Data Distribution in RPG of NiFi Cluster

[oppo]

Hi, 
 
I have three nodes in NiFi cluster. Slave3 is the primary, slave2 is the 
coordinator.
 
I visit web UI of slave2 node, and create a process group, add listSFTP and RPG 
to do the data distribution. The input port of top diagram will forward to the 
group and link to FetchSFTP. But I found all 6 files from ListSFTP were just 
forwarded to one node slave1. See attachment.
 
I expect 6 files should be forwarded to slave1 and slave2 (or including slave3) 
in round-robin way. 
 
Does anyone know how is going on here?
 
Thanks and Regards.

Kui

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