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Varnish Cache Plus

Accept

Description

The accept vmod sanitizes content negotiations headers, most notably the Accept-Language header. As backends can deliver different objects for the same URL based on these headers, it can be needed to normalize them to avoid object duplication.

The vmod follows RFC 7231 and evaluates a list of possible candidates and returns a match to the user’s header, if any, according to the quality (the q parameter) specified by the client for each choice.

Note: Varnish already handles the Accept-Encoding header, so you should NOT do it in VCL.

Example

import accept;

sub vcl_init {
  # our server can only return html, json, and its default, plain text
  new format = accept.rule("text/plain");
  format.add("text/html");
  format.add("application/json");

  # also, the content is available in english (the default)
  # as well as french
  new lang = accept.rule("en");
  lang.add("fr");
}

sub vcl_recv {
  # only leave one choice for each header
  set req.http.accept = format.filter(req.http.accept);
  set req.http.accept-language = lang.filter(req.http.accept-language);
}

API

rule

OBJECT rule(STRING string)

Create a new rule object, using string as fallback in case no match is found.

Arguments:

  • string accepts type STRING

Type: Object

Returns: Object.

.add

VOID .add(STRING string)

This is a method of the rule object, and adds string to the list of acceptable candidates.

Arguments:

  • string accepts type STRING

Type: Method

Returns: None

.remove

VOID .remove(STRING string)

This method removes string from the list of candidates.

Arguments:

  • string accepts type STRING

Type: Method

Returns: None

.filter

STRING .filter(STRING string)

Process string and compares it with the list of candidates. The one with the highest quality is returned, or, failing that, the fallback string specified at the rule object creation is used.

Arguments:

  • string accepts type STRING

Type: Method

Returns: String

Availability

The accept VMOD is available in Varnish Cache Plus version 6.0.1r1 and later.