Put Helm annotations and labels on already deployed Kubernetes resources to adopt them inside a Helm Release automatically

adopt-helm-resources.sh

#!/bin/bash

LOCAL_EXIT_CODE=0

RELEASE_NAME="istiod"
RELEASE_NAMESPACE="istio-system"
HELM_CHART_PATH="./istio/istiod"
HELM_EXTRA_VALUES_PATH="./istio/common/istio.yaml"


# Get a JSON with the resources potentially adopted by this release
RESOURCES_TO_ADOPT_JSON=$(helm template "${RELEASE_NAME}" --namespace "${RELEASE_NAMESPACE}" --create-namespace "${HELM_CHART_PATH}" -f "${HELM_EXTRA_VALUES_PATH}" | \
  kubectl apply -f - --dry-run=client -o json | \
  jq -c '.items[] | {"kind": .kind, "name": .metadata.name, "namespace": .metadata.namespace}')

# TODO
echo "${RESOURCES_TO_ADOPT_JSON}" | while IFS= read -r line; do

  printf "[info] Object found, processing: %s \n" "${line}"

  KIND=$(echo $line | jq '.kind' | tr -d '"')
  NAME=$(echo $line | jq '.name' | tr -d '"')
  NAMESPACE=$(echo $line | jq '.namespace' | tr -d '"')

  # Detect empty namespaces: they are commonly CRDs
  if [ -z "${NAMESPACE}" ] || [ "${NAMESPACE}" = "null" ]; then
    kubectl label "${KIND}" "${NAME}" app.kubernetes.io/managed-by=Helm
    kubectl annotate "${KIND}" "${NAME}" meta.helm.sh/release-name="${RELEASE_NAME}"
    kubectl annotate "${KIND}" "${NAME}" meta.helm.sh/release-namespace="${RELEASE_NAMESPACE}"
  else
    kubectl label "${KIND}" "${NAME}" --namespace="${NAMESPACE}" app.kubernetes.io/managed-by=Helm
    kubectl annotate "${KIND}" "${NAME}" --namespace="${NAMESPACE}" meta.helm.sh/release-name="${RELEASE_NAME}"
    kubectl annotate "${KIND}" "${NAME}" --namespace="${NAMESPACE}" meta.helm.sh/release-namespace="${RELEASE_NAMESPACE}"
  fi

  printf "%s\n\n" "[ok] Processed"

done