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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs.
Revision 1.88 by root, Fri Sep 11 15:02:17 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
38	# monitoring	35	# monitoring
…		…
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable 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	Ports allow you to register C<rcv> handlers that can match all or just	67	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	68	some messages. Messages send to ports will not be queued, regardless of
		69	anything was listening for them or not.
76		70
77	=item port id - C<noderef#portname>	71	=item port ID - C<nodeid#portname>
78		72
79	A port ID is 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
80	separator, and a port name (a printable string of unspecified format). An	74	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		75
84	=item node	76	=item node
85		77
86	A node is a single process containing at least one port - the node port,	78	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	79	which enables nodes to manage each other remotely, and to create new
88	ports.	80	ports.
89		81
90	Nodes are either private (single-process only), slaves (connected to a	82	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	83	(no listening ports). Private nodes cannot talk to other private nodes
		84	currently.
92		85
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
94		87
95	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
96	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
97	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.
98		92
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	93	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		94
102	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
103	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.
104		99
105	Before using an unresolved node reference in a message you first have to	100	=item seed nodes
106	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.
107		127
108	=back	128	=back
109		129
110	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
111		131
…		…
126	use base "Exporter";	146	use base "Exporter";
127		147
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
129		149
130	our @EXPORT = qw(	150	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	152	configure
133	snd rcv mon kil reg psub spawn	153	snd rcv mon mon_guard kil reg psub spawn cal
134	port	154	port
135	);	155	);
136		156
137	our $SELF;	157	our $SELF;
138		158
…		…
142	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
143	}	163	}
144		164
145	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
146		166
147	The C<NODE> function returns, and the C<$NODE> variable contains the	167	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	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
149	C<initialise_node>.	169	a call to C<configure>.
150		170
151	=item $noderef = node_of $port	171	=item $nodeid = node_of $port
152		172
153	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.
154		174
155	=item initialise_node $noderef, $seednode, $seednode...	175	=item configure $profile, key => value...
156		176
157	=item initialise_node "slave/", $master, $master...	177	=item configure key => value...
158		178
159	Before a node can talk to other nodes on the network it has to initialise	179	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	180	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
162		183
163	This function initialises a node - it must be called exactly once (or	184	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	185	never) before calling other AnyEvent::MP functions.
165		186
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	187	=over 4
178		188
179	=item public nodes	189	=item step 1, gathering configuration from profiles
180		190
181	For public nodes, C<$noderef> (supplied either directly to	191	The function first looks up a profile in the aemp configuration (see the
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	192	L<aemp> commandline utility). The profile name can be specified via the
183	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.
184		195
185	After resolving, the node will bind itself on all endpoints and try to	196	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		197
190	=item slave nodes	198	First, all remaining key => value pairs (all of which are conveniently
		199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
191		203
192	When the C<$noderef> (either as given or overriden by the config file)	204	That means that the values specified in the profile have highest priority
193	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,
194	node. Slave nodes cannot be contacted from outside and will route most of	206	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		207
197	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
198	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
199	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.
200	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.
201		229
202	=back	230	=back
203		231
204	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.
205	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.
206	server.
207		234
208	Example: become a public node listening on the guessed noderef, or the one	235	configure
209	specified via C<aemp> for the current node. This should be the most common
210	form of invocation for "daemon"-type nodes.
211		236
212	initialise_node;	237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
213		239
214	Example: become a slave node to any of the the seednodes specified via	240	configure nodeid => "anon/";
215	C<aemp>. This form is often used for commandline clients.
216		241
217	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).
218		245
219	Example: become a slave node to any of the specified master servers. This	246	# use the aemp commandline utility
220	form is also often used for commandline clients.	247	# aemp profile seed nodeid anon/ binds '*:4040'
221		248
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	249	# then use it
		250	configure profile => "seed";
223		251
224	Example: become a public node, and try to contact some well-known master	252	# or simply use aemp from the shell again:
225	servers to become part of the network.	253	# aemp run profile seed
226		254
227	initialise_node undef, "master1", "master2";	255	# or provide a nicer-to-remember nodeid
228		256	# aemp run profile seed nodeid "$(hostname)"
229	Example: become a public node listening on port C<4041>.
230
231	initialise_node 4041;
232
233	Example: become a public node, only visible on localhost port 4044.
234
235	initialise_node "localhost:4044";
236
237	=item $cv = resolve_node $noderef
238
239	Takes an unresolved node reference that may contain hostnames and
240	abbreviated IDs, resolves all of them and returns a resolved node
241	reference.
242
243	In addition to C<address:port> pairs allowed in resolved noderefs, the
244	following forms are supported:
245
246	=over 4
247
248	=item the empty string
249
250	An empty-string component gets resolved as if the default port (4040) was
251	specified.
252
253	=item naked port numbers (e.g. C<1234>)
254
255	These are resolved by prepending the local nodename and a colon, to be
256	further resolved.
257
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
259
260	These are resolved by using AnyEvent::DNS to resolve them, optionally
261	looking up SRV records for the C<aemp=4040> port, if no port was
262	specified.
263
264	=back
265		257
266	=item $SELF	258	=item $SELF
267		259
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	261	blocks.
270		262
271	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
272		264
273	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
276		268
277	=item snd $port, type => @data	269	=item snd $port, type => @data
278		270
279	=item snd $port, @msg	271	=item snd $port, @msg
280		272
281	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
282	a local or a remote port, and must be a port ID.	274	local or a remote port, and must be a port ID.
283		275
284	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
285	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
286	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.
287		280
288	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
289	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
290	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.
291		287
292	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
293	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
294	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
295	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
296	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
297		294
298	=item $local_port = port	295	=item $local_port = port
299		296
300	Create a new local port object and returns its port ID. Initially it has	297	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	298	no callbacks set and will throw an error when it receives messages.
…		…
386		383
387	=cut	384	=cut
388		385
389	sub rcv($@) {	386	sub rcv($@) {
390	my $port = shift;	387	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	388	my ($nodeid, $portid) = split /#/, $port, 2;
392		389
393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	390	$NODE{$nodeid} == $NODE{""}
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	391	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		392
396	while (@_) {	393	while (@_) {
397	if (ref $_[0]) {	394	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	395	if (my $self = $PORT_DATA{$portid}) {
…		…
477	$res	474	$res
478	}	475	}
479	}	476	}
480	}	477	}
481		478
482	=item $guard = mon $port, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483		480
484	=item $guard = mon $port, $rcvport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485		482
486	=item $guard = mon $port	483	=item $guard = mon $port # kill $SELF when $port dies
487		484
488	=item $guard = mon $port, $rcvport, @msg	485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		486
490	Monitor the given port and do something when the port is killed or	487	Monitor the given port and do something when the port is killed or
491	messages to it were lost, and optionally return a guard that can be used	488	messages to it were lost, and optionally return a guard that can be used
492	to stop monitoring again.	489	to stop monitoring again.
493
494	C<mon> effectively guarantees that, in the absence of hardware failures,
495	that after starting the monitor, either all messages sent to the port
496	will arrive, or the monitoring action will be invoked after possible
497	message loss has been detected. No messages will be lost "in between"
498	(after the first lost message no further messages will be received by the
499	port). After the monitoring action was invoked, further messages might get
500	delivered again.
501		490
502	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	494	C<eval> if unsure.
506		495
507	In the second form (another port given), the other port (C<$rcvport>)	496	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	498	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	499	port is killed with the same reason.
511		500
512	The third form (kill self) is the same as the second form, except that	501	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	502	C<$rvport> defaults to C<$SELF>.
514		503
515	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
516	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.
517		509
518	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
519	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
520	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
521	even monitoring requests can get lost (for exmaple, when the connection	513	even monitoring requests can get lost (for example, when the connection
522	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
523	these problems do not exist.	515	these problems do not exist.
524		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
525	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
526		535
527	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
528		537
529	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
…		…
535	mon $port, $self => "restart";	544	mon $port, $self => "restart";
536		545
537	=cut	546	=cut
538		547
539	sub mon {	548	sub mon {
540	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
541		550
542	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
543		552
544	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,';
545		554
546	unless (ref $cb) {	555	unless (ref $cb) {
547	if (@_) {	556	if (@_) {
…		…
567	is killed, the references will be freed.	576	is killed, the references will be freed.
568		577
569	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
570		579
571	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
572	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>):
573		582
574	$port->rcv (start => sub {	583	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
577	});	586	});
578	});	587	});
579		588
580	=cut	589	=cut
…		…
589		598
590	=item kil $port[, @reason]	599	=item kil $port[, @reason]
591		600
592	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
593		602
594	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
595	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
596		606
597	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
598	C<mon>, see below).	608	C<mon>, see above).
599		609
600	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
601	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
602		612
603	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
…		…
608	=item $port = spawn $node, $initfunc[, @initdata]	618	=item $port = spawn $node, $initfunc[, @initdata]
609		619
610	Creates a port on the node C<$node> (which can also be a port ID, in which	620	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	621	case it's the node where that port resides).
612		622
613	The port ID of the newly created port is return immediately, and it is	623	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	624	possible to immediately start sending messages or to monitor the port.
615		625
616	After the port has been created, the init function is	626	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	627	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	629	specify a function in the main program, use C<::name>.
620		630
621	If the function doesn't exist, then the node tries to C<require>	631	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	634	exists or it runs out of package names.
625		635
626	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
627	object (C<$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.
628		640
629	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
630	in the init function, monitor the original port. This two-way monitoring	642	port, and in the remote init function, immediately monitor the passed
631	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<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
632		649
633	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
634		651
635	# this node, executed from within a port context:	652	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
651		668
652	sub _spawn {	669	sub _spawn {
653	my $port = shift;	670	my $port = shift;
654	my $init = shift;	671	my $init = shift;
655		672
		673	# rcv will create the actual port
656	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
657	eval {	675	eval {
658	&{ load_func $init }	676	&{ load_func $init }
659	};	677	};
660	_self_die if $@;	678	_self_die if $@;
661	}	679	}
662		680
663	sub spawn(@) {	681	sub spawn(@) {
664	my ($noderef, undef) = split /#/, shift, 2;	682	my ($nodeid, undef) = split /#/, shift, 2;
665		683
666	my $id = "$RUNIQ." . $ID++;	684	my $id = "$RUNIQ." . $ID++;
667		685
668	$_[0] =~ /::/	686	$_[0] =~ /::/
669	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";
670		688
671	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672		690
673	"$noderef#$id"	691	"$nodeid#$id"
674	}	692	}
675		693
676	=back	694	=item after $timeout, @msg
677		695
678	=head1 NODE MESSAGES	696	=item after $timeout, $callback
679		697
680	Nodes understand the following messages sent to them. Many of them take	698	Either sends the given message, or call the given callback, after the
681	arguments called C<@reply>, which will simply be used to compose a reply	699	specified number of seconds.
682	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
683	the remaining arguments are simply the message data.
684		700
685	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.
686		704
687	=over 4
688
689	=cut	705	=cut
690		706
691	=item lookup => $name, @reply	707	sub after($@) {
		708	my ($timeout, @action) = @_;
692		709
693	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	}
694		717
695	=item devnull => ...	718	=item cal $port, @msg, $callback[, $timeout]
696		719
697	Generic data sink/CPU heat conversion.	720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
698		722
699	=item relay => $port, @msg	723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
700		725
701	Simply forwards the message to the given port.	726	A reply message sent to the port is passed to the C<$callback> as-is.
702		727
703	=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.
704		731
705	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
706	form C<@reply, $@, @evalres> is sent.	733	instead, so it eventually gets cleaned-up.
707		734
708	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.
709		738
710	snd $othernode, eval => "exit";	739	=cut
711		740
712	=item time => @reply	741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
713		744
714	Replies the the current node time to C<@reply>.	745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
715		750
716	Example: tell the current node to send the current time to C<$myport> in a	751	if (defined $timeout) {
717	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	}
718		763
719	snd $NODE, time => $myport, timereply => 1, 2;	764	push @_, $port;
720	# => snd $myport, timereply => 1, 2, <time>	765	&snd;
		766
		767	$port
		768	}
721		769
722	=back	770	=back
723		771
724	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
725		773
…		…
735		783
736	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
737		785
738	=over 4	786	=over 4
739		787
740	=item * Node references contain the recipe on how to contact them.	788	=item * Node IDs are arbitrary strings in AEMP.
741		789
742	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
743	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
744	convenience functionality.	792	configuration or DNS), but will otherwise discover other odes itself.
745
746	This means that AEMP requires a less tightly controlled environment at the
747	cost of longer node references and a slightly higher management overhead.
748		793
749	=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
750	uses "local ports are like remote ports".	795	uses "local ports are like remote ports".
751		796
752	The failure modes for local ports are quite different (runtime errors	797	The failure modes for local ports are quite different (runtime errors
…		…
765		810
766	Erlang uses processes that selectively receive messages, and therefore	811	Erlang uses processes that selectively receive messages, and therefore
767	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
768	useful purpose. For the same reason the pattern-matching abilities of	813	useful purpose. For the same reason the pattern-matching abilities of
769	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
770	filter messages without dequeing them.	815	filter messages without dequeuing them.
771		816
772	(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).
773		818
774	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	819	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
775		820
…		…
781		826
782	Erlang makes few guarantees on messages delivery - messages can get lost	827	Erlang makes few guarantees on messages delivery - messages can get lost
783	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,
784	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).
785		830
786	AEMP guarantees correct ordering, and the guarantee that there are no	831	AEMP guarantees correct ordering, and the guarantee that after one message
787	holes in the message sequence.	832	is lost, all following ones sent to the same port are lost as well, until
788		833	monitoring raises an error, so there are no silent "holes" in the message
789	=item * In Erlang, processes can be declared dead and later be found to be	834	sequence.
790	alive.
791
792	In Erlang it can happen that a monitored process is declared dead and
793	linked processes get killed, but later it turns out that the process is
794	still alive - and can receive messages.
795
796	In AEMP, when port monitoring detects a port as dead, then that port will
797	eventually be killed - it cannot happen that a node detects a port as dead
798	and then later sends messages to it, finding it is still alive.
799		835
800	=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.
801		837
802	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
803	known to other nodes for a completely different process, causing messages	839	known to other nodes for a completely different process, causing messages
…		…
807	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.
808		844
809	=item * Erlang uses unprotected connections, AEMP uses secure	845	=item * Erlang uses unprotected connections, AEMP uses secure
810	authentication and can use TLS.	846	authentication and can use TLS.
811		847
812	AEMP can use a proven protocol - SSL/TLS - to protect connections and	848	AEMP can use a proven protocol - TLS - to protect connections and
813	securely authenticate nodes.	849	securely authenticate nodes.
814		850
815	=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
816	communications.	852	communications.
817		853
818	The AEMP protocol, unlike the Erlang protocol, supports both	854	The AEMP protocol, unlike the Erlang protocol, supports both programming
819	language-independent text-only protocols (good for debugging) and binary,	855	language independent text-only protocols (good for debugging) and binary,
820	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.
821		858
822	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
823	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
824	protocol simple.	861	protocol simple.
825		862
826	=item * AEMP has more flexible monitoring options than Erlang.	863	=item * AEMP has more flexible monitoring options than Erlang.
827		864
828	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
…		…
831	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
832	on a per-process basis.	869	on a per-process basis.
833		870
834	=item * Erlang tries to hide remote/local connections, AEMP does not.	871	=item * Erlang tries to hide remote/local connections, AEMP does not.
835		872
836	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
837	as linking is (except linking is unreliable in Erlang).	874	same way as linking is (except linking is unreliable in Erlang).
838		875
839	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
840	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
841	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
842	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
843	more reliable.	880	reliable (no need for C<spawn_link>).
844		881
845	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
846	(hard to do in Erlang).	883	(hard to do in Erlang).
847		884
848	=back	885	=back
849		886
850	=head1 RATIONALE	887	=head1 RATIONALE
851		888
852	=over 4	889	=over 4
853		890
854	=item Why strings for ports and noderefs, why not objects?	891	=item Why strings for port and node IDs, why not objects?
855		892
856	We considered "objects", but found that the actual number of methods	893	We considered "objects", but found that the actual number of methods
857	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
858	the network frequently, the serialising/deserialising would add lots of	895	the network frequently, the serialising/deserialising would add lots of
859	overhead, as well as having to keep a proxy object.	896	overhead, as well as having to keep a proxy object everywhere.
860		897
861	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
862	procedures to be "valid".	899	procedures to be "valid".
863		900
864	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
865	can't become much cheaper.	902	global hash - it can't become much cheaper.
866		903
867	=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?
868		905
869	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
870	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
871	default.	908	default (although all nodes will accept it).
872		909
873	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
874	faster for small messages and b) most importantly, after years of	911	faster for small messages and b) most importantly, after years of
875	experience we found that object serialisation is causing more problems	912	experience we found that object serialisation is causing more problems
876	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
877	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
878	always have to re-think your design.	915	always have to re-think your design.
879		916
880	Keeping your messages simple, concentrating on data structures rather than	917	Keeping your messages simple, concentrating on data structures rather than
881	objects, will keep your messages clean, tidy and efficient.	918	objects, will keep your messages clean, tidy and efficient.
882		919
883	=back	920	=back
884		921
885	=head1 SEE ALSO	922	=head1 SEE ALSO
886		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
887	L<AnyEvent>.	934	L<AnyEvent>.
888		935
889	=head1 AUTHOR	936	=head1 AUTHOR
890		937
891	Marc Lehmann <schmorp@schmorp.de>	938	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs.
Revision 1.88 by root, Fri Sep 11 15:02:17 2009 UTC