perf(core): server-side response caching using the Web Cache API

src/app.ts

@@ -196,6 +196,11 @@ export class App<State> {
       req: Request,
       conn: Deno.ServeHandlerInfo = DEFAULT_CONN_INFO,
     ) => {
+      if (this.config.cache && req.method === "GET") {
+        const cachedResponse = await this.config.cache.match(req);
+        if (cachedResponse) return cachedResponse;
+      }
+
       const url = new URL(req.url);
       // Prevent open redirect attacks
       url.pathname = url.pathname.replace(/\/+/g, "/");
@@ -225,24 +230,28 @@ export class App<State> {
         span.setAttribute("http.route", pattern);
       }
 
+      let response: Response;
       try {
-        if (handlers.length === 1 && handlers[0].length === 1) {
-          return handlers[0][0](ctx);
-        }
-        return await runMiddlewares(handlers, ctx);
+        response = handlers.length === 1 && handlers[0].length === 1
+          ? await handlers[0][0](ctx)
+          : await runMiddlewares(handlers, ctx);
       } catch (err) {
         if (err instanceof HttpError) {
           if (err.status >= 500) {
             // deno-lint-ignore no-console
             console.error(err);
           }
-          return new Response(err.message, { status: err.status });
+          response = new Response(err.message, { status: err.status });
+        } else {
+          // deno-lint-ignore no-console
+          console.error(err);
+          response = new Response("Internal server error", { status: 500 });
         }
-
-        // deno-lint-ignore no-console
-        console.error(err);
-        return new Response("Internal server error", { status: 500 });
       }
+      if (this.config.cache && req.method === "GET") {
+        await this.config.cache.put(req, response.clone());
+      }
+      return response;
     };
   }
 

src/config.ts

@@ -16,6 +16,10 @@ export interface FreshConfig {
    */
   basePath?: string;
   staticDir?: string;
+  /**
+   * Server-side cache that stores responses for corresponding GET requests.
+   */
+  cache?: Cache;
 }
 
 /**
@@ -32,6 +36,10 @@ export interface ResolvedFreshConfig {
    * The mode Fresh can run in.
    */
   mode: "development" | "production";
+  /**
+   * Server-side cache that stores responses for corresponding GET requests.
+   */
+  cache?: Cache;
 }
 
 export function parseRootPath(root: string, cwd: string): string {
@@ -65,6 +73,7 @@ export function normalizeConfig(options: FreshConfig): ResolvedFreshConfig {
     basePath: options.basePath ?? "",
     staticDir: options.staticDir ?? path.join(root, "static"),
     mode: "production",
+    cache: options.cache,
   };
 }
 

www/main.ts

@@ -1,7 +1,9 @@
 import "./telemetry.ts";
 import { App, fsRoutes, staticFiles, trailingSlashes } from "fresh";
 
-export const app = new App({ root: import.meta.url })
+const cache = await caches.open("fresh");
+
+export const app = new App({ root: import.meta.url, cache })
   .use(staticFiles())
   .use(trailingSlashes("never"));