Cache more assets both in browser + Fastly (#17663)

JamesMGreene · web-flow · commit a40ff31b4b77 · 2021-02-03T22:16:54.000Z
* Cache archived asset JS/CSS for a day

* Don't waste time with ETag calculations

* Add a comment about the expiration length

* Cache images and fonts for a day

* Cache GraphQL data files for a week

* Set Fastly surrogate-key header on all responses

* Update test to account for new response header
diff --git a/middleware/archived-enterprise-versions-assets.js b/middleware/archived-enterprise-versions-assets.js
@@ -3,6 +3,8 @@ const patterns = require('../lib/patterns')
 const isArchivedVersion = require('../lib/is-archived-version')
 const got = require('got')
 
+const ONE_DAY = 24 * 60 * 60 // 1 day in seconds
+
 // This module handles requests for the CSS and JS assets for
 // deprecated GitHub Enterprise versions by routing them to static content in
 // help-docs-archived-enterprise-versions
@@ -26,6 +28,8 @@ module.exports = async (req, res, next) => {
     res.set('content-length', r.headers['content-length'])
     res.set('x-is-archived', 'true')
     res.set('x-robots-tag', 'noindex')
+    // Allow the browser and Fastly to cache these
+    res.set('cache-control', `public, max-age=${ONE_DAY}`)
     res.send(r.body)
   } catch (err) {
     next()
diff --git a/middleware/index.js b/middleware/index.js
@@ -37,8 +37,10 @@ module.exports = function (app) {
   app.use(require('./handle-csrf-errors')) // Must come before regular handle-errors
 
   // *** Headers ***
+  app.set('etag', false) // We will manage our own ETags if desired
   app.use(require('compression')())
   app.use(require('./disable-caching-on-safari'))
+  app.use(require('./set-fastly-surrogate-key'))
 
   // *** Config and context for redirects ***
   app.use(require('./req-utils')) // Must come before record-redirect and events
@@ -66,10 +68,20 @@ module.exports = function (app) {
     etag: false,
     immutable: true,
     lastModified: false,
-    maxAge: '28 days'
+    maxAge: '28 days' // Could be infinite given our fingerprinting
+  }))
+  app.use('/assets', express.static('assets', {
+    index: false,
+    etag: false,
+    lastModified: false,
+    maxAge: '1 day' // Relatively short in case we update images
+  }))
+  app.use('/public', express.static('data/graphql', {
+    index: false,
+    etag: false,
+    lastModified: false,
+    maxAge: '7 days' // A bit longer since releases are more sparse
   }))
-  app.use('/assets', express.static('assets'))
-  app.use('/public', express.static('data/graphql'))
   app.use('/events', instrument('./events'))
   app.use('/csrf', instrument('./csrf-route'))
   app.use('/search', instrument('./search'))
diff --git a/middleware/set-fastly-surrogate-key.js b/middleware/set-fastly-surrogate-key.js
@@ -0,0 +1,12 @@
+module.exports = (req, res, next) => {
+  // Fastly provides a Soft Purge feature that allows you to mark content as outdated (stale) instead of permanently
+  // purging and thereby deleting it from Fastly's caches. Objects invalidated with Soft Purge will be treated as
+  // outdated (stale) while Fastly fetches a new version from origin.
+  //
+  // Use of a surrogate key is required for soft purging
+  // https://docs.fastly.com/en/guides/soft-purges
+  // https://docs.fastly.com/en/guides/getting-started-with-surrogate-keys
+  res.set('surrogate-key', 'all-the-things')
+
+  next()
+}
diff --git a/tests/rendering/server.js b/tests/rendering/server.js
@@ -66,7 +66,7 @@ describe('server', () => {
     const res = await get('/en')
     expect(res.headers['cache-control']).toBe('private, no-store')
     expect(res.headers['surrogate-control']).toBe('private, no-store')
-    expect(res.headers).not.toHaveProperty('surrogate-key')
+    expect(res.headers['surrogate-key']).toBe('all-the-things')
   })
 
   test('does not render duplicate <html> or <body> tags', async () => {
