getting-started.md

Getting Started

KubeSat pacakge requires NATs server, Redis server, and python libraries.

Install KubeSat package

Clone a Github repository and move to the directory.

git clone https://github.com/IBM/spacetech-kubesat.git
cd spacetech-kubesat

The KubeSat package has been developed and tested on Python 3.8. Install conda and create a new virtual environment for keeping dependencies separate from your system Python installation, as an example

conda env create -n kubesat -f conda-env.yaml

Activate the environment.

conda activate kubesat

Install the KubeSat package.

python setup.py install

Environment setup

KubeSat package requires NATs server and Redis server. You can install and start them on your local system. If docker is installed and running, you can use the following commands:

Start NATs server.

docker run --rm --name nats-server -p 4222:4222 nats

Start Redis server.

docker run --rm --name redis-server -p 6379:6379 redis

Create a hello service

Create a hello_service.py python file with the following code. This application sends and receives hello messages using NATs. A send_hello_message function sends a hello message every two seconds to a public.hello subject. A receive_hello_message funcion is triggered when a new message comes on the public.hello topic.

import asyncio
import time

from kubesat.base_service import BaseService

SERVICE_TYPE = 'hello'
hello = BaseService(service_type=SERVICE_TYPE,
                    config_path='./service.json')


@hello.schedule_callback(2)
# Send a hello message every two seconds.
async def send_hello_message(nats, shared_storage, logger):
    message = nats.create_message({"message": "hello"})

    # Send a hello message to public.hello subject
    await nats.send_message("public.hello", message)
    print(f"SEND : {message.encode_json()}")


@hello.subscribe_nats_callback("public.hello")
# Subscribe public.hello subject
async def receive_hello_message(message, nats, shared_storage, logger):
    message_json = message.encode_json()
    print(f"RECEIVED : {message_json}")
    shared_storage["last_sent"] = message_json['time_sent']


@hello.startup_callback
# Invoke the startup function at the start time
async def startup(nats_handler, shared_storage, logger):
    print(f"{SERVICE_TYPE} in {hello.sender_id} has started.")

if __name__ == '__main__':
    # Start the hello service
    hello.run()

The service requires configuration file to get a sender ID. Create service.json file in the same directory with hello_service.py.

{
    "sender_id": "node_01",
    "shared_storage": {}
}

Start the application.

python hello_service.py

Congratulations! You completed KubeSat application development. You can continue the next example in Manage Kubernetes Resources.