# Squid vs. Varnish vs. Nginx

> 在选择代理服务器的时候，我首先想到的就是3个著名的Proxy Server: Squid, Varnish, Nginx ，但是这3者具体有哪些区别，各有什么优劣，却没有系统梳理过。考虑到我的不同应用场景，以及未来需要系统实践的方向，所以收集和整理相关信息。

## varnish和squid差异

> 以下差异对比取自 [What is the fundamental difference between varnish and squid caching architectures?](https://www.quora.com/What-is-the-fundamental-difference-between-varnish-and-squid-caching-architectures) ，该文是2013年1月28日，已经是7年历史可能和现状不符，有待后续修正

* Squid是一个转发代理(open proxy)，但是也支持配置作为反向代理；然而Varnish从一开始就是构建为反向代理
* 从概念上来说，Varnish更适合作为反向HTTP代理，但是Squid的开发历史悠久，所以具备了很多Varnish没有的功能
  * Squid内建了SSL支持，而Varnish需要结合stud，nginx或者stunnel来实现SSL
  * Squid支持更为广泛的流媒体对象
  * Squid支持杀毒插件(antivirus-plugins)
* Varnish的优势在于
  * 极其巧妙的配置系统VCL提供了极具伸缩性的运行策略：从一系列user-agent请求重写URL来适合特定网络，这种模式对于Squid配置则非常复杂
  * Varnish的性能比Squid要好：Squid是单进程程序只能运行在一个CPU核心，而Varnish是多线程程序
  * Varnish具有更好的伸缩性：可以基于更多或更少的任何对象的缓存清理功能

## 参考

* [What is the fundamental difference between varnish and squid caching architectures?](https://www.quora.com/What-is-the-fundamental-difference-between-varnish-and-squid-caching-architectures)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://huataihuang.gitbook.io/cloud-atlas-draft/service/proxy/squid_vs_varnish_vs_nginx.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.