[AOLSERVER] Null responses

[Cyan o. <cy...@ru...>]

Hi

I'm hoping there are still some subscribers to this list ;)

I'm trying to debug a strange condition we're seeing on a small percentage
of our connections: connections are being closed by the server without any
response being sent back on the connection (verified by looking at network
packet traces and inserting a logging transparent proxy between the client
and server).  The network packet pattern we see is:

<normal TCP setup - SYN, SYN/ACK, ACK>

Request data (in a single frame, or multiple), ACK

Then the connection is closed by the server after 10 - 70 ms, without any
data being sent, with a FIN/ACK (still getting confirmation on this - these
logs are from the other side of the man-in-the-middle proxy I'm using to
get debugging info).

For some of the failed requests, the server processing never gets as far as
the start of our Tcl code (a preauth filter that starts with an ns_log that
doesn't show up in the server log).

For others the request is processed normally and an access.log message
written indicating that a response was generated with HTTP code 200, but no
packet shows up on the network.

There is no pattern to the failed requests (sometimes requests for
favicon.ico fail), and retrying the exact request shortly afterwards often
succeeds.

Has anyone seen anything like this before, or have any advice on how to
narrow down the cause further?

We're running a slightly patched version of the last 4.5.2 rc, on Ubuntu
12.04.5 64bit on Amazon EC2 instances, with Tcl 8.6.1

Thanks

Cyan