BptkServer

The BptkServer class provides a REST-API using the Flask framework.

You will typically start the framework by instantiating the bptk class within a Jupyer notebook, as follows:

from BPTK_Py.server import BptkServer
from flask_cors import CORS

from model import bptk # assuming your model is in a file called model.py that sets up bptk

# Calling the BptkServer class
application = BptkServer(__name__, bptk)
CORS(application)

if __name__ == "__main__":
   application.run()

Assuming you save that code in a file called application.py, you can then start the server fro the command line as follows:

export FLASK_ENV=development
export FLASK_APP=application.py
python -m flask run

The server is now available on port 5000 and you can call the endpoints documented below.

Our Introduction to BPTK repository on GitHub contains an introductory notebook that illustrates how to use the BPTK Rest API.

class BptkServer(import_name, bptk_factory=None, external_state_adapter=None): This class provides a Flask-based server that provides a REST-API for running bptk scenarios. The class inherts the properties and methods of Flask and doesn’t expose any further public methods.

GET /: The root endpoint returns a simple html page for test purposes.

POST /(instance_uuid)/begin-session: This endpoint starts a session for single step simulation. There can only be one session per instance at a time. Currently only System Dynamics scenarios are supported for both SD DSL and XMILE models.

POST /(instance_uuid)/end-session: This endpoint ends a session for single step simulation and resets the internal cache.

GET /(instance_uuid)/flat-session-results: Returns the accumulated results of a session, from the first step to the last step that was run in a flat format.

POST /(instance_uuid)/keep-alive

This endpoint sets the “last accessed time” of the instance to the current time to prevent the instance from timeing out.

Arguments: None

POST /(instance_uuid)/run-step

This endpoint advances the relevant scenarios by one timestep and returns the data for that timestep.

Arguments:

settings: JSON: Dictionary structure with a key “settings” that contains the settings to apply for that step. These can be constants and points.
flatResults: boolean: When set to true, a flat version of the results is returned.

GET /(instance_uuid)/session-results: Returns the accumulated results of a session, from the first step to the last step that was run.

POST /agents: For an agent-based or hybrid model, this endpoint returns all the agents in the model with their corresponding states and properties.

PUT /agents: For an agent-based or hybrid model, this endpoint returns all the agents in the model with their corresponding states and properties.

POST /equations: This endpoint returns all available equations given the name of a scenario manager and of a scenario.

GET /full-metrics: Returns metrics in JSON format. Following metrics are returned: - Instance count - Creation time und current timestep of each instance

GET /load-state: Loads all instances using the external state adapter

GET /metrics: Returns metrics in a prometheus compatible format.

POST /run: Given a JSON dictionary that defines the relevant simulation scenarios and equations, this endpoint runs those scenarios and returns the data generated by the simulations.

PUT /run: Given a JSON dictionary that defines the relevant simulation scenarios and equations, this endpoint runs those scenarios and returns the data generated by the simulations.

GET /save-state: Save all instances with the provided external state adapter.

GET /scenarios: The endpoint returns all available scenarios for the current simulation.

POST /start-instance

This endpoint starts a new instance of BPTK on the server side, so that simulations can run in a “private” session. The endpoint returns an instance_id, which is needed to identify the instance in later calls.

Arguments: timeout (dict,optional): The timeout period after which the instance is delete if it is not accessed in the meantime. The timer is reset every time the instance is accessed. The timeout dictionary can have the following keys: weeks, days, hours, minutes, seconds, milliseconds, microseconds. Values must be integers.