Re: [Postgres-xc-developers] Yet another analysis of "GTM error, could not obtain snapshot"

[Masataka S. <pg...@gm...>]

My mailer might have wrong. Please ignore the second mail.

On 17 February 2014 17:39, Masataka Saito <pg...@gm...> wrote:
> Hi,
>
> I got a report that an error message "GTM error, could not obtain
> snapshot" still produced. I looked deeply in the proxy, then I found
> an another bug and misc errors.
>
> I explain the summary of them and attached patches.
> All suggestions are welcome.
>
> 01_fix_proxy_connid.patch:
>  A proxy assigns an connection ID to the connection from back-end. A
> connection ID is sent to the GTM when back-end requires a new
> transaction ID, back-end disconnected and so on. If a back-end
> disconnected, the GTM releases transactions related on the back-end.
>   On the other hand, a proxy renumbers the connection ID to fill a
> gapping entry in the connection array. But it is not notified to the
> GTM, and it causes the release of a transaction that is not related to
> disconnected back-end.
>  The patch makes the connection ID static by separating the connection
> ID from the index of the connection array.
>
> 01_fix_proxy_ereport_again.patch:
>  I fixed the issue before -- when GTM proxy received an error response
> to a command, GTM proxy reported error using an unrelated connection
> to the command -- but the patch had mistake. This is the patch that
> fixes it in right way.
>
> 01_fix_proxy_redundancy.patch:
>  A GTM proxy has some redundant code. This patch eliminates them.
>
> Regards.