text: # Copyright (c) 2010-2013 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.
  
  """
  Disk File Interface for the Swift Object Server
  
  The `DiskFile`, `DiskFileWriter` and `DiskFileReader` classes combined define
  the on-disk abstraction layer for supporting the object server REST API
  interfaces (excluding `REPLICATE`). Other implementations wishing to provide
  an alternative backend for the object server must implement the three
  classes. An example alternative implementation can be found in the
  `mem_server.py` and `mem_diskfile.py` modules along size this one.
  
  The `DiskFileManager` is a reference implemenation specific class and is not
  part of the backend API.
  
  The remaining methods in this module are considered implementation specific and
  are also not considered part of the backend API.
  """
  
  import cPickle as pickle
  import errno
  import os
  import time
  import uuid
  import hashlib
  import logging
  import traceback
  from os.path import basename, dirname, exists, getmtime, join
  from random import shuffle
  from tempfile import mkstemp
  from contextlib import contextmanager
  from collections import defaultdict
  
  from xattr import getxattr, setxattr
  from eventlet import Timeout
  
  from swift import gettext_ as _
  from swift.common.constraints import check_mount
  from swift.common.utils import mkdirs, normalize_timestamp, \
      storage_directory, hash_path, renamer, fallocate, fsync, \
      fdatasync, drop_buffer_cache, ThreadPool, lock_path, write_pickle, \
      config_true_value, listdir, split_path, ismount, remove_file
  from swift.common.exceptions import DiskFileQuarantined, DiskFileNotExist, \
      DiskFileCollision, DiskFileNoSpace, DiskFileDeviceUnavailable, \
      DiskFileDeleted, DiskFileError, DiskFileNotOpen, PathNotDir, \
      ReplicationLockTimeout, DiskFileExpired
  from swift.common.swob import multi_range_iterator
  
  
  PICKLE_PROTOCOL = 2
  ONE_WEEK = 604800
  HASH_FILE = 'hashes.pkl'
  METADATA_KEY = 'user.swift.metadata'
  # These are system-set metadata keys that cannot be changed with a POST.
  # They should be lowercase.
  DATAFILE_SYSTEM_META = set('content-length content-type deleted etag'.split())
  DATADIR = 'objects'
  ASYNCDIR = 'async_pending'
  
  
  def read_metadata(fd):
      """
      Helper function to read the pickled metadata from an object file.
  
      :param fd: file descriptor or filename to load the metadata from
  
      :returns: dictionary of metadata
      """
      metadata = ''
      key = 0
      try:
          while True:
              metadata += getxattr(fd, '%s%s' % (METADATA_KEY, (key or '')))
              key += 1
      except IOError:
          pass
      return pickle.loads(metadata)
  
  
  def write_metadata(fd, metadata):
      """
      Helper function to write pickled metadata for an object file.
  
      :param fd: file descriptor or filename to write the metadata
      :param metadata: metadata to write
      """
      metastr = pickle.dumps(metadata, PICKLE_PROTOCOL)
      key = 0
      while metastr:
          setxattr(fd, '%s%s' % (METADATA_KEY, key or ''), metastr[:254])
          metastr = metastr[254:]
          key += 1
  
  
  def quarantine_renamer(device_path, corrupted_file_path):
      """
      In the case that a file is corrupted, move it to a quarantined
      area to allow replication to fix it.
  
      :params device_path: The path to the device the corrupted file is on.
      :params corrupted_file_path: The path to the file you want quarantined.
  
      :returns: path (str) of directory the file was moved to
      :raises OSError: re-raises non errno.EEXIST / errno.ENOTEMPTY
                       exceptions from rename
      """
      from_dir = dirname(corrupted_file_path)
      to_dir = join(device_path, 'quarantined', 'objects', basename(from_dir))
      invalidate_hash(dirname(from_dir))
      try:
          renamer(from_dir, to_dir)
      except OSError as e:
          if e.errno not in (errno.EEXIST, errno.ENOTEMPTY):
              raise
          to_dir = "%s-%s" % (to_dir, uuid.uuid4().hex)
          renamer(from_dir, to_dir)
      return to_dir
  
  
  def get_ondisk_files(files, datadir):
      """
      Given a simple list of files names, determine the files to use.
  
      :params files: simple set of files as a python list
      :params datadir: directory name files are from for convenience
      :returns: a tuple of data, meta and ts (tombstone) files, in one of
                two states:
  
      * ts_file is not None, data_file is None, meta_file is None
  
        object is considered deleted
  
      * data_file is not None, ts_file is None
  
        object exists, and optionally has fast-POST metadata
      """
      files.sort(reverse=True)
      data_file = meta_file = ts_file = None
      for afile in files:
          assert ts_file is None, "On-disk file search loop" \
              " continuing after tombstone, %s, encountered" % ts_file
          assert data_file is None, "On-disk file search loop" \
              " continuing after data file, %s, encountered" % data_file
          if afile.endswith('.ts'):
              meta_file = None
              ts_file = join(datadir, afile)
              break
          if afile.endswith('.meta') and not meta_file:
              meta_file = join(datadir, afile)
              # NOTE: this does not exit this loop, since a fast-POST
              # operation just updates metadata, writing one or more
              # .meta files, the data file will have an older timestamp,
              # so we keep looking.
              continue
          if afile.endswith('.data'):
              data_file = join(datadir, afile)
              break
      assert ((data_file is None and meta_file is None and ts_file is None)
              or (ts_file is not None and data_file is None
                  and meta_file is None)
              or (data_file is not None and ts_file is None)), \
          "On-disk file search algorithm contract is broken: data_file:" \
          " %s, meta_file: %s, ts_file: %s" % (data_file, meta_file, ts_file)
      return data_file, meta_file, ts_file
  
  
  def hash_cleanup_listdir(hsh_path, reclaim_age=ONE_WEEK):
      """
      List contents of a hash directory and clean up any old files.
  
      :param hsh_path: object hash path
      :param reclaim_age: age in seconds at which to remove tombstones
      :returns: list of files remaining in the directory, reverse sorted
      """
      files = listdir(hsh_path)
      if len(files) == 1:
          if files[0].endswith('.ts'):
              # remove tombstones older than reclaim_age
              ts = files[0].rsplit('.', 1)[0]
              if (time.time() - float(ts)) > reclaim_age:
                  remove_file(join(hsh_path, files[0]))
                  files.remove(files[0])
      elif files:
          files.sort(reverse=True)
          data_file, meta_file, ts_file = get_ondisk_files(files, '')
          newest_file = data_file or ts_file
          for filename in list(files):
              if ((filename < newest_file)
                      or (meta_file
                          and filename.endswith('.meta')
                          and filename < meta_file)):
                  remove_file(join(hsh_path, filename))
                  files.remove(filename)
      return files
  
  
  def hash_suffix(path, reclaim_age):
      """
      Performs reclamation and returns an md5 of all (remaining) files.
  
      :param reclaim_age: age in seconds at which to remove tombstones
      :raises PathNotDir: if given path is not a valid directory
      :raises OSError: for non-ENOTDIR errors
      """
      md5 = hashlib.md5()
      try:
          path_contents = sorted(os.listdir(path))
      except OSError as err:
          if err.errno in (errno.ENOTDIR, errno.ENOENT):
              raise PathNotDir()
          raise
      for hsh in path_contents:
          hsh_path = join(path, hsh)
          try:
              files = hash_cleanup_listdir(hsh_path, reclaim_age)
          except OSError as err:
              if err.errno == errno.ENOTDIR:
                  partition_path = dirname(path)
                  objects_path = dirname(partition_path)
                  device_path = dirname(objects_path)
                  quar_path = quarantine_renamer(device_path, hsh_path)
                  logging.exception(
                      _('Quarantined %s to %s because it is not a directory') %
                      (hsh_path, quar_path))
                  continue
              raise
          if not files:
              try:
                  os.rmdir(hsh_path)
              except OSError:
                  pass
          for filename in files:
              md5.update(filename)
      try:
          os.rmdir(path)
      except OSError:
          pass
      return md5.hexdigest()
  
  
  def invalidate_hash(suffix_dir):
      """
      Invalidates the hash for a suffix_dir in the partition's hashes file.
  
      :param suffix_dir: absolute path to suffix dir whose hash needs
                         invalidating
      """
  
      suffix = basename(suffix_dir)
      partition_dir = dirname(suffix_dir)
      hashes_file = join(partition_dir, HASH_FILE)
      with lock_path(partition_dir):
          try:
              with open(hashes_file, 'rb') as fp:
                  hashes = pickle.load(fp)
              if suffix in hashes and not hashes[suffix]:
                  return
          except Exception:
              return
          hashes[suffix] = None
          write_pickle(hashes, hashes_file, partition_dir, PICKLE_PROTOCOL)
  
  
  def get_hashes(partition_dir, recalculate=None, do_listdir=False,
                 reclaim_age=ONE_WEEK):
      """
      Get a list of hashes for the suffix dir.  do_listdir causes it to mistrust
      the hash cache for suffix existence at the (unexpectedly high) cost of a
      listdir.  reclaim_age is just passed on to hash_suffix.
  
      :param partition_dir: absolute path of partition to get hashes for
      :param recalculate: list of suffixes which should be recalculated when got
      :param do_listdir: force existence check for all hashes in the partition
      :param reclaim_age: age at which to remove tombstones
  
      :returns: tuple of (number of suffix dirs hashed, dictionary of hashes)
      """
  
      hashed = 0
      hashes_file = join(partition_dir, HASH_FILE)
      modified = False
      force_rewrite = False
      hashes = {}
      mtime = -1
  
      if recalculate is None:
          recalculate = []
  
      try:
          with open(hashes_file, 'rb') as fp:
              hashes = pickle.load(fp)
          mtime = getmtime(hashes_file)
      except Exception:
          do_listdir = True
          force_rewrite = True
      if do_listdir:
          for suff in os.listdir(partition_dir):
              if len(suff) == 3:
                  hashes.setdefault(suff, None)
          modified = True
      hashes.update((hash_, None) for hash_ in recalculate)
      for suffix, hash_ in hashes.items():
          if not hash_:
              suffix_dir = join(partition_dir, suffix)
              try:
                  hashes[suffix] = hash_suffix(suffix_dir, reclaim_age)
                  hashed += 1
              except PathNotDir:
                  del hashes[suffix]
              except OSError:
                  logging.exception(_('Error hashing suffix'))
              modified = True
      if modified:
          with lock_path(partition_dir):
              if force_rewrite or not exists(hashes_file) or \
                      getmtime(hashes_file) == mtime:
                  write_pickle(
                      hashes, hashes_file, partition_dir, PICKLE_PROTOCOL)
                  return hashed, hashes
          return get_hashes(partition_dir, recalculate, do_listdir,
                            reclaim_age)
      else:
          return hashed, hashes
  
  
  class AuditLocation(object):
      """
      Represents an object location to be audited.
  
      Other than being a bucket of data, the only useful thing this does is
      stringify to a filesystem path so the auditor's logs look okay.
      """
  
      def __init__(self, path, device, partition):
          self.path, self.device, self.partition = path, device, partition
  
      def __str__(self):
          return str(self.path)
  
  
  def object_audit_location_generator(devices, mount_check=True, logger=None,
                                      device_dirs=None):
      """
      Given a devices path (e.g. "/srv/node"), yield an AuditLocation for all
      objects stored under that directory if device_dirs isn't set.  If
      device_dirs is set, only yield AuditLocation for the objects under the
      entries in device_dirs. The AuditLocation only knows the path to the hash
      directory, not to the .data file therein (if any). This is to avoid a
      double listdir(hash_dir); the DiskFile object will always do one, so
      we don't.
  
      :param devices: parent directory of the devices to be audited
      :param mount_check: flag to check if a mount check should be performed
                          on devices
      :param logger: a logger object
      :device_dirs: a list of directories under devices to traverse
      """
      if not device_dirs:
          device_dirs = listdir(devices)
      else:
          # remove bogus devices and duplicates from device_dirs
          device_dirs = list(
              set(listdir(devices)).intersection(set(device_dirs)))
      # randomize devices in case of process restart before sweep completed
      shuffle(device_dirs)
  
      for device in device_dirs:
          if mount_check and not \
                  ismount(os.path.join(devices, device)):
              if logger:
                  logger.debug(
                      _('Skipping %s as it is not mounted'), device)
              continue
          datadir_path = os.path.join(devices, device, DATADIR)
          partitions = listdir(datadir_path)
          for partition in partitions:
              part_path = os.path.join(datadir_path, partition)
              try:
                  suffixes = listdir(part_path)
              except OSError as e:
                  if e.errno != errno.ENOTDIR:
                      raise
                  continue
              for asuffix in suffixes:
                  suff_path = os.path.join(part_path, asuffix)
                  try:
                      hashes = listdir(suff_path)
                  except OSError as e:
                      if e.errno != errno.ENOTDIR:
                          raise
                      continue
                  for hsh in hashes:
                      hsh_path = os.path.join(suff_path, hsh)
                      yield AuditLocation(hsh_path, device, partition)
  
  
  class DiskFileManager(object):
      """
      Management class for devices, providing common place for shared parameters
      and methods not provided by the DiskFile class (which primarily services
      the object server REST API layer).
  
      The `get_diskfile()` method is how this implementation creates a `DiskFile`
      object.
  
      .. note::
  
          This class is reference implementation specific and not part of the
          pluggable on-disk backend API.
  
      .. note::
  
          TODO(portante): Not sure what the right name to recommend here, as
          "manager" seemed generic enough, though suggestions are welcome.
  
      :param conf: caller provided configuration object
      :param logger: caller provided logger
      """
      def __init__(self, conf, logger):
          self.logger = logger
          self.devices = conf.get('devices', '/srv/node')
          self.disk_chunk_size = int(conf.get('disk_chunk_size', 65536))
          self.keep_cache_size = int(conf.get('keep_cache_size', 5242880))
          self.bytes_per_sync = int(conf.get('mb_per_sync', 512)) * 1024 * 1024
          self.mount_check = config_true_value(conf.get('mount_check', 'true'))
          self.reclaim_age = int(conf.get('reclaim_age', ONE_WEEK))
          self.replication_one_per_device = config_true_value(
              conf.get('replication_one_per_device', 'true'))
          self.replication_lock_timeout = int(conf.get(
              'replication_lock_timeout', 15))
          threads_per_disk = int(conf.get('threads_per_disk', '0'))
          self.threadpools = defaultdict(
              lambda: ThreadPool(nthreads=threads_per_disk))
  
      def construct_dev_path(self, device):
          """
          Construct the path to a device without checking if it is mounted.
  
          :param device: name of target device
          :returns: full path to the device
          """
          return os.path.join(self.devices, device)
  
      def get_dev_path(self, device, mount_check=None):
          """
          Return the path to a device, checking to see that it is a proper mount
          point based on a configuration parameter.
  
          :param device: name of target device
          :param mount_check: whether or not to check mountedness of device.
                              Defaults to bool(self.mount_check).
          :returns: full path to the device, None if the path to the device is
                    not a proper mount point.
          """
          should_check = self.mount_check if mount_check is None else mount_check
          if should_check and not check_mount(self.devices, device):
              dev_path = None
          else:
              dev_path = os.path.join(self.devices, device)
          return dev_path
  
      @contextmanager
      def replication_lock(self, device):
          """
          A context manager that will lock on the device given, if
          configured to do so.
  
          :raises ReplicationLockTimeout: If the lock on the device
              cannot be granted within the configured timeout.
          """
          if self.replication_one_per_device:
              dev_path = self.get_dev_path(device)
              with lock_path(
                      dev_path,
                      timeout=self.replication_lock_timeout,
                      timeout_class=ReplicationLockTimeout):
                  yield True
          else:
              yield True
  
      def pickle_async_update(self, device, account, container, obj, data,
                              timestamp):
          device_path = self.construct_dev_path(device)
          async_dir = os.path.join(device_path, ASYNCDIR)
          ohash = hash_path(account, container, obj)
          self.threadpools[device].run_in_thread(
              write_pickle,
              data,
              os.path.join(async_dir, ohash[-3:], ohash + '-' +
                           normalize_timestamp(timestamp)),
              os.path.join(device_path, 'tmp'))
          self.logger.increment('async_pendings')
  
      def get_diskfile(self, device, partition, account, container, obj,
                       **kwargs):
          dev_path = self.get_dev_path(device)
          if not dev_path:
              raise DiskFileDeviceUnavailable()
          return DiskFile(self, dev_path, self.threadpools[device],
                          partition, account, container, obj, **kwargs)
  
      def object_audit_location_generator(self, device_dirs=None):
          return object_audit_location_generator(self.devices, self.mount_check,
                                                 self.logger, device_dirs)
  
      def get_diskfile_from_audit_location(self, audit_location):
          dev_path = self.get_dev_path(audit_location.device, mount_check=False)
          return DiskFile.from_hash_dir(
              self, audit_location.path, dev_path,
              audit_location.partition)
  
      def get_diskfile_from_hash(self, device, partition, object_hash, **kwargs):
          """
          Returns a DiskFile instance for an object at the given
          object_hash. Just in case someone thinks of refactoring, be
          sure DiskFileDeleted is *not* raised, but the DiskFile
          instance representing the tombstoned object is returned
          instead.
  
          :raises DiskFileNotExist: if the object does not exist
          """
          dev_path = self.get_dev_path(device)
          if not dev_path:
              raise DiskFileDeviceUnavailable()
          object_path = os.path.join(
              dev_path, DATADIR, partition, object_hash[-3:], object_hash)
          try:
              filenames = hash_cleanup_listdir(object_path, self.reclaim_age)
          except OSError as err:
              if err.errno == errno.ENOTDIR:
                  quar_path = quarantine_renamer(dev_path, object_path)
                  logging.exception(
                      _('Quarantined %s to %s because it is not a '
                        'directory') % (object_path, quar_path))
                  raise DiskFileNotExist()
              if err.errno != errno.ENOENT:
                  raise
              raise DiskFileNotExist()
          if not filenames:
              raise DiskFileNotExist()
          try:
              metadata = read_metadata(os.path.join(object_path, filenames[-1]))
          except EOFError:
              raise DiskFileNotExist()
          try:
              account, container, obj = split_path(
                  metadata.get('name', ''), 3, 3, True)
          except ValueError:
              raise DiskFileNotExist()
          return DiskFile(self, dev_path, self.threadpools[device],
                          partition, account, container, obj, **kwargs)
  
      def get_hashes(self, device, partition, suffix):
          dev_path = self.get_dev_path(device)
          if not dev_path:
              raise DiskFileDeviceUnavailable()
          partition_path = os.path.join(dev_path, DATADIR, partition)
          if not os.path.exists(partition_path):
              mkdirs(partition_path)
          suffixes = suffix.split('-') if suffix else []
          _junk, hashes = self.threadpools[device].force_run_in_thread(
              get_hashes, partition_path, recalculate=suffixes)
          return hashes
  
      def _listdir(self, path):
          try:
              return os.listdir(path)
          except OSError as err:
              if err.errno != errno.ENOENT:
                  self.logger.error(
                      'ERROR: Skipping %r due to error with listdir attempt: %s',
                      path, err)
          return []
  
      def yield_suffixes(self, device, partition):
          """
          Yields tuples of (full_path, suffix_only) for suffixes stored
          on the given device and partition.
          """
          dev_path = self.get_dev_path(device)
          if not dev_path:
              raise DiskFileDeviceUnavailable()
          partition_path = os.path.join(dev_path, DATADIR, partition)
          for suffix in self._listdir(partition_path):
              if len(suffix) != 3:
                  continue
              try:
                  int(suffix, 16)
              except ValueError:
                  continue
              yield (os.path.join(partition_path, suffix), suffix)
  
      def yield_hashes(self, device, partition, suffixes=None):
          """
          Yields tuples of (full_path, hash_only, timestamp) for object
          information stored for the given device, partition, and
          (optionally) suffixes. If suffixes is None, all stored
          suffixes will be searched for object hashes. Note that if
          suffixes is not None but empty, such as [], then nothing will
          be yielded.
          """
          dev_path = self.get_dev_path(device)
          if not dev_path:
              raise DiskFileDeviceUnavailable()
          if suffixes is None:
              suffixes = self.yield_suffixes(device, partition)
          else:
              partition_path = os.path.join(dev_path, DATADIR, partition)
              suffixes = (
                  (os.path.join(partition_path, suffix), suffix)
                  for suffix in suffixes)
          for suffix_path, suffix in suffixes:
              for object_hash in self._listdir(suffix_path):
                  object_path = os.path.join(suffix_path, object_hash)
                  for name in hash_cleanup_listdir(
                          object_path, self.reclaim_age):
                      ts, ext = name.rsplit('.', 1)
                      yield (object_path, object_hash, ts)
                      break
  
  
  class DiskFileWriter(object):
      """
      Encapsulation of the write context for servicing PUT REST API
      requests. Serves as the context manager object for the
      :class:`swift.obj.diskfile.DiskFile` class's
      :func:`swift.obj.diskfile.DiskFile.create` method.
  
      .. note::
  
          It is the responsibility of the
          :func:`swift.obj.diskfile.DiskFile.create` method context manager to
          close the open file descriptor.
  
      .. note::
  
          The arguments to the constructor are considered implementation
          specific. The API does not define the constructor arguments.
  
      :param name: name of object from REST API
      :param datadir: on-disk directory object will end up in on
                      :func:`swift.obj.diskfile.DiskFileWriter.put`
      :param fd: open file descriptor of temporary file to receive data
      :param tmppath: full path name of the opened file descriptor
      :param bytes_per_sync: number bytes written between sync calls
      :param threadpool: internal thread pool to use for disk operations
      """
      def __init__(self, name, datadir, fd, tmppath, bytes_per_sync, threadpool):
          # Parameter tracking
          self._name = name
          self._datadir = datadir
          self._fd = fd
          self._tmppath = tmppath
          self._bytes_per_sync = bytes_per_sync
          self._threadpool = threadpool
  
          # Internal attributes
          self._upload_size = 0
          self._last_sync = 0
          self._extension = '.data'
  
      def write(self, chunk):
          """
          Write a chunk of data to disk. All invocations of this method must
          come before invoking the :func:
  
          For this implementation, the data is written into a temporary file.
  
          :param chunk: the chunk of data to write as a string object
  
          :returns: the total number of bytes written to an object
          """
  
          def _write_entire_chunk(chunk):
              while chunk:
                  written = os.write(self._fd, chunk)
                  self._upload_size += written
                  chunk = chunk[written:]
  
          self._threadpool.run_in_thread(_write_entire_chunk, chunk)
  
          # For large files sync every 512MB (by default) written
          diff = self._upload_size - self._last_sync
          if diff >= self._bytes_per_sync:
              self._threadpool.force_run_in_thread(fdatasync, self._fd)
              drop_buffer_cache(self._fd, self._last_sync, diff)
              self._last_sync = self._upload_size
  
          return self._upload_size
  
      def _finalize_put(self, metadata, target_path):
          # Write the metadata before calling fsync() so that both data and
          # metadata are flushed to disk.
          write_metadata(self._fd, metadata)
          # We call fsync() before calling drop_cache() to lower the amount of
          # redundant work the drop cache code will perform on the pages (now
          # that after fsync the pages will be all clean).
          fsync(self._fd)
          # From the Department of the Redundancy Department, make sure we call
          # drop_cache() after fsync() to avoid redundant work (pages all
          # clean).
          drop_buffer_cache(self._fd, 0, self._upload_size)
          invalidate_hash(dirname(self._datadir))
          # After the rename completes, this object will be available for other
          # requests to reference.
          renamer(self._tmppath, target_path)
          try:
              hash_cleanup_listdir(self._datadir)
          except OSError:
              logging.exception(_('Problem cleaning up %s'), self._datadir)
  
      def put(self, metadata):
          """
          Finalize writing the file on disk.
  
          For this implementation, this method is responsible for renaming the
          temporary file to the final name and directory location.  This method
          should be called after the final call to
          :func:`swift.obj.diskfile.DiskFileWriter.write`.
  
          :param metadata: dictionary of metadata to be associated with the
                           object
          """
          timestamp = normalize_timestamp(metadata['X-Timestamp'])
          metadata['name'] = self._name
          target_path = join(self._datadir, timestamp + self._extension)
  
          self._threadpool.force_run_in_thread(
              self._finalize_put, metadata, target_path)
  
  
  class DiskFileReader(object):
      """
      Encapsulation of the WSGI read context for servicing GET REST API
      requests. Serves as the context manager object for the
      :class:`swift.obj.diskfile.DiskFile` class's
      :func:`swift.obj.diskfile.DiskFile.reader` method.
  
      .. note::
  
          The quarantining behavior of this method is considered implementation
          specific, and is not required of the API.
  
      .. note::
  
          The arguments to the constructor are considered implementation
          specific. The API does not define the constructor arguments.
  
      :param fp: open file object pointer reference
      :param data_file: on-disk data file name for the object
      :param obj_size: verified on-disk size of the object
      :param etag: expected metadata etag value for entire file
      :param threadpool: thread pool to use for read operations
      :param disk_chunk_size: size of reads from disk in bytes
      :param keep_cache_size: maximum object size that will be kept in cache
      :param device_path: on-disk device path, used when quarantining an obj
      :param logger: logger caller wants this object to use
      :param quarantine_hook: 1-arg callable called w/reason when quarantined
      :param keep_cache: should resulting reads be kept in the buffer cache
      """
      def __init__(self, fp, data_file, obj_size, etag, threadpool,
                   disk_chunk_size, keep_cache_size, device_path, logger,
                   quarantine_hook, keep_cache=False):
          # Parameter tracking
          self._fp = fp
          self._data_file = data_file
          self._obj_size = obj_size
          self._etag = etag
          self._threadpool = threadpool
          self._disk_chunk_size = disk_chunk_size
          self._device_path = device_path
          self._logger = logger
          self._quarantine_hook = quarantine_hook
          if keep_cache:
              # Caller suggests we keep this in cache, only do it if the
              # object's size is less than the maximum.
              self._keep_cache = obj_size < keep_cache_size
          else:
              self._keep_cache = False
  
          # Internal Attributes
          self._iter_etag = None
          self._bytes_read = 0
          self._started_at_0 = False
          self._read_to_eof = False
          self._suppress_file_closing = False
          self._quarantined_dir = None
  
      def __iter__(self):
          """Returns an iterator over the data file."""
          try:
              dropped_cache = 0
              self._bytes_read = 0
              self._started_at_0 = False
              self._read_to_eof = False
              if self._fp.tell() == 0:
                  self._started_at_0 = True
                  self._iter_etag = hashlib.md5()
              while True:
                  chunk = self._threadpool.run_in_thread(
                      self._fp.read, self._disk_chunk_size)
                  if chunk:
                      if self._iter_etag:
                          self._iter_etag.update(chunk)
                      self._bytes_read += len(chunk)
                      if self._bytes_read - dropped_cache > (1024 * 1024):
                          self._drop_cache(self._fp.fileno(), dropped_cache,
                                           self._bytes_read - dropped_cache)
                          dropped_cache = self._bytes_read
                      yield chunk
                  else:
                      self._read_to_eof = True
                      self._drop_cache(self._fp.fileno(), dropped_cache,
                                       self._bytes_read - dropped_cache)
                      break
          finally:
              if not self._suppress_file_closing:
                  self.close()
  
      def app_iter_range(self, start, stop):
          """Returns an iterator over the data file for range (start, stop)"""
          if start or start == 0:
              self._fp.seek(start)
          if stop is not None:
              length = stop - start
          else:
              length = None
          try:
              for chunk in self:
                  if length is not None:
                      length -= len(chunk)
                      if length < 0:
                          # Chop off the extra:
                          yield chunk[:length]
                          break
                  yield chunk
          finally:
              if not self._suppress_file_closing:
                  self.close()
  
      def app_iter_ranges(self, ranges, content_type, boundary, size):
          """Returns an iterator over the data file for a set of ranges"""
          if not ranges:
              yield ''
          else:
              try:
                  self._suppress_file_closing = True
                  for chunk in multi_range_iterator(
                          ranges, content_type, boundary, size,
                          self.app_iter_range):
                      yield chunk
              finally:
                  self._suppress_file_closing = False
                  self.close()
  
      def _drop_cache(self, fd, offset, length):
          """Method for no-oping buffer cache drop method."""
          if not self._keep_cache:
              drop_buffer_cache(fd, offset, length)
  
      def _quarantine(self, msg):
          self._quarantined_dir = self._threadpool.run_in_thread(
              quarantine_renamer, self._device_path, self._data_file)
          self._logger.warn("Quarantined object %s: %s" % (
              self._data_file, msg))
          self._logger.increment('quarantines')
          self._quarantine_hook(msg)
  
      def _handle_close_quarantine(self):
          """Check if file needs to be quarantined"""
          if self._bytes_read != self._obj_size:
              self._quarantine(
                  "Bytes read: %s, does not match metadata: %s" % (
                      self._bytes_read, self._obj_size))
          elif self._iter_etag and \
                  self._etag != self._iter_etag.hexdigest():
              self._quarantine(
                  "ETag %s and file's md5 %s do not match" % (
                      self._etag, self._iter_etag.hexdigest()))
  
      def close(self):
          """
          Close the open file handle if present.
  
          For this specific implementation, this method will handle quarantining
          the file if necessary.
          """
          if self._fp:
              try:
                  if self._started_at_0 and self._read_to_eof:
                      self._handle_close_quarantine()
              except DiskFileQuarantined:
                  raise
              except (Exception, Timeout) as e:
                  self._logger.error(_(
                      'ERROR DiskFile %(data_file)s'
                      ' close failure: %(exc)s : %(stack)s'),
                      {'exc': e, 'stack': ''.join(traceback.format_stack()),
                       'data_file': self._data_file})
              finally:
                  fp, self._fp = self._fp, None
                  fp.close()
  
  
  class DiskFile(object):
      """
      Manage object files.
  
      This specific implementation manages object files on a disk formatted with
      a POSIX-compliant file system that supports extended attributes as
      metadata on a file or directory.
  
      .. note::
  
          The arguments to the constructor are considered implementation
          specific. The API does not define the constructor arguments.
  
      :param mgr: associated DiskFileManager instance
      :param device_path: path to the target device or drive
      :param threadpool: thread pool to use for blocking operations
      :param partition: partition on the device in which the object lives
      :param account: account name for the object
      :param container: container name for the object
      :param obj: object name for the object
      """
  
      def __init__(self, mgr, device_path, threadpool, partition,
                   account=None, container=None, obj=None, _datadir=None):
          self._mgr = mgr
          self._device_path = device_path
          self._threadpool = threadpool or ThreadPool(nthreads=0)
          self._logger = mgr.logger
          self._disk_chunk_size = mgr.disk_chunk_size
          self._bytes_per_sync = mgr.bytes_per_sync
          if account and container and obj:
              self._name = '/' + '/'.join((account, container, obj))
              self._account = account
              self._container = container
              self._obj = obj
              name_hash = hash_path(account, container, obj)
              self._datadir = join(
                  device_path, storage_directory(DATADIR, partition, name_hash))
          else:
              # gets populated when we read the metadata
              self._name = None
              self._account = None
              self._container = None
              self._obj = None
              self._datadir = None
          self._tmpdir = join(device_path, 'tmp')
          self._metadata = None
          self._data_file = None
          self._fp = None
          self._quarantined_dir = None
          self._content_length = None
          if _datadir:
              self._datadir = _datadir
          else:
              name_hash = hash_path(account, container, obj)
              self._datadir = join(
                  device_path, storage_directory(DATADIR, partition, name_hash))
  
      @property
      def account(self):
          return self._account
  
      @property
      def container(self):
          return self._container
  
      @property
      def obj(self):
          return self._obj
  
      @property
      def content_length(self):
          if self._metadata is None:
              raise DiskFileNotOpen()
          return self._content_length
  
      @property
      def timestamp(self):
          if self._metadata is None:
              raise DiskFileNotOpen()
          return self._metadata.get('X-Timestamp')
  
      @classmethod
      def from_hash_dir(cls, mgr, hash_dir_path, device_path, partition):
          return cls(mgr, device_path, None, partition, _datadir=hash_dir_path)
  
      def open(self):
          """
          Open the object.
  
          This implementation opens the data file representing the object, reads
          the associated metadata in the extended attributes, additionally
          combining metadata from fast-POST `.meta` files.
  
          .. note::
  
              An implementation is allowed to raise any of the following
              exceptions, but is only required to raise `DiskFileNotExist` when
              the object representation does not exist.
  
          :raises DiskFileCollision: on name mis-match with metadata
          :raises DiskFileNotExist: if the object does not exist
          :raises DiskFileDeleted: if the object was previously deleted
          :raises DiskFileQuarantined: if while reading metadata of the file
                                       some data did pass cross checks
          :returns: itself for use as a context manager
          """
          data_file, meta_file, ts_file = self._get_ondisk_file()
          if not data_file:
              raise self._construct_exception_from_ts_file(ts_file)
          self._fp = self._construct_from_data_file(
              data_file, meta_file)
          # This method must populate the internal _metadata attribute.
          self._metadata = self._metadata or {}
          self._data_file = data_file
          return self
  
      def __enter__(self):
          """
          Context enter.
  
          .. note::
  
              An implemenation shall raise `DiskFileNotOpen` when has not
              previously invoked the :func:`swift.obj.diskfile.DiskFile.open`
              method.
          """
          if self._metadata is None:
              raise DiskFileNotOpen()
          return self
  
      def __exit__(self, t, v, tb):
          """
          Context exit.
  
          .. note::
  
              This method will be invoked by the object server while servicing
              the REST API *before* the object has actually been read. It is the
              responsibility of the implementation to properly handle that.
          """
          if self._fp is not None:
              fp, self._fp = self._fp, None
              fp.close()
  
      def _quarantine(self, data_file, msg):
          """
          Quarantine a file; responsible for incrementing the associated logger's
          count of quarantines.
  
          :param data_file: full path of data file to quarantine
          :param msg: reason for quarantining to be included in the exception
          :returns: DiskFileQuarantined exception object
          """
          self._quarantined_dir = self._threadpool.run_in_thread(
              quarantine_renamer, self._device_path, data_file)
          self._logger.warn("Quarantined object %s: %s" % (
              data_file, msg))
          self._logger.increment('quarantines')
          return DiskFileQuarantined(msg)
  
      def _get_ondisk_file(self):
          """
          Do the work to figure out if the data directory exists, and if so,
          determine the on-disk files to use.
  
          :returns: a tuple of data, meta and ts (tombstone) files, in one of
                    three states:
  
          * all three are None
  
            data directory does not exist, or there are no files in
            that directory
  
          * ts_file is not None, data_file is None, meta_file is None
  
            object is considered deleted
  
          * data_file is not None, ts_file is None
  
            object exists, and optionally has fast-POST metadata
          """
          try:
              files = os.listdir(self._datadir)
          except OSError as err:
              if err.errno == errno.ENOTDIR:
                  # If there's a file here instead of a directory, quarantine
                  # it; something's gone wrong somewhere.
                  raise self._quarantine(
                      # hack: quarantine_renamer actually renames the directory
                      # enclosing the filename you give it, but here we just
                      # want this one file and not its parent.
                      os.path.join(self._datadir, "made-up-filename"),
                      "Expected directory, found file at %s" % self._datadir)
              elif err.errno != errno.ENOENT:
                  raise DiskFileError(
                      "Error listing directory %s: %s" % (self._datadir, err))
              # The data directory does not exist, so the object cannot exist.
              fileset = (None, None, None)
          else:
              fileset = get_ondisk_files(files, self._datadir)
          return fileset
  
      def _construct_exception_from_ts_file(self, ts_file):
          """
          If a tombstone is present it means the object is considered
          deleted. We just need to pull the metadata from the tombstone file
          which has the timestamp to construct the deleted exception. If there
          was no tombstone, just report it does not exist.
  
          :param ts_file: the tombstone file name found on disk
          :returns: DiskFileDeleted if the ts_file was provided, else
                    DiskFileNotExist
          """
          if not ts_file:
              exc = DiskFileNotExist()
          else:
              try:
                  metadata = self._failsafe_read_metadata(ts_file, ts_file)
              except DiskFileQuarantined:
                  # If the tombstone's corrupted, quarantine it and pretend it
                  # wasn't there
                  exc = DiskFileNotExist()
              else:
                  # All well and good that we have found a tombstone file, but
                  # we don't have a data file so we are just going to raise an
                  # exception that we could not find the object, providing the
                  # tombstone's timestamp.
                  exc = DiskFileDeleted(metadata=metadata)
          return exc
  
      def _verify_name_matches_hash(self, data_file):
          hash_from_fs = os.path.basename(self._datadir)
          hash_from_name = hash_path(self._name.lstrip('/'))
          if hash_from_fs != hash_from_name:
              raise self._quarantine(
                  data_file,
                  "Hash of name in metadata does not match directory name")
  
      def _verify_data_file(self, data_file, fp):
          """
          Verify the metadata's name value matches what we think the object is
          named.
  
          :param data_file: data file name being consider, used when quarantines
                            occur
          :param fp: open file pointer so that we can `fstat()` the file to
                     verify the on-disk size with Content-Length metadata value
          :raises DiskFileCollision: if the metadata stored name does not match
                                     the referenced name of the file
          :raises DiskFileExpired: if the object has expired
          :raises DiskFileQuarantined: if data inconsistencies were detected
                                       between the metadata and the file-system
                                       metadata
          """
          try:
              mname = self._metadata['name']
          except KeyError:
              raise self._quarantine(data_file, "missing name metadata")
          else:
              if mname != self._name:
                  self._logger.error(
                      _('Client path %(client)s does not match '
                        'path stored in object metadata %(meta)s'),
                      {'client': self._name, 'meta': mname})
                  raise DiskFileCollision('Client path does not match path '
                                          'stored in object metadata')
          try:
              x_delete_at = int(self._metadata['X-Delete-At'])
          except KeyError:
              pass
          except ValueError:
              # Quarantine, the x-delete-at key is present but not an
              # integer.
              raise self._quarantine(
                  data_file, "bad metadata x-delete-at value %s" % (
                      self._metadata['X-Delete-At']))
          else:
              if x_delete_at <= time.time():
                  raise DiskFileExpired(metadata=self._metadata)
          try:
              metadata_size = int(self._metadata['Content-Length'])
          except KeyError:
              raise self._quarantine(
                  data_file, "missing content-length in metadata")
          except ValueError:
              # Quarantine, the content-length key is present but not an
              # integer.
              raise self._quarantine(
                  data_file, "bad metadata content-length value %s" % (
                      self._metadata['Content-Length']))
          fd = fp.fileno()
          try:
              statbuf = os.fstat(fd)
          except OSError as err:
              # Quarantine, we can't successfully stat the file.
              raise self._quarantine(data_file, "not stat-able: %s" % err)
          else:
              obj_size = statbuf.st_size
          if obj_size != metadata_size:
              raise self._quarantine(
                  data_file, "metadata content-length %s does"
                  " not match actual object size %s" % (
                      metadata_size, statbuf.st_size))
          self._content_length = obj_size
          return obj_size
  
      def _failsafe_read_metadata(self, source, quarantine_filename=None):
          # Takes source and filename separately so we can read from an open
          # file if we have one
          try:
              return read_metadata(source)
          except Exception as err:
              raise self._quarantine(
                  quarantine_filename,
                  "Exception reading metadata: %s" % err)
  
      def _construct_from_data_file(self, data_file, meta_file):
          """
          Open the `.data` file to fetch its metadata, and fetch the metadata
          from the fast-POST `.meta` file as well if it exists, merging them
          properly.
  
          :param data_file: on-disk `.data` file being considered
          :param meta_file: on-disk fast-POST `.meta` file being considered
          :returns: an opened data file pointer
          :raises DiskFileError: various exceptions from
                      :func:`swift.obj.diskfile.DiskFile._verify_data_file`
          """
          fp = open(data_file, 'rb')
          datafile_metadata = self._failsafe_read_metadata(fp, data_file)
          if meta_file:
              self._metadata = self._failsafe_read_metadata(meta_file, meta_file)
              sys_metadata = dict(
                  [(key, val) for key, val in datafile_metadata.iteritems()
                   if key.lower() in DATAFILE_SYSTEM_META])
              self._metadata.update(sys_metadata)
          else:
              self._metadata = datafile_metadata
          if self._name is None:
              # If we don't know our name, we were just given a hash dir at
              # instantiation, so we'd better validate that the name hashes back
              # to us
              self._name = self._metadata['name']
              self._verify_name_matches_hash(data_file)
          self._verify_data_file(data_file, fp)
          return fp
  
      def get_metadata(self):
          """
          Provide the metadata for a previously opened object as a dictionary.
  
          :returns: object's metadata dictionary
          :raises DiskFileNotOpen: if the
              :func:`swift.obj.diskfile.DiskFile.open` method was not previously
              invoked
          """
          if self._metadata is None:
              raise DiskFileNotOpen()
          return self._metadata
  
      def read_metadata(self):
          """
          Return the metadata for an object without requiring the caller to open
          the object first.
  
          :returns: metadata dictionary for an object
          :raises DiskFileError: this implementation will raise the same
                              errors as the `open()` method.
          """
          with self.open():
              return self.get_metadata()
  
      def reader(self, keep_cache=False,
                 _quarantine_hook=lambda m: None):
          """
          Return a :class:`swift.common.swob.Response` class compatible
          "`app_iter`" object as defined by
          :class:`swift.obj.diskfile.DiskFileReader`.
  
          For this implementation, the responsibility of closing the open file
          is passed to the :class:`swift.obj.diskfile.DiskFileReader` object.
  
          :param keep_cache: caller's preference for keeping data read in the
                             OS buffer cache
          :param _quarantine_hook: 1-arg callable called when obj quarantined;
                                   the arg is the reason for quarantine.
                                   Default is to ignore it.
                                   Not needed by the REST layer.
          :returns: a :class:`swift.obj.diskfile.DiskFileReader` object
          """
          dr = DiskFileReader(
              self._fp, self._data_file, int(self._metadata['Content-Length']),
              self._metadata['ETag'], self._threadpool, self._disk_chunk_size,
              self._mgr.keep_cache_size, self._device_path, self._logger,
              quarantine_hook=_quarantine_hook, keep_cache=keep_cache)
          # At this point the reader object is now responsible for closing
          # the file pointer.
          self._fp = None
          return dr
  
      @contextmanager
      def create(self, size=None):
          """
          Context manager to create a file. We create a temporary file first, and
          then return a DiskFileWriter object to encapsulate the state.
  
          .. note::
  
              An implementation is not required to perform on-disk
              preallocations even if the parameter is specified. But if it does
              and it fails, it must raise a `DiskFileNoSpace` exception.
  
          :param size: optional initial size of file to explicitly allocate on
                       disk
          :raises DiskFileNoSpace: if a size is specified and allocation fails
          """
          if not exists(self._tmpdir):
              mkdirs(self._tmpdir)
          fd, tmppath = mkstemp(dir=self._tmpdir)
          try:
              if size is not None and size > 0:
                  try:
                      fallocate(fd, size)
                  except OSError:
                      raise DiskFileNoSpace()
              yield DiskFileWriter(self._name, self._datadir, fd, tmppath,
                                   self._bytes_per_sync, self._threadpool)
          finally:
              try:
                  os.close(fd)
              except OSError:
                  pass
              try:
                  os.unlink(tmppath)
              except OSError:
                  pass
  
      def write_metadata(self, metadata):
          """
          Write a block of metadata to an object without requiring the caller to
          create the object first. Supports fast-POST behavior semantics.
  
          :param metadata: dictionary of metadata to be associated with the
                           object
          :raises DiskFileError: this implementation will raise the same
                              errors as the `create()` method.
          """
          with self.create() as writer:
              writer._extension = '.meta'
              writer.put(metadata)
  
      def delete(self, timestamp):
          """
          Delete the object.
  
          This implementation creates a tombstone file using the given
          timestamp, and removes any older versions of the object file. Any
          file that has an older timestamp than timestamp will be deleted.
  
          .. note::
  
              An implementation is free to use or ignore the timestamp
              parameter.
  
          :param timestamp: timestamp to compare with each file
          :raises DiskFileError: this implementation will raise the same
                              errors as the `create()` method.
          """
          timestamp = normalize_timestamp(timestamp)
  
          with self.create() as deleter:
              deleter._extension = '.ts'
              deleter.put({'X-Timestamp': timestamp})
  