Utility functions for operating on files and data objects in KBase data stores like Shock and the Workspace.

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DataFileUtil is the lowest level wrapper around the KBase data stores, including the workspace, shock, and handle services. It thus handles operations on files, including file transfer and compression, as well as operations on KBase data objects.

Assuming DataFileUtil is being called in the context of a set of local SDK modules calling each other, all file operations occur in the KBase job execution environment.

For any given type of data, the developer should use the appropriate existing SDK module for that data type regardless of whether the data is an object or a file. This appropriate data type module should also contain the logic for deciding how the data is stored, including which KIDL type specification is used as well as which data store.

Some examples of methods available in DataFileUtil:

• Download from external URL
• File un/compression (gzip, tar, zip)
• Upload to shock
• Download from shock
• Download from staging area to scratch space in SDK Docker container
• Upload/download from WS
• Copy shock node and gain permissions, files and their metadata

All methods can be browsed in the DataFileUtil KIDL type spec: https://github.com/kbaseapps/DataFileUtil/blob/master/DataFileUtil.spec

Data that will be used frequently should be stored in a workspace object, if you can retrieve and parse it faster than the entire raw data file. Even better if there is a standard format for the data type, which can serve as the de facto data storage structure stored as a file shock and as a reference in an appropriate workspace object. If the data is too large you may need to split it into multiple workspace objects.

Note that there may be limits on the size of data, number of files, and time of data transfer as well as requirements for network speed.

Translate a workspace name to id:

dfu = DataFileUtil(self.callback_url)
  if wsname:
      self.log('Translating workspace name to id')
      if not isinstance(wsname, six.string_types):
          raise ValueError('wsname must be a string')
      wsid = dfu.ws_name_to_id(wsname)
      self.log('translation done')

Download a file from shock:

params = {'shock_id': handle['id'],
                  'unpack': 'uncompress',
                  'file_path': os.path.join(self.scratch, handle['id'])
                  }
        # download
dfu = DataFileUtil(self.callback_url)
ret = dfu.shock_to_file(params)

fwdpath = dfu.download_web_file(
                        {'file_url': fwd,
                        'download_type': download_type}).get(
                                        'copy_file_path')
revpath = dfu.download_web_file(
            {'file_url': rev,
            'download_type': download_type}).get(
                            'copy_file_path') if rev else None

Retrieval of the remote filename:

• DFU will use the Content-Disposition header from the remote URL to set the filename, if present
• Without the above header, we will fall back to using the URL path for the filename, including extension (but minus any query parameters or hash value).
• If the filename is longer than 255 characters, then we will truncate it to that maximum length (without losing the extension).
• If we are unable to retrieve a filename from a header or the URL, then the file will be assigned a UUID without any extension.

SDK, SDK module, docker container, execution environment, narrative, code cell, shock, shock node, shock service, app chain, workspace, workspace object, workspace service, reference, handle service, scratch space.