Allows to change defaults opts

This change introduces to possibility for the consumer application
to change the default oslo.messaging config options.

Same API interface as oslo.db have been taken.
The first option is executor_thread_pool_size.

This option was called rpc_thread_pool_size, but because it's used by
notification and rpc 'executor_thread_pool_size' looks a better name.

Changing executor_thread_pool_size default will be useful for ceilometer
the default of 64 is really to small to consume many notifications at
once for batching them. When is clearly sufficient for rpc stuffs.

Change-Id: Iea0d7a72e38d27c600403c815258aa5eee0d0c8c

oslo_messaging/_drivers/impl_zmq.py

@@ -465,7 +465,8 @@ class ZmqBaseReactor(ConsumerBase):
         self.sockets = []
         self.subscribe = {}
 
-        self.pool = eventlet.greenpool.GreenPool(conf.rpc_thread_pool_size)
+        self.pool = eventlet.greenpool.GreenPool(
+            conf.executor_thread_pool_size)
 
     def register(self, proxy, in_addr, zmq_type_in,
                  in_bind=True, subscribe=None):

oslo_messaging/_executors/impl_pooledexecutor.py

@@ -25,9 +25,10 @@ from oslo_utils import excutils
 from oslo_messaging._executors import base
 
 _pool_opts = [
-    cfg.IntOpt('rpc_thread_pool_size',
+    cfg.IntOpt('executor_thread_pool_size',
                default=64,
-               help='Size of RPC thread pool.'),
+               deprecated_name="rpc_thread_pool_size",
+               help='Size of executor thread pool.'),
 ]
 
 
@@ -103,7 +104,8 @@ class PooledExecutor(base.ExecutorBase):
 
     def start(self):
         if self._executor is None:
-            self._executor = self._executor_cls(self.conf.rpc_thread_pool_size)
+            self._executor = self._executor_cls(
+                self.conf.executor_thread_pool_size)
         self._tombstone.clear()
         if self._poller is None or not self._poller.is_alive():
             self._poller = self._thread_cls(target=self._runner)

oslo_messaging/opts.py

@@ -76,3 +76,23 @@ def list_opts():
     :returns: a list of (group_name, opts) tuples
     """
     return [(g, copy.deepcopy(o)) for g, o in _opts]
+
+
+def set_defaults(conf, executor_thread_pool_size=None):
+    """Set defaults for configuration variables.
+
+    Overrides default options values.
+
+    :param conf: Config instance specified to set default options in it. Using
+     of instances instead of a global config object prevents conflicts between
+     options declaration.
+    :type conf: oslo.config.cfg.ConfigOpts instance.
+
+    :keyword executor_thread_pool_size: Size of executor thread pool.
+    :type executor_thread_pool_size: int
+    :default executor_thread_pool_size: None
+
+    """
+    if executor_thread_pool_size is not None:
+        conf.set_default('executor_thread_pool_size',
+                         executor_thread_pool_size)

oslo_messaging/tests/test_opts.py

@@ -15,6 +15,9 @@
 import stevedore
 import testtools
 
+import mock
+
+from oslo_messaging._executors import impl_thread
 try:
     from oslo_messaging import opts
 except ImportError:
@@ -55,3 +58,8 @@ class OptsTestCase(test_utils.BaseTestCase):
 
         self.assertIsNotNone(result)
         self._test_list_opts(result)
+
+    def test_defaults(self):
+        impl_thread.ThreadExecutor(self.conf, mock.Mock(), mock.Mock())
+        opts.set_defaults(self.conf, executor_thread_pool_size=100)
+        self.assertEqual(100, self.conf.executor_thread_pool_size)