Kubernetes ConfigMap Compare and Swap

k8s_configmap_cas.sh

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

#
# Usage Example: ./k8s_configmap_cas.sh -n namespace configmap-name '{"key":"value1"}' '{"key":"value2"}'
#

NAMESPACE=
while getopts n: o; do
  case $o in
    (n) NAMESPACE=$OPTARG;;
    (*) exit 1
  esac
done
shift "$((OPTIND - 1))"

CONFIGMAP_NAME=$1
CONFIGMAP_DATA_OLD=$2
CONFIGMAP_DATA_NEW=$3


if [ -z "$NAMESPACE" ]
then
  NAMESPACE_OPTION=
else
  NAMESPACE_OPTION="--namespace $NAMESPACE"
fi


CONFIGMAP_DESC=$(kubectl get configmap "$CONFIGMAP_NAME" --no-headers --output json $NAMESPACE_OPTION)
CONFIGMAP_DATA_EXIST=$(echo "$CONFIGMAP_DESC" | jq -c .data)
RESOURCE_VERSION="$(echo "$CONFIGMAP_DESC" | jq .metadata.resourceVersion)"

if [ "$CONFIGMAP_DATA_EXIST" != "$CONFIGMAP_DATA_OLD" ]
then
  exit 2
fi

echo "
apiVersion: v1
kind: ConfigMap
metadata:
  name: $CONFIGMAP_NAME
  resourceVersion: $RESOURCE_VERSION
data: $CONFIGMAP_DATA_NEW
" | kubectl replace --filename - $NAMESPACE_OPTION

k8s_configmap_cas_test.sh

#!/usr/bin/env bash

for VARIABLE in {1..10}
do
  for (( ; ; ))
  do
    NUM_OLD=$(kubectl get configmap my-config -o json | jq -r .data.num)
    NUM_NEW=$(echo "$NUM_OLD + 1" | bc)
    if ./cas-configmap.sh my-config "{\"num\":\"$NUM_OLD\"}" "{\"num\":\"$NUM_NEW\"}"
    then
      break
    fi
  done
done