#!/bin/bash
set -ex

# This script monitors the lifecycle state of the current AWS EC2 instance and triggers
# a termination script when the instance state is set to "Terminated".
# The script uses the AWS Instance Metadata Service (IMDS) to determine the state of the instance.
# The termination script to be triggered and the termination message are read from a config JSON file.
# The script expects a grace period in minutes as an argument, which it passes to the termination script.
# The script runs in an infinite loop, checking the instance state every 60 seconds.
#
# This script must be executed as <%= node['cluster']['cluster_admin_user'] %> because
# because only this user has sudoers privileges to execute the termination hook.

CONFIG_PATH="<%= node['cluster']['shared_dir_login_nodes'] %>/loginmgtd_config.json"
CONFIG_JSON=$(cat $CONFIG_PATH)
TERMINATION_SCRIPT_PATH=$(echo $CONFIG_JSON | jq -r .termination_script_path)
TERMINATION_MESSAGE=$(echo $CONFIG_JSON | jq -r .termination_message)
GRACETIME_PERIOD=$(echo $CONFIG_JSON | jq -r .gracetime_period)
DAEMON_SLEEP_SECONDS=60

IMDS_ENDPOINT="http://169.254.169.254"

while true; do
  IMDS_TOKEN=$(curl -X PUT "$IMDS_ENDPOINT/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 3600")

  INSTANCE_LIFECYCLE_STATE=$(curl -H "X-aws-ec2-metadata-token: $IMDS_TOKEN" -v "$IMDS_ENDPOINT/latest/meta-data/autoscaling/target-lifecycle-state")
  if [[ "$INSTANCE_LIFECYCLE_STATE" == "Terminated" ]]; then
    break
  fi
  sleep $DAEMON_SLEEP_SECONDS
done

sudo "$TERMINATION_SCRIPT_PATH" "$TERMINATION_MESSAGE" "$GRACETIME_PERIOD"