ADNS.Cache

Caching asynchronous DNS resolver built on top of GNU ADNS http://www.chiark.greenend.org.uk/~ian/adns/.

• Resolves several IP addresses for one host (if available) in round-robin fashion.
• Limits number of parallel requests (so DNS resolving continues to work even under heavy load).
• Errors are cached too (for one minute).
• Handles CNAMEs (hsdns returns error for them).

You should link your program with the threaded runtime-system when using this module. In GHC, this is accomplished by specifying -threaded on the command-line.

This cache is tested in a long running web-crawler (used in http://bazqux.com) so it should be safe to use it in real world applications.

DNS cache

data DnsCache

Asynchronous DNS cache.

withDnsCache :: (DnsCache -> IO a) -> IO a

Create cache and run action passed.

stopDnsCache :: DnsCache -> IO ()

Wait till all running resolvers are finished and block further resolvers.

DNS lookup

resolveA :: DnsCache -> HostName -> IO (Either String HostAddress)

Resolve A DNS record.

Utils

showHostAddress :: HostAddress -> String

Show HostAddress in standard 123.45.67.89 format.

Unlike inet_ntoa this function is pure and thread-safe.