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enc

External Node Classifier (ENC)​

Overview​

The ENC (puppet_enc.rb) is the script that Puppet Server calls to determine a node's environment, parameters, and tags. It is configured in puppet.conf:

[server]
node_terminus = exec
external_nodes = /etc/puppetlabs/code/environments/production/puppet_enc.rb

Why the ENC lives on the production branch​

Each environment under /etc/puppetlabs/code/environments/ is a full git clone checked out at a specific tag (e.g. v1_5_3). Puppet Server's external_nodes setting points to a single, fixed path — it cannot dynamically select an ENC per environment.

Because of this, puppet_enc.rb always runs from the production environment. It calls the API to determine the node's actual environment (via linuxaid_tag), and returns it in the YAML output. Puppet Server then uses that environment to load the correct environment.conf, modulepath, and Hiera data from the corresponding environment directory.

If the ENC needs to be fixed or updated, only the production environment's copy needs to change — making it a single point of maintenance.

Branch naming: master == production​

The master branch in git corresponds to the production environment on the Puppet Server. This mapping is handled by gfetch, which clones/checks out the master branch into the production environment directory. When a node has no linuxaid_tag set (or the tag is empty), the ENC falls back to the production environment.