SW-448: keep results for non existing paths in cache

SAS/DataManagement/StorageQueryService/cache.py

@@ -128,7 +128,7 @@ class CacheManager:
                     # Furthermore, once a deeper level du results is stored in the memory cache, then it is also available for fast lookup.
                     # We just don't store these deep levels on disk.
                     sub_cache = { path:du_result for path,du_result in self._cache['path_du_results'].items()
-                                  if self.getDepthToProjectsDir(path) <= 1 }
+                                  if self.getDepthToProjectsDir(path) <= 1 and du_result.get('found') }
                     cache_str = str(sub_cache)
 
                 with open(tmp_path, 'w') as file:
@@ -154,24 +154,24 @@ class CacheManager:
                 if path in path_cache:
                     otdb_id = du_result.get('otdb_id')
 
-            if du_result['found']:
-                if not path in path_cache or path_cache[path]['disk_usage'] != du_result['disk_usage']:
-                    # update the cache entry, even when no du result found,
-                    # cause that will save disk queries next time.
-                    logger.info('updating cache entry: %s', du_result)
-                    path_cache[path] = du_result
+            if not path in path_cache or path_cache[path]['disk_usage'] != du_result['disk_usage']:
+                # update the cache entry, even when no du result found,
+                # cause that will save disk queries next time.
+                logger.info('updating cache entry: %s', du_result)
+                path_cache[path] = du_result
 
-                path_cache[path]['cache_timestamp'] = datetime.datetime.utcnow()
-                path_cache[path]['needs_update'] = False
+            if otdb_id != None:
+                otdb_id2path_cache[otdb_id] = path
 
-                if otdb_id != None:
-                    otdb_id2path_cache[otdb_id] = path
-            else:
-                if path in path_cache:
-                    # no need to keep unknown path in cache
-                    del path_cache[path]
-                    if otdb_id != None and otdb_id in otdb_id2path_cache:
-                        del otdb_id2path_cache[otdb_id]
+            if not du_result['found']:
+                # even when the du for the path is not found,
+                # keep a copy in the cache for fast lookup by clients
+                # Make sure the size is 0
+                du_result['disk_usage'] = 0
+                du_result['disk_usage_readable'] = humanreadablesize(0)
+
+            path_cache[path]['cache_timestamp'] = datetime.datetime.utcnow()
+            path_cache[path]['needs_update'] = False
 
         self._writeCacheToDisk()