libmemcached - memcached_fetch() does not fetch value for all the keys mentinoed memcached_mget() call

I want to perform multi get operation using libmemcached 0.32 (client library for memcached). There is group of 13 keys which I passed as argument to memcached_mg开发者_如何学运维et() and then call memcached_fetch() in loop to retrieve the key, value pairs till it returns NULL.

I found it does not fetch all values consistently. Most of the time its able to fetch 3 to 5 key value pairs out of 13 before loop terminates.

I have following questions 1> Are there any limitations for using multi get in libmemcached? 2> Why couldn't memcached_fetch() retrieve all key value pairs?

Please note: I am using unix socket for communication between client and memcached daemon and giving expiration time as 3000 in memcached_set to avoid time out problem.

Thanks in advance