I use gwan for image generation, so I need to set correct content type, but G-WAN 3.12.26 after some load adds its own header with content type text/html and returns page with 2 http headers.
How to reproduce this:
use setheaders.c servlet from gwan package, start gwan and open this page, lets say http://localhost/?setheaders.c and you will get this (correct response):
HTTP/1.1 200 OK
Date: Sat, 29 Dec 2012 20:37:52 GMT
Last-Modified: Sat, 29 Dec 2012 20:37:52 GMT
Content-type: text/html
Content-Length: 371
Connection: close
<!DOCTYPE HTML><html lang="en"><head><title>Setting response headers</title><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><link href="imgs/style.css" rel="stylesheet" type="text/css"></head><body style="margin:16px;"><h1>Setting response headers</h1><br>This reply was made with custom HTTP headers, look at the servlet source code.<br></body></html>`
now run apache bench: ab -n 1000 'http://localhost/?setheaders.c' (1000 requests were enough for my system).
DO NOT RESTART GWAN, open http://localhost/?setheaders.c again and this is what you should get (incorrect response, 2 http headers):
HTTP/1.1 200 OK
Server: G-WAN
Date: Sat, 29 Dec 2012 20:43:34 GMT
Last-Modified: Fri, 16 Jan 1970 16:53:33 GMT
ETag: "be86ada7-14b40d-16f"
Vary: Accept-Encoding
Accept-Ranges: bytes
Content-Type: text/html; charset=UTF-8
Content-Length: 367
Content-Encoding: gzip
Connection: close
HTTP/1.1 200 OK
Date: Sat, 29 Dec 2012 20:43:34 GMT
Last-Modified: Sat, 29 Dec 2012 20:43:34 GMT
Content-type: text/html
Content-Length: 371
Connection: close
<!DOCTYPE HTML><html lang="en"><head><title>Setting response headers</title><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><link href="imgs/style.css" rel="stylesheet" type="text/css"></head><body style="margin:16px;"><h1>Setting response headers</h1><br>This reply was made with custom HTTP headers, look at the servlet source code.<br></body></html>
GWAN returns correct response if gzip and x-gzip are not set as acceptable encoding in request header (Accept-Encoding: gzip, x-gzip).
Is it possible to solve this modifying just servlet? If yes, then how?
Are you setting the MIME type like shown in fractal.c:
// -------------------------------------------------------------------------
// specify a MIME type so we don't have to build custom HTTP headers
// -------------------------------------------------------------------------
char *mime = (char*)get_env(argv, REPLY_MIME_TYPE);
// note that we setup the FILE EXTENTION, not the MIME type:
mime[0] = '.'; mime[1] = 'g'; mime[2] = 'i'; mime[3] = 'f'; mime[4] = 0;
If you do so then there's no way to confuse the automatic headers feature.
Other than that, v3.12 has had many instability problems (file time failures, pthread failures, signals failures, etc.) due to our direct syscalls and GLIBC wrappers - an effort initially intended to make the program run on all versions of Linux.
We have found (thanks to the many reports like yours) that rather than trying to fix those issues one by one (pointlessly fighting GLIBC, a moving target with many different releases each having its own bugs and specificities) a much safer path is to ditch GLIBC.
That's what G-WAN v4 will do, just a few days from now.