Use a singleton to store the memory cache in an internal WeakMap for the current request (#2356)

Author: jpreynat

src/lib/cache/memory.ts

@@ -1,6 +1,6 @@
-import { CacheBackend, CacheEntry } from './types';
+import { CacheBackend } from './types';
 import { NON_IMMUTABLE_LOCAL_CACHE_MAX_AGE_SECONDS, isCacheEntryImmutable } from './utils';
-import { getGlobalContext } from '../waitUntil';
+import { singleton } from '../async';
 
 export const memoryCache: CacheBackend = {
     name: 'memory',
@@ -66,13 +66,7 @@ export const memoryCache: CacheBackend = {
 /**
  * With next-on-pages, the code seems to be isolated between the middleware and the handler.
  * To share the cache between the two, we use a global variable.
+ * By using a singleton, we ensure that the cache is only created once and stored in the
+ * current request context.
  */
-async function getMemoryCache(): Promise<Map<string, CacheEntry>> {
-    let globalThisForMemoryCache: any = await getGlobalContext();
-
-    if (!globalThisForMemoryCache.gitbookMemoryCache) {
-        globalThisForMemoryCache.gitbookMemoryCache = new Map();
-    }
-
-    return globalThisForMemoryCache.gitbookMemoryCache;
-}
+const getMemoryCache = singleton(async () => new Map());

src/lib/waitUntil.ts

@@ -12,7 +12,7 @@ export async function getGlobalContext(): Promise<object> {
 
     // We lazy-load the next-on-pages package to avoid errors when running tests because of 'server-only'.
     const { getOptionalRequestContext } = await import('@cloudflare/next-on-pages');
-    return getOptionalRequestContext()?.ctx ?? globalThis;
+    return getOptionalRequestContext()?.cf ?? globalThis;
 }
 
 /**