<p>The Python API is available to read objects from a cluster. By cloning we can say:</p>

<ol>
<li>Get a copy of an existing Kubernetes object using <code>kubectl get</code></li>
<li>Change the properties of the object</li>
<li>Apply the new object</li>
</ol>

<p>Until recently, the option to <a href="https://medium.com/@jonathan.johnson/export-has-been-deprecated-in-1-14-51cfef5a0cb7" rel="nofollow noreferrer"><code>--export</code> api was deprecated in 1.14</a>. How can we use the Python Kubernetes API to do the steps from 1-3 described above?</p>

<p>There are multiple questions about how to extract the <a href="https://github.com/kubernetes-client/python/issues/977" rel="nofollow noreferrer">code from Python API to YAML</a>, but it's unclear how to transform the Kubernetes API object. </p>

<p>After looking at the requirement, I spent a couple of hours researching the Kubernetes Python API. <a href="https://github.com/kubernetes-client/python/issues/340" rel="nofollow noreferrer">Issue 340</a> and others ask about how to transform the Kubernetes API object into a <code>dict</code>, but the only workaround I found was to <a href="https://github.com/kubernetes-client/python/issues/574#issuecomment-405400414" rel="nofollow noreferrer">retrieve the raw data</a> and then convert to JSON.</p>

<ul>
<li>The following code uses the Kubernetes API to get a <code>deployment</code> and its related <code>hpa</code> from the namespaced objects, but retrieving their raw values as JSON. </li>
<li>Then, after transforming the data into a dict, you can alternatively clean up the data by <a href="https://stackoverflow.com/questions/12118695/efficient-way-to-remove-keys-with-empty-strings-from-a-dict/59959570#59959570">removing null references</a>.</li>
<li>Once you are done, you can transform the <code>dict</code> as YAML payload to then <a href="https://stackoverflow.com/questions/12470665/how-can-i-write-data-in-yaml-format-in-a-file/18210750#18210750">save the YAML to the file system</a> </li>
<li>Finally, you can apply either using <code>kubectl</code> or the Kubernetes Python API.</li>
</ul>

<p>Note:</p>

<ul>
<li>Make sure to set <code>KUBECONFIG=config</code> so that you can point to a cluster</li>
<li>Make sure to adjust the values of <code>origin_obj_name = "istio-ingressgateway"</code> and <code>origin_obj_namespace = "istio-system"</code> with the name of the corresponding objects to be cloned in the given namespace.</li>
</ul>

<pre class="lang-py prettyprint-override"><code>import os
import logging
import yaml
import json
logging.basicConfig(level = logging.INFO)

import crayons
from kubernetes import client, config
from kubernetes.client.rest import ApiException

LOGGER = logging.getLogger(" IngressGatewayCreator ")

class IngressGatewayCreator:

    @staticmethod
    def clone_default_ingress(clone_context):
        # Clone the deployment
        IngressGatewayCreator.clone_deployment_object(clone_context)

        # Clone the deployment's HPA
        IngressGatewayCreator.clone_hpa_object(clone_context)

    @staticmethod
    def clone_deployment_object(clone_context):
        kubeconfig = os.getenv('KUBECONFIG')
        config.load_kube_config(kubeconfig)
        v1apps = client.AppsV1beta1Api()

        deployment_name = clone_context.origin_obj_name
        namespace = clone_context.origin_obj_namespace

        try:
            # gets an instance of the api without deserialization to model
            # https://github.com/kubernetes-client/python/issues/574#issuecomment-405400414
            deployment = v1apps.read_namespaced_deployment(deployment_name, namespace, _preload_content=False)

        except ApiException as error:
            if error.status == 404:
                LOGGER.info("Deployment %s not found in namespace %s", deployment_name, namespace)
                return
            raise

        # Clone the object deployment as a dic
        cloned_dict = IngressGatewayCreator.clone_k8s_object(deployment, clone_context)

        # Change additional objects
        cloned_dict["spec"]["selector"]["matchLabels"]["istio"] = clone_context.name
        cloned_dict["spec"]["template"]["metadata"]["labels"]["istio"] = clone_context.name

        # Save the deployment template in the output dir
        context.save_clone_as_yaml(cloned_dict, "deployment")

    @staticmethod
    def clone_hpa_object(clone_context):
        kubeconfig = os.getenv('KUBECONFIG')
        config.load_kube_config(kubeconfig)
        hpas = client.AutoscalingV1Api()

        hpa_name = clone_context.origin_obj_name
        namespace = clone_context.origin_obj_namespace

        try:
            # gets an instance of the api without deserialization to model
            # https://github.com/kubernetes-client/python/issues/574#issuecomment-405400414
            hpa = hpas.read_namespaced_horizontal_pod_autoscaler(hpa_name, namespace, _preload_content=False)

        except ApiException as error:
            if error.status == 404:
                LOGGER.info("HPA %s not found in namespace %s", hpa_name, namespace)
                return
            raise

        # Clone the object deployment as a dic
        cloned_dict = IngressGatewayCreator.clone_k8s_object(hpa, clone_context)

        # Change additional objects
        cloned_dict["spec"]["scaleTargetRef"]["name"] = clone_context.name

        # Save the deployment template in the output dir
        context.save_clone_as_yaml(cloned_dict, "hpa")

    @staticmethod
    def clone_k8s_object(k8s_object, clone_context):
        # Manipilate in the dict level, not k8s api, but from the fetched raw object
        # https://github.com/kubernetes-client/python/issues/574#issuecomment-405400414
        cloned_obj = json.loads(k8s_object.data)

        labels = cloned_obj['metadata']['labels']
        labels['istio'] = clone_context.name

        cloned_obj['status'] = None

        # Scrub by removing the "null" and "None" values
        cloned_obj = IngressGatewayCreator.scrub_dict(cloned_obj)

        # Patch the metadata with the name and labels adjusted
        cloned_obj['metadata'] = {
            "name": clone_context.name,
            "namespace": clone_context.origin_obj_namespace,
            "labels": labels
        }

        return cloned_obj

    # https://stackoverflow.com/questions/12118695/efficient-way-to-remove-keys-with-empty-strings-from-a-dict/59959570#59959570
    @staticmethod
    def scrub_dict(d):
        new_dict = {}
        for k, v in d.items():
            if isinstance(v, dict):
                v = IngressGatewayCreator.scrub_dict(v)
            if isinstance(v, list):
                v = IngressGatewayCreator.scrub_list(v)
            if not v in (u'', None, {}):
                new_dict[k] = v
        return new_dict

    # https://stackoverflow.com/questions/12118695/efficient-way-to-remove-keys-with-empty-strings-from-a-dict/59959570#59959570
    @staticmethod
    def scrub_list(d):
        scrubbed_list = []
        for i in d:
            if isinstance(i, dict):
                i = IngressGatewayCreator.scrub_dict(i)
            scrubbed_list.append(i)
        return scrubbed_list


class IngressGatewayContext:

    def __init__(self, manifest_dir, name, hostname, nats, type):
        self.manifest_dir = manifest_dir
        self.name = name
        self.hostname = hostname
        self.nats = nats
        self.ingress_type = type

        self.origin_obj_name = "istio-ingressgateway"
        self.origin_obj_namespace = "istio-system"

    def save_clone_as_yaml(self, k8s_object, kind):
        try:
            # Just try to create if it doesn't exist
            os.makedirs(self.manifest_dir)

        except FileExistsError:
            LOGGER.debug("Dir already exists %s", self.manifest_dir)

        full_file_path = os.path.join(self.manifest_dir, self.name + '-' + kind + '.yaml')

        # Store in the file-system with the name provided
        # https://stackoverflow.com/questions/12470665/how-can-i-write-data-in-yaml-format-in-a-file/18210750#18210750
        with open(full_file_path, 'w') as yaml_file:
            yaml.dump(k8s_object, yaml_file, default_flow_style=False)

        LOGGER.info(crayons.yellow("Saved %s '%s' at %s: \n%s"), kind, self.name, full_file_path, k8s_object)

try:
    k8s_clone_name = "http2-ingressgateway"
    hostname = "my-nlb-awesome.a.company.com"
    nats = ["123.345.678.11", "333.444.222.111", "33.221.444.23"]
    manifest_dir = "out/clones"

    context = IngressGatewayContext(manifest_dir, k8s_clone_name, hostname, nats, "nlb")

    IngressGatewayCreator.clone_default_ingress(context)

except Exception as err:
  print("ERROR: {}".format(err))
</code></pre>
