[Postgres-xl-developers] Recovering GTM after failure

Mason Sharp msharp at translattice.com
Sun Jan 25 06:12:12 PST 2015


On Thu, Jan 22, 2015 at 12:38 PM, Adrian Nicoara <anicoara at uwaterloo.ca>
wrote:

> Hello,
>
> I tried to find a description of what happens when the GTM fails. So
> far, I could only find:
>
> http://www.pgcon.org/2012/schedule/attachments/224_Postgres-XC_tutorial.pdf
>
> slide 95, that describes the requirement of a standby GTM for
> failover, with synchronous changes done among the GTM processes.
> In the absence of such a process, does the entire cluster have to be
> rebooted? I tried to reason out how the running transaction set, and
> new GXID is recovered from the data nodes/coordinators, but couldn't
> puzzle it out.
>
>
You should not have to reboot the cluster. GTM periodically writes to a
state file, every 1000 transactions. When it restarts, it reads that file
and jumps ahead 1000 transactions, meaning there may be a gap of missing
internal transaction ids, but at least transaction ids will not be reused.

Regards,

Mason
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