TemplateHelper¶
The TemplateHelper plugin is a connector plugin that adds Python classes and methods to client metadata instances for use in templates. This allows you to easily reuse code that is common amongst multiple templates and add convenience methods.
Using TemplateHelper¶
First, mkdir /var/lib/bcfg2/TemplateHelper
and add
TemplateHelper to your plugins
line in /etc/bcfg2.conf
.
Restart bcfg2-server
.
Now, any .py
file placed in /var/lib/bcfg2/TemplateHelper/
will be read and added to matching client metadata objects. See
Writing Helpers below for more information on how to
write TemplateHelper scripts.
TemplateHelper does not support group- or host-specific helpers. All helpers will be available to all clients.
Writing Helpers¶
A helper module is just a Python module with three special conditions:
- The filename must end with
.py
- The module must have an attribute,
__export__
, that lists all of the classes, functions, variables, or other symbols you wish to export from the module. data
,name
,fam
,Index
, andHandleEvent
are reserved names. You should not include symbols with a reserved name in__export__
. Additionally, including symbols that start with an underscore or double underscore is bad form, and may also produce errors.
See examples/TemplateHelper
for examples of helper modules.
Usage¶
Specific helpers can be referred to in
templates as metadata.TemplateHelper[<modulename>]
. That accesses
a HelperModule object will have, as attributes, all symbols listed in
__export__
. For example, consider this helper module:
__export__ = ["hello"]
def hello(metadata):
return "Hello, %s!" % metadata.hostname
To use this in a Genshi template, we could do:
${metadata.TemplateHelper['hello'].hello(metadata)}
The template would produce:
Hello, foo.example.com!
Note that the client metadata object is not passed to a helper module in any magical way; if you want to access the client metadata object in a helper function or class, you must pass the object to the function manually.