Open Stack

On Thu, Feb 6, 2014 at 8:16 PM, Matthew Gilliard
<matthew.gilliard at gmail.com> wrote:
> Hello everyone.
>
>   wrt these bugs: https://bugs.launchpad.net/nova/+bug/1276203
> https://bugs.launchpad.net/nova/+bug/1272830 - I'd just like to make sure
> that the approach I'm planning makes sense.
>
>   To summarise: Currently there are a number of methods in
> compute/manager.py that use the @periodic_task decorator.  Some of them also
> do their own checks about how often they are called, and use a convention of
> polling period = 0 to disable the method by returning early (although this
> is sometimes implemented as <=0 [1] and sometimes as ==0 [2]).  In the
> decorator itself though, a polling period of 0 is used to mean "call this
> method any time any other period task is run" [3].  It's difficult to
> predict how often this might be, and it may not be at regular intervals.
>
>   I'd like to make this more consistent and predictable.  My plan is to use
> the following:
>
>   - Any positive integer: the method is called every <this many> seconds,
> best effort is made not to call it more or less often.
>   - 0: the method will be called regularly at the default period.  Currently
> hard-coded to 60s [4] this could be made into a config option
>   - Any negative integer: the method will not be called
>
>   All this logic would be contained in the decorator so that the methods
> themselves can just get on with whatever business they have.  So far, I hope
> this isn't too contentious - just clean code.  Is there any case that I've
> missed?  The fix will necessarily be a breaking change.  So how do you
> suggest I approach that aspect?  As it's common code, should I actually be
> looking to make these changes in Oslo first then porting them in?

The decorator comes from oslo, so you're talking about changing the
default flag behaviour for pretty much every openstack project here.
How do we do this in a way which doesn't have unexpected side effects
for deployments?

Michael

-- 
Rackspace Australia