Expire live caption state after inactivity and tune stream limits

routes/liveCaptions.js

@@ -1,19 +1,36 @@
 var express = require('express');
 var router = express.Router();
+const { rateLimit } = require("express-rate-limit");
 
 const sessionChecker = require("../middleware/sessionChecker.js");
 
 const MAX_BUFFER_SIZE = 300;
 const DEFAULT_INITIAL_LIMIT = 40;
 const MAX_INITIAL_LIMIT = 120;
+const INACTIVITY_RESET_MS = 10 * 60 * 1000;
 const CAPTION_META_KEYS = new Set(["sequence", "createdAt", "original", "draft", "sourceLang", "lang", "isDraft", "status", "translations"]);
 
 const liveCaptionState = {
     startedAt: Date.now(),
+    lastIngestAt: 0,
     latestSequence: 0,
     captions: [],
 };
 
+const liveCaptionsLimiter = rateLimit({
+    windowMs: 10 * 60 * 1000,
+    limit: 6000,
+    standardHeaders: "draft-8",
+    legacyHeaders: false,
+    keyGenerator: (req) => {
+        const forwarded = req.headers["x-forwarded-for"]?.split(",")[0];
+        const ip = forwarded || req.ip || "";
+        return ip.includes(":") ? ip.split(":")[0] : ip;
+    },
+});
+
+router.use(liveCaptionsLimiter);
+
 const normalizeLang = (lang = "") => {
     const value = String(lang || "").trim().toLowerCase();
     if (!value) return "";
@@ -82,8 +99,22 @@ const getAvailableLanguages = () => {
     return Array.from(langs).filter(Boolean).sort();
 };
 
+const resetLiveCaptionState = () => {
+    liveCaptionState.startedAt = Date.now();
+    liveCaptionState.lastIngestAt = 0;
+    liveCaptionState.latestSequence = 0;
+    liveCaptionState.captions = [];
+};
+
+const maybeResetForInactivity = () => {
+    if (!liveCaptionState.lastIngestAt) return;
+    if ((Date.now() - liveCaptionState.lastIngestAt) < INACTIVITY_RESET_MS) return;
+    resetLiveCaptionState();
+};
+
 router.get("/stream", sessionChecker, async (req, res) => {
     try {
+        maybeResetForInactivity();
         const sinceSequence = Number.parseInt(req.query?.sinceSequence, 10);
         const requestedLimit = Number.parseInt(req.query?.limit, 10);
         const initialLimit = Number.isFinite(requestedLimit)
@@ -150,6 +181,7 @@ router.post("/ingest", async (req, res) => {
         };
 
         liveCaptionState.latestSequence = sequence;
+        liveCaptionState.lastIngestAt = Date.now();
         liveCaptionState.captions.push(caption);
         if (liveCaptionState.captions.length > MAX_BUFFER_SIZE) {
             liveCaptionState.captions.splice(0, liveCaptionState.captions.length - MAX_BUFFER_SIZE);
@@ -170,9 +202,7 @@ router.post("/ingest", async (req, res) => {
 router.post("/reset", async (_, res) => {
     try {
         // TODO: Add admin authorization before exposing this endpoint.
-        liveCaptionState.startedAt = Date.now();
-        liveCaptionState.latestSequence = 0;
-        liveCaptionState.captions = [];
+        resetLiveCaptionState();
         return res.json({ status: "ok" });
     } catch (error) {
         console.error("Error resetting live captions state", error);