In regards to your nifi expression language.:    Test in a simple flow, and inspect the flowfile's attributes to insure topicName is correct.    Then take it to the kafka processor.  If you are not seeing the results of the expression, something isnt right, or the value doesnt except Expression Language.  Look at the (?) on any property to see what is accepted.   I suspect the expression language is invalid as well, so make sure you test and confirm the attribute is as expected before trying to use it deeper in your flow.   In regards to mapping.   What i suggest could be DistributedMapCache or even a flow that does a lookup against some other service.  With this concept you provide a mapping key value pairs that correspond to your consumer and producer topics.  When you lookup a key, For Example:  "alerts_Consumer_Topic_Name" the value would be "alerts_Producer_Topic_Name".   If this is stored outside of nifi, then these values can be managed and changed outside of the scope of the nifi flow.   Example flow with DistributeMapCache:   https://github.com/ds-steven-matison/NiFi-Templates/blob/main/DistributedCache_Demo.xml ... View more

Sometimes I need to increase the timeouts in the processor configurations.    You may also need to reduce the execution time for the processor incase the endpoint cannot handle too many requests at once. ... View more

@Rohit1997jio  If your endpoint test works with Postman, and your invokeHttp is setup similary, the above error suggest the nifi node cannot connect to the endpoint.  You would need to ensure you have network connectivity from nifi host to endpoint.    ... View more