Questions about the promise modules protocol

[amousset]

Hi everyone!

I'd like to thank you for the addition of the new promise modules that allow powerful extension of CFEngine!

I'm starting to implement some, and have a couple of questions about the modules and protocol specs.

result_classes

In the python implementation I read:

evaluate_promise should return either a result or a (result, result_classes) pair

But don't see that mentioned in the specs (only the result field). Is it part of the protocol?

action_policy

In the specs I read:

action_policy, if not default, will be sent to the module, for dry-run/no-changes functionality

But when trying to use an action body I get:

./main.cf:20:0: error: Common attribute 'action' not implemented for custom promises (git)

promise_type parameter

For validation operation in JSON, the spec example gives:

{"operation": "evaluate_promise", "log_level": "info", "promise_type": "git", "promiser": "/opt/cfengine/masterfiles", "attributes": {"repo": "https://github.com/cfengine/masterfiles"}}

But when testing, it appears the promise_type parameter is not passed.

Using a binary module

The interpreter parameter is mandatory, which makes using a binary promise module a bit weird. I managed to run it with:

promise agent git
{
  interpreter => "/path/to/module";
  # We ignore it in the module
  path => "/path/to/module";
}

[amousset]

Another one:

{"operation": "terminate", "log_level": "info"}

in the doc but log_level does not seem to be there.

[amousset]

FYI I'm currently working on a Rust implementation in https://github.com/Normation/cfengine-promise-rust

[olehermanse]

FYI I'm currently working on a Rust implementation in https://github.com/Normation/cfengine-promise-rust

Very cool! Be sure to update us on releases :)

[olehermanse]

in the doc but log_level does not seem to be there.

Thanks, created a ticket for this as well: https://tracker.mender.io/browse/CFE-3564

[olehermanse]

Hey, @amousset!

Thanks for testing out promise modules, a complete overview of what is currently implemented and what is missing can be found in the epic:

https://tracker.mender.io/browse/CFE-1939

In the python implementation I read:

evaluate_promise should return either a result or a (result, result_classes) pair

But don't see that mentioned in the specs (only the result field). Is it part of the protocol?

Thank you for pointing this out. I have updated the spec here:

#4482

Common attribute 'action' not implemented for custom promises (git)

Correct, ticket to implement is here: https://tracker.mender.io/browse/CFE-3433

But when testing, it appears the promise_type parameter is not passed.

Created a bug ticket to fix this here: https://tracker.mender.io/browse/CFE-3563

The interpreter parameter is mandatory, which makes using a binary promise module a bit weird.

Created a ticket to improve this: https://tracker.mender.io/browse/CFE-3562

Hope that helps!