asynchronous refactoring

- don't execute celery tasks directly
- introduce optional parameters to fileserver tasks to allow chaining
- handle user/group/key create and delete tasks in new osusers.signals
  class
- adapt unit tests
- change TaskResults model to store the task signatures
- generalize the local settings' logging configuration

gnuviechadmin/taskresults/models.py

@@ -12,15 +12,21 @@ from gnuviechadmin.celery import app
 
 
 class TaskResultManager(models.Manager):
-    def create_task_result(self, asyncresult, name):
-        taskresult = self.create(task_id=asyncresult.id, task_name=name)
+    def create_task_result(self, creator, signature, notes=''):
+        sigstr = str(signature)
+        result = signature.apply_async()
+        taskresult = self.create(
+            task_id=result.task_id, creator=creator, signature=sigstr,
+            notes=notes)
         return taskresult
 
 
 @python_2_unicode_compatible
 class TaskResult(models.Model):
     task_id = models.CharField(_('Task id'), max_length=36)
-    task_name = models.CharField(_('Task name'), max_length=64)
+    signature = models.TextField(_('Task signature'))
+    creator = models.TextField(_('Task creator'))
+    notes = models.TextField(_('Task notes'))
     result = models.TextField(_('Task result'))
     finished = models.BooleanField(default=False)
     state = models.CharField(_('Task state'), max_length=16)
@@ -32,8 +38,8 @@ class TaskResult(models.Model):
         verbose_name_plural = _('Task results')
 
     def __str__(self):
-        return "{task_name} ({task_id}): {finished}".format(
-            task_name=self.task_name,
+        return "{creator} ({task_id}): {finished}".format(
+            creator=self.creator,
             task_id=self.task_id,
             finished=_('yes') if self.finished else _('no')
         )
@@ -41,7 +47,8 @@ class TaskResult(models.Model):
     def fetch_result(self):
         if not self.finished:
             ar = app.AsyncResult(self.task_id)
-            res = ar.get(no_ack=True, timeout=1)
-            self.result = str(res)
             self.state = ar.state
-            self.finished = True
+            if ar.ready():
+                res = ar.get()
+                self.result = str(res)
+                self.finished = True