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4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::MP; |
7 | use AnyEvent::MP; |
8 | |
8 | |
9 | $NODE # contains this node's noderef |
9 | $NODE # contains this node's node ID |
10 | NODE # returns this node's noderef |
10 | NODE # returns this node's node ID |
11 | NODE $port # returns the noderef of the port |
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12 | |
11 | |
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12 | $SELF # receiving/own port id in rcv callbacks |
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13 | |
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14 | # initialise the node so it can send/receive messages |
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15 | configure; |
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16 | |
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17 | # ports are message destinations |
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18 | |
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19 | # sending messages |
13 | snd $port, type => data...; |
20 | snd $port, type => data...; |
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21 | snd $port, @msg; |
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22 | snd @msg_with_first_element_being_a_port; |
14 | |
23 | |
15 | $SELF # receiving/own port id in rcv callbacks |
24 | # creating/using ports, the simple way |
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25 | my $simple_port = port { my @msg = @_ }; |
16 | |
26 | |
17 | rcv $port, smartmatch => $cb->($port, @msg); |
27 | # creating/using ports, tagged message matching |
18 | |
28 | my $port = port; |
19 | # examples: |
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20 | rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; |
29 | rcv $port, ping => sub { snd $_[0], "pong" }; |
21 | rcv $port1, pong => sub { warn "pong received\n" }; |
30 | rcv $port, pong => sub { warn "pong received\n" }; |
22 | snd $port2, ping => $port1; |
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23 | |
31 | |
24 | # more, smarter, matches (_any_ is exported by this module) |
32 | # create a port on another node |
25 | rcv $port, [child_died => $pid] => sub { ... |
33 | my $port = spawn $node, $initfunc, @initdata; |
26 | rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 |
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27 | |
34 | |
28 | # monitoring |
35 | # monitoring |
29 | mon $port, $cb->(@msg) # callback is invoked on death |
36 | mon $port, $cb->(@msg) # callback is invoked on death |
30 | mon $port, $otherport # kill otherport on abnormal death |
37 | mon $port, $otherport # kill otherport on abnormal death |
31 | mon $port, $otherport, @msg # send message on death |
38 | mon $port, $otherport, @msg # send message on death |
32 | |
39 | |
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40 | =head1 CURRENT STATUS |
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41 | |
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42 | bin/aemp - stable. |
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43 | AnyEvent::MP - stable API, should work. |
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44 | AnyEvent::MP::Intro - explains most concepts. |
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45 | AnyEvent::MP::Kernel - mostly stable. |
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46 | AnyEvent::MP::Global - stable but incomplete, protocol not yet final. |
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47 | |
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48 | stay tuned. |
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49 | |
33 | =head1 DESCRIPTION |
50 | =head1 DESCRIPTION |
34 | |
51 | |
35 | This module (-family) implements a simple message passing framework. |
52 | This module (-family) implements a simple message passing framework. |
36 | |
53 | |
37 | Despite its simplicity, you can securely message other processes running |
54 | Despite its simplicity, you can securely message other processes running |
38 | on the same or other hosts. |
55 | on the same or other hosts, and you can supervise entities remotely. |
39 | |
56 | |
40 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
57 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
41 | manual page. |
58 | manual page and the examples under F<eg/>. |
42 | |
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43 | At the moment, this module family is severly broken and underdocumented, |
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44 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
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45 | stay tuned! The basic API should be finished, however. |
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46 | |
59 | |
47 | =head1 CONCEPTS |
60 | =head1 CONCEPTS |
48 | |
61 | |
49 | =over 4 |
62 | =over 4 |
50 | |
63 | |
51 | =item port |
64 | =item port |
52 | |
65 | |
53 | A port is something you can send messages to (with the C<snd> function). |
66 | Not to be confused with a TCP port, a "port" is something you can send |
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67 | messages to (with the C<snd> function). |
54 | |
68 | |
55 | Some ports allow you to register C<rcv> handlers that can match specific |
69 | Ports allow you to register C<rcv> handlers that can match all or just |
56 | messages. All C<rcv> handlers will receive messages they match, messages |
70 | some messages. Messages send to ports will not be queued, regardless of |
57 | will not be queued. |
71 | anything was listening for them or not. |
58 | |
72 | |
59 | =item port id - C<noderef#portname> |
73 | =item port ID - C<nodeid#portname> |
60 | |
74 | |
61 | A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as |
75 | A port ID is the concatenation of a node ID, a hash-mark (C<#>) as |
62 | separator, and a port name (a printable string of unspecified format). An |
76 | separator, and a port name (a printable string of unspecified format). |
63 | exception is the the node port, whose ID is identical to its node |
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64 | reference. |
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65 | |
77 | |
66 | =item node |
78 | =item node |
67 | |
79 | |
68 | A node is a single process containing at least one port - the node |
80 | A node is a single process containing at least one port - the node port, |
69 | port. You can send messages to node ports to find existing ports or to |
81 | which enables nodes to manage each other remotely, and to create new |
70 | create new ports, among other things. |
82 | ports. |
71 | |
83 | |
72 | Nodes are either private (single-process only), slaves (connected to a |
84 | Nodes are either public (have one or more listening ports) or private |
73 | master node only) or public nodes (connectable from unrelated nodes). |
85 | (no listening ports). Private nodes cannot talk to other private nodes |
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86 | currently. |
74 | |
87 | |
75 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
88 | =item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*> |
76 | |
89 | |
77 | A node reference is a string that either simply identifies the node (for |
90 | A node ID is a string that uniquely identifies the node within a |
78 | private and slave nodes), or contains a recipe on how to reach a given |
91 | network. Depending on the configuration used, node IDs can look like a |
79 | node (for public nodes). |
92 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
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93 | doesn't interpret node IDs in any way. |
80 | |
94 | |
81 | This recipe is simply a comma-separated list of C<address:port> pairs (for |
95 | =item binds - C<ip:port> |
82 | TCP/IP, other protocols might look different). |
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83 | |
96 | |
84 | Node references come in two flavours: resolved (containing only numerical |
97 | Nodes can only talk to each other by creating some kind of connection to |
85 | addresses) or unresolved (where hostnames are used instead of addresses). |
98 | each other. To do this, nodes should listen on one or more local transport |
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99 | endpoints - binds. Currently, only standard C<ip:port> specifications can |
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100 | be used, which specify TCP ports to listen on. |
86 | |
101 | |
87 | Before using an unresolved node reference in a message you first have to |
102 | =item seed nodes |
88 | resolve it. |
103 | |
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104 | When a node starts, it knows nothing about the network. To teach the node |
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105 | about the network it first has to contact some other node within the |
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106 | network. This node is called a seed. |
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107 | |
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108 | Apart from the fact that other nodes know them as seed nodes and they have |
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109 | to have fixed listening addresses, seed nodes are perfectly normal nodes - |
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110 | any node can function as a seed node for others. |
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111 | |
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112 | In addition to discovering the network, seed nodes are also used to |
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113 | maintain the network and to connect nodes that otherwise would have |
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114 | trouble connecting. They form the backbone of an AnyEvent::MP network. |
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115 | |
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116 | Seed nodes are expected to be long-running, and at least one seed node |
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117 | should always be available. They should also be relatively responsive - a |
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118 | seed node that blocks for long periods will slow down everybody else. |
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119 | |
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120 | =item seeds - C<host:port> |
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121 | |
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122 | Seeds are transport endpoint(s) (usually a hostname/IP address and a |
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123 | TCP port) of nodes thta should be used as seed nodes. |
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124 | |
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125 | The nodes listening on those endpoints are expected to be long-running, |
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126 | and at least one of those should always be available. When nodes run out |
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127 | of connections (e.g. due to a network error), they try to re-establish |
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128 | connections to some seednodes again to join the network. |
89 | |
129 | |
90 | =back |
130 | =back |
91 | |
131 | |
92 | =head1 VARIABLES/FUNCTIONS |
132 | =head1 VARIABLES/FUNCTIONS |
93 | |
133 | |
… | |
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95 | |
135 | |
96 | =cut |
136 | =cut |
97 | |
137 | |
98 | package AnyEvent::MP; |
138 | package AnyEvent::MP; |
99 | |
139 | |
100 | use AnyEvent::MP::Base; |
140 | use AnyEvent::MP::Kernel; |
101 | |
141 | |
102 | use common::sense; |
142 | use common::sense; |
103 | |
143 | |
104 | use Carp (); |
144 | use Carp (); |
105 | |
145 | |
106 | use AE (); |
146 | use AE (); |
107 | |
147 | |
108 | use base "Exporter"; |
148 | use base "Exporter"; |
109 | |
149 | |
110 | our $VERSION = '0.1'; |
150 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
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151 | |
111 | our @EXPORT = qw( |
152 | our @EXPORT = qw( |
112 | NODE $NODE *SELF node_of _any_ |
153 | NODE $NODE *SELF node_of after |
113 | resolve_node initialise_node |
154 | configure |
114 | snd rcv mon kil reg psub |
155 | snd rcv mon mon_guard kil reg psub spawn |
115 | port |
156 | port |
116 | ); |
157 | ); |
117 | |
158 | |
118 | our $SELF; |
159 | our $SELF; |
119 | |
160 | |
… | |
… | |
123 | kil $SELF, die => $msg; |
164 | kil $SELF, die => $msg; |
124 | } |
165 | } |
125 | |
166 | |
126 | =item $thisnode = NODE / $NODE |
167 | =item $thisnode = NODE / $NODE |
127 | |
168 | |
128 | The C<NODE> function returns, and the C<$NODE> variable contains |
169 | The C<NODE> function returns, and the C<$NODE> variable contains, the node |
129 | the noderef of the local node. The value is initialised by a call |
170 | ID of the node running in the current process. This value is initialised by |
130 | to C<become_public> or C<become_slave>, after which all local port |
171 | a call to C<configure>. |
131 | identifiers become invalid. |
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132 | |
172 | |
133 | =item $noderef = node_of $port |
173 | =item $nodeid = node_of $port |
134 | |
174 | |
135 | Extracts and returns the noderef from a portid or a noderef. |
175 | Extracts and returns the node ID from a port ID or a node ID. |
136 | |
176 | |
137 | =item initialise_node $noderef, $seednode, $seednode... |
177 | =item configure $profile, key => value... |
138 | |
178 | |
139 | =item initialise_node "slave/", $master, $master... |
179 | =item configure key => value... |
140 | |
180 | |
141 | Before a node can talk to other nodes on the network it has to initialise |
181 | Before a node can talk to other nodes on the network (i.e. enter |
142 | itself - the minimum a node needs to know is it's own name, and optionally |
182 | "distributed mode") it has to configure itself - the minimum a node needs |
143 | it should know the noderefs of some other nodes in the network. |
183 | to know is its own name, and optionally it should know the addresses of |
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184 | some other nodes in the network to discover other nodes. |
144 | |
185 | |
145 | This function initialises a node - it must be called exactly once (or |
186 | This function configures a node - it must be called exactly once (or |
146 | never) before calling other AnyEvent::MP functions. |
187 | never) before calling other AnyEvent::MP functions. |
147 | |
188 | |
148 | All arguments are noderefs, which can be either resolved or unresolved. |
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149 | |
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150 | There are two types of networked nodes, public nodes and slave nodes: |
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151 | |
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152 | =over 4 |
189 | =over 4 |
153 | |
190 | |
154 | =item public nodes |
191 | =item step 1, gathering configuration from profiles |
155 | |
192 | |
156 | For public nodes, C<$noderef> must either be a (possibly unresolved) |
193 | The function first looks up a profile in the aemp configuration (see the |
157 | noderef, in which case it will be resolved, or C<undef> (or missing), in |
194 | L<aemp> commandline utility). The profile name can be specified via the |
158 | which case the noderef will be guessed. |
195 | named C<profile> parameter or can simply be the first parameter). If it is |
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196 | missing, then the nodename (F<uname -n>) will be used as profile name. |
159 | |
197 | |
160 | Afterwards, the node will bind itself on all endpoints and try to connect |
198 | The profile data is then gathered as follows: |
161 | to all additional C<$seednodes> that are specified. Seednodes are optional |
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162 | and can be used to quickly bootstrap the node into an existing network. |
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163 | |
199 | |
164 | =item slave nodes |
200 | First, all remaining key => value pairs (all of which are conveniently |
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201 | undocumented at the moment) will be interpreted as configuration |
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202 | data. Then they will be overwritten by any values specified in the global |
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203 | default configuration (see the F<aemp> utility), then the chain of |
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204 | profiles chosen by the profile name (and any C<parent> attributes). |
165 | |
205 | |
166 | When the C<$noderef> is the special string C<slave/>, then the node will |
206 | That means that the values specified in the profile have highest priority |
167 | become a slave node. Slave nodes cannot be contacted from outside and will |
207 | and the values specified directly via C<configure> have lowest priority, |
168 | route most of their traffic to the master node that they attach to. |
208 | and can only be used to specify defaults. |
169 | |
209 | |
170 | At least one additional noderef is required: The node will try to connect |
210 | If the profile specifies a node ID, then this will become the node ID of |
171 | to all of them and will become a slave attached to the first node it can |
211 | this process. If not, then the profile name will be used as node ID. The |
172 | successfully connect to. |
212 | special node ID of C<anon/> will be replaced by a random node ID. |
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213 | |
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214 | =item step 2, bind listener sockets |
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215 | |
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216 | The next step is to look up the binds in the profile, followed by binding |
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217 | aemp protocol listeners on all binds specified (it is possible and valid |
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218 | to have no binds, meaning that the node cannot be contacted form the |
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219 | outside. This means the node cannot talk to other nodes that also have no |
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220 | binds, but it can still talk to all "normal" nodes). |
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221 | |
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222 | If the profile does not specify a binds list, then a default of C<*> is |
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223 | used, meaning the node will bind on a dynamically-assigned port on every |
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224 | local IP address it finds. |
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225 | |
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226 | =item step 3, connect to seed nodes |
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227 | |
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228 | As the last step, the seeds list from the profile is passed to the |
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229 | L<AnyEvent::MP::Global> module, which will then use it to keep |
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230 | connectivity with at least one node at any point in time. |
173 | |
231 | |
174 | =back |
232 | =back |
175 | |
233 | |
176 | This function will block until all nodes have been resolved and, for slave |
234 | Example: become a distributed node using the locla node name as profile. |
177 | nodes, until it has successfully established a connection to a master |
235 | This should be the most common form of invocation for "daemon"-type nodes. |
178 | server. |
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179 | |
236 | |
180 | Example: become a public node listening on the default node. |
237 | configure |
181 | |
238 | |
182 | initialise_node; |
239 | Example: become an anonymous node. This form is often used for commandline |
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240 | clients. |
183 | |
241 | |
184 | Example: become a public node, and try to contact some well-known master |
242 | configure nodeid => "anon/"; |
185 | servers to become part of the network. |
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186 | |
243 | |
187 | initialise_node undef, "master1", "master2"; |
244 | Example: configure a node using a profile called seed, which si suitable |
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245 | for a seed node as it binds on all local addresses on a fixed port (4040, |
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246 | customary for aemp). |
188 | |
247 | |
189 | Example: become a public node listening on port C<4041>. |
248 | # use the aemp commandline utility |
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249 | # aemp profile seed nodeid anon/ binds '*:4040' |
190 | |
250 | |
191 | initialise_node 4041; |
251 | # then use it |
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252 | configure profile => "seed"; |
192 | |
253 | |
193 | Example: become a public node, only visible on localhost port 4044. |
254 | # or simply use aemp from the shell again: |
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255 | # aemp run profile seed |
194 | |
256 | |
195 | initialise_node "locahost:4044"; |
257 | # or provide a nicer-to-remember nodeid |
196 | |
258 | # aemp run profile seed nodeid "$(hostname)" |
197 | Example: become a slave node to any of the specified master servers. |
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198 | |
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199 | initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
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200 | |
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201 | =item $cv = resolve_node $noderef |
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202 | |
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203 | Takes an unresolved node reference that may contain hostnames and |
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204 | abbreviated IDs, resolves all of them and returns a resolved node |
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205 | reference. |
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206 | |
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207 | In addition to C<address:port> pairs allowed in resolved noderefs, the |
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208 | following forms are supported: |
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209 | |
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210 | =over 4 |
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211 | |
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212 | =item the empty string |
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213 | |
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214 | An empty-string component gets resolved as if the default port (4040) was |
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215 | specified. |
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216 | |
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217 | =item naked port numbers (e.g. C<1234>) |
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218 | |
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219 | These are resolved by prepending the local nodename and a colon, to be |
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220 | further resolved. |
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221 | |
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222 | =item hostnames (e.g. C<localhost:1234>, C<localhost>) |
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223 | |
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224 | These are resolved by using AnyEvent::DNS to resolve them, optionally |
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225 | looking up SRV records for the C<aemp=4040> port, if no port was |
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226 | specified. |
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227 | |
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228 | =back |
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229 | |
259 | |
230 | =item $SELF |
260 | =item $SELF |
231 | |
261 | |
232 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
262 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
233 | blocks. |
263 | blocks. |
234 | |
264 | |
235 | =item SELF, %SELF, @SELF... |
265 | =item *SELF, SELF, %SELF, @SELF... |
236 | |
266 | |
237 | Due to some quirks in how perl exports variables, it is impossible to |
267 | Due to some quirks in how perl exports variables, it is impossible to |
238 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
268 | just export C<$SELF>, all the symbols named C<SELF> are exported by this |
239 | module, but only C<$SELF> is currently used. |
269 | module, but only C<$SELF> is currently used. |
240 | |
270 | |
241 | =item snd $port, type => @data |
271 | =item snd $port, type => @data |
242 | |
272 | |
243 | =item snd $port, @msg |
273 | =item snd $port, @msg |
244 | |
274 | |
245 | Send the given message to the given port ID, which can identify either |
275 | Send the given message to the given port, which can identify either a |
246 | a local or a remote port, and can be either a string or soemthignt hat |
276 | local or a remote port, and must be a port ID. |
247 | stringifies a sa port ID (such as a port object :). |
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248 | |
277 | |
249 | While the message can be about anything, it is highly recommended to use a |
278 | While the message can be almost anything, it is highly recommended to |
250 | string as first element (a portid, or some word that indicates a request |
279 | use a string as first element (a port ID, or some word that indicates a |
251 | type etc.). |
280 | request type etc.) and to consist if only simple perl values (scalars, |
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281 | arrays, hashes) - if you think you need to pass an object, think again. |
252 | |
282 | |
253 | The message data effectively becomes read-only after a call to this |
283 | The message data logically becomes read-only after a call to this |
254 | function: modifying any argument is not allowed and can cause many |
284 | function: modifying any argument (or values referenced by them) is |
255 | problems. |
285 | forbidden, as there can be considerable time between the call to C<snd> |
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286 | and the time the message is actually being serialised - in fact, it might |
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287 | never be copied as within the same process it is simply handed to the |
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288 | receiving port. |
256 | |
289 | |
257 | The type of data you can transfer depends on the transport protocol: when |
290 | The type of data you can transfer depends on the transport protocol: when |
258 | JSON is used, then only strings, numbers and arrays and hashes consisting |
291 | JSON is used, then only strings, numbers and arrays and hashes consisting |
259 | of those are allowed (no objects). When Storable is used, then anything |
292 | of those are allowed (no objects). When Storable is used, then anything |
260 | that Storable can serialise and deserialise is allowed, and for the local |
293 | that Storable can serialise and deserialise is allowed, and for the local |
261 | node, anything can be passed. |
294 | node, anything can be passed. Best rely only on the common denominator of |
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295 | these. |
262 | |
296 | |
263 | =item $local_port = port |
297 | =item $local_port = port |
264 | |
298 | |
265 | Create a new local port object that can be used either as a pattern |
299 | Create a new local port object and returns its port ID. Initially it has |
266 | matching port ("full port") or a single-callback port ("miniport"), |
300 | no callbacks set and will throw an error when it receives messages. |
267 | depending on how C<rcv> callbacks are bound to the object. |
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268 | |
301 | |
269 | =item $port = port { my @msg = @_; $finished } |
302 | =item $local_port = port { my @msg = @_ } |
270 | |
303 | |
271 | Creates a "miniport", that is, a very lightweight port without any pattern |
304 | Creates a new local port, and returns its ID. Semantically the same as |
272 | matching behind it, and returns its ID. Semantically the same as creating |
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273 | a port and calling C<rcv $port, $callback> on it. |
305 | creating a port and calling C<rcv $port, $callback> on it. |
274 | |
306 | |
275 | The block will be called for every message received on the port. When the |
307 | The block will be called for every message received on the port, with the |
276 | callback returns a true value its job is considered "done" and the port |
308 | global variable C<$SELF> set to the port ID. Runtime errors will cause the |
277 | will be destroyed. Otherwise it will stay alive. |
309 | port to be C<kil>ed. The message will be passed as-is, no extra argument |
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310 | (i.e. no port ID) will be passed to the callback. |
278 | |
311 | |
279 | The message will be passed as-is, no extra argument (i.e. no port id) will |
312 | If you want to stop/destroy the port, simply C<kil> it: |
280 | be passed to the callback. |
|
|
281 | |
313 | |
282 | If you need the local port id in the callback, this works nicely: |
314 | my $port = port { |
283 | |
315 | my @msg = @_; |
284 | my $port; $port = port { |
316 | ... |
285 | snd $otherport, reply => $port; |
317 | kil $SELF; |
286 | }; |
318 | }; |
287 | |
319 | |
288 | =cut |
320 | =cut |
289 | |
321 | |
290 | sub rcv($@); |
322 | sub rcv($@); |
|
|
323 | |
|
|
324 | sub _kilme { |
|
|
325 | die "received message on port without callback"; |
|
|
326 | } |
291 | |
327 | |
292 | sub port(;&) { |
328 | sub port(;&) { |
293 | my $id = "$UNIQ." . $ID++; |
329 | my $id = "$UNIQ." . $ID++; |
294 | my $port = "$NODE#$id"; |
330 | my $port = "$NODE#$id"; |
295 | |
331 | |
296 | if (@_) { |
332 | rcv $port, shift || \&_kilme; |
297 | rcv $port, shift; |
|
|
298 | } else { |
|
|
299 | $PORT{$id} = sub { }; # nop |
|
|
300 | } |
|
|
301 | |
333 | |
302 | $port |
334 | $port |
303 | } |
335 | } |
304 | |
336 | |
305 | =item reg $port, $name |
|
|
306 | |
|
|
307 | =item reg $name |
|
|
308 | |
|
|
309 | Registers the given port (or C<$SELF><<< if missing) under the name |
|
|
310 | C<$name>. If the name already exists it is replaced. |
|
|
311 | |
|
|
312 | A port can only be registered under one well known name. |
|
|
313 | |
|
|
314 | A port automatically becomes unregistered when it is killed. |
|
|
315 | |
|
|
316 | =cut |
|
|
317 | |
|
|
318 | sub reg(@) { |
|
|
319 | my $port = @_ > 1 ? shift : $SELF || Carp::croak 'reg: called with one argument only, but $SELF not set,'; |
|
|
320 | |
|
|
321 | $REG{$_[0]} = $port; |
|
|
322 | } |
|
|
323 | |
|
|
324 | =item rcv $port, $callback->(@msg) |
337 | =item rcv $local_port, $callback->(@msg) |
325 | |
338 | |
326 | Replaces the callback on the specified miniport (after converting it to |
339 | Replaces the default callback on the specified port. There is no way to |
327 | one if required). |
340 | remove the default callback: use C<sub { }> to disable it, or better |
328 | |
341 | C<kil> the port when it is no longer needed. |
329 | =item rcv $port, tagstring => $callback->(@msg), ... |
|
|
330 | |
|
|
331 | =item rcv $port, $smartmatch => $callback->(@msg), ... |
|
|
332 | |
|
|
333 | =item rcv $port, [$smartmatch...] => $callback->(@msg), ... |
|
|
334 | |
|
|
335 | Register callbacks to be called on matching messages on the given full |
|
|
336 | port (after converting it to one if required) and return the port. |
|
|
337 | |
|
|
338 | The callback has to return a true value when its work is done, after |
|
|
339 | which is will be removed, or a false value in which case it will stay |
|
|
340 | registered. |
|
|
341 | |
342 | |
342 | The global C<$SELF> (exported by this module) contains C<$port> while |
343 | The global C<$SELF> (exported by this module) contains C<$port> while |
343 | executing the callback. |
344 | executing the callback. Runtime errors during callback execution will |
|
|
345 | result in the port being C<kil>ed. |
344 | |
346 | |
345 | Runtime errors wdurign callback execution will result in the port being |
347 | The default callback received all messages not matched by a more specific |
346 | C<kil>ed. |
348 | C<tag> match. |
347 | |
349 | |
348 | If the match is an array reference, then it will be matched against the |
350 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
349 | first elements of the message, otherwise only the first element is being |
|
|
350 | matched. |
|
|
351 | |
351 | |
352 | Any element in the match that is specified as C<_any_> (a function |
352 | Register (or replace) callbacks to be called on messages starting with the |
353 | exported by this module) matches any single element of the message. |
353 | given tag on the given port (and return the port), or unregister it (when |
|
|
354 | C<$callback> is C<$undef> or missing). There can only be one callback |
|
|
355 | registered for each tag. |
354 | |
356 | |
355 | While not required, it is highly recommended that the first matching |
357 | The original message will be passed to the callback, after the first |
356 | element is a string identifying the message. The one-string-only match is |
358 | element (the tag) has been removed. The callback will use the same |
357 | also the most efficient match (by far). |
359 | environment as the default callback (see above). |
358 | |
360 | |
359 | Example: create a port and bind receivers on it in one go. |
361 | Example: create a port and bind receivers on it in one go. |
360 | |
362 | |
361 | my $port = rcv port, |
363 | my $port = rcv port, |
362 | msg1 => sub { ...; 0 }, |
364 | msg1 => sub { ... }, |
363 | msg2 => sub { ...; 0 }, |
365 | msg2 => sub { ... }, |
364 | ; |
366 | ; |
365 | |
367 | |
366 | Example: create a port, bind receivers and send it in a message elsewhere |
368 | Example: create a port, bind receivers and send it in a message elsewhere |
367 | in one go: |
369 | in one go: |
368 | |
370 | |
369 | snd $otherport, reply => |
371 | snd $otherport, reply => |
370 | rcv port, |
372 | rcv port, |
371 | msg1 => sub { ...; 0 }, |
373 | msg1 => sub { ... }, |
372 | ... |
374 | ... |
373 | ; |
375 | ; |
374 | |
376 | |
|
|
377 | Example: temporarily register a rcv callback for a tag matching some port |
|
|
378 | (e.g. for a rpc reply) and unregister it after a message was received. |
|
|
379 | |
|
|
380 | rcv $port, $otherport => sub { |
|
|
381 | my @reply = @_; |
|
|
382 | |
|
|
383 | rcv $SELF, $otherport; |
|
|
384 | }; |
|
|
385 | |
375 | =cut |
386 | =cut |
376 | |
387 | |
377 | sub rcv($@) { |
388 | sub rcv($@) { |
378 | my $port = shift; |
389 | my $port = shift; |
379 | my ($noderef, $portid) = split /#/, $port, 2; |
390 | my ($nodeid, $portid) = split /#/, $port, 2; |
380 | |
391 | |
381 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
392 | $NODE{$nodeid} == $NODE{""} |
382 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
393 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
383 | |
394 | |
384 | if (@_ == 1) { |
395 | while (@_) { |
|
|
396 | if (ref $_[0]) { |
|
|
397 | if (my $self = $PORT_DATA{$portid}) { |
|
|
398 | "AnyEvent::MP::Port" eq ref $self |
|
|
399 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
400 | |
|
|
401 | $self->[2] = shift; |
|
|
402 | } else { |
385 | my $cb = shift; |
403 | my $cb = shift; |
386 | delete $PORT_DATA{$portid}; |
|
|
387 | $PORT{$portid} = sub { |
404 | $PORT{$portid} = sub { |
388 | local $SELF = $port; |
405 | local $SELF = $port; |
389 | eval { |
406 | eval { &$cb }; _self_die if $@; |
390 | &$cb |
407 | }; |
391 | and kil $port; |
|
|
392 | }; |
408 | } |
393 | _self_die if $@; |
409 | } elsif (defined $_[0]) { |
394 | }; |
|
|
395 | } else { |
|
|
396 | my $self = $PORT_DATA{$portid} ||= do { |
410 | my $self = $PORT_DATA{$portid} ||= do { |
397 | my $self = bless { |
411 | my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
398 | id => $port, |
|
|
399 | }, "AnyEvent::MP::Port"; |
|
|
400 | |
412 | |
401 | $PORT{$portid} = sub { |
413 | $PORT{$portid} = sub { |
402 | local $SELF = $port; |
414 | local $SELF = $port; |
403 | |
415 | |
404 | eval { |
|
|
405 | for (@{ $self->{rc0}{$_[0]} }) { |
416 | if (my $cb = $self->[1]{$_[0]}) { |
406 | $_ && &{$_->[0]} |
417 | shift; |
407 | && undef $_; |
418 | eval { &$cb }; _self_die if $@; |
408 | } |
419 | } else { |
409 | |
|
|
410 | for (@{ $self->{rcv}{$_[0]} }) { |
|
|
411 | $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
|
|
412 | && &{$_->[0]} |
420 | &{ $self->[0] }; |
413 | && undef $_; |
|
|
414 | } |
|
|
415 | |
|
|
416 | for (@{ $self->{any} }) { |
|
|
417 | $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
|
|
418 | && &{$_->[0]} |
|
|
419 | && undef $_; |
|
|
420 | } |
421 | } |
421 | }; |
422 | }; |
422 | _self_die if $@; |
423 | |
|
|
424 | $self |
423 | }; |
425 | }; |
424 | |
426 | |
425 | $self |
|
|
426 | }; |
|
|
427 | |
|
|
428 | "AnyEvent::MP::Port" eq ref $self |
427 | "AnyEvent::MP::Port" eq ref $self |
429 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
428 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
430 | |
429 | |
431 | while (@_) { |
|
|
432 | my ($match, $cb) = splice @_, 0, 2; |
430 | my ($tag, $cb) = splice @_, 0, 2; |
433 | |
431 | |
434 | if (!ref $match) { |
432 | if (defined $cb) { |
435 | push @{ $self->{rc0}{$match} }, [$cb]; |
433 | $self->[1]{$tag} = $cb; |
436 | } elsif (("ARRAY" eq ref $match && !ref $match->[0])) { |
|
|
437 | my ($type, @match) = @$match; |
|
|
438 | @match |
|
|
439 | ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] |
|
|
440 | : push @{ $self->{rc0}{$match->[0]} }, [$cb]; |
|
|
441 | } else { |
434 | } else { |
442 | push @{ $self->{any} }, [$cb, $match]; |
435 | delete $self->[1]{$tag}; |
443 | } |
436 | } |
444 | } |
437 | } |
445 | } |
438 | } |
446 | |
439 | |
447 | $port |
440 | $port |
… | |
… | |
483 | $res |
476 | $res |
484 | } |
477 | } |
485 | } |
478 | } |
486 | } |
479 | } |
487 | |
480 | |
488 | =item $guard = mon $port, $cb->(@reason) |
481 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
489 | |
482 | |
490 | =item $guard = mon $port, $rcvport |
483 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
491 | |
484 | |
492 | =item $guard = mon $port |
485 | =item $guard = mon $port # kill $SELF when $port dies |
493 | |
486 | |
494 | =item $guard = mon $port, $rcvport, @msg |
487 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
495 | |
488 | |
496 | Monitor the given port and do something when the port is killed, and |
489 | Monitor the given port and do something when the port is killed or |
497 | optionally return a guard that can be used to stop monitoring again. |
490 | messages to it were lost, and optionally return a guard that can be used |
|
|
491 | to stop monitoring again. |
498 | |
492 | |
499 | In the first form (callback), the callback is simply called with any |
493 | In the first form (callback), the callback is simply called with any |
500 | number of C<@reason> elements (no @reason means that the port was deleted |
494 | number of C<@reason> elements (no @reason means that the port was deleted |
501 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
495 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
502 | C<eval> if unsure. |
496 | C<eval> if unsure. |
503 | |
497 | |
504 | In the second form (another port given), the other port (C<$rcvport) |
498 | In the second form (another port given), the other port (C<$rcvport>) |
505 | will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
499 | will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on |
506 | "normal" kils nothing happens, while under all other conditions, the other |
500 | "normal" kils nothing happens, while under all other conditions, the other |
507 | port is killed with the same reason. |
501 | port is killed with the same reason. |
508 | |
502 | |
509 | The third form (kill self) is the same as the second form, except that |
503 | The third form (kill self) is the same as the second form, except that |
510 | C<$rvport> defaults to C<$SELF>. |
504 | C<$rvport> defaults to C<$SELF>. |
511 | |
505 | |
512 | In the last form (message), a message of the form C<@msg, @reason> will be |
506 | In the last form (message), a message of the form C<@msg, @reason> will be |
513 | C<snd>. |
507 | C<snd>. |
|
|
508 | |
|
|
509 | Monitoring-actions are one-shot: once messages are lost (and a monitoring |
|
|
510 | alert was raised), they are removed and will not trigger again. |
514 | |
511 | |
515 | As a rule of thumb, monitoring requests should always monitor a port from |
512 | As a rule of thumb, monitoring requests should always monitor a port from |
516 | a local port (or callback). The reason is that kill messages might get |
513 | a local port (or callback). The reason is that kill messages might get |
517 | lost, just like any other message. Another less obvious reason is that |
514 | lost, just like any other message. Another less obvious reason is that |
518 | even monitoring requests can get lost (for exmaple, when the connection |
515 | even monitoring requests can get lost (for example, when the connection |
519 | to the other node goes down permanently). When monitoring a port locally |
516 | to the other node goes down permanently). When monitoring a port locally |
520 | these problems do not exist. |
517 | these problems do not exist. |
521 | |
518 | |
|
|
519 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
520 | after starting the monitor, either all messages sent to the port will |
|
|
521 | arrive, or the monitoring action will be invoked after possible message |
|
|
522 | loss has been detected. No messages will be lost "in between" (after |
|
|
523 | the first lost message no further messages will be received by the |
|
|
524 | port). After the monitoring action was invoked, further messages might get |
|
|
525 | delivered again. |
|
|
526 | |
|
|
527 | Inter-host-connection timeouts and monitoring depend on the transport |
|
|
528 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
|
|
529 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
|
|
530 | non-idle connection, and usually around two hours for idle conenctions). |
|
|
531 | |
|
|
532 | This means that monitoring is good for program errors and cleaning up |
|
|
533 | stuff eventually, but they are no replacement for a timeout when you need |
|
|
534 | to ensure some maximum latency. |
|
|
535 | |
522 | Example: call a given callback when C<$port> is killed. |
536 | Example: call a given callback when C<$port> is killed. |
523 | |
537 | |
524 | mon $port, sub { warn "port died because of <@_>\n" }; |
538 | mon $port, sub { warn "port died because of <@_>\n" }; |
525 | |
539 | |
526 | Example: kill ourselves when C<$port> is killed abnormally. |
540 | Example: kill ourselves when C<$port> is killed abnormally. |
… | |
… | |
532 | mon $port, $self => "restart"; |
546 | mon $port, $self => "restart"; |
533 | |
547 | |
534 | =cut |
548 | =cut |
535 | |
549 | |
536 | sub mon { |
550 | sub mon { |
537 | my ($noderef, $port) = split /#/, shift, 2; |
551 | my ($nodeid, $port) = split /#/, shift, 2; |
538 | |
552 | |
539 | my $node = $NODE{$noderef} || add_node $noderef; |
553 | my $node = $NODE{$nodeid} || add_node $nodeid; |
540 | |
554 | |
541 | my $cb = @_ ? $_[0] : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
555 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
542 | |
556 | |
543 | unless (ref $cb) { |
557 | unless (ref $cb) { |
544 | if (@_) { |
558 | if (@_) { |
545 | # send a kill info message |
559 | # send a kill info message |
546 | my (@msg) = @_; |
560 | my (@msg) = ($cb, @_); |
547 | $cb = sub { snd @msg, @_ }; |
561 | $cb = sub { snd @msg, @_ }; |
548 | } else { |
562 | } else { |
549 | # simply kill other port |
563 | # simply kill other port |
550 | my $port = $cb; |
564 | my $port = $cb; |
551 | $cb = sub { kil $port, @_ if @_ }; |
565 | $cb = sub { kil $port, @_ if @_ }; |
… | |
… | |
564 | is killed, the references will be freed. |
578 | is killed, the references will be freed. |
565 | |
579 | |
566 | Optionally returns a guard that will stop the monitoring. |
580 | Optionally returns a guard that will stop the monitoring. |
567 | |
581 | |
568 | This function is useful when you create e.g. timers or other watchers and |
582 | This function is useful when you create e.g. timers or other watchers and |
569 | want to free them when the port gets killed: |
583 | want to free them when the port gets killed (note the use of C<psub>): |
570 | |
584 | |
571 | $port->rcv (start => sub { |
585 | $port->rcv (start => sub { |
572 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
586 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub { |
573 | undef $timer if 0.9 < rand; |
587 | undef $timer if 0.9 < rand; |
574 | }); |
588 | }); |
575 | }); |
589 | }); |
576 | |
590 | |
577 | =cut |
591 | =cut |
… | |
… | |
586 | |
600 | |
587 | =item kil $port[, @reason] |
601 | =item kil $port[, @reason] |
588 | |
602 | |
589 | Kill the specified port with the given C<@reason>. |
603 | Kill the specified port with the given C<@reason>. |
590 | |
604 | |
591 | If no C<@reason> is specified, then the port is killed "normally" (linked |
605 | If no C<@reason> is specified, then the port is killed "normally" (ports |
592 | ports will not be kileld, or even notified). |
606 | monitoring other ports will not necessarily die because a port dies |
|
|
607 | "normally"). |
593 | |
608 | |
594 | Otherwise, linked ports get killed with the same reason (second form of |
609 | Otherwise, linked ports get killed with the same reason (second form of |
595 | C<mon>, see below). |
610 | C<mon>, see above). |
596 | |
611 | |
597 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
612 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
598 | will be reported as reason C<< die => $@ >>. |
613 | will be reported as reason C<< die => $@ >>. |
599 | |
614 | |
600 | Transport/communication errors are reported as C<< transport_error => |
615 | Transport/communication errors are reported as C<< transport_error => |
601 | $message >>. |
616 | $message >>. |
602 | |
617 | |
603 | =back |
|
|
604 | |
|
|
605 | =head1 NODE MESSAGES |
|
|
606 | |
|
|
607 | Nodes understand the following messages sent to them. Many of them take |
|
|
608 | arguments called C<@reply>, which will simply be used to compose a reply |
|
|
609 | message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and |
|
|
610 | the remaining arguments are simply the message data. |
|
|
611 | |
|
|
612 | While other messages exist, they are not public and subject to change. |
|
|
613 | |
|
|
614 | =over 4 |
|
|
615 | |
|
|
616 | =cut |
618 | =cut |
617 | |
619 | |
618 | =item lookup => $name, @reply |
620 | =item $port = spawn $node, $initfunc[, @initdata] |
619 | |
621 | |
620 | Replies with the port ID of the specified well-known port, or C<undef>. |
622 | Creates a port on the node C<$node> (which can also be a port ID, in which |
|
|
623 | case it's the node where that port resides). |
621 | |
624 | |
622 | =item devnull => ... |
625 | The port ID of the newly created port is returned immediately, and it is |
|
|
626 | possible to immediately start sending messages or to monitor the port. |
623 | |
627 | |
624 | Generic data sink/CPU heat conversion. |
628 | After the port has been created, the init function is called on the remote |
|
|
629 | node, in the same context as a C<rcv> callback. This function must be a |
|
|
630 | fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To |
|
|
631 | specify a function in the main program, use C<::name>. |
625 | |
632 | |
626 | =item relay => $port, @msg |
633 | If the function doesn't exist, then the node tries to C<require> |
|
|
634 | the package, then the package above the package and so on (e.g. |
|
|
635 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
|
|
636 | exists or it runs out of package names. |
627 | |
637 | |
628 | Simply forwards the message to the given port. |
638 | The init function is then called with the newly-created port as context |
|
|
639 | object (C<$SELF>) and the C<@initdata> values as arguments. It I<must> |
|
|
640 | call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise |
|
|
641 | the port might not get created. |
629 | |
642 | |
630 | =item eval => $string[ @reply] |
643 | A common idiom is to pass a local port, immediately monitor the spawned |
|
|
644 | port, and in the remote init function, immediately monitor the passed |
|
|
645 | local port. This two-way monitoring ensures that both ports get cleaned up |
|
|
646 | when there is a problem. |
631 | |
647 | |
632 | Evaluates the given string. If C<@reply> is given, then a message of the |
648 | C<spawn> guarantees that the C<$initfunc> has no visible effects on the |
633 | form C<@reply, $@, @evalres> is sent. |
649 | caller before C<spawn> returns (by delaying invocation when spawn is |
|
|
650 | called for the local node). |
634 | |
651 | |
635 | Example: crash another node. |
652 | Example: spawn a chat server port on C<$othernode>. |
636 | |
653 | |
637 | snd $othernode, eval => "exit"; |
654 | # this node, executed from within a port context: |
|
|
655 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
|
|
656 | mon $server; |
638 | |
657 | |
639 | =item time => @reply |
658 | # init function on C<$othernode> |
|
|
659 | sub connect { |
|
|
660 | my ($srcport) = @_; |
640 | |
661 | |
641 | Replies the the current node time to C<@reply>. |
662 | mon $srcport; |
642 | |
663 | |
643 | Example: tell the current node to send the current time to C<$myport> in a |
664 | rcv $SELF, sub { |
644 | C<timereply> message. |
665 | ... |
|
|
666 | }; |
|
|
667 | } |
645 | |
668 | |
646 | snd $NODE, time => $myport, timereply => 1, 2; |
669 | =cut |
647 | # => snd $myport, timereply => 1, 2, <time> |
670 | |
|
|
671 | sub _spawn { |
|
|
672 | my $port = shift; |
|
|
673 | my $init = shift; |
|
|
674 | |
|
|
675 | # rcv will create the actual port |
|
|
676 | local $SELF = "$NODE#$port"; |
|
|
677 | eval { |
|
|
678 | &{ load_func $init } |
|
|
679 | }; |
|
|
680 | _self_die if $@; |
|
|
681 | } |
|
|
682 | |
|
|
683 | sub spawn(@) { |
|
|
684 | my ($nodeid, undef) = split /#/, shift, 2; |
|
|
685 | |
|
|
686 | my $id = "$RUNIQ." . $ID++; |
|
|
687 | |
|
|
688 | $_[0] =~ /::/ |
|
|
689 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
|
|
690 | |
|
|
691 | snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; |
|
|
692 | |
|
|
693 | "$nodeid#$id" |
|
|
694 | } |
|
|
695 | |
|
|
696 | =item after $timeout, @msg |
|
|
697 | |
|
|
698 | =item after $timeout, $callback |
|
|
699 | |
|
|
700 | Either sends the given message, or call the given callback, after the |
|
|
701 | specified number of seconds. |
|
|
702 | |
|
|
703 | This is simply a utility function that comes in handy at times - the |
|
|
704 | AnyEvent::MP author is not convinced of the wisdom of having it, though, |
|
|
705 | so it may go away in the future. |
|
|
706 | |
|
|
707 | =cut |
|
|
708 | |
|
|
709 | sub after($@) { |
|
|
710 | my ($timeout, @action) = @_; |
|
|
711 | |
|
|
712 | my $t; $t = AE::timer $timeout, 0, sub { |
|
|
713 | undef $t; |
|
|
714 | ref $action[0] |
|
|
715 | ? $action[0]() |
|
|
716 | : snd @action; |
|
|
717 | }; |
|
|
718 | } |
648 | |
719 | |
649 | =back |
720 | =back |
650 | |
721 | |
651 | =head1 AnyEvent::MP vs. Distributed Erlang |
722 | =head1 AnyEvent::MP vs. Distributed Erlang |
652 | |
723 | |
… | |
… | |
662 | |
733 | |
663 | Despite the similarities, there are also some important differences: |
734 | Despite the similarities, there are also some important differences: |
664 | |
735 | |
665 | =over 4 |
736 | =over 4 |
666 | |
737 | |
667 | =item * Node references contain the recipe on how to contact them. |
738 | =item * Node IDs are arbitrary strings in AEMP. |
668 | |
739 | |
669 | Erlang relies on special naming and DNS to work everywhere in the |
740 | Erlang relies on special naming and DNS to work everywhere in the same |
670 | same way. AEMP relies on each node knowing it's own address(es), with |
741 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
671 | convenience functionality. |
742 | configuration or DNS), but will otherwise discover other odes itself. |
672 | |
743 | |
673 | This means that AEMP requires a less tightly controlled environment at the |
744 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
674 | cost of longer node references and a slightly higher management overhead. |
745 | uses "local ports are like remote ports". |
|
|
746 | |
|
|
747 | The failure modes for local ports are quite different (runtime errors |
|
|
748 | only) then for remote ports - when a local port dies, you I<know> it dies, |
|
|
749 | when a connection to another node dies, you know nothing about the other |
|
|
750 | port. |
|
|
751 | |
|
|
752 | Erlang pretends remote ports are as reliable as local ports, even when |
|
|
753 | they are not. |
|
|
754 | |
|
|
755 | AEMP encourages a "treat remote ports differently" philosophy, with local |
|
|
756 | ports being the special case/exception, where transport errors cannot |
|
|
757 | occur. |
675 | |
758 | |
676 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
759 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
677 | |
760 | |
678 | Erlang uses processes that selctively receive messages, and therefore |
761 | Erlang uses processes that selectively receive messages, and therefore |
679 | needs a queue. AEMP is event based, queuing messages would serve no useful |
762 | needs a queue. AEMP is event based, queuing messages would serve no |
680 | purpose. |
763 | useful purpose. For the same reason the pattern-matching abilities of |
|
|
764 | AnyEvent::MP are more limited, as there is little need to be able to |
|
|
765 | filter messages without dequeuing them. |
681 | |
766 | |
682 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
767 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
683 | |
768 | |
684 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
769 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
685 | |
770 | |
686 | Sending messages in Erlang is synchronous and blocks the process. AEMP |
771 | Sending messages in Erlang is synchronous and blocks the process (and |
687 | sends are immediate, connection establishment is handled in the |
772 | so does not need a queue that can overflow). AEMP sends are immediate, |
688 | background. |
773 | connection establishment is handled in the background. |
689 | |
774 | |
690 | =item * Erlang can silently lose messages, AEMP cannot. |
775 | =item * Erlang suffers from silent message loss, AEMP does not. |
691 | |
776 | |
692 | Erlang makes few guarantees on messages delivery - messages can get lost |
777 | Erlang makes few guarantees on messages delivery - messages can get lost |
693 | without any of the processes realising it (i.e. you send messages a, b, |
778 | without any of the processes realising it (i.e. you send messages a, b, |
694 | and c, and the other side only receives messages a and c). |
779 | and c, and the other side only receives messages a and c). |
695 | |
780 | |
696 | AEMP guarantees correct ordering, and the guarantee that there are no |
781 | AEMP guarantees correct ordering, and the guarantee that after one message |
697 | holes in the message sequence. |
782 | is lost, all following ones sent to the same port are lost as well, until |
698 | |
783 | monitoring raises an error, so there are no silent "holes" in the message |
699 | =item * In Erlang, processes can be declared dead and later be found to be |
784 | sequence. |
700 | alive. |
|
|
701 | |
|
|
702 | In Erlang it can happen that a monitored process is declared dead and |
|
|
703 | linked processes get killed, but later it turns out that the process is |
|
|
704 | still alive - and can receive messages. |
|
|
705 | |
|
|
706 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
707 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
708 | and then later sends messages to it, finding it is still alive. |
|
|
709 | |
785 | |
710 | =item * Erlang can send messages to the wrong port, AEMP does not. |
786 | =item * Erlang can send messages to the wrong port, AEMP does not. |
711 | |
787 | |
712 | In Erlang it is quite possible that a node that restarts reuses a process |
788 | In Erlang it is quite likely that a node that restarts reuses a process ID |
713 | ID known to other nodes for a completely different process, causing |
789 | known to other nodes for a completely different process, causing messages |
714 | messages destined for that process to end up in an unrelated process. |
790 | destined for that process to end up in an unrelated process. |
715 | |
791 | |
716 | AEMP never reuses port IDs, so old messages or old port IDs floating |
792 | AEMP never reuses port IDs, so old messages or old port IDs floating |
717 | around in the network will not be sent to an unrelated port. |
793 | around in the network will not be sent to an unrelated port. |
718 | |
794 | |
719 | =item * Erlang uses unprotected connections, AEMP uses secure |
795 | =item * Erlang uses unprotected connections, AEMP uses secure |
720 | authentication and can use TLS. |
796 | authentication and can use TLS. |
721 | |
797 | |
722 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
798 | AEMP can use a proven protocol - TLS - to protect connections and |
723 | securely authenticate nodes. |
799 | securely authenticate nodes. |
724 | |
800 | |
725 | =item * The AEMP protocol is optimised for both text-based and binary |
801 | =item * The AEMP protocol is optimised for both text-based and binary |
726 | communications. |
802 | communications. |
727 | |
803 | |
728 | The AEMP protocol, unlike the Erlang protocol, supports both |
804 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
729 | language-independent text-only protocols (good for debugging) and binary, |
805 | language independent text-only protocols (good for debugging) and binary, |
730 | language-specific serialisers (e.g. Storable). |
806 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
|
|
807 | used, the protocol is actually completely text-based. |
731 | |
808 | |
732 | It has also been carefully designed to be implementable in other languages |
809 | It has also been carefully designed to be implementable in other languages |
733 | with a minimum of work while gracefully degrading fucntionality to make the |
810 | with a minimum of work while gracefully degrading functionality to make the |
734 | protocol simple. |
811 | protocol simple. |
735 | |
812 | |
736 | =item * AEMP has more flexible monitoring options than Erlang. |
813 | =item * AEMP has more flexible monitoring options than Erlang. |
737 | |
814 | |
738 | In Erlang, you can chose to receive I<all> exit signals as messages |
815 | In Erlang, you can chose to receive I<all> exit signals as messages |
… | |
… | |
741 | Erlang, as one can choose between automatic kill, exit message or callback |
818 | Erlang, as one can choose between automatic kill, exit message or callback |
742 | on a per-process basis. |
819 | on a per-process basis. |
743 | |
820 | |
744 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
821 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
745 | |
822 | |
746 | Monitoring in Erlang is not an indicator of process death/crashes, |
823 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
747 | as linking is (except linking is unreliable in Erlang). |
824 | same way as linking is (except linking is unreliable in Erlang). |
748 | |
825 | |
749 | In AEMP, you don't "look up" registered port names or send to named ports |
826 | In AEMP, you don't "look up" registered port names or send to named ports |
750 | that might or might not be persistent. Instead, you normally spawn a port |
827 | that might or might not be persistent. Instead, you normally spawn a port |
751 | on the remote node. The init function monitors the you, and you monitor |
828 | on the remote node. The init function monitors you, and you monitor the |
752 | the remote port. Since both monitors are local to the node, they are much |
829 | remote port. Since both monitors are local to the node, they are much more |
753 | more reliable. |
830 | reliable (no need for C<spawn_link>). |
754 | |
831 | |
755 | This also saves round-trips and avoids sending messages to the wrong port |
832 | This also saves round-trips and avoids sending messages to the wrong port |
756 | (hard to do in Erlang). |
833 | (hard to do in Erlang). |
757 | |
834 | |
758 | =back |
835 | =back |
759 | |
836 | |
|
|
837 | =head1 RATIONALE |
|
|
838 | |
|
|
839 | =over 4 |
|
|
840 | |
|
|
841 | =item Why strings for port and node IDs, why not objects? |
|
|
842 | |
|
|
843 | We considered "objects", but found that the actual number of methods |
|
|
844 | that can be called are quite low. Since port and node IDs travel over |
|
|
845 | the network frequently, the serialising/deserialising would add lots of |
|
|
846 | overhead, as well as having to keep a proxy object everywhere. |
|
|
847 | |
|
|
848 | Strings can easily be printed, easily serialised etc. and need no special |
|
|
849 | procedures to be "valid". |
|
|
850 | |
|
|
851 | And as a result, a miniport consists of a single closure stored in a |
|
|
852 | global hash - it can't become much cheaper. |
|
|
853 | |
|
|
854 | =item Why favour JSON, why not a real serialising format such as Storable? |
|
|
855 | |
|
|
856 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
|
|
857 | format, but currently there is no way to make a node use Storable by |
|
|
858 | default (although all nodes will accept it). |
|
|
859 | |
|
|
860 | The default framing protocol is JSON because a) JSON::XS is many times |
|
|
861 | faster for small messages and b) most importantly, after years of |
|
|
862 | experience we found that object serialisation is causing more problems |
|
|
863 | than it solves: Just like function calls, objects simply do not travel |
|
|
864 | easily over the network, mostly because they will always be a copy, so you |
|
|
865 | always have to re-think your design. |
|
|
866 | |
|
|
867 | Keeping your messages simple, concentrating on data structures rather than |
|
|
868 | objects, will keep your messages clean, tidy and efficient. |
|
|
869 | |
|
|
870 | =back |
|
|
871 | |
760 | =head1 SEE ALSO |
872 | =head1 SEE ALSO |
|
|
873 | |
|
|
874 | L<AnyEvent::MP::Intro> - a gentle introduction. |
|
|
875 | |
|
|
876 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
|
|
877 | |
|
|
878 | L<AnyEvent::MP::Global> - network maintainance and port groups, to find |
|
|
879 | your applications. |
|
|
880 | |
|
|
881 | L<AnyEvent::MP::LogCatcher> - simple service to display log messages from |
|
|
882 | all nodes. |
761 | |
883 | |
762 | L<AnyEvent>. |
884 | L<AnyEvent>. |
763 | |
885 | |
764 | =head1 AUTHOR |
886 | =head1 AUTHOR |
765 | |
887 | |