An http error 500 is reported in the RHEV Admin Portal when trying to commit or undo a snapshot preview.

Issue

• Recovering Virtual Machine from preview results in error 500 in RHEV Manager.

• Having created a snapshot preview for a Virtual Machine, clicking on Commit or Undo results in an http error 500.

• The engine logs contain some null pointer exceptions;

2015-04-17 08:40:44,297 INFO  [org.ovirt.engine.core.bll.TryBackToAllSnapshotsOfVmCommand] (ajp-/127.0.0.1:8702-1) [8c12cbc] Running command: TryBackToAllSnapshotsOfVmCommand internal: false. Entities affected :  ID: d7472993-0db5-4268-8
3f3-4058be0707c7 Type: VM
2015-04-17 08:40:44,419 INFO  [org.ovirt.engine.core.bll.MacPoolManager] (ajp-/127.0.0.1:8702-1) [8c12cbc] MacPoolManager::freeMac(mac = 00:1a:4a:84:49:15) - entered
2015-04-17 08:40:44,465 ERROR [org.ovirt.engine.core.bll.TryBackToAllSnapshotsOfVmCommand] (ajp-/127.0.0.1:8702-1) [8c12cbc] Command org.ovirt.engine.core.bll.TryBackToAllSnapshotsOfVmCommand throw exception: java.lang.NullPointerException
        at org.ovirt.engine.core.utils.ovf.OvfWriter.BuildDisk(OvfWriter.java:163) [engine-utils.jar:]
        at org.ovirt.engine.core.utils.ovf.OvfManager.BuildOvf(OvfManager.java:93) [engine-utils.jar:]


2015-04-17 10:52:47,821 INFO  [org.ovirt.engine.core.bll.RestoreAllSnapshotsCommand] (ajp-/127.0.0.1:8702-4) [2152b586] Running command: RestoreAllSnapshotsCommand internal: false. Entities affected :  ID: d7472993-0db5-4268-83f3-4058be0707c7 Type: VM
2015-04-17 10:52:47,860 INFO  [org.ovirt.engine.core.bll.RestoreFromSnapshotCommand] (ajp-/127.0.0.1:8702-4) [59f22c3] Running command: RestoreFromSnapshotCommand internal: true. Entities affected :  ID: 00000000-0000-0000-0000-000000000000 Type: Storage
2015-04-17 10:52:47,862 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.GetImageInfoVDSCommand] (ajp-/127.0.0.1:8702-4) [59f22c3] START, GetImageInfoVDSCommand( storagePoolId = 5e7618f0-91a2-11e2-a02a-0022191f8985, ignoreFailoverLimit = false, compatabilityVersion = null, storageDomainId = ebb924d3-2a61-4134-9a78-28cd3efabb0e, imageGroupId = c421b912-53e7-4614-bb46-e620888cd68f, imageId = 975fa668-080d-4040-bd0c-32fe83869474), log id: 23bea30f
2015-04-17 10:52:48,211 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.GetImageInfoVDSCommand] (ajp-/127.0.0.1:8702-4) [59f22c3] FINISH, GetImageInfoVDSCommand, return: org.ovirt.engine.core.common.businessentities.DiskImage@1a51dae9, log id: 23bea30f
2015-04-17 10:52:48,214 ERROR [org.ovirt.engine.core.bll.RestoreFromSnapshotCommand] (ajp-/127.0.0.1:8702-4) [59f22c3] Command org.ovirt.engine.core.bll.RestoreFromSnapshotCommand throw exception: java.lang.NullPointerException
        at org.ovirt.engine.core.bll.RestoreFromSnapshotCommand.RemoveOtherImageAndParents(RestoreFromSnapshotCommand.java:78) [engine-bll.jar:]
        at org.ovirt.engine.core.bll.RestoreFromSnapshotCommand.RemoveImages(RestoreFromSnapshotCommand.java:49) [engine-bll.jar:]


2015-04-17 10:56:16,578 INFO  [org.ovirt.engine.core.bll.RestoreAllSnapshotsCommand] (ajp-/127.0.0.1:8702-5) [504cf27e] Running command: RestoreAllSnapshotsCommand internal: false. Entities affected :  ID: d7472993-0db5-4268-83f3-4058be0
707c7 Type: VM
2015-04-17 10:56:16,589 INFO  [org.ovirt.engine.core.bll.RestoreFromSnapshotCommand] (ajp-/127.0.0.1:8702-5) [d3540b7] Running command: RestoreFromSnapshotCommand internal: true. Entities affected :  ID: 00000000-0000-0000-0000-000000000
000 Type: Storage
2015-04-17 10:56:16,590 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.GetImageInfoVDSCommand] (ajp-/127.0.0.1:8702-5) [d3540b7] START, GetImageInfoVDSCommand( storagePoolId = 5e7618f0-91a2-11e2-a02a-0022191f8985, ignoreFailoverLimit =
 false, compatabilityVersion = null, storageDomainId = ebb924d3-2a61-4134-9a78-28cd3efabb0e, imageGroupId = c421b912-53e7-4614-bb46-e620888cd68f, imageId = 975fa668-080d-4040-bd0c-32fe83869474), log id: 4b20f646
2015-04-17 10:56:16,969 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.GetImageInfoVDSCommand] (ajp-/127.0.0.1:8702-5) [d3540b7] FINISH, GetImageInfoVDSCommand, return: org.ovirt.engine.core.common.businessentities.DiskImage@1a51dae9, log id: 4b20f646
2015-04-17 10:56:16,971 ERROR [org.ovirt.engine.core.bll.RestoreFromSnapshotCommand] (ajp-/127.0.0.1:8702-5) [d3540b7] Command org.ovirt.engine.core.bll.RestoreFromSnapshotCommand throw exception: java.lang.NullPointerException
        at org.ovirt.engine.core.bll.RestoreFromSnapshotCommand.RemoveOtherImageAndParents(RestoreFromSnapshotCommand.java:78) [engine-bll.jar:]
        at org.ovirt.engine.core.bll.RestoreFromSnapshotCommand.RemoveImages(RestoreFromSnapshotCommand.java:49) [engine-bll.jar:]