senlin/doc/source/getting_started/webhook.rst

Webhook

Webhook is used to trigger a specific action on a senlin entity, for instance the actions that change the size of a specified cluster.

How to use

1. Create a cluster, e.g.

senlin cluster-create -p $PROFILE_ID -c 2 -i 1 -a 5 test-cluster

2. Attach a ScalingPolicy to the cluster:

senlin cluster-policy-attach -p $POLICY_ID test-cluster

3. Create a webhook and specify test-cluster as the obj_id, cluster as the obj_type and CLUSTER_SCALE_OUT or CLUSTER_SCALE_IN as the action. Senlin service will return the webhook information with its webhook_url. User can use this url to trigger cluster scale_out or scale_in action.

senlin webhook-create -t cluster -i test-cluster \
    -a CLUSTER_SCALE_OUT \
    -c 'user=$USER_ID;password=$PASSWORD' \
    test-webhook

4. Trigger the webhook by sending a POST request to its URL, for example:

curl http://<webhook_url>

The webhook url can be used in two different ways:

• Sending a simple POST request to the url (no headers or body). For example:

curl -i -X 'POST' $WEBHOOK_URL.

This will directly trigger a cluster scaling operation and the scaling behavior is determined by the ScalingPolicy attached to the cluster. If no ScalingPolicy is attached to the cluster, by default 1 node will be added/deleted;

• Pass extra parameters in the request body for the action execution when triggering the webhook. e.g.

curl -i -X 'POST' $WEBHOOK_URL \
    -H 'Content-type: application/json' \
    --data '{"params": {"count": 2}}'

Using this approach, users can specify more details for controlling the scaling behavior. If a ScalingPolicy has been attached to this cluster, parameters passed in from the request will override the outcome from the scaling policy.

Note: The webhook_url can only be got at the first time the webhook is created. Anyone who has the webhook_url can trigger the cluster scaling action.