presto-main/src/main/java/io/prestosql/operator/DriverContext.java/DriverContext/finished
class DriverContext:    public void finished()
    {
        if (!finished.compareAndSet(false, true)) {
            // already finished
            return;
        }
        executionEndTime.set(DateTime.now());
        endNanos.set(System.nanoTime());

        pipelineContext.driverFinished(this);
    }