Mon, 06 Apr 2009
Ruby DNS Testing - First Glance
DNS is one of those 'small config change here, errors a long way over there
later' technologies that always leaves me a little worried about the
knock on effect of my changes. As a simple, coarse, safeguard at work we
use Nagios to check that a canary record in each zone can be resolved
from each DNS server. It's far from a perfect solution but it does catch
some of the bigger errors and typos.
In order to beef up this safety net (and encourage me
to spend time using a language other than Perl) I've been
investigating some of the testing options available in ruby, namely
RSpec and Cucumber. I have to say the testing libraries themselves are
actually nice to use and easy to pick up even for a
non-rubyists like me. On the other hand I quickly developed a strong
dislike of the ruby resolv library that actually does the
DNS queries. The lack of decent tutorials or documentation for
anything beyond the very basic uses and the (to me) very awkward API
nearly had me running back to the safety of
Net::DNS
, a mature and widely used perl module. There is a ruby port that I'll
have a look at in the future
For the testing itself I started writing RSpec stories against my own DNS and found the API easy to use. Testing existing configs against local policies is simple - for example all our domains should list at least three name servers -
it "should have at least 3 NS records" do
@resolver = Resolv::DNS.new
@nameservers = @resolver.getresources( domain, Resolv::DNS::Resource::IN::NS)
@nameservers.should have_at_least(3).items
end
After doing some more scut work and testing other record types I moved onwards and upwards to Cucumber. I'm not sure I'd be able to gift someone else with writing the scenarios but they'll be easier to show business people than raw rspec stories. They'll also be very handy in migration meetings (an executable todo list), if it's not on the page it's not getting done.
Feature: Mass DNS Resolution
In order to present a consistent brand image
As a System Administrator
I want to ensure no domains point away from our main IP
Scenario Outline: Resolve a name to a number
Given a hostname of <hostname>
Then I should see the IP address 266.266.266.266
Examples:
| hostname |
| example.org |
| www.example.org |
Next time I work somewhere with ISO 27xxx compliance requirements I'll see if the controls can be written like this and have automatic verification run from them. Cucumber is a little wordy for my tastes but I can see where that could be a strength when presenting to the right audience (such as compliance auditors).
Next time we have a set of DNS migrations I'll be using at least one of these tools to write before and after test cases to ensure nothing gets missed or slips through the cracks. Once I've been through a couple I'll write up in more detail what we end up with.
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Posted: 2009/04/06 15:46 | /ruby | Permanent link to this entry | This entry and same date
Fri, 11 Jul 2008
Randexp - Generating test data with Ruby regexs
While paging through reddit programming recently
(seems only fair since they linked to me ;)) I stumbled on to the very
nifty Randexp gem, a
library that uses regular expression patterns to generate data that would
satisfy the pattern. Or in less tech terms - a really good test data
generator.
# install randexp
$ irb
require "rubygems"
require "randexp"
# simple fake phone number -
/020(7|8) \d{3} \d{4}/.gen
# build a reusable class.
class Randgen
def self.version()
/\d{1,3}\.\d{1,4}/.gen
end
end
# and use it.
/[:version:]/.gen
I especially like the ability to make your own character classes. I'm not a ruby guy but I can see this being very useful in lots of little data generation scripts and test harnesses.
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Posted: 2008/07/11 18:29 | /ruby | Permanent link to this entry | This entry and same date
Wed, 14 Mar 2007
Playing with Facter
I'm on-call tonight so I invested some time in facter, "A
cross-platform Ruby library for retrieving facts from operating
systems." While facter is an interesting command line program
(its extension mechanism is quite nice) its main claim to fame is that
it's used by puppet (which I'm slowly evaluating as a CFEngine
replacement) to determine facts about a machine.
While the docs are a little light on the ground the tgz contains a couple
of examples and after some playing around I think I've got a basic Linux
Bonding fact ready. For your viewing pleasure, the
Facter Linux Network
Bonding custom fact. It's not amazingly powerful or complex but it does
seem to do what I want and it gave me a reason to look around the Ruby
Dir class so it's not all bad. I've mostly put it up to show
how easy it is for someone with very little ruby knowledge to extend
facter.
Note: I also discovered that you can't do a confine :bonding =>
:true, facter works on literal string values, not on true or false.
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Posted: 2007/03/14 23:20 | /ruby | Permanent link to this entry | This entry and same date
Mon, 12 Mar 2007
daemon_percentages.rb and Ruby Autovivification
Both Jim Weirich and
Ben Summers were kind enough to
email me about my Daemon
Logging Percentages and Playing with Ruby Idioms post. They sent
me an explanation on how to do the hash assignment in a way I find much
nicer, so with no more delays I present - Option 4:
tally = Hash.new(0)
tally[daemon] += 1
It really is that simple - and I still missed it by a mile. I've updated the script to use this and I wanted to say thank you for the pointer, so thank you both.
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Posted: 2007/03/12 21:06 | /ruby | Permanent link to this entry | This entry and same date
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