设置：具有 5 个节点的副本集，版本 3.4.5。
尝试使用 rs.stepDown(60, 30) 切换 PRIMARY 但始终出现错误：
rs0:PRIMARY> rs.stepDown(60, 30)
{
"ok" : 0,
"errmsg" : "No electable secondaries caught up as of 2017-07-11T00:21:11.205+0000. Please use {force: true} to force node to step down.",
"code" : 50,
"codeName" : "ExceededTimeLimit"
}
但是，在并行终端中运行的 rs.printSlaveReplicationInfo() 确认所有副本均已完全赶上：
rs0:PRIMARY> rs.printSlaveReplicationInfo()
source: X.X.X.X:27017
syncedTo: Tue Jul 11 2017 00:21:11 GMT+0000 (UTC)
0 secs (0 hrs) behind the primary
source: X.X.X.X:27017
syncedTo: Tue Jul 11 2017 00:21:11 GMT+0000 (UTC)
0 secs (0 hrs) …