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Specification of the Puppet Language, Catalog, Extension points
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Clarification on resource api's :is key #132

Closed russellshackleford closed 5 years ago

russellshackleford commented 5 years ago

If the :is value is nil, the resources were not found by get.

Clear enough. The resource isn't there and needs to run through create

If there is no :is key, the runtime did not have a cached state available.

I'm not sure what this is supposed to mean. Does this mean it doesn't show up as a resource but that the resource might actually be there? If that's the case, I don't know what set is supposed to do about it. Can someone please clarify? Thanks!

DavidS commented 5 years ago

In the case that the runtime does not provide a cached value, the provider needs to figure out the current state (if that is relevant to its operations) by itself. You can have a look at the code handling that in SimpleProvider:

https://github.com/puppetlabs/puppet-resource_api/blob/9dd87a93c8e0926a90745058df5005d311825426/lib/puppet/resource_api/simple_provider.rb#L11-L15

russellshackleford commented 5 years ago

Thanks for the reply. So I'm reading this as: if the resource isn't already cached, then get itself needs to be called manually from within set and harvest just the bits relevant to name. Can you please confirm this? Thanks!

DavidS commented 5 years ago

What exactly needs to happen is entirely up to the implementer of the provider. There is no requirement to call the get function.

For example, the provider could be talking to an API that is itself idempotent, and never needs to know the current state. In this case the set method would not have to do any additional work if is is missing.

Alternatively, if the provider is using a third-party library to manage the resources, it might be more economical to directly call out into that library instead of going through get again.

Finally, if your usecase is very simple, inheriting from the SimpleProvider and only implementing get, create, update, and delete would completely avoid that for you.

russellshackleford commented 5 years ago

Thanks for the clarification!