pathwaycom/pathway · error · ValueError

start_from_timestamp_ms must not be set when start_from='{st

Error message

start_from_timestamp_ms must not be set when start_from='{start_from}'

What it means

Error "start_from_timestamp_ms must not be set when start_from='{start_from}'" thrown in pathwaycom/pathway.

Source

Thrown at python/pathway/io/_utils.py:692

    The engine reserves ``-1`` in this field as an internal sentinel for
    ``start_from="end"``, so an explicit timestamp must be non-negative —
    otherwise a user-provided ``-1`` would silently turn into "start from
    the end of the stream" instead of raising an error.
    """
    if start_from == "timestamp":
        if start_from_timestamp_ms is None:
            raise ValueError(
                "start_from_timestamp_ms is required when start_from='timestamp'"
            )
        if start_from_timestamp_ms < 0:
            raise ValueError(
                "start_from_timestamp_ms must be a non-negative number of"
                f" milliseconds since the UNIX epoch; got {start_from_timestamp_ms}"
            )
        return start_from_timestamp_ms
    if start_from_timestamp_ms is not None:
        raise ValueError(
            f"start_from_timestamp_ms must not be set when start_from='{start_from}'"
        )
    return -1 if start_from == "end" else None


def _get_unique_name(
    name: str | None, kwargs: dict[str, Any], stacklevel: int = 6
) -> str:
    deprecated_name = kwargs.get("persistent_id")
    if name is not None:
        if deprecated_name is not None:
            raise ValueError(
                "'persistent_id' and 'name' should not be used together. Please use 'name' only."
            )
        return name
    if deprecated_name is not None:
        warnings.warn(
            "'persistent_id' is deprecated. Please use 'name' instead.",

View on GitHub (pinned to fa2f74a464)

Solutions

1. Remove the start_from_timestamp_ms argument, or set start_from='timestamp'.

Example fix

pw.io.kafka.read(rdkafka_settings, topic='t', start_from='earliest')

When it happens

Trigger: Thrown at python/pathway/io/_utils.py:692 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of pathwaycom/pathway@fa2f74a464 (2026-08-15). Data as JSON: /api/errors/3de383dc56f23712. Report an issue: GitHub.