Logstash-input-mongodb plugin issues

I'm using (logstash-input-mongodb) plugin right now, but it is really slow, I checked the logstash log, it seems that my data has too many nested list. Have no idea how to improve the performance, I only have 500MB data store in mongodb. Wondering if there is any other plugins than this one.

the work I'm doing is to extract data from mongo and then import them into ES, I wrote some ruby code by using elasticsearch-ruby api to achieve this , but the importing speed is still very slow, cause the api only takes one insertion once a time , and the worst thing is the data that transported to ES can not used by kibana. hope someone can give me some help! Thank you

Any help?