1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | AnyEvent::MP - multi-processing/message-passing framework |
3 | AnyEvent::MP - erlang-style multi-processing/message-passing framework |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::MP; |
7 | use AnyEvent::MP; |
8 | |
8 | |
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 | |
15 | # initialise the node so it can send/receive messages |
14 | # initialise the node so it can send/receive messages |
16 | initialise_node; # -OR- |
15 | configure; |
17 | initialise_node "localhost:4040"; # -OR- |
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18 | initialise_node "slave/", "localhost:4040" |
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19 | |
16 | |
20 | # ports are message endpoints |
17 | # ports are message destinations |
21 | |
18 | |
22 | # sending messages |
19 | # sending messages |
23 | snd $port, type => data...; |
20 | snd $port, type => data...; |
24 | snd $port, @msg; |
21 | snd $port, @msg; |
25 | snd @msg_with_first_element_being_a_port; |
22 | snd @msg_with_first_element_being_a_port; |
26 | |
23 | |
27 | # creating/using ports, the simple way |
24 | # creating/using ports, the simple way |
28 | my $simple_port = port { my @msg = @_; 0 }; |
25 | my $simple_port = port { my @msg = @_ }; |
29 | |
26 | |
30 | # creating/using ports, tagged message matching |
27 | # creating/using ports, tagged message matching |
31 | my $port = port; |
28 | my $port = port; |
32 | rcv $port, ping => sub { snd $_[0], "pong"; 0 }; |
29 | rcv $port, ping => sub { snd $_[0], "pong" }; |
33 | rcv $port, pong => sub { warn "pong received\n"; 0 }; |
30 | rcv $port, pong => sub { warn "pong received\n" }; |
34 | |
31 | |
35 | # create a port on another node |
32 | # create a port on another node |
36 | my $port = spawn $node, $initfunc, @initdata; |
33 | my $port = spawn $node, $initfunc, @initdata; |
37 | |
34 | |
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35 | # destroy a port again |
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36 | kil $port; # "normal" kill |
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37 | kil $port, my_error => "everything is broken"; # error kill |
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38 | |
38 | # monitoring |
39 | # monitoring |
39 | mon $port, $cb->(@msg) # callback is invoked on death |
40 | mon $localport, $cb->(@msg) # callback is invoked on death |
40 | mon $port, $otherport # kill otherport on abnormal death |
41 | mon $localport, $otherport # kill otherport on abnormal death |
41 | mon $port, $otherport, @msg # send message on death |
42 | mon $localport, $otherport, @msg # send message on death |
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43 | |
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44 | # temporarily execute code in port context |
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45 | peval $port, sub { die "kill the port!" }; |
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46 | |
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47 | # execute callbacks in $SELF port context |
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48 | my $timer = AE::timer 1, 0, psub { |
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49 | die "kill the port, delayed"; |
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50 | }; |
42 | |
51 | |
43 | =head1 CURRENT STATUS |
52 | =head1 CURRENT STATUS |
44 | |
53 | |
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54 | bin/aemp - stable. |
45 | AnyEvent::MP - stable API, should work |
55 | AnyEvent::MP - stable API, should work. |
46 | AnyEvent::MP::Intro - outdated |
56 | AnyEvent::MP::Intro - explains most concepts. |
47 | AnyEvent::MP::Kernel - WIP |
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48 | AnyEvent::MP::Transport - mostly stable |
57 | AnyEvent::MP::Kernel - mostly stable API. |
49 | |
58 | AnyEvent::MP::Global - stable API. |
50 | stay tuned. |
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51 | |
59 | |
52 | =head1 DESCRIPTION |
60 | =head1 DESCRIPTION |
53 | |
61 | |
54 | This module (-family) implements a simple message passing framework. |
62 | This module (-family) implements a simple message passing framework. |
55 | |
63 | |
56 | Despite its simplicity, you can securely message other processes running |
64 | Despite its simplicity, you can securely message other processes running |
57 | on the same or other hosts. |
65 | on the same or other hosts, and you can supervise entities remotely. |
58 | |
66 | |
59 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
67 | For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
60 | manual page. |
68 | manual page and the examples under F<eg/>. |
61 | |
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62 | At the moment, this module family is severly broken and underdocumented, |
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63 | so do not use. This was uploaded mainly to reserve the CPAN namespace - |
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64 | stay tuned! |
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65 | |
69 | |
66 | =head1 CONCEPTS |
70 | =head1 CONCEPTS |
67 | |
71 | |
68 | =over 4 |
72 | =over 4 |
69 | |
73 | |
70 | =item port |
74 | =item port |
71 | |
75 | |
72 | A port is something you can send messages to (with the C<snd> function). |
76 | Not to be confused with a TCP port, a "port" is something you can send |
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77 | messages to (with the C<snd> function). |
73 | |
78 | |
74 | Ports allow you to register C<rcv> handlers that can match all or just |
79 | Ports allow you to register C<rcv> handlers that can match all or just |
75 | some messages. Messages will not be queued. |
80 | some messages. Messages send to ports will not be queued, regardless of |
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81 | anything was listening for them or not. |
76 | |
82 | |
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83 | Ports are represented by (printable) strings called "port IDs". |
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84 | |
77 | =item port id - C<noderef#portname> |
85 | =item port ID - C<nodeid#portname> |
78 | |
86 | |
79 | A port ID is the concatenation of a noderef, a hash-mark (C<#>) as |
87 | A port ID is the concatenation of a node ID, a hash-mark (C<#>) as |
80 | separator, and a port name (a printable string of unspecified format). An |
88 | separator, and a port name (a printable string of unspecified format). |
81 | exception is the the node port, whose ID is identical to its node |
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82 | reference. |
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83 | |
89 | |
84 | =item node |
90 | =item node |
85 | |
91 | |
86 | A node is a single process containing at least one port - the node port, |
92 | A node is a single process containing at least one port - the node port, |
87 | which provides nodes to manage each other remotely, and to create new |
93 | which enables nodes to manage each other remotely, and to create new |
88 | ports. |
94 | ports. |
89 | |
95 | |
90 | Nodes are either private (single-process only), slaves (connected to a |
96 | Nodes are either public (have one or more listening ports) or private |
91 | master node only) or public nodes (connectable from unrelated nodes). |
97 | (no listening ports). Private nodes cannot talk to other private nodes |
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98 | currently, but all nodes can talk to public nodes. |
92 | |
99 | |
93 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
100 | Nodes is represented by (printable) strings called "node IDs". |
94 | |
101 | |
95 | A node reference is a string that either simply identifies the node (for |
102 | =item node ID - C<[A-Za-z0-9_\-.:]*> |
96 | private and slave nodes), or contains a recipe on how to reach a given |
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97 | node (for public nodes). |
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98 | |
103 | |
99 | This recipe is simply a comma-separated list of C<address:port> pairs (for |
104 | A node ID is a string that uniquely identifies the node within a |
100 | TCP/IP, other protocols might look different). |
105 | network. Depending on the configuration used, node IDs can look like a |
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106 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
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107 | doesn't interpret node IDs in any way except to uniquely identify a node. |
101 | |
108 | |
102 | Node references come in two flavours: resolved (containing only numerical |
109 | =item binds - C<ip:port> |
103 | addresses) or unresolved (where hostnames are used instead of addresses). |
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104 | |
110 | |
105 | Before using an unresolved node reference in a message you first have to |
111 | Nodes can only talk to each other by creating some kind of connection to |
106 | resolve it. |
112 | each other. To do this, nodes should listen on one or more local transport |
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113 | endpoints - binds. |
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114 | |
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115 | Currently, only standard C<ip:port> specifications can be used, which |
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116 | specify TCP ports to listen on. So a bind is basically just a tcp socket |
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117 | in listening mode thta accepts conenctions form other nodes. |
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118 | |
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119 | =item seed nodes |
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120 | |
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121 | When a node starts, it knows nothing about the network it is in - it |
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122 | needs to connect to at least one other node that is already in the |
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123 | network. These other nodes are called "seed nodes". |
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124 | |
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125 | Seed nodes themselves are not special - they are seed nodes only because |
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126 | some other node I<uses> them as such, but any node can be used as seed |
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127 | node for other nodes, and eahc node cna use a different set of seed nodes. |
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128 | |
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129 | In addition to discovering the network, seed nodes are also used to |
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130 | maintain the network - all nodes using the same seed node form are part of |
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131 | the same network. If a network is split into multiple subnets because e.g. |
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132 | the network link between the parts goes down, then using the same seed |
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133 | nodes for all nodes ensures that eventually the subnets get merged again. |
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134 | |
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135 | Seed nodes are expected to be long-running, and at least one seed node |
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136 | should always be available. They should also be relatively responsive - a |
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137 | seed node that blocks for long periods will slow down everybody else. |
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138 | |
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139 | For small networks, it's best if every node uses the same set of seed |
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140 | nodes. For large networks, it can be useful to specify "regional" seed |
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141 | nodes for most nodes in an area, and use all seed nodes as seed nodes for |
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142 | each other. What's important is that all seed nodes connections form a |
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143 | complete graph, so that the network cannot split into separate subnets |
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144 | forever. |
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145 | |
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146 | Seed nodes are represented by seed IDs. |
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147 | |
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148 | =item seed IDs - C<host:port> |
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149 | |
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150 | Seed IDs are transport endpoint(s) (usually a hostname/IP address and a |
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151 | TCP port) of nodes that should be used as seed nodes. |
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152 | |
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153 | =item global nodes |
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154 | |
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155 | An AEMP network needs a discovery service - nodes need to know how to |
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156 | connect to other nodes they only know by name. In addition, AEMP offers a |
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157 | distributed "group database", which maps group names to a list of strings |
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158 | - for example, to register worker ports. |
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159 | |
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160 | A network needs at least one global node to work, and allows every node to |
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161 | be a global node. |
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162 | |
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163 | Any node that loads the L<AnyEvent::MP::Global> module becomes a global |
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164 | node and tries to keep connections to all other nodes. So while it can |
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165 | make sense to make every node "global" in small networks, it usually makes |
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166 | sense to only make seed nodes into global nodes in large networks (nodes |
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167 | keep connections to seed nodes and global nodes, so makign them the same |
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168 | reduces overhead). |
107 | |
169 | |
108 | =back |
170 | =back |
109 | |
171 | |
110 | =head1 VARIABLES/FUNCTIONS |
172 | =head1 VARIABLES/FUNCTIONS |
111 | |
173 | |
… | |
… | |
123 | |
185 | |
124 | use AE (); |
186 | use AE (); |
125 | |
187 | |
126 | use base "Exporter"; |
188 | use base "Exporter"; |
127 | |
189 | |
128 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
190 | our $VERSION = '1.30'; |
129 | |
191 | |
130 | our @EXPORT = qw( |
192 | our @EXPORT = qw( |
131 | NODE $NODE *SELF node_of _any_ |
193 | NODE $NODE *SELF node_of after |
132 | resolve_node initialise_node |
194 | configure |
133 | snd rcv mon kil reg psub spawn |
195 | snd rcv mon mon_guard kil psub peval spawn cal |
134 | port |
196 | port |
135 | ); |
197 | ); |
136 | |
198 | |
137 | our $SELF; |
199 | our $SELF; |
138 | |
200 | |
… | |
… | |
142 | kil $SELF, die => $msg; |
204 | kil $SELF, die => $msg; |
143 | } |
205 | } |
144 | |
206 | |
145 | =item $thisnode = NODE / $NODE |
207 | =item $thisnode = NODE / $NODE |
146 | |
208 | |
147 | The C<NODE> function returns, and the C<$NODE> variable contains the |
209 | The C<NODE> function returns, and the C<$NODE> variable contains, the node |
148 | noderef of the local node. The value is initialised by a call to |
210 | ID of the node running in the current process. This value is initialised by |
149 | C<initialise_node>. |
211 | a call to C<configure>. |
150 | |
212 | |
151 | =item $noderef = node_of $port |
213 | =item $nodeid = node_of $port |
152 | |
214 | |
153 | Extracts and returns the noderef from a port ID or a noderef. |
215 | Extracts and returns the node ID from a port ID or a node ID. |
154 | |
216 | |
155 | =item initialise_node $noderef, $seednode, $seednode... |
217 | =item configure $profile, key => value... |
156 | |
218 | |
157 | =item initialise_node "slave/", $master, $master... |
219 | =item configure key => value... |
158 | |
220 | |
159 | Before a node can talk to other nodes on the network it has to initialise |
221 | Before a node can talk to other nodes on the network (i.e. enter |
160 | itself - the minimum a node needs to know is it's own name, and optionally |
222 | "distributed mode") it has to configure itself - the minimum a node needs |
161 | it should know the noderefs of some other nodes in the network. |
223 | to know is its own name, and optionally it should know the addresses of |
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224 | some other nodes in the network to discover other nodes. |
162 | |
225 | |
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226 | The key/value pairs are basically the same ones as documented for the |
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227 | F<aemp> command line utility (sans the set/del prefix). |
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228 | |
163 | This function initialises a node - it must be called exactly once (or |
229 | This function configures a node - it must be called exactly once (or |
164 | never) before calling other AnyEvent::MP functions. |
230 | never) before calling other AnyEvent::MP functions. |
165 | |
231 | |
166 | All arguments (optionally except for the first) are noderefs, which can be |
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167 | either resolved or unresolved. |
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168 | |
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169 | The first argument will be looked up in the configuration database first |
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170 | (if it is C<undef> then the current nodename will be used instead) to find |
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171 | the relevant configuration profile (see L<aemp>). If none is found then |
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172 | the default configuration is used. The configuration supplies additional |
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173 | seed/master nodes and can override the actual noderef. |
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174 | |
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175 | There are two types of networked nodes, public nodes and slave nodes: |
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176 | |
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177 | =over 4 |
232 | =over 4 |
178 | |
233 | |
179 | =item public nodes |
234 | =item step 1, gathering configuration from profiles |
180 | |
235 | |
181 | For public nodes, C<$noderef> (supplied either directly to |
236 | The function first looks up a profile in the aemp configuration (see the |
182 | C<initialise_node> or indirectly via a profile or the nodename) must be a |
237 | L<aemp> commandline utility). The profile name can be specified via the |
183 | noderef (possibly unresolved, in which case it will be resolved). |
238 | named C<profile> parameter or can simply be the first parameter). If it is |
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239 | missing, then the nodename (F<uname -n>) will be used as profile name. |
184 | |
240 | |
185 | After resolving, the node will bind itself on all endpoints and try to |
241 | The profile data is then gathered as follows: |
186 | connect to all additional C<$seednodes> that are specified. Seednodes are |
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187 | optional and can be used to quickly bootstrap the node into an existing |
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188 | network. |
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189 | |
242 | |
190 | =item slave nodes |
243 | First, all remaining key => value pairs (all of which are conveniently |
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244 | undocumented at the moment) will be interpreted as configuration |
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245 | data. Then they will be overwritten by any values specified in the global |
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246 | default configuration (see the F<aemp> utility), then the chain of |
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247 | profiles chosen by the profile name (and any C<parent> attributes). |
191 | |
248 | |
192 | When the C<$noderef> (either as given or overriden by the config file) |
249 | That means that the values specified in the profile have highest priority |
193 | is the special string C<slave/>, then the node will become a slave |
250 | and the values specified directly via C<configure> have lowest priority, |
194 | node. Slave nodes cannot be contacted from outside and will route most of |
251 | and can only be used to specify defaults. |
195 | their traffic to the master node that they attach to. |
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196 | |
252 | |
197 | At least one additional noderef is required (either by specifying it |
253 | If the profile specifies a node ID, then this will become the node ID of |
198 | directly or because it is part of the configuration profile): The node |
254 | this process. If not, then the profile name will be used as node ID. The |
199 | will try to connect to all of them and will become a slave attached to the |
255 | special node ID of C<anon/> will be replaced by a random node ID. |
200 | first node it can successfully connect to. |
256 | |
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257 | =item step 2, bind listener sockets |
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258 | |
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259 | The next step is to look up the binds in the profile, followed by binding |
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260 | aemp protocol listeners on all binds specified (it is possible and valid |
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261 | to have no binds, meaning that the node cannot be contacted form the |
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262 | outside. This means the node cannot talk to other nodes that also have no |
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263 | binds, but it can still talk to all "normal" nodes). |
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264 | |
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265 | If the profile does not specify a binds list, then a default of C<*> is |
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266 | used, meaning the node will bind on a dynamically-assigned port on every |
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267 | local IP address it finds. |
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268 | |
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269 | =item step 3, connect to seed nodes |
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270 | |
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271 | As the last step, the seed ID list from the profile is passed to the |
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272 | L<AnyEvent::MP::Global> module, which will then use it to keep |
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273 | connectivity with at least one node at any point in time. |
201 | |
274 | |
202 | =back |
275 | =back |
203 | |
276 | |
204 | This function will block until all nodes have been resolved and, for slave |
277 | Example: become a distributed node using the local node name as profile. |
205 | nodes, until it has successfully established a connection to a master |
278 | This should be the most common form of invocation for "daemon"-type nodes. |
206 | server. |
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207 | |
279 | |
208 | Example: become a public node listening on the guessed noderef, or the one |
280 | configure |
209 | specified via C<aemp> for the current node. This should be the most common |
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210 | form of invocation for "daemon"-type nodes. |
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211 | |
281 | |
212 | initialise_node; |
282 | Example: become an anonymous node. This form is often used for commandline |
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283 | clients. |
213 | |
284 | |
214 | Example: become a slave node to any of the the seednodes specified via |
285 | configure nodeid => "anon/"; |
215 | C<aemp>. This form is often used for commandline clients. |
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216 | |
286 | |
217 | initialise_node "slave/"; |
287 | Example: configure a node using a profile called seed, which si suitable |
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288 | for a seed node as it binds on all local addresses on a fixed port (4040, |
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289 | customary for aemp). |
218 | |
290 | |
219 | Example: become a slave node to any of the specified master servers. This |
291 | # use the aemp commandline utility |
220 | form is also often used for commandline clients. |
292 | # aemp profile seed nodeid anon/ binds '*:4040' |
221 | |
293 | |
222 | initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
294 | # then use it |
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295 | configure profile => "seed"; |
223 | |
296 | |
224 | Example: become a public node, and try to contact some well-known master |
297 | # or simply use aemp from the shell again: |
225 | servers to become part of the network. |
298 | # aemp run profile seed |
226 | |
299 | |
227 | initialise_node undef, "master1", "master2"; |
300 | # or provide a nicer-to-remember nodeid |
228 | |
301 | # aemp run profile seed nodeid "$(hostname)" |
229 | Example: become a public node listening on port C<4041>. |
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230 | |
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231 | initialise_node 4041; |
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232 | |
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233 | Example: become a public node, only visible on localhost port 4044. |
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234 | |
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235 | initialise_node "localhost:4044"; |
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236 | |
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237 | =item $cv = resolve_node $noderef |
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238 | |
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239 | Takes an unresolved node reference that may contain hostnames and |
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240 | abbreviated IDs, resolves all of them and returns a resolved node |
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241 | reference. |
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242 | |
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243 | In addition to C<address:port> pairs allowed in resolved noderefs, the |
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244 | following forms are supported: |
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245 | |
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246 | =over 4 |
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247 | |
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248 | =item the empty string |
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249 | |
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250 | An empty-string component gets resolved as if the default port (4040) was |
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251 | specified. |
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252 | |
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253 | =item naked port numbers (e.g. C<1234>) |
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254 | |
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255 | These are resolved by prepending the local nodename and a colon, to be |
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256 | further resolved. |
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257 | |
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258 | =item hostnames (e.g. C<localhost:1234>, C<localhost>) |
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259 | |
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260 | These are resolved by using AnyEvent::DNS to resolve them, optionally |
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261 | looking up SRV records for the C<aemp=4040> port, if no port was |
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262 | specified. |
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263 | |
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264 | =back |
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265 | |
302 | |
266 | =item $SELF |
303 | =item $SELF |
267 | |
304 | |
268 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
305 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
269 | blocks. |
306 | blocks. |
270 | |
307 | |
271 | =item SELF, %SELF, @SELF... |
308 | =item *SELF, SELF, %SELF, @SELF... |
272 | |
309 | |
273 | Due to some quirks in how perl exports variables, it is impossible to |
310 | Due to some quirks in how perl exports variables, it is impossible to |
274 | just export C<$SELF>, all the symbols called C<SELF> are exported by this |
311 | just export C<$SELF>, all the symbols named C<SELF> are exported by this |
275 | module, but only C<$SELF> is currently used. |
312 | module, but only C<$SELF> is currently used. |
276 | |
313 | |
277 | =item snd $port, type => @data |
314 | =item snd $port, type => @data |
278 | |
315 | |
279 | =item snd $port, @msg |
316 | =item snd $port, @msg |
280 | |
317 | |
281 | Send the given message to the given port ID, which can identify either |
318 | Send the given message to the given port, which can identify either a |
282 | a local or a remote port, and must be a port ID. |
319 | local or a remote port, and must be a port ID. |
283 | |
320 | |
284 | While the message can be about anything, it is highly recommended to use a |
321 | While the message can be almost anything, it is highly recommended to |
285 | string as first element (a port ID, or some word that indicates a request |
322 | use a string as first element (a port ID, or some word that indicates a |
286 | type etc.). |
323 | request type etc.) and to consist if only simple perl values (scalars, |
|
|
324 | arrays, hashes) - if you think you need to pass an object, think again. |
287 | |
325 | |
288 | The message data effectively becomes read-only after a call to this |
326 | The message data logically becomes read-only after a call to this |
289 | function: modifying any argument is not allowed and can cause many |
327 | function: modifying any argument (or values referenced by them) is |
290 | problems. |
328 | forbidden, as there can be considerable time between the call to C<snd> |
|
|
329 | and the time the message is actually being serialised - in fact, it might |
|
|
330 | never be copied as within the same process it is simply handed to the |
|
|
331 | receiving port. |
291 | |
332 | |
292 | The type of data you can transfer depends on the transport protocol: when |
333 | The type of data you can transfer depends on the transport protocol: when |
293 | JSON is used, then only strings, numbers and arrays and hashes consisting |
334 | JSON is used, then only strings, numbers and arrays and hashes consisting |
294 | of those are allowed (no objects). When Storable is used, then anything |
335 | of those are allowed (no objects). When Storable is used, then anything |
295 | that Storable can serialise and deserialise is allowed, and for the local |
336 | that Storable can serialise and deserialise is allowed, and for the local |
296 | node, anything can be passed. |
337 | node, anything can be passed. Best rely only on the common denominator of |
|
|
338 | these. |
297 | |
339 | |
298 | =item $local_port = port |
340 | =item $local_port = port |
299 | |
341 | |
300 | Create a new local port object and returns its port ID. Initially it has |
342 | Create a new local port object and returns its port ID. Initially it has |
301 | no callbacks set and will throw an error when it receives messages. |
343 | no callbacks set and will throw an error when it receives messages. |
… | |
… | |
348 | The default callback received all messages not matched by a more specific |
390 | The default callback received all messages not matched by a more specific |
349 | C<tag> match. |
391 | C<tag> match. |
350 | |
392 | |
351 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
393 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
352 | |
394 | |
353 | Register callbacks to be called on messages starting with the given tag on |
395 | Register (or replace) callbacks to be called on messages starting with the |
354 | the given port (and return the port), or unregister it (when C<$callback> |
396 | given tag on the given port (and return the port), or unregister it (when |
355 | is C<$undef>). |
397 | C<$callback> is C<$undef> or missing). There can only be one callback |
|
|
398 | registered for each tag. |
356 | |
399 | |
357 | The original message will be passed to the callback, after the first |
400 | The original message will be passed to the callback, after the first |
358 | element (the tag) has been removed. The callback will use the same |
401 | element (the tag) has been removed. The callback will use the same |
359 | environment as the default callback (see above). |
402 | environment as the default callback (see above). |
360 | |
403 | |
… | |
… | |
372 | rcv port, |
415 | rcv port, |
373 | msg1 => sub { ... }, |
416 | msg1 => sub { ... }, |
374 | ... |
417 | ... |
375 | ; |
418 | ; |
376 | |
419 | |
|
|
420 | Example: temporarily register a rcv callback for a tag matching some port |
|
|
421 | (e.g. for an rpc reply) and unregister it after a message was received. |
|
|
422 | |
|
|
423 | rcv $port, $otherport => sub { |
|
|
424 | my @reply = @_; |
|
|
425 | |
|
|
426 | rcv $SELF, $otherport; |
|
|
427 | }; |
|
|
428 | |
377 | =cut |
429 | =cut |
378 | |
430 | |
379 | sub rcv($@) { |
431 | sub rcv($@) { |
380 | my $port = shift; |
432 | my $port = shift; |
381 | my ($noderef, $portid) = split /#/, $port, 2; |
433 | my ($nodeid, $portid) = split /#/, $port, 2; |
382 | |
434 | |
383 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
435 | $NODE{$nodeid} == $NODE{""} |
384 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
436 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
385 | |
437 | |
386 | while (@_) { |
438 | while (@_) { |
387 | if (ref $_[0]) { |
439 | if (ref $_[0]) { |
388 | if (my $self = $PORT_DATA{$portid}) { |
440 | if (my $self = $PORT_DATA{$portid}) { |
389 | "AnyEvent::MP::Port" eq ref $self |
441 | "AnyEvent::MP::Port" eq ref $self |
390 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
442 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
391 | |
443 | |
392 | $self->[2] = shift; |
444 | $self->[0] = shift; |
393 | } else { |
445 | } else { |
394 | my $cb = shift; |
446 | my $cb = shift; |
395 | $PORT{$portid} = sub { |
447 | $PORT{$portid} = sub { |
396 | local $SELF = $port; |
448 | local $SELF = $port; |
397 | eval { &$cb }; _self_die if $@; |
449 | eval { &$cb }; _self_die if $@; |
398 | }; |
450 | }; |
399 | } |
451 | } |
400 | } elsif (defined $_[0]) { |
452 | } elsif (defined $_[0]) { |
401 | my $self = $PORT_DATA{$portid} ||= do { |
453 | my $self = $PORT_DATA{$portid} ||= do { |
402 | my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
454 | my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
403 | |
455 | |
404 | $PORT{$portid} = sub { |
456 | $PORT{$portid} = sub { |
405 | local $SELF = $port; |
457 | local $SELF = $port; |
406 | |
458 | |
407 | if (my $cb = $self->[1]{$_[0]}) { |
459 | if (my $cb = $self->[1]{$_[0]}) { |
… | |
… | |
429 | } |
481 | } |
430 | |
482 | |
431 | $port |
483 | $port |
432 | } |
484 | } |
433 | |
485 | |
|
|
486 | =item peval $port, $coderef[, @args] |
|
|
487 | |
|
|
488 | Evaluates the given C<$codref> within the contetx of C<$port>, that is, |
|
|
489 | when the code throews an exception the C<$port> will be killed. |
|
|
490 | |
|
|
491 | Any remaining args will be passed to the callback. Any return values will |
|
|
492 | be returned to the caller. |
|
|
493 | |
|
|
494 | This is useful when you temporarily want to execute code in the context of |
|
|
495 | a port. |
|
|
496 | |
|
|
497 | Example: create a port and run some initialisation code in it's context. |
|
|
498 | |
|
|
499 | my $port = port { ... }; |
|
|
500 | |
|
|
501 | peval $port, sub { |
|
|
502 | init |
|
|
503 | or die "unable to init"; |
|
|
504 | }; |
|
|
505 | |
|
|
506 | =cut |
|
|
507 | |
|
|
508 | sub peval($$) { |
|
|
509 | local $SELF = shift; |
|
|
510 | my $cb = shift; |
|
|
511 | |
|
|
512 | if (wantarray) { |
|
|
513 | my @res = eval { &$cb }; |
|
|
514 | _self_die if $@; |
|
|
515 | @res |
|
|
516 | } else { |
|
|
517 | my $res = eval { &$cb }; |
|
|
518 | _self_die if $@; |
|
|
519 | $res |
|
|
520 | } |
|
|
521 | } |
|
|
522 | |
434 | =item $closure = psub { BLOCK } |
523 | =item $closure = psub { BLOCK } |
435 | |
524 | |
436 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
525 | Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
437 | closure is executed, sets up the environment in the same way as in C<rcv> |
526 | closure is executed, sets up the environment in the same way as in C<rcv> |
438 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
527 | callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
|
|
528 | |
|
|
529 | The effect is basically as if it returned C<< sub { peval $SELF, sub { |
|
|
530 | BLOCK }, @_ } >>. |
439 | |
531 | |
440 | This is useful when you register callbacks from C<rcv> callbacks: |
532 | This is useful when you register callbacks from C<rcv> callbacks: |
441 | |
533 | |
442 | rcv delayed_reply => sub { |
534 | rcv delayed_reply => sub { |
443 | my ($delay, @reply) = @_; |
535 | my ($delay, @reply) = @_; |
… | |
… | |
467 | $res |
559 | $res |
468 | } |
560 | } |
469 | } |
561 | } |
470 | } |
562 | } |
471 | |
563 | |
472 | =item $guard = mon $port, $cb->(@reason) |
564 | =item $guard = mon $port, $cb->(@reason) # call $cb when $port dies |
473 | |
565 | |
474 | =item $guard = mon $port, $rcvport |
566 | =item $guard = mon $port, $rcvport # kill $rcvport when $port dies |
475 | |
567 | |
476 | =item $guard = mon $port |
568 | =item $guard = mon $port # kill $SELF when $port dies |
477 | |
569 | |
478 | =item $guard = mon $port, $rcvport, @msg |
570 | =item $guard = mon $port, $rcvport, @msg # send a message when $port dies |
479 | |
571 | |
480 | Monitor the given port and do something when the port is killed or |
572 | Monitor the given port and do something when the port is killed or |
481 | messages to it were lost, and optionally return a guard that can be used |
573 | messages to it were lost, and optionally return a guard that can be used |
482 | to stop monitoring again. |
574 | to stop monitoring again. |
483 | |
|
|
484 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
485 | that after starting the monitor, either all messages sent to the port |
|
|
486 | will arrive, or the monitoring action will be invoked after possible |
|
|
487 | message loss has been detected. No messages will be lost "in between" |
|
|
488 | (after the first lost message no further messages will be received by the |
|
|
489 | port). After the monitoring action was invoked, further messages might get |
|
|
490 | delivered again. |
|
|
491 | |
575 | |
492 | In the first form (callback), the callback is simply called with any |
576 | In the first form (callback), the callback is simply called with any |
493 | number of C<@reason> elements (no @reason means that the port was deleted |
577 | number of C<@reason> elements (no @reason means that the port was deleted |
494 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
578 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
495 | C<eval> if unsure. |
579 | C<eval> if unsure. |
496 | |
580 | |
497 | In the second form (another port given), the other port (C<$rcvport>) |
581 | In the second form (another port given), the other port (C<$rcvport>) |
498 | will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
582 | will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on |
499 | "normal" kils nothing happens, while under all other conditions, the other |
583 | "normal" kils nothing happens, while under all other conditions, the other |
500 | port is killed with the same reason. |
584 | port is killed with the same reason. |
501 | |
585 | |
502 | The third form (kill self) is the same as the second form, except that |
586 | The third form (kill self) is the same as the second form, except that |
503 | C<$rvport> defaults to C<$SELF>. |
587 | C<$rvport> defaults to C<$SELF>. |
504 | |
588 | |
505 | In the last form (message), a message of the form C<@msg, @reason> will be |
589 | In the last form (message), a message of the form C<@msg, @reason> will be |
506 | C<snd>. |
590 | C<snd>. |
|
|
591 | |
|
|
592 | Monitoring-actions are one-shot: once messages are lost (and a monitoring |
|
|
593 | alert was raised), they are removed and will not trigger again. |
507 | |
594 | |
508 | As a rule of thumb, monitoring requests should always monitor a port from |
595 | As a rule of thumb, monitoring requests should always monitor a port from |
509 | a local port (or callback). The reason is that kill messages might get |
596 | a local port (or callback). The reason is that kill messages might get |
510 | lost, just like any other message. Another less obvious reason is that |
597 | lost, just like any other message. Another less obvious reason is that |
511 | even monitoring requests can get lost (for exmaple, when the connection |
598 | even monitoring requests can get lost (for example, when the connection |
512 | to the other node goes down permanently). When monitoring a port locally |
599 | to the other node goes down permanently). When monitoring a port locally |
513 | these problems do not exist. |
600 | these problems do not exist. |
514 | |
601 | |
|
|
602 | C<mon> effectively guarantees that, in the absence of hardware failures, |
|
|
603 | after starting the monitor, either all messages sent to the port will |
|
|
604 | arrive, or the monitoring action will be invoked after possible message |
|
|
605 | loss has been detected. No messages will be lost "in between" (after |
|
|
606 | the first lost message no further messages will be received by the |
|
|
607 | port). After the monitoring action was invoked, further messages might get |
|
|
608 | delivered again. |
|
|
609 | |
|
|
610 | Inter-host-connection timeouts and monitoring depend on the transport |
|
|
611 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
|
|
612 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
|
|
613 | non-idle connection, and usually around two hours for idle connections). |
|
|
614 | |
|
|
615 | This means that monitoring is good for program errors and cleaning up |
|
|
616 | stuff eventually, but they are no replacement for a timeout when you need |
|
|
617 | to ensure some maximum latency. |
|
|
618 | |
515 | Example: call a given callback when C<$port> is killed. |
619 | Example: call a given callback when C<$port> is killed. |
516 | |
620 | |
517 | mon $port, sub { warn "port died because of <@_>\n" }; |
621 | mon $port, sub { warn "port died because of <@_>\n" }; |
518 | |
622 | |
519 | Example: kill ourselves when C<$port> is killed abnormally. |
623 | Example: kill ourselves when C<$port> is killed abnormally. |
… | |
… | |
525 | mon $port, $self => "restart"; |
629 | mon $port, $self => "restart"; |
526 | |
630 | |
527 | =cut |
631 | =cut |
528 | |
632 | |
529 | sub mon { |
633 | sub mon { |
530 | my ($noderef, $port) = split /#/, shift, 2; |
634 | my ($nodeid, $port) = split /#/, shift, 2; |
531 | |
635 | |
532 | my $node = $NODE{$noderef} || add_node $noderef; |
636 | my $node = $NODE{$nodeid} || add_node $nodeid; |
533 | |
637 | |
534 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
638 | my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
535 | |
639 | |
536 | unless (ref $cb) { |
640 | unless (ref $cb) { |
537 | if (@_) { |
641 | if (@_) { |
… | |
… | |
546 | } |
650 | } |
547 | |
651 | |
548 | $node->monitor ($port, $cb); |
652 | $node->monitor ($port, $cb); |
549 | |
653 | |
550 | defined wantarray |
654 | defined wantarray |
551 | and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
655 | and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }) |
552 | } |
656 | } |
553 | |
657 | |
554 | =item $guard = mon_guard $port, $ref, $ref... |
658 | =item $guard = mon_guard $port, $ref, $ref... |
555 | |
659 | |
556 | Monitors the given C<$port> and keeps the passed references. When the port |
660 | Monitors the given C<$port> and keeps the passed references. When the port |
557 | is killed, the references will be freed. |
661 | is killed, the references will be freed. |
558 | |
662 | |
559 | Optionally returns a guard that will stop the monitoring. |
663 | Optionally returns a guard that will stop the monitoring. |
560 | |
664 | |
561 | This function is useful when you create e.g. timers or other watchers and |
665 | This function is useful when you create e.g. timers or other watchers and |
562 | want to free them when the port gets killed: |
666 | want to free them when the port gets killed (note the use of C<psub>): |
563 | |
667 | |
564 | $port->rcv (start => sub { |
668 | $port->rcv (start => sub { |
565 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
669 | my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub { |
566 | undef $timer if 0.9 < rand; |
670 | undef $timer if 0.9 < rand; |
567 | }); |
671 | }); |
568 | }); |
672 | }); |
569 | |
673 | |
570 | =cut |
674 | =cut |
… | |
… | |
579 | |
683 | |
580 | =item kil $port[, @reason] |
684 | =item kil $port[, @reason] |
581 | |
685 | |
582 | Kill the specified port with the given C<@reason>. |
686 | Kill the specified port with the given C<@reason>. |
583 | |
687 | |
584 | If no C<@reason> is specified, then the port is killed "normally" (linked |
688 | If no C<@reason> is specified, then the port is killed "normally" - |
585 | ports will not be kileld, or even notified). |
689 | monitor callback will be invoked, but the kil will not cause linked ports |
|
|
690 | (C<mon $mport, $lport> form) to get killed. |
586 | |
691 | |
587 | Otherwise, linked ports get killed with the same reason (second form of |
692 | If a C<@reason> is specified, then linked ports (C<mon $mport, $lport> |
588 | C<mon>, see below). |
693 | form) get killed with the same reason. |
589 | |
694 | |
590 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
695 | Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
591 | will be reported as reason C<< die => $@ >>. |
696 | will be reported as reason C<< die => $@ >>. |
592 | |
697 | |
593 | Transport/communication errors are reported as C<< transport_error => |
698 | Transport/communication errors are reported as C<< transport_error => |
… | |
… | |
598 | =item $port = spawn $node, $initfunc[, @initdata] |
703 | =item $port = spawn $node, $initfunc[, @initdata] |
599 | |
704 | |
600 | Creates a port on the node C<$node> (which can also be a port ID, in which |
705 | Creates a port on the node C<$node> (which can also be a port ID, in which |
601 | case it's the node where that port resides). |
706 | case it's the node where that port resides). |
602 | |
707 | |
603 | The port ID of the newly created port is return immediately, and it is |
708 | The port ID of the newly created port is returned immediately, and it is |
604 | permissible to immediately start sending messages or monitor the port. |
709 | possible to immediately start sending messages or to monitor the port. |
605 | |
710 | |
606 | After the port has been created, the init function is |
711 | After the port has been created, the init function is called on the remote |
607 | called. This function must be a fully-qualified function name |
712 | node, in the same context as a C<rcv> callback. This function must be a |
608 | (e.g. C<MyApp::Chat::Server::init>). To specify a function in the main |
713 | fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To |
609 | program, use C<::name>. |
714 | specify a function in the main program, use C<::name>. |
610 | |
715 | |
611 | If the function doesn't exist, then the node tries to C<require> |
716 | If the function doesn't exist, then the node tries to C<require> |
612 | the package, then the package above the package and so on (e.g. |
717 | the package, then the package above the package and so on (e.g. |
613 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
718 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
614 | exists or it runs out of package names. |
719 | exists or it runs out of package names. |
615 | |
720 | |
616 | The init function is then called with the newly-created port as context |
721 | The init function is then called with the newly-created port as context |
617 | object (C<$SELF>) and the C<@initdata> values as arguments. |
722 | object (C<$SELF>) and the C<@initdata> values as arguments. It I<must> |
|
|
723 | call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise |
|
|
724 | the port might not get created. |
618 | |
725 | |
619 | A common idiom is to pass your own port, monitor the spawned port, and |
726 | A common idiom is to pass a local port, immediately monitor the spawned |
620 | in the init function, monitor the original port. This two-way monitoring |
727 | port, and in the remote init function, immediately monitor the passed |
621 | ensures that both ports get cleaned up when there is a problem. |
728 | local port. This two-way monitoring ensures that both ports get cleaned up |
|
|
729 | when there is a problem. |
|
|
730 | |
|
|
731 | C<spawn> guarantees that the C<$initfunc> has no visible effects on the |
|
|
732 | caller before C<spawn> returns (by delaying invocation when spawn is |
|
|
733 | called for the local node). |
622 | |
734 | |
623 | Example: spawn a chat server port on C<$othernode>. |
735 | Example: spawn a chat server port on C<$othernode>. |
624 | |
736 | |
625 | # this node, executed from within a port context: |
737 | # this node, executed from within a port context: |
626 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
738 | my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
… | |
… | |
641 | |
753 | |
642 | sub _spawn { |
754 | sub _spawn { |
643 | my $port = shift; |
755 | my $port = shift; |
644 | my $init = shift; |
756 | my $init = shift; |
645 | |
757 | |
|
|
758 | # rcv will create the actual port |
646 | local $SELF = "$NODE#$port"; |
759 | local $SELF = "$NODE#$port"; |
647 | eval { |
760 | eval { |
648 | &{ load_func $init } |
761 | &{ load_func $init } |
649 | }; |
762 | }; |
650 | _self_die if $@; |
763 | _self_die if $@; |
651 | } |
764 | } |
652 | |
765 | |
653 | sub spawn(@) { |
766 | sub spawn(@) { |
654 | my ($noderef, undef) = split /#/, shift, 2; |
767 | my ($nodeid, undef) = split /#/, shift, 2; |
655 | |
768 | |
656 | my $id = "$RUNIQ." . $ID++; |
769 | my $id = "$RUNIQ." . $ID++; |
657 | |
770 | |
658 | $_[0] =~ /::/ |
771 | $_[0] =~ /::/ |
659 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
772 | or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
660 | |
773 | |
661 | ($NODE{$noderef} || add_node $noderef) |
774 | snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; |
662 | ->send (["", "AnyEvent::MP::_spawn" => $id, @_]); |
|
|
663 | |
775 | |
664 | "$noderef#$id" |
776 | "$nodeid#$id" |
665 | } |
777 | } |
666 | |
778 | |
667 | =back |
779 | =item after $timeout, @msg |
668 | |
780 | |
669 | =head1 NODE MESSAGES |
781 | =item after $timeout, $callback |
670 | |
782 | |
671 | Nodes understand the following messages sent to them. Many of them take |
783 | Either sends the given message, or call the given callback, after the |
672 | arguments called C<@reply>, which will simply be used to compose a reply |
784 | specified number of seconds. |
673 | message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and |
|
|
674 | the remaining arguments are simply the message data. |
|
|
675 | |
785 | |
676 | While other messages exist, they are not public and subject to change. |
786 | This is simply a utility function that comes in handy at times - the |
|
|
787 | AnyEvent::MP author is not convinced of the wisdom of having it, though, |
|
|
788 | so it may go away in the future. |
677 | |
789 | |
678 | =over 4 |
|
|
679 | |
|
|
680 | =cut |
790 | =cut |
681 | |
791 | |
682 | =item lookup => $name, @reply |
792 | sub after($@) { |
|
|
793 | my ($timeout, @action) = @_; |
683 | |
794 | |
684 | Replies with the port ID of the specified well-known port, or C<undef>. |
795 | my $t; $t = AE::timer $timeout, 0, sub { |
|
|
796 | undef $t; |
|
|
797 | ref $action[0] |
|
|
798 | ? $action[0]() |
|
|
799 | : snd @action; |
|
|
800 | }; |
|
|
801 | } |
685 | |
802 | |
686 | =item devnull => ... |
803 | =item cal $port, @msg, $callback[, $timeout] |
687 | |
804 | |
688 | Generic data sink/CPU heat conversion. |
805 | A simple form of RPC - sends a message to the given C<$port> with the |
|
|
806 | given contents (C<@msg>), but adds a reply port to the message. |
689 | |
807 | |
690 | =item relay => $port, @msg |
808 | The reply port is created temporarily just for the purpose of receiving |
|
|
809 | the reply, and will be C<kil>ed when no longer needed. |
691 | |
810 | |
692 | Simply forwards the message to the given port. |
811 | A reply message sent to the port is passed to the C<$callback> as-is. |
693 | |
812 | |
694 | =item eval => $string[ @reply] |
813 | If an optional time-out (in seconds) is given and it is not C<undef>, |
|
|
814 | then the callback will be called without any arguments after the time-out |
|
|
815 | elapsed and the port is C<kil>ed. |
695 | |
816 | |
696 | Evaluates the given string. If C<@reply> is given, then a message of the |
817 | If no time-out is given (or it is C<undef>), then the local port will |
697 | form C<@reply, $@, @evalres> is sent. |
818 | monitor the remote port instead, so it eventually gets cleaned-up. |
698 | |
819 | |
699 | Example: crash another node. |
820 | Currently this function returns the temporary port, but this "feature" |
|
|
821 | might go in future versions unless you can make a convincing case that |
|
|
822 | this is indeed useful for something. |
700 | |
823 | |
701 | snd $othernode, eval => "exit"; |
824 | =cut |
702 | |
825 | |
703 | =item time => @reply |
826 | sub cal(@) { |
|
|
827 | my $timeout = ref $_[-1] ? undef : pop; |
|
|
828 | my $cb = pop; |
704 | |
829 | |
705 | Replies the the current node time to C<@reply>. |
830 | my $port = port { |
|
|
831 | undef $timeout; |
|
|
832 | kil $SELF; |
|
|
833 | &$cb; |
|
|
834 | }; |
706 | |
835 | |
707 | Example: tell the current node to send the current time to C<$myport> in a |
836 | if (defined $timeout) { |
708 | C<timereply> message. |
837 | $timeout = AE::timer $timeout, 0, sub { |
|
|
838 | undef $timeout; |
|
|
839 | kil $port; |
|
|
840 | $cb->(); |
|
|
841 | }; |
|
|
842 | } else { |
|
|
843 | mon $_[0], sub { |
|
|
844 | kil $port; |
|
|
845 | $cb->(); |
|
|
846 | }; |
|
|
847 | } |
709 | |
848 | |
710 | snd $NODE, time => $myport, timereply => 1, 2; |
849 | push @_, $port; |
711 | # => snd $myport, timereply => 1, 2, <time> |
850 | &snd; |
|
|
851 | |
|
|
852 | $port |
|
|
853 | } |
712 | |
854 | |
713 | =back |
855 | =back |
714 | |
856 | |
715 | =head1 AnyEvent::MP vs. Distributed Erlang |
857 | =head1 AnyEvent::MP vs. Distributed Erlang |
716 | |
858 | |
717 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
859 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
718 | == aemp node, Erlang process == aemp port), so many of the documents and |
860 | == aemp node, Erlang process == aemp port), so many of the documents and |
719 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
861 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
720 | sample: |
862 | sample: |
721 | |
863 | |
722 | http://www.Erlang.se/doc/programming_rules.shtml |
864 | http://www.erlang.se/doc/programming_rules.shtml |
723 | http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
865 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
724 | http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
866 | http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 |
725 | http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
867 | http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
726 | |
868 | |
727 | Despite the similarities, there are also some important differences: |
869 | Despite the similarities, there are also some important differences: |
728 | |
870 | |
729 | =over 4 |
871 | =over 4 |
730 | |
872 | |
731 | =item * Node references contain the recipe on how to contact them. |
873 | =item * Node IDs are arbitrary strings in AEMP. |
732 | |
874 | |
733 | Erlang relies on special naming and DNS to work everywhere in the |
875 | Erlang relies on special naming and DNS to work everywhere in the same |
734 | same way. AEMP relies on each node knowing it's own address(es), with |
876 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
735 | convenience functionality. |
877 | configuration or DNS), and possibly the addresses of some seed nodes, but |
|
|
878 | will otherwise discover other nodes (and their IDs) itself. |
736 | |
879 | |
737 | This means that AEMP requires a less tightly controlled environment at the |
|
|
738 | cost of longer node references and a slightly higher management overhead. |
|
|
739 | |
|
|
740 | =item Erlang has a "remote ports are like local ports" philosophy, AEMP |
880 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
741 | uses "local ports are like remote ports". |
881 | uses "local ports are like remote ports". |
742 | |
882 | |
743 | The failure modes for local ports are quite different (runtime errors |
883 | The failure modes for local ports are quite different (runtime errors |
744 | only) then for remote ports - when a local port dies, you I<know> it dies, |
884 | only) then for remote ports - when a local port dies, you I<know> it dies, |
745 | when a connection to another node dies, you know nothing about the other |
885 | when a connection to another node dies, you know nothing about the other |
… | |
… | |
752 | ports being the special case/exception, where transport errors cannot |
892 | ports being the special case/exception, where transport errors cannot |
753 | occur. |
893 | occur. |
754 | |
894 | |
755 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
895 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
756 | |
896 | |
757 | Erlang uses processes that selectively receive messages, and therefore |
897 | Erlang uses processes that selectively receive messages out of order, and |
758 | needs a queue. AEMP is event based, queuing messages would serve no |
898 | therefore needs a queue. AEMP is event based, queuing messages would serve |
759 | useful purpose. For the same reason the pattern-matching abilities of |
899 | no useful purpose. For the same reason the pattern-matching abilities |
760 | AnyEvent::MP are more limited, as there is little need to be able to |
900 | of AnyEvent::MP are more limited, as there is little need to be able to |
761 | filter messages without dequeing them. |
901 | filter messages without dequeuing them. |
762 | |
902 | |
763 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
903 | This is not a philosophical difference, but simply stems from AnyEvent::MP |
|
|
904 | being event-based, while Erlang is process-based. |
|
|
905 | |
|
|
906 | You cna have a look at L<Coro::MP> for a more Erlang-like process model on |
|
|
907 | top of AEMP and Coro threads. |
764 | |
908 | |
765 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
909 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
766 | |
910 | |
767 | Sending messages in Erlang is synchronous and blocks the process (and |
911 | Sending messages in Erlang is synchronous and blocks the process until |
|
|
912 | a conenction has been established and the message sent (and so does not |
768 | so does not need a queue that can overflow). AEMP sends are immediate, |
913 | need a queue that can overflow). AEMP sends return immediately, connection |
769 | connection establishment is handled in the background. |
914 | establishment is handled in the background. |
770 | |
915 | |
771 | =item * Erlang suffers from silent message loss, AEMP does not. |
916 | =item * Erlang suffers from silent message loss, AEMP does not. |
772 | |
917 | |
773 | Erlang makes few guarantees on messages delivery - messages can get lost |
918 | Erlang implements few guarantees on messages delivery - messages can get |
774 | without any of the processes realising it (i.e. you send messages a, b, |
919 | lost without any of the processes realising it (i.e. you send messages a, |
775 | and c, and the other side only receives messages a and c). |
920 | b, and c, and the other side only receives messages a and c). |
776 | |
921 | |
777 | AEMP guarantees correct ordering, and the guarantee that there are no |
922 | AEMP guarantees (modulo hardware errors) correct ordering, and the |
|
|
923 | guarantee that after one message is lost, all following ones sent to the |
|
|
924 | same port are lost as well, until monitoring raises an error, so there are |
778 | holes in the message sequence. |
925 | no silent "holes" in the message sequence. |
779 | |
926 | |
780 | =item * In Erlang, processes can be declared dead and later be found to be |
927 | If you want your software to be very reliable, you have to cope with |
781 | alive. |
928 | corrupted and even out-of-order messages in both Erlang and AEMP. AEMP |
782 | |
929 | simply tries to work better in common error cases, such as when a network |
783 | In Erlang it can happen that a monitored process is declared dead and |
930 | link goes down. |
784 | linked processes get killed, but later it turns out that the process is |
|
|
785 | still alive - and can receive messages. |
|
|
786 | |
|
|
787 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
788 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
789 | and then later sends messages to it, finding it is still alive. |
|
|
790 | |
931 | |
791 | =item * Erlang can send messages to the wrong port, AEMP does not. |
932 | =item * Erlang can send messages to the wrong port, AEMP does not. |
792 | |
933 | |
793 | In Erlang it is quite likely that a node that restarts reuses a process ID |
934 | In Erlang it is quite likely that a node that restarts reuses an Erlang |
794 | known to other nodes for a completely different process, causing messages |
935 | process ID known to other nodes for a completely different process, |
795 | destined for that process to end up in an unrelated process. |
936 | causing messages destined for that process to end up in an unrelated |
|
|
937 | process. |
796 | |
938 | |
797 | AEMP never reuses port IDs, so old messages or old port IDs floating |
939 | AEMP does not reuse port IDs, so old messages or old port IDs floating |
798 | around in the network will not be sent to an unrelated port. |
940 | around in the network will not be sent to an unrelated port. |
799 | |
941 | |
800 | =item * Erlang uses unprotected connections, AEMP uses secure |
942 | =item * Erlang uses unprotected connections, AEMP uses secure |
801 | authentication and can use TLS. |
943 | authentication and can use TLS. |
802 | |
944 | |
803 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
945 | AEMP can use a proven protocol - TLS - to protect connections and |
804 | securely authenticate nodes. |
946 | securely authenticate nodes. |
805 | |
947 | |
806 | =item * The AEMP protocol is optimised for both text-based and binary |
948 | =item * The AEMP protocol is optimised for both text-based and binary |
807 | communications. |
949 | communications. |
808 | |
950 | |
809 | The AEMP protocol, unlike the Erlang protocol, supports both |
951 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
810 | language-independent text-only protocols (good for debugging) and binary, |
952 | language independent text-only protocols (good for debugging), and binary, |
811 | language-specific serialisers (e.g. Storable). |
953 | language-specific serialisers (e.g. Storable). By default, unless TLS is |
|
|
954 | used, the protocol is actually completely text-based. |
812 | |
955 | |
813 | It has also been carefully designed to be implementable in other languages |
956 | It has also been carefully designed to be implementable in other languages |
814 | with a minimum of work while gracefully degrading fucntionality to make the |
957 | with a minimum of work while gracefully degrading functionality to make the |
815 | protocol simple. |
958 | protocol simple. |
816 | |
959 | |
817 | =item * AEMP has more flexible monitoring options than Erlang. |
960 | =item * AEMP has more flexible monitoring options than Erlang. |
818 | |
961 | |
819 | In Erlang, you can chose to receive I<all> exit signals as messages |
962 | In Erlang, you can chose to receive I<all> exit signals as messages or |
820 | or I<none>, there is no in-between, so monitoring single processes is |
963 | I<none>, there is no in-between, so monitoring single Erlang processes is |
821 | difficult to implement. Monitoring in AEMP is more flexible than in |
964 | difficult to implement. |
822 | Erlang, as one can choose between automatic kill, exit message or callback |
965 | |
823 | on a per-process basis. |
966 | Monitoring in AEMP is more flexible than in Erlang, as one can choose |
|
|
967 | between automatic kill, exit message or callback on a per-port basis. |
824 | |
968 | |
825 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
969 | =item * Erlang tries to hide remote/local connections, AEMP does not. |
826 | |
970 | |
827 | Monitoring in Erlang is not an indicator of process death/crashes, |
971 | Monitoring in Erlang is not an indicator of process death/crashes, in the |
828 | as linking is (except linking is unreliable in Erlang). |
972 | same way as linking is (except linking is unreliable in Erlang). |
829 | |
973 | |
830 | In AEMP, you don't "look up" registered port names or send to named ports |
974 | In AEMP, you don't "look up" registered port names or send to named ports |
831 | that might or might not be persistent. Instead, you normally spawn a port |
975 | that might or might not be persistent. Instead, you normally spawn a port |
832 | on the remote node. The init function monitors the you, and you monitor |
976 | on the remote node. The init function monitors you, and you monitor the |
833 | the remote port. Since both monitors are local to the node, they are much |
977 | remote port. Since both monitors are local to the node, they are much more |
834 | more reliable. |
978 | reliable (no need for C<spawn_link>). |
835 | |
979 | |
836 | This also saves round-trips and avoids sending messages to the wrong port |
980 | This also saves round-trips and avoids sending messages to the wrong port |
837 | (hard to do in Erlang). |
981 | (hard to do in Erlang). |
838 | |
982 | |
839 | =back |
983 | =back |
840 | |
984 | |
841 | =head1 RATIONALE |
985 | =head1 RATIONALE |
842 | |
986 | |
843 | =over 4 |
987 | =over 4 |
844 | |
988 | |
845 | =item Why strings for ports and noderefs, why not objects? |
989 | =item Why strings for port and node IDs, why not objects? |
846 | |
990 | |
847 | We considered "objects", but found that the actual number of methods |
991 | We considered "objects", but found that the actual number of methods |
848 | thatc an be called are very low. Since port IDs and noderefs travel over |
992 | that can be called are quite low. Since port and node IDs travel over |
849 | the network frequently, the serialising/deserialising would add lots of |
993 | the network frequently, the serialising/deserialising would add lots of |
850 | overhead, as well as having to keep a proxy object. |
994 | overhead, as well as having to keep a proxy object everywhere. |
851 | |
995 | |
852 | Strings can easily be printed, easily serialised etc. and need no special |
996 | Strings can easily be printed, easily serialised etc. and need no special |
853 | procedures to be "valid". |
997 | procedures to be "valid". |
854 | |
998 | |
855 | And a a miniport consists of a single closure stored in a global hash - it |
999 | And as a result, a port with just a default receiver consists of a single |
856 | can't become much cheaper. |
1000 | code reference stored in a global hash - it can't become much cheaper. |
857 | |
1001 | |
858 | =item Why favour JSON, why not real serialising format such as Storable? |
1002 | =item Why favour JSON, why not a real serialising format such as Storable? |
859 | |
1003 | |
860 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
1004 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
861 | format, but currently there is no way to make a node use Storable by |
1005 | format, but currently there is no way to make a node use Storable by |
862 | default. |
1006 | default (although all nodes will accept it). |
863 | |
1007 | |
864 | The default framing protocol is JSON because a) JSON::XS is many times |
1008 | The default framing protocol is JSON because a) JSON::XS is many times |
865 | faster for small messages and b) most importantly, after years of |
1009 | faster for small messages and b) most importantly, after years of |
866 | experience we found that object serialisation is causing more problems |
1010 | experience we found that object serialisation is causing more problems |
867 | than it gains: Just like function calls, objects simply do not travel |
1011 | than it solves: Just like function calls, objects simply do not travel |
868 | easily over the network, mostly because they will always be a copy, so you |
1012 | easily over the network, mostly because they will always be a copy, so you |
869 | always have to re-think your design. |
1013 | always have to re-think your design. |
870 | |
1014 | |
871 | Keeping your messages simple, concentrating on data structures rather than |
1015 | Keeping your messages simple, concentrating on data structures rather than |
872 | objects, will keep your messages clean, tidy and efficient. |
1016 | objects, will keep your messages clean, tidy and efficient. |
873 | |
1017 | |
874 | =back |
1018 | =back |
875 | |
1019 | |
876 | =head1 SEE ALSO |
1020 | =head1 SEE ALSO |
877 | |
1021 | |
|
|
1022 | L<AnyEvent::MP::Intro> - a gentle introduction. |
|
|
1023 | |
|
|
1024 | L<AnyEvent::MP::Kernel> - more, lower-level, stuff. |
|
|
1025 | |
|
|
1026 | L<AnyEvent::MP::Global> - network maintenance and port groups, to find |
|
|
1027 | your applications. |
|
|
1028 | |
|
|
1029 | L<AnyEvent::MP::DataConn> - establish data connections between nodes. |
|
|
1030 | |
|
|
1031 | L<AnyEvent::MP::LogCatcher> - simple service to display log messages from |
|
|
1032 | all nodes. |
|
|
1033 | |
878 | L<AnyEvent>. |
1034 | L<AnyEvent>. |
879 | |
1035 | |
880 | =head1 AUTHOR |
1036 | =head1 AUTHOR |
881 | |
1037 | |
882 | Marc Lehmann <schmorp@schmorp.de> |
1038 | Marc Lehmann <schmorp@schmorp.de> |