August 2019
Beginner to intermediate
232 pages
3h 50m
Chinese
Content preview from Web容量规划之美
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62
第
3
章
收集与度量本身的卷相关的元数据（与度量相关联）并不少见。这也监控所需成
本有直接的影响。此外，可悲的是，
90%
以上的度量和收集的元数据从未被读取，
换句话说，从来没使用过。
Netflix
和
Twitter
都存在这种情况。
注意
对一些常用的监控工具的利弊的讨论
，
参阅
Caskey Dickson
在
LISA
’
13
会议上的演讲
（
https://www.usenix.org/conference/lisa13/working-
theory-monitoring
）。
本章我们将讨论特定的度量指标的统计数据，如缓存命中率和磁盘使用率，你会
因为不同的目的进行度量并用图表展现结果，以便更好地描述我们面对的场景。
关于如何设置特定的工具来进行测量，还有很多其他的信息来源，大多数专业的
系统管理员已经安装了这样的工具。
接受观察员效应
接受度量系统的观察者效应引入了另外一个任务
，
要求服务以正常行为运转
。
采集传输度量指标会消耗一些系统资源
，
良好的监控工具努力做到轻量级以确
保不妨碍系统的主要工作
，
但是还是会有一些额外消耗
。
在这方面
Arun
的经
验是建立一个
Java
应用程序的话
，
使用
YourKit
对代码的入侵性太强
，
而使用
Sun Studio
（
即使在虚拟机环境
）
会比较轻量级
。
对于延迟敏感的系统来说低
开销是尤其重要的
，
比如小于
100
毫秒的应用程序
。
这意味着测量系统的资源将以某种小的方式
（
希望
，
非常小
）
影响系统的行为
，
并且
，
通过扩展最终记录测量值
。
这通常被称为观测器效应
。
我们的理念是将服务器上的负载及将数据产生的微小代价一起作为业务处理的 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.