[postgres-xl-general] oldest xmin is far in the past

Tomas Vondra tomas.vondra at 2ndquadrant.com
Thu Jan 11 07:38:51 PST 2018


Hi,

On 01/11/2018 06:43 AM, Christophe Pettus wrote:
> We're getting this warning out of the Postgres-XL cluster, on all data notes:
> 
> WARNING,01000,"oldest xmin is far in the past",,"Close open transactions soon to avoid wraparound problems.",,,,,,,""
> 
> Connected to the coordinator, no prepared transactions are open, and a VACUUM does not seem to cure it.  The tables in the primary database are not "old" in terms of XID age, so I'm not quite sure what the source of this is.  Thoughts?
> 

Have you checked prepared (and regular idle) transactions on all the
nodes, or just the one coordinator? My guess is something went wrong and
there's a prepared transaction on one of the nodes.

To explain, in XL cluster the nodes report their local xmin to the GTM,
the GTM maintains a global xmin and reports it back to the nodes. So if
there's one node reporting very old xmin, it'll "spread" to the whole
cluster causing issues like this.

BTW which XL version is this? I don't recall any recent bug fixes in
this area, though.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services



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