Fix rendering of hdparm.conf file

Use the charmhelpers.core.templating template rendering logic
instead of the charmhelpers.core.services template rendering logic
when generating the hdparm.conf file.

Change-Id: I4b9718e49336d72501585279c0fc0cfcd465abb2
Closes-Bug: #1660240

ceph/__init__.py

@@ -28,6 +28,7 @@ import pyudev
 from datetime import datetime
 
 from charmhelpers.core import hookenv
+from charmhelpers.core import templating
 from charmhelpers.core.host import (
     chownr,
     cmp_pkgrevno,
@@ -46,7 +47,6 @@ from charmhelpers.core.hookenv import (
     DEBUG,
     ERROR,
     WARNING)
-from charmhelpers.core.services import render_template
 from charmhelpers.fetch import (
     apt_cache,
     add_source, apt_install, apt_update)
@@ -64,6 +64,7 @@ from charmhelpers.contrib.openstack.utils import (
 
 CEPH_BASE_DIR = os.path.join(os.sep, 'var', 'lib', 'ceph')
 OSD_BASE_DIR = os.path.join(CEPH_BASE_DIR, 'osd')
+HDPARM_FILE = os.path.join(os.sep, 'etc', 'hdparm.conf')
 
 LEADER = 'leader'
 PEON = 'peon'
@@ -229,14 +230,21 @@ def persist_settings(settings_dict):
         The settings_dict should be in the form of {"uuid": {"key":"value"}}
         :param settings_dict: dict of settings to save
     """
-    hdparm_path = os.path.join(os.sep, 'etc', 'hdparm.conf')
+    if not settings_dict:
+        return
+
     try:
-        with open(hdparm_path, 'w') as hdparm:
-            hdparm.write(render_template('hdparm.conf', settings_dict))
+        templating.render(source='hdparm.conf', target=HDPARM_FILE,
+                          context=settings_dict)
     except IOError as err:
         log("Unable to open {path} because of error: {error}".format(
-            path=hdparm_path,
-            error=err.message), level=ERROR)
+            path=HDPARM_FILE, error=err.message), level=ERROR)
+    except Exception as e:
+        # The templating.render can raise a jinja2 exception if the
+        # template is not found. Rather than polluting the import
+        # space of this charm, simply catch Exception
+        log('Unable to render {path} due to error: {error}'.format(
+            path=HDPARM_FILE, error=e.message), level=ERROR)
 
 
 def set_max_sectors_kb(dev_name, max_sectors_size):

unit_tests/test_disk_tuning.py

@@ -0,0 +1,43 @@
+# Copyright 2017 Canonical Ltd
+#
+# 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 ceph
+import mock
+import unittest
+
+
+class DiskTuningTestCase(unittest.TestCase):
+    def setUp(self):
+        super(DiskTuningTestCase, self).setUp()
+
+    @mock.patch.object(ceph, 'templating')
+    def test_persist_settings(self, _templating):
+        renderer = _templating.render
+        settings = {
+            'drive_settings': {
+                'some-random-uuid': {
+                    'read_ahead_sect': 256
+                }
+            }
+        }
+        ceph.persist_settings(settings)
+        renderer.assert_called_once_with(source='hdparm.conf',
+                                         target=ceph.HDPARM_FILE,
+                                         context=settings)
+
+    @mock.patch.object(ceph, 'templating')
+    def test_persist_settings_empty_dict(self, _templating):
+        renderer = _templating.render
+        ceph.persist_settings({})
+        assert not renderer.called, 'renderer should not have been called'