[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 1.86 by root, Wed Sep 9 01:47:01 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
38	# monitoring	35	# monitoring
…		…
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
49		47
50	stay tuned.	48	stay tuned.
51		49
52	=head1 DESCRIPTION	50	=head1 DESCRIPTION
53		51
54	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
55		53
56	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
58		56
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	58	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		59
66	=head1 CONCEPTS	60	=head1 CONCEPTS
67		61
68	=over 4	62	=over 4
69		63
70	=item port	64	=item port
71		65
72	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
73		68
74	Ports allow you to register C<rcv> handlers that can match all or just	69	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	70	some messages. Messages send to ports will not be queued, regardless of
		71	anything was listening for them or not.
76		72
77	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
78		74
79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
80	separator, and a port name (a printable string of unspecified format). An	76	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		77
84	=item node	78	=item node
85		79
86	A node is a single process containing at least one port - the node port,	80	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	81	which enables nodes to manage each other remotely, and to create new
88	ports.	82	ports.
89		83
90	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
92		87
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
94		89
95	A node reference is a string that either simply identifies the node (for	90	A node ID is a string that uniquely identifies the node within a
96	private and slave nodes), or contains a recipe on how to reach a given	91	network. Depending on the configuration used, node IDs can look like a
97	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
98		94
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		96
102	Node references come in two flavours: resolved (containing only numerical	97	Nodes can only talk to each other by creating some kind of connection to
103	addresses) or unresolved (where hostnames are used instead of addresses).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
104		101
105	Before using an unresolved node reference in a message you first have to	102	=item seed nodes
106	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of an AnyEvent::MP network.
		115
		116	Seed nodes are expected to be long-running, and at least one seed node
		117	should always be available. They should also be relatively responsive - a
		118	seed node that blocks for long periods will slow down everybody else.
		119
		120	=item seeds - C<host:port>
		121
		122	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		123	TCP port) of nodes thta should be used as seed nodes.
		124
		125	The nodes listening on those endpoints are expected to be long-running,
		126	and at least one of those should always be available. When nodes run out
		127	of connections (e.g. due to a network error), they try to re-establish
		128	connections to some seednodes again to join the network.
107		129
108	=back	130	=back
109		131
110	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
111		133
…		…
126	use base "Exporter";	148	use base "Exporter";
127		149
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
129		151
130	our @EXPORT = qw(	152	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	153	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	154	configure
133	snd rcv mon kil reg psub spawn	155	snd rcv mon mon_guard kil reg psub spawn
134	port	156	port
135	);	157	);
136		158
137	our $SELF;	159	our $SELF;
138		160
…		…
142	kil $SELF, die => $msg;	164	kil $SELF, die => $msg;
143	}	165	}
144		166
145	=item $thisnode = NODE / $NODE	167	=item $thisnode = NODE / $NODE
146		168
147	The C<NODE> function returns, and the C<$NODE> variable contains the	169	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	170	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	171	a call to C<configure>.
150		172
151	=item $noderef = node_of $port	173	=item $nodeid = node_of $port
152		174
153	Extracts and returns the noderef from a port ID or a noderef.	175	Extracts and returns the node ID from a port ID or a node ID.
154		176
155	=item initialise_node $noderef, $seednode, $seednode...	177	=item configure $profile, key => value...
156		178
157	=item initialise_node "slave/", $master, $master...	179	=item configure key => value...
158		180
159	Before a node can talk to other nodes on the network it has to initialise	181	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	182	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	183	to know is its own name, and optionally it should know the addresses of
		184	some other nodes in the network to discover other nodes.
162		185
163	This function initialises a node - it must be called exactly once (or	186	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	187	never) before calling other AnyEvent::MP functions.
165		188
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	189	=over 4
178		190
179	=item public nodes	191	=item step 1, gathering configuration from profiles
180		192
181	For public nodes, C<$noderef> (supplied either directly to	193	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	194	L<aemp> commandline utility). The profile name can be specified via the
183	noderef (possibly unresolved, in which case it will be resolved).	195	named C<profile> parameter or can simply be the first parameter). If it is
		196	missing, then the nodename (F<uname -n>) will be used as profile name.
184		197
185	After resolving, the node will bind itself on all endpoints and try to	198	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		199
190	=item slave nodes	200	First, all remaining key => value pairs (all of which are conveniently
		201	undocumented at the moment) will be interpreted as configuration
		202	data. Then they will be overwritten by any values specified in the global
		203	default configuration (see the F<aemp> utility), then the chain of
		204	profiles chosen by the profile name (and any C<parent> attributes).
191		205
192	When the C<$noderef> (either as given or overriden by the config file)	206	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	207	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	208	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		209
197	At least one additional noderef is required (either by specifying it	210	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	211	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	212	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.	213
		214	=item step 2, bind listener sockets
		215
		216	The next step is to look up the binds in the profile, followed by binding
		217	aemp protocol listeners on all binds specified (it is possible and valid
		218	to have no binds, meaning that the node cannot be contacted form the
		219	outside. This means the node cannot talk to other nodes that also have no
		220	binds, but it can still talk to all "normal" nodes).
		221
		222	If the profile does not specify a binds list, then a default of C<*> is
		223	used, meaning the node will bind on a dynamically-assigned port on every
		224	local IP address it finds.
		225
		226	=item step 3, connect to seed nodes
		227
		228	As the last step, the seeds list from the profile is passed to the
		229	L<AnyEvent::MP::Global> module, which will then use it to keep
		230	connectivity with at least one node at any point in time.
201		231
202	=back	232	=back
203		233
204	This function will block until all nodes have been resolved and, for slave	234	Example: become a distributed node using the locla node name as profile.
205	nodes, until it has successfully established a connection to a master	235	This should be the most common form of invocation for "daemon"-type nodes.
206	server.
207		236
208	Example: become a public node listening on the guessed noderef, or the one	237	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		238
212	initialise_node;	239	Example: become an anonymous node. This form is often used for commandline
		240	clients.
213		241
214	Example: become a slave node to any of the the seednodes specified via	242	configure nodeid => "anon/";
215	C<aemp>. This form is often used for commandline clients.
216		243
217	initialise_node "slave/";	244	Example: configure a node using a profile called seed, which si suitable
		245	for a seed node as it binds on all local addresses on a fixed port (4040,
		246	customary for aemp).
218		247
219	Example: become a slave node to any of the specified master servers. This	248	# use the aemp commandline utility
220	form is also often used for commandline clients.	249	# aemp profile seed nodeid anon/ binds '*:4040'
221		250
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	251	# then use it
		252	configure profile => "seed";
223		253
224	Example: become a public node, and try to contact some well-known master	254	# or simply use aemp from the shell again:
225	servers to become part of the network.	255	# aemp run profile seed
226		256
227	initialise_node undef, "master1", "master2";	257	# or provide a nicer-to-remember nodeid
228		258	# 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		259
266	=item $SELF	260	=item $SELF
267		261
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	262	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	263	blocks.
270		264
271	=item SELF, %SELF, @SELF...	265	=item *SELF, SELF, %SELF, @SELF...
272		266
273	Due to some quirks in how perl exports variables, it is impossible to	267	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	268	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	269	module, but only C<$SELF> is currently used.
276		270
277	=item snd $port, type => @data	271	=item snd $port, type => @data
278		272
279	=item snd $port, @msg	273	=item snd $port, @msg
280		274
281	Send the given message to the given port ID, which can identify either	275	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.	276	local or a remote port, and must be a port ID.
283		277
284	While the message can be about anything, it is highly recommended to use a	278	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	279	use a string as first element (a port ID, or some word that indicates a
286	type etc.).	280	request type etc.) and to consist if only simple perl values (scalars,
		281	arrays, hashes) - if you think you need to pass an object, think again.
287		282
288	The message data effectively becomes read-only after a call to this	283	The message data logically becomes read-only after a call to this
289	function: modifying any argument is not allowed and can cause many	284	function: modifying any argument (or values referenced by them) is
290	problems.	285	forbidden, as there can be considerable time between the call to C<snd>
		286	and the time the message is actually being serialised - in fact, it might
		287	never be copied as within the same process it is simply handed to the
		288	receiving port.
291		289
292	The type of data you can transfer depends on the transport protocol: when	290	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	291	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	292	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	293	that Storable can serialise and deserialise is allowed, and for the local
296	node, anything can be passed.	294	node, anything can be passed. Best rely only on the common denominator of
		295	these.
297		296
298	=item $local_port = port	297	=item $local_port = port
299		298
300	Create a new local port object and returns its port ID. Initially it has	299	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	300	no callbacks set and will throw an error when it receives messages.
…		…
386		385
387	=cut	386	=cut
388		387
389	sub rcv($@) {	388	sub rcv($@) {
390	my $port = shift;	389	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	390	my ($nodeid, $portid) = split /#/, $port, 2;
392		391
393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	392	$NODE{$nodeid} == $NODE{""}
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	393	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		394
396	while (@_) {	395	while (@_) {
397	if (ref $_[0]) {	396	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	397	if (my $self = $PORT_DATA{$portid}) {
…		…
477	$res	476	$res
478	}	477	}
479	}	478	}
480	}	479	}
481		480
482	=item $guard = mon $port, $cb->(@reason)	481	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483		482
484	=item $guard = mon $port, $rcvport	483	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485		484
486	=item $guard = mon $port	485	=item $guard = mon $port # kill $SELF when $port dies
487		486
488	=item $guard = mon $port, $rcvport, @msg	487	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		488
490	Monitor the given port and do something when the port is killed or	489	Monitor the given port and do something when the port is killed or
491	messages to it were lost, and optionally return a guard that can be used	490	messages to it were lost, and optionally return a guard that can be used
492	to stop monitoring again.	491	to stop monitoring again.
493
494	C<mon> effectively guarantees that, in the absence of hardware failures,
495	that after starting the monitor, either all messages sent to the port
496	will arrive, or the monitoring action will be invoked after possible
497	message loss has been detected. No messages will be lost "in between"
498	(after the first lost message no further messages will be received by the
499	port). After the monitoring action was invoked, further messages might get
500	delivered again.
501		492
502	In the first form (callback), the callback is simply called with any	493	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	496	C<eval> if unsure.
506		497
507	In the second form (another port given), the other port (C<$rcvport>)	498	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	500	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	501	port is killed with the same reason.
511		502
512	The third form (kill self) is the same as the second form, except that	503	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	504	C<$rvport> defaults to C<$SELF>.
514		505
515	In the last form (message), a message of the form C<@msg, @reason> will be	506	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	507	C<snd>.
		508
		509	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		510	alert was raised), they are removed and will not trigger again.
517		511
518	As a rule of thumb, monitoring requests should always monitor a port from	512	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	513	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	514	lost, just like any other message. Another less obvious reason is that
521	even monitoring requests can get lost (for exmaple, when the connection	515	even monitoring requests can get lost (for example, when the connection
522	to the other node goes down permanently). When monitoring a port locally	516	to the other node goes down permanently). When monitoring a port locally
523	these problems do not exist.	517	these problems do not exist.
524		518
		519	C<mon> effectively guarantees that, in the absence of hardware failures,
		520	after starting the monitor, either all messages sent to the port will
		521	arrive, or the monitoring action will be invoked after possible message
		522	loss has been detected. No messages will be lost "in between" (after
		523	the first lost message no further messages will be received by the
		524	port). After the monitoring action was invoked, further messages might get
		525	delivered again.
		526
		527	Inter-host-connection timeouts and monitoring depend on the transport
		528	used. The only transport currently implemented is TCP, and AnyEvent::MP
		529	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		530	non-idle connection, and usually around two hours for idle conenctions).
		531
		532	This means that monitoring is good for program errors and cleaning up
		533	stuff eventually, but they are no replacement for a timeout when you need
		534	to ensure some maximum latency.
		535
525	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
526		537
527	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
528		539
529	Example: kill ourselves when C<$port> is killed abnormally.	540	Example: kill ourselves when C<$port> is killed abnormally.
…		…
535	mon $port, $self => "restart";	546	mon $port, $self => "restart";
536		547
537	=cut	548	=cut
538		549
539	sub mon {	550	sub mon {
540	my ($noderef, $port) = split /#/, shift, 2;	551	my ($nodeid, $port) = split /#/, shift, 2;
541		552
542	my $node = $NODE{$noderef} \|\| add_node $noderef;	553	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
543		554
544	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
545		556
546	unless (ref $cb) {	557	unless (ref $cb) {
547	if (@_) {	558	if (@_) {
…		…
567	is killed, the references will be freed.	578	is killed, the references will be freed.
568		579
569	Optionally returns a guard that will stop the monitoring.	580	Optionally returns a guard that will stop the monitoring.
570		581
571	This function is useful when you create e.g. timers or other watchers and	582	This function is useful when you create e.g. timers or other watchers and
572	want to free them when the port gets killed:	583	want to free them when the port gets killed (note the use of C<psub>):
573		584
574	$port->rcv (start => sub {	585	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	587	undef $timer if 0.9 < rand;
577	});	588	});
578	});	589	});
579		590
580	=cut	591	=cut
…		…
589		600
590	=item kil $port[, @reason]	601	=item kil $port[, @reason]
591		602
592	Kill the specified port with the given C<@reason>.	603	Kill the specified port with the given C<@reason>.
593		604
594	If no C<@reason> is specified, then the port is killed "normally" (linked	605	If no C<@reason> is specified, then the port is killed "normally" (ports
595	ports will not be kileld, or even notified).	606	monitoring other ports will not necessarily die because a port dies
		607	"normally").
596		608
597	Otherwise, linked ports get killed with the same reason (second form of	609	Otherwise, linked ports get killed with the same reason (second form of
598	C<mon>, see below).	610	C<mon>, see above).
599		611
600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
601	will be reported as reason C<< die => $@ >>.	613	will be reported as reason C<< die => $@ >>.
602		614
603	Transport/communication errors are reported as C<< transport_error =>	615	Transport/communication errors are reported as C<< transport_error =>
…		…
608	=item $port = spawn $node, $initfunc[, @initdata]	620	=item $port = spawn $node, $initfunc[, @initdata]
609		621
610	Creates a port on the node C<$node> (which can also be a port ID, in which	622	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	623	case it's the node where that port resides).
612		624
613	The port ID of the newly created port is return immediately, and it is	625	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	626	possible to immediately start sending messages or to monitor the port.
615		627
616	After the port has been created, the init function is	628	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	629	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	630	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	631	specify a function in the main program, use C<::name>.
620		632
621	If the function doesn't exist, then the node tries to C<require>	633	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	634	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	636	exists or it runs out of package names.
625		637
626	The init function is then called with the newly-created port as context	638	The init function is then called with the newly-created port as context
627	object (C<$SELF>) and the C<@initdata> values as arguments.	639	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		640	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		641	the port might not get created.
628		642
629	A common idiom is to pass your own port, monitor the spawned port, and	643	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	644	port, and in the remote init function, immediately monitor the passed
631	ensures that both ports get cleaned up when there is a problem.	645	local port. This two-way monitoring ensures that both ports get cleaned up
		646	when there is a problem.
		647
		648	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
632		651
633	Example: spawn a chat server port on C<$othernode>.	652	Example: spawn a chat server port on C<$othernode>.
634		653
635	# this node, executed from within a port context:	654	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
651		670
652	sub _spawn {	671	sub _spawn {
653	my $port = shift;	672	my $port = shift;
654	my $init = shift;	673	my $init = shift;
655		674
		675	# rcv will create the actual port
656	local $SELF = "$NODE#$port";	676	local $SELF = "$NODE#$port";
657	eval {	677	eval {
658	&{ load_func $init }	678	&{ load_func $init }
659	};	679	};
660	_self_die if $@;	680	_self_die if $@;
661	}	681	}
662		682
663	sub spawn(@) {	683	sub spawn(@) {
664	my ($noderef, undef) = split /#/, shift, 2;	684	my ($nodeid, undef) = split /#/, shift, 2;
665		685
666	my $id = "$RUNIQ." . $ID++;	686	my $id = "$RUNIQ." . $ID++;
667		687
668	$_[0] =~ /::/	688	$_[0] =~ /::/
669	or Carp::croak "spawn init function must be a fully-qualified name, caught";	689	or Carp::croak "spawn init function must be a fully-qualified name, caught";
670		690
671	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672		692
673	"$noderef#$id"	693	"$nodeid#$id"
674	}	694	}
675		695
676	=back	696	=item after $timeout, @msg
677		697
678	=head1 NODE MESSAGES	698	=item after $timeout, $callback
679		699
680	Nodes understand the following messages sent to them. Many of them take	700	Either sends the given message, or call the given callback, after the
681	arguments called C<@reply>, which will simply be used to compose a reply	701	specified number of seconds.
682	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
683	the remaining arguments are simply the message data.
684		702
685	While other messages exist, they are not public and subject to change.	703	This is simply a utility function that comes in handy at times - the
		704	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		705	so it may go away in the future.
686		706
687	=over 4
688
689	=cut	707	=cut
690		708
691	=item lookup => $name, @reply	709	sub after($@) {
		710	my ($timeout, @action) = @_;
692		711
693	Replies with the port ID of the specified well-known port, or C<undef>.	712	my $t; $t = AE::timer $timeout, 0, sub {
694		713	undef $t;
695	=item devnull => ...	714	ref $action[0]
696		715	? $action[0]()
697	Generic data sink/CPU heat conversion.	716	: snd @action;
698		717	};
699	=item relay => $port, @msg	718	}
700
701	Simply forwards the message to the given port.
702
703	=item eval => $string[ @reply]
704
705	Evaluates the given string. If C<@reply> is given, then a message of the
706	form C<@reply, $@, @evalres> is sent.
707
708	Example: crash another node.
709
710	snd $othernode, eval => "exit";
711
712	=item time => @reply
713
714	Replies the the current node time to C<@reply>.
715
716	Example: tell the current node to send the current time to C<$myport> in a
717	C<timereply> message.
718
719	snd $NODE, time => $myport, timereply => 1, 2;
720	# => snd $myport, timereply => 1, 2, <time>
721		719
722	=back	720	=back
723		721
724	=head1 AnyEvent::MP vs. Distributed Erlang	722	=head1 AnyEvent::MP vs. Distributed Erlang
725		723
…		…
735		733
736	Despite the similarities, there are also some important differences:	734	Despite the similarities, there are also some important differences:
737		735
738	=over 4	736	=over 4
739		737
740	=item * Node references contain the recipe on how to contact them.	738	=item * Node IDs are arbitrary strings in AEMP.
741		739
742	Erlang relies on special naming and DNS to work everywhere in the	740	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	741	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
744	convenience functionality.	742	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		743
749	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
750	uses "local ports are like remote ports".	745	uses "local ports are like remote ports".
751		746
752	The failure modes for local ports are quite different (runtime errors	747	The failure modes for local ports are quite different (runtime errors
…		…
765		760
766	Erlang uses processes that selectively receive messages, and therefore	761	Erlang uses processes that selectively receive messages, and therefore
767	needs a queue. AEMP is event based, queuing messages would serve no	762	needs a queue. AEMP is event based, queuing messages would serve no
768	useful purpose. For the same reason the pattern-matching abilities of	763	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	764	AnyEvent::MP are more limited, as there is little need to be able to
770	filter messages without dequeing them.	765	filter messages without dequeuing them.
771		766
772	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	767	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
773		768
774	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
775		770
…		…
781		776
782	Erlang makes few guarantees on messages delivery - messages can get lost	777	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,	778	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).	779	and c, and the other side only receives messages a and c).
785		780
786	AEMP guarantees correct ordering, and the guarantee that there are no	781	AEMP guarantees correct ordering, and the guarantee that after one message
787	holes in the message sequence.	782	is lost, all following ones sent to the same port are lost as well, until
788		783	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	784	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		785
800	=item * Erlang can send messages to the wrong port, AEMP does not.	786	=item * Erlang can send messages to the wrong port, AEMP does not.
801		787
802	In Erlang it is quite likely that a node that restarts reuses a process ID	788	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	789	known to other nodes for a completely different process, causing messages
…		…
807	around in the network will not be sent to an unrelated port.	793	around in the network will not be sent to an unrelated port.
808		794
809	=item * Erlang uses unprotected connections, AEMP uses secure	795	=item * Erlang uses unprotected connections, AEMP uses secure
810	authentication and can use TLS.	796	authentication and can use TLS.
811		797
812	AEMP can use a proven protocol - SSL/TLS - to protect connections and	798	AEMP can use a proven protocol - TLS - to protect connections and
813	securely authenticate nodes.	799	securely authenticate nodes.
814		800
815	=item * The AEMP protocol is optimised for both text-based and binary	801	=item * The AEMP protocol is optimised for both text-based and binary
816	communications.	802	communications.
817		803
818	The AEMP protocol, unlike the Erlang protocol, supports both	804	The AEMP protocol, unlike the Erlang protocol, supports both programming
819	language-independent text-only protocols (good for debugging) and binary,	805	language independent text-only protocols (good for debugging) and binary,
820	language-specific serialisers (e.g. Storable).	806	language-specific serialisers (e.g. Storable). By default, unless TLS is
		807	used, the protocol is actually completely text-based.
821		808
822	It has also been carefully designed to be implementable in other languages	809	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	810	with a minimum of work while gracefully degrading functionality to make the
824	protocol simple.	811	protocol simple.
825		812
826	=item * AEMP has more flexible monitoring options than Erlang.	813	=item * AEMP has more flexible monitoring options than Erlang.
827		814
828	In Erlang, you can chose to receive I<all> exit signals as messages	815	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	818	Erlang, as one can choose between automatic kill, exit message or callback
832	on a per-process basis.	819	on a per-process basis.
833		820
834	=item * Erlang tries to hide remote/local connections, AEMP does not.	821	=item * Erlang tries to hide remote/local connections, AEMP does not.
835		822
836	Monitoring in Erlang is not an indicator of process death/crashes,	823	Monitoring in Erlang is not an indicator of process death/crashes, in the
837	as linking is (except linking is unreliable in Erlang).	824	same way as linking is (except linking is unreliable in Erlang).
838		825
839	In AEMP, you don't "look up" registered port names or send to named ports	826	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	827	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	828	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	829	remote port. Since both monitors are local to the node, they are much more
843	more reliable.	830	reliable (no need for C<spawn_link>).
844		831
845	This also saves round-trips and avoids sending messages to the wrong port	832	This also saves round-trips and avoids sending messages to the wrong port
846	(hard to do in Erlang).	833	(hard to do in Erlang).
847		834
848	=back	835	=back
849		836
850	=head1 RATIONALE	837	=head1 RATIONALE
851		838
852	=over 4	839	=over 4
853		840
854	=item Why strings for ports and noderefs, why not objects?	841	=item Why strings for port and node IDs, why not objects?
855		842
856	We considered "objects", but found that the actual number of methods	843	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	844	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	845	the network frequently, the serialising/deserialising would add lots of
859	overhead, as well as having to keep a proxy object.	846	overhead, as well as having to keep a proxy object everywhere.
860		847
861	Strings can easily be printed, easily serialised etc. and need no special	848	Strings can easily be printed, easily serialised etc. and need no special
862	procedures to be "valid".	849	procedures to be "valid".
863		850
864	And a a miniport consists of a single closure stored in a global hash - it	851	And as a result, a miniport consists of a single closure stored in a
865	can't become much cheaper.	852	global hash - it can't become much cheaper.
866		853
867	=item Why favour JSON, why not real serialising format such as Storable?	854	=item Why favour JSON, why not a real serialising format such as Storable?
868		855
869	In fact, any AnyEvent::MP node will happily accept Storable as framing	856	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	857	format, but currently there is no way to make a node use Storable by
871	default.	858	default (although all nodes will accept it).
872		859
873	The default framing protocol is JSON because a) JSON::XS is many times	860	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	861	faster for small messages and b) most importantly, after years of
875	experience we found that object serialisation is causing more problems	862	experience we found that object serialisation is causing more problems
876	than it gains: Just like function calls, objects simply do not travel	863	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	864	easily over the network, mostly because they will always be a copy, so you
878	always have to re-think your design.	865	always have to re-think your design.
879		866
880	Keeping your messages simple, concentrating on data structures rather than	867	Keeping your messages simple, concentrating on data structures rather than
881	objects, will keep your messages clean, tidy and efficient.	868	objects, will keep your messages clean, tidy and efficient.
882		869
883	=back	870	=back
884		871
885	=head1 SEE ALSO	872	=head1 SEE ALSO
886		873
		874	L<AnyEvent::MP::Intro> - a gentle introduction.
		875
		876	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		877
		878	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		879	your applications.
		880
		881	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		882	all nodes.
		883
887	L<AnyEvent>.	884	L<AnyEvent>.
888		885
889	=head1 AUTHOR	886	=head1 AUTHOR
890		887
891	Marc Lehmann <schmorp@schmorp.de>	888	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs.
Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC