helm_adopter.sh

#!/bin/bash

function helm::adopt() {
  local chart_name=${1}
  local release_name=${2}
  local manifest_file_path=${3}
  local tiller_namespace=${4:-kube-system}

  # Check that the release has not been created yet
  if [[ "$(kubectl get -n ${tiller_namespace} cm -l NAME=${release_name},OWNER=TILLER -o name)" != "" ]] ; then
    >&2 echo "Error! Helm release '${release_name}' already exists!"
    return 1
  fi

  # Determine the length of specified manifest for stubbing
  local manifest_file_length=$(cat ${manifest_file_path} | wc -c)

  # Create chart with stub manifest
  local chart_dir=$(mktemp -d)
  cat > ${chart_dir}/Chart.yaml <<-YAML
apiVersion: v1
appVersion: 1.0
name: ${chart_name}
version: 0.1.0
YAML
  mkdir ${chart_dir}/templates
  cat > ${chart_dir}/templates/stub.yaml <<- YAML
{{ repeat ${manifest_file_length} "#" }}
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: helm-${release_name}-stub
YAML

  # Install chart
  if ! helm install -n ${release_name} ${chart_dir} ; then
    >&2 echo "Error! Installation of stub chart failed!"

    helm delete --purge ${release_name}
    rm -rf ${chart_dir}
    exit 1
  fi

  # Patch release cm storage
  local stub=$(printf '#%.0s' $(seq 1 ${manifest_file_length}))
  local release_data=$(kubectl get -n ${tiller_namespace} cm/${release_name}.v1 -o json | jq .data.release -r)
  local updated_release_data=$(echo ${release_data} | base64 -d | zcat | sed "s/${stub}/$(sed -z 's/\n/\\n/g' ${manifest_file_path} | sed -z 's/\//\\\//g')/" | gzip -9 | base64 -w0)
  kubectl patch -n ${tiller_namespace} cm/${release_name}.v1 -p '{"data":{"release":"'${updated_release_data}'"}}'

  # Check the release
  if ! helm list -q | grep '^'${release_name}'$' > /dev/null ; then
    >&2 echo "Error! Adoption of ${release_name} failed!"

    kubectl delete cm helm-adoption-${release_name}
    kubectl delete cm -l NAME=${release_name},OWNER=TILLER
    return 1
  fi

  # Remove stub manifest and related resource, and prepare final chart
  local manifest_file_name=$(basename ${manifest_file_path})
  rm ${chart_dir}/templates/stub.yaml
  cp ${manifest_file_path} ${chart_dir}/templates/${manifest_file_name}
  if helm upgrade ${release_name} ${chart_dir} ; then
    rm -rf ${release_name}
    mv ${chart_dir} ${chart_name}
  else
    helm delete --purge ${release_name}
    rm -rf ${chart_dir}
    exit 1
  fi
}

function usage() {
    local script_name=$(basename "$0")
    printf "Example:\n  ./$script_name foo bar-prod manifest.yaml\n\n"
    printf "Usage:\n  ./$script_name CHART_NAME RELEASE_NAME MANIFEST_FILE_TO_ADOPT [TILLER_NAMESPACE]\n"
}

if [[ "$#" -gt 2 && "$#" -lt 5 ]] ; then
    helm::adopt $1 $2 $3 $4
elif [[ "$#" -eq 0 ]]; then
    usage
else
    usage
    echo
    >&2 echo "Error! Illegal number of parameters!"
    exit 1
fi