Backend file should finish creating file before map it.
Backend file should finish creating file before map it.


Former-commit-id: 0698eff4d6b35da1572aeadce08128bd91624607
larryxiao/peloton-1,omegaga/peloton,larryxiao/peloton,ranxian/peloton,omegaga/peloton,ranxian/peloton,larryxiao/peloton,omegaga/peloton,larryxiao/peloton,ranxian/peloton,ranxian/peloton,larryxiao/peloton-1,larryxiao/peloton,amaliujia/CMUDB-peloton,larryxiao/peloton,larryxiao/peloton,omegaga/peloton,amaliujia/CMUDB-peloton,larryxiao/peloton-1,amaliujia/CMUDB-peloton,omegaga/peloton,larryxiao/peloton-1,larryxiao/peloton,ranxian/peloton,omegaga/peloton,larryxiao/peloton-1,omegaga/peloton,ranxian/peloton,larryxiao/peloton-1,amaliujia/CMUDB-peloton,amaliujia/CMUDB-peloton,amaliujia/CMUDB-peloton,larryxiao/peloton-1,amaliujia/CMUDB-peloton