August 2019
Beginner to intermediate
232 pages
3h 50m
Chinese
Content preview from Web容量规划之美
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83
测量
：
容量的单位
到达某种我们在图中不会遇到的值（可能不安全）时，我们有十足的把握，我们
的
CPU
容量是足够的。
但是，这完全是一个假设。让我们通过另外一种形式的容量规划来确认它：受控
的负载测试。
在负载均衡的环境下找到 Web 服务器的上限
捕获
Web
服务器资源的上限可以由至少一个你可能的设计来决定：使用负载均衡
服务。为了确定服务承载真实流量的上限，通过从现有负载均衡池中“撤”服务
器的方式来增加生产环境负载（例如调整
HAProxy
的权重），这就增加了剩余服
务器上的负载，仔细研究这些服务器并测量它对资源的影响。我们要强调使用真
实流量，而不是运行仿真模型或试图对
Web
服务器资源在一个类基准的环境里建
模的重要性。
我们模拟的负载均衡测试验证了我们在前面章节中所做出的假设，即：
CPU
使用
与忙碌
Apache
进程之间的关系保持（大致）不变。图
3-9
描述了活动的
Apache
进程的增长及其相应的
CPU
使用率的增加，它由一台
Web
服务器在其每日的高峰
和低谷之间通过
RRD
生成，按总
CPU
增长排列。它确认了
CPU
使用量确实随着
繁忙的
Apache
进程数目增提升，至少在
CPU
为
40%~90%
之间是这样的情况。
这表明，在当前环境中使用
CPU
作为
Web
服务器上的容量的单个度量指标是安全
的。此外，它直接与
Web
服务器的工作相关，而且将来很有希望与网站流量相关。
基于此信息，我们设置当前总
CPU
的上限为
85%
，它有足够余量处理偶尔的峰值，
同时还能有效利用服务器。
84
第
3
章
图
3
-
9
：总的 CPU 与繁忙的 Apache ...
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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.