[openstack-hypervisor] Add list-nics action

Add action to list-nics on the hypervisor. This is used to gather
candidate for the external network nic.

Change-Id: Ife70804d035a900d5fe95059b26d3006860506da
Signed-off-by: Guillaume Boutry <guillaume.boutry@canonical.com>

charms/openstack-hypervisor/charmcraft.yaml

@@ -58,6 +58,10 @@ actions:
         type: string
         description: IP address to use for service configuration
     additionalProperties: false
+  list-nics:
+    description: |
+      List host NICS, and which one are candidates for use as external NIC.
+    additionalProperties: false
 
 requires:
   amqp:

charms/openstack-hypervisor/src/charm.py

@@ -27,6 +27,7 @@ import os
 import secrets
 import socket
 import string
+import subprocess
 from typing import (
     List,
     Optional,
@@ -173,6 +174,10 @@ class HypervisorOperatorCharm(sunbeam_charm.OSBaseOperatorCharm):
             self.on.set_hypervisor_local_settings_action,
             self._set_hypervisor_local_settings_action,
         )
+        self.framework.observe(
+            self.on.list_nics_action,
+            self._list_nics_action,
+        )
         self.framework.observe(
             self.on.install,
             self._on_install,
@@ -320,6 +325,39 @@ class HypervisorOperatorCharm(sunbeam_charm.OSBaseOperatorCharm):
         if new_snap_settings:
             self.set_snap_data(new_snap_settings)
 
+    def _list_nics_action(self, event: ActionEvent):
+        """Run list_nics action."""
+        cache = self.get_snap_cache()
+        hypervisor = cache["openstack-hypervisor"]
+
+        if not hypervisor.present:
+            event.fail("Hypervisor is not installed")
+            return
+
+        process = subprocess.run(
+            [
+                "snap",
+                "run",
+                "openstack-hypervisor",
+                "--verbose",
+                "list-nics",
+                "--format",
+                "json",
+            ],
+            capture_output=True,
+        )
+
+        stderr = process.stderr.decode("utf-8")
+        logger.debug("logs: %s", stderr)
+        stdout = process.stdout.decode("utf-8")
+        logger.debug("stdout: %s", stdout)
+        if process.returncode != 0:
+            event.fail(stderr)
+            return
+
+        # cli returns a json dict with keys "nics" and "candidate"
+        event.set_results({"result": stdout})
+
     def ensure_services_running(self):
         """Ensure systemd services running."""
         # This should taken care of by the snap

charms/openstack-hypervisor/tests/unit/test_charm.py

@@ -15,11 +15,14 @@
 """Tests for Openstack hypervisor charm."""
 
 import base64
+import json
 from unittest.mock import (
     MagicMock,
 )
 
 import charm
+import ops
+import ops.testing
 import ops_sunbeam.test_utils as test_utils
 
 
@@ -35,7 +38,13 @@ class _HypervisorOperatorCharm(charm.HypervisorOperatorCharm):
 class TestCharm(test_utils.CharmTestCase):
     """Test charm to test relations."""
 
-    PATCHES = ["socket", "snap", "get_local_ip_by_default_route", "os"]
+    PATCHES = [
+        "socket",
+        "snap",
+        "get_local_ip_by_default_route",
+        "os",
+        "subprocess",
+    ]
 
     def setUp(self):
         """Setup OpenStack Hypervisor tests."""
@@ -277,3 +286,53 @@ class TestCharm(test_utils.CharmTestCase):
             "masakari.enable": True,
         }
         hypervisor_snap_mock.set.assert_any_call(expect_settings, typed=True)
+
+    def test_list_nics_snap_not_installed(self):
+        """Check action raises ActionFailed if snap is not installed."""
+        self.harness.begin()
+        hypervisor_snap_mock = MagicMock()
+        hypervisor_snap_mock.present = False
+        self.snap.SnapCache.return_value = {
+            "openstack-hypervisor": hypervisor_snap_mock
+        }
+        with self.assertRaises(ops.testing.ActionFailed):
+            self.harness.run_action("list-nics")
+
+    def test_list_nics(self):
+        """Check action returns nics."""
+        self.harness.begin()
+        hypervisor_snap_mock = MagicMock()
+        hypervisor_snap_mock.present = True
+        self.snap.SnapCache.return_value = {
+            "openstack-hypervisor": hypervisor_snap_mock
+        }
+        subprocess_run_mock = MagicMock()
+        subprocess_run_mock.return_value = MagicMock(
+            stdout=bytes(
+                json.dumps({"nics": ["eth0", "eth1"], "candidates": ["eth2"]}),
+                "utf-8",
+            ),
+            stderr=b"yes things went well",
+            returncode=0,
+        )
+        self.subprocess.run = subprocess_run_mock
+        action_output = self.harness.run_action("list-nics")
+        assert "candidates" in action_output.results["result"]
+
+    def test_list_nics_error(self):
+        """Check action raises ActionFailed if subprocess returns non-zero."""
+        self.harness.begin()
+        hypervisor_snap_mock = MagicMock()
+        hypervisor_snap_mock.present = True
+        self.snap.SnapCache.return_value = {
+            "openstack-hypervisor": hypervisor_snap_mock
+        }
+        subprocess_run_mock = MagicMock()
+        subprocess_run_mock.return_value = MagicMock(
+            stdout=b"",
+            stderr=b"things did not go well",
+            returncode=1,
+        )
+        self.subprocess.run = subprocess_run_mock
+        with self.assertRaises(ops.testing.ActionFailed):
+            self.harness.run_action("list-nics")