Support node labelling by an ops version of this layer

.gitignore

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 .tox/
 __pycache__/
 *.pyc
+*.egg-info
+.coverage

LICENSE

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ops/charms/node_base.py

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+"""Library shared between kubernetes control plane and kubernetes worker charms."""
+
+import json
+import logging
+from subprocess import run
+from os import PathLike
+import time
+from typing import Union, List, Mapping, Optional, Protocol, Tuple
+
+from ops import Model, Object, CharmMeta, StoredState
+
+log = logging.getLogger(__name__)
+
+
+class Charm(Protocol):
+    def get_node_name(self) -> str:
+        ...
+
+    def get_cloud_name(self) -> str:
+        ...
+
+    model: Model
+
+    meta: CharmMeta
+
+
+class LabelMaker(Object):
+    """Use to apply labels to a kubernetes node."""
+
+    _stored = StoredState()
+
+    class NodeLabelError(Exception):
+        """Raised when there's an error labeling a node."""
+
+        pass
+
+    def __init__(self, charm: Charm, kubeconfig_path: Union[PathLike, str]):
+        super().__init__(parent=charm, key="NodeBase")
+        self.kubeconfig_path = kubeconfig_path
+        self.charm = charm
+        self._stored.set_default(current_labels=dict())
+
+    @staticmethod
+    def _retried_call(
+        cmd: List[str], retry_msg: str, timeout: int = 180
+    ) -> Tuple[str, str]:
+        deadline = time.time() + timeout
+        while time.time() < deadline:
+            rc = run(cmd)
+            if rc.returncode == 0:
+                return rc.stdout, rc.stderr
+            log.info(retry_msg)
+            time.sleep(1)
+        else:
+            raise LabelMaker.NodeLabelError(retry_msg)
+
+    def active_labels(self) -> Optional[Mapping[str, str]]:
+        """
+        Returns all existing labels if the api server fetch from the node,
+        otherwise returns None indicating the node cannot be relabeled.
+        """
+        cmd = "kubectl --kubeconfig={0} get node {1} -o=jsonpath='{.metadata.labels}"
+        cmd = cmd.format(self.kubeconfig_path, self.charm.get_node_name())
+        retry_msg = "Failed to get labels. Will retry."
+        try:
+            label_json = LabelMaker._retried_call(cmd.split(), retry_msg)
+        except LabelMaker.NodeLabelError:
+            return None
+        try:
+            return json.loads(label_json)
+        except json.JSONDecodeError:
+            return None
+
+    def set_label(self, label: str, value: str) -> None:
+        """
+        Add a label to this node.
+
+        @param str label: Label name to apply
+        @param str value: Value to associate with the label
+        @raises LabelMaker.NodeLabelError: if the label cannot be added
+        """
+        cmd = "kubectl --kubeconfig={0} label node {1} {2}={3} --overwrite"
+        cmd = cmd.format(self.kubeconfig_path, self.charm.get_node_name(), label, value)
+        retry_msg = "Failed to apply label {0}={1}. Will retry.".format(label, value)
+        LabelMaker._retried_call(cmd.split(), retry_msg)
+
+    def remove_label(self, label: str) -> None:
+        """
+        Remove a label to this node.
+
+        @param str label: Label name to remove
+        @raises LabelMaker.NodeLabelError: if the label cannot be removed
+        """
+        cmd = "kubectl --kubeconfig={0} label node {1} {2}-"
+        cmd = cmd.format(self.kubeconfig_path, self.charm.get_node_name(), label)
+        retry_msg = "Failed to remove label {0}. Will retry.".format(label)
+        LabelMaker._retried_call(cmd.split(), retry_msg)
+
+    def apply_node_labels(self) -> None:
+        """
+        Parse the `labels` configuration option and apply the labels to the
+        node.
+
+        @raises LabelMaker.NodeLabelError: if the label cannot be added or removed
+        """
+        # Get the user's configured labels.
+        config = self.charm.model.config
+        user_labels = {}
+        for item in config.get("labels").split(" "):
+            try:
+                key, val = item.split("=")
+            except ValueError:
+                log.info(f"Skipping malformed option: {item}.")
+            else:
+                user_labels[key] = val
+        # Collect the current label state.
+        current_labels = self._stored.current_labels
+
+        try:
+            # Remove any labels that the user has removed from the config.
+            for key in list(current_labels.keys()):
+                if key not in user_labels:
+                    self.remove_label(key)
+                    del self._stored.current_labels[key]
+
+            # Add any new labels.
+            for key, val in user_labels.items():
+                self.set_label(key, val)
+                self._stored.current_labels[key] = val
+
+            # Set the juju-application and juju-charm labels.
+            self.set_label("juju-application", self.charm.model.app.name)
+            self.set_label("juju-charm", self.charm.meta.name)
+
+            # Set the juju.io/cloud label.
+            juju_io_cloud_labels = [
+                ("aws", "ec2"),
+                ("gcp", "gce"),
+                ("openstack", "openstack"),
+                ("vsphere", "vsphere"),
+                ("azure", "azure"),
+            ]
+            for endpoint, label in juju_io_cloud_labels:
+                if endpoint == self.charm.get_cloud_name():
+                    self.set_label("juju.io/cloud", label)
+                    break
+            else:
+                # none of the endpoints matched, remove the label
+                self.remove_label("juju.io/cloud")
+
+        except self.NodeLabelError as ex:
+            log.exception(str(ex))
+            raise

ops/pyproject.toml

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+[build-system]
+requires = ["setuptools>=61.0"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "charm-lib-node-base"
+version = "0.0.0"
+authors = [
+  {name="Adam Dyess", email="[email protected]"},
+]
+description = "Charm library for node-base"
+readme = "README.md"
+requires-python = ">=3.8"
+dependencies = [
+  "ops",
+]
+classifiers = [
+  "License :: OSI Approved :: Apache Software License",
+  "Programming Language :: Python :: 3",
+]
+
+[project.urls]
+"Homepage" = "https://github.com/charmed-kubernetes/layer-kubernetes-node-base"
+"Bug Tracker" = "https://github.com/charmed-kubernetes/layer-kubernetes-node-base/issues"

ops/tests/unit/test_ops.py

@@ -0,0 +1,2 @@
+def test_pass():
+    pass