diff --git a/common/check_unevaluated_dids b/common/check_unevaluated_dids
index d342885..0c5517a 100755
--- a/common/check_unevaluated_dids
+++ b/common/check_unevaluated_dids
@@ -1,58 +1,60 @@
-#!/usr/bin/env python
-# Copyright European Organization for Nuclear Research (CERN) 2013
+#!/usr/bin/env python3
+# Copyright European Organization for Nuclear Research (CERN) since 2012
 #
 # 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
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# Authors:
-# - Vincent Garonne, <vincent.garonne@cern.ch>, 2013
-# - Thomas Beermann, <thomas.beermann@cern.ch>, 2019
+#    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.
 
 """
 Probe to check the backlog of dids waiting for rule evaluation.
 """
-from __future__ import print_function
 
 import sys
 
 from prometheus_client import CollectorRegistry, Gauge, push_to_gateway
-from rucio.common.config import config_get
-from rucio.db.sqla.session import BASE, get_session
+from sqlalchemy import func, select
+
+from rucio.common.config import config_get_list
+from rucio.db.sqla import models
+from rucio.db.sqla.session import get_session
 
 from utils.common import probe_metrics
 
 # Exit statuses
 OK, WARNING, CRITICAL, UNKNOWN = 0, 1, 2, 3
 
-if BASE.metadata.schema:
-    schema = BASE.metadata.schema + '.'
-else:
-    schema = ''
-
-count_sql = 'SELECT COUNT(*) FROM {schema}updated_dids'.format(schema=schema)
+count_sql = select(
+    func.count()
+).select_from(
+    models.UpdatedDID
+)
 
-PROM_SERVERS = config_get('monitor', 'prometheus_servers', raise_exception=False, default='')
-if PROM_SERVERS != '':
-    PROM_SERVERS = PROM_SERVERS.split(',')
+PROM_SERVERS = config_get_list('monitor', 'prometheus_servers', raise_exception=False, default=[])
 
-if __name__ == "__main__":
+if __name__ == '__main__':
     try:
         session = get_session()
-        result = session.execute(count_sql).fetchone()[0]
+        result = session.execute(count_sql).scalar_one()
         probe_metrics.gauge(name='judge.waiting_dids').set(result)
 
         registry = CollectorRegistry()
         Gauge('judge_waiting_dids', '', registry=registry).set(result)
 
-        if len(PROM_SERVERS):
-            for server in PROM_SERVERS:
-                try:
-                    push_to_gateway(server.strip(), job='check_unevaluated_dids', registry=registry)
-                except:
-                    continue
+        for server in PROM_SERVERS:
+            try:
+                push_to_gateway(server, job='check_unevaluated_dids', registry=registry)
+            except Exception:
+                continue
 
         print(result)
-    except:
+    except Exception:
         sys.exit(UNKNOWN)
     sys.exit(OK)