Refactor: DistributedJobManager with pub/sub status change notifications (#25)

* Add pubsub to render_queue and base_worker

* Refactor: Convert ZeroconfServer to Singleton with Class Methods

* New API for subjob servers to notify parent job servers of status changes

* Refactor: Move all subjob related methods to distributed_job_manager.py

* Rewrite for wait_for_subjobs

* Fix: DistributedJobManager.find_available_servers() takes 1 positional argument but 3 were given

* DistributedJobManager should now notify / be notified abotu background job changes

* Fix the make_ready api. Change children keyname to be id@hostname so it can be unique

* Fixes

* Image sequence to movie needs to find the actual start frame

* Fix: subjob_status_change did not return a valid response

* Fix client renderer selection

* Small fix for subjob status checking

* Fix issue with divide_frames_equally

* Fix issue where downloads were not occurring

* Fix issue where old status was being reported

* Add docstrings and code cleanup

lib/workers/blender_worker.py

@@ -124,12 +124,20 @@ class BlenderRenderWorker(BaseRenderWorker):
         output_dir_files = os.listdir(os.path.dirname(self.output_path))
         if self.total_frames > 1 and len(output_dir_files) > 1 and not self.parent:
             logger.info("Generating preview for image sequence")
+
+            # Calculate what the real start frame # is if we have child objects
+            start_frame = self.start_frame
+            if self.children:
+                min_child_frame = min(int(child["start_frame"]) for child in self.children.values())
+                start_frame = min(min_child_frame, self.start_frame)
+                logger.debug(f"Post processing start frame #{start_frame}")
+
             try:
                 pattern = os.path.splitext(self.output_path)[0] + "_%04d" + most_common_extension(output_dir_files)
                 image_sequence_to_video(source_glob_pattern=pattern,
                                         output_path=self.output_path + '.mov',
                                         framerate=self.scene_info['fps'],
-                                        start_frame=self.start_frame)
+                                        start_frame=start_frame)
                 logger.info('Successfully generated preview video from image sequence')
             except Exception as e:
                 logger.error(f'Error generating video from image sequence: {e}')