Add an upstream ProxySQL container to our docker-compose. Configure
ProxySQL to manage database connections for our unit and integration
tests.
Fixes#5873
This changeset adds a second DB connect string for the SA for use in
read-only queries that are not themselves dependencies for read-write
queries. In other words, this is attempting to only catch things like
rate-limit `SELECT`s and other coarse-counting, so we can potentially
move those read queries off the read-write primary database.
It also adds a second DB connect string to the OCSP Updater. This is a
little trickier, as the subsequent `UPDATE`s _are_ dependent on the
output of the `SELECT`, but in this case it's operating on data batches,
and a few seconds' replication latency are several orders of magnitude
below the threshold for update frequency, so any certificates that
aren't caught on run `n` can be caught on run `n+1`.
Since we export DB metrics to Prometheus, this also refactors
`InitDBMetrics` to take a DB Address (host:port tuple) and User out of
the DB connection DSN and include those as labels in the metrics.
Fixes#5550Fixes#4985
Samantha