… | |
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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 | |
13 | $SELF # receiving/own port id in rcv callbacks |
12 | $SELF # receiving/own port id in rcv callbacks |
14 | |
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 | |
15 | # ports are message endpoints |
17 | # ports are message destinations |
16 | |
18 | |
17 | # sending messages |
19 | # sending messages |
18 | snd $port, type => data...; |
20 | snd $port, type => data...; |
19 | snd $port, @msg; |
21 | snd $port, @msg; |
20 | snd @msg_with_first_element_being_a_port; |
22 | snd @msg_with_first_element_being_a_port; |
21 | |
23 | |
22 | # miniports |
24 | # creating/using ports, the simple way |
23 | my $miniport = port { my @msg = @_; 0 }; |
25 | my $simple_port = port { my @msg = @_ }; |
24 | |
26 | |
25 | # full ports |
27 | # creating/using ports, tagged message matching |
26 | my $port = port; |
28 | my $port = port; |
27 | rcv $port, smartmatch => $cb->(@msg); |
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28 | rcv $port, ping => sub { snd $_[0], "pong"; 0 }; |
29 | rcv $port, ping => sub { snd $_[0], "pong" }; |
29 | rcv $port, pong => sub { warn "pong received\n"; 0 }; |
30 | rcv $port, pong => sub { warn "pong received\n" }; |
30 | |
31 | |
31 | # remote ports |
32 | # create a port on another node |
32 | my $port = spawn $node, $initfunc, @initdata; |
33 | my $port = spawn $node, $initfunc, @initdata; |
33 | |
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34 | # more, smarter, matches (_any_ is exported by this module) |
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35 | rcv $port, [child_died => $pid] => sub { ... |
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36 | rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 |
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37 | |
34 | |
38 | # monitoring |
35 | # monitoring |
39 | mon $port, $cb->(@msg) # callback is invoked on death |
36 | mon $port, $cb->(@msg) # callback is invoked on death |
40 | mon $port, $otherport # kill otherport on abnormal death |
37 | mon $port, $otherport # kill otherport on abnormal death |
41 | mon $port, $otherport, @msg # send message on death |
38 | mon $port, $otherport, @msg # send message on death |
42 | |
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 | |
43 | =head1 DESCRIPTION |
50 | =head1 DESCRIPTION |
44 | |
51 | |
45 | This module (-family) implements a simple message passing framework. |
52 | This module (-family) implements a simple message passing framework. |
46 | |
53 | |
47 | Despite its simplicity, you can securely message other processes running |
54 | Despite its simplicity, you can securely message other processes running |
48 | on the same or other hosts. |
55 | on the same or other hosts, and you can supervise entities remotely. |
49 | |
56 | |
50 | 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> |
51 | manual page. |
58 | manual page and the examples under F<eg/>. |
52 | |
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53 | At the moment, this module family is severly broken and underdocumented, |
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54 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
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55 | stay tuned! The basic API should be finished, however. |
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56 | |
59 | |
57 | =head1 CONCEPTS |
60 | =head1 CONCEPTS |
58 | |
61 | |
59 | =over 4 |
62 | =over 4 |
60 | |
63 | |
61 | =item port |
64 | =item port |
62 | |
65 | |
63 | 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). |
64 | |
68 | |
65 | 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 |
66 | messages. All C<rcv> handlers will receive messages they match, messages |
70 | some messages. Messages send to ports will not be queued, regardless of |
67 | will not be queued. |
71 | anything was listening for them or not. |
68 | |
72 | |
69 | =item port id - C<noderef#portname> |
73 | =item port ID - C<nodeid#portname> |
70 | |
74 | |
71 | 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 |
72 | separator, and a port name (a printable string of unspecified format). An |
76 | separator, and a port name (a printable string of unspecified format). |
73 | exception is the the node port, whose ID is identical to its node |
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74 | reference. |
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75 | |
77 | |
76 | =item node |
78 | =item node |
77 | |
79 | |
78 | 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, |
79 | 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 |
80 | create new ports, among other things. |
82 | ports. |
81 | |
83 | |
82 | Nodes are either private (single-process only), slaves (connected to a |
84 | Nodes are either public (have one or more listening ports) or private |
83 | 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. |
84 | |
87 | |
85 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
88 | =item node ID - C<[a-za-Z0-9_\-.:]+> |
86 | |
89 | |
87 | 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 |
88 | 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 |
89 | 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. |
90 | |
94 | |
91 | This recipe is simply a comma-separated list of C<address:port> pairs (for |
95 | =item binds - C<ip:port> |
92 | TCP/IP, other protocols might look different). |
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93 | |
96 | |
94 | 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 |
95 | 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. |
96 | |
101 | |
97 | Before using an unresolved node reference in a message you first have to |
102 | =item seeds - C<host:port> |
98 | 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 | Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes |
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109 | are expected to be long-running, and at least one of those should always |
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110 | be available. When nodes run out of connections (e.g. due to a network |
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111 | error), they try to re-establish connections to some seednodes again to |
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112 | join the network. |
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113 | |
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114 | Apart from being sued for seeding, seednodes are not special in any way - |
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115 | every public node can be a seednode. |
99 | |
116 | |
100 | =back |
117 | =back |
101 | |
118 | |
102 | =head1 VARIABLES/FUNCTIONS |
119 | =head1 VARIABLES/FUNCTIONS |
103 | |
120 | |
… | |
… | |
118 | use base "Exporter"; |
135 | use base "Exporter"; |
119 | |
136 | |
120 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
137 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
121 | |
138 | |
122 | our @EXPORT = qw( |
139 | our @EXPORT = qw( |
123 | NODE $NODE *SELF node_of _any_ |
140 | NODE $NODE *SELF node_of after |
124 | resolve_node initialise_node |
141 | configure |
125 | snd rcv mon kil reg psub spawn |
142 | snd rcv mon mon_guard kil reg psub spawn |
126 | port |
143 | port |
127 | ); |
144 | ); |
128 | |
145 | |
129 | our $SELF; |
146 | our $SELF; |
130 | |
147 | |
… | |
… | |
134 | kil $SELF, die => $msg; |
151 | kil $SELF, die => $msg; |
135 | } |
152 | } |
136 | |
153 | |
137 | =item $thisnode = NODE / $NODE |
154 | =item $thisnode = NODE / $NODE |
138 | |
155 | |
139 | The C<NODE> function returns, and the C<$NODE> variable contains |
156 | The C<NODE> function returns, and the C<$NODE> variable contains, the node |
140 | the noderef of the local node. The value is initialised by a call |
157 | ID of the node running in the current process. This value is initialised by |
141 | to C<become_public> or C<become_slave>, after which all local port |
158 | a call to C<configure>. |
142 | identifiers become invalid. |
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143 | |
159 | |
144 | =item $noderef = node_of $port |
160 | =item $nodeid = node_of $port |
145 | |
161 | |
146 | Extracts and returns the noderef from a portid or a noderef. |
162 | Extracts and returns the node ID from a port ID or a node ID. |
147 | |
163 | |
148 | =item initialise_node $noderef, $seednode, $seednode... |
164 | =item configure $profile, key => value... |
149 | |
165 | |
150 | =item initialise_node "slave/", $master, $master... |
166 | =item configure key => value... |
151 | |
167 | |
152 | Before a node can talk to other nodes on the network it has to initialise |
168 | Before a node can talk to other nodes on the network (i.e. enter |
153 | itself - the minimum a node needs to know is it's own name, and optionally |
169 | "distributed mode") it has to configure itself - the minimum a node needs |
154 | it should know the noderefs of some other nodes in the network. |
170 | to know is its own name, and optionally it should know the addresses of |
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171 | some other nodes in the network to discover other nodes. |
155 | |
172 | |
156 | This function initialises a node - it must be called exactly once (or |
173 | This function configures a node - it must be called exactly once (or |
157 | never) before calling other AnyEvent::MP functions. |
174 | never) before calling other AnyEvent::MP functions. |
158 | |
175 | |
159 | All arguments are noderefs, which can be either resolved or unresolved. |
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160 | |
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161 | There are two types of networked nodes, public nodes and slave nodes: |
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162 | |
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163 | =over 4 |
176 | =over 4 |
164 | |
177 | |
165 | =item public nodes |
178 | =item step 1, gathering configuration from profiles |
166 | |
179 | |
167 | For public nodes, C<$noderef> must either be a (possibly unresolved) |
180 | The function first looks up a profile in the aemp configuration (see the |
168 | noderef, in which case it will be resolved, or C<undef> (or missing), in |
181 | L<aemp> commandline utility). The profile name can be specified via the |
169 | which case the noderef will be guessed. |
182 | named C<profile> parameter or can simply be the first parameter). If it is |
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183 | missing, then the nodename (F<uname -n>) will be used as profile name. |
170 | |
184 | |
171 | Afterwards, the node will bind itself on all endpoints and try to connect |
185 | The profile data is then gathered as follows: |
172 | to all additional C<$seednodes> that are specified. Seednodes are optional |
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173 | and can be used to quickly bootstrap the node into an existing network. |
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174 | |
186 | |
175 | =item slave nodes |
187 | First, all remaining key => value pairs (all of which are conveniently |
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188 | undocumented at the moment) will be interpreted as configuration |
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189 | data. Then they will be overwritten by any values specified in the global |
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190 | default configuration (see the F<aemp> utility), then the chain of |
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191 | profiles chosen by the profile name (and any C<parent> attributes). |
176 | |
192 | |
177 | When the C<$noderef> is the special string C<slave/>, then the node will |
193 | That means that the values specified in the profile have highest priority |
178 | become a slave node. Slave nodes cannot be contacted from outside and will |
194 | and the values specified directly via C<configure> have lowest priority, |
179 | route most of their traffic to the master node that they attach to. |
195 | and can only be used to specify defaults. |
180 | |
196 | |
181 | At least one additional noderef is required: The node will try to connect |
197 | If the profile specifies a node ID, then this will become the node ID of |
182 | to all of them and will become a slave attached to the first node it can |
198 | this process. If not, then the profile name will be used as node ID. The |
183 | successfully connect to. |
199 | special node ID of C<anon/> will be replaced by a random node ID. |
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200 | |
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201 | =item step 2, bind listener sockets |
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202 | |
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203 | The next step is to look up the binds in the profile, followed by binding |
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204 | aemp protocol listeners on all binds specified (it is possible and valid |
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205 | to have no binds, meaning that the node cannot be contacted form the |
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206 | outside. This means the node cannot talk to other nodes that also have no |
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207 | binds, but it can still talk to all "normal" nodes). |
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208 | |
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209 | If the profile does not specify a binds list, then a default of C<*> is |
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210 | used, meaning the node will bind on a dynamically-assigned port on every |
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211 | local IP address it finds. |
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212 | |
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213 | =item step 3, connect to seed nodes |
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214 | |
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215 | As the last step, the seeds list from the profile is passed to the |
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216 | L<AnyEvent::MP::Global> module, which will then use it to keep |
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217 | connectivity with at least one node at any point in time. |
184 | |
218 | |
185 | =back |
219 | =back |
186 | |
220 | |
187 | This function will block until all nodes have been resolved and, for slave |
221 | Example: become a distributed node using the locla node name as profile. |
188 | nodes, until it has successfully established a connection to a master |
222 | This should be the most common form of invocation for "daemon"-type nodes. |
189 | server. |
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190 | |
223 | |
191 | Example: become a public node listening on the default node. |
224 | configure |
192 | |
225 | |
193 | initialise_node; |
226 | Example: become an anonymous node. This form is often used for commandline |
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227 | clients. |
194 | |
228 | |
195 | Example: become a public node, and try to contact some well-known master |
229 | configure nodeid => "anon/"; |
196 | servers to become part of the network. |
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197 | |
230 | |
198 | initialise_node undef, "master1", "master2"; |
231 | Example: configure a node using a profile called seed, which si suitable |
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232 | for a seed node as it binds on all local addresses on a fixed port (4040, |
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233 | customary for aemp). |
199 | |
234 | |
200 | Example: become a public node listening on port C<4041>. |
235 | # use the aemp commandline utility |
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236 | # aemp profile seed nodeid anon/ binds '*:4040' |
201 | |
237 | |
202 | initialise_node 4041; |
238 | # then use it |
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239 | configure profile => "seed"; |
203 | |
240 | |
204 | Example: become a public node, only visible on localhost port 4044. |
241 | # or simply use aemp from the shell again: |
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242 | # aemp run profile seed |
205 | |
243 | |
206 | initialise_node "locahost:4044"; |
244 | # or provide a nicer-to-remember nodeid |
207 | |
245 | # aemp run profile seed nodeid "$(hostname)" |
208 | Example: become a slave node to any of the specified master servers. |
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209 | |
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210 | initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
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211 | |
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212 | =item $cv = resolve_node $noderef |
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213 | |
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214 | Takes an unresolved node reference that may contain hostnames and |
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215 | abbreviated IDs, resolves all of them and returns a resolved node |
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216 | reference. |
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217 | |
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218 | In addition to C<address:port> pairs allowed in resolved noderefs, the |
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219 | following forms are supported: |
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220 | |
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221 | =over 4 |
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222 | |
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223 | =item the empty string |
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224 | |
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225 | An empty-string component gets resolved as if the default port (4040) was |
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226 | specified. |
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227 | |
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228 | =item naked port numbers (e.g. C<1234>) |
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229 | |
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230 | These are resolved by prepending the local nodename and a colon, to be |
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231 | further resolved. |
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232 | |
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233 | =item hostnames (e.g. C<localhost:1234>, C<localhost>) |
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234 | |
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235 | These are resolved by using AnyEvent::DNS to resolve them, optionally |
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236 | looking up SRV records for the C<aemp=4040> port, if no port was |
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237 | specified. |
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238 | |
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239 | =back |
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240 | |
246 | |
241 | =item $SELF |
247 | =item $SELF |
242 | |
248 | |
243 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
249 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
244 | blocks. |
250 | blocks. |
245 | |
251 | |
246 | =item SELF, %SELF, @SELF... |
252 | =item *SELF, SELF, %SELF, @SELF... |
247 | |
253 | |
248 | Due to some quirks in how perl exports variables, it is impossible to |
254 | Due to some quirks in how perl exports variables, it is impossible to |
249 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
255 | just export C<$SELF>, all the symbols named C<SELF> are exported by this |
250 | module, but only C<$SELF> is currently used. |
256 | module, but only C<$SELF> is currently used. |
251 | |
257 | |
252 | =item snd $port, type => @data |
258 | =item snd $port, type => @data |
253 | |
259 | |
254 | =item snd $port, @msg |
260 | =item snd $port, @msg |
255 | |
261 | |
256 | Send the given message to the given port ID, which can identify either |
262 | Send the given message to the given port, which can identify either a |
257 | a local or a remote port, and can be either a string or soemthignt hat |
263 | local or a remote port, and must be a port ID. |
258 | stringifies a sa port ID (such as a port object :). |
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259 | |
264 | |
260 | While the message can be about anything, it is highly recommended to use a |
265 | While the message can be almost anything, it is highly recommended to |
261 | string as first element (a portid, or some word that indicates a request |
266 | use a string as first element (a port ID, or some word that indicates a |
262 | type etc.). |
267 | request type etc.) and to consist if only simple perl values (scalars, |
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268 | arrays, hashes) - if you think you need to pass an object, think again. |
263 | |
269 | |
264 | The message data effectively becomes read-only after a call to this |
270 | The message data logically becomes read-only after a call to this |
265 | function: modifying any argument is not allowed and can cause many |
271 | function: modifying any argument (or values referenced by them) is |
266 | problems. |
272 | forbidden, as there can be considerable time between the call to C<snd> |
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273 | and the time the message is actually being serialised - in fact, it might |
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274 | never be copied as within the same process it is simply handed to the |
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275 | receiving port. |
267 | |
276 | |
268 | The type of data you can transfer depends on the transport protocol: when |
277 | The type of data you can transfer depends on the transport protocol: when |
269 | JSON is used, then only strings, numbers and arrays and hashes consisting |
278 | JSON is used, then only strings, numbers and arrays and hashes consisting |
270 | of those are allowed (no objects). When Storable is used, then anything |
279 | of those are allowed (no objects). When Storable is used, then anything |
271 | that Storable can serialise and deserialise is allowed, and for the local |
280 | that Storable can serialise and deserialise is allowed, and for the local |
272 | node, anything can be passed. |
281 | node, anything can be passed. Best rely only on the common denominator of |
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282 | these. |
273 | |
283 | |
274 | =item $local_port = port |
284 | =item $local_port = port |
275 | |
285 | |
276 | Create a new local port object that can be used either as a pattern |
286 | Create a new local port object and returns its port ID. Initially it has |
277 | matching port ("full port") or a single-callback port ("miniport"), |
287 | no callbacks set and will throw an error when it receives messages. |
278 | depending on how C<rcv> callbacks are bound to the object. |
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279 | |
288 | |
280 | =item $port = port { my @msg = @_; $finished } |
289 | =item $local_port = port { my @msg = @_ } |
281 | |
290 | |
282 | Creates a "miniport", that is, a very lightweight port without any pattern |
291 | Creates a new local port, and returns its ID. Semantically the same as |
283 | matching behind it, and returns its ID. Semantically the same as creating |
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284 | a port and calling C<rcv $port, $callback> on it. |
292 | creating a port and calling C<rcv $port, $callback> on it. |
285 | |
293 | |
286 | The block will be called for every message received on the port. When the |
294 | The block will be called for every message received on the port, with the |
287 | callback returns a true value its job is considered "done" and the port |
295 | global variable C<$SELF> set to the port ID. Runtime errors will cause the |
288 | will be destroyed. Otherwise it will stay alive. |
296 | port to be C<kil>ed. The message will be passed as-is, no extra argument |
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297 | (i.e. no port ID) will be passed to the callback. |
289 | |
298 | |
290 | The message will be passed as-is, no extra argument (i.e. no port id) will |
299 | If you want to stop/destroy the port, simply C<kil> it: |
291 | be passed to the callback. |
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292 | |
300 | |
293 | If you need the local port id in the callback, this works nicely: |
301 | my $port = port { |
294 | |
302 | my @msg = @_; |
295 | my $port; $port = port { |
303 | ... |
296 | snd $otherport, reply => $port; |
304 | kil $SELF; |
297 | }; |
305 | }; |
298 | |
306 | |
299 | =cut |
307 | =cut |
300 | |
308 | |
301 | sub rcv($@); |
309 | sub rcv($@); |
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310 | |
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311 | sub _kilme { |
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312 | die "received message on port without callback"; |
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313 | } |
302 | |
314 | |
303 | sub port(;&) { |
315 | sub port(;&) { |
304 | my $id = "$UNIQ." . $ID++; |
316 | my $id = "$UNIQ." . $ID++; |
305 | my $port = "$NODE#$id"; |
317 | my $port = "$NODE#$id"; |
306 | |
318 | |
307 | if (@_) { |
319 | rcv $port, shift || \&_kilme; |
308 | rcv $port, shift; |
|
|
309 | } else { |
|
|
310 | $PORT{$id} = sub { }; # nop |
|
|
311 | } |
|
|
312 | |
320 | |
313 | $port |
321 | $port |
314 | } |
322 | } |
315 | |
323 | |
316 | =item reg $port, $name |
|
|
317 | |
|
|
318 | =item reg $name |
|
|
319 | |
|
|
320 | Registers the given port (or C<$SELF><<< if missing) under the name |
|
|
321 | C<$name>. If the name already exists it is replaced. |
|
|
322 | |
|
|
323 | A port can only be registered under one well known name. |
|
|
324 | |
|
|
325 | A port automatically becomes unregistered when it is killed. |
|
|
326 | |
|
|
327 | =cut |
|
|
328 | |
|
|
329 | sub reg(@) { |
|
|
330 | my $port = @_ > 1 ? shift : $SELF || Carp::croak 'reg: called with one argument only, but $SELF not set,'; |
|
|
331 | |
|
|
332 | $REG{$_[0]} = $port; |
|
|
333 | } |
|
|
334 | |
|
|
335 | =item rcv $port, $callback->(@msg) |
324 | =item rcv $local_port, $callback->(@msg) |
336 | |
325 | |
337 | Replaces the callback on the specified miniport (after converting it to |
326 | Replaces the default callback on the specified port. There is no way to |
338 | one if required). |
327 | remove the default callback: use C<sub { }> to disable it, or better |
339 | |
328 | C<kil> the port when it is no longer needed. |
340 | =item rcv $port, tagstring => $callback->(@msg), ... |
|
|
341 | |
|
|
342 | =item rcv $port, $smartmatch => $callback->(@msg), ... |
|
|
343 | |
|
|
344 | =item rcv $port, [$smartmatch...] => $callback->(@msg), ... |
|
|
345 | |
|
|
346 | Register callbacks to be called on matching messages on the given full |
|
|
347 | port (after converting it to one if required) and return the port. |
|
|
348 | |
|
|
349 | The callback has to return a true value when its work is done, after |
|
|
350 | which is will be removed, or a false value in which case it will stay |
|
|
351 | registered. |
|
|
352 | |
329 | |
353 | The global C<$SELF> (exported by this module) contains C<$port> while |
330 | The global C<$SELF> (exported by this module) contains C<$port> while |
354 | executing the callback. |
331 | executing the callback. Runtime errors during callback execution will |
|
|
332 | result in the port being C<kil>ed. |
355 | |
333 | |
356 | Runtime errors during callback execution will result in the port being |
334 | The default callback received all messages not matched by a more specific |
357 | C<kil>ed. |
335 | C<tag> match. |
358 | |
336 | |
359 | If the match is an array reference, then it will be matched against the |
337 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
360 | first elements of the message, otherwise only the first element is being |
|
|
361 | matched. |
|
|
362 | |
338 | |
363 | Any element in the match that is specified as C<_any_> (a function |
339 | Register (or replace) callbacks to be called on messages starting with the |
364 | exported by this module) matches any single element of the message. |
340 | given tag on the given port (and return the port), or unregister it (when |
|
|
341 | C<$callback> is C<$undef> or missing). There can only be one callback |
|
|
342 | registered for each tag. |
365 | |
343 | |
366 | While not required, it is highly recommended that the first matching |
344 | The original message will be passed to the callback, after the first |
367 | element is a string identifying the message. The one-string-only match is |
345 | element (the tag) has been removed. The callback will use the same |
368 | also the most efficient match (by far). |
346 | environment as the default callback (see above). |
369 | |
347 | |
370 | Example: create a port and bind receivers on it in one go. |
348 | Example: create a port and bind receivers on it in one go. |
371 | |
349 | |
372 | my $port = rcv port, |
350 | my $port = rcv port, |
373 | msg1 => sub { ...; 0 }, |
351 | msg1 => sub { ... }, |
374 | msg2 => sub { ...; 0 }, |
352 | msg2 => sub { ... }, |
375 | ; |
353 | ; |
376 | |
354 | |
377 | Example: create a port, bind receivers and send it in a message elsewhere |
355 | Example: create a port, bind receivers and send it in a message elsewhere |
378 | in one go: |
356 | in one go: |
379 | |
357 | |
380 | snd $otherport, reply => |
358 | snd $otherport, reply => |
381 | rcv port, |
359 | rcv port, |
382 | msg1 => sub { ...; 0 }, |
360 | msg1 => sub { ... }, |
383 | ... |
361 | ... |
384 | ; |
362 | ; |
385 | |
363 | |
|
|
364 | Example: temporarily register a rcv callback for a tag matching some port |
|
|
365 | (e.g. for a rpc reply) and unregister it after a message was received. |
|
|
366 | |
|
|
367 | rcv $port, $otherport => sub { |
|
|
368 | my @reply = @_; |
|
|
369 | |
|
|
370 | rcv $SELF, $otherport; |
|
|
371 | }; |
|
|
372 | |
386 | =cut |
373 | =cut |
387 | |
374 | |
388 | sub rcv($@) { |
375 | sub rcv($@) { |
389 | my $port = shift; |
376 | my $port = shift; |
390 | my ($noderef, $portid) = split /#/, $port, 2; |
377 | my ($nodeid, $portid) = split /#/, $port, 2; |
391 | |
378 | |
392 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
379 | $NODE{$nodeid} == $NODE{""} |
393 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
380 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
394 | |
381 | |
395 | if (@_ == 1) { |
382 | while (@_) { |
|
|
383 | if (ref $_[0]) { |
|
|
384 | if (my $self = $PORT_DATA{$portid}) { |
|
|
385 | "AnyEvent::MP::Port" eq ref $self |
|
|
386 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
387 | |
|
|
388 | $self->[2] = shift; |
|
|
389 | } else { |
396 | my $cb = shift; |
390 | my $cb = shift; |
397 | delete $PORT_DATA{$portid}; |
|
|
398 | $PORT{$portid} = sub { |
391 | $PORT{$portid} = sub { |
399 | local $SELF = $port; |
392 | local $SELF = $port; |
400 | eval { |
393 | eval { &$cb }; _self_die if $@; |
401 | &$cb |
394 | }; |
402 | and kil $port; |
|
|
403 | }; |
395 | } |
404 | _self_die if $@; |
396 | } elsif (defined $_[0]) { |
405 | }; |
|
|
406 | } else { |
|
|
407 | my $self = $PORT_DATA{$portid} ||= do { |
397 | my $self = $PORT_DATA{$portid} ||= do { |
408 | my $self = bless { |
398 | my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
409 | id => $port, |
|
|
410 | }, "AnyEvent::MP::Port"; |
|
|
411 | |
399 | |
412 | $PORT{$portid} = sub { |
400 | $PORT{$portid} = sub { |
413 | local $SELF = $port; |
401 | local $SELF = $port; |
414 | |
402 | |
415 | eval { |
|
|
416 | for (@{ $self->{rc0}{$_[0]} }) { |
403 | if (my $cb = $self->[1]{$_[0]}) { |
417 | $_ && &{$_->[0]} |
404 | shift; |
418 | && undef $_; |
405 | eval { &$cb }; _self_die if $@; |
419 | } |
406 | } else { |
420 | |
|
|
421 | for (@{ $self->{rcv}{$_[0]} }) { |
|
|
422 | $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
|
|
423 | && &{$_->[0]} |
407 | &{ $self->[0] }; |
424 | && undef $_; |
|
|
425 | } |
|
|
426 | |
|
|
427 | for (@{ $self->{any} }) { |
|
|
428 | $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
|
|
429 | && &{$_->[0]} |
|
|
430 | && undef $_; |
|
|
431 | } |
408 | } |
432 | }; |
409 | }; |
433 | _self_die if $@; |
410 | |
|
|
411 | $self |
434 | }; |
412 | }; |
435 | |
413 | |
436 | $self |
|
|
437 | }; |
|
|
438 | |
|
|
439 | "AnyEvent::MP::Port" eq ref $self |
414 | "AnyEvent::MP::Port" eq ref $self |
440 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
415 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
441 | |
416 | |
442 | while (@_) { |
|
|
443 | my ($match, $cb) = splice @_, 0, 2; |
417 | my ($tag, $cb) = splice @_, 0, 2; |
444 | |
418 | |
445 | if (!ref $match) { |
419 | if (defined $cb) { |
446 | push @{ $self->{rc0}{$match} }, [$cb]; |
420 | $self->[1]{$tag} = $cb; |
447 | } elsif (("ARRAY" eq ref $match && !ref $match->[0])) { |
|
|
448 | my ($type, @match) = @$match; |
|
|
449 | @match |
|
|
450 | ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] |
|
|
451 | : push @{ $self->{rc0}{$match->[0]} }, [$cb]; |
|
|
452 | } else { |
421 | } else { |
453 | push @{ $self->{any} }, [$cb, $match]; |
422 | delete $self->[1]{$tag}; |
454 | } |
423 | } |
455 | } |
424 | } |
456 | } |
425 | } |
457 | |
426 | |
458 | $port |
427 | $port |
… | |
… | |
494 | $res |
463 | $res |
495 | } |
464 | } |
496 | } |
465 | } |
497 | } |
466 | } |
498 | |
467 | |
499 | =item $guard = mon $port, $cb->(@reason) |
468 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
500 | |
469 | |
501 | =item $guard = mon $port, $rcvport |
470 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
502 | |
471 | |
503 | =item $guard = mon $port |
472 | =item $guard = mon $port # kill $SELF when $port dies |
504 | |
473 | |
505 | =item $guard = mon $port, $rcvport, @msg |
474 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
506 | |
475 | |
507 | Monitor the given port and do something when the port is killed or |
476 | Monitor the given port and do something when the port is killed or |
508 | messages to it were lost, and optionally return a guard that can be used |
477 | messages to it were lost, and optionally return a guard that can be used |
509 | to stop monitoring again. |
478 | to stop monitoring again. |
510 | |
|
|
511 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
512 | that after starting the monitor, either all messages sent to the port |
|
|
513 | will arrive, or the monitoring action will be invoked after possible |
|
|
514 | message loss has been detected. No messages will be lost "in between" |
|
|
515 | (after the first lost message no further messages will be received by the |
|
|
516 | port). After the monitoring action was invoked, further messages might get |
|
|
517 | delivered again. |
|
|
518 | |
479 | |
519 | In the first form (callback), the callback is simply called with any |
480 | In the first form (callback), the callback is simply called with any |
520 | number of C<@reason> elements (no @reason means that the port was deleted |
481 | number of C<@reason> elements (no @reason means that the port was deleted |
521 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
482 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
522 | C<eval> if unsure. |
483 | C<eval> if unsure. |
523 | |
484 | |
524 | In the second form (another port given), the other port (C<$rcvport>) |
485 | In the second form (another port given), the other port (C<$rcvport>) |
525 | will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
486 | will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on |
526 | "normal" kils nothing happens, while under all other conditions, the other |
487 | "normal" kils nothing happens, while under all other conditions, the other |
527 | port is killed with the same reason. |
488 | port is killed with the same reason. |
528 | |
489 | |
529 | The third form (kill self) is the same as the second form, except that |
490 | The third form (kill self) is the same as the second form, except that |
530 | C<$rvport> defaults to C<$SELF>. |
491 | C<$rvport> defaults to C<$SELF>. |
531 | |
492 | |
532 | In the last form (message), a message of the form C<@msg, @reason> will be |
493 | In the last form (message), a message of the form C<@msg, @reason> will be |
533 | C<snd>. |
494 | C<snd>. |
|
|
495 | |
|
|
496 | Monitoring-actions are one-shot: once messages are lost (and a monitoring |
|
|
497 | alert was raised), they are removed and will not trigger again. |
534 | |
498 | |
535 | As a rule of thumb, monitoring requests should always monitor a port from |
499 | As a rule of thumb, monitoring requests should always monitor a port from |
536 | a local port (or callback). The reason is that kill messages might get |
500 | a local port (or callback). The reason is that kill messages might get |
537 | lost, just like any other message. Another less obvious reason is that |
501 | lost, just like any other message. Another less obvious reason is that |
538 | even monitoring requests can get lost (for exmaple, when the connection |
502 | even monitoring requests can get lost (for example, when the connection |
539 | to the other node goes down permanently). When monitoring a port locally |
503 | to the other node goes down permanently). When monitoring a port locally |
540 | these problems do not exist. |
504 | these problems do not exist. |
541 | |
505 | |
|
|
506 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
507 | after starting the monitor, either all messages sent to the port will |
|
|
508 | arrive, or the monitoring action will be invoked after possible message |
|
|
509 | loss has been detected. No messages will be lost "in between" (after |
|
|
510 | the first lost message no further messages will be received by the |
|
|
511 | port). After the monitoring action was invoked, further messages might get |
|
|
512 | delivered again. |
|
|
513 | |
|
|
514 | Inter-host-connection timeouts and monitoring depend on the transport |
|
|
515 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
|
|
516 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
|
|
517 | non-idle connection, and usually around two hours for idle conenctions). |
|
|
518 | |
|
|
519 | This means that monitoring is good for program errors and cleaning up |
|
|
520 | stuff eventually, but they are no replacement for a timeout when you need |
|
|
521 | to ensure some maximum latency. |
|
|
522 | |
542 | Example: call a given callback when C<$port> is killed. |
523 | Example: call a given callback when C<$port> is killed. |
543 | |
524 | |
544 | mon $port, sub { warn "port died because of <@_>\n" }; |
525 | mon $port, sub { warn "port died because of <@_>\n" }; |
545 | |
526 | |
546 | Example: kill ourselves when C<$port> is killed abnormally. |
527 | Example: kill ourselves when C<$port> is killed abnormally. |
… | |
… | |
552 | mon $port, $self => "restart"; |
533 | mon $port, $self => "restart"; |
553 | |
534 | |
554 | =cut |
535 | =cut |
555 | |
536 | |
556 | sub mon { |
537 | sub mon { |
557 | my ($noderef, $port) = split /#/, shift, 2; |
538 | my ($nodeid, $port) = split /#/, shift, 2; |
558 | |
539 | |
559 | my $node = $NODE{$noderef} || add_node $noderef; |
540 | my $node = $NODE{$nodeid} || add_node $nodeid; |
560 | |
541 | |
561 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
542 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
562 | |
543 | |
563 | unless (ref $cb) { |
544 | unless (ref $cb) { |
564 | if (@_) { |
545 | if (@_) { |
… | |
… | |
584 | is killed, the references will be freed. |
565 | is killed, the references will be freed. |
585 | |
566 | |
586 | Optionally returns a guard that will stop the monitoring. |
567 | Optionally returns a guard that will stop the monitoring. |
587 | |
568 | |
588 | This function is useful when you create e.g. timers or other watchers and |
569 | This function is useful when you create e.g. timers or other watchers and |
589 | want to free them when the port gets killed: |
570 | want to free them when the port gets killed (note the use of C<psub>): |
590 | |
571 | |
591 | $port->rcv (start => sub { |
572 | $port->rcv (start => sub { |
592 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
573 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub { |
593 | undef $timer if 0.9 < rand; |
574 | undef $timer if 0.9 < rand; |
594 | }); |
575 | }); |
595 | }); |
576 | }); |
596 | |
577 | |
597 | =cut |
578 | =cut |
… | |
… | |
606 | |
587 | |
607 | =item kil $port[, @reason] |
588 | =item kil $port[, @reason] |
608 | |
589 | |
609 | Kill the specified port with the given C<@reason>. |
590 | Kill the specified port with the given C<@reason>. |
610 | |
591 | |
611 | If no C<@reason> is specified, then the port is killed "normally" (linked |
592 | If no C<@reason> is specified, then the port is killed "normally" (ports |
612 | ports will not be kileld, or even notified). |
593 | monitoring other ports will not necessarily die because a port dies |
|
|
594 | "normally"). |
613 | |
595 | |
614 | Otherwise, linked ports get killed with the same reason (second form of |
596 | Otherwise, linked ports get killed with the same reason (second form of |
615 | C<mon>, see below). |
597 | C<mon>, see above). |
616 | |
598 | |
617 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
599 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
618 | will be reported as reason C<< die => $@ >>. |
600 | will be reported as reason C<< die => $@ >>. |
619 | |
601 | |
620 | Transport/communication errors are reported as C<< transport_error => |
602 | Transport/communication errors are reported as C<< transport_error => |
… | |
… | |
625 | =item $port = spawn $node, $initfunc[, @initdata] |
607 | =item $port = spawn $node, $initfunc[, @initdata] |
626 | |
608 | |
627 | Creates a port on the node C<$node> (which can also be a port ID, in which |
609 | Creates a port on the node C<$node> (which can also be a port ID, in which |
628 | case it's the node where that port resides). |
610 | case it's the node where that port resides). |
629 | |
611 | |
630 | The port ID of the newly created port is return immediately, and it is |
612 | The port ID of the newly created port is returned immediately, and it is |
631 | permissible to immediately start sending messages or monitor the port. |
613 | possible to immediately start sending messages or to monitor the port. |
632 | |
614 | |
633 | After the port has been created, the init function is |
615 | After the port has been created, the init function is called on the remote |
634 | called. This function must be a fully-qualified function name |
616 | node, in the same context as a C<rcv> callback. This function must be a |
635 | (e.g. C<MyApp::Chat::Server::init>). To specify a function in the main |
617 | fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To |
636 | program, use C<::name>. |
618 | specify a function in the main program, use C<::name>. |
637 | |
619 | |
638 | If the function doesn't exist, then the node tries to C<require> |
620 | If the function doesn't exist, then the node tries to C<require> |
639 | the package, then the package above the package and so on (e.g. |
621 | the package, then the package above the package and so on (e.g. |
640 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
622 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
641 | exists or it runs out of package names. |
623 | exists or it runs out of package names. |
642 | |
624 | |
643 | The init function is then called with the newly-created port as context |
625 | The init function is then called with the newly-created port as context |
644 | object (C<$SELF>) and the C<@initdata> values as arguments. |
626 | object (C<$SELF>) and the C<@initdata> values as arguments. |
645 | |
627 | |
646 | A common idiom is to pass your own port, monitor the spawned port, and |
628 | A common idiom is to pass a local port, immediately monitor the spawned |
647 | in the init function, monitor the original port. This two-way monitoring |
629 | port, and in the remote init function, immediately monitor the passed |
648 | ensures that both ports get cleaned up when there is a problem. |
630 | local port. This two-way monitoring ensures that both ports get cleaned up |
|
|
631 | when there is a problem. |
649 | |
632 | |
650 | Example: spawn a chat server port on C<$othernode>. |
633 | Example: spawn a chat server port on C<$othernode>. |
651 | |
634 | |
652 | # this node, executed from within a port context: |
635 | # this node, executed from within a port context: |
653 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
636 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
… | |
… | |
676 | }; |
659 | }; |
677 | _self_die if $@; |
660 | _self_die if $@; |
678 | } |
661 | } |
679 | |
662 | |
680 | sub spawn(@) { |
663 | sub spawn(@) { |
681 | my ($noderef, undef) = split /#/, shift, 2; |
664 | my ($nodeid, undef) = split /#/, shift, 2; |
682 | |
665 | |
683 | my $id = "$RUNIQ." . $ID++; |
666 | my $id = "$RUNIQ." . $ID++; |
684 | |
667 | |
685 | $_[0] =~ /::/ |
668 | $_[0] =~ /::/ |
686 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
669 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
687 | |
670 | |
688 | ($NODE{$noderef} || add_node $noderef) |
671 | snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; |
689 | ->send (["", "AnyEvent::MP::_spawn" => $id, @_]); |
|
|
690 | |
672 | |
691 | "$noderef#$id" |
673 | "$nodeid#$id" |
692 | } |
674 | } |
693 | |
675 | |
694 | =back |
676 | =item after $timeout, @msg |
695 | |
677 | |
696 | =head1 NODE MESSAGES |
678 | =item after $timeout, $callback |
697 | |
679 | |
698 | Nodes understand the following messages sent to them. Many of them take |
680 | Either sends the given message, or call the given callback, after the |
699 | arguments called C<@reply>, which will simply be used to compose a reply |
681 | specified number of seconds. |
700 | message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and |
|
|
701 | the remaining arguments are simply the message data. |
|
|
702 | |
682 | |
703 | While other messages exist, they are not public and subject to change. |
683 | This is simply a utility function that comes in handy at times - the |
|
|
684 | AnyEvent::MP author is not convinced of the wisdom of having it, though, |
|
|
685 | so it may go away in the future. |
704 | |
686 | |
705 | =over 4 |
|
|
706 | |
|
|
707 | =cut |
687 | =cut |
708 | |
688 | |
709 | =item lookup => $name, @reply |
689 | sub after($@) { |
|
|
690 | my ($timeout, @action) = @_; |
710 | |
691 | |
711 | Replies with the port ID of the specified well-known port, or C<undef>. |
692 | my $t; $t = AE::timer $timeout, 0, sub { |
712 | |
693 | undef $t; |
713 | =item devnull => ... |
694 | ref $action[0] |
714 | |
695 | ? $action[0]() |
715 | Generic data sink/CPU heat conversion. |
696 | : snd @action; |
716 | |
697 | }; |
717 | =item relay => $port, @msg |
698 | } |
718 | |
|
|
719 | Simply forwards the message to the given port. |
|
|
720 | |
|
|
721 | =item eval => $string[ @reply] |
|
|
722 | |
|
|
723 | Evaluates the given string. If C<@reply> is given, then a message of the |
|
|
724 | form C<@reply, $@, @evalres> is sent. |
|
|
725 | |
|
|
726 | Example: crash another node. |
|
|
727 | |
|
|
728 | snd $othernode, eval => "exit"; |
|
|
729 | |
|
|
730 | =item time => @reply |
|
|
731 | |
|
|
732 | Replies the the current node time to C<@reply>. |
|
|
733 | |
|
|
734 | Example: tell the current node to send the current time to C<$myport> in a |
|
|
735 | C<timereply> message. |
|
|
736 | |
|
|
737 | snd $NODE, time => $myport, timereply => 1, 2; |
|
|
738 | # => snd $myport, timereply => 1, 2, <time> |
|
|
739 | |
699 | |
740 | =back |
700 | =back |
741 | |
701 | |
742 | =head1 AnyEvent::MP vs. Distributed Erlang |
702 | =head1 AnyEvent::MP vs. Distributed Erlang |
743 | |
703 | |
… | |
… | |
753 | |
713 | |
754 | Despite the similarities, there are also some important differences: |
714 | Despite the similarities, there are also some important differences: |
755 | |
715 | |
756 | =over 4 |
716 | =over 4 |
757 | |
717 | |
758 | =item * Node references contain the recipe on how to contact them. |
718 | =item * Node IDs are arbitrary strings in AEMP. |
759 | |
719 | |
760 | Erlang relies on special naming and DNS to work everywhere in the |
720 | Erlang relies on special naming and DNS to work everywhere in the same |
761 | same way. AEMP relies on each node knowing it's own address(es), with |
721 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
762 | convenience functionality. |
722 | configuration or DNS), but will otherwise discover other odes itself. |
763 | |
723 | |
764 | This means that AEMP requires a less tightly controlled environment at the |
724 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
765 | cost of longer node references and a slightly higher management overhead. |
725 | uses "local ports are like remote ports". |
|
|
726 | |
|
|
727 | The failure modes for local ports are quite different (runtime errors |
|
|
728 | only) then for remote ports - when a local port dies, you I<know> it dies, |
|
|
729 | when a connection to another node dies, you know nothing about the other |
|
|
730 | port. |
|
|
731 | |
|
|
732 | Erlang pretends remote ports are as reliable as local ports, even when |
|
|
733 | they are not. |
|
|
734 | |
|
|
735 | AEMP encourages a "treat remote ports differently" philosophy, with local |
|
|
736 | ports being the special case/exception, where transport errors cannot |
|
|
737 | occur. |
766 | |
738 | |
767 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
739 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
768 | |
740 | |
769 | Erlang uses processes that selctively receive messages, and therefore |
741 | Erlang uses processes that selectively receive messages, and therefore |
770 | needs a queue. AEMP is event based, queuing messages would serve no useful |
742 | needs a queue. AEMP is event based, queuing messages would serve no |
771 | purpose. |
743 | useful purpose. For the same reason the pattern-matching abilities of |
|
|
744 | AnyEvent::MP are more limited, as there is little need to be able to |
|
|
745 | filter messages without dequeuing them. |
772 | |
746 | |
773 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
747 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
774 | |
748 | |
775 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
749 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
776 | |
750 | |
777 | Sending messages in Erlang is synchronous and blocks the process. AEMP |
751 | Sending messages in Erlang is synchronous and blocks the process (and |
778 | sends are immediate, connection establishment is handled in the |
752 | so does not need a queue that can overflow). AEMP sends are immediate, |
779 | background. |
753 | connection establishment is handled in the background. |
780 | |
754 | |
781 | =item * Erlang can silently lose messages, AEMP cannot. |
755 | =item * Erlang suffers from silent message loss, AEMP does not. |
782 | |
756 | |
783 | Erlang makes few guarantees on messages delivery - messages can get lost |
757 | Erlang makes few guarantees on messages delivery - messages can get lost |
784 | without any of the processes realising it (i.e. you send messages a, b, |
758 | without any of the processes realising it (i.e. you send messages a, b, |
785 | and c, and the other side only receives messages a and c). |
759 | and c, and the other side only receives messages a and c). |
786 | |
760 | |
787 | AEMP guarantees correct ordering, and the guarantee that there are no |
761 | AEMP guarantees correct ordering, and the guarantee that after one message |
788 | holes in the message sequence. |
762 | is lost, all following ones sent to the same port are lost as well, until |
789 | |
763 | monitoring raises an error, so there are no silent "holes" in the message |
790 | =item * In Erlang, processes can be declared dead and later be found to be |
764 | sequence. |
791 | alive. |
|
|
792 | |
|
|
793 | In Erlang it can happen that a monitored process is declared dead and |
|
|
794 | linked processes get killed, but later it turns out that the process is |
|
|
795 | still alive - and can receive messages. |
|
|
796 | |
|
|
797 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
798 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
799 | and then later sends messages to it, finding it is still alive. |
|
|
800 | |
765 | |
801 | =item * Erlang can send messages to the wrong port, AEMP does not. |
766 | =item * Erlang can send messages to the wrong port, AEMP does not. |
802 | |
767 | |
803 | In Erlang it is quite possible that a node that restarts reuses a process |
768 | In Erlang it is quite likely that a node that restarts reuses a process ID |
804 | ID known to other nodes for a completely different process, causing |
769 | known to other nodes for a completely different process, causing messages |
805 | messages destined for that process to end up in an unrelated process. |
770 | destined for that process to end up in an unrelated process. |
806 | |
771 | |
807 | AEMP never reuses port IDs, so old messages or old port IDs floating |
772 | AEMP never reuses port IDs, so old messages or old port IDs floating |
808 | around in the network will not be sent to an unrelated port. |
773 | around in the network will not be sent to an unrelated port. |
809 | |
774 | |
810 | =item * Erlang uses unprotected connections, AEMP uses secure |
775 | =item * Erlang uses unprotected connections, AEMP uses secure |
811 | authentication and can use TLS. |
776 | authentication and can use TLS. |
812 | |
777 | |
813 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
778 | AEMP can use a proven protocol - TLS - to protect connections and |
814 | securely authenticate nodes. |
779 | securely authenticate nodes. |
815 | |
780 | |
816 | =item * The AEMP protocol is optimised for both text-based and binary |
781 | =item * The AEMP protocol is optimised for both text-based and binary |
817 | communications. |
782 | communications. |
818 | |
783 | |
819 | The AEMP protocol, unlike the Erlang protocol, supports both |
784 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
820 | language-independent text-only protocols (good for debugging) and binary, |
785 | language independent text-only protocols (good for debugging) and binary, |
821 | language-specific serialisers (e.g. Storable). |
786 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
|
|
787 | used, the protocol is actually completely text-based. |
822 | |
788 | |
823 | It has also been carefully designed to be implementable in other languages |
789 | It has also been carefully designed to be implementable in other languages |
824 | with a minimum of work while gracefully degrading fucntionality to make the |
790 | with a minimum of work while gracefully degrading functionality to make the |
825 | protocol simple. |
791 | protocol simple. |
826 | |
792 | |
827 | =item * AEMP has more flexible monitoring options than Erlang. |
793 | =item * AEMP has more flexible monitoring options than Erlang. |
828 | |
794 | |
829 | In Erlang, you can chose to receive I<all> exit signals as messages |
795 | In Erlang, you can chose to receive I<all> exit signals as messages |
… | |
… | |
832 | Erlang, as one can choose between automatic kill, exit message or callback |
798 | Erlang, as one can choose between automatic kill, exit message or callback |
833 | on a per-process basis. |
799 | on a per-process basis. |
834 | |
800 | |
835 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
801 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
836 | |
802 | |
837 | Monitoring in Erlang is not an indicator of process death/crashes, |
803 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
838 | as linking is (except linking is unreliable in Erlang). |
804 | same way as linking is (except linking is unreliable in Erlang). |
839 | |
805 | |
840 | In AEMP, you don't "look up" registered port names or send to named ports |
806 | In AEMP, you don't "look up" registered port names or send to named ports |
841 | that might or might not be persistent. Instead, you normally spawn a port |
807 | that might or might not be persistent. Instead, you normally spawn a port |
842 | on the remote node. The init function monitors the you, and you monitor |
808 | on the remote node. The init function monitors you, and you monitor the |
843 | the remote port. Since both monitors are local to the node, they are much |
809 | remote port. Since both monitors are local to the node, they are much more |
844 | more reliable. |
810 | reliable (no need for C<spawn_link>). |
845 | |
811 | |
846 | This also saves round-trips and avoids sending messages to the wrong port |
812 | This also saves round-trips and avoids sending messages to the wrong port |
847 | (hard to do in Erlang). |
813 | (hard to do in Erlang). |
848 | |
814 | |
849 | =back |
815 | =back |
850 | |
816 | |
|
|
817 | =head1 RATIONALE |
|
|
818 | |
|
|
819 | =over 4 |
|
|
820 | |
|
|
821 | =item Why strings for port and node IDs, why not objects? |
|
|
822 | |
|
|
823 | We considered "objects", but found that the actual number of methods |
|
|
824 | that can be called are quite low. Since port and node IDs travel over |
|
|
825 | the network frequently, the serialising/deserialising would add lots of |
|
|
826 | overhead, as well as having to keep a proxy object everywhere. |
|
|
827 | |
|
|
828 | Strings can easily be printed, easily serialised etc. and need no special |
|
|
829 | procedures to be "valid". |
|
|
830 | |
|
|
831 | And as a result, a miniport consists of a single closure stored in a |
|
|
832 | global hash - it can't become much cheaper. |
|
|
833 | |
|
|
834 | =item Why favour JSON, why not a real serialising format such as Storable? |
|
|
835 | |
|
|
836 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
|
|
837 | format, but currently there is no way to make a node use Storable by |
|
|
838 | default (although all nodes will accept it). |
|
|
839 | |
|
|
840 | The default framing protocol is JSON because a) JSON::XS is many times |
|
|
841 | faster for small messages and b) most importantly, after years of |
|
|
842 | experience we found that object serialisation is causing more problems |
|
|
843 | than it solves: Just like function calls, objects simply do not travel |
|
|
844 | easily over the network, mostly because they will always be a copy, so you |
|
|
845 | always have to re-think your design. |
|
|
846 | |
|
|
847 | Keeping your messages simple, concentrating on data structures rather than |
|
|
848 | objects, will keep your messages clean, tidy and efficient. |
|
|
849 | |
|
|
850 | =back |
|
|
851 | |
851 | =head1 SEE ALSO |
852 | =head1 SEE ALSO |
|
|
853 | |
|
|
854 | L<AnyEvent::MP::Intro> - a gentle introduction. |
|
|
855 | |
|
|
856 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
|
|
857 | |
|
|
858 | L<AnyEvent::MP::Global> - network maintainance and port groups, to find |
|
|
859 | your applications. |
852 | |
860 | |
853 | L<AnyEvent>. |
861 | L<AnyEvent>. |
854 | |
862 | |
855 | =head1 AUTHOR |
863 | =head1 AUTHOR |
856 | |
864 | |