Add delta time to stale-while-revalidate header

As per specification (RFC 5861), the cache control parameter
stale-while-revalidate accepts a duration in seconds
on how long serving stale (but unvalidated) requests is
considered to be acceptable. As far as I can tell omitting
this duration is not allowed by RFC 5861 at all.

At least some cloud providers refuse to accept this header
when it omits a duration, while they accept it when containing
a duration.

As far as I can tell the next.js interpretation of leaving out a value
was that it means "infinite". This commit approximates an infinite
duration with 1 year, which is consistent with the maxage parameter
sent for requests without revalidation.

packages/next/src/server/send-payload/revalidate-headers.ts

@@ -22,9 +22,9 @@ export function setRevalidateHeaders(
 
     res.setHeader(
       'Cache-Control',
-      `s-maxage=${options.revalidate}, stale-while-revalidate`
+      `s-maxage=${options.revalidate}, stale-while-revalidate=31536000`
     )
   } else if (options.revalidate === false) {
-    res.setHeader('Cache-Control', `s-maxage=31536000, stale-while-revalidate`)
+    res.setHeader('Cache-Control', `s-maxage=31536000, stale-while-revalidate=31536000`)
   }
 }

test/e2e/prerender.test.ts

@@ -599,7 +599,7 @@ describe('Prerender', () => {
         expect(initialRes.headers.get('cache-control')).toBe(
           isDeploy
             ? 'public, max-age=0, must-revalidate'
-            : 's-maxage=2, stale-while-revalidate'
+            : 's-maxage=2, stale-while-revalidate=31536000'
         )
       })
     }
@@ -1265,7 +1265,7 @@ describe('Prerender', () => {
         expect(initialRes.headers.get('cache-control')).toBe(
           isDeploy
             ? 'public, max-age=0, must-revalidate'
-            : 's-maxage=31536000, stale-while-revalidate'
+            : 's-maxage=31536000, stale-while-revalidate=31536000'
         )
         const initialHtml = await initialRes.text()
         expect(initialHtml).toMatch(/hello.*?world/)

test/integration/not-found-revalidate/test/index.test.js

@@ -101,7 +101,7 @@ const runTests = () => {
 
     const props = JSON.parse($('#props').text())
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
     expect(res.status).toBe(200)
     expect(props.found).toBe(true)
@@ -114,7 +114,7 @@ const runTests = () => {
 
     const props2 = JSON.parse($('#props').text())
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
     expect(res.status).toBe(200)
     expect(props2.found).toBe(true)
@@ -127,7 +127,7 @@ const runTests = () => {
 
     const props3 = JSON.parse($('#props').text())
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
     expect(res.status).toBe(200)
     expect(props3.found).toBe(true)
@@ -157,7 +157,7 @@ const runTests = () => {
 
     const props = JSON.parse($('#props').text())
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
     expect(res.status).toBe(200)
     expect(props.found).toBe(true)
@@ -170,7 +170,7 @@ const runTests = () => {
 
     const props2 = JSON.parse($('#props').text())
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
     expect(res.status).toBe(200)
     expect(props2.found).toBe(true)
@@ -183,7 +183,7 @@ const runTests = () => {
 
     const props3 = JSON.parse($('#props').text())
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
     expect(res.status).toBe(200)
     expect(props3.found).toBe(true)

test/production/standalone-mode/required-server-files/pages/gssp.js

@@ -5,7 +5,7 @@ import next from 'next' // force a warning during `next build`
 import { useRouter } from 'next/router'
 
 export async function getServerSideProps({ res }) {
-  res.setHeader('cache-control', 's-maxage=1, stale-while-revalidate')
+  res.setHeader('cache-control', 's-maxage=1, stale-while-revalidate=31536000')
 
   const data = await fs.promises.readFile(
     path.join(process.cwd(), 'data.txt'),

test/production/standalone-mode/required-server-files/required-server-files-i18n.test.ts

@@ -171,7 +171,7 @@ describe('should set-up next', () => {
     })
     expect(res.status).toBe(200)
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
 
     await waitFor(2000)
@@ -182,7 +182,7 @@ describe('should set-up next', () => {
     })
     expect(res2.status).toBe(404)
     expect(res2.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
   })
 
@@ -194,7 +194,7 @@ describe('should set-up next', () => {
     })
     expect(res.status).toBe(200)
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
 
     await next.patchFile('standalone/data.txt', 'hide')
@@ -206,7 +206,7 @@ describe('should set-up next', () => {
 
     expect(res2.status).toBe(404)
     expect(res2.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
   })
 

test/production/standalone-mode/required-server-files/required-server-files.test.ts

@@ -192,13 +192,13 @@ describe('should set-up next', () => {
       case: 'redirect no revalidate',
       path: '/optional-ssg/redirect-1',
       dest: '/somewhere',
-      cacheControl: 's-maxage=31536000, stale-while-revalidate',
+      cacheControl: 's-maxage=31536000, stale-while-revalidate=31536000',
     },
     {
       case: 'redirect with revalidate',
       path: '/optional-ssg/redirect-2',
       dest: '/somewhere-else',
-      cacheControl: 's-maxage=5, stale-while-revalidate',
+      cacheControl: 's-maxage=5, stale-while-revalidate=31536000',
     },
   ])(
     `should have correct cache-control for $case`,
@@ -233,13 +233,13 @@ describe('should set-up next', () => {
       case: 'notFound no revalidate',
       path: '/optional-ssg/not-found-1',
       dest: '/somewhere',
-      cacheControl: 's-maxage=31536000, stale-while-revalidate',
+      cacheControl: 's-maxage=31536000, stale-while-revalidate=31536000',
     },
     {
       case: 'notFound with revalidate',
       path: '/optional-ssg/not-found-2',
       dest: '/somewhere-else',
-      cacheControl: 's-maxage=5, stale-while-revalidate',
+      cacheControl: 's-maxage=5, stale-while-revalidate=31536000',
     },
   ])(
     `should have correct cache-control for $case`,
@@ -266,7 +266,7 @@ describe('should set-up next', () => {
     const res = await fetchViaHTTP(appPort, '/optional-ssg/props-no-revalidate')
     expect(res.status).toBe(200)
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=31536000, stale-while-revalidate'
+      's-maxage=31536000, stale-while-revalidate=31536000'
     )
     const $ = cheerio.load(await res.text())
     expect(JSON.parse($('#props').text()).params).toEqual({
@@ -280,7 +280,7 @@ describe('should set-up next', () => {
     )
     expect(dataRes.status).toBe(200)
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=31536000, stale-while-revalidate'
+      's-maxage=31536000, stale-while-revalidate=31536000'
     )
     expect((await dataRes.json()).pageProps.params).toEqual({
       rest: ['props-no-revalidate'],
@@ -442,7 +442,7 @@ describe('should set-up next', () => {
     })
     expect(res.status).toBe(200)
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
 
     await waitFor(2000)
@@ -453,7 +453,7 @@ describe('should set-up next', () => {
     })
     expect(res2.status).toBe(404)
     expect(res2.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
   })
 
@@ -465,7 +465,7 @@ describe('should set-up next', () => {
     })
     expect(res.status).toBe(200)
     expect(res.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
 
     await next.patchFile('standalone/data.txt', 'hide')
@@ -477,7 +477,7 @@ describe('should set-up next', () => {
 
     expect(res2.status).toBe(404)
     expect(res2.headers.get('cache-control')).toBe(
-      's-maxage=1, stale-while-revalidate'
+      's-maxage=1, stale-while-revalidate=31536000'
     )
   })