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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.83 by root, Tue Sep 8 01:38:16 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, 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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.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 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-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 the	168	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	noderef of the local node. The value is initialised by a call to	169	ID of the node running in the current process. This value is initialised by
150	C<initialise_node>.	170	a call to C<configure>.
151		171
152	=item $noderef = node_of $port	172	=item $nodeid = node_of $port
153		173
154	Extracts and returns the noderef from a port ID or a noderef.	174	Extracts and returns the node ID from a port ID or a node ID.
155		175
156	=item initialise_node $noderef, $seednode, $seednode...	176	=item configure $profile, key => value...
157		177
158	=item initialise_node "slave/", $master, $master...	178	=item configure key => value...
159		179
160	Before a node can talk to other nodes on the network it has to initialise	180	Before a node can talk to other nodes on the network (i.e. enter
161	itself - the minimum a node needs to know is it's own name, and optionally	181	"distributed mode") it has to configure itself - the minimum a node needs
162	it should know the noderefs of some other nodes in the network.	182	to know is its own name, and optionally it should know the addresses of
		183	some other nodes in the network to discover other nodes.
163		184
164	This function initialises a node - it must be called exactly once (or	185	This function configures a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	186	never) before calling other AnyEvent::MP functions.
166		187
167	All arguments (optionally except for the first) are noderefs, which can be
168	either resolved or unresolved.
169
170	The first argument will be looked up in the configuration database first
171	(if it is C<undef> then the current nodename will be used instead) to find
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175
176	There are two types of networked nodes, public nodes and slave nodes:
177
178	=over 4	188	=over 4
179		189
180	=item public nodes	190	=item step 1, gathering configuration from profiles
181		191
182	For public nodes, C<$noderef> (supplied either directly to	192	The function first looks up a profile in the aemp configuration (see the
183	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
184	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.
185		196
186	After resolving, the node will bind itself on all endpoints and try to	197	The profile data is then gathered as follows:
187	connect to all additional C<$seednodes> that are specified. Seednodes are
188	optional and can be used to quickly bootstrap the node into an existing
189	network.
190		198
191	=item slave nodes	199	First, all remaining key => value pairs (all of which are conveniently
		200	undocumented at the moment) will be interpreted as configuration
		201	data. Then they will be overwritten by any values specified in the global
		202	default configuration (see the F<aemp> utility), then the chain of
		203	profiles chosen by the profile name (and any C<parent> attributes).
192		204
193	When the C<$noderef> (either as given or overriden by the config file)	205	That means that the values specified in the profile have highest priority
194	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,
195	node. Slave nodes cannot be contacted from outside and will route most of	207	and can only be used to specify defaults.
196	their traffic to the master node that they attach to.
197		208
198	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
199	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
200	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.
201	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.
202		230
203	=back	231	=back
204		232
205	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.
206	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.
207	server.
208		235
209	Example: become a public node listening on the guessed noderef, or the one	236	configure
210	specified via C<aemp> for the current node. This should be the most common
211	form of invocation for "daemon"-type nodes.
212		237
213	initialise_node;	238	Example: become an anonymous node. This form is often used for commandline
		239	clients.
214		240
215	Example: become a slave node to any of the the seednodes specified via	241	configure nodeid => "anon/";
216	C<aemp>. This form is often used for commandline clients.
217		242
218	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).
219		246
220	Example: become a slave node to any of the specified master servers. This	247	# use the aemp commandline utility
221	form is also often used for commandline clients.	248	# aemp profile seed nodeid anon/ binds '*:4040'
222		249
223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	250	# then use it
		251	configure profile => "seed";
224		252
225	Example: become a public node, and try to contact some well-known master	253	# or simply use aemp from the shell again:
226	servers to become part of the network.	254	# aemp run profile seed
227		255
228	initialise_node undef, "master1", "master2";	256	# or provide a nicer-to-remember nodeid
229		257	# aemp run profile seed nodeid "$(hostname)"
230	Example: become a public node listening on port C<4041>.
231
232	initialise_node 4041;
233
234	Example: become a public node, only visible on localhost port 4044.
235
236	initialise_node "localhost:4044";
237
238	=item $cv = resolve_node $noderef
239
240	Takes an unresolved node reference that may contain hostnames and
241	abbreviated IDs, resolves all of them and returns a resolved node
242	reference.
243
244	In addition to C<address:port> pairs allowed in resolved noderefs, the
245	following forms are supported:
246
247	=over 4
248
249	=item the empty string
250
251	An empty-string component gets resolved as if the default port (4040) was
252	specified.
253
254	=item naked port numbers (e.g. C<1234>)
255
256	These are resolved by prepending the local nodename and a colon, to be
257	further resolved.
258
259	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
260
261	These are resolved by using AnyEvent::DNS to resolve them, optionally
262	looking up SRV records for the C<aemp=4040> port, if no port was
263	specified.
264
265	=back
266		258
267	=item $SELF	259	=item $SELF
268		260
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	261	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	262	blocks.
271		263
272	=item SELF, %SELF, @SELF...	264	=item *SELF, SELF, %SELF, @SELF...
273		265
274	Due to some quirks in how perl exports variables, it is impossible to	266	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	267	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	268	module, but only C<$SELF> is currently used.
277		269
278	=item snd $port, type => @data	270	=item snd $port, type => @data
279		271
280	=item snd $port, @msg	272	=item snd $port, @msg
281		273
282	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
283	a local or a remote port, and must be a port ID.	275	local or a remote port, and must be a port ID.
284		276
285	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
286	string as first element (a port ID, or some word that indicates a request	278	use a string as first element (a port ID, or some word that indicates a
287	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.
288		281
289	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
290	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
291	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.
292		288
293	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
294	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
295	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
296	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
297	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
298		295
299	=item $local_port = port	296	=item $local_port = port
300		297
301	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
302	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.
…		…
349	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
350	C<tag> match.	347	C<tag> match.
351		348
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	349	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		350
354	Register callbacks to be called on messages starting with the given tag on	351	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	352	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	353	C<$callback> is C<$undef> or missing). There can only be one callback
		354	registered for each tag.
357		355
358	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
359	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
360	environment as the default callback (see above).	358	environment as the default callback (see above).
361		359
…		…
373	rcv port,	371	rcv port,
374	msg1 => sub { ... },	372	msg1 => sub { ... },
375	...	373	...
376	;	374	;
377		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, $otherport;
		383	};
		384
378	=cut	385	=cut
379		386
380	sub rcv($@) {	387	sub rcv($@) {
381	my $port = shift;	388	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	389	my ($nodeid, $portid) = split /#/, $port, 2;
383		390
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	391	$NODE{$nodeid} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	392	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		393
387	while (@_) {	394	while (@_) {
388	if (ref $_[0]) {	395	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	396	if (my $self = $PORT_DATA{$portid}) {
…		…
468	$res	475	$res
469	}	476	}
470	}	477	}
471	}	478	}
472		479
473	=item $guard = mon $port, $cb->(@reason)	480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474		481
475	=item $guard = mon $port, $rcvport	482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476		483
477	=item $guard = mon $port	484	=item $guard = mon $port # kill $SELF when $port dies
478		485
479	=item $guard = mon $port, $rcvport, @msg	486	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		487
481	Monitor the given port and do something when the port is killed or	488	Monitor the given port and do something when the port is killed or
482	messages to it were lost, and optionally return a guard that can be used	489	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	490	to stop monitoring again.
484
485	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port
487	will arrive, or the monitoring action will be invoked after possible
488	message loss has been detected. No messages will be lost "in between"
489	(after the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get
491	delivered again.
492		491
493	In the first form (callback), the callback is simply called with any	492	In the first form (callback), the callback is simply called with any
494	number of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
495	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
496	C<eval> if unsure.	495	C<eval> if unsure.
497		496
498	In the second form (another port given), the other port (C<$rcvport>)	497	In the second form (another port given), the other port (C<$rcvport>)
499	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
500	"normal" kils nothing happens, while under all other conditions, the other	499	"normal" kils nothing happens, while under all other conditions, the other
501	port is killed with the same reason.	500	port is killed with the same reason.
502		501
503	The third form (kill self) is the same as the second form, except that	502	The third form (kill self) is the same as the second form, except that
504	C<$rvport> defaults to C<$SELF>.	503	C<$rvport> defaults to C<$SELF>.
505		504
506	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
507	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.
508		510
509	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
510	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
511	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
512	even monitoring requests can get lost (for exmaple, when the connection	514	even monitoring requests can get lost (for example, when the connection
513	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
514	these problems do not exist.	516	these problems do not exist.
515		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
516	Example: call a given callback when C<$port> is killed.	535	Example: call a given callback when C<$port> is killed.
517		536
518	mon $port, sub { warn "port died because of <@_>\n" };	537	mon $port, sub { warn "port died because of <@_>\n" };
519		538
520	Example: kill ourselves when C<$port> is killed abnormally.	539	Example: kill ourselves when C<$port> is killed abnormally.
…		…
526	mon $port, $self => "restart";	545	mon $port, $self => "restart";
527		546
528	=cut	547	=cut
529		548
530	sub mon {	549	sub mon {
531	my ($noderef, $port) = split /#/, shift, 2;	550	my ($nodeid, $port) = split /#/, shift, 2;
532		551
533	my $node = $NODE{$noderef} \|\| add_node $noderef;	552	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
534		553
535	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,';
536		555
537	unless (ref $cb) {	556	unless (ref $cb) {
538	if (@_) {	557	if (@_) {
…		…
558	is killed, the references will be freed.	577	is killed, the references will be freed.
559		578
560	Optionally returns a guard that will stop the monitoring.	579	Optionally returns a guard that will stop the monitoring.
561		580
562	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
563	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>):
564		583
565	$port->rcv (start => sub {	584	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	585	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	586	undef $timer if 0.9 < rand;
568	});	587	});
569	});	588	});
570		589
571	=cut	590	=cut
…		…
580		599
581	=item kil $port[, @reason]	600	=item kil $port[, @reason]
582		601
583	Kill the specified port with the given C<@reason>.	602	Kill the specified port with the given C<@reason>.
584		603
585	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
586	ports will not be kileld, or even notified).	605	monitoring other ports will not necessarily die because a port dies
		606	"normally").
587		607
588	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
589	C<mon>, see below).	609	C<mon>, see above).
590		610
591	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
592	will be reported as reason C<< die => $@ >>.	612	will be reported as reason C<< die => $@ >>.
593		613
594	Transport/communication errors are reported as C<< transport_error =>	614	Transport/communication errors are reported as C<< transport_error =>
…		…
599	=item $port = spawn $node, $initfunc[, @initdata]	619	=item $port = spawn $node, $initfunc[, @initdata]
600		620
601	Creates a port on the node C<$node> (which can also be a port ID, in which	621	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	622	case it's the node where that port resides).
603		623
604	The port ID of the newly created port is return immediately, and it is	624	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	625	possible to immediately start sending messages or to monitor the port.
606		626
607	After the port has been created, the init function is	627	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	628	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	629	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	630	specify a function in the main program, use C<::name>.
611		631
612	If the function doesn't exist, then the node tries to C<require>	632	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	633	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	635	exists or it runs out of package names.
616		636
617	The init function is then called with the newly-created port as context	637	The init function is then called with the newly-created port as context
618	object (C<$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.
619		641
620	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
621	in the init function, monitor the original port. This two-way monitoring	643	port, and in the remote init function, immediately monitor the passed
622	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<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
623		650
624	Example: spawn a chat server port on C<$othernode>.	651	Example: spawn a chat server port on C<$othernode>.
625		652
626	# this node, executed from within a port context:	653	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
642		669
643	sub _spawn {	670	sub _spawn {
644	my $port = shift;	671	my $port = shift;
645	my $init = shift;	672	my $init = shift;
646		673
		674	# rcv will create the actual port
647	local $SELF = "$NODE#$port";	675	local $SELF = "$NODE#$port";
648	eval {	676	eval {
649	&{ load_func $init }	677	&{ load_func $init }
650	};	678	};
651	_self_die if $@;	679	_self_die if $@;
652	}	680	}
653		681
654	sub spawn(@) {	682	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	683	my ($nodeid, undef) = split /#/, shift, 2;
656		684
657	my $id = "$RUNIQ." . $ID++;	685	my $id = "$RUNIQ." . $ID++;
658		686
659	$_[0] =~ /::/	687	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		689
662	($NODE{$noderef} \|\| add_node $noderef)	690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		691
665	"$noderef#$id"	692	"$nodeid#$id"
666	}	693	}
667		694
668	=back	695	=item after $timeout, @msg
669		696
670	=head1 NODE MESSAGES	697	=item after $timeout, $callback
671		698
672	Nodes understand the following messages sent to them. Many of them take	699	Either sends the given message, or call the given callback, after the
673	arguments called C<@reply>, which will simply be used to compose a reply	700	specified number of seconds.
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
675	the remaining arguments are simply the message data.
676		701
677	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.
678		705
679	=over 4
680
681	=cut	706	=cut
682		707
683	=item lookup => $name, @reply	708	sub after($@) {
		709	my ($timeout, @action) = @_;
684		710
685	Replies with the port ID of the specified well-known port, or C<undef>.	711	my $t; $t = AE::timer $timeout, 0, sub {
686		712	undef $t;
687	=item devnull => ...	713	ref $action[0]
688		714	? $action[0]()
689	Generic data sink/CPU heat conversion.	715	: snd @action;
690		716	};
691	=item relay => $port, @msg	717	}
692
693	Simply forwards the message to the given port.
694
695	=item eval => $string[ @reply]
696
697	Evaluates the given string. If C<@reply> is given, then a message of the
698	form C<@reply, $@, @evalres> is sent.
699
700	Example: crash another node.
701
702	snd $othernode, eval => "exit";
703
704	=item time => @reply
705
706	Replies the the current node time to C<@reply>.
707
708	Example: tell the current node to send the current time to C<$myport> in a
709	C<timereply> message.
710
711	snd $NODE, time => $myport, timereply => 1, 2;
712	# => snd $myport, timereply => 1, 2, <time>
713		718
714	=back	719	=back
715		720
716	=head1 AnyEvent::MP vs. Distributed Erlang	721	=head1 AnyEvent::MP vs. Distributed Erlang
717		722
…		…
727		732
728	Despite the similarities, there are also some important differences:	733	Despite the similarities, there are also some important differences:
729		734
730	=over 4	735	=over 4
731		736
732	=item * Node references contain the recipe on how to contact them.	737	=item * Node IDs are arbitrary strings in AEMP.
733		738
734	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
735	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
736	convenience functionality.	741	configuration or DNS), but will otherwise discover other odes itself.
737		742
738	This means that AEMP requires a less tightly controlled environment at the
739	cost of longer node references and a slightly higher management overhead.
740
741	=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
742	uses "local ports are like remote ports".	744	uses "local ports are like remote ports".
743		745
744	The failure modes for local ports are quite different (runtime errors	746	The failure modes for local ports are quite different (runtime errors
745	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,
746	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
…		…
757		759
758	Erlang uses processes that selectively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
759	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
760	useful purpose. For the same reason the pattern-matching abilities of	762	useful purpose. For the same reason the pattern-matching abilities of
761	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
762	filter messages without dequeing them.	764	filter messages without dequeuing them.
763		765
764	(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).
765		767
766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
767		769
…		…
773		775
774	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
775	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,
776	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).
777		779
778	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that after one message
779	holes in the message sequence.	781	is lost, all following ones sent to the same port are lost as well, until
780		782	monitoring raises an error, so there are no silent "holes" in the message
781	=item * In Erlang, processes can be declared dead and later be found to be	783	sequence.
782	alive.
783
784	In Erlang it can happen that a monitored process is declared dead and
785	linked processes get killed, but later it turns out that the process is
786	still alive - and can receive messages.
787
788	In AEMP, when port monitoring detects a port as dead, then that port will
789	eventually be killed - it cannot happen that a node detects a port as dead
790	and then later sends messages to it, finding it is still alive.
791		784
792	=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.
793		786
794	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
795	known to other nodes for a completely different process, causing messages	788	known to other nodes for a completely different process, causing messages
…		…
799	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.
800		793
801	=item * Erlang uses unprotected connections, AEMP uses secure	794	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	795	authentication and can use TLS.
803		796
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	797	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	798	securely authenticate nodes.
806		799
807	=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
808	communications.	801	communications.
809		802
810	The AEMP protocol, unlike the Erlang protocol, supports both	803	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	804	language independent text-only protocols (good for debugging) and binary,
812	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.
813		807
814	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
815	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
816	protocol simple.	810	protocol simple.
817		811
818	=item * AEMP has more flexible monitoring options than Erlang.	812	=item * AEMP has more flexible monitoring options than Erlang.
819		813
820	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
…		…
823	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
824	on a per-process basis.	818	on a per-process basis.
825		819
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	820	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		821
828	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
829	as linking is (except linking is unreliable in Erlang).	823	same way as linking is (except linking is unreliable in Erlang).
830		824
831	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
832	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
833	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
834	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
835	more reliable.	829	reliable (no need for C<spawn_link>).
836		830
837	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
838	(hard to do in Erlang).	832	(hard to do in Erlang).
839		833
840	=back	834	=back
841		835
842	=head1 RATIONALE	836	=head1 RATIONALE
843		837
844	=over 4	838	=over 4
845		839
846	=item Why strings for ports and noderefs, why not objects?	840	=item Why strings for port and node IDs, why not objects?
847		841
848	We considered "objects", but found that the actual number of methods	842	We considered "objects", but found that the actual number of methods
849	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
850	the network frequently, the serialising/deserialising would add lots of	844	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	845	overhead, as well as having to keep a proxy object everywhere.
852		846
853	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
854	procedures to be "valid".	848	procedures to be "valid".
855		849
856	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
857	can't become much cheaper.	851	global hash - it can't become much cheaper.
858		852
859	=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?
860		854
861	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
862	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
863	default.	857	default (although all nodes will accept it).
864		858
865	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
866	faster for small messages and b) most importantly, after years of	860	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	861	experience we found that object serialisation is causing more problems
868	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
869	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
870	always have to re-think your design.	864	always have to re-think your design.
871		865
872	Keeping your messages simple, concentrating on data structures rather than	866	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	867	objects, will keep your messages clean, tidy and efficient.
874		868
875	=back	869	=back
876		870
877	=head1 SEE ALSO	871	=head1 SEE ALSO
878		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
879	L<AnyEvent>.	883	L<AnyEvent>.
880		884
881	=head1 AUTHOR	885	=head1 AUTHOR
882		886
883	Marc Lehmann <schmorp@schmorp.de>	887	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.83 by root, Tue Sep 8 01:38:16 2009 UTC