Fix snapshots garbage collection (#4188)

* Cleanup orphan entries from snapshot store ref for primary storage

* Add debug message

Author: nvazquez

engine/schema/src/main/java/org/apache/cloudstack/storage/datastore/db/SnapshotDataStoreDao.java

@@ -71,4 +71,6 @@ public interface SnapshotDataStoreDao extends GenericDao<SnapshotDataStoreVO, Lo
     List<SnapshotDataStoreVO> listAllByVolumeAndDataStore(long volumeId, DataStoreRole role);
 
     List<SnapshotDataStoreVO> listByState(ObjectInDataStoreStateMachine.State... states);
+
+    SnapshotDataStoreVO findDestroyedReferenceBySnapshot(long snapshotId, DataStoreRole role);
 }

engine/storage/src/main/java/org/apache/cloudstack/storage/image/db/SnapshotDataStoreDaoImpl.java

@@ -461,6 +461,15 @@ public List<SnapshotDataStoreVO> listByState(ObjectInDataStoreStateMachine.State
         return listBy(sc, null);
     }
 
+    @Override
+    public SnapshotDataStoreVO findDestroyedReferenceBySnapshot(long snapshotId, DataStoreRole role) {
+        SearchCriteria<SnapshotDataStoreVO> sc = snapshotSearch.create();
+        sc.setParameters("snapshot_id", snapshotId);
+        sc.setParameters("store_role", role);
+        sc.setParameters("state", State.Destroyed);
+        return findOneBy(sc);
+    }
+
     private boolean isSnapshotChainingRequired(long volumeId) {
 
         hypervisorsSupportingSnapshotsChaining.add(Hypervisor.HypervisorType.XenServer);

server/src/main/java/com/cloud/storage/StorageManagerImpl.java

@@ -1393,8 +1393,11 @@ public void cleanupSecondaryStorage(boolean recurring) {
                         }
 
                         _snapshotDao.remove(destroyedSnapshotStoreVO.getSnapshotId());
-                        SnapshotDataStoreVO snapshotOnPrimary = _snapshotStoreDao.findBySnapshot(destroyedSnapshotStoreVO.getSnapshotId(), DataStoreRole.Primary);
+                        SnapshotDataStoreVO snapshotOnPrimary = _snapshotStoreDao.findDestroyedReferenceBySnapshot(destroyedSnapshotStoreVO.getSnapshotId(), DataStoreRole.Primary);
                         if (snapshotOnPrimary != null) {
+                            if (s_logger.isDebugEnabled()) {
+                                s_logger.debug("Deleting snapshot on primary store reference DB entry: " + snapshotOnPrimary);
+                            }
                             _snapshotStoreDao.remove(snapshotOnPrimary.getId());
                         }
                         _snapshotStoreDao.remove(destroyedSnapshotStoreVO.getId());