Create a PDB for all deployments in the default Kubernetes namespace with a minAvailable of 50%

create_pdbs.sh

#!/usr/bin/env bash
set -e

template() {
cat <<EOF
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: {{NAME}}
  namespace: default
spec:
  minAvailable: 50%
  selector:
    matchLabels:
      app: {{APP_SELECTOR}}
      {{TIER_SELECTOR}}
EOF
}

deployments() {
  kubectl get deployment -o json \
    | jq -r '.items [] | .metadata | .name + "," + .labels.app + "," + .labels.tier'
}

pod_count() {
  local count=$(                        \
    kubectl get deployment "$1" -o json \
      | jq '.status.replicas'           \
  )

  if [[ $count == "" ]]; then
    echo 0
  else
    echo $count
  fi
}

render() {
  if [[ $# -lt 2 ]] || [[ $# -gt 3 ]]; then
    echo "$@"
    exit 1
  fi

  NAME="$1"
  APP_SELECTOR="$2"
  TIER_SELECTOR=""

  if [[ -n "$3" ]]; then
    TIER_SELECTOR="tier: $3"
  fi

  sed -e 's/{{NAME}}/'"$NAME"'/'                                        \
    -e 's/{{APP_SELECTOR}}/'"$APP_SELECTOR"'/'                          \
    -e 's/{{TIER_SELECTOR}}/'"$TIER_SELECTOR"'/' <<< $(template)
}

main() {
  kubectl delete pdb --all

  for i in $(deployments); do
    IFS=, read name app_selector tier_selector <<< $i

    if [[ $(pod_count $name) -lt 2 ]]; then
      continue
    fi

    render $name $app_selector $tier_selector \
      | kubectl create -f -
  done
}

main "$@"