Apache NiFi Configuration Best Practices
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Offload Nodes

Flowfiles that remain on a disconnected node can be rebalanced to other active nodes in the cluster via offloading. In the Cluster Management dialog, select the "Offload" icon () for a Disconnected node. This will stop all processors, terminate all processors, stop transmitting on all remote process groups and rebalance flowfiles to the other connected nodes in the cluster.

Nodes that remain in "Offloading" state due to errors encountered (out of memory, no network connection, etc.) can be reconnected to the cluster by restarting NiFi on the node. Offloaded nodes can be either reconnected to the cluster (by selecting Connect or restarting NiFi on the node) or deleted from the cluster.