Look at the current number of idle VMs during resize logic

appengine/gce-backend/instance_group_managers.py

 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Utilities for operating on instance group managers."""
 
 import logging
 
 from google.appengine.ext import ndb
 
@@ skipping 291 matching lines @@
     logging.warning('InstanceTemplateRevision does not exist: %s', key)
     return
 
   if not parent.project:
     logging.warning('InstanceTemplateRevision project unspecified: %s', key)
     return
 
   api = gce.Project(parent.project)
   response = api.get_instance_group_manager(get_name(entity), key.id())
 
+  # Find out how many VMs are created (i.e. not currently being created

[Vadim Sh., 2016/07/20 20:57:23]

"are idle" ?

[smut, 2016/07/20 21:00:37]

Done.

+  # or deleted). This helps avoid doing too many VM actions simultaneously.
+  current_size = response.get('currentActions', {}).get('none')
+  if not current_size:

[Vadim Sh., 2016/07/20 20:57:23]

zero idle VMs is not allowed?..

should it be "if current_size is None"?

[smut, 2016/07/20 21:00:37]

True story. Probably not necessary anyway, unless GCE randomly changes their
response structure.

+    logging.error('Unexpected response: %s', json.dumps(response, indent=2))
+    return
+
   # Try to reach the target size, but avoid increasing the number of
   # instances by more than the resize limit. For now, the target size
   # is just the minimum size.
-  target_size = min(entity.minimum_size, response['targetSize'] + RESIZE_LIMIT)
-  if response['targetSize'] >= target_size:
+  target_size = min(entity.minimum_size, current_size + RESIZE_LIMIT)
+  if current_size >= target_size:
     return
 
   api.resize_managed_instance_group(response['name'], key.id(), target_size)
 
 
 def schedule_resize():
   """Enqueues tasks to resize instance group managers."""
   for instance_template in models.InstanceTemplate.query():
     if instance_template.active:
       instance_template_revision = instance_template.active.get()
       if instance_template_revision:
         for instance_group_manager_key in instance_template_revision.active:
           if not utils.enqueue_task(
               '/internal/queues/resize-instance-group',
               'resize-instance-group',
               params={
                   'key': instance_group_manager_key.urlsafe(),
               },
           ):
             logging.warning(
                 'Failed to enqueue task for InstanceGroupManager: %s',
                 instance_group_manager_key,
             )