fix: update cache on 304 response

These responses mean that the data we have in cache is still valid, but they may come with a fresh maxage policy.
ForbesLindesay · Apr 12, 2019 · dde4d50 · dde4d50
1 parent 89f798e
commit dde4d50
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Showing 4 changed files with 66 additions and 1 deletion.
diff --git a/src/FileCache.ts b/src/FileCache.ts
@@ -75,6 +75,33 @@ export default class FileCache implements ICache {
     });
   }
 
+  updateResponseHeaders(url: string, response: Pick<CachedResponse, 'headers' | 'requestTimestamp'>) {
+    const key = resolve(this._location, getCacheKey(url));
+    fs.readFile(key + '.json', 'utf8', function (err, data) {
+      if (err) {
+        console.warn('Error writing to cache: ' + err.message);
+        return;
+      }
+      let parsed = null;
+      try {
+        parsed = JSON.parse(data);
+      } catch (ex) {
+        console.warn('Error writing to cache: ' + ex.message);
+        return;
+      }
+      fs.writeFile(key + '.json', JSON.stringify({
+        statusCode: parsed.statusCode,
+        headers: response.headers,
+        requestHeaders: parsed.requestHeaders,
+        requestTimestamp: response.requestTimestamp
+      }, null, '  '), function (err) {
+        if (err) {
+          console.warn('Error writing to cache: ' + err.message);
+        }
+      });
+    });
+  }
+
   invalidateResponse(url: string, callback: (err: NodeJS.ErrnoException | null) => void): void {
     const key = resolve(this._location, getCacheKey(url));
     fs.unlink(key + '.json', (err?: NodeJS.ErrnoException | null) => {

diff --git a/src/ICache.ts b/src/ICache.ts
@@ -3,6 +3,7 @@ import {CachedResponse} from './CachedResponse';
 interface ICache {
   getResponse(url: string, cb: (err: Error | null, response: CachedResponse | null) => void): void;
   setResponse(url: string, response: CachedResponse | null): void;
+  updateResponseHeaders?: (url: string, response: Pick<CachedResponse, 'headers' | 'requestTimestamp'>) => void;
   invalidateResponse(url: string, cb: (err: Error | null) => void): void;
 }
 

diff --git a/src/MemoryCache.ts b/src/MemoryCache.ts
@@ -34,6 +34,15 @@ export default class MemoryCache {
       callback(null, null);
     }
   }
+
+  updateResponseHeaders(url: string, response: Pick<CachedResponse, 'headers' | 'requestTimestamp'>) {
+    this._cache[url] = {
+      ...this._cache[url],
+      headers: response.headers,
+      requestTimestamp: response.requestTimestamp
+    };
+  }
+
   setResponse(url: string, response: CachedResponse): void {
     const cache = this._cache;
     response.body.pipe(concat((body) => {
@@ -46,6 +55,7 @@ export default class MemoryCache {
       };
     }));
   }
+
   invalidateResponse(url: string, callback: (err: NodeJS.ErrnoException | null) => void) {
     const cache = this._cache;
     delete cache[url];

diff --git a/src/index.ts b/src/index.ts
@@ -222,7 +222,34 @@ function _request(method: HttpVerb, url: string, options: Options, callback: Cal
         if (res.statusCode === 304 && cachedResponse) { // Not Modified
           // prevent leakage of file handles
           res.body.resume();
-          const response = new Response(cachedResponse.statusCode, cachedResponse.headers, cachedResponse.body, url);
+          let resultBody = cachedResponse.body;
+          const c = (cache as ICache);
+          if (c.updateResponseHeaders) {
+            c.updateResponseHeaders(url, {
+              headers: res.headers,
+              requestTimestamp: timestamp,
+            });
+          } else {
+            const cachedResponseBody = new PassThrough();
+            const newResultBody = new PassThrough();
+            resultBody.on('data', (data: Buffer) => {
+              cachedResponseBody.write(data);
+              newResultBody.write(data);
+            });
+            resultBody.on('end', () => {
+              cachedResponseBody.end();
+              newResultBody.end();
+            });
+            resultBody = newResultBody;
+            (cache as ICache).setResponse(url, {
+              statusCode: cachedResponse.statusCode,
+              headers: res.headers,
+              body: cachedResponseBody,
+              requestHeaders: cachedResponse.requestHeaders,
+              requestTimestamp: timestamp,
+            });
+          }
+          const response = new Response(cachedResponse.statusCode, cachedResponse.headers, resultBody, url);
           (response as any).fromCache = true;
           (response as any).fromNotModified = true;
           return callback(null, response);