Blocking Time Appears for Page Task Elements
Problem phenomenon
In the picture, Element within Element Waterfall Chart has a large amount of blocking time.
Cause of the problem
As can be seen from the figure, the website uses a large number of concurrent Request at the same time (the starting time of Request is the same), but the concurrent number of browsers is fully occupied, and the remaining downloads will be blocked until the previous Element processing is completed. This is why Thunder downloads files faster than direct downloads from browsers, because they modify and connect the files.
In addition, the number of links is also different under different Network environments, HTTP protocol versions, browsers and version numbers. We haven't officially given the specific number of connections. I collected them online. They are here for reference only.
1.
In order to solve the blocking problem, we can decentralize the domain names of certain URLs. For example, image domain names are generally used like img.abc.com. When a page contains more than 20 pictures, at least 10 Request will be blocked., and if we disperse it to img0.abc.com/img1.abc.com/img2.abc.com/... and other different domain names, at least these 20 pictures Request will be processed concurrently, and the website opening speed will be significantly improved. Similarly, some css/js domain names can be processed similarly.
2.
We know that the website address of Taobao is: taobao.com, but if you look closely, the domain name used in the pictures on Taobao's page is img.alicdn.com. Why not img.taobao.com? Because websites like Taobao use very large cookies. If you use the later domain name, a very long cookie will be included every time the Request picture is displayed. This is a great waste of Network resources and makes network request slower. To solve this problem, a separate domain name is necessary.