Safari Sends Two HTTP Req. Same Time/Socket

Question

I have an IPad Safari sending two HTTP requests (two different PNG) files within 30 ms.

I thought that even on a Keep Alive HTTP 1.1 connection there should be a clear

Answer 1

I think that this may be due to browser adhering to HTTP 1.1 Spec 8.2.4. which does allow client to retry the request if client is connected to server thru a middle layer and doesn't get a response from server before the connection is closed.

I have seen this error and have found following links to be helpful.

https://www.ravellosystems.com/blog/beware-http-requests-automatic-retries/

http://geek.starbean.net/?p=393

Answer 2

It looks like HTTP pipelining:

HTTP pipelining is a technique in which multiple HTTP requests are sent on a single TCP connection without waiting for the corresponding responses.

Answer 3

I am seeing this too from a mobile safari client. The only workaround I was able to find is to disable keepalive for the whole server in Nginx. We don't get duplicate requests and/or pipelining might not work from the Safari client when keepalive is disabled.

In Nginx, there is a keepalive_disable option, but it only works for POST requests on certain browsers, and doesn't have many options. We ended up disabling keepalive on that server using keepalive_timeout 0; I hope there is a better solution in the future.

I would think that a correct use of pipelining would submit multiple differing requests, instead of duplicate requests.