[PATCH 0/1 conductor] BZ 784499 add check to ensure task exists before saving

[Tzu-Mainn Chen]

Here's the original situation:

    begin
      .
      .
      .
      task.instance.state = dcloud_to_instance_state(dcloud_instance.state)
      task.instance.save!
      task.state = Task::STATE_FINISHED
    rescue Exception => ex
      task.state = Task::STATE_FAILED
      task.message = ex.message
    ensure
      task.save!
    end

Due to optimistic locking, the above code gives stale object exceptions if the task is
successfully deleted.  My understanding is that this is because the after_save method in
instance_observer.rb will (under certain circumstances), delete itself and its tasks,
meaning task.save! will fail.

The patch replaces

      task.save!

with
      task.save! if Task.exists?(task.id)

If there's a better way to handle this (or if my logic is wrong), please let me know!


Mainn

[PATCH] BZ 784499 added check to ensure task exists before saving

[Tzu-Mainn Chen]

---
 src/app/util/taskomatic.rb |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/app/util/taskomatic.rb b/src/app/util/taskomatic.rb
index b8a7809..5b8dd97 100644
--- a/src/app/util/taskomatic.rb
+++ b/src/app/util/taskomatic.rb
@@ -70,7 +70,7 @@ module Taskomatic
       task.state = Task::STATE_FAILED
       task.message = ex.message
     ensure
-      task.save!
+      task.save! if Task.exists?(task.id)
     end
   end
 
-- 
1.7.6.5

[Jan Provazník]

On 02/03/2012 04:09 PM, Tzu-Mainn Chen wrote:
>  Here's the original situation:
>
>       begin
>         .
>         .
>         .
>         task.instance.state = dcloud_to_instance_state(dcloud_instance.state)
>         task.instance.save!
>         task.state = Task::STATE_FINISHED
>       rescue Exception =>  ex
>         task.state = Task::STATE_FAILED
>         task.message = ex.message
>       ensure
>         task.save!
>       end
>
>  Due to optimistic locking, the above code gives stale object exceptions if the task is
> successfully deleted.  My understanding is that this is because the after_save method in
> instance_observer.rb will (under certain circumstances), delete itself and its tasks,
> meaning task.save! will fail.
>
>  The patch replaces
>
>         task.save!
>
>  with
>         task.save! if Task.exists?(task.id)
>
>  If there's a better way to handle this (or if my logic is wrong), please let me
> know!
>
>
>  Mainn
>  
ACK

BTW, I'm surprised by behaviour of "dcloud_instance.send(action)" - I 
thought that it's async call, but it updates dcloud_instance.state directly.

Then it's possible that an instance's state is changed to 'stopped' 
right after "dcloud_instance.send" call.And if it's last instance in a 
deployment, the deployment is destroyed (with instances).

Jan