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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.103 by root, Sat Oct 17 01:42:39 2009 UTC vs.
Revision 1.130 by root, Fri Mar 9 17:05:26 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 = 1.22;	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() {
…		…
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	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
197	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
198		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
		261
199	=over 4	262	=over 4
200		263
201	=item step 1, gathering configuration from profiles	264	=item step 1, gathering configuration from profiles
202		265
203	The function first looks up a profile in the aemp configuration (see the	266	The function first looks up a profile in the aemp configuration (see the
…		…
216	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
217	and the values specified directly via C<configure> have lowest priority,	280	and the values specified directly via C<configure> have lowest priority,
218	and can only be used to specify defaults.	281	and can only be used to specify defaults.
219		282
220	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
221	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
222	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>.
223		292
224	=item step 2, bind listener sockets	293	=item step 2, bind listener sockets
225		294
226	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
227	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
…		…
233	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
234	local IP address it finds.	303	local IP address it finds.
235		304
236	=item step 3, connect to seed nodes	305	=item step 3, connect to seed nodes
237		306
238	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
239	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
240	connectivity with at least one node at any point in time.	309	connectivity with at least one node at any point in time.
241		310
242	=back	311	=back
243		312
244	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.
245	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.
246		315
247	configure	316	configure
248		317
249	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
250	clients.	319	commandline clients.
251		320
252	configure nodeid => "anon/";	321	configure nodeid => "myscript/%n/%u";
253		322
254	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
255	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,
256	customary for aemp).	325	customary for aemp).
257		326
258	# use the aemp commandline utility	327	# use the aemp commandline utility
259	# aemp profile seed nodeid anon/ binds '*:4040'	328	# aemp profile seed binds '*:4040'
260		329
261	# then use it	330	# then use it
262	configure profile => "seed";	331	configure profile => "seed";
263		332
264	# or simply use aemp from the shell again:	333	# or simply use aemp from the shell again:
…		…
334	sub _kilme {	403	sub _kilme {
335	die "received message on port without callback";	404	die "received message on port without callback";
336	}	405	}
337		406
338	sub port(;&) {	407	sub port(;&) {
339	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
340	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
341		410
342	rcv $port, shift \|\| \&_kilme;	411	rcv $port, shift \|\| \&_kilme;
343		412
344	$port	413	$port
…		…
492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	561	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
493	closure is executed, sets up the environment in the same way as in C<rcv>	562	closure is executed, sets up the environment in the same way as in C<rcv>
494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	563	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
495		564
496	The effect is basically as if it returned C<< sub { peval $SELF, sub {	565	The effect is basically as if it returned C<< sub { peval $SELF, sub {
497	BLOCK } } >>.	566	BLOCK }, @_ } >>.
498		567
499	This is useful when you register callbacks from C<rcv> callbacks:	568	This is useful when you register callbacks from C<rcv> callbacks:
500		569
501	rcv delayed_reply => sub {	570	rcv delayed_reply => sub {
502	my ($delay, @reply) = @_;	571	my ($delay, @reply) = @_;
…		…
617	}	686	}
618		687
619	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
620		689
621	defined wantarray	690	defined wantarray
622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
623	}	692	}
624		693
625	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
626		695
627	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
…		…
650		719
651	=item kil $port[, @reason]	720	=item kil $port[, @reason]
652		721
653	Kill the specified port with the given C<@reason>.	722	Kill the specified port with the given C<@reason>.
654		723
655	If no C<@reason> is specified, then the port is killed "normally" (ports	724	If no C<@reason> is specified, then the port is killed "normally" -
656	monitoring other ports will not necessarily die because a port dies	725	monitor callback will be invoked, but the kil will not cause linked ports
657	"normally").	726	(C<mon $mport, $lport> form) to get killed.
658		727
659	Otherwise, linked ports get killed with the same reason (second form of	728	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
660	C<mon>, see above).	729	form) get killed with the same reason.
661		730
662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	731	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
663	will be reported as reason C<< die => $@ >>.	732	will be reported as reason C<< die => $@ >>.
664		733
665	Transport/communication errors are reported as C<< transport_error =>	734	Transport/communication errors are reported as C<< transport_error =>
…		…
731	}	800	}
732		801
733	sub spawn(@) {	802	sub spawn(@) {
734	my ($nodeid, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
735		804
736	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
737		806
738	$_[0] =~ /::/	807	$_[0] =~ /::/
739	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";
740		809
741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
742		811
743	"$nodeid#$id"	812	"$nodeid#$id"
744	}	813	}
		814
745		815
746	=item after $timeout, @msg	816	=item after $timeout, @msg
747		817
748	=item after $timeout, $callback	818	=item after $timeout, $callback
749		819
…		…
764	ref $action[0]	834	ref $action[0]
765	? $action[0]()	835	? $action[0]()
766	: snd @action;	836	: snd @action;
767	};	837	};
768	}	838	}
		839
		840	#=item $cb2 = timeout $seconds, $cb[, @args]
769		841
770	=item cal $port, @msg, $callback[, $timeout]	842	=item cal $port, @msg, $callback[, $timeout]
771		843
772	A simple form of RPC - sends a message to the given C<$port> with the	844	A simple form of RPC - sends a message to the given C<$port> with the
773	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.
…		…
819	$port	891	$port
820	}	892	}
821		893
822	=back	894	=back
823		895
		896	=head1 DISTRIBUTED DATABASE
		897
		898	AnyEvent::MP comes with a simple distributed database. The database will
		899	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		900	the global nodes for their needs.
		901
		902	The database consists of a two-level hash - a hash contains a hash which
		903	contains values.
		904
		905	The top level hash key is called "family", and the second-level hash key
		906	is called "subkey" or simply "key".
		907
		908	The family must be alphanumeric, i.e. start with a letter and consist
		909	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		910	pretty much like Perl module names.
		911
		912	As the family namespace is global, it is recommended to prefix family names
		913	with the name of the application or module using it.
		914
		915	The subkeys must be non-empty strings, with no further restrictions.
		916
		917	The values should preferably be strings, but other perl scalars should
		918	work as well (such as undef, arrays and hashes).
		919
		920	Every database entry is owned by one node - adding the same family/subkey
		921	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		922	but the result might be nondeterministic, i.e. the key might have
		923	different values on different nodes.
		924
		925	Different subkeys in the same family can be owned by different nodes
		926	without problems, and in fact, this is the common method to create worker
		927	pools. For example, a worker port for image scaling might do this:
		928
		929	db_set my_image_scalers => $port;
		930
		931	And clients looking for an image scaler will want to get the
		932	C<my_image_scalers> keys from time to time:
		933
		934	db_keys my_image_scalers => sub {
		935	@ports = @{ $_[0] };
		936	};
		937
		938	Or better yet, they want to monitor the database family, so they always
		939	have a reasonable up-to-date copy:
		940
		941	db_mon my_image_scalers => sub {
		942	@ports = keys %{ $_[0] };
		943	};
		944
		945	In general, you can set or delete single subkeys, but query and monitor
		946	whole families only.
		947
		948	If you feel the need to monitor or query a single subkey, try giving it
		949	it's own family.
		950
		951	=over
		952
		953	=item db_set $family => $subkey [=> $value]
		954
		955	Sets (or replaces) a key to the database - if C<$value> is omitted,
		956	C<undef> is used instead.
		957
		958	=item db_del $family => $subkey...
		959
		960	Deletes one or more subkeys from the database family.
		961
		962	=item $guard = db_reg $family => $subkey [=> $value]
		963
		964	Sets the key on the database and returns a guard. When the guard is
		965	destroyed, the key is deleted from the database. If C<$value> is missing,
		966	then C<undef> is used.
		967
		968	=item db_family $family => $cb->(\%familyhash)
		969
		970	Queries the named database C<$family> and call the callback with the
		971	family represented as a hash. You can keep and freely modify the hash.
		972
		973	=item db_keys $family => $cb->(\@keys)
		974
		975	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		976	them as array reference to the callback.
		977
		978	=item db_values $family => $cb->(\@values)
		979
		980	Same as C<db_family>, except it only queries the family I<values> and passes them
		981	as array reference to the callback.
		982
		983	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		984
		985	Creates a monitor on the given database family. Each time a key is set
		986	or or is deleted the callback is called with a hash containing the
		987	database family and three lists of added, changed and deleted subkeys,
		988	respectively. If no keys have changed then the array reference might be
		989	C<undef> or even missing.
		990
		991	The family hash reference and the key arrays belong to AnyEvent::MP and
		992	B<must not be modified or stored> by the callback. When in doubt, make a
		993	copy.
		994
		995	As soon as possible after the monitoring starts, the callback will be
		996	called with the intiial contents of the family, even if it is empty,
		997	i.e. there will always be a timely call to the callback with the current
		998	contents.
		999
		1000	It is possible that the callback is called with a change event even though
		1001	the subkey is already present and the value has not changed.
		1002
		1003	The monitoring stops when the guard object is destroyed.
		1004
		1005	Example: on every change to the family "mygroup", print out all keys.
		1006
		1007	my $guard = db_mon mygroup => sub {
		1008	my ($family, $a, $c, $d) = @_;
		1009	print "mygroup members: ", (join " ", keys %$family), "\n";
		1010	};
		1011
		1012	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1013
		1014	my $guard; $guard = db_mon My::Module::workers => sub {
		1015	my ($family, $a, $c, $d) = @_;
		1016	return unless %$family;
		1017	undef $guard;
		1018	print "My::Module::workers now nonempty\n";
		1019	};
		1020
		1021	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1022
		1023	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1024	my ($family, $a, $c, $d) = @_;
		1025
		1026	print "+$_=$family->{$_}\n" for @$a;
		1027	print "*$_=$family->{$_}\n" for @$c;
		1028	print "-$_=$family->{$_}\n" for @$d;
		1029	};
		1030
		1031	=cut
		1032
		1033	=back
		1034
824	=head1 AnyEvent::MP vs. Distributed Erlang	1035	=head1 AnyEvent::MP vs. Distributed Erlang
825		1036
826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1037	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
827	== aemp node, Erlang process == aemp port), so many of the documents and	1038	== aemp node, Erlang process == aemp port), so many of the documents and
828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1039	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
…		…
859	ports being the special case/exception, where transport errors cannot	1070	ports being the special case/exception, where transport errors cannot
860	occur.	1071	occur.
861		1072
862	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1073	=item * Erlang uses processes and a mailbox, AEMP does not queue.
863		1074
864	Erlang uses processes that selectively receive messages, and therefore	1075	Erlang uses processes that selectively receive messages out of order, and
865	needs a queue. AEMP is event based, queuing messages would serve no	1076	therefore needs a queue. AEMP is event based, queuing messages would serve
866	useful purpose. For the same reason the pattern-matching abilities of	1077	no useful purpose. For the same reason the pattern-matching abilities
867	AnyEvent::MP are more limited, as there is little need to be able to	1078	of AnyEvent::MP are more limited, as there is little need to be able to
868	filter messages without dequeuing them.	1079	filter messages without dequeuing them.
869		1080
870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1081	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1082	being event-based, while Erlang is process-based.
		1083
		1084	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1085	top of AEMP and Coro threads.
871		1086
872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1087	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
873		1088
874	Sending messages in Erlang is synchronous and blocks the process (and	1089	Sending messages in Erlang is synchronous and blocks the process until
		1090	a conenction has been established and the message sent (and so does not
875	so does not need a queue that can overflow). AEMP sends are immediate,	1091	need a queue that can overflow). AEMP sends return immediately, connection
876	connection establishment is handled in the background.	1092	establishment is handled in the background.
877		1093
878	=item * Erlang suffers from silent message loss, AEMP does not.	1094	=item * Erlang suffers from silent message loss, AEMP does not.
879		1095
880	Erlang implements few guarantees on messages delivery - messages can get	1096	Erlang implements few guarantees on messages delivery - messages can get
881	lost without any of the processes realising it (i.e. you send messages a,	1097	lost without any of the processes realising it (i.e. you send messages a,
882	b, and c, and the other side only receives messages a and c).	1098	b, and c, and the other side only receives messages a and c).
883		1099
884	AEMP guarantees correct ordering, and the guarantee that after one message	1100	AEMP guarantees (modulo hardware errors) correct ordering, and the
885	is lost, all following ones sent to the same port are lost as well, until	1101	guarantee that after one message is lost, all following ones sent to the
886	monitoring raises an error, so there are no silent "holes" in the message	1102	same port are lost as well, until monitoring raises an error, so there are
887	sequence.	1103	no silent "holes" in the message sequence.
		1104
		1105	If you want your software to be very reliable, you have to cope with
		1106	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1107	simply tries to work better in common error cases, such as when a network
		1108	link goes down.
888		1109
889	=item * Erlang can send messages to the wrong port, AEMP does not.	1110	=item * Erlang can send messages to the wrong port, AEMP does not.
890		1111
891	In Erlang it is quite likely that a node that restarts reuses a process ID	1112	In Erlang it is quite likely that a node that restarts reuses an Erlang
892	known to other nodes for a completely different process, causing messages	1113	process ID known to other nodes for a completely different process,
893	destined for that process to end up in an unrelated process.	1114	causing messages destined for that process to end up in an unrelated
		1115	process.
894		1116
895	AEMP never reuses port IDs, so old messages or old port IDs floating	1117	AEMP does not reuse port IDs, so old messages or old port IDs floating
896	around in the network will not be sent to an unrelated port.	1118	around in the network will not be sent to an unrelated port.
897		1119
898	=item * Erlang uses unprotected connections, AEMP uses secure	1120	=item * Erlang uses unprotected connections, AEMP uses secure
899	authentication and can use TLS.	1121	authentication and can use TLS.
900		1122
…		…
903		1125
904	=item * The AEMP protocol is optimised for both text-based and binary	1126	=item * The AEMP protocol is optimised for both text-based and binary
905	communications.	1127	communications.
906		1128
907	The AEMP protocol, unlike the Erlang protocol, supports both programming	1129	The AEMP protocol, unlike the Erlang protocol, supports both programming
908	language independent text-only protocols (good for debugging) and binary,	1130	language independent text-only protocols (good for debugging), and binary,
909	language-specific serialisers (e.g. Storable). By default, unless TLS is	1131	language-specific serialisers (e.g. Storable). By default, unless TLS is
910	used, the protocol is actually completely text-based.	1132	used, the protocol is actually completely text-based.
911		1133
912	It has also been carefully designed to be implementable in other languages	1134	It has also been carefully designed to be implementable in other languages
913	with a minimum of work while gracefully degrading functionality to make the	1135	with a minimum of work while gracefully degrading functionality to make the
914	protocol simple.	1136	protocol simple.
915		1137
916	=item * AEMP has more flexible monitoring options than Erlang.	1138	=item * AEMP has more flexible monitoring options than Erlang.
917		1139
918	In Erlang, you can chose to receive I<all> exit signals as messages	1140	In Erlang, you can chose to receive I<all> exit signals as messages or
919	or I<none>, there is no in-between, so monitoring single processes is	1141	I<none>, there is no in-between, so monitoring single Erlang processes is
920	difficult to implement. Monitoring in AEMP is more flexible than in	1142	difficult to implement.
921	Erlang, as one can choose between automatic kill, exit message or callback	1143
922	on a per-process basis.	1144	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1145	between automatic kill, exit message or callback on a per-port basis.
923		1146
924	=item * Erlang tries to hide remote/local connections, AEMP does not.	1147	=item * Erlang tries to hide remote/local connections, AEMP does not.
925		1148
926	Monitoring in Erlang is not an indicator of process death/crashes, in the	1149	Monitoring in Erlang is not an indicator of process death/crashes, in the
927	same way as linking is (except linking is unreliable in Erlang).	1150	same way as linking is (except linking is unreliable in Erlang).
…		…
949	overhead, as well as having to keep a proxy object everywhere.	1172	overhead, as well as having to keep a proxy object everywhere.
950		1173
951	Strings can easily be printed, easily serialised etc. and need no special	1174	Strings can easily be printed, easily serialised etc. and need no special
952	procedures to be "valid".	1175	procedures to be "valid".
953		1176
954	And as a result, a miniport consists of a single closure stored in a	1177	And as a result, a port with just a default receiver consists of a single
955	global hash - it can't become much cheaper.	1178	code reference stored in a global hash - it can't become much cheaper.
956		1179
957	=item Why favour JSON, why not a real serialising format such as Storable?	1180	=item Why favour JSON, why not a real serialising format such as Storable?
958		1181
959	In fact, any AnyEvent::MP node will happily accept Storable as framing	1182	In fact, any AnyEvent::MP node will happily accept Storable as framing
960	format, but currently there is no way to make a node use Storable by	1183	format, but currently there is no way to make a node use Storable by
…		…
976		1199
977	L<AnyEvent::MP::Intro> - a gentle introduction.	1200	L<AnyEvent::MP::Intro> - a gentle introduction.
978		1201
979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1202	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
980		1203
981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1204	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
982	your applications.	1205	your applications.
		1206
		1207	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
983		1208
984	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from	1209	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
985	all nodes.	1210	all nodes.
986		1211
987	L<AnyEvent>.	1212	L<AnyEvent>.

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.103 by root, Sat Oct 17 01:42:39 2009 UTC vs. Revision 1.130 by root, Fri Mar 9 17:05:26 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.103 by root, Sat Oct 17 01:42:39 2009 UTC vs.
Revision 1.130 by root, Fri Mar 9 17:05:26 2012 UTC