Is there a way to let elasticsearch-hadoop auto-generate doc id?

I'm using elasticsearch-hadoop-2.2.0 running against hadoop 2.4.1, if not specifying "es.mapping.id", it throws following exception:
16/03/11 16:30:56 INFO mapreduce.Job: Task Id : attempt_1452685769492_240664_r_000000_2, Status : FAILED
Error: org.elasticsearch.hadoop.rest.EsHadoopInvalidRequest: id must not be null
at org.elasticsearch.hadoop.rest.RestClient.checkResponse(RestClient.java:467)
at org.elasticsearch.hadoop.rest.RestClient.execute(RestClient.java:425)
at org.elasticsearch.hadoop.rest.RestClient.execute(RestClient.java:415)
at org.elasticsearch.hadoop.rest.RestClient.bulk(RestClient.java:145)
at org.elasticsearch.hadoop.rest.RestRepository.tryFlush(RestRepository.java:225)
at org.elasticsearch.hadoop.rest.RestRepository.flush(RestRepository.java:248)
at org.elasticsearch.hadoop.rest.RestRepository.close(RestRepository.java:267)
at ...

What's your ES mapping ? How do you call ES-Hadoop? Troubleshooting

sorry for late, it works fine. The exception due to my wrong config.