Improve task attributes update

Avoid calling the database several times.
Several attributes can be updated in one call.

app/tasks.py

@@ -21,7 +21,7 @@ from . import utils, models
 class TaskWorker(Worker):
     """
     Modified version of the rq worker which updates
-    the task status in the CSEntry database
+    the task status and end time in the CSEntry database
     """
 
     def save_exception(self, job, *exc_info):
@@ -37,7 +37,8 @@ class TaskWorker(Worker):
                 traceback.format_exception(*exc_info))
             db.session.commit()
 
-    def update_task_attribute(self, job, name, value):
+    def update_task_attributes(self, job, attributes):
+        """Update the attributes of the task linked to the given job"""
         # The task is created after enqueueing the job.
         # If the job is processed very quickly, the task might
         # not be found in the database. We wait up to 3 seconds.
@@ -51,22 +52,32 @@ class TaskWorker(Worker):
         else:
             self.log.error(f'Task {job.id} not found! Task attribute not updated!')
             return
-        setattr(task, name, value)
+        for name, value in attributes.items():
+            setattr(task, name, value)
         db.session.commit()
 
     def move_to_failed_queue(self, job, *exc_info):
-        self.update_task_attribute(job, 'ended_at', job.ended_at)
-        self.update_task_attribute(job, 'status', models.JobStatus.FAILED)
+        # This could be achieved by passing a custom exception handler
+        # when initializing the worker. As we already subclass it, it's
+        # easier to override the default handler in case of failure
+        self.update_task_attributes(job, {
+            'ended_at': job.ended_at,
+            'status': models.JobStatus.FAILED,
+        })
         self.save_exception(job, *exc_info)
         super().move_to_failed_queue(job, *exc_info)
 
     def handle_job_success(self, job, queue, started_job_registry):
-        self.update_task_attribute(job, 'ended_at', job.ended_at)
-        self.update_task_attribute(job, 'status', models.JobStatus.FINISHED)
+        self.update_task_attributes(job, {
+            'ended_at': job.ended_at,
+            'status': models.JobStatus.FINISHED,
+        })
         super().handle_job_success(job, queue, started_job_registry)
 
     def prepare_job_execution(self, job):
-        self.update_task_attribute(job, 'status', models.JobStatus.STARTED)
+        self.update_task_attributes(job, {
+            'status': models.JobStatus.STARTED,
+        })
         super().prepare_job_execution(job)