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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.57 by root, Sat Aug 15 04:34:34 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; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
38	# monitoring	35	# monitoring
…		…
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable API, protocol not yet final.
49		47
50	stay tuned.	48	stay tuned.
51		49
52	=head1 DESCRIPTION	50	=head1 DESCRIPTION
53		51
54	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
55		53
56	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
58		56
59	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>
60	manual page.	58	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		59
66	=head1 CONCEPTS	60	=head1 CONCEPTS
67		61
68	=over 4	62	=over 4
69		63
70	=item port	64	=item port
71		65
72	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).
73		67
74	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
75	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.
76		71
77	=item port id - C<noderef#portname>	72	=item port ID - C<nodeid#portname>
78		73
79	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
80	separator, and a port name (a printable string of unspecified format). An	75	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		76
84	=item node	77	=item node
85		78
86	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,
87	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
88	ports.	81	ports.
89		82
90	Nodes are either private (single-process only), slaves (connected to a	83	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	84	(no listening ports). Private nodes cannot talk to other private nodes
		85	currently.
92		86
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	87	=item node ID - C<[a-za-Z0-9_\-.:]+>
94		88
95	A node reference is a string that either simply identifies the node (for	89	A node ID is a string that uniquely identifies the node within a
96	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
97	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.
98		93
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	94	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		95
102	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
103	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.
104		100
105	Before using an unresolved node reference in a message you first have to	101	=item seeds - C<host:port>
106	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.
107		115
108	=back	116	=back
109		117
110	=head1 VARIABLES/FUNCTIONS	118	=head1 VARIABLES/FUNCTIONS
111		119
…		…
126	use base "Exporter";	134	use base "Exporter";
127		135
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
129		137
130	our @EXPORT = qw(	138	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	139	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	140	configure
133	snd rcv mon kil reg psub spawn	141	snd rcv mon mon_guard kil reg psub spawn
134	port	142	port
135	);	143	);
136		144
137	our $SELF;	145	our $SELF;
138		146
…		…
142	kil $SELF, die => $msg;	150	kil $SELF, die => $msg;
143	}	151	}
144		152
145	=item $thisnode = NODE / $NODE	153	=item $thisnode = NODE / $NODE
146		154
147	The C<NODE> function returns, and the C<$NODE> variable contains the	155	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef 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
149	C<initialise_node>.	157	a call to C<configure>.
150		158
151	=item $noderef = node_of $port	159	=item $nodeid = node_of $port
152		160
153	Extracts and returns the noderef from a port ID or a noderef.	161	Extracts and returns the node ID from a port ID or a node ID.
154		162
155	=item initialise_node $noderef, $seednode, $seednode...	163	=item configure key => value...
156		164
157	=item initialise_node "slave/", $master, $master...
158
159	Before a node can talk to other nodes on the network it has to initialise	165	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	166	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	167	to know is its own name, and optionally it should know the addresses of
		168	some other nodes in the network to discover other nodes.
162		169
163	This function initialises a node - it must be called exactly once (or	170	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	171	never) before calling other AnyEvent::MP functions.
165		172
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	173	=over 4
178		174
179	=item public nodes	175	=item step 1, gathering configuration from profiles
180		176
181	For public nodes, C<$noderef> (supplied either directly to	177	The function first looks up a profile in the aemp configuration (see the
182	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
183	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.
184		181
185	After resolving, the node will bind itself on all endpoints and try to	182	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		183
190	=item slave nodes	184	First, all remaining key => value pairs (all of which are conveniently
		185	undocumented at the moment) will be interpreted as configuration
		186	data. Then they will be overwritten by any values specified in the global
		187	default configuration (see the F<aemp> utility), then the chain of
		188	profiles chosen by the profile name (and any C<parent> attributes).
191		189
192	When the C<$noderef> (either as given or overriden by the config file)	190	That means that the values specified in the profile have highest priority
193	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,
194	node. Slave nodes cannot be contacted from outside and will route most of	192	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		193
197	At least one additional noderef is required (either by specifying it	194	If the profile specifies a node ID, then this will become the node ID of
198	directly or because it is part of the configuration profile): The node	195	this process. If not, then the profile name will be used as node ID. The
199	will try to connect to all of them and will become a slave attached to the	196	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.
201		197
202	Note that slave nodes cannot change their name, and consequently, their	198	=item step 2, bind listener sockets
203	master, so if the master goes down, the slave node will not function well	199
204	anymore until it can re-establish conenciton to its master. This makes	200	The next step is to look up the binds in the profile, followed by binding
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.	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.
206		215
207	=back	216	=back
208		217
209	This function will block until all nodes have been resolved and, for slave	218	Example: become a distributed node using the locla node name as profile.
210	nodes, until it has successfully established a connection to a master	219	This should be the most common form of invocation for "daemon"-type nodes.
211	server.
212		220
213	All the seednodes will also be specially marked to automatically retry	221	configure
214	connecting to them infinitely.
215		222
216	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
217	specified via C<aemp> for the current node. This should be the most common	224	clients.
218	form of invocation for "daemon"-type nodes.
219		225
220	initialise_node;	226	configure nodeid => "anon/";
221		227
222	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
223	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).
224		231
225	initialise_node "slave/";	232	# use the aemp commandline utility
		233	# aemp profile seed nodeid anon/ binds '*:4040'
226		234
227	Example: become a slave node to any of the specified master servers. This	235	# then use it
228	form is also often used for commandline clients.	236	configure profile => "seed";
229		237
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	238	# or simply use aemp from the shell again:
		239	# aemp run profile seed
231		240
232	Example: become a public node, and try to contact some well-known master	241	# or provide a nicer-to-remember nodeid
233	servers to become part of the network.	242	# aemp run profile seed nodeid "$(hostname)"
234
235	initialise_node undef, "master1", "master2";
236
237	Example: become a public node listening on port C<4041>.
238
239	initialise_node 4041;
240
241	Example: become a public node, only visible on localhost port 4044.
242
243	initialise_node "localhost:4044";
244
245	=item $cv = resolve_node $noderef
246
247	Takes an unresolved node reference that may contain hostnames and
248	abbreviated IDs, resolves all of them and returns a resolved node
249	reference.
250
251	In addition to C<address:port> pairs allowed in resolved noderefs, the
252	following forms are supported:
253
254	=over 4
255
256	=item the empty string
257
258	An empty-string component gets resolved as if the default port (4040) was
259	specified.
260
261	=item naked port numbers (e.g. C<1234>)
262
263	These are resolved by prepending the local nodename and a colon, to be
264	further resolved.
265
266	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
267
268	These are resolved by using AnyEvent::DNS to resolve them, optionally
269	looking up SRV records for the C<aemp=4040> port, if no port was
270	specified.
271
272	=back
273		243
274	=item $SELF	244	=item $SELF
275		245
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	246	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	247	blocks.
278		248
279	=item SELF, %SELF, @SELF...	249	=item *SELF, SELF, %SELF, @SELF...
280		250
281	Due to some quirks in how perl exports variables, it is impossible to	251	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	252	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	253	module, but only C<$SELF> is currently used.
284		254
285	=item snd $port, type => @data	255	=item snd $port, type => @data
286		256
287	=item snd $port, @msg	257	=item snd $port, @msg
288		258
289	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
290	a local or a remote port, and must be a port ID.	260	local or a remote port, and must be a port ID.
291		261
292	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
293	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
294	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.
295		266
296	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
297	function: modifying any argument is not allowed and can cause many	268	function: modifying any argument (or values referenced by them) is
298	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.
299		273
300	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
301	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
302	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
303	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
304	node, anything can be passed.	278	node, anything can be passed. Best rely only on the common denominator of
		279	these.
305		280
306	=item $local_port = port	281	=item $local_port = port
307		282
308	Create a new local port object and returns its port ID. Initially it has	283	Create a new local port object and returns its port ID. Initially it has
309	no callbacks set and will throw an error when it receives messages.	284	no callbacks set and will throw an error when it receives messages.
…		…
394		369
395	=cut	370	=cut
396		371
397	sub rcv($@) {	372	sub rcv($@) {
398	my $port = shift;	373	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	374	my ($nodeid, $portid) = split /#/, $port, 2;
400		375
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	376	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	377	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		378
404	while (@_) {	379	while (@_) {
405	if (ref $_[0]) {	380	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	381	if (my $self = $PORT_DATA{$portid}) {
…		…
485	$res	460	$res
486	}	461	}
487	}	462	}
488	}	463	}
489		464
490	=item $guard = mon $port, $cb->(@reason)	465	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
491		466
492	=item $guard = mon $port, $rcvport	467	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
493		468
494	=item $guard = mon $port	469	=item $guard = mon $port # kill $SELF when $port dies
495		470
496	=item $guard = mon $port, $rcvport, @msg	471	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		472
498	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
499	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
500	to stop monitoring again.	475	to stop monitoring again.
501		476
502	C<mon> effectively guarantees that, in the absence of hardware failures,	477	C<mon> effectively guarantees that, in the absence of hardware failures,
503	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
504	will arrive, or the monitoring action will be invoked after possible	479	arrive, or the monitoring action will be invoked after possible message
505	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
506	(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
507	port). After the monitoring action was invoked, further messages might get	482	port). After the monitoring action was invoked, further messages might get
508	delivered again.	483	delivered again.
		484
		485	Note that monitoring-actions are one-shot: once messages are lost (and a
		486	monitoring alert was raised), they are removed and will not trigger again.
509		487
510	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
511	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
512	"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
513	C<eval> if unsure.	491	C<eval> if unsure.
514		492
515	In the second form (another port given), the other port (C<$rcvport>)	493	In the second form (another port given), the other port (C<$rcvport>)
516	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	494	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
517	"normal" kils nothing happens, while under all other conditions, the other	495	"normal" kils nothing happens, while under all other conditions, the other
518	port is killed with the same reason.	496	port is killed with the same reason.
519		497
520	The third form (kill self) is the same as the second form, except that	498	The third form (kill self) is the same as the second form, except that
521	C<$rvport> defaults to C<$SELF>.	499	C<$rvport> defaults to C<$SELF>.
…		…
524	C<snd>.	502	C<snd>.
525		503
526	As a rule of thumb, monitoring requests should always monitor a port from	504	As a rule of thumb, monitoring requests should always monitor a port from
527	a local port (or callback). The reason is that kill messages might get	505	a local port (or callback). The reason is that kill messages might get
528	lost, just like any other message. Another less obvious reason is that	506	lost, just like any other message. Another less obvious reason is that
529	even monitoring requests can get lost (for exmaple, when the connection	507	even monitoring requests can get lost (for example, when the connection
530	to the other node goes down permanently). When monitoring a port locally	508	to the other node goes down permanently). When monitoring a port locally
531	these problems do not exist.	509	these problems do not exist.
532		510
533	Example: call a given callback when C<$port> is killed.	511	Example: call a given callback when C<$port> is killed.
534		512
…		…
543	mon $port, $self => "restart";	521	mon $port, $self => "restart";
544		522
545	=cut	523	=cut
546		524
547	sub mon {	525	sub mon {
548	my ($noderef, $port) = split /#/, shift, 2;	526	my ($nodeid, $port) = split /#/, shift, 2;
549		527
550	my $node = $NODE{$noderef} \|\| add_node $noderef;	528	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
551		529
552	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,';
553		531
554	unless (ref $cb) {	532	unless (ref $cb) {
555	if (@_) {	533	if (@_) {
…		…
575	is killed, the references will be freed.	553	is killed, the references will be freed.
576		554
577	Optionally returns a guard that will stop the monitoring.	555	Optionally returns a guard that will stop the monitoring.
578		556
579	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
580	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>):
581		559
582	$port->rcv (start => sub {	560	$port->rcv (start => sub {
583	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	561	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
584	undef $timer if 0.9 < rand;	562	undef $timer if 0.9 < rand;
585	});	563	});
586	});	564	});
587		565
588	=cut	566	=cut
…		…
597		575
598	=item kil $port[, @reason]	576	=item kil $port[, @reason]
599		577
600	Kill the specified port with the given C<@reason>.	578	Kill the specified port with the given C<@reason>.
601		579
602	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
603	ports will not be kileld, or even notified).	581	monitoring other ports will not necessarily die because a port dies
		582	"normally").
604		583
605	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
606	C<mon>, see below).	585	C<mon>, see above).
607		586
608	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
609	will be reported as reason C<< die => $@ >>.	588	will be reported as reason C<< die => $@ >>.
610		589
611	Transport/communication errors are reported as C<< transport_error =>	590	Transport/communication errors are reported as C<< transport_error =>
…		…
616	=item $port = spawn $node, $initfunc[, @initdata]	595	=item $port = spawn $node, $initfunc[, @initdata]
617		596
618	Creates a port on the node C<$node> (which can also be a port ID, in which	597	Creates a port on the node C<$node> (which can also be a port ID, in which
619	case it's the node where that port resides).	598	case it's the node where that port resides).
620		599
621	The port ID of the newly created port is return immediately, and it is	600	The port ID of the newly created port is returned immediately, and it is
622	permissible to immediately start sending messages or monitor the port.	601	possible to immediately start sending messages or to monitor the port.
623		602
624	After the port has been created, the init function is	603	After the port has been created, the init function is called on the remote
625	called. This function must be a fully-qualified function name	604	node, in the same context as a C<rcv> callback. This function must be a
626	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	605	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
627	program, use C<::name>.	606	specify a function in the main program, use C<::name>.
628		607
629	If the function doesn't exist, then the node tries to C<require>	608	If the function doesn't exist, then the node tries to C<require>
630	the package, then the package above the package and so on (e.g.	609	the package, then the package above the package and so on (e.g.
631	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
632	exists or it runs out of package names.	611	exists or it runs out of package names.
633		612
634	The init function is then called with the newly-created port as context	613	The init function is then called with the newly-created port as context
635	object (C<$SELF>) and the C<@initdata> values as arguments.	614	object (C<$SELF>) and the C<@initdata> values as arguments.
636		615
637	A common idiom is to pass your own port, monitor the spawned port, and	616	A common idiom is to pass a local port, immediately monitor the spawned
638	in the init function, monitor the original port. This two-way monitoring	617	port, and in the remote init function, immediately monitor the passed
639	ensures that both ports get cleaned up when there is a problem.	618	local port. This two-way monitoring ensures that both ports get cleaned up
		619	when there is a problem.
640		620
641	Example: spawn a chat server port on C<$othernode>.	621	Example: spawn a chat server port on C<$othernode>.
642		622
643	# this node, executed from within a port context:	623	# this node, executed from within a port context:
644	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
667	};	647	};
668	_self_die if $@;	648	_self_die if $@;
669	}	649	}
670		650
671	sub spawn(@) {	651	sub spawn(@) {
672	my ($noderef, undef) = split /#/, shift, 2;	652	my ($nodeid, undef) = split /#/, shift, 2;
673		653
674	my $id = "$RUNIQ." . $ID++;	654	my $id = "$RUNIQ." . $ID++;
675		655
676	$_[0] =~ /::/	656	$_[0] =~ /::/
677	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";
678		658
679	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	659	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
680		660
681	"$noderef#$id"	661	"$nodeid#$id"
		662	}
		663
		664	=item after $timeout, @msg
		665
		666	=item after $timeout, $callback
		667
		668	Either sends the given message, or call the given callback, after the
		669	specified number of seconds.
		670
		671	This is simply a utility function that comes in handy at times - the
		672	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		673	so it may go away in the future.
		674
		675	=cut
		676
		677	sub after($@) {
		678	my ($timeout, @action) = @_;
		679
		680	my $t; $t = AE::timer $timeout, 0, sub {
		681	undef $t;
		682	ref $action[0]
		683	? $action[0]()
		684	: snd @action;
		685	};
682	}	686	}
683		687
684	=back	688	=back
685		689
686	=head1 AnyEvent::MP vs. Distributed Erlang	690	=head1 AnyEvent::MP vs. Distributed Erlang
…		…
697		701
698	Despite the similarities, there are also some important differences:	702	Despite the similarities, there are also some important differences:
699		703
700	=over 4	704	=over 4
701		705
702	=item * Node references contain the recipe on how to contact them.	706	=item * Node IDs are arbitrary strings in AEMP.
703		707
704	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
705	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
706	convenience functionality.	710	configuration or DNS), but will otherwise discover other odes itself.
707
708	This means that AEMP requires a less tightly controlled environment at the
709	cost of longer node references and a slightly higher management overhead.
710		711
711	=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
712	uses "local ports are like remote ports".	713	uses "local ports are like remote ports".
713		714
714	The failure modes for local ports are quite different (runtime errors	715	The failure modes for local ports are quite different (runtime errors
…		…
727		728
728	Erlang uses processes that selectively receive messages, and therefore	729	Erlang uses processes that selectively receive messages, and therefore
729	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
730	useful purpose. For the same reason the pattern-matching abilities of	731	useful purpose. For the same reason the pattern-matching abilities of
731	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
732	filter messages without dequeing them.	733	filter messages without dequeuing them.
733		734
734	(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).
735		736
736	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	737	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
737		738
…		…
743		744
744	Erlang makes few guarantees on messages delivery - messages can get lost	745	Erlang makes few guarantees on messages delivery - messages can get lost
745	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,
746	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).
747		748
748	AEMP guarantees correct ordering, and the guarantee that there are no	749	AEMP guarantees correct ordering, and the guarantee that after one message
749	holes in the message sequence.	750	is lost, all following ones sent to the same port are lost as well, until
750		751	monitoring raises an error, so there are no silent "holes" in the message
751	=item * In Erlang, processes can be declared dead and later be found to be	752	sequence.
752	alive.
753
754	In Erlang it can happen that a monitored process is declared dead and
755	linked processes get killed, but later it turns out that the process is
756	still alive - and can receive messages.
757
758	In AEMP, when port monitoring detects a port as dead, then that port will
759	eventually be killed - it cannot happen that a node detects a port as dead
760	and then later sends messages to it, finding it is still alive.
761		753
762	=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.
763		755
764	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
765	known to other nodes for a completely different process, causing messages	757	known to other nodes for a completely different process, causing messages
…		…
769	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.
770		762
771	=item * Erlang uses unprotected connections, AEMP uses secure	763	=item * Erlang uses unprotected connections, AEMP uses secure
772	authentication and can use TLS.	764	authentication and can use TLS.
773		765
774	AEMP can use a proven protocol - SSL/TLS - to protect connections and	766	AEMP can use a proven protocol - TLS - to protect connections and
775	securely authenticate nodes.	767	securely authenticate nodes.
776		768
777	=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
778	communications.	770	communications.
779		771
780	The AEMP protocol, unlike the Erlang protocol, supports both	772	The AEMP protocol, unlike the Erlang protocol, supports both programming
781	language-independent text-only protocols (good for debugging) and binary,	773	language independent text-only protocols (good for debugging) and binary,
782	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.
783		776
784	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
785	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
786	protocol simple.	779	protocol simple.
787		780
788	=item * AEMP has more flexible monitoring options than Erlang.	781	=item * AEMP has more flexible monitoring options than Erlang.
789		782
790	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
…		…
793	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
794	on a per-process basis.	787	on a per-process basis.
795		788
796	=item * Erlang tries to hide remote/local connections, AEMP does not.	789	=item * Erlang tries to hide remote/local connections, AEMP does not.
797		790
798	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
799	as linking is (except linking is unreliable in Erlang).	792	same way as linking is (except linking is unreliable in Erlang).
800		793
801	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
802	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
803	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
804	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
805	more reliable.	798	reliable (no need for C<spawn_link>).
806		799
807	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
808	(hard to do in Erlang).	801	(hard to do in Erlang).
809		802
810	=back	803	=back
811		804
812	=head1 RATIONALE	805	=head1 RATIONALE
813		806
814	=over 4	807	=over 4
815		808
816	=item Why strings for ports and noderefs, why not objects?	809	=item Why strings for port and node IDs, why not objects?
817		810
818	We considered "objects", but found that the actual number of methods	811	We considered "objects", but found that the actual number of methods
819	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
820	the network frequently, the serialising/deserialising would add lots of	813	the network frequently, the serialising/deserialising would add lots of
821	overhead, as well as having to keep a proxy object.	814	overhead, as well as having to keep a proxy object everywhere.
822		815
823	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
824	procedures to be "valid".	817	procedures to be "valid".
825		818
826	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
827	can't become much cheaper.	820	global hash - it can't become much cheaper.
828		821
829	=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?
830		823
831	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
832	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
833	default.	826	default (although all nodes will accept it).
834		827
835	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
836	faster for small messages and b) most importantly, after years of	829	faster for small messages and b) most importantly, after years of
837	experience we found that object serialisation is causing more problems	830	experience we found that object serialisation is causing more problems
838	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
839	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
840	always have to re-think your design.	833	always have to re-think your design.
841		834
842	Keeping your messages simple, concentrating on data structures rather than	835	Keeping your messages simple, concentrating on data structures rather than
843	objects, will keep your messages clean, tidy and efficient.	836	objects, will keep your messages clean, tidy and efficient.
844		837
845	=back	838	=back
846		839
847	=head1 SEE ALSO	840	=head1 SEE ALSO
848		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
849	L<AnyEvent>.	849	L<AnyEvent>.
850		850
851	=head1 AUTHOR	851	=head1 AUTHOR
852		852
853	Marc Lehmann <schmorp@schmorp.de>	853	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC