[Bug 1083155] [NEW] Unable to set Content-MD5 header when using chunked transfer encoding

[James Page]

Public bug reported:

I came across this when debugging test failures of Openstack Glance with
Webob 1.1.1 as found in 12.04+

Taking the following code from glance:

    def download(self, response, result):
        size = result['meta']['size']
        checksum = result['meta']['checksum']
        response.headers['Content-Length'] = size
        response.headers['Content-Type'] = 'application/octet-stream'
        if checksum:
            response.headers['Content-MD5'] = checksum
        response.app_iter = common.size_checked_iter(
                response, result['meta'], size, result['data'], self.notifier)

This should create a response with appropriate headers (including a MD5
checksum) and then use the iterator to return the content (potentially a
large image) to the calling client; however when:

 response.app_iter = ...

occurs the MD5 that was set in the preceeding line is set back to 'None'
in the response object; result is a chunked transfer encoded response
without a checksum (which should be supported).  I traced this back to
webob/response.py:

    def _app_iter__set(self, value):
        if self._app_iter is not None:
            # Undo the automatically-set content-length
            self.content_length = None
            self.content_md5 = None
        self._app_iter = value

During construction of the object, neither the app_iter or body is
specified and as a result the body is set to '' (and the app_iter to [
'' ]).  So even though no data has ever been provided, the md5 sum is
dropped as soon as the iterator is provided.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: python-webob 1.1.1-1ubuntu1
ProcVersionSignature: Ubuntu 3.5.0-18.29-generic 3.5.7
Uname: Linux 3.5.0-18-generic x86_64
ApportVersion: 2.6.1-0ubuntu6
Architecture: amd64
Date: Mon Nov 26 13:12:45 2012
MarkForUpload: True
PackageArchitecture: all
SourcePackage: python-webob
UpgradeStatus: Upgraded to quantal on 2012-06-11 (168 days ago)

** Affects: python-webob (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug quantal running-unity

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Title:
  Unable to set Content-MD5 header when using chunked transfer encoding

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