fix: limit concurrent ls to 2 in flight calls

app/client/components/file-browsers/snapshot-tree-browser.tsx

@@ -5,7 +5,6 @@ import { FileBrowser, type FileBrowserUiProps } from "~/client/components/file-b
 import { useFileBrowser } from "~/client/hooks/use-file-browser";
 import { parseError } from "~/client/lib/errors";
 import { isPathWithin, normalizeAbsolutePath } from "@zerobyte/core/utils";
-import { logger } from "~/client/lib/logger";
 
 function createPathPrefixFns(basePath: string) {
 	return {
@@ -84,16 +83,6 @@ export const SnapshotTreeBrowser = (props: SnapshotTreeBrowserProps) => {
 				}),
 			);
 		},
-		prefetchFolder: (displayPath) => {
-			void queryClient
-				.prefetchQuery(
-					listSnapshotFilesOptions({
-						path: { shortId: repositoryId, snapshotId },
-						query: { path: displayPath, offset: 0, limit: pageSize },
-					}),
-				)
-				.catch((e) => logger.error(e));
-		},
 		pathTransform: displayPathFns,
 	});
 

app/client/modules/backups/routes/backup-details.tsx

@@ -63,9 +63,7 @@ export function ScheduleDetailsPage(props: Props) {
 	const queryClient = useQueryClient();
 	const navigate = useNavigate();
 	const searchParams = useSearch({ from: "/(dashboard)/backups/$backupId/" });
-	const [selectedSnapshotId, setSelectedSnapshotId] = useState<string | undefined>(
-		initialSnapshotId ?? loaderData.snapshots?.at(-1)?.short_id,
-	);
+	const [selectedSnapshotId, setSelectedSnapshotId] = useState<string | undefined>(initialSnapshotId);
 	const [showDeleteConfirm, setShowDeleteConfirm] = useState(false);
 	const [snapshotToDelete, setSnapshotToDelete] = useState<string | null>(null);
 

app/server/modules/repositories/__tests__/repositories.service.test.ts

@@ -208,6 +208,95 @@ describe("repositoriesService repository stats", () => {
 	});
 });
 
+describe("repositoriesService.listSnapshotFiles", () => {
+	afterEach(() => {
+		vi.restoreAllMocks();
+	});
+
+	test("limits concurrent restic ls commands per repository", async () => {
+		const repository = await createTestRepository(session.organizationId);
+		let active = 0;
+		let maxActive = 0;
+		let releaseAll = false;
+		const releaseWaiters: Array<() => void> = [];
+
+		const releaseWaitingCommands = () => {
+			const waiters = releaseWaiters.splice(0);
+			for (const release of waiters) {
+				release();
+			}
+		};
+
+		const lsSpy = vi.spyOn(restic, "ls").mockImplementation((_config, snapshotId, _path, options) =>
+			Effect.promise(async () => {
+				active++;
+				maxActive = Math.max(maxActive, active);
+
+				try {
+					if (!releaseAll) {
+						await new Promise<void>((resolve) => releaseWaiters.push(resolve));
+					}
+
+					return {
+						snapshot: {
+							id: snapshotId,
+							short_id: snapshotId,
+							time: new Date().toISOString(),
+							tree: "tree",
+							paths: ["/"],
+							hostname: "host",
+							struct_type: "snapshot" as const,
+							message_type: "snapshot" as const,
+						},
+						nodes: [],
+						pagination: {
+							offset: options.offset ?? 0,
+							limit: options.limit ?? 500,
+							total: 0,
+							hasMore: false,
+						},
+					};
+				} finally {
+					active--;
+				}
+			}),
+		);
+
+		const calls = Array.from({ length: 4 }, (_, index) =>
+			withContext({ organizationId: session.organizationId, userId: session.user.id }, () =>
+				repositoriesService.listSnapshotFiles(repository.shortId, `snapshot-${index}`, "/", {
+					offset: 0,
+					limit: 100,
+				}),
+			),
+		);
+
+		try {
+			await waitForExpect(() => {
+				expect(releaseWaiters).toHaveLength(2);
+			});
+			expect(maxActive).toBe(2);
+
+			releaseWaitingCommands();
+
+			await waitForExpect(() => {
+				expect(releaseWaiters).toHaveLength(2);
+			});
+			expect(maxActive).toBe(2);
+
+			releaseWaitingCommands();
+			await Promise.all(calls);
+		} finally {
+			releaseAll = true;
+			releaseWaitingCommands();
+			await Promise.allSettled(calls);
+		}
+
+		expect(lsSpy).toHaveBeenCalledTimes(4);
+		expect(maxActive).toBeLessThanOrEqual(2);
+	});
+});
+
 describe("repositoriesService.dumpSnapshot", () => {
 	afterEach(() => {
 		vi.restoreAllMocks();

app/server/modules/repositories/repositories.service.ts

@@ -42,6 +42,7 @@ import type { ParsedTask, TaskInput } from "../tasks/tasks.schemas";
 import { Effect } from "effect";
 
 const runningDoctors = new Map<string, AbortController>();
+const lsLimiters = new Map<string, Effect.Semaphore>();
 const RESTORE_TASK_RESOURCE_TYPE = "repository";
 
 type RestoreTaskInput = Extract<TaskInput, { kind: "restore" }>;
@@ -99,6 +100,15 @@ const updateActiveRestoreTask = (restoreId: string, eventName: string, update: (
 	}
 };
 
+const getLsLimiter = (repositoryId: string) => {
+	let limiter = lsLimiters.get(repositoryId);
+	if (!limiter) {
+		limiter = Effect.unsafeMakeSemaphore(2);
+		lsLimiters.set(repositoryId, limiter);
+	}
+	return limiter;
+};
+
 const findActiveRestoreTask = (
 	organizationId: string,
 	repositoryShortId: string,
@@ -472,7 +482,9 @@ const listSnapshotFiles = async (
 	const releaseLock = await repoMutex.acquireShared(repository.id, `ls:${snapshotId}`);
 	try {
 		const result = await runEffectPromise(
-			restic.ls(repository.config, snapshotId, path, { organizationId, offset, limit }),
+			restic
+				.ls(repository.config, snapshotId, path, { organizationId, offset, limit })
+				.pipe(getLsLimiter(repository.id).withPermits(1)),
 		);
 
 		if (!result.snapshot) {