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[Bug 1160900] Re: Caching metadata fails when using memcached

 

** Changed in: nova
       Status: Fix Committed => Fix Released

** Changed in: nova
    Milestone: None => havana-1

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https://bugs.launchpad.net/bugs/1160900

Title:
  Caching metadata fails when using memcached

Status in OpenStack Compute (Nova):
  Fix Released
Status in OpenStack Compute (nova) grizzly series:
  Fix Released

Bug description:
  Value stored into the memorycache contains the 'nova.db' module
  itself. This is not an issue for the local implementation, but
  memcached needs a serialised version of the values.

  Trying to save the metadata value results in:

  2013-03-27 11:11:45.611 28474 ERROR nova.api.metadata.handler [-] Failed to get metadata for instance id: 7f655b96-7c99-44e2-9c83-1a62e6ddb3da
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler Traceback (most recent call last):
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler   File "/usr/lib/python2.7/dist-packages/nova/api/metadata/handler.py", line 179, in _handle_instance_id_request
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler     remote_address)
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler   File "/usr/lib/python2.7/dist-packages/nova/api/metadata/handler.py", line 94, in get_metadata_by_instance_id
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler     self._cache.set(cache_key, data, CACHE_EXPIRATION)
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler   File "/usr/lib/python2.7/dist-packages/memcache.py", line 565, in set
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler     return self._set("set", key, val, time, min_compress_len)
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler   File "/usr/lib/python2.7/dist-packages/memcache.py", line 802, in _set
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler     return _unsafe_set()
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler   File "/usr/lib/python2.7/dist-packages/memcache.py", line 780, in _unsafe_set
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler     store_info = self._val_to_store_info(val, min_compress_len)
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler   File "/usr/lib/python2.7/dist-packages/memcache.py", line 751, in _val_to_store_info
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler     pickler.dump(val)
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler   File "/usr/lib/python2.7/copy_reg.py", line 70, in _reduce_ex
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler     raise TypeError, "can't pickle %s objects" % base.__name__
  2013-03-27 11:11:45.611 28474 TRACE nova.api.metadata.handler TypeError: can't pickle module objects

  The metadata request then fails completely. Complete faliure is
  addressed by bug 1160883, but the structure of metadata cache needs to
  be fixed too.

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