lvm telemetry & status scraper

[wasndas]

Using horizontal communication between subsystems causes circular dependencies, which should be avoided,
a central service (actor) should be available with the current status of actors & hardware and telemetry of all subsystems.

1. An interface for polling (and pushing data) current status & telemetry
2. Data should be hierachical as a n-ary tree, with node base names as the actor names.
3. Snapshot feature storing data somewhere (files, database, ...)
4. Maybe listening to the rabbitmq exchange is sufficient,
   
   easy to implement - see this example:

import asyncio
import aio_pika as apika
from clu.client import AMQPClient, AMQPReply

class AMQPClientScrap(AMQPClient):
    async def handle_reply(self, message: apika.IncomingMessage) -> AMQPReply:
        """Handles a reply received from the exchange.
        """
        reply = AMQPReply(message, log=self.log)
        print(f"{reply.sender} {reply.body}")

async def main(loop):
    client = await AMQPClientScrap('lvm.scrap', host='localhost').start()

if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.create_task(main(loop))
    print("waiting ...")
    loop.run_forever()

output of the example:

# lvm_scraper.py
<Task pending name='Task-1' coro=<main() running at <stdin>:1>>
waiting ...
lvm.sci.pwi {}
lvm.sci.pwi {'is_tracking': False, 'is_connected': False, 'is_slewing': False, 'is_enabled': False, 'ra_j2000_hours': 0.0, 'dec_j2000_degs': 0.0, 'ra_apparent_hours': 0.0, 'dec_apparent_degs': 0.0, 'altitude_degs': 0.0, 'azimuth_degs': 0.0, 'field_angle_rate_at_target_degs_per_sec': 0.0, 'field_angle_here_degs': 0.0, 'field_angle_at_target_degs': 0.0, 'axis0': {'dist_to_target_arcsec': 0.0, 'is_enabled': False, 'position_degs': 0.0, 'rms_error_arcsec': 0.0, 'servo_error_arcsec': 0.0}, 'axis1': {'dist_to_target_arcsec': 0.0, 'is_enabled': False, 'position_degs': 0.0, 'rms_error_arcsec': 0.0, 'servo_error_arcsec': 0.0}, 'model': {'filename': '', 'num_points_enabled': 0, 'num_points_total': 0, 'rms_error_arcsec': 0.0}, 'geometry': 0}
lvm.skye.foc {}
lvm.skye.foc {'DeviceEncoderPosition': 0.0, 'AtHome': True, 'Units': 'STEPS'}
lvm.sci.foc {}
lvm.sci.foc {'text': 'move to negative'}
lvm.sci.foc {'DeviceEncoderPosition': -10435.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -20870.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -31305.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -41740.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -52175.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -62610.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -73045.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -83480.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -93915.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -104350.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -114785.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -125220.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -135655.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -146090.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -156525.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -166960.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -177395.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -187830.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -198265.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -208700.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'DeviceEncoderPosition': -208700.0, 'Units': 'STEPS', 'Velocity': 0.0}
lvm.sci.foc {'AtLimit': True, 'DeviceEncoderPosition': -208700.0, 'Units': 'STEPS'}

[wasndas]

... the rabbitmq exchange scraper is implemented here