Comment 8 for bug 1820612

As for why the PUT /allocations/71111e00-7913-4de9-8f45-ce13fcb8a104 request is failing with this:

{
   'allocations':[
      {
         'resource_provider':{
            'uuid':u'4ce95dcf-4c42-47cf-bd1e-48a0f4a5ecec'
         },
         'resources':{
            u'VCPU':4,
            u'MEMORY_MB':2048,
            u'DISK_GB':20
         }
      },
      {
         'resource_provider':{
            'uuid':u'57990d7c-7b10-40ee-916f-324bf7784eed'
         },
         'resources':{
            u'VCPU':4,
            u'MEMORY_MB':2048,
            u'DISK_GB':20
         }
      }
   ]
}

I'm not really sure. As you noted, the first resource provider 4ce95dcf-4c42-47cf-bd1e-48a0f4a5ecec is the source host, and the second resource provider 57990d7c-7b10-40ee-916f-324bf7784eed is the forced destination host for the live migration. Placement should be replacing the allocation against provider 4ce95dcf-4c42-47cf-bd1e-48a0f4a5ecec rather than adding to it, so maybe this is a bug in Placement. Can you trace the request to the placement API logs and see if there is anything obvious there?