Script and systemd service to apply I/O highest priority and best effort scheduling class to the etcd process

ionice-etcd-systemd.sh

cat <<'EOT' >/usr/local/bin/ionice-etcd.sh
#!/usr/bin/env bash
echo "Starting ionice etcd process watcher..."
while true; do
  PID=$(pgrep etcd)
  if [ "$PID" != "" ]; then
    if [ "$(ionice -p $PID)" != "best-effort: prio 0" ]; then
      echo "Setting I/O highest priority and best effort scheduling class for etcd PID: $PID"
      ionice -c2 -n0 -p $PID
    fi
  fi
  sleep 60
done
EOT

chmod 0755 /usr/local/bin/ionice-etcd.sh

cat <<EOT >/etc/systemd/system/ionice-etcd.service
[Unit]
Description=ionice for etcd
After=kubelet.service

[Service]
DevicePolicy=closed
ExecStart=/usr/local/bin/ionice-etcd.sh
PrivateTmp=yes
ProtectSystem=strict
Restart=on-failure
TimeoutStartSec=10

[Install]
WantedBy=multi-user.target
EOT

systemctl daemon-reload
systemctl enable ionice-etcd
systemctl start ionice-etcd

Written for Ubuntu

This I/O disk tuning is detailed in the etcd docs: https://etcd.io/docs/v3.2/tuning/#disk

This service will watch the etcd process in case it is restarted and re-apply the tuning.