code: def wal_archive(self, wal_path, concurrency=1):
          
  
          # Upload the segment expressly indicated.  It's special
          # relative to other uploads when parallel wal-push is enabled,
          # in that it's not desirable to tweak its .ready/.done files
          # in archive_status.
          xlog_dir = os.path.dirname(wal_path)
          segment = WalSegment(wal_path, explicit=True)
          uploader = WalUploader(self.layout, self.creds, self.gpg_key_id)
          group = WalTransferGroup(uploader)
          group.start(segment)
  
          # Upload any additional wal segments up to the specified
          # concurrency by scanning the Postgres archive_status
          # directory.
          started = 1
          seg_stream = WalSegment.from_ready_archive_status(xlog_dir)
          while started < concurrency:
              try:
                  other_segment = next(seg_stream)
              except StopIteration:
                  break
  
              if other_segment.path != wal_path:
                  group.start(other_segment)
                  started += 1
  
          try:
              # Wait for uploads to finish.
              group.join()
          except EnvironmentError as e:
              if e.errno == errno.ENOENT:
                  print(e)
                  raise UserException(
                      msg='could not find file for wal-push',
                      detail=('The operating system reported: {0} {1}'
                              .format(e.strerror, repr(e.filename))))
              raise
docs: Uploads a WAL file to S3 or Windows Azure Blob Service
  
          This code is intended to typically be called from Postgres's
          archive_command feature.