def find_existing_replacements(reporting_conn, old_host):
    """ Determine if a request has already been requested

    Args:
    reporting_conn - A MySQL connect to the reporting server
    old_host - The hostname for the host to be replaced

    Returns:
    If a replacement has been requested, a dict with the following elements:
        new_host - The hostname of the new server
        new_instance - The instance id of the new server
        created_at - When the request was created

    If a replacement has not been requested, then return None.
    """
    cursor = reporting_conn.cursor()

    sql = ("SELECT new_host, new_instance, created_at "
           "FROM mysqlops.host_replacement_log "
           "WHERE old_host = %(old_host)s ")
    params = {'old_host': old_host.hostname}
    cursor.execute(sql, params)
    ret = cursor.fetchone()

    if ret:
        new_host = {
            'new_host': ret['new_host'],
            'new_instance': ret['new_instance'],
            'created_at': ret['created_at']
        }
        return new_host
    else:
        return None