Reject oversized replay payloads and chunk recorder flushes

src/app/api/record/route.ts

@@ -8,7 +8,7 @@ import { parseToken } from '@/lib/jwt';
 import { fetchAccount, fetchTeam } from '@/lib/load';
 import { getRecorderConfig } from '@/lib/recorder';
 import { parseRequest } from '@/lib/request';
-import { badRequest, forbidden, json, serverError } from '@/lib/response';
+import { badRequest, forbidden, json, payloadTooLarge, serverError } from '@/lib/response';
 import { getWebsite } from '@/queries/prisma';
 import { saveRecording } from '@/queries/sql';
 import { saveHeatmapEvents } from '@/queries/sql/heatmap/saveHeatmapEvents';
@@ -18,6 +18,8 @@ interface Cache {
   visitId: string;
 }
 
+const MAX_RECORD_REQUEST_BYTES = 1_000_000;
+
 const schema = z.discriminatedUnion('type', [
   z.object({
     type: z.literal('record'),
@@ -73,8 +75,38 @@ function getUrlPath(url: string) {
   }
 }
 
+async function getRequestBodySize(request: Request): Promise<number | null> {
+  const contentLength = request.headers.get('content-length');
+
+  if (contentLength) {
+    const size = Number(contentLength);
+
+    if (Number.isFinite(size)) {
+      return size;
+    }
+  }
+
+  try {
+    const text = await request.clone().text();
+
+    return new TextEncoder().encode(text).length;
+  } catch {
+    return null;
+  }
+}
+
 export async function POST(request: Request) {
   try {
+    const requestBodySize = await getRequestBodySize(request);
+
+    if (requestBodySize && requestBodySize > MAX_RECORD_REQUEST_BYTES) {
+      return payloadTooLarge({
+        reason: 'payload_too_large',
+        maxBytes: MAX_RECORD_REQUEST_BYTES,
+        size: requestBodySize,
+      });
+    }
+
     const { body, error } = await parseRequest(request, schema, { skipAuth: true });
 
     if (error) {

src/lib/response.ts

@@ -36,6 +36,15 @@ export function forbidden(error?: Record<string, any>) {
   );
 }
 
+export function payloadTooLarge(error?: Record<string, any>) {
+  return Response.json(
+    {
+      error: { message: 'Payload too large', code: 'payload-too-large', status: 413, ...error },
+    },
+    { status: 413 },
+  );
+}
+
 export function notFound(error?: Record<string, any>) {
   return Response.json(
     { error: { message: 'Not found', code: 'not-found', status: 404, ...error } },

src/recorder/index.js

@@ -23,6 +23,7 @@ import { record } from 'rrweb';
 
   const REPLAY_FLUSH_EVENT_COUNT = 100;
   const REPLAY_FLUSH_INTERVAL = 2000;
+  const REPLAY_MAX_PAYLOAD_SIZE = 900000;
   const HEATMAP_FLUSH_EVENT_COUNT = 20;
   const HEATMAP_FLUSH_INTERVAL = 5000;
 
@@ -45,12 +46,8 @@ import { record } from 'rrweb';
 
   const getSessionCache = () => window.umami?.getSession?.()?.cache;
 
-  const sendPayload = (type, payload, useKeepalive = false) => {
-    const cache = getSessionCache();
-
-    if (!cache) return;
-
-    const body = JSON.stringify({
+  const getPayloadBody = (type, payload) =>
+    JSON.stringify({
       type,
       payload: {
         website,
@@ -58,7 +55,28 @@ import { record } from 'rrweb';
       },
     });
 
-    const keepalive = useKeepalive && body.length < 60000;
+  const getPayloadSize = body => {
+    try {
+      return new Blob([body]).size;
+    } catch {
+      return body.length;
+    }
+  };
+
+  const getReplayPayloadSize = (events, timestamp) =>
+    getPayloadSize(getPayloadBody('record', { events, timestamp }));
+
+  const isReplayPayloadTooLarge = (events, timestamp) =>
+    getReplayPayloadSize(events, timestamp) > REPLAY_MAX_PAYLOAD_SIZE;
+
+  const sendPayload = (type, payload, useKeepalive = false) => {
+    const cache = getSessionCache();
+
+    if (!cache) return;
+
+    const body = getPayloadBody(type, payload);
+
+    const keepalive = useKeepalive && getPayloadSize(body) < 60000;
 
     return fetch(endpoint, {
       keepalive,
@@ -72,20 +90,55 @@ import { record } from 'rrweb';
     }).catch(() => {});
   };
 
+  const sendReplayEvents = (events, timestamp, useKeepalive = false) => {
+    let chunk = [];
+    let chunkOffset = 0;
+
+    events.forEach(event => {
+      const candidate = [...chunk, event];
+
+      if (isReplayPayloadTooLarge(candidate, timestamp + chunkOffset)) {
+        if (chunk.length) {
+          sendPayload(
+            'record',
+            {
+              events: chunk,
+              timestamp: timestamp + chunkOffset,
+            },
+            useKeepalive,
+          );
+          chunk = [];
+          chunkOffset += 1;
+        }
+
+        if (isReplayPayloadTooLarge([event], timestamp + chunkOffset)) {
+          chunkOffset += 1;
+          return;
+        }
+      }
+
+      chunk.push(event);
+    });
+
+    if (chunk.length) {
+      sendPayload(
+        'record',
+        {
+          events: chunk,
+          timestamp: timestamp + chunkOffset,
+        },
+        useKeepalive,
+      );
+    }
+  };
+
   const flushReplay = (useKeepalive = false) => {
     if (!replayBuffer.length) return;
 
     const events = replayBuffer;
     replayBuffer = [];
 
-    sendPayload(
-      'record',
-      {
-        events,
-        timestamp: Math.floor(Date.now() / 1000),
-      },
-      useKeepalive,
-    );
+    sendReplayEvents(events, Math.floor(Date.now() / 1000), useKeepalive);
   };
 
   const flushHeatmap = (useKeepalive = false) => {
@@ -273,9 +326,19 @@ import { record } from 'rrweb';
           return;
         }
 
+        if (
+          replayBuffer.length &&
+          isReplayPayloadTooLarge([...replayBuffer, event], Math.floor(Date.now() / 1000))
+        ) {
+          flushReplay();
+        }
+
         replayBuffer.push(event);
 
-        if (replayBuffer.length >= REPLAY_FLUSH_EVENT_COUNT) {
+        if (
+          replayBuffer.length >= REPLAY_FLUSH_EVENT_COUNT ||
+          isReplayPayloadTooLarge(replayBuffer, Math.floor(Date.now() / 1000))
+        ) {
           flushReplay();
         }
       },