[users@httpd] Apache translates a 401 to 502 from a backend proxy

[Sachin Shetty <ss...@egnyte.com>]

Hi,

Our proxy setup is Apache ==> Haproxy ==> Cherry Py Server Pool

We are seeing some weird issues with Apache translating a 401 from a backend
haproxy to 502 to the client. The request gets logged as 401 in haproxy
logs, but apache logs it as 502 and sends a 502 back to the client. This can
be easily reproduced by sending a multipart post request to Apache which
forwards to haproxy and haproxy forwards it to cherry py server. Cherry py
server sends a 401 back without attempting to read the post request due to
some business rules.

We see the following in the apache log:

[Tue Sep 20 13:00:39 2011] [debug] mod_proxy_http.c(56): proxy: HTTP:
canonicalising URL //localhost:9910/put_file
[Tue Sep 20 13:00:39 2011] [debug] proxy_util.c(1525): [client 127.0.0.1]
proxy: *: found reverse proxy worker for http://localhost:9910/put_file
[Tue Sep 20 13:00:39 2011] [debug] mod_proxy.c(993): Running scheme http
handler (attempt 0)
[Tue Sep 20 13:00:39 2011] [debug] mod_proxy_http.c(1962): proxy: HTTP:
serving URL http://localhost:9910/put_file
[Tue Sep 20 13:00:39 2011] [debug] proxy_util.c(2011): proxy: HTTP: has
acquired connection for (*)
[Tue Sep 20 13:00:39 2011] [debug] proxy_util.c(2067): proxy: connecting
http://localhost:9910/put_file to localhost:9910
[Tue Sep 20 13:00:39 2011] [debug] proxy_util.c(2193): proxy: connected
/put_file to localhost:9910
[Tue Sep 20 13:00:39 2011] [debug] proxy_util.c(2444): proxy: HTTP: fam 2
socket created to connect to *
[Tue Sep 20 13:00:39 2011] [debug] proxy_util.c(2576): proxy: HTTP:
connection complete to 127.0.0.1:9910 (localhost)
[Tue Sep 20 13:00:39 2011] [info] [client 127.0.0.1] (32)Broken pipe:
core_output_filter: writing data to the network
[Tue Sep 20 13:00:39 2011] [error] (103)Software caused connection abort:
proxy: pass request body failed to 127.0.0.1:9910 (localhost)
[Tue Sep 20 13:00:39 2011] [error] proxy: pass request body failed to
127.0.0.1:9910 (localhost) from 127.0.0.1 ()
[Tue Sep 20 13:00:39 2011] [debug] proxy_util.c(2029): proxy: HTTP: has
released connection for (*)

It almost seems like Apache is expecting the data (whatever is available) to
be read by the downstream process which does not happen. 

A few interesting things:
1. When I remove apache from the chain and hit haproxy directly for testing,
I see a proper 401 status code as expected
2. When I post a smaller file, say 2KB, it works fine, I see a 401 status
code as returned the backend proxy. But when I post a 150+ KB file, it fails
with 502 even though the proxy still returned 401.

I can send the tcpdump as well if anybody is interested. 

Thanks
Sachin


---------------------------------------------------------------------
The official User-To-User support forum of the Apache HTTP Server Project.
See <URL:http://httpd.apache.org/userslist.html> for more info.
To unsubscribe, e-mail: users-unsubscribe@httpd.apache.org
   "   from the digest: users-digest-unsubscribe@httpd.apache.org
For additional commands, e-mail: users-help@httpd.apache.org