Made use of tpool for gethostbyname configurable by environment variable.

eventlet/green/socket.py

@@ -6,6 +6,7 @@ _fileobject = __socket._fileobject
 from eventlet.hubs import get_hub
 from eventlet.greenio import GreenSocket as socket
 from eventlet.greenio import SSL as _SSL  # for exceptions
+import os
 import sys
 import warnings
 
@@ -17,9 +18,11 @@ def socketpair(*args):
     return socket(one), socket(two)
 
 def gethostbyname(name):
+    can_use_tpool = os.environ.get("EVENTLET_TPOOL_GETHOSTBYNAME",
+                                   '').lower() == "yes"
     if getattr(get_hub(), 'uses_twisted_reactor', None):
         globals()['gethostbyname'] = _gethostbyname_twisted
-    elif sys.platform.startswith('darwin'):
+    elif sys.platform.startswith('darwin') or not can_use_tpool:
         # the thread primitives on Darwin have some bugs that make
         # it undesirable to use tpool for hostname lookups
         globals()['gethostbyname'] = __socket.gethostbyname

eventlet/util.py

@@ -69,7 +69,7 @@ except ImportError:
         return connection
 
 socket_already_wrapped = False
-def wrap_socket_with_coroutine_socket(use_thread_pool=False):
+def wrap_socket_with_coroutine_socket(use_thread_pool=None):
     global socket_already_wrapped
     if socket_already_wrapped:
         return
@@ -84,6 +84,11 @@ def wrap_socket_with_coroutine_socket(use_thread_pool=False):
     except ImportError:
         pass
 
+    if use_thread_pool is None:
+        # if caller doesn't specify, use the environment variable
+        # to decide whether to use tpool or not
+        use_thread_pool = os.environ.get("EVENTLET_TPOOL_GETHOSTBYNAME",
+                                         '').lower() == "yes"
     if use_thread_pool:
         try:
             from eventlet import tpool