OpenStack Study: gzip.py

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# Copyright 2013 Red Hat, Inc.

# All Rights Reserved.

#

# Licensed under the Apache License, Version 2.0 (the "License"); you may

# not use this file except in compliance with the License. You may obtain

# a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the

# License for the specific language governing permissions and limitations

# under the License.

"""

Use gzip compression if the client accepts it.

"""

import re

from glance.common import wsgi

import glance.openstack.common.log as logging

LOG = logging.getLogger(__name__)

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class GzipMiddleware(wsgi.Middleware):

re_zip = re.compile(r'\bgzip\b')

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    def __init__(self, app):

        LOG.info(_("Initialized gzip middleware"))

        super(GzipMiddleware, self).__init__(app)

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    def process_response(self, response):

        request = response.request

        accept_encoding = request.headers.get('Accept-Encoding', '')

        if self.re_zip.search(accept_encoding):

            # NOTE(flaper87): Webob removes the content-md5 when

            # app_iter is called. We'll keep it and reset it later

            checksum = response.headers.get("Content-MD5")

            # NOTE(flaper87): We'll use lazy for images so

            # that they can be compressed without reading

            # the whole content in memory. Notice that using

            # lazy will set response's content-length to 0.

            content_type = response.headers["Content-Type"]

            lazy = content_type == "application/octet-stream"

            # NOTE(flaper87): Webob takes care of the compression

            # process, it will replace the body either with a

            # compressed body or a generator - used for lazy com

            # pression - depending on the lazy value.

            #

            # Webob itself will set the Content-Encoding header.

            response.encode_content(lazy=lazy)

            if checksum:

                response.headers['Content-MD5'] = checksum

        return response