Logstash Json filter unexpectedly fires for large nested JSON

Question

This is my logstash configuration:

input { redis { host => "127.0.0.1" data_type => "list" key => "logstash" } } filter { json { source => 'appData' } } output { elasticsearch { host => '127.0.0.1' } } 

The appData application works well - it's plain JSON, but elasticsearch starts to give parsing errors when large nested JSONs are passed to appData.

Is there an alternative to the JSON filter? or there somewhere I see debug logs to indicate a problem.