Hi Josh,
Here's what we found. I would love to hear about other approaches because
we're still debating and building out our service.
1. Yes it's a great way to escape from parameterized classes. If you ever
needed to 'include' a class in two places, parameterized classes makes this
difficult or impossible.
2. I don't recommend using automatic hiera lookup. There are some subtle
gotchas in it especially when using hashes in hiera. In my office our
recommended practice is as almost as you wrote it, class bar ($foo =
hiera('bar::foo')) { ... }. Hiera automatic lookup is a good way to allow
an easier transition from parameterized classes so it may still be a good
choice for you. As Ashley points out, read the latest docs!
3. If you explicitly use the hiera() call, you'll get nice "variable not
found" messages when you make a mistake. Clear error messages are rare in
puppet so don't underestimate their value.
4. Don't over complicate your hiera tree. It's not the place for
everything. Pick your largest collection of system-to-system variation and
put that in hiera.
In our office we identified three variations that we *wanted* to put in
hiera:
1. Variation between servers *within* an instance of our service
2. Variation between similar servers across different instances of our
service (eg. Identity of the zookeeper in production, staging & QA)
3. Version differences between instances of our service. IE. use hiera to
manage the pipeline of releases.
What we *actually* put into hiera was only #2. When #1 started creeping
into hiera things got very messy. #1 is better handled by managing server
Roles. #3 should never go into Hiera - but I'm still arguing this point
with my co-workers.
Caveate Emptor: We're still hemming and hawwing about all this.
Cheers, Larry Fast
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