Comment 4 for bug 662912

Developments:

- qastaging is exhibiting the same behavior. (staging is dead because of a failed restore; I've investigated that separately.)

- The logging code is now in place. I can verify by seeing "Using upstream librarian http://launchpadlibrarian.net:80" in the log output.

- The logging code indicates that the 404 is not caused by any of the problems I logged. It's the same as before.

2010-10-27 16:17:57+0000 [-] Starting factory <twisted.web.proxy.ProxyClientFact
ory instance at 0x76c6560>2010-10-27 16:17:57+0000 [ProxyClient,client] 91.189.90.174 - - [27/Oct/2010:16:
17:56 +0000] "GET /42395443/tdGJABsFQRvCCFlFQFUZlZSJOd9.txt HTTP/1.0" 404 146 "-
" "Python-urllib/2.6"
2010-10-27 16:17:57+0000 [ProxyClient,client] Stopping factory <twisted.web.prox
y.ProxyClientFactory instance at 0x76c6560>

Again, that's a file that seems to match up just fine with the SQL query we ran in comment 1.

Therefore, I'm left with exploring what the ProxyClientFactory is, and seeing if it might have anything to do with this (because I don't see that part of the log in devel); and then re-checking the SQL results.