Merge ~mthaddon/charm-k8s-discourse/+git/charm-k8s-discourse:app-name into charm-k8s-discourse:master

[Tom Haddon]

Ensure we always set event.database to a non-empty string - PG isn't able to infer this in a CMR situation

Ensure we always set event.database to a non-empty string - PG isn't able to infer this in a CMR situation

[Tom Haddon (mthaddon)]

I've tested this locally both with an in-model PostgreSQL db, and using CMR with a db in an IaaS model.

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

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

[Jay Kuri (jk0ne)]

Confirmed that this works. ready for merge.

review: Approve

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

Change successfully merged at revision fc9fdfd2a84a21bd9e1b14badef7c6ac9205728a

[Stuart Bishop (stub)]

This is working around a bug in the postgresql-k8s charm, which should now be fixed. No harm being explicit though.

diff --git a/src/charm.py b/src/charm.py
index d0239e4..bb5c4f6 100755
--- a/src/charm.py
+++ b/src/charm.py
@@ -234,12 +234,16 @@ class DiscourseCharm(CharmBase):
           from inside the event handler per https://github.com/canonical/ops-lib-pgsql/issues/2
         """
         self.stored.has_db_relation = True
+        # Ensure event.database is always set to a non-empty string. PostgreSQL
+        # can infer this if it's in the same model as Discourse, but not if
+        # we're using cross-model relations.
+        db_name = self.model.config["db_name"] or self.framework.model.app.name
         # Per https://github.com/canonical/ops-lib-pgsql/issues/2,
         # changing the setting in the config will not take effect,
         # unless the relation is dropped and recreated.
         if self.model.unit.is_leader():
-            event.database = self.model.config["db_name"]
-        elif event.database != self.model.config["db_name"]:
+            event.database = db_name
+        elif event.database != db_name:
             # Leader has not yet set requirements. Defer, in case this unit
             # becomes leader and needs to perform that operation.
             event.defer()