Let's say you have two backends: backend0 and backend1. Supposing backend1 has failed, recoverying it (by re-synchronizing data from backend0) is expected to have a pgpool client reconnection. From the point of view of pgpool, the clients must disconnect and reconnect in order to complete a data synchronization. However, this disconnection can be very quick. The interesting part is that data synchronization (a kind of copy of the postgresql data directory) will happen while backend0 is available por reads and writes. At the end of the data transfer (1st stage), a postgresql feature (WAL archiving) helps with the synchronization of newer data (2nd stage) that has been transferred at the 1st stage. At 2nd stage is when clients must disconnect and reconnect. Pgpool has the ability to normally accept connections during 1st stage. At 2nd stage, pgpool waits until clients disconnect or until client_idle_limit_in_recovery seconds happen. Then clients get disconnected. If clients try to connect while 2nd stage happen, pgpool will block them until it finishes. Clients won't get disconnected, just will sit waiting until connection happens.
I hope this helps. Daniel ________________________________ From: Crespo, Daniel @ SDS Sent: Tuesday, March 17, 2009 4:05 PM To: 'DM'; pgpool-general@pgfoundry.org Subject: RE: [Pgpool-general] Is there a option Yes. Look for the following keywords: pcp_recovery_node (pgpool client program) client_idle_limit_in_recovery (parameter in pgpool.conf) pgpool_copy_backup (script) pgpool_switch_xlog (script) pgpool_remote_start (script) Daniel ________________________________ From: pgpool-general-boun...@pgfoundry.org [mailto:pgpool-general-boun...@pgfoundry.org] On Behalf Of DM Sent: Tuesday, March 17, 2009 2:57 PM To: pgpool-general@pgfoundry.org Subject: Re: [Pgpool-general] Is there a option Hi All, Sorry I wanted to ask the question the other way round. In Pgpool is it possible to recover / sync the 2nd DB without quiescing the first. Thanks Deepak On Tue, Mar 17, 2009 at 9:48 AM, DM <dm.a...@gmail.com> wrote: Hi All, In pgpool Is it possible to do quiescing of a db while (recovering)/syncing the 2nd DB? Thanks Deepak
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