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Revision 1.146 by root, Mon Jun 20 08:19:19 2016 UTC vs.
Revision 1.149 by root, Wed Aug 17 19:44:07 2016 UTC

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118each other. To do this, nodes should listen on one or more local transport 118each other. To do this, nodes should listen on one or more local transport
119endpoints - binds. 119endpoints - binds.
120 120
121Currently, only standard C<ip:port> specifications can be used, which 121Currently, only standard C<ip:port> specifications can be used, which
122specify TCP ports to listen on. So a bind is basically just a tcp socket 122specify TCP ports to listen on. So a bind is basically just a tcp socket
123in listening mode that accepts conenctions form other nodes. 123in listening mode that accepts connections from other nodes.
124 124
125=item seed nodes 125=item seed nodes
126 126
127When a node starts, it knows nothing about the network it is in - it 127When a node starts, it knows nothing about the network it is in - it
128needs to connect to at least one other node that is already in the 128needs to connect to at least one other node that is already in the
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131Seed nodes themselves are not special - they are seed nodes only because 131Seed nodes themselves are not special - they are seed nodes only because
132some other node I<uses> them as such, but any node can be used as seed 132some other node I<uses> them as such, but any node can be used as seed
133node for other nodes, and eahc node can use a different set of seed nodes. 133node for other nodes, and eahc node can use a different set of seed nodes.
134 134
135In addition to discovering the network, seed nodes are also used to 135In addition to discovering the network, seed nodes are also used to
136maintain the network - all nodes using the same seed node form are part of 136maintain the network - all nodes using the same seed node are part of the
137the same network. If a network is split into multiple subnets because e.g. 137same network. If a network is split into multiple subnets because e.g. the
138the network link between the parts goes down, then using the same seed 138network link between the parts goes down, then using the same seed nodes
139nodes for all nodes ensures that eventually the subnets get merged again. 139for all nodes ensures that eventually the subnets get merged again.
140 140
141Seed nodes are expected to be long-running, and at least one seed node 141Seed nodes are expected to be long-running, and at least one seed node
142should always be available. They should also be relatively responsive - a 142should always be available. They should also be relatively responsive - a
143seed node that blocks for long periods will slow down everybody else. 143seed node that blocks for long periods will slow down everybody else.
144 144
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311 311
312=item step 2, bind listener sockets 312=item step 2, bind listener sockets
313 313
314The next step is to look up the binds in the profile, followed by binding 314The next step is to look up the binds in the profile, followed by binding
315aemp protocol listeners on all binds specified (it is possible and valid 315aemp protocol listeners on all binds specified (it is possible and valid
316to have no binds, meaning that the node cannot be contacted form the 316to have no binds, meaning that the node cannot be contacted from the
317outside. This means the node cannot talk to other nodes that also have no 317outside. This means the node cannot talk to other nodes that also have no
318binds, but it can still talk to all "normal" nodes). 318binds, but it can still talk to all "normal" nodes).
319 319
320If the profile does not specify a binds list, then a default of C<*> is 320If the profile does not specify a binds list, then a default of C<*> is
321used, meaning the node will bind on a dynamically-assigned port on every 321used, meaning the node will bind on a dynamically-assigned port on every
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1165top of AEMP and Coro threads. 1165top of AEMP and Coro threads.
1166 1166
1167=item * Erlang sends are synchronous, AEMP sends are asynchronous. 1167=item * Erlang sends are synchronous, AEMP sends are asynchronous.
1168 1168
1169Sending messages in Erlang is synchronous and blocks the process until 1169Sending messages in Erlang is synchronous and blocks the process until
1170a conenction has been established and the message sent (and so does not 1170a connection has been established and the message sent (and so does not
1171need a queue that can overflow). AEMP sends return immediately, connection 1171need a queue that can overflow). AEMP sends return immediately, connection
1172establishment is handled in the background. 1172establishment is handled in the background.
1173 1173
1174=item * Erlang suffers from silent message loss, AEMP does not. 1174=item * Erlang suffers from silent message loss, AEMP does not.
1175 1175
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1314C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon> 1314C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
1315passes a hash as first argument, and an extra C<$chg> argument that can be 1315passes a hash as first argument, and an extra C<$chg> argument that can be
1316ignored: 1316ignored:
1317 1317
1318 db_mon $group => sub { 1318 db_mon $group => sub {
1319 my ($ports, $add, $chg, $lde) = @_; 1319 my ($ports, $add, $chg, $del) = @_;
1320 $ports = [keys %$ports]; 1320 $ports = [keys %$ports];
1321 1321
1322 # now $ports, $add and $del are the same as 1322 # now $ports, $add and $del are the same as
1323 # were originally passed by grp_mon. 1323 # were originally passed by grp_mon.
1324 ... 1324 ...

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