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charms/worker/k8s/lib/charms/kubernetes_libs/v0/etcd.py
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| # Copyright 2024 Canonical Ltd. | ||
| # See LICENSE file for licensing details. | ||
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| # 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. | ||
|
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| """Charm library for the etcd reactive relation. | ||
| The module defines an interface for a charm that requires the etcd relation. | ||
| It encapsulates the functionality and events related to managing the etcd relation, | ||
| including connection, availability of data, and handling of TLS credentials. | ||
| It uses events to handle state changes in the etcd relation, such as when a connection is | ||
| established (`EtcdConnected`), when etcd data is available (`EtcdAvailable`), and when TLS data | ||
| for etcd is available (`EtcdTLSAvailable`). | ||
| A class `EtcdReactiveRequires` is defined, which provides an abstraction over the charm's | ||
| requires relation to etcd. It encapsulates the functionality to check the status of the | ||
| relation, get connection details, and handle client credentials. | ||
| This module also provides helper methods for handling client credentials, such as | ||
| saving them to local files and retrieving them from the relation data. | ||
| You can use this charm library in your charm by adding it as a dependency in your | ||
| `charmcraft.yaml` file and then importing the relevant classes and functions. | ||
| Example usage: | ||
| ```python | ||
| from charms.kubernetes_libs.v0.etcd import EtcdReactiveRequires | ||
| ... | ||
| def __init__(self, *args): | ||
| self.etcd = EtcdReactiveRequires(self) | ||
| ... | ||
| # Handle the events from the relation | ||
| self.framework.observe(self.etcd.on.connected, self._on_etcd_connected) | ||
| self.framework.observe(self.etcd.on.available, self._on_etcd_available) | ||
| self.framework.observe(self.etcd.on.tls_available, self._on_etcd_tls_available) | ||
| ``` | ||
| """ | ||
|
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| import hashlib | ||
| import json | ||
| import logging | ||
| import os | ||
| from functools import cached_property | ||
| from typing import Optional | ||
|
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| from ops.framework import EventBase, EventSource, Object, ObjectEvents, StoredState | ||
| from ops.model import Relation | ||
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| # The unique Charmhub library identifier, never change it | ||
| LIBID = "2d422394fe044d61ad1dc044ed051d1b" | ||
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| # Increment this major API version when introducing breaking changes | ||
| LIBAPI = 0 | ||
|
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| # Increment this PATCH version before using `charmcraft publish-lib` or reset | ||
| # to 0 if you are raising the major API version | ||
| LIBPATCH = 1 | ||
|
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| log = logging.getLogger(__name__) | ||
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|
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| class EtcdAvailable(EventBase): | ||
| """Event emitted when the etcd relation data is available.""" | ||
|
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| pass | ||
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| class EtcdConnected(EventBase): | ||
| """Event emitted when the etcd relation is connected.""" | ||
|
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| pass | ||
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| class EtcdTLSAvailable(EventBase): | ||
| """Event emitted when the etcd relation TLS data is available.""" | ||
|
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| pass | ||
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| class EtcdConsumerEvents(ObjectEvents): | ||
| """Events emitted by the etcd translation interface.""" | ||
|
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| available = EventSource(EtcdAvailable) | ||
| connected = EventSource(EtcdConnected) | ||
| tls_available = EventSource(EtcdTLSAvailable) | ||
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| class EtcdReactiveRequires(Object): | ||
| """Requires side of the etcd interface. | ||
| This class is a translation interface that wraps the requires side | ||
| of the reactive etcd interface. | ||
| """ | ||
|
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| state = StoredState() | ||
| on = EtcdConsumerEvents() | ||
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| def __init__(self, charm, endpoint="etcd"): | ||
| super().__init__(charm, f"relation-{endpoint}") | ||
| self.charm = charm | ||
| self.endpoint = endpoint | ||
|
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| self.state.set_default( | ||
| connected=False, available=False, tls_available=False, connection_string="" | ||
| ) | ||
|
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||
| for event in ( | ||
| charm.on[endpoint].relation_created, | ||
| charm.on[endpoint].relation_joined, | ||
| charm.on[endpoint].relation_changed, | ||
| charm.on[endpoint].relation_departed, | ||
| charm.on[endpoint].relation_broken, | ||
| ): | ||
| self.framework.observe(event, self._check_relation) | ||
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| def _check_relation(self, _: EventBase): | ||
| """Check if the relation is available and emit the appropriate event.""" | ||
| if self.relation: | ||
| self.state.connected = True | ||
| self.on.connected.emit() | ||
| # etcd is available only if the connection string is available | ||
| if self.get_connection_string(): | ||
| self.state.available = True | ||
| self.on.available.emit() | ||
| # etcd tls is available only if the tls data is available | ||
| # (i.e. client cert, client key, ca cert) | ||
| cert = self.get_client_credentials() | ||
| if cert["client_cert"] and cert["client_key"] and cert["client_ca"]: | ||
| self.state.tls_available = True | ||
| self.on.tls_available.emit() | ||
|
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||
| def _get_dict_hash(self, data: dict) -> str: | ||
| """Generate a SHA-256 hash for a dictionary. | ||
| This function converts the dictionary into a JSON string, ensuring it | ||
| is sorted in order. It then generates a SHA-256 hash of this string. | ||
| Args: | ||
| data(dict): The dictionary to be hashed. | ||
| Returns: | ||
| str: The hexadecimal representation of the hash of the dictionary. | ||
| """ | ||
| dump = json.dumps(data, sort_keys=True) | ||
| hash_obj = hashlib.sha256() | ||
| hash_obj.update(dump.encode()) | ||
| return hash_obj.hexdigest() | ||
|
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||
| @property | ||
| def is_ready(self): | ||
| """Check if the relation is available and emit the appropriate event.""" | ||
| if self.relation: | ||
| if self.get_connection_string(): | ||
| cert = self.get_client_credentials() | ||
| if all(cert.get(key) for key in ["client_cert", "client_key", "client_ca"]): | ||
| return True | ||
| return False | ||
|
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| def get_connection_string(self) -> str: | ||
| """Return the connection string for etcd.""" | ||
| remote_data = self._remote_data | ||
| if remote_data: | ||
| return remote_data.get("connection_string") | ||
| return "" | ||
|
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| def get_client_credentials(self) -> dict: | ||
| """Return the client credentials for etcd.""" | ||
| remote_data = self._remote_data | ||
| return { | ||
| "client_cert": remote_data.get("client_cert"), | ||
| "client_key": remote_data.get("client_key"), | ||
| "client_ca": remote_data.get("client_ca"), | ||
| } | ||
|
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| @cached_property | ||
| def relation(self) -> Optional[Relation]: | ||
| """Return the relation object for this interface.""" | ||
| return self.model.get_relation(self.endpoint) | ||
|
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||
| @property | ||
| def _remote_data(self): | ||
| """Return the remote relation data for this interface.""" | ||
| if not (self.relation and self.relation.units): | ||
| return {} | ||
|
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| first_unit = next(iter(self.relation.units), None) | ||
| data = self.relation.data[first_unit] | ||
| return data | ||
|
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| def save_client_credentials(self, ca_path, cert_path, key_path): | ||
| """Save all the client certificates for etcd to local files.""" | ||
| credentials = {"client_key": key_path, "client_cert": cert_path, "client_ca": ca_path} | ||
| for key, path in credentials.items(): | ||
| self._save_remote_data(key, path) | ||
|
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| def _save_remote_data(self, key: str, path: str): | ||
| """Save the remote data to a file.""" | ||
| value = self._remote_data.get(key) | ||
| if value: | ||
| parent = os.path.dirname(path) | ||
| if not os.path.isdir(parent): | ||
| os.makedirs(parent) | ||
| with open(path, "w") as stream: | ||
| stream.write(value) |
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