Merge ~mthaddon/charm-k8s-ingress/+git/charm-k8s-ingress:master into charm-k8s-ingress:master

[Tom Haddon]

Only define k8s ingress and k8s service if we're the leader, to avoid collision in case of scale out

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

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[🤖 prod-jenkaas-is (prod-jenkaas-is)]

PASSED: Continuous integration, rev:56a29e5557c9dbce4fe0c3c0a90a75bfa7da1799
https://jenkins.canonical.com/is/job/lp-charm-k8s-ingress-ci/4/
Executed test runs:
    SUCCESS: https://jenkins.canonical.com/is/job/lp-charm-test/34/
    None: https://jenkins.canonical.com/is/job/lp-update-mp/49141/

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review: Approve (continuous-integration)

[Jon Seager (jnsgruk)]

Good call :)

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision 9b917e496f37699c2b1e025320113ae31ec5f61a

diff --git a/src/charm.py b/src/charm.py
index 3bd55ff..5e48538 100755
--- a/src/charm.py
+++ b/src/charm.py
@@ -208,7 +208,9 @@ class CharmK8SIngressCharm(CharmBase):
     def _on_config_changed(self, _):
         """Handle the config changed event."""
         msg = ""
-        if self.config["service-name"]:
+        # We only want to do anything here if we're the leader to avoid
+        # collision if we've scaled out this application.
+        if self.unit.is_leader() and self.config["service-name"]:
             self._define_service()
             self._define_ingress()
             # It's not recommended to do this via ActiveStatus, but we don't
diff --git a/tests/unit/test_charm.py b/tests/unit/test_charm.py
index 2bca57e..b861cb0 100644
--- a/tests/unit/test_charm.py
+++ b/tests/unit/test_charm.py
@@ -23,6 +23,8 @@ class TestCharm(unittest.TestCase):
     @mock.patch('charm.CharmK8SIngressCharm._define_service')
     def test_config_changed(self, _define_service, _define_ingress, _report_service_ips):
         """Test our config changed handler."""
+        # First of all test, with leader set to True.
+        self.harness.set_leader(True)
         _report_service_ips.return_value = ["10.0.1.12"]
         # Confirm our _define_ingress and _define_service methods haven't been called.
         self.assertEqual(_define_ingress.call_count, 0)
@@ -38,6 +40,19 @@ class TestCharm(unittest.TestCase):
         self.assertEqual(_define_service.call_count, 1)
         # Confirm status is as expected.
         self.assertEqual(self.harness.charm.unit.status, ActiveStatus('Ingress with service IP(s): 10.0.1.12'))
+        # And now test with leader is False.
+        _define_ingress.reset_mock()
+        _define_service.reset_mock()
+        self.harness.set_leader(False)
+        self.harness.update_config({"service-name": ""})
+        self.assertEqual(_define_ingress.call_count, 0)
+        self.assertEqual(_define_service.call_count, 0)
+        # Leader False, but service-name defined should still do nothing.
+        self.harness.update_config({"service-name": "gunicorn"})
+        self.assertEqual(_define_ingress.call_count, 0)
+        self.assertEqual(_define_service.call_count, 0)
+        # Confirm status is as expected.
+        self.assertEqual(self.harness.charm.unit.status, ActiveStatus())
 
     def test_get_k8s_ingress(self):
         """Test getting our definition of a k8s ingress."""