Backend

The function of backend instances is performing model persistance. They provide functions that allow its callers to store and retrieve modules.

The backend configuration is one of the properties in the server configuration. Schema does not set limits on which backend implementations are available and instead offers an interface that allows dynamic imports of backend implementations, requiring only a module parameter that is a Python module name of the concrete backend implementation. The exact minimal schema is as follows:

---
$schema: 'http://json-schema.org/schema#'
id: 'aimm://server/backend/main.yaml#'
type: object
required:
    - module
properties:
    module:
        type: string
...

All backend implementations need to implement the following interface:

Only one instance of a backend can be configured on a aimm server and its configuration depends on the concrete implementation of the interface. Two kinds of backend implementations are available with the aimm package - sqlite and event backend.

SQLite

SQLite backend stores all the models into a SQLite database. The configuration needs to follow the schema:

---
$schema: 'http://json-schema.org/schema#'
id: 'aimm://server/backend/sqlite.yaml#'
type: object
required:
    - path
properties:
    path:
        type: string
...

Only configuration property is path - path to the SQLite file where data is stored.

Event

The event backend makes use of Hat’s event infrastructure to create and access events that contain model blobs. It requires a connection to hat event server to be configured and its configuration needs to follow the schema:

---
$schema: 'http://json-schema.org/schema#'
id: 'aimm://server/backend/event.yaml#'
type: object
required:
    - model_prefix
properties:
    model_prefix:
        type: array
        items:
            type: string
...

The only configurable property, model_prefix is the prefix of the model blob event’s types. The events that the model raises will have the following structure:

• event type: [<model_prefix>, <instance_id>]

• source timestamp: None

• payload: dictionary that follows the schema:

  ---
  type: object
  required:
      - type
      - instance
  properties:
      type:
          type: string
          description: |
              model type, used to pair with deserialization function,
              when needed
      instance:
          type: string
          description: base64 encoded serialized instance
  ...