fix(server): online and storage statistics (#14792)

#### PR Dependency Tree


* **PR #14792** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Admin dashboard returns more accurate sync and storage timelines with
carry‑forwarded minute buckets and corrected current totals.

* **Bug Fixes**
* Active-user flushes are debounced/scheduled to prevent overlapping
writes and reduce stale counts.
* Snapshot writes now retry and will skip gracefully when lock
contention prevents completion, avoiding partial snapshots.

* **Tests**
* New e2e tests cover carry‑forward behavior, no backfill outside
requested windows, and storage history accuracy.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/__tests__/e2e/workspace/admin-analytics.spec.ts

@@ -1,4 +1,5 @@
 import { PrismaClient } from '@prisma/client';
+import Sinon from 'sinon';
 
 import { app, e2e, Mockers } from '../test';
 
@@ -389,6 +390,201 @@ e2e(
   }
 );
 
+e2e(
+  'adminDashboard should carry forward missing sync and storage samples',
+  async t => {
+    const now = new Date('2026-04-05T08:55:00.000Z');
+    const clock = Sinon.useFakeTimers({ now, toFake: ['Date'] });
+
+    try {
+      const admin = await app.create(Mockers.User, {
+        feature: 'administrator',
+      });
+      await app.login(admin);
+
+      const owner = await app.create(Mockers.User);
+      const workspace = await app.create(Mockers.Workspace, {
+        owner: { id: owner.id },
+      });
+
+      const db = app.get(PrismaClient);
+      await ensureAnalyticsTables(db);
+
+      const minute = new Date();
+      minute.setSeconds(0, 0);
+      const sampleStartMinute = new Date(minute.getTime() - 30 * 60 * 1000);
+      const sampleEndMinute = new Date(
+        sampleStartMinute.getTime() + 2 * 60 * 1000
+      );
+
+      await db.$executeRaw`
+      INSERT INTO sync_active_users_minutely (minute_ts, active_users, updated_at)
+      VALUES
+        (${sampleStartMinute}, 5, NOW()),
+        (${sampleEndMinute}, 7, NOW())
+      ON CONFLICT (minute_ts)
+      DO UPDATE SET active_users = EXCLUDED.active_users, updated_at = EXCLUDED.updated_at
+    `;
+
+      await db.$executeRaw`
+      INSERT INTO workspace_admin_stats (
+        workspace_id, snapshot_count, snapshot_size, blob_count, blob_size, member_count, public_page_count, features, updated_at
+      )
+      VALUES (${workspace.id}, 1, 130, 1, 70, 1, 0, ARRAY[]::text[], NOW())
+      ON CONFLICT (workspace_id)
+      DO UPDATE SET
+        snapshot_count = EXCLUDED.snapshot_count,
+        snapshot_size = EXCLUDED.snapshot_size,
+        blob_count = EXCLUDED.blob_count,
+        blob_size = EXCLUDED.blob_size,
+        member_count = EXCLUDED.member_count,
+        public_page_count = EXCLUDED.public_page_count,
+        features = EXCLUDED.features,
+        updated_at = EXCLUDED.updated_at
+    `;
+
+      const today = new Date();
+      const currentDay = new Date(
+        Date.UTC(
+          today.getUTCFullYear(),
+          today.getUTCMonth(),
+          today.getUTCDate()
+        )
+      );
+      const twoDaysAgo = new Date(
+        currentDay.getTime() - 2 * 24 * 60 * 60 * 1000
+      );
+
+      await db.$executeRaw`
+      INSERT INTO workspace_admin_stats_daily (
+        workspace_id, date, snapshot_size, blob_size, member_count, updated_at
+      )
+      VALUES (${workspace.id}, ${twoDaysAgo}, 100, 50, 1, NOW())
+      ON CONFLICT (workspace_id, date)
+      DO UPDATE SET
+        snapshot_size = EXCLUDED.snapshot_size,
+        blob_size = EXCLUDED.blob_size,
+        member_count = EXCLUDED.member_count,
+        updated_at = EXCLUDED.updated_at
+    `;
+
+      const result = await gql(
+        `
+      query AdminDashboard($input: AdminDashboardInput) {
+        adminDashboard(input: $input) {
+          syncActiveUsers
+          syncActiveUsersTimeline {
+            minute
+            activeUsers
+          }
+          workspaceStorageBytes
+          blobStorageBytes
+          workspaceStorageHistory {
+            date
+            value
+          }
+          blobStorageHistory {
+            date
+            value
+          }
+        }
+      }
+    `,
+        {
+          input: {
+            storageHistoryDays: 3,
+            syncHistoryHours: 2,
+          },
+        }
+      );
+
+      t.falsy(result.errors);
+      const dashboard = result.data!.adminDashboard;
+      t.is(dashboard.syncActiveUsers, 7);
+      const missingMinute = new Date(sampleStartMinute.getTime() + 60 * 1000);
+      t.is(
+        dashboard.syncActiveUsersTimeline.find(
+          (point: { minute: string }) =>
+            point.minute === missingMinute.toISOString()
+        )?.activeUsers,
+        5
+      );
+      const workspaceHistory = dashboard.workspaceStorageHistory.map(
+        (point: { value: number }) => point.value
+      );
+      const blobHistory = dashboard.blobStorageHistory.map(
+        (point: { value: number }) => point.value
+      );
+      t.is(workspaceHistory.length, 3);
+      t.is(blobHistory.length, 3);
+      t.is(workspaceHistory[0], workspaceHistory[1]);
+      t.is(blobHistory[0], blobHistory[1]);
+      t.is(
+        workspaceHistory[workspaceHistory.length - 1],
+        dashboard.workspaceStorageBytes
+      );
+      t.is(blobHistory[blobHistory.length - 1], dashboard.blobStorageBytes);
+    } finally {
+      clock.restore();
+    }
+  }
+);
+
+e2e(
+  'adminDashboard should not backfill sync samples older than the requested window',
+  async t => {
+    const now = new Date('2026-04-05T08:55:00.000Z');
+    const clock = Sinon.useFakeTimers({ now, toFake: ['Date'] });
+
+    try {
+      const admin = await app.create(Mockers.User, {
+        feature: 'administrator',
+      });
+      await app.login(admin);
+
+      const db = app.get(PrismaClient);
+      await ensureAnalyticsTables(db);
+
+      const staleMinute = new Date('2026-04-05T05:55:00.000Z');
+      await db.$executeRaw`
+        INSERT INTO sync_active_users_minutely (minute_ts, active_users, updated_at)
+        VALUES (${staleMinute}, 9, NOW())
+        ON CONFLICT (minute_ts)
+        DO UPDATE SET active_users = EXCLUDED.active_users, updated_at = EXCLUDED.updated_at
+      `;
+
+      const result = await gql(
+        `
+          query AdminDashboard($input: AdminDashboardInput) {
+            adminDashboard(input: $input) {
+              syncActiveUsers
+              syncActiveUsersTimeline {
+                activeUsers
+              }
+            }
+          }
+        `,
+        {
+          input: {
+            syncHistoryHours: 1,
+          },
+        }
+      );
+
+      t.falsy(result.errors);
+      const dashboard = result.data!.adminDashboard;
+      t.is(dashboard.syncActiveUsers, 0);
+      t.true(
+        dashboard.syncActiveUsersTimeline.every(
+          (point: { activeUsers: number }) => point.activeUsers === 0
+        )
+      );
+    } finally {
+      clock.restore();
+    }
+  }
+);
+
 e2e(
   'Doc analytics and lastAccessedMembers should enforce permissions and privacy',
   async t => {