Cloud State component

Richard Su rwsu at redhat.com
Fri May 11 23:59:17 UTC 2012


On 05/11/2012 04:27 AM, Jan Provazník wrote:
> Hi,
> there is a new proposal described here: 
> https://www.aeolusproject.org/redmine/projects/aeolus/wiki/Cloud_State
>
> Any ideas/thoughts/feedback would be appreciated.
>
> Jan

Jan

I like the idea of separating the instance status checking and updates 
out of conductor main and breaking up the code along functional lines.

I have a couple of questions:

1.
Does the engine periodically poll for instance state? I assume yes.  Or 
is it through some other mechanism to be determined.

2.
Assuming new engine is integrated into conductor, what happens if the 
application is restarted? Are instance updates atomic between conductor 
and the engine? Imagine a scenario where conductor and engine has state 
A for an instance. The engine polls the instance and now sees state B 
and saves it to the database to its own model. The app is then restarted 
before the callback to conductor is made. Engine polls instance again 
and sees state B matching what's in the database, so no callback is 
made, and conductor continues to reflect state as A.

We can say that the first status update by the engine is always called 
back to conductor. The engine would need to be smart enough to know if 
the update is the first since it started up.

Having the engine not integrated into conductor and having it run as its 
own service would make this more tricky.

- Richard




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