# Nginx X-Accel-Redirect stripping Content-Encoding header

**URL:** <https://www.ruby-forum.com/t/nginx-x-accel-redirect-stripping-content-encoding-header/245648>\
**Category:** NGINX\
**Created:** [June 28, 2013, 12:21pm UTC](https://www.ruby-forum.com/t/nginx-x-accel-redirect-stripping-content-encoding-header/245648 "2013-06-28T12:21:40Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\
**Post date:** [June 28, 2013, 12:21pm UTC](https://www.ruby-forum.com/t/nginx-x-accel-redirect-stripping-content-encoding-header/245648/1 "2013-06-28T12:21:40Z")

</div>

I have Nginx setup to allow requests to be served with the  
X-Accel-Redirect  
header. This works fine for images, but I’m trying to get it to work for  
Javascript files that are already gzip’ed on the disk.

It appears Nginx is stripping off the ‘Content-Encoding: gzip’ header.  
This  
makes the browser not unzip the content when it receives it, which  
obviously  
makes it not work.

Is it possible to make Nginx preserve the Content-Encoding header to  
allow  
pre-gzipped content through X-Accel-Redirect? Or is there another way to  
allow this work?

The headers seen are:

With Accel = doesn’t work

Accept-Ranges:bytes  
Cache-Control:max-age=1209600, s-maxage=120960  
Connection:keep-alive  
Content-Length:125499  
Content-Type:application/javascript  
Date:Fri, 28 Jun 2013 09:52:33 GMT  
ETag:“51c8efa3-1ea3b”  
Expires:Fri, 12 Jul 2013 09:52:33 GMT  
Last-Modified:Tue, 25 Jun 2013 01:17:23 GMT  
Server:nginx/1.4.1

No accel = works

Cache-Control:max-age=1209600, s-maxage=120960  
Connection:keep-alive  
Content-Encoding:gzip  
Content-Length:125499  
Content-Type:application/javascript  
Date:Fri, 28 Jun 2013 09:53:04 GMT  
Expires:Fri, 12 Jul 2013 09:53:04 GMT  
HTTP1/0 200 Ok:  
Pragma:cache  
Server:nginx/1.4.1  
X-Powered-By:PHP/5.4.9

In case it’s relevant, the code that is serving the content is:

```auto
public static function proxyFile($fileNameToServe, $mimeType, 
$alreadyGzip
= false){
        $seconds_to_cache = 3600 * 24 * 7 * 2;

        if ($alreadyGzip) {
            header('Content-Encoding: gzip');
            $filesize = filesize($fileNameToServe);
            header('Content-Length: '.$filesize);
        }

        if(defined('X-ACCEL-REDIRECT') == true &&
constant('X-ACCEL-REDIRECT') == true){
            $filenameToProxy = str_replace(PATH_TO_ROOT."var/cache",
'/protected_files', $fileNameToServe );
            sendProxyHeaders($mimeType, $seconds_to_cache);
            header("X-Accel-Redirect: ".$filenameToProxy);
            exit(0);
        }
        else{
            sendProxyHeaders($mimeType, $seconds_to_cache);
            $fileHandle = fopen($fileNameToServe, 'r');

            if($fileHandle == false){
                throw new \Exception("Failed to open file 
[$fileNameToServe]
for serving.");
            }

            while (!feof($fileHandle)) {
                $contents = fread($fileHandle, 8192);
                echo $contents;
            }

            fclose($fileHandle);
        }

        exit(0);
    }

    function sendProxyHeaders($mimeType, $seconds_to_cache,
$secondsForCDNToCache = false){
      $currentTimeStamp = gmdate("D, d M Y H:i:s", time()) . " GMT";
      $timeStamp = gmdate("D, d M Y H:i:s", time() + $seconds_to_cache) 
. "
GMT";

      if($secondsForCDNToCache === false){
        $secondsForCDNToCache = intval($seconds_to_cache / 10);
      }

      header("HTTP1/0 200 Ok");
      header("Content-Type: $mimeType");
      header("Date: $currentTimeStamp");
      header("Expires: $timeStamp");
      header("Pragma: cache");

      //max-age = browser max age
      //s-maxage = intermediate (cache e.g. CDN)
      header("Cache-Control: max-age=$seconds_to_cache,
s-maxage=$secondsForCDNToCache");
    }

```

Posted at Nginx Forum:

> **[Nginx X-Accel-Redirect stripping Content-Encoding header](https://forum.nginx.org/read.php?2,240406,240406#msg-240406)**
>
> I have Nginx setup to allow requests to be served with the X-Accel-Redirect header. This works fine for images, but I'm trying to get it to work for Javascript files that are already gzip'ed on the disk. It appears Nginx is stripping off the...

---

<div class="post-metadata">

**Author:** ![Danack](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ecc23a/32.png) [@Danack](https://www.ruby-forum.com/u/Danack)\
**Post date:** [June 28, 2013, 12:38pm UTC](https://www.ruby-forum.com/t/nginx-x-accel-redirect-stripping-content-encoding-header/245648/2 "2013-06-28T12:38:36Z")

</div>

Hello!

On Fri, Jun 28, 2013 at 06:21:08AM -0400, Danack wrote:

> allow this work?  
> Any headers from the original response (the one with X-Accel-Redirect)  
> might be preserved using the $upstream\_http\_\* variables. Something  
> like this should work:

```
location /files/ {
    internal;
    add_header Content-Encoding $upstream_http_content_encoding;
}

```

This might not work well with nginx gzip filter though.

Better solution might be to just return X-Accel-Redirect to an  
unrompressed file, and use gzip\_static to serve precompressed  
files if they are available and supported by a client, see  
[Module ngx\_http\_gzip\_static\_module](http://nginx.org/r/gzip_static).

–  
Maxim D.

> **[nginx: donation](http://nginx.org/en/donation.html)**

---

<div class="post-metadata">

**Author:** ![Danack](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ecc23a/32.png) [@Danack](https://www.ruby-forum.com/u/Danack)\
**Post date:** [June 28, 2013, 2:30pm UTC](https://www.ruby-forum.com/t/nginx-x-accel-redirect-stripping-content-encoding-header/245648/3 "2013-06-28T14:30:10Z")

</div>

> Something like this should work:
> 
> ```
> location /files/ {
> internal;
> add_header Content-Encoding $upstream_http_content_encoding;
> }
> 
> ```

Thanks yep that worked.

> This might not work well with nginx gzip filter though.

And yes, I had to turn gzip off for the internal location used for  
x-accel-redirect, otherwise it was setting the Content-Encoding header  
twice.

> Better solution might be to just return X-Accel-Redirect to an  
> uncompressed file, and use gzip\_static to serve precompressed  
> files if they are available and supported by a client, see  
> [Module ngx\_http\_gzip\_static\_module](http://nginx.org/r/gzip_static).

Thanks for the tip.

cheers  
Dan

Posted at Nginx Forum:  
[http://forum.nginx.org/read.php?2,240406,240410#msg-240410](http://forum.nginx.org/read.php?2,240406,240410#msg-240410)