Sometimes I'd like that puppet does something if a certain file is on the system.

[pier4r]

Countless times I wanted to know if a file was there, as a switch for certain resources.

### file exists with external facts
$file_to_check_fact_path = '/etc/facter/facts.d/file_exists_itself.sh'
$file_to_check = $file_to_check_fact_path #check itself

file { $file_to_check_fact_path:
	ensure  => 'file',
	mode    => 'a+x',
	content =>"#!/bin/bash
# cat test.sh
files_to_check_arr=( '${file_to_check_fact_path}' )

for file_to_check in \${files_to_check_arr[@]}; do
test -f \"\${file_to_check}\" && {
	echo \"\${file_to_check}=present\"
} || {
	echo \"\${file_to_check}=absent\"
}
done
	",
}

notify { 'test_external_fact': message => $facts[$file_to_check_fact_path] }

This may be suboptimal, but at least works. Is there anything better?

[bitvijays]

@pier4r Hope you are doing well. Maybe have a look at Exec OnlyIf and Exec Unless

[pier4r]

Hi! I know those. Anyway with an exec I cannot say "deploy those resources (say a firewall rule) only if this file exists", or at least I cannot see how I can build it.

For this a fact in this case helps as I can then treat it as a variable.

[swells-ac]

I am not sure if you are just talking about random files. You can setup your hosts to have files that contain a role or something else. Than map that by using custom facts and hierdata. So say have a file that has "testing" in it. Then you can map that back to have separate environment for it.

[XMol]

Hi @pier4r,

I think it is safe to say that facts are your best option in this case. Especially when your Puppet client isn't also a master and compiles the catalog for itself, the master cannot know whether files exist on the client without facts.

That is a direct consequence from the catalog compilation process. Before the master compiles a catalog, it gathers all external data. The sole option to react dynamically during catalog compilation are (Puppet) functions, which are run on the Puppet master. In theory, you could implement a function that contacts your client node to check whether a specific file exists. That sounds like a bad idea to me because of all the requirements attached to that. With enough determination however...

Ciao,
Xavier.

[binford2k]

I have a module that lets you do partial catalog enforcement based on conditions you set, binford2k-assert. That said, in general you don't want your configuration to be indeterminate. You want to specify all the conditions you care about. In other words, rather than checking to see if a file exists and then reacting appropriately, your code should specify whether the file should exist in the first place.

[pier4r]

This is true, in an ideal world we should determine things beforehand.

Anyway in less ideal world (that is most likely what happens in many cases), things are a bit more complicated.
Example: puppet apply based execution that requires modules to be installed (locally). Some part of the code requires functions in the yet-to-be-installed modules. It is not really possible (for my knowledge) to put a "care about this piece of code only when the module is there" in puppet without a facts that enables the piece of code only if the module is installed (i.e: a file exists).

If there more cleaner way, I am all ears!

Last but not least: in general I think that while one should know what is best, it should be possible to encourage also "what is possible with the tool X" type of discussions.

[binford2k]

It is not really possible (for my knowledge) to put a "care about this piece of code only when the module is there" in puppet

There is though. r10k puppetfile install && puppet apply manifests/site.pp

Instead of making your code reactive to the various states that your codebase can be in, just ensure codebase consistency before enforcing it.

[pier4r]

"Instead of making your code reactive to the various states that your codebase can be in, just ensure codebase consistency before enforcing it."

Yes I agree, if one has the knowledge how to piece things together.

Interesting, I didn't think to deploy r10k together with puppet apply. I was thinking puppet should do everything on its own (otherwise I should wrap things with script, more or less always)