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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC vs.
Revision 1.82 by root, Mon Sep 7 18:42:09 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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.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-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 seeds - C<host:port>
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	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		109	are expected to be long-running, and at least one of those should always
		110	be available. When nodes run out of connections (e.g. due to a network
		111	error), they try to re-establish connections to some seednodes again to
		112	join the network.
		113
		114	Apart from being sued for seeding, seednodes are not special in any way -
		115	every public node can be a seednode.
107		116
108	=back	117	=back
109		118
110	=head1 VARIABLES/FUNCTIONS	119	=head1 VARIABLES/FUNCTIONS
111		120
…		…
126	use base "Exporter";	135	use base "Exporter";
127		136
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
129		138
130	our @EXPORT = qw(	139	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	140	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	141	configure
133	snd rcv mon kil reg psub spawn	142	snd rcv mon mon_guard kil reg psub spawn
134	port	143	port
135	);	144	);
136		145
137	our $SELF;	146	our $SELF;
138		147
…		…
142	kil $SELF, die => $msg;	151	kil $SELF, die => $msg;
143	}	152	}
144		153
145	=item $thisnode = NODE / $NODE	154	=item $thisnode = NODE / $NODE
146		155
147	The C<NODE> function returns, and the C<$NODE> variable contains the	156	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	157	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	158	a call to C<configure>.
150		159
151	=item $noderef = node_of $port	160	=item $nodeid = node_of $port
152		161
153	Extracts and returns the noderef from a port ID or a noderef.	162	Extracts and returns the node ID from a port ID or a node ID.
154		163
155	=item initialise_node $noderef, $seednode, $seednode...	164	=item configure $profile, key => value...
156		165
157	=item initialise_node "slave/", $master, $master...	166	=item configure key => value...
158		167
159	Before a node can talk to other nodes on the network it has to initialise	168	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	169	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
162		172
163	This function initialises a node - it must be called exactly once (or	173	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
165		175
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	176	=over 4
178		177
179	=item public nodes	178	=item step 1, gathering configuration from profiles
180		179
181	For public nodes, C<$noderef> (supplied either directly to	180	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	181	L<aemp> commandline utility). The profile name can be specified via the
183	noderef (possibly unresolved, in which case it will be resolved).	182	named C<profile> parameter or can simply be the first parameter). If it is
		183	missing, then the nodename (F<uname -n>) will be used as profile name.
184		184
185	After resolving, the node will bind itself on all endpoints and try to	185	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		186
190	=item slave nodes	187	First, all remaining key => value pairs (all of which are conveniently
		188	undocumented at the moment) will be interpreted as configuration
		189	data. Then they will be overwritten by any values specified in the global
		190	default configuration (see the F<aemp> utility), then the chain of
		191	profiles chosen by the profile name (and any C<parent> attributes).
191		192
192	When the C<$noderef> (either as given or overriden by the config file)	193	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	194	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	195	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		196
197	At least one additional noderef is required (either by specifying it	197	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	198	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	199	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.	200
		201	=item step 2, bind listener sockets
		202
		203	The next step is to look up the binds in the profile, followed by binding
		204	aemp protocol listeners on all binds specified (it is possible and valid
		205	to have no binds, meaning that the node cannot be contacted form the
		206	outside. This means the node cannot talk to other nodes that also have no
		207	binds, but it can still talk to all "normal" nodes).
		208
		209	If the profile does not specify a binds list, then a default of C<*> is
		210	used, meaning the node will bind on a dynamically-assigned port on every
		211	local IP address it finds.
		212
		213	=item step 3, connect to seed nodes
		214
		215	As the last step, the seeds list from the profile is passed to the
		216	L<AnyEvent::MP::Global> module, which will then use it to keep
		217	connectivity with at least one node at any point in time.
201		218
202	=back	219	=back
203		220
204	This function will block until all nodes have been resolved and, for slave	221	Example: become a distributed node using the locla node name as profile.
205	nodes, until it has successfully established a connection to a master	222	This should be the most common form of invocation for "daemon"-type nodes.
206	server.
207		223
208	Example: become a public node listening on the guessed noderef, or the one	224	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		225
212	initialise_node;	226	Example: become an anonymous node. This form is often used for commandline
		227	clients.
213		228
214	Example: become a slave node to any of the the seednodes specified via	229	configure nodeid => "anon/";
215	C<aemp>. This form is often used for commandline clients.
216		230
217	initialise_node "slave/";	231	Example: configure a node using a profile called seed, which si suitable
		232	for a seed node as it binds on all local addresses on a fixed port (4040,
		233	customary for aemp).
218		234
219	Example: become a slave node to any of the specified master servers. This	235	# use the aemp commandline utility
220	form is also often used for commandline clients.	236	# aemp profile seed nodeid anon/ binds '*:4040'
221		237
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	238	# then use it
		239	configure profile => "seed";
223		240
224	Example: become a public node, and try to contact some well-known master	241	# or simply use aemp from the shell again:
225	servers to become part of the network.	242	# aemp run profile seed
226		243
227	initialise_node undef, "master1", "master2";	244	# or provide a nicer-to-remember nodeid
228		245	# 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		246
266	=item $SELF	247	=item $SELF
267		248
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	249	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	250	blocks.
270		251
271	=item SELF, %SELF, @SELF...	252	=item *SELF, SELF, %SELF, @SELF...
272		253
273	Due to some quirks in how perl exports variables, it is impossible to	254	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	256	module, but only C<$SELF> is currently used.
276		257
277	=item snd $port, type => @data	258	=item snd $port, type => @data
278		259
279	=item snd $port, @msg	260	=item snd $port, @msg
280		261
281	Send the given message to the given port ID, which can identify either	262	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.	263	local or a remote port, and must be a port ID.
283		264
284	While the message can be about anything, it is highly recommended to use a	265	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	266	use a string as first element (a port ID, or some word that indicates a
286	type etc.).	267	request type etc.) and to consist if only simple perl values (scalars,
		268	arrays, hashes) - if you think you need to pass an object, think again.
287		269
288	The message data effectively becomes read-only after a call to this	270	The message data logically becomes read-only after a call to this
289	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
290	problems.	272	forbidden, as there can be considerable time between the call to C<snd>
		273	and the time the message is actually being serialised - in fact, it might
		274	never be copied as within the same process it is simply handed to the
		275	receiving port.
291		276
292	The type of data you can transfer depends on the transport protocol: when	277	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	278	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	279	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	280	that Storable can serialise and deserialise is allowed, and for the local
296	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
297		283
298	=item $local_port = port	284	=item $local_port = port
299		285
300	Create a new local port object and returns its port ID. Initially it has	286	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	287	no callbacks set and will throw an error when it receives messages.
…		…
386		372
387	=cut	373	=cut
388		374
389	sub rcv($@) {	375	sub rcv($@) {
390	my $port = shift;	376	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	377	my ($nodeid, $portid) = split /#/, $port, 2;
392		378
393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	379	$NODE{$nodeid} == $NODE{""}
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	380	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		381
396	while (@_) {	382	while (@_) {
397	if (ref $_[0]) {	383	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	384	if (my $self = $PORT_DATA{$portid}) {
…		…
477	$res	463	$res
478	}	464	}
479	}	465	}
480	}	466	}
481		467
482	=item $guard = mon $port, $cb->(@reason)	468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483		469
484	=item $guard = mon $port, $rcvport	470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485		471
486	=item $guard = mon $port	472	=item $guard = mon $port # kill $SELF when $port dies
487		473
488	=item $guard = mon $port, $rcvport, @msg	474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		475
490	Monitor the given port and do something when the port is killed or	476	Monitor the given port and do something when the port is killed or
491	messages to it were lost, and optionally return a guard that can be used	477	messages to it were lost, and optionally return a guard that can be used
492	to stop monitoring again.	478	to stop monitoring again.
493
494	C<mon> effectively guarantees that, in the absence of hardware failures,
495	that after starting the monitor, either all messages sent to the port
496	will arrive, or the monitoring action will be invoked after possible
497	message loss has been detected. No messages will be lost "in between"
498	(after the first lost message no further messages will be received by the
499	port). After the monitoring action was invoked, further messages might get
500	delivered again.
501		479
502	In the first form (callback), the callback is simply called with any	480	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	481	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	482	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	483	C<eval> if unsure.
506		484
507	In the second form (another port given), the other port (C<$rcvport>)	485	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	486	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	487	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	488	port is killed with the same reason.
511		489
512	The third form (kill self) is the same as the second form, except that	490	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	491	C<$rvport> defaults to C<$SELF>.
514		492
515	In the last form (message), a message of the form C<@msg, @reason> will be	493	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	494	C<snd>.
		495
		496	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		497	alert was raised), they are removed and will not trigger again.
517		498
518	As a rule of thumb, monitoring requests should always monitor a port from	499	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	500	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	501	lost, just like any other message. Another less obvious reason is that
521	even monitoring requests can get lost (for exmaple, when the connection	502	even monitoring requests can get lost (for example, when the connection
522	to the other node goes down permanently). When monitoring a port locally	503	to the other node goes down permanently). When monitoring a port locally
523	these problems do not exist.	504	these problems do not exist.
524		505
		506	C<mon> effectively guarantees that, in the absence of hardware failures,
		507	after starting the monitor, either all messages sent to the port will
		508	arrive, or the monitoring action will be invoked after possible message
		509	loss has been detected. No messages will be lost "in between" (after
		510	the first lost message no further messages will be received by the
		511	port). After the monitoring action was invoked, further messages might get
		512	delivered again.
		513
		514	Inter-host-connection timeouts and monitoring depend on the transport
		515	used. The only transport currently implemented is TCP, and AnyEvent::MP
		516	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		517	non-idle connection, and usually around two hours for idle conenctions).
		518
		519	This means that monitoring is good for program errors and cleaning up
		520	stuff eventually, but they are no replacement for a timeout when you need
		521	to ensure some maximum latency.
		522
525	Example: call a given callback when C<$port> is killed.	523	Example: call a given callback when C<$port> is killed.
526		524
527	mon $port, sub { warn "port died because of <@_>\n" };	525	mon $port, sub { warn "port died because of <@_>\n" };
528		526
529	Example: kill ourselves when C<$port> is killed abnormally.	527	Example: kill ourselves when C<$port> is killed abnormally.
…		…
535	mon $port, $self => "restart";	533	mon $port, $self => "restart";
536		534
537	=cut	535	=cut
538		536
539	sub mon {	537	sub mon {
540	my ($noderef, $port) = split /#/, shift, 2;	538	my ($nodeid, $port) = split /#/, shift, 2;
541		539
542	my $node = $NODE{$noderef} \|\| add_node $noderef;	540	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
543		541
544	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	542	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
545		543
546	unless (ref $cb) {	544	unless (ref $cb) {
547	if (@_) {	545	if (@_) {
…		…
567	is killed, the references will be freed.	565	is killed, the references will be freed.
568		566
569	Optionally returns a guard that will stop the monitoring.	567	Optionally returns a guard that will stop the monitoring.
570		568
571	This function is useful when you create e.g. timers or other watchers and	569	This function is useful when you create e.g. timers or other watchers and
572	want to free them when the port gets killed:	570	want to free them when the port gets killed (note the use of C<psub>):
573		571
574	$port->rcv (start => sub {	572	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	573	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	574	undef $timer if 0.9 < rand;
577	});	575	});
578	});	576	});
579		577
580	=cut	578	=cut
…		…
589		587
590	=item kil $port[, @reason]	588	=item kil $port[, @reason]
591		589
592	Kill the specified port with the given C<@reason>.	590	Kill the specified port with the given C<@reason>.
593		591
594	If no C<@reason> is specified, then the port is killed "normally" (linked	592	If no C<@reason> is specified, then the port is killed "normally" (ports
595	ports will not be kileld, or even notified).	593	monitoring other ports will not necessarily die because a port dies
		594	"normally").
596		595
597	Otherwise, linked ports get killed with the same reason (second form of	596	Otherwise, linked ports get killed with the same reason (second form of
598	C<mon>, see below).	597	C<mon>, see above).
599		598
600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
601	will be reported as reason C<< die => $@ >>.	600	will be reported as reason C<< die => $@ >>.
602		601
603	Transport/communication errors are reported as C<< transport_error =>	602	Transport/communication errors are reported as C<< transport_error =>
…		…
608	=item $port = spawn $node, $initfunc[, @initdata]	607	=item $port = spawn $node, $initfunc[, @initdata]
609		608
610	Creates a port on the node C<$node> (which can also be a port ID, in which	609	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	610	case it's the node where that port resides).
612		611
613	The port ID of the newly created port is return immediately, and it is	612	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	613	possible to immediately start sending messages or to monitor the port.
615		614
616	After the port has been created, the init function is	615	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	616	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	617	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	618	specify a function in the main program, use C<::name>.
620		619
621	If the function doesn't exist, then the node tries to C<require>	620	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	621	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	623	exists or it runs out of package names.
625		624
626	The init function is then called with the newly-created port as context	625	The init function is then called with the newly-created port as context
627	object (C<$SELF>) and the C<@initdata> values as arguments.	626	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		627	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		628	the port might not get created.
628		629
629	A common idiom is to pass your own port, monitor the spawned port, and	630	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	631	port, and in the remote init function, immediately monitor the passed
631	ensures that both ports get cleaned up when there is a problem.	632	local port. This two-way monitoring ensures that both ports get cleaned up
		633	when there is a problem.
		634
		635	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		636	caller before C<spawn> returns (by delaying invocation when spawn is
		637	called for the local node).
632		638
633	Example: spawn a chat server port on C<$othernode>.	639	Example: spawn a chat server port on C<$othernode>.
634		640
635	# this node, executed from within a port context:	641	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	642	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
651		657
652	sub _spawn {	658	sub _spawn {
653	my $port = shift;	659	my $port = shift;
654	my $init = shift;	660	my $init = shift;
655		661
		662	# rcv will create the actual port
656	local $SELF = "$NODE#$port";	663	local $SELF = "$NODE#$port";
657	eval {	664	eval {
658	&{ load_func $init }	665	&{ load_func $init }
659	};	666	};
660	_self_die if $@;	667	_self_die if $@;
661	}	668	}
662		669
663	sub spawn(@) {	670	sub spawn(@) {
664	my ($noderef, undef) = split /#/, shift, 2;	671	my ($nodeid, undef) = split /#/, shift, 2;
665		672
666	my $id = "$RUNIQ." . $ID++;	673	my $id = "$RUNIQ." . $ID++;
667		674
668	$_[0] =~ /::/	675	$_[0] =~ /::/
669	or Carp::croak "spawn init function must be a fully-qualified name, caught";	676	or Carp::croak "spawn init function must be a fully-qualified name, caught";
670		677
671	($NODE{$noderef} \|\| add_node $noderef)	678	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
673		679
674	"$noderef#$id"	680	"$nodeid#$id"
675	}	681	}
676		682
677	=back	683	=item after $timeout, @msg
678		684
679	=head1 NODE MESSAGES	685	=item after $timeout, $callback
680		686
681	Nodes understand the following messages sent to them. Many of them take	687	Either sends the given message, or call the given callback, after the
682	arguments called C<@reply>, which will simply be used to compose a reply	688	specified number of seconds.
683	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
684	the remaining arguments are simply the message data.
685		689
686	While other messages exist, they are not public and subject to change.	690	This is simply a utility function that comes in handy at times - the
		691	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		692	so it may go away in the future.
687		693
688	=over 4
689
690	=cut	694	=cut
691		695
692	=item lookup => $name, @reply	696	sub after($@) {
		697	my ($timeout, @action) = @_;
693		698
694	Replies with the port ID of the specified well-known port, or C<undef>.	699	my $t; $t = AE::timer $timeout, 0, sub {
695		700	undef $t;
696	=item devnull => ...	701	ref $action[0]
697		702	? $action[0]()
698	Generic data sink/CPU heat conversion.	703	: snd @action;
699		704	};
700	=item relay => $port, @msg	705	}
701
702	Simply forwards the message to the given port.
703
704	=item eval => $string[ @reply]
705
706	Evaluates the given string. If C<@reply> is given, then a message of the
707	form C<@reply, $@, @evalres> is sent.
708
709	Example: crash another node.
710
711	snd $othernode, eval => "exit";
712
713	=item time => @reply
714
715	Replies the the current node time to C<@reply>.
716
717	Example: tell the current node to send the current time to C<$myport> in a
718	C<timereply> message.
719
720	snd $NODE, time => $myport, timereply => 1, 2;
721	# => snd $myport, timereply => 1, 2, <time>
722		706
723	=back	707	=back
724		708
725	=head1 AnyEvent::MP vs. Distributed Erlang	709	=head1 AnyEvent::MP vs. Distributed Erlang
726		710
…		…
736		720
737	Despite the similarities, there are also some important differences:	721	Despite the similarities, there are also some important differences:
738		722
739	=over 4	723	=over 4
740		724
741	=item * Node references contain the recipe on how to contact them.	725	=item * Node IDs are arbitrary strings in AEMP.
742		726
743	Erlang relies on special naming and DNS to work everywhere in the	727	Erlang relies on special naming and DNS to work everywhere in the same
744	same way. AEMP relies on each node knowing it's own address(es), with	728	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
745	convenience functionality.	729	configuration or DNS), but will otherwise discover other odes itself.
746
747	This means that AEMP requires a less tightly controlled environment at the
748	cost of longer node references and a slightly higher management overhead.
749		730
750	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	731	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
751	uses "local ports are like remote ports".	732	uses "local ports are like remote ports".
752		733
753	The failure modes for local ports are quite different (runtime errors	734	The failure modes for local ports are quite different (runtime errors
…		…
766		747
767	Erlang uses processes that selectively receive messages, and therefore	748	Erlang uses processes that selectively receive messages, and therefore
768	needs a queue. AEMP is event based, queuing messages would serve no	749	needs a queue. AEMP is event based, queuing messages would serve no
769	useful purpose. For the same reason the pattern-matching abilities of	750	useful purpose. For the same reason the pattern-matching abilities of
770	AnyEvent::MP are more limited, as there is little need to be able to	751	AnyEvent::MP are more limited, as there is little need to be able to
771	filter messages without dequeing them.	752	filter messages without dequeuing them.
772		753
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	754	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
774		755
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	756	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		757
…		…
782		763
783	Erlang makes few guarantees on messages delivery - messages can get lost	764	Erlang makes few guarantees on messages delivery - messages can get lost
784	without any of the processes realising it (i.e. you send messages a, b,	765	without any of the processes realising it (i.e. you send messages a, b,
785	and c, and the other side only receives messages a and c).	766	and c, and the other side only receives messages a and c).
786		767
787	AEMP guarantees correct ordering, and the guarantee that there are no	768	AEMP guarantees correct ordering, and the guarantee that after one message
788	holes in the message sequence.	769	is lost, all following ones sent to the same port are lost as well, until
789		770	monitoring raises an error, so there are no silent "holes" in the message
790	=item * In Erlang, processes can be declared dead and later be found to be	771	sequence.
791	alive.
792
793	In Erlang it can happen that a monitored process is declared dead and
794	linked processes get killed, but later it turns out that the process is
795	still alive - and can receive messages.
796
797	In AEMP, when port monitoring detects a port as dead, then that port will
798	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.
800		772
801	=item * Erlang can send messages to the wrong port, AEMP does not.	773	=item * Erlang can send messages to the wrong port, AEMP does not.
802		774
803	In Erlang it is quite likely that a node that restarts reuses a process ID	775	In Erlang it is quite likely that a node that restarts reuses a process ID
804	known to other nodes for a completely different process, causing messages	776	known to other nodes for a completely different process, causing messages
…		…
808	around in the network will not be sent to an unrelated port.	780	around in the network will not be sent to an unrelated port.
809		781
810	=item * Erlang uses unprotected connections, AEMP uses secure	782	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	783	authentication and can use TLS.
812		784
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	785	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	786	securely authenticate nodes.
815		787
816	=item * The AEMP protocol is optimised for both text-based and binary	788	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	789	communications.
818		790
819	The AEMP protocol, unlike the Erlang protocol, supports both	791	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	792	language independent text-only protocols (good for debugging) and binary,
821	language-specific serialisers (e.g. Storable).	793	language-specific serialisers (e.g. Storable). By default, unless TLS is
		794	used, the protocol is actually completely text-based.
822		795
823	It has also been carefully designed to be implementable in other languages	796	It has also been carefully designed to be implementable in other languages
824	with a minimum of work while gracefully degrading fucntionality to make the	797	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	798	protocol simple.
826		799
827	=item * AEMP has more flexible monitoring options than Erlang.	800	=item * AEMP has more flexible monitoring options than Erlang.
828		801
829	In Erlang, you can chose to receive I<all> exit signals as messages	802	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
832	Erlang, as one can choose between automatic kill, exit message or callback	805	Erlang, as one can choose between automatic kill, exit message or callback
833	on a per-process basis.	806	on a per-process basis.
834		807
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	808	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		809
837	Monitoring in Erlang is not an indicator of process death/crashes,	810	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	811	same way as linking is (except linking is unreliable in Erlang).
839		812
840	In AEMP, you don't "look up" registered port names or send to named ports	813	In AEMP, you don't "look up" registered port names or send to named ports
841	that might or might not be persistent. Instead, you normally spawn a port	814	that might or might not be persistent. Instead, you normally spawn a port
842	on the remote node. The init function monitors the you, and you monitor	815	on the remote node. The init function monitors you, and you monitor the
843	the remote port. Since both monitors are local to the node, they are much	816	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	817	reliable (no need for C<spawn_link>).
845		818
846	This also saves round-trips and avoids sending messages to the wrong port	819	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	820	(hard to do in Erlang).
848		821
849	=back	822	=back
850		823
851	=head1 RATIONALE	824	=head1 RATIONALE
852		825
853	=over 4	826	=over 4
854		827
855	=item Why strings for ports and noderefs, why not objects?	828	=item Why strings for port and node IDs, why not objects?
856		829
857	We considered "objects", but found that the actual number of methods	830	We considered "objects", but found that the actual number of methods
858	thatc an be called are very low. Since port IDs and noderefs travel over	831	that can be called are quite low. Since port and node IDs travel over
859	the network frequently, the serialising/deserialising would add lots of	832	the network frequently, the serialising/deserialising would add lots of
860	overhead, as well as having to keep a proxy object.	833	overhead, as well as having to keep a proxy object everywhere.
861		834
862	Strings can easily be printed, easily serialised etc. and need no special	835	Strings can easily be printed, easily serialised etc. and need no special
863	procedures to be "valid".	836	procedures to be "valid".
864		837
865	And a a miniport consists of a single closure stored in a global hash - it	838	And as a result, a miniport consists of a single closure stored in a
866	can't become much cheaper.	839	global hash - it can't become much cheaper.
867		840
868	=item Why favour JSON, why not real serialising format such as Storable?	841	=item Why favour JSON, why not a real serialising format such as Storable?
869		842
870	In fact, any AnyEvent::MP node will happily accept Storable as framing	843	In fact, any AnyEvent::MP node will happily accept Storable as framing
871	format, but currently there is no way to make a node use Storable by	844	format, but currently there is no way to make a node use Storable by
872	default.	845	default (although all nodes will accept it).
873		846
874	The default framing protocol is JSON because a) JSON::XS is many times	847	The default framing protocol is JSON because a) JSON::XS is many times
875	faster for small messages and b) most importantly, after years of	848	faster for small messages and b) most importantly, after years of
876	experience we found that object serialisation is causing more problems	849	experience we found that object serialisation is causing more problems
877	than it gains: Just like function calls, objects simply do not travel	850	than it solves: Just like function calls, objects simply do not travel
878	easily over the network, mostly because they will always be a copy, so you	851	easily over the network, mostly because they will always be a copy, so you
879	always have to re-think your design.	852	always have to re-think your design.
880		853
881	Keeping your messages simple, concentrating on data structures rather than	854	Keeping your messages simple, concentrating on data structures rather than
882	objects, will keep your messages clean, tidy and efficient.	855	objects, will keep your messages clean, tidy and efficient.
883		856
884	=back	857	=back
885		858
886	=head1 SEE ALSO	859	=head1 SEE ALSO
887		860
		861	L<AnyEvent::MP::Intro> - a gentle introduction.
		862
		863	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		864
		865	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		866	your applications.
		867
		868	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		869	all nodes.
		870
888	L<AnyEvent>.	871	L<AnyEvent>.
889		872
890	=head1 AUTHOR	873	=head1 AUTHOR
891		874
892	Marc Lehmann <schmorp@schmorp.de>	875	Marc Lehmann <schmorp@schmorp.de>

Diff Legend

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

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC vs. Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC vs.
Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC