From 07c26e50dc62ef7157ee8ad7ab7ff1edf9b1c1da Mon Sep 17 00:00:00 2001
From: Adriano Petrich <apetrich@redhat.com>
Date: Wed, 6 Jun 2018 16:32:09 +0100
Subject: [PATCH] Make cron-triggers not play catchup

Currently if the API is stopped for a length and restarted the crontrigger
jobs will have their next execution in the past and will do a catchup
running a lot of times. That happens because the next execution is
calculated based on the first time it was executed. This change makes it be
the next execution time be the max of the calculated time and utcnow so
that if the server is lagging we keep uptodate with the calculated next
execution times.

Change-Id: I05b35261b1adbe17a1b0316eee95da12634c3978
Closes-bug: 1719882
---
 mistral/services/periodic.py                   | 5 ++++-
 mistral/tests/unit/engine/test_cron_trigger.py | 8 ++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/mistral/services/periodic.py b/mistral/services/periodic.py
index d5e2b660b..b10ea50a0 100644
--- a/mistral/services/periodic.py
+++ b/mistral/services/periodic.py
@@ -12,6 +12,7 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 
+import datetime
 import json
 
 from oslo_config import cfg
@@ -121,9 +122,11 @@ def advance_cron_trigger(t):
                 delete_trust=False
             )
         else:  # if remaining execution = None or > 0.
+            # In case the we are lagging or if the api stopped for some time
+            # we use the max of the current time or the next scheduled time.
             next_time = triggers.get_next_execution_time(
                 t.pattern,
-                t.next_execution_time
+                max(datetime.datetime.utcnow(), t.next_execution_time)
             )
 
             # Update the cron trigger with next execution details
diff --git a/mistral/tests/unit/engine/test_cron_trigger.py b/mistral/tests/unit/engine/test_cron_trigger.py
index 9089ac65b..5791e0818 100644
--- a/mistral/tests/unit/engine/test_cron_trigger.py
+++ b/mistral/tests/unit/engine/test_cron_trigger.py
@@ -12,6 +12,7 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 import datetime
+import time
 
 import mock
 from oslo_config import cfg
@@ -120,7 +121,9 @@ class ProcessCronTriggerTest(base.EngineTestCase):
 
         next_trigger = next_triggers[0]
         next_execution_time_before = next_trigger.next_execution_time
+        ts_before = datetime.datetime.utcnow()
 
+        time.sleep(1)  # this is to simulate lagging
         periodic.process_cron_triggers_v2(None, None)
 
         next_triggers = triggers.get_next_cron_triggers()
@@ -130,6 +133,11 @@ class ProcessCronTriggerTest(base.EngineTestCase):
         next_trigger = next_triggers[0]
         next_execution_time_after = next_trigger.next_execution_time
 
+        self.assertGreater(
+            next_execution_time_after,
+            ts_before
+        )
+
         self.assertNotEqual(
             next_execution_time_before,
             next_execution_time_after