fix: use database clock and separate migrations table for slack module

Address reviewer feedback:
- Use a dedicated migrations table to avoid conflicts with the parent plugin
- Use database-native now() instead of JS Date for timestamp columns
- Use database-level interval arithmetic for cleanup retention cutoff

Signed-off-by: Erik Miller <erik.miller@gusto.com>

plugins/notifications-backend-module-slack/src/lib/SlackNotificationProcessor.test.ts

@@ -1688,6 +1688,7 @@ describe('SlackNotificationProcessor', () => {
       const db = jest
         .fn()
         .mockImplementation(() => createQueryBuilder()) as unknown as Knex;
+      (db as any).fn = { now: jest.fn().mockReturnValue(new Date()) };
       return { db, store, storeKey };
     }
 

plugins/notifications-backend-module-slack/src/lib/SlackNotificationProcessor.ts

@@ -547,10 +547,11 @@ export class SlackNotificationProcessor implements NotificationProcessor {
     ts: string,
   ): Promise<void> {
     try {
+      const now = this.db!.fn.now();
       await this.db!('slack_message_timestamps')
-        .insert({ origin, scope, channel, ts, created_at: new Date() })
+        .insert({ origin, scope, channel, ts, created_at: now })
         .onConflict(['origin', 'scope', 'channel'])
-        .merge({ ts, created_at: new Date() });
+        .merge({ ts, created_at: now });
     } catch (error) {
       this.logger.warn('Failed to persist Slack message timestamp', {
         origin,

plugins/notifications-backend-module-slack/src/module.ts

@@ -18,6 +18,7 @@ import {
   createBackendModule,
   resolvePackagePath,
 } from '@backstage/backend-plugin-api';
+import { Knex } from 'knex';
 import { metricsServiceRef } from '@backstage/backend-plugin-api/alpha';
 import { notificationsProcessingExtensionPoint } from '@backstage/plugin-notifications-node';
 import { SlackNotificationProcessor } from './lib/SlackNotificationProcessor';
@@ -32,7 +33,17 @@ const MIGRATIONS_DIR = resolvePackagePath(
   'migrations',
 );
 
-const CLEANUP_RETENTION_MS = 24 * 60 * 60 * 1000; // 24 hours
+const DB_MIGRATIONS_TABLE = 'notifications_module_slack__knex_migrations';
+const CLEANUP_RETENTION_SECONDS = 24 * 60 * 60; // 24 hours
+
+function nowMinus(knex: Knex, seconds: number): Knex.Raw {
+  if (knex.client.config.client.includes('sqlite3')) {
+    return knex.raw(`datetime('now', ?)`, [`-${seconds} seconds`]);
+  } else if (knex.client.config.client.includes('mysql')) {
+    return knex.raw(`now() - interval ${seconds} second`);
+  }
+  return knex.raw(`now() - interval '${seconds} seconds'`);
+}
 
 /**
  * The Slack notification processor for use with the notifications plugin.
@@ -92,6 +103,7 @@ export const notificationsModuleSlack = createBackendModule({
         if (!database.migrations?.skip) {
           await db.migrate.latest({
             directory: MIGRATIONS_DIR,
+            tableName: DB_MIGRATIONS_TABLE,
           });
         }
 
@@ -112,9 +124,12 @@ export const notificationsModuleSlack = createBackendModule({
           initialDelay: { hours: 2 },
           scope: 'global',
           fn: async () => {
-            const cutoff = new Date(Date.now() - CLEANUP_RETENTION_MS);
             const deleted = await db('slack_message_timestamps')
-              .where('created_at', '<=', cutoff)
+              .where(
+                'created_at',
+                '<=',
+                nowMinus(db, CLEANUP_RETENTION_SECONDS),
+              )
               .delete();
             logger.info('Cleaned up old Slack message timestamps', {
               deleted,