apache/beam · error · ValueError

Please provide exactly one of a list of feature names to fet

Error message

Please provide exactly one of a list of feature names to fetch from online store (`feature_names`) or a feature service name for the Feast online feature store (`feature_service_name`).

What it means

Validation in `_validate_feature_names`, invoked from the handler's `__init__`, requires exactly one of `feature_names` (list) or `feature_service_name`. Passing neither, or passing both, raises this ValueError because the handler cannot decide how to resolve features from the Feast online store.

Source

Thrown at sdks/python/apache_beam/transforms/enrichment_handlers/feast_feature_store.py:61

def download_fs_yaml_file(gcs_fs_yaml_file: str):
  """Download the feature store config file for Feast."""
  try:
    with FileSystems.open(gcs_fs_yaml_file, 'r') as gcs_file:
      with tempfile.NamedTemporaryFile(suffix=LOCAL_FEATURE_STORE_YAML_FILENAME,
                                       delete=False) as local_file:
        local_file.write(gcs_file.read())
        return Path(local_file.name)
  except Exception:
    raise RuntimeError(
        'error downloading the file %s locally to load the '
        'Feast feature store.' % gcs_fs_yaml_file)


def _validate_feature_names(feature_names, feature_service_name):
  """Check if one of `feature_names` or `feature_service_name` is provided."""
  if ((not feature_names and not feature_service_name) or
      bool(feature_names and feature_service_name)):
    raise ValueError(
        'Please provide exactly one of a list of feature names to fetch '
        'from online store (`feature_names`) or a feature service name for '
        'the Feast online feature store (`feature_service_name`).')


def _validate_feature_store_yaml_path_exists(fs_yaml_file):
  """Check if the feature store yaml path exists."""
  if not FileSystems.exists(fs_yaml_file):
    raise ValueError(
        'The feature store yaml path (%s) does not exist.' % fs_yaml_file)


def _validate_entity_key_exists(entity_id, entity_row_fn):
  """Checks if the entity key or a lambda to build entity key exists."""
  if ((not entity_row_fn and not entity_id) or
      bool(entity_row_fn and entity_id)):
    raise ValueError(
        "Please specify exactly one of a `entity_id` or a lambda "

View on GitHub (pinned to 12126d8942)

Solutions

Pass exactly one of `feature_names` or `feature_service_name`; delete the other argument.
If migrating to a feature service, remove the `feature_names` list entirely (empty list still counts as absent, but keep code clean).
Check defaults in your wrapper/config class that may inject both values.

Example fix

// before
FeastFeatureStoreEnrichmentHandler(..., feature_names=['f1'], feature_service_name='daily_fs')
// after
FeastFeatureStoreEnrichmentHandler(..., feature_service_name='daily_fs')

Defensive patterns

Strategy: validation

Validate before calling

assert bool(feature_names) != bool(feature_service_name), 'provide exactly one of feature_names or feature_service_name'

Prevention

Use keyword-only parameters so the exclusivity is documented.
Centralize handler construction in one factory function that enforces exclusivity.
Never default both options in config files.

When it happens

Trigger: Constructing `FeastFeatureStoreEnrichmentHandler(feature_store_yaml_path=...)` with both `feature_names=[...]` and `feature_service_name='fs'`, or with neither argument (both None/empty).

Common situations: Copy-pasting a config and forgetting to delete the other option; converting from feature_names to feature_service and leaving both; initializing with defaults and forgetting to set either.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/a3e4cadcac7337af. Report an issue: GitHub.