I’ve been asked to reverse engineer an app that uses postgresql in the back end.
I can see that there is some database replica
tion going on… based on my reading, I *think it’s called streaming replication.
The settings on the master server look like this:
wal_level = hot_standby
max_wal_senders = 5
wal_keep_segments = 32
My question is this: what impacts the delay between creating a new record on the master, and when it shows up / is replicated to the slave?
From reading the manual, (http://www.postgresql.org/docs/current/static/hot-standby.html) I see that the model it uses is “eventual consistency”… paragraph 4 on that page states:
The data on the standby takes some time to arrive from the primary
server so there will be a measurable delay between primary and
standby. Running the same query nearly simultaneously on both primary
and standby might therefore return differing results. We say that data
on the standby is eventually consistent with the primary.
But is there any pattern / ways to guesstimate how long it’ll take? Or is it really just arbitrary?
If you can point me in the right direction, I’d appreciate it.
Thanks.