arrowhead-client 0.0.0a0

Arrowhead system and service client library

ARROWHEAD CLIENT PYTHON LIBRARY

This is a library for the creation of client service providers and consumer for the Arrowhead Framework, a service-oriented framework developed for industrial automation.

About

The Arrowhead Client Python Library is a library to make it easy to create your own Arrowhead Framework systems and services in Python. This library provides classes that interface with the Arrowhead Core Systems, and uses Flask to provide services.

Development status

This library has not yet reached a stable development version, and a lot will change. Currently, it is working, but it's still missing many crucial features, such as:

• Error handling
• Logging
• Testing
• Support for the following core services
  • Eventhandler
  • Gateway
  • Gatekeeper
• Support for the following security modes (access policies):
  • Token security
  • Insecure security

As more Arrowhead Core Systems mature and are added to the official docker container, those will be added to this list.

External Depencies

To run an Arrowhead system you need to have the Arrowhead core systems up and running, and the correct certificates need to be provided. A guide on how to create your own certificates can be found on the Arrowhead github.

Requirements

• Python 3.7
• Requests
• Flask

How To Use

Currently, you need to create separate systems for providers and consumers, a system cannot easily do both. It is possible to do both, but it is not clean.

Providing Services

To provide services, use the ProviderSystem from the arrowhead_system.system.provider module. Services can be added to the provider with the provided_services decorator. The provided_services decorator will create a service, register the service with the provider. Then when the provider is started, the provider will automatically register the service with the service registry.

Code Example

import datetime
from arrowhead_client.system.provider import ProviderSystem

# Create provider
time_provider = TimeProvider(
		'time_provider',
		'localhost',
		1337,
		'',
		keyfile='certificates/time_provider.key'
		certfile='certificates/time_provider.crt')

# Add service
@time_provider.provided_service('echo', '/time/echo', 'HTTP-SECURE-JSON', 'GET')
def echo():
	return {'now': str(datetime.datetime.now())}

if __name__ == '__main__':
	time_provider.run_forever()

Consuming Services

To consume services, use the ConsumerSystem from the arrowhead_client.system.consumer module to create a consumer system. The add_consumed_services method is used to query the orchestrator and to set up the consumer to consume the service.

Code Examples

from arrowhead_client.system.consumer import ConsumerSystem

time_consumer = ConsumerSystem(
		'consumer_test',
		'localhost',
        '1338',
        '',
        'certificates/consumer_test.key',
        'certificates/consumer_test.crt')

# Add orchestration rules
time_consumer.add_orchestration_rule('echo', 'GET')

if __name__ == '__main__':
    # Consume service provided by the 'get_time' rule
    echo = time_consumer.consume_service('echo')
    print(echo['echo'])