MongoDB shard stopped with no reason - mongodb

Question

I have a website ( Analytics Service ) for website and i have about +3K concurrent user .. i'm using php with MongoDB
MongoDB architecture is ( 1 Query , 3 Config server , 2 Shard ) . i'm sure that my mongo configuration is working fine . but shard 1 stopped suddenly with no reason. and when i tried to run sudo services mongod restart mongo doesn't run. when i view the log file i get the last lines
2016-10-15T09:35:52.334-0400 I CONTROL [main] ***** SERVER RESTARTED *****
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] MongoDB starting : pid=2168 port=27017 dbpath=/var/lib/mongodb 64-bit host=Analytics-DB-shard-01
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] db version v3.2.8
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] git version: ed70e33130c977bda0024c125b56d15957sdaaf0
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] OpenSSL version: OpenSSL 1.0.1f 6 Jan 2014
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] allocator: tcmalloc
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] modules: none
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] build environment:
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] distmod: ubuntu1404
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] distarch: x86_64
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] target_arch: x86_64
2016-10-15T09:35:52.343-0400 I CONTROL [initandlisten] options: { config: "/etc/mongod.conf", net: { bindIp: "127.0.0.1", port: 27017 }, storage: { dbPath: "/var/lib/mongodb", journal: { enabled: true } }, systemLog: { destination: "file", logAppend: true, path: "/var/log/mongodb/mongod.log" } }
2016-10-15T09:35:52.373-0400 E NETWORK [initandlisten] Failed to unlink socket file /tmp/mongodb-27017.sock errno:1 Operation not permitted
2016-10-15T09:35:52.373-0400 I - [initandlisten] Fatal Assertion 28578
2016-10-15T09:35:52.373-0400 I - [initandlisten]
***aborting after fassert() failure
i can't figure out mongo problems but i'm trying to manage it to work correctly as much as possible .. any idea how to make sure that it won't dropped again ?