We have a 10 node cluster (v0.7.9) split into 2 datacenters.  Three times we have seen nodes move themselves to different locations in the ring.  In each case, the move unbalanced the ring. In one case a node moved to the opposite side of the ring.

 

Sometime after the first spontaneous move we started using Datastax OpsCenter.  The next 2 moves showed up in its event log like:

5/20/2012 11:23am - Info -  Host 12.34.56.78 moved from '12345' to '54321'

 

where '12345' and '54321' are the old and new tokens.

 

Anyone know whats causing this?