Network.DNS.Cache

DNS cache to resolve domains concurrently.

Documentation

data DNSCacheConf

Configuration for DNS cache.

Constructors

DNSCacheConf

Fields

resolvConfs :: [ResolvConf]

A list of resolvers (cache DNS servers). A domain is resolved by the resolvers concurrently. The first reply is used regardless of success/failure at this moment

maxConcurrency :: Int

Capability of how many domains can be resolved concurrently

minTTL :: NominalDiffTime

The minimum bound of cache duration for success replies in seconds.

maxTTL :: NominalDiffTime

The maximum bound of cache duration for success replies in seconds.

negativeTTL :: NominalDiffTime

The cache duration for failure replies in seconds.

data DNSCache

An abstract data for DNS cache. Cached domains are expired every 10 seconds according to their TTL.

withDNSCache :: DNSCacheConf -> (DNSCache -> IO a) -> IO a

A basic function to create DNS cache. Domains should be resolved in the function of the second argument.

Looking up

lookup :: DNSCache -> Domain -> IO (Maybe HostAddress)

Lookup Domain in the cache. If not exist, queries are sent to DNS servers and resolved IP addresses are cached.

lookupCache :: DNSCache -> Domain -> IO (Maybe HostAddress)

Lookup Domain only in the cache.

Resolving

data Result

Information of positive result.

Constructors

Hit HostAddress

An address obtained from the cache.

Resolved HostAddress

An address resolved from cache DNS servers.

Numeric HostAddress

Specified domain is IP address. So, it is converted into a numeric address.

Instances

Eq Result

Show Result

resolve :: DNSCache -> Domain -> IO (Either DNSError Result)

Lookup Domain in the cache. If not exist, queries are sent to DNS servers and resolved IP addresses are cached.

resolveCache :: DNSCache -> Domain -> IO (Maybe (Either DNSError Result))

Lookup Domain only in the cache.

Waiting

wait :: DNSCache -> (Int -> Bool) -> IO ()

Wait until the predicate in the second argument is satisfied. The predicate are given the number of the current resolving domains.

For instance, if you ensure that no resolvings are going on:

wait cache (== 0)

If you want to ensure that capability of concurrent resolving is not full:

wait cache (< maxCon)

where maxCon represents maxConcurrency in DNSCacheConf.