On 2021-06-16 18:02, Julien Rouhaud wrote:
On Wed, Jun 16, 2021 at 05:36:24PM -0700, Dean Gibson (DB Administrator) wrote:
Is this reasonable thinking?
I'd think that one would want a *wal_keep_size* to cover the pending updates
while the standby server might be unavailable, however long one might
anticipate that would be.
It's usually a better approach to use a replication slot, to keep all the
required WAL files, and only when needed. See
https://www.postgresql.org/docs/current/warm-standby.html#STREAMING-REPLICATION-SLOTS
for more details.
Note that a replication slot will keep all WAL files, which might eventually
lead to an outage if the standby doesn't come back before the filesystem
containing the logs get full. You can cap the maximum amount of retained WAL
files since pg 13 using max_slot_wal_keep_size, see
https://www.postgresql.org/docs/current/runtime-config-replication.html#GUC-MAX-SLOT-WAL-KEEP-SIZE.
Granted, but the same question arises about the value for
max_slot_wal_keep_size. Setting either too low risks data loss, &
setting either too high results in unnecessary disk space used. The
question was, is the estimated VALUE reasonable under the circumstances?
