upgrade MySQL engine of AWS RDS

upgrade_rds.sh

#!/bin/bash
set -e
if [ $# -lt 2 ];then
  echo "Usage: $(basename "$0") your-rds-identifier target-version"
  exit -1
fi

###########################################################
#   Funcitons
###########################################################
function logger(){ echo "[$(date +%Y/%m/%dT%H:%M:%S)] $1"; }
function prompt(){
  while true
  do
    read -rp "$1 (y/N):> " yn
    case "$yn" in [yY]*) break ;; [nN]*) echo "canceled";exit 1;;  *) ;; esac
  done
}

function create_readreplica(){
  logger "start to create read replica ${RDS_SLAVE_ID} at ${MASTER_AZ}"
  aws rds create-db-instance-read-replica \
    --db-instance-identifier "${RDS_SLAVE_ID}" \
    --source-db-instance-identifier "${RDS_MASTER_ID}" \
    --availability-zone "${MASTER_AZ}"

  while true
  do
    master_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_MASTER_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    slave_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_SLAVE_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    logger "create status (master/slave): ${master_status}/${slave_status}"
    if [ "${master_status}" = "available" ] && [ "${slave_status}" = "available" ] ;then break;fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
  logger "read replica ${RDS_SLAVE_ID} created at ${MASTER_AZ}"
}

function upgrade_readreplica(){
  logger "start to  upgrade read replica ${RDS_SLAVE_ID} from ${CURRENT_VERSION} to ${TARGET_VERSION}"
  aws rds modify-db-instance \
    --db-instance-identifier "${RDS_SLAVE_ID}" \
    --engine-version "${TARGET_VERSION}" \
    --allow-major-version-upgrade \
    --apply-immediately
  while true
  do
    upgrade_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_SLAVE_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    logger "waiting for start upgrading... ${RDS_SLAVE_ID} status is : ${upgrade_status}"
    if [ "${upgrade_status}" = "upgrading" ] ;then break;fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
  while true
  do
    upgrade_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_SLAVE_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    logger "now upgrading... status is : ${upgrade_status}"
    if [ "${upgrade_status}" = "available" ] ;then break;fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
  logger "read replica upgrade completed"
}

function promote_readreplica(){
  logger "start to promote read replica"
  aws rds promote-read-replica --db-instance-identifier "${RDS_SLAVE_ID}"
  while true
  do
    promote_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_SLAVE_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    statusinfo=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_SLAVE_ID}" \
      --query 'DBInstances[].StatusInfos[]' \
      --out text)
    logger "now promoting... status is : ${promote_status}/ status info : ${statusinfo}"
    if [ "${promote_status}" == "backing-up" ] || [ "${promote_status}" == "available" ] && [ "${statusinfo}" = "" ];then break;fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
}

function switch_endpoint(){
  logger "rename from ${RDS_MASTER_ID} to ${RDS_MASTER_ID_old}"
  aws rds modify-db-instance \
    --db-instance-identifier "${RDS_MASTER_ID}" \
    --new-db-instance-identifier "${RDS_MASTER_ID_old}" \
    --apply-immediately
  while true
  do
    rds_master_count=$(aws rds describe-db-instances \
      --query "length(DBInstances[?DBInstanceIdentifier==\`${RDS_MASTER_ID}\`])")
    if [ "${rds_master_count}" -eq 0 ];then
      break
    else
      logger "waiting for renamed from ${RDS_MASTER_ID} to ${RDS_MASTER_ID_old}"
    fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
  logger "rename from ${RDS_MASTER_ID} to ${RDS_MASTER_ID_old} completed"

  logger "rename from ${RDS_SLAVE_ID} to ${RDS_MASTER_ID}"
  aws rds modify-db-instance \
    --db-instance-identifier "${RDS_SLAVE_ID}" \
    --new-db-instance-identifier "${RDS_MASTER_ID}" \
    --apply-immediately
  while true
  do
    rds_master_count=$(aws rds describe-db-instances \
      --query "length(DBInstances[?DBInstanceIdentifier==\`${RDS_MASTER_ID}\`])")
    if [ "${rds_master_count}" -eq 1 ];then
      break
    else
      logger "waiting for renamed from ${RDS_SLAVE_ID} to ${RDS_MASTER_ID}"
    fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
  while true
  do
    master_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_MASTER_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    logger "rds status is : ${master_status}"
    if [ "${master_status}" = "available" ] ;then break;fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
}

function update_config(){
  while true
  do
    sleep "${LOOP_INTERVAL_SEC}"
    master_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_MASTER_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    logger "rds status is : ${master_status}"
    if [ "${master_status}" = "available" ] ;then break;fi
  done
  aws rds modify-db-instance \
    --db-instance-identifier "${RDS_MASTER_ID}" \
    --backup-retention-period "${BACKUP_RETENTION}" \
    --preferred-backup-window "${BACKUP_TIME_WINDOW}" \
    --copy-tags-to-snapshot \
    --monitoring-interval "${MONITORING_INTERVAL}" \
    --monitoring-role-arn "${MONITORING_RORE_ARN}" \
    --apply-immediately
  while true
  do
    master_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_MASTER_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    logger "waiting for configured ${RDS_MASTER_ID} status is : ${master_status}"
    if [ "${master_status}" != "available" ] ;then break;fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
  while true
  do
    master_status=$(aws rds describe-db-instances \
      --db-instance-identifier "${RDS_MASTER_ID}" \
      --query 'DBInstances[].DBInstanceStatus' \
      --out text)
    logger "waiting for configured ${RDS_MASTER_ID} status is : ${master_status}"
    if [ "${master_status}" = "available" ] ;then break;fi
    sleep "${LOOP_INTERVAL_SEC}"
  done
}

###########################################################
#   Main
###########################################################

################################
### Get Paramters
readonly RDS_MASTER_ID=$1
readonly TARGET_VERSION=$2
readonly LOOP_INTERVAL_SEC=10
readonly CURRENT_VERSION=$(aws rds describe-db-instances \
  --db-instance-identifier "${RDS_MASTER_ID}" \
  --query 'DBInstances[].EngineVersion' \
  --out text)
readonly MASTER_AZ=$(aws rds describe-db-instances \
  --db-instance-identifier "${RDS_MASTER_ID}" \
  --query 'DBInstances[].AvailabilityZone' \
  --out text)
readonly MONITORING_RORE_ARN=$(aws rds describe-db-instances \
  --db-instance-identifier "${RDS_MASTER_ID}" \
  --query 'DBInstances[].MonitoringRoleArn' \
  --out text)
readonly MONITORING_INTERVAL=$(aws rds describe-db-instances \
  --db-instance-identifier "${RDS_MASTER_ID}" \
  --query 'DBInstances[].MonitoringInterval' \
  --out text)
readonly BACKUP_TIME_WINDOW=$(aws rds describe-db-instances \
  --db-instance-identifier "${RDS_MASTER_ID}" \
  --query 'DBInstances[].PreferredBackupWindow' \
  --out text)
readonly BACKUP_RETENTION=$(aws rds describe-db-instances \
  --db-instance-identifier "${RDS_MASTER_ID}" \
  --query 'DBInstances[].BackupRetentionPeriod' \
  --out text)

readonly RDS_SLAVE_ID=${RDS_MASTER_ID}-slave
readonly RDS_MASTER_ID_old=${RDS_MASTER_ID}-$(echo "${CURRENT_VERSION}" | tr . -)

################################
### Create Readreplica
echo "-------------------"
echo "master          : ${RDS_MASTER_ID}"
echo "read replica    : ${RDS_SLAVE_ID}"
echo "current version : ${CURRENT_VERSION}"
echo "target  version : ${TARGET_VERSION}"
echo "az              : ${MASTER_AZ}"
echo "-------------------"
prompt "start to create read replica"
create_readreplica
upgrade_readreplica

################################
### Upgrade and Switching
readonly SLAVE_VERSION=$(aws rds describe-db-instances \
  --db-instance-identifier "${RDS_SLAVE_ID}" \
  --query 'DBInstances[].EngineVersion' \
  --out text)
echo "-------------------"
echo "master                : ${RDS_MASTER_ID}"
echo "read replica          : ${RDS_SLAVE_ID}"
echo "backup instance       : ${RDS_MASTER_ID_old}"
echo "master version        : ${CURRENT_VERSION}"
echo "target version        : ${TARGET_VERSION}"
echo "read replica  version : ${SLAVE_VERSION}"
echo "CONFIG-------------"
echo "az                    : ${MASTER_AZ}"
echo "backup retantion      : ${BACKUP_RETENTION}"
echo "backup window         : ${BACKUP_TIME_WINDOW}"
echo "monitoring role       : ${MONITORING_RORE_ARN}"
echo "monitoring interval   : ${MONITORING_INTERVAL}"
echo "-------------------"
echo "start switching master and read replica."
prompt "[caution!] downtime occured while switching"
promote_readreplica
switch_endpoint
update_config

logger "Completed !!"