ConnectionMetrics
data class ConnectionMetrics(val queryTimer: Timer, val queryErrorCounter: Counter, val txErrorCounter: Counter, val txAwaitTimer: Timer, val txSubmitTimer: Timer, val txExecuteTimer: Timer)
The query and transaction meters an xtdb.api.Xtdb.Connection records into.
The connection owns them so they fire for every frontend alike — pgwire, in-process ADBC, Flight SQL. They're registered once per node and shared by its connections; a node without a meter registry has none at all, hence the connection's whole ConnectionMetrics is nullable rather than each meter within it.