Rudder

We want to have a system to be able to override node properties values (or add new ones) from the node itself, by third-party system (so the values are not managed by Rudder, just use by it).

The values would be usable only on the node, and so in techniques or if the ${node.properties[...] | node} is used.

From an implementation point of view, we propose to add a /var/rudder/local/properties.d/ directories on node.

External systems can put json file into it, with the same convention as node properties json file, i.e:

{
  "properties":{
    "property_key1":"local node prop",
    "property_key2":{
      "more":"local node prop",
      "and":"local node prop",
    },
  }
}

The agent then load node properties from /var/rudder/cfengine-community/inputs/properties.d/ and from /var/rudder/local/properties.d/, and merge them at the "properties"'s children level with local properties winning;

So if Rudder properties was:

{
  "properties":{
    "property_key0":"from rudder",
    "property_key1":{
      "key1":"from rudder",
    },
  }
}

The results would be:

{
  "properties":{
    "property_key0":"from rudder",
    "property_key1":"local node prop",
    "property_key2":{
      "more":"local node prop",
      "and":"local node prop",
    },
  }
}

So property_key0 was kept from Rudder's node properties (because no override), property_key1 was overriden (from a json value to a string one in the example, but it's not mandatory to be it like that), and property_key2 was only present in local node property and was added to context.