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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.57 by root, Sat Aug 15 04:34:34 2009 UTC vs.
Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
38	# monitoring	35	# monitoring
…		…
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
49		47
50	stay tuned.	48	stay tuned.
51		49
52	=head1 DESCRIPTION	50	=head1 DESCRIPTION
53		51
54	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
55		53
56	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
58		56
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	58	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		59
66	=head1 CONCEPTS	60	=head1 CONCEPTS
67		61
68	=over 4	62	=over 4
69		63
70	=item port	64	=item port
71		65
72	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
73		68
74	Ports allow you to register C<rcv> handlers that can match all or just	69	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	70	some messages. Messages send to ports will not be queued, regardless of
		71	anything was listening for them or not.
76		72
77	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
78		74
79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
80	separator, and a port name (a printable string of unspecified format). An	76	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		77
84	=item node	78	=item node
85		79
86	A node is a single process containing at least one port - the node port,	80	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	81	which enables nodes to manage each other remotely, and to create new
88	ports.	82	ports.
89		83
90	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
92		87
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
94		89
95	A node reference is a string that either simply identifies the node (for	90	A node ID is a string that uniquely identifies the node within a
96	private and slave nodes), or contains a recipe on how to reach a given	91	network. Depending on the configuration used, node IDs can look like a
97	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
98		94
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		96
102	Node references come in two flavours: resolved (containing only numerical	97	Nodes can only talk to each other by creating some kind of connection to
103	addresses) or unresolved (where hostnames are used instead of addresses).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
104		101
105	Before using an unresolved node reference in a message you first have to	102	=item seed nodes
106	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of 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.
		118
		119	=item seeds - C<host:port>
		120
		121	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		122	TCP port) of nodes thta should be used as seed nodes.
		123
		124	The nodes listening on those endpoints are expected to be long-running,
		125	and at least one of those should always be available. When nodes run out
		126	of connections (e.g. due to a network error), they try to re-establish
		127	connections to some seednodes again to join the network.
107		128
108	=back	129	=back
109		130
110	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
111		132
…		…
126	use base "Exporter";	147	use base "Exporter";
127		148
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
129		150
130	our @EXPORT = qw(	151	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	152	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	153	configure
133	snd rcv mon kil reg psub spawn	154	snd rcv mon mon_guard kil reg psub spawn
134	port	155	port
135	);	156	);
136		157
137	our $SELF;	158	our $SELF;
138		159
…		…
142	kil $SELF, die => $msg;	163	kil $SELF, die => $msg;
143	}	164	}
144		165
145	=item $thisnode = NODE / $NODE	166	=item $thisnode = NODE / $NODE
146		167
147	The C<NODE> function returns, and the C<$NODE> variable contains the	168	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	169	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	170	a call to C<configure>.
150		171
151	=item $noderef = node_of $port	172	=item $nodeid = node_of $port
152		173
153	Extracts and returns the noderef from a port ID or a noderef.	174	Extracts and returns the node ID from a port ID or a node ID.
154		175
155	=item initialise_node $noderef, $seednode, $seednode...	176	=item configure $profile, key => value...
156		177
157	=item initialise_node "slave/", $master, $master...	178	=item configure key => value...
158		179
159	Before a node can talk to other nodes on the network it has to initialise	180	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	181	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	182	to know is its own name, and optionally it should know the addresses of
		183	some other nodes in the network to discover other nodes.
162		184
163	This function initialises a node - it must be called exactly once (or	185	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	186	never) before calling other AnyEvent::MP functions.
165		187
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	188	=over 4
178		189
179	=item public nodes	190	=item step 1, gathering configuration from profiles
180		191
181	For public nodes, C<$noderef> (supplied either directly to	192	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	193	L<aemp> commandline utility). The profile name can be specified via the
183	noderef (possibly unresolved, in which case it will be resolved).	194	named C<profile> parameter or can simply be the first parameter). If it is
		195	missing, then the nodename (F<uname -n>) will be used as profile name.
184		196
185	After resolving, the node will bind itself on all endpoints and try to	197	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		198
190	=item slave nodes	199	First, all remaining key => value pairs (all of which are conveniently
		200	undocumented at the moment) will be interpreted as configuration
		201	data. Then they will be overwritten by any values specified in the global
		202	default configuration (see the F<aemp> utility), then the chain of
		203	profiles chosen by the profile name (and any C<parent> attributes).
191		204
192	When the C<$noderef> (either as given or overriden by the config file)	205	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	206	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	207	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		208
197	At least one additional noderef is required (either by specifying it	209	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	210	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	211	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.
201		212
202	Note that slave nodes cannot change their name, and consequently, their	213	=item step 2, bind listener sockets
203	master, so if the master goes down, the slave node will not function well	214
204	anymore until it can re-establish conenciton to its master. This makes	215	The next step is to look up the binds in the profile, followed by binding
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.	216	aemp protocol listeners on all binds specified (it is possible and valid
		217	to have no binds, meaning that the node cannot be contacted form the
		218	outside. This means the node cannot talk to other nodes that also have no
		219	binds, but it can still talk to all "normal" nodes).
		220
		221	If the profile does not specify a binds list, then a default of C<*> is
		222	used, meaning the node will bind on a dynamically-assigned port on every
		223	local IP address it finds.
		224
		225	=item step 3, connect to seed nodes
		226
		227	As the last step, the seeds list from the profile is passed to the
		228	L<AnyEvent::MP::Global> module, which will then use it to keep
		229	connectivity with at least one node at any point in time.
206		230
207	=back	231	=back
208		232
209	This function will block until all nodes have been resolved and, for slave	233	Example: become a distributed node using the locla node name as profile.
210	nodes, until it has successfully established a connection to a master	234	This should be the most common form of invocation for "daemon"-type nodes.
211	server.
212		235
213	All the seednodes will also be specially marked to automatically retry	236	configure
214	connecting to them infinitely.
215		237
216	Example: become a public node listening on the guessed noderef, or the one	238	Example: become an anonymous node. This form is often used for commandline
217	specified via C<aemp> for the current node. This should be the most common	239	clients.
218	form of invocation for "daemon"-type nodes.
219		240
220	initialise_node;	241	configure nodeid => "anon/";
221		242
222	Example: become a slave node to any of the the seednodes specified via	243	Example: configure a node using a profile called seed, which si suitable
223	C<aemp>. This form is often used for commandline clients.	244	for a seed node as it binds on all local addresses on a fixed port (4040,
		245	customary for aemp).
224		246
225	initialise_node "slave/";	247	# use the aemp commandline utility
		248	# aemp profile seed nodeid anon/ binds '*:4040'
226		249
227	Example: become a slave node to any of the specified master servers. This	250	# then use it
228	form is also often used for commandline clients.	251	configure profile => "seed";
229		252
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	253	# or simply use aemp from the shell again:
		254	# aemp run profile seed
231		255
232	Example: become a public node, and try to contact some well-known master	256	# or provide a nicer-to-remember nodeid
233	servers to become part of the network.	257	# aemp run profile seed nodeid "$(hostname)"
234
235	initialise_node undef, "master1", "master2";
236
237	Example: become a public node listening on port C<4041>.
238
239	initialise_node 4041;
240
241	Example: become a public node, only visible on localhost port 4044.
242
243	initialise_node "localhost:4044";
244
245	=item $cv = resolve_node $noderef
246
247	Takes an unresolved node reference that may contain hostnames and
248	abbreviated IDs, resolves all of them and returns a resolved node
249	reference.
250
251	In addition to C<address:port> pairs allowed in resolved noderefs, the
252	following forms are supported:
253
254	=over 4
255
256	=item the empty string
257
258	An empty-string component gets resolved as if the default port (4040) was
259	specified.
260
261	=item naked port numbers (e.g. C<1234>)
262
263	These are resolved by prepending the local nodename and a colon, to be
264	further resolved.
265
266	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
267
268	These are resolved by using AnyEvent::DNS to resolve them, optionally
269	looking up SRV records for the C<aemp=4040> port, if no port was
270	specified.
271
272	=back
273		258
274	=item $SELF	259	=item $SELF
275		260
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	261	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	262	blocks.
278		263
279	=item SELF, %SELF, @SELF...	264	=item *SELF, SELF, %SELF, @SELF...
280		265
281	Due to some quirks in how perl exports variables, it is impossible to	266	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	267	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	268	module, but only C<$SELF> is currently used.
284		269
285	=item snd $port, type => @data	270	=item snd $port, type => @data
286		271
287	=item snd $port, @msg	272	=item snd $port, @msg
288		273
289	Send the given message to the given port ID, which can identify either	274	Send the given message to the given port, which can identify either a
290	a local or a remote port, and must be a port ID.	275	local or a remote port, and must be a port ID.
291		276
292	While the message can be about anything, it is highly recommended to use a	277	While the message can be almost anything, it is highly recommended to
293	string as first element (a port ID, or some word that indicates a request	278	use a string as first element (a port ID, or some word that indicates a
294	type etc.).	279	request type etc.) and to consist if only simple perl values (scalars,
		280	arrays, hashes) - if you think you need to pass an object, think again.
295		281
296	The message data effectively becomes read-only after a call to this	282	The message data logically becomes read-only after a call to this
297	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
298	problems.	284	forbidden, as there can be considerable time between the call to C<snd>
		285	and the time the message is actually being serialised - in fact, it might
		286	never be copied as within the same process it is simply handed to the
		287	receiving port.
299		288
300	The type of data you can transfer depends on the transport protocol: when	289	The type of data you can transfer depends on the transport protocol: when
301	JSON is used, then only strings, numbers and arrays and hashes consisting	290	JSON is used, then only strings, numbers and arrays and hashes consisting
302	of those are allowed (no objects). When Storable is used, then anything	291	of those are allowed (no objects). When Storable is used, then anything
303	that Storable can serialise and deserialise is allowed, and for the local	292	that Storable can serialise and deserialise is allowed, and for the local
304	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
305		295
306	=item $local_port = port	296	=item $local_port = port
307		297
308	Create a new local port object and returns its port ID. Initially it has	298	Create a new local port object and returns its port ID. Initially it has
309	no callbacks set and will throw an error when it receives messages.	299	no callbacks set and will throw an error when it receives messages.
…		…
394		384
395	=cut	385	=cut
396		386
397	sub rcv($@) {	387	sub rcv($@) {
398	my $port = shift;	388	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	389	my ($nodeid, $portid) = split /#/, $port, 2;
400		390
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	391	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	392	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		393
404	while (@_) {	394	while (@_) {
405	if (ref $_[0]) {	395	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	396	if (my $self = $PORT_DATA{$portid}) {
…		…
485	$res	475	$res
486	}	476	}
487	}	477	}
488	}	478	}
489		479
490	=item $guard = mon $port, $cb->(@reason)	480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
491		481
492	=item $guard = mon $port, $rcvport	482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
493		483
494	=item $guard = mon $port	484	=item $guard = mon $port # kill $SELF when $port dies
495		485
496	=item $guard = mon $port, $rcvport, @msg	486	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		487
498	Monitor the given port and do something when the port is killed or	488	Monitor the given port and do something when the port is killed or
499	messages to it were lost, and optionally return a guard that can be used	489	messages to it were lost, and optionally return a guard that can be used
500	to stop monitoring again.	490	to stop monitoring again.
501
502	C<mon> effectively guarantees that, in the absence of hardware failures,
503	that after starting the monitor, either all messages sent to the port
504	will arrive, or the monitoring action will be invoked after possible
505	message loss has been detected. No messages will be lost "in between"
506	(after the first lost message no further messages will be received by the
507	port). After the monitoring action was invoked, further messages might get
508	delivered again.
509		491
510	In the first form (callback), the callback is simply called with any	492	In the first form (callback), the callback is simply called with any
511	number of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
512	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
513	C<eval> if unsure.	495	C<eval> if unsure.
514		496
515	In the second form (another port given), the other port (C<$rcvport>)	497	In the second form (another port given), the other port (C<$rcvport>)
516	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
517	"normal" kils nothing happens, while under all other conditions, the other	499	"normal" kils nothing happens, while under all other conditions, the other
518	port is killed with the same reason.	500	port is killed with the same reason.
519		501
520	The third form (kill self) is the same as the second form, except that	502	The third form (kill self) is the same as the second form, except that
521	C<$rvport> defaults to C<$SELF>.	503	C<$rvport> defaults to C<$SELF>.
522		504
523	In the last form (message), a message of the form C<@msg, @reason> will be	505	In the last form (message), a message of the form C<@msg, @reason> will be
524	C<snd>.	506	C<snd>.
		507
		508	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		509	alert was raised), they are removed and will not trigger again.
525		510
526	As a rule of thumb, monitoring requests should always monitor a port from	511	As a rule of thumb, monitoring requests should always monitor a port from
527	a local port (or callback). The reason is that kill messages might get	512	a local port (or callback). The reason is that kill messages might get
528	lost, just like any other message. Another less obvious reason is that	513	lost, just like any other message. Another less obvious reason is that
529	even monitoring requests can get lost (for exmaple, when the connection	514	even monitoring requests can get lost (for example, when the connection
530	to the other node goes down permanently). When monitoring a port locally	515	to the other node goes down permanently). When monitoring a port locally
531	these problems do not exist.	516	these problems do not exist.
532		517
		518	C<mon> effectively guarantees that, in the absence of hardware failures,
		519	after starting the monitor, either all messages sent to the port will
		520	arrive, or the monitoring action will be invoked after possible message
		521	loss has been detected. No messages will be lost "in between" (after
		522	the first lost message no further messages will be received by the
		523	port). After the monitoring action was invoked, further messages might get
		524	delivered again.
		525
		526	Inter-host-connection timeouts and monitoring depend on the transport
		527	used. The only transport currently implemented is TCP, and AnyEvent::MP
		528	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		529	non-idle connection, and usually around two hours for idle conenctions).
		530
		531	This means that monitoring is good for program errors and cleaning up
		532	stuff eventually, but they are no replacement for a timeout when you need
		533	to ensure some maximum latency.
		534
533	Example: call a given callback when C<$port> is killed.	535	Example: call a given callback when C<$port> is killed.
534		536
535	mon $port, sub { warn "port died because of <@_>\n" };	537	mon $port, sub { warn "port died because of <@_>\n" };
536		538
537	Example: kill ourselves when C<$port> is killed abnormally.	539	Example: kill ourselves when C<$port> is killed abnormally.
…		…
543	mon $port, $self => "restart";	545	mon $port, $self => "restart";
544		546
545	=cut	547	=cut
546		548
547	sub mon {	549	sub mon {
548	my ($noderef, $port) = split /#/, shift, 2;	550	my ($nodeid, $port) = split /#/, shift, 2;
549		551
550	my $node = $NODE{$noderef} \|\| add_node $noderef;	552	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
551		553
552	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	554	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
553		555
554	unless (ref $cb) {	556	unless (ref $cb) {
555	if (@_) {	557	if (@_) {
…		…
575	is killed, the references will be freed.	577	is killed, the references will be freed.
576		578
577	Optionally returns a guard that will stop the monitoring.	579	Optionally returns a guard that will stop the monitoring.
578		580
579	This function is useful when you create e.g. timers or other watchers and	581	This function is useful when you create e.g. timers or other watchers and
580	want to free them when the port gets killed:	582	want to free them when the port gets killed (note the use of C<psub>):
581		583
582	$port->rcv (start => sub {	584	$port->rcv (start => sub {
583	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	585	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
584	undef $timer if 0.9 < rand;	586	undef $timer if 0.9 < rand;
585	});	587	});
586	});	588	});
587		589
588	=cut	590	=cut
…		…
597		599
598	=item kil $port[, @reason]	600	=item kil $port[, @reason]
599		601
600	Kill the specified port with the given C<@reason>.	602	Kill the specified port with the given C<@reason>.
601		603
602	If no C<@reason> is specified, then the port is killed "normally" (linked	604	If no C<@reason> is specified, then the port is killed "normally" (ports
603	ports will not be kileld, or even notified).	605	monitoring other ports will not necessarily die because a port dies
		606	"normally").
604		607
605	Otherwise, linked ports get killed with the same reason (second form of	608	Otherwise, linked ports get killed with the same reason (second form of
606	C<mon>, see below).	609	C<mon>, see above).
607		610
608	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
609	will be reported as reason C<< die => $@ >>.	612	will be reported as reason C<< die => $@ >>.
610		613
611	Transport/communication errors are reported as C<< transport_error =>	614	Transport/communication errors are reported as C<< transport_error =>
…		…
616	=item $port = spawn $node, $initfunc[, @initdata]	619	=item $port = spawn $node, $initfunc[, @initdata]
617		620
618	Creates a port on the node C<$node> (which can also be a port ID, in which	621	Creates a port on the node C<$node> (which can also be a port ID, in which
619	case it's the node where that port resides).	622	case it's the node where that port resides).
620		623
621	The port ID of the newly created port is return immediately, and it is	624	The port ID of the newly created port is returned immediately, and it is
622	permissible to immediately start sending messages or monitor the port.	625	possible to immediately start sending messages or to monitor the port.
623		626
624	After the port has been created, the init function is	627	After the port has been created, the init function is called on the remote
625	called. This function must be a fully-qualified function name	628	node, in the same context as a C<rcv> callback. This function must be a
626	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	629	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
627	program, use C<::name>.	630	specify a function in the main program, use C<::name>.
628		631
629	If the function doesn't exist, then the node tries to C<require>	632	If the function doesn't exist, then the node tries to C<require>
630	the package, then the package above the package and so on (e.g.	633	the package, then the package above the package and so on (e.g.
631	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
632	exists or it runs out of package names.	635	exists or it runs out of package names.
633		636
634	The init function is then called with the newly-created port as context	637	The init function is then called with the newly-created port as context
635	object (C<$SELF>) and the C<@initdata> values as arguments.	638	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		639	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		640	the port might not get created.
636		641
637	A common idiom is to pass your own port, monitor the spawned port, and	642	A common idiom is to pass a local port, immediately monitor the spawned
638	in the init function, monitor the original port. This two-way monitoring	643	port, and in the remote init function, immediately monitor the passed
639	ensures that both ports get cleaned up when there is a problem.	644	local port. This two-way monitoring ensures that both ports get cleaned up
		645	when there is a problem.
		646
		647	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
640		650
641	Example: spawn a chat server port on C<$othernode>.	651	Example: spawn a chat server port on C<$othernode>.
642		652
643	# this node, executed from within a port context:	653	# this node, executed from within a port context:
644	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
659		669
660	sub _spawn {	670	sub _spawn {
661	my $port = shift;	671	my $port = shift;
662	my $init = shift;	672	my $init = shift;
663		673
		674	# rcv will create the actual port
664	local $SELF = "$NODE#$port";	675	local $SELF = "$NODE#$port";
665	eval {	676	eval {
666	&{ load_func $init }	677	&{ load_func $init }
667	};	678	};
668	_self_die if $@;	679	_self_die if $@;
669	}	680	}
670		681
671	sub spawn(@) {	682	sub spawn(@) {
672	my ($noderef, undef) = split /#/, shift, 2;	683	my ($nodeid, undef) = split /#/, shift, 2;
673		684
674	my $id = "$RUNIQ." . $ID++;	685	my $id = "$RUNIQ." . $ID++;
675		686
676	$_[0] =~ /::/	687	$_[0] =~ /::/
677	or Carp::croak "spawn init function must be a fully-qualified name, caught";	688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
678		689
679	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
680		691
681	"$noderef#$id"	692	"$nodeid#$id"
		693	}
		694
		695	=item after $timeout, @msg
		696
		697	=item after $timeout, $callback
		698
		699	Either sends the given message, or call the given callback, after the
		700	specified number of seconds.
		701
		702	This is simply a utility function that comes in handy at times - the
		703	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		704	so it may go away in the future.
		705
		706	=cut
		707
		708	sub after($@) {
		709	my ($timeout, @action) = @_;
		710
		711	my $t; $t = AE::timer $timeout, 0, sub {
		712	undef $t;
		713	ref $action[0]
		714	? $action[0]()
		715	: snd @action;
		716	};
682	}	717	}
683		718
684	=back	719	=back
685		720
686	=head1 AnyEvent::MP vs. Distributed Erlang	721	=head1 AnyEvent::MP vs. Distributed Erlang
…		…
697		732
698	Despite the similarities, there are also some important differences:	733	Despite the similarities, there are also some important differences:
699		734
700	=over 4	735	=over 4
701		736
702	=item * Node references contain the recipe on how to contact them.	737	=item * Node IDs are arbitrary strings in AEMP.
703		738
704	Erlang relies on special naming and DNS to work everywhere in the	739	Erlang relies on special naming and DNS to work everywhere in the same
705	same way. AEMP relies on each node knowing it's own address(es), with	740	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
706	convenience functionality.	741	configuration or DNS), but will otherwise discover other odes itself.
707
708	This means that AEMP requires a less tightly controlled environment at the
709	cost of longer node references and a slightly higher management overhead.
710		742
711	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
712	uses "local ports are like remote ports".	744	uses "local ports are like remote ports".
713		745
714	The failure modes for local ports are quite different (runtime errors	746	The failure modes for local ports are quite different (runtime errors
…		…
727		759
728	Erlang uses processes that selectively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
729	needs a queue. AEMP is event based, queuing messages would serve no	761	needs a queue. AEMP is event based, queuing messages would serve no
730	useful purpose. For the same reason the pattern-matching abilities of	762	useful purpose. For the same reason the pattern-matching abilities of
731	AnyEvent::MP are more limited, as there is little need to be able to	763	AnyEvent::MP are more limited, as there is little need to be able to
732	filter messages without dequeing them.	764	filter messages without dequeuing them.
733		765
734	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
735		767
736	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
737		769
…		…
743		775
744	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
745	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
746	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
747		779
748	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that after one message
749	holes in the message sequence.	781	is lost, all following ones sent to the same port are lost as well, until
750		782	monitoring raises an error, so there are no silent "holes" in the message
751	=item * In Erlang, processes can be declared dead and later be found to be	783	sequence.
752	alive.
753
754	In Erlang it can happen that a monitored process is declared dead and
755	linked processes get killed, but later it turns out that the process is
756	still alive - and can receive messages.
757
758	In AEMP, when port monitoring detects a port as dead, then that port will
759	eventually be killed - it cannot happen that a node detects a port as dead
760	and then later sends messages to it, finding it is still alive.
761		784
762	=item * Erlang can send messages to the wrong port, AEMP does not.	785	=item * Erlang can send messages to the wrong port, AEMP does not.
763		786
764	In Erlang it is quite likely that a node that restarts reuses a process ID	787	In Erlang it is quite likely that a node that restarts reuses a process ID
765	known to other nodes for a completely different process, causing messages	788	known to other nodes for a completely different process, causing messages
…		…
769	around in the network will not be sent to an unrelated port.	792	around in the network will not be sent to an unrelated port.
770		793
771	=item * Erlang uses unprotected connections, AEMP uses secure	794	=item * Erlang uses unprotected connections, AEMP uses secure
772	authentication and can use TLS.	795	authentication and can use TLS.
773		796
774	AEMP can use a proven protocol - SSL/TLS - to protect connections and	797	AEMP can use a proven protocol - TLS - to protect connections and
775	securely authenticate nodes.	798	securely authenticate nodes.
776		799
777	=item * The AEMP protocol is optimised for both text-based and binary	800	=item * The AEMP protocol is optimised for both text-based and binary
778	communications.	801	communications.
779		802
780	The AEMP protocol, unlike the Erlang protocol, supports both	803	The AEMP protocol, unlike the Erlang protocol, supports both programming
781	language-independent text-only protocols (good for debugging) and binary,	804	language independent text-only protocols (good for debugging) and binary,
782	language-specific serialisers (e.g. Storable).	805	language-specific serialisers (e.g. Storable). By default, unless TLS is
		806	used, the protocol is actually completely text-based.
783		807
784	It has also been carefully designed to be implementable in other languages	808	It has also been carefully designed to be implementable in other languages
785	with a minimum of work while gracefully degrading fucntionality to make the	809	with a minimum of work while gracefully degrading functionality to make the
786	protocol simple.	810	protocol simple.
787		811
788	=item * AEMP has more flexible monitoring options than Erlang.	812	=item * AEMP has more flexible monitoring options than Erlang.
789		813
790	In Erlang, you can chose to receive I<all> exit signals as messages	814	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
793	Erlang, as one can choose between automatic kill, exit message or callback	817	Erlang, as one can choose between automatic kill, exit message or callback
794	on a per-process basis.	818	on a per-process basis.
795		819
796	=item * Erlang tries to hide remote/local connections, AEMP does not.	820	=item * Erlang tries to hide remote/local connections, AEMP does not.
797		821
798	Monitoring in Erlang is not an indicator of process death/crashes,	822	Monitoring in Erlang is not an indicator of process death/crashes, in the
799	as linking is (except linking is unreliable in Erlang).	823	same way as linking is (except linking is unreliable in Erlang).
800		824
801	In AEMP, you don't "look up" registered port names or send to named ports	825	In AEMP, you don't "look up" registered port names or send to named ports
802	that might or might not be persistent. Instead, you normally spawn a port	826	that might or might not be persistent. Instead, you normally spawn a port
803	on the remote node. The init function monitors the you, and you monitor	827	on the remote node. The init function monitors you, and you monitor the
804	the remote port. Since both monitors are local to the node, they are much	828	remote port. Since both monitors are local to the node, they are much more
805	more reliable.	829	reliable (no need for C<spawn_link>).
806		830
807	This also saves round-trips and avoids sending messages to the wrong port	831	This also saves round-trips and avoids sending messages to the wrong port
808	(hard to do in Erlang).	832	(hard to do in Erlang).
809		833
810	=back	834	=back
811		835
812	=head1 RATIONALE	836	=head1 RATIONALE
813		837
814	=over 4	838	=over 4
815		839
816	=item Why strings for ports and noderefs, why not objects?	840	=item Why strings for port and node IDs, why not objects?
817		841
818	We considered "objects", but found that the actual number of methods	842	We considered "objects", but found that the actual number of methods
819	thatc an be called are very low. Since port IDs and noderefs travel over	843	that can be called are quite low. Since port and node IDs travel over
820	the network frequently, the serialising/deserialising would add lots of	844	the network frequently, the serialising/deserialising would add lots of
821	overhead, as well as having to keep a proxy object.	845	overhead, as well as having to keep a proxy object everywhere.
822		846
823	Strings can easily be printed, easily serialised etc. and need no special	847	Strings can easily be printed, easily serialised etc. and need no special
824	procedures to be "valid".	848	procedures to be "valid".
825		849
826	And a a miniport consists of a single closure stored in a global hash - it	850	And as a result, a miniport consists of a single closure stored in a
827	can't become much cheaper.	851	global hash - it can't become much cheaper.
828		852
829	=item Why favour JSON, why not real serialising format such as Storable?	853	=item Why favour JSON, why not a real serialising format such as Storable?
830		854
831	In fact, any AnyEvent::MP node will happily accept Storable as framing	855	In fact, any AnyEvent::MP node will happily accept Storable as framing
832	format, but currently there is no way to make a node use Storable by	856	format, but currently there is no way to make a node use Storable by
833	default.	857	default (although all nodes will accept it).
834		858
835	The default framing protocol is JSON because a) JSON::XS is many times	859	The default framing protocol is JSON because a) JSON::XS is many times
836	faster for small messages and b) most importantly, after years of	860	faster for small messages and b) most importantly, after years of
837	experience we found that object serialisation is causing more problems	861	experience we found that object serialisation is causing more problems
838	than it gains: Just like function calls, objects simply do not travel	862	than it solves: Just like function calls, objects simply do not travel
839	easily over the network, mostly because they will always be a copy, so you	863	easily over the network, mostly because they will always be a copy, so you
840	always have to re-think your design.	864	always have to re-think your design.
841		865
842	Keeping your messages simple, concentrating on data structures rather than	866	Keeping your messages simple, concentrating on data structures rather than
843	objects, will keep your messages clean, tidy and efficient.	867	objects, will keep your messages clean, tidy and efficient.
844		868
845	=back	869	=back
846		870
847	=head1 SEE ALSO	871	=head1 SEE ALSO
848		872
		873	L<AnyEvent::MP::Intro> - a gentle introduction.
		874
		875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		876
		877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		878	your applications.
		879
		880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		881	all nodes.
		882
849	L<AnyEvent>.	883	L<AnyEvent>.
850		884
851	=head1 AUTHOR	885	=head1 AUTHOR
852		886
853	Marc Lehmann <schmorp@schmorp.de>	887	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.57 by root, Sat Aug 15 04:34:34 2009 UTC vs. Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC

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Revision 1.57 by root, Sat Aug 15 04:34:34 2009 UTC vs.
Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC