1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | AnyEvent::MP - multi-processing/message-passing framework |
3 | AnyEvent::MP - erlang-style multi-processing/message-passing framework |
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 | |
|
|
12 | $SELF # receiving/own port id in rcv callbacks |
|
|
13 | |
|
|
14 | # initialise the node so it can send/receive messages |
|
|
15 | configure; |
|
|
16 | |
|
|
17 | # ports are message destinations |
|
|
18 | |
|
|
19 | # sending messages |
13 | snd $port, type => data...; |
20 | snd $port, type => data...; |
|
|
21 | snd $port, @msg; |
|
|
22 | snd @msg_with_first_element_being_a_port; |
14 | |
23 | |
15 | $SELF # receiving/own port id in rcv callbacks |
24 | # creating/using ports, the simple way |
|
|
25 | my $simple_port = port { my @msg = @_ }; |
16 | |
26 | |
17 | rcv $port, smartmatch => $cb->($port, @msg); |
27 | # creating/using ports, tagged message matching |
18 | |
28 | my $port = port; |
19 | # examples: |
|
|
20 | rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; |
29 | rcv $port, ping => sub { snd $_[0], "pong" }; |
21 | rcv $port1, pong => sub { warn "pong received\n" }; |
30 | rcv $port, pong => sub { warn "pong received\n" }; |
22 | snd $port2, ping => $port1; |
|
|
23 | |
31 | |
24 | # more, smarter, matches (_any_ is exported by this module) |
32 | # create a port on another node |
25 | rcv $port, [child_died => $pid] => sub { ... |
33 | my $port = spawn $node, $initfunc, @initdata; |
26 | rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 |
34 | |
|
|
35 | # destroy a port again |
|
|
36 | kil $port; # "normal" kill |
|
|
37 | kil $port, my_error => "everything is broken"; # error kill |
|
|
38 | |
|
|
39 | # monitoring |
|
|
40 | mon $port, $cb->(@msg) # callback is invoked on death |
|
|
41 | mon $port, $localport # kill localport on abnormal death |
|
|
42 | mon $port, $localport, @msg # send message on death |
|
|
43 | |
|
|
44 | # temporarily execute code in port context |
|
|
45 | peval $port, sub { die "kill the port!" }; |
|
|
46 | |
|
|
47 | # execute callbacks in $SELF port context |
|
|
48 | my $timer = AE::timer 1, 0, psub { |
|
|
49 | die "kill the port, delayed"; |
|
|
50 | }; |
27 | |
51 | |
28 | =head1 DESCRIPTION |
52 | =head1 DESCRIPTION |
29 | |
53 | |
30 | This module (-family) implements a simple message passing framework. |
54 | This module (-family) implements a simple message passing framework. |
31 | |
55 | |
32 | Despite its simplicity, you can securely message other processes running |
56 | Despite its simplicity, you can securely message other processes running |
33 | on the same or other hosts. |
57 | on the same or other hosts, and you can supervise entities remotely. |
34 | |
58 | |
35 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
59 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
36 | manual page. |
60 | manual page and the examples under F<eg/>. |
37 | |
|
|
38 | At the moment, this module family is severly broken and underdocumented, |
|
|
39 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
|
|
40 | stay tuned! The basic API should be finished, however. |
|
|
41 | |
61 | |
42 | =head1 CONCEPTS |
62 | =head1 CONCEPTS |
43 | |
63 | |
44 | =over 4 |
64 | =over 4 |
45 | |
65 | |
46 | =item port |
66 | =item port |
47 | |
67 | |
48 | A port is something you can send messages to (with the C<snd> function). |
68 | Not to be confused with a TCP port, a "port" is something you can send |
|
|
69 | messages to (with the C<snd> function). |
49 | |
70 | |
50 | Some ports allow you to register C<rcv> handlers that can match specific |
71 | Ports allow you to register C<rcv> handlers that can match all or just |
51 | messages. All C<rcv> handlers will receive messages they match, messages |
72 | some messages. Messages send to ports will not be queued, regardless of |
52 | will not be queued. |
73 | anything was listening for them or not. |
53 | |
74 | |
|
|
75 | Ports are represented by (printable) strings called "port IDs". |
|
|
76 | |
54 | =item port id - C<noderef#portname> |
77 | =item port ID - C<nodeid#portname> |
55 | |
78 | |
56 | A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as |
79 | A port ID is the concatenation of a node ID, a hash-mark (C<#>) |
57 | separator, and a port name (a printable string of unspecified format). An |
80 | as separator, and a port name (a printable string of unspecified |
58 | exception is the the node port, whose ID is identical to its node |
81 | format created by AnyEvent::MP). |
59 | reference. |
|
|
60 | |
82 | |
61 | =item node |
83 | =item node |
62 | |
84 | |
63 | A node is a single process containing at least one port - the node |
85 | A node is a single process containing at least one port - the node port, |
64 | port. You can send messages to node ports to find existing ports or to |
86 | which enables nodes to manage each other remotely, and to create new |
65 | create new ports, among other things. |
87 | ports. |
66 | |
88 | |
67 | Nodes are either private (single-process only), slaves (connected to a |
89 | Nodes are either public (have one or more listening ports) or private |
68 | master node only) or public nodes (connectable from unrelated nodes). |
90 | (no listening ports). Private nodes cannot talk to other private nodes |
|
|
91 | currently, but all nodes can talk to public nodes. |
69 | |
92 | |
70 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
93 | Nodes is represented by (printable) strings called "node IDs". |
71 | |
94 | |
72 | A node reference is a string that either simply identifies the node (for |
95 | =item node ID - C<[A-Za-z0-9_\-.:]*> |
73 | private and slave nodes), or contains a recipe on how to reach a given |
|
|
74 | node (for public nodes). |
|
|
75 | |
96 | |
76 | This recipe is simply a comma-separated list of C<address:port> pairs (for |
97 | A node ID is a string that uniquely identifies the node within a |
77 | TCP/IP, other protocols might look different). |
98 | network. Depending on the configuration used, node IDs can look like a |
|
|
99 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
|
|
100 | doesn't interpret node IDs in any way except to uniquely identify a node. |
78 | |
101 | |
79 | Node references come in two flavours: resolved (containing only numerical |
102 | =item binds - C<ip:port> |
80 | addresses) or unresolved (where hostnames are used instead of addresses). |
|
|
81 | |
103 | |
82 | Before using an unresolved node reference in a message you first have to |
104 | Nodes can only talk to each other by creating some kind of connection to |
83 | resolve it. |
105 | each other. To do this, nodes should listen on one or more local transport |
|
|
106 | endpoints - binds. |
|
|
107 | |
|
|
108 | Currently, only standard C<ip:port> specifications can be used, which |
|
|
109 | specify TCP ports to listen on. So a bind is basically just a tcp socket |
|
|
110 | in listening mode thta accepts conenctions form other nodes. |
|
|
111 | |
|
|
112 | =item seed nodes |
|
|
113 | |
|
|
114 | When a node starts, it knows nothing about the network it is in - it |
|
|
115 | needs to connect to at least one other node that is already in the |
|
|
116 | network. These other nodes are called "seed nodes". |
|
|
117 | |
|
|
118 | Seed nodes themselves are not special - they are seed nodes only because |
|
|
119 | some other node I<uses> them as such, but any node can be used as seed |
|
|
120 | node for other nodes, and eahc node cna use a different set of seed nodes. |
|
|
121 | |
|
|
122 | In addition to discovering the network, seed nodes are also used to |
|
|
123 | maintain the network - all nodes using the same seed node form are part of |
|
|
124 | the same network. If a network is split into multiple subnets because e.g. |
|
|
125 | the network link between the parts goes down, then using the same seed |
|
|
126 | nodes for all nodes ensures that eventually the subnets get merged again. |
|
|
127 | |
|
|
128 | Seed nodes are expected to be long-running, and at least one seed node |
|
|
129 | should always be available. They should also be relatively responsive - a |
|
|
130 | seed node that blocks for long periods will slow down everybody else. |
|
|
131 | |
|
|
132 | For small networks, it's best if every node uses the same set of seed |
|
|
133 | nodes. For large networks, it can be useful to specify "regional" seed |
|
|
134 | nodes for most nodes in an area, and use all seed nodes as seed nodes for |
|
|
135 | each other. What's important is that all seed nodes connections form a |
|
|
136 | complete graph, so that the network cannot split into separate subnets |
|
|
137 | forever. |
|
|
138 | |
|
|
139 | Seed nodes are represented by seed IDs. |
|
|
140 | |
|
|
141 | =item seed IDs - C<host:port> |
|
|
142 | |
|
|
143 | Seed IDs are transport endpoint(s) (usually a hostname/IP address and a |
|
|
144 | TCP port) of nodes that should be used as seed nodes. |
|
|
145 | |
|
|
146 | =item global nodes |
|
|
147 | |
|
|
148 | An AEMP network needs a discovery service - nodes need to know how to |
|
|
149 | connect to other nodes they only know by name. In addition, AEMP offers a |
|
|
150 | distributed "group database", which maps group names to a list of strings |
|
|
151 | - for example, to register worker ports. |
|
|
152 | |
|
|
153 | A network needs at least one global node to work, and allows every node to |
|
|
154 | be a global node. |
|
|
155 | |
|
|
156 | Any node that loads the L<AnyEvent::MP::Global> module becomes a global |
|
|
157 | node and tries to keep connections to all other nodes. So while it can |
|
|
158 | make sense to make every node "global" in small networks, it usually makes |
|
|
159 | sense to only make seed nodes into global nodes in large networks (nodes |
|
|
160 | keep connections to seed nodes and global nodes, so makign them the same |
|
|
161 | reduces overhead). |
84 | |
162 | |
85 | =back |
163 | =back |
86 | |
164 | |
87 | =head1 VARIABLES/FUNCTIONS |
165 | =head1 VARIABLES/FUNCTIONS |
88 | |
166 | |
… | |
… | |
90 | |
168 | |
91 | =cut |
169 | =cut |
92 | |
170 | |
93 | package AnyEvent::MP; |
171 | package AnyEvent::MP; |
94 | |
172 | |
|
|
173 | use AnyEvent::MP::Config (); |
95 | use AnyEvent::MP::Base; |
174 | use AnyEvent::MP::Kernel; |
|
|
175 | use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID); |
96 | |
176 | |
97 | use common::sense; |
177 | use common::sense; |
98 | |
178 | |
99 | use Carp (); |
179 | use Carp (); |
100 | |
180 | |
101 | use AE (); |
181 | use AE (); |
|
|
182 | use Guard (); |
102 | |
183 | |
103 | use base "Exporter"; |
184 | use base "Exporter"; |
104 | |
185 | |
105 | our $VERSION = '0.1'; |
186 | our $VERSION = $AnyEvent::MP::Config::VERSION; |
|
|
187 | |
106 | our @EXPORT = qw( |
188 | our @EXPORT = qw( |
107 | NODE $NODE *SELF node_of _any_ |
189 | NODE $NODE *SELF node_of after |
108 | resolve_node |
190 | configure |
109 | become_slave become_public |
191 | snd rcv mon mon_guard kil psub peval spawn cal |
110 | snd rcv mon kil reg psub |
|
|
111 | port |
192 | port |
|
|
193 | db_set db_del db_reg |
|
|
194 | db_mon db_family db_keys db_values |
112 | ); |
195 | ); |
113 | |
196 | |
114 | our $SELF; |
197 | our $SELF; |
115 | |
198 | |
116 | sub _self_die() { |
199 | sub _self_die() { |
… | |
… | |
119 | kil $SELF, die => $msg; |
202 | kil $SELF, die => $msg; |
120 | } |
203 | } |
121 | |
204 | |
122 | =item $thisnode = NODE / $NODE |
205 | =item $thisnode = NODE / $NODE |
123 | |
206 | |
124 | The C<NODE> function returns, and the C<$NODE> variable contains |
207 | The C<NODE> function returns, and the C<$NODE> variable contains, the node |
125 | the noderef of the local node. The value is initialised by a call |
208 | ID of the node running in the current process. This value is initialised by |
126 | to C<become_public> or C<become_slave>, after which all local port |
209 | a call to C<configure>. |
127 | identifiers become invalid. |
|
|
128 | |
210 | |
129 | =item $noderef = node_of $portid |
211 | =item $nodeid = node_of $port |
130 | |
212 | |
131 | Extracts and returns the noderef from a portid or a noderef. |
213 | Extracts and returns the node ID from a port ID or a node ID. |
132 | |
214 | |
133 | =item $cv = resolve_node $noderef |
215 | =item configure $profile, key => value... |
134 | |
216 | |
135 | Takes an unresolved node reference that may contain hostnames and |
217 | =item configure key => value... |
136 | abbreviated IDs, resolves all of them and returns a resolved node |
|
|
137 | reference. |
|
|
138 | |
218 | |
139 | In addition to C<address:port> pairs allowed in resolved noderefs, the |
219 | Before a node can talk to other nodes on the network (i.e. enter |
140 | following forms are supported: |
220 | "distributed mode") it has to configure itself - the minimum a node needs |
|
|
221 | to know is its own name, and optionally it should know the addresses of |
|
|
222 | some other nodes in the network to discover other nodes. |
|
|
223 | |
|
|
224 | This function configures a node - it must be called exactly once (or |
|
|
225 | never) before calling other AnyEvent::MP functions. |
|
|
226 | |
|
|
227 | The key/value pairs are basically the same ones as documented for the |
|
|
228 | F<aemp> command line utility (sans the set/del prefix), with these additions: |
141 | |
229 | |
142 | =over 4 |
230 | =over 4 |
143 | |
231 | |
144 | =item the empty string |
232 | =item norc => $boolean (default false) |
145 | |
233 | |
146 | An empty-string component gets resolved as if the default port (4040) was |
234 | If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not> |
147 | specified. |
235 | be consulted - all configuraiton options must be specified in the |
|
|
236 | C<configure> call. |
148 | |
237 | |
149 | =item naked port numbers (e.g. C<1234>) |
238 | =item force => $boolean (default false) |
150 | |
239 | |
151 | These are resolved by prepending the local nodename and a colon, to be |
240 | IF true, then the values specified in the C<configure> will take |
152 | further resolved. |
241 | precedence over any values configured via the rc file. The default is for |
|
|
242 | the rc file to override any options specified in the program. |
153 | |
243 | |
154 | =item hostnames (e.g. C<localhost:1234>, C<localhost>) |
244 | =item secure => $pass->(@msg) |
155 | |
245 | |
156 | These are resolved by using AnyEvent::DNS to resolve them, optionally |
246 | In addition to specifying a boolean, you can specify a code reference that |
157 | looking up SRV records for the C<aemp=4040> port, if no port was |
247 | is called for every code execution attempt - the execution request is |
158 | specified. |
248 | granted iff the callback returns a true value. |
|
|
249 | |
|
|
250 | Most of the time the callback should look only at |
|
|
251 | C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the |
|
|
252 | actual message (which can be about anything, and is mostly provided for |
|
|
253 | diagnostic purposes). |
|
|
254 | |
|
|
255 | See F<semp setsecure> for more info. |
159 | |
256 | |
160 | =back |
257 | =back |
|
|
258 | |
|
|
259 | =over 4 |
|
|
260 | |
|
|
261 | =item step 1, gathering configuration from profiles |
|
|
262 | |
|
|
263 | The function first looks up a profile in the aemp configuration (see the |
|
|
264 | L<aemp> commandline utility). The profile name can be specified via the |
|
|
265 | named C<profile> parameter or can simply be the first parameter). If it is |
|
|
266 | missing, then the nodename (F<uname -n>) will be used as profile name. |
|
|
267 | |
|
|
268 | The profile data is then gathered as follows: |
|
|
269 | |
|
|
270 | First, all remaining key => value pairs (all of which are conveniently |
|
|
271 | undocumented at the moment) will be interpreted as configuration |
|
|
272 | data. Then they will be overwritten by any values specified in the global |
|
|
273 | default configuration (see the F<aemp> utility), then the chain of |
|
|
274 | profiles chosen by the profile name (and any C<parent> attributes). |
|
|
275 | |
|
|
276 | That means that the values specified in the profile have highest priority |
|
|
277 | and the values specified directly via C<configure> have lowest priority, |
|
|
278 | and can only be used to specify defaults. |
|
|
279 | |
|
|
280 | If the profile specifies a node ID, then this will become the node ID of |
|
|
281 | this process. If not, then the profile name will be used as node ID, with |
|
|
282 | a unique randoms tring (C</%u>) appended. |
|
|
283 | |
|
|
284 | The node ID can contain some C<%> sequences that are expanded: C<%n> |
|
|
285 | is expanded to the local nodename, C<%u> is replaced by a random |
|
|
286 | strign to make the node unique. For example, the F<aemp> commandline |
|
|
287 | utility uses C<aemp/%n/%u> as nodename, which might expand to |
|
|
288 | C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>. |
|
|
289 | |
|
|
290 | =item step 2, bind listener sockets |
|
|
291 | |
|
|
292 | The next step is to look up the binds in the profile, followed by binding |
|
|
293 | aemp protocol listeners on all binds specified (it is possible and valid |
|
|
294 | to have no binds, meaning that the node cannot be contacted form the |
|
|
295 | outside. This means the node cannot talk to other nodes that also have no |
|
|
296 | binds, but it can still talk to all "normal" nodes). |
|
|
297 | |
|
|
298 | If the profile does not specify a binds list, then a default of C<*> is |
|
|
299 | used, meaning the node will bind on a dynamically-assigned port on every |
|
|
300 | local IP address it finds. |
|
|
301 | |
|
|
302 | =item step 3, connect to seed nodes |
|
|
303 | |
|
|
304 | As the last step, the seed ID list from the profile is passed to the |
|
|
305 | L<AnyEvent::MP::Global> module, which will then use it to keep |
|
|
306 | connectivity with at least one node at any point in time. |
|
|
307 | |
|
|
308 | =back |
|
|
309 | |
|
|
310 | Example: become a distributed node using the local node name as profile. |
|
|
311 | This should be the most common form of invocation for "daemon"-type nodes. |
|
|
312 | |
|
|
313 | configure |
|
|
314 | |
|
|
315 | Example: become a semi-anonymous node. This form is often used for |
|
|
316 | commandline clients. |
|
|
317 | |
|
|
318 | configure nodeid => "myscript/%n/%u"; |
|
|
319 | |
|
|
320 | Example: configure a node using a profile called seed, which is suitable |
|
|
321 | for a seed node as it binds on all local addresses on a fixed port (4040, |
|
|
322 | customary for aemp). |
|
|
323 | |
|
|
324 | # use the aemp commandline utility |
|
|
325 | # aemp profile seed binds '*:4040' |
|
|
326 | |
|
|
327 | # then use it |
|
|
328 | configure profile => "seed"; |
|
|
329 | |
|
|
330 | # or simply use aemp from the shell again: |
|
|
331 | # aemp run profile seed |
|
|
332 | |
|
|
333 | # or provide a nicer-to-remember nodeid |
|
|
334 | # aemp run profile seed nodeid "$(hostname)" |
161 | |
335 | |
162 | =item $SELF |
336 | =item $SELF |
163 | |
337 | |
164 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
338 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
165 | blocks. |
339 | blocks. |
166 | |
340 | |
167 | =item SELF, %SELF, @SELF... |
341 | =item *SELF, SELF, %SELF, @SELF... |
168 | |
342 | |
169 | Due to some quirks in how perl exports variables, it is impossible to |
343 | Due to some quirks in how perl exports variables, it is impossible to |
170 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
344 | just export C<$SELF>, all the symbols named C<SELF> are exported by this |
171 | module, but only C<$SELF> is currently used. |
345 | module, but only C<$SELF> is currently used. |
172 | |
346 | |
173 | =item snd $portid, type => @data |
347 | =item snd $port, type => @data |
174 | |
348 | |
175 | =item snd $portid, @msg |
349 | =item snd $port, @msg |
176 | |
350 | |
177 | Send the given message to the given port ID, which can identify either |
351 | Send the given message to the given port, which can identify either a |
178 | a local or a remote port, and can be either a string or soemthignt hat |
352 | local or a remote port, and must be a port ID. |
179 | stringifies a sa port ID (such as a port object :). |
|
|
180 | |
353 | |
181 | While the message can be about anything, it is highly recommended to use a |
354 | While the message can be almost anything, it is highly recommended to |
182 | string as first element (a portid, or some word that indicates a request |
355 | use a string as first element (a port ID, or some word that indicates a |
183 | type etc.). |
356 | request type etc.) and to consist if only simple perl values (scalars, |
|
|
357 | arrays, hashes) - if you think you need to pass an object, think again. |
184 | |
358 | |
185 | The message data effectively becomes read-only after a call to this |
359 | The message data logically becomes read-only after a call to this |
186 | function: modifying any argument is not allowed and can cause many |
360 | function: modifying any argument (or values referenced by them) is |
187 | problems. |
361 | forbidden, as there can be considerable time between the call to C<snd> |
|
|
362 | and the time the message is actually being serialised - in fact, it might |
|
|
363 | never be copied as within the same process it is simply handed to the |
|
|
364 | receiving port. |
188 | |
365 | |
189 | The type of data you can transfer depends on the transport protocol: when |
366 | The type of data you can transfer depends on the transport protocol: when |
190 | JSON is used, then only strings, numbers and arrays and hashes consisting |
367 | JSON is used, then only strings, numbers and arrays and hashes consisting |
191 | of those are allowed (no objects). When Storable is used, then anything |
368 | of those are allowed (no objects). When Storable is used, then anything |
192 | that Storable can serialise and deserialise is allowed, and for the local |
369 | that Storable can serialise and deserialise is allowed, and for the local |
193 | node, anything can be passed. |
370 | node, anything can be passed. Best rely only on the common denominator of |
|
|
371 | these. |
194 | |
372 | |
195 | =item kil $portid[, @reason] |
373 | =item $local_port = port |
196 | |
374 | |
197 | Kill the specified port with the given C<@reason>. |
375 | Create a new local port object and returns its port ID. Initially it has |
|
|
376 | no callbacks set and will throw an error when it receives messages. |
198 | |
377 | |
199 | If no C<@reason> is specified, then the port is killed "normally" (linked |
378 | =item $local_port = port { my @msg = @_ } |
200 | ports will not be kileld, or even notified). |
|
|
201 | |
379 | |
202 | Otherwise, linked ports get killed with the same reason (second form of |
380 | Creates a new local port, and returns its ID. Semantically the same as |
203 | C<mon>, see below). |
381 | creating a port and calling C<rcv $port, $callback> on it. |
204 | |
382 | |
205 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
383 | The block will be called for every message received on the port, with the |
206 | will be reported as reason C<< die => $@ >>. |
384 | global variable C<$SELF> set to the port ID. Runtime errors will cause the |
|
|
385 | port to be C<kil>ed. The message will be passed as-is, no extra argument |
|
|
386 | (i.e. no port ID) will be passed to the callback. |
207 | |
387 | |
208 | Transport/communication errors are reported as C<< transport_error => |
388 | If you want to stop/destroy the port, simply C<kil> it: |
209 | $message >>. |
|
|
210 | |
389 | |
211 | =item $guard = mon $portid, $cb->(@reason) |
390 | my $port = port { |
|
|
391 | my @msg = @_; |
|
|
392 | ... |
|
|
393 | kil $SELF; |
|
|
394 | }; |
212 | |
395 | |
213 | =item $guard = mon $portid, $otherport |
396 | =cut |
214 | |
397 | |
215 | =item $guard = mon $portid, $otherport, @msg |
398 | sub rcv($@); |
216 | |
399 | |
|
|
400 | my $KILME = sub { |
|
|
401 | (my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g; |
|
|
402 | kil $SELF, unhandled_message => "no callback found for message '$tag'"; |
|
|
403 | }; |
|
|
404 | |
|
|
405 | sub port(;&) { |
|
|
406 | my $id = $UNIQ . ++$ID; |
|
|
407 | my $port = "$NODE#$id"; |
|
|
408 | |
|
|
409 | rcv $port, shift || $KILME; |
|
|
410 | |
|
|
411 | $port |
|
|
412 | } |
|
|
413 | |
|
|
414 | =item rcv $local_port, $callback->(@msg) |
|
|
415 | |
|
|
416 | Replaces the default callback on the specified port. There is no way to |
|
|
417 | remove the default callback: use C<sub { }> to disable it, or better |
|
|
418 | C<kil> the port when it is no longer needed. |
|
|
419 | |
|
|
420 | The global C<$SELF> (exported by this module) contains C<$port> while |
|
|
421 | executing the callback. Runtime errors during callback execution will |
|
|
422 | result in the port being C<kil>ed. |
|
|
423 | |
|
|
424 | The default callback receives all messages not matched by a more specific |
|
|
425 | C<tag> match. |
|
|
426 | |
|
|
427 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
|
|
428 | |
|
|
429 | Register (or replace) callbacks to be called on messages starting with the |
|
|
430 | given tag on the given port (and return the port), or unregister it (when |
|
|
431 | C<$callback> is C<$undef> or missing). There can only be one callback |
|
|
432 | registered for each tag. |
|
|
433 | |
|
|
434 | The original message will be passed to the callback, after the first |
|
|
435 | element (the tag) has been removed. The callback will use the same |
|
|
436 | environment as the default callback (see above). |
|
|
437 | |
|
|
438 | Example: create a port and bind receivers on it in one go. |
|
|
439 | |
|
|
440 | my $port = rcv port, |
|
|
441 | msg1 => sub { ... }, |
|
|
442 | msg2 => sub { ... }, |
|
|
443 | ; |
|
|
444 | |
|
|
445 | Example: create a port, bind receivers and send it in a message elsewhere |
|
|
446 | in one go: |
|
|
447 | |
|
|
448 | snd $otherport, reply => |
|
|
449 | rcv port, |
|
|
450 | msg1 => sub { ... }, |
|
|
451 | ... |
|
|
452 | ; |
|
|
453 | |
|
|
454 | Example: temporarily register a rcv callback for a tag matching some port |
|
|
455 | (e.g. for an rpc reply) and unregister it after a message was received. |
|
|
456 | |
|
|
457 | rcv $port, $otherport => sub { |
|
|
458 | my @reply = @_; |
|
|
459 | |
|
|
460 | rcv $SELF, $otherport; |
|
|
461 | }; |
|
|
462 | |
|
|
463 | =cut |
|
|
464 | |
|
|
465 | sub rcv($@) { |
|
|
466 | my $port = shift; |
|
|
467 | my ($nodeid, $portid) = split /#/, $port, 2; |
|
|
468 | |
|
|
469 | $NODE{$nodeid} == $NODE{""} |
|
|
470 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
|
|
471 | |
|
|
472 | while (@_) { |
|
|
473 | if (ref $_[0]) { |
|
|
474 | if (my $self = $PORT_DATA{$portid}) { |
|
|
475 | "AnyEvent::MP::Port" eq ref $self |
|
|
476 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
477 | |
|
|
478 | $self->[0] = shift; |
|
|
479 | } else { |
|
|
480 | my $cb = shift; |
|
|
481 | $PORT{$portid} = sub { |
|
|
482 | local $SELF = $port; |
|
|
483 | eval { &$cb }; _self_die if $@; |
|
|
484 | }; |
|
|
485 | } |
|
|
486 | } elsif (defined $_[0]) { |
|
|
487 | my $self = $PORT_DATA{$portid} ||= do { |
|
|
488 | my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
|
|
489 | |
|
|
490 | $PORT{$portid} = sub { |
|
|
491 | local $SELF = $port; |
|
|
492 | |
|
|
493 | if (my $cb = $self->[1]{$_[0]}) { |
|
|
494 | shift; |
|
|
495 | eval { &$cb }; _self_die if $@; |
|
|
496 | } else { |
|
|
497 | &{ $self->[0] }; |
|
|
498 | } |
|
|
499 | }; |
|
|
500 | |
|
|
501 | $self |
|
|
502 | }; |
|
|
503 | |
|
|
504 | "AnyEvent::MP::Port" eq ref $self |
|
|
505 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
506 | |
|
|
507 | my ($tag, $cb) = splice @_, 0, 2; |
|
|
508 | |
|
|
509 | if (defined $cb) { |
|
|
510 | $self->[1]{$tag} = $cb; |
|
|
511 | } else { |
|
|
512 | delete $self->[1]{$tag}; |
|
|
513 | } |
|
|
514 | } |
|
|
515 | } |
|
|
516 | |
|
|
517 | $port |
|
|
518 | } |
|
|
519 | |
|
|
520 | =item peval $port, $coderef[, @args] |
|
|
521 | |
|
|
522 | Evaluates the given C<$codref> within the contetx of C<$port>, that is, |
|
|
523 | when the code throews an exception the C<$port> will be killed. |
|
|
524 | |
|
|
525 | Any remaining args will be passed to the callback. Any return values will |
|
|
526 | be returned to the caller. |
|
|
527 | |
|
|
528 | This is useful when you temporarily want to execute code in the context of |
|
|
529 | a port. |
|
|
530 | |
|
|
531 | Example: create a port and run some initialisation code in it's context. |
|
|
532 | |
|
|
533 | my $port = port { ... }; |
|
|
534 | |
|
|
535 | peval $port, sub { |
|
|
536 | init |
|
|
537 | or die "unable to init"; |
|
|
538 | }; |
|
|
539 | |
|
|
540 | =cut |
|
|
541 | |
|
|
542 | sub peval($$) { |
|
|
543 | local $SELF = shift; |
|
|
544 | my $cb = shift; |
|
|
545 | |
|
|
546 | if (wantarray) { |
|
|
547 | my @res = eval { &$cb }; |
|
|
548 | _self_die if $@; |
|
|
549 | @res |
|
|
550 | } else { |
|
|
551 | my $res = eval { &$cb }; |
|
|
552 | _self_die if $@; |
|
|
553 | $res |
|
|
554 | } |
|
|
555 | } |
|
|
556 | |
|
|
557 | =item $closure = psub { BLOCK } |
|
|
558 | |
|
|
559 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
|
|
560 | closure is executed, sets up the environment in the same way as in C<rcv> |
|
|
561 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
|
|
562 | |
|
|
563 | The effect is basically as if it returned C<< sub { peval $SELF, sub { |
|
|
564 | BLOCK }, @_ } >>. |
|
|
565 | |
|
|
566 | This is useful when you register callbacks from C<rcv> callbacks: |
|
|
567 | |
|
|
568 | rcv delayed_reply => sub { |
|
|
569 | my ($delay, @reply) = @_; |
|
|
570 | my $timer = AE::timer $delay, 0, psub { |
|
|
571 | snd @reply, $SELF; |
|
|
572 | }; |
|
|
573 | }; |
|
|
574 | |
|
|
575 | =cut |
|
|
576 | |
|
|
577 | sub psub(&) { |
|
|
578 | my $cb = shift; |
|
|
579 | |
|
|
580 | my $port = $SELF |
|
|
581 | or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
|
|
582 | |
|
|
583 | sub { |
|
|
584 | local $SELF = $port; |
|
|
585 | |
|
|
586 | if (wantarray) { |
|
|
587 | my @res = eval { &$cb }; |
|
|
588 | _self_die if $@; |
|
|
589 | @res |
|
|
590 | } else { |
|
|
591 | my $res = eval { &$cb }; |
|
|
592 | _self_die if $@; |
|
|
593 | $res |
|
|
594 | } |
|
|
595 | } |
|
|
596 | } |
|
|
597 | |
|
|
598 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
|
|
599 | |
|
|
600 | =item $guard = mon $port # kill $SELF when $port dies |
|
|
601 | |
|
|
602 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
|
|
603 | |
|
|
604 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
|
|
605 | |
217 | Monitor the given port and do something when the port is killed. |
606 | Monitor the given port and do something when the port is killed or |
|
|
607 | messages to it were lost, and optionally return a guard that can be used |
|
|
608 | to stop monitoring again. |
218 | |
609 | |
219 | In the first form, the callback is simply called with any number |
610 | The first two forms distinguish between "normal" and "abnormal" kil's: |
|
|
611 | |
|
|
612 | In the first form (another port given), if the C<$port> is C<kil>'ed with |
|
|
613 | a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the |
|
|
614 | same reason. That is, on "normal" kil's nothing happens, while under all |
|
|
615 | other conditions, the other port is killed with the same reason. |
|
|
616 | |
|
|
617 | The second form (kill self) is the same as the first form, except that |
|
|
618 | C<$rvport> defaults to C<$SELF>. |
|
|
619 | |
|
|
620 | The remaining forms don't distinguish between "normal" and "abnormal" kil's |
|
|
621 | - it's up to the callback or receiver to check whether the C<@reason> is |
|
|
622 | empty and act accordingly. |
|
|
623 | |
|
|
624 | In the third form (callback), the callback is simply called with any |
220 | of C<@reason> elements (no @reason means that the port was deleted |
625 | number of C<@reason> elements (empty @reason means that the port was deleted |
221 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
626 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
222 | C<eval> if unsure. |
627 | C<eval> if unsure. |
223 | |
628 | |
224 | In the second form, the other port will be C<kil>'ed with C<@reason>, iff |
629 | In the last form (message), a message of the form C<$rcvport, @msg, |
225 | a @reason was specified, i.e. on "normal" kils nothing happens, while |
630 | @reason> will be C<snd>. |
226 | under all other conditions, the other port is killed with the same reason. |
|
|
227 | |
631 | |
228 | In the last form, a message of the form C<@msg, @reason> will be C<snd>. |
632 | Monitoring-actions are one-shot: once messages are lost (and a monitoring |
|
|
633 | alert was raised), they are removed and will not trigger again, even if it |
|
|
634 | turns out that the port is still alive. |
|
|
635 | |
|
|
636 | As a rule of thumb, monitoring requests should always monitor a remote |
|
|
637 | port locally (using a local C<$rcvport> or a callback). The reason is that |
|
|
638 | kill messages might get lost, just like any other message. Another less |
|
|
639 | obvious reason is that even monitoring requests can get lost (for example, |
|
|
640 | when the connection to the other node goes down permanently). When |
|
|
641 | monitoring a port locally these problems do not exist. |
|
|
642 | |
|
|
643 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
644 | after starting the monitor, either all messages sent to the port will |
|
|
645 | arrive, or the monitoring action will be invoked after possible message |
|
|
646 | loss has been detected. No messages will be lost "in between" (after |
|
|
647 | the first lost message no further messages will be received by the |
|
|
648 | port). After the monitoring action was invoked, further messages might get |
|
|
649 | delivered again. |
|
|
650 | |
|
|
651 | Inter-host-connection timeouts and monitoring depend on the transport |
|
|
652 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
|
|
653 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
|
|
654 | non-idle connection, and usually around two hours for idle connections). |
|
|
655 | |
|
|
656 | This means that monitoring is good for program errors and cleaning up |
|
|
657 | stuff eventually, but they are no replacement for a timeout when you need |
|
|
658 | to ensure some maximum latency. |
229 | |
659 | |
230 | Example: call a given callback when C<$port> is killed. |
660 | Example: call a given callback when C<$port> is killed. |
231 | |
661 | |
232 | mon $port, sub { warn "port died because of <@_>\n" }; |
662 | mon $port, sub { warn "port died because of <@_>\n" }; |
233 | |
663 | |
234 | Example: kill ourselves when C<$port> is killed abnormally. |
664 | Example: kill ourselves when C<$port> is killed abnormally. |
235 | |
665 | |
236 | mon $port, $self; |
666 | mon $port; |
237 | |
667 | |
238 | Example: send us a restart message another C<$port> is killed. |
668 | Example: send us a restart message when another C<$port> is killed. |
239 | |
669 | |
240 | mon $port, $self => "restart"; |
670 | mon $port, $self => "restart"; |
241 | |
671 | |
242 | =cut |
672 | =cut |
243 | |
673 | |
244 | sub mon { |
674 | sub mon { |
245 | my ($noderef, $port) = split /#/, shift, 2; |
675 | my ($nodeid, $port) = split /#/, shift, 2; |
246 | |
676 | |
247 | my $node = $NODE{$noderef} || add_node $noderef; |
677 | my $node = $NODE{$nodeid} || add_node $nodeid; |
248 | |
678 | |
249 | my $cb = shift; |
679 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
250 | |
680 | |
251 | unless (ref $cb) { |
681 | unless (ref $cb) { |
252 | if (@_) { |
682 | if (@_) { |
253 | # send a kill info message |
683 | # send a kill info message |
254 | my (@msg) = ($cb, @_); |
684 | my (@msg) = ($cb, @_); |
… | |
… | |
261 | } |
691 | } |
262 | |
692 | |
263 | $node->monitor ($port, $cb); |
693 | $node->monitor ($port, $cb); |
264 | |
694 | |
265 | defined wantarray |
695 | defined wantarray |
266 | and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
696 | and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) }) |
267 | } |
697 | } |
268 | |
698 | |
269 | =item $guard = mon_guard $port, $ref, $ref... |
699 | =item $guard = mon_guard $port, $ref, $ref... |
270 | |
700 | |
271 | Monitors the given C<$port> and keeps the passed references. When the port |
701 | Monitors the given C<$port> and keeps the passed references. When the port |
272 | is killed, the references will be freed. |
702 | is killed, the references will be freed. |
273 | |
703 | |
274 | Optionally returns a guard that will stop the monitoring. |
704 | Optionally returns a guard that will stop the monitoring. |
275 | |
705 | |
276 | This function is useful when you create e.g. timers or other watchers and |
706 | This function is useful when you create e.g. timers or other watchers and |
277 | want to free them when the port gets killed: |
707 | want to free them when the port gets killed (note the use of C<psub>): |
278 | |
708 | |
279 | $port->rcv (start => sub { |
709 | $port->rcv (start => sub { |
280 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
710 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub { |
281 | undef $timer if 0.9 < rand; |
711 | undef $timer if 0.9 < rand; |
282 | }); |
712 | }); |
283 | }); |
713 | }); |
284 | |
714 | |
285 | =cut |
715 | =cut |
286 | |
716 | |
287 | sub mon_guard { |
717 | sub mon_guard { |
288 | my ($port, @refs) = @_; |
718 | my ($port, @refs) = @_; |
289 | |
719 | |
|
|
720 | #TODO: mon-less form? |
|
|
721 | |
290 | mon $port, sub { 0 && @refs } |
722 | mon $port, sub { 0 && @refs } |
291 | } |
723 | } |
292 | |
724 | |
293 | =item lnk $port1, $port2 |
725 | =item kil $port[, @reason] |
294 | |
726 | |
295 | Link two ports. This is simply a shorthand for: |
727 | Kill the specified port with the given C<@reason>. |
296 | |
728 | |
297 | mon $port1, $port2; |
729 | If no C<@reason> is specified, then the port is killed "normally" - |
298 | mon $port2, $port1; |
730 | monitor callback will be invoked, but the kil will not cause linked ports |
|
|
731 | (C<mon $mport, $lport> form) to get killed. |
299 | |
732 | |
300 | It means that if either one is killed abnormally, the other one gets |
733 | If a C<@reason> is specified, then linked ports (C<mon $mport, $lport> |
301 | killed as well. |
734 | form) get killed with the same reason. |
302 | |
735 | |
303 | =item $local_port = port |
736 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
|
|
737 | will be reported as reason C<< die => $@ >>. |
304 | |
738 | |
305 | Create a new local port object that supports message matching. |
739 | Transport/communication errors are reported as C<< transport_error => |
|
|
740 | $message >>. |
306 | |
741 | |
307 | =item $portid = port { my @msg = @_; $finished } |
742 | Common idioms: |
308 | |
743 | |
309 | Creates a "mini port", that is, a very lightweight port without any |
744 | # silently remove yourself, do not kill linked ports |
310 | pattern matching behind it, and returns its ID. |
745 | kil $SELF; |
311 | |
746 | |
312 | The block will be called for every message received on the port. When the |
747 | # report a failure in some detail |
313 | callback returns a true value its job is considered "done" and the port |
748 | kil $SELF, failure_mode_1 => "it failed with too high temperature"; |
314 | will be destroyed. Otherwise it will stay alive. |
|
|
315 | |
749 | |
316 | The message will be passed as-is, no extra argument (i.e. no port id) will |
750 | # do not waste much time with killing, just die when something goes wrong |
317 | be passed to the callback. |
751 | open my $fh, "<file" |
|
|
752 | or die "file: $!"; |
318 | |
753 | |
319 | If you need the local port id in the callback, this works nicely: |
754 | =item $port = spawn $node, $initfunc[, @initdata] |
320 | |
755 | |
321 | my $port; $port = miniport { |
756 | Creates a port on the node C<$node> (which can also be a port ID, in which |
322 | snd $otherport, reply => $port; |
757 | case it's the node where that port resides). |
|
|
758 | |
|
|
759 | The port ID of the newly created port is returned immediately, and it is |
|
|
760 | possible to immediately start sending messages or to monitor the port. |
|
|
761 | |
|
|
762 | After the port has been created, the init function is called on the remote |
|
|
763 | node, in the same context as a C<rcv> callback. This function must be a |
|
|
764 | fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To |
|
|
765 | specify a function in the main program, use C<::name>. |
|
|
766 | |
|
|
767 | If the function doesn't exist, then the node tries to C<require> |
|
|
768 | the package, then the package above the package and so on (e.g. |
|
|
769 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
|
|
770 | exists or it runs out of package names. |
|
|
771 | |
|
|
772 | The init function is then called with the newly-created port as context |
|
|
773 | object (C<$SELF>) and the C<@initdata> values as arguments. It I<must> |
|
|
774 | call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise |
|
|
775 | the port might not get created. |
|
|
776 | |
|
|
777 | A common idiom is to pass a local port, immediately monitor the spawned |
|
|
778 | port, and in the remote init function, immediately monitor the passed |
|
|
779 | local port. This two-way monitoring ensures that both ports get cleaned up |
|
|
780 | when there is a problem. |
|
|
781 | |
|
|
782 | C<spawn> guarantees that the C<$initfunc> has no visible effects on the |
|
|
783 | caller before C<spawn> returns (by delaying invocation when spawn is |
|
|
784 | called for the local node). |
|
|
785 | |
|
|
786 | Example: spawn a chat server port on C<$othernode>. |
|
|
787 | |
|
|
788 | # this node, executed from within a port context: |
|
|
789 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
|
|
790 | mon $server; |
|
|
791 | |
|
|
792 | # init function on C<$othernode> |
|
|
793 | sub connect { |
|
|
794 | my ($srcport) = @_; |
|
|
795 | |
|
|
796 | mon $srcport; |
|
|
797 | |
|
|
798 | rcv $SELF, sub { |
|
|
799 | ... |
|
|
800 | }; |
|
|
801 | } |
|
|
802 | |
|
|
803 | =cut |
|
|
804 | |
|
|
805 | sub _spawn { |
|
|
806 | my $port = shift; |
|
|
807 | my $init = shift; |
|
|
808 | |
|
|
809 | # rcv will create the actual port |
|
|
810 | local $SELF = "$NODE#$port"; |
|
|
811 | eval { |
|
|
812 | &{ load_func $init } |
323 | }; |
813 | }; |
|
|
814 | _self_die if $@; |
|
|
815 | } |
|
|
816 | |
|
|
817 | sub spawn(@) { |
|
|
818 | my ($nodeid, undef) = split /#/, shift, 2; |
|
|
819 | |
|
|
820 | my $id = $RUNIQ . ++$ID; |
|
|
821 | |
|
|
822 | $_[0] =~ /::/ |
|
|
823 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
|
|
824 | |
|
|
825 | snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; |
|
|
826 | |
|
|
827 | "$nodeid#$id" |
|
|
828 | } |
|
|
829 | |
|
|
830 | |
|
|
831 | =item after $timeout, @msg |
|
|
832 | |
|
|
833 | =item after $timeout, $callback |
|
|
834 | |
|
|
835 | Either sends the given message, or call the given callback, after the |
|
|
836 | specified number of seconds. |
|
|
837 | |
|
|
838 | This is simply a utility function that comes in handy at times - the |
|
|
839 | AnyEvent::MP author is not convinced of the wisdom of having it, though, |
|
|
840 | so it may go away in the future. |
324 | |
841 | |
325 | =cut |
842 | =cut |
326 | |
843 | |
327 | sub port(;&) { |
844 | sub after($@) { |
328 | my $id = "$UNIQ." . $ID++; |
845 | my ($timeout, @action) = @_; |
329 | my $port = "$NODE#$id"; |
|
|
330 | |
846 | |
331 | if (@_) { |
847 | my $t; $t = AE::timer $timeout, 0, sub { |
332 | my $cb = shift; |
848 | undef $t; |
333 | $PORT{$id} = sub { |
849 | ref $action[0] |
334 | local $SELF = $port; |
850 | ? $action[0]() |
335 | eval { |
851 | : snd @action; |
336 | &$cb |
852 | }; |
337 | and kil $id; |
853 | } |
338 | }; |
854 | |
339 | _self_die if $@; |
855 | #=item $cb2 = timeout $seconds, $cb[, @args] |
|
|
856 | |
|
|
857 | =item cal $port, @msg, $callback[, $timeout] |
|
|
858 | |
|
|
859 | A simple form of RPC - sends a message to the given C<$port> with the |
|
|
860 | given contents (C<@msg>), but adds a reply port to the message. |
|
|
861 | |
|
|
862 | The reply port is created temporarily just for the purpose of receiving |
|
|
863 | the reply, and will be C<kil>ed when no longer needed. |
|
|
864 | |
|
|
865 | A reply message sent to the port is passed to the C<$callback> as-is. |
|
|
866 | |
|
|
867 | If an optional time-out (in seconds) is given and it is not C<undef>, |
|
|
868 | then the callback will be called without any arguments after the time-out |
|
|
869 | elapsed and the port is C<kil>ed. |
|
|
870 | |
|
|
871 | If no time-out is given (or it is C<undef>), then the local port will |
|
|
872 | monitor the remote port instead, so it eventually gets cleaned-up. |
|
|
873 | |
|
|
874 | Currently this function returns the temporary port, but this "feature" |
|
|
875 | might go in future versions unless you can make a convincing case that |
|
|
876 | this is indeed useful for something. |
|
|
877 | |
|
|
878 | =cut |
|
|
879 | |
|
|
880 | sub cal(@) { |
|
|
881 | my $timeout = ref $_[-1] ? undef : pop; |
|
|
882 | my $cb = pop; |
|
|
883 | |
|
|
884 | my $port = port { |
|
|
885 | undef $timeout; |
|
|
886 | kil $SELF; |
|
|
887 | &$cb; |
|
|
888 | }; |
|
|
889 | |
|
|
890 | if (defined $timeout) { |
|
|
891 | $timeout = AE::timer $timeout, 0, sub { |
|
|
892 | undef $timeout; |
|
|
893 | kil $port; |
|
|
894 | $cb->(); |
340 | }; |
895 | }; |
341 | } else { |
896 | } else { |
342 | my $self = bless { |
897 | mon $_[0], sub { |
343 | id => "$NODE#$id", |
898 | kil $port; |
344 | }, "AnyEvent::MP::Port"; |
899 | $cb->(); |
345 | |
|
|
346 | $PORT_DATA{$id} = $self; |
|
|
347 | $PORT{$id} = sub { |
|
|
348 | local $SELF = $port; |
|
|
349 | |
|
|
350 | eval { |
|
|
351 | for (@{ $self->{rc0}{$_[0]} }) { |
|
|
352 | $_ && &{$_->[0]} |
|
|
353 | && undef $_; |
|
|
354 | } |
|
|
355 | |
|
|
356 | for (@{ $self->{rcv}{$_[0]} }) { |
|
|
357 | $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
|
|
358 | && &{$_->[0]} |
|
|
359 | && undef $_; |
|
|
360 | } |
|
|
361 | |
|
|
362 | for (@{ $self->{any} }) { |
|
|
363 | $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
|
|
364 | && &{$_->[0]} |
|
|
365 | && undef $_; |
|
|
366 | } |
|
|
367 | }; |
|
|
368 | _self_die if $@; |
|
|
369 | }; |
900 | }; |
370 | } |
901 | } |
371 | |
902 | |
|
|
903 | push @_, $port; |
|
|
904 | &snd; |
|
|
905 | |
372 | $port |
906 | $port |
373 | } |
907 | } |
374 | |
908 | |
375 | =item reg $portid, $name |
909 | =back |
376 | |
910 | |
377 | Registers the given port under the name C<$name>. If the name already |
911 | =head1 DISTRIBUTED DATABASE |
378 | exists it is replaced. |
|
|
379 | |
912 | |
380 | A port can only be registered under one well known name. |
913 | AnyEvent::MP comes with a simple distributed database. The database will |
|
|
914 | be mirrored asynchronously on all global nodes. Other nodes bind to one |
|
|
915 | of the global nodes for their needs. Every node has a "local database" |
|
|
916 | which contains all the values that are set locally. All local databases |
|
|
917 | are merged together to form the global database, which can be queried. |
381 | |
918 | |
382 | A port automatically becomes unregistered when it is killed. |
919 | The database structure is that of a two-level hash - the database hash |
|
|
920 | contains hashes which contain values, similarly to a perl hash of hashes, |
|
|
921 | i.e.: |
|
|
922 | |
|
|
923 | $DATABASE{$family}{$subkey} = $value |
|
|
924 | |
|
|
925 | The top level hash key is called "family", and the second-level hash key |
|
|
926 | is called "subkey" or simply "key". |
|
|
927 | |
|
|
928 | The family must be alphanumeric, i.e. start with a letter and consist |
|
|
929 | of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>, |
|
|
930 | pretty much like Perl module names. |
|
|
931 | |
|
|
932 | As the family namespace is global, it is recommended to prefix family names |
|
|
933 | with the name of the application or module using it. |
|
|
934 | |
|
|
935 | The subkeys must be non-empty strings, with no further restrictions. |
|
|
936 | |
|
|
937 | The values should preferably be strings, but other perl scalars should |
|
|
938 | work as well (such as C<undef>, arrays and hashes). |
|
|
939 | |
|
|
940 | Every database entry is owned by one node - adding the same family/subkey |
|
|
941 | combination on multiple nodes will not cause discomfort for AnyEvent::MP, |
|
|
942 | but the result might be nondeterministic, i.e. the key might have |
|
|
943 | different values on different nodes. |
|
|
944 | |
|
|
945 | Different subkeys in the same family can be owned by different nodes |
|
|
946 | without problems, and in fact, this is the common method to create worker |
|
|
947 | pools. For example, a worker port for image scaling might do this: |
|
|
948 | |
|
|
949 | db_set my_image_scalers => $port; |
|
|
950 | |
|
|
951 | And clients looking for an image scaler will want to get the |
|
|
952 | C<my_image_scalers> keys from time to time: |
|
|
953 | |
|
|
954 | db_keys my_image_scalers => sub { |
|
|
955 | @ports = @{ $_[0] }; |
|
|
956 | }; |
|
|
957 | |
|
|
958 | Or better yet, they want to monitor the database family, so they always |
|
|
959 | have a reasonable up-to-date copy: |
|
|
960 | |
|
|
961 | db_mon my_image_scalers => sub { |
|
|
962 | @ports = keys %{ $_[0] }; |
|
|
963 | }; |
|
|
964 | |
|
|
965 | In general, you can set or delete single subkeys, but query and monitor |
|
|
966 | whole families only. |
|
|
967 | |
|
|
968 | If you feel the need to monitor or query a single subkey, try giving it |
|
|
969 | it's own family. |
|
|
970 | |
|
|
971 | =over |
|
|
972 | |
|
|
973 | =item $guard = db_set $family => $subkey [=> $value] |
|
|
974 | |
|
|
975 | Sets (or replaces) a key to the database - if C<$value> is omitted, |
|
|
976 | C<undef> is used instead. |
|
|
977 | |
|
|
978 | When called in non-void context, C<db_set> returns a guard that |
|
|
979 | automatically calls C<db_del> when it is destroyed. |
|
|
980 | |
|
|
981 | =item db_del $family => $subkey... |
|
|
982 | |
|
|
983 | Deletes one or more subkeys from the database family. |
|
|
984 | |
|
|
985 | =item $guard = db_reg $family => $port => $value |
|
|
986 | |
|
|
987 | =item $guard = db_reg $family => $port |
|
|
988 | |
|
|
989 | =item $guard = db_reg $family |
|
|
990 | |
|
|
991 | Registers a port in the given family and optionally returns a guard to |
|
|
992 | remove it. |
|
|
993 | |
|
|
994 | This function basically does the same as: |
|
|
995 | |
|
|
996 | db_set $family => $port => $value |
|
|
997 | |
|
|
998 | Except that the port is monitored and automatically removed from the |
|
|
999 | database family when it is kil'ed. |
|
|
1000 | |
|
|
1001 | If C<$value> is missing, C<undef> is used. If C<$port> is missing, then |
|
|
1002 | C<$SELF> is used. |
|
|
1003 | |
|
|
1004 | This function is most useful to register a port in some port group (which |
|
|
1005 | is just another name for a database family), and have it removed when the |
|
|
1006 | port is gone. This works best when the port is a local port. |
383 | |
1007 | |
384 | =cut |
1008 | =cut |
385 | |
1009 | |
386 | sub reg(@) { |
1010 | sub db_reg($$;$) { |
387 | my ($portid, $name) = @_; |
1011 | my $family = shift; |
|
|
1012 | my $port = @_ ? shift : $SELF; |
388 | |
1013 | |
389 | $REG{$name} = $portid; |
1014 | my $clr = sub { db_del $family => $port }; |
|
|
1015 | mon $port, $clr; |
|
|
1016 | |
|
|
1017 | db_set $family => $port => $_[0]; |
|
|
1018 | |
|
|
1019 | defined wantarray |
|
|
1020 | and &Guard::guard ($clr) |
390 | } |
1021 | } |
391 | |
1022 | |
392 | =item rcv $portid, tagstring => $callback->(@msg), ... |
1023 | =item db_family $family => $cb->(\%familyhash) |
393 | |
1024 | |
394 | =item rcv $portid, $smartmatch => $callback->(@msg), ... |
1025 | Queries the named database C<$family> and call the callback with the |
|
|
1026 | family represented as a hash. You can keep and freely modify the hash. |
395 | |
1027 | |
396 | =item rcv $portid, [$smartmatch...] => $callback->(@msg), ... |
1028 | =item db_keys $family => $cb->(\@keys) |
397 | |
1029 | |
398 | Register callbacks to be called on matching messages on the given port. |
1030 | Same as C<db_family>, except it only queries the family I<subkeys> and passes |
|
|
1031 | them as array reference to the callback. |
399 | |
1032 | |
400 | The callback has to return a true value when its work is done, after |
1033 | =item db_values $family => $cb->(\@values) |
401 | which is will be removed, or a false value in which case it will stay |
|
|
402 | registered. |
|
|
403 | |
1034 | |
404 | The global C<$SELF> (exported by this module) contains C<$portid> while |
1035 | Same as C<db_family>, except it only queries the family I<values> and passes them |
405 | executing the callback. |
1036 | as array reference to the callback. |
406 | |
1037 | |
407 | Runtime errors wdurign callback execution will result in the port being |
1038 | =item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted) |
408 | C<kil>ed. |
|
|
409 | |
1039 | |
410 | If the match is an array reference, then it will be matched against the |
1040 | Creates a monitor on the given database family. Each time a key is set |
411 | first elements of the message, otherwise only the first element is being |
1041 | or or is deleted the callback is called with a hash containing the |
412 | matched. |
1042 | database family and three lists of added, changed and deleted subkeys, |
|
|
1043 | respectively. If no keys have changed then the array reference might be |
|
|
1044 | C<undef> or even missing. |
413 | |
1045 | |
414 | Any element in the match that is specified as C<_any_> (a function |
1046 | If not called in void context, a guard object is returned that, when |
415 | exported by this module) matches any single element of the message. |
1047 | destroyed, stops the monitor. |
416 | |
1048 | |
417 | While not required, it is highly recommended that the first matching |
1049 | The family hash reference and the key arrays belong to AnyEvent::MP and |
418 | element is a string identifying the message. The one-string-only match is |
1050 | B<must not be modified or stored> by the callback. When in doubt, make a |
419 | also the most efficient match (by far). |
1051 | copy. |
|
|
1052 | |
|
|
1053 | As soon as possible after the monitoring starts, the callback will be |
|
|
1054 | called with the intiial contents of the family, even if it is empty, |
|
|
1055 | i.e. there will always be a timely call to the callback with the current |
|
|
1056 | contents. |
|
|
1057 | |
|
|
1058 | It is possible that the callback is called with a change event even though |
|
|
1059 | the subkey is already present and the value has not changed. |
|
|
1060 | |
|
|
1061 | The monitoring stops when the guard object is destroyed. |
|
|
1062 | |
|
|
1063 | Example: on every change to the family "mygroup", print out all keys. |
|
|
1064 | |
|
|
1065 | my $guard = db_mon mygroup => sub { |
|
|
1066 | my ($family, $a, $c, $d) = @_; |
|
|
1067 | print "mygroup members: ", (join " ", keys %$family), "\n"; |
|
|
1068 | }; |
|
|
1069 | |
|
|
1070 | Exmaple: wait until the family "My::Module::workers" is non-empty. |
|
|
1071 | |
|
|
1072 | my $guard; $guard = db_mon My::Module::workers => sub { |
|
|
1073 | my ($family, $a, $c, $d) = @_; |
|
|
1074 | return unless %$family; |
|
|
1075 | undef $guard; |
|
|
1076 | print "My::Module::workers now nonempty\n"; |
|
|
1077 | }; |
|
|
1078 | |
|
|
1079 | Example: print all changes to the family "AnyRvent::Fantasy::Module". |
|
|
1080 | |
|
|
1081 | my $guard = db_mon AnyRvent::Fantasy::Module => sub { |
|
|
1082 | my ($family, $a, $c, $d) = @_; |
|
|
1083 | |
|
|
1084 | print "+$_=$family->{$_}\n" for @$a; |
|
|
1085 | print "*$_=$family->{$_}\n" for @$c; |
|
|
1086 | print "-$_=$family->{$_}\n" for @$d; |
|
|
1087 | }; |
420 | |
1088 | |
421 | =cut |
1089 | =cut |
422 | |
1090 | |
423 | sub rcv($@) { |
|
|
424 | my ($noderef, $port) = split /#/, shift, 2; |
|
|
425 | |
|
|
426 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
|
|
427 | or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught"; |
|
|
428 | |
|
|
429 | my $self = $PORT_DATA{$port} |
|
|
430 | or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; |
|
|
431 | |
|
|
432 | "AnyEvent::MP::Port" eq ref $self |
|
|
433 | or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; |
|
|
434 | |
|
|
435 | while (@_) { |
|
|
436 | my ($match, $cb) = splice @_, 0, 2; |
|
|
437 | |
|
|
438 | if (!ref $match) { |
|
|
439 | push @{ $self->{rc0}{$match} }, [$cb]; |
|
|
440 | } elsif (("ARRAY" eq ref $match && !ref $match->[0])) { |
|
|
441 | my ($type, @match) = @$match; |
|
|
442 | @match |
|
|
443 | ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] |
|
|
444 | : push @{ $self->{rc0}{$match->[0]} }, [$cb]; |
|
|
445 | } else { |
|
|
446 | push @{ $self->{any} }, [$cb, $match]; |
|
|
447 | } |
|
|
448 | } |
|
|
449 | } |
|
|
450 | |
|
|
451 | =item $closure = psub { BLOCK } |
|
|
452 | |
|
|
453 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
|
|
454 | closure is executed, sets up the environment in the same way as in C<rcv> |
|
|
455 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
|
|
456 | |
|
|
457 | This is useful when you register callbacks from C<rcv> callbacks: |
|
|
458 | |
|
|
459 | rcv delayed_reply => sub { |
|
|
460 | my ($delay, @reply) = @_; |
|
|
461 | my $timer = AE::timer $delay, 0, psub { |
|
|
462 | snd @reply, $SELF; |
|
|
463 | }; |
|
|
464 | }; |
|
|
465 | |
|
|
466 | =cut |
|
|
467 | |
|
|
468 | sub psub(&) { |
|
|
469 | my $cb = shift; |
|
|
470 | |
|
|
471 | my $port = $SELF |
|
|
472 | or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
|
|
473 | |
|
|
474 | sub { |
|
|
475 | local $SELF = $port; |
|
|
476 | |
|
|
477 | if (wantarray) { |
|
|
478 | my @res = eval { &$cb }; |
|
|
479 | _self_die if $@; |
|
|
480 | @res |
|
|
481 | } else { |
|
|
482 | my $res = eval { &$cb }; |
|
|
483 | _self_die if $@; |
|
|
484 | $res |
|
|
485 | } |
|
|
486 | } |
|
|
487 | } |
|
|
488 | |
|
|
489 | =back |
1091 | =back |
490 | |
1092 | |
491 | =head1 FUNCTIONS FOR NODES |
|
|
492 | |
|
|
493 | =over 4 |
|
|
494 | |
|
|
495 | =item become_public $noderef |
|
|
496 | |
|
|
497 | Tells the node to become a public node, i.e. reachable from other nodes. |
|
|
498 | |
|
|
499 | The first argument is the (unresolved) node reference of the local node |
|
|
500 | (if missing then the empty string is used). |
|
|
501 | |
|
|
502 | It is quite common to not specify anything, in which case the local node |
|
|
503 | tries to listen on the default port, or to only specify a port number, in |
|
|
504 | which case AnyEvent::MP tries to guess the local addresses. |
|
|
505 | |
|
|
506 | =cut |
|
|
507 | |
|
|
508 | =back |
|
|
509 | |
|
|
510 | =head1 NODE MESSAGES |
|
|
511 | |
|
|
512 | Nodes understand the following messages sent to them. Many of them take |
|
|
513 | arguments called C<@reply>, which will simply be used to compose a reply |
|
|
514 | message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and |
|
|
515 | the remaining arguments are simply the message data. |
|
|
516 | |
|
|
517 | While other messages exist, they are not public and subject to change. |
|
|
518 | |
|
|
519 | =over 4 |
|
|
520 | |
|
|
521 | =cut |
|
|
522 | |
|
|
523 | =item lookup => $name, @reply |
|
|
524 | |
|
|
525 | Replies with the port ID of the specified well-known port, or C<undef>. |
|
|
526 | |
|
|
527 | =item devnull => ... |
|
|
528 | |
|
|
529 | Generic data sink/CPU heat conversion. |
|
|
530 | |
|
|
531 | =item relay => $port, @msg |
|
|
532 | |
|
|
533 | Simply forwards the message to the given port. |
|
|
534 | |
|
|
535 | =item eval => $string[ @reply] |
|
|
536 | |
|
|
537 | Evaluates the given string. If C<@reply> is given, then a message of the |
|
|
538 | form C<@reply, $@, @evalres> is sent. |
|
|
539 | |
|
|
540 | Example: crash another node. |
|
|
541 | |
|
|
542 | snd $othernode, eval => "exit"; |
|
|
543 | |
|
|
544 | =item time => @reply |
|
|
545 | |
|
|
546 | Replies the the current node time to C<@reply>. |
|
|
547 | |
|
|
548 | Example: tell the current node to send the current time to C<$myport> in a |
|
|
549 | C<timereply> message. |
|
|
550 | |
|
|
551 | snd $NODE, time => $myport, timereply => 1, 2; |
|
|
552 | # => snd $myport, timereply => 1, 2, <time> |
|
|
553 | |
|
|
554 | =back |
|
|
555 | |
|
|
556 | =head1 AnyEvent::MP vs. Distributed Erlang |
1093 | =head1 AnyEvent::MP vs. Distributed Erlang |
557 | |
1094 | |
558 | AnyEvent::MP got lots of its ideas from distributed erlang (erlang node |
1095 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
559 | == aemp node, erlang process == aemp port), so many of the documents and |
1096 | == aemp node, Erlang process == aemp port), so many of the documents and |
560 | programming techniques employed by erlang apply to AnyEvent::MP. Here is a |
1097 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
561 | sample: |
1098 | sample: |
562 | |
1099 | |
563 | http://www.erlang.se/doc/programming_rules.shtml |
1100 | http://www.erlang.se/doc/programming_rules.shtml |
564 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
1101 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
565 | http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 |
1102 | http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 |
… | |
… | |
567 | |
1104 | |
568 | Despite the similarities, there are also some important differences: |
1105 | Despite the similarities, there are also some important differences: |
569 | |
1106 | |
570 | =over 4 |
1107 | =over 4 |
571 | |
1108 | |
572 | =item * Node references contain the recipe on how to contact them. |
1109 | =item * Node IDs are arbitrary strings in AEMP. |
573 | |
1110 | |
574 | Erlang relies on special naming and DNS to work everywhere in the |
1111 | Erlang relies on special naming and DNS to work everywhere in the same |
575 | same way. AEMP relies on each node knowing it's own address(es), with |
1112 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
576 | convenience functionality. |
1113 | configuration or DNS), and possibly the addresses of some seed nodes, but |
|
|
1114 | will otherwise discover other nodes (and their IDs) itself. |
577 | |
1115 | |
578 | This means that AEMP requires a less tightly controlled environment at the |
1116 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
579 | cost of longer node references and a slightly higher management overhead. |
1117 | uses "local ports are like remote ports". |
|
|
1118 | |
|
|
1119 | The failure modes for local ports are quite different (runtime errors |
|
|
1120 | only) then for remote ports - when a local port dies, you I<know> it dies, |
|
|
1121 | when a connection to another node dies, you know nothing about the other |
|
|
1122 | port. |
|
|
1123 | |
|
|
1124 | Erlang pretends remote ports are as reliable as local ports, even when |
|
|
1125 | they are not. |
|
|
1126 | |
|
|
1127 | AEMP encourages a "treat remote ports differently" philosophy, with local |
|
|
1128 | ports being the special case/exception, where transport errors cannot |
|
|
1129 | occur. |
580 | |
1130 | |
581 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
1131 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
582 | |
1132 | |
583 | Erlang uses processes that selctively receive messages, and therefore |
1133 | Erlang uses processes that selectively receive messages out of order, and |
584 | needs a queue. AEMP is event based, queuing messages would serve no useful |
1134 | therefore needs a queue. AEMP is event based, queuing messages would serve |
585 | purpose. |
1135 | no useful purpose. For the same reason the pattern-matching abilities |
|
|
1136 | of AnyEvent::MP are more limited, as there is little need to be able to |
|
|
1137 | filter messages without dequeuing them. |
586 | |
1138 | |
587 | (But see L<Coro::MP> for a more erlang-like process model on top of AEMP). |
1139 | This is not a philosophical difference, but simply stems from AnyEvent::MP |
|
|
1140 | being event-based, while Erlang is process-based. |
|
|
1141 | |
|
|
1142 | You cna have a look at L<Coro::MP> for a more Erlang-like process model on |
|
|
1143 | top of AEMP and Coro threads. |
588 | |
1144 | |
589 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
1145 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
590 | |
1146 | |
591 | Sending messages in erlang is synchronous and blocks the process. AEMP |
1147 | Sending messages in Erlang is synchronous and blocks the process until |
592 | sends are immediate, connection establishment is handled in the |
1148 | a conenction has been established and the message sent (and so does not |
593 | background. |
1149 | need a queue that can overflow). AEMP sends return immediately, connection |
|
|
1150 | establishment is handled in the background. |
594 | |
1151 | |
595 | =item * Erlang can silently lose messages, AEMP cannot. |
1152 | =item * Erlang suffers from silent message loss, AEMP does not. |
596 | |
1153 | |
597 | Erlang makes few guarantees on messages delivery - messages can get lost |
1154 | Erlang implements few guarantees on messages delivery - messages can get |
598 | without any of the processes realising it (i.e. you send messages a, b, |
1155 | lost without any of the processes realising it (i.e. you send messages a, |
599 | and c, and the other side only receives messages a and c). |
1156 | b, and c, and the other side only receives messages a and c). |
600 | |
1157 | |
601 | AEMP guarantees correct ordering, and the guarantee that there are no |
1158 | AEMP guarantees (modulo hardware errors) correct ordering, and the |
|
|
1159 | guarantee that after one message is lost, all following ones sent to the |
|
|
1160 | same port are lost as well, until monitoring raises an error, so there are |
602 | holes in the message sequence. |
1161 | no silent "holes" in the message sequence. |
603 | |
1162 | |
604 | =item * In erlang, processes can be declared dead and later be found to be |
1163 | If you want your software to be very reliable, you have to cope with |
605 | alive. |
1164 | corrupted and even out-of-order messages in both Erlang and AEMP. AEMP |
606 | |
1165 | simply tries to work better in common error cases, such as when a network |
607 | In erlang it can happen that a monitored process is declared dead and |
1166 | link goes down. |
608 | linked processes get killed, but later it turns out that the process is |
|
|
609 | still alive - and can receive messages. |
|
|
610 | |
|
|
611 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
612 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
613 | and then later sends messages to it, finding it is still alive. |
|
|
614 | |
1167 | |
615 | =item * Erlang can send messages to the wrong port, AEMP does not. |
1168 | =item * Erlang can send messages to the wrong port, AEMP does not. |
616 | |
1169 | |
617 | In erlang it is quite possible that a node that restarts reuses a process |
1170 | In Erlang it is quite likely that a node that restarts reuses an Erlang |
618 | ID known to other nodes for a completely different process, causing |
1171 | process ID known to other nodes for a completely different process, |
619 | messages destined for that process to end up in an unrelated process. |
1172 | causing messages destined for that process to end up in an unrelated |
|
|
1173 | process. |
620 | |
1174 | |
621 | AEMP never reuses port IDs, so old messages or old port IDs floating |
1175 | AEMP does not reuse port IDs, so old messages or old port IDs floating |
622 | around in the network will not be sent to an unrelated port. |
1176 | around in the network will not be sent to an unrelated port. |
623 | |
1177 | |
624 | =item * Erlang uses unprotected connections, AEMP uses secure |
1178 | =item * Erlang uses unprotected connections, AEMP uses secure |
625 | authentication and can use TLS. |
1179 | authentication and can use TLS. |
626 | |
1180 | |
627 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
1181 | AEMP can use a proven protocol - TLS - to protect connections and |
628 | securely authenticate nodes. |
1182 | securely authenticate nodes. |
629 | |
1183 | |
630 | =item * The AEMP protocol is optimised for both text-based and binary |
1184 | =item * The AEMP protocol is optimised for both text-based and binary |
631 | communications. |
1185 | communications. |
632 | |
1186 | |
633 | The AEMP protocol, unlike the erlang protocol, supports both |
1187 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
634 | language-independent text-only protocols (good for debugging) and binary, |
1188 | language independent text-only protocols (good for debugging), and binary, |
635 | language-specific serialisers (e.g. Storable). |
1189 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
|
|
1190 | used, the protocol is actually completely text-based. |
636 | |
1191 | |
637 | It has also been carefully designed to be implementable in other languages |
1192 | It has also been carefully designed to be implementable in other languages |
638 | with a minimum of work while gracefully degrading fucntionality to make the |
1193 | with a minimum of work while gracefully degrading functionality to make the |
639 | protocol simple. |
1194 | protocol simple. |
640 | |
1195 | |
|
|
1196 | =item * AEMP has more flexible monitoring options than Erlang. |
|
|
1197 | |
|
|
1198 | In Erlang, you can chose to receive I<all> exit signals as messages or |
|
|
1199 | I<none>, there is no in-between, so monitoring single Erlang processes is |
|
|
1200 | difficult to implement. |
|
|
1201 | |
|
|
1202 | Monitoring in AEMP is more flexible than in Erlang, as one can choose |
|
|
1203 | between automatic kill, exit message or callback on a per-port basis. |
|
|
1204 | |
|
|
1205 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
|
|
1206 | |
|
|
1207 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
|
|
1208 | same way as linking is (except linking is unreliable in Erlang). |
|
|
1209 | |
|
|
1210 | In AEMP, you don't "look up" registered port names or send to named ports |
|
|
1211 | that might or might not be persistent. Instead, you normally spawn a port |
|
|
1212 | on the remote node. The init function monitors you, and you monitor the |
|
|
1213 | remote port. Since both monitors are local to the node, they are much more |
|
|
1214 | reliable (no need for C<spawn_link>). |
|
|
1215 | |
|
|
1216 | This also saves round-trips and avoids sending messages to the wrong port |
|
|
1217 | (hard to do in Erlang). |
|
|
1218 | |
641 | =back |
1219 | =back |
642 | |
1220 | |
|
|
1221 | =head1 RATIONALE |
|
|
1222 | |
|
|
1223 | =over 4 |
|
|
1224 | |
|
|
1225 | =item Why strings for port and node IDs, why not objects? |
|
|
1226 | |
|
|
1227 | We considered "objects", but found that the actual number of methods |
|
|
1228 | that can be called are quite low. Since port and node IDs travel over |
|
|
1229 | the network frequently, the serialising/deserialising would add lots of |
|
|
1230 | overhead, as well as having to keep a proxy object everywhere. |
|
|
1231 | |
|
|
1232 | Strings can easily be printed, easily serialised etc. and need no special |
|
|
1233 | procedures to be "valid". |
|
|
1234 | |
|
|
1235 | And as a result, a port with just a default receiver consists of a single |
|
|
1236 | code reference stored in a global hash - it can't become much cheaper. |
|
|
1237 | |
|
|
1238 | =item Why favour JSON, why not a real serialising format such as Storable? |
|
|
1239 | |
|
|
1240 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
|
|
1241 | format, but currently there is no way to make a node use Storable by |
|
|
1242 | default (although all nodes will accept it). |
|
|
1243 | |
|
|
1244 | The default framing protocol is JSON because a) JSON::XS is many times |
|
|
1245 | faster for small messages and b) most importantly, after years of |
|
|
1246 | experience we found that object serialisation is causing more problems |
|
|
1247 | than it solves: Just like function calls, objects simply do not travel |
|
|
1248 | easily over the network, mostly because they will always be a copy, so you |
|
|
1249 | always have to re-think your design. |
|
|
1250 | |
|
|
1251 | Keeping your messages simple, concentrating on data structures rather than |
|
|
1252 | objects, will keep your messages clean, tidy and efficient. |
|
|
1253 | |
|
|
1254 | =back |
|
|
1255 | |
|
|
1256 | =head1 PORTING FROM AnyEvent::MP VERSION 1.X |
|
|
1257 | |
|
|
1258 | AEMP version 2 has a few major incompatible changes compared to version 1: |
|
|
1259 | |
|
|
1260 | =over 4 |
|
|
1261 | |
|
|
1262 | =item AnyEvent::MP::Global no longer has group management functions. |
|
|
1263 | |
|
|
1264 | At least not officially - the grp_* functions are still exported and might |
|
|
1265 | work, but they will be removed in some later release. |
|
|
1266 | |
|
|
1267 | AnyEvent::MP now comes with a distributed database that is more |
|
|
1268 | powerful. Its database families map closely to port groups, but the API |
|
|
1269 | has changed (the functions are also now exported by AnyEvent::MP). Here is |
|
|
1270 | a rough porting guide: |
|
|
1271 | |
|
|
1272 | grp_reg $group, $port # old |
|
|
1273 | db_reg $group, $port # new |
|
|
1274 | |
|
|
1275 | $list = grp_get $group # old |
|
|
1276 | db_keys $group, sub { my $list = shift } # new |
|
|
1277 | |
|
|
1278 | grp_mon $group, $cb->(\@ports, $add, $del) # old |
|
|
1279 | db_mon $group, $cb->(\%ports, $add, $change, $del) # new |
|
|
1280 | |
|
|
1281 | C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is |
|
|
1282 | no longer instant, because the local node might not have a copy of the |
|
|
1283 | group. You can either modify your code to allow for a callback, or use |
|
|
1284 | C<db_mon> to keep an updated copy of the group: |
|
|
1285 | |
|
|
1286 | my $local_group_copy; |
|
|
1287 | db_mon $group => sub { $local_group_copy = $_[0] }; |
|
|
1288 | |
|
|
1289 | # now "keys %$local_group_copy" always returns the most up-to-date |
|
|
1290 | # list of ports in the group. |
|
|
1291 | |
|
|
1292 | C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon> |
|
|
1293 | passes a hash as first argument, and an extra C<$chg> argument that can be |
|
|
1294 | ignored: |
|
|
1295 | |
|
|
1296 | db_mon $group => sub { |
|
|
1297 | my ($ports, $add, $chg, $lde) = @_; |
|
|
1298 | $ports = [keys %$ports]; |
|
|
1299 | |
|
|
1300 | # now $ports, $add and $del are the same as |
|
|
1301 | # were originally passed by grp_mon. |
|
|
1302 | ... |
|
|
1303 | }; |
|
|
1304 | |
|
|
1305 | =item Nodes not longer connect to all other nodes. |
|
|
1306 | |
|
|
1307 | In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global> |
|
|
1308 | module, which in turn would create connections to all other nodes in the |
|
|
1309 | network (helped by the seed nodes). |
|
|
1310 | |
|
|
1311 | In version 2.x, global nodes still connect to all other global nodes, but |
|
|
1312 | other nodes don't - now every node either is a global node itself, or |
|
|
1313 | attaches itself to another global node. |
|
|
1314 | |
|
|
1315 | If a node isn't a global node itself, then it attaches itself to one |
|
|
1316 | of its seed nodes. If that seed node isn't a global node yet, it will |
|
|
1317 | automatically be upgraded to a global node. |
|
|
1318 | |
|
|
1319 | So in many cases, nothing needs to be changed - one just has to make sure |
|
|
1320 | that all seed nodes are meshed together with the other seed nodes (as with |
|
|
1321 | AEMP 1.x), and other nodes specify them as seed nodes. This is most easily |
|
|
1322 | achieved by specifying the same set of seed nodes for all nodes in the |
|
|
1323 | network. |
|
|
1324 | |
|
|
1325 | Not opening a connection to every other node is usually an advantage, |
|
|
1326 | except when you need the lower latency of an already established |
|
|
1327 | connection. To ensure a node establishes a connection to another node, |
|
|
1328 | you can monitor the node port (C<mon $node, ...>), which will attempt to |
|
|
1329 | create the connection (and notify you when the connection fails). |
|
|
1330 | |
|
|
1331 | =item Listener-less nodes (nodes without binds) are gone. |
|
|
1332 | |
|
|
1333 | And are not coming back, at least not in their old form. If no C<binds> |
|
|
1334 | are specified for a node, AnyEvent::MP assumes a default of C<*:*>. |
|
|
1335 | |
|
|
1336 | There are vague plans to implement some form of routing domains, which |
|
|
1337 | might or might not bring back listener-less nodes, but don't count on it. |
|
|
1338 | |
|
|
1339 | The fact that most connections are now optional somewhat mitigates this, |
|
|
1340 | as a node can be effectively unreachable from the outside without any |
|
|
1341 | problems, as long as it isn't a global node and only reaches out to other |
|
|
1342 | nodes (as opposed to being contacted from other nodes). |
|
|
1343 | |
|
|
1344 | =item $AnyEvent::MP::Kernel::WARN has gone. |
|
|
1345 | |
|
|
1346 | AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now |
|
|
1347 | uses this, and so should your programs. |
|
|
1348 | |
|
|
1349 | Every module now documents what kinds of messages it generates, with |
|
|
1350 | AnyEvent::MP acting as a catch all. |
|
|
1351 | |
|
|
1352 | On the positive side, this means that instead of setting |
|
|
1353 | C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> - |
|
|
1354 | much less to type. |
|
|
1355 | |
|
|
1356 | =back |
|
|
1357 | |
|
|
1358 | =head1 LOGGING |
|
|
1359 | |
|
|
1360 | AnyEvent::MP does not normally log anything by itself, but sinc eit is the |
|
|
1361 | root of the contetx hierarchy for AnyEvent::MP modules, it will receive |
|
|
1362 | all log messages by submodules. |
|
|
1363 | |
643 | =head1 SEE ALSO |
1364 | =head1 SEE ALSO |
|
|
1365 | |
|
|
1366 | L<AnyEvent::MP::Intro> - a gentle introduction. |
|
|
1367 | |
|
|
1368 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
|
|
1369 | |
|
|
1370 | L<AnyEvent::MP::Global> - network maintenance and port groups, to find |
|
|
1371 | your applications. |
|
|
1372 | |
|
|
1373 | L<AnyEvent::MP::DataConn> - establish data connections between nodes. |
|
|
1374 | |
|
|
1375 | L<AnyEvent::MP::LogCatcher> - simple service to display log messages from |
|
|
1376 | all nodes. |
644 | |
1377 | |
645 | L<AnyEvent>. |
1378 | L<AnyEvent>. |
646 | |
1379 | |
647 | =head1 AUTHOR |
1380 | =head1 AUTHOR |
648 | |
1381 | |