On Thursday, January 21, 2016 at 4:20:38 PM UTC-6, Mike Reed wrote:
Hello all,
>
> I've got a module that I've been working on in an attempt to make things a
> little smarter and I figured using a hash would be an elegant solution to
> my problem. The short story is that I've got various video cards in our
> production environment and I'd like to have a module that determines what
> driver will be installed, depending on the make of the card.
>
> I've written some custom facts to help determine the class of the machine,
> what the video card id is and additionally, if the nvidia driver is
> currently installed. These facts have been working fine for quite some
> time and I can check the values by running a facter -p, which results in
> something like:
>
> nvidia_installed => false
> video_card_id => 17c2
> class => workstation
>
> With that said, here's the module that I've written:
>
> class nvidia::driver_install (
>
> $model_hash = {
> 009d => "$::nvidia::params::quadro_fx_4500_driver",
> 06dc => "$::nvidia::params::quadro_6000_driver",
> 06d9 => "$::nvidia::params::quadro_5000_driver",
> 11ba => "$::nvidia::params::quadro_K5000_driver",
> 17c2 => "$::nvidia::params::gtx_titanx_driver",
> 17f0 => "$::nvidia::params::quadro_M6000_driver",
> }
>
> ) inherits nvidia::params {
>
> if ($::is_virtual == true) and ($::class == 'server') {
> notify { 'This is a virtual machine and the nvidia driver doesn\'t get
> intalled' :
> }
> # only run nvidia installer if the machine is a workstation and the
> driver is not already installed
> } elsif ($::class == 'workstation') and ($::nvidia_installed == 'false')
> {
> if ($::video_card_id == $model_hash[key]) {
> notify { "Installing driver for ($model_hash[key])" : }
> exec { 'kdm-stop' :
> command => '/usr/bin/service kdm stop' ,
> unless => '/usr/bin/service kdm status | grep -i "stop" ' ,
> before => Exec['nvidia-driver-install'] ,
> }
> # install nvidia driver
> exec { 'nvidia-driver-install' :
> command => "/usr/src/($model_hash[value]).run -s -X -N
> --force-tls=new --no-x-check --no-cc-version-check" ,
> require => File["/usr/src/($model_hash[value]).run"] ,
> notify => Exec['reboot_after_nvidia'] ,
> }
> # reboot after nvidia install
> exec { 'reboot_after_nvidia' :
> command => "/sbin/reboot" ,
> refreshonly => true ,
> }
> }
> }
> }
>
> In addition, I've got most of my parameters saved into the
> ::nvidia::params.pp file of the module, which then points to hiera for its
> values:
>
> $quadro_fx_4500_driver = hiera('nvidia::quadro_fx_4500_driver')
> $quadro_6000_driver = hiera('nvidia::quadro_6000_driver')
> $quadro_5000_driver = hiera('nvidia::quadro_5000_driver')
> $quadro_K5000_driver = hiera('nvidia::quadro_K5000_driver')
> $quadro_M6000_driver = hiera('nvidia::quadro_M6000_driver')
> $gtx_titanx_driver = hiera('nvidia::gtx_titanx_driver')
>
> These values all resolve and if I use them by name (without the hash),
> things seem to work.
>
> My first question is, does it appear that my logic is correct?
>
I guess you're asking about the structure of your class and your approach
to the problem. The word "logic" is not usually used in that sense for
Puppet DSL code. Anyway, it looks like the general form and approach is
probably feasible.
After reading the puppet docs about data types and hashes in particular,
> it appears to me that I've got the correct syntax.
>
Yes and no. Your *syntax* appears valid, but in the immortal words of
Inego Montoya, "I don't think it means what you think it means".
As Thomas Müller also observed, you are using a bare word "key" to attempt
to extract a value from your hash. At least if the hash takes its default
value, there will be no entry with that key. As far as I can tell, there
is not even a variable $key that you might have meant instead. Later, you
use the bare word "value" in similar fashion.
The easiest way to determine whether a hash contains an entry having a
given key is via Puppet's 'in' operator
<https://docs.puppetlabs.com/puppet/4.3/reference/lang_expressions.html#in>,
something like this:
if ($::video_card_id in $model_hash) { # ...
Where you want to extract the value from the hash entry having a given key,
then that takes the form of an (associative) array access, just like in
Ruby (or Python or Perl):
$model_hash[$::video_card_id]
or a somewhat more bash-like form with curly braces (analogous to the
curly-brace form usable for Puppet variables whose values have other types):
${model_hash[$::video_card_id]}
. Where you want to interpolate a variable's value into a double-quoted
string, you should use the latter form. If you want to interpolate a value
drawn from an array element or hash entry, then you *must* use the
curly-brace form:
notify { "Installing driver for (${model_hash[$::video_card_id]})" :
}
> With the above module in place, I can run a puppet job; but nothing ever
> gets applied to the host (no errors are ever reported and the jobs
> completes successfully).
>
That confirms that your syntax is correct.
> This leads me to believe that I'm using the hash incorrectly and because
> of that, values aren't being determined and therefore this particular piece
> of the module doesn't get applied. Might you have any thoughts on why this
> doesn't appear to work?
>
Yes. Though your hash usage complies with Puppet syntax, its semantics
appear to be completely wrong, as described above.
>
> Also, as a bonus question, if I wanted to use this code in another module,
> is it as simple as "include ::nvidia::driver_install"?
>
It depends on what you mean by "use this code". Almost anywhere in any of
your manifests you can use an 'include' statement such as you present to
instruct Puppet's catalog builder to evaluate class ::nvidia::driver_install
if it has not been evaluated already, and to ensure that it is included in
the target node's catalog. There are other things you might mean, however,
that Puppet does not provide. In particular, Puppet has no mechanism for
C-like code interpolation. The 'include' statement does not do that.
As bonus answers, I suggest some changes to your code:
- Puppet classes represent *state*, not actions. Accordingly, their
names should be nouns or perhaps adjectives, not verbs. This is
non-trivial, as choosing well-suited names helps with thinking
appropriately about your code as you write it, and also as you use it.
- It is unclear to me why you make $model_hash a class parameter, but
also provide a default value such as the one you do. If you intend the
value to be set via automated data binding then the default value provided
is way overkill. If you intend the default value to be determined entirely
by class nvidia::params then it would be better to create the hash in a
class variable of that params class, from which the values are being drawn
anyway, and to reference it by name. (You do know that you can have class
variables that are not class parameters, right?) Or if you intend the
parameter to *always* take the value specified then it should be an
ordinary class variable, not a class parameter at all.
- Although Puppet permits them, in most contexts it is poor style to use
bare strings. Quote your strings -- with single quotes (') unless you need
to interpolate a variable value. Example: '009d', not 009d.
- It is a bad idea to reboot in the middle of a Puppet run. Instead,
schedule a reboot for after the run finishes. For example, use the command
'/sbin/shutdown -r +5', and force the Exec by which it is applied to run
last (maybe by putting it in a run stage that is sequenced after stage
"main").
- If you plan to apply this class any time after initial provisioning
then you should consider whether you need to make more accommodation for
any users that happen to be logged in at the time, and for any jobs that
may be running.
John
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