May 2024
Intermediate
278 pages
5h 24m
Chinese
Content preview from 构建可扩展分布式系统：方法与实践
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124
｜
第
7
章
在代理中，每个队列由单个线程管理。这意味着，如果底层节点上的队列数至少与核心
数一样多，那么可以提高多核节点上的吞吐量。相反，如果你的代理节点上高利用率队
列数远比核心数多，那么你可能会遇到一些性能下降。
与大多数消息代理一样，
RabbitMQ
在消费速率跟生产速率相当时表现最佳。当队列增
长到大约有数万条消息时，管理队列的线程将承受更多的开销。默认情况下，代理使用
运行节点
40%
的可用内存。当达到此限制时，代理将开始限制生产者，降低代理接受消
息的速度，直到内存使用率降至
40%
阈值以下。内存阈值是可配置的，它是一个可以根
据你的工作负载进行调整以优化消息吞吐量的设置
注
5
。
1
7.2.3
数据安全与性能权衡
所有消息传递系统都面临着性能与可靠性权衡的两难境地。在这种特殊情况下，核心问
题是消息传递的可靠性，通常称为数据安全。你希望自己的消息在生产者和消费者之间
以最小的延迟传输，当然你也不希望在此过程中丢失任何消息。然而要是真有这么简单
就好了。可别忘了，这些是分布式系统。
当一条消息从生产者传递到消费者时，你必须在设计中考虑多种故障场景。其包括：
•
生产者向代理发送消息，但代理未成功接受该消息。
•
消息在队列中的时候代理崩溃了。
•
消息已成功传递给消费者，但消费者在完全处理该消息之前出故障了。
如果你的应用程序能够容忍消息丢失，那么你可以选择性能最大化的选项。如果偶尔丢
失一条来自即时消息传递应用程序的消息，那么这可能并不重要。在这种情况下，你的
系统可以忽略消息安全问题并全速运行。但采购系统就不一样 ...
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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.