Обсуждение: Strategies for validating WAL-shipping replication
We've set up WAL-shipping replication on one of our database servers, and the question is whether it runs correctly. Is there an easy way to access some tables and see if the data matches (possibly in single-user mode)? Stopping replication and starting the server for real on the replica means that we have to set up things from scratch, right? (This is a bit annoying because of the amount of data which has to be copied from the master.) -- Florian Weimer <fweimer@bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
Florian Weimer a écrit : > We've set up WAL-shipping replication on one of our database servers, > and the question is whether it runs correctly. Is there an easy way > to access some tables and see if the data matches (possibly in > single-user mode)? > Nope. The only way you can look at data on a "on-recovery" server (the log shipping slave) is to stop the recovery process. > Stopping replication and starting the server for real on the replica > means that we have to set up things from scratch, right? (This is a > bit annoying because of the amount of data which has to be copied from > the master.) > Yes. -- Guillaume. http://www.postgresqlfr.org http://dalibo.com
There is not such a possibility. However it's on TODO list: http://wiki.postgresql.org/wiki/Todo I'm waiting for this feature too. I can understand your fear about the data, that you can not query for it. I had the same :) So script as much as you can, for the rest create a formal procedure - then repeat it few times and check if everything is correct. After several tries you'll believe your data are safe. I've a good comfort level with this. You can also check & resetup your production from time to time. On Oct 20, 8:31 am, fwei...@bfk.de (Florian Weimer) wrote: > We've set up WAL-shipping replication on one of our database servers, > and the question is whether it runs correctly. Is there an easy way > to access some tables and see if the data matches (possibly in > single-user mode)? > > Stopping replication and starting the server for real on the replica > means that we have to set up things from scratch, right? (This is a > bit annoying because of the amount of data which has to be copied from > the master.) > > -- > Florian Weimer <fwei...@bfk.de> > BFK edv-consulting GmbH http://www.bfk.de/ > Kriegsstraße 100 tel: +49-721-96201-1 > D-76133 Karlsruhe fax: +49-721-96201-99 > > -- > Sent via pgsql-admin mailing list (pgsql-ad...@postgresql.org) > To make changes to your subscription:http://www.postgresql.org/mailpref/pgsql-admin
On Mon, 2008-10-20 at 01:08 -0700, wstrzalka wrote: > There is not such a possibility. However it's on TODO list: > http://wiki.postgresql.org/wiki/Todo > I'm waiting for this feature too. > > I can understand your fear about the data, that you can not query for > it. Please test the Hot Standby patch... -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support
Florian Weimer wrote: > We've set up WAL-shipping replication on one of our database servers, > and the question is whether it runs correctly. Is there an easy way > to access some tables and see if the data matches (possibly in > single-user mode)? > > Stopping replication and starting the server for real on the replica > means that we have to set up things from scratch, right? (This is a > bit annoying because of the amount of data which has to be copied from > the master.) The OmniTI guys gave a talk some time ago on how they used Solaris ZFS to create a filesystem snapshot, on which they stopped the recovery and started postmaster. This could run queries. The original copy continues running recovery, and whenever you want to "update your slave", you stop the second postmaster, delete the snapshot, and create a new one. Cumbersome ... -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support
On Mon, 2008-10-20 at 08:31 +0200, Florian Weimer wrote: > We've set up WAL-shipping replication on one of our database servers, > and the question is whether it runs correctly. There's two answers here. The first is that the code used is exactly the same as crash recovery. So if you trust crash recovery you should trust archive recovery, which means WAL shipping. The differences are all about where you start and stop WAL replay. The second is that any form of replication requires testing. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support