From 9d95a808572246ddfea5fa4cda513698cee5ef02 Mon Sep 17 00:00:00 2001
From: Hampus <hampus@fluxer.app>
Date: Mon, 31 Aug 2026 22:38:00 +0200
Subject: [PATCH] fix(worker): renew the deletion queue lock during a rebuild
 (#2287)

---
 .../KVAccountDeletionQueueService.ts          | 16 +++++-
 .../KVAccountDeletionQueueRebuildLock.test.ts | 54 +++++++++++++++++++
 .../tasks/UserProcessPendingDeletions.ts      |  2 +-
 3 files changed, 70 insertions(+), 2 deletions(-)
 create mode 100644 fluxer_api/src/api/infrastructure/tests/KVAccountDeletionQueueRebuildLock.test.ts

diff --git a/fluxer_api/src/api/infrastructure/KVAccountDeletionQueueService.ts b/fluxer_api/src/api/infrastructure/KVAccountDeletionQueueService.ts
index 661175056..e8d0554fa 100644
--- a/fluxer_api/src/api/infrastructure/KVAccountDeletionQueueService.ts
+++ b/fluxer_api/src/api/infrastructure/KVAccountDeletionQueueService.ts
@@ -59,7 +59,7 @@ export class KVAccountDeletionQueueService {
 		}
 	}
 
-	async rebuildState(): Promise<void> {
+	async rebuildState(lockToken: string | null = null): Promise<void> {
 		Logger.info('Starting deletion queue rebuild from primary database');
 		try {
 			await this.kvClient.del(QUEUE_KEY);
@@ -91,6 +91,9 @@ export class KVAccountDeletionQueueService {
 				totalQueued += batchQueued;
 				totalProcessed += users.length;
 				pageState = page.pageState;
+				if (lockToken !== null) {
+					await this.renewRebuildLock(lockToken);
+				}
 				if (totalProcessed % 10000 === 0) {
 					Logger.debug({totalProcessed, totalQueued}, 'Deletion queue rebuild progress');
 				}
@@ -174,6 +177,17 @@ export class KVAccountDeletionQueueService {
 		}
 	}
 
+	private async renewRebuildLock(token: string): Promise<void> {
+		try {
+			const renewed = await this.kvClient.extendLock(REBUILD_LOCK_KEY, token, REBUILD_LOCK_TTL);
+			if (!renewed) {
+				Logger.warn({token}, 'Deletion queue rebuild lock was no longer held on renewal');
+			}
+		} catch (error) {
+			Logger.error({error, token}, 'Failed to renew deletion queue rebuild lock');
+		}
+	}
+
 	async releaseRebuildLock(token: string): Promise<boolean> {
 		try {
 			const released = await this.kvClient.releaseLock(REBUILD_LOCK_KEY, token);
diff --git a/fluxer_api/src/api/infrastructure/tests/KVAccountDeletionQueueRebuildLock.test.ts b/fluxer_api/src/api/infrastructure/tests/KVAccountDeletionQueueRebuildLock.test.ts
new file mode 100644
index 000000000..75f7a35c7
--- /dev/null
+++ b/fluxer_api/src/api/infrastructure/tests/KVAccountDeletionQueueRebuildLock.test.ts
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {ms} from 'itty-time';
+import {afterEach, describe, expect, it, vi} from 'vitest';
+import {createUserID} from '../../BrandedTypes';
+import type {User} from '../../models/User';
+import {MockKVProvider} from '../../test/mocks/MockKVProvider';
+import type {UserRepository} from '../../user/repositories/UserRepository';
+import {KVAccountDeletionQueueService} from '../KVAccountDeletionQueueService';
+
+const PAGE_DURATION_MS = ms('3 minutes');
+const PAGE_COUNT = 3;
+
+function createPendingUser(index: number): User {
+	return {
+		id: createUserID(BigInt(7000 + index)),
+		pendingDeletionAt: new Date('2026-06-01T00:00:00.000Z'),
+		deletionReasonCode: 0,
+	} as unknown as User;
+}
+
+function createSlowUserRepository(): UserRepository {
+	let page = 0;
+	return {
+		async scanAllUsersPage() {
+			vi.advanceTimersByTime(PAGE_DURATION_MS);
+			page += 1;
+			return {
+				users: [createPendingUser(page)],
+				pageState: page < PAGE_COUNT ? `page-${page}` : null,
+			};
+		},
+	} as unknown as UserRepository;
+}
+
+describe('KVAccountDeletionQueueService rebuild lock', () => {
+	afterEach(() => {
+		vi.useRealTimers();
+	});
+
+	it('keeps holding the rebuild lock across a scan longer than the lock ttl', async () => {
+		vi.useFakeTimers();
+		vi.setSystemTime(new Date('2026-06-01T00:00:00.000Z'));
+		const kvClient = new MockKVProvider();
+		const service = new KVAccountDeletionQueueService(kvClient, createSlowUserRepository());
+		const token = await service.acquireRebuildLock();
+		expect(token).not.toBeNull();
+
+		await service.rebuildState(token);
+
+		expect(await service.acquireRebuildLock()).toBeNull();
+		expect(await service.releaseRebuildLock(token!)).toBe(true);
+	});
+});
diff --git a/fluxer_api/src/api/worker/tasks/UserProcessPendingDeletions.ts b/fluxer_api/src/api/worker/tasks/UserProcessPendingDeletions.ts
index 72b2b6ec8..90f6dd504 100644
--- a/fluxer_api/src/api/worker/tasks/UserProcessPendingDeletions.ts
+++ b/fluxer_api/src/api/worker/tasks/UserProcessPendingDeletions.ts
@@ -18,7 +18,7 @@ const userProcessPendingDeletions: WorkerTaskHandler = async (_payload, helpers)
 			const lockToken = await deletionQueueService.acquireRebuildLock();
 			if (lockToken) {
 				try {
-					await deletionQueueService.rebuildState();
+					await deletionQueueService.rebuildState(lockToken);
 					await deletionQueueService.releaseRebuildLock(lockToken);
 				} catch (error) {
 					await deletionQueueService.releaseRebuildLock(lockToken);