apache/beam · error · ValueError

publish_time_field must be a non-empty field name.

Error message

publish_time_field must be a non-empty field name.

What it means

read_from_pubsub validates publish_time_field: it must be a non-empty field name because it becomes a column on each output Row carrying the message's publish time; an empty string would create an unnamed, unqueryable field.

Solutions

1. Remove the publish_time_field key entirely to disable it
2. Or provide an actual field name like publish_time
3. Strip/sanitize the config value before passing it

Example fix

// before
publish_time_field: ''
// after
publish_time_field: publish_time

if publish_time_field is not None and not publish_time_field.strip():
    publish_time_field = None  # or raise

def is_valid_field_name(name):
    return isinstance(name, str) and bool(name.strip())

try:
    read_from_pubsub(..., publish_time_field=ptf)
except ValueError as e:
    if 'non-empty field name' in str(e):
        ptf = None  # disable the feature

When it happens

Trigger: publish_time_field='' or ' ' passed to read_from_pubsub (is not None passes, but .strip() is empty).

Common situations: YAML key publish_time_field: '' left empty after editing config; user intends to disable it but leaves an empty string instead of removing the key.

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

• Either a topic or subscription must be provided.
• Either data (%r) or attributes (%r) must be set.
• Invalid PubSub project name: %r.
• Only one of topic or subscription should be provided.
• PubSub subscription must be in the form "projects/

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/3a6ad0a7c36939c8. Report an issue: GitHub.

Appendix: source

Thrown at sdks/python/apache_beam/yaml/yaml_io.py:392

      uses message publishing time as the timestamp.

      Timestamp values should be in one of two formats:

      - A numerical value representing the number of milliseconds since the
        Unix epoch.
      - A string in RFC 3339 format, UTC timezone. Example:
        ``2015-10-29T23:41:41.123Z``. The sub-second component of the
        timestamp is optional, and digits beyond the first three (i.e., time
        units smaller than milliseconds) may be ignored.
    publish_time_field: Field to add to output messages with the Pub/Sub
      message publish time. If None, no such field is added.
  """
  if topic and subscription:
    raise TypeError('Only one of topic and subscription may be specified.')
  elif not topic and not subscription:
    raise TypeError('One of topic or subscription may be specified.')
  if publish_time_field is not None and not publish_time_field.strip():
    raise ValueError('publish_time_field must be a non-empty field name.')
  has_publish_time_field = publish_time_field is not None
  payload_schema, parser = _create_parser(format, schema)
  extra_fields: list[schema_pb2.Field] = []
  if not attributes and not attributes_map and not has_publish_time_field:
    mapper = lambda msg: parser(msg)
  else:
    if isinstance(attributes, str):
      attributes = [attributes]
    if attributes:
      extra_fields.extend(
          [schemas.schema_field(attr, str) for attr in attributes])
    if attributes_map:
      extra_fields.append(
          schemas.schema_field(attributes_map, Mapping[str, str]))
    if has_publish_time_field:
      extra_fields.append(
          schemas.schema_field(publish_time_field, Optional[Timestamp]))

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