Description of problem:
During a VG metadata locking intensive test, I saw this failure momentarily while attempting to get the sync percent of an active mirror. This is a test that has passed on other clusters, so this is probably a difficult to recreate timing issue. 


Nov  2 05:41:42 mckinley-02 qarshd[63209]: Running cmdline: lvs lock_stress/mckinley-02.28583 --noheadings -o copy_percent | awk {'print $1'}
Nov  2 05:41:42 mckinley-02 lvmetad[4892]: vg_lookup vgid btouMp-IJi0-TLFq-x0EO-G2qH-21dy-jpCZC3 name lock_stress found incomplete mapping uuid none name none

This cmd when run again later was fine:
[root@mckinley-02 ~]# lvs lock_stress/mckinley-02.28583 --noheadings -o copy_percent 
  100.00  

This test does lots of creates/conversions/etc to exclusively active volumes from different machines all located on the same VG. Here's what was done on this machine prior to this lvs cmd failing:

Creating a 5 redundant legged cmirror named mckinley-02.28583
  Logical volume "mckinley-02.28583" created.

Down converting cmirror from 5 legs to 1 on mckinley-02
  Retrying ex lock on VG lock_stress
  Logical volume lock_stress/mckinley-02.28583 converted.
Now... down converting cmirror from  legs to linear on mckinley-02
  Logical volume lock_stress/mckinley-02.28583 converted.

Up converting linear to a 2 redundant legged cmirror on mckinley-02
  Logical volume lock_stress/mckinley-02.28583 being converted.
  lock_stress/mckinley-02.28583: Converted: 0.00%
  lock_stress/mckinley-02.28583: Converted: 100.00%

Nov  2 05:41:42 mckinley-02 qarshd[63209]: Running cmdline: lvs lock_stress/mckinley-02.28583 --noheadings -o copy_percent | awk {'print $1'}
Nov  2 05:41:42 mckinley-02 lvmetad[4892]: vg_lookup vgid btouMp-IJi0-TLFq-x0EO-G2qH-21dy-jpCZC3 name lock_stress found incomplete mapping uuid none name none

  Volume group "lock_stress" not found
  Cannot process volume group lock_stress





Version-Release number of selected component (if applicable):
3.10.0-957.el7.x86_64

lvm2-2.02.180-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
lvm2-libs-2.02.180-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
lvm2-cluster-2.02.180-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
lvm2-lockd-2.02.180-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
cmirror-2.02.180-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
device-mapper-1.02.149-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
device-mapper-libs-1.02.149-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
device-mapper-event-1.02.149-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018
device-mapper-event-libs-1.02.149-10.el7_6.2    BUILT: Wed Oct 31 03:55:58 CDT 2018


How reproducible:
Just once so far