What causes "input connection is not a valid protocol: {err:?}" in databendlabs/databend?

Recreate the named connection with a valid STORAGE_TYPE (e.g. 's3','gcs','oss','azblob')

input connection is not a valid protocol

Error message

input connection is not a valid protocol: {err:?}

What it means

apply_uri_connection compares the storage_type of the referenced named connection with the protocol parsed from the URI. If the connection's storage_type cannot be parsed as an OpenDAL Scheme, this InvalidInput error is thrown, meaning the stored connection has an unrecognized or invalid storage type.

Solutions

Recreate the named connection with a valid STORAGE_TYPE (e.g. 's3','gcs','oss','azblob')
Inspect the connection definition (SHOW CONNECTIONS / meta inspect) and fix storage_type
Upgrade/repair legacy connections whose storage_type strings no longer parse

Example fix

-- before (invalid storage type)
CREATE CONNECTION c STORAGE_TYPE='s3legacy' ...;
-- after
CREATE CONNECTION c STORAGE_TYPE='s3' ENDPOINT_URL='https://s3.amazonaws.com';

Defensive patterns

Strategy: validation

Validate before calling

let stored = get_connection(name)?.storage_type;
if opendal::Scheme::from_str(&stored).is_err() {
    return Err(format!("connection {name} has invalid storage_type {stored:?}; recreate it"));
}

Try / catch

match err.kind() { ErrorKind::InvalidInput if msg.contains("not a valid protocol") => /* recreate/repair the named connection */, _ => return Err(err) }

Prevention

Create connections only with valid STORAGE_TYPE values
Audit old connections after version upgrades
Validate storage_type against the Scheme enum when provisioning

When it happens

Trigger: Using CONNECTION_NAME to apply a stored connection whose storage_type string is not a valid scheme (corrupted or legacy meta record, hand-edited connection), during resolve_uri_connection.

Common situations: Connections created by older versions with scheme strings no longer parseable; corrupted meta-service records; typos in storage_type when a connection was created via API.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of databendlabs/databend@288d84d76e (2026-09-11). Data as JSON: /api/errors/b0b799234c3e80c0. Report an issue: GitHub.

Appendix: source

Thrown at src/query/sql/src/planner/binder/location.rs:565

        return Err(Error::new(
            ErrorKind::InvalidInput,
            anyhow!("can not use connection_name when create connection"),
        ));
    }

    parse_uri_location_resolved(l, parts).await
}

pub fn apply_uri_connection(
    l: &mut UriLocation,
    name: &str,
    conn: UserDefinedConnection,
) -> Result<()> {
    let protocol = l.protocol.parse::<Scheme>()?;
    let proto = conn.storage_type.parse::<Scheme>().map_err(|err| {
        Error::new(
            ErrorKind::InvalidInput,
            anyhow!("input connection is not a valid protocol: {err:?}"),
        )
    })?;
    if proto != protocol {
        return Err(Error::new(
            ErrorKind::InvalidInput,
            anyhow!(
                "protocol from connection_name={name} ({proto}) not match with uri protocol ({protocol})."
            ),
        ));
    }
    l.connection.check().map_err(|_| {
        Error::new(
            ErrorKind::InvalidInput,
            anyhow!("connection_name can not be used with other connection options"),
        )
    })?;
    l.connection = Connection::new(conn.storage_params);

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