cache-event-task.md

Task Service - Cache Event Task Documentation

Subscribe for Cache events

Current implementation uses NATS as a messaging system for events. There are two environment variables that need to be set for subscribing for cache events.

NATS_ADDR="example.com:4222"
NATS_SUBJECT="subject"

Event Task definition

In order to create a Task upon receiving a Cache event an event task template must be available. Event task JSON templates are stored in Storage. Currently, a Mongo database collection named eventTask is used for storing event task templates. Below is an example of event task template definition:

{
  "key": "did:web:did.actor:alice",
  "namespace": "Login",
  "scope": "Administration",
  "taskName": "exampleTask"
}

The taskName field must be a valid task definition name. See: Tasks

Create Task for Cache event

Every Cache event contains the key, namespace, and scope for a created/updated entry in cache. The task service gets an event task template from storage, if available, and adds a Task in task queue passing the metadata from the event. The added Task must execute a policy (rather than call an external URL). The event metadata can be accessed inside the executed policy by key. Example:

key := input.key
namespace := input.namespace
scope := input.scope