Help needed to filter unwanted charators from kafka message in logstash

[Rameswar_m]

hi ,
i am new to logstash , i am trying to pull the dta from mongo to kibana via logstash
from kafka i am getting message below and my logstash conf is :

message:

�{"_id" : {"$oid" : "59da4346140f1dc01e861e4b"},"name" : "Boston","loc" : {"type" : "Point","coordinates" : [71.0603, 42.3583]}}rs0rs0pTracer.port��ҝ��͊�é�c�����W

i have used below filter:

filter{

mutate {

gsub => [
   "message", "rs0", "",
   #"message", "c", "",
   #"message", "W", "",
   "message", "pTracer.port", "",
   "message", "[^0-9A-Za-z\:\{\}\"\,]/", ""  
]

}

data is comings as :

�{"_id" : {"$oid" : "59da464d140f1dc01e861e4c"},"name" : "FED","loc" : {"type" : "Point","coordinates" : [51.8781, 176.6461]}}��ҝ������с�c�����W

i need data like this:

{"_id" : {"$oid" : "59da3ace140f1dc01e861e49"},"name" : "FED","loc" : {"type" : "Point","coordinates" : [51.8781, 176.6461]}}