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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.114 by root, Thu Apr 22 16:06:19 2010 UTC vs.
Revision 1.132 by root, Sat Mar 10 20:34:11 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 prot again	35	# destroy a port again
36	kil $port; # "normal" kill	36	kil $port; # "normal" kill
37	kil $port, my_error => "everything is broken"; # error kill	37	kil $port, my_error => "everything is broken"; # error kill
38		38
39	# monitoring	39	# monitoring
40	mon $localport, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
41	mon $localport, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
42	mon $localport, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
43		43
44	# temporarily execute code in port context	44	# temporarily execute code in port context
45	peval $port, sub { die "kill the port!" };	45	peval $port, sub { die "kill the port!" };
46		46
47	# execute callbacks in $SELF port context	47	# execute callbacks in $SELF port context
…		…
78		78
79	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
80	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
81	anything was listening for them or not.	81	anything was listening for them or not.
82		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
83	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
84		86
85	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<#>)
86	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).
87		90
88	=item node	91	=item node
89		92
90	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,
91	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
92	ports.	95	ports.
93		96
94	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
95	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
96	currently.	99	currently, but all nodes can talk to public nodes.
97		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
99		104
100	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
101	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
102	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
103	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
104		109
105	=item binds - C<ip:port>	110	=item binds - C<ip:port>
106		111
107	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
108	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
109	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
110	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.
111		119
112	=item seed nodes	120	=item seed nodes
113		121
114	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
115	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
116	network. This node is called a seed.	124	network. These other nodes are called "seed nodes".
117		125
118	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
119	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
120	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.
121		129
122	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
123	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
124	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.
125		135
126	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
127	should always be available. They should also be relatively responsive - a	137	should always be available. They should also be relatively responsive - a
128	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.
129		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
130	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
131		150
132	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
133	TCP port) of nodes that should be used as seed nodes.	152	TCP port) of nodes that should be used as seed nodes.
134		153
135	The nodes listening on those endpoints are expected to be long-running,	154	=item global nodes
136	and at least one of those should always be available. When nodes run out	155
137	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
138	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).
139		170
140	=back	171	=back
141		172
142	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
143		174
…		…
145		176
146	=cut	177	=cut
147		178
148	package AnyEvent::MP;	179	package AnyEvent::MP;
149		180
		181	use AnyEvent::MP::Config ();
150	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
151		184
152	use common::sense;	185	use common::sense;
153		186
154	use Carp ();	187	use Carp ();
155		188
156	use AE ();	189	use AE ();
		190	use Guard ();
157		191
158	use base "Exporter";	192	use base "Exporter";
159		193
160	our $VERSION = 1.28;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
161		195
162	our @EXPORT = qw(	196	our @EXPORT = qw(
163	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
164	configure	198	configure
165	snd rcv mon mon_guard kil psub peval spawn cal	199	snd rcv mon mon_guard kil psub peval spawn cal
166	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
167	);	203	);
168		204
169	our $SELF;	205	our $SELF;
170		206
171	sub _self_die() {	207	sub _self_die() {
…		…
191	Before a node can talk to other nodes on the network (i.e. enter	227	Before a node can talk to other nodes on the network (i.e. enter
192	"distributed mode") it has to configure itself - the minimum a node needs	228	"distributed mode") it has to configure itself - the minimum a node needs
193	to know is its own name, and optionally it should know the addresses of	229	to know is its own name, and optionally it should know the addresses of
194	some other nodes in the network to discover other nodes.	230	some other nodes in the network to discover other nodes.
195		231
196	The key/value pairs are basically the same ones as documented for the
197	F<aemp> command line utility (sans the set/del prefix).
198
199	This function configures a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
200	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
		234
		235	The key/value pairs are basically the same ones as documented for the
		236	F<aemp> command line utility (sans the set/del prefix), with these additions:
		237
		238	=over 4
		239
		240	=item norc => $boolean (default false)
		241
		242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		243	be consulted - all configuraiton options must be specified in the
		244	C<configure> call.
		245
		246	=item force => $boolean (default false)
		247
		248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
		251
		252	=item secure => $pass->($nodeid)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every remote execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	See F<semp setsecure> for more info.
		259
		260	=back
201		261
202	=over 4	262	=over 4
203		263
204	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
205		265
…		…
219	That means that the values specified in the profile have highest priority	279	That means that the values specified in the profile have highest priority
220	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
221	and can only be used to specify defaults.	281	and can only be used to specify defaults.
222		282
223	If the profile specifies a node ID, then this will become the node ID of	283	If the profile specifies a node ID, then this will become the node ID of
224	this process. If not, then the profile name will be used as node ID. The	284	this process. If not, then the profile name will be used as node ID, with
225	special node ID of C<anon/> will be replaced by a random node ID.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
226		292
227	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
228		294
229	The next step is to look up the binds in the profile, followed by binding	295	The next step is to look up the binds in the profile, followed by binding
230	aemp protocol listeners on all binds specified (it is possible and valid	296	aemp protocol listeners on all binds specified (it is possible and valid
…		…
236	used, meaning the node will bind on a dynamically-assigned port on every	302	used, meaning the node will bind on a dynamically-assigned port on every
237	local IP address it finds.	303	local IP address it finds.
238		304
239	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
240		306
241	As the last step, the seeds list from the profile is passed to the	307	As the last step, the seed ID list from the profile is passed to the
242	L<AnyEvent::MP::Global> module, which will then use it to keep	308	L<AnyEvent::MP::Global> module, which will then use it to keep
243	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
244		310
245	=back	311	=back
246		312
247	Example: become a distributed node using the local node name as profile.	313	Example: become a distributed node using the local node name as profile.
248	This should be the most common form of invocation for "daemon"-type nodes.	314	This should be the most common form of invocation for "daemon"-type nodes.
249		315
250	configure	316	configure
251		317
252	Example: become an anonymous node. This form is often used for commandline	318	Example: become a semi-anonymous node. This form is often used for
253	clients.	319	commandline clients.
254		320
255	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
256		322
257	Example: configure a node using a profile called seed, which si suitable	323	Example: configure a node using a profile called seed, which is suitable
258	for a seed node as it binds on all local addresses on a fixed port (4040,	324	for a seed node as it binds on all local addresses on a fixed port (4040,
259	customary for aemp).	325	customary for aemp).
260		326
261	# use the aemp commandline utility	327	# use the aemp commandline utility
262	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
263		329
264	# then use it	330	# then use it
265	configure profile => "seed";	331	configure profile => "seed";
266		332
267	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
332		398
333	=cut	399	=cut
334		400
335	sub rcv($@);	401	sub rcv($@);
336		402
337	sub _kilme {	403	my $KILME = sub {
338	die "received message on port without callback";	404	die "received message on port without callback";
339	}	405	};
340		406
341	sub port(;&) {	407	sub port(;&) {
342	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
343	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
344		410
345	rcv $port, shift \|\| \&_kilme;	411	rcv $port, shift \|\| $KILME;
346		412
347	$port	413	$port
348	}	414	}
349		415
350	=item rcv $local_port, $callback->(@msg)	416	=item rcv $local_port, $callback->(@msg)
…		…
620	}	686	}
621		687
622	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
623		689
624	defined wantarray	690	defined wantarray
625	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
626	}	692	}
627		693
628	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
629		695
630	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
…		…
734	}	800	}
735		801
736	sub spawn(@) {	802	sub spawn(@) {
737	my ($nodeid, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
738		804
739	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
740		806
741	$_[0] =~ /::/	807	$_[0] =~ /::/
742	or Carp::croak "spawn init function must be a fully-qualified name, caught";	808	or Carp::croak "spawn init function must be a fully-qualified name, caught";
743		809
744	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
745		811
746	"$nodeid#$id"	812	"$nodeid#$id"
747	}	813	}
		814
748		815
749	=item after $timeout, @msg	816	=item after $timeout, @msg
750		817
751	=item after $timeout, $callback	818	=item after $timeout, $callback
752		819
…		…
767	ref $action[0]	834	ref $action[0]
768	? $action[0]()	835	? $action[0]()
769	: snd @action;	836	: snd @action;
770	};	837	};
771	}	838	}
		839
		840	#=item $cb2 = timeout $seconds, $cb[, @args]
772		841
773	=item cal $port, @msg, $callback[, $timeout]	842	=item cal $port, @msg, $callback[, $timeout]
774		843
775	A simple form of RPC - sends a message to the given C<$port> with the	844	A simple form of RPC - sends a message to the given C<$port> with the
776	given contents (C<@msg>), but adds a reply port to the message.	845	given contents (C<@msg>), but adds a reply port to the message.
…		…
822	$port	891	$port
823	}	892	}
824		893
825	=back	894	=back
826		895
		896	=head1 DISTRIBUTED DATABASE
		897
		898	AnyEvent::MP comes with a simple distributed database. The database will
		899	be mirrored asynchronously on all global nodes. Other nodes bind to one
		900	of the global nodes for their needs. Every node has a "local database"
		901	which contains all the values that are set locally. All local databases
		902	are merged together to form the global database, which can be queried.
		903
		904	The database structure is that of a two-level hash - the database hash
		905	contains hashes which contain values, similarly to a perl hash of hashes,
		906	i.e.:
		907
		908	$DATABASE{$family}{$subkey} = $value
		909
		910	The top level hash key is called "family", and the second-level hash key
		911	is called "subkey" or simply "key".
		912
		913	The family must be alphanumeric, i.e. start with a letter and consist
		914	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		915	pretty much like Perl module names.
		916
		917	As the family namespace is global, it is recommended to prefix family names
		918	with the name of the application or module using it.
		919
		920	The subkeys must be non-empty strings, with no further restrictions.
		921
		922	The values should preferably be strings, but other perl scalars should
		923	work as well (such as C<undef>, arrays and hashes).
		924
		925	Every database entry is owned by one node - adding the same family/subkey
		926	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		927	but the result might be nondeterministic, i.e. the key might have
		928	different values on different nodes.
		929
		930	Different subkeys in the same family can be owned by different nodes
		931	without problems, and in fact, this is the common method to create worker
		932	pools. For example, a worker port for image scaling might do this:
		933
		934	db_set my_image_scalers => $port;
		935
		936	And clients looking for an image scaler will want to get the
		937	C<my_image_scalers> keys from time to time:
		938
		939	db_keys my_image_scalers => sub {
		940	@ports = @{ $_[0] };
		941	};
		942
		943	Or better yet, they want to monitor the database family, so they always
		944	have a reasonable up-to-date copy:
		945
		946	db_mon my_image_scalers => sub {
		947	@ports = keys %{ $_[0] };
		948	};
		949
		950	In general, you can set or delete single subkeys, but query and monitor
		951	whole families only.
		952
		953	If you feel the need to monitor or query a single subkey, try giving it
		954	it's own family.
		955
		956	=over
		957
		958	=item db_set $family => $subkey [=> $value]
		959
		960	Sets (or replaces) a key to the database - if C<$value> is omitted,
		961	C<undef> is used instead.
		962
		963	=item db_del $family => $subkey...
		964
		965	Deletes one or more subkeys from the database family.
		966
		967	=item $guard = db_reg $family => $subkey [=> $value]
		968
		969	Sets the key on the database and returns a guard. When the guard is
		970	destroyed, the key is deleted from the database. If C<$value> is missing,
		971	then C<undef> is used.
		972
		973	=item db_family $family => $cb->(\%familyhash)
		974
		975	Queries the named database C<$family> and call the callback with the
		976	family represented as a hash. You can keep and freely modify the hash.
		977
		978	=item db_keys $family => $cb->(\@keys)
		979
		980	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		981	them as array reference to the callback.
		982
		983	=item db_values $family => $cb->(\@values)
		984
		985	Same as C<db_family>, except it only queries the family I<values> and passes them
		986	as array reference to the callback.
		987
		988	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		989
		990	Creates a monitor on the given database family. Each time a key is set
		991	or or is deleted the callback is called with a hash containing the
		992	database family and three lists of added, changed and deleted subkeys,
		993	respectively. If no keys have changed then the array reference might be
		994	C<undef> or even missing.
		995
		996	If not called in void context, a guard object is returned that, when
		997	destroyed, stops the monitor.
		998
		999	The family hash reference and the key arrays belong to AnyEvent::MP and
		1000	B<must not be modified or stored> by the callback. When in doubt, make a
		1001	copy.
		1002
		1003	As soon as possible after the monitoring starts, the callback will be
		1004	called with the intiial contents of the family, even if it is empty,
		1005	i.e. there will always be a timely call to the callback with the current
		1006	contents.
		1007
		1008	It is possible that the callback is called with a change event even though
		1009	the subkey is already present and the value has not changed.
		1010
		1011	The monitoring stops when the guard object is destroyed.
		1012
		1013	Example: on every change to the family "mygroup", print out all keys.
		1014
		1015	my $guard = db_mon mygroup => sub {
		1016	my ($family, $a, $c, $d) = @_;
		1017	print "mygroup members: ", (join " ", keys %$family), "\n";
		1018	};
		1019
		1020	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1021
		1022	my $guard; $guard = db_mon My::Module::workers => sub {
		1023	my ($family, $a, $c, $d) = @_;
		1024	return unless %$family;
		1025	undef $guard;
		1026	print "My::Module::workers now nonempty\n";
		1027	};
		1028
		1029	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1030
		1031	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1032	my ($family, $a, $c, $d) = @_;
		1033
		1034	print "+$_=$family->{$_}\n" for @$a;
		1035	print "*$_=$family->{$_}\n" for @$c;
		1036	print "-$_=$family->{$_}\n" for @$d;
		1037	};
		1038
		1039	=cut
		1040
		1041	=back
		1042
827	=head1 AnyEvent::MP vs. Distributed Erlang	1043	=head1 AnyEvent::MP vs. Distributed Erlang
828		1044
829	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1045	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
830	== aemp node, Erlang process == aemp port), so many of the documents and	1046	== aemp node, Erlang process == aemp port), so many of the documents and
831	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1047	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
…		…
862	ports being the special case/exception, where transport errors cannot	1078	ports being the special case/exception, where transport errors cannot
863	occur.	1079	occur.
864		1080
865	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1081	=item * Erlang uses processes and a mailbox, AEMP does not queue.
866		1082
867	Erlang uses processes that selectively receive messages, and therefore	1083	Erlang uses processes that selectively receive messages out of order, and
868	needs a queue. AEMP is event based, queuing messages would serve no	1084	therefore needs a queue. AEMP is event based, queuing messages would serve
869	useful purpose. For the same reason the pattern-matching abilities of	1085	no useful purpose. For the same reason the pattern-matching abilities
870	AnyEvent::MP are more limited, as there is little need to be able to	1086	of AnyEvent::MP are more limited, as there is little need to be able to
871	filter messages without dequeuing them.	1087	filter messages without dequeuing them.
872		1088
873	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1089	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1090	being event-based, while Erlang is process-based.
		1091
		1092	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1093	top of AEMP and Coro threads.
874		1094
875	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1095	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
876		1096
877	Sending messages in Erlang is synchronous and blocks the process (and	1097	Sending messages in Erlang is synchronous and blocks the process until
		1098	a conenction has been established and the message sent (and so does not
878	so does not need a queue that can overflow). AEMP sends are immediate,	1099	need a queue that can overflow). AEMP sends return immediately, connection
879	connection establishment is handled in the background.	1100	establishment is handled in the background.
880		1101
881	=item * Erlang suffers from silent message loss, AEMP does not.	1102	=item * Erlang suffers from silent message loss, AEMP does not.
882		1103
883	Erlang implements few guarantees on messages delivery - messages can get	1104	Erlang implements few guarantees on messages delivery - messages can get
884	lost without any of the processes realising it (i.e. you send messages a,	1105	lost without any of the processes realising it (i.e. you send messages a,
885	b, and c, and the other side only receives messages a and c).	1106	b, and c, and the other side only receives messages a and c).
886		1107
887	AEMP guarantees correct ordering, and the guarantee that after one message	1108	AEMP guarantees (modulo hardware errors) correct ordering, and the
888	is lost, all following ones sent to the same port are lost as well, until	1109	guarantee that after one message is lost, all following ones sent to the
889	monitoring raises an error, so there are no silent "holes" in the message	1110	same port are lost as well, until monitoring raises an error, so there are
890	sequence.	1111	no silent "holes" in the message sequence.
		1112
		1113	If you want your software to be very reliable, you have to cope with
		1114	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1115	simply tries to work better in common error cases, such as when a network
		1116	link goes down.
891		1117
892	=item * Erlang can send messages to the wrong port, AEMP does not.	1118	=item * Erlang can send messages to the wrong port, AEMP does not.
893		1119
894	In Erlang it is quite likely that a node that restarts reuses a process ID	1120	In Erlang it is quite likely that a node that restarts reuses an Erlang
895	known to other nodes for a completely different process, causing messages	1121	process ID known to other nodes for a completely different process,
896	destined for that process to end up in an unrelated process.	1122	causing messages destined for that process to end up in an unrelated
		1123	process.
897		1124
898	AEMP never reuses port IDs, so old messages or old port IDs floating	1125	AEMP does not reuse port IDs, so old messages or old port IDs floating
899	around in the network will not be sent to an unrelated port.	1126	around in the network will not be sent to an unrelated port.
900		1127
901	=item * Erlang uses unprotected connections, AEMP uses secure	1128	=item * Erlang uses unprotected connections, AEMP uses secure
902	authentication and can use TLS.	1129	authentication and can use TLS.
903		1130
…		…
906		1133
907	=item * The AEMP protocol is optimised for both text-based and binary	1134	=item * The AEMP protocol is optimised for both text-based and binary
908	communications.	1135	communications.
909		1136
910	The AEMP protocol, unlike the Erlang protocol, supports both programming	1137	The AEMP protocol, unlike the Erlang protocol, supports both programming
911	language independent text-only protocols (good for debugging) and binary,	1138	language independent text-only protocols (good for debugging), and binary,
912	language-specific serialisers (e.g. Storable). By default, unless TLS is	1139	language-specific serialisers (e.g. Storable). By default, unless TLS is
913	used, the protocol is actually completely text-based.	1140	used, the protocol is actually completely text-based.
914		1141
915	It has also been carefully designed to be implementable in other languages	1142	It has also been carefully designed to be implementable in other languages
916	with a minimum of work while gracefully degrading functionality to make the	1143	with a minimum of work while gracefully degrading functionality to make the
917	protocol simple.	1144	protocol simple.
918		1145
919	=item * AEMP has more flexible monitoring options than Erlang.	1146	=item * AEMP has more flexible monitoring options than Erlang.
920		1147
921	In Erlang, you can chose to receive I<all> exit signals as messages	1148	In Erlang, you can chose to receive I<all> exit signals as messages or
922	or I<none>, there is no in-between, so monitoring single processes is	1149	I<none>, there is no in-between, so monitoring single Erlang processes is
923	difficult to implement. Monitoring in AEMP is more flexible than in	1150	difficult to implement.
924	Erlang, as one can choose between automatic kill, exit message or callback	1151
925	on a per-process basis.	1152	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1153	between automatic kill, exit message or callback on a per-port basis.
926		1154
927	=item * Erlang tries to hide remote/local connections, AEMP does not.	1155	=item * Erlang tries to hide remote/local connections, AEMP does not.
928		1156
929	Monitoring in Erlang is not an indicator of process death/crashes, in the	1157	Monitoring in Erlang is not an indicator of process death/crashes, in the
930	same way as linking is (except linking is unreliable in Erlang).	1158	same way as linking is (except linking is unreliable in Erlang).
…		…
953		1181
954	Strings can easily be printed, easily serialised etc. and need no special	1182	Strings can easily be printed, easily serialised etc. and need no special
955	procedures to be "valid".	1183	procedures to be "valid".
956		1184
957	And as a result, a port with just a default receiver consists of a single	1185	And as a result, a port with just a default receiver consists of a single
958	closure stored in a global hash - it can't become much cheaper.	1186	code reference stored in a global hash - it can't become much cheaper.
959		1187
960	=item Why favour JSON, why not a real serialising format such as Storable?	1188	=item Why favour JSON, why not a real serialising format such as Storable?
961		1189
962	In fact, any AnyEvent::MP node will happily accept Storable as framing	1190	In fact, any AnyEvent::MP node will happily accept Storable as framing
963	format, but currently there is no way to make a node use Storable by	1191	format, but currently there is no way to make a node use Storable by

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.114 by root, Thu Apr 22 16:06:19 2010 UTC vs. Revision 1.132 by root, Sat Mar 10 20:34:11 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.114 by root, Thu Apr 22 16:06:19 2010 UTC vs.
Revision 1.132 by root, Sat Mar 10 20:34:11 2012 UTC