public long generateNewScannerId() {
    return (scannerIdGen.incrementAndGet() & 0x00000000FFFFFFFFL) | serverNameHash;
  }
Generate a new style scanner id to prevent collision with previous started server or other RSs.
We have 64 bits to use. The first 32 bits are MurmurHash32 of ServerName string "host,port,ts".
The ServerName contains both host, port, and start timestamp so it can prevent collision. The
lowest 32bit is generated by atomic int.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ScannerIdGenerator.java