ngx_headers_more - Set and clear input and output headers...more than "add"!

This module is not distributed with the Nginx source. See the installation instructions.

This document describes headers-more-nginx-module v0.15 released on 6 July 2011.

# set the Server output header
more_set_headers 'Server: my-server';

# set and clear output headers
location /bar {
    more_set_headers 'X-MyHeader: blah' 'X-MyHeader2: foo';
    more_set_headers -t 'text/plain text/css' 'Content-Type: text/foo';
    more_set_headers -s '400 404 500 503' -s 413 'Foo: Bar';
    more_clear_headers 'Transfer-Encoding' 'Content-Type';
    
    # your proxy_pass/memcached_pass/or any other config goes here...
}

# set output headers
location /type {
    more_set_headers 'Content-Type: text/plain';
    # ...
}

# set input headers
location /foo {
    set $my_host 'my dog';
    more_set_input_headers 'Host: $my_host';
    more_set_input_headers -t 'text/plain' 'X-Foo: bah';
   
    # now $host and $http_host have their new values...
    # ...
}

# replace input header X-Foo *only* if it already exists
more_set_input_headers -r 'X-Foo: howdy';

This module allows you to add, set, or clear any output or input header that you specify.

This is an enhanced version of the standard headers module because it provides more utilities like resetting or clearing "builtin headers" like Content-Type, Content-Length, and Server.

It also allows you to specify an optional HTTP status code criteria using the -s option and an optional content type criteria using the -t option while modifying the output headers with the more_set_headers and more_clear_headers directives. For example,

more_set_headers -s 404 -t 'text/html' 'X-Foo: Bar';

Input headers can be modified as well. For example

location /foo {
    more_set_input_headers 'Host: foo' 'User-Agent: faked';
    # now $host, $http_host, $user_agent, and
    #   $http_user_agent all have their new values.
}

The option -t is also available in the more_set_input_headers and more_clear_input_headers directives (for request header filtering) while the -s option is not allowed.

Unlike the standard headers module, this module's directives will by default apply to all the status codes, including 4xx and 5xx.

syntax: more_set_headers [-t <content-type list>]... [-s <status-code list>]... <new-header>...

default: no

context: http, server, location, location if

phase: output filter

Adds or replaces the specified output headers when the response status code matches the codes specified by the -s option AND the response content type matches the types specified by the -t option.

If either -s or -t is not specified or has an empty list value, then no match is required. Therefore, the following directive set the Server output header to the custom value for any status code and any content type:

  more_set_headers    "Server: my_server";

A single directive can set/add multiple output headers. For example

  more_set_headers 'Foo: bar' 'Baz: bah';

Multiple occurrences of the options are allowed in a single directive. Their values will be merged together. For instance

  more_set_headers -s 404 -s '500 503' 'Foo: bar';

is equivalent to

  more_set_headers -s '404 500 503' 'Foo: bar';

The new header should be the one of the forms:

1. Name: Value
2. Name:
3. Name

The last two effectively clear the value of the header Name.

Nginx variables are allowed in header values. For example:

   set $my_var "dog";
   more_set_headers "Server: $my_var";

But variables won't work in header keys due to performance considerations.

Multiple set/clear header directives are allowed in a single location, and they're executed sequentially.

Directives inherited from an upper level scope (say, http block or server blocks) are executed before the directives in the location block.

Note that although more_set_headers is allowed in location if blocks, it is not allowed in the server if blocks, as in

  ?  # This is NOT allowed!
  ?  server {
  ?      if ($args ~ 'download') {
  ?          more_set_headers 'Foo: Bar';
  ?      }
  ?      ...
  ?  }

Behind the scene, use of this directive and its friend more_clear_headers will (lazily) register an ouput header filter that modifies r->headers_out the way you specify.

syntax: more_clear_headers [-t <content-type list>]... [-s <status-code list>]... <new-header>...

default: no

context: http, server, location, location if

phase: output filter

Clears the specified output headers.

In fact,

   more_clear_headers -s 404 -t 'text/plain' Foo Baz;

is exactly equivalent to

   more_set_headers -s 404 -t 'text/plain' "Foo: " "Baz: ";

or

   more_set_headers -s 404 -t 'text/plain' Foo Baz

See more_set_headers for more details.

Wildcard * can also be used to specify a header name pattern. For example, the following directive effectively clears any output headers starting by "X-Hidden-":

more_clear_headers 'X-Hidden-*';

The * wildcard support was first introduced in v0.09.

syntax: more_set_input_headers [-r] [-t <content-type list>]... <new-header>...

default: no

context: http, server, location, location if

phase: rewrite tail

Very much like more_set_headers except that it operates on input headers (or request headers) and it only supports the -t option.

Behind the scene, use of this directive and its friend more_clear_input_headers will (lazily) register a rewrite phase handler that modifies r->headers_in the way you specify. Note that it always run at the end of the rewrite so that it runs after the standard rewrite module and works in subrequests as well.

If the -r option is specified, then the headers will be replaced to the new values only if they already exist.

syntax: more_clear_input_headers [-t <content-type list>]... <new-header>...

default: no

context: http, server, location, location if

phase: rewrite tail

Clears the specified input headers.

In fact,

   more_clear_input_headers -s 404 -t 'text/plain' Foo Baz;

is exactly equivalent to

   more_set_input_headers -s 404 -t 'text/plain' "Foo: " "Baz: ";

or

   more_set_input_headers -s 404 -t 'text/plain' Foo Baz

See more_set_input_headers for more details.

• Unlike the standard headers module, this module does not automatically take care of the constraint among the Expires, Cache-Control, and Last-Modified headers. You have to get them right yourself or use the headers module together with this module.

Grab the nginx source code from nginx.org, for example, the version 1.0.5 (see nginx compatibility), and then build the source with this module:

$ wget 'http://nginx.org/download/nginx-1.0.5.tar.gz'
$ tar -xzvf nginx-1.0.5.tar.gz
$ cd nginx-1.0.5/

# Here we assume you would install you nginx under /opt/nginx/.
$ ./configure --prefix=/opt/nginx \
    --add-module=/path/to/headers-more-nginx-module
 
$ make -j2
$ make install

Download the latest version of the release tarball of this module from headers-more-nginx-module file list.

Also, this module is included and enabled by default in the ngx_openresty bundle.

The following versions of Nginx should work with this module:

• 1.0.x (last tested: 1.0.6)
• 0.9.x (last tested: 0.9.4)
• 0.8.x (last tested: 0.8.54)
• 0.7.x >= 0.7.44 (last tested: 0.7.68)

Earlier versions of Nginx like 0.6.x and 0.5.x will not work.

If you find that any particular version of Nginx above 0.7.44 does not work with this module, please consider reporting a bug.

Although a lot of effort has been put into testing and code tuning, there must be some serious bugs lurking somewhere in this module. So whenever you are bitten by any quirks, please don't hesitate to

1. send a bug report or even patches to agentzh@gmail.com,
2. or create a ticket on the issue tracking interface provided by GitHub.

Available on github at agentzh/headers-more-nginx-module.

• now more_set_headers supports overriding charset in Content-Type. thanks ML.
• fixed an issue in more_clear_headers: we should remove all the instances of the headers specified, not only the first occurrence. thanks Li Yang.
• back-ported a bugfix from ngx_lua: in output header set, we should always set the header->hash to 1. thanks moodydeath for reporting it.
• fixed a bug when clearing the Accept-Ranges header. thanks Bo Blangstrup.

• now we postpone the rewrite phase handler only once rather than on every main request previously. this will save some CPU cycles on every request if more_set_input_headers or more_clear_input_headers are used.
• fixed two spots where we did not check against null pointers when out of memory.
• now we use the 2-clause bsd license instead.
• various coding style fixes.

• fixed a bug in rewrite phase postponing algorithm which may cause ngx_eval's eval block running after ngx_rewrite's directives. thanks Liseen Wan (xunxin).

• fixed a bug in the Content-Type output header setting handler. we should always clear r->headers_out.content_type_lowcase, or it'll confuse output filters like that of the gzip module.

• fixed the variables-in-Range-header issue in more_set_input_headers reported by Alexander Vetrin.

• now we can remove an input and output header completely, including both custom and builtin headers.

• fixed a memory initialization issue for more_set_input_headers without the -r option, we should always initialize hv.replace even when replace == 0. This may result in server segfaults and was introduced in v0.08.
• implemented wildcard support in more_clear_headers. Thanks Bernd Dorn.

• applied the patch from Bernd Dorn to add the -r option to the more_set_input_headers directive.

• fixed the more_clear_headers directive for builtin headers like Server and Last-Modified by always inserting an empty header when absent. Thanks Sebastiaan Deckers for reporting it.

• now the input header handler runs at the end of the rewrite phase such that it works in subrequests by default.

• fixed variables in more_set_input_headers by registering the handler in the access phase instead of the rewrite phase.

This module comes with a Perl-driven test suite. The test cases are declarative too. Thanks to the Test::Nginx module in the Perl world.

To run it on your side:

$ PATH=/path/to/your/nginx-with-headers-more-module:$PATH prove -r t

To run the test suite with valgrind's memcheck, use the following commands:

$ export PATH=/path/to/your/nginx-with-headers-more-module:$PATH
$ TEST_NGINX_USE_VALGRIND=1 prove -r t

You need to terminate any Nginx processes before running the test suite if you have changed the Nginx server binary.

Because a single nginx server (by default, localhost:1984) is used across all the test scripts (.t files), it's meaningless to run the test suite in parallel by specifying -jN when invoking the prove utility.

Some parts of the test suite requires modules proxy, rewrite, and echo to be enabled as well when building Nginx.

• Support variables in new headers' keys.

You'll be very welcomed to submit patches to the author or just ask for a commit bit to the source repository on GitHub.

• Zhang "agentzh" Yichun (章亦春) <agentzh@gmail.com>
• Bernd Dorn ( http://www.lovelysystems.com/ )

This wiki page is also maintained by the author himself, and everybody is encouraged to improve this page as well.

The code base is borrowed directly from the standard headers module in Nginx 0.8.24. This part of code is copyrighted by Igor Sysoev.

Copyright (c) 2009, 2010, 2011, Taobao Inc., Alibaba Group ( http://www.taobao.com ).

Copyright (c) 2009, 2010, 2011, Zhang "agentzh" Yichun (章亦春) agentzh@gmail.com.

Copyright (c) 2010, 2011, Bernd Dorn.

This module is licensed under the terms of the BSD license.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

• The original thread on the Nginx mailing list that inspires this module's development: "A question about add_header replication".
• The orginal announcement thread on the Nginx mailing list: "The "headers_more" module: Set and clear output headers...more than 'add'!".
• The original blog post about this module's initial development.
• The echo module for Nginx module's automated testing.
• The standard headers module.