Set random maintenance windows on all RDS instances within limits

rds_random_maintenance_windows.sh

#!/usr/bin/env bash

set -xe

REGION="eu-west-1"

# list RDS instances to a file
aws rds --region ${REGION} describe-db-instances | jq -r '.DBInstances[].DBInstanceIdentifier' > rds.log

# loop over the rds instances in the file
while read rds; do
    # Random hour
    HOUR=`shuf -i 2-5 -n 1`
    HOUREND=$((HOUR+1))
    # Random day
    DAYS[0]="Sat"
    DAYS[1]="Sun"
    size=${#DAYS[@]}
    index=$(($RANDOM % $size))
    DAY=${DAYS[$index]}

    aws rds modify-db-instance --region ${REGION} --db-instance-identifier ${rds} --preferred-maintenance-window ${DAY}:0${HOUR}:00-${DAY}:0${HOUREND}:00
    sleep 3
    
    echo ${RDS} set to ${DAY} from ${HOUR} to ${HOUREND}

done <rds.log