text: # Copyright (c) 2010-2015 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.
  
  import os
  from os.path import join
  import random
  import time
  import itertools
  from collections import defaultdict
  import six.moves.cPickle as pickle
  import shutil
  
  from eventlet import (GreenPile, GreenPool, Timeout, sleep, hubs, tpool,
                        spawn)
  from eventlet.support.greenlets import GreenletExit
  
  from swift import gettext_ as _
  from swift.common.utils import (
      whataremyips, unlink_older_than, compute_eta, get_logger,
      dump_recon_cache, mkdirs, config_true_value, list_from_csv, get_hub,
      tpool_reraise, GreenAsyncPile, Timestamp, remove_file)
  from swift.common.swob import HeaderKeyDict
  from swift.common.bufferedhttp import http_connect
  from swift.common.daemon import Daemon
  from swift.common.ring.utils import is_local_device
  from swift.obj.ssync_sender import Sender as ssync_sender
  from swift.common.http import HTTP_OK, HTTP_NOT_FOUND, \
      HTTP_INSUFFICIENT_STORAGE
  from swift.obj.diskfile import DiskFileRouter, get_data_dir, \
      get_tmp_dir
  from swift.common.storage_policy import POLICIES, EC_POLICY
  from swift.common.exceptions import ConnectionTimeout, DiskFileError, \
      SuffixSyncError
  
  SYNC, REVERT = ('sync_only', 'sync_revert')
  
  
  hubs.use_hub(get_hub())
  
  
  def _get_partners(frag_index, part_nodes):
      """
      Returns the left and right partners of the node whose index is
      equal to the given frag_index.
  
      :param frag_index: a fragment index
      :param part_nodes: a list of primary nodes
      :returns: [<node-to-left>, <node-to-right>]
      """
      return [
          part_nodes[(frag_index - 1) % len(part_nodes)],
          part_nodes[(frag_index + 1) % len(part_nodes)],
      ]
  
  
  class RebuildingECDiskFileStream(object):
      """
      This class wraps the the reconstructed fragment archive data and
      metadata in the DiskFile interface for ssync.
      """
  
      def __init__(self, datafile_metadata, frag_index, rebuilt_fragment_iter):
          # start with metadata from a participating FA
          self.datafile_metadata = datafile_metadata
  
          # the new FA is going to have the same length as others in the set
          self._content_length = self.datafile_metadata['Content-Length']
  
          # update the FI and delete the ETag, the obj server will
          # recalc on the other side...
          self.datafile_metadata['X-Object-Sysmeta-Ec-Frag-Index'] = frag_index
          for etag_key in ('ETag', 'Etag'):
              self.datafile_metadata.pop(etag_key, None)
  
          self.frag_index = frag_index
          self.rebuilt_fragment_iter = rebuilt_fragment_iter
  
      def get_metadata(self):
          return self.datafile_metadata
  
      def get_datafile_metadata(self):
          return self.datafile_metadata
  
      @property
      def content_length(self):
          return self._content_length
  
      def reader(self):
          for chunk in self.rebuilt_fragment_iter:
              yield chunk
  
  
  class ObjectReconstructor(Daemon):
      """
      Reconstruct objects using erasure code.  And also rebalance EC Fragment
      Archive objects off handoff nodes.
  
      Encapsulates most logic and data needed by the object reconstruction
      process. Each call to .reconstruct() performs one pass.  It's up to the
      caller to do this in a loop.
      """
  
      def __init__(self, conf, logger=None):
          """
          :param conf: configuration object obtained from ConfigParser
          :param logger: logging object
          """
          self.conf = conf
          self.logger = logger or get_logger(
              conf, log_route='object-reconstructor')
          self.devices_dir = conf.get('devices', '/srv/node')
          self.mount_check = config_true_value(conf.get('mount_check', 'true'))
          self.swift_dir = conf.get('swift_dir', '/etc/swift')
          self.bind_ip = conf.get('bind_ip', '0.0.0.0')
          self.servers_per_port = int(conf.get('servers_per_port', '0') or 0)
          self.port = None if self.servers_per_port else \
              int(conf.get('bind_port', 6000))
          self.concurrency = int(conf.get('concurrency', 1))
          self.stats_interval = int(conf.get('stats_interval', '300'))
          self.ring_check_interval = int(conf.get('ring_check_interval', 15))
          self.next_check = time.time() + self.ring_check_interval
          self.reclaim_age = int(conf.get('reclaim_age', 86400 * 7))
          self.partition_times = []
          self.interval = int(conf.get('interval') or
                              conf.get('run_pause') or 30)
          self.http_timeout = int(conf.get('http_timeout', 60))
          self.lockup_timeout = int(conf.get('lockup_timeout', 1800))
          self.recon_cache_path = conf.get('recon_cache_path',
                                           '/var/cache/swift')
          self.rcache = os.path.join(self.recon_cache_path, "object.recon")
          # defaults subject to change after beta
          self.conn_timeout = float(conf.get('conn_timeout', 0.5))
          self.node_timeout = float(conf.get('node_timeout', 10))
          self.network_chunk_size = int(conf.get('network_chunk_size', 65536))
          self.disk_chunk_size = int(conf.get('disk_chunk_size', 65536))
          self.headers = {
              'Content-Length': '0',
              'user-agent': 'obj-reconstructor %s' % os.getpid()}
          self.handoffs_first = config_true_value(conf.get('handoffs_first',
                                                           False))
          self._df_router = DiskFileRouter(conf, self.logger)
  
      def load_object_ring(self, policy):
          """
          Make sure the policy's rings are loaded.
  
          :param policy: the StoragePolicy instance
          :returns: appropriate ring object
          """
          policy.load_ring(self.swift_dir)
          return policy.object_ring
  
      def check_ring(self, object_ring):
          """
          Check to see if the ring has been updated
  
          :param object_ring: the ring to check
          :returns: boolean indicating whether or not the ring has changed
          """
          if time.time() > self.next_check:
              self.next_check = time.time() + self.ring_check_interval
              if object_ring.has_changed():
                  return False
          return True
  
      def _full_path(self, node, part, path, policy):
          return '%(replication_ip)s:%(replication_port)s' \
              '/%(device)s/%(part)s%(path)s ' \
              'policy#%(policy)d frag#%(frag_index)s' % {
                  'replication_ip': node['replication_ip'],
                  'replication_port': node['replication_port'],
                  'device': node['device'],
                  'part': part, 'path': path,
                  'policy': policy,
                  'frag_index': node.get('index', 'handoff'),
              }
  
      def _get_response(self, node, part, path, headers, policy):
          """
          Helper method for reconstruction that GETs a single EC fragment
          archive
  
          :param node: the node to GET from
          :param part: the partition
          :param path: full path of the desired EC archive
          :param headers: the headers to send
          :param policy: an instance of
                         :class:`~swift.common.storage_policy.BaseStoragePolicy`
          :returns: response
          """
          resp = None
          try:
              with ConnectionTimeout(self.conn_timeout):
                  conn = http_connect(node['ip'], node['port'], node['device'],
                                      part, 'GET', path, headers=headers)
              with Timeout(self.node_timeout):
                  resp = conn.getresponse()
              if resp.status not in [HTTP_OK, HTTP_NOT_FOUND]:
                  self.logger.warning(
                      _("Invalid response %(resp)s from %(full_path)s"),
                      {'resp': resp.status,
                       'full_path': self._full_path(node, part, path, policy)})
                  resp = None
              elif resp.status == HTTP_NOT_FOUND:
                  resp = None
          except (Exception, Timeout):
              self.logger.exception(
                  _("Trying to GET %(full_path)s"), {
                      'full_path': self._full_path(node, part, path, policy)})
          return resp
  
      def reconstruct_fa(self, job, node, datafile_metadata):
          """
          Reconstructs a fragment archive - this method is called from ssync
          after a remote node responds that is missing this object - the local
          diskfile is opened to provide metadata - but to reconstruct the
          missing fragment archive we must connect to multiple object servers.
  
          :param job: job from ssync_sender
          :param node: node that we're rebuilding to
          :param datafile_metadata:  the datafile metadata to attach to
                                     the rebuilt fragment archive
          :returns: a DiskFile like class for use by ssync
          :raises DiskFileError: if the fragment archive cannot be reconstructed
          """
  
          part_nodes = job['policy'].object_ring.get_part_nodes(
              job['partition'])
          part_nodes.remove(node)
  
          # the fragment index we need to reconstruct is the position index
          # of the node we're rebuilding to within the primary part list
          fi_to_rebuild = node['index']
  
          # KISS send out connection requests to all nodes, see what sticks
          headers = self.headers.copy()
          headers['X-Backend-Storage-Policy-Index'] = int(job['policy'])
          pile = GreenAsyncPile(len(part_nodes))
          path = datafile_metadata['name']
          for node in part_nodes:
              pile.spawn(self._get_response, node, job['partition'],
                         path, headers, job['policy'])
          responses = []
          etag = None
          for resp in pile:
              if not resp:
                  continue
              resp.headers = HeaderKeyDict(resp.getheaders())
              if str(fi_to_rebuild) == \
                      resp.headers.get('X-Object-Sysmeta-Ec-Frag-Index'):
                  continue
              if resp.headers.get('X-Object-Sysmeta-Ec-Frag-Index') in set(
                      r.headers.get('X-Object-Sysmeta-Ec-Frag-Index')
                      for r in responses):
                  continue
              responses.append(resp)
              etag = sorted(responses, reverse=True,
                            key=lambda r: Timestamp(
                                r.headers.get('X-Backend-Timestamp')
                            ))[0].headers.get('X-Object-Sysmeta-Ec-Etag')
              responses = [r for r in responses if
                           r.headers.get('X-Object-Sysmeta-Ec-Etag') == etag]
  
              if len(responses) >= job['policy'].ec_ndata:
                  break
          else:
              self.logger.error(
                  'Unable to get enough responses (%s/%s) '
                  'to reconstruct %s with ETag %s' % (
                      len(responses), job['policy'].ec_ndata,
                      self._full_path(node, job['partition'],
                                      datafile_metadata['name'], job['policy']),
                      etag))
              raise DiskFileError('Unable to reconstruct EC archive')
  
          rebuilt_fragment_iter = self.make_rebuilt_fragment_iter(
              responses[:job['policy'].ec_ndata], path, job['policy'],
              fi_to_rebuild)
          return RebuildingECDiskFileStream(datafile_metadata, fi_to_rebuild,
                                            rebuilt_fragment_iter)
  
      def _reconstruct(self, policy, fragment_payload, frag_index):
          return policy.pyeclib_driver.reconstruct(fragment_payload,
                                                   [frag_index])[0]
  
      def make_rebuilt_fragment_iter(self, responses, path, policy, frag_index):
          """
          Turn a set of connections from backend object servers into a generator
          that yields up the rebuilt fragment archive for frag_index.
          """
  
          def _get_one_fragment(resp):
              buff = ''
              remaining_bytes = policy.fragment_size
              while remaining_bytes:
                  chunk = resp.read(remaining_bytes)
                  if not chunk:
                      break
                  remaining_bytes -= len(chunk)
                  buff += chunk
              return buff
  
          def fragment_payload_iter():
              # We need a fragment from each connections, so best to
              # use a GreenPile to keep them ordered and in sync
              pile = GreenPile(len(responses))
              while True:
                  for resp in responses:
                      pile.spawn(_get_one_fragment, resp)
                  try:
                      with Timeout(self.node_timeout):
                          fragment_payload = [fragment for fragment in pile]
                  except (Exception, Timeout):
                      self.logger.exception(
                          _("Error trying to rebuild %(path)s "
                            "policy#%(policy)d frag#%(frag_index)s"),
                          {'path': path,
                           'policy': policy,
                           'frag_index': frag_index,
                           })
                      break
                  if not all(fragment_payload):
                      break
                  rebuilt_fragment = self._reconstruct(
                      policy, fragment_payload, frag_index)
                  yield rebuilt_fragment
  
          return fragment_payload_iter()
  
      def stats_line(self):
          """
          Logs various stats for the currently running reconstruction pass.
          """
          if (self.device_count and self.part_count and
                  self.reconstruction_device_count):
              elapsed = (time.time() - self.start) or 0.000001
              rate = self.reconstruction_part_count / elapsed
              total_part_count = (self.part_count *
                                  self.device_count /
                                  self.reconstruction_device_count)
              self.logger.info(
                  _("%(reconstructed)d/%(total)d (%(percentage).2f%%)"
                    " partitions of %(device)d/%(dtotal)d "
                    "(%(dpercentage).2f%%) devices"
                    " reconstructed in %(time).2fs "
                    "(%(rate).2f/sec, %(remaining)s remaining)"),
                  {'reconstructed': self.reconstruction_part_count,
                   'total': self.part_count,
                   'percentage':
                   self.reconstruction_part_count * 100.0 / self.part_count,
                   'device': self.reconstruction_device_count,
                   'dtotal': self.device_count,
                   'dpercentage':
                   self.reconstruction_device_count * 100.0 / self.device_count,
                   'time': time.time() - self.start, 'rate': rate,
                   'remaining': '%d%s' %
                   compute_eta(self.start,
                               self.reconstruction_part_count,
                               total_part_count)})
  
              if self.suffix_count and self.partition_times:
                  self.logger.info(
                      _("%(checked)d suffixes checked - "
                        "%(hashed).2f%% hashed, %(synced).2f%% synced"),
                      {'checked': self.suffix_count,
                       'hashed': (self.suffix_hash * 100.0) / self.suffix_count,
                       'synced': (self.suffix_sync * 100.0) / self.suffix_count})
                  self.partition_times.sort()
                  self.logger.info(
                      _("Partition times: max %(max).4fs, "
                        "min %(min).4fs, med %(med).4fs"),
                      {'max': self.partition_times[-1],
                       'min': self.partition_times[0],
                       'med': self.partition_times[
                           len(self.partition_times) // 2]})
          else:
              self.logger.info(
                  _("Nothing reconstructed for %s seconds."),
                  (time.time() - self.start))
  
      def kill_coros(self):
          """Utility function that kills all coroutines currently running."""
          for coro in list(self.run_pool.coroutines_running):
              try:
                  coro.kill(GreenletExit)
              except GreenletExit:
                  pass
  
      def heartbeat(self):
          """
          Loop that runs in the background during reconstruction.  It
          periodically logs progress.
          """
          while True:
              sleep(self.stats_interval)
              self.stats_line()
  
      def detect_lockups(self):
          """
          In testing, the pool.waitall() call very occasionally failed to return.
          This is an attempt to make sure the reconstructor finishes its
          reconstruction pass in some eventuality.
          """
          while True:
              sleep(self.lockup_timeout)
              if self.reconstruction_count == self.last_reconstruction_count:
                  self.logger.error(_("Lockup detected.. killing live coros."))
                  self.kill_coros()
              self.last_reconstruction_count = self.reconstruction_count
  
      def _get_hashes(self, policy, path, recalculate=None, do_listdir=False):
          df_mgr = self._df_router[policy]
          hashed, suffix_hashes = tpool_reraise(
              df_mgr._get_hashes, path, recalculate=recalculate,
              do_listdir=do_listdir, reclaim_age=self.reclaim_age)
          self.logger.update_stats('suffix.hashes', hashed)
          return suffix_hashes
  
      def get_suffix_delta(self, local_suff, local_index,
                           remote_suff, remote_index):
          """
          Compare the local suffix hashes with the remote suffix hashes
          for the given local and remote fragment indexes.  Return those
          suffixes which should be synced.
  
          :param local_suff: the local suffix hashes (from _get_hashes)
          :param local_index: the local fragment index for the job
          :param remote_suff: the remote suffix hashes (from remote
                              REPLICATE request)
          :param remote_index: the remote fragment index for the job
  
          :returns: a list of strings, the suffix dirs to sync
          """
          suffixes = []
          for suffix, sub_dict_local in local_suff.items():
              sub_dict_remote = remote_suff.get(suffix, {})
              if (sub_dict_local.get(None) != sub_dict_remote.get(None) or
                      sub_dict_local.get(local_index) !=
                      sub_dict_remote.get(remote_index)):
                  suffixes.append(suffix)
          return suffixes
  
      def rehash_remote(self, node, job, suffixes):
          try:
              with Timeout(self.http_timeout):
                  conn = http_connect(
                      node['replication_ip'], node['replication_port'],
                      node['device'], job['partition'], 'REPLICATE',
                      '/' + '-'.join(sorted(suffixes)),
                      headers=self.headers)
                  conn.getresponse().read()
          except (Exception, Timeout):
              self.logger.exception(
                  _("Trying to sync suffixes with %s") % self._full_path(
                      node, job['partition'], '', job['policy']))
  
      def _get_suffixes_to_sync(self, job, node):
          """
          For SYNC jobs we need to make a remote REPLICATE request to get
          the remote node's current suffix's hashes and then compare to our
          local suffix's hashes to decide which suffixes (if any) are out
          of sync.
  
          :param: the job dict, with the keys defined in ``_get_part_jobs``
          :param node: the remote node dict
          :returns: a (possibly empty) list of strings, the suffixes to be
                    synced with the remote node.
          """
          # get hashes from the remote node
          remote_suffixes = None
          try:
              with Timeout(self.http_timeout):
                  resp = http_connect(
                      node['replication_ip'], node['replication_port'],
                      node['device'], job['partition'], 'REPLICATE',
                      '', headers=self.headers).getresponse()
              if resp.status == HTTP_INSUFFICIENT_STORAGE:
                  self.logger.error(
                      _('%s responded as unmounted'),
                      self._full_path(node, job['partition'], '',
                                      job['policy']))
              elif resp.status != HTTP_OK:
                  full_path = self._full_path(node, job['partition'], '',
                                              job['policy'])
                  self.logger.error(
                      _("Invalid response %(resp)s from %(full_path)s"),
                      {'resp': resp.status, 'full_path': full_path})
              else:
                  remote_suffixes = pickle.loads(resp.read())
          except (Exception, Timeout):
              # all exceptions are logged here so that our caller can
              # safely catch our exception and continue to the next node
              # without logging
              self.logger.exception('Unable to get remote suffix hashes '
                                    'from %r' % self._full_path(
                                        node, job['partition'], '',
                                        job['policy']))
  
          if remote_suffixes is None:
              raise SuffixSyncError('Unable to get remote suffix hashes')
  
          suffixes = self.get_suffix_delta(job['hashes'],
                                           job['frag_index'],
                                           remote_suffixes,
                                           node['index'])
          # now recalculate local hashes for suffixes that don't
          # match so we're comparing the latest
          local_suff = self._get_hashes(job['policy'], job['path'],
                                        recalculate=suffixes)
  
          suffixes = self.get_suffix_delta(local_suff,
                                           job['frag_index'],
                                           remote_suffixes,
                                           node['index'])
  
          self.suffix_count += len(suffixes)
          return suffixes
  
      def delete_reverted_objs(self, job, objects, frag_index):
          """
          For EC we can potentially revert only some of a partition
          so we'll delete reverted objects here. Note that we delete
          the fragment index of the file we sent to the remote node.
  
          :param job: the job being processed
          :param objects: a dict of objects to be deleted, each entry maps
                          hash=>timestamp
          :param frag_index: (int) the fragment index of data files to be deleted
          """
          df_mgr = self._df_router[job['policy']]
          for object_hash, timestamps in objects.items():
              try:
                  df = df_mgr.get_diskfile_from_hash(
                      job['local_dev']['device'], job['partition'],
                      object_hash, job['policy'],
                      frag_index=frag_index)
                  df.purge(timestamps['ts_data'], frag_index)
              except DiskFileError:
                  self.logger.exception(
                      'Unable to purge DiskFile (%r %r %r)',
                      object_hash, timestamps['ts_data'], frag_index)
                  continue
  
      def process_job(self, job):
          """
          Sync the local partition with the remote node(s) according to
          the parameters of the job.  For primary nodes, the SYNC job type
          will define both left and right hand sync_to nodes to ssync with
          as defined by this primary nodes index in the node list based on
          the fragment index found in the partition.  For non-primary
          nodes (either handoff revert, or rebalance) the REVERT job will
          define a single node in sync_to which is the proper/new home for
          the fragment index.
  
          N.B. ring rebalancing can be time consuming and handoff nodes'
          fragment indexes do not have a stable order, it's possible to
          have more than one REVERT job for a partition, and in some rare
          failure conditions there may even also be a SYNC job for the
          same partition - but each one will be processed separately
          because each job will define a separate list of node(s) to
          'sync_to'.
  
          :param: the job dict, with the keys defined in ``_get_job_info``
          """
          self.headers['X-Backend-Storage-Policy-Index'] = int(job['policy'])
          begin = time.time()
          if job['job_type'] == REVERT:
              self._revert(job, begin)
          else:
              self._sync(job, begin)
          self.partition_times.append(time.time() - begin)
          self.reconstruction_count += 1
  
      def _sync(self, job, begin):
          """
          Process a SYNC job.
          """
          self.logger.increment(
              'partition.update.count.%s' % (job['local_dev']['device'],))
          # after our left and right partners, if there's some sort of
          # failure we'll continue onto the remaining primary nodes and
          # make sure they're in sync - or potentially rebuild missing
          # fragments we find
          dest_nodes = itertools.chain(
              job['sync_to'],
              # I think we could order these based on our index to better
              # protect against a broken chain
              [
                  n for n in
                  job['policy'].object_ring.get_part_nodes(job['partition'])
                  if n['id'] != job['local_dev']['id'] and
                  n['id'] not in (m['id'] for m in job['sync_to'])
              ],
          )
          syncd_with = 0
          for node in dest_nodes:
              if syncd_with >= len(job['sync_to']):
                  # success!
                  break
  
              try:
                  suffixes = self._get_suffixes_to_sync(job, node)
              except SuffixSyncError:
                  continue
  
              if not suffixes:
                  syncd_with += 1
                  continue
  
              # ssync any out-of-sync suffixes with the remote node
              success, _ = ssync_sender(
                  self, node, job, suffixes)()
              # let remote end know to rehash it's suffixes
              self.rehash_remote(node, job, suffixes)
              # update stats for this attempt
              self.suffix_sync += len(suffixes)
              self.logger.update_stats('suffix.syncs', len(suffixes))
              if success:
                  syncd_with += 1
          self.logger.timing_since('partition.update.timing', begin)
  
      def _revert(self, job, begin):
          """
          Process a REVERT job.
          """
          self.logger.increment(
              'partition.delete.count.%s' % (job['local_dev']['device'],))
          # we'd desperately like to push this partition back to it's
          # primary location, but if that node is down, the next best thing
          # is one of the handoff locations - which *might* be us already!
          dest_nodes = itertools.chain(
              job['sync_to'],
              job['policy'].object_ring.get_more_nodes(job['partition']),
          )
          syncd_with = 0
          reverted_objs = {}
          for node in dest_nodes:
              if syncd_with >= len(job['sync_to']):
                  break
              if node['id'] == job['local_dev']['id']:
                  # this is as good a place as any for this data for now
                  break
              success, in_sync_objs = ssync_sender(
                  self, node, job, job['suffixes'])()
              self.rehash_remote(node, job, job['suffixes'])
              if success:
                  syncd_with += 1
                  reverted_objs.update(in_sync_objs)
          if syncd_with >= len(job['sync_to']):
              self.delete_reverted_objs(
                  job, reverted_objs, job['frag_index'])
          self.logger.timing_since('partition.delete.timing', begin)
  
      def _get_part_jobs(self, local_dev, part_path, partition, policy):
          """
          Helper function to build jobs for a partition, this method will
          read the suffix hashes and create job dictionaries to describe
          the needed work.  There will be one job for each fragment index
          discovered in the partition.
  
          For a fragment index which corresponds to this node's ring
          index, a job with job_type SYNC will be created to ensure that
          the left and right hand primary ring nodes for the part have the
          corresponding left and right hand fragment archives.
  
          A fragment index (or entire partition) for which this node is
          not the primary corresponding node, will create job(s) with
          job_type REVERT to ensure that fragment archives are pushed to
          the correct node and removed from this one.
  
          A partition may result in multiple jobs.  Potentially many
          REVERT jobs, and zero or one SYNC job.
  
          :param local_dev:  the local device
          :param part_path: full path to partition
          :param partition: partition number
          :param policy: the policy
  
          :returns: a list of dicts of job info
          """
          # find all the fi's in the part, and which suffixes have them
          hashes = self._get_hashes(policy, part_path, do_listdir=True)
          non_data_fragment_suffixes = []
          data_fi_to_suffixes = defaultdict(list)
          for suffix, fi_hash in hashes.items():
              if not fi_hash:
                  # this is for sanity and clarity, normally an empty
                  # suffix would get del'd from the hashes dict, but an
                  # OSError trying to re-hash the suffix could leave the
                  # value empty - it will log the exception; but there's
                  # no way to properly address this suffix at this time.
                  continue
              data_frag_indexes = [f for f in fi_hash if f is not None]
              if not data_frag_indexes:
                  non_data_fragment_suffixes.append(suffix)
              else:
                  for fi in data_frag_indexes:
                      data_fi_to_suffixes[fi].append(suffix)
  
          # helper to ensure consistent structure of jobs
          def build_job(job_type, frag_index, suffixes, sync_to):
              return {
                  'job_type': job_type,
                  'frag_index': frag_index,
                  'suffixes': suffixes,
                  'sync_to': sync_to,
                  'partition': partition,
                  'path': part_path,
                  'hashes': hashes,
                  'policy': policy,
                  'local_dev': local_dev,
                  # ssync likes to have it handy
                  'device': local_dev['device'],
              }
  
          # aggregate jobs for all the fragment index in this part
          jobs = []
  
          # check the primary nodes - to see if the part belongs here
          part_nodes = policy.object_ring.get_part_nodes(partition)
          for node in part_nodes:
              if node['id'] == local_dev['id']:
                  # this partition belongs here, we'll need a sync job
                  frag_index = node['index']
                  try:
                      suffixes = data_fi_to_suffixes.pop(frag_index)
                  except KeyError:
                      suffixes = []
                  sync_job = build_job(
                      job_type=SYNC,
                      frag_index=frag_index,
                      suffixes=suffixes,
                      sync_to=_get_partners(frag_index, part_nodes),
                  )
                  # ssync callback to rebuild missing fragment_archives
                  sync_job['sync_diskfile_builder'] = self.reconstruct_fa
                  jobs.append(sync_job)
                  break
  
          # assign remaining data fragment suffixes to revert jobs
          ordered_fis = sorted((len(suffixes), fi) for fi, suffixes
                               in data_fi_to_suffixes.items())
          for count, fi in ordered_fis:
              revert_job = build_job(
                  job_type=REVERT,
                  frag_index=fi,
                  suffixes=data_fi_to_suffixes[fi],
                  sync_to=[part_nodes[fi]],
              )
              jobs.append(revert_job)
  
          # now we need to assign suffixes that have no data fragments
          if non_data_fragment_suffixes:
              if jobs:
                  # the first job will be either the sync_job, or the
                  # revert_job for the fragment index that is most common
                  # among the suffixes
                  jobs[0]['suffixes'].extend(non_data_fragment_suffixes)
              else:
                  # this is an unfortunate situation, we need a revert job to
                  # push partitions off this node, but none of the suffixes
                  # have any data fragments to hint at which node would be a
                  # good candidate to receive the tombstones.
                  jobs.append(build_job(
                      job_type=REVERT,
                      frag_index=None,
                      suffixes=non_data_fragment_suffixes,
                      # this is super safe
                      sync_to=part_nodes,
                      # something like this would be probably be better
                      # sync_to=random.sample(part_nodes, 3),
                  ))
          # return a list of jobs for this part
          return jobs
  
      def collect_parts(self, override_devices=None,
                        override_partitions=None):
          """
          Helper for yielding partitions in the top level reconstructor
          """
          override_devices = override_devices or []
          override_partitions = override_partitions or []
          ips = whataremyips(self.bind_ip)
          for policy in POLICIES:
              if policy.policy_type != EC_POLICY:
                  continue
              self._diskfile_mgr = self._df_router[policy]
              self.load_object_ring(policy)
              data_dir = get_data_dir(policy)
              local_devices = list(itertools.ifilter(
                  lambda dev: dev and is_local_device(
                      ips, self.port,
                      dev['replication_ip'], dev['replication_port']),
                  policy.object_ring.devs))
  
              if override_devices:
                  self.device_count = len(override_devices)
              else:
                  self.device_count = len(local_devices)
  
              for local_dev in local_devices:
                  if override_devices and (local_dev['device'] not in
                                           override_devices):
                      continue
                  self.reconstruction_device_count += 1
                  dev_path = self._df_router[policy].get_dev_path(
                      local_dev['device'])
                  if not dev_path:
                      self.logger.warn(_('%s is not mounted'),
                                       local_dev['device'])
                      continue
                  obj_path = join(dev_path, data_dir)
                  tmp_path = join(dev_path, get_tmp_dir(int(policy)))
                  unlink_older_than(tmp_path, time.time() -
                                    self.reclaim_age)
                  if not os.path.exists(obj_path):
                      try:
                          mkdirs(obj_path)
                      except Exception:
                          self.logger.exception(
                              'Unable to create %s' % obj_path)
                      continue
                  try:
                      partitions = os.listdir(obj_path)
                  except OSError:
                      self.logger.exception(
                          'Unable to list partitions in %r' % obj_path)
                      continue
  
                  self.part_count += len(partitions)
                  for partition in partitions:
                      part_path = join(obj_path, partition)
                      if not (partition.isdigit() and
                              os.path.isdir(part_path)):
                          self.logger.warning(
                              'Unexpected entity in data dir: %r' % part_path)
                          remove_file(part_path)
                          self.reconstruction_part_count += 1
                          continue
                      partition = int(partition)
                      if override_partitions and (partition not in
                                                  override_partitions):
                          continue
                      part_info = {
                          'local_dev': local_dev,
                          'policy': policy,
                          'partition': partition,
                          'part_path': part_path,
                      }
                      yield part_info
                      self.reconstruction_part_count += 1
  
      def build_reconstruction_jobs(self, part_info):
          """
          Helper function for collect_jobs to build jobs for reconstruction
          using EC style storage policy
          """
          jobs = self._get_part_jobs(**part_info)
          random.shuffle(jobs)
          if self.handoffs_first:
              # Move the handoff revert jobs to the front of the list
              jobs.sort(key=lambda job: job['job_type'], reverse=True)
          self.job_count += len(jobs)
          return jobs
  
      def _reset_stats(self):
          self.start = time.time()
          self.job_count = 0
          self.part_count = 0
          self.device_count = 0
          self.suffix_count = 0
          self.suffix_sync = 0
          self.suffix_hash = 0
          self.reconstruction_count = 0
          self.reconstruction_part_count = 0
          self.reconstruction_device_count = 0
          self.last_reconstruction_count = -1
  
      def delete_partition(self, path):
          self.logger.info(_("Removing partition: %s"), path)
          tpool.execute(shutil.rmtree, path, ignore_errors=True)
  
      def reconstruct(self, **kwargs):
          """Run a reconstruction pass"""
          self._reset_stats()
          self.partition_times = []
  
          stats = spawn(self.heartbeat)
          lockup_detector = spawn(self.detect_lockups)
          sleep()  # Give spawns a cycle
  
          try:
              self.run_pool = GreenPool(size=self.concurrency)
              for part_info in self.collect_parts(**kwargs):
                  if not self.check_ring(part_info['policy'].object_ring):
                      self.logger.info(_("Ring change detected. Aborting "
                                         "current reconstruction pass."))
                      return
                  jobs = self.build_reconstruction_jobs(part_info)
                  if not jobs:
                      # If this part belongs on this node, _get_part_jobs
                      # will *always* build a sync_job - even if there's
                      # no suffixes in the partition that needs to sync.
                      # If there's any suffixes in the partition then our
                      # job list would have *at least* one revert job.
                      # Therefore we know this part a) doesn't belong on
                      # this node and b) doesn't have any suffixes in it.
                      self.run_pool.spawn(self.delete_partition,
                                          part_info['part_path'])
                  for job in jobs:
                      self.run_pool.spawn(self.process_job, job)
              with Timeout(self.lockup_timeout):
                  self.run_pool.waitall()
          except (Exception, Timeout):
              self.logger.exception(_("Exception in top-level"
                                      "reconstruction loop"))
              self.kill_coros()
          finally:
              stats.kill()
              lockup_detector.kill()
              self.stats_line()
  
      def run_once(self, *args, **kwargs):
          start = time.time()
          self.logger.info(_("Running object reconstructor in script mode."))
          override_devices = list_from_csv(kwargs.get('devices'))
          override_partitions = [int(p) for p in
                                 list_from_csv(kwargs.get('partitions'))]
          self.reconstruct(
              override_devices=override_devices,
              override_partitions=override_partitions)
          total = (time.time() - start) / 60
          self.logger.info(
              _("Object reconstruction complete (once). (%.02f minutes)"), total)
          if not (override_partitions or override_devices):
              dump_recon_cache({'object_reconstruction_time': total,
                                'object_reconstruction_last': time.time()},
                               self.rcache, self.logger)
  
      def run_forever(self, *args, **kwargs):
          self.logger.info(_("Starting object reconstructor in daemon mode."))
          # Run the reconstructor continually
          while True:
              start = time.time()
              self.logger.info(_("Starting object reconstruction pass."))
              # Run the reconstructor
              self.reconstruct()
              total = (time.time() - start) / 60
              self.logger.info(
                  _("Object reconstruction complete. (%.02f minutes)"), total)
              dump_recon_cache({'object_reconstruction_time': total,
                                'object_reconstruction_last': time.time()},
                               self.rcache, self.logger)
              self.logger.debug('reconstruction sleeping for %s seconds.',
                                self.interval)
              sleep(self.interval)
  