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Reviewed:  https://review.openstack.org/529352
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=d72b33b986525a9b2c7aa08b609ae386de1d0e89
Submitter: Zuul
Branch:    master

commit d72b33b986525a9b2c7aa08b609ae386de1d0e89
Author: Matthew Booth <mbooth@xxxxxxxxxx>
Date:   Sat Dec 16 20:27:08 2017 +0000

    Fix an error in _get_host_states when deleting a compute node
    
    _get_host_states returns a generator which closes over seen_nodes, which
    is local, and self.host_state_map, which is global. It also modifies
    self.host_state_map, and will remove entries whose compute nodes are no
    longer present.
    
    If a compute node is deleted while a filter is still evaluating the
    generator returned by _get_host_states, the entry in self.host_state_map
    will be deleted if _get_host_states is called again. This will cause a
    KeyError when the first generator comes to evaluate the entry for the
    deleted compute node.
    
    We fix this by modifying the returned generator expression to check
    that a host_state_map entry still exists before returning it. An
    existing unit test is modified to exhibit the bug.
    
    Change-Id: Ibb7c43a0abc433f93fc3de71146263e6d5923666
    Closes-Bug: #1739323


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

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https://bugs.launchpad.net/bugs/1739323

Title:
  KeyError in host_manager for _get_host_states

Status in OpenStack Compute (nova):
  Fix Released
Status in OpenStack Compute (nova) ocata series:
  In Progress
Status in OpenStack Compute (nova) pike series:
  In Progress

Bug description:
  https://github.com/openstack/nova/blob/master/nova/scheduler/host_manager.py#L674-L718

  In _get_host_states, a list of all computes nodes is retrieved with a
  `state_key` of `(host, node)`.

  https://github.com/openstack/nova/blob/master/nova/scheduler/host_manager.py#L692
  https://github.com/openstack/nova/blob/master/nova/scheduler/host_manager.py#L708

  The small piece of code here removes all of the dead compute nodes
  from host_state_map

  https://github.com/openstack/nova/blob/master/nova/scheduler/host_manager.py#L708

  However, the result is returned by iterating over all seen nodes and
  using that index for host_state_map, some of which have been deleted
  by the code above, resulting in a KeyError.

  https://github.com/openstack/nova/blob/master/nova/scheduler/host_manager.py#L718

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