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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.63 by root, Thu Aug 27 21:29:37 2009 UTC vs.
Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
36	# monitoring	35	# monitoring
…		…
38	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
39	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
40		39
41	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
42		41
		42	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - WIP
46	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable API, protocol not yet final.
47		47
48	stay tuned.	48	stay tuned.
49		49
50	=head1 DESCRIPTION	50	=head1 DESCRIPTION
51		51
52	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
53		53
54	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
56		56
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page.	58	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		59
64	=head1 CONCEPTS	60	=head1 CONCEPTS
65		61
66	=over 4	62	=over 4
67		63
68	=item port	64	=item port
69		65
70	A port is something you can send messages to (with the C<snd> function).	66	A port is something you can send messages to (with the C<snd> function).
71		67
72	Ports allow you to register C<rcv> handlers that can match all or just	68	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages will not be queued.	69	some messages. Messages send to ports will not be queued, regardless of
		70	anything was listening for them or not.
74		71
75	=item port ID - C<noderef#portname>	72	=item port ID - C<nodeid#portname>
76		73
77	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	74	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
78	separator, and a port name (a printable string of unspecified format). An	75	separator, and a port name (a printable string of unspecified format).
79	exception is the the node port, whose ID is identical to its node
80	reference.
81		76
82	=item node	77	=item node
83		78
84	A node is a single process containing at least one port - the node port,	79	A node is a single process containing at least one port - the node port,
85	which provides nodes to manage each other remotely, and to create new	80	which enables nodes to manage each other remotely, and to create new
86	ports.	81	ports.
87		82
88	Nodes are either private (single-process only), slaves (can only talk to	83	Nodes are either public (have one or more listening ports) or private
89	public nodes, but do not need an open port) or public nodes (connectable	84	(no listening ports). Private nodes cannot talk to other private nodes
90	from any other node).	85	currently.
91		86
92	=item node ID - C<[a-za-Z0-9_\-.:]+>	87	=item node ID - C<[a-za-Z0-9_\-.:]+>
93		88
94	A node ID is a string that either simply identifies the node (for	89	A node ID is a string that uniquely identifies the node within a
95	private and slave nodes), or contains a recipe on how to reach a given	90	network. Depending on the configuration used, node IDs can look like a
96	node (for public nodes).	91	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		92	doesn't interpret node IDs in any way.
97		93
98	This recipe is simply a comma-separated list of C<address:port> pairs (for	94	=item binds - C<ip:port>
99	TCP/IP, other protocols might look different).
100		95
101	Node references come in two flavours: resolved (containing only numerical	96	Nodes can only talk to each other by creating some kind of connection to
102	addresses) or unresolved (where hostnames are used instead of addresses).	97	each other. To do this, nodes should listen on one or more local transport
		98	endpoints - binds. Currently, only standard C<ip:port> specifications can
		99	be used, which specify TCP ports to listen on.
103		100
104	Before using an unresolved node reference in a message you first have to	101	=item seeds - C<host:port>
105	resolve it.	102
		103	When a node starts, it knows nothing about the network. To teach the node
		104	about the network it first has to contact some other node within the
		105	network. This node is called a seed.
		106
		107	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		108	are expected to be long-running, and at least one of those should always
		109	be available. When nodes run out of connections (e.g. due to a network
		110	error), they try to re-establish connections to some seednodes again to
		111	join the network.
		112
		113	Apart from being sued for seeding, seednodes are not special in any way -
		114	every public node can be a seednode.
106		115
107	=back	116	=back
108		117
109	=head1 VARIABLES/FUNCTIONS	118	=head1 VARIABLES/FUNCTIONS
110		119
…		…
126		135
127	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
128		137
129	our @EXPORT = qw(	138	our @EXPORT = qw(
130	NODE $NODE *SELF node_of after	139	NODE $NODE *SELF node_of after
131	resolve_node initialise_node	140	configure
132	snd rcv mon mon_guard kil reg psub spawn	141	snd rcv mon mon_guard kil reg psub spawn
133	port	142	port
134	);	143	);
135		144
136	our $SELF;	145	our $SELF;
…		…
141	kil $SELF, die => $msg;	150	kil $SELF, die => $msg;
142	}	151	}
143		152
144	=item $thisnode = NODE / $NODE	153	=item $thisnode = NODE / $NODE
145		154
146	The C<NODE> function returns, and the C<$NODE> variable contains the	155	The C<NODE> function returns, and the C<$NODE> variable contains, the node
147	node id of the local node. The value is initialised by a call to	156	ID of the node running in the current process. This value is initialised by
148	C<initialise_node>.	157	a call to C<configure>.
149		158
150	=item $nodeid = node_of $port	159	=item $nodeid = node_of $port
151		160
152	Extracts and returns the noderef from a port ID or a node ID.	161	Extracts and returns the node ID from a port ID or a node ID.
153		162
154	=item initialise_node $profile_name	163	=item configure key => value...
155		164
156	Before a node can talk to other nodes on the network it has to initialise	165	Before a node can talk to other nodes on the network (i.e. enter
157	itself - the minimum a node needs to know is it's own name, and optionally	166	"distributed mode") it has to configure itself - the minimum a node needs
158	it should know the noderefs of some other nodes in the network.	167	to know is its own name, and optionally it should know the addresses of
		168	some other nodes in the network to discover other nodes.
159		169
160	This function initialises a node - it must be called exactly once (or	170	This function configures a node - it must be called exactly once (or
161	never) before calling other AnyEvent::MP functions.	171	never) before calling other AnyEvent::MP functions.
162		172
163	All arguments (optionally except for the first) are noderefs, which can be
164	either resolved or unresolved.
165
166	The first argument will be looked up in the configuration database first
167	(if it is C<undef> then the current nodename will be used instead) to find
168	the relevant configuration profile (see L<aemp>). If none is found then
169	the default configuration is used. The configuration supplies additional
170	seed/master nodes and can override the actual noderef.
171
172	There are two types of networked nodes, public nodes and slave nodes:
173
174	=over 4	173	=over 4
175		174
176	=item public nodes	175	=item step 1, gathering configuration from profiles
177		176
178	For public nodes, C<$noderef> (supplied either directly to	177	The function first looks up a profile in the aemp configuration (see the
179	C<initialise_node> or indirectly via a profile or the nodename) must be a	178	L<aemp> commandline utility). The profile name can be specified via the
180	noderef (possibly unresolved, in which case it will be resolved).	179	named C<profile> parameter. If it is missing, then the nodename (F<uname
		180	-n>) will be used as profile name.
181		181
182	After resolving, the node will bind itself on all endpoints.	182	The profile data is then gathered as follows:
183		183
184	=item slave nodes	184	First, all remaining key => value pairs (all of which are conveniently
		185	undocumented at the moment) will be interpreted as configuration
		186	data. Then they will be overwritten by any values specified in the global
		187	default configuration (see the F<aemp> utility), then the chain of
		188	profiles chosen by the profile name (and any C<parent> attributes).
185		189
186	When the C<$noderef> (either as given or overriden by the config file)	190	That means that the values specified in the profile have highest priority
187	is the special string C<slave/>, then the node will become a slave	191	and the values specified directly via C<configure> have lowest priority,
188	node. Slave nodes cannot be contacted from outside, and cannot talk to	192	and can only be used to specify defaults.
189	each other (at least in this version of AnyEvent::MP).
190		193
191	Slave nodes work by creating connections to all public nodes, using the	194	If the profile specifies a node ID, then this will become the node ID of
192	L<AnyEvent::MP::Global> service.	195	this process. If not, then the profile name will be used as node ID. The
		196	special node ID of C<anon/> will be replaced by a random node ID.
		197
		198	=item step 2, bind listener sockets
		199
		200	The next step is to look up the binds in the profile, followed by binding
		201	aemp protocol listeners on all binds specified (it is possible and valid
		202	to have no binds, meaning that the node cannot be contacted form the
		203	outside. This means the node cannot talk to other nodes that also have no
		204	binds, but it can still talk to all "normal" nodes).
		205
		206	If the profile does not specify a binds list, then a default of C<*> is
		207	used, meaning the node will bind on a dynamically-assigned port on every
		208	local IP address it finds.
		209
		210	=item step 3, connect to seed nodes
		211
		212	As the last step, the seeds list from the profile is passed to the
		213	L<AnyEvent::MP::Global> module, which will then use it to keep
		214	connectivity with at least one node at any point in time.
193		215
194	=back	216	=back
195		217
196	After initialising itself, the node will connect to all additional	218	Example: become a distributed node using the locla node name as profile.
197	C<$seednodes> that are specified diretcly or via a profile. Seednodes are	219	This should be the most common form of invocation for "daemon"-type nodes.
198	optional and can be used to quickly bootstrap the node into an existing
199	network.
200		220
201	All the seednodes will also be specially marked to automatically retry	221	configure
202	connecting to them indefinitely, so make sure that seednodes are really
203	reliable and up (this might also change in the future).
204		222
205	Example: become a public node listening on the guessed noderef, or the one	223	Example: become an anonymous node. This form is often used for commandline
206	specified via C<aemp> for the current node. This should be the most common	224	clients.
207	form of invocation for "daemon"-type nodes.
208		225
209	initialise_node;	226	configure nodeid => "anon/";
210		227
211	Example: become a slave node to any of the the seednodes specified via	228	Example: configure a node using a profile called seed, which si suitable
212	C<aemp>. This form is often used for commandline clients.	229	for a seed node as it binds on all local addresses on a fixed port (4040,
		230	customary for aemp).
213		231
214	initialise_node "slave/";	232	# use the aemp commandline utility
		233	# aemp profile seed nodeid anon/ binds '*:4040'
215		234
216	Example: become a public node, and try to contact some well-known master	235	# then use it
217	servers to become part of the network.	236	configure profile => "seed";
218		237
219	initialise_node undef, "master1", "master2";	238	# or simply use aemp from the shell again:
		239	# aemp run profile seed
220		240
221	Example: become a public node listening on port C<4041>.	241	# or provide a nicer-to-remember nodeid
222		242	# aemp run profile seed nodeid "$(hostname)"
223	initialise_node 4041;
224
225	Example: become a public node, only visible on localhost port 4044.
226
227	initialise_node "localhost:4044";
228
229	=item $cv = resolve_node $noderef
230
231	Takes an unresolved node reference that may contain hostnames and
232	abbreviated IDs, resolves all of them and returns a resolved node
233	reference.
234
235	In addition to C<address:port> pairs allowed in resolved noderefs, the
236	following forms are supported:
237
238	=over 4
239
240	=item the empty string
241
242	An empty-string component gets resolved as if the default port (4040) was
243	specified.
244
245	=item naked port numbers (e.g. C<1234>)
246
247	These are resolved by prepending the local nodename and a colon, to be
248	further resolved.
249
250	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
251
252	These are resolved by using AnyEvent::DNS to resolve them, optionally
253	looking up SRV records for the C<aemp=4040> port, if no port was
254	specified.
255
256	=back
257		243
258	=item $SELF	244	=item $SELF
259		245
260	Contains the current port id while executing C<rcv> callbacks or C<psub>	246	Contains the current port id while executing C<rcv> callbacks or C<psub>
261	blocks.	247	blocks.
262		248
263	=item SELF, %SELF, @SELF...	249	=item *SELF, SELF, %SELF, @SELF...
264		250
265	Due to some quirks in how perl exports variables, it is impossible to	251	Due to some quirks in how perl exports variables, it is impossible to
266	just export C<$SELF>, all the symbols called C<SELF> are exported by this	252	just export C<$SELF>, all the symbols named C<SELF> are exported by this
267	module, but only C<$SELF> is currently used.	253	module, but only C<$SELF> is currently used.
268		254
269	=item snd $port, type => @data	255	=item snd $port, type => @data
270		256
271	=item snd $port, @msg	257	=item snd $port, @msg
272		258
273	Send the given message to the given port ID, which can identify either	259	Send the given message to the given port, which can identify either a
274	a local or a remote port, and must be a port ID.	260	local or a remote port, and must be a port ID.
275		261
276	While the message can be about anything, it is highly recommended to use a	262	While the message can be almost anything, it is highly recommended to
277	string as first element (a port ID, or some word that indicates a request	263	use a string as first element (a port ID, or some word that indicates a
278	type etc.).	264	request type etc.) and to consist if only simple perl values (scalars,
		265	arrays, hashes) - if you think you need to pass an object, think again.
279		266
280	The message data effectively becomes read-only after a call to this	267	The message data logically becomes read-only after a call to this
281	function: modifying any argument is not allowed and can cause many	268	function: modifying any argument (or values referenced by them) is
282	problems.	269	forbidden, as there can be considerable time between the call to C<snd>
		270	and the time the message is actually being serialised - in fact, it might
		271	never be copied as within the same process it is simply handed to the
		272	receiving port.
283		273
284	The type of data you can transfer depends on the transport protocol: when	274	The type of data you can transfer depends on the transport protocol: when
285	JSON is used, then only strings, numbers and arrays and hashes consisting	275	JSON is used, then only strings, numbers and arrays and hashes consisting
286	of those are allowed (no objects). When Storable is used, then anything	276	of those are allowed (no objects). When Storable is used, then anything
287	that Storable can serialise and deserialise is allowed, and for the local	277	that Storable can serialise and deserialise is allowed, and for the local
288	node, anything can be passed.	278	node, anything can be passed. Best rely only on the common denominator of
		279	these.
289		280
290	=item $local_port = port	281	=item $local_port = port
291		282
292	Create a new local port object and returns its port ID. Initially it has	283	Create a new local port object and returns its port ID. Initially it has
293	no callbacks set and will throw an error when it receives messages.	284	no callbacks set and will throw an error when it receives messages.
…		…
378		369
379	=cut	370	=cut
380		371
381	sub rcv($@) {	372	sub rcv($@) {
382	my $port = shift;	373	my $port = shift;
383	my ($noderef, $portid) = split /#/, $port, 2;	374	my ($nodeid, $portid) = split /#/, $port, 2;
384		375
385	$NODE{$noderef} == $NODE{""}	376	$NODE{$nodeid} == $NODE{""}
386	or Carp::croak "$port: rcv can only be called on local ports, caught";	377	or Carp::croak "$port: rcv can only be called on local ports, caught";
387		378
388	while (@_) {	379	while (@_) {
389	if (ref $_[0]) {	380	if (ref $_[0]) {
390	if (my $self = $PORT_DATA{$portid}) {	381	if (my $self = $PORT_DATA{$portid}) {
…		…
469	$res	460	$res
470	}	461	}
471	}	462	}
472	}	463	}
473		464
474	=item $guard = mon $port, $cb->(@reason)	465	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
475		466
476	=item $guard = mon $port, $rcvport	467	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
477		468
478	=item $guard = mon $port	469	=item $guard = mon $port # kill $SELF when $port dies
479		470
480	=item $guard = mon $port, $rcvport, @msg	471	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
481		472
482	Monitor the given port and do something when the port is killed or	473	Monitor the given port and do something when the port is killed or
483	messages to it were lost, and optionally return a guard that can be used	474	messages to it were lost, and optionally return a guard that can be used
484	to stop monitoring again.	475	to stop monitoring again.
485		476
486	C<mon> effectively guarantees that, in the absence of hardware failures,	477	C<mon> effectively guarantees that, in the absence of hardware failures,
487	that after starting the monitor, either all messages sent to the port	478	after starting the monitor, either all messages sent to the port will
488	will arrive, or the monitoring action will be invoked after possible	479	arrive, or the monitoring action will be invoked after possible message
489	message loss has been detected. No messages will be lost "in between"	480	loss has been detected. No messages will be lost "in between" (after
490	(after the first lost message no further messages will be received by the	481	the first lost message no further messages will be received by the
491	port). After the monitoring action was invoked, further messages might get	482	port). After the monitoring action was invoked, further messages might get
492	delivered again.	483	delivered again.
493		484
494	Note that monitoring-actions are one-shot: once released, they are removed	485	Note that monitoring-actions are one-shot: once messages are lost (and a
495	and will not trigger again.	486	monitoring alert was raised), they are removed and will not trigger again.
496		487
497	In the first form (callback), the callback is simply called with any	488	In the first form (callback), the callback is simply called with any
498	number of C<@reason> elements (no @reason means that the port was deleted	489	number of C<@reason> elements (no @reason means that the port was deleted
499	"normally"). Note also that I<< the callback B<must> never die >>, so use	490	"normally"). Note also that I<< the callback B<must> never die >>, so use
500	C<eval> if unsure.	491	C<eval> if unsure.
501		492
502	In the second form (another port given), the other port (C<$rcvport>)	493	In the second form (another port given), the other port (C<$rcvport>)
503	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	494	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
504	"normal" kils nothing happens, while under all other conditions, the other	495	"normal" kils nothing happens, while under all other conditions, the other
505	port is killed with the same reason.	496	port is killed with the same reason.
506		497
507	The third form (kill self) is the same as the second form, except that	498	The third form (kill self) is the same as the second form, except that
508	C<$rvport> defaults to C<$SELF>.	499	C<$rvport> defaults to C<$SELF>.
…		…
511	C<snd>.	502	C<snd>.
512		503
513	As a rule of thumb, monitoring requests should always monitor a port from	504	As a rule of thumb, monitoring requests should always monitor a port from
514	a local port (or callback). The reason is that kill messages might get	505	a local port (or callback). The reason is that kill messages might get
515	lost, just like any other message. Another less obvious reason is that	506	lost, just like any other message. Another less obvious reason is that
516	even monitoring requests can get lost (for exmaple, when the connection	507	even monitoring requests can get lost (for example, when the connection
517	to the other node goes down permanently). When monitoring a port locally	508	to the other node goes down permanently). When monitoring a port locally
518	these problems do not exist.	509	these problems do not exist.
519		510
520	Example: call a given callback when C<$port> is killed.	511	Example: call a given callback when C<$port> is killed.
521		512
…		…
530	mon $port, $self => "restart";	521	mon $port, $self => "restart";
531		522
532	=cut	523	=cut
533		524
534	sub mon {	525	sub mon {
535	my ($noderef, $port) = split /#/, shift, 2;	526	my ($nodeid, $port) = split /#/, shift, 2;
536		527
537	my $node = $NODE{$noderef} \|\| add_node $noderef;	528	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
538		529
539	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	530	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
540		531
541	unless (ref $cb) {	532	unless (ref $cb) {
542	if (@_) {	533	if (@_) {
…		…
562	is killed, the references will be freed.	553	is killed, the references will be freed.
563		554
564	Optionally returns a guard that will stop the monitoring.	555	Optionally returns a guard that will stop the monitoring.
565		556
566	This function is useful when you create e.g. timers or other watchers and	557	This function is useful when you create e.g. timers or other watchers and
567	want to free them when the port gets killed:	558	want to free them when the port gets killed (note the use of C<psub>):
568		559
569	$port->rcv (start => sub {	560	$port->rcv (start => sub {
570	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	561	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
571	undef $timer if 0.9 < rand;	562	undef $timer if 0.9 < rand;
572	});	563	});
573	});	564	});
574		565
575	=cut	566	=cut
…		…
584		575
585	=item kil $port[, @reason]	576	=item kil $port[, @reason]
586		577
587	Kill the specified port with the given C<@reason>.	578	Kill the specified port with the given C<@reason>.
588		579
589	If no C<@reason> is specified, then the port is killed "normally" (linked	580	If no C<@reason> is specified, then the port is killed "normally" (ports
590	ports will not be kileld, or even notified).	581	monitoring other ports will not necessarily die because a port dies
		582	"normally").
591		583
592	Otherwise, linked ports get killed with the same reason (second form of	584	Otherwise, linked ports get killed with the same reason (second form of
593	C<mon>, see below).	585	C<mon>, see above).
594		586
595	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	587	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
596	will be reported as reason C<< die => $@ >>.	588	will be reported as reason C<< die => $@ >>.
597		589
598	Transport/communication errors are reported as C<< transport_error =>	590	Transport/communication errors are reported as C<< transport_error =>
…		…
603	=item $port = spawn $node, $initfunc[, @initdata]	595	=item $port = spawn $node, $initfunc[, @initdata]
604		596
605	Creates a port on the node C<$node> (which can also be a port ID, in which	597	Creates a port on the node C<$node> (which can also be a port ID, in which
606	case it's the node where that port resides).	598	case it's the node where that port resides).
607		599
608	The port ID of the newly created port is return immediately, and it is	600	The port ID of the newly created port is returned immediately, and it is
609	permissible to immediately start sending messages or monitor the port.	601	possible to immediately start sending messages or to monitor the port.
610		602
611	After the port has been created, the init function is	603	After the port has been created, the init function is called on the remote
612	called. This function must be a fully-qualified function name	604	node, in the same context as a C<rcv> callback. This function must be a
613	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	605	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
614	program, use C<::name>.	606	specify a function in the main program, use C<::name>.
615		607
616	If the function doesn't exist, then the node tries to C<require>	608	If the function doesn't exist, then the node tries to C<require>
617	the package, then the package above the package and so on (e.g.	609	the package, then the package above the package and so on (e.g.
618	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
619	exists or it runs out of package names.	611	exists or it runs out of package names.
620		612
621	The init function is then called with the newly-created port as context	613	The init function is then called with the newly-created port as context
622	object (C<$SELF>) and the C<@initdata> values as arguments.	614	object (C<$SELF>) and the C<@initdata> values as arguments.
623		615
624	A common idiom is to pass your own port, monitor the spawned port, and	616	A common idiom is to pass a local port, immediately monitor the spawned
625	in the init function, monitor the original port. This two-way monitoring	617	port, and in the remote init function, immediately monitor the passed
626	ensures that both ports get cleaned up when there is a problem.	618	local port. This two-way monitoring ensures that both ports get cleaned up
		619	when there is a problem.
627		620
628	Example: spawn a chat server port on C<$othernode>.	621	Example: spawn a chat server port on C<$othernode>.
629		622
630	# this node, executed from within a port context:	623	# this node, executed from within a port context:
631	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
654	};	647	};
655	_self_die if $@;	648	_self_die if $@;
656	}	649	}
657		650
658	sub spawn(@) {	651	sub spawn(@) {
659	my ($noderef, undef) = split /#/, shift, 2;	652	my ($nodeid, undef) = split /#/, shift, 2;
660		653
661	my $id = "$RUNIQ." . $ID++;	654	my $id = "$RUNIQ." . $ID++;
662		655
663	$_[0] =~ /::/	656	$_[0] =~ /::/
664	or Carp::croak "spawn init function must be a fully-qualified name, caught";	657	or Carp::croak "spawn init function must be a fully-qualified name, caught";
665		658
666	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	659	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
667		660
668	"$noderef#$id"	661	"$nodeid#$id"
669	}	662	}
670		663
671	=item after $timeout, @msg	664	=item after $timeout, @msg
672		665
673	=item after $timeout, $callback	666	=item after $timeout, $callback
674		667
675	Either sends the given message, or call the given callback, after the	668	Either sends the given message, or call the given callback, after the
676	specified number of seconds.	669	specified number of seconds.
677		670
678	This is simply a utility function that come sin handy at times.	671	This is simply a utility function that comes in handy at times - the
		672	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		673	so it may go away in the future.
679		674
680	=cut	675	=cut
681		676
682	sub after($@) {	677	sub after($@) {
683	my ($timeout, @action) = @_;	678	my ($timeout, @action) = @_;
…		…
706		701
707	Despite the similarities, there are also some important differences:	702	Despite the similarities, there are also some important differences:
708		703
709	=over 4	704	=over 4
710		705
711	=item * Node references contain the recipe on how to contact them.	706	=item * Node IDs are arbitrary strings in AEMP.
712		707
713	Erlang relies on special naming and DNS to work everywhere in the	708	Erlang relies on special naming and DNS to work everywhere in the same
714	same way. AEMP relies on each node knowing it's own address(es), with	709	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
715	convenience functionality.	710	configuration or DNS), but will otherwise discover other odes itself.
716
717	This means that AEMP requires a less tightly controlled environment at the
718	cost of longer node references and a slightly higher management overhead.
719		711
720	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	712	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
721	uses "local ports are like remote ports".	713	uses "local ports are like remote ports".
722		714
723	The failure modes for local ports are quite different (runtime errors	715	The failure modes for local ports are quite different (runtime errors
…		…
736		728
737	Erlang uses processes that selectively receive messages, and therefore	729	Erlang uses processes that selectively receive messages, and therefore
738	needs a queue. AEMP is event based, queuing messages would serve no	730	needs a queue. AEMP is event based, queuing messages would serve no
739	useful purpose. For the same reason the pattern-matching abilities of	731	useful purpose. For the same reason the pattern-matching abilities of
740	AnyEvent::MP are more limited, as there is little need to be able to	732	AnyEvent::MP are more limited, as there is little need to be able to
741	filter messages without dequeing them.	733	filter messages without dequeuing them.
742		734
743	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	735	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
744		736
745	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	737	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
746		738
…		…
752		744
753	Erlang makes few guarantees on messages delivery - messages can get lost	745	Erlang makes few guarantees on messages delivery - messages can get lost
754	without any of the processes realising it (i.e. you send messages a, b,	746	without any of the processes realising it (i.e. you send messages a, b,
755	and c, and the other side only receives messages a and c).	747	and c, and the other side only receives messages a and c).
756		748
757	AEMP guarantees correct ordering, and the guarantee that there are no	749	AEMP guarantees correct ordering, and the guarantee that after one message
758	holes in the message sequence.	750	is lost, all following ones sent to the same port are lost as well, until
759		751	monitoring raises an error, so there are no silent "holes" in the message
760	=item * In Erlang, processes can be declared dead and later be found to be	752	sequence.
761	alive.
762
763	In Erlang it can happen that a monitored process is declared dead and
764	linked processes get killed, but later it turns out that the process is
765	still alive - and can receive messages.
766
767	In AEMP, when port monitoring detects a port as dead, then that port will
768	eventually be killed - it cannot happen that a node detects a port as dead
769	and then later sends messages to it, finding it is still alive.
770		753
771	=item * Erlang can send messages to the wrong port, AEMP does not.	754	=item * Erlang can send messages to the wrong port, AEMP does not.
772		755
773	In Erlang it is quite likely that a node that restarts reuses a process ID	756	In Erlang it is quite likely that a node that restarts reuses a process ID
774	known to other nodes for a completely different process, causing messages	757	known to other nodes for a completely different process, causing messages
…		…
778	around in the network will not be sent to an unrelated port.	761	around in the network will not be sent to an unrelated port.
779		762
780	=item * Erlang uses unprotected connections, AEMP uses secure	763	=item * Erlang uses unprotected connections, AEMP uses secure
781	authentication and can use TLS.	764	authentication and can use TLS.
782		765
783	AEMP can use a proven protocol - SSL/TLS - to protect connections and	766	AEMP can use a proven protocol - TLS - to protect connections and
784	securely authenticate nodes.	767	securely authenticate nodes.
785		768
786	=item * The AEMP protocol is optimised for both text-based and binary	769	=item * The AEMP protocol is optimised for both text-based and binary
787	communications.	770	communications.
788		771
789	The AEMP protocol, unlike the Erlang protocol, supports both	772	The AEMP protocol, unlike the Erlang protocol, supports both programming
790	language-independent text-only protocols (good for debugging) and binary,	773	language independent text-only protocols (good for debugging) and binary,
791	language-specific serialisers (e.g. Storable).	774	language-specific serialisers (e.g. Storable). By default, unless TLS is
		775	used, the protocol is actually completely text-based.
792		776
793	It has also been carefully designed to be implementable in other languages	777	It has also been carefully designed to be implementable in other languages
794	with a minimum of work while gracefully degrading fucntionality to make the	778	with a minimum of work while gracefully degrading functionality to make the
795	protocol simple.	779	protocol simple.
796		780
797	=item * AEMP has more flexible monitoring options than Erlang.	781	=item * AEMP has more flexible monitoring options than Erlang.
798		782
799	In Erlang, you can chose to receive I<all> exit signals as messages	783	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
802	Erlang, as one can choose between automatic kill, exit message or callback	786	Erlang, as one can choose between automatic kill, exit message or callback
803	on a per-process basis.	787	on a per-process basis.
804		788
805	=item * Erlang tries to hide remote/local connections, AEMP does not.	789	=item * Erlang tries to hide remote/local connections, AEMP does not.
806		790
807	Monitoring in Erlang is not an indicator of process death/crashes,	791	Monitoring in Erlang is not an indicator of process death/crashes, in the
808	as linking is (except linking is unreliable in Erlang).	792	same way as linking is (except linking is unreliable in Erlang).
809		793
810	In AEMP, you don't "look up" registered port names or send to named ports	794	In AEMP, you don't "look up" registered port names or send to named ports
811	that might or might not be persistent. Instead, you normally spawn a port	795	that might or might not be persistent. Instead, you normally spawn a port
812	on the remote node. The init function monitors the you, and you monitor	796	on the remote node. The init function monitors you, and you monitor the
813	the remote port. Since both monitors are local to the node, they are much	797	remote port. Since both monitors are local to the node, they are much more
814	more reliable.	798	reliable (no need for C<spawn_link>).
815		799
816	This also saves round-trips and avoids sending messages to the wrong port	800	This also saves round-trips and avoids sending messages to the wrong port
817	(hard to do in Erlang).	801	(hard to do in Erlang).
818		802
819	=back	803	=back
820		804
821	=head1 RATIONALE	805	=head1 RATIONALE
822		806
823	=over 4	807	=over 4
824		808
825	=item Why strings for ports and noderefs, why not objects?	809	=item Why strings for port and node IDs, why not objects?
826		810
827	We considered "objects", but found that the actual number of methods	811	We considered "objects", but found that the actual number of methods
828	thatc an be called are very low. Since port IDs and noderefs travel over	812	that can be called are quite low. Since port and node IDs travel over
829	the network frequently, the serialising/deserialising would add lots of	813	the network frequently, the serialising/deserialising would add lots of
830	overhead, as well as having to keep a proxy object.	814	overhead, as well as having to keep a proxy object everywhere.
831		815
832	Strings can easily be printed, easily serialised etc. and need no special	816	Strings can easily be printed, easily serialised etc. and need no special
833	procedures to be "valid".	817	procedures to be "valid".
834		818
835	And a a miniport consists of a single closure stored in a global hash - it	819	And as a result, a miniport consists of a single closure stored in a
836	can't become much cheaper.	820	global hash - it can't become much cheaper.
837		821
838	=item Why favour JSON, why not real serialising format such as Storable?	822	=item Why favour JSON, why not a real serialising format such as Storable?
839		823
840	In fact, any AnyEvent::MP node will happily accept Storable as framing	824	In fact, any AnyEvent::MP node will happily accept Storable as framing
841	format, but currently there is no way to make a node use Storable by	825	format, but currently there is no way to make a node use Storable by
842	default.	826	default (although all nodes will accept it).
843		827
844	The default framing protocol is JSON because a) JSON::XS is many times	828	The default framing protocol is JSON because a) JSON::XS is many times
845	faster for small messages and b) most importantly, after years of	829	faster for small messages and b) most importantly, after years of
846	experience we found that object serialisation is causing more problems	830	experience we found that object serialisation is causing more problems
847	than it gains: Just like function calls, objects simply do not travel	831	than it solves: Just like function calls, objects simply do not travel
848	easily over the network, mostly because they will always be a copy, so you	832	easily over the network, mostly because they will always be a copy, so you
849	always have to re-think your design.	833	always have to re-think your design.
850		834
851	Keeping your messages simple, concentrating on data structures rather than	835	Keeping your messages simple, concentrating on data structures rather than
852	objects, will keep your messages clean, tidy and efficient.	836	objects, will keep your messages clean, tidy and efficient.
853		837
854	=back	838	=back
855		839
856	=head1 SEE ALSO	840	=head1 SEE ALSO
857		841
		842	L<AnyEvent::MP::Intro> - a gentle introduction.
		843
		844	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		845
		846	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		847	your applications.
		848
858	L<AnyEvent>.	849	L<AnyEvent>.
859		850
860	=head1 AUTHOR	851	=head1 AUTHOR
861		852
862	Marc Lehmann <schmorp@schmorp.de>	853	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.63 by root, Thu Aug 27 21:29:37 2009 UTC vs. Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC

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Revision 1.63 by root, Thu Aug 27 21:29:37 2009 UTC vs.
Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC