Open Stack

Thanks for sharing.



On Fri, Aug 10, 2012 at 12:31 PM, John Dickinson <me at not.mn> wrote:

> In a standard swift deployment, the proxy server is running behind a load
> balancer and/or an SSL terminator. At SwiftStack, we discovered an issue
> that may arise from some config parameters in this layer, and we'd like to
> share it with other swift deployers.
>
> Symptom:
>
> Users updating metadata (ie POST) on larger objects get 503 error
> responses. However, there are no error responses logged by swift.
>
> Cause:
>
> Since POSTs are implemented, by default, as a server-side copy in swift
> and there is no traffic between the user and swift during the server-side
> copy, the LB or SSL terminator times out before the operation is done.
>
> Solution:
>
> Two options:
>
> 1) Raise the timeout in the LB/SSL terminator config. For example, with
> pound change the "TimeOut" for the swift backend. pound defaults to 15
> seconds. The appropriate value is however log it takes to do a server side
> copy of your largest object. If you have a 1gbps network, it will take
> about 160 seconds to copy a 5GB object ((8*5*2**30)/((2**30)/4) -- the
> divide by 4 is because the 1gbps link is used to read one stream (the
> original) and write the new copy (3 replicas)).
>
> 2) Change the behavior of POSTs to not do a server-side copy. This will
> make POSTs faster, but it will prevent all metadata values from being
> updated (notably, Content-Type will not be able to be modified with a
> POST). Also, this will not make the issue go away with user-initiated
> server-side copies.
>
> I would recommend the first solution, unless your workload makes heavy use
> of POSTs.
>
> Hoep this helps.
>
> --John
>
>
>
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