@pavan srikar yes, that makes sense. When you start the DistirbutedMapCache server is starts a server on each NiFi node.The DIstributedMapCache Client should be configured to point at one specific node, so that every node pulls cache entries from same server. - A little back history: The DistibrutedMapCacheServer and DistirbutedMapCacheClient controller services date back to original NiFi releases versions. Back in those days there was no zero master clustering which we have now. There was a dedicated server that ran a NiFi Cluster Manager (NCM). At that time the DistributedMapCacheServer could only be setup on the NCM. - Once NiFi moved away from having a NCM, the functionality of these controller services was not changed to avoid breaking flows of user who moved to latest versions. The DistirbutedMapCacheServer does not offer HA (if node hosting server goes down, cache becomes unavailable). To provide HA here, new external HA caches options have been added as options. - thanks, Matt ... View more

The Correlation Attribute property is the name of one attribute, so if you want to correlate on two attributes you need to make a new attribute that is the combined value of the two attributes, or do the back to back merge as you mentioned. ... View more