Net_DNS2 includes a built-in local cache to improve query performance. The cache is disabled by default, and can use shared memory, using the PHP Shmop Extension, or a flat file.

The local cache is only used for lookup queries, and is disabled for Updates.

Shared Memory

Net_DNS2 uses the Shmop Extension. If you do not have the extension installed, and you specify to use the shared memory cache, Net_DNS2 will throw an exception.

Example

$r = new Net_DNS2_Resolver(array(

        'cache_type'    => 'shared',
        'cache_file'    => '/tmp/net_dns2.cache',
        'cache_size'    => 100000
));

Flat File

Net_DNS2 can use a flat file to store the cache information. The cache_file must be in a location PHP can write to, and has enough space to hold a file cache_size bytes big.

Example

$r = new Net_DNS2_Resolver(array(

        'cache_type'    => 'file',
        'cache_file'    => '/tmp/net_dns2.cache',
        'cache_size'    => 100000
));

Serialization Method

You can also adjust the serialization method used when storing the cache data. By default, Net_DNS2 uses the PHP serialize()/unserialize(), but you can also use JSON encoding.

JSON encoding is much faster then the PHP serialize functions, but it loses the class information of the objects- everything comes back as stdClass objects.

To change the serialization method, set “cache_serializer” to either “serialize” or “json”.

Example

$r = new Net_DNS2_Resolver(array(

        'cache_type'        => 'file',
        'cache_file'        => '/tmp/net_dns2.cache',
        'cache_size'        => 100000,
        'cache_serializer'  => 'json'
));

The speed difference is significant.

A Query lookup against Google DNS- NO cache
time: 0.0340800285339

        Net_DNS2_RR_A Object
        (
            [address] => 199.59.148.82
            [name] => twitter.com
            [type] => A
            [class] => IN
            [ttl] => 28
            [rdlength] => 4
            [rdata] => 
        )


with cache + serialize
time: 0.00258994102478

        Net_DNS2_RR_A Object
        (
            [address] => 199.59.148.82
            [name] => twitter.com
            [type] => A
            [class] => IN
            [ttl] => 28
            [rdlength] => 4
            [rdata] => 
        )


with cache + json
time: 0.00178384780884

        stdClass Object
        (
            [address] => 199.59.148.82
            [name] => twitter.com
            [type] => A
            [class] => IN
            [ttl] => 28
            [rdlength] => 4
            [rdata] => 
        )