Skip to main content

Test for undefined fact in puppet with strict_variables

One of my very early frustrations with puppet was that it allows variables to be used when they were undefined. Primarily this bit me by not catching typos in variable names which were often very hard to track down. I was very pleased when Puppetlabs introduced a strict_variables mode which throws an error if a manifest attempts to use an undefined variable.

I recently need to check for the existence of a fact. Without strict_variables, this is straight-forward:

if $::some_fact {  # do stuff here}

If the fact "some_fact" exists, the variable is a non-empty string and evaluates as true in boolean context. If the fact doesn't exist, the variable is an empty string which evaluates as false in boolean context.

But, with strict_variables enforced, this throws an error:

Error: Undefined variable "::some_fact"; Undefined variable "some_fact" at line ...

The solution is to use the getvar function from stdlib:

if getvar('::some_fact') {  # do stuff here}

This works exactly the same as in the previous example, but doesn't throw an error if "some_fact" doesn't exist.

Labels:

Comments

Post a Comment

Popular posts from this blog

Python logging with rich - writing to stderr - plain output when writing to file

Rich is a Python library for writing rich text (with color and style) to the terminal, and for displaying advanced content such as tables, markdown, and syntax highlighted code. Rich provides RichHandler , a logging handler for python's logging module which will format and colorize text written by the module. However, RichHandler writes to stdout by default. More specifically, it writes to a rich Console object which, by default, writes to stdout. To make RichHandler write to stderr by default, you must pass in a Console object which has been configured to write to stderr: import logging from rich.console import Console from rich.logging import RichHandler DATEFMT = "%Y-%m- %d T%H:%M:%SZ" FORMAT = " %(message)s " logging . basicConfig( level = "NOTSET" , format = FORMAT, datefmt = DATEFMT, handlers = [RichHandler(console = Console(stderr = True ))], ) logger = logging . getLogger(__name__) logger . i...
Post a Comment
Read more

Fix python import order on save in vim with ruff and ale

My IDE of choice is vim. I use various tools to perform linting and code formatting, and configure them all with ALE  (the Asynchronous Lint Engine). After using several discrete tools ( black , isort , flake8 , etc) I have settled on using Ruff to do my python code formatting and linting. Here's the relevant fragment of my ALE config in my .vimrc: " ALE config let g :ale_fixers = { \ 'python' : [ 'ruff' , 'ruff_format' ], \} let g :ale_linters = { \ 'python' : [ 'ruff' ], \} let g :ale_python_ruff_use_global = 1 One of the last remaining wrinkles I had was getting Ruff to automatically sort import statements. Sorting imports is performed by the Ruff linter, not the formatter, which is documented here . The fix on the command line is to add an option, like this: ruff check --select I --fix The difficulty I had was getting this to happen in the editor when the file was saved. It turns out, all I needed to do was ...
Post a Comment
Read more

Escaping special characters in wget username or password

I recently offered to help out with the hosting of a WordPress  site. It’s currently hosted somewhere with no shell access – just ftp – and there are a lot of images to transfer. I quickly figured out I could use wget to mirror the site, using something like: wget -m ftp://username:password@example.com However, this broke in this case because the username for the site contained an @ character (the username was user@example.com ). Turns out the solution was to encode the special chars using HTML notation. This is the command that did the trick: wget -m ftp://user%40example.com:password@example.com
Post a Comment
Read more