From b89f2f2f99aa107504a2815d379906a97672d1cc Mon Sep 17 00:00:00 2001
From: Gorka Eguileor <geguileo@redhat.com>
Date: Sun, 3 Feb 2019 12:01:10 +0100
Subject: [PATCH] Workaround for driver stats bug

Some drivers don't have a working stats cache as they should, and so
they return an empty dictionary when we try to retrieve their cached
stats by passing refresh=False.

On such drivers is HPE's 3PAR.

This patch works around this by checking returned value and call it
again with refresh=True if the backend doesn't work as it should.
---
 HISTORY.rst            |  2 +-
 cinderlib/cinderlib.py | 15 +++++++++++++++
 cinderlib/exception.py |  1 +
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/HISTORY.rst b/HISTORY.rst
index 3920b8b..8018510 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -8,7 +8,7 @@ History
 - Bug fixes:
 
   - Support MultiOpt configuration parameters
-
+  - Workaround for Cinder cached stats bug
 
 0.3.4 (2019-01-26)
 ------------------
diff --git a/cinderlib/cinderlib.py b/cinderlib/cinderlib.py
index aaf1c1c..b5ccdad 100644
--- a/cinderlib/cinderlib.py
+++ b/cinderlib/cinderlib.py
@@ -38,6 +38,7 @@ from oslo_utils import importutils
 import urllib3
 
 import cinderlib
+from cinderlib import exception
 from cinderlib import nos_brick
 from cinderlib import objects
 from cinderlib import persistence
@@ -46,6 +47,8 @@ from cinderlib import serialization
 
 __all__ = ['setup', 'Backend']
 
+LOG = logging.getLogger(__name__)
+
 
 class Backend(object):
     """Representation of a Cinder Driver.
@@ -120,6 +123,18 @@ class Backend(object):
 
     def stats(self, refresh=False):
         stats_data = self.driver.get_volume_stats(refresh=refresh)
+        # TODO(geguileo): Remove this workaround for some drivers' bug that
+        # don't have a working stats cache once they are fixed.
+        if not refresh and not stats_data:
+            LOG.warning('Refreshing cache to work around driver stats cache '
+                        'bug')
+            stats_data = self.driver.get_volume_stats(refresh=True)
+
+        if not stats_data:
+            msg = 'Driver not returning stats data'
+            LOG.error(msg)
+            raise exception.VolumeDriverException(message=msg)
+
         # Fill pools for legacy driver reports
         if stats_data and 'pools' not in stats_data:
             pool = stats_data.copy()
diff --git a/cinderlib/exception.py b/cinderlib/exception.py
index 798934f..9915740 100644
--- a/cinderlib/exception.py
+++ b/cinderlib/exception.py
@@ -21,6 +21,7 @@ VolumeNotFound = exception.VolumeNotFound
 SnapshotNotFound = exception.SnapshotNotFound
 ConnectionNotFound = exception.VolumeAttachmentNotFound
 InvalidVolume = exception.InvalidVolume
+VolumeDriverException = exception.VolumeDriverException
 
 
 class InvalidPersistence(Exception):