Poller

This module provides a general framework and mechanism for polling.

class ska_tango_base.poller.poller.Poller

A generic hardware polling mechanism.

__init__(poll_model: PollModel[PollRequestT, PollResponseT], poll_rate: float = 1.0, logger: Logger | None = None) → None

Initialise a new instance.

Parameters:

• poll_model – an object that this poller will call to both execute polls and provide with results

• poll_rate – how long (in seconds) to wait after polling, before polling again

• logger – a logger for this poller to use for logging

kill_polling_thread() → None

Kill the polling thread.

This leaves the poller in a broken state and should only be called before the poller is intended to be discarded.

start_polling() → None

Start polling.

stop_polling() → None

Stop polling.

class ska_tango_base.poller.poller.PollModel

Abstract base class for a polling model.

get_request() → PollRequestT

Return the polling request to be executed at the next poll.

This is a hook called by the poller each polling loop, to obtain instructions on what it should do on the next poll.

Returns:

attribute request to be executed at the next poll.

Raises:

NotImplementedError – because this class is abstract

poll(poll_request: PollRequestT) → PollResponseT

Perform a single poll.

This is a hook called by the poller each polling loop.

Parameters:

poll_request – specification of what is to be done on the poll. It might, for example, contain a list of reads and writes to be executed.

Returns:

responses from this poll

Raises:

NotImplementedError – because this class is abstract.

polling_started() → None

Respond to polling having started.

This is a hook called by the poller when it starts polling, and should not raise any exceptions.

polling_stopped() → None

Respond to polling having stopped.

This is a hook called by the poller when it stops polling, and should not raise any exceptions.

poll_succeeded(poll_response: PollResponseT) → None

Handle successful completion of a poll.

This is a hook called by the poller upon the successful completion of a poll.

Parameters:

poll_response – The response to the poll, containing for example any values read.

poll_failed(exception: Exception) → None

Respond to an exception being raised by a poll attempt.

This is a hook called by the poller when an exception occurs. The polling loop itself never raises exceptions. It catches everything and simply calls this hook to let the polling model know what it caught. This hook may not raise an exception itself.

Parameters:

exception – the exception that was raised by a recent poll attempt.

class ska_tango_base.poller.poller.PollRequestT

Type variable for object specifying what the poller should do next poll.

alias of TypeVar(‘PollRequestT’)

class ska_tango_base.poller.poller.PollResponseT

Type variable for object containing the result of the previous poll.

alias of TypeVar(‘PollResponseT’)