1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | AnyEvent::MP - multi-processing/message-passing framework |
3 | AnyEvent::MP - erlang-style multi-processing/message-passing framework |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::MP; |
7 | use AnyEvent::MP; |
8 | |
8 | |
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30 | rcv $port, pong => sub { warn "pong received\n" }; |
30 | rcv $port, pong => sub { warn "pong received\n" }; |
31 | |
31 | |
32 | # create a port on another node |
32 | # create a port on another node |
33 | my $port = spawn $node, $initfunc, @initdata; |
33 | my $port = spawn $node, $initfunc, @initdata; |
34 | |
34 | |
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35 | # destroy a port again |
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36 | kil $port; # "normal" kill |
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37 | kil $port, my_error => "everything is broken"; # error kill |
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38 | |
35 | # monitoring |
39 | # monitoring |
36 | mon $port, $cb->(@msg) # callback is invoked on death |
40 | mon $port, $cb->(@msg) # callback is invoked on death |
37 | mon $port, $otherport # kill otherport on abnormal death |
41 | mon $port, $localport # kill localport on abnormal death |
38 | mon $port, $otherport, @msg # send message on death |
42 | mon $port, $localport, @msg # send message on death |
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43 | |
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44 | # temporarily execute code in port context |
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45 | peval $port, sub { die "kill the port!" }; |
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46 | |
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47 | # execute callbacks in $SELF port context |
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48 | my $timer = AE::timer 1, 0, psub { |
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49 | die "kill the port, delayed"; |
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50 | }; |
39 | |
51 | |
40 | =head1 CURRENT STATUS |
52 | =head1 CURRENT STATUS |
41 | |
53 | |
42 | bin/aemp - stable. |
54 | bin/aemp - stable. |
43 | AnyEvent::MP - stable API, should work. |
55 | AnyEvent::MP - stable API, should work. |
44 | AnyEvent::MP::Intro - explains most concepts. |
56 | AnyEvent::MP::Intro - explains most concepts. |
45 | AnyEvent::MP::Kernel - mostly stable. |
57 | AnyEvent::MP::Kernel - mostly stable API. |
46 | AnyEvent::MP::Global - stable but incomplete, protocol not yet final. |
58 | AnyEvent::MP::Global - stable API. |
47 | |
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48 | stay tuned. |
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49 | |
59 | |
50 | =head1 DESCRIPTION |
60 | =head1 DESCRIPTION |
51 | |
61 | |
52 | This module (-family) implements a simple message passing framework. |
62 | This module (-family) implements a simple message passing framework. |
53 | |
63 | |
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68 | |
78 | |
69 | Ports allow you to register C<rcv> handlers that can match all or just |
79 | Ports allow you to register C<rcv> handlers that can match all or just |
70 | some messages. Messages send to ports will not be queued, regardless of |
80 | some messages. Messages send to ports will not be queued, regardless of |
71 | anything was listening for them or not. |
81 | anything was listening for them or not. |
72 | |
82 | |
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83 | Ports are represented by (printable) strings called "port IDs". |
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84 | |
73 | =item port ID - C<nodeid#portname> |
85 | =item port ID - C<nodeid#portname> |
74 | |
86 | |
75 | A port ID is the concatenation of a node ID, a hash-mark (C<#>) as |
87 | A port ID is the concatenation of a node ID, a hash-mark (C<#>) |
76 | separator, and a port name (a printable string of unspecified format). |
88 | as separator, and a port name (a printable string of unspecified |
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89 | format created by AnyEvent::MP). |
77 | |
90 | |
78 | =item node |
91 | =item node |
79 | |
92 | |
80 | A node is a single process containing at least one port - the node port, |
93 | A node is a single process containing at least one port - the node port, |
81 | which enables nodes to manage each other remotely, and to create new |
94 | which enables nodes to manage each other remotely, and to create new |
82 | ports. |
95 | ports. |
83 | |
96 | |
84 | Nodes are either public (have one or more listening ports) or private |
97 | Nodes are either public (have one or more listening ports) or private |
85 | (no listening ports). Private nodes cannot talk to other private nodes |
98 | (no listening ports). Private nodes cannot talk to other private nodes |
86 | currently. |
99 | currently, but all nodes can talk to public nodes. |
87 | |
100 | |
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101 | Nodes is represented by (printable) strings called "node IDs". |
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102 | |
88 | =item node ID - C<[a-za-Z0-9_\-.:]+> |
103 | =item node ID - C<[A-Za-z0-9_\-.:]*> |
89 | |
104 | |
90 | A node ID is a string that uniquely identifies the node within a |
105 | A node ID is a string that uniquely identifies the node within a |
91 | network. Depending on the configuration used, node IDs can look like a |
106 | network. Depending on the configuration used, node IDs can look like a |
92 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
107 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
93 | doesn't interpret node IDs in any way. |
108 | doesn't interpret node IDs in any way except to uniquely identify a node. |
94 | |
109 | |
95 | =item binds - C<ip:port> |
110 | =item binds - C<ip:port> |
96 | |
111 | |
97 | Nodes can only talk to each other by creating some kind of connection to |
112 | Nodes can only talk to each other by creating some kind of connection to |
98 | each other. To do this, nodes should listen on one or more local transport |
113 | each other. To do this, nodes should listen on one or more local transport |
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114 | endpoints - binds. |
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115 | |
99 | endpoints - binds. Currently, only standard C<ip:port> specifications can |
116 | Currently, only standard C<ip:port> specifications can be used, which |
100 | be used, which specify TCP ports to listen on. |
117 | specify TCP ports to listen on. So a bind is basically just a tcp socket |
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118 | in listening mode thta accepts conenctions form other nodes. |
101 | |
119 | |
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120 | =item seed nodes |
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121 | |
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122 | When a node starts, it knows nothing about the network it is in - it |
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123 | needs to connect to at least one other node that is already in the |
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124 | network. These other nodes are called "seed nodes". |
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125 | |
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126 | Seed nodes themselves are not special - they are seed nodes only because |
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127 | some other node I<uses> them as such, but any node can be used as seed |
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128 | node for other nodes, and eahc node cna use a different set of seed nodes. |
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129 | |
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130 | In addition to discovering the network, seed nodes are also used to |
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131 | maintain the network - all nodes using the same seed node form are part of |
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132 | the same network. If a network is split into multiple subnets because e.g. |
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133 | the network link between the parts goes down, then using the same seed |
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134 | nodes for all nodes ensures that eventually the subnets get merged again. |
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135 | |
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136 | Seed nodes are expected to be long-running, and at least one seed node |
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137 | should always be available. They should also be relatively responsive - a |
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138 | seed node that blocks for long periods will slow down everybody else. |
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139 | |
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140 | For small networks, it's best if every node uses the same set of seed |
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141 | nodes. For large networks, it can be useful to specify "regional" seed |
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142 | nodes for most nodes in an area, and use all seed nodes as seed nodes for |
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143 | each other. What's important is that all seed nodes connections form a |
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144 | complete graph, so that the network cannot split into separate subnets |
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145 | forever. |
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146 | |
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147 | Seed nodes are represented by seed IDs. |
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148 | |
102 | =item seeds - C<host:port> |
149 | =item seed IDs - C<host:port> |
103 | |
150 | |
104 | When a node starts, it knows nothing about the network. To teach the node |
151 | Seed IDs are transport endpoint(s) (usually a hostname/IP address and a |
105 | about the network it first has to contact some other node within the |
152 | TCP port) of nodes that should be used as seed nodes. |
106 | network. This node is called a seed. |
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107 | |
153 | |
108 | Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes |
154 | =item global nodes |
109 | are expected to be long-running, and at least one of those should always |
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110 | be available. When nodes run out of connections (e.g. due to a network |
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111 | error), they try to re-establish connections to some seednodes again to |
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112 | join the network. |
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113 | |
155 | |
114 | Apart from being sued for seeding, seednodes are not special in any way - |
156 | An AEMP network needs a discovery service - nodes need to know how to |
115 | every public node can be a seednode. |
157 | connect to other nodes they only know by name. In addition, AEMP offers a |
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158 | distributed "group database", which maps group names to a list of strings |
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159 | - for example, to register worker ports. |
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160 | |
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161 | A network needs at least one global node to work, and allows every node to |
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162 | be a global node. |
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163 | |
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164 | Any node that loads the L<AnyEvent::MP::Global> module becomes a global |
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165 | node and tries to keep connections to all other nodes. So while it can |
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166 | make sense to make every node "global" in small networks, it usually makes |
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167 | sense to only make seed nodes into global nodes in large networks (nodes |
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168 | keep connections to seed nodes and global nodes, so makign them the same |
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169 | reduces overhead). |
116 | |
170 | |
117 | =back |
171 | =back |
118 | |
172 | |
119 | =head1 VARIABLES/FUNCTIONS |
173 | =head1 VARIABLES/FUNCTIONS |
120 | |
174 | |
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122 | |
176 | |
123 | =cut |
177 | =cut |
124 | |
178 | |
125 | package AnyEvent::MP; |
179 | package AnyEvent::MP; |
126 | |
180 | |
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181 | use AnyEvent::MP::Config (); |
127 | use AnyEvent::MP::Kernel; |
182 | use AnyEvent::MP::Kernel; |
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183 | use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID); |
128 | |
184 | |
129 | use common::sense; |
185 | use common::sense; |
130 | |
186 | |
131 | use Carp (); |
187 | use Carp (); |
132 | |
188 | |
133 | use AE (); |
189 | use AE (); |
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190 | use Guard (); |
134 | |
191 | |
135 | use base "Exporter"; |
192 | use base "Exporter"; |
136 | |
193 | |
137 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
194 | our $VERSION = $AnyEvent::MP::Config::VERSION; |
138 | |
195 | |
139 | our @EXPORT = qw( |
196 | our @EXPORT = qw( |
140 | NODE $NODE *SELF node_of after |
197 | NODE $NODE *SELF node_of after |
141 | configure |
198 | configure |
142 | snd rcv mon mon_guard kil reg psub spawn |
199 | snd rcv mon mon_guard kil psub peval spawn cal |
143 | port |
200 | port |
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201 | db_set db_del db_reg |
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202 | db_mon db_family db_keys db_values |
144 | ); |
203 | ); |
145 | |
204 | |
146 | our $SELF; |
205 | our $SELF; |
147 | |
206 | |
148 | sub _self_die() { |
207 | sub _self_die() { |
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171 | some other nodes in the network to discover other nodes. |
230 | some other nodes in the network to discover other nodes. |
172 | |
231 | |
173 | This function configures a node - it must be called exactly once (or |
232 | This function configures a node - it must be called exactly once (or |
174 | never) before calling other AnyEvent::MP functions. |
233 | never) before calling other AnyEvent::MP functions. |
175 | |
234 | |
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235 | The key/value pairs are basically the same ones as documented for the |
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236 | F<aemp> command line utility (sans the set/del prefix), with these additions: |
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237 | |
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238 | =over 4 |
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239 | |
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240 | =item norc => $boolean (default false) |
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241 | |
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242 | If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not> |
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243 | be consulted - all configuraiton options must be specified in the |
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244 | C<configure> call. |
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245 | |
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246 | =item force => $boolean (default false) |
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247 | |
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248 | IF true, then the values specified in the C<configure> will take |
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249 | precedence over any values configured via the rc file. The default is for |
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250 | the rc file to override any options specified in the program. |
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251 | |
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252 | =item secure => $pass->(@msg) |
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253 | |
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254 | In addition to specifying a boolean, you can specify a code reference that |
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255 | is called for every code execution attempt - the execution request is |
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256 | granted iff the callback returns a true value. |
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257 | |
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258 | Most of the time the callback should look only at |
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259 | C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the |
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260 | actual message (which can be about anything, and is mostly provided for |
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261 | diagnostic purposes). |
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262 | |
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263 | See F<semp setsecure> for more info. |
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264 | |
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265 | =back |
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266 | |
176 | =over 4 |
267 | =over 4 |
177 | |
268 | |
178 | =item step 1, gathering configuration from profiles |
269 | =item step 1, gathering configuration from profiles |
179 | |
270 | |
180 | The function first looks up a profile in the aemp configuration (see the |
271 | The function first looks up a profile in the aemp configuration (see the |
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193 | That means that the values specified in the profile have highest priority |
284 | That means that the values specified in the profile have highest priority |
194 | and the values specified directly via C<configure> have lowest priority, |
285 | and the values specified directly via C<configure> have lowest priority, |
195 | and can only be used to specify defaults. |
286 | and can only be used to specify defaults. |
196 | |
287 | |
197 | If the profile specifies a node ID, then this will become the node ID of |
288 | If the profile specifies a node ID, then this will become the node ID of |
198 | this process. If not, then the profile name will be used as node ID. The |
289 | this process. If not, then the profile name will be used as node ID, with |
199 | special node ID of C<anon/> will be replaced by a random node ID. |
290 | a unique randoms tring (C</%u>) appended. |
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291 | |
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292 | The node ID can contain some C<%> sequences that are expanded: C<%n> |
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293 | is expanded to the local nodename, C<%u> is replaced by a random |
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294 | strign to make the node unique. For example, the F<aemp> commandline |
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295 | utility uses C<aemp/%n/%u> as nodename, which might expand to |
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296 | C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>. |
200 | |
297 | |
201 | =item step 2, bind listener sockets |
298 | =item step 2, bind listener sockets |
202 | |
299 | |
203 | The next step is to look up the binds in the profile, followed by binding |
300 | The next step is to look up the binds in the profile, followed by binding |
204 | aemp protocol listeners on all binds specified (it is possible and valid |
301 | aemp protocol listeners on all binds specified (it is possible and valid |
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210 | used, meaning the node will bind on a dynamically-assigned port on every |
307 | used, meaning the node will bind on a dynamically-assigned port on every |
211 | local IP address it finds. |
308 | local IP address it finds. |
212 | |
309 | |
213 | =item step 3, connect to seed nodes |
310 | =item step 3, connect to seed nodes |
214 | |
311 | |
215 | As the last step, the seeds list from the profile is passed to the |
312 | As the last step, the seed ID list from the profile is passed to the |
216 | L<AnyEvent::MP::Global> module, which will then use it to keep |
313 | L<AnyEvent::MP::Global> module, which will then use it to keep |
217 | connectivity with at least one node at any point in time. |
314 | connectivity with at least one node at any point in time. |
218 | |
315 | |
219 | =back |
316 | =back |
220 | |
317 | |
221 | Example: become a distributed node using the locla node name as profile. |
318 | Example: become a distributed node using the local node name as profile. |
222 | This should be the most common form of invocation for "daemon"-type nodes. |
319 | This should be the most common form of invocation for "daemon"-type nodes. |
223 | |
320 | |
224 | configure |
321 | configure |
225 | |
322 | |
226 | Example: become an anonymous node. This form is often used for commandline |
323 | Example: become a semi-anonymous node. This form is often used for |
227 | clients. |
324 | commandline clients. |
228 | |
325 | |
229 | configure nodeid => "anon/"; |
326 | configure nodeid => "myscript/%n/%u"; |
230 | |
327 | |
231 | Example: configure a node using a profile called seed, which si suitable |
328 | Example: configure a node using a profile called seed, which is suitable |
232 | for a seed node as it binds on all local addresses on a fixed port (4040, |
329 | for a seed node as it binds on all local addresses on a fixed port (4040, |
233 | customary for aemp). |
330 | customary for aemp). |
234 | |
331 | |
235 | # use the aemp commandline utility |
332 | # use the aemp commandline utility |
236 | # aemp profile seed nodeid anon/ binds '*:4040' |
333 | # aemp profile seed binds '*:4040' |
237 | |
334 | |
238 | # then use it |
335 | # then use it |
239 | configure profile => "seed"; |
336 | configure profile => "seed"; |
240 | |
337 | |
241 | # or simply use aemp from the shell again: |
338 | # or simply use aemp from the shell again: |
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306 | |
403 | |
307 | =cut |
404 | =cut |
308 | |
405 | |
309 | sub rcv($@); |
406 | sub rcv($@); |
310 | |
407 | |
311 | sub _kilme { |
408 | my $KILME = sub { |
312 | die "received message on port without callback"; |
409 | (my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g; |
313 | } |
410 | kil $SELF, unhandled_message => "no callback found for message '$tag'"; |
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411 | }; |
314 | |
412 | |
315 | sub port(;&) { |
413 | sub port(;&) { |
316 | my $id = "$UNIQ." . $ID++; |
414 | my $id = $UNIQ . ++$ID; |
317 | my $port = "$NODE#$id"; |
415 | my $port = "$NODE#$id"; |
318 | |
416 | |
319 | rcv $port, shift || \&_kilme; |
417 | rcv $port, shift || $KILME; |
320 | |
418 | |
321 | $port |
419 | $port |
322 | } |
420 | } |
323 | |
421 | |
324 | =item rcv $local_port, $callback->(@msg) |
422 | =item rcv $local_port, $callback->(@msg) |
… | |
… | |
329 | |
427 | |
330 | The global C<$SELF> (exported by this module) contains C<$port> while |
428 | The global C<$SELF> (exported by this module) contains C<$port> while |
331 | executing the callback. Runtime errors during callback execution will |
429 | executing the callback. Runtime errors during callback execution will |
332 | result in the port being C<kil>ed. |
430 | result in the port being C<kil>ed. |
333 | |
431 | |
334 | The default callback received all messages not matched by a more specific |
432 | The default callback receives all messages not matched by a more specific |
335 | C<tag> match. |
433 | C<tag> match. |
336 | |
434 | |
337 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
435 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
338 | |
436 | |
339 | Register (or replace) callbacks to be called on messages starting with the |
437 | Register (or replace) callbacks to be called on messages starting with the |
… | |
… | |
360 | msg1 => sub { ... }, |
458 | msg1 => sub { ... }, |
361 | ... |
459 | ... |
362 | ; |
460 | ; |
363 | |
461 | |
364 | Example: temporarily register a rcv callback for a tag matching some port |
462 | Example: temporarily register a rcv callback for a tag matching some port |
365 | (e.g. for a rpc reply) and unregister it after a message was received. |
463 | (e.g. for an rpc reply) and unregister it after a message was received. |
366 | |
464 | |
367 | rcv $port, $otherport => sub { |
465 | rcv $port, $otherport => sub { |
368 | my @reply = @_; |
466 | my @reply = @_; |
369 | |
467 | |
370 | rcv $SELF, $otherport; |
468 | rcv $SELF, $otherport; |
… | |
… | |
383 | if (ref $_[0]) { |
481 | if (ref $_[0]) { |
384 | if (my $self = $PORT_DATA{$portid}) { |
482 | if (my $self = $PORT_DATA{$portid}) { |
385 | "AnyEvent::MP::Port" eq ref $self |
483 | "AnyEvent::MP::Port" eq ref $self |
386 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
484 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
387 | |
485 | |
388 | $self->[2] = shift; |
486 | $self->[0] = shift; |
389 | } else { |
487 | } else { |
390 | my $cb = shift; |
488 | my $cb = shift; |
391 | $PORT{$portid} = sub { |
489 | $PORT{$portid} = sub { |
392 | local $SELF = $port; |
490 | local $SELF = $port; |
393 | eval { &$cb }; _self_die if $@; |
491 | eval { &$cb }; _self_die if $@; |
394 | }; |
492 | }; |
395 | } |
493 | } |
396 | } elsif (defined $_[0]) { |
494 | } elsif (defined $_[0]) { |
397 | my $self = $PORT_DATA{$portid} ||= do { |
495 | my $self = $PORT_DATA{$portid} ||= do { |
398 | my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
496 | my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
399 | |
497 | |
400 | $PORT{$portid} = sub { |
498 | $PORT{$portid} = sub { |
401 | local $SELF = $port; |
499 | local $SELF = $port; |
402 | |
500 | |
403 | if (my $cb = $self->[1]{$_[0]}) { |
501 | if (my $cb = $self->[1]{$_[0]}) { |
… | |
… | |
425 | } |
523 | } |
426 | |
524 | |
427 | $port |
525 | $port |
428 | } |
526 | } |
429 | |
527 | |
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528 | =item peval $port, $coderef[, @args] |
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529 | |
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530 | Evaluates the given C<$codref> within the contetx of C<$port>, that is, |
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531 | when the code throews an exception the C<$port> will be killed. |
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532 | |
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533 | Any remaining args will be passed to the callback. Any return values will |
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534 | be returned to the caller. |
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535 | |
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536 | This is useful when you temporarily want to execute code in the context of |
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537 | a port. |
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538 | |
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539 | Example: create a port and run some initialisation code in it's context. |
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540 | |
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541 | my $port = port { ... }; |
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542 | |
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543 | peval $port, sub { |
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544 | init |
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545 | or die "unable to init"; |
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546 | }; |
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547 | |
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548 | =cut |
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549 | |
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|
550 | sub peval($$) { |
|
|
551 | local $SELF = shift; |
|
|
552 | my $cb = shift; |
|
|
553 | |
|
|
554 | if (wantarray) { |
|
|
555 | my @res = eval { &$cb }; |
|
|
556 | _self_die if $@; |
|
|
557 | @res |
|
|
558 | } else { |
|
|
559 | my $res = eval { &$cb }; |
|
|
560 | _self_die if $@; |
|
|
561 | $res |
|
|
562 | } |
|
|
563 | } |
|
|
564 | |
430 | =item $closure = psub { BLOCK } |
565 | =item $closure = psub { BLOCK } |
431 | |
566 | |
432 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
567 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
433 | closure is executed, sets up the environment in the same way as in C<rcv> |
568 | closure is executed, sets up the environment in the same way as in C<rcv> |
434 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
569 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
|
|
570 | |
|
|
571 | The effect is basically as if it returned C<< sub { peval $SELF, sub { |
|
|
572 | BLOCK }, @_ } >>. |
435 | |
573 | |
436 | This is useful when you register callbacks from C<rcv> callbacks: |
574 | This is useful when you register callbacks from C<rcv> callbacks: |
437 | |
575 | |
438 | rcv delayed_reply => sub { |
576 | rcv delayed_reply => sub { |
439 | my ($delay, @reply) = @_; |
577 | my ($delay, @reply) = @_; |
… | |
… | |
463 | $res |
601 | $res |
464 | } |
602 | } |
465 | } |
603 | } |
466 | } |
604 | } |
467 | |
605 | |
|
|
606 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
|
|
607 | |
|
|
608 | =item $guard = mon $port # kill $SELF when $port dies |
|
|
609 | |
468 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
610 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
469 | |
|
|
470 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
|
|
471 | |
|
|
472 | =item $guard = mon $port # kill $SELF when $port dies |
|
|
473 | |
611 | |
474 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
612 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
475 | |
613 | |
476 | Monitor the given port and do something when the port is killed or |
614 | Monitor the given port and do something when the port is killed or |
477 | messages to it were lost, and optionally return a guard that can be used |
615 | messages to it were lost, and optionally return a guard that can be used |
478 | to stop monitoring again. |
616 | to stop monitoring again. |
479 | |
617 | |
|
|
618 | The first two forms distinguish between "normal" and "abnormal" kil's: |
|
|
619 | |
|
|
620 | In the first form (another port given), if the C<$port> is C<kil>'ed with |
|
|
621 | a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the |
|
|
622 | same reason. That is, on "normal" kil's nothing happens, while under all |
|
|
623 | other conditions, the other port is killed with the same reason. |
|
|
624 | |
|
|
625 | The second form (kill self) is the same as the first form, except that |
|
|
626 | C<$rvport> defaults to C<$SELF>. |
|
|
627 | |
|
|
628 | The remaining forms don't distinguish between "normal" and "abnormal" kil's |
|
|
629 | - it's up to the callback or receiver to check whether the C<@reason> is |
|
|
630 | empty and act accordingly. |
|
|
631 | |
480 | In the first form (callback), the callback is simply called with any |
632 | In the third form (callback), the callback is simply called with any |
481 | number of C<@reason> elements (no @reason means that the port was deleted |
633 | number of C<@reason> elements (empty @reason means that the port was deleted |
482 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
634 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
483 | C<eval> if unsure. |
635 | C<eval> if unsure. |
484 | |
636 | |
485 | In the second form (another port given), the other port (C<$rcvport>) |
|
|
486 | will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on |
|
|
487 | "normal" kils nothing happens, while under all other conditions, the other |
|
|
488 | port is killed with the same reason. |
|
|
489 | |
|
|
490 | The third form (kill self) is the same as the second form, except that |
|
|
491 | C<$rvport> defaults to C<$SELF>. |
|
|
492 | |
|
|
493 | In the last form (message), a message of the form C<@msg, @reason> will be |
637 | In the last form (message), a message of the form C<$rcvport, @msg, |
494 | C<snd>. |
638 | @reason> will be C<snd>. |
495 | |
639 | |
496 | Monitoring-actions are one-shot: once messages are lost (and a monitoring |
640 | Monitoring-actions are one-shot: once messages are lost (and a monitoring |
497 | alert was raised), they are removed and will not trigger again. |
641 | alert was raised), they are removed and will not trigger again, even if it |
|
|
642 | turns out that the port is still alive. |
498 | |
643 | |
499 | As a rule of thumb, monitoring requests should always monitor a port from |
644 | As a rule of thumb, monitoring requests should always monitor a remote |
500 | a local port (or callback). The reason is that kill messages might get |
645 | port locally (using a local C<$rcvport> or a callback). The reason is that |
501 | lost, just like any other message. Another less obvious reason is that |
646 | kill messages might get lost, just like any other message. Another less |
502 | even monitoring requests can get lost (for example, when the connection |
647 | obvious reason is that even monitoring requests can get lost (for example, |
503 | to the other node goes down permanently). When monitoring a port locally |
648 | when the connection to the other node goes down permanently). When |
504 | these problems do not exist. |
649 | monitoring a port locally these problems do not exist. |
505 | |
650 | |
506 | C<mon> effectively guarantees that, in the absence of hardware failures, |
651 | C<mon> effectively guarantees that, in the absence of hardware failures, |
507 | after starting the monitor, either all messages sent to the port will |
652 | after starting the monitor, either all messages sent to the port will |
508 | arrive, or the monitoring action will be invoked after possible message |
653 | arrive, or the monitoring action will be invoked after possible message |
509 | loss has been detected. No messages will be lost "in between" (after |
654 | loss has been detected. No messages will be lost "in between" (after |
… | |
… | |
512 | delivered again. |
657 | delivered again. |
513 | |
658 | |
514 | Inter-host-connection timeouts and monitoring depend on the transport |
659 | Inter-host-connection timeouts and monitoring depend on the transport |
515 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
660 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
516 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
661 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
517 | non-idle connection, and usually around two hours for idle conenctions). |
662 | non-idle connection, and usually around two hours for idle connections). |
518 | |
663 | |
519 | This means that monitoring is good for program errors and cleaning up |
664 | This means that monitoring is good for program errors and cleaning up |
520 | stuff eventually, but they are no replacement for a timeout when you need |
665 | stuff eventually, but they are no replacement for a timeout when you need |
521 | to ensure some maximum latency. |
666 | to ensure some maximum latency. |
522 | |
667 | |
… | |
… | |
554 | } |
699 | } |
555 | |
700 | |
556 | $node->monitor ($port, $cb); |
701 | $node->monitor ($port, $cb); |
557 | |
702 | |
558 | defined wantarray |
703 | defined wantarray |
559 | and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
704 | and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) }) |
560 | } |
705 | } |
561 | |
706 | |
562 | =item $guard = mon_guard $port, $ref, $ref... |
707 | =item $guard = mon_guard $port, $ref, $ref... |
563 | |
708 | |
564 | Monitors the given C<$port> and keeps the passed references. When the port |
709 | Monitors the given C<$port> and keeps the passed references. When the port |
… | |
… | |
587 | |
732 | |
588 | =item kil $port[, @reason] |
733 | =item kil $port[, @reason] |
589 | |
734 | |
590 | Kill the specified port with the given C<@reason>. |
735 | Kill the specified port with the given C<@reason>. |
591 | |
736 | |
592 | If no C<@reason> is specified, then the port is killed "normally" (ports |
737 | If no C<@reason> is specified, then the port is killed "normally" - |
593 | monitoring other ports will not necessarily die because a port dies |
738 | monitor callback will be invoked, but the kil will not cause linked ports |
594 | "normally"). |
739 | (C<mon $mport, $lport> form) to get killed. |
595 | |
740 | |
596 | Otherwise, linked ports get killed with the same reason (second form of |
741 | If a C<@reason> is specified, then linked ports (C<mon $mport, $lport> |
597 | C<mon>, see above). |
742 | form) get killed with the same reason. |
598 | |
743 | |
599 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
744 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
600 | will be reported as reason C<< die => $@ >>. |
745 | will be reported as reason C<< die => $@ >>. |
601 | |
746 | |
602 | Transport/communication errors are reported as C<< transport_error => |
747 | Transport/communication errors are reported as C<< transport_error => |
603 | $message >>. |
748 | $message >>. |
604 | |
749 | |
605 | =cut |
750 | Common idioms: |
|
|
751 | |
|
|
752 | # silently remove yourself, do not kill linked ports |
|
|
753 | kil $SELF; |
|
|
754 | |
|
|
755 | # report a failure in some detail |
|
|
756 | kil $SELF, failure_mode_1 => "it failed with too high temperature"; |
|
|
757 | |
|
|
758 | # do not waste much time with killing, just die when something goes wrong |
|
|
759 | open my $fh, "<file" |
|
|
760 | or die "file: $!"; |
606 | |
761 | |
607 | =item $port = spawn $node, $initfunc[, @initdata] |
762 | =item $port = spawn $node, $initfunc[, @initdata] |
608 | |
763 | |
609 | Creates a port on the node C<$node> (which can also be a port ID, in which |
764 | Creates a port on the node C<$node> (which can also be a port ID, in which |
610 | case it's the node where that port resides). |
765 | case it's the node where that port resides). |
… | |
… | |
621 | the package, then the package above the package and so on (e.g. |
776 | 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 |
777 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
623 | exists or it runs out of package names. |
778 | exists or it runs out of package names. |
624 | |
779 | |
625 | The init function is then called with the newly-created port as context |
780 | The init function is then called with the newly-created port as context |
626 | object (C<$SELF>) and the C<@initdata> values as arguments. |
781 | object (C<$SELF>) and the C<@initdata> values as arguments. It I<must> |
|
|
782 | call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise |
|
|
783 | the port might not get created. |
627 | |
784 | |
628 | A common idiom is to pass a local port, immediately monitor the spawned |
785 | A common idiom is to pass a local port, immediately monitor the spawned |
629 | port, and in the remote init function, immediately monitor the passed |
786 | port, and in the remote init function, immediately monitor the passed |
630 | local port. This two-way monitoring ensures that both ports get cleaned up |
787 | local port. This two-way monitoring ensures that both ports get cleaned up |
631 | when there is a problem. |
788 | when there is a problem. |
632 | |
789 | |
|
|
790 | C<spawn> guarantees that the C<$initfunc> has no visible effects on the |
|
|
791 | caller before C<spawn> returns (by delaying invocation when spawn is |
|
|
792 | called for the local node). |
|
|
793 | |
633 | Example: spawn a chat server port on C<$othernode>. |
794 | Example: spawn a chat server port on C<$othernode>. |
634 | |
795 | |
635 | # this node, executed from within a port context: |
796 | # this node, executed from within a port context: |
636 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
797 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
637 | mon $server; |
798 | mon $server; |
… | |
… | |
651 | |
812 | |
652 | sub _spawn { |
813 | sub _spawn { |
653 | my $port = shift; |
814 | my $port = shift; |
654 | my $init = shift; |
815 | my $init = shift; |
655 | |
816 | |
|
|
817 | # rcv will create the actual port |
656 | local $SELF = "$NODE#$port"; |
818 | local $SELF = "$NODE#$port"; |
657 | eval { |
819 | eval { |
658 | &{ load_func $init } |
820 | &{ load_func $init } |
659 | }; |
821 | }; |
660 | _self_die if $@; |
822 | _self_die if $@; |
661 | } |
823 | } |
662 | |
824 | |
663 | sub spawn(@) { |
825 | sub spawn(@) { |
664 | my ($nodeid, undef) = split /#/, shift, 2; |
826 | my ($nodeid, undef) = split /#/, shift, 2; |
665 | |
827 | |
666 | my $id = "$RUNIQ." . $ID++; |
828 | my $id = $RUNIQ . ++$ID; |
667 | |
829 | |
668 | $_[0] =~ /::/ |
830 | $_[0] =~ /::/ |
669 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
831 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
670 | |
832 | |
671 | snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; |
833 | snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; |
672 | |
834 | |
673 | "$nodeid#$id" |
835 | "$nodeid#$id" |
674 | } |
836 | } |
|
|
837 | |
675 | |
838 | |
676 | =item after $timeout, @msg |
839 | =item after $timeout, @msg |
677 | |
840 | |
678 | =item after $timeout, $callback |
841 | =item after $timeout, $callback |
679 | |
842 | |
… | |
… | |
695 | ? $action[0]() |
858 | ? $action[0]() |
696 | : snd @action; |
859 | : snd @action; |
697 | }; |
860 | }; |
698 | } |
861 | } |
699 | |
862 | |
|
|
863 | #=item $cb2 = timeout $seconds, $cb[, @args] |
|
|
864 | |
|
|
865 | =item cal $port, @msg, $callback[, $timeout] |
|
|
866 | |
|
|
867 | A simple form of RPC - sends a message to the given C<$port> with the |
|
|
868 | given contents (C<@msg>), but adds a reply port to the message. |
|
|
869 | |
|
|
870 | The reply port is created temporarily just for the purpose of receiving |
|
|
871 | the reply, and will be C<kil>ed when no longer needed. |
|
|
872 | |
|
|
873 | A reply message sent to the port is passed to the C<$callback> as-is. |
|
|
874 | |
|
|
875 | If an optional time-out (in seconds) is given and it is not C<undef>, |
|
|
876 | then the callback will be called without any arguments after the time-out |
|
|
877 | elapsed and the port is C<kil>ed. |
|
|
878 | |
|
|
879 | If no time-out is given (or it is C<undef>), then the local port will |
|
|
880 | monitor the remote port instead, so it eventually gets cleaned-up. |
|
|
881 | |
|
|
882 | Currently this function returns the temporary port, but this "feature" |
|
|
883 | might go in future versions unless you can make a convincing case that |
|
|
884 | this is indeed useful for something. |
|
|
885 | |
|
|
886 | =cut |
|
|
887 | |
|
|
888 | sub cal(@) { |
|
|
889 | my $timeout = ref $_[-1] ? undef : pop; |
|
|
890 | my $cb = pop; |
|
|
891 | |
|
|
892 | my $port = port { |
|
|
893 | undef $timeout; |
|
|
894 | kil $SELF; |
|
|
895 | &$cb; |
|
|
896 | }; |
|
|
897 | |
|
|
898 | if (defined $timeout) { |
|
|
899 | $timeout = AE::timer $timeout, 0, sub { |
|
|
900 | undef $timeout; |
|
|
901 | kil $port; |
|
|
902 | $cb->(); |
|
|
903 | }; |
|
|
904 | } else { |
|
|
905 | mon $_[0], sub { |
|
|
906 | kil $port; |
|
|
907 | $cb->(); |
|
|
908 | }; |
|
|
909 | } |
|
|
910 | |
|
|
911 | push @_, $port; |
|
|
912 | &snd; |
|
|
913 | |
|
|
914 | $port |
|
|
915 | } |
|
|
916 | |
|
|
917 | =back |
|
|
918 | |
|
|
919 | =head1 DISTRIBUTED DATABASE |
|
|
920 | |
|
|
921 | AnyEvent::MP comes with a simple distributed database. The database will |
|
|
922 | be mirrored asynchronously on all global nodes. Other nodes bind to one |
|
|
923 | of the global nodes for their needs. Every node has a "local database" |
|
|
924 | which contains all the values that are set locally. All local databases |
|
|
925 | are merged together to form the global database, which can be queried. |
|
|
926 | |
|
|
927 | The database structure is that of a two-level hash - the database hash |
|
|
928 | contains hashes which contain values, similarly to a perl hash of hashes, |
|
|
929 | i.e.: |
|
|
930 | |
|
|
931 | $DATABASE{$family}{$subkey} = $value |
|
|
932 | |
|
|
933 | The top level hash key is called "family", and the second-level hash key |
|
|
934 | is called "subkey" or simply "key". |
|
|
935 | |
|
|
936 | The family must be alphanumeric, i.e. start with a letter and consist |
|
|
937 | of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>, |
|
|
938 | pretty much like Perl module names. |
|
|
939 | |
|
|
940 | As the family namespace is global, it is recommended to prefix family names |
|
|
941 | with the name of the application or module using it. |
|
|
942 | |
|
|
943 | The subkeys must be non-empty strings, with no further restrictions. |
|
|
944 | |
|
|
945 | The values should preferably be strings, but other perl scalars should |
|
|
946 | work as well (such as C<undef>, arrays and hashes). |
|
|
947 | |
|
|
948 | Every database entry is owned by one node - adding the same family/subkey |
|
|
949 | combination on multiple nodes will not cause discomfort for AnyEvent::MP, |
|
|
950 | but the result might be nondeterministic, i.e. the key might have |
|
|
951 | different values on different nodes. |
|
|
952 | |
|
|
953 | Different subkeys in the same family can be owned by different nodes |
|
|
954 | without problems, and in fact, this is the common method to create worker |
|
|
955 | pools. For example, a worker port for image scaling might do this: |
|
|
956 | |
|
|
957 | db_set my_image_scalers => $port; |
|
|
958 | |
|
|
959 | And clients looking for an image scaler will want to get the |
|
|
960 | C<my_image_scalers> keys from time to time: |
|
|
961 | |
|
|
962 | db_keys my_image_scalers => sub { |
|
|
963 | @ports = @{ $_[0] }; |
|
|
964 | }; |
|
|
965 | |
|
|
966 | Or better yet, they want to monitor the database family, so they always |
|
|
967 | have a reasonable up-to-date copy: |
|
|
968 | |
|
|
969 | db_mon my_image_scalers => sub { |
|
|
970 | @ports = keys %{ $_[0] }; |
|
|
971 | }; |
|
|
972 | |
|
|
973 | In general, you can set or delete single subkeys, but query and monitor |
|
|
974 | whole families only. |
|
|
975 | |
|
|
976 | If you feel the need to monitor or query a single subkey, try giving it |
|
|
977 | it's own family. |
|
|
978 | |
|
|
979 | =over |
|
|
980 | |
|
|
981 | =item $guard = db_set $family => $subkey [=> $value] |
|
|
982 | |
|
|
983 | Sets (or replaces) a key to the database - if C<$value> is omitted, |
|
|
984 | C<undef> is used instead. |
|
|
985 | |
|
|
986 | When called in non-void context, C<db_set> returns a guard that |
|
|
987 | automatically calls C<db_del> when it is destroyed. |
|
|
988 | |
|
|
989 | =item db_del $family => $subkey... |
|
|
990 | |
|
|
991 | Deletes one or more subkeys from the database family. |
|
|
992 | |
|
|
993 | =item $guard = db_reg $family => $port => $value |
|
|
994 | |
|
|
995 | =item $guard = db_reg $family => $port |
|
|
996 | |
|
|
997 | =item $guard = db_reg $family |
|
|
998 | |
|
|
999 | Registers a port in the given family and optionally returns a guard to |
|
|
1000 | remove it. |
|
|
1001 | |
|
|
1002 | This function basically does the same as: |
|
|
1003 | |
|
|
1004 | db_set $family => $port => $value |
|
|
1005 | |
|
|
1006 | Except that the port is monitored and automatically removed from the |
|
|
1007 | database family when it is kil'ed. |
|
|
1008 | |
|
|
1009 | If C<$value> is missing, C<undef> is used. If C<$port> is missing, then |
|
|
1010 | C<$SELF> is used. |
|
|
1011 | |
|
|
1012 | This function is most useful to register a port in some port group (which |
|
|
1013 | is just another name for a database family), and have it removed when the |
|
|
1014 | port is gone. This works best when the port is a local port. |
|
|
1015 | |
|
|
1016 | =cut |
|
|
1017 | |
|
|
1018 | sub db_reg($$;$) { |
|
|
1019 | my $family = shift; |
|
|
1020 | my $port = @_ ? shift : $SELF; |
|
|
1021 | |
|
|
1022 | my $clr = sub { db_del $family => $port }; |
|
|
1023 | mon $port, $clr; |
|
|
1024 | |
|
|
1025 | db_set $family => $port => $_[0]; |
|
|
1026 | |
|
|
1027 | defined wantarray |
|
|
1028 | and &Guard::guard ($clr) |
|
|
1029 | } |
|
|
1030 | |
|
|
1031 | =item db_family $family => $cb->(\%familyhash) |
|
|
1032 | |
|
|
1033 | Queries the named database C<$family> and call the callback with the |
|
|
1034 | family represented as a hash. You can keep and freely modify the hash. |
|
|
1035 | |
|
|
1036 | =item db_keys $family => $cb->(\@keys) |
|
|
1037 | |
|
|
1038 | Same as C<db_family>, except it only queries the family I<subkeys> and passes |
|
|
1039 | them as array reference to the callback. |
|
|
1040 | |
|
|
1041 | =item db_values $family => $cb->(\@values) |
|
|
1042 | |
|
|
1043 | Same as C<db_family>, except it only queries the family I<values> and passes them |
|
|
1044 | as array reference to the callback. |
|
|
1045 | |
|
|
1046 | =item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted) |
|
|
1047 | |
|
|
1048 | Creates a monitor on the given database family. Each time a key is set |
|
|
1049 | or or is deleted the callback is called with a hash containing the |
|
|
1050 | database family and three lists of added, changed and deleted subkeys, |
|
|
1051 | respectively. If no keys have changed then the array reference might be |
|
|
1052 | C<undef> or even missing. |
|
|
1053 | |
|
|
1054 | If not called in void context, a guard object is returned that, when |
|
|
1055 | destroyed, stops the monitor. |
|
|
1056 | |
|
|
1057 | The family hash reference and the key arrays belong to AnyEvent::MP and |
|
|
1058 | B<must not be modified or stored> by the callback. When in doubt, make a |
|
|
1059 | copy. |
|
|
1060 | |
|
|
1061 | As soon as possible after the monitoring starts, the callback will be |
|
|
1062 | called with the intiial contents of the family, even if it is empty, |
|
|
1063 | i.e. there will always be a timely call to the callback with the current |
|
|
1064 | contents. |
|
|
1065 | |
|
|
1066 | It is possible that the callback is called with a change event even though |
|
|
1067 | the subkey is already present and the value has not changed. |
|
|
1068 | |
|
|
1069 | The monitoring stops when the guard object is destroyed. |
|
|
1070 | |
|
|
1071 | Example: on every change to the family "mygroup", print out all keys. |
|
|
1072 | |
|
|
1073 | my $guard = db_mon mygroup => sub { |
|
|
1074 | my ($family, $a, $c, $d) = @_; |
|
|
1075 | print "mygroup members: ", (join " ", keys %$family), "\n"; |
|
|
1076 | }; |
|
|
1077 | |
|
|
1078 | Exmaple: wait until the family "My::Module::workers" is non-empty. |
|
|
1079 | |
|
|
1080 | my $guard; $guard = db_mon My::Module::workers => sub { |
|
|
1081 | my ($family, $a, $c, $d) = @_; |
|
|
1082 | return unless %$family; |
|
|
1083 | undef $guard; |
|
|
1084 | print "My::Module::workers now nonempty\n"; |
|
|
1085 | }; |
|
|
1086 | |
|
|
1087 | Example: print all changes to the family "AnyRvent::Fantasy::Module". |
|
|
1088 | |
|
|
1089 | my $guard = db_mon AnyRvent::Fantasy::Module => sub { |
|
|
1090 | my ($family, $a, $c, $d) = @_; |
|
|
1091 | |
|
|
1092 | print "+$_=$family->{$_}\n" for @$a; |
|
|
1093 | print "*$_=$family->{$_}\n" for @$c; |
|
|
1094 | print "-$_=$family->{$_}\n" for @$d; |
|
|
1095 | }; |
|
|
1096 | |
|
|
1097 | =cut |
|
|
1098 | |
700 | =back |
1099 | =back |
701 | |
1100 | |
702 | =head1 AnyEvent::MP vs. Distributed Erlang |
1101 | =head1 AnyEvent::MP vs. Distributed Erlang |
703 | |
1102 | |
704 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
1103 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
705 | == aemp node, Erlang process == aemp port), so many of the documents and |
1104 | == aemp node, Erlang process == aemp port), so many of the documents and |
706 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
1105 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
707 | sample: |
1106 | sample: |
708 | |
1107 | |
709 | http://www.Erlang.se/doc/programming_rules.shtml |
1108 | http://www.erlang.se/doc/programming_rules.shtml |
710 | http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
1109 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
711 | http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
1110 | http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 |
712 | http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
1111 | http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
713 | |
1112 | |
714 | Despite the similarities, there are also some important differences: |
1113 | Despite the similarities, there are also some important differences: |
715 | |
1114 | |
716 | =over 4 |
1115 | =over 4 |
717 | |
1116 | |
718 | =item * Node IDs are arbitrary strings in AEMP. |
1117 | =item * Node IDs are arbitrary strings in AEMP. |
719 | |
1118 | |
720 | Erlang relies on special naming and DNS to work everywhere in the same |
1119 | Erlang relies on special naming and DNS to work everywhere in the same |
721 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
1120 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
722 | configuration or DNS), but will otherwise discover other odes itself. |
1121 | configuration or DNS), and possibly the addresses of some seed nodes, but |
|
|
1122 | will otherwise discover other nodes (and their IDs) itself. |
723 | |
1123 | |
724 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
1124 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
725 | uses "local ports are like remote ports". |
1125 | uses "local ports are like remote ports". |
726 | |
1126 | |
727 | The failure modes for local ports are quite different (runtime errors |
1127 | The failure modes for local ports are quite different (runtime errors |
… | |
… | |
736 | ports being the special case/exception, where transport errors cannot |
1136 | ports being the special case/exception, where transport errors cannot |
737 | occur. |
1137 | occur. |
738 | |
1138 | |
739 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
1139 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
740 | |
1140 | |
741 | Erlang uses processes that selectively receive messages, and therefore |
1141 | Erlang uses processes that selectively receive messages out of order, and |
742 | needs a queue. AEMP is event based, queuing messages would serve no |
1142 | therefore needs a queue. AEMP is event based, queuing messages would serve |
743 | useful purpose. For the same reason the pattern-matching abilities of |
1143 | no useful purpose. For the same reason the pattern-matching abilities |
744 | AnyEvent::MP are more limited, as there is little need to be able to |
1144 | of AnyEvent::MP are more limited, as there is little need to be able to |
745 | filter messages without dequeuing them. |
1145 | filter messages without dequeuing them. |
746 | |
1146 | |
747 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
1147 | This is not a philosophical difference, but simply stems from AnyEvent::MP |
|
|
1148 | being event-based, while Erlang is process-based. |
|
|
1149 | |
|
|
1150 | You cna have a look at L<Coro::MP> for a more Erlang-like process model on |
|
|
1151 | top of AEMP and Coro threads. |
748 | |
1152 | |
749 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
1153 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
750 | |
1154 | |
751 | Sending messages in Erlang is synchronous and blocks the process (and |
1155 | Sending messages in Erlang is synchronous and blocks the process until |
|
|
1156 | a conenction has been established and the message sent (and so does not |
752 | so does not need a queue that can overflow). AEMP sends are immediate, |
1157 | need a queue that can overflow). AEMP sends return immediately, connection |
753 | connection establishment is handled in the background. |
1158 | establishment is handled in the background. |
754 | |
1159 | |
755 | =item * Erlang suffers from silent message loss, AEMP does not. |
1160 | =item * Erlang suffers from silent message loss, AEMP does not. |
756 | |
1161 | |
757 | Erlang makes few guarantees on messages delivery - messages can get lost |
1162 | Erlang implements few guarantees on messages delivery - messages can get |
758 | without any of the processes realising it (i.e. you send messages a, b, |
1163 | lost without any of the processes realising it (i.e. you send messages a, |
759 | and c, and the other side only receives messages a and c). |
1164 | b, and c, and the other side only receives messages a and c). |
760 | |
1165 | |
761 | AEMP guarantees correct ordering, and the guarantee that after one message |
1166 | AEMP guarantees (modulo hardware errors) correct ordering, and the |
762 | is lost, all following ones sent to the same port are lost as well, until |
1167 | guarantee that after one message is lost, all following ones sent to the |
763 | monitoring raises an error, so there are no silent "holes" in the message |
1168 | same port are lost as well, until monitoring raises an error, so there are |
764 | sequence. |
1169 | no silent "holes" in the message sequence. |
|
|
1170 | |
|
|
1171 | If you want your software to be very reliable, you have to cope with |
|
|
1172 | corrupted and even out-of-order messages in both Erlang and AEMP. AEMP |
|
|
1173 | simply tries to work better in common error cases, such as when a network |
|
|
1174 | link goes down. |
765 | |
1175 | |
766 | =item * Erlang can send messages to the wrong port, AEMP does not. |
1176 | =item * Erlang can send messages to the wrong port, AEMP does not. |
767 | |
1177 | |
768 | In Erlang it is quite likely that a node that restarts reuses a process ID |
1178 | In Erlang it is quite likely that a node that restarts reuses an Erlang |
769 | known to other nodes for a completely different process, causing messages |
1179 | process ID known to other nodes for a completely different process, |
770 | destined for that process to end up in an unrelated process. |
1180 | causing messages destined for that process to end up in an unrelated |
|
|
1181 | process. |
771 | |
1182 | |
772 | AEMP never reuses port IDs, so old messages or old port IDs floating |
1183 | AEMP does not reuse port IDs, so old messages or old port IDs floating |
773 | around in the network will not be sent to an unrelated port. |
1184 | around in the network will not be sent to an unrelated port. |
774 | |
1185 | |
775 | =item * Erlang uses unprotected connections, AEMP uses secure |
1186 | =item * Erlang uses unprotected connections, AEMP uses secure |
776 | authentication and can use TLS. |
1187 | authentication and can use TLS. |
777 | |
1188 | |
… | |
… | |
780 | |
1191 | |
781 | =item * The AEMP protocol is optimised for both text-based and binary |
1192 | =item * The AEMP protocol is optimised for both text-based and binary |
782 | communications. |
1193 | communications. |
783 | |
1194 | |
784 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
1195 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
785 | language independent text-only protocols (good for debugging) and binary, |
1196 | language independent text-only protocols (good for debugging), and binary, |
786 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
1197 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
787 | used, the protocol is actually completely text-based. |
1198 | used, the protocol is actually completely text-based. |
788 | |
1199 | |
789 | It has also been carefully designed to be implementable in other languages |
1200 | It has also been carefully designed to be implementable in other languages |
790 | with a minimum of work while gracefully degrading functionality to make the |
1201 | with a minimum of work while gracefully degrading functionality to make the |
791 | protocol simple. |
1202 | protocol simple. |
792 | |
1203 | |
793 | =item * AEMP has more flexible monitoring options than Erlang. |
1204 | =item * AEMP has more flexible monitoring options than Erlang. |
794 | |
1205 | |
795 | In Erlang, you can chose to receive I<all> exit signals as messages |
1206 | In Erlang, you can chose to receive I<all> exit signals as messages or |
796 | or I<none>, there is no in-between, so monitoring single processes is |
1207 | I<none>, there is no in-between, so monitoring single Erlang processes is |
797 | difficult to implement. Monitoring in AEMP is more flexible than in |
1208 | difficult to implement. |
798 | Erlang, as one can choose between automatic kill, exit message or callback |
1209 | |
799 | on a per-process basis. |
1210 | Monitoring in AEMP is more flexible than in Erlang, as one can choose |
|
|
1211 | between automatic kill, exit message or callback on a per-port basis. |
800 | |
1212 | |
801 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
1213 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
802 | |
1214 | |
803 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
1215 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
804 | same way as linking is (except linking is unreliable in Erlang). |
1216 | same way as linking is (except linking is unreliable in Erlang). |
… | |
… | |
826 | overhead, as well as having to keep a proxy object everywhere. |
1238 | overhead, as well as having to keep a proxy object everywhere. |
827 | |
1239 | |
828 | Strings can easily be printed, easily serialised etc. and need no special |
1240 | Strings can easily be printed, easily serialised etc. and need no special |
829 | procedures to be "valid". |
1241 | procedures to be "valid". |
830 | |
1242 | |
831 | And as a result, a miniport consists of a single closure stored in a |
1243 | And as a result, a port with just a default receiver consists of a single |
832 | global hash - it can't become much cheaper. |
1244 | code reference stored in a global hash - it can't become much cheaper. |
833 | |
1245 | |
834 | =item Why favour JSON, why not a real serialising format such as Storable? |
1246 | =item Why favour JSON, why not a real serialising format such as Storable? |
835 | |
1247 | |
836 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
1248 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
837 | format, but currently there is no way to make a node use Storable by |
1249 | format, but currently there is no way to make a node use Storable by |
… | |
… | |
847 | Keeping your messages simple, concentrating on data structures rather than |
1259 | Keeping your messages simple, concentrating on data structures rather than |
848 | objects, will keep your messages clean, tidy and efficient. |
1260 | objects, will keep your messages clean, tidy and efficient. |
849 | |
1261 | |
850 | =back |
1262 | =back |
851 | |
1263 | |
|
|
1264 | =head1 PORTING FROM AnyEvent::MP VERSION 1.X |
|
|
1265 | |
|
|
1266 | AEMP version 2 has a few major incompatible changes compared to version 1: |
|
|
1267 | |
|
|
1268 | =over 4 |
|
|
1269 | |
|
|
1270 | =item AnyEvent::MP::Global no longer has group management functions. |
|
|
1271 | |
|
|
1272 | AnyEvent::MP now comes with a distributed database that is more |
|
|
1273 | powerful. Its database families map closely to port groups, but the API |
|
|
1274 | has changed (the functions are also now exported by AnyEvent::MP). Here is |
|
|
1275 | a rough porting guide: |
|
|
1276 | |
|
|
1277 | grp_reg $group, $port # old |
|
|
1278 | db_reg $group, $port # new |
|
|
1279 | |
|
|
1280 | $list = grp_get $group # old |
|
|
1281 | db_keys $group, sub { my $list = shift } # new |
|
|
1282 | |
|
|
1283 | grp_mon $group, $cb->(\@ports, $add, $del) # old |
|
|
1284 | db_mon $group, $cb->(\%ports, $add, $change, $del) # new |
|
|
1285 | |
|
|
1286 | C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is |
|
|
1287 | no longer instant, because the local node might not have a copy of the |
|
|
1288 | group. You can either modify your code to allow for a callback, or use |
|
|
1289 | C<db_mon> to keep an updated copy of the group: |
|
|
1290 | |
|
|
1291 | my $local_group_copy; |
|
|
1292 | db_mon $group => sub { $local_group_copy = $_[0] }; |
|
|
1293 | |
|
|
1294 | # now "keys %$local_group_copy" always returns the most up-to-date |
|
|
1295 | # list of ports in the group. |
|
|
1296 | |
|
|
1297 | C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon> |
|
|
1298 | passes a hash as first argument, and an extra C<$chg> argument that can be |
|
|
1299 | ignored: |
|
|
1300 | |
|
|
1301 | db_mon $group => sub { |
|
|
1302 | my ($ports, $add, $chg, $lde) = @_; |
|
|
1303 | $ports = [keys %$ports]; |
|
|
1304 | |
|
|
1305 | # now $ports, $add and $del are the same as |
|
|
1306 | # were originally passed by grp_mon. |
|
|
1307 | ... |
|
|
1308 | }; |
|
|
1309 | |
|
|
1310 | =item Nodes not longer connect to all other nodes. |
|
|
1311 | |
|
|
1312 | In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global> |
|
|
1313 | module, which in turn would create connections to all other nodes in the |
|
|
1314 | network (helped by the seed nodes). |
|
|
1315 | |
|
|
1316 | In version 2.x, global nodes still connect to all other global nodes, but |
|
|
1317 | other nodes don't - now every node either is a global node itself, or |
|
|
1318 | attaches itself to another global node. |
|
|
1319 | |
|
|
1320 | If a node isn't a global node itself, then it attaches itself to one |
|
|
1321 | of its seed nodes. If that seed node isn't a global node yet, it will |
|
|
1322 | automatically be upgraded to a global node. |
|
|
1323 | |
|
|
1324 | So in many cases, nothing needs to be changed - one just has to make sure |
|
|
1325 | that all seed nodes are meshed together with the other seed nodes (as with |
|
|
1326 | AEMP 1.x), and other nodes specify them as seed nodes. This is most easily |
|
|
1327 | achieved by specifying the same set of seed nodes for all nodes in the |
|
|
1328 | network. |
|
|
1329 | |
|
|
1330 | Not opening a connection to every other node is usually an advantage, |
|
|
1331 | except when you need the lower latency of an already established |
|
|
1332 | connection. To ensure a node establishes a connection to another node, |
|
|
1333 | you can monitor the node port (C<mon $node, ...>), which will attempt to |
|
|
1334 | create the connection (and notify you when the connection fails). |
|
|
1335 | |
|
|
1336 | =item Listener-less nodes (nodes without binds) are gone. |
|
|
1337 | |
|
|
1338 | And are not coming back, at least not in their old form. If no C<binds> |
|
|
1339 | are specified for a node, AnyEvent::MP assumes a default of C<*:*>. |
|
|
1340 | |
|
|
1341 | There are vague plans to implement some form of routing domains, which |
|
|
1342 | might or might not bring back listener-less nodes, but don't count on it. |
|
|
1343 | |
|
|
1344 | The fact that most connections are now optional somewhat mitigates this, |
|
|
1345 | as a node can be effectively unreachable from the outside without any |
|
|
1346 | problems, as long as it isn't a global node and only reaches out to other |
|
|
1347 | nodes (as opposed to being contacted from other nodes). |
|
|
1348 | |
|
|
1349 | =item $AnyEvent::MP::Kernel::WARN has gone. |
|
|
1350 | |
|
|
1351 | AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now |
|
|
1352 | uses this, and so should your programs. |
|
|
1353 | |
|
|
1354 | Every module now documents what kinds of messages it generates, with |
|
|
1355 | AnyEvent::MP acting as a catch all. |
|
|
1356 | |
|
|
1357 | On the positive side, this means that instead of setting |
|
|
1358 | C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> - |
|
|
1359 | much less to type. |
|
|
1360 | |
|
|
1361 | =back |
|
|
1362 | |
|
|
1363 | =head1 LOGGING |
|
|
1364 | |
|
|
1365 | AnyEvent::MP does not normally log anything by itself, but sinc eit is the |
|
|
1366 | root of the contetx hierarchy for AnyEvent::MP modules, it will receive |
|
|
1367 | all log messages by submodules. |
|
|
1368 | |
852 | =head1 SEE ALSO |
1369 | =head1 SEE ALSO |
853 | |
1370 | |
854 | L<AnyEvent::MP::Intro> - a gentle introduction. |
1371 | L<AnyEvent::MP::Intro> - a gentle introduction. |
855 | |
1372 | |
856 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
1373 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
857 | |
1374 | |
858 | L<AnyEvent::MP::Global> - network maintainance and port groups, to find |
1375 | L<AnyEvent::MP::Global> - network maintenance and port groups, to find |
859 | your applications. |
1376 | your applications. |
|
|
1377 | |
|
|
1378 | L<AnyEvent::MP::DataConn> - establish data connections between nodes. |
|
|
1379 | |
|
|
1380 | L<AnyEvent::MP::LogCatcher> - simple service to display log messages from |
|
|
1381 | all nodes. |
860 | |
1382 | |
861 | L<AnyEvent>. |
1383 | L<AnyEvent>. |
862 | |
1384 | |
863 | =head1 AUTHOR |
1385 | =head1 AUTHOR |
864 | |
1386 | |