dupeguru/hscommon/jobprogress/performer.py

# Created By: Virgil Dupras
# Created On: 2010-11-19
# Copyright 2011 Hardcoded Software (http://www.hardcoded.net)
#
# This software is licensed under the "GPLv3" License as described in the "LICENSE" file,
# which should be included with this package. The terms are also available at
# http://www.gnu.org/licenses/gpl-3.0.html

from threading import Thread
import sys

from .job import Job, JobInProgressError, JobCancelled


class ThreadedJobPerformer:
    """Run threaded jobs and track progress.

    To run a threaded job, first create a job with _create_job(), then call _run_threaded(), with
    your work function as a parameter.

    Example:

    j = self._create_job()
    self._run_threaded(self.some_work_func, (arg1, arg2, j))
    """

    _job_running = False
    last_error = None

    # --- Protected
    def create_job(self):
        if self._job_running:
            raise JobInProgressError()
        self.last_progress = -1
        self.last_desc = ""
        self.job_cancelled = False
        return Job(1, self._update_progress)

    def _async_run(self, *args):
        target = args[0]
        args = tuple(args[1:])
        self._job_running = True
        self.last_error = None
        try:
            target(*args)
        except JobCancelled:
            pass
        except Exception as e:
            self.last_error = e
            self.last_traceback = sys.exc_info()[2]
        finally:
            self._job_running = False
            self.last_progress = None

    def reraise_if_error(self):
        """Reraises the error that happened in the thread if any.

        Call this after the caller of run_threaded detected that self._job_running returned to False
        """
        if self.last_error is not None:
            raise self.last_error.with_traceback(self.last_traceback)

    def _update_progress(self, newprogress, newdesc=""):
        self.last_progress = newprogress
        if newdesc:
            self.last_desc = newdesc
        return not self.job_cancelled

    def run_threaded(self, target, args=()):
        if self._job_running:
            raise JobInProgressError()
        args = (target,) + args
        Thread(target=self._async_run, args=args).start()