docs: maintanance mode impact (#3858)

src/lib/services/maintenance-service.test.ts

@@ -0,0 +1,44 @@
+import { SchedulerService } from './scheduler-service';
+import MaintenanceService from './maintenance-service';
+import { IUnleashStores } from '../types';
+import SettingService from './setting-service';
+import { createTestConfig } from '../../test/config/test-config';
+
+test('Maintenance on should pause scheduler', async () => {
+    const config = createTestConfig();
+    const schedulerService = new SchedulerService(config.getLogger);
+    const maintenanceService = new MaintenanceService(
+        {} as IUnleashStores,
+        config,
+        { insert() {} } as unknown as SettingService,
+        schedulerService,
+    );
+
+    await maintenanceService.toggleMaintenanceMode(
+        { enabled: true },
+        'irrelevant user',
+    );
+
+    expect(schedulerService.getMode()).toBe('paused');
+    schedulerService.stop();
+});
+
+test('Maintenance off should resume scheduler', async () => {
+    const config = createTestConfig();
+    const schedulerService = new SchedulerService(config.getLogger);
+    schedulerService.pause();
+    const maintenanceService = new MaintenanceService(
+        {} as IUnleashStores,
+        config,
+        { insert() {} } as unknown as SettingService,
+        schedulerService,
+    );
+
+    await maintenanceService.toggleMaintenanceMode(
+        { enabled: false },
+        'irrelevant user',
+    );
+
+    expect(schedulerService.getMode()).toBe('active');
+    schedulerService.stop();
+});

website/docs/reference/maintenance-mode.mdx

@@ -25,3 +25,18 @@ Maintenance mode is controlled from the "maintenance" section of the Unleash adm
 When maintenance mode is enabled, a warning banner appears at the top of the Unleash dashboard, indicating that any changes made during this period will not be saved and may result in errors.
 
 ![Maintenance mode banner when maintenance mod is toggled on](/img/maintenance-banner.png)
+
+## Maintenance mode and scheduled jobs
+
+When maintenance mode is enabled all internal jobs performed by Unleash such as updating metrics and statistics are paused. When maintenance mode is toggled back to disabled later, all scheduled
+jobs are resumed.
+
+## Maintenance mode and read-only DB user
+
+When maintenance mode is enabled most DB operations are suspended so you can use even read-only DB user. There's one exception though.
+Unleash DB user role needs a DELETE and UPDATE permission on the unleash_session table.
+
+```
+GRANT DELETE ON unleash_session TO my_db_role;
+GRANT UPDATE ON unleash_session TO my_db_role;
+```