I've had some flow files get stuck in a queue because they were failing to go through an AttributesToJSON process. The process was giving a "FlowFileAccessException: failed to read content of StandardFlowFileRecord". I read here that this exception is wrapping an IOException thrown from the content repository: https://nifi.apache.org/docs/nifi-docs/html/developer-guide.html Further reading lead me to believe that my machine had too low of a limit for number of concurrently open files allowed. So I increased hard and soft limits to 50000 as suggested here: https://nifi.apache.org/quickstart.html I logged off and on, and even restarted nifi to be sure nifi was using the new limit for concurrently open file handlers. Still, the AttributesToJSON process gives the same exception. The attributes in the FlowFiles I am converting to JSON are not very large either. Is there something else that I can try?