我在本地创建了 mongo db 副本集，如下所示：
mongod --port 27021 --dbpath /cm1/mongodb/rs0-1 --replSet rs0 --smallfiles --oplogSize 128.
我已经开始的所有3（1主，次级2）的实例与mongo --port 27022。
副本集正在工作，数据从主节点流向辅助节点。
如果我关闭 mongodb 实例之一，其余 2 个实例会抛出错误。日志如下：
2017-07-25T13:01:24.904+0530 I REPL [ReplicationExecutor] Error in heartbeat request to localhost:27021; HostUnreachable: Connection refused
2017-07-25T13:01:24.904+0530 I ASIO [NetworkInterfaceASIO-Replication-0] Connecting to localhost:27021
2017-07-25T13:01:24.906+0530 I ASIO [NetworkInterfaceASIO-Replication-0] Failed to connect to localhost:27021 - HostUnreachable: Connection refused
2017-07-25T13:01:24.906+0530 I ASIO [NetworkInterfaceASIO-Replication-0] Dropping all pooled connections to localhost:27021 due to failed operation on a connection
2017-07-25T13:01:24.906+0530 I REPL …mongodb ×1