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:

[code]
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");
}

[/code]