[chef] Re: Re: Re: Re: Puppet+Hiera vs. Chef, or handling the occasional special snowflake server

[Lamont Granquist < >]

On 10/07/2015 08:39 AM, Daniel DeLeo wrote:
> Attributes at the “normal” level belong to the node and are NOT wiped 
> for each run. All of the other levels belong to an external thing 
> (role, environment, policyfile) so they are wiped and recreated.

Note that tags are implemented as normal attributes so they are easy 
ways to use normal attributes and have a nice understandable API, where 
you expect them to persist and generally expect one-offs to occur and 
have a nice 'knife tag' command line API to use.

In general, normal attributes cause all kinds of issues when people use 
them to set attributes from cookbooks.  Since normal attributes do 
persist and don't get cleared once they're set in a cookbook they're set 
on the node.  That can be confusing when you delete the line from the 
cookbook which set the normal attribute and then expect the setting to 
be gone in the next run but its not.  For that reason we generally 
discourage their use.  It can be very confusing to have a chef-client 
run behaving some way and you look through the cookbooks and roles and 
it simply "cant" be doing that, but then you 'knife node show' and 
discover a normal attribute that someone set on the node.

It is particularly bad that normal attributes came first and 'node.set' 
is a kind of obvious API to use to set attributes, but which sets a 
'normal' attribute.  And the word 'normal' sounds like the kind of thing 
that's not bad to use -- but generally it is.

However, for one-offs and tags they're fine.  You can also 'tag' nodes 
with a role that sets the attributes (or a role-cookbook or 
role-with-cookbook-that-acts-like-role-cookbook) and that way you can 
easily see that kind of 'tag' on the run_list.  Might create clutter on 
the run_list, but that's generally going to be a more flexible approach 
than tags and you don't risk any normal-attributes confusion (again 
though the run_list itself is a normal attribute, so you're using them 
under the covers, but in a way that you've been trained to expect their 
behavior).