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

map $http_host $name {
    hostnames;

    default       0;

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

Creates a variable whose value depends on the value of another variable. The directive supports three special parameters:

default value

sets a value for the second variable when the value of the first variable cannot be found.

hostnames

allows to specify hostnames with a prefix or suffix mask, as source values, for example,

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

The following two records

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

can be combined:

.example.com  1;

include file

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

map_hash_bucket_size 32|64|128;

Sets the bucket size for the map variables hash tables. Default value depends on the size of the processor's cache line. For more information, please refer to Setting Up Hashes.

map_hash_max_size 2048;

Sets the maximum size of the map variables hash tables. For more information, please refer to Setting Up Hashes.