Python script to convert container env blocks to config maps in Kubernetes configs

k8s-convert-env.py

import json, argparse, sys, os, time
from os.path import basename


def getFileContents(filename):
  with open(filename, 'r') as f:
    return f.read()

def writeToFile(filename, contents):
  file = open(filename, "w") 
  file.write(contents) 
  file.close()

def buildConfigMap(envVars, namespace, name):
  configMap = {
    "apiVersion": "v1",
    "kind": "ConfigMap",
    "metadata": {
      "name": "{}-configmap-{}".format(namespace, name),
      "namespace": namespace
    },
    "data": {}
  }
  for e in envVars:
    configMap["data"][e["name"]] = e["value"]
  return configMap

def getCurrentTimeString():
  return time.strftime("%Y%m%d%H%M%S", time.gmtime(time.time()))

def createBackupFile(originalFile):
  contents = getFileContents(originalFile)
  fname = "{}.bak-{}".format(originalFile, getCurrentTimeString())
  writeToFile(fname, contents)
  return fname

def main():

  parser = argparse.ArgumentParser()
  parser.add_argument("-f", "--file", help="Path to the kubernetes deployment file", type=str)
  args = parser.parse_args()

  if args.file == "" or args.file == None:
    print("Usage: python k8s-conver-env.py -n [K8S_NAMESPACE] -f [K8S_DEPLOYMENT_FILE_PATH]\n")
    sys.exit(1)

  inFilename = args.file.strip()
  new_files_created = []

  try:
    conf = json.loads(getFileContents(inFilename))
  except Exception, e:
    print("Error parsing JSON K8s config: {}\n".format(str(e)))
    sys.exit(1)

  if 'metadata' not in conf or 'namespace' not in conf['metadata']:
    print("Input kubernetes deployment config is invalid!\n")
    sys.exit(1)

  namespace = conf['metadata']['namespace']

  if 'spec' in conf and 'template' in conf['spec'] and 'spec' in conf['spec']['template'] and 'containers' in conf['spec']['template']['spec']:

    # If the config is valid, then create a backup of the original config file
    new_files_created.append(createBackupFile(inFilename))

    for c in conf['spec']['template']['spec']['containers']:
      if 'env' in c:
        # Write the individual config maps files for each container
        confMapFilePath = "{}/{}-{}-{}.json".format(os.path.dirname(inFilename), "00-configmap", namespace, c["name"])
        new_files_created.append(confMapFilePath)
        writeToFile(confMapFilePath, json.dumps(buildConfigMap(c['env'], namespace, c["name"]), indent=4, sort_keys=True))
        # Set the config map reference
        c['envFrom'] = [{"configMapRef": {"name": "{}-configmap-{}".format(namespace, c["name"])}}]
        # Delete the old environment variable block
        del(c['env'])

    # Overwrite the original input file with the new config
    writeToFile(inFilename, json.dumps(conf, indent=4, sort_keys=True))

    print("The following files have been created:")
    for f in new_files_created:
      if f.find(".bak") >= 0:
        print("\t -> {} (original backup)".format(f))
      else:
        print("\t -> {}".format(f))
      


if __name__ == "__main__":
  main()