From 8d950d0ae7bbbce10a413f23262888b6195997ff Mon Sep 17 00:00:00 2001
From: Eric Peterson <ericpeterson@spotify.com>
Date: Fri, 15 Jan 2021 18:02:37 +0100
Subject: [PATCH] Stream files directly from GCS instead of buffering and
 sending.

---
 .../src/stages/publish/googleStorage.ts       | 25 +++++++------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/packages/techdocs-common/src/stages/publish/googleStorage.ts b/packages/techdocs-common/src/stages/publish/googleStorage.ts
index e6b2c26943..f92b905f73 100644
--- a/packages/techdocs-common/src/stages/publish/googleStorage.ts
+++ b/packages/techdocs-common/src/stages/publish/googleStorage.ts
@@ -169,30 +169,23 @@ export class GoogleGCSPublish implements PublisherBase {
       // Files with different extensions (CSS, HTML) need to be served with different headers
       const fileExtension = path.extname(filePath);
       const responseHeaders = getHeadersForFileExtension(fileExtension);
+      res.writeHead(200, {
+        ...{
+          'Transfer-Encoding': 'chunked',
+        },
+        ...responseHeaders,
+      });
 
-      const fileStreamChunks: Array<any> = [];
+      // Pipe file chunks directly from storage to client.
       this.storageClient
         .bucket(this.bucketName)
         .file(filePath)
         .createReadStream()
         .on('error', err => {
           this.logger.warn(err.message);
-          res.status(404).send(err.message);
+          res.destroy(err);
         })
-        .on('data', chunk => {
-          fileStreamChunks.push(chunk);
-        })
-        .on('end', () => {
-          const fileContent = Buffer.concat(fileStreamChunks);
-          // Inject response headers
-          for (const [headerKey, headerValue] of Object.entries(
-            responseHeaders,
-          )) {
-            res.setHeader(headerKey, headerValue);
-          }
-
-          res.send(fileContent);
-        });
+        .pipe(res);
     };
   }