… | |
… | |
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 |
34 | |
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35 | # monitoring |
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36 | mon $port, $cb->(@msg) # callback is invoked on death |
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37 | mon $port, $otherport # kill otherport on abnormal death |
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38 | mon $port, $otherport, @msg # send message on death |
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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 - uptodate, but incomplete. |
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45 | AnyEvent::MP::Kernel - mostly stable. |
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46 | AnyEvent::MP::Global - stable API, protocol not yet final. |
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47 | |
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48 | stay tuned. |
27 | |
49 | |
28 | =head1 DESCRIPTION |
50 | =head1 DESCRIPTION |
29 | |
51 | |
30 | This module (-family) implements a simple message passing framework. |
52 | This module (-family) implements a simple message passing framework. |
31 | |
53 | |
32 | Despite its simplicity, you can securely message other processes running |
54 | Despite its simplicity, you can securely message other processes running |
33 | on the same or other hosts. |
55 | on the same or other hosts, and you can supervise entities remotely. |
34 | |
56 | |
35 | 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> |
36 | manual page. |
58 | manual page and the examples under F<eg/>. |
37 | |
59 | |
38 | At the moment, this module family is severly broken and underdocumented, |
60 | At the moment, this module family is a bit underdocumented. |
39 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
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40 | stay tuned! The basic API should be finished, however. |
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41 | |
61 | |
42 | =head1 CONCEPTS |
62 | =head1 CONCEPTS |
43 | |
63 | |
44 | =over 4 |
64 | =over 4 |
45 | |
65 | |
46 | =item port |
66 | =item port |
47 | |
67 | |
48 | A port is something you can send messages to (with the C<snd> function). |
68 | A port is something you can send messages to (with the C<snd> function). |
49 | |
69 | |
50 | Some ports allow you to register C<rcv> handlers that can match specific |
70 | Ports allow you to register C<rcv> handlers that can match all or just |
51 | messages. All C<rcv> handlers will receive messages they match, messages |
71 | some messages. Messages send to ports will not be queued, regardless of |
52 | will not be queued. |
72 | anything was listening for them or not. |
53 | |
73 | |
54 | =item port id - C<noderef#portname> |
74 | =item port ID - C<nodeid#portname> |
55 | |
75 | |
56 | A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as |
76 | A port ID is the concatenation of a node ID, a hash-mark (C<#>) as |
57 | separator, and a port name (a printable string of unspecified format). An |
77 | separator, and a port name (a printable string of unspecified format). |
58 | exception is the the node port, whose ID is identical to its node |
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59 | reference. |
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60 | |
78 | |
61 | =item node |
79 | =item node |
62 | |
80 | |
63 | A node is a single process containing at least one port - the node |
81 | A node is a single process containing at least one port - the node port, |
64 | port. You can send messages to node ports to find existing ports or to |
82 | which enables nodes to manage each other remotely, and to create new |
65 | create new ports, among other things. |
83 | ports. |
66 | |
84 | |
67 | Nodes are either private (single-process only), slaves (connected to a |
85 | Nodes are either public (have one or more listening ports) or private |
68 | master node only) or public nodes (connectable from unrelated nodes). |
86 | (no listening ports). Private nodes cannot talk to other private nodes |
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87 | currently. |
69 | |
88 | |
70 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
89 | =item node ID - C<[a-za-Z0-9_\-.:]+> |
71 | |
90 | |
72 | A node reference is a string that either simply identifies the node (for |
91 | A node ID is a string that uniquely identifies the node within a |
73 | private and slave nodes), or contains a recipe on how to reach a given |
92 | network. Depending on the configuration used, node IDs can look like a |
74 | node (for public nodes). |
93 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
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94 | doesn't interpret node IDs in any way. |
75 | |
95 | |
76 | This recipe is simply a comma-separated list of C<address:port> pairs (for |
96 | =item binds - C<ip:port> |
77 | TCP/IP, other protocols might look different). |
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78 | |
97 | |
79 | Node references come in two flavours: resolved (containing only numerical |
98 | Nodes can only talk to each other by creating some kind of connection to |
80 | addresses) or unresolved (where hostnames are used instead of addresses). |
99 | each other. To do this, nodes should listen on one or more local transport |
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100 | endpoints - binds. Currently, only standard C<ip:port> specifications can |
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101 | be used, which specify TCP ports to listen on. |
81 | |
102 | |
82 | Before using an unresolved node reference in a message you first have to |
103 | =item seeds - C<host:port> |
83 | resolve it. |
104 | |
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105 | When a node starts, it knows nothing about the network. To teach the node |
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106 | about the network it first has to contact some other node within the |
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107 | network. This node is called a seed. |
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108 | |
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109 | Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes |
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110 | are expected to be long-running, and at least one of those should always |
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111 | be available. When nodes run out of connections (e.g. due to a network |
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112 | error), they try to re-establish connections to some seednodes again to |
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113 | join the network. |
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114 | |
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115 | Apart from being sued for seeding, seednodes are not special in any way - |
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116 | every public node can be a seednode. |
84 | |
117 | |
85 | =back |
118 | =back |
86 | |
119 | |
87 | =head1 VARIABLES/FUNCTIONS |
120 | =head1 VARIABLES/FUNCTIONS |
88 | |
121 | |
… | |
… | |
90 | |
123 | |
91 | =cut |
124 | =cut |
92 | |
125 | |
93 | package AnyEvent::MP; |
126 | package AnyEvent::MP; |
94 | |
127 | |
95 | use AnyEvent::MP::Base; |
128 | use AnyEvent::MP::Kernel; |
96 | |
129 | |
97 | use common::sense; |
130 | use common::sense; |
98 | |
131 | |
99 | use Carp (); |
132 | use Carp (); |
100 | |
133 | |
101 | use AE (); |
134 | use AE (); |
102 | |
135 | |
103 | use base "Exporter"; |
136 | use base "Exporter"; |
104 | |
137 | |
105 | our $VERSION = '0.1'; |
138 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
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139 | |
106 | our @EXPORT = qw( |
140 | our @EXPORT = qw( |
107 | NODE $NODE *SELF node_of _any_ |
141 | NODE $NODE *SELF node_of after |
108 | resolve_node initialise_node |
142 | configure |
109 | snd rcv mon kil reg psub |
143 | snd rcv mon mon_guard kil reg psub spawn |
110 | port |
144 | port |
111 | ); |
145 | ); |
112 | |
146 | |
113 | our $SELF; |
147 | our $SELF; |
114 | |
148 | |
… | |
… | |
118 | kil $SELF, die => $msg; |
152 | kil $SELF, die => $msg; |
119 | } |
153 | } |
120 | |
154 | |
121 | =item $thisnode = NODE / $NODE |
155 | =item $thisnode = NODE / $NODE |
122 | |
156 | |
123 | The C<NODE> function returns, and the C<$NODE> variable contains |
157 | The C<NODE> function returns, and the C<$NODE> variable contains, the node |
124 | the noderef of the local node. The value is initialised by a call |
158 | ID of the node running in the current process. This value is initialised by |
125 | to C<become_public> or C<become_slave>, after which all local port |
159 | a call to C<configure>. |
126 | identifiers become invalid. |
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127 | |
160 | |
128 | =item $noderef = node_of $portid |
161 | =item $nodeid = node_of $port |
129 | |
162 | |
130 | Extracts and returns the noderef from a portid or a noderef. |
163 | Extracts and returns the node ID from a port ID or a node ID. |
131 | |
164 | |
132 | =item $cv = resolve_node $noderef |
165 | =item configure key => value... |
133 | |
166 | |
134 | Takes an unresolved node reference that may contain hostnames and |
167 | Before a node can talk to other nodes on the network (i.e. enter |
135 | abbreviated IDs, resolves all of them and returns a resolved node |
168 | "distributed mode") it has to configure itself - the minimum a node needs |
136 | reference. |
169 | to know is its own name, and optionally it should know the addresses of |
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170 | some other nodes in the network to discover other nodes. |
137 | |
171 | |
138 | In addition to C<address:port> pairs allowed in resolved noderefs, the |
172 | This function configures a node - it must be called exactly once (or |
139 | following forms are supported: |
173 | never) before calling other AnyEvent::MP functions. |
140 | |
174 | |
141 | =over 4 |
175 | =over 4 |
142 | |
176 | |
143 | =item the empty string |
177 | =item step 1, gathering configuration from profiles |
144 | |
178 | |
145 | An empty-string component gets resolved as if the default port (4040) was |
179 | The function first looks up a profile in the aemp configuration (see the |
146 | specified. |
180 | L<aemp> commandline utility). The profile name can be specified via the |
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181 | named C<profile> parameter. If it is missing, then the nodename (F<uname |
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182 | -n>) will be used as profile name. |
147 | |
183 | |
148 | =item naked port numbers (e.g. C<1234>) |
184 | The profile data is then gathered as follows: |
149 | |
185 | |
150 | These are resolved by prepending the local nodename and a colon, to be |
186 | First, all remaining key => value pairs (all of which are conviniently |
151 | further resolved. |
187 | undocumented at the moment) will be interpreted as configuration |
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188 | data. Then they will be overwritten by any values specified in the global |
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189 | default configuration (see the F<aemp> utility), then the chain of |
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190 | profiles chosen by the profile name (and any C<parent> attributes). |
152 | |
191 | |
153 | =item hostnames (e.g. C<localhost:1234>, C<localhost>) |
192 | That means that the values specified in the profile have highest priority |
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193 | and the values specified directly via C<configure> have lowest priority, |
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194 | and can only be used to specify defaults. |
154 | |
195 | |
155 | These are resolved by using AnyEvent::DNS to resolve them, optionally |
196 | If the profile specifies a node ID, then this will become the node ID of |
156 | looking up SRV records for the C<aemp=4040> port, if no port was |
197 | this process. If not, then the profile name will be used as node ID. The |
157 | specified. |
198 | special node ID of C<anon/> will be replaced by a random node ID. |
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199 | |
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200 | =item step 2, bind listener sockets |
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201 | |
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202 | The next step is to look up the binds in the profile, followed by binding |
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203 | aemp protocol listeners on all binds specified (it is possible and valid |
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204 | to have no binds, meaning that the node cannot be contacted form the |
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205 | outside. This means the node cannot talk to other nodes that also have no |
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206 | binds, but it can still talk to all "normal" nodes). |
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207 | |
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208 | If the profile does not specify a binds list, then a default of C<*> is |
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209 | used, meaning the node will bind on a dynamically-assigned port on every |
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210 | local IP address it finds. |
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211 | |
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212 | =item step 3, connect to seed nodes |
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213 | |
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214 | As the last step, the seeds list from the profile is passed to the |
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215 | L<AnyEvent::MP::Global> module, which will then use it to keep |
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216 | connectivity with at least one node at any point in time. |
158 | |
217 | |
159 | =back |
218 | =back |
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219 | |
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220 | Example: become a distributed node using the locla node name as profile. |
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221 | This should be the most common form of invocation for "daemon"-type nodes. |
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222 | |
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223 | configure |
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224 | |
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225 | Example: become an anonymous node. This form is often used for commandline |
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226 | clients. |
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227 | |
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228 | configure nodeid => "anon/"; |
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229 | |
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230 | Example: configure a node using a profile called seed, which si suitable |
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231 | for a seed node as it binds on all local addresses on a fixed port (4040, |
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232 | customary for aemp). |
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233 | |
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234 | # use the aemp commandline utility |
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235 | # aemp profile seed nodeid anon/ binds '*:4040' |
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236 | |
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237 | # then use it |
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238 | configure profile => "seed"; |
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239 | |
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240 | # or simply use aemp from the shell again: |
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241 | # aemp run profile seed |
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242 | |
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243 | # or provide a nicer-to-remember nodeid |
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244 | # aemp run profile seed nodeid "$(hostname)" |
160 | |
245 | |
161 | =item $SELF |
246 | =item $SELF |
162 | |
247 | |
163 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
248 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
164 | blocks. |
249 | blocks. |
165 | |
250 | |
166 | =item SELF, %SELF, @SELF... |
251 | =item *SELF, SELF, %SELF, @SELF... |
167 | |
252 | |
168 | Due to some quirks in how perl exports variables, it is impossible to |
253 | Due to some quirks in how perl exports variables, it is impossible to |
169 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
254 | just export C<$SELF>, all the symbols named C<SELF> are exported by this |
170 | module, but only C<$SELF> is currently used. |
255 | module, but only C<$SELF> is currently used. |
171 | |
256 | |
172 | =item snd $portid, type => @data |
257 | =item snd $port, type => @data |
173 | |
258 | |
174 | =item snd $portid, @msg |
259 | =item snd $port, @msg |
175 | |
260 | |
176 | Send the given message to the given port ID, which can identify either |
261 | Send the given message to the given port, which can identify either a |
177 | a local or a remote port, and can be either a string or soemthignt hat |
262 | local or a remote port, and must be a port ID. |
178 | stringifies a sa port ID (such as a port object :). |
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179 | |
263 | |
180 | While the message can be about anything, it is highly recommended to use a |
264 | While the message can be almost anything, it is highly recommended to |
181 | string as first element (a portid, or some word that indicates a request |
265 | use a string as first element (a port ID, or some word that indicates a |
182 | type etc.). |
266 | request type etc.) and to consist if only simple perl values (scalars, |
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267 | arrays, hashes) - if you think you need to pass an object, think again. |
183 | |
268 | |
184 | The message data effectively becomes read-only after a call to this |
269 | The message data logically becomes read-only after a call to this |
185 | function: modifying any argument is not allowed and can cause many |
270 | function: modifying any argument (or values referenced by them) is |
186 | problems. |
271 | forbidden, as there can be considerable time between the call to C<snd> |
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272 | and the time the message is actually being serialised - in fact, it might |
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273 | never be copied as within the same process it is simply handed to the |
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274 | receiving port. |
187 | |
275 | |
188 | The type of data you can transfer depends on the transport protocol: when |
276 | The type of data you can transfer depends on the transport protocol: when |
189 | JSON is used, then only strings, numbers and arrays and hashes consisting |
277 | JSON is used, then only strings, numbers and arrays and hashes consisting |
190 | of those are allowed (no objects). When Storable is used, then anything |
278 | of those are allowed (no objects). When Storable is used, then anything |
191 | that Storable can serialise and deserialise is allowed, and for the local |
279 | that Storable can serialise and deserialise is allowed, and for the local |
192 | node, anything can be passed. |
280 | node, anything can be passed. Best rely only on the common denominator of |
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281 | these. |
193 | |
282 | |
194 | =item kil $portid[, @reason] |
283 | =item $local_port = port |
195 | |
284 | |
196 | Kill the specified port with the given C<@reason>. |
285 | Create a new local port object and returns its port ID. Initially it has |
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286 | no callbacks set and will throw an error when it receives messages. |
197 | |
287 | |
198 | If no C<@reason> is specified, then the port is killed "normally" (linked |
288 | =item $local_port = port { my @msg = @_ } |
199 | ports will not be kileld, or even notified). |
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200 | |
289 | |
201 | Otherwise, linked ports get killed with the same reason (second form of |
290 | Creates a new local port, and returns its ID. Semantically the same as |
202 | C<mon>, see below). |
291 | creating a port and calling C<rcv $port, $callback> on it. |
203 | |
292 | |
204 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
293 | The block will be called for every message received on the port, with the |
205 | will be reported as reason C<< die => $@ >>. |
294 | global variable C<$SELF> set to the port ID. Runtime errors will cause the |
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295 | port to be C<kil>ed. The message will be passed as-is, no extra argument |
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296 | (i.e. no port ID) will be passed to the callback. |
206 | |
297 | |
207 | Transport/communication errors are reported as C<< transport_error => |
298 | If you want to stop/destroy the port, simply C<kil> it: |
208 | $message >>. |
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209 | |
299 | |
210 | =item $guard = mon $portid, $cb->(@reason) |
300 | my $port = port { |
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301 | my @msg = @_; |
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302 | ... |
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303 | kil $SELF; |
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304 | }; |
211 | |
305 | |
212 | =item $guard = mon $portid, $otherport |
306 | =cut |
213 | |
307 | |
214 | =item $guard = mon $portid, $otherport, @msg |
308 | sub rcv($@); |
215 | |
309 | |
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310 | sub _kilme { |
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311 | die "received message on port without callback"; |
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312 | } |
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313 | |
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314 | sub port(;&) { |
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315 | my $id = "$UNIQ." . $ID++; |
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316 | my $port = "$NODE#$id"; |
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317 | |
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318 | rcv $port, shift || \&_kilme; |
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319 | |
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320 | $port |
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321 | } |
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322 | |
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323 | =item rcv $local_port, $callback->(@msg) |
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324 | |
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325 | Replaces the default callback on the specified port. There is no way to |
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326 | remove the default callback: use C<sub { }> to disable it, or better |
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327 | C<kil> the port when it is no longer needed. |
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328 | |
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329 | The global C<$SELF> (exported by this module) contains C<$port> while |
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330 | executing the callback. Runtime errors during callback execution will |
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331 | result in the port being C<kil>ed. |
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332 | |
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333 | The default callback received all messages not matched by a more specific |
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334 | C<tag> match. |
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335 | |
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336 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
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337 | |
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338 | Register (or replace) callbacks to be called on messages starting with the |
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339 | given tag on the given port (and return the port), or unregister it (when |
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340 | C<$callback> is C<$undef> or missing). There can only be one callback |
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341 | registered for each tag. |
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342 | |
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343 | The original message will be passed to the callback, after the first |
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344 | element (the tag) has been removed. The callback will use the same |
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345 | environment as the default callback (see above). |
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346 | |
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347 | Example: create a port and bind receivers on it in one go. |
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348 | |
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349 | my $port = rcv port, |
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350 | msg1 => sub { ... }, |
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351 | msg2 => sub { ... }, |
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352 | ; |
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353 | |
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354 | Example: create a port, bind receivers and send it in a message elsewhere |
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355 | in one go: |
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356 | |
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357 | snd $otherport, reply => |
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358 | rcv port, |
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359 | msg1 => sub { ... }, |
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360 | ... |
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361 | ; |
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362 | |
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363 | Example: temporarily register a rcv callback for a tag matching some port |
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364 | (e.g. for a rpc reply) and unregister it after a message was received. |
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365 | |
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366 | rcv $port, $otherport => sub { |
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367 | my @reply = @_; |
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368 | |
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369 | rcv $SELF, $otherport; |
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370 | }; |
|
|
371 | |
|
|
372 | =cut |
|
|
373 | |
|
|
374 | sub rcv($@) { |
|
|
375 | my $port = shift; |
|
|
376 | my ($nodeid, $portid) = split /#/, $port, 2; |
|
|
377 | |
|
|
378 | $NODE{$nodeid} == $NODE{""} |
|
|
379 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
|
|
380 | |
|
|
381 | while (@_) { |
|
|
382 | if (ref $_[0]) { |
|
|
383 | if (my $self = $PORT_DATA{$portid}) { |
|
|
384 | "AnyEvent::MP::Port" eq ref $self |
|
|
385 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
386 | |
|
|
387 | $self->[2] = shift; |
|
|
388 | } else { |
|
|
389 | my $cb = shift; |
|
|
390 | $PORT{$portid} = sub { |
|
|
391 | local $SELF = $port; |
|
|
392 | eval { &$cb }; _self_die if $@; |
|
|
393 | }; |
|
|
394 | } |
|
|
395 | } elsif (defined $_[0]) { |
|
|
396 | my $self = $PORT_DATA{$portid} ||= do { |
|
|
397 | my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
|
|
398 | |
|
|
399 | $PORT{$portid} = sub { |
|
|
400 | local $SELF = $port; |
|
|
401 | |
|
|
402 | if (my $cb = $self->[1]{$_[0]}) { |
|
|
403 | shift; |
|
|
404 | eval { &$cb }; _self_die if $@; |
|
|
405 | } else { |
|
|
406 | &{ $self->[0] }; |
|
|
407 | } |
|
|
408 | }; |
|
|
409 | |
|
|
410 | $self |
|
|
411 | }; |
|
|
412 | |
|
|
413 | "AnyEvent::MP::Port" eq ref $self |
|
|
414 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
415 | |
|
|
416 | my ($tag, $cb) = splice @_, 0, 2; |
|
|
417 | |
|
|
418 | if (defined $cb) { |
|
|
419 | $self->[1]{$tag} = $cb; |
|
|
420 | } else { |
|
|
421 | delete $self->[1]{$tag}; |
|
|
422 | } |
|
|
423 | } |
|
|
424 | } |
|
|
425 | |
|
|
426 | $port |
|
|
427 | } |
|
|
428 | |
|
|
429 | =item $closure = psub { BLOCK } |
|
|
430 | |
|
|
431 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
|
|
432 | closure is executed, sets up the environment in the same way as in C<rcv> |
|
|
433 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
|
|
434 | |
|
|
435 | This is useful when you register callbacks from C<rcv> callbacks: |
|
|
436 | |
|
|
437 | rcv delayed_reply => sub { |
|
|
438 | my ($delay, @reply) = @_; |
|
|
439 | my $timer = AE::timer $delay, 0, psub { |
|
|
440 | snd @reply, $SELF; |
|
|
441 | }; |
|
|
442 | }; |
|
|
443 | |
|
|
444 | =cut |
|
|
445 | |
|
|
446 | sub psub(&) { |
|
|
447 | my $cb = shift; |
|
|
448 | |
|
|
449 | my $port = $SELF |
|
|
450 | or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
|
|
451 | |
|
|
452 | sub { |
|
|
453 | local $SELF = $port; |
|
|
454 | |
|
|
455 | if (wantarray) { |
|
|
456 | my @res = eval { &$cb }; |
|
|
457 | _self_die if $@; |
|
|
458 | @res |
|
|
459 | } else { |
|
|
460 | my $res = eval { &$cb }; |
|
|
461 | _self_die if $@; |
|
|
462 | $res |
|
|
463 | } |
|
|
464 | } |
|
|
465 | } |
|
|
466 | |
|
|
467 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
|
|
468 | |
|
|
469 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
|
|
470 | |
|
|
471 | =item $guard = mon $port # kill $SELF when $port dies |
|
|
472 | |
|
|
473 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
|
|
474 | |
216 | Monitor the given port and do something when the port is killed. |
475 | Monitor the given port and do something when the port is killed or |
|
|
476 | messages to it were lost, and optionally return a guard that can be used |
|
|
477 | to stop monitoring again. |
217 | |
478 | |
|
|
479 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
480 | after starting the monitor, either all messages sent to the port will |
|
|
481 | arrive, or the monitoring action will be invoked after possible message |
|
|
482 | loss has been detected. No messages will be lost "in between" (after |
|
|
483 | the first lost message no further messages will be received by the |
|
|
484 | port). After the monitoring action was invoked, further messages might get |
|
|
485 | delivered again. |
|
|
486 | |
|
|
487 | Note that monitoring-actions are one-shot: once messages are lost (and a |
|
|
488 | monitoring alert was raised), they are removed and will not trigger again. |
|
|
489 | |
218 | In the first form, the callback is simply called with any number |
490 | In the first form (callback), the callback is simply called with any |
219 | of C<@reason> elements (no @reason means that the port was deleted |
491 | number of C<@reason> elements (no @reason means that the port was deleted |
220 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
492 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
221 | C<eval> if unsure. |
493 | C<eval> if unsure. |
222 | |
494 | |
223 | In the second form, the other port will be C<kil>'ed with C<@reason>, iff |
495 | In the second form (another port given), the other port (C<$rcvport>) |
224 | a @reason was specified, i.e. on "normal" kils nothing happens, while |
496 | will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
225 | under all other conditions, the other port is killed with the same reason. |
497 | "normal" kils nothing happens, while under all other conditions, the other |
|
|
498 | port is killed with the same reason. |
226 | |
499 | |
|
|
500 | The third form (kill self) is the same as the second form, except that |
|
|
501 | C<$rvport> defaults to C<$SELF>. |
|
|
502 | |
227 | In the last form, a message of the form C<@msg, @reason> will be C<snd>. |
503 | In the last form (message), a message of the form C<@msg, @reason> will be |
|
|
504 | C<snd>. |
|
|
505 | |
|
|
506 | As a rule of thumb, monitoring requests should always monitor a port from |
|
|
507 | a local port (or callback). The reason is that kill messages might get |
|
|
508 | lost, just like any other message. Another less obvious reason is that |
|
|
509 | even monitoring requests can get lost (for exmaple, when the connection |
|
|
510 | to the other node goes down permanently). When monitoring a port locally |
|
|
511 | these problems do not exist. |
228 | |
512 | |
229 | Example: call a given callback when C<$port> is killed. |
513 | Example: call a given callback when C<$port> is killed. |
230 | |
514 | |
231 | mon $port, sub { warn "port died because of <@_>\n" }; |
515 | mon $port, sub { warn "port died because of <@_>\n" }; |
232 | |
516 | |
233 | Example: kill ourselves when C<$port> is killed abnormally. |
517 | Example: kill ourselves when C<$port> is killed abnormally. |
234 | |
518 | |
235 | mon $port, $self; |
519 | mon $port; |
236 | |
520 | |
237 | Example: send us a restart message another C<$port> is killed. |
521 | Example: send us a restart message when another C<$port> is killed. |
238 | |
522 | |
239 | mon $port, $self => "restart"; |
523 | mon $port, $self => "restart"; |
240 | |
524 | |
241 | =cut |
525 | =cut |
242 | |
526 | |
243 | sub mon { |
527 | sub mon { |
244 | my ($noderef, $port) = split /#/, shift, 2; |
528 | my ($nodeid, $port) = split /#/, shift, 2; |
245 | |
529 | |
246 | my $node = $NODE{$noderef} || add_node $noderef; |
530 | my $node = $NODE{$nodeid} || add_node $nodeid; |
247 | |
531 | |
248 | my $cb = shift; |
532 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
249 | |
533 | |
250 | unless (ref $cb) { |
534 | unless (ref $cb) { |
251 | if (@_) { |
535 | if (@_) { |
252 | # send a kill info message |
536 | # send a kill info message |
253 | my (@msg) = ($cb, @_); |
537 | my (@msg) = ($cb, @_); |
… | |
… | |
271 | is killed, the references will be freed. |
555 | is killed, the references will be freed. |
272 | |
556 | |
273 | Optionally returns a guard that will stop the monitoring. |
557 | Optionally returns a guard that will stop the monitoring. |
274 | |
558 | |
275 | This function is useful when you create e.g. timers or other watchers and |
559 | This function is useful when you create e.g. timers or other watchers and |
276 | want to free them when the port gets killed: |
560 | want to free them when the port gets killed (note the use of C<psub>): |
277 | |
561 | |
278 | $port->rcv (start => sub { |
562 | $port->rcv (start => sub { |
279 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
563 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub { |
280 | undef $timer if 0.9 < rand; |
564 | undef $timer if 0.9 < rand; |
281 | }); |
565 | }); |
282 | }); |
566 | }); |
283 | |
567 | |
284 | =cut |
568 | =cut |
285 | |
569 | |
286 | sub mon_guard { |
570 | sub mon_guard { |
287 | my ($port, @refs) = @_; |
571 | my ($port, @refs) = @_; |
288 | |
572 | |
|
|
573 | #TODO: mon-less form? |
|
|
574 | |
289 | mon $port, sub { 0 && @refs } |
575 | mon $port, sub { 0 && @refs } |
290 | } |
576 | } |
291 | |
577 | |
292 | =item lnk $port1, $port2 |
578 | =item kil $port[, @reason] |
293 | |
579 | |
294 | Link two ports. This is simply a shorthand for: |
580 | Kill the specified port with the given C<@reason>. |
295 | |
581 | |
296 | mon $port1, $port2; |
582 | If no C<@reason> is specified, then the port is killed "normally" (ports |
297 | mon $port2, $port1; |
583 | monitoring other ports will not necessarily die because a port dies |
|
|
584 | "normally"). |
298 | |
585 | |
299 | It means that if either one is killed abnormally, the other one gets |
586 | Otherwise, linked ports get killed with the same reason (second form of |
300 | killed as well. |
587 | C<mon>, see above). |
301 | |
588 | |
302 | =item $local_port = port |
589 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
|
|
590 | will be reported as reason C<< die => $@ >>. |
303 | |
591 | |
304 | Create a new local port object that can be used either as a pattern |
592 | Transport/communication errors are reported as C<< transport_error => |
305 | matching port ("full port") or a single-callback port ("miniport"), |
593 | $message >>. |
306 | depending on how C<rcv> callbacks are bound to the object. |
|
|
307 | |
594 | |
308 | =item $portid = port { my @msg = @_; $finished } |
|
|
309 | |
|
|
310 | Creates a "mini port", that is, a very lightweight port without any |
|
|
311 | pattern matching behind it, and returns its ID. |
|
|
312 | |
|
|
313 | The block will be called for every message received on the port. When the |
|
|
314 | callback returns a true value its job is considered "done" and the port |
|
|
315 | will be destroyed. Otherwise it will stay alive. |
|
|
316 | |
|
|
317 | The message will be passed as-is, no extra argument (i.e. no port id) will |
|
|
318 | be passed to the callback. |
|
|
319 | |
|
|
320 | If you need the local port id in the callback, this works nicely: |
|
|
321 | |
|
|
322 | my $port; $port = port { |
|
|
323 | snd $otherport, reply => $port; |
|
|
324 | }; |
|
|
325 | |
|
|
326 | =cut |
595 | =cut |
327 | |
596 | |
328 | sub port(;&) { |
597 | =item $port = spawn $node, $initfunc[, @initdata] |
329 | my $id = "$UNIQ." . $ID++; |
|
|
330 | my $port = "$NODE#$id"; |
|
|
331 | |
598 | |
332 | if (@_) { |
599 | Creates a port on the node C<$node> (which can also be a port ID, in which |
333 | my $cb = shift; |
600 | case it's the node where that port resides). |
334 | $PORT{$id} = sub { |
601 | |
335 | local $SELF = $port; |
602 | The port ID of the newly created port is returned immediately, and it is |
336 | eval { |
603 | possible to immediately start sending messages or to monitor the port. |
337 | &$cb |
604 | |
338 | and kil $id; |
605 | After the port has been created, the init function is called on the remote |
|
|
606 | node, in the same context as a C<rcv> callback. This function must be a |
|
|
607 | fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To |
|
|
608 | specify a function in the main program, use C<::name>. |
|
|
609 | |
|
|
610 | If the function doesn't exist, then the node tries to C<require> |
|
|
611 | the package, then the package above the package and so on (e.g. |
|
|
612 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
|
|
613 | exists or it runs out of package names. |
|
|
614 | |
|
|
615 | The init function is then called with the newly-created port as context |
|
|
616 | object (C<$SELF>) and the C<@initdata> values as arguments. |
|
|
617 | |
|
|
618 | A common idiom is to pass a local port, immediately monitor the spawned |
|
|
619 | port, and in the remote init function, immediately monitor the passed |
|
|
620 | local port. This two-way monitoring ensures that both ports get cleaned up |
|
|
621 | when there is a problem. |
|
|
622 | |
|
|
623 | Example: spawn a chat server port on C<$othernode>. |
|
|
624 | |
|
|
625 | # this node, executed from within a port context: |
|
|
626 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
|
|
627 | mon $server; |
|
|
628 | |
|
|
629 | # init function on C<$othernode> |
|
|
630 | sub connect { |
|
|
631 | my ($srcport) = @_; |
|
|
632 | |
|
|
633 | mon $srcport; |
|
|
634 | |
|
|
635 | rcv $SELF, sub { |
339 | }; |
636 | ... |
340 | _self_die if $@; |
|
|
341 | }; |
|
|
342 | } else { |
|
|
343 | my $self = bless { |
|
|
344 | id => "$NODE#$id", |
|
|
345 | }, "AnyEvent::MP::Port"; |
|
|
346 | |
|
|
347 | $PORT_DATA{$id} = $self; |
|
|
348 | $PORT{$id} = sub { |
|
|
349 | local $SELF = $port; |
|
|
350 | |
|
|
351 | eval { |
|
|
352 | for (@{ $self->{rc0}{$_[0]} }) { |
|
|
353 | $_ && &{$_->[0]} |
|
|
354 | && undef $_; |
|
|
355 | } |
|
|
356 | |
|
|
357 | for (@{ $self->{rcv}{$_[0]} }) { |
|
|
358 | $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
|
|
359 | && &{$_->[0]} |
|
|
360 | && undef $_; |
|
|
361 | } |
|
|
362 | |
|
|
363 | for (@{ $self->{any} }) { |
|
|
364 | $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
|
|
365 | && &{$_->[0]} |
|
|
366 | && undef $_; |
|
|
367 | } |
|
|
368 | }; |
|
|
369 | _self_die if $@; |
|
|
370 | }; |
637 | }; |
371 | } |
638 | } |
372 | |
639 | |
373 | $port |
|
|
374 | } |
|
|
375 | |
|
|
376 | =item reg $portid, $name |
|
|
377 | |
|
|
378 | Registers the given port under the name C<$name>. If the name already |
|
|
379 | exists it is replaced. |
|
|
380 | |
|
|
381 | A port can only be registered under one well known name. |
|
|
382 | |
|
|
383 | A port automatically becomes unregistered when it is killed. |
|
|
384 | |
|
|
385 | =cut |
640 | =cut |
386 | |
641 | |
387 | sub reg(@) { |
642 | sub _spawn { |
388 | my ($portid, $name) = @_; |
|
|
389 | |
|
|
390 | $REG{$name} = $portid; |
|
|
391 | } |
|
|
392 | |
|
|
393 | =item rcv $portid, $callback->(@msg) |
|
|
394 | |
|
|
395 | Replaces the callback on the specified miniport (or newly created port |
|
|
396 | object, see C<port>). Full ports are configured with the following calls: |
|
|
397 | |
|
|
398 | =item rcv $portid, tagstring => $callback->(@msg), ... |
|
|
399 | |
|
|
400 | =item rcv $portid, $smartmatch => $callback->(@msg), ... |
|
|
401 | |
|
|
402 | =item rcv $portid, [$smartmatch...] => $callback->(@msg), ... |
|
|
403 | |
|
|
404 | Register callbacks to be called on matching messages on the given port. |
|
|
405 | |
|
|
406 | The callback has to return a true value when its work is done, after |
|
|
407 | which is will be removed, or a false value in which case it will stay |
|
|
408 | registered. |
|
|
409 | |
|
|
410 | The global C<$SELF> (exported by this module) contains C<$portid> while |
|
|
411 | executing the callback. |
|
|
412 | |
|
|
413 | Runtime errors wdurign callback execution will result in the port being |
|
|
414 | C<kil>ed. |
|
|
415 | |
|
|
416 | If the match is an array reference, then it will be matched against the |
|
|
417 | first elements of the message, otherwise only the first element is being |
|
|
418 | matched. |
|
|
419 | |
|
|
420 | Any element in the match that is specified as C<_any_> (a function |
|
|
421 | exported by this module) matches any single element of the message. |
|
|
422 | |
|
|
423 | While not required, it is highly recommended that the first matching |
|
|
424 | element is a string identifying the message. The one-string-only match is |
|
|
425 | also the most efficient match (by far). |
|
|
426 | |
|
|
427 | =cut |
|
|
428 | |
|
|
429 | sub rcv($@) { |
|
|
430 | my $portid = shift; |
643 | my $port = shift; |
431 | my ($noderef, $port) = split /#/, $port, 2; |
644 | my $init = shift; |
432 | |
645 | |
433 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
646 | local $SELF = "$NODE#$port"; |
434 | or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught"; |
647 | eval { |
435 | |
648 | &{ load_func $init } |
436 | my $self = $PORT_DATA{$port} |
|
|
437 | or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; |
|
|
438 | |
|
|
439 | "AnyEvent::MP::Port" eq ref $self |
|
|
440 | or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; |
|
|
441 | |
|
|
442 | while (@_) { |
|
|
443 | my ($match, $cb) = splice @_, 0, 2; |
|
|
444 | |
|
|
445 | if (!ref $match) { |
|
|
446 | push @{ $self->{rc0}{$match} }, [$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 { |
|
|
453 | push @{ $self->{any} }, [$cb, $match]; |
|
|
454 | } |
|
|
455 | } |
|
|
456 | |
|
|
457 | $portid |
|
|
458 | } |
|
|
459 | |
|
|
460 | =item $closure = psub { BLOCK } |
|
|
461 | |
|
|
462 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
|
|
463 | closure is executed, sets up the environment in the same way as in C<rcv> |
|
|
464 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
|
|
465 | |
|
|
466 | This is useful when you register callbacks from C<rcv> callbacks: |
|
|
467 | |
|
|
468 | rcv delayed_reply => sub { |
|
|
469 | my ($delay, @reply) = @_; |
|
|
470 | my $timer = AE::timer $delay, 0, psub { |
|
|
471 | snd @reply, $SELF; |
|
|
472 | }; |
|
|
473 | }; |
649 | }; |
474 | |
|
|
475 | =cut |
|
|
476 | |
|
|
477 | sub psub(&) { |
|
|
478 | my $cb = shift; |
|
|
479 | |
|
|
480 | my $port = $SELF |
|
|
481 | or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
|
|
482 | |
|
|
483 | sub { |
|
|
484 | local $SELF = $port; |
|
|
485 | |
|
|
486 | if (wantarray) { |
|
|
487 | my @res = eval { &$cb }; |
|
|
488 | _self_die if $@; |
650 | _self_die if $@; |
489 | @res |
651 | } |
490 | } else { |
652 | |
491 | my $res = eval { &$cb }; |
653 | sub spawn(@) { |
492 | _self_die if $@; |
654 | my ($nodeid, undef) = split /#/, shift, 2; |
493 | $res |
655 | |
494 | } |
656 | my $id = "$RUNIQ." . $ID++; |
|
|
657 | |
|
|
658 | $_[0] =~ /::/ |
|
|
659 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
|
|
660 | |
|
|
661 | snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; |
|
|
662 | |
|
|
663 | "$nodeid#$id" |
|
|
664 | } |
|
|
665 | |
|
|
666 | =item after $timeout, @msg |
|
|
667 | |
|
|
668 | =item after $timeout, $callback |
|
|
669 | |
|
|
670 | Either sends the given message, or call the given callback, after the |
|
|
671 | specified number of seconds. |
|
|
672 | |
|
|
673 | This is simply a utility function that comes in handy at times - the |
|
|
674 | AnyEvent::MP author is not convinced of the wisdom of having it, though, |
|
|
675 | so it may go away in the future. |
|
|
676 | |
|
|
677 | =cut |
|
|
678 | |
|
|
679 | sub after($@) { |
|
|
680 | my ($timeout, @action) = @_; |
|
|
681 | |
|
|
682 | my $t; $t = AE::timer $timeout, 0, sub { |
|
|
683 | undef $t; |
|
|
684 | ref $action[0] |
|
|
685 | ? $action[0]() |
|
|
686 | : snd @action; |
495 | } |
687 | }; |
496 | } |
688 | } |
497 | |
689 | |
498 | =back |
690 | =back |
499 | |
691 | |
500 | =head1 FUNCTIONS FOR NODES |
692 | =head1 AnyEvent::MP vs. Distributed Erlang |
|
|
693 | |
|
|
694 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
|
|
695 | == aemp node, Erlang process == aemp port), so many of the documents and |
|
|
696 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
|
|
697 | sample: |
|
|
698 | |
|
|
699 | http://www.Erlang.se/doc/programming_rules.shtml |
|
|
700 | http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
|
|
701 | http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
|
|
702 | http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
|
|
703 | |
|
|
704 | Despite the similarities, there are also some important differences: |
501 | |
705 | |
502 | =over 4 |
706 | =over 4 |
503 | |
707 | |
504 | =item become_public $noderef |
708 | =item * Node IDs are arbitrary strings in AEMP. |
505 | |
709 | |
506 | Tells the node to become a public node, i.e. reachable from other nodes. |
|
|
507 | |
|
|
508 | The first argument is the (unresolved) node reference of the local node |
|
|
509 | (if missing then the empty string is used). |
|
|
510 | |
|
|
511 | It is quite common to not specify anything, in which case the local node |
|
|
512 | tries to listen on the default port, or to only specify a port number, in |
|
|
513 | which case AnyEvent::MP tries to guess the local addresses. |
|
|
514 | |
|
|
515 | =cut |
|
|
516 | |
|
|
517 | =back |
|
|
518 | |
|
|
519 | =head1 NODE MESSAGES |
|
|
520 | |
|
|
521 | Nodes understand the following messages sent to them. Many of them take |
|
|
522 | arguments called C<@reply>, which will simply be used to compose a reply |
|
|
523 | message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and |
|
|
524 | the remaining arguments are simply the message data. |
|
|
525 | |
|
|
526 | While other messages exist, they are not public and subject to change. |
|
|
527 | |
|
|
528 | =over 4 |
|
|
529 | |
|
|
530 | =cut |
|
|
531 | |
|
|
532 | =item lookup => $name, @reply |
|
|
533 | |
|
|
534 | Replies with the port ID of the specified well-known port, or C<undef>. |
|
|
535 | |
|
|
536 | =item devnull => ... |
|
|
537 | |
|
|
538 | Generic data sink/CPU heat conversion. |
|
|
539 | |
|
|
540 | =item relay => $port, @msg |
|
|
541 | |
|
|
542 | Simply forwards the message to the given port. |
|
|
543 | |
|
|
544 | =item eval => $string[ @reply] |
|
|
545 | |
|
|
546 | Evaluates the given string. If C<@reply> is given, then a message of the |
|
|
547 | form C<@reply, $@, @evalres> is sent. |
|
|
548 | |
|
|
549 | Example: crash another node. |
|
|
550 | |
|
|
551 | snd $othernode, eval => "exit"; |
|
|
552 | |
|
|
553 | =item time => @reply |
|
|
554 | |
|
|
555 | Replies the the current node time to C<@reply>. |
|
|
556 | |
|
|
557 | Example: tell the current node to send the current time to C<$myport> in a |
|
|
558 | C<timereply> message. |
|
|
559 | |
|
|
560 | snd $NODE, time => $myport, timereply => 1, 2; |
|
|
561 | # => snd $myport, timereply => 1, 2, <time> |
|
|
562 | |
|
|
563 | =back |
|
|
564 | |
|
|
565 | =head1 AnyEvent::MP vs. Distributed Erlang |
|
|
566 | |
|
|
567 | AnyEvent::MP got lots of its ideas from distributed erlang (erlang node |
|
|
568 | == aemp node, erlang process == aemp port), so many of the documents and |
|
|
569 | programming techniques employed by erlang apply to AnyEvent::MP. Here is a |
|
|
570 | sample: |
|
|
571 | |
|
|
572 | http://www.erlang.se/doc/programming_rules.shtml |
|
|
573 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
|
|
574 | http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 |
|
|
575 | http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
|
|
576 | |
|
|
577 | Despite the similarities, there are also some important differences: |
|
|
578 | |
|
|
579 | =over 4 |
|
|
580 | |
|
|
581 | =item * Node references contain the recipe on how to contact them. |
|
|
582 | |
|
|
583 | Erlang relies on special naming and DNS to work everywhere in the |
710 | Erlang relies on special naming and DNS to work everywhere in the same |
584 | same way. AEMP relies on each node knowing it's own address(es), with |
711 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
585 | convenience functionality. |
712 | configuraiton or DNS), but will otherwise discover other odes itself. |
586 | |
713 | |
587 | This means that AEMP requires a less tightly controlled environment at the |
714 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
588 | cost of longer node references and a slightly higher management overhead. |
715 | uses "local ports are like remote ports". |
|
|
716 | |
|
|
717 | The failure modes for local ports are quite different (runtime errors |
|
|
718 | only) then for remote ports - when a local port dies, you I<know> it dies, |
|
|
719 | when a connection to another node dies, you know nothing about the other |
|
|
720 | port. |
|
|
721 | |
|
|
722 | Erlang pretends remote ports are as reliable as local ports, even when |
|
|
723 | they are not. |
|
|
724 | |
|
|
725 | AEMP encourages a "treat remote ports differently" philosophy, with local |
|
|
726 | ports being the special case/exception, where transport errors cannot |
|
|
727 | occur. |
589 | |
728 | |
590 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
729 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
591 | |
730 | |
592 | Erlang uses processes that selctively receive messages, and therefore |
731 | Erlang uses processes that selectively receive messages, and therefore |
593 | needs a queue. AEMP is event based, queuing messages would serve no useful |
732 | needs a queue. AEMP is event based, queuing messages would serve no |
594 | purpose. |
733 | useful purpose. For the same reason the pattern-matching abilities of |
|
|
734 | AnyEvent::MP are more limited, as there is little need to be able to |
|
|
735 | filter messages without dequeing them. |
595 | |
736 | |
596 | (But see L<Coro::MP> for a more erlang-like process model on top of AEMP). |
737 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
597 | |
738 | |
598 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
739 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
599 | |
740 | |
600 | Sending messages in erlang is synchronous and blocks the process. AEMP |
741 | Sending messages in Erlang is synchronous and blocks the process (and |
601 | sends are immediate, connection establishment is handled in the |
742 | so does not need a queue that can overflow). AEMP sends are immediate, |
602 | background. |
743 | connection establishment is handled in the background. |
603 | |
744 | |
604 | =item * Erlang can silently lose messages, AEMP cannot. |
745 | =item * Erlang suffers from silent message loss, AEMP does not. |
605 | |
746 | |
606 | Erlang makes few guarantees on messages delivery - messages can get lost |
747 | Erlang makes few guarantees on messages delivery - messages can get lost |
607 | without any of the processes realising it (i.e. you send messages a, b, |
748 | without any of the processes realising it (i.e. you send messages a, b, |
608 | and c, and the other side only receives messages a and c). |
749 | and c, and the other side only receives messages a and c). |
609 | |
750 | |
610 | AEMP guarantees correct ordering, and the guarantee that there are no |
751 | AEMP guarantees correct ordering, and the guarantee that after one message |
611 | holes in the message sequence. |
752 | is lost, all following ones sent to the same port are lost as well, until |
612 | |
753 | monitoring raises an error, so there are no silent "holes" in the message |
613 | =item * In erlang, processes can be declared dead and later be found to be |
754 | sequence. |
614 | alive. |
|
|
615 | |
|
|
616 | In erlang it can happen that a monitored process is declared dead and |
|
|
617 | linked processes get killed, but later it turns out that the process is |
|
|
618 | still alive - and can receive messages. |
|
|
619 | |
|
|
620 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
621 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
622 | and then later sends messages to it, finding it is still alive. |
|
|
623 | |
755 | |
624 | =item * Erlang can send messages to the wrong port, AEMP does not. |
756 | =item * Erlang can send messages to the wrong port, AEMP does not. |
625 | |
757 | |
626 | In erlang it is quite possible that a node that restarts reuses a process |
758 | In Erlang it is quite likely that a node that restarts reuses a process ID |
627 | ID known to other nodes for a completely different process, causing |
759 | known to other nodes for a completely different process, causing messages |
628 | messages destined for that process to end up in an unrelated process. |
760 | destined for that process to end up in an unrelated process. |
629 | |
761 | |
630 | AEMP never reuses port IDs, so old messages or old port IDs floating |
762 | AEMP never reuses port IDs, so old messages or old port IDs floating |
631 | around in the network will not be sent to an unrelated port. |
763 | around in the network will not be sent to an unrelated port. |
632 | |
764 | |
633 | =item * Erlang uses unprotected connections, AEMP uses secure |
765 | =item * Erlang uses unprotected connections, AEMP uses secure |
634 | authentication and can use TLS. |
766 | authentication and can use TLS. |
635 | |
767 | |
636 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
768 | AEMP can use a proven protocol - TLS - to protect connections and |
637 | securely authenticate nodes. |
769 | securely authenticate nodes. |
638 | |
770 | |
639 | =item * The AEMP protocol is optimised for both text-based and binary |
771 | =item * The AEMP protocol is optimised for both text-based and binary |
640 | communications. |
772 | communications. |
641 | |
773 | |
642 | The AEMP protocol, unlike the erlang protocol, supports both |
774 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
643 | language-independent text-only protocols (good for debugging) and binary, |
775 | language independent text-only protocols (good for debugging) and binary, |
644 | language-specific serialisers (e.g. Storable). |
776 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
|
|
777 | used, the protocol is actually completely text-based. |
645 | |
778 | |
646 | It has also been carefully designed to be implementable in other languages |
779 | It has also been carefully designed to be implementable in other languages |
647 | with a minimum of work while gracefully degrading fucntionality to make the |
780 | with a minimum of work while gracefully degrading functionality to make the |
648 | protocol simple. |
781 | protocol simple. |
649 | |
782 | |
|
|
783 | =item * AEMP has more flexible monitoring options than Erlang. |
|
|
784 | |
|
|
785 | In Erlang, you can chose to receive I<all> exit signals as messages |
|
|
786 | or I<none>, there is no in-between, so monitoring single processes is |
|
|
787 | difficult to implement. Monitoring in AEMP is more flexible than in |
|
|
788 | Erlang, as one can choose between automatic kill, exit message or callback |
|
|
789 | on a per-process basis. |
|
|
790 | |
|
|
791 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
|
|
792 | |
|
|
793 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
|
|
794 | same way as linking is (except linking is unreliable in Erlang). |
|
|
795 | |
|
|
796 | In AEMP, you don't "look up" registered port names or send to named ports |
|
|
797 | that might or might not be persistent. Instead, you normally spawn a port |
|
|
798 | on the remote node. The init function monitors you, and you monitor the |
|
|
799 | remote port. Since both monitors are local to the node, they are much more |
|
|
800 | reliable (no need for C<spawn_link>). |
|
|
801 | |
|
|
802 | This also saves round-trips and avoids sending messages to the wrong port |
|
|
803 | (hard to do in Erlang). |
|
|
804 | |
650 | =back |
805 | =back |
651 | |
806 | |
|
|
807 | =head1 RATIONALE |
|
|
808 | |
|
|
809 | =over 4 |
|
|
810 | |
|
|
811 | =item Why strings for port and node IDs, why not objects? |
|
|
812 | |
|
|
813 | We considered "objects", but found that the actual number of methods |
|
|
814 | that can be called are quite low. Since port and node IDs travel over |
|
|
815 | the network frequently, the serialising/deserialising would add lots of |
|
|
816 | overhead, as well as having to keep a proxy object everywhere. |
|
|
817 | |
|
|
818 | Strings can easily be printed, easily serialised etc. and need no special |
|
|
819 | procedures to be "valid". |
|
|
820 | |
|
|
821 | And as a result, a miniport consists of a single closure stored in a |
|
|
822 | global hash - it can't become much cheaper. |
|
|
823 | |
|
|
824 | =item Why favour JSON, why not a real serialising format such as Storable? |
|
|
825 | |
|
|
826 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
|
|
827 | format, but currently there is no way to make a node use Storable by |
|
|
828 | default (although all nodes will accept it). |
|
|
829 | |
|
|
830 | The default framing protocol is JSON because a) JSON::XS is many times |
|
|
831 | faster for small messages and b) most importantly, after years of |
|
|
832 | experience we found that object serialisation is causing more problems |
|
|
833 | than it solves: Just like function calls, objects simply do not travel |
|
|
834 | easily over the network, mostly because they will always be a copy, so you |
|
|
835 | always have to re-think your design. |
|
|
836 | |
|
|
837 | Keeping your messages simple, concentrating on data structures rather than |
|
|
838 | objects, will keep your messages clean, tidy and efficient. |
|
|
839 | |
|
|
840 | =back |
|
|
841 | |
652 | =head1 SEE ALSO |
842 | =head1 SEE ALSO |
|
|
843 | |
|
|
844 | L<AnyEvent::MP::Intro> - a gentle introduction. |
|
|
845 | |
|
|
846 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
|
|
847 | |
|
|
848 | L<AnyEvent::MP::Global> - network maintainance and port groups, to find |
|
|
849 | your applications. |
653 | |
850 | |
654 | L<AnyEvent>. |
851 | L<AnyEvent>. |
655 | |
852 | |
656 | =head1 AUTHOR |
853 | =head1 AUTHOR |
657 | |
854 | |