Updated pr to address @GutoVeronezi change requests.

Author: Sina Kashipazha

engine/schema/src/main/java/com/cloud/capacity/dao/CapacityDaoImpl.java

@@ -27,6 +27,7 @@
 import javax.inject.Inject;
 
 import org.apache.log4j.Logger;
+import org.apache.commons.lang3.StringUtils;
 import org.springframework.stereotype.Component;
 
 import org.apache.cloudstack.storage.datastore.db.PrimaryDataStoreDao;
@@ -433,14 +434,14 @@ public Ternary<Long, Long, Long> findCapacityByZoneAndHostTag(Long zoneId, Strin
         PreparedStatement pstmt;
 
         StringBuilder allocatedSql = new StringBuilder(LIST_ALLOCATED_CAPACITY_GROUP_BY_CAPACITY_AND_ZONE);
-        if (hostTag != null && ! hostTag.isEmpty()) {
+        if (StringUtils.isNotEmpty(hostTag)) {
             allocatedSql.append(LEFT_JOIN_VM_TEMPLATE);
         }
         allocatedSql.append(WHERE_STATE_IS_NOT_DESTRUCTIVE);
         if (zoneId != null) {
             allocatedSql.append(" AND vi.data_center_id = ?");
         }
-        if (hostTag != null && ! hostTag.isEmpty()) {
+        if (StringUtils.isNotEmpty(hostTag)) {
             allocatedSql.append(" AND (vm_template.template_tag = '").append(hostTag).append("'");
             allocatedSql.append(" OR service_offering.host_tag = '").append(hostTag).append("')");
         }

engine/schema/src/main/java/com/cloud/vm/dao/UserVmDaoImpl.java

@@ -749,7 +749,7 @@ public List<Ternary<Integer, Integer, Integer>> countVmsBySize(long dcId, int li
                 result.add(new Ternary<Integer, Integer, Integer>(rs.getInt(1), rs.getInt(2), rs.getInt(3)));
             }
         } catch (Exception e) {
-            s_logger.warn("Error counting vms by size", e);
+            s_logger.warn("Error counting vms by size for dcId= " + dcId, e);
         }
         return result;
     }

engine/schema/src/main/java/com/cloud/vm/dao/VMInstanceDaoImpl.java

@@ -823,7 +823,7 @@ public Long countByZoneAndStateAndHostTag(long dcId, State state, String hostTag
                 return rs.getLong(1);
             }
         } catch (Exception e) {
-            s_logger.warn("Error counting vms by host tag", e);
+            s_logger.warn(String.format("Error counting vms by host tag for dcId= %s, hostTag= %s", dcId, hostTag), e);
         }
         return 0L;
     }