… | |
… | |
11 | NODE $port # returns the noderef of the port |
11 | NODE $port # returns the noderef of the port |
12 | |
12 | |
13 | $SELF # receiving/own port id in rcv callbacks |
13 | $SELF # receiving/own port id in rcv callbacks |
14 | |
14 | |
15 | # initialise the node so it can send/receive messages |
15 | # initialise the node so it can send/receive messages |
16 | initialise_node; # -OR- |
16 | initialise_node; |
17 | initialise_node "localhost:4040"; # -OR- |
|
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18 | initialise_node "slave/", "localhost:4040" |
|
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19 | |
17 | |
20 | # ports are message endpoints |
18 | # ports are message endpoints |
21 | |
19 | |
22 | # sending messages |
20 | # sending messages |
23 | snd $port, type => data...; |
21 | snd $port, type => data...; |
… | |
… | |
40 | mon $port, $otherport # kill otherport on abnormal death |
38 | mon $port, $otherport # kill otherport on abnormal death |
41 | mon $port, $otherport, @msg # send message on death |
39 | mon $port, $otherport, @msg # send message on death |
42 | |
40 | |
43 | =head1 CURRENT STATUS |
41 | =head1 CURRENT STATUS |
44 | |
42 | |
|
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43 | bin/aemp - stable. |
45 | AnyEvent::MP - stable API, should work |
44 | AnyEvent::MP - stable API, should work. |
46 | AnyEvent::MP::Intro - outdated |
45 | AnyEvent::MP::Intro - uptodate, but incomplete. |
47 | AnyEvent::MP::Kernel - WIP |
|
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48 | AnyEvent::MP::Transport - mostly stable |
46 | AnyEvent::MP::Kernel - mostly stable. |
|
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47 | AnyEvent::MP::Global - stable API, protocol not yet final. |
49 | |
48 | |
50 | stay tuned. |
49 | stay tuned. |
51 | |
50 | |
52 | =head1 DESCRIPTION |
51 | =head1 DESCRIPTION |
53 | |
52 | |
54 | This module (-family) implements a simple message passing framework. |
53 | This module (-family) implements a simple message passing framework. |
55 | |
54 | |
56 | Despite its simplicity, you can securely message other processes running |
55 | Despite its simplicity, you can securely message other processes running |
57 | on the same or other hosts. |
56 | on the same or other hosts, and you can supervise entities remotely. |
58 | |
57 | |
59 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
58 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
60 | manual page. |
59 | manual page and the examples under F<eg/>. |
61 | |
60 | |
62 | At the moment, this module family is severly broken and underdocumented, |
61 | At the moment, this module family is a bit underdocumented. |
63 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
|
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64 | stay tuned! |
|
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65 | |
62 | |
66 | =head1 CONCEPTS |
63 | =head1 CONCEPTS |
67 | |
64 | |
68 | =over 4 |
65 | =over 4 |
69 | |
66 | |
70 | =item port |
67 | =item port |
71 | |
68 | |
72 | A port is something you can send messages to (with the C<snd> function). |
69 | A port is something you can send messages to (with the C<snd> function). |
73 | |
70 | |
74 | Ports allow you to register C<rcv> handlers that can match all or just |
71 | Ports allow you to register C<rcv> handlers that can match all or just |
75 | some messages. Messages will not be queued. |
72 | some messages. Messages send to ports will not be queued, regardless of |
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73 | anything was listening for them or not. |
76 | |
74 | |
77 | =item port id - C<noderef#portname> |
75 | =item port ID - C<nodeid#portname> |
78 | |
76 | |
79 | A port ID is the concatenation of a noderef, a hash-mark (C<#>) as |
77 | A port ID is the concatenation of a node ID, a hash-mark (C<#>) as |
80 | separator, and a port name (a printable string of unspecified format). An |
78 | separator, and a port name (a printable string of unspecified format). |
81 | exception is the the node port, whose ID is identical to its node |
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82 | reference. |
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83 | |
79 | |
84 | =item node |
80 | =item node |
85 | |
81 | |
86 | A node is a single process containing at least one port - the node port, |
82 | A node is a single process containing at least one port - the node port, |
87 | which provides nodes to manage each other remotely, and to create new |
83 | which enables nodes to manage each other remotely, and to create new |
88 | ports. |
84 | ports. |
89 | |
85 | |
90 | Nodes are either private (single-process only), slaves (connected to a |
86 | Nodes are either public (have one or more listening ports) or private |
91 | master node only) or public nodes (connectable from unrelated nodes). |
87 | (no listening ports). Private nodes cannot talk to other private nodes |
|
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88 | currently. |
92 | |
89 | |
93 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
90 | =item node ID - C<[a-za-Z0-9_\-.:]+> |
94 | |
91 | |
95 | A node reference is a string that either simply identifies the node (for |
92 | A node ID is a string that uniquely identifies the node within a |
96 | private and slave nodes), or contains a recipe on how to reach a given |
93 | network. Depending on the configuration used, node IDs can look like a |
97 | node (for public nodes). |
94 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
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95 | doesn't interpret node IDs in any way. |
98 | |
96 | |
99 | This recipe is simply a comma-separated list of C<address:port> pairs (for |
97 | =item binds - C<ip:port> |
100 | TCP/IP, other protocols might look different). |
|
|
101 | |
98 | |
102 | Node references come in two flavours: resolved (containing only numerical |
99 | Nodes can only talk to each other by creating some kind of connection to |
103 | addresses) or unresolved (where hostnames are used instead of addresses). |
100 | each other. To do this, nodes should listen on one or more local transport |
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101 | endpoints - binds. Currently, only standard C<ip:port> specifications can |
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102 | be used, which specify TCP ports to listen on. |
104 | |
103 | |
105 | Before using an unresolved node reference in a message you first have to |
104 | =item seeds - C<host:port> |
106 | resolve it. |
105 | |
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106 | When a node starts, it knows nothing about the network. To teach the node |
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107 | about the network it first has to contact some other node within the |
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108 | network. This node is called a seed. |
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109 | |
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110 | Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes |
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111 | are expected to be long-running, and at least one of those should always |
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112 | be available. When nodes run out of connections (e.g. due to a network |
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113 | error), they try to re-establish connections to some seednodes again to |
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114 | join the network. |
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115 | |
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116 | Apart from being sued for seeding, seednodes are not special in any way - |
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117 | every public node can be a seednode. |
107 | |
118 | |
108 | =back |
119 | =back |
109 | |
120 | |
110 | =head1 VARIABLES/FUNCTIONS |
121 | =head1 VARIABLES/FUNCTIONS |
111 | |
122 | |
… | |
… | |
126 | use base "Exporter"; |
137 | use base "Exporter"; |
127 | |
138 | |
128 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
139 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
129 | |
140 | |
130 | our @EXPORT = qw( |
141 | our @EXPORT = qw( |
131 | NODE $NODE *SELF node_of _any_ |
142 | NODE $NODE *SELF node_of after |
132 | resolve_node initialise_node |
143 | initialise_node |
133 | snd rcv mon kil reg psub spawn |
144 | snd rcv mon mon_guard kil reg psub spawn |
134 | port |
145 | port |
135 | ); |
146 | ); |
136 | |
147 | |
137 | our $SELF; |
148 | our $SELF; |
138 | |
149 | |
… | |
… | |
142 | kil $SELF, die => $msg; |
153 | kil $SELF, die => $msg; |
143 | } |
154 | } |
144 | |
155 | |
145 | =item $thisnode = NODE / $NODE |
156 | =item $thisnode = NODE / $NODE |
146 | |
157 | |
147 | The C<NODE> function returns, and the C<$NODE> variable contains the |
158 | The C<NODE> function returns, and the C<$NODE> variable contains, the node |
148 | noderef of the local node. The value is initialised by a call to |
159 | ID of the node running in the current process. This value is initialised by |
149 | C<initialise_node>. |
160 | a call to C<initialise_node>. |
150 | |
161 | |
151 | =item $noderef = node_of $port |
162 | =item $nodeid = node_of $port |
152 | |
163 | |
153 | Extracts and returns the noderef from a port ID or a noderef. |
164 | Extracts and returns the node ID from a port ID or a node ID. |
154 | |
165 | |
155 | =item initialise_node $noderef, $seednode, $seednode... |
166 | =item initialise_node $profile_name, key => value... |
156 | |
167 | |
157 | =item initialise_node "slave/", $master, $master... |
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158 | |
|
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159 | Before a node can talk to other nodes on the network it has to initialise |
168 | Before a node can talk to other nodes on the network (i.e. enter |
160 | itself - the minimum a node needs to know is it's own name, and optionally |
169 | "distributed mode") it has to initialise itself - the minimum a node needs |
161 | it should know the noderefs of some other nodes in the network. |
170 | to know is its own name, and optionally it should know the addresses of |
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171 | some other nodes in the network to discover other nodes. |
162 | |
172 | |
163 | This function initialises a node - it must be called exactly once (or |
173 | This function initialises a node - it must be called exactly once (or |
164 | never) before calling other AnyEvent::MP functions. |
174 | never) before calling other AnyEvent::MP functions. |
165 | |
175 | |
166 | All arguments (optionally except for the first) are noderefs, which can be |
176 | The first argument is a profile name. If it is C<undef> or missing, then |
167 | either resolved or unresolved. |
177 | the current nodename will be used instead (i.e. F<uname -n>). |
168 | |
178 | |
169 | The first argument will be looked up in the configuration database first |
179 | The function first looks up the profile in the aemp configuration (see the |
170 | (if it is C<undef> then the current nodename will be used instead) to find |
180 | L<aemp> commandline utility). the profile is calculated as follows: |
171 | the relevant configuration profile (see L<aemp>). If none is found then |
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172 | the default configuration is used. The configuration supplies additional |
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173 | seed/master nodes and can override the actual noderef. |
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174 | |
181 | |
175 | There are two types of networked nodes, public nodes and slave nodes: |
182 | First, all remaining key => value pairs (all of which are conviniently |
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183 | undocumented at the moment) will be used. Then they will be overwritten by |
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184 | any values specified in the global default configuration (see the F<aemp> |
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185 | utility), then the chain of profiles selected, if any. That means that |
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186 | the values specified in the profile have highest priority and the values |
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187 | specified via C<initialise_node> have lowest priority. |
176 | |
188 | |
177 | =over 4 |
189 | If the profile specifies a node ID, then this will become the node ID of |
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190 | this process. If not, then the profile name will be used as node ID. The |
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191 | special node ID of C<anon/> will be replaced by a random node ID. |
178 | |
192 | |
179 | =item public nodes |
193 | The next step is to look up the binds in the profile, followed by binding |
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194 | aemp protocol listeners on all binds specified (it is possible and valid |
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195 | to have no binds, meaning that the node cannot be contacted form the |
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196 | outside. This means the node cannot talk to other nodes that also have no |
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197 | binds, but it can still talk to all "normal" nodes). |
180 | |
198 | |
181 | For public nodes, C<$noderef> (supplied either directly to |
199 | If the profile does not specify a binds list, then a default of C<*> is |
182 | C<initialise_node> or indirectly via a profile or the nodename) must be a |
200 | used. |
183 | noderef (possibly unresolved, in which case it will be resolved). |
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184 | |
201 | |
185 | After resolving, the node will bind itself on all endpoints and try to |
202 | Lastly, the seeds list from the profile is passed to the |
186 | connect to all additional C<$seednodes> that are specified. Seednodes are |
203 | L<AnyEvent::MP::Global> module, which will then use it to keep |
187 | optional and can be used to quickly bootstrap the node into an existing |
204 | connectivity with at least on of those seed nodes at any point in time. |
188 | network. |
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189 | |
205 | |
190 | =item slave nodes |
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191 | |
|
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192 | When the C<$noderef> (either as given or overriden by the config file) |
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193 | is the special string C<slave/>, then the node will become a slave |
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194 | node. Slave nodes cannot be contacted from outside and will route most of |
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195 | their traffic to the master node that they attach to. |
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196 | |
|
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197 | At least one additional noderef is required (either by specifying it |
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198 | directly or because it is part of the configuration profile): The node |
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199 | will try to connect to all of them and will become a slave attached to the |
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200 | first node it can successfully connect to. |
|
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201 | |
|
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202 | Note that slave nodes cannot change their name, and consequently, their |
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203 | master, so if the master goes down, the slave node will not function well |
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204 | anymore until it can re-establish conenciton to its master. This makes |
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205 | slave nodes unsuitable for long-term nodes or fault-tolerant networks. |
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206 | |
|
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207 | =back |
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208 | |
|
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209 | This function will block until all nodes have been resolved and, for slave |
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210 | nodes, until it has successfully established a connection to a master |
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211 | server. |
|
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212 | |
|
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213 | All the seednodes will also be specially marked to automatically retry |
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214 | connecting to them infinitely. |
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215 | |
|
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216 | Example: become a public node listening on the guessed noderef, or the one |
206 | Example: become a distributed node listening on the guessed noderef, or |
217 | specified via C<aemp> for the current node. This should be the most common |
207 | the one specified via C<aemp> for the current node. This should be the |
218 | form of invocation for "daemon"-type nodes. |
208 | most common form of invocation for "daemon"-type nodes. |
219 | |
209 | |
220 | initialise_node; |
210 | initialise_node; |
221 | |
211 | |
222 | Example: become a slave node to any of the the seednodes specified via |
212 | Example: become an anonymous node. This form is often used for commandline |
223 | C<aemp>. This form is often used for commandline clients. |
213 | clients. |
224 | |
214 | |
225 | initialise_node "slave/"; |
215 | initialise_node "anon/"; |
226 | |
216 | |
227 | Example: become a slave node to any of the specified master servers. This |
217 | Example: become a distributed node. If there is no profile of the given |
228 | form is also often used for commandline clients. |
218 | name, or no binds list was specified, resolve C<localhost:4044> and bind |
229 | |
219 | on the resulting addresses. |
230 | initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
|
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231 | |
|
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232 | Example: become a public node, and try to contact some well-known master |
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233 | servers to become part of the network. |
|
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234 | |
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235 | initialise_node undef, "master1", "master2"; |
|
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236 | |
|
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237 | Example: become a public node listening on port C<4041>. |
|
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238 | |
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239 | initialise_node 4041; |
|
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240 | |
|
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241 | Example: become a public node, only visible on localhost port 4044. |
|
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242 | |
220 | |
243 | initialise_node "localhost:4044"; |
221 | initialise_node "localhost:4044"; |
244 | |
|
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245 | =item $cv = resolve_node $noderef |
|
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246 | |
|
|
247 | Takes an unresolved node reference that may contain hostnames and |
|
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248 | abbreviated IDs, resolves all of them and returns a resolved node |
|
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249 | reference. |
|
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250 | |
|
|
251 | In addition to C<address:port> pairs allowed in resolved noderefs, the |
|
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252 | following forms are supported: |
|
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253 | |
|
|
254 | =over 4 |
|
|
255 | |
|
|
256 | =item the empty string |
|
|
257 | |
|
|
258 | An empty-string component gets resolved as if the default port (4040) was |
|
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259 | specified. |
|
|
260 | |
|
|
261 | =item naked port numbers (e.g. C<1234>) |
|
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262 | |
|
|
263 | These are resolved by prepending the local nodename and a colon, to be |
|
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264 | further resolved. |
|
|
265 | |
|
|
266 | =item hostnames (e.g. C<localhost:1234>, C<localhost>) |
|
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267 | |
|
|
268 | These are resolved by using AnyEvent::DNS to resolve them, optionally |
|
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269 | looking up SRV records for the C<aemp=4040> port, if no port was |
|
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270 | specified. |
|
|
271 | |
|
|
272 | =back |
|
|
273 | |
222 | |
274 | =item $SELF |
223 | =item $SELF |
275 | |
224 | |
276 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
225 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
277 | blocks. |
226 | blocks. |
278 | |
227 | |
279 | =item SELF, %SELF, @SELF... |
228 | =item *SELF, SELF, %SELF, @SELF... |
280 | |
229 | |
281 | Due to some quirks in how perl exports variables, it is impossible to |
230 | Due to some quirks in how perl exports variables, it is impossible to |
282 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
231 | just export C<$SELF>, all the symbols named C<SELF> are exported by this |
283 | module, but only C<$SELF> is currently used. |
232 | module, but only C<$SELF> is currently used. |
284 | |
233 | |
285 | =item snd $port, type => @data |
234 | =item snd $port, type => @data |
286 | |
235 | |
287 | =item snd $port, @msg |
236 | =item snd $port, @msg |
288 | |
237 | |
289 | Send the given message to the given port ID, which can identify either |
238 | Send the given message to the given port, which can identify either a |
290 | a local or a remote port, and must be a port ID. |
239 | local or a remote port, and must be a port ID. |
291 | |
240 | |
292 | While the message can be about anything, it is highly recommended to use a |
241 | While the message can be almost anything, it is highly recommended to |
293 | string as first element (a port ID, or some word that indicates a request |
242 | use a string as first element (a port ID, or some word that indicates a |
294 | type etc.). |
243 | request type etc.) and to consist if only simple perl values (scalars, |
|
|
244 | arrays, hashes) - if you think you need to pass an object, think again. |
295 | |
245 | |
296 | The message data effectively becomes read-only after a call to this |
246 | The message data logically becomes read-only after a call to this |
297 | function: modifying any argument is not allowed and can cause many |
247 | function: modifying any argument (or values referenced by them) is |
298 | problems. |
248 | forbidden, as there can be considerable time between the call to C<snd> |
|
|
249 | and the time the message is actually being serialised - in fact, it might |
|
|
250 | never be copied as within the same process it is simply handed to the |
|
|
251 | receiving port. |
299 | |
252 | |
300 | The type of data you can transfer depends on the transport protocol: when |
253 | The type of data you can transfer depends on the transport protocol: when |
301 | JSON is used, then only strings, numbers and arrays and hashes consisting |
254 | JSON is used, then only strings, numbers and arrays and hashes consisting |
302 | of those are allowed (no objects). When Storable is used, then anything |
255 | of those are allowed (no objects). When Storable is used, then anything |
303 | that Storable can serialise and deserialise is allowed, and for the local |
256 | that Storable can serialise and deserialise is allowed, and for the local |
304 | node, anything can be passed. |
257 | node, anything can be passed. Best rely only on the common denominator of |
|
|
258 | these. |
305 | |
259 | |
306 | =item $local_port = port |
260 | =item $local_port = port |
307 | |
261 | |
308 | Create a new local port object and returns its port ID. Initially it has |
262 | Create a new local port object and returns its port ID. Initially it has |
309 | no callbacks set and will throw an error when it receives messages. |
263 | no callbacks set and will throw an error when it receives messages. |
… | |
… | |
396 | |
350 | |
397 | sub rcv($@) { |
351 | sub rcv($@) { |
398 | my $port = shift; |
352 | my $port = shift; |
399 | my ($noderef, $portid) = split /#/, $port, 2; |
353 | my ($noderef, $portid) = split /#/, $port, 2; |
400 | |
354 | |
401 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
355 | $NODE{$noderef} == $NODE{""} |
402 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
356 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
403 | |
357 | |
404 | while (@_) { |
358 | while (@_) { |
405 | if (ref $_[0]) { |
359 | if (ref $_[0]) { |
406 | if (my $self = $PORT_DATA{$portid}) { |
360 | if (my $self = $PORT_DATA{$portid}) { |
… | |
… | |
485 | $res |
439 | $res |
486 | } |
440 | } |
487 | } |
441 | } |
488 | } |
442 | } |
489 | |
443 | |
490 | =item $guard = mon $port, $cb->(@reason) |
444 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
491 | |
445 | |
492 | =item $guard = mon $port, $rcvport |
446 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
493 | |
447 | |
494 | =item $guard = mon $port |
448 | =item $guard = mon $port # kill $SELF when $port dies |
495 | |
449 | |
496 | =item $guard = mon $port, $rcvport, @msg |
450 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
497 | |
451 | |
498 | Monitor the given port and do something when the port is killed or |
452 | Monitor the given port and do something when the port is killed or |
499 | messages to it were lost, and optionally return a guard that can be used |
453 | messages to it were lost, and optionally return a guard that can be used |
500 | to stop monitoring again. |
454 | to stop monitoring again. |
501 | |
455 | |
502 | C<mon> effectively guarantees that, in the absence of hardware failures, |
456 | C<mon> effectively guarantees that, in the absence of hardware failures, |
503 | that after starting the monitor, either all messages sent to the port |
457 | after starting the monitor, either all messages sent to the port will |
504 | will arrive, or the monitoring action will be invoked after possible |
458 | arrive, or the monitoring action will be invoked after possible message |
505 | message loss has been detected. No messages will be lost "in between" |
459 | loss has been detected. No messages will be lost "in between" (after |
506 | (after the first lost message no further messages will be received by the |
460 | the first lost message no further messages will be received by the |
507 | port). After the monitoring action was invoked, further messages might get |
461 | port). After the monitoring action was invoked, further messages might get |
508 | delivered again. |
462 | delivered again. |
|
|
463 | |
|
|
464 | Note that monitoring-actions are one-shot: once messages are lost (and a |
|
|
465 | monitoring alert was raised), they are removed and will not trigger again. |
509 | |
466 | |
510 | In the first form (callback), the callback is simply called with any |
467 | In the first form (callback), the callback is simply called with any |
511 | number of C<@reason> elements (no @reason means that the port was deleted |
468 | number of C<@reason> elements (no @reason means that the port was deleted |
512 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
469 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
513 | C<eval> if unsure. |
470 | C<eval> if unsure. |
… | |
… | |
575 | is killed, the references will be freed. |
532 | is killed, the references will be freed. |
576 | |
533 | |
577 | Optionally returns a guard that will stop the monitoring. |
534 | Optionally returns a guard that will stop the monitoring. |
578 | |
535 | |
579 | This function is useful when you create e.g. timers or other watchers and |
536 | This function is useful when you create e.g. timers or other watchers and |
580 | want to free them when the port gets killed: |
537 | want to free them when the port gets killed (note the use of C<psub>): |
581 | |
538 | |
582 | $port->rcv (start => sub { |
539 | $port->rcv (start => sub { |
583 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
540 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub { |
584 | undef $timer if 0.9 < rand; |
541 | undef $timer if 0.9 < rand; |
585 | }); |
542 | }); |
586 | }); |
543 | }); |
587 | |
544 | |
588 | =cut |
545 | =cut |
… | |
… | |
597 | |
554 | |
598 | =item kil $port[, @reason] |
555 | =item kil $port[, @reason] |
599 | |
556 | |
600 | Kill the specified port with the given C<@reason>. |
557 | Kill the specified port with the given C<@reason>. |
601 | |
558 | |
602 | If no C<@reason> is specified, then the port is killed "normally" (linked |
559 | If no C<@reason> is specified, then the port is killed "normally" (ports |
603 | ports will not be kileld, or even notified). |
560 | monitoring other ports will not necessarily die because a port dies |
|
|
561 | "normally"). |
604 | |
562 | |
605 | Otherwise, linked ports get killed with the same reason (second form of |
563 | Otherwise, linked ports get killed with the same reason (second form of |
606 | C<mon>, see below). |
564 | C<mon>, see above). |
607 | |
565 | |
608 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
566 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
609 | will be reported as reason C<< die => $@ >>. |
567 | will be reported as reason C<< die => $@ >>. |
610 | |
568 | |
611 | Transport/communication errors are reported as C<< transport_error => |
569 | Transport/communication errors are reported as C<< transport_error => |
… | |
… | |
616 | =item $port = spawn $node, $initfunc[, @initdata] |
574 | =item $port = spawn $node, $initfunc[, @initdata] |
617 | |
575 | |
618 | Creates a port on the node C<$node> (which can also be a port ID, in which |
576 | Creates a port on the node C<$node> (which can also be a port ID, in which |
619 | case it's the node where that port resides). |
577 | case it's the node where that port resides). |
620 | |
578 | |
621 | The port ID of the newly created port is return immediately, and it is |
579 | The port ID of the newly created port is returned immediately, and it is |
622 | permissible to immediately start sending messages or monitor the port. |
580 | possible to immediately start sending messages or to monitor the port. |
623 | |
581 | |
624 | After the port has been created, the init function is |
582 | After the port has been created, the init function is called on the remote |
625 | called. This function must be a fully-qualified function name |
583 | node, in the same context as a C<rcv> callback. This function must be a |
626 | (e.g. C<MyApp::Chat::Server::init>). To specify a function in the main |
584 | fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To |
627 | program, use C<::name>. |
585 | specify a function in the main program, use C<::name>. |
628 | |
586 | |
629 | If the function doesn't exist, then the node tries to C<require> |
587 | If the function doesn't exist, then the node tries to C<require> |
630 | the package, then the package above the package and so on (e.g. |
588 | the package, then the package above the package and so on (e.g. |
631 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
589 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
632 | exists or it runs out of package names. |
590 | exists or it runs out of package names. |
633 | |
591 | |
634 | The init function is then called with the newly-created port as context |
592 | The init function is then called with the newly-created port as context |
635 | object (C<$SELF>) and the C<@initdata> values as arguments. |
593 | object (C<$SELF>) and the C<@initdata> values as arguments. |
636 | |
594 | |
637 | A common idiom is to pass your own port, monitor the spawned port, and |
595 | A common idiom is to pass a local port, immediately monitor the spawned |
638 | in the init function, monitor the original port. This two-way monitoring |
596 | port, and in the remote init function, immediately monitor the passed |
639 | ensures that both ports get cleaned up when there is a problem. |
597 | local port. This two-way monitoring ensures that both ports get cleaned up |
|
|
598 | when there is a problem. |
640 | |
599 | |
641 | Example: spawn a chat server port on C<$othernode>. |
600 | Example: spawn a chat server port on C<$othernode>. |
642 | |
601 | |
643 | # this node, executed from within a port context: |
602 | # this node, executed from within a port context: |
644 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
603 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
… | |
… | |
679 | snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; |
638 | snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; |
680 | |
639 | |
681 | "$noderef#$id" |
640 | "$noderef#$id" |
682 | } |
641 | } |
683 | |
642 | |
|
|
643 | =item after $timeout, @msg |
|
|
644 | |
|
|
645 | =item after $timeout, $callback |
|
|
646 | |
|
|
647 | Either sends the given message, or call the given callback, after the |
|
|
648 | specified number of seconds. |
|
|
649 | |
|
|
650 | This is simply a utility function that comes in handy at times - the |
|
|
651 | AnyEvent::MP author is not convinced of the wisdom of having it, though, |
|
|
652 | so it may go away in the future. |
|
|
653 | |
|
|
654 | =cut |
|
|
655 | |
|
|
656 | sub after($@) { |
|
|
657 | my ($timeout, @action) = @_; |
|
|
658 | |
|
|
659 | my $t; $t = AE::timer $timeout, 0, sub { |
|
|
660 | undef $t; |
|
|
661 | ref $action[0] |
|
|
662 | ? $action[0]() |
|
|
663 | : snd @action; |
|
|
664 | }; |
|
|
665 | } |
|
|
666 | |
684 | =back |
667 | =back |
685 | |
668 | |
686 | =head1 AnyEvent::MP vs. Distributed Erlang |
669 | =head1 AnyEvent::MP vs. Distributed Erlang |
687 | |
670 | |
688 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
671 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
… | |
… | |
697 | |
680 | |
698 | Despite the similarities, there are also some important differences: |
681 | Despite the similarities, there are also some important differences: |
699 | |
682 | |
700 | =over 4 |
683 | =over 4 |
701 | |
684 | |
702 | =item * Node references contain the recipe on how to contact them. |
685 | =item * Node IDs are arbitrary strings in AEMP. |
703 | |
686 | |
704 | Erlang relies on special naming and DNS to work everywhere in the |
687 | Erlang relies on special naming and DNS to work everywhere in the same |
705 | same way. AEMP relies on each node knowing it's own address(es), with |
688 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
706 | convenience functionality. |
689 | configuraiton or DNS), but will otherwise discover other odes itself. |
707 | |
|
|
708 | This means that AEMP requires a less tightly controlled environment at the |
|
|
709 | cost of longer node references and a slightly higher management overhead. |
|
|
710 | |
690 | |
711 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
691 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
712 | uses "local ports are like remote ports". |
692 | uses "local ports are like remote ports". |
713 | |
693 | |
714 | The failure modes for local ports are quite different (runtime errors |
694 | The failure modes for local ports are quite different (runtime errors |
… | |
… | |
743 | |
723 | |
744 | Erlang makes few guarantees on messages delivery - messages can get lost |
724 | Erlang makes few guarantees on messages delivery - messages can get lost |
745 | without any of the processes realising it (i.e. you send messages a, b, |
725 | without any of the processes realising it (i.e. you send messages a, b, |
746 | and c, and the other side only receives messages a and c). |
726 | and c, and the other side only receives messages a and c). |
747 | |
727 | |
748 | AEMP guarantees correct ordering, and the guarantee that there are no |
728 | AEMP guarantees correct ordering, and the guarantee that after one message |
749 | holes in the message sequence. |
729 | is lost, all following ones sent to the same port are lost as well, until |
750 | |
730 | monitoring raises an error, so there are no silent "holes" in the message |
751 | =item * In Erlang, processes can be declared dead and later be found to be |
731 | sequence. |
752 | alive. |
|
|
753 | |
|
|
754 | In Erlang it can happen that a monitored process is declared dead and |
|
|
755 | linked processes get killed, but later it turns out that the process is |
|
|
756 | still alive - and can receive messages. |
|
|
757 | |
|
|
758 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
759 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
760 | and then later sends messages to it, finding it is still alive. |
|
|
761 | |
732 | |
762 | =item * Erlang can send messages to the wrong port, AEMP does not. |
733 | =item * Erlang can send messages to the wrong port, AEMP does not. |
763 | |
734 | |
764 | In Erlang it is quite likely that a node that restarts reuses a process ID |
735 | In Erlang it is quite likely that a node that restarts reuses a process ID |
765 | known to other nodes for a completely different process, causing messages |
736 | known to other nodes for a completely different process, causing messages |
… | |
… | |
769 | around in the network will not be sent to an unrelated port. |
740 | around in the network will not be sent to an unrelated port. |
770 | |
741 | |
771 | =item * Erlang uses unprotected connections, AEMP uses secure |
742 | =item * Erlang uses unprotected connections, AEMP uses secure |
772 | authentication and can use TLS. |
743 | authentication and can use TLS. |
773 | |
744 | |
774 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
745 | AEMP can use a proven protocol - TLS - to protect connections and |
775 | securely authenticate nodes. |
746 | securely authenticate nodes. |
776 | |
747 | |
777 | =item * The AEMP protocol is optimised for both text-based and binary |
748 | =item * The AEMP protocol is optimised for both text-based and binary |
778 | communications. |
749 | communications. |
779 | |
750 | |
780 | The AEMP protocol, unlike the Erlang protocol, supports both |
751 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
781 | language-independent text-only protocols (good for debugging) and binary, |
752 | language independent text-only protocols (good for debugging) and binary, |
782 | language-specific serialisers (e.g. Storable). |
753 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
|
|
754 | used, the protocol is actually completely text-based. |
783 | |
755 | |
784 | It has also been carefully designed to be implementable in other languages |
756 | It has also been carefully designed to be implementable in other languages |
785 | with a minimum of work while gracefully degrading fucntionality to make the |
757 | with a minimum of work while gracefully degrading functionality to make the |
786 | protocol simple. |
758 | protocol simple. |
787 | |
759 | |
788 | =item * AEMP has more flexible monitoring options than Erlang. |
760 | =item * AEMP has more flexible monitoring options than Erlang. |
789 | |
761 | |
790 | In Erlang, you can chose to receive I<all> exit signals as messages |
762 | In Erlang, you can chose to receive I<all> exit signals as messages |
… | |
… | |
793 | Erlang, as one can choose between automatic kill, exit message or callback |
765 | Erlang, as one can choose between automatic kill, exit message or callback |
794 | on a per-process basis. |
766 | on a per-process basis. |
795 | |
767 | |
796 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
768 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
797 | |
769 | |
798 | Monitoring in Erlang is not an indicator of process death/crashes, |
770 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
799 | as linking is (except linking is unreliable in Erlang). |
771 | same way as linking is (except linking is unreliable in Erlang). |
800 | |
772 | |
801 | In AEMP, you don't "look up" registered port names or send to named ports |
773 | In AEMP, you don't "look up" registered port names or send to named ports |
802 | that might or might not be persistent. Instead, you normally spawn a port |
774 | that might or might not be persistent. Instead, you normally spawn a port |
803 | on the remote node. The init function monitors the you, and you monitor |
775 | on the remote node. The init function monitors you, and you monitor the |
804 | the remote port. Since both monitors are local to the node, they are much |
776 | remote port. Since both monitors are local to the node, they are much more |
805 | more reliable. |
777 | reliable (no need for C<spawn_link>). |
806 | |
778 | |
807 | This also saves round-trips and avoids sending messages to the wrong port |
779 | This also saves round-trips and avoids sending messages to the wrong port |
808 | (hard to do in Erlang). |
780 | (hard to do in Erlang). |
809 | |
781 | |
810 | =back |
782 | =back |
811 | |
783 | |
812 | =head1 RATIONALE |
784 | =head1 RATIONALE |
813 | |
785 | |
814 | =over 4 |
786 | =over 4 |
815 | |
787 | |
816 | =item Why strings for ports and noderefs, why not objects? |
788 | =item Why strings for port and node IDs, why not objects? |
817 | |
789 | |
818 | We considered "objects", but found that the actual number of methods |
790 | We considered "objects", but found that the actual number of methods |
819 | thatc an be called are very low. Since port IDs and noderefs travel over |
791 | that can be called are quite low. Since port and node IDs travel over |
820 | the network frequently, the serialising/deserialising would add lots of |
792 | the network frequently, the serialising/deserialising would add lots of |
821 | overhead, as well as having to keep a proxy object. |
793 | overhead, as well as having to keep a proxy object everywhere. |
822 | |
794 | |
823 | Strings can easily be printed, easily serialised etc. and need no special |
795 | Strings can easily be printed, easily serialised etc. and need no special |
824 | procedures to be "valid". |
796 | procedures to be "valid". |
825 | |
797 | |
826 | And a a miniport consists of a single closure stored in a global hash - it |
798 | And as a result, a miniport consists of a single closure stored in a |
827 | can't become much cheaper. |
799 | global hash - it can't become much cheaper. |
828 | |
800 | |
829 | =item Why favour JSON, why not real serialising format such as Storable? |
801 | =item Why favour JSON, why not a real serialising format such as Storable? |
830 | |
802 | |
831 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
803 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
832 | format, but currently there is no way to make a node use Storable by |
804 | format, but currently there is no way to make a node use Storable by |
833 | default. |
805 | default (although all nodes will accept it). |
834 | |
806 | |
835 | The default framing protocol is JSON because a) JSON::XS is many times |
807 | The default framing protocol is JSON because a) JSON::XS is many times |
836 | faster for small messages and b) most importantly, after years of |
808 | faster for small messages and b) most importantly, after years of |
837 | experience we found that object serialisation is causing more problems |
809 | experience we found that object serialisation is causing more problems |
838 | than it gains: Just like function calls, objects simply do not travel |
810 | than it solves: Just like function calls, objects simply do not travel |
839 | easily over the network, mostly because they will always be a copy, so you |
811 | easily over the network, mostly because they will always be a copy, so you |
840 | always have to re-think your design. |
812 | always have to re-think your design. |
841 | |
813 | |
842 | Keeping your messages simple, concentrating on data structures rather than |
814 | Keeping your messages simple, concentrating on data structures rather than |
843 | objects, will keep your messages clean, tidy and efficient. |
815 | objects, will keep your messages clean, tidy and efficient. |
844 | |
816 | |
845 | =back |
817 | =back |
846 | |
818 | |
847 | =head1 SEE ALSO |
819 | =head1 SEE ALSO |
848 | |
820 | |
|
|
821 | L<AnyEvent::MP::Intro> - a gentle introduction. |
|
|
822 | |
|
|
823 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
|
|
824 | |
|
|
825 | L<AnyEvent::MP::Global> - network maintainance and port groups, to find |
|
|
826 | your applications. |
|
|
827 | |
849 | L<AnyEvent>. |
828 | L<AnyEvent>. |
850 | |
829 | |
851 | =head1 AUTHOR |
830 | =head1 AUTHOR |
852 | |
831 | |
853 | Marc Lehmann <schmorp@schmorp.de> |
832 | Marc Lehmann <schmorp@schmorp.de> |