apache/beam · error · ValueError

Could not find an expansion service jar for the managed…

Error message

Could not find an expansion service jar for the managed transform

What it means

SchemaAwareExternalTransform could not locate an expansion service jar for the requested managed transform (the auto-discovery of a bundled managed-transform jar failed), so there is nothing to send the transform payload to.

Solutions

  1. Point --flexrspecified or the transform's expansion_service argument at a running expansion service endpoint
  2. Build/use the Beam managed transform expansion service jar and pass its classpath
  3. Pin a Beam version whose bundled jars include the managed transform you need
Defensive patterns

Strategy: fallback

When it happens

Trigger: Thrown at sdks/python/apache_beam/transforms/external.py:473 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/ff1c45e1a6008c1c. Report an issue: GitHub.

Appendix: source

Thrown at sdks/python/apache_beam/transforms/external.py:473

    _kwargs = kwargs
    if rearrange_based_on_discovery:
      config = SchemaAwareExternalTransform.discover_config(
          self._expansion_service, identifier)
      self._payload_builder = ExplicitSchemaTransformPayloadBuilder(
          identifier,
          named_tuple_to_schema(config.configuration_schema),
          **_kwargs)

      if self._managed_replacement:
        # We have to do the replacement at the expansion instead of at
        # construction
        # since we don't have access to the PipelineOptions object at the
        # construction.
        underlying_transform_id = (
            self._managed_replacement.underlying_transform_identifier)
        if not (underlying_transform_id
                in MANAGED_TRANSFORM_URN_TO_JAR_TARGET_MAPPING):
          raise ValueError(
              'Could not find an expansion service jar for the managed ' +
              'transform ' + underlying_transform_id)
        managed_expansion_service_jar = (
            MANAGED_TRANSFORM_URN_TO_JAR_TARGET_MAPPING
        )[underlying_transform_id]
        self._managed_expansion_service = BeamJarExpansionService(
            managed_expansion_service_jar)
        managed_config = SchemaAwareExternalTransform.discover_config(
            self._managed_expansion_service,
            MANAGED_SCHEMA_TRANSFORM_IDENTIFIER)

        yaml_config = yaml.dump(kwargs)
        self._managed_payload_builder = (
            ExplicitSchemaTransformPayloadBuilder(
                MANAGED_SCHEMA_TRANSFORM_IDENTIFIER,
                named_tuple_to_schema(managed_config.configuration_schema),
                transform_identifier=underlying_transform_id,
                config=yaml_config))

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