LR - 小布老师LR概述

今天开始由于项目需要，开始学习LR。和QTP一样，学习先从看视频学起，这种方式比较适合我这种不想动手的懒人。于是先从基础学起。今天第一讲，LR概述。以下是我从小布老师视频得到的一些启发。

http://www.boobooke.com/v/bbk1059/

1.A客户端 - B应用服务器 - C数据库服务器
其中，A-B为网络延迟时间，B为应用服务器处理时间，C为数据库服务器处理时间，总处理时间为三者之和。

2.性能测试的类型
   - Component Testing: Find the behavior. and performance of each tier.
   - Load Testing: Find out whether the system can handle the expected load upon deployment under realworld conditions.
   - Stress Testing: Find the system's breaking point. Apply testing that measures whether the system's environment is properly configured to handle expected or potentially unexpected high transaction volumes.
   - Volume Testing: Find the stability of the system with respect to handling large amounts of data over extended time periods.

3.性能测试贯穿于软件生命周期（从这里知道了deployment的真正含义）
   - Planning and Design: What is the best server to support 1000 users?
   - Development: Does the system response time meet requirements?
   - Deployment: Is the system reliable enough to go into production?(系统开发完了，要开始部署了，现在国内就停留在这个时候做性能测试)
   - Production: What is the cause of performance degradation?
   - Evolution: How many users can be added without decreasing system performance?

http://www.boobooke.com/v/bbk1060/

LR组成：
1. 脚本录制开发工具VuGen: Virtual users are processes or threads running on the load generator. 即VUsers就是进程/线程。
2. 集中控制器Controller: 就像手工性能测试时的coordinator，统一指挥VU(Virtual User)向后台发请求。可以做到毫秒级的同步。
3. 结果分析器Analysis
4. 压力机Load generator。用LR的话，只需要几台计算机。这几台机器称为Load generator: 压力产生器。由这些计算机发请求到后台去。相当于物理的机器，而非软件。Load generators, also known as hosts or injectors, are used to run the Vusers that generate load on the application under test(AUT).

LR支持的协议：
LR就是模拟客户端向服务器端发送请求包。做性能测试，首先就是要研究客户端和服务器端采用的是什么协议的通讯。比如我们要模拟浏览器上网访问一个网站，用的就是http协议，有时要用https协议。通过outlook发送请求到邮箱服务器，用的是pop3协议。因此，对协议支持的多少是表征测试工具的重要指标。

Scenario:
A scenario is a file that defines the scripts to execute, the number of Vusers to run, the goals of the test, the computer that will host the Vusers, and the conditions under which to run the load test.
Elements of a Scenario: Vusers, scripts, number of load generators, real-time monitors, run-time settings.
实际上它是一个配置文件，规定了有多少用户，这些用户怎么跑，跑在什么样的机器上，跑多长时间等。