fix: retry transient flagged storage reads

(cherry picked from commit 1a5eca3)

Author: ndycode

lib/storage/flagged-storage-file.ts

@@ -1,13 +1,41 @@
 import type { FlaggedAccountStorageV1 } from "../storage.js";
+import { sleep } from "../utils.js";
+
+const RETRYABLE_READ_CODES = new Set(["EBUSY", "EPERM", "EAGAIN"]);
+
+function isRetryableReadError(error: unknown): boolean {
+	const code = (error as NodeJS.ErrnoException | undefined)?.code;
+	return typeof code === "string" && RETRYABLE_READ_CODES.has(code);
+}
+
+async function readFileWithRetry(
+	path: string,
+	deps: {
+		readFile: typeof import("node:fs").promises.readFile;
+		sleep?: (ms: number) => Promise<void>;
+	},
+): Promise<string> {
+	for (let attempt = 0; ; attempt += 1) {
+		try {
+			return await deps.readFile(path, "utf-8");
+		} catch (error) {
+			if (!isRetryableReadError(error) || attempt >= 3) {
+				throw error;
+			}
+			await (deps.sleep ?? sleep)(10 * 2 ** attempt);
+		}
+	}
+}
 
 export async function loadFlaggedAccountsFromFile(
 	path: string,
 	deps: {
 		readFile: typeof import("node:fs").promises.readFile;
 		normalizeFlaggedStorage: (data: unknown) => FlaggedAccountStorageV1;
+		sleep?: (ms: number) => Promise<void>;
 	},
 ): Promise<FlaggedAccountStorageV1> {
-	const content = await deps.readFile(path, "utf-8");
+	const content = await readFileWithRetry(path, deps);
 	const data = JSON.parse(content) as unknown;
 	return deps.normalizeFlaggedStorage(data);
 }