mongodb在没有设置副本集的情况下，崩溃前的log里出现多次isMaster命令

command admin.$cmd command: isMaster { ismaster: 1 } numYields:0 reslen:189 locks:{} protocol:op_query 1600ms



serverStatus was very slow: { after basic: 600, after asserts: 1001, after backgroundFlushing:

1302, after connections: 1701, after dur: 2194, after extra_info: 3300, after globalLock: 3995,

after locks: 5002, after network: 5304, after opLatencies: 5600, after opcounters: 5799,

after opcountersRepl: 6104, after repl: 6500, after security: 6802, after storageEngine: 7500,

after tcmalloc: 8601, after wiredTiger: 32799, at end: 37100 }