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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
36	# monitoring	35	# monitoring
…		…
38	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
39	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
40		39
41	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
42		41
		42	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - WIP
46	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
47		47
48	stay tuned.	48	stay tuned.
49		49
50	=head1 DESCRIPTION	50	=head1 DESCRIPTION
51		51
52	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
53		53
54	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
56		56
57	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>
58	manual page.	58	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		59
64	=head1 CONCEPTS	60	=head1 CONCEPTS
65		61
66	=over 4	62	=over 4
67		63
68	=item port	64	=item port
69		65
70	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).
71		68
72	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
73	some messages. Messages send to ports will not be queued, regardless of	70	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	71	anything was listening for them or not.
75		72
76	=item port ID - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
77		74
78	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
79	separator, and a port name (a printable string of unspecified format). An	76	separator, and a port name (a printable string of unspecified format).
80	exception is the the node port, whose ID is identical to its node
81	reference.
82		77
83	=item node	78	=item node
84		79
85	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,
86	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
87	ports.	82	ports.
88		83
89	Nodes are either private (single-process only), slaves (can only talk to	84	Nodes are either public (have one or more listening ports) or private
90	public nodes, but do not need an open port) or public nodes (connectable	85	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	86	currently.
92		87
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
94		89
95	A node ID is a string that uniquely identifies the node within a	90	A node ID is a string that uniquely identifies the node within a
96	network. Depending on the configuration used, node IDs can look like a	91	network. Depending on the configuration used, node IDs can look like a
97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
98	doesn't interpret node IDs in any way.	93	doesn't interpret node IDs in any way.
…		…
102	Nodes can only talk to each other by creating some kind of connection to	97	Nodes can only talk to each other by creating some kind of connection to
103	each other. To do this, nodes should listen on one or more local transport	98	each other. To do this, nodes should listen on one or more local transport
104	endpoints - binds. Currently, only standard C<ip:port> specifications can	99	endpoints - binds. Currently, only standard C<ip:port> specifications can
105	be used, which specify TCP ports to listen on.	100	be used, which specify TCP ports to listen on.
106		101
107	=item seeds - C<host:port>	102	=item seed nodes
108		103
109	When a node starts, it knows nothing about the network. To teach the node	104	When a node starts, it knows nothing about the network. To teach the node
110	about the network it first has to contact some other node within the	105	about the network it first has to contact some other node within the
111	network. This node is called a seed.	106	network. This node is called a seed.
112		107
113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of an AnyEvent::MP network.
		115
114	are expected to be long-running, and at least one of those should always	116	Seed nodes are expected to be long-running, and at least one seed node
115	be available. When nodes run out of connections (e.g. due to a network	117	should always be available. They should also be relatively responsive - a
116	error), they try to re-establish connections to some seednodes again to	118	seed node that blocks for long periods will slow down everybody else.
117	join the network.	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.
118		129
119	=back	130	=back
120		131
121	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
122		133
…		…
138		149
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
140		151
141	our @EXPORT = qw(	152	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	153	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	154	configure
144	snd rcv mon mon_guard kil reg psub spawn	155	snd rcv mon mon_guard kil reg psub spawn
145	port	156	port
146	);	157	);
147		158
148	our $SELF;	159	our $SELF;
…		…
153	kil $SELF, die => $msg;	164	kil $SELF, die => $msg;
154	}	165	}
155		166
156	=item $thisnode = NODE / $NODE	167	=item $thisnode = NODE / $NODE
157		168
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	169	The C<NODE> function returns, and the C<$NODE> variable contains, the node
159	ID of the node running in the current process. This value is initialised by	170	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	171	a call to C<configure>.
161		172
162	=item $nodeid = node_of $port	173	=item $nodeid = node_of $port
163		174
164	Extracts and returns the node ID part from a port ID or a node ID.	175	Extracts and returns the node ID from a port ID or a node ID.
165		176
166	=item initialise_node $profile_name	177	=item configure $profile, key => value...
		178
		179	=item configure key => value...
167		180
168	Before a node can talk to other nodes on the network (i.e. enter	181	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to initialise itself - the minimum a node needs	182	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	183	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.	184	some other nodes in the network to discover other nodes.
172		185
173	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
174	never) before calling other AnyEvent::MP functions.	187	never) before calling other AnyEvent::MP functions.
175		188
176	The first argument is a profile name. If it is C<undef> or missing, then	189	=over 4
177	the current nodename will be used instead (i.e. F<uname -n>).
178		190
		191	=item step 1, gathering configuration from profiles
		192
179	The function then looks up the profile in the aemp configuration (see the	193	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	194	L<aemp> commandline utility). The profile name can be specified via the
		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.
		197
		198	The profile data is then gathered as follows:
		199
		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).
		205
		206	That means that the values specified in the profile have highest priority
		207	and the values specified directly via C<configure> have lowest priority,
		208	and can only be used to specify defaults.
181		209
182	If the profile specifies a node ID, then this will become the node ID of	210	If the profile specifies a node ID, then this will become the node ID of
183	this process. If not, then the profile name will be used as node ID. The	211	this process. If not, then the profile name will be used as node ID. The
184	special node ID of C<anon/> will be replaced by a random node ID.	212	special node ID of C<anon/> will be replaced by a random node ID.
		213
		214	=item step 2, bind listener sockets
185		215
186	The next step is to look up the binds in the profile, followed by binding	216	The next step is to look up the binds in the profile, followed by binding
187	aemp protocol listeners on all binds specified (it is possible and valid	217	aemp protocol listeners on all binds specified (it is possible and valid
188	to have no binds, meaning that the node cannot be contacted form the	218	to have no binds, meaning that the node cannot be contacted form the
189	outside. This means the node cannot talk to other nodes that also have no	219	outside. This means the node cannot talk to other nodes that also have no
190	binds, but it can still talk to all "normal" nodes).	220	binds, but it can still talk to all "normal" nodes).
191		221
192	If the profile does not specify a binds list, then the node ID will be	222	If the profile does not specify a binds list, then a default of C<*> is
193	treated as if it were of the form C<host:port>, which will be resolved and	223	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	224	local IP address it finds.
195		225
		226	=item step 3, connect to seed nodes
		227
196	Lastly, the seeds list from the profile is passed to the	228	As the last step, the seeds list from the profile is passed to the
197	L<AnyEvent::MP::Global> module, which will then use it to keep	229	L<AnyEvent::MP::Global> module, which will then use it to keep
198	connectivity with at least on of those seed nodes at any point in time.	230	connectivity with at least one node at any point in time.
199		231
200	Example: become a distributed node listening on the guessed noderef, or	232	=back
201	the one specified via C<aemp> for the current node. This should be the	233
		234	Example: become a distributed node using the locla node name as profile.
202	most common form of invocation for "daemon"-type nodes.	235	This should be the most common form of invocation for "daemon"-type nodes.
203		236
204	initialise_node;	237	configure
205		238
206	Example: become an anonymous node. This form is often used for commandline	239	Example: become an anonymous node. This form is often used for commandline
207	clients.	240	clients.
208		241
209	initialise_node "anon/";	242	configure nodeid => "anon/";
210		243
211	Example: become a distributed node. If there is no profile of the given	244	Example: configure a node using a profile called seed, which si suitable
212	name, or no binds list was specified, resolve C<localhost:4044> and bind	245	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	246	customary for aemp).
214		247
215	initialise_node "localhost:4044";	248	# use the aemp commandline utility
		249	# aemp profile seed nodeid anon/ binds '*:4040'
		250
		251	# then use it
		252	configure profile => "seed";
		253
		254	# or simply use aemp from the shell again:
		255	# aemp run profile seed
		256
		257	# or provide a nicer-to-remember nodeid
		258	# aemp run profile seed nodeid "$(hostname)"
216		259
217	=item $SELF	260	=item $SELF
218		261
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	262	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	263	blocks.
221		264
222	=item SELF, %SELF, @SELF...	265	=item *SELF, SELF, %SELF, @SELF...
223		266
224	Due to some quirks in how perl exports variables, it is impossible to	267	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	268	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	269	module, but only C<$SELF> is currently used.
227		270
228	=item snd $port, type => @data	271	=item snd $port, type => @data
229		272
230	=item snd $port, @msg	273	=item snd $port, @msg
231		274
232	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
233	a local or a remote port, and must be a port ID.	276	local or a remote port, and must be a port ID.
234		277
235	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
236	string as first element (a port ID, or some word that indicates a request	279	use a string as first element (a port ID, or some word that indicates a
237	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.
238		282
239	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
240	function: modifying any argument is not allowed and can cause many	284	function: modifying any argument (or values referenced by them) is
241	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.
242		289
243	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
244	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
245	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
246	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
247	node, anything can be passed.	294	node, anything can be passed. Best rely only on the common denominator of
		295	these.
248		296
249	=item $local_port = port	297	=item $local_port = port
250		298
251	Create a new local port object and returns its port ID. Initially it has	299	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	300	no callbacks set and will throw an error when it receives messages.
…		…
337		385
338	=cut	386	=cut
339		387
340	sub rcv($@) {	388	sub rcv($@) {
341	my $port = shift;	389	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	390	my ($nodeid, $portid) = split /#/, $port, 2;
343		391
344	$NODE{$noderef} == $NODE{""}	392	$NODE{$nodeid} == $NODE{""}
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	393	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		394
347	while (@_) {	395	while (@_) {
348	if (ref $_[0]) {	396	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	397	if (my $self = $PORT_DATA{$portid}) {
…		…
428	$res	476	$res
429	}	477	}
430	}	478	}
431	}	479	}
432		480
433	=item $guard = mon $port, $cb->(@reason)	481	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
434		482
435	=item $guard = mon $port, $rcvport	483	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
436		484
437	=item $guard = mon $port	485	=item $guard = mon $port # kill $SELF when $port dies
438		486
439	=item $guard = mon $port, $rcvport, @msg	487	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		488
441	Monitor the given port and do something when the port is killed or	489	Monitor the given port and do something when the port is killed or
442	messages to it were lost, and optionally return a guard that can be used	490	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	491	to stop monitoring again.
444
445	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port
447	will arrive, or the monitoring action will be invoked after possible
448	message loss has been detected. No messages will be lost "in between"
449	(after the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get
451	delivered again.
452
453	Note that monitoring-actions are one-shot: once released, they are removed
454	and will not trigger again.
455		492
456	In the first form (callback), the callback is simply called with any	493	In the first form (callback), the callback is simply called with any
457	number of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
459	C<eval> if unsure.	496	C<eval> if unsure.
460		497
461	In the second form (another port given), the other port (C<$rcvport>)	498	In the second form (another port given), the other port (C<$rcvport>)
462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
463	"normal" kils nothing happens, while under all other conditions, the other	500	"normal" kils nothing happens, while under all other conditions, the other
464	port is killed with the same reason.	501	port is killed with the same reason.
465		502
466	The third form (kill self) is the same as the second form, except that	503	The third form (kill self) is the same as the second form, except that
467	C<$rvport> defaults to C<$SELF>.	504	C<$rvport> defaults to C<$SELF>.
468		505
469	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
470	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.
471		511
472	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
473	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
474	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
475	even monitoring requests can get lost (for exmaple, when the connection	515	even monitoring requests can get lost (for example, when the connection
476	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
477	these problems do not exist.	517	these problems do not exist.
478		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
479	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
480		537
481	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
482		539
483	Example: kill ourselves when C<$port> is killed abnormally.	540	Example: kill ourselves when C<$port> is killed abnormally.
…		…
489	mon $port, $self => "restart";	546	mon $port, $self => "restart";
490		547
491	=cut	548	=cut
492		549
493	sub mon {	550	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	551	my ($nodeid, $port) = split /#/, shift, 2;
495		552
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	553	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		554
498	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,';
499		556
500	unless (ref $cb) {	557	unless (ref $cb) {
501	if (@_) {	558	if (@_) {
…		…
521	is killed, the references will be freed.	578	is killed, the references will be freed.
522		579
523	Optionally returns a guard that will stop the monitoring.	580	Optionally returns a guard that will stop the monitoring.
524		581
525	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
526	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>):
527		584
528	$port->rcv (start => sub {	585	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	587	undef $timer if 0.9 < rand;
531	});	588	});
532	});	589	});
533		590
534	=cut	591	=cut
…		…
543		600
544	=item kil $port[, @reason]	601	=item kil $port[, @reason]
545		602
546	Kill the specified port with the given C<@reason>.	603	Kill the specified port with the given C<@reason>.
547		604
548	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
549	ports will not be kileld, or even notified).	606	monitoring other ports will not necessarily die because a port dies
		607	"normally").
550		608
551	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
552	C<mon>, see below).	610	C<mon>, see above).
553		611
554	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
555	will be reported as reason C<< die => $@ >>.	613	will be reported as reason C<< die => $@ >>.
556		614
557	Transport/communication errors are reported as C<< transport_error =>	615	Transport/communication errors are reported as C<< transport_error =>
…		…
562	=item $port = spawn $node, $initfunc[, @initdata]	620	=item $port = spawn $node, $initfunc[, @initdata]
563		621
564	Creates a port on the node C<$node> (which can also be a port ID, in which	622	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	623	case it's the node where that port resides).
566		624
567	The port ID of the newly created port is return immediately, and it is	625	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	626	possible to immediately start sending messages or to monitor the port.
569		627
570	After the port has been created, the init function is	628	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	629	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	630	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	631	specify a function in the main program, use C<::name>.
574		632
575	If the function doesn't exist, then the node tries to C<require>	633	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	634	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	636	exists or it runs out of package names.
579		637
580	The init function is then called with the newly-created port as context	638	The init function is then called with the newly-created port as context
581	object (C<$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.
582		642
583	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
584	in the init function, monitor the original port. This two-way monitoring	644	port, and in the remote init function, immediately monitor the passed
585	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<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
586		651
587	Example: spawn a chat server port on C<$othernode>.	652	Example: spawn a chat server port on C<$othernode>.
588		653
589	# this node, executed from within a port context:	654	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
605		670
606	sub _spawn {	671	sub _spawn {
607	my $port = shift;	672	my $port = shift;
608	my $init = shift;	673	my $init = shift;
609		674
		675	# rcv will create the actual port
610	local $SELF = "$NODE#$port";	676	local $SELF = "$NODE#$port";
611	eval {	677	eval {
612	&{ load_func $init }	678	&{ load_func $init }
613	};	679	};
614	_self_die if $@;	680	_self_die if $@;
615	}	681	}
616		682
617	sub spawn(@) {	683	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	684	my ($nodeid, undef) = split /#/, shift, 2;
619		685
620	my $id = "$RUNIQ." . $ID++;	686	my $id = "$RUNIQ." . $ID++;
621		687
622	$_[0] =~ /::/	688	$_[0] =~ /::/
623	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";
624		690
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		692
627	"$noderef#$id"	693	"$nodeid#$id"
628	}	694	}
629		695
630	=item after $timeout, @msg	696	=item after $timeout, @msg
631		697
632	=item after $timeout, $callback	698	=item after $timeout, $callback
633		699
634	Either sends the given message, or call the given callback, after the	700	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	701	specified number of seconds.
636		702
637	This is simply a utility function that come sin handy at times.	703	This is simply a utility function that comes in handy at times - the
		704	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		705	so it may go away in the future.
638		706
639	=cut	707	=cut
640		708
641	sub after($@) {	709	sub after($@) {
642	my ($timeout, @action) = @_;	710	my ($timeout, @action) = @_;
…		…
669		737
670	=item * Node IDs are arbitrary strings in AEMP.	738	=item * Node IDs are arbitrary strings in AEMP.
671		739
672	Erlang relies on special naming and DNS to work everywhere in the same	740	Erlang relies on special naming and DNS to work everywhere in the same
673	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	741	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	configuraiton or DNS), but will otherwise discover other odes itself.	742	configuration or DNS), but will otherwise discover other odes itself.
675		743
676	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
677	uses "local ports are like remote ports".	745	uses "local ports are like remote ports".
678		746
679	The failure modes for local ports are quite different (runtime errors	747	The failure modes for local ports are quite different (runtime errors
…		…
692		760
693	Erlang uses processes that selectively receive messages, and therefore	761	Erlang uses processes that selectively receive messages, and therefore
694	needs a queue. AEMP is event based, queuing messages would serve no	762	needs a queue. AEMP is event based, queuing messages would serve no
695	useful purpose. For the same reason the pattern-matching abilities of	763	useful purpose. For the same reason the pattern-matching abilities of
696	AnyEvent::MP are more limited, as there is little need to be able to	764	AnyEvent::MP are more limited, as there is little need to be able to
697	filter messages without dequeing them.	765	filter messages without dequeuing them.
698		766
699	(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).
700		768
701	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
702		770
…		…
708		776
709	Erlang makes few guarantees on messages delivery - messages can get lost	777	Erlang makes few guarantees on messages delivery - messages can get lost
710	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,
711	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).
712		780
713	AEMP guarantees correct ordering, and the guarantee that there are no	781	AEMP guarantees correct ordering, and the guarantee that after one message
714	holes in the message sequence.	782	is lost, all following ones sent to the same port are lost as well, until
715		783	monitoring raises an error, so there are no silent "holes" in the message
716	=item * In Erlang, processes can be declared dead and later be found to be	784	sequence.
717	alive.
718
719	In Erlang it can happen that a monitored process is declared dead and
720	linked processes get killed, but later it turns out that the process is
721	still alive - and can receive messages.
722
723	In AEMP, when port monitoring detects a port as dead, then that port will
724	eventually be killed - it cannot happen that a node detects a port as dead
725	and then later sends messages to it, finding it is still alive.
726		785
727	=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.
728		787
729	In Erlang it is quite likely that a node that restarts reuses a process ID	788	In Erlang it is quite likely that a node that restarts reuses a process ID
730	known to other nodes for a completely different process, causing messages	789	known to other nodes for a completely different process, causing messages
…		…
734	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.
735		794
736	=item * Erlang uses unprotected connections, AEMP uses secure	795	=item * Erlang uses unprotected connections, AEMP uses secure
737	authentication and can use TLS.	796	authentication and can use TLS.
738		797
739	AEMP can use a proven protocol - SSL/TLS - to protect connections and	798	AEMP can use a proven protocol - TLS - to protect connections and
740	securely authenticate nodes.	799	securely authenticate nodes.
741		800
742	=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
743	communications.	802	communications.
744		803
745	The AEMP protocol, unlike the Erlang protocol, supports both	804	The AEMP protocol, unlike the Erlang protocol, supports both programming
746	language-independent text-only protocols (good for debugging) and binary,	805	language independent text-only protocols (good for debugging) and binary,
747	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.
748		808
749	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
750	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
751	protocol simple.	811	protocol simple.
752		812
753	=item * AEMP has more flexible monitoring options than Erlang.	813	=item * AEMP has more flexible monitoring options than Erlang.
754		814
755	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
…		…
758	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
759	on a per-process basis.	819	on a per-process basis.
760		820
761	=item * Erlang tries to hide remote/local connections, AEMP does not.	821	=item * Erlang tries to hide remote/local connections, AEMP does not.
762		822
763	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
764	as linking is (except linking is unreliable in Erlang).	824	same way as linking is (except linking is unreliable in Erlang).
765		825
766	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
767	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
768	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
769	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
770	more reliable.	830	reliable (no need for C<spawn_link>).
771		831
772	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
773	(hard to do in Erlang).	833	(hard to do in Erlang).
774		834
775	=back	835	=back
776		836
777	=head1 RATIONALE	837	=head1 RATIONALE
778		838
779	=over 4	839	=over 4
780		840
781	=item Why strings for ports and noderefs, why not objects?	841	=item Why strings for port and node IDs, why not objects?
782		842
783	We considered "objects", but found that the actual number of methods	843	We considered "objects", but found that the actual number of methods
784	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
785	the network frequently, the serialising/deserialising would add lots of	845	the network frequently, the serialising/deserialising would add lots of
786	overhead, as well as having to keep a proxy object.	846	overhead, as well as having to keep a proxy object everywhere.
787		847
788	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
789	procedures to be "valid".	849	procedures to be "valid".
790		850
791	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
792	can't become much cheaper.	852	global hash - it can't become much cheaper.
793		853
794	=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?
795		855
796	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
797	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
798	default.	858	default (although all nodes will accept it).
799		859
800	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
801	faster for small messages and b) most importantly, after years of	861	faster for small messages and b) most importantly, after years of
802	experience we found that object serialisation is causing more problems	862	experience we found that object serialisation is causing more problems
803	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
804	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
805	always have to re-think your design.	865	always have to re-think your design.
806		866
807	Keeping your messages simple, concentrating on data structures rather than	867	Keeping your messages simple, concentrating on data structures rather than
808	objects, will keep your messages clean, tidy and efficient.	868	objects, will keep your messages clean, tidy and efficient.
809		869
810	=back	870	=back
811		871
812	=head1 SEE ALSO	872	=head1 SEE ALSO
813		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
814	L<AnyEvent>.	884	L<AnyEvent>.
815		885
816	=head1 AUTHOR	886	=head1 AUTHOR
817		887
818	Marc Lehmann <schmorp@schmorp.de>	888	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs. Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC

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Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.86 by root, Wed Sep 9 01:47:01 2009 UTC