presto-main/src/main/java/io/prestosql/execution/QueryManagerStats.java/QueryManagerStats/getRunningQueries
class QueryManagerStats:    @Managed
    public long getRunningQueries()
    {
        // This is not startedQueries - completeQueries, since queries can finish without ever starting (cancelled before started, for example)
        return runningQueries.get();
    }