n2vc/k8s_juju_conn.py

# Copyright 2019 Canonical Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
#     Unless required by applicable law or agreed to in writing, software
#     distributed under the License is distributed on an "AS IS" BASIS,
#     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#     See the License for the specific language governing permissions and
#     limitations under the License.

import asyncio
from typing import Union
import os
import uuid
import yaml
import tempfile
import binascii

from n2vc.config import EnvironConfig
from n2vc.definitions import RelationEndpoint
from n2vc.exceptions import K8sException
from n2vc.k8s_conn import K8sConnector
from n2vc.kubectl import Kubectl
from .exceptions import MethodNotImplemented
from n2vc.libjuju import Libjuju
from n2vc.utils import obj_to_dict, obj_to_yaml
from n2vc.store import MotorStore
from n2vc.vca.cloud import Cloud
from n2vc.vca.connection import get_connection


RBAC_LABEL_KEY_NAME = "rbac-id"
RBAC_STACK_PREFIX = "juju-credential"


def generate_rbac_id():
    return binascii.hexlify(os.urandom(4)).decode()


class K8sJujuConnector(K8sConnector):
    libjuju = None

    def __init__(
        self,
        fs: object,
        db: object,
        kubectl_command: str = "/usr/bin/kubectl",
        juju_command: str = "/usr/bin/juju",
        log: object = None,
        loop: object = None,
        on_update_db=None,
    ):
        """
        :param fs: file system for kubernetes and helm configuration
        :param db: Database object
        :param kubectl_command: path to kubectl executable
        :param helm_command: path to helm executable
        :param log: logger
        :param: loop: Asyncio loop
        """

        # parent class
        K8sConnector.__init__(self, db, log=log, on_update_db=on_update_db)

        self.fs = fs
        self.loop = loop or asyncio.get_event_loop()
        self.log.debug("Initializing K8S Juju connector")

        db_uri = EnvironConfig(prefixes=["OSMLCM_", "OSMMON_"]).get("database_uri")
        self._store = MotorStore(db_uri)
        self.loading_libjuju = asyncio.Lock(loop=self.loop)
        self.uninstall_locks = {}

        self.log.debug("K8S Juju connector initialized")
        # TODO: Remove these commented lines:
        # self.authenticated = False
        # self.models = {}
        # self.juju_secret = ""

    """Initialization"""

    async def init_env(
        self,
        k8s_creds: str,
        namespace: str = "kube-system",
        reuse_cluster_uuid: str = None,
        **kwargs,
    ) -> (str, bool):
        """
        It prepares a given K8s cluster environment to run Juju bundles.

        :param k8s_creds: credentials to access a given K8s cluster, i.e. a valid
            '.kube/config'
        :param namespace: optional namespace to be used for juju. By default,
            'kube-system' will be used
        :param reuse_cluster_uuid: existing cluster uuid for reuse
        :param: kwargs: Additional parameters
            vca_id (str): VCA ID

        :return: uuid of the K8s cluster and True if connector has installed some
            software in the cluster
            (on error, an exception will be raised)
        """
        libjuju = await self._get_libjuju(kwargs.get("vca_id"))

        cluster_uuid = reuse_cluster_uuid or str(uuid.uuid4())
        kubectl = self._get_kubectl(k8s_creds)

        # CREATING RESOURCES IN K8S
        rbac_id = generate_rbac_id()
        metadata_name = "{}-{}".format(RBAC_STACK_PREFIX, rbac_id)
        labels = {RBAC_STACK_PREFIX: rbac_id}

        # Create cleanup dictionary to clean up created resources
        # if it fails in the middle of the process
        cleanup_data = []
        try:
            self.log.debug("Initializing K8s cluster for juju")
            kubectl.create_cluster_role(name=metadata_name, labels=labels)
            self.log.debug("Cluster role created")
            cleanup_data.append(
                {"delete": kubectl.delete_cluster_role, "args": (metadata_name,)}
            )

            kubectl.create_service_account(name=metadata_name, labels=labels)
            self.log.debug("Service account created")
            cleanup_data.append(
                {"delete": kubectl.delete_service_account, "args": (metadata_name,)}
            )

            kubectl.create_cluster_role_binding(name=metadata_name, labels=labels)
            self.log.debug("Role binding created")
            cleanup_data.append(
                {
                    "delete": kubectl.delete_cluster_role_binding,
                    "args": (metadata_name,),
                }
            )
            token, client_cert_data = await kubectl.get_secret_data(metadata_name)

            default_storage_class = kubectl.get_default_storage_class()
            self.log.debug("Default storage class: {}".format(default_storage_class))
            await libjuju.add_k8s(
                name=cluster_uuid,
                rbac_id=rbac_id,
                token=token,
                client_cert_data=client_cert_data,
                configuration=kubectl.configuration,
                storage_class=default_storage_class,
                credential_name=self._get_credential_name(cluster_uuid),
            )
            self.log.debug("K8s cluster added to juju controller")
            return cluster_uuid, True
        except Exception as e:
            self.log.error("Error initializing k8scluster: {}".format(e), exc_info=True)
            if len(cleanup_data) > 0:
                self.log.debug("Cleaning up created resources in k8s cluster...")
                for item in cleanup_data:
                    delete_function = item["delete"]
                    delete_args = item["args"]
                    delete_function(*delete_args)
                self.log.debug("Cleanup finished")
            raise e

    """Repo Management"""

    async def repo_add(
        self,
        name: str,
        url: str,
        _type: str = "charm",
        cert: str = None,
        user: str = None,
        password: str = None,
    ):
        raise MethodNotImplemented()

    async def repo_list(self):
        raise MethodNotImplemented()

    async def repo_remove(self, name: str):
        raise MethodNotImplemented()

    async def synchronize_repos(self, cluster_uuid: str, name: str):
        """
        Returns None as currently add_repo is not implemented
        """
        return None

    """Reset"""

    async def reset(
        self,
        cluster_uuid: str,
        force: bool = False,
        uninstall_sw: bool = False,
        **kwargs,
    ) -> bool:
        """Reset a cluster

        Resets the Kubernetes cluster by removing the model that represents it.

        :param cluster_uuid str: The UUID of the cluster to reset
        :param force: Force reset
        :param uninstall_sw: Boolean to uninstall sw
        :param: kwargs: Additional parameters
            vca_id (str): VCA ID

        :return: Returns True if successful or raises an exception.
        """

        try:
            self.log.debug("[reset] Removing k8s cloud")
            libjuju = await self._get_libjuju(kwargs.get("vca_id"))

            cloud = Cloud(cluster_uuid, self._get_credential_name(cluster_uuid))

            cloud_creds = await libjuju.get_cloud_credentials(cloud)

            await libjuju.remove_cloud(cluster_uuid)

            credentials = self.get_credentials(cluster_uuid=cluster_uuid)

            kubectl = self._get_kubectl(credentials)

            delete_functions = [
                kubectl.delete_cluster_role_binding,
                kubectl.delete_service_account,
                kubectl.delete_cluster_role,
            ]

            credential_attrs = cloud_creds[0].result["attrs"]
            if RBAC_LABEL_KEY_NAME in credential_attrs:
                rbac_id = credential_attrs[RBAC_LABEL_KEY_NAME]
                metadata_name = "{}-{}".format(RBAC_STACK_PREFIX, rbac_id)
                for delete_func in delete_functions:
                    try:
                        delete_func(metadata_name)
                    except Exception as e:
                        self.log.warning("Cannot remove resource in K8s {}".format(e))

        except Exception as e:
            self.log.debug("Caught exception during reset: {}".format(e))
            raise e
        return True

    """Deployment"""

    async def install(
        self,
        cluster_uuid: str,
        kdu_model: str,
        kdu_instance: str,
        atomic: bool = True,
        timeout: float = 1800,
        params: dict = None,
        db_dict: dict = None,
        kdu_name: str = None,
        namespace: str = None,
        **kwargs,
    ) -> bool:
        """Install a bundle

        :param cluster_uuid str: The UUID of the cluster to install to
        :param kdu_model str: The name or path of a bundle to install
        :param kdu_instance: Kdu instance name
        :param atomic bool: If set, waits until the model is active and resets
                            the cluster on failure.
        :param timeout int: The time, in seconds, to wait for the install
                            to finish
        :param params dict: Key-value pairs of instantiation parameters
        :param kdu_name: Name of the KDU instance to be installed
        :param namespace: K8s namespace to use for the KDU instance
        :param kwargs: Additional parameters
            vca_id (str): VCA ID

        :return: If successful, returns ?
        """
        libjuju = await self._get_libjuju(kwargs.get("vca_id"))
        bundle = kdu_model

        if not db_dict:
            raise K8sException("db_dict must be set")
        if not bundle:
            raise K8sException("bundle must be set")

        if bundle.startswith("cs:"):
            # For Juju Bundles provided by the Charm Store
            pass
        elif bundle.startswith("ch:"):
            # For Juju Bundles provided by the Charm Hub (this only works for juju version >= 2.9)
            pass
        elif bundle.startswith("http"):
            # Download the file
            pass
        else:
            new_workdir = kdu_model.strip(kdu_model.split("/")[-1])
            os.chdir(new_workdir)
            bundle = "local:{}".format(kdu_model)

        # default namespace to kdu_instance
        if not namespace:
            namespace = kdu_instance

        self.log.debug("Checking for model named {}".format(namespace))

        # Create the new model
        self.log.debug("Adding model: {}".format(namespace))
        cloud = Cloud(cluster_uuid, self._get_credential_name(cluster_uuid))
        await libjuju.add_model(namespace, cloud)

        # if model:
        # TODO: Instantiation parameters

        """
        "Juju bundle that models the KDU, in any of the following ways:
            - <juju-repo>/<juju-bundle>
            - <juju-bundle folder under k8s_models folder in the package>
            - <juju-bundle tgz file (w/ or w/o extension) under k8s_models folder
                in the package>
            - <URL_where_to_fetch_juju_bundle>
        """
        try:
            previous_workdir = os.getcwd()
        except FileNotFoundError:
            previous_workdir = "/app/storage"

        self.log.debug("[install] deploying {}".format(bundle))
        instantiation_params = params.get("overlay") if params else None
        await libjuju.deploy(
            bundle,
            model_name=namespace,
            wait=atomic,
            timeout=timeout,
            instantiation_params=instantiation_params,
        )
        os.chdir(previous_workdir)

        # update information in the database (first, the VCA status, and then, the namespace)
        if self.on_update_db:
            await self.on_update_db(
                cluster_uuid,
                kdu_instance,
                filter=db_dict["filter"],
                vca_id=kwargs.get("vca_id"),
            )

        self.db.set_one(
            table="nsrs",
            q_filter={"_admin.deployed.K8s.kdu-instance": kdu_instance},
            update_dict={"_admin.deployed.K8s.$.namespace": namespace},
        )

        return True

    async def scale(
        self,
        kdu_instance: str,
        scale: int,
        resource_name: str,
        total_timeout: float = 1800,
        namespace: str = None,
        **kwargs,
    ) -> bool:
        """Scale an application in a model

        :param: kdu_instance str:        KDU instance name
        :param: scale int:               Scale to which to set the application
        :param: resource_name str:       The application name in the Juju Bundle
        :param: timeout float:           The time, in seconds, to wait for the install
                                         to finish
        :param namespace str: The namespace (model) where the Bundle was deployed
        :param kwargs:                   Additional parameters
                                            vca_id (str): VCA ID

        :return: If successful, returns True
        """

        model_name = self._obtain_namespace(
            kdu_instance=kdu_instance, namespace=namespace
        )
        try:
            libjuju = await self._get_libjuju(kwargs.get("vca_id"))
            await libjuju.scale_application(
                model_name=model_name,
                application_name=resource_name,
                scale=scale,
                total_timeout=total_timeout,
            )
        except Exception as e:
            error_msg = "Error scaling application {} of the model {} of the kdu instance {}: {}".format(
                resource_name, model_name, kdu_instance, e
            )
            self.log.error(error_msg)
            raise K8sException(message=error_msg)
        return True

    async def get_scale_count(
        self, resource_name: str, kdu_instance: str, namespace: str = None, **kwargs
    ) -> int:
        """Get an application scale count

        :param: resource_name str:       The application name in the Juju Bundle
        :param: kdu_instance str:        KDU instance name
        :param namespace str: The namespace (model) where the Bundle was deployed
        :param kwargs:                   Additional parameters
                                            vca_id (str): VCA ID
        :return: Return application instance count
        """

        model_name = self._obtain_namespace(
            kdu_instance=kdu_instance, namespace=namespace
        )
        try:
            libjuju = await self._get_libjuju(kwargs.get("vca_id"))
            status = await libjuju.get_model_status(model_name=model_name)
            return len(status.applications[resource_name].units)
        except Exception as e:
            error_msg = (
                f"Error getting scale count from application {resource_name} of the model {model_name} of "
                f"the kdu instance {kdu_instance}: {e}"
            )
            self.log.error(error_msg)
            raise K8sException(message=error_msg)

    async def instances_list(self, cluster_uuid: str) -> list:
        """
        returns a list of deployed releases in a cluster

        :param cluster_uuid: the cluster
        :return:
        """
        return []

    async def upgrade(
        self,
        cluster_uuid: str,
        kdu_instance: str,
        kdu_model: str = None,
        params: dict = None,
    ) -> str:
        """Upgrade a model

        :param cluster_uuid str: The UUID of the cluster to upgrade
        :param kdu_instance str: The unique name of the KDU instance
        :param kdu_model str: The name or path of the bundle to upgrade to
        :param params dict: Key-value pairs of instantiation parameters

        :return: If successful, reference to the new revision number of the
                 KDU instance.
        """

        # TODO: Loop through the bundle and upgrade each charm individually

        """
        The API doesn't have a concept of bundle upgrades, because there are
        many possible changes: charm revision, disk, number of units, etc.

        As such, we are only supporting a limited subset of upgrades. We'll
        upgrade the charm revision but leave storage and scale untouched.

        Scale changes should happen through OSM constructs, and changes to
        storage would require a redeployment of the service, at least in this
        initial release.
        """
        raise MethodNotImplemented()

    """Rollback"""

    async def rollback(
        self, cluster_uuid: str, kdu_instance: str, revision: int = 0
    ) -> str:
        """Rollback a model

        :param cluster_uuid str: The UUID of the cluster to rollback
        :param kdu_instance str: The unique name of the KDU instance
        :param revision int: The revision to revert to. If omitted, rolls back
                             the previous upgrade.

        :return: If successful, returns the revision of active KDU instance,
                 or raises an exception
        """
        raise MethodNotImplemented()

    """Deletion"""

    async def uninstall(
        self, cluster_uuid: str, kdu_instance: str, namespace: str = None, **kwargs
    ) -> bool:
        """Uninstall a KDU instance

        :param cluster_uuid str: The UUID of the cluster
        :param kdu_instance str: The unique name of the KDU instance
        :param namespace str: The namespace (model) where the Bundle was deployed
        :param kwargs: Additional parameters
            vca_id (str): VCA ID

        :return: Returns True if successful, or raises an exception
        """
        model_name = self._obtain_namespace(
            kdu_instance=kdu_instance, namespace=namespace
        )

        self.log.debug(f"[uninstall] Destroying model: {model_name}")

        will_not_delete = False
        if model_name not in self.uninstall_locks:
            self.uninstall_locks[model_name] = asyncio.Lock(loop=self.loop)
        delete_lock = self.uninstall_locks[model_name]

        while delete_lock.locked():
            will_not_delete = True
            await asyncio.sleep(0.1)

        if will_not_delete:
            self.log.info("Model {} deleted by another worker.".format(model_name))
            return True

        try:
            async with delete_lock:
                libjuju = await self._get_libjuju(kwargs.get("vca_id"))

                await libjuju.destroy_model(model_name, total_timeout=3600)
        finally:
            self.uninstall_locks.pop(model_name)

        self.log.debug(f"[uninstall] Model {model_name} destroyed")
        return True

    async def upgrade_charm(
        self,
        ee_id: str = None,
        path: str = None,
        charm_id: str = None,
        charm_type: str = None,
        timeout: float = None,
    ) -> str:
        """This method upgrade charms in VNFs

        Args:
            ee_id:  Execution environment id
            path:   Local path to the charm
            charm_id:   charm-id
            charm_type: Charm type can be lxc-proxy-charm, native-charm or k8s-proxy-charm
            timeout: (Float)    Timeout for the ns update operation

        Returns:
            The output of the update operation if status equals to "completed"
        """
        raise K8sException(
            "KDUs deployed with Juju Bundle do not support charm upgrade"
        )

    async def exec_primitive(
        self,
        cluster_uuid: str = None,
        kdu_instance: str = None,
        primitive_name: str = None,
        timeout: float = 300,
        params: dict = None,
        db_dict: dict = None,
        namespace: str = None,
        **kwargs,
    ) -> str:
        """Exec primitive (Juju action)

        :param cluster_uuid str: The UUID of the cluster
        :param kdu_instance str: The unique name of the KDU instance
        :param primitive_name: Name of action that will be executed
        :param timeout: Timeout for action execution
        :param params: Dictionary of all the parameters needed for the action
        :param db_dict: Dictionary for any additional data
        :param namespace str: The namespace (model) where the Bundle was deployed
        :param kwargs: Additional parameters
            vca_id (str): VCA ID

        :return: Returns the output of the action
        """
        libjuju = await self._get_libjuju(kwargs.get("vca_id"))

        namespace = self._obtain_namespace(
            kdu_instance=kdu_instance, namespace=namespace
        )

        if not params or "application-name" not in params:
            raise K8sException(
                "Missing application-name argument, \
                                argument needed for K8s actions"
            )
        try:
            self.log.debug(
                "[exec_primitive] Getting model "
                "{} for the kdu_instance: {}".format(namespace, kdu_instance)
            )
            application_name = params["application-name"]
            actions = await libjuju.get_actions(
                application_name=application_name, model_name=namespace
            )
            if primitive_name not in actions:
                raise K8sException("Primitive {} not found".format(primitive_name))
            output, status = await libjuju.execute_action(
                application_name=application_name,
                model_name=namespace,
                action_name=primitive_name,
                **params,
            )

            if status != "completed":
                raise K8sException(
                    "status is not completed: {} output: {}".format(status, output)
                )
            if self.on_update_db:
                await self.on_update_db(
                    cluster_uuid=cluster_uuid,
                    kdu_instance=kdu_instance,
                    filter=db_dict["filter"],
                )

            return output

        except Exception as e:
            error_msg = "Error executing primitive {}: {}".format(primitive_name, e)
            self.log.error(error_msg)
            raise K8sException(message=error_msg)

    """Introspection"""

    async def inspect_kdu(self, kdu_model: str) -> dict:
        """Inspect a KDU

        Inspects a bundle and returns a dictionary of config parameters and
        their default values.

        :param kdu_model str: The name or path of the bundle to inspect.

        :return: If successful, returns a dictionary of available parameters
                 and their default values.
        """

        kdu = {}
        if not os.path.exists(kdu_model):
            raise K8sException("file {} not found".format(kdu_model))

        with open(kdu_model, "r") as f:
            bundle = yaml.safe_load(f.read())

            """
            {
                'description': 'Test bundle',
                'bundle': 'kubernetes',
                'applications': {
                    'mariadb-k8s': {
                        'charm': 'cs:~charmed-osm/mariadb-k8s-20',
                        'scale': 1,
                        'options': {
                            'password': 'manopw',
                            'root_password': 'osm4u',
                            'user': 'mano'
                        },
                        'series': 'kubernetes'
                    }
                }
            }
            """
            # TODO: This should be returned in an agreed-upon format
            kdu = bundle["applications"]

        return kdu

    async def help_kdu(self, kdu_model: str) -> str:
        """View the README

                If available, returns the README of the bundle.

                :param kdu_model str: The name or path of a bundle
        f
                :return: If found, returns the contents of the README.
        """
        readme = None

        files = ["README", "README.txt", "README.md"]
        path = os.path.dirname(kdu_model)
        for file in os.listdir(path):
            if file in files:
                with open(file, "r") as f:
                    readme = f.read()
                    break

        return readme

    async def status_kdu(
        self,
        cluster_uuid: str,
        kdu_instance: str,
        complete_status: bool = False,
        yaml_format: bool = False,
        namespace: str = None,
        **kwargs,
    ) -> Union[str, dict]:
        """Get the status of the KDU

        Get the current status of the KDU instance.

        :param cluster_uuid str: The UUID of the cluster
        :param kdu_instance str: The unique id of the KDU instance
        :param complete_status: To get the complete_status of the KDU
        :param yaml_format: To get the status in proper format for NSR record
        :param namespace str: The namespace (model) where the Bundle was deployed
        :param: kwargs: Additional parameters
            vca_id (str): VCA ID

        :return: Returns a dictionary containing namespace, state, resources,
                 and deployment_time and returns complete_status if complete_status is True
        """
        libjuju = await self._get_libjuju(kwargs.get("vca_id"))
        status = {}

        model_name = self._obtain_namespace(
            kdu_instance=kdu_instance, namespace=namespace
        )
        model_status = await libjuju.get_model_status(model_name=model_name)

        if not complete_status:
            for name in model_status.applications:
                application = model_status.applications[name]
                status[name] = {"status": application["status"]["status"]}
        else:
            if yaml_format:
                return obj_to_yaml(model_status)
            else:
                return obj_to_dict(model_status)

        return status

    async def add_relation(
        self, provider: RelationEndpoint, requirer: RelationEndpoint
    ):
        """
        Add relation between two charmed endpoints

        :param: provider: Provider relation endpoint
        :param: requirer: Requirer relation endpoint
        """
        self.log.debug(f"adding new relation between {provider} and {requirer}")
        cross_model_relation = (
            provider.model_name != requirer.model_name
            or provider.vca_id != requirer.vca_id
        )
        try:
            if cross_model_relation:
                # Cross-model relation
                provider_libjuju = await self._get_libjuju(provider.vca_id)
                requirer_libjuju = await self._get_libjuju(requirer.vca_id)
                offer = await provider_libjuju.offer(provider)
                if offer:
                    saas_name = await requirer_libjuju.consume(
                        requirer.model_name, offer, provider_libjuju
                    )
                    await requirer_libjuju.add_relation(
                        requirer.model_name, requirer.endpoint, saas_name
                    )
            else:
                # Standard relation
                vca_id = provider.vca_id
                model = provider.model_name
                libjuju = await self._get_libjuju(vca_id)
                # add juju relations between two applications
                await libjuju.add_relation(
                    model_name=model,
                    endpoint_1=provider.endpoint,
                    endpoint_2=requirer.endpoint,
                )
        except Exception as e:
            message = f"Error adding relation between {provider} and {requirer}: {e}"
            self.log.error(message)
            raise Exception(message=message)

    async def update_vca_status(
        self, vcastatus: dict, kdu_instance: str, namespace: str = None, **kwargs
    ):
        """
        Add all configs, actions, executed actions of all applications in a model to vcastatus dict

        :param vcastatus dict: dict containing vcastatus
        :param kdu_instance str: The unique id of the KDU instance
        :param namespace str: The namespace (model) where the Bundle was deployed
        :param: kwargs: Additional parameters
            vca_id (str): VCA ID

        :return: None
        """

        model_name = self._obtain_namespace(
            kdu_instance=kdu_instance, namespace=namespace
        )

        libjuju = await self._get_libjuju(kwargs.get("vca_id"))
        try:
            for vca_model_name in vcastatus:
                # Adding executed actions
                vcastatus[vca_model_name][
                    "executedActions"
                ] = await libjuju.get_executed_actions(model_name=model_name)

                for application in vcastatus[vca_model_name]["applications"]:
                    # Adding application actions
                    vcastatus[vca_model_name]["applications"][application][
                        "actions"
                    ] = {}
                    # Adding application configs
                    vcastatus[vca_model_name]["applications"][application][
                        "configs"
                    ] = await libjuju.get_application_configs(
                        model_name=model_name, application_name=application
                    )

        except Exception as e:
            self.log.debug("Error in updating vca status: {}".format(str(e)))

    async def get_services(
        self, cluster_uuid: str, kdu_instance: str, namespace: str
    ) -> list:
        """Return a list of services of a kdu_instance"""

        namespace = self._obtain_namespace(
            kdu_instance=kdu_instance, namespace=namespace
        )

        credentials = self.get_credentials(cluster_uuid=cluster_uuid)
        kubectl = self._get_kubectl(credentials)
        return kubectl.get_services(
            field_selector="metadata.namespace={}".format(namespace)
        )

    async def get_service(
        self, cluster_uuid: str, service_name: str, namespace: str
    ) -> object:
        """Return data for a specific service inside a namespace"""

        credentials = self.get_credentials(cluster_uuid=cluster_uuid)
        kubectl = self._get_kubectl(credentials)
        return kubectl.get_services(
            field_selector="metadata.name={},metadata.namespace={}".format(
                service_name, namespace
            )
        )[0]

    def get_credentials(self, cluster_uuid: str) -> str:
        """
        Get Cluster Kubeconfig
        """
        k8scluster = self.db.get_one(
            "k8sclusters", q_filter={"_id": cluster_uuid}, fail_on_empty=False
        )

        self.db.encrypt_decrypt_fields(
            k8scluster.get("credentials"),
            "decrypt",
            ["password", "secret"],
            schema_version=k8scluster["schema_version"],
            salt=k8scluster["_id"],
        )

        return yaml.safe_dump(k8scluster.get("credentials"))

    def _get_credential_name(self, cluster_uuid: str) -> str:
        """
        Get credential name for a k8s cloud

        We cannot use the cluster_uuid for the credential name directly,
        because it cannot start with a number, it must start with a letter.
        Therefore, the k8s cloud credential name will be "cred-" followed
        by the cluster uuid.

        :param: cluster_uuid:   Cluster UUID of the kubernetes cloud (=cloud_name)

        :return:                Name to use for the credential name.
        """
        return "cred-{}".format(cluster_uuid)

    def get_namespace(self, cluster_uuid: str) -> str:
        """Get the namespace UUID
        Gets the namespace's unique name

        :param cluster_uuid str: The UUID of the cluster
        :returns: The namespace UUID, or raises an exception
        """
        pass

    @staticmethod
    def generate_kdu_instance_name(**kwargs):
        db_dict = kwargs.get("db_dict")
        kdu_name = kwargs.get("kdu_name", None)
        if kdu_name:
            kdu_instance = "{}-{}".format(kdu_name, db_dict["filter"]["_id"])
        else:
            kdu_instance = db_dict["filter"]["_id"]
        return kdu_instance

    async def _get_libjuju(self, vca_id: str = None) -> Libjuju:
        """
        Get libjuju object

        :param: vca_id: VCA ID
                        If None, get a libjuju object with a Connection to the default VCA
                        Else, geta libjuju object with a Connection to the specified VCA
        """
        if not vca_id:
            while self.loading_libjuju.locked():
                await asyncio.sleep(0.1)
            if not self.libjuju:
                async with self.loading_libjuju:
                    vca_connection = await get_connection(self._store)
                    self.libjuju = Libjuju(vca_connection, loop=self.loop, log=self.log)
            return self.libjuju
        else:
            vca_connection = await get_connection(self._store, vca_id)
            return Libjuju(vca_connection, loop=self.loop, log=self.log, n2vc=self)

    def _get_kubectl(self, credentials: str) -> Kubectl:
        """
        Get Kubectl object

        :param: kubeconfig_credentials: Kubeconfig credentials
        """
        kubecfg = tempfile.NamedTemporaryFile()
        with open(kubecfg.name, "w") as kubecfg_file:
            kubecfg_file.write(credentials)
        return Kubectl(config_file=kubecfg.name)

    def _obtain_namespace(self, kdu_instance: str, namespace: str = None) -> str:
        """
        Obtain the namespace/model name to use in the instantiation of a Juju Bundle in K8s. The default namespace is
        the kdu_instance name. However, if the user passes the namespace where he wants to deploy the bundle,
        that namespace will be used.

        :param kdu_instance: the default KDU instance name
        :param namespace: the namespace passed by the User
        """

        # deault the namespace/model name to the kdu_instance name TODO -> this should be the real return... But
        #  once the namespace is not passed in most methods, I had to do this in another way. But I think this should
        #  be the procedure in the future return namespace if namespace else kdu_instance

        # TODO -> has referred above, this should be avoided in the future, this is temporary, in order to avoid
        #  compatibility issues
        return (
            namespace
            if namespace
            else self._obtain_namespace_from_db(kdu_instance=kdu_instance)
        )

    def _obtain_namespace_from_db(self, kdu_instance: str) -> str:
        db_nsrs = self.db.get_one(
            table="nsrs", q_filter={"_admin.deployed.K8s.kdu-instance": kdu_instance}
        )
        for k8s in db_nsrs["_admin"]["deployed"]["K8s"]:
            if k8s.get("kdu-instance") == kdu_instance:
                return k8s.get("namespace")
        return ""