1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
.. -*- mode: rst -*-
.. _server-plugins-connectors-templatehelper:
==============
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
:ref:`Writing Helpers` below for more information on how to write
TemplateHelper scripts.
TemplateHelper supports group- and host-specific helpers, so you could
create, e.g., ``foo.py.G80_test`` to create a helper that only applied
to machines in the group ``test``.
Writing Helpers
===============
A helper module is just a Python module with three special conditions:
* The filename must end with ``.py`` (before any specificity
strings, e.g., ``.G80_foo`` or ``.H_blah.example.com``
* 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``, ``handle_event``, ``name``, and ``specific`` 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 has, 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 TGenshi 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.
|
