Switch to futurist for concurrency

As we're being used inside of services more and those services
frequently use things like eventlet, allow people to pass in
an Executor object from futurist to override the default
ThreadPoolExecutor object.

Change-Id: I6c04defc28998d49199383a6cc6d5f5611a99e25

lower-constraints.txt

@@ -9,6 +9,7 @@ extras==1.0.0
 fixtures==3.0.0
 future==0.16.0
 futures==3.0.0
+futurist==2.1.0
 ipaddress==1.0.17
 iso8601==0.1.11
 jmespath==0.9.0

openstack/cloud/_object_store.py

@@ -45,9 +45,6 @@ OBJECT_CONTAINER_ACLS = {
 
 class ObjectStoreCloudMixin(_normalize.Normalizer):
 
-    def __init__(self):
-        self.__pool_executor = None
-
     @property
     def _object_store_client(self):
         if 'object-store' not in self._raw_clients:
@@ -55,16 +52,6 @@ class ObjectStoreCloudMixin(_normalize.Normalizer):
             self._raw_clients['object-store'] = raw_client
         return self._raw_clients['object-store']
 
-    @property
-    def _pool_executor(self):
-        if not self.__pool_executor:
-            # TODO(mordred) Make this configurable - and probably use Futurist
-            # instead of concurrent.futures so that people using Eventlet will
-            # be happier.
-            self.__pool_executor = concurrent.futures.ThreadPoolExecutor(
-                max_workers=5)
-        return self.__pool_executor
-
     def list_containers(self, full_listing=True, prefix=None):
         """List containers.
 

openstack/connection.py

@@ -179,6 +179,7 @@ Additional information about the services can be found in the
 import warnings
 import weakref
 
+import futurist
 import keystoneauth1.exceptions
 import requestsexceptions
 import six
@@ -276,6 +277,7 @@ class Connection(
                  service_types=None,
                  global_request_id=None,
                  strict_proxies=False,
+                 pool_executor=None,
                  **kwargs):
         """Create a connection to a cloud.
 
@@ -343,6 +345,11 @@ class Connection(
             where it can be expected that the deployer config is correct and
             errors should be reported immediately.
             Default false.
+        :param pool_executor:
+        :type pool_executor: :class:`~futurist.Executor`
+            A futurist ``Executor`` object to be used for concurrent background
+            activities. Defaults to None in which case a ThreadPoolExecutor
+            will be created if needed.
         :param kwargs: If a config is not provided, the rest of the parameters
             provided are assumed to be arguments to be passed to the
             CloudRegion constructor.
@@ -378,7 +385,7 @@ class Connection(
 
         self._session = None
         self._proxies = {}
-        self.__pool_executor = None
+        self.__pool_executor = pool_executor
         self._global_request_id = global_request_id
         self.use_direct_get = use_direct_get
         self.strict_mode = strict
@@ -491,6 +498,13 @@ class Connection(
         except keystoneauth1.exceptions.ClientException as e:
             raise exceptions.raise_from_response(e.response)
 
+    @property
+    def _pool_executor(self):
+        if not self.__pool_executor:
+            self.__pool_executor = futurist.ThreadPoolExecutor(
+                max_workers=5)
+        return self.__pool_executor
+
     def close(self):
         """Release any resources held open."""
         if self.__pool_executor:

releasenotes/notes/futurist-b54b0f449d410997.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    Switched to the ``futurist`` library for managing background
+    concurrent tasks. Introduced a new ``pool_executor`` parameter
+    to `Connection` that allows passing any any futurist Executor
+    for cases where the default ``ThreadPoolExecutor`` would not
+    be appropriate.

requirements.txt

@@ -14,7 +14,7 @@ munch>=2.1.0 # MIT
 decorator>=4.4.1 # BSD
 jmespath>=0.9.0 # MIT
 ipaddress>=1.0.17;python_version<'3.3' # PSF
-futures>=3.0.0;python_version=='2.7' or python_version=='2.6' # BSD
+futurist>=2.1.0 # Apache-2.0
 iso8601>=0.1.11 # MIT
 netifaces>=0.10.4 # MIT