Azure DevOps: stop the agent by issuing a shutdown if the agent is idle and it ran at least one job. If a job is running, it waits for it to finish. Useful with EC2 spot based instances as agents.

shutdown-agent-if-idle.sh

# Create a service:
cat > /lib/systemd/system/azure-devops-shutdown-when-idle.service<<'EOF'
[Unit]
Description=Issues as shutdown in case the agent is idle, to avoid long running ec2 spot instances

[Service]
Type=simple
ExecStart=/bin/bash /root/shutdown_when_idle.sh

[Install]
WantedBy=multi-user.target
EOF

cat >/root/shutdown_when_idle.sh<<'EOF'
# Azure DevOps: shutdown agent when idle
# This script will continuously check if there's a job running, and if there's nothing, then it will issue a shutdown
# It's mainly designed to be used together with EC2 spot instances, since we're using them just once / build.

# Check if the agent ran at least one job, if not wait max $max_minutes
max_minutes=5
start_time=$(date +%s)
max_seconds=$(( $max_minutes * 60 )) # minutes * seconds
while [[ "$(($(date +%s) - $start_time))" -lt "$max_seconds" ]];do
  if [[ "$(ls /azp/agent/_diag | grep Worker_* | wc -l)" -eq "0" ]];then
    echo "The agent did not run any job so far, waiting max $max_minutes minutes"
  else
    echo "Job log file found"
	  break
  fi
  sleep 1
done

# Number of processes of azure devops in idle (2).
IDLE_PROC_COUNT=2

# If the load is higher than $IDLE_PROC_COUNT, it means there's a job running, otherwise issue a shutdown.
while :; do
  if [[ "$(ps --forest --no-headers -g  `systemctl show --property MainPID --value azure-devops-agent` | wc -l )" -gt ${IDLE_PROC_COUNT} ]]; then
	  echo A job is currently running
    sleep 1s
  else
	  echo Job seems to have finished. Issuing a shutdown
	  shutdown -h now
  fi
  sleep 1
done
EOF

systemctl daemon-reload
systemctl enable azure-devops-shutdown-when-idle