… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::MP; |
7 | use AnyEvent::MP; |
8 | |
8 | |
9 | NODE # returns this node identifier |
|
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10 | $NODE # contains this node identifier |
9 | $NODE # contains this node's noderef |
|
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10 | NODE # returns this node's noderef |
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11 | NODE $port # returns the noderef of the port |
11 | |
12 | |
12 | snd $port, type => data...; |
13 | snd $port, type => data...; |
|
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14 | |
|
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15 | $SELF # receiving/own port id in rcv callbacks |
13 | |
16 | |
14 | rcv $port, smartmatch => $cb->($port, @msg); |
17 | rcv $port, smartmatch => $cb->($port, @msg); |
15 | |
18 | |
16 | # examples: |
19 | # examples: |
17 | rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; |
20 | rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; |
… | |
… | |
27 | This module (-family) implements a simple message passing framework. |
30 | This module (-family) implements a simple message passing framework. |
28 | |
31 | |
29 | Despite its simplicity, you can securely message other processes running |
32 | Despite its simplicity, you can securely message other processes running |
30 | on the same or other hosts. |
33 | on the same or other hosts. |
31 | |
34 | |
|
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35 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
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36 | manual page. |
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37 | |
32 | At the moment, this module family is severly brokena nd underdocumented, |
38 | At the moment, this module family is severly broken and underdocumented, |
33 | so do not use. This was uploaded mainly to resreve the CPAN namespace - |
39 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
34 | stay tuned! |
40 | stay tuned! The basic API should be finished, however. |
35 | |
41 | |
36 | =head1 CONCEPTS |
42 | =head1 CONCEPTS |
37 | |
43 | |
38 | =over 4 |
44 | =over 4 |
39 | |
45 | |
… | |
… | |
82 | |
88 | |
83 | use AE (); |
89 | use AE (); |
84 | |
90 | |
85 | use base "Exporter"; |
91 | use base "Exporter"; |
86 | |
92 | |
87 | our $VERSION = '0.02'; |
93 | our $VERSION = '0.1'; |
88 | our @EXPORT = qw( |
94 | our @EXPORT = qw( |
89 | NODE $NODE $PORT snd rcv mon del _any_ |
95 | NODE $NODE *SELF node_of _any_ |
90 | create_port create_port_on |
|
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91 | create_miniport |
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92 | become_slave become_public |
96 | become_slave become_public |
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97 | snd rcv mon kil reg psub |
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98 | port |
93 | ); |
99 | ); |
94 | |
100 | |
|
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101 | our $SELF; |
|
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102 | |
|
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103 | sub _self_die() { |
|
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104 | my $msg = $@; |
|
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105 | $msg =~ s/\n+$// unless ref $msg; |
|
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106 | kil $SELF, die => $msg; |
|
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107 | } |
|
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108 | |
95 | =item NODE / $NODE |
109 | =item $thisnode = NODE / $NODE |
96 | |
110 | |
97 | The C<NODE ()> function and the C<$NODE> variable contain the noderef of |
111 | The C<NODE> function returns, and the C<$NODE> variable contains |
98 | the local node. The value is initialised by a call to C<become_public> or |
112 | the noderef of the local node. The value is initialised by a call |
99 | C<become_slave>, after which all local port identifiers become invalid. |
113 | to C<become_public> or C<become_slave>, after which all local port |
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114 | identifiers become invalid. |
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115 | |
|
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116 | =item $noderef = node_of $portid |
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117 | |
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118 | Extracts and returns the noderef from a portid or a noderef. |
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119 | |
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120 | =item $SELF |
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121 | |
|
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122 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
|
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123 | blocks. |
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124 | |
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125 | =item SELF, %SELF, @SELF... |
|
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126 | |
|
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127 | Due to some quirks in how perl exports variables, it is impossible to |
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128 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
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129 | module, but only C<$SELF> is currently used. |
100 | |
130 | |
101 | =item snd $portid, type => @data |
131 | =item snd $portid, type => @data |
102 | |
132 | |
103 | =item snd $portid, @msg |
133 | =item snd $portid, @msg |
104 | |
134 | |
… | |
… | |
118 | JSON is used, then only strings, numbers and arrays and hashes consisting |
148 | JSON is used, then only strings, numbers and arrays and hashes consisting |
119 | of those are allowed (no objects). When Storable is used, then anything |
149 | of those are allowed (no objects). When Storable is used, then anything |
120 | that Storable can serialise and deserialise is allowed, and for the local |
150 | that Storable can serialise and deserialise is allowed, and for the local |
121 | node, anything can be passed. |
151 | node, anything can be passed. |
122 | |
152 | |
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153 | =item kil $portid[, @reason] |
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154 | |
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155 | Kill the specified port with the given C<@reason>. |
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156 | |
|
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157 | If no C<@reason> is specified, then the port is killed "normally" (linked |
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158 | ports will not be kileld, or even notified). |
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159 | |
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160 | Otherwise, linked ports get killed with the same reason (second form of |
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161 | C<mon>, see below). |
|
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162 | |
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163 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
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164 | will be reported as reason C<< die => $@ >>. |
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165 | |
|
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166 | Transport/communication errors are reported as C<< transport_error => |
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167 | $message >>. |
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168 | |
123 | =item $guard = mon $portid, $cb->() |
169 | =item $guard = mon $portid, $cb->(@reason) |
124 | |
170 | |
125 | Monitor the given port and call the given callback when the port is |
171 | =item $guard = mon $portid, $otherport |
126 | destroyed or connection to it's node is lost. |
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127 | |
172 | |
128 | #TODO |
173 | =item $guard = mon $portid, $otherport, @msg |
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174 | |
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175 | Monitor the given port and do something when the port is killed. |
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176 | |
|
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177 | In the first form, the callback is simply called with any number |
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178 | of C<@reason> elements (no @reason means that the port was deleted |
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179 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
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180 | C<eval> if unsure. |
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181 | |
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182 | In the second form, the other port will be C<kil>'ed with C<@reason>, iff |
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183 | a @reason was specified, i.e. on "normal" kils nothing happens, while |
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184 | under all other conditions, the other port is killed with the same reason. |
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185 | |
|
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186 | In the last form, a message of the form C<@msg, @reason> will be C<snd>. |
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187 | |
|
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188 | Example: call a given callback when C<$port> is killed. |
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189 | |
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190 | mon $port, sub { warn "port died because of <@_>\n" }; |
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191 | |
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192 | Example: kill ourselves when C<$port> is killed abnormally. |
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193 | |
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194 | mon $port, $self; |
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195 | |
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196 | Example: send us a restart message another C<$port> is killed. |
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197 | |
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198 | mon $port, $self => "restart"; |
129 | |
199 | |
130 | =cut |
200 | =cut |
131 | |
201 | |
132 | sub mon { |
202 | sub mon { |
133 | my ($noderef, $port) = split /#/, shift, 2; |
203 | my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift); |
134 | |
204 | |
135 | my $node = AnyEvent::MP::Base::add_node $noderef; |
205 | my $node = $NODE{$noderef} || add_node $noderef; |
136 | |
206 | |
137 | my $cb = shift; |
207 | #TODO: ports must not be references |
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208 | if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) { |
|
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209 | if (@_) { |
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210 | # send a kill info message |
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211 | my (@msg) = ($cb, @_); |
|
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212 | $cb = sub { snd @msg, @_ }; |
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213 | } else { |
|
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214 | # simply kill other port |
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215 | my $port = $cb; |
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216 | $cb = sub { kil $port, @_ if @_ }; |
|
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217 | } |
|
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218 | } |
138 | |
219 | |
139 | $node->monitor ($port, $cb); |
220 | $node->monitor ($port, $cb); |
140 | |
221 | |
141 | defined wantarray |
222 | defined wantarray |
142 | and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
223 | and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
143 | } |
224 | } |
144 | |
225 | |
145 | =item $local_port = create_port |
226 | =item $guard = mon_guard $port, $ref, $ref... |
146 | |
227 | |
147 | Create a new local port object. See the next section for allowed methods. |
228 | Monitors the given C<$port> and keeps the passed references. When the port |
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229 | is killed, the references will be freed. |
148 | |
230 | |
149 | =cut |
231 | Optionally returns a guard that will stop the monitoring. |
150 | |
232 | |
151 | sub create_port { |
233 | This function is useful when you create e.g. timers or other watchers and |
152 | my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++; |
234 | want to free them when the port gets killed: |
153 | |
235 | |
154 | my $self = bless { |
236 | $port->rcv (start => sub { |
155 | id => "$NODE#$id", |
237 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
156 | names => [$id], |
238 | undef $timer if 0.9 < rand; |
157 | }, "AnyEvent::MP::Port"; |
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158 | |
|
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159 | $AnyEvent::MP::Base::PORT{$id} = sub { |
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160 | unshift @_, $self; |
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161 | |
|
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162 | for (@{ $self->{rc0}{$_[1]} }) { |
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163 | $_ && &{$_->[0]} |
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164 | && undef $_; |
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165 | } |
239 | }); |
166 | |
|
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167 | for (@{ $self->{rcv}{$_[1]} }) { |
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168 | $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
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169 | && &{$_->[0]} |
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170 | && undef $_; |
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171 | } |
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172 | |
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173 | for (@{ $self->{any} }) { |
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174 | $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
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175 | && &{$_->[0]} |
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176 | && undef $_; |
|
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177 | } |
|
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178 | }; |
240 | }); |
179 | |
241 | |
180 | $self |
242 | =cut |
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243 | |
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244 | sub mon_guard { |
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245 | my ($port, @refs) = @_; |
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246 | |
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247 | mon $port, sub { 0 && @refs } |
181 | } |
248 | } |
182 | |
249 | |
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250 | =item lnk $port1, $port2 |
|
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251 | |
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252 | Link two ports. This is simply a shorthand for: |
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253 | |
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254 | mon $port1, $port2; |
|
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255 | mon $port2, $port1; |
|
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256 | |
|
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257 | It means that if either one is killed abnormally, the other one gets |
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258 | killed as well. |
|
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259 | |
|
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260 | =item $local_port = port |
|
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261 | |
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262 | Create a new local port object that supports message matching. |
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263 | |
183 | =item $portid = miniport { my @msg = @_; $finished } |
264 | =item $portid = port { my @msg = @_; $finished } |
184 | |
265 | |
185 | Creates a "mini port", that is, a very lightweight port without any |
266 | Creates a "mini port", that is, a very lightweight port without any |
186 | pattern matching behind it, and returns its ID. |
267 | pattern matching behind it, and returns its ID. |
187 | |
268 | |
188 | The block will be called for every message received on the port. When the |
269 | The block will be called for every message received on the port. When the |
… | |
… | |
198 | snd $otherport, reply => $port; |
279 | snd $otherport, reply => $port; |
199 | }; |
280 | }; |
200 | |
281 | |
201 | =cut |
282 | =cut |
202 | |
283 | |
203 | sub miniport(&) { |
284 | sub port(;&) { |
|
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285 | my $id = "$UNIQ." . $ID++; |
|
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286 | my $port = "$NODE#$id"; |
|
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287 | |
|
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288 | if (@_) { |
204 | my $cb = shift; |
289 | my $cb = shift; |
205 | my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++; |
290 | $PORT{$id} = sub { |
206 | |
291 | local $SELF = $port; |
207 | $AnyEvent::MP::Base::PORT{$id} = sub { |
292 | eval { |
208 | &$cb |
293 | &$cb |
209 | and del $id; |
294 | and kil $id; |
|
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295 | }; |
|
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296 | _self_die if $@; |
|
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297 | }; |
|
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298 | } else { |
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299 | my $self = bless { |
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300 | id => "$NODE#$id", |
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301 | }, "AnyEvent::MP::Port"; |
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302 | |
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303 | $PORT_DATA{$id} = $self; |
|
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304 | $PORT{$id} = sub { |
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305 | local $SELF = $port; |
|
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306 | |
|
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307 | eval { |
|
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308 | for (@{ $self->{rc0}{$_[0]} }) { |
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309 | $_ && &{$_->[0]} |
|
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310 | && undef $_; |
|
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311 | } |
|
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312 | |
|
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313 | for (@{ $self->{rcv}{$_[0]} }) { |
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314 | $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
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315 | && &{$_->[0]} |
|
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316 | && undef $_; |
|
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317 | } |
|
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318 | |
|
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319 | for (@{ $self->{any} }) { |
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320 | $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
|
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321 | && &{$_->[0]} |
|
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322 | && undef $_; |
|
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323 | } |
|
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324 | }; |
|
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325 | _self_die if $@; |
|
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326 | }; |
210 | }; |
327 | } |
211 | |
328 | |
212 | "$NODE#$id" |
329 | $port |
213 | } |
330 | } |
214 | |
331 | |
215 | package AnyEvent::MP::Port; |
332 | =item reg $portid, $name |
216 | |
333 | |
217 | =back |
334 | Registers the given port under the name C<$name>. If the name already |
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335 | exists it is replaced. |
218 | |
336 | |
219 | =head1 METHODS FOR PORT OBJECTS |
337 | A port can only be registered under one well known name. |
220 | |
338 | |
221 | =over 4 |
339 | A port automatically becomes unregistered when it is killed. |
222 | |
340 | |
223 | =item "$port" |
|
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224 | |
|
|
225 | A port object stringifies to its port ID, so can be used directly for |
|
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226 | C<snd> operations. |
|
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227 | |
|
|
228 | =cut |
341 | =cut |
229 | |
342 | |
230 | use overload |
343 | sub reg(@) { |
231 | '""' => sub { $_[0]{id} }, |
344 | my ($portid, $name) = @_; |
232 | fallback => 1; |
|
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233 | |
345 | |
234 | sub TO_JSON { $_[0]{id} } |
346 | $REG{$name} = $portid; |
|
|
347 | } |
235 | |
348 | |
236 | =item $port->rcv (type => $callback->($port, @msg)) |
349 | =item rcv $portid, tagstring => $callback->(@msg), ... |
237 | |
350 | |
238 | =item $port->rcv ($smartmatch => $callback->($port, @msg)) |
351 | =item rcv $portid, $smartmatch => $callback->(@msg), ... |
239 | |
352 | |
240 | =item $port->rcv ([$smartmatch...] => $callback->($port, @msg)) |
353 | =item rcv $portid, [$smartmatch...] => $callback->(@msg), ... |
241 | |
354 | |
242 | Register a callback on the given port. |
355 | Register callbacks to be called on matching messages on the given port. |
243 | |
356 | |
244 | The callback has to return a true value when its work is done, after |
357 | The callback has to return a true value when its work is done, after |
245 | which is will be removed, or a false value in which case it will stay |
358 | which is will be removed, or a false value in which case it will stay |
246 | registered. |
359 | registered. |
247 | |
360 | |
|
|
361 | The global C<$SELF> (exported by this module) contains C<$portid> while |
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362 | executing the callback. |
|
|
363 | |
|
|
364 | Runtime errors wdurign callback execution will result in the port being |
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365 | C<kil>ed. |
|
|
366 | |
248 | If the match is an array reference, then it will be matched against the |
367 | If the match is an array reference, then it will be matched against the |
249 | first elements of the message, otherwise only the first element is being |
368 | first elements of the message, otherwise only the first element is being |
250 | matched. |
369 | matched. |
251 | |
370 | |
252 | Any element in the match that is specified as C<_any_> (a function |
371 | Any element in the match that is specified as C<_any_> (a function |
… | |
… | |
257 | also the most efficient match (by far). |
376 | also the most efficient match (by far). |
258 | |
377 | |
259 | =cut |
378 | =cut |
260 | |
379 | |
261 | sub rcv($@) { |
380 | sub rcv($@) { |
262 | my ($self, $match, $cb) = @_; |
381 | my ($noderef, $port) = split /#/, shift, 2; |
263 | |
382 | |
|
|
383 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
|
|
384 | or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught"; |
|
|
385 | |
|
|
386 | my $self = $PORT_DATA{$port} |
|
|
387 | or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; |
|
|
388 | |
|
|
389 | "AnyEvent::MP::Port" eq ref $self |
|
|
390 | or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; |
|
|
391 | |
|
|
392 | while (@_) { |
|
|
393 | my ($match, $cb) = splice @_, 0, 2; |
|
|
394 | |
264 | if (!ref $match) { |
395 | if (!ref $match) { |
265 | push @{ $self->{rc0}{$match} }, [$cb]; |
396 | push @{ $self->{rc0}{$match} }, [$cb]; |
266 | } elsif (("ARRAY" eq ref $match && !ref $match->[0])) { |
397 | } elsif (("ARRAY" eq ref $match && !ref $match->[0])) { |
267 | my ($type, @match) = @$match; |
398 | my ($type, @match) = @$match; |
268 | @match |
399 | @match |
269 | ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] |
400 | ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] |
270 | : push @{ $self->{rc0}{$match->[0]} }, [$cb]; |
401 | : push @{ $self->{rc0}{$match->[0]} }, [$cb]; |
271 | } else { |
402 | } else { |
272 | push @{ $self->{any} }, [$cb, $match]; |
403 | push @{ $self->{any} }, [$cb, $match]; |
|
|
404 | } |
273 | } |
405 | } |
274 | } |
406 | } |
275 | |
407 | |
276 | =item $port->register ($name) |
408 | =item $closure = psub { BLOCK } |
277 | |
409 | |
278 | Registers the given port under the well known name C<$name>. If the name |
410 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
279 | already exists it is replaced. |
411 | closure is executed, sets up the environment in the same way as in C<rcv> |
|
|
412 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
280 | |
413 | |
281 | A port can only be registered under one well known name. |
414 | This is useful when you register callbacks from C<rcv> callbacks: |
282 | |
415 | |
283 | =cut |
416 | rcv delayed_reply => sub { |
|
|
417 | my ($delay, @reply) = @_; |
|
|
418 | my $timer = AE::timer $delay, 0, psub { |
|
|
419 | snd @reply, $SELF; |
|
|
420 | }; |
|
|
421 | }; |
284 | |
422 | |
285 | sub register { |
423 | =cut |
286 | my ($self, $name) = @_; |
|
|
287 | |
424 | |
288 | $self->{wkname} = $name; |
425 | sub psub(&) { |
289 | $AnyEvent::MP::Base::WKP{$name} = "$self"; |
426 | my $cb = shift; |
|
|
427 | |
|
|
428 | my $port = $SELF |
|
|
429 | or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
|
|
430 | |
|
|
431 | sub { |
|
|
432 | local $SELF = $port; |
|
|
433 | |
|
|
434 | if (wantarray) { |
|
|
435 | my @res = eval { &$cb }; |
|
|
436 | _self_die if $@; |
|
|
437 | @res |
|
|
438 | } else { |
|
|
439 | my $res = eval { &$cb }; |
|
|
440 | _self_die if $@; |
|
|
441 | $res |
|
|
442 | } |
|
|
443 | } |
290 | } |
444 | } |
291 | |
445 | |
292 | =item $port->destroy |
|
|
293 | |
|
|
294 | Explicitly destroy/remove/nuke/vaporise the port. |
|
|
295 | |
|
|
296 | Ports are normally kept alive by there mere existance alone, and need to |
|
|
297 | be destroyed explicitly. |
|
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298 | |
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299 | =cut |
|
|
300 | |
|
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301 | sub destroy { |
|
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302 | my ($self) = @_; |
|
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303 | |
|
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304 | AnyEvent::MP::Base::del $self->{id}; |
|
|
305 | |
|
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306 | delete $AnyEvent::MP::Base::WKP{ $self->{wkname} }; |
|
|
307 | |
|
|
308 | delete $AnyEvent::MP::Base::PORT{$_} |
|
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309 | for @{ $self->{names} }; |
|
|
310 | } |
|
|
311 | |
|
|
312 | =back |
446 | =back |
313 | |
447 | |
314 | =head1 FUNCTIONS FOR NODES |
448 | =head1 FUNCTIONS FOR NODES |
315 | |
449 | |
316 | =over 4 |
450 | =over 4 |
317 | |
|
|
318 | =item mon $noderef, $callback->($noderef, $status, $) |
|
|
319 | |
|
|
320 | Monitors the given noderef. |
|
|
321 | |
451 | |
322 | =item become_public endpoint... |
452 | =item become_public endpoint... |
323 | |
453 | |
324 | Tells the node to become a public node, i.e. reachable from other nodes. |
454 | Tells the node to become a public node, i.e. reachable from other nodes. |
325 | |
455 | |
… | |
… | |
345 | |
475 | |
346 | =over 4 |
476 | =over 4 |
347 | |
477 | |
348 | =cut |
478 | =cut |
349 | |
479 | |
350 | =item wkp => $name, @reply |
480 | =item lookup => $name, @reply |
351 | |
481 | |
352 | Replies with the port ID of the specified well-known port, or C<undef>. |
482 | Replies with the port ID of the specified well-known port, or C<undef>. |
353 | |
483 | |
354 | =item devnull => ... |
484 | =item devnull => ... |
355 | |
485 | |
… | |
… | |
378 | snd $NODE, time => $myport, timereply => 1, 2; |
508 | snd $NODE, time => $myport, timereply => 1, 2; |
379 | # => snd $myport, timereply => 1, 2, <time> |
509 | # => snd $myport, timereply => 1, 2, <time> |
380 | |
510 | |
381 | =back |
511 | =back |
382 | |
512 | |
|
|
513 | =head1 AnyEvent::MP vs. Distributed Erlang |
|
|
514 | |
|
|
515 | AnyEvent::MP got lots of its ideas from distributed erlang (erlang node |
|
|
516 | == aemp node, erlang process == aemp port), so many of the documents and |
|
|
517 | programming techniques employed by erlang apply to AnyEvent::MP. Here is a |
|
|
518 | sample: |
|
|
519 | |
|
|
520 | http://www.erlang.se/doc/programming_rules.shtml |
|
|
521 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
|
|
522 | http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 |
|
|
523 | http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
|
|
524 | |
|
|
525 | Despite the similarities, there are also some important differences: |
|
|
526 | |
|
|
527 | =over 4 |
|
|
528 | |
|
|
529 | =item * Node references contain the recipe on how to contact them. |
|
|
530 | |
|
|
531 | Erlang relies on special naming and DNS to work everywhere in the |
|
|
532 | same way. AEMP relies on each node knowing it's own address(es), with |
|
|
533 | convenience functionality. |
|
|
534 | |
|
|
535 | This means that AEMP requires a less tightly controlled environment at the |
|
|
536 | cost of longer node references and a slightly higher management overhead. |
|
|
537 | |
|
|
538 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
|
|
539 | |
|
|
540 | Erlang uses processes that selctively receive messages, and therefore |
|
|
541 | needs a queue. AEMP is event based, queuing messages would serve no useful |
|
|
542 | purpose. |
|
|
543 | |
|
|
544 | (But see L<Coro::MP> for a more erlang-like process model on top of AEMP). |
|
|
545 | |
|
|
546 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
|
|
547 | |
|
|
548 | Sending messages in erlang is synchronous and blocks the process. AEMP |
|
|
549 | sends are immediate, connection establishment is handled in the |
|
|
550 | background. |
|
|
551 | |
|
|
552 | =item * Erlang can silently lose messages, AEMP cannot. |
|
|
553 | |
|
|
554 | Erlang makes few guarantees on messages delivery - messages can get lost |
|
|
555 | without any of the processes realising it (i.e. you send messages a, b, |
|
|
556 | and c, and the other side only receives messages a and c). |
|
|
557 | |
|
|
558 | AEMP guarantees correct ordering, and the guarantee that there are no |
|
|
559 | holes in the message sequence. |
|
|
560 | |
|
|
561 | =item * In erlang, processes can be declared dead and later be found to be |
|
|
562 | alive. |
|
|
563 | |
|
|
564 | In erlang it can happen that a monitored process is declared dead and |
|
|
565 | linked processes get killed, but later it turns out that the process is |
|
|
566 | still alive - and can receive messages. |
|
|
567 | |
|
|
568 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
569 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
570 | and then later sends messages to it, finding it is still alive. |
|
|
571 | |
|
|
572 | =item * Erlang can send messages to the wrong port, AEMP does not. |
|
|
573 | |
|
|
574 | In erlang it is quite possible that a node that restarts reuses a process |
|
|
575 | ID known to other nodes for a completely different process, causing |
|
|
576 | messages destined for that process to end up in an unrelated process. |
|
|
577 | |
|
|
578 | AEMP never reuses port IDs, so old messages or old port IDs floating |
|
|
579 | around in the network will not be sent to an unrelated port. |
|
|
580 | |
|
|
581 | =item * Erlang uses unprotected connections, AEMP uses secure |
|
|
582 | authentication and can use TLS. |
|
|
583 | |
|
|
584 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
|
|
585 | securely authenticate nodes. |
|
|
586 | |
|
|
587 | =back |
|
|
588 | |
383 | =head1 SEE ALSO |
589 | =head1 SEE ALSO |
384 | |
590 | |
385 | L<AnyEvent>. |
591 | L<AnyEvent>. |
386 | |
592 | |
387 | =head1 AUTHOR |
593 | =head1 AUTHOR |