How can I add header conditionally in nginx configuration?

Question

How can I add header conditionally in nginx(1.4.6 ubuntu) configuration?

At first I tried like this.

 location / {       add_header X-TEST-0 always-0;        set $true 1;       if ($true) {           add_header X-TEST-1 only-true;       }        add_header X-TEST-2 always-2;   }     

Although I expected my nginx set all header(X-TEST-0,1,2), it added header only X-TEST-1.

Next I tried like this.

 location / {       add_header X-TEST-0 always-0;        ##set $true 1;       ##if ($true) {       ##    add_header X-TEST-1 only-true;       ##}        add_header X-TEST-2 always-2;   }     

My nginx added header X-TEST-1 and X-TEST-2 as I expected.

My quastions are...

1. How can I add header conditionally?

2. Why does nginx add only X-TEST-1 with my first example above?

Thanks in advance!

Answer 1

This is simple if you think differently and use a map.

map $variable  $headervalue {     1        only-true;     default  ''; }  # ...later... location / {     add_header X-TEST-1   $headervalue; } 

If $variable is 1, $headervalue will be set and hence the header will be added. By default $headervalue will be empty and the header will not be added.

This is efficient because Nginx only evaluates the map when it's needed (when it gets to a point where $headervalue is referenced).

See similar: https://serverfault.com/questions/598085/nginx-add-header-conditional-on-an-upstream-http-variable