From 4a213a9d8e4f2505e57f59efe152bd1a2ea80f84 Mon Sep 17 00:00:00 2001
From: Andre Anjos <andre.anjos@idiap.ch>
Date: Fri, 20 May 2016 11:30:42 +0200
Subject: [PATCH] [experiments] Improve on job parent searching to avoid
double-assignment
---
beat/web/experiments/models.py | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/beat/web/experiments/models.py b/beat/web/experiments/models.py
index 6114d2944..b4279b74e 100644
--- a/beat/web/experiments/models.py
+++ b/beat/web/experiments/models.py
@@ -1020,11 +1020,21 @@ class Block(models.Model):
from ..backend.models import Job
- # search for other jobs with similar outputs and has no children yet
- similar = Job.objects.select_for_update().filter(\
- block__outputs__in=self.outputs.all(), child=None).first()
-
- Job(block=self, parent=similar).save()
+ # search for other jobs with similar outputs that have no children yet
+ # do this carefully, as other experiments may be scheduled at the same
+ # time, invalidating our "parent" choice
+ parent = Job.objects.filter(block__outputs__in=self.outputs.all(),
+ child=None).first()
+ if parent is not None: #(candidate only) try to lock it
+ while True:
+ parent = Job.objects.select_for_update().get(pk=parent.pk)
+ if parent.child_ is not None: #was taken meanwhile, retry
+ parent = parent.child
+ continue
+ Job(block=self, parent=parent).save()
+ break
+ else:
+ Job(block=self).save()
# checks if the job is immediately runnable - if so, tries to
# make it runnable (check caches and other)
--
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