| Example of a replicated quote server. The server maintains state which consists of a list
of quotes and their corresponding values. When it is started, it tries to reach other
quote servers to get its initial state. If it does not receive any response after 5
seconds, it assumes it is the first server and starts processing requests. When it
receives a view notification it checks whether there are more members in the view than in
its previous view. If this is the case, it broadcasts a request for the state to all
members. Integration of different states is simply the union of all states (with the
danger of overwriting mutually inconsistent state). This mechanism allows both for
fast discovery of initial servers, and - in the case of partition merging - for
reintegration of existing servers. Broadcasting the state request upon every view change
(only when new members are joined) causes potentially a lot of network traffic, but it is
assumes that there will not be more than 5 quote servers at most.
author:
Bela Ban |
