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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.85 by root, Tue Sep 8 01:54:13 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $somple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, type matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
38	# monitoring	35	# monitoring
…		…
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
49		47
50	stay tuned.	48	stay tuned.
51		49
52	=head1 DESCRIPTION	50	=head1 DESCRIPTION
53		51
54	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
55		53
56	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
58		56
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	58	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		59
66	=head1 CONCEPTS	60	=head1 CONCEPTS
67		61
68	=over 4	62	=over 4
69		63
70	=item port	64	=item port
71		65
72	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
73		68
74	Some ports allow you to register C<rcv> handlers that can match specific	69	Ports allow you to register C<rcv> handlers that can match all or just
75	messages. All C<rcv> handlers will receive messages they match, messages	70	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	71	anything was listening for them or not.
77		72
78	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
79		74
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
81	separator, and a port name (a printable string of unspecified format). An	76	separator, and a port name (a printable string of unspecified format).
82	exception is the the node port, whose ID is identical to its node
83	reference.
84		77
85	=item node	78	=item node
86		79
87	A node is a single process containing at least one port - the node	80	A node is a single process containing at least one port - the node port,
88	port. You can send messages to node ports to find existing ports or to	81	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	82	ports.
90		83
91	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
93		87
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
95		89
96	A node reference is a string that either simply identifies the node (for	90	A node ID is a string that uniquely identifies the node within a
97	private and slave nodes), or contains a recipe on how to reach a given	91	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
99		94
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		96
103	Node references come in two flavours: resolved (containing only numerical	97	Nodes can only talk to each other by creating some kind of connection to
104	addresses) or unresolved (where hostnames are used instead of addresses).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
105		101
106	Before using an unresolved node reference in a message you first have to	102	=item seed nodes
107	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of the AnyEvent::MP network.
		115
		116	Seed nodes are expected to be long-running, and at least one seed node
		117	should always be available. 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.
108		129
109	=back	130	=back
110		131
111	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
112		133
…		…
127	use base "Exporter";	148	use base "Exporter";
128		149
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
130		151
131	our @EXPORT = qw(	152	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	153	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	154	configure
134	snd rcv mon kil reg psub spawn	155	snd rcv mon mon_guard kil reg psub spawn
135	port	156	port
136	);	157	);
137		158
138	our $SELF;	159	our $SELF;
139		160
…		…
143	kil $SELF, die => $msg;	164	kil $SELF, die => $msg;
144	}	165	}
145		166
146	=item $thisnode = NODE / $NODE	167	=item $thisnode = NODE / $NODE
147		168
148	The C<NODE> function returns, and the C<$NODE> variable contains	169	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	the noderef of the local node. The value is initialised by a call	170	ID of the node running in the current process. This value is initialised by
150	to C<become_public> or C<become_slave>, after which all local port	171	a call to C<configure>.
151	identifiers become invalid.
152		172
153	=item $noderef = node_of $port	173	=item $nodeid = node_of $port
154		174
155	Extracts and returns the noderef from a portid or a noderef.	175	Extracts and returns the node ID from a port ID or a node ID.
156		176
157	=item initialise_node $noderef, $seednode, $seednode...	177	=item configure $profile, key => value...
158		178
159	=item initialise_node "slave/", $master, $master...	179	=item configure key => value...
160		180
161	Before a node can talk to other nodes on the network it has to initialise	181	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	182	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	183	to know is its own name, and optionally it should know the addresses of
		184	some other nodes in the network to discover other nodes.
164		185
165	This function initialises a node - it must be called exactly once (or	186	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	187	never) before calling other AnyEvent::MP functions.
167		188
168	All arguments (optionally except for the first) are noderefs, which can be
169	either resolved or unresolved.
170
171	The first argument will be looked up in the configuration database first
172	(if it is C<undef> then the current nodename will be used instead) to find
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176
177	There are two types of networked nodes, public nodes and slave nodes:
178
179	=over 4	189	=over 4
180		190
181	=item public nodes	191	=item step 1, gathering configuration from profiles
182		192
183	For public nodes, C<$noderef> (supplied either directly to	193	The function first looks up a profile in the aemp configuration (see the
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	194	L<aemp> commandline utility). The profile name can be specified via the
185	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.
186		197
187	After resolving, the node will bind itself on all endpoints and try to	198	The profile data is then gathered as follows:
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191		199
192	=item slave nodes	200	First, all remaining key => value pairs (all of which are conveniently
		201	undocumented at the moment) will be interpreted as configuration
		202	data. Then they will be overwritten by any values specified in the global
		203	default configuration (see the F<aemp> utility), then the chain of
		204	profiles chosen by the profile name (and any C<parent> attributes).
193		205
194	When the C<$noderef> (either as given or overriden by the config file)	206	That means that the values specified in the profile have highest priority
195	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,
196	node. Slave nodes cannot be contacted from outside and will route most of	208	and can only be used to specify defaults.
197	their traffic to the master node that they attach to.
198		209
199	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
200	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
201	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.
202	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.
203		231
204	=back	232	=back
205		233
206	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.
207	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.
208	server.
209		236
210	Example: become a public node listening on the guessed noderef, or the one	237	configure
211	specified via C<aemp> for the current node. This should be the most common
212	form of invocation for "daemon"-type nodes.
213		238
214	initialise_node;	239	Example: become an anonymous node. This form is often used for commandline
		240	clients.
215		241
216	Example: become a slave node to any of the the seednodes specified via	242	configure nodeid => "anon/";
217	C<aemp>. This form is often used for commandline clients.
218		243
219	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).
220		247
221	Example: become a slave node to any of the specified master servers. This	248	# use the aemp commandline utility
222	form is also often used for commandline clients.	249	# aemp profile seed nodeid anon/ binds '*:4040'
223		250
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	251	# then use it
		252	configure profile => "seed";
225		253
226	Example: become a public node, and try to contact some well-known master	254	# or simply use aemp from the shell again:
227	servers to become part of the network.	255	# aemp run profile seed
228		256
229	initialise_node undef, "master1", "master2";	257	# or provide a nicer-to-remember nodeid
230		258	# aemp run profile seed nodeid "$(hostname)"
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236
237	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4
249
250	=item the empty string
251
252	An empty-string component gets resolved as if the default port (4040) was
253	specified.
254
255	=item naked port numbers (e.g. C<1234>)
256
257	These are resolved by prepending the local nodename and a colon, to be
258	further resolved.
259
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
261
262	These are resolved by using AnyEvent::DNS to resolve them, optionally
263	looking up SRV records for the C<aemp=4040> port, if no port was
264	specified.
265
266	=back
267		259
268	=item $SELF	260	=item $SELF
269		261
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	262	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	263	blocks.
272		264
273	=item SELF, %SELF, @SELF...	265	=item *SELF, SELF, %SELF, @SELF...
274		266
275	Due to some quirks in how perl exports variables, it is impossible to	267	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	268	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	269	module, but only C<$SELF> is currently used.
278		270
279	=item snd $port, type => @data	271	=item snd $port, type => @data
280		272
281	=item snd $port, @msg	273	=item snd $port, @msg
282		274
283	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
284	a local or a remote port, and can be either a string or soemthignt hat	276	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		277
287	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
288	string as first element (a portid, or some word that indicates a request	279	use a string as first element (a port ID, or some word that indicates a
289	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.
290		282
291	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
292	function: modifying any argument is not allowed and can cause many	284	function: modifying any argument (or values referenced by them) is
293	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.
294		289
295	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
296	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
297	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
298	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
299	node, anything can be passed.	294	node, anything can be passed. Best rely only on the common denominator of
		295	these.
300		296
301	=item $local_port = port	297	=item $local_port = port
302		298
303	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
304	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.
…		…
351	The default callback received all messages not matched by a more specific	347	The default callback received all messages not matched by a more specific
352	C<tag> match.	348	C<tag> match.
353		349
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	350	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		351
356	Register callbacks to be called on messages starting with the given tag on	352	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	353	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	354	C<$callback> is C<$undef> or missing). There can only be one callback
		355	registered for each tag.
359		356
360	The original message will be passed to the callback, after the first	357	The original message will be passed to the callback, after the first
361	element (the tag) has been removed. The callback will use the same	358	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	359	environment as the default callback (see above).
363		360
…		…
375	rcv port,	372	rcv port,
376	msg1 => sub { ... },	373	msg1 => sub { ... },
377	...	374	...
378	;	375	;
379		376
		377	Example: temporarily register a rcv callback for a tag matching some port
		378	(e.g. for a rpc reply) and unregister it after a message was received.
		379
		380	rcv $port, $otherport => sub {
		381	my @reply = @_;
		382
		383	rcv $SELF, $otherport;
		384	};
		385
380	=cut	386	=cut
381		387
382	sub rcv($@) {	388	sub rcv($@) {
383	my $port = shift;	389	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	390	my ($nodeid, $portid) = split /#/, $port, 2;
385		391
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	392	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	393	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		394
389	while (@_) {	395	while (@_) {
390	if (ref $_[0]) {	396	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	397	if (my $self = $PORT_DATA{$portid}) {
…		…
470	$res	476	$res
471	}	477	}
472	}	478	}
473	}	479	}
474		480
475	=item $guard = mon $port, $cb->(@reason)	481	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		482
477	=item $guard = mon $port, $rcvport	483	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		484
479	=item $guard = mon $port	485	=item $guard = mon $port # kill $SELF when $port dies
480		486
481	=item $guard = mon $port, $rcvport, @msg	487	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		488
483	Monitor the given port and do something when the port is killed or	489	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	490	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	491	to stop monitoring again.
486
487	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port
489	will arrive, or the monitoring action will be invoked after possible
490	message loss has been detected. No messages will be lost "in between"
491	(after the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get
493	delivered again.
494		492
495	In the first form (callback), the callback is simply called with any	493	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	496	C<eval> if unsure.
499		497
500	In the second form (another port given), the other port (C<$rcvport>)	498	In the second form (another port given), the other port (C<$rcvport>)
501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
502	"normal" kils nothing happens, while under all other conditions, the other	500	"normal" kils nothing happens, while under all other conditions, the other
503	port is killed with the same reason.	501	port is killed with the same reason.
504		502
505	The third form (kill self) is the same as the second form, except that	503	The third form (kill self) is the same as the second form, except that
506	C<$rvport> defaults to C<$SELF>.	504	C<$rvport> defaults to C<$SELF>.
507		505
508	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
509	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.
510		511
511	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
512	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
513	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
514	even monitoring requests can get lost (for exmaple, when the connection	515	even monitoring requests can get lost (for example, when the connection
515	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
516	these problems do not exist.	517	these problems do not exist.
517		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
518	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
519		537
520	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
521		539
522	Example: kill ourselves when C<$port> is killed abnormally.	540	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	546	mon $port, $self => "restart";
529		547
530	=cut	548	=cut
531		549
532	sub mon {	550	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	551	my ($nodeid, $port) = split /#/, shift, 2;
534		552
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	553	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		554
537	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,';
538		556
539	unless (ref $cb) {	557	unless (ref $cb) {
540	if (@_) {	558	if (@_) {
…		…
560	is killed, the references will be freed.	578	is killed, the references will be freed.
561		579
562	Optionally returns a guard that will stop the monitoring.	580	Optionally returns a guard that will stop the monitoring.
563		581
564	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
565	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>):
566		584
567	$port->rcv (start => sub {	585	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	587	undef $timer if 0.9 < rand;
570	});	588	});
571	});	589	});
572		590
573	=cut	591	=cut
…		…
582		600
583	=item kil $port[, @reason]	601	=item kil $port[, @reason]
584		602
585	Kill the specified port with the given C<@reason>.	603	Kill the specified port with the given C<@reason>.
586		604
587	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
588	ports will not be kileld, or even notified).	606	monitoring other ports will not necessarily die because a port dies
		607	"normally").
589		608
590	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
591	C<mon>, see below).	610	C<mon>, see above).
592		611
593	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
594	will be reported as reason C<< die => $@ >>.	613	will be reported as reason C<< die => $@ >>.
595		614
596	Transport/communication errors are reported as C<< transport_error =>	615	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	620	=item $port = spawn $node, $initfunc[, @initdata]
602		621
603	Creates a port on the node C<$node> (which can also be a port ID, in which	622	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	623	case it's the node where that port resides).
605		624
606	The port ID of the newly created port is return immediately, and it is	625	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	626	possible to immediately start sending messages or to monitor the port.
608		627
609	After the port has been created, the init function is	628	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	629	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	630	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	631	specify a function in the main program, use C<::name>.
613		632
614	If the function doesn't exist, then the node tries to C<require>	633	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	634	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	636	exists or it runs out of package names.
618		637
619	The init function is then called with the newly-created port as context	638	The init function is then called with the newly-created port as context
620	object (C<$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.
621		642
622	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
623	in the init function, monitor the original port. This two-way monitoring	644	port, and in the remote init function, immediately monitor the passed
624	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<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
625		651
626	Example: spawn a chat server port on C<$othernode>.	652	Example: spawn a chat server port on C<$othernode>.
627		653
628	# this node, executed from within a port context:	654	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
644		670
645	sub _spawn {	671	sub _spawn {
646	my $port = shift;	672	my $port = shift;
647	my $init = shift;	673	my $init = shift;
648		674
		675	# rcv will create the actual port
649	local $SELF = "$NODE#$port";	676	local $SELF = "$NODE#$port";
650	eval {	677	eval {
651	&{ load_func $init }	678	&{ load_func $init }
652	};	679	};
653	_self_die if $@;	680	_self_die if $@;
654	}	681	}
655		682
656	sub spawn(@) {	683	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	684	my ($nodeid, undef) = split /#/, shift, 2;
658		685
659	my $id = "$RUNIQ." . $ID++;	686	my $id = "$RUNIQ." . $ID++;
660		687
661	$_[0] =~ /::/	688	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	689	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		690
664	($NODE{$noderef} \|\| add_node $noderef)	691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		692
667	"$noderef#$id"	693	"$nodeid#$id"
668	}	694	}
669		695
670	=back	696	=item after $timeout, @msg
671		697
672	=head1 NODE MESSAGES	698	=item after $timeout, $callback
673		699
674	Nodes understand the following messages sent to them. Many of them take	700	Either sends the given message, or call the given callback, after the
675	arguments called C<@reply>, which will simply be used to compose a reply	701	specified number of seconds.
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
677	the remaining arguments are simply the message data.
678		702
679	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.
680		706
681	=over 4
682
683	=cut	707	=cut
684		708
685	=item lookup => $name, @reply	709	sub after($@) {
		710	my ($timeout, @action) = @_;
686		711
687	Replies with the port ID of the specified well-known port, or C<undef>.	712	my $t; $t = AE::timer $timeout, 0, sub {
688		713	undef $t;
689	=item devnull => ...	714	ref $action[0]
690		715	? $action[0]()
691	Generic data sink/CPU heat conversion.	716	: snd @action;
692		717	};
693	=item relay => $port, @msg	718	}
694
695	Simply forwards the message to the given port.
696
697	=item eval => $string[ @reply]
698
699	Evaluates the given string. If C<@reply> is given, then a message of the
700	form C<@reply, $@, @evalres> is sent.
701
702	Example: crash another node.
703
704	snd $othernode, eval => "exit";
705
706	=item time => @reply
707
708	Replies the the current node time to C<@reply>.
709
710	Example: tell the current node to send the current time to C<$myport> in a
711	C<timereply> message.
712
713	snd $NODE, time => $myport, timereply => 1, 2;
714	# => snd $myport, timereply => 1, 2, <time>
715		719
716	=back	720	=back
717		721
718	=head1 AnyEvent::MP vs. Distributed Erlang	722	=head1 AnyEvent::MP vs. Distributed Erlang
719		723
…		…
729		733
730	Despite the similarities, there are also some important differences:	734	Despite the similarities, there are also some important differences:
731		735
732	=over 4	736	=over 4
733		737
734	=item * Node references contain the recipe on how to contact them.	738	=item * Node IDs are arbitrary strings in AEMP.
735		739
736	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
737	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
738	convenience functionality.	742	configuration or DNS), but will otherwise discover other odes itself.
739		743
740	This means that AEMP requires a less tightly controlled environment at the	744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	745	uses "local ports are like remote ports".
		746
		747	The failure modes for local ports are quite different (runtime errors
		748	only) then for remote ports - when a local port dies, you I<know> it dies,
		749	when a connection to another node dies, you know nothing about the other
		750	port.
		751
		752	Erlang pretends remote ports are as reliable as local ports, even when
		753	they are not.
		754
		755	AEMP encourages a "treat remote ports differently" philosophy, with local
		756	ports being the special case/exception, where transport errors cannot
		757	occur.
742		758
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	759	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		760
745	Erlang uses processes that selctively receive messages, and therefore	761	Erlang uses processes that selectively receive messages, and therefore
746	needs a queue. AEMP is event based, queuing messages would serve no useful	762	needs a queue. AEMP is event based, queuing messages would serve no
747	purpose.	763	useful purpose. For the same reason the pattern-matching abilities of
		764	AnyEvent::MP are more limited, as there is little need to be able to
		765	filter messages without dequeuing them.
748		766
749	(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).
750		768
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		770
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	771	Sending messages in Erlang is synchronous and blocks the process (and
754	sends are immediate, connection establishment is handled in the	772	so does not need a queue that can overflow). AEMP sends are immediate,
755	background.	773	connection establishment is handled in the background.
756		774
757	=item * Erlang can silently lose messages, AEMP cannot.	775	=item * Erlang suffers from silent message loss, AEMP does not.
758		776
759	Erlang makes few guarantees on messages delivery - messages can get lost	777	Erlang makes few guarantees on messages delivery - messages can get lost
760	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,
761	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).
762		780
763	AEMP guarantees correct ordering, and the guarantee that there are no	781	AEMP guarantees correct ordering, and the guarantee that after one message
764	holes in the message sequence.	782	is lost, all following ones sent to the same port are lost as well, until
765		783	monitoring raises an error, so there are no silent "holes" in the message
766	=item * In Erlang, processes can be declared dead and later be found to be	784	sequence.
767	alive.
768
769	In Erlang it can happen that a monitored process is declared dead and
770	linked processes get killed, but later it turns out that the process is
771	still alive - and can receive messages.
772
773	In AEMP, when port monitoring detects a port as dead, then that port will
774	eventually be killed - it cannot happen that a node detects a port as dead
775	and then later sends messages to it, finding it is still alive.
776		785
777	=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.
778		787
779	In Erlang it is quite possible that a node that restarts reuses a process	788	In Erlang it is quite likely that a node that restarts reuses a process ID
780	ID known to other nodes for a completely different process, causing	789	known to other nodes for a completely different process, causing messages
781	messages destined for that process to end up in an unrelated process.	790	destined for that process to end up in an unrelated process.
782		791
783	AEMP never reuses port IDs, so old messages or old port IDs floating	792	AEMP never reuses port IDs, so old messages or old port IDs floating
784	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.
785		794
786	=item * Erlang uses unprotected connections, AEMP uses secure	795	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	796	authentication and can use TLS.
788		797
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	798	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	799	securely authenticate nodes.
791		800
792	=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
793	communications.	802	communications.
794		803
795	The AEMP protocol, unlike the Erlang protocol, supports both	804	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	805	language independent text-only protocols (good for debugging) and binary,
797	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.
798		808
799	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
800	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
801	protocol simple.	811	protocol simple.
802		812
803	=item * AEMP has more flexible monitoring options than Erlang.	813	=item * AEMP has more flexible monitoring options than Erlang.
804		814
805	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
…		…
808	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
809	on a per-process basis.	819	on a per-process basis.
810		820
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	821	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		822
813	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
814	as linking is (except linking is unreliable in Erlang).	824	same way as linking is (except linking is unreliable in Erlang).
815		825
816	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
817	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
818	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
819	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
820	more reliable.	830	reliable (no need for C<spawn_link>).
821		831
822	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
823	(hard to do in Erlang).	833	(hard to do in Erlang).
824		834
825	=back	835	=back
826		836
827	=head1 RATIONALE	837	=head1 RATIONALE
828		838
829	=over 4	839	=over 4
830		840
831	=item Why strings for ports and noderefs, why not objects?	841	=item Why strings for port and node IDs, why not objects?
832		842
833	We considered "objects", but found that the actual number of methods	843	We considered "objects", but found that the actual number of methods
834	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
835	the network frequently, the serialising/deserialising would add lots of	845	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	846	overhead, as well as having to keep a proxy object everywhere.
837		847
838	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
839	procedures to be "valid".	849	procedures to be "valid".
840		850
841	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
842	can't become much cheaper.	852	global hash - it can't become much cheaper.
843		853
844	=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?
845		855
846	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
847	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
848	default.	858	default (although all nodes will accept it).
849		859
850	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
851	faster for small messages and b) most importantly, after years of	861	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	862	experience we found that object serialisation is causing more problems
853	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
854	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
855	always have to re-think your design.	865	always have to re-think your design.
856		866
857	Keeping your messages simple, concentrating on data structures rather than	867	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	868	objects, will keep your messages clean, tidy and efficient.
859		869
860	=back	870	=back
861		871
862	=head1 SEE ALSO	872	=head1 SEE ALSO
863		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
864	L<AnyEvent>.	884	L<AnyEvent>.
865		885
866	=head1 AUTHOR	886	=head1 AUTHOR
867		887
868	Marc Lehmann <schmorp@schmorp.de>	888	Marc Lehmann <schmorp@schmorp.de>

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs. Revision 1.85 by root, Tue Sep 8 01:54:13 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.85 by root, Tue Sep 8 01:54:13 2009 UTC