Github user cestella commented on a diff in the pull request:
https://github.com/apache/metron/pull/673#discussion_r129865954
--- Diff: metron-deployment/packaging/ambari/README.md ---
@@ -0,0 +1,86 @@
+# Ambari Management Pack Development
+Typically, Ambari Management Pack development will be done in the Vagrant
environments. These instructions are specific to Vagrant, but can be adapted
for other environemnts (e.g. make sure to be on the correct nodes for server vs
agent files)
+
+
+# Adding a new property
+1. Add the property to the appropriate `*-env.xml` file found in
`METRON.CURRENT/configuration`.
+ ```
+ <property>
+ <name>new_property</name>
+ <description>New Property description</description>
+ <value>Default Value</value>
+ <display-name>New Property Pretty Name</display-name>
+ </property>
+ ```
+
+2. Reference the property in
`METRON.CURRENT/package/scriptes/params/params_linux.py`, unless it will be
used in Ambari's status command. It will be stored in a variable. The name
doesn't have to match, but it's preferred that it does.
+Make sure to use replace `metron-env` the correct `*-env` file, as noted
above.
+ ```
+ new_property = config['configurations']['metron-env']['new_property']
+ ```
+If this property will be used in the status command, instead make this
change in `METRON.CURRENT/package/scriptes/params/status_params.py`.
+Afterwards, in `params_linux.py`, reference the new property:
+ ```
+ new_property = status_params.new_property
+ ```
+This behavior is because Ambari doesn't send all parameters to the status,
so it needs to be explicitly provided.
+
+3. Ambari master services can then import the params as such
+
+ ```
+ from params import params
+ env.set_params(params)
+ ```
+
+4. The `*_commands.py` files receive the params as an input from the
master services. Once this is done, they can be accessed via the variable we
set above:
+ ```
+ self.__params.new_property
+ ```
+
+ Ambari also has a custom `format` function that can access properties
when producing strings as output:
--- End diff --
What about referencing properties in the `.j2` files? you talk about
adding a new property, but how do we actually hook in the value into the config?
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