Getting sporadic MapperParsingException errors for elasticsearch output (logstash 2.2.2)


I'm using logstash 2.2.2 to read from rabbitmq and post to my ES cluster (1.7.4), and I'm getting occasional "MapperParsingException[object mapping for [email_queue] tried to parse field [payload] as object, but got EOF, has a concrete value been provided to it?" as an error, but the value under "payload" is clearly an object (i.e. a complex nested hash) when looking at the logs. I tried piping the same json into logstash with a file input, and it indexed without issues. I was running logstash 1.4.2 previously and wasn't getting these issues, but I still got this issue with 2.1.3.

This means the field "mail_queue.payload" is sometime not an object, hence the mapping conflict reported by elasticsearch.