# 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.

""" Object Server for Swift """

import six
import six.moves.cPickle as pickle
from six.moves.urllib.parse import unquote
import json
import os
import multiprocessing
import time
import traceback
import socket

from eventlet import sleep, wsgi, Timeout, tpool
from eventlet.greenthread import spawn

from swift.common.utils import public, get_logger, \
    config_true_value, timing_stats, replication, \
    normalize_delete_at_timestamp, get_log_line, Timestamp, \
    get_expirer_container, parse_mime_headers, \
    iter_multipart_mime_documents, extract_swift_bytes, safe_json_loads, \
    config_auto_int_value, split_path, get_redirect_data, \
    normalize_timestamp, md5
from swift.common.bufferedhttp import http_connect
from swift.common.constraints import check_object_creation, \
    valid_timestamp, check_utf8, AUTO_CREATE_ACCOUNT_PREFIX
from swift.common.exceptions import ConnectionTimeout, DiskFileQuarantined, \
    DiskFileNotExist, DiskFileCollision, DiskFileNoSpace, DiskFileDeleted, \
    DiskFileDeviceUnavailable, DiskFileExpired, ChunkReadTimeout, \
    ChunkReadError, DiskFileXattrNotSupported
from swift.common.request_helpers import \
    OBJECT_SYSMETA_CONTAINER_UPDATE_OVERRIDE_PREFIX
from swift.obj import ssync_receiver
from swift.common.http import is_success, HTTP_MOVED_PERMANENTLY
from swift.common.base_storage_server import BaseStorageServer
from swift.common.header_key_dict import HeaderKeyDict
from swift.common.request_helpers import get_name_and_placement, \
    is_user_meta, is_sys_or_user_meta, is_object_transient_sysmeta, \
    resolve_etag_is_at_header, is_sys_meta, validate_internal_obj
from swift.common.swob import HTTPAccepted, HTTPBadRequest, HTTPCreated, \
    HTTPInternalServerError, HTTPNoContent, HTTPNotFound, \
    HTTPPreconditionFailed, HTTPRequestTimeout, HTTPUnprocessableEntity, \
    HTTPClientDisconnect, HTTPMethodNotAllowed, Request, Response, \
    HTTPInsufficientStorage, HTTPForbidden, HTTPException, HTTPConflict, \
    HTTPServerError, bytes_to_wsgi, wsgi_to_bytes, wsgi_to_str, normalize_etag
from swift.obj.diskfile import RESERVED_DATAFILE_META, DiskFileRouter
from swift.obj.expirer import build_task_obj


def iter_mime_headers_and_bodies(wsgi_input, mime_boundary, read_chunk_size):
    mime_documents_iter = iter_multipart_mime_documents(
        wsgi_input, mime_boundary, read_chunk_size)

    for file_like in mime_documents_iter:
        hdrs = parse_mime_headers(file_like)
        yield (hdrs, file_like)


def drain(file_like, read_size, timeout):
    """
    Read and discard any bytes from file_like.

    :param file_like: file-like object to read from
    :param read_size: how big a chunk to read at a time
    :param timeout: how long to wait for a read (use None for no timeout)

    :raises ChunkReadTimeout: if no chunk was read in time
    """

    while True:
        with ChunkReadTimeout(timeout):
            chunk = file_like.read(read_size)
            if not chunk:
                break


def get_obj_name_and_placement(request):
    """
    Split and validate path for an object.

    :param request: a swob request

    :returns: a tuple of path parts and storage policy
    """
    device, partition, account, container, obj, policy = \
        get_name_and_placement(request, 5, 5, True)
    validate_internal_obj(account, container, obj)
    return device, partition, account, container, obj, policy


def _make_backend_fragments_header(fragments):
    if fragments:
        result = {}
        for ts, frag_list in fragments.items():
            result[ts.internal] = frag_list
        return json.dumps(result)
    return None


class EventletPlungerString(bytes):
    """
    Eventlet won't send headers until it's accumulated at least
    eventlet.wsgi.MINIMUM_CHUNK_SIZE bytes or the app iter is exhausted.
    If we want to send the response body behind Eventlet's back, perhaps
    with some zero-copy wizardry, then we have to unclog the plumbing in
    eventlet.wsgi to force the headers out, so we use an
    EventletPlungerString to empty out all of Eventlet's buffers.
    """
    def __len__(self):
        return wsgi.MINIMUM_CHUNK_SIZE + 1


class ObjectController(BaseStorageServer):
    """Implements the WSGI application for the Swift Object Server."""

    server_type = 'object-server'

    def __init__(self, conf, logger=None):
        """
        Creates a new WSGI application for the Swift Object Server. An
        example configuration is given at
        <source-dir>/etc/object-server.conf-sample or
        /etc/swift/object-server.conf-sample.
        """
        super(ObjectController, self).__init__(conf)
        self.logger = logger or get_logger(conf, log_route='object-server')
        self.node_timeout = float(conf.get('node_timeout', 3))
        self.container_update_timeout = float(
            conf.get('container_update_timeout', 1))
        self.conn_timeout = float(conf.get('conn_timeout', 0.5))
        self.client_timeout = float(conf.get('client_timeout', 60))
        self.disk_chunk_size = int(conf.get('disk_chunk_size', 65536))
        self.network_chunk_size = int(conf.get('network_chunk_size', 65536))
        self.log_requests = config_true_value(conf.get('log_requests', 'true'))
        self.max_upload_time = int(conf.get('max_upload_time', 86400))
        self.slow = int(conf.get('slow', 0))
        self.keep_cache_private = \
            config_true_value(conf.get('keep_cache_private', 'false'))
        self.keep_cache_slo_manifest = \
            config_true_value(conf.get('keep_cache_slo_manifest', 'false'))

        default_allowed_headers = '''
            content-disposition,
            content-encoding,
            x-delete-at,
            x-object-manifest,
            x-static-large-object,
            cache-control,
            content-language,
            expires,
            x-robots-tag
        '''
        extra_allowed_headers = [
            header.strip().lower() for header in conf.get(
                'allowed_headers', default_allowed_headers).split(',')
            if header.strip()
        ]
        self.allowed_headers = set()
        for header in extra_allowed_headers:
            if header not in RESERVED_DATAFILE_META:
                self.allowed_headers.add(header)
        if conf.get('auto_create_account_prefix'):
            self.logger.warning('Option auto_create_account_prefix is '
                                'deprecated. Configure '
                                'auto_create_account_prefix under the '
                                'swift-constraints section of '
                                'swift.conf. This option will '
                                'be ignored in a future release.')
            self.auto_create_account_prefix = \
                conf['auto_create_account_prefix']
        else:
            self.auto_create_account_prefix = AUTO_CREATE_ACCOUNT_PREFIX

        self.expiring_objects_account = self.auto_create_account_prefix + \
            (conf.get('expiring_objects_account_name') or 'expiring_objects')
        self.expiring_objects_container_divisor = \
            int(conf.get('expiring_objects_container_divisor') or 86400)
        # Initialization was successful, so now apply the network chunk size
        # parameter as the default read / write buffer size for the network
        # sockets.
        #
        # NOTE WELL: This is a class setting, so until we get set this on a
        # per-connection basis, this affects reading and writing on ALL
        # sockets, those between the proxy servers and external clients, and
        # those between the proxy servers and the other internal servers.
        #
        # ** Because the primary motivation for this is to optimize how data
        # is written back to the proxy server, we could use the value from the
        # disk_chunk_size parameter. However, it affects all created sockets
        # using this class so we have chosen to tie it to the
        # network_chunk_size parameter value instead.
        if six.PY2:
            socket._fileobject.default_bufsize = self.network_chunk_size
        # TODO: find a way to enable similar functionality in py3

        # Provide further setup specific to an object server implementation.
        self.setup(conf)

    def setup(self, conf):
        """
        Implementation specific setup. This method is called at the very end
        by the constructor to allow a specific implementation to modify
        existing attributes or add its own attributes.

        :param conf: WSGI configuration parameter
        """

        # Common on-disk hierarchy shared across account, container and object
        # servers.
        self._diskfile_router = DiskFileRouter(conf, self.logger)
        # This is populated by global_conf_callback way below as the semaphore
        # is shared by all workers.
        if 'replication_semaphore' in conf:
            # The value was put in a list so it could get past paste
            self.replication_semaphore = conf['replication_semaphore'][0]
        else:
            self.replication_semaphore = None
        self.replication_failure_threshold = int(
            conf.get('replication_failure_threshold') or 100)
        self.replication_failure_ratio = float(
            conf.get('replication_failure_ratio') or 1.0)

        servers_per_port = int(conf.get('servers_per_port', '0') or 0)
        if servers_per_port:
            # The typical servers-per-port deployment also uses one port per
            # disk, so you really get N servers per disk. In that case,
            # having a pool of 20 threads per server per disk is far too
            # much. For example, given a 60-disk chassis and 4 servers per
            # disk, the default configuration will give us 21 threads per
            # server (the main thread plus the twenty tpool threads), for a
            # total of around 60 * 21 * 4 = 5040 threads. This is clearly
            # too high.
            #
            # Instead, we use a tpool size of 1, giving us 2 threads per
            # process. In the example above, that's 60 * 2 * 4 = 480
            # threads, which is reasonable since there are 240 processes.
            default_tpool_size = 1
        else:
            # If we're not using servers-per-port, then leave the tpool size
            # alone. The default (20) is typically good enough for one
            # object server handling requests for many disks.
            default_tpool_size = None

        tpool_size = config_auto_int_value(
            conf.get('eventlet_tpool_num_threads'),
            default_tpool_size)

        if tpool_size:
            tpool.set_num_threads(tpool_size)

    def get_diskfile(self, device, partition, account, container, obj,
                     policy, **kwargs):
        """
        Utility method for instantiating a DiskFile object supporting a given
        REST API.

        An implementation of the object server that wants to use a different
        DiskFile class would simply over-ride this method to provide that
        behavior.
        """
        return self._diskfile_router[policy].get_diskfile(
            device, partition, account, container, obj, policy, **kwargs)

    def async_update(self, op, account, container, obj, host, partition,
                     contdevice, headers_out, objdevice, policy,
                     logger_thread_locals=None, container_path=None):
        """
        Sends or saves an async update.

        :param op: operation performed (ex: 'PUT', or 'DELETE')
        :param account: account name for the object
        :param container: container name for the object
        :param obj: object name
        :param host: host that the container is on
        :param partition: partition that the container is on
        :param contdevice: device name that the container is on
        :param headers_out: dictionary of headers to send in the container
                            request
        :param objdevice: device name that the object is in
        :param policy: the associated BaseStoragePolicy instance
        :param logger_thread_locals: The thread local values to be set on the
                                     self.logger to retain transaction
                                     logging information.
        :param container_path: optional path in the form `<account/container>`
            to which the update should be sent. If given this path will be used
            instead of constructing a path from the ``account`` and
            ``container`` params.
        """
        if logger_thread_locals:
            self.logger.thread_locals = logger_thread_locals
        headers_out['user-agent'] = 'object-server %s' % os.getpid()
        if container_path:
            # use explicitly specified container path
            full_path = '/%s/%s' % (container_path, obj)
        else:
            full_path = '/%s/%s/%s' % (account, container, obj)

        redirect_data = None
        if all([host, partition, contdevice]):
            try:
                with ConnectionTimeout(self.conn_timeout):
                    ip, port = host.rsplit(':', 1)
                    conn = http_connect(ip, port, contdevice, partition, op,
                                        full_path, headers_out)
                with Timeout(self.node_timeout):
                    response = conn.getresponse()
                    response.read()
                if is_success(response.status):
                    return

                if response.status == HTTP_MOVED_PERMANENTLY:
                    try:
                        redirect_data = get_redirect_data(response)
                    except ValueError as err:
                        self.logger.error(
                            'Container update failed for %r; problem with '
                            'redirect location: %s' % (obj, err))
                else:
                    self.logger.error(
                        'ERROR Container update failed '
                        '(saving for async update later): %(status)d '
                        'response from %(ip)s:%(port)s/%(dev)s',
                        {'status': response.status, 'ip': ip, 'port': port,
                         'dev': contdevice})
            except (Exception, Timeout):
                self.logger.exception(
                    'ERROR container update failed with '
                    '%(ip)s:%(port)s/%(dev)s (saving for async update later)',
                    {'ip': ip, 'port': port, 'dev': contdevice})
        data = {'op': op, 'account': account, 'container': container,
                'obj': obj, 'headers': headers_out}
        if redirect_data:
            self.logger.debug(
                'Update to %(path)s redirected to %(redirect)s',
                {'path': full_path, 'redirect': redirect_data[0]})
            container_path = redirect_data[0]
        if container_path:
            data['container_path'] = container_path
        timestamp = headers_out.get('x-meta-timestamp',
                                    headers_out.get('x-timestamp'))
        self._diskfile_router[policy].pickle_async_update(
            objdevice, account, container, obj, data, timestamp, policy)

    def container_update(self, op, account, container, obj, request,
                         headers_out, objdevice, policy):
        """
        Update the container when objects are updated.

        :param op: operation performed (ex: 'PUT', or 'DELETE')
        :param account: account name for the object
        :param container: container name for the object
        :param obj: object name
        :param request: the original request object driving the update
        :param headers_out: dictionary of headers to send in the container
                            request(s)
        :param objdevice: device name that the object is in
        :param policy:  the BaseStoragePolicy instance
        """
        headers_in = request.headers
        conthosts = [h.strip() for h in
                     headers_in.get('X-Container-Host', '').split(',')]
        contdevices = [d.strip() for d in
                       headers_in.get('X-Container-Device', '').split(',')]
        contpartition = headers_in.get('X-Container-Partition', '')

        if len(conthosts) != len(contdevices):
            # This shouldn't happen unless there's a bug in the proxy,
            # but if there is, we want to know about it.
            self.logger.error(
                'ERROR Container update failed: different '
                'numbers of hosts and devices in request: '
                '"%(hosts)s" vs "%(devices)s"', {
                    'hosts': headers_in.get('X-Container-Host', ''),
                    'devices': headers_in.get('X-Container-Device', '')})
            return

        contpath = headers_in.get('X-Backend-Quoted-Container-Path')
        if contpath:
            contpath = unquote(contpath)
        else:
            contpath = headers_in.get('X-Backend-Container-Path')

        if contpath:
            try:
                # TODO: this is very late in request handling to be validating
                # a header - if we did *not* check and the header was bad
                # presumably the update would fail and we would fall back to an
                # async update to the root container, which might be best
                # course of action rather than aborting update altogether?
                split_path('/' + contpath, minsegs=2, maxsegs=2)
            except ValueError:
                self.logger.error(
                    "Invalid X-Backend-Container-Path, should be of the form "
                    "'account/container' but got %r." % contpath)
                # fall back to updating root container
                contpath = None

        if contpartition:
            # In py3, zip() continues to work for our purposes... But when
            # we want to log an error, consumed items are not longer present
            # in the zip, making the logs useless for operators. So, list().
            updates = list(zip(conthosts, contdevices))
        else:
            updates = []

        headers_out['x-trans-id'] = headers_in.get('x-trans-id', '-')
        headers_out['referer'] = request.as_referer()
        headers_out['X-Backend-Storage-Policy-Index'] = int(policy)
        update_greenthreads = []
        for conthost, contdevice in updates:
            gt = spawn(self.async_update, op, account, container, obj,
                       conthost, contpartition, contdevice, headers_out,
                       objdevice, policy,
                       logger_thread_locals=self.logger.thread_locals,
                       container_path=contpath)
            update_greenthreads.append(gt)
        # Wait a little bit to see if the container updates are successful.
        # If we immediately return after firing off the greenthread above, then
        # we're more likely to confuse the end-user who does a listing right
        # after getting a successful response to the object create. The
        # `container_update_timeout` bounds the length of time we wait so that
        # one slow container server doesn't make the entire request lag.
        try:
            with Timeout(self.container_update_timeout):
                for gt in update_greenthreads:
                    gt.wait()
        except Timeout:
            # updates didn't go through, log it and return
            self.logger.debug(
                'Container update timeout (%.4fs) waiting for %s',
                self.container_update_timeout, updates)

    def delete_at_update(self, op, delete_at, account, container, obj,
                         request, objdevice, policy):
        """
        Update the expiring objects container when objects are updated.

        :param op: operation performed (ex: 'PUT', or 'DELETE')
        :param delete_at: scheduled delete in UNIX seconds, int
        :param account: account name for the object
        :param container: container name for the object
        :param obj: object name
        :param request: the original request driving the update
        :param objdevice: device name that the object is in
        :param policy: the BaseStoragePolicy instance (used for tmp dir)
        """
        if config_true_value(
                request.headers.get('x-backend-replication', 'f')):
            return
        delete_at = normalize_delete_at_timestamp(delete_at)
        updates = [(None, None)]

        partition = None
        hosts = contdevices = [None]
        headers_in = request.headers
        headers_out = HeaderKeyDict({
            # system accounts are always Policy-0
            'X-Backend-Storage-Policy-Index': 0,
            'x-timestamp': request.timestamp.internal,
            'x-trans-id': headers_in.get('x-trans-id', '-'),
            'referer': request.as_referer()})
        if op != 'DELETE':
            hosts = headers_in.get('X-Delete-At-Host', None)
            if hosts is None:
                # If header is missing, no update needed as sufficient other
                # object servers should perform the required update.
                return
            delete_at_container = headers_in.get('X-Delete-At-Container', None)
            if not delete_at_container:
                # older proxy servers did not send X-Delete-At-Container so for
                # backwards compatibility calculate the value here, but also
                # log a warning because this is prone to inconsistent
                # expiring_objects_container_divisor configurations.
                # See https://bugs.launchpad.net/swift/+bug/1187200
                self.logger.warning(
                    'X-Delete-At-Container header must be specified for '
                    'expiring objects background %s to work properly. Making '
                    'best guess as to the container name for now.' % op)
                delete_at_container = get_expirer_container(
                    delete_at, self.expiring_objects_container_divisor,
                    account, container, obj)
            partition = headers_in.get('X-Delete-At-Partition', None)
            contdevices = headers_in.get('X-Delete-At-Device', '')
            updates = [upd for upd in
                       zip((h.strip() for h in hosts.split(',')),
                           (c.strip() for c in contdevices.split(',')))
                       if all(upd) and partition]
            if not updates:
                updates = [(None, None)]
            headers_out['x-size'] = '0'
            headers_out['x-content-type'] = 'text/plain'
            headers_out['x-etag'] = 'd41d8cd98f00b204e9800998ecf8427e'
        else:
            if not config_true_value(
                request.headers.get(
                    'X-Backend-Clean-Expiring-Object-Queue', 't')):
                return

            # DELETEs of old expiration data have no way of knowing what the
            # old X-Delete-At-Container was at the time of the initial setting
            # of the data, so a best guess is made here.
            # Worst case is a DELETE is issued now for something that doesn't
            # exist there and the original data is left where it is, where
            # it will be ignored when the expirer eventually tries to issue the
            # object DELETE later since the X-Delete-At value won't match up.
            delete_at_container = get_expirer_container(
                delete_at, self.expiring_objects_container_divisor,
                account, container, obj)
        delete_at_container = normalize_delete_at_timestamp(
            delete_at_container)

        for host, contdevice in updates:
            self.async_update(
                op, self.expiring_objects_account, delete_at_container,
                build_task_obj(delete_at, account, container, obj),
                host, partition, contdevice, headers_out, objdevice,
                policy)

    def _make_timeout_reader(self, file_like):
        def timeout_reader():
            with ChunkReadTimeout(self.client_timeout):
                try:
                    return file_like.read(self.network_chunk_size)
                except (IOError, ValueError):
                    raise ChunkReadError
        return timeout_reader

    def _read_put_commit_message(self, mime_documents_iter):
        rcvd_commit = False
        try:
            with ChunkReadTimeout(self.client_timeout):
                commit_hdrs, commit_iter = next(mime_documents_iter)
                if commit_hdrs.get('X-Document', None) == "put commit":
                    rcvd_commit = True
            drain(commit_iter, self.network_chunk_size, self.client_timeout)
        except ChunkReadError:
            raise HTTPClientDisconnect()
        except ChunkReadTimeout:
            raise HTTPRequestTimeout()
        except StopIteration:
            raise HTTPBadRequest(body="couldn't find PUT commit MIME doc")
        return rcvd_commit

    def _read_metadata_footer(self, mime_documents_iter):
        try:
            with ChunkReadTimeout(self.client_timeout):
                footer_hdrs, footer_iter = next(mime_documents_iter)
        except ChunkReadError:
            raise HTTPClientDisconnect()
        except ChunkReadTimeout:
            raise HTTPRequestTimeout()
        except StopIteration:
            raise HTTPBadRequest(body="couldn't find footer MIME doc")
        return self._parse_footer(footer_hdrs, footer_iter)

    def _parse_footer(self, footer_hdrs, footer_iter):
        """
        Validate footer metadata and translate JSON body into HeaderKeyDict.
        """
        timeout_reader = self._make_timeout_reader(footer_iter)
        try:
            footer_body = b''.join(iter(timeout_reader, b''))
        except ChunkReadError:
            raise HTTPClientDisconnect()
        except ChunkReadTimeout:
            raise HTTPRequestTimeout()

        footer_md5 = footer_hdrs.get('Content-MD5')
        if not footer_md5:
            raise HTTPBadRequest(body="no Content-MD5 in footer")
        if footer_md5 != md5(footer_body, usedforsecurity=False).hexdigest():
            raise HTTPUnprocessableEntity(body="footer MD5 mismatch")

        try:
            return HeaderKeyDict(json.loads(footer_body))
        except ValueError:
            raise HTTPBadRequest("invalid JSON for footer doc")

    def _check_container_override(self, update_headers, metadata,
                                  footers=None):
        """
        Applies any overrides to the container update headers.

        Overrides may be in the x-object-sysmeta-container-update- namespace or
        the x-backend-container-update-override- namespace. The former is
        preferred and is used by proxy middlewares. The latter is historical
        but is still used with EC policy PUT requests; for backwards
        compatibility the header names used with EC policy requests have not
        been changed to the sysmeta namespace - that way the EC PUT path of a
        newer proxy will remain compatible with an object server that pre-dates
        the introduction of the x-object-sysmeta-container-update- namespace
        and vice-versa.

        :param update_headers: a dict of headers used in the container update
        :param metadata: a dict that may container override items
        :param footers: another dict that may container override items, at a
                        higher priority than metadata
        """
        footers = footers or {}
        # the order of this list is significant:
        # x-object-sysmeta-container-update-override-* headers take precedence
        # over x-backend-container-update-override-* headers
        override_prefixes = ['x-backend-container-update-override-',
                             OBJECT_SYSMETA_CONTAINER_UPDATE_OVERRIDE_PREFIX]
        for override_prefix in override_prefixes:
            for key, val in metadata.items():
                if key.lower().startswith(override_prefix):
                    override = key.lower().replace(override_prefix, 'x-')
                    update_headers[override] = val
            # apply x-backend-container-update-override* from footers *before*
            # x-object-sysmeta-container-update-override-* from headers
            for key, val in footers.items():
                if key.lower().startswith(override_prefix):
                    override = key.lower().replace(override_prefix, 'x-')
                    update_headers[override] = val

    @public
    @timing_stats()
    def POST(self, request):
        """Handle HTTP POST requests for the Swift Object Server."""
        device, partition, account, container, obj, policy = \
            get_obj_name_and_placement(request)

        req_timestamp = valid_timestamp(request)
        new_delete_at = int(request.headers.get('X-Delete-At') or 0)
        if new_delete_at and new_delete_at < req_timestamp:
            return HTTPBadRequest(body='X-Delete-At in past', request=request,
                                  content_type='text/plain')
        next_part_power = request.headers.get('X-Backend-Next-Part-Power')
        try:
            disk_file = self.get_diskfile(
                device, partition, account, container, obj,
                policy=policy, open_expired=config_true_value(
                    request.headers.get('x-backend-replication', 'false')),
                next_part_power=next_part_power)
        except DiskFileDeviceUnavailable:
            return HTTPInsufficientStorage(drive=device, request=request)
        try:
            orig_metadata = disk_file.read_metadata(current_time=req_timestamp)
        except DiskFileXattrNotSupported:
            return HTTPInsufficientStorage(drive=device, request=request)
        except (DiskFileNotExist, DiskFileQuarantined):
            return HTTPNotFound(request=request)
        orig_timestamp = Timestamp(orig_metadata.get('X-Timestamp', 0))
        orig_ctype_timestamp = disk_file.content_type_timestamp
        req_ctype_time = '0'
        req_ctype = request.headers.get('Content-Type')
        if req_ctype:
            req_ctype_time = request.headers.get('Content-Type-Timestamp',
                                                 req_timestamp.internal)
        req_ctype_timestamp = Timestamp(req_ctype_time)
        if orig_timestamp >= req_timestamp \
                and orig_ctype_timestamp >= req_ctype_timestamp:
            return HTTPConflict(
                request=request,
                headers={'X-Backend-Timestamp': orig_timestamp.internal})

        if req_timestamp > orig_timestamp:
            metadata = {'X-Timestamp': req_timestamp.internal}
            metadata.update(val for val in request.headers.items()
                            if (is_user_meta('object', val[0]) or
                                is_object_transient_sysmeta(val[0])))
            headers_to_copy = (
                request.headers.get(
                    'X-Backend-Replication-Headers', '').split() +
                list(self.allowed_headers))
            for header_key in headers_to_copy:
                if header_key in request.headers:
                    header_caps = bytes_to_wsgi(
                        wsgi_to_bytes(header_key).title())
                    metadata[header_caps] = request.headers[header_key]
            orig_delete_at = int(orig_metadata.get('X-Delete-At') or 0)
            if orig_delete_at != new_delete_at:
                if new_delete_at:
                    self.delete_at_update(
                        'PUT', new_delete_at, account, container, obj, request,
                        device, policy)
                if orig_delete_at:
                    self.delete_at_update('DELETE', orig_delete_at, account,
                                          container, obj, request, device,
                                          policy)
        else:
            # preserve existing metadata, only content-type may be updated
            metadata = dict(disk_file.get_metafile_metadata())

        if req_ctype_timestamp > orig_ctype_timestamp:
            # we have a new content-type, add to metadata and container update
            content_type_headers = {
                'Content-Type': request.headers['Content-Type'],
                'Content-Type-Timestamp': req_ctype_timestamp.internal
            }
            metadata.update(content_type_headers)
        else:
            # send existing content-type with container update
            content_type_headers = {
                'Content-Type': disk_file.content_type,
                'Content-Type-Timestamp': orig_ctype_timestamp.internal
            }
            if orig_ctype_timestamp != disk_file.data_timestamp:
                # only add to metadata if it's not the datafile content-type
                metadata.update(content_type_headers)

        try:
            disk_file.write_metadata(metadata)
        except (DiskFileXattrNotSupported, DiskFileNoSpace):
            return HTTPInsufficientStorage(drive=device, request=request)

        if (content_type_headers['Content-Type-Timestamp']
                != disk_file.data_timestamp):
            # Current content-type is not from the datafile, but the datafile
            # content-type may have a swift_bytes param that was appended by
            # SLO and we must continue to send that with the container update.
            # Do this (rather than use a separate header) for backwards
            # compatibility because there may be 'legacy' container updates in
            # async pending that have content-types with swift_bytes params, so
            # we have to be able to handle those in container server anyway.
            _, swift_bytes = extract_swift_bytes(
                disk_file.get_datafile_metadata()['Content-Type'])
            if swift_bytes:
                content_type_headers['Content-Type'] += (';swift_bytes=%s'
                                                         % swift_bytes)

        update_headers = HeaderKeyDict({
            'x-size': orig_metadata['Content-Length'],
            'x-content-type': content_type_headers['Content-Type'],
            'x-timestamp': disk_file.data_timestamp.internal,
            'x-content-type-timestamp':
            content_type_headers['Content-Type-Timestamp'],
            'x-meta-timestamp': metadata['X-Timestamp'],
            'x-etag': orig_metadata['ETag']})

        # Special cases for backwards compatibility.
        # For EC policy, send X-Object-Sysmeta-Ec-Etag which is same as the
        # X-Backend-Container-Update-Override-Etag value sent with the original
        # PUT. Similarly send X-Object-Sysmeta-Ec-Content-Length which is the
        # same as the X-Backend-Container-Update-Override-Size value. We have
        # to send Etag and size with a POST container update because the
        # original PUT container update may have failed or be in async_pending.
        if 'X-Object-Sysmeta-Ec-Etag' in orig_metadata:
            update_headers['X-Etag'] = orig_metadata[
                'X-Object-Sysmeta-Ec-Etag']
        if 'X-Object-Sysmeta-Ec-Content-Length' in orig_metadata:
            update_headers['X-Size'] = orig_metadata[
                'X-Object-Sysmeta-Ec-Content-Length']

        self._check_container_override(update_headers, orig_metadata)

        # object POST updates are PUT to the container server
        self.container_update(
            'PUT', account, container, obj, request, update_headers,
            device, policy)

        # Add current content-type and sysmeta to response
        resp_headers = {
            'X-Backend-Content-Type': content_type_headers['Content-Type']}
        for key, value in orig_metadata.items():
            if is_sys_meta('object', key):
                resp_headers[key] = value

        return HTTPAccepted(request=request, headers=resp_headers)

    def _pre_create_checks(self, request, device, partition,
                           account, container, obj, policy):
        req_timestamp = valid_timestamp(request)
        error_response = check_object_creation(request, obj)
        if error_response:
            raise error_response
        try:
            fsize = request.message_length()
        except ValueError as e:
            raise HTTPBadRequest(body=str(e), request=request,
                                 content_type='text/plain')
        # In case of multipart-MIME put, the proxy sends a chunked request,
        # but may let us know the real content length so we can verify that
        # we have enough disk space to hold the object.
        if fsize is None:
            fsize = request.headers.get('X-Backend-Obj-Content-Length')
            if fsize is not None:
                try:
                    fsize = int(fsize)
                except ValueError as e:
                    raise HTTPBadRequest(body=str(e), request=request,
                                         content_type='text/plain')
        # SSYNC will include Frag-Index header for subrequests, in which case
        # get_diskfile will ignore non-matching on-disk data files
        frag_index = request.headers.get('X-Backend-Ssync-Frag-Index')
        next_part_power = request.headers.get('X-Backend-Next-Part-Power')
        try:
            disk_file = self.get_diskfile(
                device, partition, account, container, obj,
                policy=policy, frag_index=frag_index,
                next_part_power=next_part_power)
        except DiskFileDeviceUnavailable:
            raise HTTPInsufficientStorage(drive=device, request=request)
        try:
            orig_metadata = disk_file.read_metadata(current_time=req_timestamp)
            orig_timestamp = disk_file.data_timestamp
        except DiskFileXattrNotSupported:
            raise HTTPInsufficientStorage(drive=device, request=request)
        except DiskFileDeleted as e:
            orig_metadata = {}
            orig_timestamp = e.timestamp
        except (DiskFileNotExist, DiskFileQuarantined):
            orig_metadata = {}
            orig_timestamp = Timestamp(0)
        # Checks for If-None-Match
        if request.if_none_match is not None and orig_metadata:
            if '*' in request.if_none_match:
                # File exists already so return 412
                raise HTTPPreconditionFailed(request=request)
            if orig_metadata.get('ETag') in request.if_none_match:
                # The current ETag matches, so raise 412
                raise HTTPPreconditionFailed(request=request)
        if orig_timestamp >= req_timestamp:
            raise HTTPConflict(
                request=request,
                headers={'X-Backend-Timestamp': orig_timestamp.internal})
        return disk_file, fsize, orig_metadata

    def _do_multi_stage_mime_continue_headers(self, request, obj_input):
        """
        If the proxy wants to send us object metadata after the object body, it
        sets some headers. We have to tell the proxy, in the 100 Continue
        response, that we're able to parse a multipart MIME document and
        extract the object and metadata from it. If we don't, then the proxy
        won't actually send the footer metadata.

        If the proxy doesn't want to do any of that, this is the identity
        function for obj_input and multi_stage_mime_state will be False-y.

        :returns: a tuple, (obj_input, multi_stage_mime_state)
        """
        have_metadata_footer = False
        use_multiphase_commit = False

        hundred_continue_headers = []
        if config_true_value(
                request.headers.get(
                    'X-Backend-Obj-Multiphase-Commit')):
            use_multiphase_commit = True
            hundred_continue_headers.append(
                ('X-Obj-Multiphase-Commit', 'yes'))

        if config_true_value(
                request.headers.get('X-Backend-Obj-Metadata-Footer')):
            have_metadata_footer = True
            hundred_continue_headers.append(
                ('X-Obj-Metadata-Footer', 'yes'))

        if have_metadata_footer or use_multiphase_commit:
            obj_input.set_hundred_continue_response_headers(
                hundred_continue_headers)
            mime_boundary = wsgi_to_bytes(request.headers.get(
                'X-Backend-Obj-Multipart-Mime-Boundary'))
            if not mime_boundary:
                raise HTTPBadRequest("no MIME boundary")

            with ChunkReadTimeout(self.client_timeout):
                mime_documents_iter = iter_mime_headers_and_bodies(
                    request.environ['wsgi.input'],
                    mime_boundary, self.network_chunk_size)
                _junk_hdrs, obj_input = next(mime_documents_iter)
            multi_stage_mime_state = {
                'have_metadata_footer': have_metadata_footer,
                'use_multiphase_commit': use_multiphase_commit,
                'mime_documents_iter': mime_documents_iter,
            }
        else:
            multi_stage_mime_state = {}
        return obj_input, multi_stage_mime_state

    def _stage_obj_data(self, request, device, obj_input, writer, fsize):
        """
        Feed the object_input into the writer.

        :returns: a tuple, (upload_size, etag)
        """
        writer.open()
        elapsed_time = 0
        upload_expiration = time.time() + self.max_upload_time
        timeout_reader = self._make_timeout_reader(obj_input)
        for chunk in iter(timeout_reader, b''):
            start_time = time.time()
            if start_time > upload_expiration:
                self.logger.increment('PUT.timeouts')
                raise HTTPRequestTimeout(request=request)
            writer.write(chunk)
            elapsed_time += time.time() - start_time
        upload_size, etag = writer.chunks_finished()
        if fsize is not None and fsize != upload_size:
            raise HTTPClientDisconnect(request=request)
        if upload_size:
            self.logger.transfer_rate(
                'PUT.' + device + '.timing', elapsed_time,
                upload_size)
        return upload_size, etag

    def _get_request_metadata(self, request, upload_size, etag):
        """
        Pull object metadata off the request.

        :returns: metadata, a dict of object metadata
        """
        metadata = {
            'X-Timestamp': request.timestamp.internal,
            'Content-Type': request.headers['content-type'],
            'Content-Length': str(upload_size),
            'ETag': etag,
        }
        metadata.update(val for val in request.headers.items()
                        if (is_sys_or_user_meta('object', val[0]) or
                            is_object_transient_sysmeta(val[0])))
        headers_to_copy = (
            request.headers.get(
                'X-Backend-Replication-Headers', '').split() +
            list(self.allowed_headers))
        for header_key in headers_to_copy:
            if header_key in request.headers:
                header_caps = bytes_to_wsgi(
                    wsgi_to_bytes(header_key).title())
                metadata[header_caps] = request.headers[header_key]
        return metadata

    def _read_mime_footers_metadata(self, have_metadata_footer,
                                    mime_documents_iter, **kwargs):
        """
        Read footer metadata from the bottom of the multi-stage MIME body.

        :returns: metadata, a dict
        """
        if have_metadata_footer:
            metadata = self._read_metadata_footer(
                mime_documents_iter)
            footer_etag = metadata.pop('etag', '').lower()
            if footer_etag:
                metadata['ETag'] = footer_etag
        else:
            metadata = {}
        return metadata

    def _apply_extra_metadata(self, request, metadata, footers_metadata):
        """
        Apply extra metadata precedence to prepare metadata for storage.
        """
        metadata.update(val for val in footers_metadata.items()
                        if (is_sys_or_user_meta('object', val[0]) or
                            is_object_transient_sysmeta(val[0])))
        # N.B. footers_metadata is a HeaderKeyDict
        received_etag = normalize_etag(footers_metadata.get(
            'etag', request.headers.get('etag', '')))
        if received_etag and received_etag != metadata['ETag']:
            raise HTTPUnprocessableEntity(request=request)

    def _send_multi_stage_continue_headers(self, request,
                                           use_multiphase_commit,
                                           mime_documents_iter, **kwargs):
        """
        If the PUT requires a two-phase commit (a data and a commit phase) send
        the proxy server another 100-continue response to indicate that we are
        finished writing object data
        """
        if use_multiphase_commit:
            request.environ['wsgi.input'].\
                send_hundred_continue_response()
            if not self._read_put_commit_message(mime_documents_iter):
                raise HTTPServerError(request=request)

    def _drain_mime_request(self, mime_documents_iter, **kwargs):
        """
        Drain any remaining MIME docs from the socket. There shouldn't be any,
        but we must read the whole request body.
        """
        try:
            while True:
                with ChunkReadTimeout(self.client_timeout):
                    _junk_hdrs, _junk_body = next(mime_documents_iter)
                drain(_junk_body, self.network_chunk_size,
                      self.client_timeout)
        except ChunkReadError:
            raise HTTPClientDisconnect()
        except ChunkReadTimeout:
            raise HTTPRequestTimeout()
        except StopIteration:
            pass

    def _post_commit_updates(self, request, device,
                             account, container, obj, policy,
                             orig_metadata, footers_metadata, metadata):
        orig_delete_at = int(orig_metadata.get('X-Delete-At') or 0)
        new_delete_at = int(request.headers.get('X-Delete-At') or 0)
        if orig_delete_at != new_delete_at:
            if new_delete_at:
                self.delete_at_update(
                    'PUT', new_delete_at, account, container, obj, request,
                    device, policy)
            if orig_delete_at:
                self.delete_at_update(
                    'DELETE', orig_delete_at, account, container, obj,
                    request, device, policy)

        update_headers = HeaderKeyDict({
            'x-size': metadata['Content-Length'],
            'x-content-type': metadata['Content-Type'],
            'x-timestamp': metadata['X-Timestamp'],
            'x-etag': metadata['ETag']})
        # apply any container update header overrides sent with request
        self._check_container_override(update_headers, request.headers,
                                       footers_metadata)
        self.container_update(
            'PUT', account, container, obj, request,
            update_headers, device, policy)

    @public
    @timing_stats()
    def PUT(self, request):
        """Handle HTTP PUT requests for the Swift Object Server."""
        device, partition, account, container, obj, policy = \
            get_obj_name_and_placement(request)
        disk_file, fsize, orig_metadata = self._pre_create_checks(
            request, device, partition, account, container, obj, policy)
        writer = disk_file.writer(size=fsize)
        try:
            obj_input = request.environ['wsgi.input']
            obj_input, multi_stage_mime_state = \
                self._do_multi_stage_mime_continue_headers(request, obj_input)
            upload_size, etag = self._stage_obj_data(
                request, device, obj_input, writer, fsize)
            metadata = self._get_request_metadata(request, upload_size, etag)
            if multi_stage_mime_state:
                footers_metadata = self._read_mime_footers_metadata(
                    **multi_stage_mime_state)
            else:
                footers_metadata = {}
            self._apply_extra_metadata(request, metadata, footers_metadata)
            writer.put(metadata)
            if multi_stage_mime_state:
                self._send_multi_stage_continue_headers(
                    request, **multi_stage_mime_state)
            if not config_true_value(
                    request.headers.get('X-Backend-No-Commit', False)):
                writer.commit(request.timestamp)
            if multi_stage_mime_state:
                self._drain_mime_request(**multi_stage_mime_state)
        except (DiskFileXattrNotSupported, DiskFileNoSpace):
            return HTTPInsufficientStorage(drive=device, request=request)
        except ChunkReadError:
            return HTTPClientDisconnect(request=request)
        except ChunkReadTimeout:
            return HTTPRequestTimeout(request=request)
        finally:
            writer.close()
        self._post_commit_updates(request, device,
                                  account, container, obj, policy,
                                  orig_metadata, footers_metadata, metadata)
        return HTTPCreated(request=request, etag=etag)

    @public
    @timing_stats()
    def GET(self, request):
        """Handle HTTP GET requests for the Swift Object Server."""
        device, partition, account, container, obj, policy = \
            get_obj_name_and_placement(request)
        request.headers.setdefault('X-Timestamp',
                                   normalize_timestamp(time.time()))
        req_timestamp = valid_timestamp(request)
        frag_prefs = safe_json_loads(
            request.headers.get('X-Backend-Fragment-Preferences'))
        try:
            disk_file = self.get_diskfile(
                device, partition, account, container, obj,
                policy=policy, frag_prefs=frag_prefs,
                open_expired=config_true_value(
                    request.headers.get('x-backend-replication', 'false')))
        except DiskFileDeviceUnavailable:
            return HTTPInsufficientStorage(drive=device, request=request)
        try:
            with disk_file.open(current_time=req_timestamp):
                metadata = disk_file.get_metadata()
                ignore_range_headers = set(
                    h.strip().lower()
                    for h in request.headers.get(
                        'X-Backend-Ignore-Range-If-Metadata-Present',
                        '').split(','))
                if ignore_range_headers.intersection(
                        h.lower() for h in metadata):
                    request.headers.pop('Range', None)
                obj_size = int(metadata['Content-Length'])
                file_x_ts = Timestamp(metadata['X-Timestamp'])
                keep_cache = (
                    self.keep_cache_private
                    or (
                        "X-Auth-Token" not in request.headers
                        and "X-Storage-Token" not in request.headers
                    )
                    or (
                        self.keep_cache_slo_manifest
                        and config_true_value(
                            metadata.get("X-Static-Large-Object")
                        )
                    )
                )
                conditional_etag = resolve_etag_is_at_header(request, metadata)
                response = Response(
                    app_iter=disk_file.reader(keep_cache=keep_cache),
                    request=request, conditional_response=True,
                    conditional_etag=conditional_etag)
                response.headers['Content-Type'] = metadata.get(
                    'Content-Type', 'application/octet-stream')
                for key, value in metadata.items():
                    if (is_sys_or_user_meta('object', key) or
                            is_object_transient_sysmeta(key) or
                            key.lower() in self.allowed_headers):
                        response.headers[key] = value
                response.etag = metadata['ETag']
                response.last_modified = file_x_ts.ceil()
                response.content_length = obj_size
                try:
                    response.content_encoding = metadata[
                        'Content-Encoding']
                except KeyError:
                    pass
                response.headers['X-Timestamp'] = file_x_ts.normal
                response.headers['X-Backend-Timestamp'] = file_x_ts.internal
                response.headers['X-Backend-Data-Timestamp'] = \
                    disk_file.data_timestamp.internal
                if disk_file.durable_timestamp:
                    response.headers['X-Backend-Durable-Timestamp'] = \
                        disk_file.durable_timestamp.internal
                response.headers['X-Backend-Fragments'] = \
                    _make_backend_fragments_header(disk_file.fragments)
                resp = request.get_response(response)
        except DiskFileXattrNotSupported:
            return HTTPInsufficientStorage(drive=device, request=request)
        except (DiskFileNotExist, DiskFileQuarantined) as e:
            headers = {}
            if hasattr(e, 'timestamp'):
                headers['X-Backend-Timestamp'] = e.timestamp.internal
            resp = HTTPNotFound(request=request, headers=headers,
                                conditional_response=True)
        return resp

    @public
    @timing_stats(sample_rate=0.8)
    def HEAD(self, request):
        """Handle HTTP HEAD requests for the Swift Object Server."""
        device, partition, account, container, obj, policy = \
            get_obj_name_and_placement(request)
        request.headers.setdefault('X-Timestamp',
                                   normalize_timestamp(time.time()))
        req_timestamp = valid_timestamp(request)
        frag_prefs = safe_json_loads(
            request.headers.get('X-Backend-Fragment-Preferences'))
        try:
            disk_file = self.get_diskfile(
                device, partition, account, container, obj,
                policy=policy, frag_prefs=frag_prefs,
                open_expired=config_true_value(
                    request.headers.get('x-backend-replication', 'false')))
        except DiskFileDeviceUnavailable:
            return HTTPInsufficientStorage(drive=device, request=request)
        try:
            metadata = disk_file.read_metadata(current_time=req_timestamp)
        except DiskFileXattrNotSupported:
            return HTTPInsufficientStorage(drive=device, request=request)
        except (DiskFileNotExist, DiskFileQuarantined) as e:
            headers = {}
            if hasattr(e, 'timestamp'):
                headers['X-Backend-Timestamp'] = e.timestamp.internal
            return HTTPNotFound(request=request, headers=headers,
                                conditional_response=True)
        conditional_etag = resolve_etag_is_at_header(request, metadata)
        response = Response(request=request, conditional_response=True,
                            conditional_etag=conditional_etag)
        response.headers['Content-Type'] = metadata.get(
            'Content-Type', 'application/octet-stream')
        for key, value in metadata.items():
            if (is_sys_or_user_meta('object', key) or
                    is_object_transient_sysmeta(key) or
                    key.lower() in self.allowed_headers):
                response.headers[key] = value
        response.etag = metadata['ETag']
        ts = Timestamp(metadata['X-Timestamp'])
        response.last_modified = ts.ceil()
        # Needed for container sync feature
        response.headers['X-Timestamp'] = ts.normal
        response.headers['X-Backend-Timestamp'] = ts.internal
        response.headers['X-Backend-Data-Timestamp'] = \
            disk_file.data_timestamp.internal
        if disk_file.durable_timestamp:
            response.headers['X-Backend-Durable-Timestamp'] = \
                disk_file.durable_timestamp.internal
        response.headers['X-Backend-Fragments'] = \
            _make_backend_fragments_header(disk_file.fragments)
        response.content_length = int(metadata['Content-Length'])
        try:
            response.content_encoding = metadata['Content-Encoding']
        except KeyError:
            pass
        return response

    @public
    @timing_stats()
    def DELETE(self, request):
        """Handle HTTP DELETE requests for the Swift Object Server."""
        device, partition, account, container, obj, policy = \
            get_obj_name_and_placement(request)
        req_timestamp = valid_timestamp(request)
        next_part_power = request.headers.get('X-Backend-Next-Part-Power')
        try:
            disk_file = self.get_diskfile(
                device, partition, account, container, obj,
                policy=policy, next_part_power=next_part_power)
        except DiskFileDeviceUnavailable:
            return HTTPInsufficientStorage(drive=device, request=request)
        try:
            orig_metadata = disk_file.read_metadata(current_time=req_timestamp)
        except DiskFileXattrNotSupported:
            return HTTPInsufficientStorage(drive=device, request=request)
        except DiskFileExpired as e:
            orig_timestamp = e.timestamp
            orig_metadata = e.metadata
            response_class = HTTPNotFound
        except DiskFileDeleted as e:
            orig_timestamp = e.timestamp
            orig_metadata = {}
            response_class = HTTPNotFound
        except (DiskFileNotExist, DiskFileQuarantined):
            orig_timestamp = 0
            orig_metadata = {}
            response_class = HTTPNotFound
        else:
            orig_timestamp = disk_file.data_timestamp
            if orig_timestamp < req_timestamp:
                response_class = HTTPNoContent
            else:
                response_class = HTTPConflict
        response_timestamp = max(orig_timestamp, req_timestamp)
        orig_delete_at = Timestamp(orig_metadata.get('X-Delete-At') or 0)
        try:
            req_if_delete_at_val = request.headers['x-if-delete-at']
            req_if_delete_at = Timestamp(req_if_delete_at_val)
        except KeyError:
            pass
        except ValueError:
            return HTTPBadRequest(
                request=request,
                body='Bad X-If-Delete-At header value')
        else:
            # request includes x-if-delete-at; we must not place a tombstone
            # if we can not verify the x-if-delete-at time
            if not orig_timestamp:
                # no object found at all
                return HTTPNotFound()
            if orig_timestamp >= req_timestamp:
                # Found a newer object -- return 409 as work item is stale
                return HTTPConflict()
            if orig_delete_at != req_if_delete_at:
                return HTTPPreconditionFailed(
                    request=request,
                    body='X-If-Delete-At and X-Delete-At do not match')
            else:
                # differentiate success from no object at all
                response_class = HTTPNoContent
        if orig_delete_at:
            self.delete_at_update('DELETE', orig_delete_at, account,
                                  container, obj, request, device,
                                  policy)
        if orig_timestamp < req_timestamp:
            try:
                disk_file.delete(req_timestamp)
            except DiskFileNoSpace:
                return HTTPInsufficientStorage(drive=device, request=request)
            self.container_update(
                'DELETE', account, container, obj, request,
                HeaderKeyDict({'x-timestamp': req_timestamp.internal}),
                device, policy)
        return response_class(
            request=request,
            headers={'X-Backend-Timestamp': response_timestamp.internal,
                     'X-Backend-Content-Type': orig_metadata.get(
                         'Content-Type', '')})

    @public
    @replication
    @timing_stats(sample_rate=0.1)
    def REPLICATE(self, request):
        """
        Handle REPLICATE requests for the Swift Object Server.  This is used
        by the object replicator to get hashes for directories.

        Note that the name REPLICATE is preserved for historical reasons as
        this verb really just returns the hashes information for the specified
        parameters and is used, for example, by both replication and EC.
        """
        device, partition, suffix_parts, policy = \
            get_name_and_placement(request, 2, 3, True)
        suffixes = suffix_parts.split('-') if suffix_parts else []
        try:
            hashes = self._diskfile_router[policy].get_hashes(
                device, partition, suffixes, policy,
                skip_rehash=bool(suffixes))
        except DiskFileDeviceUnavailable:
            resp = HTTPInsufficientStorage(drive=device, request=request)
        else:
            # force pickle protocol for compatibility with py2 nodes
            resp = Response(body=pickle.dumps(hashes, protocol=2))
        return resp

    @public
    @replication
    @timing_stats(sample_rate=0.1)
    def SSYNC(self, request):
        # the ssync sender may want to send PUT subrequests for non-durable
        # data that should not be committed; legacy behaviour has been to
        # commit all PUTs (subject to EC footer metadata), so we need to
        # indicate to the sender that this object server has been upgraded to
        # understand the X-Backend-No-Commit header.
        headers = {'X-Backend-Accept-No-Commit': True}
        return Response(app_iter=ssync_receiver.Receiver(self, request)(),
                        headers=headers)

    def __call__(self, env, start_response):
        """WSGI Application entry point for the Swift Object Server."""
        start_time = time.time()
        req = Request(env)
        self.logger.txn_id = req.headers.get('x-trans-id', None)

        if not check_utf8(wsgi_to_str(req.path_info), internal=True):
            res = HTTPPreconditionFailed(body='Invalid UTF8 or contains NULL')
        else:
            try:
                # disallow methods which have not been marked 'public'
                if req.method not in self.allowed_methods:
                    res = HTTPMethodNotAllowed()
                else:
                    res = getattr(self, req.method)(req)
            except DiskFileCollision:
                res = HTTPForbidden(request=req)
            except HTTPException as error_response:
                res = error_response
            except (Exception, Timeout):
                self.logger.exception(
                    'ERROR __call__ error with %(method)s'
                    ' %(path)s ', {'method': req.method, 'path': req.path})
                res = HTTPInternalServerError(body=traceback.format_exc())
        trans_time = time.time() - start_time
        res.fix_conditional_response()
        if self.log_requests:
            log_line = get_log_line(req, res, trans_time, '', self.log_format,
                                    self.anonymization_method,
                                    self.anonymization_salt)
            if req.method in ('REPLICATE', 'SSYNC') or \
                    'X-Backend-Replication' in req.headers:
                self.logger.debug(log_line)
            else:
                self.logger.info(log_line)
        if req.method in ('PUT', 'DELETE'):
            slow = self.slow - trans_time
            if slow > 0:
                sleep(slow)

        # To be able to zero-copy send the object, we need a few things.
        # First, we have to be responding successfully to a GET, or else we're
        # not sending the object. Second, we have to be able to extract the
        # socket file descriptor from the WSGI input object. Third, the
        # diskfile has to support zero-copy send.
        #
        # There's a good chance that this could work for 206 responses too,
        # but the common case is sending the whole object, so we'll start
        # there.
        if req.method == 'GET' and res.status_int == 200 and \
           isinstance(env['wsgi.input'], wsgi.Input):
            app_iter = getattr(res, 'app_iter', None)
            checker = getattr(app_iter, 'can_zero_copy_send', None)
            if checker and checker():
                # For any kind of zero-copy thing like sendfile or splice, we
                # need the file descriptor. Eventlet doesn't provide a clean
                # way of getting that, so we resort to this.
                wsock = env['wsgi.input'].get_socket()
                wsockfd = wsock.fileno()

                # Don't call zero_copy_send() until after we force the HTTP
                # headers out of Eventlet and into the socket.
                def zero_copy_iter():
                    # If possible, set TCP_CORK so that headers don't
                    # immediately go on the wire, but instead, wait for some
                    # response body to make the TCP frames as large as
                    # possible (and hence as few packets as possible).
                    #
                    # On non-Linux systems, we might consider TCP_NODELAY, but
                    # since the only known zero-copy-capable diskfile uses
                    # Linux-specific syscalls, we'll defer that work until
                    # someone needs it.
                    if hasattr(socket, 'TCP_CORK'):
                        wsock.setsockopt(socket.IPPROTO_TCP,
                                         socket.TCP_CORK, 1)
                    yield EventletPlungerString()
                    try:
                        app_iter.zero_copy_send(wsockfd)
                    except Exception:
                        self.logger.exception("zero_copy_send() blew up")
                        raise
                    yield b''

                # Get headers ready to go out
                res(env, start_response)
                return zero_copy_iter()
            else:
                return res(env, start_response)
        else:
            return res(env, start_response)


def global_conf_callback(preloaded_app_conf, global_conf):
    """
    Callback for swift.common.wsgi.run_wsgi during the global_conf
    creation so that we can add our replication_semaphore, used to
    limit the number of concurrent SSYNC_REQUESTS across all
    workers.

    :param preloaded_app_conf: The preloaded conf for the WSGI app.
                               This conf instance will go away, so
                               just read from it, don't write.
    :param global_conf: The global conf that will eventually be
                        passed to the app_factory function later.
                        This conf is created before the worker
                        subprocesses are forked, so can be useful to
                        set up semaphores, shared memory, etc.
    """
    replication_concurrency = int(
        preloaded_app_conf.get('replication_concurrency') or 4)
    if replication_concurrency:
        # Have to put the value in a list so it can get past paste
        global_conf['replication_semaphore'] = [
            multiprocessing.BoundedSemaphore(replication_concurrency)]


def app_factory(global_conf, **local_conf):
    """paste.deploy app factory for creating WSGI object server apps"""
    conf = global_conf.copy()
    conf.update(local_conf)
    return ObjectController(conf)
