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CentralHub

This process monitors external NGTS processes through Pyro4.

The way the class monitors status is a series of boolean values representing ok or not, and a corresponding set of integers. When a process checks in, the integer value of the check state is set to _ntimes (e.g. 5) and then every time the status poll loop checks the state, it decrements this counter. If the counter is 0 then the status value is set to False.

Usage

In the external process code, add the following shippet:

import Pyro4

hub = Pyro4.Proxy('PYRONAME:central.hub')

and then in the polling loop add the following:

hub.report_in('<name>')

where name is the name of the process type (case insensitive). For example with the transparency code:

hub.report_in('transparency')

The variables _ntimes and _sleeptime control the timeouts for each monitored process. If a process has not reported in for _ntimes loops of _sleeptime seconds, the status is set to False.

Return values

To check if everything updated ok, report_in returns a list of status dictionaries. For example a successful update may look like:

[{'name': 'transparency',
    'previous': {'connections': 0, 'status': False},
    'ok': True}]

A failure (for example using an incorrect name) may look like this:

[{'reason': "No monitor for lkjnasg. Available monitors: ['alcor',
    'cloud_watcher', 'microphones', 'rain_sensor', 'transparency']",
    'ok': False}]

Possible errors

If there are connection issues, this will result in report_in hanging and blocking the calling code. Pyro4 will raise a timeout exception which is worth catching and handling properly. Note this will not occur when creating the Pyro4.Proxy object, but rather when calling a method on this object.