Add database config class (#6513)

This encapsulates config for a given database and is the way to get new
connections.

synapse/storage/data_stores/__init__.py

@@ -13,24 +13,50 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.storage.database import Database
+import logging
+
+from synapse.storage.database import Database, make_conn
+from synapse.storage.engines import create_engine
 from synapse.storage.prepare_database import prepare_database
 
+logger = logging.getLogger(__name__)
+
 
 class DataStores(object):
     """The various data stores.
 
     These are low level interfaces to physical databases.
+
+    Attributes:
+        main (DataStore)
     """
 
-    def __init__(self, main_store_class, db_conn, hs):
+    def __init__(self, main_store_class, hs):
         # Note we pass in the main store class here as workers use a different main
         # store.
-        database = Database(hs)
 
-        # Check that db is correctly configured.
-        database.engine.check_database(db_conn.cursor())
+        self.databases = []
 
-        prepare_database(db_conn, database.engine, config=hs.config)
+        for database_config in hs.config.database.databases:
+            db_name = database_config.name
+            engine = create_engine(database_config.config)
 
-        self.main = main_store_class(database, db_conn, hs)
+            with make_conn(database_config, engine) as db_conn:
+                logger.info("Preparing database %r...", db_name)
+
+                engine.check_database(db_conn.cursor())
+                prepare_database(
+                    db_conn, engine, hs.config, data_stores=database_config.data_stores,
+                )
+
+                database = Database(hs, database_config, engine)
+
+                if "main" in database_config.data_stores:
+                    logger.info("Starting 'main' data store")
+                    self.main = main_store_class(database, db_conn, hs)
+
+                db_conn.commit()
+
+                self.databases.append(database)
+
+                logger.info("Database %r prepared", db_name)

synapse/storage/data_stores/main/client_ips.py

@@ -412,7 +412,7 @@ class ClientIpStore(ClientIpBackgroundUpdateStore):
     def _update_client_ips_batch(self):
 
         # If the DB pool has already terminated, don't try updating
-        if not self.hs.get_db_pool().running:
+        if not self.db.is_running():
             return
 
         to_update = self._batch_row_update