Historically the only database/sql driver setting exposed via JSON
config was maxDBConns. This change adds support for maxIdleConns,
connMaxLifetime, connMaxIdleTime, and renames maxDBConns to
maxOpenConns. The addition of these settings will give our SRE team a
convenient method for tuning the reuse/closure of database connections.
A new struct, DBSettings, has been added to SA. The struct, and each of
it's fields has been commented.
All new fields have been plumbed through to the relevant Boulder
components and exported as Prometheus metrics. Tests have been
added/modified to ensure that the fields are being set. There should be
no loss in coverage
Deployability concerns for the migration from maxDBConns to maxOpenConns
have been addressed with the temporary addition of the helper method
cmd.DBConfig.GetMaxOpenConns(). This method can be removed once
test/config is defaulted to using maxOpenConns. Relevant sections of the
code have TODOs added that link back to an newly opened issue.
Fixes#5199
e0510056cc