set 'manul-purge' surrogate key on assets/cb- URLs (#25028)

middleware/index.js

@@ -15,7 +15,7 @@ import handleCsrfErrors from './handle-csrf-errors.js'
 import compression from 'compression'
 import {
   setDefaultFastlySurrogateKey,
-  setManualFastlySurrogateKey,
+  setManualFastlySurrogateKeyIfChecksummed,
 } from './set-fastly-surrogate-key.js'
 import setFastlyCacheHeaders from './set-fastly-cache-headers.js'
 import catchBadAcceptLanguage from './catch-bad-accept-language.js'
@@ -115,15 +115,21 @@ export default function (app) {
 
   app.use(favicon)
 
+  // Any `/assets/cb-*` request should get the setManualFastlySurrogateKey()
+  // middleware, but it's not possible to express such a prefix in
+  // Express middlewares. Because we don't want the manual Fastly
+  // surrogate key on *all* /assets/ requests.
+  // Note, this needs to come before `assetPreprocessing` because
+  // the `assetPreprocessing` middleware will rewrite `req.url` if
+  // it applies.
+  app.use(setManualFastlySurrogateKeyIfChecksummed)
+
   // Must come before any other middleware for assets
   app.use(archivedAssetRedirects)
 
   // This must come before the express.static('assets') middleware.
   app.use(assetPreprocessing)
-  // By specifying '/assets/cb-' and not just '/assets/' we
-  // avoid possibly legacy enterprise assets URLs and asset image URLs
-  // that don't have the cache-busting piece in it.
-  app.use('/assets/cb-', setManualFastlySurrogateKey)
+
   app.use(
     '/assets/',
     express.static('assets', {

middleware/set-fastly-surrogate-key.js

@@ -32,3 +32,10 @@ export function setDefaultFastlySurrogateKey(req, res, next) {
   res.set(KEY, SURROGATE_ENUMS.DEFAULT)
   return next()
 }
+
+export function setManualFastlySurrogateKeyIfChecksummed(req, res, next) {
+  if (req.path.startsWith('/assets/cb-')) {
+    return setManualFastlySurrogateKey(req, res, next)
+  }
+  return next()
+}

tests/rendering/server.js

@@ -1034,7 +1034,16 @@ describe('static routes', () => {
     expect(res.headers['set-cookie']).toBeUndefined()
     expect(res.headers['cache-control']).toContain('public')
     expect(res.headers['cache-control']).toMatch(/max-age=\d+/)
-    expect(res.headers['surrogate-key']).toBeTruthy()
+    expect(res.headers['surrogate-key']).toBe(SURROGATE_ENUMS.MANUAL)
+  })
+
+  it('no manual surrogate key for /assets requests without caching-busting prefix', async () => {
+    const res = await get('/assets/images/site/be-social.gif')
+    expect(res.statusCode).toBe(200)
+    expect(res.headers['set-cookie']).toBeUndefined()
+    expect(res.headers['cache-control']).toContain('public')
+    expect(res.headers['cache-control']).toMatch(/max-age=\d+/)
+    expect(res.headers['surrogate-key']).toBe(SURROGATE_ENUMS.DEFAULT)
   })
 
   it('serves schema files from the /data/graphql directory at /public', async () => {