Cannot sending data from mongodb into elasticsearch using logstash

Question:

Hi all, i have an issue when i try to get data from mongodb to elasticsearch using logstash-input-mongodb. There is no document that get into elastic but when i stdout using rubydebug, logstash show me the documents in mongodb. After that i check the indices in elastic, they create the index but there is no document. 0 Doc in index that i created.

This my configuration file:

input {
mongodb {
uri => 'mongodb://***:*********@localhost:27017/logs'
placeholder_db_dir => 'E:\ELK\logstash-5.5.0\db_dir'
placeholder_db_name => 'logstash_sqlite.db'
collection => 'tx_log'
batch_size => 5000
generateId => 'true'
parse_method => "simple"
}
}
output {
elasticsearch {
hosts => ["localhost:9200"]
index => "tx_logs"
}
stdout { codec => rubydebug }
}

and this is some output from logstash console after they print the data on the console:
s
D, [2017-09-18T14:20:16.807000 #26876] DEBUG -- : MONGODB | localhost:27017 | logs.listCollections | STARTED | {"listCollections"=>1, "cursor"=>{}, "filter"=>{:name=>{"$not"=>/system.|$/}}}
D, [2017-09-18T14:20:16.812000 #26876] DEBUG -- : MONGODB | localhost:27017 | gosdev_logs.listCollections | SUCCEEDED | 0.004s

and it looping forever.
Thanks

Answer：
so ladies and gentlemen, i already solved this problem. just add this filter:

filter {
mutate {
remove_field => [ "_id" ]
}
}

because, logstash generate mongo_id and _id with the same value