From bc44dfc48404fd3aee58a662099952568ed71f58 Mon Sep 17 00:00:00 2001
From: Daniel Roe <daniel@roe.dev>
Date: Wed, 6 Mar 2024 14:29:07 +0000
Subject: [PATCH] perf(nuxt): use fallthrough cache for prerender (#26104)

---
 packages/nuxt/package.json                    |  1 +
 packages/nuxt/src/core/nitro.ts               | 14 +++++-----
 .../src/core/runtime/nitro/cache-driver.ts    | 27 +++++++++++++++++++
 pnpm-lock.yaml                                |  3 +++
 4 files changed, 39 insertions(+), 6 deletions(-)
 create mode 100644 packages/nuxt/src/core/runtime/nitro/cache-driver.ts

diff --git a/packages/nuxt/package.json b/packages/nuxt/package.json
index 217211b572..2bde9e7c9f 100644
--- a/packages/nuxt/package.json
+++ b/packages/nuxt/package.json
@@ -109,6 +109,7 @@
     "unimport": "^3.7.1",
     "unplugin": "^1.8.2",
     "unplugin-vue-router": "^0.7.0",
+    "unstorage": "^1.10.1",
     "untyped": "^1.4.2",
     "vue": "^3.4.21",
     "vue-bundle-renderer": "^2.0.0",
diff --git a/packages/nuxt/src/core/nitro.ts b/packages/nuxt/src/core/nitro.ts
index 8a78dbfa75..9bb9fddfa9 100644
--- a/packages/nuxt/src/core/nitro.ts
+++ b/packages/nuxt/src/core/nitro.ts
@@ -1,3 +1,4 @@
+import { pathToFileURL } from 'node:url'
 import { existsSync, promises as fsp, readFileSync } from 'node:fs'
 import { cpus } from 'node:os'
 import { join, normalize, relative, resolve } from 'pathe'
@@ -6,7 +7,7 @@ import { randomUUID } from 'uncrypto'
 import { joinURL, withTrailingSlash } from 'ufo'
 import { build, copyPublicAssets, createDevServer, createNitro, prepare, prerender, scanHandlers, writeTypes } from 'nitropack'
 import type { Nitro, NitroConfig } from 'nitropack'
-import { findPath, logger, resolveIgnorePatterns, resolveNuxtModule } from '@nuxt/kit'
+import { findPath, logger, resolveIgnorePatterns, resolveNuxtModule, resolvePath } from '@nuxt/kit'
 import escapeRE from 'escape-string-regexp'
 import { defu } from 'defu'
 import fsExtra from 'fs-extra'
@@ -392,11 +393,12 @@ export async function initNitro (nuxt: Nuxt & { _nitro?: Nitro }) {
     }
   })
 
-  // Set prerender-only options
-  nitro.options._config.storage ||= {}
-  nitro.options._config.storage['internal:nuxt:prerender'] = { driver: 'memory' }
-  nitro.options._config.storage['internal:nuxt:prerender:island'] = { driver: 'lruCache', max: 1000 }
-  nitro.options._config.storage['internal:nuxt:prerender:payload'] = { driver: 'lruCache', max: 1000 }
+  nitro.options._config.storage = defu(nitro.options._config.storage, {
+    'internal:nuxt:prerender': {
+      driver: pathToFileURL(await resolvePath(join(distDir, 'core/runtime/nitro/cache-driver'))).href,
+      base: resolve(nuxt.options.buildDir, 'cache/nitro/prerender')
+    }
+  })
 
   // Expose nitro to modules and kit
   nuxt._nitro = nitro
diff --git a/packages/nuxt/src/core/runtime/nitro/cache-driver.ts b/packages/nuxt/src/core/runtime/nitro/cache-driver.ts
new file mode 100644
index 0000000000..92920a4b4b
--- /dev/null
+++ b/packages/nuxt/src/core/runtime/nitro/cache-driver.ts
@@ -0,0 +1,27 @@
+import { defineDriver } from 'unstorage'
+import fsDriver from 'unstorage/drivers/fs-lite'
+import lruCache from 'unstorage/drivers/lru-cache'
+
+// Ensure we don't try to write/read from directory index for `/` paths
+const normalizeFsKey = (item: string) => item.indexOf(':') === -1 ? `${item}:index` : item
+
+export default defineDriver((opts: { base: string }) => {
+  const fs = fsDriver({ base: opts.base })
+  const lru = lruCache({ max: 1000 })
+
+  return {
+    ...fs, // fall back to file system - only the bottom three methods are used in renderer
+    async setItem (key, value, opts) {
+      await Promise.all([
+        fs.setItem(normalizeFsKey(key), value, opts),
+        lru.setItem(key, value, opts)
+      ])
+    },
+    async hasItem (key, opts) {
+      return await lru.hasItem(key, opts) || await fs.hasItem(normalizeFsKey(key), opts)
+    },
+    async getItem (key, opts) {
+      return await lru.getItem(key, opts) || await fs.getItem(normalizeFsKey(key), opts)
+    },
+  }
+})
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 3e6f527442..c51bba959d 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -395,6 +395,9 @@ importers:
       unplugin-vue-router:
         specifier: ^0.7.0
         version: 0.7.0(rollup@4.12.1)(vue-router@4.3.0)(vue@3.4.21)
+      unstorage:
+        specifier: ^1.10.1
+        version: 1.10.1
       untyped:
         specifier: ^1.4.2
         version: 1.4.2