feat(operations): jobs a request runs

Request jobs (an upload's chunks) run in gunicorn: their kind is admitted
running with the request as its worker, never claimed or recovered by the
worker, cancelled in the request, and asked by every housekeeping pass to
end its jobs that went idle. The panel can follow a job the page just
started. A job a request runs does not wait for the worker, so it does not
raise the worker-unavailable warning on the Jobs page or in the panel.

operations/models.py

@@ -26,6 +26,7 @@ class Operation(models.Model):
     ACTIVE = (QUEUED, RUNNING, CANCELLING)
     TERMINAL = (SUCCEEDED, FAILED, CANCELLED, UNCERTAIN)
     STATES = [(s, s) for s in ACTIVE + TERMINAL]
+    REQUEST = "request"  # the worker of a job a request runs
 
     id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     kind = models.CharField(max_length=64, db_index=True)
@@ -49,7 +50,8 @@ class Operation(models.Model):
     started_at = models.DateTimeField(null=True)
     finished_at = models.DateTimeField(null=True)
     heartbeat_at = models.DateTimeField(null=True)
-    worker = models.CharField(max_length=128, blank=True)  # identity of the worker that owns it
+    # identity of the owning worker; REQUEST for a job a request runs, which the worker never claims or recovers
+    worker = models.CharField(max_length=128, blank=True)
     time_limit = models.PositiveIntegerField(null=True)  # seconds, fixed at admission
     cancel_requested = models.BooleanField(default=False)
     resolved_by = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, on_delete=models.SET_NULL, related_name="+")
@@ -64,6 +66,10 @@ class Operation(models.Model):
     def __str__(self):
         return f"{self.kind} {self.id}"
 
+    @property
+    def in_request(self):
+        return self.worker == Operation.REQUEST
+
 
 class Claim(models.Model):
     SHARED = "shared"