path: root/swift/common/middleware/slo.py

# Copyright (c) 2013 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.

"""
Middleware that will provide Static Large Object (SLO) support.

This feature is very similar to Dynamic Large Object (DLO) support in that
it allows the user to upload many objects concurrently and afterwards
download them as a single object. It is different in that it does not rely
on eventually consistent container listings to do so. Instead, a user
defined manifest of the object segments is used.

----------------------
Uploading the Manifest
----------------------

After the user has uploaded the objects to be concatenated, a manifest is
uploaded. The request must be a PUT with the query parameter::

    ?multipart-manifest=put

The body of this request will be an ordered list of segment descriptions in
JSON format. The data to be supplied for each segment is:

=========== ========================================================
Key         Description
=========== ========================================================
path        the path to the segment object (not including account)
            /container/object_name
etag        (optional) the ETag given back when the segment object
            was PUT
size_bytes  (optional) the size of the complete segment object in
            bytes
range       (optional) the (inclusive) range within the object to
            use as a segment. If omitted, the entire object is used.
=========== ========================================================

The format of the list will be:

  .. code::

    [{"path": "/cont/object",
      "etag": "etagoftheobjectsegment",
      "size_bytes": 10485760,
      "range": "1048576-2097151"}, ...]

The number of object segments is limited to a configurable amount, default
1000. Each segment must be at least 1 byte. On upload, the middleware will
head every segment passed in to verify:

 1. the segment exists (i.e. the HEAD was successful);
 2. the segment meets minimum size requirements;
 3. if the user provided a non-null etag, the etag matches;
 4. if the user provided a non-null size_bytes, the size_bytes matches; and
 5. if the user provided a range, it is a singular, syntactically correct range
    that is satisfiable given the size of the object.

Note that the etag and size_bytes keys are optional; if omitted, the
verification is not performed. If any of the objects fail to verify (not
found, size/etag mismatch, below minimum size, invalid range) then the user
will receive a 4xx error response. If everything does match, the user will
receive a 2xx response and the SLO object is ready for downloading.

Behind the scenes, on success, a json manifest generated from the user input is
sent to object servers with an extra "X-Static-Large-Object: True" header
and a modified Content-Type. The items in this manifest will include the etag
and size_bytes for each segment, regardless of whether the client specified
them for verification. The parameter: swift_bytes=$total_size will be
appended to the existing Content-Type, where total_size is the sum of all
the included segments' size_bytes. This extra parameter will be hidden from
the user.

Manifest files can reference objects in separate containers, which will improve
concurrent upload speed. Objects can be referenced by multiple manifests. The
segments of a SLO manifest can even be other SLO manifests. Treat them as any
other object i.e., use the Etag and Content-Length given on the PUT of the
sub-SLO in the manifest to the parent SLO.

While uploading a manifest, a user can send Etag for verification. It needs to
be md5 of the segments' etags, if there is no range specified. For example, if
the manifest to be uploaded looks like this:

  .. code::

    [{"path": "/cont/object1",
      "etag": "etagoftheobjectsegment1",
      "size_bytes": 10485760},
     {"path": "/cont/object2",
      "etag": "etagoftheobjectsegment2",
      "size_bytes": 10485760}]

The Etag of the above manifest would be md5 of etagoftheobjectsegment1 and
etagoftheobjectsegment2. This could be computed in the following way:

  .. code::

    echo -n 'etagoftheobjectsegment1etagoftheobjectsegment2' | md5sum

If a manifest to be uploaded with a segment range looks like this:

  .. code::

    [{"path": "/cont/object1",
      "etag": "etagoftheobjectsegmentone",
      "size_bytes": 10485760,
      "range": "1-2"},
     {"path": "/cont/object2",
      "etag": "etagoftheobjectsegmenttwo",
      "size_bytes": 10485760,
      "range": "3-4"}]

While computing the Etag of the above manifest, internally each segment's etag
will be taken in the form of 'etagvalue:rangevalue;'. Hence the Etag of the
above manifest would be:

  .. code::

    echo -n 'etagoftheobjectsegmentone:1-2;etagoftheobjectsegmenttwo:3-4;' \
    | md5sum


-------------------
Range Specification
-------------------

Users now have the ability to specify ranges for SLO segments.
Users can now include an optional 'range' field in segment descriptions
to specify which bytes from the underlying object should be used for the
segment data. Only one range may be specified per segment.

  .. note::

     The 'etag' and 'size_bytes' fields still describe the backing object as a
     whole.

If a user uploads this manifest:

  .. code::

     [{"path": "/con/obj_seg_1", "size_bytes": 2097152, "range": "0-1048576"},
      {"path": "/con/obj_seg_2", "size_bytes": 2097152,
       "range": "512-1550000"},
      {"path": "/con/obj_seg_1", "size_bytes": 2097152, "range": "-2048"}]

The segment will consist of the first 1048576 bytes of /con/obj_seg_1,
followed by bytes 513 through 1550000 (inclusive) of /con/obj_seg_2, and
finally bytes 2095104 through 2097152 (i.e., the last 2048 bytes) of
/con/obj_seg_1.

  .. note::


     The minimum sized range is 1 byte. This is the same as the minimum
     segment size.


-------------------------
Retrieving a Large Object
-------------------------

A GET request to the manifest object will return the concatenation of the
objects from the manifest much like DLO. If any of the segments from the
manifest are not found or their Etag/Content Length have changed since upload,
the connection will drop. In this case a 409 Conflict will be logged in the
proxy logs and the user will receive incomplete results. Note that this will be
enforced regardless of whether the user performed per-segment validation during
upload.

The headers from this GET or HEAD request will return the metadata attached
to the manifest object itself with some exceptions::

    Content-Length: the total size of the SLO (the sum of the sizes of
                    the segments in the manifest)
    X-Static-Large-Object: True
    Etag: the etag of the SLO (generated the same way as DLO)

A GET request with the query parameter::

    ?multipart-manifest=get

will return a transformed version of the original manifest, containing
additional fields and different key names. For example, the first manifest in
the example above would look like this:

  .. code::

    [{"name": "/cont/object",
      "hash": "etagoftheobjectsegment",
      "bytes": 10485760,
      "range": "1048576-2097151"}, ...]

As you can see, some of the fields are renamed compared to the put request:
*path* is *name*, *etag* is *hash*, *size_bytes* is *bytes*.  The *range* field
remains the same (if present).

A GET request with the query parameters::

    ?multipart-manifest=get&format=raw

will return the contents of the original manifest as it was sent by the client.
The main purpose for both calls is solely debugging.

When the manifest object is uploaded you are more or less guaranteed that
every segment in the manifest exists and matched the specifications.
However, there is nothing that prevents the user from breaking the
SLO download by deleting/replacing a segment referenced in the manifest. It is
left to the user to use caution in handling the segments.

-----------------------
Deleting a Large Object
-----------------------

A DELETE request will just delete the manifest object itself.

A DELETE with a query parameter::

    ?multipart-manifest=delete

will delete all the segments referenced in the manifest and then the manifest
itself. The failure response will be similar to the bulk delete middleware.

------------------------
Modifying a Large Object
------------------------

PUTs / POSTs will work as expected, PUTs will just overwrite the manifest
object for example.

------------------
Container Listings
------------------

In a container listing the size listed for SLO manifest objects will be the
total_size of the concatenated segments in the manifest. The overall
X-Container-Bytes-Used for the container (and subsequently for the account)
will not reflect total_size of the manifest but the actual size of the json
data stored. The reason for this somewhat confusing discrepancy is we want the
container listing to reflect the size of the manifest object when it is
downloaded. We do not, however, want to count the bytes-used twice (for both
the manifest and the segments it's referring to) in the container and account
metadata which can be used for stats purposes.
"""

from collections import defaultdict
from datetime import datetime
import json
import mimetypes
import re
import six
from hashlib import md5
from swift.common.exceptions import ListingIterError, SegmentError
from swift.common.swob import Request, HTTPBadRequest, HTTPServerError, \
    HTTPMethodNotAllowed, HTTPRequestEntityTooLarge, HTTPLengthRequired, \
    HTTPOk, HTTPPreconditionFailed, HTTPException, HTTPNotFound, \
    HTTPUnauthorized, HTTPConflict, HTTPUnprocessableEntity, Response, Range
from swift.common.utils import get_logger, config_true_value, \
    get_valid_utf8_str, override_bytes_from_content_type, split_path, \
    register_swift_info, RateLimitedIterator, quote, close_if_possible, \
    closing_if_possible, LRUCache, StreamingPile
from swift.common.request_helpers import SegmentedIterable, \
    get_sys_meta_prefix, update_etag_is_at_header
from swift.common.constraints import check_utf8, MAX_BUFFERED_SLO_SEGMENTS
from swift.common.http import HTTP_NOT_FOUND, HTTP_UNAUTHORIZED, is_success
from swift.common.wsgi import WSGIContext, make_subrequest
from swift.common.middleware.bulk import get_response_body, \
    ACCEPTABLE_FORMATS, Bulk


DEFAULT_RATE_LIMIT_UNDER_SIZE = 1024 * 1024  # 1 MiB
DEFAULT_MAX_MANIFEST_SEGMENTS = 1000
DEFAULT_MAX_MANIFEST_SIZE = 1024 * 1024 * 2  # 2 MiB


REQUIRED_SLO_KEYS = set(['path'])
OPTIONAL_SLO_KEYS = set(['range', 'etag', 'size_bytes'])
ALLOWED_SLO_KEYS = REQUIRED_SLO_KEYS | OPTIONAL_SLO_KEYS

SYSMETA_SLO_ETAG = get_sys_meta_prefix('object') + 'slo-etag'
SYSMETA_SLO_SIZE = get_sys_meta_prefix('object') + 'slo-size'


def parse_and_validate_input(req_body, req_path):
    """
    Given a request body, parses it and returns a list of dictionaries.

    The output structure is nearly the same as the input structure, but it
    is not an exact copy. Given a valid input dictionary `d_in`, its
    corresponding output dictionary `d_out` will be as follows:

      * d_out['etag'] == d_in['etag']

      * d_out['path'] == d_in['path']

      * d_in['size_bytes'] can be a string ("12") or an integer (12), but
        d_out['size_bytes'] is an integer.

      * (optional) d_in['range'] is a string of the form "M-N", "M-", or
        "-N", where M and N are non-negative integers. d_out['range'] is the
        corresponding swob.Range object. If d_in does not have a key
        'range', neither will d_out.

    :raises HTTPException: on parse errors or semantic errors (e.g. bogus
        JSON structure, syntactically invalid ranges)

    :returns: a list of dictionaries on success
    """
    try:
        parsed_data = json.loads(req_body)
    except ValueError:
        raise HTTPBadRequest("Manifest must be valid JSON.\n")

    if not isinstance(parsed_data, list):
        raise HTTPBadRequest("Manifest must be a list.\n")

    # If we got here, req_path refers to an object, so this won't ever raise
    # ValueError.
    vrs, account, _junk = split_path(req_path, 3, 3, True)

    errors = []
    for seg_index, seg_dict in enumerate(parsed_data):
        if not isinstance(seg_dict, dict):
            errors.append("Index %d: not a JSON object" % seg_index)
            continue

        missing_keys = [k for k in REQUIRED_SLO_KEYS if k not in seg_dict]
        if missing_keys:
            errors.append(
                "Index %d: missing keys %s"
                % (seg_index,
                   ", ".join('"%s"' % (mk,) for mk in sorted(missing_keys))))
            continue

        extraneous_keys = [k for k in seg_dict if k not in ALLOWED_SLO_KEYS]
        if extraneous_keys:
            errors.append(
                "Index %d: extraneous keys %s"
                % (seg_index,
                   ", ".join('"%s"' % (ek,)
                             for ek in sorted(extraneous_keys))))
            continue

        if not isinstance(seg_dict['path'], six.string_types):
            errors.append("Index %d: \"path\" must be a string" % seg_index)
            continue
        if not (seg_dict.get('etag') is None or
                isinstance(seg_dict['etag'], six.string_types)):
            errors.append('Index %d: "etag" must be a string or null '
                          '(if provided)' % seg_index)
            continue

        if '/' not in seg_dict['path'].strip('/'):
            errors.append(
                "Index %d: path does not refer to an object. Path must be of "
                "the form /container/object." % seg_index)
            continue

        seg_size = seg_dict.get('size_bytes')
        if seg_size is not None:
            try:
                seg_size = int(seg_size)
                seg_dict['size_bytes'] = seg_size
            except (TypeError, ValueError):
                errors.append("Index %d: invalid size_bytes" % seg_index)
                continue
            if seg_size < 1:
                errors.append("Index %d: too small; each segment must be "
                              "at least 1 byte."
                              % (seg_index,))
                continue

        obj_path = '/'.join(['', vrs, account, seg_dict['path'].lstrip('/')])
        if req_path == quote(obj_path):
            errors.append(
                "Index %d: manifest must not include itself as a segment"
                % seg_index)
            continue

        if seg_dict.get('range'):
            try:
                seg_dict['range'] = Range('bytes=%s' % seg_dict['range'])
            except ValueError:
                errors.append("Index %d: invalid range" % seg_index)
                continue

            if len(seg_dict['range'].ranges) > 1:
                errors.append("Index %d: multiple ranges (only one allowed)"
                              % seg_index)
                continue

            # If the user *told* us the object's size, we can check range
            # satisfiability right now. If they lied about the size, we'll
            # fail that validation later.
            if (seg_size is not None and
                    len(seg_dict['range'].ranges_for_length(seg_size)) != 1):
                errors.append("Index %d: unsatisfiable range" % seg_index)
                continue

    if errors:
        error_message = "".join(e + "\n" for e in errors)
        raise HTTPBadRequest(error_message,
                             headers={"Content-Type": "text/plain"})

    return parsed_data


class SloGetContext(WSGIContext):

    max_slo_recursion_depth = 10

    def __init__(self, slo):
        self.slo = slo
        super(SloGetContext, self).__init__(slo.app)

    def _fetch_sub_slo_segments(self, req, version, acc, con, obj):
        """
        Fetch the submanifest, parse it, and return it.
        Raise exception on failures.
        """
        sub_req = make_subrequest(
            req.environ, path='/'.join(['', version, acc, con, obj]),
            method='GET',
            headers={'x-auth-token': req.headers.get('x-auth-token')},
            agent='%(orig)s SLO MultipartGET', swift_source='SLO')
        sub_resp = sub_req.get_response(self.slo.app)

        if not is_success(sub_resp.status_int):
            close_if_possible(sub_resp.app_iter)
            raise ListingIterError(
                'ERROR: while fetching %s, GET of submanifest %s '
                'failed with status %d' % (req.path, sub_req.path,
                                           sub_resp.status_int))

        try:
            with closing_if_possible(sub_resp.app_iter):
                return json.loads(''.join(sub_resp.app_iter))
        except ValueError as err:
            raise ListingIterError(
                'ERROR: while fetching %s, JSON-decoding of submanifest %s '
                'failed with %s' % (req.path, sub_req.path, err))

    def _segment_length(self, seg_dict):
        """
        Returns the number of bytes that will be fetched from the specified
        segment on a plain GET request for this SLO manifest.
        """
        seg_range = seg_dict.get('range')
        if seg_range is not None:
            # The range is of the form N-M, where N and M are both positive
            # decimal integers. We know this because this middleware is the
            # only thing that creates the SLO manifests stored in the
            # cluster.
            range_start, range_end = [int(x) for x in seg_range.split('-')]
            return range_end - range_start + 1
        else:
            return int(seg_dict['bytes'])

    def _segment_listing_iterator(self, req, version, account, segments,
                                  byteranges):
        for seg_dict in segments:
            if config_true_value(seg_dict.get('sub_slo')):
                override_bytes_from_content_type(seg_dict,
                                                 logger=self.slo.logger)

        # We handle the range stuff here so that we can be smart about
        # skipping unused submanifests. For example, if our first segment is a
        # submanifest referencing 50 MiB total, but start_byte falls in
        # the 51st MiB, then we can avoid fetching the first submanifest.
        #
        # If we were to make SegmentedIterable handle all the range
        # calculations, we would be unable to make this optimization.
        total_length = sum(self._segment_length(seg) for seg in segments)
        if not byteranges:
            byteranges = [(0, total_length - 1)]

        # Cache segments from sub-SLOs in case more than one byterange
        # includes data from a particular sub-SLO. We only cache a few sets
        # of segments so that a malicious user cannot build a giant SLO tree
        # and then GET it to run the proxy out of memory.
        #
        # LRUCache is a little awkward to use this way, but it beats doing
        # things manually.
        #
        # 20 is sort of an arbitrary choice; it's twice our max recursion
        # depth, so we know this won't expand memory requirements by too
        # much.
        cached_fetch_sub_slo_segments = \
            LRUCache(maxsize=20)(self._fetch_sub_slo_segments)

        for first_byte, last_byte in byteranges:
            byterange_listing_iter = self._byterange_listing_iterator(
                req, version, account, segments, first_byte, last_byte,
                cached_fetch_sub_slo_segments)
            for seg_info in byterange_listing_iter:
                yield seg_info

    def _byterange_listing_iterator(self, req, version, account, segments,
                                    first_byte, last_byte,
                                    cached_fetch_sub_slo_segments,
                                    recursion_depth=1):
        last_sub_path = None
        for seg_dict in segments:
            seg_length = self._segment_length(seg_dict)
            if first_byte >= seg_length:
                # don't need any bytes from this segment
                first_byte -= seg_length
                last_byte -= seg_length
                continue

            if last_byte < 0:
                # no bytes are needed from this or any future segment
                return

            seg_range = seg_dict.get('range')
            if seg_range is None:
                range_start, range_end = 0, seg_length - 1
            else:
                # We already validated and supplied concrete values
                # for the range on upload
                range_start, range_end = map(int, seg_range.split('-'))

            if config_true_value(seg_dict.get('sub_slo')):
                # do this check here so that we can avoid fetching this last
                # manifest before raising the exception
                if recursion_depth >= self.max_slo_recursion_depth:
                    raise ListingIterError("Max recursion depth exceeded")

                sub_path = get_valid_utf8_str(seg_dict['name'])
                sub_cont, sub_obj = split_path(sub_path, 2, 2, True)
                if last_sub_path != sub_path:
                    sub_segments = cached_fetch_sub_slo_segments(
                        req, version, account, sub_cont, sub_obj)
                last_sub_path = sub_path

                # Use the existing machinery to slice into the sub-SLO.
                for sub_seg_dict, sb, eb in self._byterange_listing_iterator(
                        req, version, account, sub_segments,
                        # This adjusts first_byte and last_byte to be
                        # relative to the sub-SLO.
                        range_start + max(0, first_byte),
                        min(range_end, range_start + last_byte),

                        cached_fetch_sub_slo_segments,
                        recursion_depth=recursion_depth + 1):
                    yield sub_seg_dict, sb, eb
            else:
                if isinstance(seg_dict['name'], six.text_type):
                    seg_dict['name'] = seg_dict['name'].encode("utf-8")
                yield (seg_dict,
                       max(0, first_byte) + range_start,
                       min(range_end, range_start + last_byte))

            first_byte -= seg_length
            last_byte -= seg_length

    def _need_to_refetch_manifest(self, req):
        """
        Just because a response shows that an object is a SLO manifest does not
        mean that response's body contains the entire SLO manifest. If it
        doesn't, we need to make a second request to actually get the whole
        thing.

        Note: this assumes that X-Static-Large-Object has already been found.
        """
        if req.method == 'HEAD':
            # We've already looked for SYSMETA_SLO_ETAG/SIZE in the response
            # and didn't find them. We have to fetch the whole manifest and
            # recompute.
            return True

        response_status = int(self._response_status[:3])

        # These are based on etag, and the SLO's etag is almost certainly not
        # the manifest object's etag. Still, it's highly likely that the
        # submitted If-None-Match won't match the manifest object's etag, so
        # we can avoid re-fetching the manifest if we got a successful
        # response.
        if ((req.if_match or req.if_none_match) and
                not is_success(response_status)):
            return True

        if req.range and response_status in (206, 416):
            content_range = ''
            for header, value in self._response_headers:
                if header.lower() == 'content-range':
                    content_range = value
                    break
            # e.g. Content-Range: bytes 0-14289/14290
            match = re.match('bytes (\d+)-(\d+)/(\d+)$', content_range)
            if not match:
                # Malformed or missing, so we don't know what we got.
                return True
            first_byte, last_byte, length = [int(x) for x in match.groups()]
            # If and only if we actually got back the full manifest body, then
            # we can avoid re-fetching the object.
            got_everything = (first_byte == 0 and last_byte == length - 1)
            return not got_everything

        return False

    def handle_slo_get_or_head(self, req, start_response):
        """
        Takes a request and a start_response callable and does the normal WSGI
        thing with them. Returns an iterator suitable for sending up the WSGI
        chain.

        :param req: swob.Request object; is a GET or HEAD request aimed at
                    what may be a static large object manifest (or may not).
        :param start_response: WSGI start_response callable
        """
        if req.params.get('multipart-manifest') != 'get':
            # If this object is an SLO manifest, we may have saved off the
            # large object etag during the original PUT. Send an
            # X-Backend-Etag-Is-At header so that, if the SLO etag *was*
            # saved, we can trust the object-server to respond appropriately
            # to If-Match/If-None-Match requests.
            update_etag_is_at_header(req, SYSMETA_SLO_ETAG)
        resp_iter = self._app_call(req.environ)

        # make sure this response is for a static large object manifest
        slo_marker = slo_etag = slo_size = None
        for header, value in self._response_headers:
            header = header.lower()
            if header == SYSMETA_SLO_ETAG:
                slo_etag = value
            elif header == SYSMETA_SLO_SIZE:
                slo_size = value
            elif (header == 'x-static-large-object' and
                  config_true_value(value)):
                slo_marker = value

            if slo_marker and slo_etag and slo_size:
                break

        if not slo_marker:
            # Not a static large object manifest. Just pass it through.
            start_response(self._response_status,
                           self._response_headers,
                           self._response_exc_info)
            return resp_iter

        # Handle pass-through request for the manifest itself
        if req.params.get('multipart-manifest') == 'get':
            if req.params.get('format') == 'raw':
                resp_iter = self.convert_segment_listing(
                    self._response_headers, resp_iter)
            else:
                new_headers = []
                for header, value in self._response_headers:
                    if header.lower() == 'content-type':
                        new_headers.append(('Content-Type',
                                            'application/json; charset=utf-8'))
                    else:
                        new_headers.append((header, value))
                self._response_headers = new_headers
            start_response(self._response_status,
                           self._response_headers,
                           self._response_exc_info)
            return resp_iter

        is_conditional = self._response_status.startswith(('304', '412')) and (
            req.if_match or req.if_none_match)
        if slo_etag and slo_size and (
                req.method == 'HEAD' or is_conditional):
            # Since we have length and etag, we can respond immediately
            for i, (header, _value) in enumerate(self._response_headers):
                lheader = header.lower()
                if lheader == 'etag':
                    self._response_headers[i] = (header, '"%s"' % slo_etag)
                elif lheader == 'content-length' and not is_conditional:
                    self._response_headers[i] = (header, slo_size)
            start_response(self._response_status,
                           self._response_headers,
                           self._response_exc_info)
            return resp_iter

        if self._need_to_refetch_manifest(req):
            req.environ['swift.non_client_disconnect'] = True
            close_if_possible(resp_iter)
            del req.environ['swift.non_client_disconnect']

            get_req = make_subrequest(
                req.environ, method='GET',
                headers={'x-auth-token': req.headers.get('x-auth-token')},
                agent='%(orig)s SLO MultipartGET', swift_source='SLO')
            resp_iter = self._app_call(get_req.environ)

        # Any Content-Range from a manifest is almost certainly wrong for the
        # full large object.
        resp_headers = [(h, v) for h, v in self._response_headers
                        if not h.lower() == 'content-range']

        response = self.get_or_head_response(
            req, resp_headers, resp_iter)
        return response(req.environ, start_response)

    def convert_segment_listing(self, resp_headers, resp_iter):
        """
        Converts the manifest data to match with the format
        that was put in through ?multipart-manifest=put

        :param resp_headers: response headers
        :param resp_iter: a response iterable
        """
        segments = self._get_manifest_read(resp_iter)

        for seg_dict in segments:
            seg_dict.pop('content_type', None)
            seg_dict.pop('last_modified', None)
            seg_dict.pop('sub_slo', None)
            seg_dict['path'] = seg_dict.pop('name', None)
            seg_dict['size_bytes'] = seg_dict.pop('bytes', None)
            seg_dict['etag'] = seg_dict.pop('hash', None)

        json_data = json.dumps(segments)  # convert to string
        if six.PY3:
            json_data = json_data.encode('utf-8')

        new_headers = []
        for header, value in resp_headers:
            if header.lower() == 'content-length':
                new_headers.append(('Content-Length', len(json_data)))
            else:
                new_headers.append((header, value))
        self._response_headers = new_headers

        return [json_data]

    def _get_manifest_read(self, resp_iter):
        with closing_if_possible(resp_iter):
            resp_body = ''.join(resp_iter)
        try:
            segments = json.loads(resp_body)
        except ValueError:
            segments = []

        return segments

    def get_or_head_response(self, req, resp_headers, resp_iter):
        segments = self._get_manifest_read(resp_iter)

        slo_etag = None
        content_length = None
        response_headers = []
        for header, value in resp_headers:
            lheader = header.lower()
            if lheader == SYSMETA_SLO_ETAG:
                slo_etag = value
            elif lheader == SYSMETA_SLO_SIZE:
                # it's from sysmeta, so we don't worry about non-integer
                # values here
                content_length = int(value)
            elif lheader not in ('etag', 'content-length'):
                response_headers.append((header, value))

        if slo_etag is None or content_length is None:
            etag = md5()
            content_length = 0
            for seg_dict in segments:
                if seg_dict.get('range'):
                    etag.update('%s:%s;' % (seg_dict['hash'],
                                            seg_dict['range']))
                else:
                    etag.update(seg_dict['hash'])

                if config_true_value(seg_dict.get('sub_slo')):
                    override_bytes_from_content_type(
                        seg_dict, logger=self.slo.logger)
                content_length += self._segment_length(seg_dict)
            slo_etag = etag.hexdigest()

        response_headers.append(('Content-Length', str(content_length)))
        response_headers.append(('Etag', '"%s"' % slo_etag))

        if req.method == 'HEAD':
            return self._manifest_head_response(req, response_headers)
        else:
            return self._manifest_get_response(
                req, content_length, response_headers, segments)

    def _manifest_head_response(self, req, response_headers):
        return HTTPOk(request=req, headers=response_headers, body='',
                      conditional_response=True)

    def _manifest_get_response(self, req, content_length, response_headers,
                               segments):
        if req.range:
            byteranges = [
                # For some reason, swob.Range.ranges_for_length adds 1 to the
                # last byte's position.
                (start, end - 1) for start, end
                in req.range.ranges_for_length(content_length)]
        else:
            byteranges = []

        ver, account, _junk = req.split_path(3, 3, rest_with_last=True)
        plain_listing_iter = self._segment_listing_iterator(
            req, ver, account, segments, byteranges)

        def is_small_segment(args):
            seg_dict, start_byte, end_byte = args
            start = 0 if start_byte is None else start_byte
            end = int(seg_dict['bytes']) - 1 if end_byte is None else end_byte
            is_small = (end - start + 1) < self.slo.rate_limit_under_size
            return is_small

        ratelimited_listing_iter = RateLimitedIterator(
            plain_listing_iter,
            self.slo.rate_limit_segments_per_sec,
            limit_after=self.slo.rate_limit_after_segment,
            ratelimit_if=is_small_segment)

        # self._segment_listing_iterator gives us 3-tuples of (segment dict,
        # start byte, end byte), but SegmentedIterable wants (obj path, etag,
        # size, start byte, end byte), so we clean that up here
        segment_listing_iter = (
            ("/{ver}/{acc}/{conobj}".format(
                ver=ver, acc=account, conobj=seg_dict['name'].lstrip('/')),
                seg_dict['hash'], int(seg_dict['bytes']),
                start_byte, end_byte)
            for seg_dict, start_byte, end_byte in ratelimited_listing_iter)

        segmented_iter = SegmentedIterable(
            req, self.slo.app, segment_listing_iter,
            name=req.path, logger=self.slo.logger,
            ua_suffix="SLO MultipartGET",
            swift_source="SLO",
            max_get_time=self.slo.max_get_time)

        try:
            segmented_iter.validate_first_segment()
        except (ListingIterError, SegmentError):
            # Copy from the SLO explanation in top of this file.
            # If any of the segments from the manifest are not found or
            # their Etag/Content Length no longer match the connection
            # will drop. In this case a 409 Conflict will be logged in
            # the proxy logs and the user will receive incomplete results.
            return HTTPConflict(request=req)

        response = Response(request=req, content_length=content_length,
                            headers=response_headers,
                            conditional_response=True,
                            app_iter=segmented_iter)
        return response


class StaticLargeObject(object):
    """
    StaticLargeObject Middleware

    See above for a full description.

    The proxy logs created for any subrequests made will have swift.source set
    to "SLO".

    :param app: The next WSGI filter or app in the paste.deploy chain.
    :param conf: The configuration dict for the middleware.
    """

    def __init__(self, app, conf,
                 max_manifest_segments=DEFAULT_MAX_MANIFEST_SEGMENTS,
                 max_manifest_size=DEFAULT_MAX_MANIFEST_SIZE):
        self.conf = conf
        self.app = app
        self.logger = get_logger(conf, log_route='slo')
        self.max_manifest_segments = max_manifest_segments
        self.max_manifest_size = max_manifest_size
        self.max_get_time = int(self.conf.get('max_get_time', 86400))
        self.rate_limit_under_size = int(self.conf.get(
            'rate_limit_under_size', DEFAULT_RATE_LIMIT_UNDER_SIZE))
        self.rate_limit_after_segment = int(self.conf.get(
            'rate_limit_after_segment', '10'))
        self.rate_limit_segments_per_sec = int(self.conf.get(
            'rate_limit_segments_per_sec', '1'))
        self.concurrency = min(1000, max(0, int(self.conf.get(
            'concurrency', '2'))))
        delete_concurrency = int(self.conf.get(
            'delete_concurrency', self.concurrency))
        self.bulk_deleter = Bulk(
            app, {}, delete_concurrency=delete_concurrency, logger=self.logger)

    def handle_multipart_get_or_head(self, req, start_response):
        """
        Handles the GET or HEAD of a SLO manifest.

        The response body (only on GET, of course) will consist of the
        concatenation of the segments.

        :params req: a swob.Request with a path referencing an object
        :raises HttpException: on errors
        """
        return SloGetContext(self).handle_slo_get_or_head(req, start_response)

    def handle_multipart_put(self, req, start_response):
        """
        Will handle the PUT of a SLO manifest.
        Heads every object in manifest to check if is valid and if so will
        save a manifest generated from the user input. Uses WSGIContext to
        call self and start_response and returns a WSGI iterator.

        :params req: a swob.Request with an obj in path
        :raises HttpException: on errors
        """
        try:
            vrs, account, container, obj = req.split_path(1, 4, True)
        except ValueError:
            return self.app(req.environ, start_response)
        if req.content_length > self.max_manifest_size:
            raise HTTPRequestEntityTooLarge(
                "Manifest File > %d bytes" % self.max_manifest_size)
        if req.headers.get('X-Copy-From'):
            raise HTTPMethodNotAllowed(
                'Multipart Manifest PUTs cannot be COPY requests')
        if req.content_length is None and \
                req.headers.get('transfer-encoding', '').lower() != 'chunked':
            raise HTTPLengthRequired(request=req)
        parsed_data = parse_and_validate_input(
            req.body_file.read(self.max_manifest_size),
            req.path)
        problem_segments = []

        if len(parsed_data) > self.max_manifest_segments:
            raise HTTPRequestEntityTooLarge(
                'Number of segments must be <= %d' %
                self.max_manifest_segments)
        total_size = 0
        out_content_type = req.accept.best_match(ACCEPTABLE_FORMATS)
        if not out_content_type:
            out_content_type = 'text/plain'
        data_for_storage = []
        path2indices = defaultdict(list)
        for index, seg_dict in enumerate(parsed_data):
            path2indices[seg_dict['path']].append(index)

        def do_head(obj_name):
            obj_path = '/'.join(['', vrs, account,
                                 get_valid_utf8_str(obj_name).lstrip('/')])

            sub_req = make_subrequest(
                req.environ, path=obj_path + '?',  # kill the query string
                method='HEAD',
                headers={'x-auth-token': req.headers.get('x-auth-token')},
                agent='%(orig)s SLO MultipartPUT', swift_source='SLO')
            return obj_name, sub_req.get_response(self)

        def validate_seg_dict(seg_dict, head_seg_resp):
            if not head_seg_resp.is_success:
                problem_segments.append([quote(obj_name),
                                         head_seg_resp.status])
                return 0, None

            segment_length = head_seg_resp.content_length
            if seg_dict.get('range'):
                # Since we now know the length, we can normalize the
                # range. We know that there is exactly one range
                # requested since we checked that earlier in
                # parse_and_validate_input().
                ranges = seg_dict['range'].ranges_for_length(
                    head_seg_resp.content_length)

                if not ranges:
                    problem_segments.append([quote(obj_name),
                                             'Unsatisfiable Range'])
                elif ranges == [(0, head_seg_resp.content_length)]:
                    # Just one range, and it exactly matches the object.
                    # Why'd we do this again?
                    del seg_dict['range']
                    segment_length = head_seg_resp.content_length
                else:
                    rng = ranges[0]
                    seg_dict['range'] = '%d-%d' % (rng[0], rng[1] - 1)
                    segment_length = rng[1] - rng[0]

            if segment_length < 1:
                problem_segments.append(
                    [quote(obj_name),
                     'Too small; each segment must be at least 1 byte.'])
            if seg_dict.get('size_bytes') is not None and \
                    seg_dict['size_bytes'] != head_seg_resp.content_length:
                problem_segments.append([quote(obj_name), 'Size Mismatch'])
            if seg_dict.get('etag') is not None and \
                    seg_dict['etag'] != head_seg_resp.etag:
                problem_segments.append([quote(obj_name), 'Etag Mismatch'])
            if head_seg_resp.last_modified:
                last_modified = head_seg_resp.last_modified
            else:
                # shouldn't happen
                last_modified = datetime.now()

            last_modified_formatted = \
                last_modified.strftime('%Y-%m-%dT%H:%M:%S.%f')
            seg_data = {'name': '/' + seg_dict['path'].lstrip('/'),
                        'bytes': head_seg_resp.content_length,
                        'hash': head_seg_resp.etag,
                        'content_type': head_seg_resp.content_type,
                        'last_modified': last_modified_formatted}
            if seg_dict.get('range'):
                seg_data['range'] = seg_dict['range']
            if config_true_value(
                    head_seg_resp.headers.get('X-Static-Large-Object')):
                seg_data['sub_slo'] = True
            return segment_length, seg_data

        data_for_storage = [None] * len(parsed_data)
        with StreamingPile(self.concurrency) as pile:
            for obj_name, resp in pile.asyncstarmap(do_head, (
                    (path, ) for path in path2indices)):
                for i in path2indices[obj_name]:
                    segment_length, seg_data = validate_seg_dict(
                        parsed_data[i], resp)
                    data_for_storage[i] = seg_data
                    total_size += segment_length

        if problem_segments:
            resp_body = get_response_body(
                out_content_type, {}, problem_segments)
            raise HTTPBadRequest(resp_body, content_type=out_content_type)

        slo_etag = md5()
        for seg_data in data_for_storage:
            if seg_data.get('range'):
                slo_etag.update('%s:%s;' % (seg_data['hash'],
                                            seg_data['range']))
            else:
                slo_etag.update(seg_data['hash'])

        slo_etag = slo_etag.hexdigest()
        client_etag = req.headers.get('Etag')
        if client_etag and client_etag.strip('"') != slo_etag:
            raise HTTPUnprocessableEntity(request=req)

        json_data = json.dumps(data_for_storage)
        if six.PY3:
            json_data = json_data.encode('utf-8')
        req.body = json_data
        req.headers.update({
            SYSMETA_SLO_ETAG: slo_etag,
            SYSMETA_SLO_SIZE: total_size,
            'X-Static-Large-Object': 'True',
            'Etag': md5(json_data).hexdigest(),
        })

        env = req.environ
        if not env.get('CONTENT_TYPE'):
            guessed_type, _junk = mimetypes.guess_type(req.path_info)
            env['CONTENT_TYPE'] = guessed_type or 'application/octet-stream'
        env['swift.content_type_overridden'] = True
        env['CONTENT_TYPE'] += ";swift_bytes=%d" % total_size

        def start_response_wrapper(status, headers, exc_info=None):
            for i, (header, _value) in enumerate(headers):
                if header.lower() == 'etag':
                    headers[i] = ('Etag', '"%s"' % slo_etag)
                    break
            return start_response(status, headers, exc_info)

        return self.app(env, start_response_wrapper)

    def get_segments_to_delete_iter(self, req):
        """
        A generator function to be used to delete all the segments and
        sub-segments referenced in a manifest.

        :params req: a swob.Request with an SLO manifest in path
        :raises HTTPPreconditionFailed: on invalid UTF8 in request path
        :raises HTTPBadRequest: on too many buffered sub segments and
                                on invalid SLO manifest path
        """
        if not check_utf8(req.path_info):
            raise HTTPPreconditionFailed(
                request=req, body='Invalid UTF8 or contains NULL')
        vrs, account, container, obj = req.split_path(4, 4, True)

        segments = [{
            'sub_slo': True,
            'name': ('/%s/%s' % (container, obj)).decode('utf-8')}]
        while segments:
            if len(segments) > MAX_BUFFERED_SLO_SEGMENTS:
                raise HTTPBadRequest(
                    'Too many buffered slo segments to delete.')
            seg_data = segments.pop(0)
            if seg_data.get('sub_slo'):
                try:
                    segments.extend(
                        self.get_slo_segments(seg_data['name'], req))
                except HTTPException as err:
                    # allow bulk delete response to report errors
                    seg_data['error'] = {'code': err.status_int,
                                         'message': err.body}

                # add manifest back to be deleted after segments
                seg_data['sub_slo'] = False
                segments.append(seg_data)
            else:
                seg_data['name'] = seg_data['name'].encode('utf-8')
                yield seg_data

    def get_slo_segments(self, obj_name, req):
        """
        Performs a swob.Request and returns the SLO manifest's segments.

        :raises HTTPServerError: on unable to load obj_name or
                                 on unable to load the SLO manifest data.
        :raises HTTPBadRequest: on not an SLO manifest
        :raises HTTPNotFound: on SLO manifest not found
        :returns: SLO manifest's segments
        """
        vrs, account, _junk = req.split_path(2, 3, True)
        new_env = req.environ.copy()
        new_env['REQUEST_METHOD'] = 'GET'
        del(new_env['wsgi.input'])
        new_env['QUERY_STRING'] = 'multipart-manifest=get'
        new_env['CONTENT_LENGTH'] = 0
        new_env['HTTP_USER_AGENT'] = \
            '%s MultipartDELETE' % new_env.get('HTTP_USER_AGENT')
        new_env['swift.source'] = 'SLO'
        new_env['PATH_INFO'] = (
            '/%s/%s/%s' % (vrs, account, obj_name.lstrip('/').encode('utf-8'))
        )
        resp = Request.blank('', new_env).get_response(self.app)

        if resp.is_success:
            if config_true_value(resp.headers.get('X-Static-Large-Object')):
                try:
                    return json.loads(resp.body)
                except ValueError:
                    raise HTTPServerError('Unable to load SLO manifest')
            else:
                raise HTTPBadRequest('Not an SLO manifest')
        elif resp.status_int == HTTP_NOT_FOUND:
            raise HTTPNotFound('SLO manifest not found')
        elif resp.status_int == HTTP_UNAUTHORIZED:
            raise HTTPUnauthorized('401 Unauthorized')
        else:
            raise HTTPServerError('Unable to load SLO manifest or segment.')

    def handle_multipart_delete(self, req):
        """
        Will delete all the segments in the SLO manifest and then, if
        successful, will delete the manifest file.

        :params req: a swob.Request with an obj in path
        :returns: swob.Response whose app_iter set to Bulk.handle_delete_iter
        """
        req.headers['Content-Type'] = None  # Ignore content-type from client
        resp = HTTPOk(request=req)
        out_content_type = req.accept.best_match(ACCEPTABLE_FORMATS)
        if out_content_type:
            resp.content_type = out_content_type
        resp.app_iter = self.bulk_deleter.handle_delete_iter(
            req, objs_to_delete=self.get_segments_to_delete_iter(req),
            user_agent='MultipartDELETE', swift_source='SLO',
            out_content_type=out_content_type)
        return resp

    def __call__(self, env, start_response):
        """
        WSGI entry point
        """
        if env.get('swift.slo_override'):
            return self.app(env, start_response)

        req = Request(env)
        try:
            vrs, account, container, obj = req.split_path(4, 4, True)
        except ValueError:
            return self.app(env, start_response)

        try:
            if req.method == 'PUT' and \
                    req.params.get('multipart-manifest') == 'put':
                return self.handle_multipart_put(req, start_response)
            if req.method == 'DELETE' and \
                    req.params.get('multipart-manifest') == 'delete':
                return self.handle_multipart_delete(req)(env, start_response)
            if req.method == 'GET' or req.method == 'HEAD':
                return self.handle_multipart_get_or_head(req, start_response)
            if 'X-Static-Large-Object' in req.headers:
                raise HTTPBadRequest(
                    request=req,
                    body='X-Static-Large-Object is a reserved header. '
                    'To create a static large object add query param '
                    'multipart-manifest=put.')
        except HTTPException as err_resp:
            return err_resp(env, start_response)

        return self.app(env, start_response)


def filter_factory(global_conf, **local_conf):
    conf = global_conf.copy()
    conf.update(local_conf)

    max_manifest_segments = int(conf.get('max_manifest_segments',
                                         DEFAULT_MAX_MANIFEST_SEGMENTS))
    max_manifest_size = int(conf.get('max_manifest_size',
                                     DEFAULT_MAX_MANIFEST_SIZE))

    register_swift_info('slo',
                        max_manifest_segments=max_manifest_segments,
                        max_manifest_size=max_manifest_size,
                        # this used to be configurable; report it as 1 for
                        # clients that might still care
                        min_segment_size=1)

    def slo_filter(app):
        return StaticLargeObject(
            app, conf,
            max_manifest_segments=max_manifest_segments,
            max_manifest_size=max_manifest_size)
    return slo_filter