Pattern question for providers

[Jeff Bachtel]

(repost from puppet-users)

When creating a provider that uses a command not in PATH, what is the
best-practice pattern for case'ing out different potential locations? As
an example, the puppetlabs rabbitmq pupmod has a rabbitmqplugins
provider that falls down on CentOS using the rabbitmq upstream package
due to rabbitmq-plugins being in /usr/lib/rabbitmq/bin .

As an aside (I don't know how often Puppet devs read this list), could
the Puppet::Util::which method perhaps be extended to add a non-user
PATH-like variable to the path search string? Something like
PUPPET_PROVIDER_PATH, if it exists, being concatenated before PATH. I
could then configure the system environment on weird hosts to provide
that variable for puppet without mucking with user/system PATH.

Thanks,

Jeff

[Luke Kanies]

I don’t know what the current best practice is, but I struggled with this a lot in early days, and I concluded that it was essentially always better to expand the PATH than build other mechanisms.

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[Jeff McCune]

It seems reasonable to modify which() [1] to take an optional PATH instead of hard-coding it to ENV['PATH'].  The method depends on PATH, so it's probably a bit "better" to inject that dependency rather than hardcode it in the method body as it is now.

Maybe def which(bin, path=ENV['PATH']) ?

https://github.com/puppetlabs/puppet/blob/780ecb238d47f1ab5d6ce18fc8e38f98a12d66c0/lib/puppet/util.rb#L178

--

Jeff McCune

[Andy Parker]

I'm not sure if changing the method signature would achieve what Jeff B is asking for. If I'm understanding this right the problem is that the PATH doesn't contain the executables that the providers need and so `which` isn't finding the executables and the provider then isn't available on the platform. If that is the case, then trying to hardcode other paths in the provider implementation would be difficult to maintain since it could be very different on every platform, and so trying to specify a new argument to which won't solve this problem.

I think the suggestion is to create a PUPPET_PROVIDER_PATH that which (or at least the provider system) always uses to search, but at that point why not just modify the PATH environment variable that puppet is running with?

 

https://github.com/puppetlabs/puppet/blob/780ecb238d47f1ab5d6ce18fc8e38f98a12d66c0/lib/puppet/util.rb#L178

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Jeff McCune

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[Jeff Bachtel]

If the method signature was changed it could make possible a pattern (with the addition of plumbing in Puppet::Provider and Puppet::Provider::Command) such as

:commands => [ 'powershell.exe', [ ENV['PATH'], 'C:\Windows\System32\Powershell1.0' ] ]

BUT, and thanks to the powershell exec provider, I found a totally usable pattern:

  commands :powershell =>
    if File.exists?("#{ENV['SYSTEMROOT']}\\sysnative\\WindowsPowershell\\v1.0\\powershell.exe")
      "#{ENV['SYSTEMROOT']}\\sysnative\\WindowsPowershell\\v1.0\\powershell.exe"
    elsif File.exists?("#{ENV['SYSTEMROOT']}\\system32\\WindowsPowershell\\v1.0\\powershell.exe")
      "#{ENV['SYSTEMROOT']}\\system32\\WindowsPowershell\\v1.0\\powershell.exe"
    else
      'powershell.exe'
    end

That pattern will suffice perfectly well for me. Setting the puppet agent path is a pretty flexible technique (I didn't realize there was a puppet.conf knob for it until your responses) but as a module writer, I don't want to tell users they have to change their puppet.conf path for very common path cases.

Thanks for all of your responses, you definitely triggered me finding a way to help myself,

Jeff

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[Stuart Cracraft]

Agreed.

[Felix Frank]

On 12/12/2013 08:08 PM, Jeff Bachtel wrote:
> :commands => [ 'powershell.exe', [ ENV['PATH'],
> 'C:\Windows\System32\Powershell1.0' ] ]
>
> BUT, and thanks to the powershell exec provider, I found a totally
> usable pattern:

s/usable/horrible/ ;-)

I think the example you sketched above is preferable.

Is ENV['PATH'] being an array specific to Windows? For a UNIX provider,
this would simply become

:commands => [ 'java', "/opt/java:#{ENV['PATH']}" ] # right?

Much cleaner, I feel.

Cheers,
Felix