From f0ded6b7759c9c2ec4b8946cdfc4abab97bb14d9 Mon Sep 17 00:00:00 2001
From: Paul Tremberth <paul.tremberth@gmail.com>
Date: Tue, 4 Jul 2017 23:18:15 +0200
Subject: [PATCH] Do not cache DNS responses when cache size is 0

---
 scrapy/resolver.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scrapy/resolver.py b/scrapy/resolver.py
index 4f4f0b04f..0aaced7e4 100644
--- a/scrapy/resolver.py
+++ b/scrapy/resolver.py
@@ -22,7 +22,8 @@ class CachingThreadedResolver(ThreadedResolver):
         # to enforce Scrapy's DNS_TIMEOUT setting's value
         timeout = (self.timeout,)
         d = super(CachingThreadedResolver, self).getHostByName(name, timeout)
-        d.addCallback(self._cache_result, name)
+        if dnscache.limit:
+            d.addCallback(self._cache_result, name)
         return d
 
     def _cache_result(self, result, name):