discovery

Scott Lystig Fritchie <>
Wed Jul 12 22:28:11 CEST 2000


>>>>> "uw" == Ulf Wiger <> writes:

uw> On 9 Jul 2000, Hal Snyder wrote:

>> We're considering a multicast group address for this purpose. But
>> maybe there's already a solution and I just haven't found it in the
>> docs.
>> Ideally isn't a cluster a fluid thing, without hard-coded physical
>> node assignments?

uw> Ideally, yes. At AXD 301, we have a more flexible (and more
uw> complicated) application controller, called RCM (Runtime
uw> Configuration Manager). Part of it will probably make its way into
uw> OTP, and it will make it easier to configure dynamic clusters on
uw> the fly.

That would be a handy thing.

At the moment, we've been using multicast IP has a hack around this
void.  If a node is rebooted or loses contact with the rest of the
cluster, an alarm eventually goes off and the lost node sends a single
"Anybody out there?  I am ''" multicast UDP packet.

The rest of the cluster is also listening for those multicast packets.
(The multicast address is configured out-of-band.)  When one arrives,
a regular Erlang message is sent to '', which automagically
triggers the mechanisms used to keep track of Erlang nodes.  I'll
volunteer Jim Larson to speak up if I've misrepresented his work or if
y'all have further questions.  :-)

-Scott



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