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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC

…		…
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
13	$SELF # receiving/own port id in rcv callbacks	13	$SELF # receiving/own port id in rcv callbacks
14		14
15	# initialise the node so it can send/receive messages	15	# initialise the node so it can send/receive messages
16	initialise_node;	16	configure;
17		17
18	# ports are message endpoints	18	# ports are message endpoints
19		19
20	# sending messages	20	# sending messages
21	snd $port, type => data...;	21	snd $port, type => data...;
22	snd $port, @msg;	22	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	23	snd @msg_with_first_element_being_a_port;
24		24
25	# creating/using ports, the simple way	25	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	26	my $simple_port = port { my @msg = @_ };
27		27
28	# creating/using ports, tagged message matching	28	# creating/using ports, tagged message matching
29	my $port = port;	29	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	31	rcv $port, pong => sub { warn "pong received\n" };
32		32
33	# create a port on another node	33	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	34	my $port = spawn $node, $initfunc, @initdata;
35		35
36	# monitoring	36	# monitoring
…		…
38	mon $port, $otherport # kill otherport on abnormal death	38	mon $port, $otherport # kill otherport on abnormal death
39	mon $port, $otherport, @msg # send message on death	39	mon $port, $otherport, @msg # send message on death
40		40
41	=head1 CURRENT STATUS	41	=head1 CURRENT STATUS
42		42
		43	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	44	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	45	AnyEvent::MP::Intro - uptodate, but incomplete.
45	AnyEvent::MP::Kernel - WIP
46	AnyEvent::MP::Transport - mostly stable	46	AnyEvent::MP::Kernel - mostly stable.
		47	AnyEvent::MP::Global - stable API, protocol not yet final.
47		48
48	stay tuned.	49	stay tuned.
49		50
50	=head1 DESCRIPTION	51	=head1 DESCRIPTION
51		52
52	This module (-family) implements a simple message passing framework.	53	This module (-family) implements a simple message passing framework.
53		54
54	Despite its simplicity, you can securely message other processes running	55	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	56	on the same or other hosts, and you can supervise entities remotely.
56		57
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page.	59	manual page and the examples under F<eg/>.
59		60
60	At the moment, this module family is severly broken and underdocumented,	61	At the moment, this module family is a bit underdocumented.
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		62
64	=head1 CONCEPTS	63	=head1 CONCEPTS
65		64
66	=over 4	65	=over 4
67		66
…		…
71		70
72	Ports allow you to register C<rcv> handlers that can match all or just	71	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages send to ports will not be queued, regardless of	72	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	73	anything was listening for them or not.
75		74
76	=item port ID - C<noderef#portname>	75	=item port ID - C<nodeid#portname>
77		76
78	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	77	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
79	separator, and a port name (a printable string of unspecified format). An	78	separator, and a port name (a printable string of unspecified format).
80	exception is the the node port, whose ID is identical to its node
81	reference.
82		79
83	=item node	80	=item node
84		81
85	A node is a single process containing at least one port - the node port,	82	A node is a single process containing at least one port - the node port,
86	which provides nodes to manage each other remotely, and to create new	83	which enables nodes to manage each other remotely, and to create new
87	ports.	84	ports.
88		85
89	Nodes are either private (single-process only), slaves (can only talk to	86	Nodes are either public (have one or more listening ports) or private
90	public nodes, but do not need an open port) or public nodes (connectable	87	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	88	currently.
92		89
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	90	=item node ID - C<[a-za-Z0-9_\-.:]+>
94		91
95	A node ID is a string that uniquely identifies the node within a	92	A node ID is a string that uniquely identifies the node within a
96	network. Depending on the configuration used, node IDs can look like a	93	network. Depending on the configuration used, node IDs can look like a
…		…
114	are expected to be long-running, and at least one of those should always	111	are expected to be long-running, and at least one of those should always
115	be available. When nodes run out of connections (e.g. due to a network	112	be available. When nodes run out of connections (e.g. due to a network
116	error), they try to re-establish connections to some seednodes again to	113	error), they try to re-establish connections to some seednodes again to
117	join the network.	114	join the network.
118		115
		116	Apart from being sued for seeding, seednodes are not special in any way -
		117	every public node can be a seednode.
		118
119	=back	119	=back
120		120
121	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
122		122
123	=over 4	123	=over 4
…		…
138		138
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
140		140
141	our @EXPORT = qw(	141	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	142	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	143	configure
144	snd rcv mon mon_guard kil reg psub spawn	144	snd rcv mon mon_guard kil reg psub spawn
145	port	145	port
146	);	146	);
147		147
148	our $SELF;	148	our $SELF;
…		…
153	kil $SELF, die => $msg;	153	kil $SELF, die => $msg;
154	}	154	}
155		155
156	=item $thisnode = NODE / $NODE	156	=item $thisnode = NODE / $NODE
157		157
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	158	The C<NODE> function returns, and the C<$NODE> variable contains, the node
159	ID of the node running in the current process. This value is initialised by	159	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	160	a call to C<configure>.
161		161
162	=item $nodeid = node_of $port	162	=item $nodeid = node_of $port
163		163
164	Extracts and returns the node ID part from a port ID or a node ID.	164	Extracts and returns the node ID from a port ID or a node ID.
165		165
166	=item initialise_node $profile_name	166	=item configure key => value...
167		167
168	Before a node can talk to other nodes on the network (i.e. enter	168	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to initialise itself - the minimum a node needs	169	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	170	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	171	some other nodes in the network to discover other nodes.
172		172
173	This function initialises a node - it must be called exactly once (or	173	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
175		175
176	The first argument is a profile name. If it is C<undef> or missing, then	176	=over 4
177	the current nodename will be used instead (i.e. F<uname -n>).
178		177
		178	=item step 1, gathering configuration from profiles
		179
179	The function then looks up the profile in the aemp configuration (see the	180	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	181	L<aemp> commandline utility). The profile name can be specified via the
		182	named C<profile> parameter. If it is missing, then the nodename (F<uname
		183	-n>) will be used as profile name.
		184
		185	The profile data is then gathered as follows:
		186
		187	First, all remaining key => value pairs (all of which are conviniently
		188	undocumented at the moment) will be interpreted as configuration
		189	data. Then they will be overwritten by any values specified in the global
		190	default configuration (see the F<aemp> utility), then the chain of
		191	profiles chosen by the profile name (and any C<parent> attributes).
		192
		193	That means that the values specified in the profile have highest priority
		194	and the values specified directly via C<configure> have lowest priority,
		195	and can only be used to specify defaults.
181		196
182	If the profile specifies a node ID, then this will become the node ID of	197	If the profile specifies a node ID, then this will become the node ID of
183	this process. If not, then the profile name will be used as node ID. The	198	this process. If not, then the profile name will be used as node ID. The
184	special node ID of C<anon/> will be replaced by a random node ID.	199	special node ID of C<anon/> will be replaced by a random node ID.
		200
		201	=item step 2, bind listener sockets
185		202
186	The next step is to look up the binds in the profile, followed by binding	203	The next step is to look up the binds in the profile, followed by binding
187	aemp protocol listeners on all binds specified (it is possible and valid	204	aemp protocol listeners on all binds specified (it is possible and valid
188	to have no binds, meaning that the node cannot be contacted form the	205	to have no binds, meaning that the node cannot be contacted form the
189	outside. This means the node cannot talk to other nodes that also have no	206	outside. This means the node cannot talk to other nodes that also have no
190	binds, but it can still talk to all "normal" nodes).	207	binds, but it can still talk to all "normal" nodes).
191		208
192	If the profile does not specify a binds list, then the node ID will be	209	If the profile does not specify a binds list, then a default of C<*> is
193	treated as if it were of the form C<host:port>, which will be resolved and	210	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	211	local IP address it finds.
195		212
		213	=item step 3, connect to seed nodes
		214
196	Lastly, the seeds list from the profile is passed to the	215	As the last step, the seeds list from the profile is passed to the
197	L<AnyEvent::MP::Global> module, which will then use it to keep	216	L<AnyEvent::MP::Global> module, which will then use it to keep
198	connectivity with at least on of those seed nodes at any point in time.	217	connectivity with at least one node at any point in time.
199		218
200	Example: become a distributed node listening on the guessed noderef, or	219	=back
201	the one specified via C<aemp> for the current node. This should be the	220
		221	Example: become a distributed node using the locla node name as profile.
202	most common form of invocation for "daemon"-type nodes.	222	This should be the most common form of invocation for "daemon"-type nodes.
203		223
204	initialise_node;	224	configure
205		225
206	Example: become an anonymous node. This form is often used for commandline	226	Example: become an anonymous node. This form is often used for commandline
207	clients.	227	clients.
208		228
209	initialise_node "anon/";	229	configure nodeid => "anon/";
210		230
211	Example: become a distributed node. If there is no profile of the given	231	Example: configure a node using a profile called seed, which si suitable
212	name, or no binds list was specified, resolve C<localhost:4044> and bind	232	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	233	customary for aemp).
214		234
215	initialise_node "localhost:4044";	235	# use the aemp commandline utility
		236	# aemp profile seed setnodeid anon/ setbinds '*:4040'
		237
		238	# then use it
		239	configure profile => "seed";
		240
		241	# or simply use aemp from the shell again:
		242	# aemp run profile seed
		243
		244	# or provide a nicer-to-remember nodeid
		245	# aemp run profile seed nodeid "$(hostname)"
216		246
217	=item $SELF	247	=item $SELF
218		248
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	249	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	250	blocks.
221		251
222	=item SELF, %SELF, @SELF...	252	=item *SELF, SELF, %SELF, @SELF...
223		253
224	Due to some quirks in how perl exports variables, it is impossible to	254	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	256	module, but only C<$SELF> is currently used.
227		257
228	=item snd $port, type => @data	258	=item snd $port, type => @data
229		259
230	=item snd $port, @msg	260	=item snd $port, @msg
231		261
232	Send the given message to the given port ID, which can identify either	262	Send the given message to the given port, which can identify either a
233	a local or a remote port, and must be a port ID.	263	local or a remote port, and must be a port ID.
234		264
235	While the message can be about anything, it is highly recommended to use a	265	While the message can be almost anything, it is highly recommended to
236	string as first element (a port ID, or some word that indicates a request	266	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	267	request type etc.) and to consist if only simple perl values (scalars,
		268	arrays, hashes) - if you think you need to pass an object, think again.
238		269
239	The message data effectively becomes read-only after a call to this	270	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
241	problems.	272	forbidden, as there can be considerable time between the call to C<snd>
		273	and the time the message is actually being serialised - in fact, it might
		274	never be copied as within the same process it is simply handed to the
		275	receiving port.
242		276
243	The type of data you can transfer depends on the transport protocol: when	277	The type of data you can transfer depends on the transport protocol: when
244	JSON is used, then only strings, numbers and arrays and hashes consisting	278	JSON is used, then only strings, numbers and arrays and hashes consisting
245	of those are allowed (no objects). When Storable is used, then anything	279	of those are allowed (no objects). When Storable is used, then anything
246	that Storable can serialise and deserialise is allowed, and for the local	280	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
248		283
249	=item $local_port = port	284	=item $local_port = port
250		285
251	Create a new local port object and returns its port ID. Initially it has	286	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	287	no callbacks set and will throw an error when it receives messages.
…		…
428	$res	463	$res
429	}	464	}
430	}	465	}
431	}	466	}
432		467
433	=item $guard = mon $port, $cb->(@reason)	468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
434		469
435	=item $guard = mon $port, $rcvport	470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
436		471
437	=item $guard = mon $port	472	=item $guard = mon $port # kill $SELF when $port dies
438		473
439	=item $guard = mon $port, $rcvport, @msg	474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		475
441	Monitor the given port and do something when the port is killed or	476	Monitor the given port and do something when the port is killed or
442	messages to it were lost, and optionally return a guard that can be used	477	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	478	to stop monitoring again.
444		479
445	C<mon> effectively guarantees that, in the absence of hardware failures,	480	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port	481	after starting the monitor, either all messages sent to the port will
447	will arrive, or the monitoring action will be invoked after possible	482	arrive, or the monitoring action will be invoked after possible message
448	message loss has been detected. No messages will be lost "in between"	483	loss has been detected. No messages will be lost "in between" (after
449	(after the first lost message no further messages will be received by the	484	the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get	485	port). After the monitoring action was invoked, further messages might get
451	delivered again.	486	delivered again.
452		487
453	Note that monitoring-actions are one-shot: once released, they are removed	488	Note that monitoring-actions are one-shot: once messages are lost (and a
454	and will not trigger again.	489	monitoring alert was raised), they are removed and will not trigger again.
455		490
456	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
457	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
459	C<eval> if unsure.	494	C<eval> if unsure.
…		…
521	is killed, the references will be freed.	556	is killed, the references will be freed.
522		557
523	Optionally returns a guard that will stop the monitoring.	558	Optionally returns a guard that will stop the monitoring.
524		559
525	This function is useful when you create e.g. timers or other watchers and	560	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	561	want to free them when the port gets killed (note the use of C<psub>):
527		562
528	$port->rcv (start => sub {	563	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	564	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	565	undef $timer if 0.9 < rand;
531	});	566	});
532	});	567	});
533		568
534	=cut	569	=cut
…		…
543		578
544	=item kil $port[, @reason]	579	=item kil $port[, @reason]
545		580
546	Kill the specified port with the given C<@reason>.	581	Kill the specified port with the given C<@reason>.
547		582
548	If no C<@reason> is specified, then the port is killed "normally" (linked	583	If no C<@reason> is specified, then the port is killed "normally" (ports
549	ports will not be kileld, or even notified).	584	monitoring other ports will not necessarily die because a port dies
		585	"normally").
550		586
551	Otherwise, linked ports get killed with the same reason (second form of	587	Otherwise, linked ports get killed with the same reason (second form of
552	C<mon>, see below).	588	C<mon>, see above).
553		589
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	590	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	591	will be reported as reason C<< die => $@ >>.
556		592
557	Transport/communication errors are reported as C<< transport_error =>	593	Transport/communication errors are reported as C<< transport_error =>
…		…
562	=item $port = spawn $node, $initfunc[, @initdata]	598	=item $port = spawn $node, $initfunc[, @initdata]
563		599
564	Creates a port on the node C<$node> (which can also be a port ID, in which	600	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	601	case it's the node where that port resides).
566		602
567	The port ID of the newly created port is return immediately, and it is	603	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	604	possible to immediately start sending messages or to monitor the port.
569		605
570	After the port has been created, the init function is	606	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	607	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	608	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	609	specify a function in the main program, use C<::name>.
574		610
575	If the function doesn't exist, then the node tries to C<require>	611	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	612	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	614	exists or it runs out of package names.
579		615
580	The init function is then called with the newly-created port as context	616	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	617	object (C<$SELF>) and the C<@initdata> values as arguments.
582		618
583	A common idiom is to pass your own port, monitor the spawned port, and	619	A common idiom is to pass a local port, immediately monitor the spawned
584	in the init function, monitor the original port. This two-way monitoring	620	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	621	local port. This two-way monitoring ensures that both ports get cleaned up
		622	when there is a problem.
586		623
587	Example: spawn a chat server port on C<$othernode>.	624	Example: spawn a chat server port on C<$othernode>.
588		625
589	# this node, executed from within a port context:	626	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
632	=item after $timeout, $callback	669	=item after $timeout, $callback
633		670
634	Either sends the given message, or call the given callback, after the	671	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	672	specified number of seconds.
636		673
637	This is simply a utility function that come sin handy at times.	674	This is simply a utility function that comes in handy at times - the
		675	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		676	so it may go away in the future.
638		677
639	=cut	678	=cut
640		679
641	sub after($@) {	680	sub after($@) {
642	my ($timeout, @action) = @_;	681	my ($timeout, @action) = @_;
…		…
708		747
709	Erlang makes few guarantees on messages delivery - messages can get lost	748	Erlang makes few guarantees on messages delivery - messages can get lost
710	without any of the processes realising it (i.e. you send messages a, b,	749	without any of the processes realising it (i.e. you send messages a, b,
711	and c, and the other side only receives messages a and c).	750	and c, and the other side only receives messages a and c).
712		751
713	AEMP guarantees correct ordering, and the guarantee that there are no	752	AEMP guarantees correct ordering, and the guarantee that after one message
714	holes in the message sequence.	753	is lost, all following ones sent to the same port are lost as well, until
715		754	monitoring raises an error, so there are no silent "holes" in the message
716	=item * In Erlang, processes can be declared dead and later be found to be	755	sequence.
717	alive.
718
719	In Erlang it can happen that a monitored process is declared dead and
720	linked processes get killed, but later it turns out that the process is
721	still alive - and can receive messages.
722
723	In AEMP, when port monitoring detects a port as dead, then that port will
724	eventually be killed - it cannot happen that a node detects a port as dead
725	and then later sends messages to it, finding it is still alive.
726		756
727	=item * Erlang can send messages to the wrong port, AEMP does not.	757	=item * Erlang can send messages to the wrong port, AEMP does not.
728		758
729	In Erlang it is quite likely that a node that restarts reuses a process ID	759	In Erlang it is quite likely that a node that restarts reuses a process ID
730	known to other nodes for a completely different process, causing messages	760	known to other nodes for a completely different process, causing messages
…		…
734	around in the network will not be sent to an unrelated port.	764	around in the network will not be sent to an unrelated port.
735		765
736	=item * Erlang uses unprotected connections, AEMP uses secure	766	=item * Erlang uses unprotected connections, AEMP uses secure
737	authentication and can use TLS.	767	authentication and can use TLS.
738		768
739	AEMP can use a proven protocol - SSL/TLS - to protect connections and	769	AEMP can use a proven protocol - TLS - to protect connections and
740	securely authenticate nodes.	770	securely authenticate nodes.
741		771
742	=item * The AEMP protocol is optimised for both text-based and binary	772	=item * The AEMP protocol is optimised for both text-based and binary
743	communications.	773	communications.
744		774
745	The AEMP protocol, unlike the Erlang protocol, supports both	775	The AEMP protocol, unlike the Erlang protocol, supports both programming
746	language-independent text-only protocols (good for debugging) and binary,	776	language independent text-only protocols (good for debugging) and binary,
747	language-specific serialisers (e.g. Storable).	777	language-specific serialisers (e.g. Storable). By default, unless TLS is
		778	used, the protocol is actually completely text-based.
748		779
749	It has also been carefully designed to be implementable in other languages	780	It has also been carefully designed to be implementable in other languages
750	with a minimum of work while gracefully degrading fucntionality to make the	781	with a minimum of work while gracefully degrading functionality to make the
751	protocol simple.	782	protocol simple.
752		783
753	=item * AEMP has more flexible monitoring options than Erlang.	784	=item * AEMP has more flexible monitoring options than Erlang.
754		785
755	In Erlang, you can chose to receive I<all> exit signals as messages	786	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
758	Erlang, as one can choose between automatic kill, exit message or callback	789	Erlang, as one can choose between automatic kill, exit message or callback
759	on a per-process basis.	790	on a per-process basis.
760		791
761	=item * Erlang tries to hide remote/local connections, AEMP does not.	792	=item * Erlang tries to hide remote/local connections, AEMP does not.
762		793
763	Monitoring in Erlang is not an indicator of process death/crashes,	794	Monitoring in Erlang is not an indicator of process death/crashes, in the
764	as linking is (except linking is unreliable in Erlang).	795	same way as linking is (except linking is unreliable in Erlang).
765		796
766	In AEMP, you don't "look up" registered port names or send to named ports	797	In AEMP, you don't "look up" registered port names or send to named ports
767	that might or might not be persistent. Instead, you normally spawn a port	798	that might or might not be persistent. Instead, you normally spawn a port
768	on the remote node. The init function monitors the you, and you monitor	799	on the remote node. The init function monitors you, and you monitor the
769	the remote port. Since both monitors are local to the node, they are much	800	remote port. Since both monitors are local to the node, they are much more
770	more reliable.	801	reliable (no need for C<spawn_link>).
771		802
772	This also saves round-trips and avoids sending messages to the wrong port	803	This also saves round-trips and avoids sending messages to the wrong port
773	(hard to do in Erlang).	804	(hard to do in Erlang).
774		805
775	=back	806	=back
776		807
777	=head1 RATIONALE	808	=head1 RATIONALE
778		809
779	=over 4	810	=over 4
780		811
781	=item Why strings for ports and noderefs, why not objects?	812	=item Why strings for port and node IDs, why not objects?
782		813
783	We considered "objects", but found that the actual number of methods	814	We considered "objects", but found that the actual number of methods
784	thatc an be called are very low. Since port IDs and noderefs travel over	815	that can be called are quite low. Since port and node IDs travel over
785	the network frequently, the serialising/deserialising would add lots of	816	the network frequently, the serialising/deserialising would add lots of
786	overhead, as well as having to keep a proxy object.	817	overhead, as well as having to keep a proxy object everywhere.
787		818
788	Strings can easily be printed, easily serialised etc. and need no special	819	Strings can easily be printed, easily serialised etc. and need no special
789	procedures to be "valid".	820	procedures to be "valid".
790		821
791	And a a miniport consists of a single closure stored in a global hash - it	822	And as a result, a miniport consists of a single closure stored in a
792	can't become much cheaper.	823	global hash - it can't become much cheaper.
793		824
794	=item Why favour JSON, why not real serialising format such as Storable?	825	=item Why favour JSON, why not a real serialising format such as Storable?
795		826
796	In fact, any AnyEvent::MP node will happily accept Storable as framing	827	In fact, any AnyEvent::MP node will happily accept Storable as framing
797	format, but currently there is no way to make a node use Storable by	828	format, but currently there is no way to make a node use Storable by
798	default.	829	default (although all nodes will accept it).
799		830
800	The default framing protocol is JSON because a) JSON::XS is many times	831	The default framing protocol is JSON because a) JSON::XS is many times
801	faster for small messages and b) most importantly, after years of	832	faster for small messages and b) most importantly, after years of
802	experience we found that object serialisation is causing more problems	833	experience we found that object serialisation is causing more problems
803	than it gains: Just like function calls, objects simply do not travel	834	than it solves: Just like function calls, objects simply do not travel
804	easily over the network, mostly because they will always be a copy, so you	835	easily over the network, mostly because they will always be a copy, so you
805	always have to re-think your design.	836	always have to re-think your design.
806		837
807	Keeping your messages simple, concentrating on data structures rather than	838	Keeping your messages simple, concentrating on data structures rather than
808	objects, will keep your messages clean, tidy and efficient.	839	objects, will keep your messages clean, tidy and efficient.
809		840
810	=back	841	=back
811		842
812	=head1 SEE ALSO	843	=head1 SEE ALSO
813		844
		845	L<AnyEvent::MP::Intro> - a gentle introduction.
		846
		847	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		848
		849	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		850	your applications.
		851
814	L<AnyEvent>.	852	L<AnyEvent>.
815		853
816	=head1 AUTHOR	854	=head1 AUTHOR
817		855
818	Marc Lehmann <schmorp@schmorp.de>	856	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC