Module Gnumed.pycommon.gmWorkerThread

"""GNUmed worker threads.

wx.CallAfter() does not seem to work with _multiprocessing_ !
"""
#=====================================================================
__author__ = "K.Hilbert <karsten.hilbert@gmx.net>"
__license__ = "GPL v2 or later"

import sys
import logging
import threading
import datetime as dt
import pickle
import copy


if __name__ == '__main__':
        sys.path.insert(0, '../../')


_log = logging.getLogger('gm.worker')

#=====================================================================
def execute_in_worker_thread(payload_function=None, payload_kwargs:dict=None, completion_callback=None, worker_name:str=None) -> int:
        """Create a thread and have it execute "payload_function".

        Args:
                payload_function: function to actually run in the thread
                payload_kwargs: keyword arguments to pass to "payload_function"
                completion_callback: must be able to consume the results of "payload_function" unless "None"
                worker_name: optional worker thread name

        Returns:
                ID of worker thread
        """
        assert (callable(payload_function)), 'payload function <%s> is not callable' % payload_function
        assert ((completion_callback is None) or callable(completion_callback)), 'completion callback <%s> is not callable' % completion_callback

        _log.debug('worker [%s]', worker_name)
        # try to decouple from calling thread
        try:
                __payload_kwargs = copy.deepcopy(payload_kwargs)
        except (copy.error, pickle.PickleError):
                _log.exception('failed to copy.deepcopy(payload_kwargs): %s', payload_kwargs)
                _log.error('using shallow copy and hoping for the best')
                __payload_kwargs = copy.copy(payload_kwargs)
        worker_thread = None

        #-------------------------------
        def _run_payload():
                """Execute the payload function.

                Defined inline so it can locally access arguments and the completion callback.
                """
                try:
                        if payload_kwargs is None:
                                payload_result = payload_function()
                        else:
                                payload_result = payload_function(**__payload_kwargs)
                        _log.debug('finished running payload function: %s', payload_function)
                except Exception:
                        _log.exception('error running payload function: %s', payload_function)
                        return

                if completion_callback is None:
                        return

                try:
                        completion_callback(payload_result)
                        _log.debug('finished running completion callback')
                except Exception:
                        _log.exception('error running completion callback: %s', completion_callback)
                _log.info('worker thread [name=%s, PID=%s] shuts down', worker_thread.name, worker_thread.ident)
                return

        #-------------------------------
        if worker_name is None:
                __thread_name = dt.datetime.now().strftime('%f-%S')
        else:
                __thread_name = '%sThread-%s' % (
                        worker_name,
                        dt.datetime.now().strftime('%f')
                )
        _log.debug('creating thread "%s"', __thread_name)
        _log.debug(' "%s" payload function: %s', __thread_name, payload_function)
        _log.debug(' "%s" results callback: %s', __thread_name, completion_callback)
        worker_thread = threading.Thread (
                target = _run_payload,
                name = __thread_name
        )
        # we don't want hung workers to prevent us from exiting GNUmed
        worker_thread.daemon = True
        _log.info('starting thread "%s"', __thread_name)
        worker_thread.start()
        _log.debug(' "%s" ident (= PID): %s', worker_thread.name, worker_thread.ident)
        # from here on, another thread executes _run_payload()
        # which executes payload_function() and, eventually,
        # completion_callback() if available,
        # return thread ident so people can join() it if needed
        return worker_thread.ident

#=====================================================================
# main
#=====================================================================
if __name__ == "__main__":

        if len(sys.argv) < 2:
                sys.exit()

        if sys.argv[1] != 'test':
                sys.exit()

        import time
        import random

        def test_print_dots(ident=None):
                """Tests executing a function in a worker thread.

                The thread slowly prints dots to stdout.
                """

                def slowly_print_dots(info=None):
                        """This slowly prints dots.

                        :param str info: some identifier

                        To be run in each thread."""
                        for idx in range(5):
                                print('* (#%s in %s)' % (idx, info))
                                time.sleep(1 + (random.random()*4))
                        return '%s' % time.localtime()

                def print_dot_end_time(end_time):
                        """Print the time printing dots ended.

                        :param str end_time: end time to print

                        Used as completion callback."""
                        print('done: %s' % end_time)

                execute_in_worker_thread (
                        payload_function = slowly_print_dots,
                        payload_kwargs = {'info': ident},
                        completion_callback = print_dot_end_time
                )

        test_print_dots('A')
        test_print_dots('B')