August 2019
Beginner to intermediate
232 pages
3h 50m
Chinese
Content preview from Web容量规划之美
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127
趋势预测
图
4
-
9
：繁忙的 Apache 进程，周视图
这是取自拥有
15
台
Web
服务器时期的
Flickr
的历史数据。我们假设数据是今天取
得的，且不知道未来的变化。我们可以假设第
3
章中的结论是正确的，
CPU
使用
率与繁忙的
Apache
进程的数量之间只是简单的倍数关系：
1.1
。如果由于某种原
因这个假设发生了变化，我们会马上知道，因为每分钟都在跟踪这些度量指标。
如图
4-9
所示，在高峰期大约有
900
个繁忙的
Apache
并发进程在运行，通过
15
个
Web
服务器来进行负载均衡。这样大概每台
Web
服务器承载
60
个进程。因此，
每个
Web
服务器大约使用总
CPU
的
66%
（我们可以查看
CPU
图形确认此假设）。
我们最感兴趣的是该示例数据的峰值，图
4-10
包含的数据跨越了一个较长的时间
轴，因此我们可以看到一些周期特征在这段时间重复发生。
图
4
-
10
：横跨六周的每周 Web 服务器峰值
128
第
4
章
这些周峰值就是我们想要跟踪并用于预测未来的需求。事实证明，对于
Flickr
来说，
这些周峰值总是在周一时发生回落。如果我们孤立这些峰值，如我们在磁盘存储
示例中做的一样，把它延伸成一条
眼需要未来的趋势线，我们会看到类似图
4-11
的结果。
图
4
-
11
：Web 服务器峰值趋势
如果我们的流量继续以目前的速度持续增长，该图预测出在接下来的 ...
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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.
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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.