Arena Persistence service

Listens on MQTT for ARENA objects to save to mongodb store.

A client then can make an HTTP request to the URL the server this service is running on the retrieve a list of persisted objects to load upon entering any scene.

Documentation

• Requirements & Architecture
• Contributing
• Changelog

Install

• Install nodejs
• npm install

Updating Mongodb

Note that updating major versions of mongodb will require setting the appropriate compatibility version per documentation

Usage

Persistence

• An ARENA object is added to persist if it has action: create and persist: true in its MQTT message.
  • If the object already exists in persist, it will be replaced in entirety.
• A persisted ARENA object can be updated if it has action: update and persist: true set in its MQTT message. The properties in its data will be merged on top of the previously saved data.
  • If an update message contains an explicit overwrite: true, then the data therein will replace what is saved in persistence.
  • If an update message contains an explicit persist: false, then the data therein will not be updated to persistence.

TTL

Adding a ttl (float seconds) to the top level MQTT message for any create action signals that the object will be automatically deleted from peristence after set duration, as well as a corresponding delete action message sent over pubsub. ttl implies that persist is true.

Templates

Any scene can be loaded as a template into another scene. This effectively clones all objects from the source scene into the destination scene.

When a template is loaded, a parent container is first created in the target scene. This parent container follows the object id naming scheme: templateNamespace|templateSceneId::instanceId, e.g. public|lobby::instance_0.

Then every object inside the designated @template scene is replicated as descendents of the parent container. In this way, the parent can be repositioned, rotated, or scaled to adjust the template all at once. The objects within the template follow the naming scheme templateNamespace|templateSceneId::instanceId::objectId, e.g. public|lobby::instance_0::cube1.

To clone an instance of a scene, send a POST request to /persist/:targetNamespace/:targetSceneId with JSON payload:

{
  action: "clone",
  namespace: <string>,     // name of source scene namespace
  sceneId: <string>,       // name of source scene sceneId
  allowNonEmptyTarget: <bool>,   // (optional) - set to `true` allow templating into a non-empty destination scene
}

After the template load, all objects behave as typical in any scene.

Notes:

• If a template source scene is empty with no objects, or the instanceid already exists within a target scene, the template load will fail.