added keepalive to DatabaseManager

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

.changeset/eleven-bees-marry.md

@@ -0,0 +1,6 @@
+---
+'@backstage/backend-common': patch
+---
+
+Added a keep-alive refresh loop to the `DatabaseManager`, keeping the connection
+pool up.

.changeset/famous-hounds-sit.md

@@ -0,0 +1,6 @@
+---
+'@backstage/backend-common': patch
+---
+
+The options part of `DatabaseManager.fromConfig` now accepts an optional logger
+field.

.changeset/shaggy-vans-repeat.md

@@ -0,0 +1,18 @@
+---
+'@backstage/create-app': patch
+---
+
+The options part of `DatabaseManager.fromConfig` now accepts an optional logger
+field. You may want to supply that logger in your backend initialization code to
+ensure that you can get relevant logging data when things happen related to the
+connection pool.
+
+In `packages/backend/src/index.ts`:
+
+```diff
+ function makeCreateEnv(config: Config) {
+   const root = getRootLogger();
+   ...
+-  const databaseManager = DatabaseManager.fromConfig(config);
++  const databaseManager = DatabaseManager.fromConfig(config, { logger: root });
+```

packages/backend-common/api-report.md

@@ -252,6 +252,7 @@ export class DatabaseManager {
 // @public
 export type DatabaseManagerOptions = {
   migrations?: PluginDatabaseManager['migrations'];
+  logger?: Logger;
 };
 
 // @public

packages/backend-common/src/database/DatabaseManager.ts

@@ -29,6 +29,8 @@ import {
 } from './connection';
 import { PluginDatabaseManager } from './types';
 import path from 'path';
+import { Logger } from 'winston';
+import { stringifyError } from '@backstage/errors';
 
 /**
  * Provides a config lookup path for a plugin's config block.
@@ -44,6 +46,7 @@ function pluginPath(pluginId: string): string {
  */
 export type DatabaseManagerOptions = {
   migrations?: PluginDatabaseManager['migrations'];
+  logger?: Logger;
 };
 
 /**
@@ -339,6 +342,31 @@ export class DatabaseManager {
       schemaOverrides,
     );
 
-    return createDatabaseClient(pluginConfig, databaseClientOverrides);
+    const client = createDatabaseClient(pluginConfig, databaseClientOverrides);
+    this.startKeepaliveLoop(pluginId, client);
+
+    return client;
+  }
+
+  private startKeepaliveLoop(pluginId: string, client: Knex): void {
+    let lastKeepaliveFailed = false;
+
+    setInterval(() => {
+      client.raw('select 1').then(
+        () => {
+          lastKeepaliveFailed = false;
+        },
+        (error: unknown) => {
+          if (!lastKeepaliveFailed) {
+            lastKeepaliveFailed = true;
+            this.options?.logger?.warn(
+              `Database keepalive failed for plugin ${pluginId}, ${stringifyError(
+                error,
+              )}`,
+            );
+          }
+        },
+      );
+    }, 60 * 1000);
   }
 }

packages/backend/src/index.ts

@@ -69,7 +69,7 @@ function makeCreateEnv(config: Config) {
     discovery,
     tokenManager,
   });
-  const databaseManager = DatabaseManager.fromConfig(config);
+  const databaseManager = DatabaseManager.fromConfig(config, { logger: root });
   const cacheManager = CacheManager.fromConfig(config);
   const taskScheduler = TaskScheduler.fromConfig(config);
 

packages/create-app/templates/default-app/packages/backend/src/index.ts

@@ -36,7 +36,7 @@ function makeCreateEnv(config: Config) {
   const reader = UrlReaders.default({ logger: root, config });
   const discovery = SingleHostDiscovery.fromConfig(config);
   const cacheManager = CacheManager.fromConfig(config);
-  const databaseManager = DatabaseManager.fromConfig(config);
+  const databaseManager = DatabaseManager.fromConfig(config, { logger: root });
   const tokenManager = ServerTokenManager.noop();
   const taskScheduler = TaskScheduler.fromConfig(config);
   const permissions = ServerPermissionClient.fromConfig(config, {