, 2;	788	my ($nodeid, undef) = split /#/, shift, 2;
684		789
685	my $id = "$RUNIQ." . $ID++;	790	my $id = "$RUNIQ." . ++$ID;
686		791
687	$_[0] =~ /::/	792	$_[0] =~ /::/
688	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";
689		794
690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	795	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
691		796
692	"$nodeid#$id"	797	"$nodeid#$id"
693	}	798	}
		799
694		800
695	=item after $timeout, @msg	801	=item after $timeout, @msg
696		802
697	=item after $timeout, $callback	803	=item after $timeout, $callback
698		804
…		…
714	? $action[0]()	820	? $action[0]()
715	: snd @action;	821	: snd @action;
716	};	822	};
717	}	823	}
718		824
		825	=item cal $port, @msg, $callback[, $timeout]
		826
		827	A simple form of RPC - sends a message to the given C<$port> with the
		828	given contents (C<@msg>), but adds a reply port to the message.
		829
		830	The reply port is created temporarily just for the purpose of receiving
		831	the reply, and will be C<kil>ed when no longer needed.
		832
		833	A reply message sent to the port is passed to the C<$callback> as-is.
		834
		835	If an optional time-out (in seconds) is given and it is not C<undef>,
		836	then the callback will be called without any arguments after the time-out
		837	elapsed and the port is C<kil>ed.
		838
		839	If no time-out is given (or it is C<undef>), then the local port will
		840	monitor the remote port instead, so it eventually gets cleaned-up.
		841
		842	Currently this function returns the temporary port, but this "feature"
		843	might go in future versions unless you can make a convincing case that
		844	this is indeed useful for something.
		845
		846	=cut
		847
		848	sub cal(@) {
		849	my $timeout = ref $_[-1] ? undef : pop;
		850	my $cb = pop;
		851
		852	my $port = port {
		853	undef $timeout;
		854	kil $SELF;
		855	&$cb;
		856	};
		857
		858	if (defined $timeout) {
		859	$timeout = AE::timer $timeout, 0, sub {
		860	undef $timeout;
		861	kil $port;
		862	$cb->();
		863	};
		864	} else {
		865	mon $_[0], sub {
		866	kil $port;
		867	$cb->();
		868	};
		869	}
		870
		871	push @_, $port;
		872	&snd;
		873
		874	$port
		875	}
		876
719	=back	877	=back
720		878
721	=head1 AnyEvent::MP vs. Distributed Erlang	879	=head1 AnyEvent::MP vs. Distributed Erlang
722		880
723	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
724	== 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
725	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
726	sample:	884	sample:
727		885
728	http://www.Erlang.se/doc/programming_rules.shtml	886	http://www.erlang.se/doc/programming_rules.shtml
729	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
730	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
731	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
732		890
733	Despite the similarities, there are also some important differences:	891	Despite the similarities, there are also some important differences:
734		892
735	=over 4	893	=over 4
736		894
737	=item * Node IDs are arbitrary strings in AEMP.	895	=item * Node IDs are arbitrary strings in AEMP.
738		896
739	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
740	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
741	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.
742		901
743	=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
744	uses "local ports are like remote ports".	903	uses "local ports are like remote ports".
745		904
746	The failure modes for local ports are quite different (runtime errors	905	The failure modes for local ports are quite different (runtime errors
…		…
755	ports being the special case/exception, where transport errors cannot	914	ports being the special case/exception, where transport errors cannot
756	occur.	915	occur.
757		916
758	=item * Erlang uses processes and a mailbox, AEMP does not queue.	917	=item * Erlang uses processes and a mailbox, AEMP does not queue.
759		918
760	Erlang uses processes that selectively receive messages, and therefore	919	Erlang uses processes that selectively receive messages out of order, and
761	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
762	useful purpose. For the same reason the pattern-matching abilities of	921	no useful purpose. For the same reason the pattern-matching abilities
763	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
764	filter messages without dequeuing them.	923	filter messages without dequeuing them.
765		924
766	(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.
767		930
768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	931	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
769		932
770	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
771	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
772	connection establishment is handled in the background.	936	establishment is handled in the background.
773		937
774	=item * Erlang suffers from silent message loss, AEMP does not.	938	=item * Erlang suffers from silent message loss, AEMP does not.
775		939
776	Erlang makes few guarantees on messages delivery - messages can get lost	940	Erlang implements few guarantees on messages delivery - messages can get
777	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,
778	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).
779		943
780	AEMP guarantees correct ordering, and the guarantee that after one message	944	AEMP guarantees (modulo hardware errors) correct ordering, and the
781	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
782	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
783	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.
784		953
785	=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.
786		955
787	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
788	known to other nodes for a completely different process, causing messages	957	process ID known to other nodes for a completely different process,
789	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.
790		960
791	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
792	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.
793		963
794	=item * Erlang uses unprotected connections, AEMP uses secure	964	=item * Erlang uses unprotected connections, AEMP uses secure
795	authentication and can use TLS.	965	authentication and can use TLS.
796		966
…		…
799		969
800	=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
801	communications.	971	communications.
802		972
803	The AEMP protocol, unlike the Erlang protocol, supports both programming	973	The AEMP protocol, unlike the Erlang protocol, supports both programming
804	language independent text-only protocols (good for debugging) and binary,	974	language independent text-only protocols (good for debugging), and binary,
805	language-specific serialisers (e.g. Storable). By default, unless TLS is	975	language-specific serialisers (e.g. Storable). By default, unless TLS is
806	used, the protocol is actually completely text-based.	976	used, the protocol is actually completely text-based.
807		977
808	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
809	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
810	protocol simple.	980	protocol simple.
811		981
812	=item * AEMP has more flexible monitoring options than Erlang.	982	=item * AEMP has more flexible monitoring options than Erlang.
813		983
814	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
815	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
816	difficult to implement. Monitoring in AEMP is more flexible than in	986	difficult to implement.
817	Erlang, as one can choose between automatic kill, exit message or callback	987
818	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.
819		990
820	=item * Erlang tries to hide remote/local connections, AEMP does not.	991	=item * Erlang tries to hide remote/local connections, AEMP does not.
821		992
822	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
823	same way as linking is (except linking is unreliable in Erlang).	994	same way as linking is (except linking is unreliable in Erlang).
…		…
845	overhead, as well as having to keep a proxy object everywhere.	1016	overhead, as well as having to keep a proxy object everywhere.
846		1017
847	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
848	procedures to be "valid".	1019	procedures to be "valid".
849		1020
850	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
851	global hash - it can't become much cheaper.	1022	code reference stored in a global hash - it can't become much cheaper.
852		1023
853	=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?
854		1025
855	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
856	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
…		…
872		1043
873	L<AnyEvent::MP::Intro> - a gentle introduction.	1044	L<AnyEvent::MP::Intro> - a gentle introduction.
874		1045
875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1046	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
876		1047
877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1048	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
878	your applications.	1049	your applications.
		1050
		1051	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
879		1052
880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1053	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
881	all nodes.	1054	all nodes.
882		1055
883	L<AnyEvent>.	1056	L<AnyEvent>.

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC vs. Revision 1.122 by root, Wed Feb 29 18:44:59 2012 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC vs.
Revision 1.122 by root, Wed Feb 29 18:44:59 2012 UTC