Make Gnocchi connection pool configurable

When CloudKitty is collecting data from Gnocchi, it opens many
connections to Gnocchi to parallelize the requests; as CloudKitty starts
to fetch the responses from Gnocchi, it releases the connections to the
pool until it starts to overflow (reaching the default limit of the
Requests connection pool). This behavior causes no problems, but
prevents the reuse of connections.

To mitigate this problem and optimize the use of connections, we propose
to add a new configuration in Gnocchi collector and fetcher to set the
connection pool maximum size when connecting to Gnocchi. The new
configuration is `http_pool_maxsize` and you can configure it in the
`cloudkitty.conf` file like:

```
[fetcher_gnocchi]
http_pool_maxsize = 50

[collector_gnocchi]
http_pool_maxsize = 50
```

The default value is defined by the `requests` library which is 10.

Change-Id: I3ee22984dc87b505924e1711bc723bc1c5f160a5
Story: 2008125
Task: 40847

cloudkitty/collector/gnocchi.py

@@ -14,6 +14,7 @@
 #    under the License.
 #
 from datetime import timedelta
+import requests
 import six
 
 from gnocchiclient import auth as gauth
@@ -30,6 +31,7 @@ from voluptuous import Required
 from voluptuous import Schema
 
 from cloudkitty import collector
+from cloudkitty.common import custom_session
 from cloudkitty import dataframe
 from cloudkitty import utils as ck_utils
 from cloudkitty.utils import tz as tzutils
@@ -67,6 +69,12 @@ collector_gnocchi_opts = [
         default='RegionOne',
         help='Region Name',
     ),
+    cfg.IntOpt(
+        'http_pool_maxsize',
+        default=requests.adapters.DEFAULT_POOLSIZE,
+        help='If the value is not defined, we use the value defined by '
+             'requests.adapters.DEFAULT_POOLSIZE',
+    )
 ]
 
 ks_loading.register_session_conf_options(cfg.CONF, COLLECTOR_GNOCCHI_OPTS)
@@ -150,7 +158,9 @@ class GnocchiCollector(collector.BaseCollector):
 
         self._conn = gclient.Client(
             '1',
-            session_options={'auth': auth_plugin, 'verify': verify},
+            session=custom_session.create_custom_session(
+                {'auth': auth_plugin, 'verify': verify},
+                CONF.collector_gnocchi.http_pool_maxsize),
             adapter_options=adapter_options,
         )
 

cloudkitty/common/custom_session.py

@@ -0,0 +1,32 @@
+# -*- coding: utf-8 -*-
+#
+#    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 logging
+import requests
+
+from keystoneauth1 import session as ks_session
+
+
+LOG = logging.getLogger(__name__)
+
+
+def create_custom_session(session_options, pool_size):
+    LOG.debug("Using custom connection pool size: %s", pool_size)
+    session = requests.Session()
+    session.adapters['http://'] = ks_session.TCPKeepAliveAdapter(
+        pool_maxsize=pool_size)
+    session.adapters['https://'] = ks_session.TCPKeepAliveAdapter(
+        pool_maxsize=pool_size)
+
+    return ks_session.Session(session=session, **session_options)

cloudkitty/fetcher/gnocchi.py

@@ -13,12 +13,15 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 #
+import requests
+
 from gnocchiclient import auth as gauth
 from gnocchiclient import client as gclient
 from keystoneauth1 import loading as ks_loading
 from oslo_config import cfg
 from oslo_log import log
 
+from cloudkitty.common import custom_session
 from cloudkitty import fetcher
 
 
@@ -61,6 +64,12 @@ gfetcher_opts = [
         default='RegionOne',
         help='Region Name',
     ),
+    cfg.IntOpt(
+        'http_pool_maxsize',
+        default=requests.adapters.DEFAULT_POOLSIZE,
+        help='If the value is not defined, we use the value defined by '
+             'requests.adapters.DEFAULT_POOLSIZE',
+    )
 ]
 
 
@@ -105,7 +114,9 @@ class GnocchiFetcher(fetcher.BaseFetcher):
 
         self._conn = gclient.Client(
             '1',
-            session_options={'auth': auth_plugin, 'verify': verify},
+            session=custom_session.create_custom_session(
+                {'auth': auth_plugin, 'verify': verify},
+                CONF.fetcher_gnocchi.http_pool_maxsize),
             adapter_options=adapter_options,
         )
 

releasenotes/notes/make-gnocchi-http-max-connections-pool-configurable-52c9f6617466ea30.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    Adds a new configuration ``http_pool_maxsize`` that defines the maximum
+    size of Gnocchi's fetcher and collector HTTP connection pools.
+
+    The default value of this new configuration is defined by the ``requests``
+    library in the ``requests.adapters.DEFAULT_POOLSIZE`` global variable.