Resolve::Hostname

Resolve::Hostname is hostname resolver with:

caching with specified TTL
reloading of name server configurations (ex: /etc/resolv.conf)
skipping system resolver (default) or not when specified
primary IP address version specification (default: IPv4)

Installation

Add this line to your application's Gemfile:

gem 'resolve-hostname'

And then execute:

$ bundle

Or install it yourself as:

$ gem install resolve-hostname

Usage

require 'resolve/hostname'

resolver = Resolve::Hostname.new
resolver.getaddress('www.google.com') #=> "173.194.72.103"
resolver.getaddress('www.google.com') #=> "173.194.72.103" # from cache

Cache TTL(seconds) setting available for each resolver instances like this:

r = Resolve::Hostname.new(:ttl => 10) # default 60 seconds

r.getaddress('www.example.com')
sleep 11
r.getaddress('www.example.com') # not from cache, but from actual dns record (and cached)

You can specify resolver_ttl with expectation for re-reading of /etc/resolv.conf in long life daemons.

r = Resolve::Hostname.new(:ttl => 10, :resolver_ttl => 20)
r.getaddress('www.example.com')

Resolver raises Resolve::Hostname::NotFoundError when any records be found, and you can stop it (nil returned):

r1 = Resolve::Hostname.new
r1.getaddress('does-not-exists.example.com') # Resolve::Hostname::NotFoundError raised

r2 = Resolve::Hostname.new(:raise_notfound => false)
r2.getaddress('does-not-exists.example.com') #=> nil

System Resolver

for /etc/hosts:

r = Resolve::Hostname.new(:system_resolver => true)
r.getaddress('my-db-server.local')

IPv6 address query

For queries about IPv6 addresses:

r = Resolve::Hostname.new(:version => :ipv6)
r.getaddress('example.com')          #=> '2001:500:88:200::10'
r.getaddress('ipv4only.example.com') #=> '192.0.43.10'

To deny other version of IP address

Specify :permit_other_version => false if you are in IPv4 network and want not to get IPv6 address:

r1 = Resolve::Hostname.new
r1.getaddress('ipv6only.example.com') #=> '2001:500:88:200::10'

r2 = Resolve::Hostname.new(:version => :ipv4, :permit_other_version => false)
r2.getaddress('ipv6only.example.com') # Resolve::Hostname::NotFoundError raised

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request

TODO

negative cache support
DNS round robin support

Copyright

MIT License.