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Re: Multi-Cluster/Zone - Devil in the Details ...
Thanks for feedback Ed. Comments in  below ...
From: Ed Leafe [ed@xxxxxxxxx]
On Feb 16, 2011, at 10:26 AM, Sandy Walsh wrote:
Isn't the instance name usually supplied by the user/originator?
[Sorry, yes the instance name is passed in on the request, but the instance ID is what's needed (assuming of course instance ID is unique across zones.)]
> Q2. If I do "instance-list", do I have to search all zones again?
If the db is not centralized/replicated, yes. Caching could certainly be an option, especially in situations where instances tend to persist for long periods.
[The db is not centralized. One per Zone.]
> One alternative is to make Host-Best-Match/Zone-Best-Match stand-alone query operations.
I don't really like this approach. It requires the requester to know too much about the implementation of the service: e.g, that there are zones, and that an instance will be placed in a particular zone. I would prefer something more along the lines of:
a. User issues a create-instance request, supplying the name of the instance to be created.
b. The top-level zone that receives the request does a zone-best-match and/or host-best-match call to determine where the instance will be created.
c. The top-level zone then passes the create-instance request to the selected zone/host.
[But what about subsequent actions ... the same zone-search would have be performed for each of them, no?]
-- Ed Leafe
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