The style guide for Zulip is to always use "primary" and "replica"
when describing database replication. Adjust a few comments under
`puppet/` that do not adhere to this.
Unfortunately, some references still remain to the insensitive and
inaccurate "master" / "slave" terminology. However, these are only in
files which we are attempting to preserve as close to the upstream
versions they are derived from (e.g. postgresql.conf,
postfix/master.cf).
Instead of SSH'ing around to them, run directly on the database hosts.
This means that the replicas do not know how many bytes behind they
are in _receiving_ the wall logs; thus, the monitoring also extends to
the primary database, which knows that information for each replica.
This also allows for detecting when there are too few active replicas.
This doesn't yet pass all Nagios checks correctly, and still has a few
flaws:
* The ideal setup code for the `nagios` user in the database isn't included.
* Some of the other details are a bit off; we need to split some host roles.
But it's better than nothing, and we can iterate from here.
Alex Vandiver
Tim Abbott
Tim Abbott