[pgpool-general: 3936] Re: "replication" mode inconsistencies
ishii at postgresql.org
Fri Aug 7 09:54:24 JST 2015
> I've done some more thinking on this, and I think the solution is
> simply *not* to record pgpool_status when *all* nodes are down (i.e.
> only record it when at least one node is up). So pgpool_status will
> always reflect the last set of nodes to which any data was written.
> Upon restart, if the up-to-date (previously "up") node is in fact down
> (regardless of whether the stale ("down") node is back up), pgpool
> will detect this in its health check and will fail; if the up-to-date
> (previously "up") node is back up, then pgpool will commence using it.
A downside of this approach is, the first health check after pgpool
restarting may take long time due to certain health checking retry
setting if the node is still down. However this downside is not new to
your approach (and there's a workaround: users can manually edit
pgpool_status file to set the node status to "down"). Besides this,
your approach seems attractive.
SRA OSS, Inc. Japan
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