Module ngx_http_map_module

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Module ngx_http_map_module

Example Configuration
Directives
map
map_hash_bucket_size
map_hash_max_size

The ngx_http_map_module module creates variables
whose values depend on values of other variables.

Example Configuration

map $http_host $name {
hostnames;

default 0;

example.com 1;
*.example.com 1;
example.org 2;
*.example.org 2;
.example.net 3;
wap.* 4;
}

map $http_user_agent $mobile {
default 0;
"~Opera Mini" 1;
}

Directives

Syntax:

map
string
$variable { ... }

Default:

—

Context:

http

Creates a new variable whose value
depends on values of one or more of the source variables
specified in the first parameter.

Before version 0.9.0 only a single variable could be
specified in the first parameter.

Since variables are evaluated only when they are used, the mere declaration
even of a large number of “map” variables
does not add any extra costs to request processing.

Parameters inside the map block specify a mapping
between source and resulting values.

Source values are specified as strings or regular expressions (0.9.6).

Strings are matched ignoring the case.

A regular expression should either start from the “~”
symbol for a case-sensitive matching, or from the “~*”
symbols (1.0.4) for case-insensitive matching.
A regular expression can contain named and positional captures
that can later be used in other directives along with the
resulting variable.

If a source value matches one of the names of special parameters
described below, it should be prefixed with the “\” symbol.

The resulting value can contain text,
variable (0.9.0), and their combination (1.11.0).

The following special parameters are also supported:

default value

sets the resulting value if the source value matches none
of the specified variants.
When default is not specified, the default
resulting value will be an empty string.

hostnames

indicates that source values can be hostnames with a prefix or suffix mask:

*.example.com 1;
example.* 1;

The following two records

example.com 1;
*.example.com 1;

can be combined:

.example.com 1;

This parameter should be specified before the list of values.

include file

includes a file with values.
There can be several inclusions.

volatile

indicates that the variable is not cacheable (1.11.7).

The search is performed in the following order of priority
and terminates on the first matching variant:

the string value without a mask

the longest string value with a prefix mask,
e.g. “*.example.com”

the longest string value with a suffix mask,
e.g. “mail.*”

the first matching regular expression
(in order of appearance in the configuration file)

the default value

Syntax:

map_hash_bucket_size size;

Default:

map_hash_bucket_size 32|64|128;

Context:

http

Sets the bucket size for the map variables hash tables.
Default value depends on the processor’s cache line size.
The details of setting up hash tables are provided in a separate
document.

Syntax:

map_hash_max_size size;

Default:

map_hash_max_size 2048;

Context:

http

Sets the maximum size of the map variables
hash tables.
The details of setting up hash tables are provided in a separate
document.