Packer Configuration for GCP spot/preemptible instances

preemptible-builder.pkr.hcl

source googlecompute preemptible-builder {
  project_id          = "<PROJECT_ID>"
  zone                = "us-west4-b" # using us-west4 because they have much cheaper spot prices right now.
  ssh_username        = "packer"
  source_image        = "debian-11-bullseye-v20230306"
  wrap_startup_script = false
  disk_size           = 10
  preemptible         = true
  metadata = {
    #if instance gets preempted, send SIGINT to packer (prevents packer from hanging for 20m trying to reconnect)
    #To see if it was really preempted, run gcloud compute operations list --filter="operationType=compute.instances.preempted"
    "shutdown-script" : "for pid in $(pgrep -U packer ssh); do sudo kill -2 $pid; done"
  }
}