I have a Phoenix PutSQL that worked in the past, but not today. From the error box, not much help. Thought maybe Hbase or Phoenix was done. Turned out one field was missing. How to investigate this issue? Digging through the logs I quickly found it: Caused by: java.sql.SQLException: ERROR 218 (23018): Constraint violation. DRONEDATA1.DATEKEY may not be null That would be nice in the error listed in NiFi. If something seems like an odd error, dig into the logs for more detailed descriptions. Also the Summary Screen is pretty awesome and will let you find a lot of information for debugging and fixing problems. The Connections tab will let you sort by Queue Size and you can see if things are backed up. If you click the system diagnostics link you will see two tabs of useful information. The first has memory usage and garbage collection. The System tab has your usage for FlowFile and Content Repositories, processors and process load. For more details, check out the following references. Reference: https://nifi.apache.org/docs/nifi-docs/html/developer-guide.html https://nifi.apache.org/docs/nifi-docs/html/administration-guide.html#flowfile-repository https://nifi.apache.org/docs.html https://community.hortonworks.com/questions/71001/debugging-nifi-flow.html https://community.hortonworks.com/questions/69004/nifi-monitoring-processor-and-nifi-service.html#answer-69684 ... View more