write_reactions.md

How to write CSF reactions

JSON reaction format

{
    "name": "reaction_name",
    "event": "event_name",
    "script": "console.log('this script will run before any action and decides what to do based on event data'); if (event['key'] == 42)  {nextAction = 'first_action'}  result = event;",
    "actions": 	{
	"first_action": {
	    "script": "console.log('this script will run *after* the action exec and decides what to exec next'); if (actionData['key'] == 'value') {nextAction = 'second_action'}",
	    "action": "dummy_action",
	    "module": "dummy"
	},
	"second_action": {
	    "script": "",
	    "action": "dummy_action",
	    "module": "dummy"
	}
    }
}

A reaction is composed of:

• name is the name of the reaction (be creative !)
• event is the name of the event the reaction respond to (a GET request to http://$CSF_ADDR:8888/v1/events will give you everything you need)
• script is the JS script that will run first before any action. Use it to decide what to do based on the event data
• actions is the different actions that can be executed or not

An action is composed of:

• module: the name of the module containing the action
• action: the name of the action (a GET to http://$CSF_ADDR:8888/v1/actions will help you)
• script: script that choose to continue the pipeline or not. Executed after the action.

Scripting

Some variables you'll need:

• event is the data sent by the event
• nextAction: set this to choose which action to run next, leave empty to stop the pipeline
• err: set this to any non-empty string and the pipeline will stop with your error message
• result: set this to pass data to an action
• actionData: the output data of the action

Every variable can be used in any script exec except actionData which is not available in the first script exec.