added setting to support disabling DNS cache: DNSCACHE_ENABLED

docs/topics/settings.rst

@@ -366,6 +366,15 @@ Default: ``False``
 Whether to collect verbose depth stats. If this is enabled, the number of
 requests for each depth is collected in the stats.
 
+.. setting:: DNSCACHE_ENABLED
+
+DNSCACHE_ENABLED
+----------------
+
+Default: ``True``
+
+Whether to enable DNS in-memory cache.
+
 .. setting:: DOWNLOADER_DEBUG
 
 DOWNLOADER_DEBUG

scrapy/crawler.py

@@ -70,7 +70,8 @@ class CrawlerProcess(Crawler):
 
     def start(self):
         super(CrawlerProcess, self).start()
-        reactor.installResolver(CachingThreadedResolver(reactor))
+        if self.settings.getbool('DNSCACHE_ENABLED'):
+            reactor.installResolver(CachingThreadedResolver(reactor))
         reactor.addSystemEventTrigger('before', 'shutdown', self.stop)
         reactor.run(installSignalHandlers=False) # blocking call
 

scrapy/settings/default_settings.py

@@ -49,6 +49,8 @@ DEPTH_LIMIT = 0
 DEPTH_STATS = True
 DEPTH_PRIORITY = 1
 
+DNSCACHE_ENABLED = True
+
 DOWNLOAD_DELAY = 0
 
 DOWNLOAD_HANDLERS = {}