Writing file templates

BundleWrap can use Mako or Jinja2 for file templating. This enables you to dynamically construct your config files. Templates reside in the files subdirectory of a bundle and are bound to a file item using the source attribute. This page explains how to get started with Mako.

The most basic example would be:

Hello, this is ${node.name}!

After template rendering, it would look like this:

Hello, this is myexamplenodename!

As you can see, ${...} can be used to insert the value of a context variable into the rendered file. By default, you have access to two variables in every template: node and repo. They are bundlewrap.node.Node and bundlewrap.repo.Repository objects, respectively. You can learn more about the attributes and methods of these objects in the API docs, but here are a few examples:

Examples

inserts the DNS hostname of the current node

${node.hostname}

a list of all nodes in your repo

% for node in repo.nodes:
${node.name}
% endfor

make exceptions for certain nodes

% if node.name == "node1":
option = foo
% elif node.name in ("node2", "node3"):
option = bar
% else:
option = baz
% endif

check for group membership

% if node.in_group("sparkle"):
enable_sparkles = 1
% endif

check for membership in any of several groups

% if node.in_any_group(("sparkle", "shiny")):
enable_fancy = 1
% endif

check for bundle

% if node.has_bundle("sparkle"):
enable_sparkles = 1
% endif

check for any of several bundles

% if node.has_any_bundle(("sparkle", "shiny")):
enable_fancy = 1
% endif

list all nodes in a group

% for gnode in repo.get_group("mygroup").nodes:
${gnode.name}
% endfor

Working with node metadata

Quite often you will attach custom metadata to your nodes in nodes.py, e.g.:

nodes = {
    "node1": {
        "metadata": {
            "interfaces": {
                "eth0": "10.1.1.47",
                "eth1": "10.1.2.47",
            },
        },
    },
}

You can easily access this information in templates:

% for interface, ip in sorted(node.metadata["interfaces"].items()):
interface ${interface}
    ip = ${ip}
% endfor

This template will render to:

interface eth0
    ip = 10.1.1.47
interface eth1
    ip = 10.1.2.47