apache/beam · error · ValueError

Invalid model update, path for

Error message

Invalid model update, path for {keys} is empty

What it means

Raised by KeyedModelHandler.update_model_paths when an UpdateDawgModelPath (or similar update spec) has an empty update_path. Every model key submitted for a hot model update must carry a non-empty new model path so the handler can locate the updated model artifacts.

Solutions

  1. Set a non-empty update_path for every update object passed to update_model_paths.
  2. Validate the update list before calling: skip or fix entries with len(update_path) == 0.
  3. Check the config/templating source to ensure the path field is populated, not an empty default.

Example fix

// before
update = UpdateModelPath(keys=['cohort-a'], update_path='', model_id='m2')
handler.update_model_paths([update])
// after
update = UpdateModelPath(keys=['cohort-a'], update_path='gs://bucket/model_v2', model_id='m2')
handler.update_model_paths([update])
Defensive patterns

Strategy: validation

Validate before calling

bad = [u for u in updates if not u.update_path]
if bad:
    raise ValueError(f'update_path missing for keys: {[u.keys for u in bad]}')

Type guard

def has_update_path(u) -> bool:
    return isinstance(u.update_path, str) and len(u.update_path) > 0

Prevention

When it happens

Trigger: Calling update_model_paths with a list of update objects where one has update_path set to '' (empty string), or constructing the update object without setting the path field.

Common situations: Building model update requests programmatically from config where a path key is missing or defaults to empty string; YAML/JSON update configs with a blank 'update_path' field; templating failures that silently drop the path value.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/de533f482fd2f03c. Report an issue: GitHub.

Appendix: source

Thrown at sdks/python/apache_beam/ml/inference/base.py:975

    # Map cohort ids to a dictionary mapping new model paths to the keys that
    # were originally in that cohort. We will use this to construct our new
    # cohorts.
    # cohort_path_mapping will be structured as follows:
    # {
    # original_cohort_id: {
    #    'update/path/1': ['key1FromOriginalCohort', key2FromOriginalCohort'],
    #    'update/path/2': ['key3FromOriginalCohort', key4FromOriginalCohort'],
    #    }
    # }
    cohort_path_mapping: dict[KeyT, dict[str, list[KeyT]]] = {}
    key_modelid_mapping: dict[KeyT, str] = {}
    seen_keys = set()
    for mp in model_paths:
      keys = mp.keys
      update_path = mp.update_path
      model_id = mp.model_id
      if len(update_path) == 0:
        raise ValueError(f'Invalid model update, path for {keys} is empty')
      for key in keys:
        if key in seen_keys:
          raise ValueError(
              f'Invalid model update: {key} appears in multiple '
              'update lists. A single model update must provide exactly one '
              'updated path per key.')
        seen_keys.add(key)
        if key not in self._key_to_id_map:
          raise ValueError(
              f'Invalid model update: {key} appears in '
              'update, but not in the original configuration.')
        key_modelid_mapping[key] = model_id
        cohort_id = self._key_to_id_map[key]
        if cohort_id not in cohort_path_mapping:
          cohort_path_mapping[cohort_id] = defaultdict(list)
        cohort_path_mapping[cohort_id][update_path].append(key)
    for key in self._key_to_id_map:
      if key not in seen_keys:

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