Memcached Session Storage Issue

Severity: Warning
Message: Unknown: Failed to write session data (user). Please verify that the current setting of session.save_path is correct (localhost:11211)
Filename: Unknown
Line Number: 0
Backtrace:



My Config File :
$config['sess_driver'] = 'memcached';
$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 0;
$config['sess_save_path'] = 'tcp://localhost:11211';
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 0;
$config['sess_regenerate_destroy'] = FALSE;



I am getting this while using rest api.
Every output is rendered with above warning.

Development Platform
Php 5.5 Standard Google App Engine.
Using Default GAE Memcache shared driver.
Codeigniter version : 3.1.6