Dell EMC PS: Optimize parsing of capacity info from backend

The backend api returns large amounts of information and
times out when there are lots of volumes. Accelerated the
process by terminating the parsing after the capacity info
is retrieved.

Closes Bug: #1661154

Change-Id: I1f0adaa8e25cd3ec74084b22bbe1573b92713959

cinder/volume/drivers/dell_emc/ps.py

@@ -138,10 +138,11 @@ class PSSeriesISCSIDriver(san.SanISCSIDriver):
         1.4.2 - Enable report discard support.
         1.4.3 - Report total_volumes in volume stats
         1.4.4 - Fixed over-subscription ratio calculation
+        1.4.5 - Optimize volume stats information parsing
 
     """
 
-    VERSION = "1.4.4"
+    VERSION = "1.4.5"
 
     # ThirdPartySytems wiki page
     CI_WIKI_NAME = "Dell_Storage_CI"
@@ -301,13 +302,12 @@ class PSSeriesISCSIDriver(san.SanISCSIDriver):
         data['reserved_percentage'] = 0
         data['QoS_support'] = False
 
-        data['total_capacity_gb'] = 0
-        data['free_capacity_gb'] = 0
+        data['total_capacity_gb'] = None
+        data['free_capacity_gb'] = None
         data['multiattach'] = False
-        data['total_volumes'] = 0
-
-        provisioned_capacity = 0
+        data['total_volumes'] = None
 
+        provisioned_capacity = None
         for line in self._eql_execute('pool', 'select',
                                       self.configuration.eqlx_pool, 'show'):
             if line.startswith('TotalCapacity:'):
@@ -322,6 +322,10 @@ class PSSeriesISCSIDriver(san.SanISCSIDriver):
             if line.startswith('TotalVolumes:'):
                 out_tup = line.rstrip().partition(' ')
                 data['total_volumes'] = int(out_tup[-1])
+            # Terminate parsing once this data is found to improve performance
+            if (data['total_capacity_gb'] and data['free_capacity_gb'] and
+               provisioned_capacity and data['total_volumes']):
+                break
 
         global_capacity = data['total_capacity_gb']
         global_free = data['free_capacity_gb']

releasenotes/notes/ps-optimize-parsing-8aa447c50f2474c7.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - Dell EMC PS Series Driver code reporting volume stats is now optimized
+    to return the information earlier and accelerate the process. This change
+    fixes bug 1661154.