Fix review comments

- Combine the various exported types; the only API surface is now the
  `PluginDatabaseClientFactory` which is a free function.
- Rename to the SingleConnectionManager class.
- Refactor the PluginEnvironment type to use databaseClientFactory for
  clarity.
- Fix mergeDatabaseConfig to not override the input dictionary.

packages/backend/src/index.ts

@@ -29,8 +29,7 @@ import {
   getRootLogger,
   useHotMemoize,
   notFoundHandler,
-  SingleDatabaseConfiguration,
-  SingleDatabaseManager,
+  SingleConnectionManager,
   SingleHostDiscovery,
   UrlReaders,
 } from '@backstage/backend-common';
@@ -55,15 +54,14 @@ function makeCreateEnv(config: ConfigReader) {
 
   root.info(`Created UrlReader ${reader}`);
 
-  const databaseConfig = new SingleDatabaseConfiguration(
+  const databaseManager = new SingleConnectionManager(
     config.getConfig('backend.database'),
   );
-  const databaseManager = new SingleDatabaseManager(databaseConfig);
 
   return (plugin: string): PluginEnvironment => {
     const logger = root.child({ type: 'plugin', plugin });
-    const databaseFactory = databaseManager.getDatabaseFactory(plugin);
-    return { logger, database: databaseFactory, config, reader, discovery };
+    const databaseFactory = databaseManager.getDatabaseClientFactory(plugin);
+    return { logger, databaseClientFactory: databaseFactory, config, reader, discovery };
   };
 }
 

packages/backend/src/plugins/auth.ts

@@ -19,9 +19,14 @@ import { PluginEnvironment } from '../types';
 
 export default async function createPlugin({
   logger,
-  database,
+  databaseClientFactory,
   config,
   discovery,
 }: PluginEnvironment) {
-  return await createRouter({ logger, config, database, discovery });
+  return await createRouter({
+    logger,
+    config,
+    database: databaseClientFactory,
+    discovery,
+  });
 }

packages/backend/src/plugins/catalog.ts

@@ -30,12 +30,12 @@ export default async function createPlugin({
   logger,
   config,
   reader,
-  database,
+  databaseClientFactory,
 }: PluginEnvironment) {
   const locationReader = new LocationReaders({ logger, reader, config });
 
   const db = await DatabaseManager.createDatabase(
-    await database.getDatabase(),
+    await databaseClientFactory(),
     { logger },
   );
   const entitiesCatalog = new DatabaseEntitiesCatalog(db);

packages/backend/src/types.ts

@@ -17,14 +17,14 @@
 import { Logger } from 'winston';
 import { Config } from '@backstage/config';
 import {
-  PluginDatabaseFactory,
+  PluginDatabaseClientFactory,
   PluginEndpointDiscovery,
   UrlReader
 } from '@backstage/backend-common';
 
 export type PluginEnvironment = {
   logger: Logger;
-  database: PluginDatabaseFactory;
+  databaseClientFactory: PluginDatabaseClientFactory;
   config: Config;
   reader: UrlReader;
   discovery: PluginEndpointDiscovery;