Wait for GCE instance is ready by try ssh in

wait-for-vm-up.bash

function wait_vm_up {
  local counter=0

  local readonly project=${1:?"project required"}
  local readonly instance=${2:?"instance required"}
  local readonly zone=${3:?"zone required"}
  local readonly user=${4:?"user required"}
  local readonly maxRetry=${5:-100}

  echo "Project: $project"
  echo "Instance: $instance"
  echo "MaxRetry: $maxRetry"

  while true ; do
    if (( $counter == $maxRetry )) ; then
      echo "Reach the retry upper limit $counter"
      exit 1
    fi

    gcloud compute ssh --quiet --zone "$zone" "$user@$instance" --tunnel-through-iap --project "$project" --command="true" 2> /dev/null

    if (( $? == 0 )) ;then
      echo "The machine is UP !!!"
      exit 0
    else
      echo "Maybe later? $counter"
      ((counter++))
      sleep 1
    fi
  done
}

wait_vm_up $@