[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 1.94 by root, Tue Sep 22 14:14:43 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
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
39	mon $port, $cb->(@msg) # callback is invoked on death	36	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $localport, $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 API.
49		46	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		47
52	=head1 DESCRIPTION	48	=head1 DESCRIPTION
53		49
54	This module (-family) implements a simple message passing framework.	50	This module (-family) implements a simple message passing framework.
55		51
56	Despite its simplicity, you can securely message other processes running	52	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	53	on the same or other hosts, and you can supervise entities remotely.
58		54
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	55	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	56	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		57
66	=head1 CONCEPTS	58	=head1 CONCEPTS
67		59
68	=over 4	60	=over 4
69		61
70	=item port	62	=item port
71		63
72	A port is something you can send messages to (with the C<snd> function).	64	Not to be confused with a TCP port, a "port" is something you can send
		65	messages to (with the C<snd> function).
73		66
74	Some ports allow you to register C<rcv> handlers that can match specific	67	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	68	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	69	anything was listening for them or not.
77		70
78	=item port id - C<noderef#portname>	71	=item port ID - C<nodeid#portname>
79		72
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	73	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	74	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		75
85	=item node	76	=item node
86		77
87	A node is a single process containing at least one port - the node	78	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	79	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	80	ports.
90		81
91	Nodes are either private (single-process only), slaves (connected to a	82	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	83	(no listening ports). Private nodes cannot talk to other private nodes
		84	currently.
93		85
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
95		87
96	A node reference is a string that either simply identifies the node (for	88	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	89	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	90	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		91	doesn't interpret node IDs in any way.
99		92
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	93	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		94
103	Node references come in two flavours: resolved (containing only numerical	95	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).	96	each other. To do this, nodes should listen on one or more local transport
		97	endpoints - binds. Currently, only standard C<ip:port> specifications can
		98	be used, which specify TCP ports to listen on.
105		99
106	Before using an unresolved node reference in a message you first have to	100	=item seed nodes
107	resolve it.	101
		102	When a node starts, it knows nothing about the network. To teach the node
		103	about the network it first has to contact some other node within the
		104	network. This node is called a seed.
		105
		106	Apart from the fact that other nodes know them as seed nodes and they have
		107	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		108	any node can function as a seed node for others.
		109
		110	In addition to discovering the network, seed nodes are also used to
		111	maintain the network and to connect nodes that otherwise would have
		112	trouble connecting. They form the backbone of an AnyEvent::MP network.
		113
		114	Seed nodes are expected to be long-running, and at least one seed node
		115	should always be available. They should also be relatively responsive - a
		116	seed node that blocks for long periods will slow down everybody else.
		117
		118	=item seeds - C<host:port>
		119
		120	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		121	TCP port) of nodes thta should be used as seed nodes.
		122
		123	The nodes listening on those endpoints are expected to be long-running,
		124	and at least one of those should always be available. When nodes run out
		125	of connections (e.g. due to a network error), they try to re-establish
		126	connections to some seednodes again to join the network.
108		127
109	=back	128	=back
110		129
111	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
112		131
127	use base "Exporter";	146	use base "Exporter";
128		147
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
130		149
131	our @EXPORT = qw(	150	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	152	configure
134	snd rcv mon kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
135	port	154	port
136	);	155	);
137		156
138	our $SELF;	157	our $SELF;
139		158
…		…
143	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
144	}	163	}
145		164
146	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
147		166
148	The C<NODE> function returns, and the C<$NODE> variable contains the	167	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	168	ID of the node running in the current process. This value is initialised by
150	C<initialise_node>.	169	a call to C<configure>.
151		170
152	=item $noderef = node_of $port	171	=item $nodeid = node_of $port
153		172
154	Extracts and returns the noderef from a port ID or a noderef.	173	Extracts and returns the node ID from a port ID or a node ID.
155		174
156	=item initialise_node $noderef, $seednode, $seednode...	175	=item configure $profile, key => value...
157		176
158	=item initialise_node "slave/", $master, $master...	177	=item configure key => value...
159		178
160	Before a node can talk to other nodes on the network it has to initialise	179	Before a node can talk to other nodes on the network (i.e. enter
161	itself - the minimum a node needs to know is it's own name, and optionally	180	"distributed mode") it has to configure itself - the minimum a node needs
162	it should know the noderefs of some other nodes in the network.	181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
163		183
164	This function initialises a node - it must be called exactly once (or	184	This function configures a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	185	never) before calling other AnyEvent::MP functions.
166		186
167	All arguments (optionally except for the first) are noderefs, which can be
168	either resolved or unresolved.
169
170	The first argument will be looked up in the configuration database first
171	(if it is C<undef> then the current nodename will be used instead) to find
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175
176	There are two types of networked nodes, public nodes and slave nodes:
177
178	=over 4	187	=over 4
179		188
180	=item public nodes	189	=item step 1, gathering configuration from profiles
181		190
182	For public nodes, C<$noderef> (supplied either directly to	191	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	192	L<aemp> commandline utility). The profile name can be specified via the
184	noderef (possibly unresolved, in which case it will be resolved).	193	named C<profile> parameter or can simply be the first parameter). If it is
		194	missing, then the nodename (F<uname -n>) will be used as profile name.
185		195
186	After resolving, the node will bind itself on all endpoints and try to	196	The profile data is then gathered as follows:
187	connect to all additional C<$seednodes> that are specified. Seednodes are
188	optional and can be used to quickly bootstrap the node into an existing
189	network.
190		197
191	=item slave nodes	198	First, all remaining key => value pairs (all of which are conveniently
		199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
192		203
193	When the C<$noderef> (either as given or overriden by the config file)	204	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	205	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	206	and can only be used to specify defaults.
196	their traffic to the master node that they attach to.
197		207
198	At least one additional noderef is required (either by specifying it	208	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	209	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	210	special node ID of C<anon/> will be replaced by a random node ID.
201	first node it can successfully connect to.	211
		212	=item step 2, bind listener sockets
		213
		214	The next step is to look up the binds in the profile, followed by binding
		215	aemp protocol listeners on all binds specified (it is possible and valid
		216	to have no binds, meaning that the node cannot be contacted form the
		217	outside. This means the node cannot talk to other nodes that also have no
		218	binds, but it can still talk to all "normal" nodes).
		219
		220	If the profile does not specify a binds list, then a default of C<*> is
		221	used, meaning the node will bind on a dynamically-assigned port on every
		222	local IP address it finds.
		223
		224	=item step 3, connect to seed nodes
		225
		226	As the last step, the seeds list from the profile is passed to the
		227	L<AnyEvent::MP::Global> module, which will then use it to keep
		228	connectivity with at least one node at any point in time.
202		229
203	=back	230	=back
204		231
205	This function will block until all nodes have been resolved and, for slave	232	Example: become a distributed node using the local node name as profile.
206	nodes, until it has successfully established a connection to a master	233	This should be the most common form of invocation for "daemon"-type nodes.
207	server.
208		234
209	Example: become a public node listening on the guessed noderef, or the one	235	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		236
213	initialise_node;	237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
214		239
215	Example: become a slave node to any of the the seednodes specified via	240	configure nodeid => "anon/";
216	C<aemp>. This form is often used for commandline clients.
217		241
218	initialise_node "slave/";	242	Example: configure a node using a profile called seed, which si suitable
		243	for a seed node as it binds on all local addresses on a fixed port (4040,
		244	customary for aemp).
219		245
220	Example: become a slave node to any of the specified master servers. This	246	# use the aemp commandline utility
221	form is also often used for commandline clients.	247	# aemp profile seed nodeid anon/ binds '*:4040'
222		248
223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	249	# then use it
		250	configure profile => "seed";
224		251
225	Example: become a public node, and try to contact some well-known master	252	# or simply use aemp from the shell again:
226	servers to become part of the network.	253	# aemp run profile seed
227		254
228	initialise_node undef, "master1", "master2";	255	# or provide a nicer-to-remember nodeid
229		256	# 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		257
267	=item $SELF	258	=item $SELF
268		259
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	261	blocks.
271		262
272	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
273		264
274	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
277		268
278	=item snd $port, type => @data	269	=item snd $port, type => @data
279		270
280	=item snd $port, @msg	271	=item snd $port, @msg
281		272
282	Send the given message to the given port ID, which can identify either	273	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.	274	local or a remote port, and must be a port ID.
284		275
285	While the message can be about anything, it is highly recommended to use a	276	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	277	use a string as first element (a port ID, or some word that indicates a
287	type etc.).	278	request type etc.) and to consist if only simple perl values (scalars,
		279	arrays, hashes) - if you think you need to pass an object, think again.
288		280
289	The message data effectively becomes read-only after a call to this	281	The message data logically becomes read-only after a call to this
290	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
291	problems.	283	forbidden, as there can be considerable time between the call to C<snd>
		284	and the time the message is actually being serialised - in fact, it might
		285	never be copied as within the same process it is simply handed to the
		286	receiving port.
292		287
293	The type of data you can transfer depends on the transport protocol: when	288	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	289	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	290	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	291	that Storable can serialise and deserialise is allowed, and for the local
297	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
298		294
299	=item $local_port = port	295	=item $local_port = port
300		296
301	Create a new local port object and returns its port ID. Initially it has	297	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.	298	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	345	The default callback received all messages not matched by a more specific
350	C<tag> match.	346	C<tag> match.
351		347
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		349
354	Register callbacks to be called on messages starting with the given tag on	350	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	351	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	352	C<$callback> is C<$undef> or missing). There can only be one callback
		353	registered for each tag.
357		354
358	The original message will be passed to the callback, after the first	355	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	356	element (the tag) has been removed. The callback will use the same
360	environment as the default callback (see above).	357	environment as the default callback (see above).
361		358
…		…
373	rcv port,	370	rcv port,
374	msg1 => sub { ... },	371	msg1 => sub { ... },
375	...	372	...
376	;	373	;
377		374
		375	Example: temporarily register a rcv callback for a tag matching some port
		376	(e.g. for a rpc reply) and unregister it after a message was received.
		377
		378	rcv $port, $otherport => sub {
		379	my @reply = @_;
		380
		381	rcv $SELF, $otherport;
		382	};
		383
378	=cut	384	=cut
379		385
380	sub rcv($@) {	386	sub rcv($@) {
381	my $port = shift;	387	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	388	my ($nodeid, $portid) = split /#/, $port, 2;
383		389
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	390	$NODE{$nodeid} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	391	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		392
387	while (@_) {	393	while (@_) {
388	if (ref $_[0]) {	394	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	395	if (my $self = $PORT_DATA{$portid}) {
…		…
468	$res	474	$res
469	}	475	}
470	}	476	}
471	}	477	}
472		478
473	=item $guard = mon $port, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474		480
475	=item $guard = mon $port, $rcvport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476		482
477	=item $guard = mon $port	483	=item $guard = mon $port # kill $SELF when $port dies
478		484
479	=item $guard = mon $port, $rcvport, @msg	485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		486
481	Monitor the given port and do something when the port is killed or	487	Monitor the given port and do something when the port is killed or
482	messages to it were lost, and optionally return a guard that can be used	488	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	489	to stop monitoring again.
484
485	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port
487	will arrive, or the monitoring action will be invoked after possible
488	message loss has been detected. No messages will be lost "in between"
489	(after the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get
491	delivered again.
492		490
493	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
494	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
495	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
496	C<eval> if unsure.	494	C<eval> if unsure.
497		495
498	In the second form (another port given), the other port (C<$rcvport>)	496	In the second form (another port given), the other port (C<$rcvport>)
499	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
500	"normal" kils nothing happens, while under all other conditions, the other	498	"normal" kils nothing happens, while under all other conditions, the other
501	port is killed with the same reason.	499	port is killed with the same reason.
502		500
503	The third form (kill self) is the same as the second form, except that	501	The third form (kill self) is the same as the second form, except that
504	C<$rvport> defaults to C<$SELF>.	502	C<$rvport> defaults to C<$SELF>.
505		503
506	In the last form (message), a message of the form C<@msg, @reason> will be	504	In the last form (message), a message of the form C<@msg, @reason> will be
507	C<snd>.	505	C<snd>.
		506
		507	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		508	alert was raised), they are removed and will not trigger again.
508		509
509	As a rule of thumb, monitoring requests should always monitor a port from	510	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	511	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	512	lost, just like any other message. Another less obvious reason is that
512	even monitoring requests can get lost (for exmaple, when the connection	513	even monitoring requests can get lost (for example, when the connection
513	to the other node goes down permanently). When monitoring a port locally	514	to the other node goes down permanently). When monitoring a port locally
514	these problems do not exist.	515	these problems do not exist.
515		516
		517	C<mon> effectively guarantees that, in the absence of hardware failures,
		518	after starting the monitor, either all messages sent to the port will
		519	arrive, or the monitoring action will be invoked after possible message
		520	loss has been detected. No messages will be lost "in between" (after
		521	the first lost message no further messages will be received by the
		522	port). After the monitoring action was invoked, further messages might get
		523	delivered again.
		524
		525	Inter-host-connection timeouts and monitoring depend on the transport
		526	used. The only transport currently implemented is TCP, and AnyEvent::MP
		527	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		528	non-idle connection, and usually around two hours for idle conenctions).
		529
		530	This means that monitoring is good for program errors and cleaning up
		531	stuff eventually, but they are no replacement for a timeout when you need
		532	to ensure some maximum latency.
		533
516	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
517		535
518	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
519		537
520	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
…		…
526	mon $port, $self => "restart";	544	mon $port, $self => "restart";
527		545
528	=cut	546	=cut
529		547
530	sub mon {	548	sub mon {
531	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
532		550
533	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
534		552
535	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	553	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
536		554
537	unless (ref $cb) {	555	unless (ref $cb) {
538	if (@_) {	556	if (@_) {
…		…
547	}	565	}
548		566
549	$node->monitor ($port, $cb);	567	$node->monitor ($port, $cb);
550		568
551	defined wantarray	569	defined wantarray
552	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	570	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
553	}	571	}
554		572
555	=item $guard = mon_guard $port, $ref, $ref...	573	=item $guard = mon_guard $port, $ref, $ref...
556		574
557	Monitors the given C<$port> and keeps the passed references. When the port	575	Monitors the given C<$port> and keeps the passed references. When the port
558	is killed, the references will be freed.	576	is killed, the references will be freed.
559		577
560	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
561		579
562	This function is useful when you create e.g. timers or other watchers and	580	This function is useful when you create e.g. timers or other watchers and
563	want to free them when the port gets killed:	581	want to free them when the port gets killed (note the use of C<psub>):
564		582
565	$port->rcv (start => sub {	583	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
568	});	586	});
569	});	587	});
570		588
571	=cut	589	=cut
…		…
580		598
581	=item kil $port[, @reason]	599	=item kil $port[, @reason]
582		600
583	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
584		602
585	If no C<@reason> is specified, then the port is killed "normally" (linked	603	If no C<@reason> is specified, then the port is killed "normally" (ports
586	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
587		606
588	Otherwise, linked ports get killed with the same reason (second form of	607	Otherwise, linked ports get killed with the same reason (second form of
589	C<mon>, see below).	608	C<mon>, see above).
590		609
591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	610	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
592	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
593		612
594	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
…		…
599	=item $port = spawn $node, $initfunc[, @initdata]	618	=item $port = spawn $node, $initfunc[, @initdata]
600		619
601	Creates a port on the node C<$node> (which can also be a port ID, in which	620	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	621	case it's the node where that port resides).
603		622
604	The port ID of the newly created port is return immediately, and it is	623	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	624	possible to immediately start sending messages or to monitor the port.
606		625
607	After the port has been created, the init function is	626	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	627	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	629	specify a function in the main program, use C<::name>.
611		630
612	If the function doesn't exist, then the node tries to C<require>	631	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	634	exists or it runs out of package names.
616		635
617	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
618	object (C<$SELF>) and the C<@initdata> values as arguments.	637	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		638	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		639	the port might not get created.
619		640
620	A common idiom is to pass your own port, monitor the spawned port, and	641	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	642	port, and in the remote init function, immediately monitor the passed
622	ensures that both ports get cleaned up when there is a problem.	643	local port. This two-way monitoring ensures that both ports get cleaned up
		644	when there is a problem.
		645
		646	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
623		649
624	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
625		651
626	# this node, executed from within a port context:	652	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
642		668
643	sub _spawn {	669	sub _spawn {
644	my $port = shift;	670	my $port = shift;
645	my $init = shift;	671	my $init = shift;
646		672
		673	# rcv will create the actual port
647	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
648	eval {	675	eval {
649	&{ load_func $init }	676	&{ load_func $init }
650	};	677	};
651	_self_die if $@;	678	_self_die if $@;
652	}	679	}
653		680
654	sub spawn(@) {	681	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	682	my ($nodeid, undef) = split /#/, shift, 2;
656		683
657	my $id = "$RUNIQ." . $ID++;	684	my $id = "$RUNIQ." . $ID++;
658		685
659	$_[0] =~ /::/	686	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	687	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		688
662	($NODE{$noderef} \|\| add_node $noderef)	689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		690
665	"$noderef#$id"	691	"$nodeid#$id"
666	}	692	}
667		693
668	=back	694	=item after $timeout, @msg
669		695
670	=head1 NODE MESSAGES	696	=item after $timeout, $callback
671		697
672	Nodes understand the following messages sent to them. Many of them take	698	Either sends the given message, or call the given callback, after the
673	arguments called C<@reply>, which will simply be used to compose a reply	699	specified number of seconds.
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
675	the remaining arguments are simply the message data.
676		700
677	While other messages exist, they are not public and subject to change.	701	This is simply a utility function that comes in handy at times - the
		702	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		703	so it may go away in the future.
678		704
679	=over 4
680
681	=cut	705	=cut
682		706
683	=item lookup => $name, @reply	707	sub after($@) {
		708	my ($timeout, @action) = @_;
684		709
685	Replies with the port ID of the specified well-known port, or C<undef>.	710	my $t; $t = AE::timer $timeout, 0, sub {
		711	undef $t;
		712	ref $action[0]
		713	? $action[0]()
		714	: snd @action;
		715	};
		716	}
686		717
687	=item devnull => ...	718	=item cal $port, @msg, $callback[, $timeout]
688		719
689	Generic data sink/CPU heat conversion.	720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
690		722
691	=item relay => $port, @msg	723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
692		725
693	Simply forwards the message to the given port.	726	A reply message sent to the port is passed to the C<$callback> as-is.
694		727
695	=item eval => $string[ @reply]	728	If an optional time-out (in seconds) is given and it is not C<undef>,
		729	then the callback will be called without any arguments after the time-out
		730	elapsed and the port is C<kil>ed.
696		731
697	Evaluates the given string. If C<@reply> is given, then a message of the	732	If no time-out is given, then the local port will monitor the remote port
698	form C<@reply, $@, @evalres> is sent.	733	instead, so it eventually gets cleaned-up.
699		734
700	Example: crash another node.	735	Currently this function returns the temporary port, but this "feature"
		736	might go in future versions unless you can make a convincing case that
		737	this is indeed useful for something.
701		738
702	snd $othernode, eval => "exit";	739	=cut
703		740
704	=item time => @reply	741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
705		744
706	Replies the the current node time to C<@reply>.	745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
707		750
708	Example: tell the current node to send the current time to C<$myport> in a	751	if (defined $timeout) {
709	C<timereply> message.	752	$timeout = AE::timer $timeout, 0, sub {
		753	undef $timeout;
		754	kil $port;
		755	$cb->();
		756	};
		757	} else {
		758	mon $_[0], sub {
		759	kil $port;
		760	$cb->();
		761	};
		762	}
710		763
711	snd $NODE, time => $myport, timereply => 1, 2;	764	push @_, $port;
712	# => snd $myport, timereply => 1, 2, <time>	765	&snd;
		766
		767	$port
		768	}
713		769
714	=back	770	=back
715		771
716	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
717		773
…		…
727		783
728	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
729		785
730	=over 4	786	=over 4
731		787
732	=item * Node references contain the recipe on how to contact them.	788	=item * Node IDs are arbitrary strings in AEMP.
733		789
734	Erlang relies on special naming and DNS to work everywhere in the	790	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	791	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
736	convenience functionality.	792	configuration or DNS), but will otherwise discover other odes itself.
737		793
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	794	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
742	uses "local ports are like remote ports".	795	uses "local ports are like remote ports".
743		796
744	The failure modes for local ports are quite different (runtime errors	797	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,	798	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	799	when a connection to another node dies, you know nothing about the other
…		…
757		810
758	Erlang uses processes that selectively receive messages, and therefore	811	Erlang uses processes that selectively receive messages, and therefore
759	needs a queue. AEMP is event based, queuing messages would serve no	812	needs a queue. AEMP is event based, queuing messages would serve no
760	useful purpose. For the same reason the pattern-matching abilities of	813	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	814	AnyEvent::MP are more limited, as there is little need to be able to
762	filter messages without dequeing them.	815	filter messages without dequeuing them.
763		816
764	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	817	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
765		818
766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	819	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
767		820
…		…
773		826
774	Erlang makes few guarantees on messages delivery - messages can get lost	827	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,	828	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).	829	and c, and the other side only receives messages a and c).
777		830
778	AEMP guarantees correct ordering, and the guarantee that there are no	831	AEMP guarantees correct ordering, and the guarantee that after one message
779	holes in the message sequence.	832	is lost, all following ones sent to the same port are lost as well, until
780		833	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	834	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		835
792	=item * Erlang can send messages to the wrong port, AEMP does not.	836	=item * Erlang can send messages to the wrong port, AEMP does not.
793		837
794	In Erlang it is quite likely that a node that restarts reuses a process ID	838	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	839	known to other nodes for a completely different process, causing messages
…		…
799	around in the network will not be sent to an unrelated port.	843	around in the network will not be sent to an unrelated port.
800		844
801	=item * Erlang uses unprotected connections, AEMP uses secure	845	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	846	authentication and can use TLS.
803		847
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	848	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	849	securely authenticate nodes.
806		850
807	=item * The AEMP protocol is optimised for both text-based and binary	851	=item * The AEMP protocol is optimised for both text-based and binary
808	communications.	852	communications.
809		853
810	The AEMP protocol, unlike the Erlang protocol, supports both	854	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	855	language independent text-only protocols (good for debugging) and binary,
812	language-specific serialisers (e.g. Storable).	856	language-specific serialisers (e.g. Storable). By default, unless TLS is
		857	used, the protocol is actually completely text-based.
813		858
814	It has also been carefully designed to be implementable in other languages	859	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	860	with a minimum of work while gracefully degrading functionality to make the
816	protocol simple.	861	protocol simple.
817		862
818	=item * AEMP has more flexible monitoring options than Erlang.	863	=item * AEMP has more flexible monitoring options than Erlang.
819		864
820	In Erlang, you can chose to receive I<all> exit signals as messages	865	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	868	Erlang, as one can choose between automatic kill, exit message or callback
824	on a per-process basis.	869	on a per-process basis.
825		870
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	871	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		872
828	Monitoring in Erlang is not an indicator of process death/crashes,	873	Monitoring in Erlang is not an indicator of process death/crashes, in the
829	as linking is (except linking is unreliable in Erlang).	874	same way as linking is (except linking is unreliable in Erlang).
830		875
831	In AEMP, you don't "look up" registered port names or send to named ports	876	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	877	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	878	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	879	remote port. Since both monitors are local to the node, they are much more
835	more reliable.	880	reliable (no need for C<spawn_link>).
836		881
837	This also saves round-trips and avoids sending messages to the wrong port	882	This also saves round-trips and avoids sending messages to the wrong port
838	(hard to do in Erlang).	883	(hard to do in Erlang).
839		884
840	=back	885	=back
841		886
842	=head1 RATIONALE	887	=head1 RATIONALE
843		888
844	=over 4	889	=over 4
845		890
846	=item Why strings for ports and noderefs, why not objects?	891	=item Why strings for port and node IDs, why not objects?
847		892
848	We considered "objects", but found that the actual number of methods	893	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	894	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	895	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	896	overhead, as well as having to keep a proxy object everywhere.
852		897
853	Strings can easily be printed, easily serialised etc. and need no special	898	Strings can easily be printed, easily serialised etc. and need no special
854	procedures to be "valid".	899	procedures to be "valid".
855		900
856	And a a miniport consists of a single closure stored in a global hash - it	901	And as a result, a miniport consists of a single closure stored in a
857	can't become much cheaper.	902	global hash - it can't become much cheaper.
858		903
859	=item Why favour JSON, why not real serialising format such as Storable?	904	=item Why favour JSON, why not a real serialising format such as Storable?
860		905
861	In fact, any AnyEvent::MP node will happily accept Storable as framing	906	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	907	format, but currently there is no way to make a node use Storable by
863	default.	908	default (although all nodes will accept it).
864		909
865	The default framing protocol is JSON because a) JSON::XS is many times	910	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	911	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	912	experience we found that object serialisation is causing more problems
868	than it gains: Just like function calls, objects simply do not travel	913	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	914	easily over the network, mostly because they will always be a copy, so you
870	always have to re-think your design.	915	always have to re-think your design.
871		916
872	Keeping your messages simple, concentrating on data structures rather than	917	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	918	objects, will keep your messages clean, tidy and efficient.
874		919
875	=back	920	=back
876		921
877	=head1 SEE ALSO	922	=head1 SEE ALSO
878		923
		924	L<AnyEvent::MP::Intro> - a gentle introduction.
		925
		926	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		927
		928	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		929	your applications.
		930
		931	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		932	all nodes.
		933
879	L<AnyEvent>.	934	L<AnyEvent>.
880		935
881	=head1 AUTHOR	936	=head1 AUTHOR
882		937
883	Marc Lehmann <schmorp@schmorp.de>	938	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs. Revision 1.94 by root, Tue Sep 22 14:14:43 2009 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.94 by root, Tue Sep 22 14:14:43 2009 UTC