November 2021
Intermediate to advanced
410 pages
12h 1m
Chinese
Content preview from MongoDB权威指南（第3版）
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管理
｜
233
13.4.5
计算延迟
对于复制来说，需要跟踪的最重要的指标之一就是从节点与主节点之间的延迟情况。
延迟
（
lag
）是指从节点相对于主节点的落后程度
，也就是主节点执行的最后一个操作的时间戳
与从节点应用的最后一个操作的时间戳之间的差值。
可以使用
rs.status()
来查看成员的复制状态，也可以运行
rs.printReplicationInfo()
或
rs.printSlaveReplicationInfo()
来快速地获取一份摘要。
rs.printReplicationInfo()
给出了主节点
oplog
的简要信息，包括它的大小和操作的日期
范围：
> rs.printReplicationInfo();
configured oplog size: 10.48576MB
log length start to end: 3590 secs (1.00hrs)
oplog first event time: Tue Apr 10 2018 09:27:57 GMT-0400 (EDT)
oplog last event time: Tue Apr 10 2018 10:27:47 GMT-0400 (EDT)
now: Tue Apr 10 2018 10:27:47 GMT-0400 (EDT)
在本例中，
oplog
大约有
10MB (10MiB)
，只能包含一个小时的操作。
在实际的部署中，
oplog
应该更大
（请参阅下一节有关更改
oplog
大小的说明）。我们希望
日志的长度 ...
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