From a452f6a9af21d9ec5f34e6cda40af0ec3971b422 Mon Sep 17 00:00:00 2001 From: Jeff McCune Date: Wed, 29 Feb 2012 12:47:08 -0800 Subject: (#12357) Add puppet_vardir custom fact Without this patch the PE modules don't have a way to identify a filesystem path where it's OK to place variable data related to managing the target node. This is a problem when a module like pe_compliance needs to write a wrapper script to the node's filesystem. This patch addresses the problem by exposing the node's Puppet[:vardir] setting as a Facter fact. This fact value will be set to `nil` if Puppet is not loaded into memory. If Puppet is loaded, e.g. using `facter --puppet` or using `puppet agent` or `puppet apply` then the fact will automatically set the value to Puppet[:vardir] The value of this setting is subject to Puppet's run_mode. This patch implements a new utility method in the standard library module named `Facter::Util::PuppetSettings.with_puppet`. The method accepts a block and will only invoke the block if the Puppet library is loaded into the Ruby process. If Puppet is not loaded, the method always returns nil. This makes it easy to define Facter facts that only give values if Puppet is loaded in memory. --- README_DEVELOPER.markdown | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) create mode 100644 README_DEVELOPER.markdown (limited to 'README_DEVELOPER.markdown') diff --git a/README_DEVELOPER.markdown b/README_DEVELOPER.markdown new file mode 100644 index 0000000..e8aa27a --- /dev/null +++ b/README_DEVELOPER.markdown @@ -0,0 +1,35 @@ +Puppet Specific Facts +===================== + +Facter is meant to stand alone and apart from Puppet. However, Facter often +runs inside Puppet and all custom facts included in the stdlib module will +almost always be evaluated in the context of Puppet and Facter working +together. + +Still, we don't want to write custom facts that blow up in the users face if +Puppet is not loaded in memory. This is often the case if the user run +`facter` without also supplying the `--puppet` flag. + +Ah! But Jeff, the custom fact won't be in the `$LOAD_PATH` unless the user +supplies `--facter`! You might say... + +Not (always) true I say! If the user happens to have a CWD of +`/stdlib/lib` then the facts will automatically be evaluated and +blow up. + +In any event, it's pretty easy to write a fact that has no value if Puppet is +not loaded. Simply do it like this: + + Facter.add(:node_vardir) do + setcode do + # This will be nil if Puppet is not available. + Facter::Util::PuppetSettings.with_puppet do + Puppet[:vardir] + end + end + end + +The `Facter::Util::PuppetSettings.with_puppet` method accepts a block and +yields to it only if the Puppet library is loaded. If the Puppet library is +not loaded, then the method silently returns `nil` which Facter interprets as +an undefined fact value. The net effect is that the fact won't be set. -- cgit v1.2.3