Heartbeat

[eendebakpt]

Fixes #98, #265 (logging, debugging), #172

Changes proposed in this pull request:

• Add a submodule qcodes.config
• Add a ZMQ logging gui
• Add logging handlers that send messages over ZMQ
• Add a heartbeat option to the server process

The PR is not ready for inclusion into master, but before making it complete (docs, tests) I would like to discuss some aspects:

• The logging GUI is completely standalone. I want it that way, so the logging can always continue to run, no matter what happens in the main process
• For communication ZMQ is used. It is an additional dependency, but one that is well known and installs out of the box
• The adding of logging handlers is optional, for the final PR I suggest to set the default to 0
• The config system is only a stub. Making a complete config system is something for another PR.
• To make the heartbeat work I set the timeout in the run_event_loop to 5 seconds. This should be made configurable again, but I am not sure about the best with. With the old default None, the heartbeat does not work.
• By default the qcodes module is not loaded in any subprocesses. Therefore to make sure the heartbeat starts in the subprocces I create an instrument like

class DummyInstrument(Instrument):

    def __init__(self, name='dummy', gates=['dac1', 'dac2', 'dac3'], **kwargs):
        super().__init__(name, **kwargs)

        # manual load
        from qcodes.utils.loggingGUI import installZMQlogger
        qlogger=installZMQlogger()

        logging.info('create DummyInstrument')
        self.add_parameter('test',
                               get_cmd=self.getfunc,
                               vals=Numbers())

    def getfunc(self):
        logging.info('DummyInstrument: getfunc')
        return os.getpid()

I am not sure why the qcodes module is not automatically loaded.

@alexcjohnson @giulioungaretti @MerlinSmiles

[qcodes-bot]

Here is an overview of what got changed by this pull request:

Issues
======
- Added 2


Complexity increasing per file
==============================
- qcodes/utils/loggingGUI.py  3

See the complete overview on Codacy

[qcodes-bot]

Issue found: Unused config imported from qcodes

[giulioungaretti]

@eendebakpt @peendebak going through this as it is really relevant to general architecture.
How does the workflow looks like?
I see a main which looks like it's the gui?
Is the logging acutally I/O bound ? I.e what happens if one pushes too many messages?

[peendebak]

@giulioungaretti

1. The GUI is in loggingGUI.py. This should be started separately from the session with qcodes.

In the qcodes process a hook an be installed in the logging module with installZMQlogger. This hook makes sure all logging messages are published (using ZMQ). The GUI acts as a subscriber to receive the messages.

The ZMQ logging hook is automatically started for instruments on a server (see run_event_loop around line 298).

2. The heartbeat is a mechanism to make sure we can always kill a process started by qcodes. To do this functionality is added to the run_event_loop that checks a special file on disk. For a separate python session this file can be modified such that all processes close themselves (https://github.com/qdev-dk/Qcodes/pull/294/files#diff-f1073d02245e5798e2dcd0033f6fdc7dR310)

Note: I do not use the heartbeat any more. By the logging I know the pid of each process, so I can kill them using the normal operating commands or a button in the logging GUI.

I suggest we split this PR and add the logging hook (and config system PR308) to master. The heartbeat code can wait I think.

[giulioungaretti]

how is your QT button killing the process still via kill pid ?
cool about the PR , let's talk about this in slack.