Move eventlet monkey patch code

Eventlet monkey patching is not recommended on top level __init__ [1],
because Apache WSGI module uses own concurrency model [2] and API
service under Apache should be runned without eventlet. This patch
moves eventlet monkey patching code to ironic.cmd module __init__
(like in nova).

[1] https://specs.openstack.org/openstack/openstack-specs/specs/eventlet-best-practices.html
[2] http://modwsgi.readthedocs.io/en/develop/user-guides/processes-and-threading.html

Closes-Bug: 1608252
Change-Id: I887a06566dcc2f09875f975f1e12ae4ff75fd348

ironic/__init__.py

@@ -1,22 +0,0 @@
-# Copyright (c) 2014 Hewlett-Packard Development Company, L.P.
-# All Rights Reserved.
-#
-# Licensed under the Apache License, Version 2.0 (the "License"); you may
-# not use this file except in compliance with the License. You may obtain
-# a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-# License for the specific language governing permissions and limitations
-# under the License.
-
-import os
-
-os.environ['EVENTLET_NO_GREENDNS'] = 'yes'
-
-import eventlet
-
-eventlet.monkey_patch(os=False)

ironic/cmd/__init__.py

@@ -13,6 +13,16 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+# NOTE(yuriyz): Do eventlet monkey patching here, not in ironic/__init__.py
+# This allows API service runs under Apache.
+import os
+
+os.environ['EVENTLET_NO_GREENDNS'] = 'yes'
+
+import eventlet
+
+eventlet.monkey_patch(os=False)
+
 import oslo_i18n as i18n
 
 i18n.install('ironic')

releasenotes/notes/apache-multiple-workers-11d4ba52c89a13e3.yaml

@@ -0,0 +1,3 @@
+---
+fixes:
+  - Fix issue with multiple threads when ironic API service runs under Apache.