enter into shard-4;
1. implement mongo command: rs.status(), show info 2 secondary 1 primary;
2. implement mongo command:db.printSlaveReplicationInfo(), show secondary one of replications behind primary 864.97hrs,
The replication log show :"Thu Feb 8 10:31:31.105 I REPL [ReplicationExecutor] Scheduling priority takeover at 2018-02-08T10:31:41.313+0800
Thu Feb 8 10:31:41.313 I REPL [ReplicationExecutor] Canceling priority takeover callback
Thu Feb 8 10:31:41.314 I REPL [ReplicationExecutor] Not starting an election for a priority takeover, since we are not electable due to: Not standing for election because member is not caught up enough to the most up-to-date member to call for priority takeover - must be within 2 seconds (mask 0x400)"
3. restart the secondary replication:
a. replication log show :the same as above;
b. rs.status show info: 1 secondary 1 primary and 1 RECOVERING;