问题
The Python API is available to read objects from a cluster. By cloning we can say:
- Get a copy of an existing Kubernetes object using
kubectl get - Change the properties of the object
- Apply the new object
Until recently, the option to --export api was deprecated in 1.14. How can we use the Python Kubernetes API to do the steps from 1-3 described above?
There are multiple questions about how to extract the code from Python API to YAML, but it's unclear how to transform the Kubernetes API object.
回答1:
After looking at the requirement, I spent a couple of hours researching the Kubernetes Python API. Issue 340 and others ask about how to transform the Kubernetes API object into a dict, but the only workaround I found was to retrieve the raw data and then convert to JSON.
- The following code uses the Kubernetes API to get a
deploymentand its relatedhpafrom the namespaced objects, but retrieving their raw values as JSON. - Then, after transforming the data into a dict, you can alternatively clean up the data by removing null references.
- Once you are done, you can transform the
dictas YAML payload to then save the YAML to the file system - Finally, you can apply either using
kubectlor the Kubernetes Python API.
Note:
- Make sure to set
KUBECONFIG=configso that you can point to a cluster - Make sure to adjust the values of
origin_obj_name = "istio-ingressgateway"andorigin_obj_namespace = "istio-system"with the name of the corresponding objects to be cloned in the given namespace.
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))
回答2:
Not python, but I've used jq in the past to quickly clone something with the small customisations required for each use case (usually cloning secrets into a new namespace).
kc get pod whatever-85pmk -o json \
| jq 'del(.status, .metadata ) | .metadata.name="newname"' \
| kc apply -f - -o yaml --dry-run
来源：https://stackoverflow.com/questions/59977058/clone-kubernetes-objects-programmatically-using-the-python-api