Table of Contents
It is quite common to need to gather information on your nodes that are not present in the standard Rudder inventory information.
As of Rudder 4.3.0, you can get more information about a node thanks to
inventory hooks. These information will be available as standard node properties.
On the node, you create inventory hooks executable and place them in /var/rudder/hooks.d.
These binaries are executed in the alphanumerical order, only if executable, and their output is checked to
ensure that it is proper JSON.
For example, one hook can output:
{
"my_prop1": ["a", "json", "array"],
"my_prop2": {"some": "more", "key": "value"}
}
When the node inventory is processed server side, the node properties will get new values, one per first-level key of all hooks.
These node properties are marked as "provided by inventory" and can not be deleted nor overwritten. Appart from that characteristic, they are normal node properties that can be used to create group, or as variables in Directives parameters.
An inventory hook can be any kind of executable that can be called without parameters, from a shell script to a C program.
Hooks are located in directory /var/rudder/hooks.d. You may need to create that directory the first time you want to add hooks:
mkdir /var/rudder/hooks.d
They need to be executable by rudder agent.
For example, this hook will create a new "hello_inventory" node property:
% cd /var/rudder/hooks.d
% cat <<EOF > hello-world
#!/bin/sh
echo '{"hello_inventory": "a simple string value from inventory"}'
EOF
% chmod +x hello-world
% rudder agent inventory
And then, after the server has processed the inventory, the node (here with ID 74d10806-b41d-4575-ab86-8becb419949b) has the corresponding property:
% curl -k -H "X-API-Token: ......" -H "Content-Type: application/json" -X GET 'https://..../rudder/api/latest/nodes/74d10806-b41d-4575-ab86-8becb419949b?include=minimal,properties' | jq '.'
{
"action": "nodeDetails",
"id": "74d10806-b41d-4575-ab86-8becb419949b",
"result": "success",
"data": {
"nodes": [
{
"id": "74d10806-b41d-4575-ab86-8becb419949b",
....
"properties": [
{
"name": "hello_inventory",
"value": "a simple string value from inventory",
"provider": "inventory"
}
]
}
]
}
}
If two hooks provide the same first-level key, then the last executed hook values for that key are kept.
You should always use the first level keys as a namespace for your hooks to avoid unwanted overriding.
