From 0abfed3e06c62b1156073bdf068a1b0ac23d2505 Mon Sep 17 00:00:00 2001
From: Guy Marriott <guy@scopey.co.nz>
Date: Tue, 30 Jul 2019 08:25:03 +1200
Subject: [PATCH] FIX Skip md5-ing the whole contents of a stream for etags

---
 src/Control/Middleware/ChangeDetectionMiddleware.php | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/Control/Middleware/ChangeDetectionMiddleware.php b/src/Control/Middleware/ChangeDetectionMiddleware.php
index 8a990d81a..1767a0161 100644
--- a/src/Control/Middleware/ChangeDetectionMiddleware.php
+++ b/src/Control/Middleware/ChangeDetectionMiddleware.php
@@ -4,6 +4,7 @@ namespace SilverStripe\Control\Middleware;
 
 use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Control\HTTPResponse;
+use SilverStripe\Control\HTTPStreamResponse;
 use SilverStripe\Core\Injector\Injectable;
 
 /**
@@ -69,6 +70,11 @@ class ChangeDetectionMiddleware implements HTTPMiddleware
             return $etag;
         }
 
+        // Skip parsing the whole body of a stream
+        if ($response instanceof HTTPStreamResponse) {
+            return false;
+        }
+
         // Generate etag from body
         return sprintf('"%s"', md5($response->getBody()));
     }