List possible k8s Deployments and Services in the limbo.

limbo-k8s-components.sh

#!/usr/bin/env bash
# limbo-k8s-components.sh
#########################
#
# Usage:
# ./limbo-k8s-components.sh [namespace]
#
# This script assumes all Deployment.spec.template.labels have an "app" label
# AND all Service.spec.selector are selecting an "app" label.
#
# The script gets a list of all "app" labels in template of all active
# deployments AND a list "app" labels in Services selectors.
#
# By comparing both lists its possible to infer which resources are in limbo,
# in other words, active but unused
#
# Augusto "meleu" Lopes
# https://github.com/meleu
#
# shellcheck disable=SC2155

readonly NAMESPACE="${1:-default}"

# getDeploymentsWithAppLabel()
# List all "app" labels being generated by all active deployments.
# arg1: namespace (optional)
getDeploymentsAppLabels() {
  kubectl get deployments \
    -n "${NAMESPACE}" \
    -o jsonpath='{.items[*].spec.template.metadata.labels.app}' \
    | tr ' ' '\n' \
    | sort -u
}


# getServicesAppSelectors()
# List all "app" selectors currently in use by all active services.
getServicesAppSelectors() {
  kubectl get services \
    -n "${NAMESPACE}" \
    -o jsonpath='{.items[*].spec.selector.app}' \
    | tr ' ' '\n' \
    | sort -u
}

main() {
  local fileFromDeployments="$(mktemp)"
  local fileFromServices="$(mktemp)"

  echo -e "\nGetting data from the '${NAMESPACE}' namespace\n"

  echo -n "Getting the list of app labels from Deployments templates..."
  getDeploymentsAppLabels > "${fileFromDeployments}"
  echo " DONE!"

  echo -n "Getting the list of app labels from Services selectors..."
  getServicesAppSelectors > "${fileFromServices}"
  echo " DONE!"

  echo -e "\n\n--> List of DEPLOYMENTS not bound to any Service:\n"
  diff "${fileFromDeployments}" "${fileFromServices}" \
    | grep '^<' \
    | cut -d' ' -f2

  echo -e "\n\n--> List of SERVICES not bound to any Deployment:\n"
  diff "${fileFromDeployments}" "${fileFromServices}" \
    | grep '^>' \
    | cut -d' ' -f2

  rm -f "${fileFromDeployments}" "${fileFromServices}"
}

main "$@"