24. Elapsed time、Latency、Connect Time的含义

前言

在 Jmeter 中一些专业名词我们是需要提前认知的，如下

1. Elapsed time
2. Latency
3. Connect Time

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Elapsed time

• 从发送请求到收到最后一个响应，所花费的时间
• 不包括渲染请求所花费的时间，同时也不包括处理客户端脚本所花费的时间

JMeter measures the elapsed time from just before sending the request to just after the last response has been received. JMeter does not include the time needed to render the response, nor does JMeter process any client code, for example Javascript.

Latency

• 从发送请求到收到第一个响应，所花费的时间
• 该时间包括组装请求、组装响应的第一部分所需的处理时间，通常长于一个字节
• Jmeter 的时间应该更接近浏览器或其他应用程序客户端所经历的时间
• 网上还有种说法，就是响应信息越大，差别越大

JMeter measures the latency from just before sending the request to just after the first response has been received. Thus the time includes all the processing needed to assemble the request as well as assembling the first part of the response, which in general will be longer than one byte. Protocol analysers (such as Wireshark) measure the time when bytes are actually sent/received over the interface. The JMeter time should be closer to that which is experienced by a browser or other application client.

Connect Time

• 建立连接所花费的时间
• 包括SSL三次握手的时间
• 注意：latency 没有减去 connect time
• 当出现链接超时等错误，这个会等于链接超时时间

JMeter measures the time it took to establish the connection, including SSL handshake. Note that connect time is not automatically subtracted from latency. In case of connection error, the metric will be equal to the time it took to face the error, for example in case of Timeout, it should be equal to connection timeout.