[DPE-5090] - Update mongodb provider to support K8s router (#462)

## Issue
mongos k8s router cannot yet make use of the mongodb_provider lib due to
the lib not be flexible to support mongos

## Solution
Update the lib so that it can support mongos

---------

Co-authored-by: Neha Oudin <17551419+Gu1nness@users.noreply.github.com>
Co-authored-by: Mehdi Bendriss <bendrissmehdi@gmail.com>

lib/charms/mongodb/v0/config_server_interface.py

@@ -42,7 +42,7 @@
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 9
+LIBPATCH = 10
 
 
 class ClusterProvider(Object):
@@ -328,6 +328,8 @@ def _on_relation_broken(self, event: RelationBrokenEvent) -> None:
         # K8s charm have a 1:Many client scheme and share connection info in a different manner.
         if self.substrate == Config.Substrate.VM:
             self.charm.remove_connection_info()
+        else:
+            self.db_initialised = False
 
     # BEGIN: helper functions
     def pass_hook_checks(self, event):

lib/charms/mongodb/v1/mongodb_provider.py

@@ -14,8 +14,8 @@
 from typing import List, Optional, Set
 
 from charms.data_platform_libs.v0.data_interfaces import DatabaseProvides
+from charms.mongodb.v0.mongo import MongoConfiguration, MongoConnection
 from charms.mongodb.v1.helpers import generate_password
-from charms.mongodb.v1.mongodb import MongoConfiguration, MongoDBConnection
 from ops.charm import CharmBase, EventBase, RelationBrokenEvent, RelationChangedEvent
 from ops.framework import Object
 from ops.model import Relation
@@ -31,17 +31,14 @@
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 10
+LIBPATCH = 11
 
 logger = logging.getLogger(__name__)
 REL_NAME = "database"
-
 MONGOS_RELATIONS = "cluster"
+MONGOS_CLIENT_RELATIONS = "mongos_proxy"
 
 # We expect the MongoDB container to use the default ports
-MONGODB_PORT = 27017
-MONGODB_VERSION = "5.0"
-PEER = "database-peers"
 
 Diff = namedtuple("Diff", "added changed deleted")
 Diff.__doc__ = """
@@ -62,24 +59,19 @@ def __init__(self, charm: CharmBase, substrate="k8s", relation_name: str = "data
             substrate: host type, either "k8s" or "vm"
             relation_name: the name of the relation
         """
-        self.relation_name = relation_name
         self.substrate = substrate
         self.charm = charm
 
-        super().__init__(charm, self.relation_name)
+        super().__init__(charm, relation_name)
         self.framework.observe(
-            charm.on[self.relation_name].relation_departed,
+            charm.on[relation_name].relation_departed,
             self.charm.check_relation_broken_or_scale_down,
         )
-        self.framework.observe(
-            charm.on[self.relation_name].relation_broken, self._on_relation_event
-        )
-        self.framework.observe(
-            charm.on[self.relation_name].relation_changed, self._on_relation_event
-        )
+        self.framework.observe(charm.on[relation_name].relation_broken, self._on_relation_event)
+        self.framework.observe(charm.on[relation_name].relation_changed, self._on_relation_event)
 
         # Charm events defined in the database provides charm library.
-        self.database_provides = DatabaseProvides(self.charm, relation_name=self.relation_name)
+        self.database_provides = DatabaseProvides(self.charm, relation_name=relation_name)
         self.framework.observe(
             self.database_provides.on.database_requested, self._on_relation_event
         )
@@ -91,7 +83,9 @@ def pass_hook_checks(self, event: EventBase) -> bool:
         if not self.charm.db_initialised:
             return False
 
-        if not self.charm.is_relation_feasible(self.relation_name):
+        if not self.charm.is_role(Config.Role.MONGOS) and not self.charm.is_relation_feasible(
+            self.get_relation_name()
+        ):
             logger.info("Skipping code for relations.")
             return False
 
@@ -164,12 +158,18 @@ def oversee_users(self, departed_relation_id: Optional[int], event):
         relation is still on the list of all relations. Therefore, for proper
         work of the function, we need to exclude departed relation from the list.
         """
-        with MongoDBConnection(self.charm.mongodb_config) as mongo:
+        with MongoConnection(self.charm.mongo_config) as mongo:
             database_users = mongo.get_users()
             relation_users = self._get_users_from_relations(departed_relation_id)
 
             for username in database_users - relation_users:
                 logger.info("Remove relation user: %s", username)
+                if (
+                    self.charm.is_role(Config.Role.MONGOS)
+                    and username == self.charm.mongo_config.username
+                ):
+                    continue
+
                 mongo.drop_user(username)
 
             for username in relation_users - database_users:
@@ -245,10 +245,10 @@ def update_app_relation_data(self) -> None:
 
         database_users = set()
 
-        with MongoDBConnection(self.charm.mongodb_config) as mongo:
+        with MongoConnection(self.charm.mongo_config) as mongo:
             database_users = mongo.get_users()
 
-        for relation in self._get_relations(rel=REL_NAME):
+        for relation in self._get_relations():
             username = self._get_username_from_relation_id(relation.id)
             password = self._get_or_set_password(relation)
             config = self._get_config(username, password)
@@ -290,16 +290,21 @@ def _get_config(self, username: str, password: Optional[str]) -> MongoConfigurat
 
         database_name = self._get_database_from_relation(relation)
 
-        return MongoConfiguration(
-            replset=self.charm.app.name,
-            database=database_name,
-            username=username,
-            password=password,
-            hosts=self.charm.mongodb_config.hosts,
-            roles=self._get_roles_from_relation(relation),
-            tls_external=False,
-            tls_internal=False,
-        )
+        mongo_args = {
+            "database": database_name,
+            "username": username,
+            "password": password,
+            "hosts": self.charm.mongo_config.hosts,
+            "roles": self._get_roles_from_relation(relation),
+            "tls_external": False,
+            "tls_internal": False,
+        }
+        if self.charm.is_role(Config.Role.MONGOS):
+            mongo_args["port"] = Config.MONGOS_PORT
+        else:
+            mongo_args["replset"] = self.charm.app.name
+
+        return MongoConfiguration(**mongo_args)
 
     def _set_relation(self, config: MongoConfiguration):
         """Save all output fields into application relation."""
@@ -318,10 +323,11 @@ def _set_relation(self, config: MongoConfiguration):
             relation.id,
             ",".join(config.hosts),
         )
-        self.database_provides.set_replset(
-            relation.id,
-            config.replset,
-        )
+        if not self.charm.is_role(Config.Role.MONGOS):
+            self.database_provides.set_replset(
+                relation.id,
+                config.replset,
+            )
         self.database_provides.set_uris(
             relation.id,
             config.uri,
@@ -332,9 +338,9 @@ def _get_username_from_relation_id(relation_id: int) -> str:
         """Construct username."""
         return f"relation-{relation_id}"
 
-    def _get_users_from_relations(self, departed_relation_id: Optional[int], rel=REL_NAME):
+    def _get_users_from_relations(self, departed_relation_id: Optional[int]):
         """Return usernames for all relations except departed relation."""
-        relations = self._get_relations(rel)
+        relations = self._get_relations()
         return set(
             [
                 self._get_username_from_relation_id(relation.id)
@@ -351,7 +357,7 @@ def _get_databases_from_relations(self, departed_relation_id: Optional[int]) ->
                 except for those databases that belong to the departing
                 relation specified.
         """
-        relations = self._get_relations(rel=REL_NAME)
+        relations = self._get_relations()
         databases = set()
         for relation in relations:
             if relation.id == departed_relation_id:
@@ -370,22 +376,25 @@ def _get_relation_from_username(self, username: str) -> Relation:
         assert match is not None, "No relation match"
         relation_id = int(match.group(1))
         logger.debug("Relation ID: %s", relation_id)
-        relation_name = (
-            MONGOS_RELATIONS if self.charm.is_role(Config.Role.CONFIG_SERVER) else REL_NAME
-        )
+        relation_name = self.get_relation_name()
         return self.model.get_relation(relation_name, relation_id)
 
-    def _get_relations(self, rel=REL_NAME) -> List[Relation]:
+    def _get_relations(self) -> List[Relation]:
         """Return the set of relations for users.
 
         We create users for either direct relations to charm or for relations through the mongos
         charm.
         """
-        return (
-            self.model.relations[MONGOS_RELATIONS]
-            if self.charm.is_role(Config.Role.CONFIG_SERVER)
-            else self.model.relations[rel]
-        )
+        return self.model.relations[self.get_relation_name()]
+
+    def get_relation_name(self):
+        """Returns the name of the relation to use."""
+        if self.charm.is_role(Config.Role.CONFIG_SERVER):
+            return MONGOS_RELATIONS
+        elif self.charm.is_role(Config.Role.MONGOS):
+            return MONGOS_CLIENT_RELATIONS
+        else:
+            return REL_NAME
 
     @staticmethod
     def _get_database_from_relation(relation: Relation) -> Optional[str]:

src/charm.py

@@ -257,6 +257,11 @@ def remote_mongodb_config(self, hosts, replset=None, standalone=None) -> MongoCo
             OperatorUser, hosts, replset=replset, standalone=standalone
         )
 
+    @property
+    def mongo_config(self) -> MongoConfiguration:
+        """Returns a MongoConfiguration object for shared libs with agnostic mongo commands."""
+        return self.mongodb_config
+
     @property
     def mongodb_config(self) -> MongoConfiguration:
         """Generates a MongoConfiguration object for this deployment of MongoDB."""

tests/unit/test_mongodb_provider.py

@@ -130,7 +130,7 @@ def test_relation_event_oversee_users_fails_to_get_relation(
                     self.harness.remove_relation_unit(relation_id, "consumer/0")
 
     @patch_network_get(private_address="1.1.1.1")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_get_users_failure(self, connection):
         """Verifies that when unable to retrieve users from mongod an exception is raised."""
         for dep_id in DEPARTED_IDS:
@@ -143,7 +143,7 @@ def test_oversee_users_get_users_failure(self, connection):
 
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_drop_user_failure(self, connection, relation_users):
         """Verifies that when unable to drop users from mongod an exception is raised."""
         # presets, such that there is a need to drop users.
@@ -163,7 +163,7 @@ def test_oversee_users_drop_user_failure(self, connection, relation_users):
 
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_get_config_failure(self, connection, relation_users):
         """Verifies that when users do not match necessary schema an AssertionError is raised."""
         # presets, such that the need to create user relations is triggered. Further presets
@@ -182,7 +182,7 @@ def test_oversee_users_get_config_failure(self, connection, relation_users):
     @patch("charm.MongoDBProvider._set_relation")
     @patch("charm.MongoDBProvider._get_config")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     @patch("charm.MongoDBProvider._diff")
     def test_oversee_users_no_config_database(
         self, diff, connection, relation_users, get_config, set_relation
@@ -205,7 +205,7 @@ def test_oversee_users_no_config_database(
     @patch("charm.MongoDBProvider._set_relation")
     @patch("charm.MongoDBProvider._get_config")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_create_user_failure(
         self, connection, relation_users, get_config, set_relation
     ):
@@ -226,7 +226,7 @@ def test_oversee_users_create_user_failure(
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_config")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_set_relation_failure(self, connection, relation_users, get_config):
         """Verifies that when adding a user with an invalid name that an exception is raised."""
         # presets, such that the need to create user relations is triggered and user naming such
@@ -245,7 +245,7 @@ def test_oversee_users_set_relation_failure(self, connection, relation_users, ge
 
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_update_get_config_failure(self, connection, relation_users):
         """Verifies that when updating a user with an invalid name that an exception is raised."""
         # presets, such that the need to update user relations is triggered and user naming such
@@ -263,7 +263,7 @@ def test_oversee_users_update_get_config_failure(self, connection, relation_user
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_config")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_update_user_failure(self, connection, relation_users, get_config):
         """Verifies that when updating users fails an exception is raised."""
         # presets, such that the need to update user relations is triggered
@@ -282,7 +282,7 @@ def test_oversee_users_update_user_failure(self, connection, relation_users, get
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_databases_from_relations")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_no_auto_delete(
         self, connection, relation_users, databases_from_relations
     ):
@@ -299,7 +299,7 @@ def test_oversee_users_no_auto_delete(
 
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_mongo_databases_failure(self, connection, relation_users):
         """Verifies failures in checking for databases with mongod result in raised exceptions."""
         self.harness.update_config({"auto-delete": True})
@@ -317,7 +317,7 @@ def test_oversee_users_mongo_databases_failure(self, connection, relation_users)
     @patch_network_get(private_address="1.1.1.1")
     @patch("charm.MongoDBProvider._get_databases_from_relations")
     @patch("charm.MongoDBProvider._get_users_from_relations")
-    @patch("charms.mongodb.v1.mongodb_provider.MongoDBConnection")
+    @patch("charms.mongodb.v1.mongodb_provider.MongoConnection")
     def test_oversee_users_drop_database_failure(
         self, connection, relation_users, databases_from_relations
     ):