问题
We are using signed URLs to deliver some video content. When browsing directly to the signed URL, looking at the network profiler, you can see the URL being connected to 4 times. Why is it doing this?
The screen shot below was a brand new, generated link so in no way was this file cached. The reason I am even to this point is cloudFront has been extremely slow to load videos for us the past week. The video in the screen shot is an hour and a half and it takes about 20-30 seconds to begin playing.
The same exact file we place on rackspace begins playing within 5 seconds.
view larger image
view larger image
what happens is the first line cancels out right away, the second line begins to download and at about 3.5mb downloaded it cancels and starts the 3rd and 4th lines. The 4th line is finally the file that begins downloading and playing
来源：https://stackoverflow.com/questions/26981372/why-does-cloudfront-deliver-sequential-connections-that-cancel-out-img-inside