On 08/28/2012 10:21 AM, Andy Osborne wrote:
Hi All, I'm trying to debug a problem at the moment where a small proportion of people visiting our sites (Squid 3.1.20 as a reverse proxy with Apache origin servers) are seeing file corruption. So far all the confirmed cases are using Windows 7 with IE 9 or a recent Chrome. Unfortunately we can't reproduce the problem on any machine we have, which is making it difficult to debug. The corruption doesn't always occur but when it does it looks like a few contiguous bytes getting one or two bits flipped.
It is extremely unlikely that a few bits get flipped by Squid, the netowrk layer or any other component except non-ECC memory. Does the server that runs Squid have ECC or non-ECC memory? Marcus
I managed to get access to a PC belonging to a client to do some testing. This machine has the problem and runs Win 7 Pro (64 bit). Unplugging it from the network and using it's ethernet cable to test using a variety of laptops (Mac, Win 7, Win XP) showed no problems. That would normally be enough to put the whole thing down to some weird Windows bug and give up. However, overriding DNS via the hosts file to point this problematic machine directly at an origin server made the problem disappear. I still think it's probably a Windows bug, but it seems that something about the reverse proxy (Squid or the machine running it) is triggering the bug. Test downloads from various locations hasn't found any difference between files downloaded directly or via the reverse proxy. Basically, all my testing shows no problems. Has anyone else seen a similar problem recently ?. One reason to support it being a Windows bug is that it only started occurring about 3 weeks ago and we haven't changed anything in our hosting set up in that time frame. It would also be a help if anyone can point me at some sites that are known to be using Squid as a reverse proxy. Seeing if they also exhibit the problem might help to narrow things down. Cheers, Andy
