rebalance.sh

#!/bin/sh

# This will allow you to rebalance the Cassandra ring
# Accepts hosts from stdin and automatically rebalances
# tokens in your ring.
#
# $ echo "one two three" | ./rebalance.sh

RING_SIZE=$(echo "2^127" | bc)

while read host
do
    if [ -z $hosts ]
    then
        hosts=$host
    else
        hosts="$hosts $host"
    fi
done

HOST_NUM=$(echo $hosts | wc -w)
INDEX=0

for host in $hosts
do
    token=$(echo "$INDEX*$RING_SIZE/$HOST_NUM" | bc)
    ssh $host "/usr/bin/nodetool move $token"
    INDEX=$((INDEX+1))
done