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HTTP

Posted by 夏泽民 Oct 31, 2019

在1991年发布了HTTP 0.9版，在1996年发布1.0版，1997年是1.1版，1.1版也是到今天为止传输最广泛的版本（初始RFC 2068 在1997年发布， 然后在1999年被 RFC 2616 取代，再在2014年被 RFC 7230 /7231/7232/7233/7234/7235取代），2015年发布了2.0版，其极大的优化了HTTP/1.1的性能和安全性，而2018年发布的3.0版，继续优化HTTP/2，激进地使用UDP取代TCP协议，目前，HTTP/3 在2019年9月26日 被 Chrome，Firefox，和Cloudflare支持 HTTP 0.9 / 1.0 0.9和1.0这两个版本，就是最传统的 request – response的模式了，HTTP 0.9版本的协议简单到极点，请求时，不支持请求头，只支持 GET 方法，没了。HTTP 1.0 扩展了0.9版，其中主要增加了几个变化：

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Gourtines

Posted by 夏泽民 Oct 31, 2019

定义于src/runtime/runtime2.go:

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Debugging

Posted by 夏泽民 Oct 31, 2019

https://software.intel.com/en-us/blogs/2014/05/10/debugging-performance-issues-in-go-programs Let’s assume you have a Go program and want to improve its performance. There are several tools available that can help with this task. These tools can help you to identify various types of hotspots (CPU, IO, memory), hotspots are the places that you need to concentrate on in order to significantly improve performance. However, another outcome is possible – the tools can help you identify obvious performance defects in the program. For example, you prepare an SQL statement before each query while you could prepare it once at program startup. Another example is if an O(N^2) algorithm somehow slipped into where an obvious O(N) exists and is expected. In order to identify such cases you need to sanity check what you see in profiles. For example for the first case significant time spent in SQL statement preparation would be the red flag.

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Exactly Once语义与事务机制

Posted by 夏泽民 Oct 28, 2019

实现Exactly Once的一种方法是让下游系统具有幂等处理特性，而在Kafka Stream中，Kafka Producer本身就是“下游”系统，因此如果能让Producer具有幂等处理特性，那就可以让Kafka Stream在一定程度上支持Exactly once语义。 为了实现Producer的幂等语义，Kafka引入了Producer ID（即PID）和Sequence Number。每个新的Producer在初始化的时候会被分配一个唯一的PID，该PID对用户完全透明而不会暴露给用户。

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kafka EOS

Posted by 夏泽民 Oct 28, 2019

在说Kafka的事务之前，先要说一下Kafka中幂等的实现。幂等和事务是Kafka 0.11.0.0版本引入的两个特性，以此来实现EOS（exactly once semantics，精确一次处理语义）。

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