pathwaycom/pathway · error · ValueError

If webserver object is specified, host and port shouldn't be

Error message

If webserver object is specified, host and port shouldn't be set

What it means

pw.io.http.rest_connector accepts either a webserver object or the deprecated host/port pair, never both. This ValueError fires when webserver is given and host or port is also not None, because the connector would not know which server configuration to use.

Source

Thrown at python/pathway/io/http/_server.py:854

        format = "custom"

    if webserver is None:
        if host is None or port is None:
            raise ValueError(
                "If webserver object isn't specified, host and port must be present"
            )
        if isinstance(port, str):
            port = int(port)
        warn(
            "The `host` and `port` arguments are deprecated. Please use `webserver` "
            "instead.",
            DeprecationWarning,
            stacklevel=2,
        )
        webserver = PathwayWebserver(host, port)
    else:
        if host is not None or port is not None:
            raise ValueError(
                "If webserver object is specified, host and port shouldn't be set"
            )

    input_table = io.python.read(
        subject=RestServerSubject(
            webserver=webserver,
            route=route,
            methods=methods,
            schema=schema,
            delete_completed_queries=delete_completed_queries,
            format=format,
            request_validator=request_validator,
            documentation=documentation,
            cache_strategy=cache_strategy,
        ),
        schema=schema,
        format="json",
        autocommit_duration_ms=autocommit_duration_ms,

View on GitHub (pinned to fa2f74a464)

Solutions

1. Remove the host and port arguments and keep only webserver=...
2. If you intended the deprecated style instead, drop the webserver argument and pass both host and port.

Example fix

# before
words, rw = pw.io.http.rest_connector(webserver=ws, host="127.0.0.1", port=9999, route="/r", schema=S)
# after
words, rw = pw.io.http.rest_connector(webserver=ws, route="/r", schema=S)

def call_connector(webserver, host, port, **kw):
    if webserver is not None:
        host = port = None  # never mix both styles
    return pw.io.http.rest_connector(webserver=webserver, host=host, port=port, **kw)

When it happens

Trigger: rest_connector(webserver=ws, host='127.0.0.1', ...) or rest_connector(webserver=ws, port=9999, ...) — any call where a webserver object coexists with a non-None host or port argument.

Common situations: Partially migrating legacy code: the developer adds webserver=... but leaves old host/port arguments in place; copy-pasting a new example into old code that already sets host/port.

Related errors

• If webserver object isn't specified, host and port must be p
• 'raw' endpoint input format requires 'value' column in schem
• Missing topic name specification
• 'simple_read' does not accept {forbidden!r}. If you need to
• Failed to install dependencies

AI-assisted analysis of pathwaycom/pathway@fa2f74a464 (2026-08-15). Data as JSON: /api/errors/e09ffa74fb33278c. Report an issue: GitHub.