… | |
… | |
8 | |
8 | |
9 | $NODE # contains this node's noderef |
9 | $NODE # contains this node's noderef |
10 | NODE # returns this node's noderef |
10 | NODE # returns this node's noderef |
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 |
|
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14 | |
|
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15 | # initialise the node so it can send/receive messages |
|
|
16 | initialise_node; # -OR- |
|
|
17 | initialise_node "localhost:4040"; # -OR- |
|
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18 | initialise_node "slave/", "localhost:4040" |
|
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19 | |
|
|
20 | # ports are message endpoints |
|
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21 | |
|
|
22 | # sending messages |
13 | snd $port, type => data...; |
23 | snd $port, type => data...; |
|
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24 | snd $port, @msg; |
|
|
25 | snd @msg_with_first_element_being_a_port; |
14 | |
26 | |
15 | $SELF # receiving/own port id in rcv callbacks |
27 | # creating/using ports, the simple way |
|
|
28 | my $simple_port = port { my @msg = @_; 0 }; |
16 | |
29 | |
17 | rcv $port, smartmatch => $cb->($port, @msg); |
30 | # creating/using ports, tagged message matching |
18 | |
31 | my $port = port; |
19 | # examples: |
|
|
20 | rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; |
32 | rcv $port, ping => sub { snd $_[0], "pong"; 0 }; |
21 | rcv $port1, pong => sub { warn "pong received\n" }; |
33 | rcv $port, pong => sub { warn "pong received\n"; 0 }; |
22 | snd $port2, ping => $port1; |
|
|
23 | |
34 | |
24 | # more, smarter, matches (_any_ is exported by this module) |
35 | # create a port on another node |
25 | rcv $port, [child_died => $pid] => sub { ... |
36 | my $port = spawn $node, $initfunc, @initdata; |
26 | rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 |
37 | |
|
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38 | # monitoring |
|
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39 | mon $port, $cb->(@msg) # callback is invoked on death |
|
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40 | mon $port, $otherport # kill otherport on abnormal death |
|
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41 | mon $port, $otherport, @msg # send message on death |
|
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42 | |
|
|
43 | =head1 CURRENT STATUS |
|
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44 | |
|
|
45 | AnyEvent::MP - stable API, should work |
|
|
46 | AnyEvent::MP::Intro - outdated |
|
|
47 | AnyEvent::MP::Kernel - WIP |
|
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48 | AnyEvent::MP::Transport - mostly stable |
|
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49 | |
|
|
50 | stay tuned. |
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 | |
… | |
… | |
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. |
37 | |
61 | |
38 | At the moment, this module family is severly broken and underdocumented, |
62 | 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 - |
63 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
40 | stay tuned! The basic API should be finished, however. |
64 | stay tuned! |
41 | |
65 | |
42 | =head1 CONCEPTS |
66 | =head1 CONCEPTS |
43 | |
67 | |
44 | =over 4 |
68 | =over 4 |
45 | |
69 | |
46 | =item port |
70 | =item port |
47 | |
71 | |
48 | A port is something you can send messages to (with the C<snd> function). |
72 | A port is something you can send messages to (with the C<snd> function). |
49 | |
73 | |
50 | Some ports allow you to register C<rcv> handlers that can match specific |
74 | 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 |
75 | some messages. Messages will not be queued. |
52 | will not be queued. |
|
|
53 | |
76 | |
54 | =item port id - C<noderef#portname> |
77 | =item port id - C<noderef#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 noderef, a hash-mark (C<#>) as |
57 | separator, and a port name (a printable string of unspecified format). An |
80 | separator, and a port name (a printable string of unspecified format). An |
58 | exception is the the node port, whose ID is identical to its node |
81 | exception is the the node port, whose ID is identical to its node |
59 | reference. |
82 | reference. |
60 | |
83 | |
61 | =item node |
84 | =item node |
62 | |
85 | |
63 | A node is a single process containing at least one port - the node |
86 | 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 |
87 | which provides nodes to manage each other remotely, and to create new |
65 | create new ports, among other things. |
88 | ports. |
66 | |
89 | |
67 | Nodes are either private (single-process only), slaves (connected to a |
90 | Nodes are either private (single-process only), slaves (can only talk to |
68 | master node only) or public nodes (connectable from unrelated nodes). |
91 | public nodes, but do not need an open port) or public nodes (connectable |
|
|
92 | from any other node). |
69 | |
93 | |
70 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
94 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
71 | |
95 | |
72 | A node reference is a string that either simply identifies the node (for |
96 | A node reference is a string that either simply identifies the node (for |
73 | private and slave nodes), or contains a recipe on how to reach a given |
97 | private and slave nodes), or contains a recipe on how to reach a given |
… | |
… | |
90 | |
114 | |
91 | =cut |
115 | =cut |
92 | |
116 | |
93 | package AnyEvent::MP; |
117 | package AnyEvent::MP; |
94 | |
118 | |
95 | use AnyEvent::MP::Base; |
119 | use AnyEvent::MP::Kernel; |
96 | |
120 | |
97 | use common::sense; |
121 | use common::sense; |
98 | |
122 | |
99 | use Carp (); |
123 | use Carp (); |
100 | |
124 | |
101 | use AE (); |
125 | use AE (); |
102 | |
126 | |
103 | use base "Exporter"; |
127 | use base "Exporter"; |
104 | |
128 | |
105 | our $VERSION = '0.1'; |
129 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
|
|
130 | |
106 | our @EXPORT = qw( |
131 | our @EXPORT = qw( |
107 | NODE $NODE *SELF node_of _any_ |
132 | NODE $NODE *SELF node_of after |
108 | resolve_node |
133 | resolve_node initialise_node |
109 | become_slave become_public |
|
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110 | snd rcv mon kil reg psub |
134 | snd rcv mon mon_guard kil reg psub spawn |
111 | port |
135 | port |
112 | ); |
136 | ); |
113 | |
137 | |
114 | our $SELF; |
138 | our $SELF; |
115 | |
139 | |
… | |
… | |
119 | kil $SELF, die => $msg; |
143 | kil $SELF, die => $msg; |
120 | } |
144 | } |
121 | |
145 | |
122 | =item $thisnode = NODE / $NODE |
146 | =item $thisnode = NODE / $NODE |
123 | |
147 | |
124 | The C<NODE> function returns, and the C<$NODE> variable contains |
148 | The C<NODE> function returns, and the C<$NODE> variable contains the |
125 | the noderef of the local node. The value is initialised by a call |
149 | noderef of the local node. The value is initialised by a call to |
126 | to C<become_public> or C<become_slave>, after which all local port |
150 | C<initialise_node>. |
127 | identifiers become invalid. |
|
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128 | |
151 | |
129 | =item $noderef = node_of $portid |
152 | =item $noderef = node_of $port |
130 | |
153 | |
131 | Extracts and returns the noderef from a portid or a noderef. |
154 | Extracts and returns the noderef from a port ID or a noderef. |
|
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155 | |
|
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156 | =item initialise_node $noderef, $seednode, $seednode... |
|
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157 | |
|
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158 | =item initialise_node "slave/", $master, $master... |
|
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159 | |
|
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160 | Before a node can talk to other nodes on the network it has to initialise |
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161 | itself - the minimum a node needs to know is it's own name, and optionally |
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162 | it should know the noderefs of some other nodes in the network. |
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163 | |
|
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164 | This function initialises a node - it must be called exactly once (or |
|
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165 | never) before calling other AnyEvent::MP functions. |
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166 | |
|
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167 | All arguments (optionally except for the first) are noderefs, which can be |
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168 | either resolved or unresolved. |
|
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169 | |
|
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170 | The first argument will be looked up in the configuration database first |
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171 | (if it is C<undef> then the current nodename will be used instead) to find |
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172 | the relevant configuration profile (see L<aemp>). If none is found then |
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173 | the default configuration is used. The configuration supplies additional |
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174 | seed/master nodes and can override the actual noderef. |
|
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175 | |
|
|
176 | There are two types of networked nodes, public nodes and slave nodes: |
|
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177 | |
|
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178 | =over 4 |
|
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179 | |
|
|
180 | =item public nodes |
|
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181 | |
|
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182 | For public nodes, C<$noderef> (supplied either directly to |
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183 | C<initialise_node> or indirectly via a profile or the nodename) must be a |
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184 | noderef (possibly unresolved, in which case it will be resolved). |
|
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185 | |
|
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186 | After resolving, the node will bind itself on all endpoints. |
|
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187 | |
|
|
188 | =item slave nodes |
|
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189 | |
|
|
190 | When the C<$noderef> (either as given or overriden by the config file) |
|
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191 | is the special string C<slave/>, then the node will become a slave |
|
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192 | node. Slave nodes cannot be contacted from outside, and cannot talk to |
|
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193 | each other (at least in this version of AnyEvent::MP). |
|
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194 | |
|
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195 | Slave nodes work by creating connections to all public nodes, using the |
|
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196 | L<AnyEvent::MP::Global> service. |
|
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197 | |
|
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198 | =back |
|
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199 | |
|
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200 | After initialising itself, the node will connect to all additional |
|
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201 | C<$seednodes> that are specified diretcly or via a profile. Seednodes are |
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202 | optional and can be used to quickly bootstrap the node into an existing |
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203 | network. |
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204 | |
|
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205 | All the seednodes will also be specially marked to automatically retry |
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206 | connecting to them indefinitely, so make sure that seednodes are really |
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207 | reliable and up (this might also change in the future). |
|
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208 | |
|
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209 | Example: become a public node listening on the guessed noderef, or the one |
|
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210 | specified via C<aemp> for the current node. This should be the most common |
|
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211 | form of invocation for "daemon"-type nodes. |
|
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212 | |
|
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213 | initialise_node; |
|
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214 | |
|
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215 | Example: become a slave node to any of the the seednodes specified via |
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216 | C<aemp>. This form is often used for commandline clients. |
|
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217 | |
|
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218 | initialise_node "slave/"; |
|
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219 | |
|
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220 | Example: become a public node, and try to contact some well-known master |
|
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221 | servers to become part of the network. |
|
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222 | |
|
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223 | initialise_node undef, "master1", "master2"; |
|
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224 | |
|
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225 | Example: become a public node listening on port C<4041>. |
|
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226 | |
|
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227 | initialise_node 4041; |
|
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228 | |
|
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229 | Example: become a public node, only visible on localhost port 4044. |
|
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230 | |
|
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231 | initialise_node "localhost:4044"; |
132 | |
232 | |
133 | =item $cv = resolve_node $noderef |
233 | =item $cv = resolve_node $noderef |
134 | |
234 | |
135 | Takes an unresolved node reference that may contain hostnames and |
235 | Takes an unresolved node reference that may contain hostnames and |
136 | abbreviated IDs, resolves all of them and returns a resolved node |
236 | abbreviated IDs, resolves all of them and returns a resolved node |
… | |
… | |
168 | |
268 | |
169 | Due to some quirks in how perl exports variables, it is impossible to |
269 | Due to some quirks in how perl exports variables, it is impossible to |
170 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
270 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
171 | module, but only C<$SELF> is currently used. |
271 | module, but only C<$SELF> is currently used. |
172 | |
272 | |
173 | =item snd $portid, type => @data |
273 | =item snd $port, type => @data |
174 | |
274 | |
175 | =item snd $portid, @msg |
275 | =item snd $port, @msg |
176 | |
276 | |
177 | Send the given message to the given port ID, which can identify either |
277 | Send the given message to the given port ID, which can identify either |
178 | a local or a remote port, and can be either a string or soemthignt hat |
278 | a local or a remote port, and must be a port ID. |
179 | stringifies a sa port ID (such as a port object :). |
|
|
180 | |
279 | |
181 | While the message can be about anything, it is highly recommended to use a |
280 | While the message can be about anything, it is highly recommended to use a |
182 | string as first element (a portid, or some word that indicates a request |
281 | string as first element (a port ID, or some word that indicates a request |
183 | type etc.). |
282 | type etc.). |
184 | |
283 | |
185 | The message data effectively becomes read-only after a call to this |
284 | The message data effectively becomes read-only after a call to this |
186 | function: modifying any argument is not allowed and can cause many |
285 | function: modifying any argument is not allowed and can cause many |
187 | problems. |
286 | problems. |
… | |
… | |
190 | JSON is used, then only strings, numbers and arrays and hashes consisting |
289 | 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 |
290 | 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 |
291 | that Storable can serialise and deserialise is allowed, and for the local |
193 | node, anything can be passed. |
292 | node, anything can be passed. |
194 | |
293 | |
195 | =item kil $portid[, @reason] |
294 | =item $local_port = port |
196 | |
295 | |
197 | Kill the specified port with the given C<@reason>. |
296 | Create a new local port object and returns its port ID. Initially it has |
|
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297 | no callbacks set and will throw an error when it receives messages. |
198 | |
298 | |
199 | If no C<@reason> is specified, then the port is killed "normally" (linked |
299 | =item $local_port = port { my @msg = @_ } |
200 | ports will not be kileld, or even notified). |
|
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201 | |
300 | |
202 | Otherwise, linked ports get killed with the same reason (second form of |
301 | Creates a new local port, and returns its ID. Semantically the same as |
203 | C<mon>, see below). |
302 | creating a port and calling C<rcv $port, $callback> on it. |
204 | |
303 | |
205 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
304 | The block will be called for every message received on the port, with the |
206 | will be reported as reason C<< die => $@ >>. |
305 | global variable C<$SELF> set to the port ID. Runtime errors will cause the |
|
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306 | port to be C<kil>ed. The message will be passed as-is, no extra argument |
|
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307 | (i.e. no port ID) will be passed to the callback. |
207 | |
308 | |
208 | Transport/communication errors are reported as C<< transport_error => |
309 | If you want to stop/destroy the port, simply C<kil> it: |
209 | $message >>. |
|
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210 | |
310 | |
|
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311 | my $port = port { |
|
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312 | my @msg = @_; |
|
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313 | ... |
|
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314 | kil $SELF; |
|
|
315 | }; |
|
|
316 | |
|
|
317 | =cut |
|
|
318 | |
|
|
319 | sub rcv($@); |
|
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320 | |
|
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321 | sub _kilme { |
|
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322 | die "received message on port without callback"; |
|
|
323 | } |
|
|
324 | |
|
|
325 | sub port(;&) { |
|
|
326 | my $id = "$UNIQ." . $ID++; |
|
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327 | my $port = "$NODE#$id"; |
|
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328 | |
|
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329 | rcv $port, shift || \&_kilme; |
|
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330 | |
|
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331 | $port |
|
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332 | } |
|
|
333 | |
|
|
334 | =item rcv $local_port, $callback->(@msg) |
|
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335 | |
|
|
336 | Replaces the default callback on the specified port. There is no way to |
|
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337 | remove the default callback: use C<sub { }> to disable it, or better |
|
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338 | C<kil> the port when it is no longer needed. |
|
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339 | |
|
|
340 | The global C<$SELF> (exported by this module) contains C<$port> while |
|
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341 | executing the callback. Runtime errors during callback execution will |
|
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342 | result in the port being C<kil>ed. |
|
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343 | |
|
|
344 | The default callback received all messages not matched by a more specific |
|
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345 | C<tag> match. |
|
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346 | |
|
|
347 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
|
|
348 | |
|
|
349 | Register (or replace) callbacks to be called on messages starting with the |
|
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350 | given tag on the given port (and return the port), or unregister it (when |
|
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351 | C<$callback> is C<$undef> or missing). There can only be one callback |
|
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352 | registered for each tag. |
|
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353 | |
|
|
354 | The original message will be passed to the callback, after the first |
|
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355 | element (the tag) has been removed. The callback will use the same |
|
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356 | environment as the default callback (see above). |
|
|
357 | |
|
|
358 | Example: create a port and bind receivers on it in one go. |
|
|
359 | |
|
|
360 | my $port = rcv port, |
|
|
361 | msg1 => sub { ... }, |
|
|
362 | msg2 => sub { ... }, |
|
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363 | ; |
|
|
364 | |
|
|
365 | Example: create a port, bind receivers and send it in a message elsewhere |
|
|
366 | in one go: |
|
|
367 | |
|
|
368 | snd $otherport, reply => |
|
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369 | rcv port, |
|
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370 | msg1 => sub { ... }, |
|
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371 | ... |
|
|
372 | ; |
|
|
373 | |
|
|
374 | Example: temporarily register a rcv callback for a tag matching some port |
|
|
375 | (e.g. for a rpc reply) and unregister it after a message was received. |
|
|
376 | |
|
|
377 | rcv $port, $otherport => sub { |
|
|
378 | my @reply = @_; |
|
|
379 | |
|
|
380 | rcv $SELF, $otherport; |
|
|
381 | }; |
|
|
382 | |
|
|
383 | =cut |
|
|
384 | |
|
|
385 | sub rcv($@) { |
|
|
386 | my $port = shift; |
|
|
387 | my ($noderef, $portid) = split /#/, $port, 2; |
|
|
388 | |
|
|
389 | $NODE{$noderef} == $NODE{""} |
|
|
390 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
|
|
391 | |
|
|
392 | while (@_) { |
|
|
393 | if (ref $_[0]) { |
|
|
394 | if (my $self = $PORT_DATA{$portid}) { |
|
|
395 | "AnyEvent::MP::Port" eq ref $self |
|
|
396 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
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397 | |
|
|
398 | $self->[2] = shift; |
|
|
399 | } else { |
|
|
400 | my $cb = shift; |
|
|
401 | $PORT{$portid} = sub { |
|
|
402 | local $SELF = $port; |
|
|
403 | eval { &$cb }; _self_die if $@; |
|
|
404 | }; |
|
|
405 | } |
|
|
406 | } elsif (defined $_[0]) { |
|
|
407 | my $self = $PORT_DATA{$portid} ||= do { |
|
|
408 | my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
|
|
409 | |
|
|
410 | $PORT{$portid} = sub { |
|
|
411 | local $SELF = $port; |
|
|
412 | |
|
|
413 | if (my $cb = $self->[1]{$_[0]}) { |
|
|
414 | shift; |
|
|
415 | eval { &$cb }; _self_die if $@; |
|
|
416 | } else { |
|
|
417 | &{ $self->[0] }; |
|
|
418 | } |
|
|
419 | }; |
|
|
420 | |
|
|
421 | $self |
|
|
422 | }; |
|
|
423 | |
|
|
424 | "AnyEvent::MP::Port" eq ref $self |
|
|
425 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
426 | |
|
|
427 | my ($tag, $cb) = splice @_, 0, 2; |
|
|
428 | |
|
|
429 | if (defined $cb) { |
|
|
430 | $self->[1]{$tag} = $cb; |
|
|
431 | } else { |
|
|
432 | delete $self->[1]{$tag}; |
|
|
433 | } |
|
|
434 | } |
|
|
435 | } |
|
|
436 | |
|
|
437 | $port |
|
|
438 | } |
|
|
439 | |
|
|
440 | =item $closure = psub { BLOCK } |
|
|
441 | |
|
|
442 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
|
|
443 | closure is executed, sets up the environment in the same way as in C<rcv> |
|
|
444 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
|
|
445 | |
|
|
446 | This is useful when you register callbacks from C<rcv> callbacks: |
|
|
447 | |
|
|
448 | rcv delayed_reply => sub { |
|
|
449 | my ($delay, @reply) = @_; |
|
|
450 | my $timer = AE::timer $delay, 0, psub { |
|
|
451 | snd @reply, $SELF; |
|
|
452 | }; |
|
|
453 | }; |
|
|
454 | |
|
|
455 | =cut |
|
|
456 | |
|
|
457 | sub psub(&) { |
|
|
458 | my $cb = shift; |
|
|
459 | |
|
|
460 | my $port = $SELF |
|
|
461 | or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
|
|
462 | |
|
|
463 | sub { |
|
|
464 | local $SELF = $port; |
|
|
465 | |
|
|
466 | if (wantarray) { |
|
|
467 | my @res = eval { &$cb }; |
|
|
468 | _self_die if $@; |
|
|
469 | @res |
|
|
470 | } else { |
|
|
471 | my $res = eval { &$cb }; |
|
|
472 | _self_die if $@; |
|
|
473 | $res |
|
|
474 | } |
|
|
475 | } |
|
|
476 | } |
|
|
477 | |
211 | =item $guard = mon $portid, $cb->(@reason) |
478 | =item $guard = mon $port, $cb->(@reason) |
212 | |
479 | |
213 | =item $guard = mon $portid, $otherport |
480 | =item $guard = mon $port, $rcvport |
214 | |
481 | |
|
|
482 | =item $guard = mon $port |
|
|
483 | |
215 | =item $guard = mon $portid, $otherport, @msg |
484 | =item $guard = mon $port, $rcvport, @msg |
216 | |
485 | |
217 | Monitor the given port and do something when the port is killed. |
486 | Monitor the given port and do something when the port is killed or |
|
|
487 | messages to it were lost, and optionally return a guard that can be used |
|
|
488 | to stop monitoring again. |
218 | |
489 | |
|
|
490 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
491 | that after starting the monitor, either all messages sent to the port |
|
|
492 | will arrive, or the monitoring action will be invoked after possible |
|
|
493 | message loss has been detected. No messages will be lost "in between" |
|
|
494 | (after the first lost message no further messages will be received by the |
|
|
495 | port). After the monitoring action was invoked, further messages might get |
|
|
496 | delivered again. |
|
|
497 | |
|
|
498 | Note that monitoring-actions are one-shot: once released, they are removed |
|
|
499 | and will not trigger again. |
|
|
500 | |
219 | In the first form, the callback is simply called with any number |
501 | In the first form (callback), the callback is simply called with any |
220 | of C<@reason> elements (no @reason means that the port was deleted |
502 | number of C<@reason> elements (no @reason means that the port was deleted |
221 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
503 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
222 | C<eval> if unsure. |
504 | C<eval> if unsure. |
223 | |
505 | |
224 | In the second form, the other port will be C<kil>'ed with C<@reason>, iff |
506 | In the second form (another port given), the other port (C<$rcvport>) |
225 | a @reason was specified, i.e. on "normal" kils nothing happens, while |
507 | will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
226 | under all other conditions, the other port is killed with the same reason. |
508 | "normal" kils nothing happens, while under all other conditions, the other |
|
|
509 | port is killed with the same reason. |
227 | |
510 | |
|
|
511 | The third form (kill self) is the same as the second form, except that |
|
|
512 | C<$rvport> defaults to C<$SELF>. |
|
|
513 | |
228 | In the last form, a message of the form C<@msg, @reason> will be C<snd>. |
514 | In the last form (message), a message of the form C<@msg, @reason> will be |
|
|
515 | C<snd>. |
|
|
516 | |
|
|
517 | As a rule of thumb, monitoring requests should always monitor a port from |
|
|
518 | a local port (or callback). The reason is that kill messages might get |
|
|
519 | lost, just like any other message. Another less obvious reason is that |
|
|
520 | even monitoring requests can get lost (for exmaple, when the connection |
|
|
521 | to the other node goes down permanently). When monitoring a port locally |
|
|
522 | these problems do not exist. |
229 | |
523 | |
230 | Example: call a given callback when C<$port> is killed. |
524 | Example: call a given callback when C<$port> is killed. |
231 | |
525 | |
232 | mon $port, sub { warn "port died because of <@_>\n" }; |
526 | mon $port, sub { warn "port died because of <@_>\n" }; |
233 | |
527 | |
234 | Example: kill ourselves when C<$port> is killed abnormally. |
528 | Example: kill ourselves when C<$port> is killed abnormally. |
235 | |
529 | |
236 | mon $port, $self; |
530 | mon $port; |
237 | |
531 | |
238 | Example: send us a restart message another C<$port> is killed. |
532 | Example: send us a restart message when another C<$port> is killed. |
239 | |
533 | |
240 | mon $port, $self => "restart"; |
534 | mon $port, $self => "restart"; |
241 | |
535 | |
242 | =cut |
536 | =cut |
243 | |
537 | |
244 | sub mon { |
538 | sub mon { |
245 | my ($noderef, $port) = split /#/, shift, 2; |
539 | my ($noderef, $port) = split /#/, shift, 2; |
246 | |
540 | |
247 | my $node = $NODE{$noderef} || add_node $noderef; |
541 | my $node = $NODE{$noderef} || add_node $noderef; |
248 | |
542 | |
249 | my $cb = shift; |
543 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
250 | |
544 | |
251 | unless (ref $cb) { |
545 | unless (ref $cb) { |
252 | if (@_) { |
546 | if (@_) { |
253 | # send a kill info message |
547 | # send a kill info message |
254 | my (@msg) = ($cb, @_); |
548 | my (@msg) = ($cb, @_); |
… | |
… | |
285 | =cut |
579 | =cut |
286 | |
580 | |
287 | sub mon_guard { |
581 | sub mon_guard { |
288 | my ($port, @refs) = @_; |
582 | my ($port, @refs) = @_; |
289 | |
583 | |
|
|
584 | #TODO: mon-less form? |
|
|
585 | |
290 | mon $port, sub { 0 && @refs } |
586 | mon $port, sub { 0 && @refs } |
291 | } |
587 | } |
292 | |
588 | |
293 | =item lnk $port1, $port2 |
589 | =item kil $port[, @reason] |
294 | |
590 | |
295 | Link two ports. This is simply a shorthand for: |
591 | Kill the specified port with the given C<@reason>. |
296 | |
592 | |
297 | mon $port1, $port2; |
593 | If no C<@reason> is specified, then the port is killed "normally" (linked |
298 | mon $port2, $port1; |
594 | ports will not be kileld, or even notified). |
299 | |
595 | |
300 | It means that if either one is killed abnormally, the other one gets |
596 | Otherwise, linked ports get killed with the same reason (second form of |
301 | killed as well. |
597 | C<mon>, see below). |
302 | |
598 | |
303 | =item $local_port = port |
599 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
|
|
600 | will be reported as reason C<< die => $@ >>. |
304 | |
601 | |
305 | Create a new local port object that supports message matching. |
602 | Transport/communication errors are reported as C<< transport_error => |
|
|
603 | $message >>. |
306 | |
604 | |
307 | =item $portid = port { my @msg = @_; $finished } |
|
|
308 | |
|
|
309 | Creates a "mini port", that is, a very lightweight port without any |
|
|
310 | pattern matching behind it, and returns its ID. |
|
|
311 | |
|
|
312 | The block will be called for every message received on the port. When the |
|
|
313 | callback returns a true value its job is considered "done" and the port |
|
|
314 | will be destroyed. Otherwise it will stay alive. |
|
|
315 | |
|
|
316 | The message will be passed as-is, no extra argument (i.e. no port id) will |
|
|
317 | be passed to the callback. |
|
|
318 | |
|
|
319 | If you need the local port id in the callback, this works nicely: |
|
|
320 | |
|
|
321 | my $port; $port = miniport { |
|
|
322 | snd $otherport, reply => $port; |
|
|
323 | }; |
|
|
324 | |
|
|
325 | =cut |
605 | =cut |
326 | |
606 | |
327 | sub port(;&) { |
607 | =item $port = spawn $node, $initfunc[, @initdata] |
328 | my $id = "$UNIQ." . $ID++; |
|
|
329 | my $port = "$NODE#$id"; |
|
|
330 | |
608 | |
331 | if (@_) { |
609 | Creates a port on the node C<$node> (which can also be a port ID, in which |
332 | my $cb = shift; |
610 | case it's the node where that port resides). |
333 | $PORT{$id} = sub { |
611 | |
334 | local $SELF = $port; |
612 | The port ID of the newly created port is return immediately, and it is |
335 | eval { |
613 | permissible to immediately start sending messages or monitor the port. |
336 | &$cb |
614 | |
337 | and kil $id; |
615 | After the port has been created, the init function is |
|
|
616 | called. This function must be a fully-qualified function name |
|
|
617 | (e.g. C<MyApp::Chat::Server::init>). To specify a function in the main |
|
|
618 | program, use C<::name>. |
|
|
619 | |
|
|
620 | If the function doesn't exist, then the node tries to C<require> |
|
|
621 | the package, then the package above the package and so on (e.g. |
|
|
622 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
|
|
623 | exists or it runs out of package names. |
|
|
624 | |
|
|
625 | The init function is then called with the newly-created port as context |
|
|
626 | object (C<$SELF>) and the C<@initdata> values as arguments. |
|
|
627 | |
|
|
628 | A common idiom is to pass your own port, monitor the spawned port, and |
|
|
629 | in the init function, monitor the original port. This two-way monitoring |
|
|
630 | ensures that both ports get cleaned up when there is a problem. |
|
|
631 | |
|
|
632 | Example: spawn a chat server port on C<$othernode>. |
|
|
633 | |
|
|
634 | # this node, executed from within a port context: |
|
|
635 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
|
|
636 | mon $server; |
|
|
637 | |
|
|
638 | # init function on C<$othernode> |
|
|
639 | sub connect { |
|
|
640 | my ($srcport) = @_; |
|
|
641 | |
|
|
642 | mon $srcport; |
|
|
643 | |
|
|
644 | rcv $SELF, sub { |
338 | }; |
645 | ... |
339 | _self_die if $@; |
|
|
340 | }; |
|
|
341 | } else { |
|
|
342 | my $self = bless { |
|
|
343 | id => "$NODE#$id", |
|
|
344 | }, "AnyEvent::MP::Port"; |
|
|
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 | }; |
646 | }; |
370 | } |
647 | } |
371 | |
648 | |
372 | $port |
|
|
373 | } |
|
|
374 | |
|
|
375 | =item reg $portid, $name |
|
|
376 | |
|
|
377 | Registers the given port under the name C<$name>. If the name already |
|
|
378 | exists it is replaced. |
|
|
379 | |
|
|
380 | A port can only be registered under one well known name. |
|
|
381 | |
|
|
382 | A port automatically becomes unregistered when it is killed. |
|
|
383 | |
|
|
384 | =cut |
649 | =cut |
385 | |
650 | |
386 | sub reg(@) { |
651 | sub _spawn { |
387 | my ($portid, $name) = @_; |
652 | my $port = shift; |
|
|
653 | my $init = shift; |
388 | |
654 | |
389 | $REG{$name} = $portid; |
655 | local $SELF = "$NODE#$port"; |
390 | } |
656 | eval { |
391 | |
657 | &{ load_func $init } |
392 | =item rcv $portid, tagstring => $callback->(@msg), ... |
|
|
393 | |
|
|
394 | =item rcv $portid, $smartmatch => $callback->(@msg), ... |
|
|
395 | |
|
|
396 | =item rcv $portid, [$smartmatch...] => $callback->(@msg), ... |
|
|
397 | |
|
|
398 | Register callbacks to be called on matching messages on the given port. |
|
|
399 | |
|
|
400 | The callback has to return a true value when its work is done, after |
|
|
401 | which is will be removed, or a false value in which case it will stay |
|
|
402 | registered. |
|
|
403 | |
|
|
404 | The global C<$SELF> (exported by this module) contains C<$portid> while |
|
|
405 | executing the callback. |
|
|
406 | |
|
|
407 | Runtime errors wdurign callback execution will result in the port being |
|
|
408 | C<kil>ed. |
|
|
409 | |
|
|
410 | If the match is an array reference, then it will be matched against the |
|
|
411 | first elements of the message, otherwise only the first element is being |
|
|
412 | matched. |
|
|
413 | |
|
|
414 | Any element in the match that is specified as C<_any_> (a function |
|
|
415 | exported by this module) matches any single element of the message. |
|
|
416 | |
|
|
417 | While not required, it is highly recommended that the first matching |
|
|
418 | element is a string identifying the message. The one-string-only match is |
|
|
419 | also the most efficient match (by far). |
|
|
420 | |
|
|
421 | =cut |
|
|
422 | |
|
|
423 | sub rcv($@) { |
|
|
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 | }; |
658 | }; |
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 $@; |
659 | _self_die if $@; |
480 | @res |
660 | } |
481 | } else { |
661 | |
482 | my $res = eval { &$cb }; |
662 | sub spawn(@) { |
483 | _self_die if $@; |
663 | my ($noderef, undef) = split /#/, shift, 2; |
484 | $res |
664 | |
485 | } |
665 | my $id = "$RUNIQ." . $ID++; |
|
|
666 | |
|
|
667 | $_[0] =~ /::/ |
|
|
668 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
|
|
669 | |
|
|
670 | snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; |
|
|
671 | |
|
|
672 | "$noderef#$id" |
|
|
673 | } |
|
|
674 | |
|
|
675 | =item after $timeout, @msg |
|
|
676 | |
|
|
677 | =item after $timeout, $callback |
|
|
678 | |
|
|
679 | Either sends the given message, or call the given callback, after the |
|
|
680 | specified number of seconds. |
|
|
681 | |
|
|
682 | This is simply a utility function that come sin handy at times. |
|
|
683 | |
|
|
684 | =cut |
|
|
685 | |
|
|
686 | sub after($@) { |
|
|
687 | my ($timeout, @action) = @_; |
|
|
688 | |
|
|
689 | my $t; $t = AE::timer $timeout, 0, sub { |
|
|
690 | undef $t; |
|
|
691 | ref $action[0] |
|
|
692 | ? $action[0]() |
|
|
693 | : snd @action; |
486 | } |
694 | }; |
487 | } |
695 | } |
488 | |
696 | |
489 | =back |
697 | =back |
490 | |
698 | |
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 |
699 | =head1 AnyEvent::MP vs. Distributed Erlang |
557 | |
700 | |
558 | AnyEvent::MP got lots of its ideas from distributed erlang (erlang node |
701 | 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 |
702 | == 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 |
703 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
561 | sample: |
704 | sample: |
562 | |
705 | |
563 | http://www.erlang.se/doc/programming_rules.shtml |
706 | http://www.Erlang.se/doc/programming_rules.shtml |
564 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
707 | 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 |
708 | http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
566 | http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
709 | http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
567 | |
710 | |
568 | Despite the similarities, there are also some important differences: |
711 | Despite the similarities, there are also some important differences: |
569 | |
712 | |
570 | =over 4 |
713 | =over 4 |
571 | |
714 | |
… | |
… | |
576 | convenience functionality. |
719 | convenience functionality. |
577 | |
720 | |
578 | This means that AEMP requires a less tightly controlled environment at the |
721 | This means that AEMP requires a less tightly controlled environment at the |
579 | cost of longer node references and a slightly higher management overhead. |
722 | cost of longer node references and a slightly higher management overhead. |
580 | |
723 | |
|
|
724 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
|
|
725 | uses "local ports are like remote ports". |
|
|
726 | |
|
|
727 | The failure modes for local ports are quite different (runtime errors |
|
|
728 | only) then for remote ports - when a local port dies, you I<know> it dies, |
|
|
729 | when a connection to another node dies, you know nothing about the other |
|
|
730 | port. |
|
|
731 | |
|
|
732 | Erlang pretends remote ports are as reliable as local ports, even when |
|
|
733 | they are not. |
|
|
734 | |
|
|
735 | AEMP encourages a "treat remote ports differently" philosophy, with local |
|
|
736 | ports being the special case/exception, where transport errors cannot |
|
|
737 | occur. |
|
|
738 | |
581 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
739 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
582 | |
740 | |
583 | Erlang uses processes that selctively receive messages, and therefore |
741 | Erlang uses processes that selectively receive messages, and therefore |
584 | needs a queue. AEMP is event based, queuing messages would serve no useful |
742 | needs a queue. AEMP is event based, queuing messages would serve no |
585 | purpose. |
743 | useful purpose. For the same reason the pattern-matching abilities of |
|
|
744 | AnyEvent::MP are more limited, as there is little need to be able to |
|
|
745 | filter messages without dequeing them. |
586 | |
746 | |
587 | (But see L<Coro::MP> for a more erlang-like process model on top of AEMP). |
747 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
588 | |
748 | |
589 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
749 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
590 | |
750 | |
591 | Sending messages in erlang is synchronous and blocks the process. AEMP |
751 | Sending messages in Erlang is synchronous and blocks the process (and |
592 | sends are immediate, connection establishment is handled in the |
752 | so does not need a queue that can overflow). AEMP sends are immediate, |
593 | background. |
753 | connection establishment is handled in the background. |
594 | |
754 | |
595 | =item * Erlang can silently lose messages, AEMP cannot. |
755 | =item * Erlang suffers from silent message loss, AEMP does not. |
596 | |
756 | |
597 | Erlang makes few guarantees on messages delivery - messages can get lost |
757 | Erlang makes few guarantees on messages delivery - messages can get lost |
598 | without any of the processes realising it (i.e. you send messages a, b, |
758 | without any of the processes realising it (i.e. you send messages a, b, |
599 | and c, and the other side only receives messages a and c). |
759 | and c, and the other side only receives messages a and c). |
600 | |
760 | |
601 | AEMP guarantees correct ordering, and the guarantee that there are no |
761 | AEMP guarantees correct ordering, and the guarantee that there are no |
602 | holes in the message sequence. |
762 | holes in the message sequence. |
603 | |
763 | |
604 | =item * In erlang, processes can be declared dead and later be found to be |
764 | =item * In Erlang, processes can be declared dead and later be found to be |
605 | alive. |
765 | alive. |
606 | |
766 | |
607 | In erlang it can happen that a monitored process is declared dead and |
767 | In Erlang it can happen that a monitored process is declared dead and |
608 | linked processes get killed, but later it turns out that the process is |
768 | linked processes get killed, but later it turns out that the process is |
609 | still alive - and can receive messages. |
769 | still alive - and can receive messages. |
610 | |
770 | |
611 | In AEMP, when port monitoring detects a port as dead, then that port will |
771 | 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 |
772 | 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. |
773 | and then later sends messages to it, finding it is still alive. |
614 | |
774 | |
615 | =item * Erlang can send messages to the wrong port, AEMP does not. |
775 | =item * Erlang can send messages to the wrong port, AEMP does not. |
616 | |
776 | |
617 | In erlang it is quite possible that a node that restarts reuses a process |
777 | In Erlang it is quite likely that a node that restarts reuses a process ID |
618 | ID known to other nodes for a completely different process, causing |
778 | known to other nodes for a completely different process, causing messages |
619 | messages destined for that process to end up in an unrelated process. |
779 | destined for that process to end up in an unrelated process. |
620 | |
780 | |
621 | AEMP never reuses port IDs, so old messages or old port IDs floating |
781 | AEMP never reuses port IDs, so old messages or old port IDs floating |
622 | around in the network will not be sent to an unrelated port. |
782 | around in the network will not be sent to an unrelated port. |
623 | |
783 | |
624 | =item * Erlang uses unprotected connections, AEMP uses secure |
784 | =item * Erlang uses unprotected connections, AEMP uses secure |
… | |
… | |
628 | securely authenticate nodes. |
788 | securely authenticate nodes. |
629 | |
789 | |
630 | =item * The AEMP protocol is optimised for both text-based and binary |
790 | =item * The AEMP protocol is optimised for both text-based and binary |
631 | communications. |
791 | communications. |
632 | |
792 | |
633 | The AEMP protocol, unlike the erlang protocol, supports both |
793 | The AEMP protocol, unlike the Erlang protocol, supports both |
634 | language-independent text-only protocols (good for debugging) and binary, |
794 | language-independent text-only protocols (good for debugging) and binary, |
635 | language-specific serialisers (e.g. Storable). |
795 | language-specific serialisers (e.g. Storable). |
636 | |
796 | |
637 | It has also been carefully designed to be implementable in other languages |
797 | 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 |
798 | with a minimum of work while gracefully degrading fucntionality to make the |
639 | protocol simple. |
799 | protocol simple. |
640 | |
800 | |
|
|
801 | =item * AEMP has more flexible monitoring options than Erlang. |
|
|
802 | |
|
|
803 | In Erlang, you can chose to receive I<all> exit signals as messages |
|
|
804 | or I<none>, there is no in-between, so monitoring single processes is |
|
|
805 | difficult to implement. Monitoring in AEMP is more flexible than in |
|
|
806 | Erlang, as one can choose between automatic kill, exit message or callback |
|
|
807 | on a per-process basis. |
|
|
808 | |
|
|
809 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
|
|
810 | |
|
|
811 | Monitoring in Erlang is not an indicator of process death/crashes, |
|
|
812 | as linking is (except linking is unreliable in Erlang). |
|
|
813 | |
|
|
814 | In AEMP, you don't "look up" registered port names or send to named ports |
|
|
815 | that might or might not be persistent. Instead, you normally spawn a port |
|
|
816 | on the remote node. The init function monitors the you, and you monitor |
|
|
817 | the remote port. Since both monitors are local to the node, they are much |
|
|
818 | more reliable. |
|
|
819 | |
|
|
820 | This also saves round-trips and avoids sending messages to the wrong port |
|
|
821 | (hard to do in Erlang). |
|
|
822 | |
|
|
823 | =back |
|
|
824 | |
|
|
825 | =head1 RATIONALE |
|
|
826 | |
|
|
827 | =over 4 |
|
|
828 | |
|
|
829 | =item Why strings for ports and noderefs, why not objects? |
|
|
830 | |
|
|
831 | We considered "objects", but found that the actual number of methods |
|
|
832 | thatc an be called are very low. Since port IDs and noderefs travel over |
|
|
833 | the network frequently, the serialising/deserialising would add lots of |
|
|
834 | overhead, as well as having to keep a proxy object. |
|
|
835 | |
|
|
836 | Strings can easily be printed, easily serialised etc. and need no special |
|
|
837 | procedures to be "valid". |
|
|
838 | |
|
|
839 | And a a miniport consists of a single closure stored in a global hash - it |
|
|
840 | can't become much cheaper. |
|
|
841 | |
|
|
842 | =item Why favour JSON, why not real serialising format such as Storable? |
|
|
843 | |
|
|
844 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
|
|
845 | format, but currently there is no way to make a node use Storable by |
|
|
846 | default. |
|
|
847 | |
|
|
848 | The default framing protocol is JSON because a) JSON::XS is many times |
|
|
849 | faster for small messages and b) most importantly, after years of |
|
|
850 | experience we found that object serialisation is causing more problems |
|
|
851 | than it gains: Just like function calls, objects simply do not travel |
|
|
852 | easily over the network, mostly because they will always be a copy, so you |
|
|
853 | always have to re-think your design. |
|
|
854 | |
|
|
855 | Keeping your messages simple, concentrating on data structures rather than |
|
|
856 | objects, will keep your messages clean, tidy and efficient. |
|
|
857 | |
641 | =back |
858 | =back |
642 | |
859 | |
643 | =head1 SEE ALSO |
860 | =head1 SEE ALSO |
644 | |
861 | |
645 | L<AnyEvent>. |
862 | L<AnyEvent>. |