Right - examining the current state isn't a good way to determine what happened with one particular request. This is exactly one of the reasons some providers create Jobs for all actions. Checking the resource "later" to see why something bad happened is fragile since other opertaons might have happened since then, erasing any "error message" type of state info. And relying on event/error logs is hard since correlating one particular action with a flood of events is tricky - especially in a multi-user environment where several actions could be underway at once. If each action resulted in a Job URI being returned then the client can check that Job resource when its convinient for them - and this could be quite useful in both happy and unhappy situations.
And to be clear, a Job doesn't necessarily need to be a a full new resource, it could (under the covers) map to a grouping of event logs entries but the point is that from a client's perspective they have an easy mechanism (e.g. issue a GET to a single URI) that returns all of the info needed to determine what happened with one particular operation. thanks -Doug ______________________________________________________ STSM | Standards Architect | IBM Software Group (919) 254-6905 | IBM 444-6905 | [email protected] The more I'm around some people, the more I like my dog. Eoghan Glynn <[email protected]> 06/29/2012 06:00 AM To Doug Davis/Raleigh/IBM@IBMUS cc [email protected], Jay Pipes <[email protected]> Subject Re: [Openstack] Nova and asynchronous instance launching > Note that I do distinguish between a 'real' async op (where you > really return little more than a 202) and one that returns a > skeleton of the resource being created - like instance.create() does > now. So the latter approach at least provides a way to poll on the resource status, so as to figure out if and when it becomes usable. In the happy-path, eventually the instance status transitions to ACTIVE and away we go. However, considering the unhappy-path for a second, is there a place for surfacing some more context as to why the new instance unexpectedly went into the ERROR state? For example even just an indication that failure occurred in the scheduler (e.g. resource starvation) or on the target compute node. Is the thought that such information may be operationally sensitive, or just TMI for a typical cloud user? Cheers, Eoghan
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