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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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