nginx sets content-type text/html on redirect

Question

I set up nginx as a reverse proxy for Drupal. Static files are served from a different domain. It works well, imagecache files are generated well, too. But the problem is: when the derivated image does not exist, the request for this image returns a redirect with the content-type:text/html, and Facebook or jQueryMobile (only when running in an iPhone, not in desktop browser) does not like it.

The context: when a file is requested from mycdn.com, if it does not exist, it is redirect to mysite.com which is a site that does the reverse proxy. So, it can be seen that imagecache does nothing here, just a use case. The question here: why nginx adds a text/html when it does a redirect?

Here is the scenario:

GET http://mycdn.com/sites/default/files/imagecache/gallery/myfile.jpg

Server  nginx
Date    Tue, 26 Jul 2011 05:28:09 GMT
Content-Type    text/html
Content-Length  154
Connection  keep-alive
Location    http://mysite.com/sites/default/files/imagecache/gallery/myfile.jpg
Expires Thu, 25 Aug 2011 05:28:09 GMT
Cache-Control   max-age=2592000

then the result of the redirect

GET http://mysite.com/sites/default/files/imagecache/gallery/myfile.jpg
Server  nginx
Date    Tue, 26 Jul 2011 05:28:10 GMT
Content-Type    image/jpeg
Connection  keep-alive
X-Powered-By    PHP/5.2.17
Expires Tue, 09 Aug 2011 05:28:10 GMT
Cache-Control   max-age=1209600, private, must-revalidate
Etag    "58a657c2ee47424f202387000c191b7e"
Set-Cookie  DRUPAL_UID=64; expires=Thu, 18-Aug-2011 09:01:29 GMT; path=/; domain=.thongtincongnghe.com
Vary    Cookie,Accept-Encoding,User-Agent
Last-Modified   Tue, 26 Jul 2011 05:28:10 GMT
Content-Encoding    gzip
Content-Length  1400

nginx configuration on mycdn.com (I removed unrelated info):

server {
    listen       80;
    server_name mycdn.com;
    root   /home/ttcn/public_html;
    expires 30d;

    location / {
        try_files $uri @redirect;
    }

    location @redirect {
        rewrite ^(.*)$ http://mysite.com$1;
    }
}

Brief, with a desktop browser, there is no difference. Everything works flawlessly. But jQueryMobile on a mobile does not work (until the derivated image is generated, through a desktop browsing), Facebook OpenGraph does not work (I put the derivated image url in the og:image value) - it does not take that image until it exists on the server.

Answer 1

There is nothing wrong with the redirect having a content type of text/html. On the contrary, it is actually mandated by the HTTP/1.1 specification itself:

The temporary URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

The cache control header might be confusing Webkit mobile. Have you tried add expires off; inside the location @redirect block?