openstack team mailing list archive

[Peter Portante <peter.a.portante@xxxxxxxxx>]

On Mon, Jun 3, 2013 at 8:41 AM, Luse, Paul E <paul.e.luse@xxxxxxxxx> wrote:
> Hi Peter,
>
> I'd ask that Edward may want to chime in on object variation as I may not understand that one correctly - again I'm proposing to just implement the redirect response blueprint and reference object variation as a potential user simply because John mentioned it in his original write-up of the redirect response blueprint.  Edward?

But if there is not concrete need for the redirection, why implement it?

>
> Wrt your second question, there are copies of the rings on object servers as well and they are used for lookup in various scenarios, replication for one.  As an example take a small 6 node cluster where all servers are running all services, if an admin adds/deletes a device from the ring they do so on one of the nodes and then copes the .gz file to all the others.  During the window when the first node detects the new ring file and .gz files are copied to all the other nodes and detected/brought into memory, any responses fielded by the proxy service on the other nodes will have older ring info than the first node updated.  Another case could be a larger cluster where there's a proxy tier and a capacity tier (not all services running everywhere).  The admin could update the ring on any node and copy the ring files on the nodes in any order - if any capacity node gets an update before any proxy node you can run into the same scenario.  The ring versions blueprint was John's so he may have additions/corrections....

So the copies of the RIng is not used by the server, but by the
account reaper, container updater, container sync, object updater, and
object replicator. Why would we want to get the object server involved
here as well? It feels like that information could be localized in the
proxy servers, but perhaps another discussion.

Have you looked at the Pete Zaitcev's work on the LFS patch? It seems
like keeping this level of information in the proxy server,
specifically in a form of the object server controllers would be a
good place for this kind of thing.

>
> Thanks
> Paul
>
>
> -----Original Message-----
> From: Peter Portante [mailto:peter.a.portante@xxxxxxxxx]
> Sent: Monday, June 03, 2013 3:50 AM
> To: Luse, Paul E
> Cc: openstack@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Openstack] [Swift] Storage Server Redirection
>
> Hi Paul,
>
> Can you explain more about the two use cases referenced?
>
> Object Variation seems like a nice idea, but can you clarify how the mechanism would work to get at the variations? Any examples? From the current descriptions, it seems like the LFS Patch could help here without adding anything to the object server.
>
> Regarding the ring updates, given that rings are used by the proxy servers, and as far as I can tell, the object servers don't know about the rings, how would object servers have more up-to-date knowledge to perform the redirect?
>
> Thanks,
>
> -peter
>
>
> On Fri, May 31, 2013 at 7:53 PM, Luse, Paul E <paul.e.luse@xxxxxxxxx> wrote:
>> I'm looking at tacking this item:
>>
>>
>>
>> https://blueprints.launchpad.net/swift/+spec/support-storage-server-re
>> directs
>>
>>
>>
>> and wanted to get some feedback on the following observations/thoughts:
>>
>>
>>
>> 1) This is a capability that would be checked in independent of other
>> blueprints that might use it (2 are mentioned in the link above) and
>> unit test code would be the only way to initially exercise it; it
>> essentially enables other activities at this point
>>
>>
>>
>> 2) The basic idea is that an object server (via middleware or
>> otherwise) will be given the ability to respond to a request to
>> indicate 'not me but I know who should handle this'.  I'm thinking
>> this makes more sense as a 5xx response with additional information
>> (partition, nodes) about the route included in the response body (as
>> opposed to a 3xx code)
>>
>>
>>
>> 3) The proxy server will be modified to process the response
>> accordingly but using the partition, nodes info from the response as
>> opposed to
>> object_ring.get_nodes() to determine which nodes to use
>>
>>
>>
>> 4) Protection will be required to avoid endless redirection loops
>>
>>
>>
>> 5) This applies only to GET operations
>>
>>
>>
>> Appreciate any thoughts/feedback.,  In addition to the two usages of
>> this capability referenced in the blueprint I think there's applicable
>> to another Tiering blueprint which interests me as well.
>>
>>
>>
>> Thanks
>>
>> Paul
>>
>>
>>
>>
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