Someone decided to use a large number for their myid file. This cause session ids to go negative, and our software (Apache Accumulo) did not handle this very well. While diagnosing the problem, I noticed this in SessionImpl:
When the 40th bit in System.currentTimeMillis() is a one, sign extension will fill the upper 8 bytes of nextSid, and id will not make the session id unique. I recommend changing the right shift to the logical shift:
But, we have until the year 2022 before we have to worry about it.