HN有一个奇葩的性能问题

    收到现场实施兄弟反馈，有一个子系统非常慢，因为此系统业务比较偏，很少人使用。现场把数据库报告发回来了，数据库上完全没有任何负载。

    对于一个系统，整体慢的情况下，先用前端工具httpwatch看下到底慢在哪里。

    等到httpwatch的结果发回来，看到一些端倪（由于公司不能传图片，所以有文字描述一下）：

    在time chat这一栏，基本上深绿色和红色各占一半，且Received字节越大越慢，先对这些颜色描述一下（httpwatch9.3.39pro这个版本可以看到各种颜色的描述）:

    白色------- blocked    曾经服务慢的无法响应的情况下（没有宕机），有巨大的blocked,长的达到1分多钟。

    粉红色----- DNS Lookup

    黄色------- Connect

    浅绿色----- Send

    红色------- Wait

    深绿色----- Receive  本次是这个有问题。

 

    IE浏览器 <------> weblogic应用<-------->Oracle数据库

    Receive就是 IE浏览器 <------ weblogic应用，weblogic应用向浏览器返回数据。当时只是在浏览器的机器上与weblogic服务器上ping了一下，比公司的慢3倍，感觉还好。把现场的代码发回来，在公司部署完全没有问题。

    重新找了一个网段的服务器，分别部署weblogic和Oracle，测试通过！

The Blocked time includes any pre-processing time (such as cache lookup) and the time spent waiting for a network connection to become available. Browsers limit the number of concurrent network connections per host name (i.e. www.microsoft.com) and will queue up requests if the limit has been reached. Often the Blocked time is the most significant factor in the download time of images embedded in a web page - particularly for older browsers that will only use a maximum of two connections per hostname. Modern browsers now allow up to six connections per hostname.

Send is the time required to send the HTTP request message to the server and will depend on the amount of data that is sent to the server. For example, long Send times will result from uploading files using an HTTP POST

Wait is the idle time spent waiting for a response message from the server. This value includes delays introduced due to network latency and the time required to process the request on the web server.

Receive is the time taken to read the response message from the server. This value will depend on the size of the content returned, network bandwidth and whether HTTP compression was used.

注：最近碰到一次深绿色时间很长，原因是在页面上展示了1000条数据，页面元素很多。