df_config_dynamic.sh

#!/bin/bash

# script that reads configuration from VM tags using cloud-init
# updates the dragonfly configuration file
# and restarts the dragonfly service

# todo: make this work on GCP, and use the same script for both
# get `df-args` tag
curl http://169.254.169.254/latest/meta-data/tags/instance/df-args > /etc/dragonfly/df-args

# save default configuration if it does not exist
if [ ! -f /etc/dragonfly/df-args.default ]; then
  cp /etc/dragonfly/dragonfly.conf /etc/dragonfly/df-args.default
fi

# replace commas with new lines
sed -i 's/,/\n/g' /etc/dragonfly/df-args

# check if this is changed from the previous run
if ! cmp -s /etc/dragonfly/df-args /etc/dragonfly/df-args.prev; then
  echo "Instance tags changed, updating configuration"
  # take default and add the new args
  cat /etc/dragonfly/df-args.default /etc/dragonfly/df-args > /etc/dragonfly/dragonfly.conf
  # restart the service
  systemctl restart dragonfly.service
  # save the current tags
  cp /etc/dragonfly/df-args /etc/dragonfly/df-args.prev
else
  echo "Instance tags did not change, skipping configuration update"
fi