nodes.py

This file lets you specify or dynamically build a list of nodes in your environment.

All you have to do here is define a Python dictionary called nodes. It should look something like this:

nodes = {
    "node-1": {
        'hostname': "node-1.example.com",
    },
}

With BundleWrap, the DNS name and the internal identifier for a node ("node-1" in this case) are two separate things.

All fields for a node (including hostname) are optional. If you don't give one, BundleWrap will attempt to use the internal identifier to connect to a node:

nodes = {
    "node-1.example.com": {},
}

Dynamic node list

You are not confined to the static way of defining a node list as shown above. You can also assemble the nodes dictionary dynamically:

def get_my_nodes_from_ldap():
    [...]
    return ldap_nodes

nodes = get_my_nodes_from_ldap()

One file per node

Especially in larger installations, a single nodes.py can become inconvenient to work with. This example reads nodes from a nodes/ directory.

from glob import glob
from os.path import join

nodes = {}
for node in glob(join(repo_path, "nodes", "*.py")):
    with open(node, 'r') as f:
        exec(f.read())

Node files would then append nodes, like this:

# nodes/node-1.py
nodes['node-1'] = {
    'hostname': "node-1.example.com",
}

Alternatively, consider using TOML nodes.

Node attribute reference

This section is a reference for all possible attributes you can define for a node:

nodes = {
    'node-1': {
        # THIS PART IS EXPLAINED HERE
    },
}

All attributes can also be set at the group level, unless noted otherwise.

Regular attributes

bundles

A list of bundle names to be assigned to this node. Bundles set at group level will be added.

dummy

Set this to True to prevent BundleWrap from creating items for and connecting to this node. This is useful for unmanaged nodes because you can still assign them bundles and metadata like regular nodes and access that from managed nodes (e.g. for monitoring).

groups

A list of group names this node should be added to. Be aware that you can also define group members at the group itself and you probably should not use both methods in parallel to avoid confusion.

Cannot be set at group level.

hostname

A string used as a DNS name when connecting to this node. May also be an IP address.

Cannot be set at group level.

metadata

This can be a dictionary of arbitrary data (some type restrictions apply). You can access it from your templates as node.metadata. Use this to attach custom data (such as a list of IP addresses that should be configured on the target node) to the node. Note that you can also define metadata at the group level, but node metadata has higher priority.

You are restricted to using only the following types in metadata:

• dict
• list
• tuple
• set
• bool
• text / unicode
• bytes / str (only if decodable into text using UTF-8)
• int
• None
• bundlewrap.utils.Fault

os

Defaults to "linux".

A list of supported OSes can be obtained with bw debug -n ANY_NODE_NAME -c "print(node.OS_KNOWN)".

os_version

Set this to your OS version. Note that it must be a tuple of integers, e.g. if you're running Ubuntu 16.04 LTS, it should be (16, 4).

Tuples of integers can be used for easy comparison of versions: (12, 4) < (16, 4)

password

Which password to use when connecting to the node. Currently only supported for RouterOS.

username

Which username to use when connecting to the node. Leave this unset to use SSH configuration instead (recommended).

OS compatibility overrides

cmd_wrapper_outer

Used whenever a command needs to be run on a node. Defaults to "sudo sh -c {}". {} will be replaced by the quoted command to be run (after cmd_wrapper_inner has been applied).

You will need to override this if you're not using sudo to gain root privileges (e.g. doas) on the node.

cmd_wrapper_inner

Used whenever a command needs to be run on a node. Defaults to "export LANG=C; {}". {} will be replaced by the command to be run.

You will need to override this if the shell on your node sets environment variables differently.

lock_dir

Directory that will be used for creating locks on the node. Defaults to "/var/lib/bundlewrap". Will be created if it does not exist.

You will need to override this if /var/lib is restricted somehow on your node (SElinux, mounted readonly, etc.).

pip_command

This setting will affect how pkg_pip will behave. By default, it will use whatever pip on your system defaults to.

You will need to override this if you don't have pip, but (for example) only pip3. Be aware that this setting has no effect when using virtualenvs.

use_shadow_passwords

This setting will affect how the user item item operates. If set to False, password hashes will be written directly to /etc/passwd and thus be accessible to any user on the system. If the OS of the node is set to "openbsd", this setting has no effect as master.shadow is always used.

Dynamic node attributes

You can define callbacks that will act as read-only node attributes at runtime. For example:

@node_attribute
def uptime(node):
    return node.run("uptime").stdout.decode().strip()

After adding this to your nodes.py, you can then get an overview of all your uptimes using bw nodes -a uptime or make use of node.uptime in your bundles and other places where you have access to node objects.

Be mindful when using this feature: The primary intended purpose of this is usage with bw nodes -a (so you can see builtin attributes, metadata, and node.run() results in a single table). It is not recommended that you derive configuration from these attributes if they're using node.run(). Doing so will make bw test dependent on node access and availability, while also making bw hash non-deterministic.