Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
Hi, No one able to further clarify this? Does swift offer there read-after-create consistence like non-us-standard S3? What are the precise syntax and semantics of X-Newest header? Best, Nikolaus On 01/18/2012 10:15 AM, Nikolaus Rath wrote: Michael Barton mike-launch...@weirdlooking.com

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
copy of the Object. The COPY Object operation already has this functionality. On Fri, Jan 20, 2012 at 9:12 AM, Nikolaus Rath nikol...@rath.org mailto:nikol...@rath.org wrote: Hi, No one able to further clarify this? Does swift offer there read-after-create consistence like

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
: If a node is down, then it is ignored. That is the whole point about 3 replicas. On Fri, Jan 20, 2012 at 10:43 AM, Nikolaus Rath nikol...@rath.org mailto:nikol...@rath.org wrote: Hi, What happens if one of the nodes is down? Especially if that node holds the newest copy

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
there are 3 replicas. A PUT Object will return after 2 replicas are done. So if all nodes are up then there are at least 2 replicas. If all replica nodes are down, then the GET Object will fail. On Fri, Jan 20, 2012 at 11:21 AM, Nikolaus Rath nikol...@rath.org mailto:nikol...@rath.org wrote: Hi

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
. On Fri, Jan 20, 2012 at 1:58 PM, Nikolaus Rath nikol...@rath.org mailto:nikol...@rath.org wrote: Hi, Sorry for being so persistent, but I'm still not sure what happens if the 2 servers that carry the new replica are down, but the 1 server that has the old replica is up

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
Hi Andi, My perspective is that I'm working on an application that should work with arbitrary service providers using swift. Therefore, I'm interested in the minimal set of guarantees that I can always rely on, no matter how the service provider has configured his particular swift instance.

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
On 01/20/2012 06:35 PM, Pete Zaitcev wrote: On Fri, 20 Jan 2012 15:17:32 -0500 Nikolaus Rath nikol...@rath.org wrote: Thanks! So there is no way to reliably get the most-recent version of an object under all conditions. If you bend the conditions hard enough to hit the CAP theorem, you do

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
On 01/20/2012 05:08 PM, Caitlin Bestler wrote: If you aren’t forcing a Get to reference all servers, using the option Stephen mentioned, then you MAY get an old version before the replication process is complete. That is what is meant by “eventual consistency”. Well, but apparently this may

Re: [Openstack] Swift Consistency Guarantees?

2012-01-20 Thread Nikolaus Rath
Hi Chuck, Thanks for the detailed explanation! That pretty much answers all of my questions. I think this can (and should) placed as-is somewhere in the Swift Dokumentation and/or the Wiki. Best, Nikolaus On 01/20/2012 04:58 PM, Chuck Thier wrote: Some general notes for consistency and swift

Re: [Openstack] Swift Consistency Guarantees?

2012-01-18 Thread Nikolaus Rath
Michael Barton mike-launch...@weirdlooking.com writes: On Tue, Jan 17, 2012 at 4:55 PM, Nikolaus Rath nikol...@rath.org wrote: Amazon S3 and Google Storage make very explicit (non-) consistency guarantees for stored objects. I'm looking for a similar documentation about OpenStack's Swift

[Openstack] Swift Consistency Guarantees?

2012-01-17 Thread Nikolaus Rath
Hello, Amazon S3 and Google Storage make very explicit (non-) consistency guarantees for stored objects. I'm looking for a similar documentation about OpenStack's Swift, but haven't had much success. Could someone summarize what kind of consistency guarantees a swift server offers? For example: