KMK-ONLINE / libvmod-querystring

A general-purpose querystring manipulation module for Varnish

vmod_querystring

Varnish QueryString Module

Author:	Dridi Boukelmoune
Date:	2012-06-18
Version:	0.2
Manual section:	3

SYNOPSIS

import querystring;

DESCRIPTION

Varnish multipurpose vmod for URI query-string manipulation. Can be used to normalize for instance request URLs or Location response headers in various ways. It is recommended to at least clean incoming request URLs (removing empty parameters or query-strings), all other functions do the cleaning.

FUNCTIONS

clean

Prototype

STRING clean(STRING url)

Description

Returns the given URI without empty parameters. The query-string is removed if empty (either before or after the removal of empty parameters).

Example

set req.url = querystring.clean(req.url);

remove

Prototype

STRING remove(STRING url)

Description

Returns the given URI with its query-string removed

Example

set req.url = querystring.remove(req.url);

sort

Prototype

STRING sort(STRING url)

Description

Returns the given URI with its query-string sorted

Example

set req.url = querystring.sort(req.url);

filtersep

Prototype

STRING filtersep()

Description

Returns the separator needed by the filter and filter_except functions

filter

Prototype

STRING filter(STRING url, STRING_LIST parameter_names)

Description

Returns the given URI without the listed parameters

Example

set req.url = querystring.filter(req.url,
  "utm_source" + querystring.filtersep() +
  "utm_medium" + querystring.filtersep() +
  "utm_campaign");

filter_except

Prototype

STRING filter_except(STRING url, STRING_LIST parameter_names)

Description

Returns the given URI but only keeps the listed parameters

Example

set req.url = querystring.filter_except(req.url,
                                 "q" + querystring.filtersep() + "p");

regfilter

Prototype

STRING regfilter(STRING url, STRING parameter_names_regex)

Description

Returns the given URI without the parameters matching a regular expression

Example

set req.url = querystring.regfilter(req.url, "utm\_.*");

regfilter_except

Prototype

STRING regfilter_except(STRING url, STRING parameter_names_regex)

Description

Returns the given URI but only keeps the parameters matching a regular expression

Example

set req.url = querystring.regfilter_except(req.url, "^(q|p)$");

EXAMPLES

In your VCL you could then use this vmod along the following lines:

import querystring;

sub vcl_hash {
   # sort the URL before the request hashing
   set req.url = querystring.sort(req.url);
}

ACKNOWLEDGMENT

The sort algorithm is a mix of Jason Mooberry's Skwurly and my own QuerySort with regards for the Varnish workspace memory model of the worker threads.

COPYRIGHT

This document is licensed under the same license as the libvmod-querystring project. See LICENSE for details.

• Copyright (c) 2012-2014 Dridi Boukelmoune