Apache Nifi managed by Azure Kuberenetes

We have a Nifi application running on containers and orchestrated by Kuberenetes. Fluend was configured to push the logs from pods to Logstash only if the type is JSON (currently files are in plain text format. So It is not being pushed to Kibana) & Files in other formats won’t be pushed & stay in the server itself. To make this workable, Plain text files to be converted in to JSON format