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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.61 by root, Mon Aug 24 08:06:49 2009 UTC vs.
Revision 1.66 by root, Fri Aug 28 01:07:24 2009 UTC

…		…
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
13	$SELF # receiving/own port id in rcv callbacks	13	$SELF # receiving/own port id in rcv callbacks
14		14
15	# initialise the node so it can send/receive messages	15	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	16	initialise_node;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		17
20	# ports are message endpoints	18	# ports are message endpoints
21		19
22	# sending messages	20	# sending messages
23	snd $port, type => data...;	21	snd $port, type => data...;
…		…
70	=item port	68	=item port
71		69
72	A port is something you can send messages to (with the C<snd> function).	70	A port is something you can send messages to (with the C<snd> function).
73		71
74	Ports allow you to register C<rcv> handlers that can match all or just	72	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	73	some messages. Messages send to ports will not be queued, regardless of
		74	anything was listening for them or not.
76		75
77	=item port id - C<noderef#portname>	76	=item port ID - C<noderef#portname>
78		77
79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	78	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
80	separator, and a port name (a printable string of unspecified format). An	79	separator, and a port name (a printable string of unspecified format). An
81	exception is the the node port, whose ID is identical to its node	80	exception is the the node port, whose ID is identical to its node
82	reference.	81	reference.
…		…
85		84
86	A node is a single process containing at least one port - the node port,	85	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	86	which provides nodes to manage each other remotely, and to create new
88	ports.	87	ports.
89		88
90	Nodes are either private (single-process only), slaves (connected to a	89	Nodes are either private (single-process only), slaves (can only talk to
91	master node only) or public nodes (connectable from unrelated nodes).	90	public nodes, but do not need an open port) or public nodes (connectable
		91	from any other node).
92		92
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item node ID - C<[a-za-Z0-9_\-.:]+>
94		94
95	A node reference is a string that either simply identifies the node (for	95	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	96	network. Depending on the configuration used, node IDs can look like a
97	node (for public nodes).	97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		98	doesn't interpret node IDs in any way.
98		99
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	100	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		101
102	Node references come in two flavours: resolved (containing only numerical	102	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).	103	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
		105	be used, which specify TCP ports to listen on.
104		106
105	Before using an unresolved node reference in a message you first have to	107	=item seeds - C<host:port>
106	resolve it.	108
		109	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
		111	network. This node is called a seed.
		112
		113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		114	are expected to be long-running, and at least one of those should always
		115	be available. When nodes run out of connections (e.g. due to a network
		116	error), they try to re-establish connections to some seednodes again to
		117	join the network.
107		118
108	=back	119	=back
109		120
110	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
111		122
…		…
142	kil $SELF, die => $msg;	153	kil $SELF, die => $msg;
143	}	154	}
144		155
145	=item $thisnode = NODE / $NODE	156	=item $thisnode = NODE / $NODE
146		157
147	The C<NODE> function returns, and the C<$NODE> variable contains the	158	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	159	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	160	a call to C<initialise_node>.
150		161
151	=item $noderef = node_of $port	162	=item $nodeid = node_of $port
152		163
153	Extracts and returns the noderef from a port ID or a noderef.	164	Extracts and returns the node ID part from a port ID or a node ID.
154		165
155	=item initialise_node $noderef, $seednode, $seednode...	166	=item initialise_node $profile_name
156		167
157	=item initialise_node "slave/", $master, $master...
158
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 initialise 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 initialises 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	176	The first argument is a profile name. If it is C<undef> or missing, then
167	either resolved or unresolved.	177	the current nodename will be used instead (i.e. F<uname -n>).
168		178
169	The first argument will be looked up in the configuration database first	179	The function then looks up the profile in the aemp configuration (see the
170	(if it is C<undef> then the current nodename will be used instead) to find	180	L<aemp> commandline utility).
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		181
175	There are two types of networked nodes, public nodes and slave nodes:	182	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
		184	special node ID of C<anon/> will be replaced by a random node ID.
176		185
177	=over 4	186	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
		188	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
		190	binds, but it can still talk to all "normal" nodes).
178		191
179	=item public nodes	192	If the profile does not specify a binds list, then the node ID will be
		193	treated as if it were of the form C<host:port>, which will be resolved and
		194	used as binds list.
180		195
181	For public nodes, C<$noderef> (supplied either directly to	196	Lastly, the seeds list from the profile is passed to the
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	197	L<AnyEvent::MP::Global> module, which will then use it to keep
183	noderef (possibly unresolved, in which case it will be resolved).	198	connectivity with at least on of those seed nodes at any point in time.
184		199
185	After resolving, the node will bind itself on all endpoints and try to
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189
190	=item slave nodes
191
192	When the C<$noderef> (either as given or overriden by the config file)
193	is the special string C<slave/>, then the node will become a slave
194	node. Slave nodes cannot be contacted from outside and will route most of
195	their traffic to the master node that they attach to.
196
197	At least one additional noderef is required (either by specifying it
198	directly or because it is part of the configuration profile): The node
199	will try to connect to all of them and will become a slave attached to the
200	first node it can successfully connect to.
201
202	Note that slave nodes cannot change their name, and consequently, their
203	master, so if the master goes down, the slave node will not function well
204	anymore until it can re-establish conenciton to its master. This makes
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.
206
207	=back
208
209	This function will block until all nodes have been resolved and, for slave
210	nodes, until it has successfully established a connection to a master
211	server.
212
213	All the seednodes will also be specially marked to automatically retry
214	connecting to them infinitely.
215
216	Example: become a public node listening on the guessed noderef, or the one	200	Example: become a distributed node listening on the guessed noderef, or
217	specified via C<aemp> for the current node. This should be the most common	201	the one specified via C<aemp> for the current node. This should be the
218	form of invocation for "daemon"-type nodes.	202	most common form of invocation for "daemon"-type nodes.
219		203
220	initialise_node;	204	initialise_node;
221		205
222	Example: become a slave node to any of the the seednodes specified via	206	Example: become an anonymous node. This form is often used for commandline
223	C<aemp>. This form is often used for commandline clients.	207	clients.
224		208
225	initialise_node "slave/";	209	initialise_node "anon/";
226		210
227	Example: become a slave node to any of the specified master servers. This	211	Example: become a distributed node. If there is no profile of the given
228	form is also often used for commandline clients.	212	name, or no binds list was specified, resolve C<localhost:4044> and bind
229		213	on the resulting addresses.
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
231
232	Example: become a public node, and try to contact some well-known master
233	servers to become part of the network.
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		214
243	initialise_node "localhost:4044";	215	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		216
274	=item $SELF	217	=item $SELF
275		218
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	219	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	220	blocks.
…		…
722		665
723	Despite the similarities, there are also some important differences:	666	Despite the similarities, there are also some important differences:
724		667
725	=over 4	668	=over 4
726		669
727	=item * Node references contain the recipe on how to contact them.	670	=item * Node IDs are arbitrary strings in AEMP.
728		671
729	Erlang relies on special naming and DNS to work everywhere in the	672	Erlang relies on special naming and DNS to work everywhere in the same
730	same way. AEMP relies on each node knowing it's own address(es), with	673	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
731	convenience functionality.	674	configuraiton or DNS), but will otherwise discover other odes itself.
732
733	This means that AEMP requires a less tightly controlled environment at the
734	cost of longer node references and a slightly higher management overhead.
735		675
736	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	676	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
737	uses "local ports are like remote ports".	677	uses "local ports are like remote ports".
738		678
739	The failure modes for local ports are quite different (runtime errors	679	The failure modes for local ports are quite different (runtime errors
…		…
768		708
769	Erlang makes few guarantees on messages delivery - messages can get lost	709	Erlang makes few guarantees on messages delivery - messages can get lost
770	without any of the processes realising it (i.e. you send messages a, b,	710	without any of the processes realising it (i.e. you send messages a, b,
771	and c, and the other side only receives messages a and c).	711	and c, and the other side only receives messages a and c).
772		712
773	AEMP guarantees correct ordering, and the guarantee that there are no	713	AEMP guarantees correct ordering, and the guarantee that after one message
774	holes in the message sequence.	714	is lost, all following ones sent to the same port are lost as well, until
775		715	monitoring raises an error, so there are no silent "holes" in the message
776	=item * In Erlang, processes can be declared dead and later be found to be	716	sequence.
777	alive.
778
779	In Erlang it can happen that a monitored process is declared dead and
780	linked processes get killed, but later it turns out that the process is
781	still alive - and can receive messages.
782
783	In AEMP, when port monitoring detects a port as dead, then that port will
784	eventually be killed - it cannot happen that a node detects a port as dead
785	and then later sends messages to it, finding it is still alive.
786		717
787	=item * Erlang can send messages to the wrong port, AEMP does not.	718	=item * Erlang can send messages to the wrong port, AEMP does not.
788		719
789	In Erlang it is quite likely that a node that restarts reuses a process ID	720	In Erlang it is quite likely that a node that restarts reuses a process ID
790	known to other nodes for a completely different process, causing messages	721	known to other nodes for a completely different process, causing messages
…		…
794	around in the network will not be sent to an unrelated port.	725	around in the network will not be sent to an unrelated port.
795		726
796	=item * Erlang uses unprotected connections, AEMP uses secure	727	=item * Erlang uses unprotected connections, AEMP uses secure
797	authentication and can use TLS.	728	authentication and can use TLS.
798		729
799	AEMP can use a proven protocol - SSL/TLS - to protect connections and	730	AEMP can use a proven protocol - TLS - to protect connections and
800	securely authenticate nodes.	731	securely authenticate nodes.
801		732
802	=item * The AEMP protocol is optimised for both text-based and binary	733	=item * The AEMP protocol is optimised for both text-based and binary
803	communications.	734	communications.
804		735
805	The AEMP protocol, unlike the Erlang protocol, supports both	736	The AEMP protocol, unlike the Erlang protocol, supports both programming
806	language-independent text-only protocols (good for debugging) and binary,	737	language independent text-only protocols (good for debugging) and binary,
807	language-specific serialisers (e.g. Storable).	738	language-specific serialisers (e.g. Storable).
808		739
809	It has also been carefully designed to be implementable in other languages	740	It has also been carefully designed to be implementable in other languages
810	with a minimum of work while gracefully degrading fucntionality to make the	741	with a minimum of work while gracefully degrading functionality to make the
811	protocol simple.	742	protocol simple.
812		743
813	=item * AEMP has more flexible monitoring options than Erlang.	744	=item * AEMP has more flexible monitoring options than Erlang.
814		745
815	In Erlang, you can chose to receive I<all> exit signals as messages	746	In Erlang, you can chose to receive I<all> exit signals as messages

Diff Legend

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

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.61 by root, Mon Aug 24 08:06:49 2009 UTC vs. Revision 1.66 by root, Fri Aug 28 01:07:24 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.61 by root, Mon Aug 24 08:06:49 2009 UTC vs.
Revision 1.66 by root, Fri Aug 28 01:07:24 2009 UTC