On 2018-08-31 15:12, R.I.Pienaar wrote:
On Fri, 31 Aug 2018, at 15:03, Chadwick Banning wrote:
Would it be safe to consider this in a general context i.e. as enabling
agent-side function execution?
I dont think so - for general function calls to be usable you want to get the
value and then do some conditional logic on it. or put it in a variable and
use it in another resource etc.
That is not what this is for, this is a based placeholder to later be replaced
by the value - you cannot do any conditionals etc with it.
Imagine something like:
mysql::user{"bob":
password => Deferred(vault_lookup, "bob_pass")
}
(I am just making this syntax up, this is presumably not how it will look)
Here its fine because its a simple interpolation into a value, you cant do more
complex things with this design.
Anyway thats my understanding, Henrik might chime in too
Your example is good, except arguments are in an array - so
password = Deferred(vault_lookup, ["bob_pass"])
Note that a Deferred can take Deferred arguments. That means that the
deferred arguments will be resolved before the Deferred they are
arguments to is resolved. It does however not resolve Deferred values
created on the agent side during the resolution process (so you cannot
build loops with this).
If wanting to do really advanced things - it is possible to write
functions that take puppet language source code as argument and
evaluates that in the agent context.
The puppet context that is available is a "scripting context" with the
same restrictions as for Bolt (you cannot evaluate catalog related
expressions).
The order among the top-level deferred (i.e. various resource attributes
containing a deferred value) is undefined. And all resolution occurs
before the catalog is applied. The puppet context used during resolution
is gone by the time the catalog application starts.
Hope that provides a glimpse into some advanced stuff that could be
implemented with this, as well as some of the constraints regarding
what you cannot do.
- henrik
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