Auto-accept nodes

Use case

By default, Rudder forces an interactive action for accepting new nodes. This is done in complement to "Trust On First Use" (TOFU) cryptographic security scheme used for authentication of nodes.

Nonetheless, in numerous use cases, you need to automate node acceptation. Typically, your Rudder is part of a cloud environment where node provisioning is based on a fully automated self-service. In such an environment, you can’t have an human validating each new nodes before they start to be configured!

We will describe here an example showing how to add a server-side hook to auto-accept nodes when a new inventory comes.

Server-side hook on inventory events

Rudder allows to trigger script execution (hooks) on specific server side events. Three of these events are related to node inventory processing:

  • when a new inventory is received for a not-yet-accepted node. Hook scripts for that event are stored in directory /opt/rudder/etc/hooks.d/node-inventory-received-pending/;

  • when a new inventory is received for an already accepted node (and so, that inventory is an update). Hook scripts for that event are stored in directory /opt/rudder/etc/hooks.d/node-inventory-received-accepted/;

  • and finally when a new inventory was received but its processing by Rudder failed. Hook scripts for that event are stored in directory /opt/rudder/etc/hooks.d/node-inventory-received-failed/.

It’s the first of these cases that is of interest for reaching our goal.

Auto-acceptation hook

Rudder provides an example script to auto-accept node: /opt/rudder/etc/hooks.d/node-inventory-received-pending/auto-accept-nodes.example.

This file is just an example and should not be used directly in production. Nonetheless, it provides the main necessary steps and let space for tailored integration to your processes. The hook is fairly well documented, but still, let’s review these steps together.

Enable auto-accept hook

As explained in hooks documentation, Rudder only execute hooks that are executable and not named "example":

cd /opt/rudder/etc/hooks.d/node-inventory-received-pending/
cp auto-accept-nodes.example auto-accept-nodes
chmod +x auto-accept-nodes

Node acceptation condition: set-up

In our example, we only accept node if they have the corresponding property/value in their inventory. For that, we add the property accept:auto-accept thanks to a an inventory extension hook (yes, hooks everywhere!).

Of course, that logic is trivial and not secure. You typically want to check with your CMDB or other reference base to now if the node is actually authorized to be accepted.

Getting more information about the node in hook

In the hook, by default you only have access to a sub-set of node information, like the node ID (${RUDDER_NODE_ID}), but properties are not part of that set. The hook shows how to query that missing piece of data and extract only the relevant value for property accept thanks to jq (provided as a dependency of Rudder):

MODE=$(curl -k -X GET -H "X-API-TOKEN: $(cat /var/rudder/run/api-token)" -H "Content-Type: application/json" \
  "https://localhost/rudder/api/latest/nodes/${RUDDER_NODE_ID}?include=minimal,properties" | \
  jq -r '.data.nodes[0].properties | map(select(.name = "accept"))[0].value')

Node acceptation condition: check

Now that we have everything we need, we can play our business logic to check if the node should be auto-accepted. In the example, it’s an if; likely yours will be a bit more complex!

Accept node

Now that we know that the node can be accepted, we are doing it via an API call

curl -f -k -X POST -H "X-API-TOKEN: $(cat /var/rudder/run/api-token)" \
  "https://localhost/rudder/api/latest/nodes/pending/${RUDDER_NODE_ID}" -d 'status=accepted'

And done! That node is now managed by Rudder.

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