Brewer’s Conjecture and the Feasibility of Consistent, Available, Partition-Tolerant Web Services

2019-10-31 2027 words 5 mins read

[toc]

摘要

当设计分布式的 web 服务时, 有三个经常考虑到的属性: 一致性 (consistency), 可用性(availability)和分区容错性(partition tolerance). 三者是不可能同时达到的. 在这个文章里, 我们将会在一个异步网络模型中证明这个猜想, 然后在部分同步模型中讨论解决这个问题的方案.

TCP_NODELAY 是什么

2019-10-02 625 words 2 mins read

引言

最近在使用 curl 的时候经常注意到:

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# strrl @ eiu in ~ [11:02:50]
$ curl -v google.com
* Rebuilt URL to: google.com/
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 6152 (#0)
> GET http://google.com/ HTTP/1.1
> Host: google.com
> User-Agent: curl/7.54.0
> Accept: */*
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 301 Moved Permanently
< Location: http://www.google.com/
< Content-Type: text/html; charset=UTF-8
< Date: Wed, 02 Oct 2019 03:02:53 GMT
< Expires: Fri, 01 Nov 2019 03:02:53 GMT
< Cache-Control: public, max-age=2592000
< Server: gws
< Content-Length: 219
< X-XSS-Protection: 0
< X-Frame-Options: SAMEORIGIN
<
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<TITLE>301 Moved</TITLE></HEAD><BODY>
<H1>301 Moved</H1>
The document has moved
<A HREF="http://www.google.com/">here</A>.
</BODY></HTML>
* Connection #0 to host 127.0.0.1 left intact