pv-attach

#!/usr/bin/env bash
set -Eeuo pipefail

#  -c, --context string          context in the kubeconfig file of the PVC
#  -k, --kubeconfig string       path of the kubeconfig file of the PVC
#  -R, --mount-read-only         mount the PVC in ReadOnly mode (default false)
#  -n, --namespace string        namespace of the PVC
#  -d, --dir       string        dir to mount to (defaults to /mnt)


POSITIONAL_ARGS=()

readonly=no
dir=/mnt
empty_dirs=()

while [[ $# -gt 0 ]]; do
  case $1 in
    -c|--context)
      context=$2
      shift 2
      ;;
    -k|--kubeconfig)
      kubeconfig=$2
      shift 2
      ;;
    -R|--read-only)
      readonly=yes
      shift
      ;;
    -n|--namespace)
      namespace=$2
      shift 2
      ;;
    -i|--image)
      image=$2
      shift 2
      ;;
    -c|--command)
      command=$2
      shift 2
      ;;
    -d|--dir)
      dir=$2
      shift 2
      ;;
    -t|--empty-dir)
      empty_dirs+=( "$2" )
      shift 2
      ;;
    --*|-*)
      echo "Unknown option $1"
      exit 1
      ;;
    *)
      POSITIONAL_ARGS+=("$1") # save positional arg
      shift # past argument
      ;;
  esac
done

set -- "${POSITIONAL_ARGS[@]}"

[ -n "${image:-}" ] || image=docker.io/library/alpine:latest

kubectl_args=()

if [ -n "${context:-}" ]; then
  kubectl_args+=("--context" "$context")
fi
if [ -n "${kubeconfig:-}" ]; then
  kubectl_args+=("--kubeconfig" "$kubeconfig")
fi
if [ -n "${namespace:-}" ]; then
  kubectl_args+=("--namespace" "$namespace")
fi

kubectl() {
  command kubectl "${kubectl_args[@]}" "$@"
}

list_pvc() {
  kubectl get pvc -o name --ignore-not-found | sed "s~^persistentvolumeclaim/~~"
}

pvcs=()

if (( $# == 0 )); then
  claim_name="$(list_pvc | fzf)"
  pvcs+=( "$claim_name" )
else
  for i in "$@"; do
    pvcs+=( "$i" )
  done
fi

pod_name="pv-attach-$(uuidgen)"

node_names=()
mounts_data=""

mp_counter=0

for pvc in "${pvcs[@]}"; do
  if [[ "$pvc" == *:* ]]; then
    pvc_name="${pvc%:*}"
    pvc_mp="${pvc#*:}"
  else
    pvc_name="$pvc"
    if (( mp_counter == 0 )); then
      pvc_mp="/mnt"
    else
      pvc_mp="/mnt${mp_counter}"
    fi
  fi

  mp_counter=$(( mp_counter + 1))

  volume_name=$(kubectl get persistentvolumeclaim "$pvc_name" -o json | jq .spec.volumeName -r)

  node_name=$(kubectl -n apps get volumeattachments.storage.k8s.io -o json | jq --arg volumeName "$volume_name" '[.items | .[] | select(.spec.source.persistentVolumeName == $volumeName) | .spec.nodeName] | first // "-"' -r)
  node_names+=( "$node_name" )

  mount_data="$(jq -n --arg name "$pvc_name" --arg mp "$pvc_mp" '{"name": $name, "mp": $mp}')"
  if [ -z "$mounts_data" ]; then
    mounts_data="$mount_data"
  else
    mounts_data="$mounts_data,$mount_data"
  fi
done

mounts_data="[$mounts_data]"

template=$(cat <<-'JSON'
{
  "apiVersion": "v1",
  "spec": ({
    "volumes": (
      [
        $mountsData
          | to_entries
          | map({
            "name": "mnt\(.key)",
            "persistentVolumeClaim": {
              "claimName": .value.name
            }
          })
          | .[]
      ] + [
        $emptyDirs / " "
          | to_entries
          | map({ "name": ("emptydir" + (.key | tostring)), "emptyDir": {} })
          | .[]
      ]
    ),
    "containers": [
      {
        "name": "main",
        "workingDir": $mountsData[0].mp,
        "image": $image,
        "stdin": true,
        "stdinOnce": true,
        "tty": true,
        "volumeMounts": (
          [
            $mountsData
              | to_entries
              | map({
                "name": "mnt\(.key)",
                "mountPath": .value.mp
              })
              | .[]
          ] + [
            $emptyDirs / " "
              | to_entries
              | map({ "mountPath": .value, "name": "emptydir\(.key)" })
              | .[]
          ])
      } * (if $command == "" then {} else {
        "command": [$command]
      } end)
    ]
  } * (if $nodeName == "-" then {} else {
    "nodeSelector": {
      "kubernetes.io/hostname": $nodeName
    }
  } end))
}
JSON
)

overrides="$(jq -n \
  --arg name "$pod_name" \
  --argjson mountsData "$mounts_data" \
  --arg image "$image" \
  --arg nodeName "$node_name" \
  --arg command "${command:-}" \
  --arg emptyDirs "${empty_dirs[*]}" \
  "$template")"

exec kubectl "${kubectl_args[@]}" run \
  --image "$image" \
  --overrides "$overrides" \
  --restart Never \
  "$pod_name" \
  --rm \
  --stdin \
  --tty