Thanks for this info, I will read it now.
The idea is, I have a modified version of Cassandra for a specific
research application. I want to be able to make a supportable statement
like this:
After a state change, we wait x*gossip_interval in order to ensure with
0.9xxxx probability that all nodes have seen the change.
Thanks,
Bill
On 09/30/2014 12:02 PM, Brandon Williams wrote:
There is this very old ticket:
https://issues.apache.org/jira/browse/CASSANDRA-617
But note that is gossip simulation, not the actual gossiper Cassandra uses
(and also very antiquated.) Using the actual gossiper under simulation is
unfortunately complicated by
https://issues.apache.org/jira/browse/CASSANDRA-6881
That said, I'm pretty confident in our implementation, after beating out
the details the scuttlebutt paper won't tell you over the last years, like
how to remove a node. So the number of cycles required to answer you is,
yet, not scientifically determined in our implementation, but I feel it's
sufficient in most deployments right now, and the knob we have to turn if
not is -Dcassandra.ring_delay_ms.
On Tue, Sep 30, 2014 at 10:50 AM, William Katsak <wkat...@gmail.com> wrote:
Hello,
Forgive me if I have missed anything in the obvious locations, but I am
trying to find out if anyone has done an analysis of the gossip protocol as
implemented in Cassandra? In particular, I am interested in the the
theoretical propagation time (to all nodes) of a change. For example, if a
single node makes a change, what is the number of gossip cycles that must
elapse before we can be sure (to very high probability obviously, not 100%
sure) that everyone has seen it. For those familiar, this is obviously an
epidemic analysis, but the Scuttlebutt-style protocol makes it a bit more
complex.
If anyone already has this, it would be much appreciated.
Thanks!
-Bill Katsak
Ph.D. Student
Department of Computer Science
Rutgers University
