Cache

If you perform a query on an A or AAAA type and it doesn't exist, the cache will attempt to lookup a CNAME and then resolve that.

The constructor takes an optional object with the following properties:

• store -- implements the cache store model (optional, default MemoryStore)

Methods:

• lookup(question, cb) -- for a given question check the cache store for existence
• store(packet) -- iterates over the resource records in a packet and sends them to the cache store
• purge() -- clears the cache store of all entries

MemoryStore / Cache store model

MemoryStore(opts) -- An in memory store based on a js object

Methods:

• get(domain, key, cb)

• domain is the holder under which keys will be applied, key is the subdomain that is being queried for. If you get('example.com', 'www', cb) you are really asking for www.example.com.
• cb(err, results) -- results is an object of types and array of answers

• { 1: [{address: '127.0.0.1', ttl: 300, type: 1, class: 1}] }
• set(domain, key, data, cb)

• domain is the parent under which this key is stored. key is the subdomain we are storing, data is an object of types with an array of answers.

• set('example.com', 'www', {1: [{class:1, type:1, ttl:300, address:'127.0.0.1'}]}, cb)

• cb(err, data) -- cb merely returns the data that was passed.

• delete(domain[, key[, type]], cb) -- delete all from a domain, a domain and key, or a domain a key and a type.

Lookup

Is a mechanism that given a store performs the common resolution pattern.

Given example.com previous added to a store:

• www.example.com CNAME foo.bar.example.com.
• *.example.com A 127.0.0.1

A Lookup(store, 'example.com', {name:'www.example.com', type:1}, cb) will resolve www to the CNAME and then search for foo.bar.example.com which will return no results, and then search for *.bar.example.com which will also return no results, and ultimately searches for *.example.com which will return the desired record.

Callback will be called with (err, results) where results is an array suitable for use in Packet.answer