Warn when response body is larger than 5mb

errors/api-routes-body-size-limit.md

@@ -0,0 +1,13 @@
+# API Routes Body Size Limited to 5mb
+
+#### Why This Error Occurred
+
+API Routes are meant to respond quickly and are not intended to support responding with large amounts of data. The maximum size of responses is 5 MB.
+
+#### Possible Ways to Fix It
+
+Limit your API Route responses to less than 5 MB. If you need to support sending large files to the client, you should consider using a dedicated media host for those assets. See link below for suggestions.
+
+### Useful Links
+
+[Tips to avoid the 5 MB limit](https://vercel.com/support/articles/how-to-bypass-vercel-5mb-body-size-limit-serverless-functions)

errors/manifest.json

@@ -13,6 +13,10 @@
  "title": "amp-export-validation",
  "path": "/errors/amp-export-validation.md"
  },
+ {
+ "title": "api-routes-body-size-limit",
+ "path": "/errors/api-routes-body-size-limit.md"
+ },
  {
  "title": "api-routes-static-export",
  "path": "/errors/api-routes-static-export.md"

packages/next/server/api-utils.ts

@@ -63,6 +63,26 @@ export async function apiResolver(
  )
  }
 
+ let contentLength = 0
+ const writeData = apiRes.write
+ const endResponse = apiRes.end
+ apiRes.write = (...args: any[2]) => {
+ contentLength += Buffer.byteLength(args[0])
+ return writeData.apply(apiRes, args)
+ }
+ apiRes.end = (...args: any[2]) => {
+ if (args.length && typeof args[0] !== 'function') {
+ contentLength += Buffer.byteLength(args[0])
+ }
+
+ if (contentLength >= 5 * 1024 * 1024) {
+ console.warn(
+ `API response for ${req.url} exceeds 5MB. This will cause the request to fail in a future version. https://nextjs.org/docs/messages/api-routes-body-size-limit`
+ )
+ }
+
+ endResponse.apply(apiRes, args)
+ }
  apiRes.status = (statusCode) => sendStatusCode(apiRes, statusCode)
  apiRes.send = (data) => sendData(apiReq, apiRes, data)
  apiRes.json = (data) => sendJson(apiRes, data)

test/integration/api-support/pages/api/large-chunked-response.js

@@ -0,0 +1,6 @@
+export default (req, res) => {
+ for (let i = 0; i <= 5 * 1024 * 1024; i++) {
+ res.write('.')
+ }
+ res.end()
+}

test/integration/api-support/pages/api/large-response.js

@@ -0,0 +1,4 @@
+export default (req, res) => {
+ let body = '.'.repeat(5 * 1024 * 1024)
+ res.send(body)
+}

test/integration/api-support/test/index.test.js

@@ -398,6 +398,20 @@ function runTests(dev = false) {
  expect(data).toBe('hi')
  })
 
+ it('should warn if response body is larger than 5MB', async () => {
+ let res = await fetchViaHTTP(appPort, '/api/large-response')
+ expect(res.ok).toBeTruthy()
+ expect(stderr).toContain(
+ 'API response for /api/large-response exceeds 5MB. This will cause the request to fail in a future version.'
+ )
+
+ res = await fetchViaHTTP(appPort, '/api/large-chunked-response')
+ expect(res.ok).toBeTruthy()
+ expect(stderr).toContain(
+ 'API response for /api/large-chunked-response exceeds 5MB. This will cause the request to fail in a future version.'
+ )
+ })
+
  if (dev) {
  it('should compile only server code in development', async () => {
  await fetchViaHTTP(appPort, '/api/users')