From fe8032748e5f707ec889ed1d7fa2d78779bf039b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9A=D0=BE=D1=80=D0=B5=D0=BD=D0=B1=D0=B5=D1=80=D0=B3=20?=
 =?UTF-8?q?=D0=9C=D0=B0=D1=80=D0=BA=20=28dell=20notebook=29?=
 <mark@ideco.ru>
Date: Mon, 25 Dec 2017 01:10:48 +0500
Subject: [PATCH] Fix DNSCache race-condition (#2620)

---
 aiohttp/connector.py | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/aiohttp/connector.py b/aiohttp/connector.py
index f51641c4046..4205affaeae 100644
--- a/aiohttp/connector.py
+++ b/aiohttp/connector.py
@@ -7,7 +7,7 @@
 from contextlib import suppress
 from hashlib import md5, sha1, sha256
 from http.cookies import SimpleCookie
-from itertools import cycle, islice
+from random import shuffle
 from time import monotonic
 from types import MappingProxyType
 
@@ -547,7 +547,6 @@ class _DNSCacheTable:
 
     def __init__(self, ttl=None):
         self._addrs = {}
-        self._addrs_rr = {}
         self._timestamps = {}
         self._ttl = ttl
 
@@ -560,28 +559,24 @@ def addrs(self):
 
     def add(self, host, addrs):
         self._addrs[host] = addrs
-        self._addrs_rr[host] = cycle(addrs)
 
         if self._ttl:
             self._timestamps[host] = monotonic()
 
     def remove(self, host):
         self._addrs.pop(host, None)
-        self._addrs_rr.pop(host, None)
 
         if self._ttl:
             self._timestamps.pop(host, None)
 
     def clear(self):
         self._addrs.clear()
-        self._addrs_rr.clear()
         self._timestamps.clear()
 
     def next_addrs(self, host):
-        # Return an iterator that will get at maximum as many addrs
-        # there are for the specific host starting from the last
-        # not itereated addr.
-        return islice(self._addrs_rr[host], len(self._addrs[host]))
+        addrs = self._addrs[host].copy()
+        shuffle(addrs)
+        return addrs
 
     def expired(self, host):
         if self._ttl is None: