X-Accel-Redirect dropping custom headers

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peter....@gmail.com

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Aug 8, 2013, 12:11:50 PM8/8/13
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Hello,

I'm having trouble passing custom headers over X-Accel-Redirect. 

Eg. I set this upstream:

   ...redirect 302 etc.
    X-Accel-Redirect: /internal/stuff
    X-Foo: foobar

And have this in nginx.conf:

  location ~ '/internal/stuff' {
      internal;
      proxy_set_header X-Foo $http_x_foo;
      proxy_pass http://otherupstream;
      break;
  }

...but in otherupstream I don't get an X-Foo header. 

AFAICT the X-Accel Module doesn't pass on custom http headers it receives from upstream -- is that the case? Or am I doing it wrong? 

cheers,
peter.

Matt Gray

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Aug 8, 2013, 3:22:51 PM8/8/13
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Hello Peter,

I think the variable name needs to begin $upstream. 

In your example $upstream_http_x_foo is the x-foo response header from the upstream sending x-accel-redirect.

http://wiki.nginx.org/HttpUpstreamModule#.24upstream_http_.24HEADER


hth,

Matt
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peter sabaini

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Aug 9, 2013, 5:05:47 AM8/9/13
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Hey Matt,

thanks for the suggestion. I tested that --  I can see other upstream* variables being passed along, but the X-Foo test header I set from the X-Accel-Redirect responder doesn't show... 

Also, I found this thread which seems to suggest that the X-Accel mechanism has been limited on purpose (it's quite old though): https://www.ruby-forum.com/topic/133840 

cheers,
peter.
Matt
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Yichun Zhang (agentzh)

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Aug 9, 2013, 2:50:17 PM8/9/13
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Hello!

On Fri, Aug 9, 2013 at 2:05 AM, peter sabaini wrote:
> thanks for the suggestion. I tested that -- I can see other upstream* variables being passed along, but the X-Foo test header I set from the X-Accel-Redirect responder doesn't show...
>

The $upstream_http_HEADER variable should work with X-Accel-Redirect,
but your configuration does not work because you configured another
proxy_pass in location ~ '/internal/stuff', which overrides the
$upstream_http_HEADER variable values generated in your original
location (also with ngx_proxy). To make this work, you need a
"intermediate location" that saves the original value of
$upstream_http_HEADER. Below is a complete example that demonstrates
this and it has been tested on my side:

location = /a1 {
proxy_pass http://127.0.0.1:$server_port/a2;
}

location = /a2 {
more_set_headers 'X-Accel-Redirect: /internal/stuff';
more_set_headers 'X-Foo: foobar';
echo ok;
}

location ~ '/internal/stuff' {
internal;
set $x_foo $upstream_http_x_foo;
rewrite ^ /a3;
}

location = /a3 {
proxy_set_header X-Foo $x_foo;
proxy_pass http://127.0.0.1:$server_port/a4;
}

location = /a4 {
echo "X-Foo: $http_x_foo";
}

And accessing /a1 gives

$ curl localhost:1985/a1
X-Foo: foobar

So we're getting the expected value :) Please note that how we saved
the value of $upstream_http_x_foo into our own user variable $x_foo in
location ~ '/internal/stuff' and later use it in location = /a3.

To conclude, the $upstream_http_HEADER variable is one of those
special built-in Nginx variables that are context-sensitive. Ensure
that you are not using a new Nginx upstream module configuration when
you still need the info in a previous nginx upstream module
configuration.

Best regards,
-agentzh

peter sabaini

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Aug 11, 2013, 1:48:25 AM8/11/13
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Thanks, this did it!
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