[postgres-xl-bugs] Fwd: Database Rollback After GTM OOM + restart wipes data puts cluster in inconsistent state

Matthew Tamayo-Rios matthew.t.rios at gmail.com
Wed Dec 20 15:36:22 PST 2017


Thanks Tomas! This was the suggestion provided on the main list by Pavan
(Subject: Truncating table ...) and it worked.

I'm using PGXL 9.5r1.6, based on PG 9.5.8 (Postgres-XL 9.5r1.6).

What could cause a loss of the GTM control file? Setting up a standby GTM
is on my to do list. The GTM seems to be dying on a fairly regular schedule
(~4days) so I was tempted to just restart it every night at midnight.

Regards,
Matthew
ᐧ

On Wed, Dec 20, 2017 at 12:58 PM, Tomas Vondra <tomas.vondra at 2ndquadrant.com
> wrote:

> Hi Matthew,
>
> It'd be good to mention which Postgres-XL version you're running.
>
> In general, GTM is not reliable after a crash - it may "forget" some of
> the assigned transaction IDs etc. Which is why you should have s GTM
> standby, and fail over to it in case the primary GTM fails (instead of
> restarting the primary GTM node).
>
> (I am only assuming you don't have the GTM Standby, because you haven't
> mentioned it in your report.)
>
> In particular, the GTM probably lost the gtm.control file, which tracks
> the highest assigned XID, etc. So it uses the default "initial" value,
> which is 10000, as you can see in the error messages.
>
> So you can try modifying the file, to move the two XID fields above the
> value reported in your error message. For example:
>
>     version: 20160302
>     next_xid: 16740200
>     global_xmin: 16740200
>
> and then restart all the nodes (this may not be entirely necessary).
>
> regards
>
> --
> Tomas Vondra                  http://www.2ndQuadrant.com
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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> postgres-xl-bugs mailing list
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>
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