How to use the esper.prelude.now function in esper

run_opts = {
            'io_packet_size': job_config.io_packet_size,
            'work_packet_size': job_config.work_packet_size,
        }
        ppw = job_config.pipelines_per_worker
        if ppw != -1:
            run_opts['pipeline_instances_per_node'] = ppw

        run_pipeline(db, detach=True, run_opts=run_opts, **args)

        # Wait until it succeeds or crashes
        start = now()
        log.info('Monitoring cluster')
        result, metrics = db_wrapper.cluster.monitor(db)
        end = now() - start

        # If we crashed:
        if not result:

            # Restart the cluster if it's in a bad state
            db_wrapper.cluster.start()

            raise TestFailure("Out of memory")

        # Write out profile if run succeeded
        outputs = run_pipeline(db, no_execute=True, **args)
        try:
            outputs[0]._column._table.profiler().write_trace(
                '/app/data/traces/{}.trace'.format(run_name(db_wrapper.cluster.config(), job_config)))
        except Exception:
            log.error('Failed to write trace')

# Start the Scanner job
        log.info('Starting Scanner job')

        run_opts = {
            'io_packet_size': job_config.io_packet_size,
            'work_packet_size': job_config.work_packet_size,
        }
        ppw = job_config.pipelines_per_worker
        if ppw != -1:
            run_opts['pipeline_instances_per_node'] = ppw

        run_pipeline(db, detach=True, run_opts=run_opts, **args)

        # Wait until it succeeds or crashes
        start = now()
        log.info('Monitoring cluster')
        result, metrics = db_wrapper.cluster.monitor(db)
        end = now() - start

        # If we crashed:
        if not result:

            # Restart the cluster if it's in a bad state
            db_wrapper.cluster.start()

            raise TestFailure("Out of memory")

        # Write out profile if run succeeded
        outputs = run_pipeline(db, no_execute=True, **args)
        try:
            outputs[0]._column._table.profiler().write_trace(