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# Copyright (c) 2010-2012 OpenStack Foundation
#
# 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.
from swift import gettext_ as _
from swift.common.swob import Request, HTTPServerError
from swift.common.utils import get_logger, generate_trans_id, close_if_possible
from swift.common.wsgi import WSGIContext
class BadResponseLength(Exception):
pass
def enforce_byte_count(inner_iter, nbytes):
"""
Enforces that inner_iter yields exactly <nbytes> bytes before
exhaustion.
If inner_iter fails to do so, BadResponseLength is raised.
:param inner_iter: iterable of bytestrings
:param nbytes: number of bytes expected
"""
try:
bytes_left = nbytes
for chunk in inner_iter:
if bytes_left >= len(chunk):
yield chunk
bytes_left -= len(chunk)
else:
yield chunk[:bytes_left]
raise BadResponseLength(
"Too many bytes; truncating after %d bytes "
"with at least %d surplus bytes remaining" % (
nbytes, len(chunk) - bytes_left))
if bytes_left:
raise BadResponseLength('Expected another %d bytes' % (
bytes_left,))
finally:
close_if_possible(inner_iter)
class CatchErrorsContext(WSGIContext):
def __init__(self, app, logger, trans_id_suffix=''):
super(CatchErrorsContext, self).__init__(app)
self.logger = logger
self.trans_id_suffix = trans_id_suffix
def handle_request(self, env, start_response):
trans_id_suffix = self.trans_id_suffix
trans_id_extra = env.get('HTTP_X_TRANS_ID_EXTRA')
if trans_id_extra:
trans_id_suffix += '-' + trans_id_extra[:32]
trans_id = generate_trans_id(trans_id_suffix)
env['swift.trans_id'] = trans_id
self.logger.txn_id = trans_id
try:
# catch any errors in the pipeline
resp = self._app_call(env)
except: # noqa
self.logger.exception(_('Error: An error occurred'))
resp = HTTPServerError(request=Request(env),
body=b'An error occurred',
content_type='text/plain')
resp.headers['X-Trans-Id'] = trans_id
resp.headers['X-Openstack-Request-Id'] = trans_id
return resp(env, start_response)
# If the app specified a Content-Length, enforce that it sends that
# many bytes.
#
# If an app gives too few bytes, then the client will wait for the
# remainder before sending another HTTP request on the same socket;
# since no more bytes are coming, this will result in either an
# infinite wait or a timeout. In this case, we want to raise an
# exception to signal to the WSGI server that it should close the
# TCP connection.
#
# If an app gives too many bytes, then we can deadlock with the
# client; if the client reads its N bytes and then sends a large-ish
# request (enough to fill TCP buffers), it'll block until we read
# some of the request. However, we won't read the request since
# we'll be trying to shove the rest of our oversized response out
# the socket. In that case, we truncate the response body at N bytes
# and raise an exception to stop any more bytes from being
# generated and also to kill the TCP connection.
if env['REQUEST_METHOD'] == 'HEAD':
resp = enforce_byte_count(resp, 0)
elif self._response_headers:
content_lengths = [val for header, val in self._response_headers
if header.lower() == "content-length"]
if len(content_lengths) == 1:
try:
content_length = int(content_lengths[0])
except ValueError:
pass
else:
resp = enforce_byte_count(resp, content_length)
# make sure the response has the trans_id
if self._response_headers is None:
self._response_headers = []
self._response_headers.append(('X-Trans-Id', trans_id))
self._response_headers.append(('X-Openstack-Request-Id', trans_id))
start_response(self._response_status, self._response_headers,
self._response_exc_info)
return resp
class CatchErrorMiddleware(object):
"""
Middleware that provides high-level error handling and ensures that a
transaction id will be set for every request.
"""
def __init__(self, app, conf):
self.app = app
self.logger = get_logger(conf, log_route='catch-errors')
self.trans_id_suffix = conf.get('trans_id_suffix', '')
def __call__(self, env, start_response):
"""
If used, this should be the first middleware in pipeline.
"""
context = CatchErrorsContext(self.app,
self.logger,
self.trans_id_suffix)
return context.handle_request(env, start_response)
def filter_factory(global_conf, **local_conf):
conf = global_conf.copy()
conf.update(local_conf)
def except_filter(app):
return CatchErrorMiddleware(app, conf)
return except_filter
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