Setting up the rewriting rules for the request proved to be quite easy in Nginx. For the response, not so much (at least, not for me). I want to strip the Content-Type header from the response if the Content-Length header of the response isn't set. I have the NginxHttpHeadersMoreModule installed, so that should allow me to remove the header, but I can't seem to find a way to check for the existence of the Content-Length header of the response using a rule in Nginx's configuration. Any suggestions on how to do this would be most appreciated!
asked Jul 30, 2010 at 13:58
4 Answers
Looks like someone asked this on Stack Overflow, and there is a variable for each sent header called $sent_http_my_custom_header.
See https://web.archive.org/web/20140606142058/http://wiki.nginx.org/HttpCoreModule#.24sent_http_HEADER for the details.
Reference: https://stackoverflow.com/questions/12431496/nginx-read-custom-header-from-upstream-server
I guess you want something like the following in a location block:
if ($sent_http_content_length ~ '') {
more_clear_headers Content-Type
...
}
See $sent_http_name
(Disclaimer: I haven't tried this; I just dug through the docs because I found the question interesting. This may or may not work)
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ifonly applies to incoming client requests, you can't use upstream response headers in conditions because the response hasn't been received yet. Oct 12, 2021 at 12:06
Well checking for the nonexistence of something is always a problem... but....
I generally telnet to the port nginx is listening on and make a hand crafted http repsonse:
telnet www.stackoverflow.com 80
Trying 69.59.196.211...
Connected to stackoverflow.com.
Escape character is '^]'.
GET /index.html HTTP/1.1
host: www.stackoverflow.com
HTTP/1.1 301 Moved Permanently
Server: nginx
Date: Fri, 30 Jul 2010 14:31:02 GMT
Content-Type: text/html; charset=UTF-8
Connection: keep-alive
Location: http://stackoverflow.com/index.html
Content-Length: 158
<head><title>Document Moved</title></head>
<body><h1>Object Moved</h1>This document may be found <a HREF="http://stackoverflow.com/index.html">here</a></body>
You can also use dump header options to curl or wget. For example wget supports:
-S
--server-response
Print the headers sent by HTTP servers and responses sent by FTP
servers.
Lastly, custom logging might let you add specific response headers, for example:
log_format up_head '$remote_addr - $remote_user [$time_local] $request '
'upstream_http_content_type $upstream_http_content_type';
answered Jul 30, 2010 at 14:42
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Oh I am not so sure this is what you wanted... are you looking to verify what you have done works or how to do it? Jul 30, 2010 at 14:48
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Sorry, I guess I wasn't clear in my question. I want to know how to configure it, I already know how to see if it works ;) Thank you for your reply though! Jul 30, 2010 at 14:57
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There is a variable $content_length that according the documentation is equal to line Content-Length header of request. You probably can do
if ($content_length = 0) {
do stuff with header
}
I am not sure what value $content_length will assume, or even if it will exist if the header is absent, but you may use that as a starting point to the solution.
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This variable contains the Content-Length of the request, not the response. So unfortunately, it doesn't really help me. Jul 30, 2010 at 14:42
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Right now, documentation link to wiki returns 404, good urls don't change they say :( Also note that nginx says that if is evil you have been warned ;) Apr 14, 2017 at 14:54
Content-Typein the HTTP response basically gives the recipient carte blanche to do whatever it wants, and you may not be able to predict that behavior.