[Spread-users] Sending messages to a fixed set of servers

Christian Schnell lulli at cs.tu-berlin.de
Wed May 5 13:27:15 EDT 2004

After thinking a bit more about Lamports logical clocks, I think I 
understood a very simple solution of how to place a correct and usefull 
total order on messages (it's rather obvious).

A persistent, system-wide logical clock that spans across all messages 
for the entire run-time of a "persistent group". Before sending a 
message m, a node increments its local logical-clock value and sends 
that with m. Upon receiving a message m, a node updates its local 
logical-clock value: logical-clock = MAX(logical-clock, m.lctime + 1). 
On shutdown/startup, each node stores/restores its local logical-clock 
value. Changes in the configuration can be ignored, and by building the 
pair of (local-IP, logical-clock) I have a nice "primary key" for 
message log records.

With the totally ordered logical-clock in the message log records, it 
becomes *much* simpler to determine the set of mission messages at each 
node, correct?

Thanks for any input,

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