Occasionally, individual users will receive "blank pages" from our web server on login.
- It only happens to individual users, not all users at a given time.
- Using the same account from a different machine may or may not reproduce the problem.
- Using a different account from the same machine usually works.
- The problem will often go away on its own after about an hour.
- Switching URLs (e.g. from /foo/Default.aspx, to /foo/) will sometimes fix the problem for the user.
- Fiddler2 HTTP trace shows that the client receives HTTP headers, with a Content-Length=0, and no content.
- IIS logs show that all HTTP responses have had a non-zero byte length for the user.
- Clearing cookies and cache, or closing the browser have no effect.
- Clearing the session from the server side has no effect.
- So far we have only seen the error on one of the two web servers in the cluster.
Configuration:
- Big/IP load balancer - sticky sessions by IP address
- Windows 2008 R2 Servers - IIS 7.5
- .NET 4.0 for the application
- Seen in IE7 & IE8
Other odd, possibly related information:
- An internal tester going directly to the IIS server (not big/ip), downloaded a file from the web server and our anti-virus (Symantec) flagged the download as a DoS attack and blocked the IIS server. Downloading the same file through Big/ip did not. This seems to point to some network (TCP/IP or HTTP) error in IIS that may trigger an incomplete HTTP response.
Ideas? Answers?