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[Mike Dorman <mdorman@xxxxxxxxxxx>]

Public bug reported:

There is an implementation difference between Ceph Swift and OS Swift in
how the ETag/checksum of a dynamic large object (DLO) manifest object is
verified.

OS Swift verifies it just like any other object, md5’ing the content of the object:
https://github.com/openstack/swift/blob/master/swift/obj/server.py#L439-L459

Ceph Swift actually does the full DLO checksum across all the component objects:
https://github.com/ceph/ceph/blob/master/src/rgw/rgw_op.cc#L1765-L1781

The Glance Swift store driver assumes the OS Swift behavior, and sends an ETag of md5("") with the PUT request for the manifest object.  Technically, this is correct, since that object itself is a zero-byte object:
https://github.com/openstack/glance_store/blob/master/glance_store/_drivers/swift/store.py#L552

However, when using a Ceph Swift store, this results in a 422
Unprocessable Entity response from Swift, because the provided ETag
doesn't match the expected ETag for the DLO.

It would seem to make sense to just not send any ETag with the manifest
object PUT request.  It is not required by the API, and only marginally
improves the validation of the object.

** Affects: glance
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1387311

Title:
  Unprocessable Entity error for large images on Ceph Swift store

Status in OpenStack Image Registry and Delivery Service (Glance):
  New

Bug description:
  There is an implementation difference between Ceph Swift and OS Swift
  in how the ETag/checksum of a dynamic large object (DLO) manifest
  object is verified.

  OS Swift verifies it just like any other object, md5’ing the content of the object:
  https://github.com/openstack/swift/blob/master/swift/obj/server.py#L439-L459

  Ceph Swift actually does the full DLO checksum across all the component objects:
  https://github.com/ceph/ceph/blob/master/src/rgw/rgw_op.cc#L1765-L1781

  The Glance Swift store driver assumes the OS Swift behavior, and sends an ETag of md5("") with the PUT request for the manifest object.  Technically, this is correct, since that object itself is a zero-byte object:
  https://github.com/openstack/glance_store/blob/master/glance_store/_drivers/swift/store.py#L552

  However, when using a Ceph Swift store, this results in a 422
  Unprocessable Entity response from Swift, because the provided ETag
  doesn't match the expected ETag for the DLO.

  It would seem to make sense to just not send any ETag with the
  manifest object PUT request.  It is not required by the API, and only
  marginally improves the validation of the object.

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