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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC vs.
Revision 1.84 by root, Tue Sep 8 01:42:14 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 $somple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, type 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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.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 but incomplete, 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	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
73		68
74	Some ports allow you to register C<rcv> handlers that can match specific	69	Ports allow you to register C<rcv> handlers that can match all or just
75	messages. All C<rcv> handlers will receive messages they match, messages	70	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	71	anything was listening for them or not.
77		72
78	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
79		74
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
81	separator, and a port name (a printable string of unspecified format). An	76	separator, and a port name (a printable string of unspecified format).
82	exception is the the node port, whose ID is identical to its node
83	reference.
84		77
85	=item node	78	=item node
86		79
87	A node is a single process containing at least one port - the node	80	A node is a single process containing at least one port - the node port,
88	port. You can send messages to node ports to find existing ports or to	81	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	82	ports.
90		83
91	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
93		87
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
95		89
96	A node reference is a string that either simply identifies the node (for	90	A node ID is a string that uniquely identifies the node within a
97	private and slave nodes), or contains a recipe on how to reach a given	91	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
99		94
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		96
103	Node references come in two flavours: resolved (containing only numerical	97	Nodes can only talk to each other by creating some kind of connection to
104	addresses) or unresolved (where hostnames are used instead of addresses).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
105		101
106	Before using an unresolved node reference in a message you first have to	102	=item seed nodes
107	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of the AnyEvent::MP network.
		115
		116	Seed nodes are expected to be long-running, and at least one seed node
		117	should always be available.
		118
		119	=item seeds - C<host:port>
		120
		121	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		122	TCP port) of nodes thta should be used as seed nodes.
		123
		124	The nodes listening on those endpoints are expected to be long-running,
		125	and at least one of those should always be available. When nodes run out
		126	of connections (e.g. due to a network error), they try to re-establish
		127	connections to some seednodes again to join the network.
108		128
109	=back	129	=back
110		130
111	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
112		132
…		…
127	use base "Exporter";	147	use base "Exporter";
128		148
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
130		150
131	our @EXPORT = qw(	151	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	152	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	153	configure
134	snd rcv mon kil reg psub spawn	154	snd rcv mon mon_guard kil reg psub spawn
135	port	155	port
136	);	156	);
137		157
138	our $SELF;	158	our $SELF;
139		159
…		…
143	kil $SELF, die => $msg;	163	kil $SELF, die => $msg;
144	}	164	}
145		165
146	=item $thisnode = NODE / $NODE	166	=item $thisnode = NODE / $NODE
147		167
148	The C<NODE> function returns, and the C<$NODE> variable contains	168	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	the noderef of the local node. The value is initialised by a call	169	ID of the node running in the current process. This value is initialised by
150	to C<become_public> or C<become_slave>, after which all local port	170	a call to C<configure>.
151	identifiers become invalid.
152		171
153	=item $noderef = node_of $port	172	=item $nodeid = node_of $port
154		173
155	Extracts and returns the noderef from a portid or a noderef.	174	Extracts and returns the node ID from a port ID or a node ID.
156		175
157	=item initialise_node $noderef, $seednode, $seednode...	176	=item configure $profile, key => value...
158		177
159	=item initialise_node "slave/", $master, $master...	178	=item configure key => value...
160		179
161	Before a node can talk to other nodes on the network it has to initialise	180	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	181	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	182	to know is its own name, and optionally it should know the addresses of
		183	some other nodes in the network to discover other nodes.
164		184
165	This function initialises a node - it must be called exactly once (or	185	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	186	never) before calling other AnyEvent::MP functions.
167		187
168	All arguments (optionally except for the first) are noderefs, which can be
169	either resolved or unresolved.
170
171	The first argument will be looked up in the configuration database first
172	(if it is C<undef> then the current nodename will be used instead) to find
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176
177	There are two types of networked nodes, public nodes and slave nodes:
178
179	=over 4	188	=over 4
180		189
181	=item public nodes	190	=item step 1, gathering configuration from profiles
182		191
183	For public nodes, C<$noderef> (supplied either directly to	192	The function first looks up a profile in the aemp configuration (see the
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	193	L<aemp> commandline utility). The profile name can be specified via the
185	noderef (possibly unresolved, in which case it will be resolved).	194	named C<profile> parameter or can simply be the first parameter). If it is
		195	missing, then the nodename (F<uname -n>) will be used as profile name.
186		196
187	After resolving, the node will bind itself on all endpoints and try to	197	The profile data is then gathered as follows:
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191		198
192	=item slave nodes	199	First, all remaining key => value pairs (all of which are conveniently
		200	undocumented at the moment) will be interpreted as configuration
		201	data. Then they will be overwritten by any values specified in the global
		202	default configuration (see the F<aemp> utility), then the chain of
		203	profiles chosen by the profile name (and any C<parent> attributes).
193		204
194	When the C<$noderef> (either as given or overriden by the config file)	205	That means that the values specified in the profile have highest priority
195	is the special string C<slave/>, then the node will become a slave	206	and the values specified directly via C<configure> have lowest priority,
196	node. Slave nodes cannot be contacted from outside and will route most of	207	and can only be used to specify defaults.
197	their traffic to the master node that they attach to.
198		208
199	At least one additional noderef is required (either by specifying it	209	If the profile specifies a node ID, then this will become the node ID of
200	directly or because it is part of the configuration profile): The node	210	this process. If not, then the profile name will be used as node ID. The
201	will try to connect to all of them and will become a slave attached to the	211	special node ID of C<anon/> will be replaced by a random node ID.
202	first node it can successfully connect to.	212
		213	=item step 2, bind listener sockets
		214
		215	The next step is to look up the binds in the profile, followed by binding
		216	aemp protocol listeners on all binds specified (it is possible and valid
		217	to have no binds, meaning that the node cannot be contacted form the
		218	outside. This means the node cannot talk to other nodes that also have no
		219	binds, but it can still talk to all "normal" nodes).
		220
		221	If the profile does not specify a binds list, then a default of C<*> is
		222	used, meaning the node will bind on a dynamically-assigned port on every
		223	local IP address it finds.
		224
		225	=item step 3, connect to seed nodes
		226
		227	As the last step, the seeds list from the profile is passed to the
		228	L<AnyEvent::MP::Global> module, which will then use it to keep
		229	connectivity with at least one node at any point in time.
203		230
204	=back	231	=back
205		232
206	This function will block until all nodes have been resolved and, for slave	233	Example: become a distributed node using the locla node name as profile.
207	nodes, until it has successfully established a connection to a master	234	This should be the most common form of invocation for "daemon"-type nodes.
208	server.
209		235
210	Example: become a public node listening on the guessed noderef, or the one	236	configure
211	specified via C<aemp> for the current node. This should be the most common
212	form of invocation for "daemon"-type nodes.
213		237
214	initialise_node;	238	Example: become an anonymous node. This form is often used for commandline
		239	clients.
215		240
216	Example: become a slave node to any of the the seednodes specified via	241	configure nodeid => "anon/";
217	C<aemp>. This form is often used for commandline clients.
218		242
219	initialise_node "slave/";	243	Example: configure a node using a profile called seed, which si suitable
		244	for a seed node as it binds on all local addresses on a fixed port (4040,
		245	customary for aemp).
220		246
221	Example: become a slave node to any of the specified master servers. This	247	# use the aemp commandline utility
222	form is also often used for commandline clients.	248	# aemp profile seed nodeid anon/ binds '*:4040'
223		249
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	250	# then use it
		251	configure profile => "seed";
225		252
226	Example: become a public node, and try to contact some well-known master	253	# or simply use aemp from the shell again:
227	servers to become part of the network.	254	# aemp run profile seed
228		255
229	initialise_node undef, "master1", "master2";	256	# or provide a nicer-to-remember nodeid
230		257	# aemp run profile seed nodeid "$(hostname)"
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236
237	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4
249
250	=item the empty string
251
252	An empty-string component gets resolved as if the default port (4040) was
253	specified.
254
255	=item naked port numbers (e.g. C<1234>)
256
257	These are resolved by prepending the local nodename and a colon, to be
258	further resolved.
259
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
261
262	These are resolved by using AnyEvent::DNS to resolve them, optionally
263	looking up SRV records for the C<aemp=4040> port, if no port was
264	specified.
265
266	=back
267		258
268	=item $SELF	259	=item $SELF
269		260
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	261	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	262	blocks.
272		263
273	=item SELF, %SELF, @SELF...	264	=item *SELF, SELF, %SELF, @SELF...
274		265
275	Due to some quirks in how perl exports variables, it is impossible to	266	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	267	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	268	module, but only C<$SELF> is currently used.
278		269
279	=item snd $port, type => @data	270	=item snd $port, type => @data
280		271
281	=item snd $port, @msg	272	=item snd $port, @msg
282		273
283	Send the given message to the given port ID, which can identify either	274	Send the given message to the given port, which can identify either a
284	a local or a remote port, and can be either a string or soemthignt hat	275	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		276
287	While the message can be about anything, it is highly recommended to use a	277	While the message can be almost anything, it is highly recommended to
288	string as first element (a portid, or some word that indicates a request	278	use a string as first element (a port ID, or some word that indicates a
289	type etc.).	279	request type etc.) and to consist if only simple perl values (scalars,
		280	arrays, hashes) - if you think you need to pass an object, think again.
290		281
291	The message data effectively becomes read-only after a call to this	282	The message data logically becomes read-only after a call to this
292	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
293	problems.	284	forbidden, as there can be considerable time between the call to C<snd>
		285	and the time the message is actually being serialised - in fact, it might
		286	never be copied as within the same process it is simply handed to the
		287	receiving port.
294		288
295	The type of data you can transfer depends on the transport protocol: when	289	The type of data you can transfer depends on the transport protocol: when
296	JSON is used, then only strings, numbers and arrays and hashes consisting	290	JSON is used, then only strings, numbers and arrays and hashes consisting
297	of those are allowed (no objects). When Storable is used, then anything	291	of those are allowed (no objects). When Storable is used, then anything
298	that Storable can serialise and deserialise is allowed, and for the local	292	that Storable can serialise and deserialise is allowed, and for the local
299	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
300		295
301	=item $local_port = port	296	=item $local_port = port
302		297
303	Create a new local port object and returns its port ID. Initially it has	298	Create a new local port object and returns its port ID. Initially it has
304	no callbacks set and will throw an error when it receives messages.	299	no callbacks set and will throw an error when it receives messages.
…		…
351	The default callback received all messages not matched by a more specific	346	The default callback received all messages not matched by a more specific
352	C<tag> match.	347	C<tag> match.
353		348
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	349	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		350
356	Register callbacks to be called on messages starting with the given tag on	351	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	352	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	353	C<$callback> is C<$undef> or missing). There can only be one callback
		354	registered for each tag.
359		355
360	The original message will be passed to the callback, after the first	356	The original message will be passed to the callback, after the first
361	element (the tag) has been removed. The callback will use the same	357	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	358	environment as the default callback (see above).
363		359
…		…
375	rcv port,	371	rcv port,
376	msg1 => sub { ... },	372	msg1 => sub { ... },
377	...	373	...
378	;	374	;
379		375
		376	Example: temporarily register a rcv callback for a tag matching some port
		377	(e.g. for a rpc reply) and unregister it after a message was received.
		378
		379	rcv $port, $otherport => sub {
		380	my @reply = @_;
		381
		382	rcv $SELF, $otherport;
		383	};
		384
380	=cut	385	=cut
381		386
382	sub rcv($@) {	387	sub rcv($@) {
383	my $port = shift;	388	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	389	my ($nodeid, $portid) = split /#/, $port, 2;
385		390
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	391	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	392	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		393
389	while (@_) {	394	while (@_) {
390	if (ref $_[0]) {	395	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	396	if (my $self = $PORT_DATA{$portid}) {
…		…
470	$res	475	$res
471	}	476	}
472	}	477	}
473	}	478	}
474		479
475	=item $guard = mon $port, $cb->(@reason)	480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		481
477	=item $guard = mon $port, $rcvport	482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		483
479	=item $guard = mon $port	484	=item $guard = mon $port # kill $SELF when $port dies
480		485
481	=item $guard = mon $port, $rcvport, @msg	486	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		487
483	Monitor the given port and do something when the port is killed or	488	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	489	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	490	to stop monitoring again.
486
487	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port
489	will arrive, or the monitoring action will be invoked after possible
490	message loss has been detected. No messages will be lost "in between"
491	(after the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get
493	delivered again.
494		491
495	In the first form (callback), the callback is simply called with any	492	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	495	C<eval> if unsure.
499		496
500	In the second form (another port given), the other port (C<$rcvport>)	497	In the second form (another port given), the other port (C<$rcvport>)
501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
502	"normal" kils nothing happens, while under all other conditions, the other	499	"normal" kils nothing happens, while under all other conditions, the other
503	port is killed with the same reason.	500	port is killed with the same reason.
504		501
505	The third form (kill self) is the same as the second form, except that	502	The third form (kill self) is the same as the second form, except that
506	C<$rvport> defaults to C<$SELF>.	503	C<$rvport> defaults to C<$SELF>.
507		504
508	In the last form (message), a message of the form C<@msg, @reason> will be	505	In the last form (message), a message of the form C<@msg, @reason> will be
509	C<snd>.	506	C<snd>.
		507
		508	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		509	alert was raised), they are removed and will not trigger again.
510		510
511	As a rule of thumb, monitoring requests should always monitor a port from	511	As a rule of thumb, monitoring requests should always monitor a port from
512	a local port (or callback). The reason is that kill messages might get	512	a local port (or callback). The reason is that kill messages might get
513	lost, just like any other message. Another less obvious reason is that	513	lost, just like any other message. Another less obvious reason is that
514	even monitoring requests can get lost (for exmaple, when the connection	514	even monitoring requests can get lost (for example, when the connection
515	to the other node goes down permanently). When monitoring a port locally	515	to the other node goes down permanently). When monitoring a port locally
516	these problems do not exist.	516	these problems do not exist.
517		517
		518	C<mon> effectively guarantees that, in the absence of hardware failures,
		519	after starting the monitor, either all messages sent to the port will
		520	arrive, or the monitoring action will be invoked after possible message
		521	loss has been detected. No messages will be lost "in between" (after
		522	the first lost message no further messages will be received by the
		523	port). After the monitoring action was invoked, further messages might get
		524	delivered again.
		525
		526	Inter-host-connection timeouts and monitoring depend on the transport
		527	used. The only transport currently implemented is TCP, and AnyEvent::MP
		528	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		529	non-idle connection, and usually around two hours for idle conenctions).
		530
		531	This means that monitoring is good for program errors and cleaning up
		532	stuff eventually, but they are no replacement for a timeout when you need
		533	to ensure some maximum latency.
		534
518	Example: call a given callback when C<$port> is killed.	535	Example: call a given callback when C<$port> is killed.
519		536
520	mon $port, sub { warn "port died because of <@_>\n" };	537	mon $port, sub { warn "port died because of <@_>\n" };
521		538
522	Example: kill ourselves when C<$port> is killed abnormally.	539	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	545	mon $port, $self => "restart";
529		546
530	=cut	547	=cut
531		548
532	sub mon {	549	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	550	my ($nodeid, $port) = split /#/, shift, 2;
534		551
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	552	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		553
537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	554	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		555
539	unless (ref $cb) {	556	unless (ref $cb) {
540	if (@_) {	557	if (@_) {
…		…
560	is killed, the references will be freed.	577	is killed, the references will be freed.
561		578
562	Optionally returns a guard that will stop the monitoring.	579	Optionally returns a guard that will stop the monitoring.
563		580
564	This function is useful when you create e.g. timers or other watchers and	581	This function is useful when you create e.g. timers or other watchers and
565	want to free them when the port gets killed:	582	want to free them when the port gets killed (note the use of C<psub>):
566		583
567	$port->rcv (start => sub {	584	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	585	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	586	undef $timer if 0.9 < rand;
570	});	587	});
571	});	588	});
572		589
573	=cut	590	=cut
…		…
582		599
583	=item kil $port[, @reason]	600	=item kil $port[, @reason]
584		601
585	Kill the specified port with the given C<@reason>.	602	Kill the specified port with the given C<@reason>.
586		603
587	If no C<@reason> is specified, then the port is killed "normally" (linked	604	If no C<@reason> is specified, then the port is killed "normally" (ports
588	ports will not be kileld, or even notified).	605	monitoring other ports will not necessarily die because a port dies
		606	"normally").
589		607
590	Otherwise, linked ports get killed with the same reason (second form of	608	Otherwise, linked ports get killed with the same reason (second form of
591	C<mon>, see below).	609	C<mon>, see above).
592		610
593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
594	will be reported as reason C<< die => $@ >>.	612	will be reported as reason C<< die => $@ >>.
595		613
596	Transport/communication errors are reported as C<< transport_error =>	614	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	619	=item $port = spawn $node, $initfunc[, @initdata]
602		620
603	Creates a port on the node C<$node> (which can also be a port ID, in which	621	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	622	case it's the node where that port resides).
605		623
606	The port ID of the newly created port is return immediately, and it is	624	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	625	possible to immediately start sending messages or to monitor the port.
608		626
609	After the port has been created, the init function is	627	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	628	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	629	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	630	specify a function in the main program, use C<::name>.
613		631
614	If the function doesn't exist, then the node tries to C<require>	632	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	633	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	635	exists or it runs out of package names.
618		636
619	The init function is then called with the newly-created port as context	637	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	638	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		639	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		640	the port might not get created.
621		641
622	A common idiom is to pass your own port, monitor the spawned port, and	642	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	643	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	644	local port. This two-way monitoring ensures that both ports get cleaned up
		645	when there is a problem.
		646
		647	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
625		650
626	Example: spawn a chat server port on C<$othernode>.	651	Example: spawn a chat server port on C<$othernode>.
627		652
628	# this node, executed from within a port context:	653	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
644		669
645	sub _spawn {	670	sub _spawn {
646	my $port = shift;	671	my $port = shift;
647	my $init = shift;	672	my $init = shift;
648		673
		674	# rcv will create the actual port
649	local $SELF = "$NODE#$port";	675	local $SELF = "$NODE#$port";
650	eval {	676	eval {
651	&{ load_func $init }	677	&{ load_func $init }
652	};	678	};
653	_self_die if $@;	679	_self_die if $@;
654	}	680	}
655		681
656	sub spawn(@) {	682	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	683	my ($nodeid, undef) = split /#/, shift, 2;
658		684
659	my $id = "$RUNIQ." . $ID++;	685	my $id = "$RUNIQ." . $ID++;
660		686
661	$_[0] =~ /::/	687	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		689
664	($NODE{$noderef} \|\| add_node $noderef)	690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		691
667	"$noderef#$id"	692	"$nodeid#$id"
668	}	693	}
669		694
670	=back	695	=item after $timeout, @msg
671		696
672	=head1 NODE MESSAGES	697	=item after $timeout, $callback
673		698
674	Nodes understand the following messages sent to them. Many of them take	699	Either sends the given message, or call the given callback, after the
675	arguments called C<@reply>, which will simply be used to compose a reply	700	specified number of seconds.
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
677	the remaining arguments are simply the message data.
678		701
679	While other messages exist, they are not public and subject to change.	702	This is simply a utility function that comes in handy at times - the
		703	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		704	so it may go away in the future.
680		705
681	=over 4
682
683	=cut	706	=cut
684		707
685	=item lookup => $name, @reply	708	sub after($@) {
		709	my ($timeout, @action) = @_;
686		710
687	Replies with the port ID of the specified well-known port, or C<undef>.	711	my $t; $t = AE::timer $timeout, 0, sub {
688		712	undef $t;
689	=item devnull => ...	713	ref $action[0]
690		714	? $action[0]()
691	Generic data sink/CPU heat conversion.	715	: snd @action;
692		716	};
693	=item relay => $port, @msg	717	}
694
695	Simply forwards the message to the given port.
696
697	=item eval => $string[ @reply]
698
699	Evaluates the given string. If C<@reply> is given, then a message of the
700	form C<@reply, $@, @evalres> is sent.
701
702	Example: crash another node.
703
704	snd $othernode, eval => "exit";
705
706	=item time => @reply
707
708	Replies the the current node time to C<@reply>.
709
710	Example: tell the current node to send the current time to C<$myport> in a
711	C<timereply> message.
712
713	snd $NODE, time => $myport, timereply => 1, 2;
714	# => snd $myport, timereply => 1, 2, <time>
715		718
716	=back	719	=back
717		720
718	=head1 AnyEvent::MP vs. Distributed Erlang	721	=head1 AnyEvent::MP vs. Distributed Erlang
719		722
…		…
729		732
730	Despite the similarities, there are also some important differences:	733	Despite the similarities, there are also some important differences:
731		734
732	=over 4	735	=over 4
733		736
734	=item * Node references contain the recipe on how to contact them.	737	=item * Node IDs are arbitrary strings in AEMP.
735		738
736	Erlang relies on special naming and DNS to work everywhere in the	739	Erlang relies on special naming and DNS to work everywhere in the same
737	same way. AEMP relies on each node knowing it's own address(es), with	740	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
738	convenience functionality.	741	configuration or DNS), but will otherwise discover other odes itself.
739		742
740	This means that AEMP requires a less tightly controlled environment at the
741	cost of longer node references and a slightly higher management overhead.
742
743	=item Erlang has a "remote ports are like local ports" philosophy, AEMP	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
744	uses "local ports are like remote ports".	744	uses "local ports are like remote ports".
745		745
746	The failure modes for local ports are quite different (runtime errors	746	The failure modes for local ports are quite different (runtime errors
747	only) then for remote ports - when a local port dies, you I<know> it dies,	747	only) then for remote ports - when a local port dies, you I<know> it dies,
748	when a connection to another node dies, you know nothing about the other	748	when a connection to another node dies, you know nothing about the other
…		…
759		759
760	Erlang uses processes that selectively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
761	needs a queue. AEMP is event based, queuing messages would serve no	761	needs a queue. AEMP is event based, queuing messages would serve no
762	useful purpose. For the same reason the pattern-matching abilities of	762	useful purpose. For the same reason the pattern-matching abilities of
763	AnyEvent::MP are more limited, as there is little need to be able to	763	AnyEvent::MP are more limited, as there is little need to be able to
764	filter messages without dequeing them.	764	filter messages without dequeuing them.
765		765
766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
767		767
768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
769		769
…		…
775		775
776	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
777	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
778	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
779		779
780	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that after one message
781	holes in the message sequence.	781	is lost, all following ones sent to the same port are lost as well, until
782		782	monitoring raises an error, so there are no silent "holes" in the message
783	=item * In Erlang, processes can be declared dead and later be found to be	783	sequence.
784	alive.
785
786	In Erlang it can happen that a monitored process is declared dead and
787	linked processes get killed, but later it turns out that the process is
788	still alive - and can receive messages.
789
790	In AEMP, when port monitoring detects a port as dead, then that port will
791	eventually be killed - it cannot happen that a node detects a port as dead
792	and then later sends messages to it, finding it is still alive.
793		784
794	=item * Erlang can send messages to the wrong port, AEMP does not.	785	=item * Erlang can send messages to the wrong port, AEMP does not.
795		786
796	In Erlang it is quite likely that a node that restarts reuses a process ID	787	In Erlang it is quite likely that a node that restarts reuses a process ID
797	known to other nodes for a completely different process, causing messages	788	known to other nodes for a completely different process, causing messages
…		…
801	around in the network will not be sent to an unrelated port.	792	around in the network will not be sent to an unrelated port.
802		793
803	=item * Erlang uses unprotected connections, AEMP uses secure	794	=item * Erlang uses unprotected connections, AEMP uses secure
804	authentication and can use TLS.	795	authentication and can use TLS.
805		796
806	AEMP can use a proven protocol - SSL/TLS - to protect connections and	797	AEMP can use a proven protocol - TLS - to protect connections and
807	securely authenticate nodes.	798	securely authenticate nodes.
808		799
809	=item * The AEMP protocol is optimised for both text-based and binary	800	=item * The AEMP protocol is optimised for both text-based and binary
810	communications.	801	communications.
811		802
812	The AEMP protocol, unlike the Erlang protocol, supports both	803	The AEMP protocol, unlike the Erlang protocol, supports both programming
813	language-independent text-only protocols (good for debugging) and binary,	804	language independent text-only protocols (good for debugging) and binary,
814	language-specific serialisers (e.g. Storable).	805	language-specific serialisers (e.g. Storable). By default, unless TLS is
		806	used, the protocol is actually completely text-based.
815		807
816	It has also been carefully designed to be implementable in other languages	808	It has also been carefully designed to be implementable in other languages
817	with a minimum of work while gracefully degrading fucntionality to make the	809	with a minimum of work while gracefully degrading functionality to make the
818	protocol simple.	810	protocol simple.
819		811
820	=item * AEMP has more flexible monitoring options than Erlang.	812	=item * AEMP has more flexible monitoring options than Erlang.
821		813
822	In Erlang, you can chose to receive I<all> exit signals as messages	814	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
825	Erlang, as one can choose between automatic kill, exit message or callback	817	Erlang, as one can choose between automatic kill, exit message or callback
826	on a per-process basis.	818	on a per-process basis.
827		819
828	=item * Erlang tries to hide remote/local connections, AEMP does not.	820	=item * Erlang tries to hide remote/local connections, AEMP does not.
829		821
830	Monitoring in Erlang is not an indicator of process death/crashes,	822	Monitoring in Erlang is not an indicator of process death/crashes, in the
831	as linking is (except linking is unreliable in Erlang).	823	same way as linking is (except linking is unreliable in Erlang).
832		824
833	In AEMP, you don't "look up" registered port names or send to named ports	825	In AEMP, you don't "look up" registered port names or send to named ports
834	that might or might not be persistent. Instead, you normally spawn a port	826	that might or might not be persistent. Instead, you normally spawn a port
835	on the remote node. The init function monitors the you, and you monitor	827	on the remote node. The init function monitors you, and you monitor the
836	the remote port. Since both monitors are local to the node, they are much	828	remote port. Since both monitors are local to the node, they are much more
837	more reliable.	829	reliable (no need for C<spawn_link>).
838		830
839	This also saves round-trips and avoids sending messages to the wrong port	831	This also saves round-trips and avoids sending messages to the wrong port
840	(hard to do in Erlang).	832	(hard to do in Erlang).
841		833
842	=back	834	=back
843		835
844	=head1 RATIONALE	836	=head1 RATIONALE
845		837
846	=over 4	838	=over 4
847		839
848	=item Why strings for ports and noderefs, why not objects?	840	=item Why strings for port and node IDs, why not objects?
849		841
850	We considered "objects", but found that the actual number of methods	842	We considered "objects", but found that the actual number of methods
851	thatc an be called are very low. Since port IDs and noderefs travel over	843	that can be called are quite low. Since port and node IDs travel over
852	the network frequently, the serialising/deserialising would add lots of	844	the network frequently, the serialising/deserialising would add lots of
853	overhead, as well as having to keep a proxy object.	845	overhead, as well as having to keep a proxy object everywhere.
854		846
855	Strings can easily be printed, easily serialised etc. and need no special	847	Strings can easily be printed, easily serialised etc. and need no special
856	procedures to be "valid".	848	procedures to be "valid".
857		849
858	And a a miniport consists of a single closure stored in a global hash - it	850	And as a result, a miniport consists of a single closure stored in a
859	can't become much cheaper.	851	global hash - it can't become much cheaper.
860		852
861	=item Why favour JSON, why not real serialising format such as Storable?	853	=item Why favour JSON, why not a real serialising format such as Storable?
862		854
863	In fact, any AnyEvent::MP node will happily accept Storable as framing	855	In fact, any AnyEvent::MP node will happily accept Storable as framing
864	format, but currently there is no way to make a node use Storable by	856	format, but currently there is no way to make a node use Storable by
865	default.	857	default (although all nodes will accept it).
866		858
867	The default framing protocol is JSON because a) JSON::XS is many times	859	The default framing protocol is JSON because a) JSON::XS is many times
868	faster for small messages and b) most importantly, after years of	860	faster for small messages and b) most importantly, after years of
869	experience we found that object serialisation is causing more problems	861	experience we found that object serialisation is causing more problems
870	than it gains: Just like function calls, objects simply do not travel	862	than it solves: Just like function calls, objects simply do not travel
871	easily over the network, mostly because they will always be a copy, so you	863	easily over the network, mostly because they will always be a copy, so you
872	always have to re-think your design.	864	always have to re-think your design.
873		865
874	Keeping your messages simple, concentrating on data structures rather than	866	Keeping your messages simple, concentrating on data structures rather than
875	objects, will keep your messages clean, tidy and efficient.	867	objects, will keep your messages clean, tidy and efficient.
876		868
877	=back	869	=back
878		870
879	=head1 SEE ALSO	871	=head1 SEE ALSO
880		872
		873	L<AnyEvent::MP::Intro> - a gentle introduction.
		874
		875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		876
		877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		878	your applications.
		879
		880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		881	all nodes.
		882
881	L<AnyEvent>.	883	L<AnyEvent>.
882		884
883	=head1 AUTHOR	885	=head1 AUTHOR
884		886
885	Marc Lehmann <schmorp@schmorp.de>	887	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC vs.
Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC