systemd-wrapper

#!/usr/bin/env bash
set -o errexit

main() {
  local name="${1:-travis-worker}"

  docker stop "${name}" &>/dev/null || true
  docker rm -f "${name}" &>/dev/null || true

  local env_file
  env_file="$(tfw writeenv travis-worker)"

  set -o allexport
  # shellcheck source=/dev/null
  source "${env_file}"

  if [[ "${TRAVIS_WORKER_PROVIDER_NAME}" == gce ]]; then
    local gce_zone
    gce_zone="$(__fetch_gce_zone)"
    if [ -z "${gce_zone}" ]; then
      gce_zone=us-central1-b
    fi
    echo "TRAVIS_WORKER_GCE_ZONE=${gce_zone}" >>"${env_file}"
  fi

  if [[ ! "${TRAVIS_WORKER_LIBRATO_SOURCE}" ]]; then
    local librato_source
    librato_source="$(__build_librato_source "$(hostname)" "${name}")"
    echo "TRAVIS_WORKER_LIBRATO_SOURCE=${librato_source}" >>"${env_file}"
  fi

  if [ -f "${TRAVIS_WORKER_PRESTART_HOOK}" ]; then
    "${TRAVIS_WORKER_PRESTART_HOOK}"
  fi

  exec docker run \
    --rm \
    --name "${name}" \
    --hostname "$(hostname)" \
    --userns host \
    -v /var/tmp:/var/tmp \
    -v /var/run:/var/run \
    --env-file "${env_file}" \
    "${TRAVIS_WORKER_SELF_IMAGE}" travis-worker
}

__fetch_gce_zone() {
  curl -sSL \
    "http://metadata.google.internal/computeMetadata/v1/instance/zone" \
    -H "Metadata-Flavor: Google" |
    awk -F/ '{ print $NF }'
}

__build_librato_source() {
  local host_name="${1}"
  local name="${2}"

  if [[ "${name}" == "travis-worker" ]]; then
    echo "${host_name}"
    return
  fi

  echo "${host_name}-${name/travis-worker-/}"
}

main "$@"