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[OpenStack Infra <1783130@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.openstack.org/585033
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=d13e5a5011af75cfb6141a6b5d6aaf0f1a042aeb
Submitter: Zuul
Branch:    master

commit d13e5a5011af75cfb6141a6b5d6aaf0f1a042aeb
Author: Eric Fried <efried@xxxxxxxxxx>
Date:   Mon Jul 23 12:10:12 2018 -0500

    reshaper: Look up provider if not in inventories
    
    Per the referenced bug, we weren't accounting for the scenario where a
    reshape operation was removing *all* inventories for a provider (which
    could be fairly common). With this fix, we do a three-stage lookup of
    the provider object: If it's not in the inventories, we look in the
    allocations; if it's not in the allocations, we look it up in the
    database.
    
    Change-Id: I594bb64f87c61b7ffd39c19e0fd42c4c087a3a11
    Closes-Bug: #1783130


** Changed in: nova
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1783130

Title:
  placement reshaper doesn't clear all inventories for a resource
  provider

Status in OpenStack Compute (nova):
  Fix Released

Bug description:
  The /reshaper API is willing to accept an empty dictionary for the
  inventories attribute of a resource provider. This is intended to mean
  "clear all the inventory".

  However, the backend transformer code is not prepared to handle this:

        File "nova/api/openstack/placement/handlers/reshaper.py", line 103, in reshape
          rp_obj.reshape(context, inventory_by_rp, allocation_objects)
        File "/mnt/share/cdentsrc/nova/.tox/functional/local/lib/python2.7/site-packages/oslo_db/sqlalchemy/enginefacade.py", line 993, in wrapper
          return fn(*args, **kwargs)
        File "nova/api/openstack/placement/objects/resource_provider.py", line 4087, in reshape
          rp = new_inv_list[0].resource_provider
        File "/mnt/share/cdentsrc/nova/.tox/functional/local/lib/python2.7/site-packages/oslo_versionedobjects/base.py", line 829, in __getitem__
          return self.objects[index]
      IndexError: list index out of range

  This happening because 'new_inv_list' can be empty at

      for rp_uuid, new_inv_list in inventories.items():                                 
          LOG.debug("reshaping: *interim* inventory replacement for provider %s",       
                    rp_uuid)                                                            
          rp = new_inv_list[0].resource_provider      

  If the length of new_inv_list is zero we need to do nothing for this
  iteration though the loop.

  Then a few lines later at

      for rp_uuid, new_inv_list in inventories.items():                           
          LOG.debug("reshaping: *final* inventory replacement for provider %s",   
                    rp_uuid)                                                      
          # TODO(efried): If we wanted this to be more efficient, we could keep   
          # track of providers for which all inventories are being deleted in the 
          # above loop and just do those and skip the rest, since they're already 
          # in their final form.                                                  
          new_inv_list[0].resource_provider.set_inventory(new_inv_list)           

  We have the same IndexError problem and need to behave differently.

  A thing we might do is instead of using the resource_provider object
  on the (maybe not there) inventory objects, is create a new object: we
  have the rp_uuid.

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