Early-out ipv6 checks when running on App Engine (#1450)

4 files changed, 52 insertions, 23 deletions

diff --git a/src/urllib3/contrib/_appengine_environ.py b/src/urllib3/contrib/_appengine_environ.py
new file mode 100644
index 00000000..f3e00942
--- /dev/null
+++ b/src/urllib3/contrib/_appengine_environ.py
@@ -0,0 +1,30 @@
+"""
+This module provides means to detect the App Engine environment.
+"""
+
+import os
+
+
+def is_appengine():
+    return (is_local_appengine() or
+            is_prod_appengine() or
+            is_prod_appengine_mvms())
+
+
+def is_appengine_sandbox():
+    return is_appengine() and not is_prod_appengine_mvms()
+
+
+def is_local_appengine():
+    return ('APPENGINE_RUNTIME' in os.environ and
+            'Development/' in os.environ['SERVER_SOFTWARE'])
+
+
+def is_prod_appengine():
+    return ('APPENGINE_RUNTIME' in os.environ and
+            'Google App Engine/' in os.environ['SERVER_SOFTWARE'] and
+            not is_prod_appengine_mvms())
+
+
+def is_prod_appengine_mvms():
+    return os.environ.get('GAE_VM', False) == 'true'
diff --git a/src/urllib3/contrib/appengine.py b/src/urllib3/contrib/appengine.py
index b2951cf8..2952f114 100644
--- a/src/urllib3/contrib/appengine.py
+++ b/src/urllib3/contrib/appengine.py
@@ -41,7 +41,6 @@ urllib3 on Google App Engine:
 from __future__ import absolute_import
 import io
 import logging
-import os
 import warnings
 from ..packages.six.moves.urllib.parse import urljoin
 
@@ -58,6 +57,7 @@ from ..request import RequestMethods
 from ..response import HTTPResponse
 from ..util.timeout import Timeout
 from ..util.retry import Retry
+from . import _appengine_environ
 
 try:
     from google.appengine.api import urlfetch
@@ -280,26 +280,10 @@ class AppEngineManager(RequestMethods):
         return retries
 
 
-def is_appengine():
-    return (is_local_appengine() or
-            is_prod_appengine() or
-            is_prod_appengine_mvms())
+# Alias methods from _appengine_environ to maintain public API interface.
 
-
-def is_appengine_sandbox():
-    return is_appengine() and not is_prod_appengine_mvms()
-
-
-def is_local_appengine():
-    return ('APPENGINE_RUNTIME' in os.environ and
-            'Development/' in os.environ['SERVER_SOFTWARE'])
-
-
-def is_prod_appengine():
-    return ('APPENGINE_RUNTIME' in os.environ and
-            'Google App Engine/' in os.environ['SERVER_SOFTWARE'] and
-            not is_prod_appengine_mvms())
-
-
-def is_prod_appengine_mvms():
-    return os.environ.get('GAE_VM', False) == 'true'
+is_appengine = _appengine_environ.is_appengine
+is_appengine_sandbox = _appengine_environ.is_appengine_sandbox
+is_local_appengine = _appengine_environ.is_local_appengine
+is_prod_appengine = _appengine_environ.is_prod_appengine
+is_prod_appengine_mvms = _appengine_environ.is_prod_appengine_mvms
diff --git a/src/urllib3/util/connection.py b/src/urllib3/util/connection.py
index 5cf488f4..5ad70b2f 100644
--- a/src/urllib3/util/connection.py
+++ b/src/urllib3/util/connection.py
@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 import socket
 from .wait import NoWayToWaitForSocketError, wait_for_read
+from ..contrib import _appengine_environ
 
 
 def is_connection_dropped(conn):  # Platform-specific
@@ -105,6 +106,13 @@ def _has_ipv6(host):
     sock = None
     has_ipv6 = False
 
+    # App Engine doesn't support IPV6 sockets and actually has a quota on the
+    # number of sockets that can be used, so just early out here instead of
+    # creating a socket needlessly.
+    # See https://github.com/urllib3/urllib3/issues/1446
+    if _appengine_environ.is_appengine_sandbox():
+        return False
+
     if socket.has_ipv6:
         # has_ipv6 returns true if cPython was compiled with IPv6 support.
         # It does not tell us if the system has IPv6 support enabled. To
diff --git a/test/test_util.py b/test/test_util.py
index 73d9452a..a0c99a16 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -540,6 +540,13 @@ class TestUtil(object):
                 instance.bind.return_value = True
                 assert _has_ipv6('::1')
 
+    def test_has_ipv6_disabled_on_appengine(self):
+        gae_patch = patch(
+            'urllib3.contrib._appengine_environ.is_appengine_sandbox',
+            return_value=True)
+        with gae_patch:
+            assert not _has_ipv6('::1')
+
     def test_ip_family_ipv6_enabled(self):
         with patch('urllib3.util.connection.HAS_IPV6', True):
             assert allowed_gai_family() == socket.AF_UNSPEC